Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
PLANT ACTIVATION DISPLAY APPARATUS
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a plant
activation display apparatus which is suited for use in
a plant which is expected to smoothly, securely
perform plant operations, such as start-up, shutdown,
and emergency shutdown operations of a chemical plant,
or for plant activation evaluation through simulated
plant operations.
Description of the Related Art
Many chemical plants comprise a very large number
of plant components, including columns and vessels
such as a reactors, distillation columns, heat
exchangers, etc., and transportation apparatuses such
as pumps, sophisticated piping, valves, and the like.
The plant operations at the site of a chemical plant,
which are examined to very fine details, are described
in an operation standard or the like. The
general plant operation is usually reviewed in
accordance with the following three kinds of
informations. The first information relates to the
structure of thE> chemical plant. This information
.includes the types of units constituting the plant, the
height and local;.ion of each unit, the states of
connection between the units, equipment necessary- to
perform non-steads state operation such as start-up
operation, the .initial and final states in the plant,
etc. The second kind of information relates to the steps
of the procedure for operating the units, and the third
kind of information relates to the
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execution timing for executing each step of the
procedure.
Conventionally, in designing a plant, the plant
operation procedure for the start-up operation starts
to be examined when the basic flowsheet is completed.
This will be described below with reference to Fig. 29.
First, a designer, having the operation procedure in
mind, decides the necessary piping location and the
arrangement of pumps, main valves, etc. Then, the
designer investigates the steps of the start-up operation
procedure. The relationship between the designer's
intention to operate the plant and the plant structure
is often difficult for another designer to understand.
Usually, a plant designer is not an operator, so that
the operator often cannot fully understand the
designer's intention of the operation procedure, or the
designer cannot understand what the operator expects
the operation procedure to be.
These problems are attributable to the fact that
there are no specific methods to definitely connect the
process design, its operation procedure, and the timing
for the execution thereof, despite the intimate
relationships between them. It is to be desired, in
particular, th at the execution timing as well as the
conventional control systems are registered in a
distributed control system (DCS), and are sequentially
displayed on the display screen of an operation support
apparatus. Various problems are caused by an
indefinite representation of the relationships between
the four elemenl~s shown in rig. 29, including the plant
design, operation procedure, execution timing, and
operation support apparatus.
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For instance, even when PFD (Process Flowsheet
Diagram) and P & ID (Piping and Instrumentation
Diagram) are completed at the design phase, describing
the start-up procedure, shutdown procedure, etc. in the
manuals requires much time. The preparation of
manuals has not been systematized yet, and each
designer in charge confirms his or her planned steps of
the procedure on the completed flowsheets one after
another, which requires much time. Since errors are
likely to be m:~de and the procedure is likely to be
described in various expressions, moreover, the
procedure would be very difficult for users
(particularl,y, operators) to understand. The operation
for converting the description of the procedure into
the computer-a:Lded operation support screen is believed
to be an independent work project, which also requires
much time and labor.
Chemical plants are often modified or revamped, in
which case the operation procedure and execution timing
should be modified at the same time. Conventionally,
however, modified sections of the plant and the
associated modification of the operation procedure are
not clearly described, so that accurate modification
requires much time and labor. In this case, the
operation support screen should be also modified, which
also requires much time.
Since the relationship between the operation
procedure and the elecution timing is not clear ly
illustrated at the design phase, it is likely that the
valves, etc. are positioned at the wrong places. Such
plant thus designed will need great efforts to operate
the valves, etc. as well as complicated operations.
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In shortening the start-up time, furthermore, it
is very hard to be acquainted with the necessary
preliminary apparatuses or equipment, or to know how to
modify the operation procedure and execution timing.
If a chemical plant involves a combined unit which
integrates several units , the di f ference between the
operation procedure to operate the individual component
units separately and those for operating the combined
unit is not clear. It is often difficult, therefore,
to determine whether the operation procedure to operate
the individual units separately can be applied to the
combined unit type.
Conventionally known are several studies on the
representation of the plant operation procedure,
although they are not satisfactory yet. These studies
provide the following decision methods of operation
procedures as follows: (1) A method based on the
assumption that valve operation controls the operation
procedure for a chemical plant if it is designed so as
to form a targ et flow from the inlet of the plant to
the outlet (J.R. Rivas and D.F. Radd, AIChE J., vol. 20
(2), 320-325 (1914); O'Shima, J. Chem. Eng. Japan, vol.
11 (5), 390-395 (1918)).
(2) A so-called automatic start-up procedure
synthesis method in which the definitions of the
functions of the constituent units are strictly-
hierarchized, and the functions are connected in
succession usinc; a knowledge engineering approach
(Hwan,~ hue Suku, Shigeyuki Tomita, Ei,ji O'shima, Chem.
Eng. Reports vol.. 14 (6), 728-738 (1988)).
(3) A method for determining the plant operation
procedure b5- handling steps of procedure structured
~'~:'::
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with the plant operation as a knowledge base (R. Lakshamanan
and G. Stephanopc>ulos, Comput. Chem. Engng., vol. 12 (9/10),
985-1002 (1988); R. Lakshamanan and G. Stephanopoulos, Comput.
Chem. Engng., vol.. 12 (9/10), 1003-1021 (1988); R. H. Fusillo
and G. J. Powers, Comput. Chem. Engng., vol. 12 (9/10), 1023-
1034 (1988)).
These methods of determining the plant operation
procedure are all_ designed to determine the operation procedure
based on a given plant structure, and basically involving
description in text. There is therefore a difficulty in
describing parall'_el operations. Since the plant structure is
not clearly described in association with the operation
procedure, when t:he plant structure is changed, it is difficult
to understand the correlation between the modification of the
structure and the. resulting, necessary modification of the
operation procedure. In this case, the operation procedure
should be recons_Ldered from the beginning.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a
plant activation tracking and display apparatus which can
ensure clear illustration of the relation between the process
design, the operations and the execution timing, as well as
can permit the illustration to be used as a screen to support
the plant operation.
According to the present invention, there is provided
a plant activation tracking and display apparatus for use in a
plant in which a plurality of points of plant components are
represented by a plurality of nodes including at least one
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system input node through which an input fluid is externally
supplied to the plant, and at least one system output node,
through which an output fluid flows out from the plant,
adjacent nodes of. said plurality of nodes being connected by
means of fluid passages, at least some of said fluid passages
having at least one transportation means and/or valve means
for creating a fluid flow in a specified direction, the
apparatus further comprising: an output device including:
means for categorizing all fluids flowing through said fluid
passages, when the plant is in operation at a steady-state
condition, in accordance with type and phase of said fluids,
means for successively tracking categorized fluids with a
specified phase over said plurality of nodes from said system
input node to said system output node, and display means for
sequentially disF~laying arrays of tracked nodes of said
plurality of nodes in one direction; memory means for previous-
ly storing data which correspond to operating conditions for
each said transportation means and/or valve means; sensor
means for sensing the operating conditions for each said
transportation means and/or valve means to determine whether
the operating conditions for each said transportation means
and/or valve means are fulfilled; and output device control
means for successively determining whether said operating
conditions for each said transportation means and/or valve
means are fulfilled, starting from the system input node side,
and for causing t:he output device to make an emphatic
indication that each said transportation means and/or valve
means be operated when said conditions thereof are fulfilled,
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and to make a further emphatic indication of only fluid passages
between nodes through which fluid is caused to flow by the
operation of each said transportation means and/or valve means.
The invention also provides a plant activation track-
ing and display apparatus for evaluating plant activation
through simulated operation of a plant in which a plurality of
points of plant components are represented by a plurality of
nodes including at least one system input node through which
an input fluid is externally supplied to the plant, and at
least one system output node, through which an output fluid
flows out from the plant, adjacent nodes of said plurality of
nodes being connected by means of fluid passages, at least
some of said fluid passages having at least one transportation
means and/or valve means for creating a fluid flow in a
specified direction, the apparatus further comprising: an
input device for producing a data signal through external
input operation; an output device including means responsive
to the data signal delivered from said input device, for
categorizing all fluids flowing through said fluid passages
when the plant is in operation at a steady-state condition,
in accordance with a type and a phase of said fluids, for
successively tracking categorized fluids with a specified
phase over said plurality of nodes from said system input node
to said system output node, and for sequentially displaying
arrays of tracked nodes of said plurality of nodes in one
direction; memory means for previously storing data correspond-
ing to operating conditions for each said transportation means
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and/or valve means in response to the data signal delivered
from said input device; simulation signal output means for
outputting a simulated signal for simulatively making said
operating conditions for each said transport means and/or
valve means fulfilled to desired operating conditions; and
output device control means for successively determining
whether said operating conditions for each said transportation
means and/or valve means are fulfilled, starting from the
system input node side, depending on the presence of the
simulated signal output from said simulation signal output
means, and for causing the output device to make an emphatic
indication that each said transportation means and/or valve
means be operated when said operating conditions thereof are
fulfilled, and to make a further emphatic indication of only
fluid passages between nodes through which fluid is caused to
flow by the operation of each said transportation means and/or
valve means.
If necessary, the plant components may include a
heat exchanging component. In this case, at least one of the
nodes is connected to a node of the heat
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exchanging component through energy transfer, the heat
exchanging compcanent being displayed on the output
device, in the ~~icinity of the energy transferring
nodes in parallel relation therewith. The fluids
flowing through the fluid passages connected to that
node which exchanges energy with the node of the heat
exchanging component are regarded as identically
categorized fluids if the fluids would change in phase
state, around the node concerned. If necessary, the
plant component: include a hold-up device to be
displayed as one node.
Basically, plant operations such as start-up
operation, are intended to create flows of a fluid in a
desired state between the nodes of the plant components
by effecting "f~.oca control" between the nodes and, if
necessary, "holdup cont.rol." Thus, the present
invention is based on an understanding that the plant
operation procedure and execution timing can be
displayed in as__=;ociation with the line c:onfiQurdtion of
the plant by successively tracking each of the
categorized fluids with a specified phase from the
system input node to the system output node, and
displaying the arra~~s of the tracked nodes in one
direction. The plant operation procedure and
execution timing' displayed on the output device in the
aforesaid manner°, that is, sequence graphs of the plant
are represented along the fluid flows or in association
~~-ith the line configuration.
Automatic operation may be enabled by providing
the plant activation display apparatus of the present
invention with drive means for driving the
transportation means and/or valve means, so that the
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drive means is caused to drive the transportation
and/or valve means when the operating conditions are
fulfilled.
The plant activation display apparatus of the
present invention may be used as a simulation support
apparatus or a design support tool by replacing the
sensor means with simulation signal output means for
outputting a simulated signal for simulatively making
the operating conditions on the transport means and/or
valve means fulfilled. In this arrangement, it is
successively determined whether or not the operating
conditions for the transportation means and/or valve
means are fulfilled, starting from the one located on
the system input node side, depending on the presence
of the simulation signal from the simulation signal
output means, and the output device is caused to make
an emphatic indication to the effect that the
transportation means and/or valve means concerned
should be operated when the corresponding operating
condition is fulfilled, and an emphatic indication of
only the fluid passages between those nodes through
which flows are considered to have been caused by the
operation of th<~ transportation means and/or valve
means.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic diagram showing a
configuration oi" a distillation column system according
to a first embodiment to which a plant activation tracking
and display app<~ratus of the present invention is applied;
Fig. 2 is a schematic diagram showing a
configuration of the plant activation display apparatus
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applied to a distillation column system;
Fig. 3 is <~, flowsheet diagram showing a line
configuration o:E a distillation column in a steady
state operating condition;
Fig. 4 is a flowsheet diagram distinctively
showing fluid transportation means;
Fig. 5 is a diagram showing necessary pumps and
valves added to the flowsheet of Fig. 4;
Fig. 6 is a diagram showing an arrangement for the
hold-up;
Fig. r is a flowsheet diagram showing a line
configuration necessary for a steady-state transition
operation with Ei total reflux at the time of a start-up
operation;
Fig. 8 is a flowsheet diagram showing a line
configuration ne~cessar,y for a steady-state transition
operation with a circulation at the time of the start-
up operation;
Fig. 9 is a diagram showing a node configuration
of the distillation column system of the first
embodiment;
Fig. 10 is a sequence graph displayed on a display
device 44 shown in Fig. 2;
Fig. 11 is a flowchart illustrating steps of
procedure of the start-up operation executed by means
of an electronic: control device 40 shown in Fig. 2;
Fig. 12 is a block diagram showing a configuration
of a heat pump connected to a distillation column
system according to a second embodiment to which the
plant activation. tracking and display apparatus of the
present invention is applied;
Fig. 13 is a diagram showing a node configuration
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on the distillation column side according to the second
embodiment;
Fig. 14 is a diagram showing a node configuration
on the heat pump side according to the second
embodiment;
Fig. 15 i~, a sequence graph illustrating a case in
which only the distillation column side of the second
embodiment is activated;
Fig. 16 is a sequence graph illustrating a case in
which only the heat pump side of the second embodiment
is activated;
Fig. 16A is a sequence graph illustrating a
preliminary operation for the injection of a working
fluid in the heat pump;
Fig. 16B is a sequence graph illustrating a
preliminary operation for the circulation of a heat
exchanger working fluid in the heat pump;
Fig. 16C is a sequence graph illustrating a
preliminary operation for a circulation line of a
compressor of t:he heat pump;
Fig. 16D is a sequence graph illustrating a
preliminary operation for a drain line of the heat
pump;
Fig. 16E is a sequence graph illustrating a
preliminary operation for the ventilation of the heat
pump;
Fig. 16F is a sequence graph illustrating a
preliminary opei~ation for a superheating protection
line of the compressor of the heat pump;
Fig. li is a diagram showing a node configuration
for connecting t:he distillation column and the heat
pump;
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Fig. 18 i;> a sequence graph illustrating the
distillation column system according to the second
embodiment;
Fig. 19 i~> a timing chart illustrating operation
times for the valves and the like used when the
distillation column system is started up in accordance
with the sequence graph of Fig. 18;
Fig. 20 is. a timing chart illustrating operation
times for the valves and the like used when the start-
up time is shortened;
Fig. 21 is a diagram showing a configuration of an
evaporator;
Fig. 22 is a diagram illustrating the way of
representing a sequence graph for the evaporator;
Fig. 23 is a diagram showing a configuration of a
self-heat exchanging reactor;
Fig. 24 is a diagram illustrating the way of
representing a .sequence graph for the reactor of Fig.
23;
Fig. 25 is a block diagram showing a line
configuration for supplying two types of fluids A and B
to a tank 110;
Fig. 26 is a diagram illustrating the way of
representing a sequence graph used when the supply of
the fluid B is :started after a set amount of the fluid
A is introduced into the tank;
Fig. 27 is a diagram illustrating the way of
representing a ,sequence graph used when the fluids A
and B are simultaneously supplied to the tank;
Fig. 28 is a diagram illustrating the way of
representing a =_~equence graph equivalent to the one
shown in Fig. 26, used when the fluids A and B are
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simultaneously ~>upplied to the tank; and
Fig. 29 is a block diagram for i.Llustrating the
basic concept of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following is a description of a plant
activation display apparatus according to a first
embodiment of the present invention, as applied to a
distillation co"_umn system. Since this display
apparatus functions as a process design support tool
for a plant, the' plant design procedure will be
described first,
Line Conf.igurat~on for Steady State Operation
Let it be supposed that a pipeline configuration
for the steady ~~tate operation and internal states of
the plant are previously determined at the stage of the
basic process design. Principally, a distillation
column comprise~~ a column section, a reboiler, and a
condenser, the -last two serving as heat exchanging
elements. Fig. 3 shows the line configuration and
elevation for these elements. In Fig. 3, the arrows
indicate the directions of flows; the regular full line
represents a flow of a liquid, the thick full line a
flow of a gas-liquid mixture, the broken line a flow of
a gas, and the double line a flow of heat. A circle
(Q) indicates the point, of an inlet, outlet, or
junction of the fluid. In this case, the internal
states of the p_Lant, including the flow rate,
composition, pr<~ssure, temperature, and the phase of
the fluid, are previously determined as simulation data
for the steady :Mate operation. Also suppose that the
premises for the selection of the individual
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components, worl~;ing conditions, preliminary conditions,
etc. are previously determined, and that the properties
or reaction conditions of the fluid, such as the
reactivity (polymerizability in particular),
explosiveness, combustibility, toxicity, and
corrosiveness, and other conditions, including the
liability to cr5rstallization, solidification, scale,
slurry, etc., are given.
(Layout of Pump;, Valves, etc.)
Based on the above premises, the layout of valves,
pumps and so forth necessary for the plant operation is
determined. In making this decision, the concept of
"flow control," which is essential to the realization
of the present invention, is used.
The concept: of "flow control" includes two
meanings: The first one is related to the control of
the fluid state or creation of a fluid flow, and the
second one is related to timing control main ly for the
valve operation to create the flow, which will be
described in detail later. For the former mode of
control, it is necessary to study how to create the
flow of the fluid at a steady state as shown in the
plot plan of Fi~;. 3, and to investigate a device which
causes a change in phase of the fluid, if any, to
result in heat eexchange or a large pressure change
(flash or the like).
The schematic plot plan of Fig. 3 is therefore
prepared at the stage of PFD design. Since the types
and the locations of a material tank, condenser, reflux
tank, reboiler, bottom tank, etc. have already been
determined as known information, the locations of the
inlet point, outlet point and ,junction point (each
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indicated b,y Q;I shown in the flowsheet in Fig. 3 are
rewritten, and at the same time, elements such as
ejectors, which utilize external force to create a
fluid flow,are distinguished from those which do not
create such flow. Fig. 4 presents a flowsheet which
distinguishes fluid transportation means. In this
embodiment, those fluid transportation means which can
create a fluid flow without using external force are
indicated by labels "G," "S," and "PR." The label "G"
represents the fluid transportation means capable of
carrying the fluid through gravity, "S" the or.e capable _
of conveying th~= fluid utilizing the siphon effect, and
"PR" the one capable of transporting the fluid by means
of pressure drop originating from condensation.
As shown in Fig. 4, those fluids except vapor and
the fluids affi~ced with the above symbols and
classified accordingly need transportation means
involving external force. This transportation means may
be means for applying high pressure to the fluid to
carry it, such as a compressor, a pump, an ejector, and
a device for causing a throttle valve to cooperate with
the heating operation, or means for decompressing the
fluid to car ry- it, such as a decompressing pump, an
ejector, and a device for causing a throttle valve to
cooperate with an operation to condense gas. Any one
of means can be properly selected in accordance with
the fluid type, physical properties, etc.
According to this embodiment, as shown in Fig. 5,
it is necessary to provide a pump P1 between the inlet
point for material supply and the material supply stage
of the distillation column, a pump P2 in an intermediate
portion of a fluid passage between the reflux tank of
the condenser and the top of the
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distillation column, a pump P3 between this reflux tank
and the outlet for a distillate, and a pump P4 between
the bottom tank and the outlet for a distillate (bottom
product) at the' column bottom. Though not illustrated
in Fig. 5, preliminary devices or protection lines have
only to be added when needed by proper ly selecting such
external-force using transportation means.
In the ca~~e of the distillation column system of
this embodiment, the valves should only be arranged
according to th.e following rules. For example:
Rule 1: Dispose a valve on the discharge side of -
a pump in line for maintenance of the pump. It is to
be noted that a valve may be omitted for a pump that
pumps up a constant amount of the fluid.
Rule 2: Dispose a valve on the inlet side of
heating steam for the reboiler, and a drain valve on
the outlet side.
Rule 3: Dispose a valve at the inlet or outlet of
cooling water for the condenser.
Rule 4: Dispose a valve in the outgoing line from
the tank.
Rule 5: At least one control valve (CV) is
required when multiple lines from the tank are
connected.
Fig. 5 illustrates the arrangement of valves
according to they above rules. It is to be understood
that the types of valves depend on their usage and
the type of the fluid.
(Location of Hold-up)
When the p)Lant is operatinc at a steady state, the
hold-up does not; appear necessary. In view of a
unsteady state process, such as start-up or shutdown
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operation, the hold-up is important in determining the
execution timing of the plant operation procedure. In
other words, the aforementioned "flow control" is
executed by disposing the hold-up where necessary and
controlling its quantity. In particular, it is
necessary to provide the hold-up on the upstream side
of a pump in order to ensure stable transportation of
the fluid. Strictly speaking, the change in fluid
phase normally does not occur at uniform speed, and is
subject to fluctuation. In this respect, the hold-up
is disposed at the location before the phase change
takes place to thereby provide residence time for the
flow and absorb fluid fluctuation. It is to be
understood that the hold-up is provided to reserve the
material liquid, the distillate (bottom product) at the
column bottom, and the distillate (top product) at the
column top.
Fig. 6 shows the hold-ups arranged from the above
view points. A material supply tank Hl is disposed at
the point from 'which a raw material is supplied, a
bottom tank H5 at the bottom of the distillation
column, and a r~eflu:c tank H8 on the distillate outlet
side of the condenser. A top product tank H9 is
located on the downstream side of the top distillate
outlet, and a bottom product tank H10 is disposed on
the downstream aide of the bottom distillate outlet.
In Fig. 6, these tanks are indicated by "Q".
Line Configuration for Start-Up Operation
Then, a line configuration for the start-up
operation is in~festigated, and necessary lines are
added. The so-called total reflux operation,
circulation operation, and effluent operation are known
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as start-up operation strategies. From the economical
point of view, as well as in light of shortening
the start-up operation time, it is necessary
only to examines the former two operations, i.e., the
total reflux operation and the circulation operation,
as the line configuration for the start-up operation.
(Line Configuration for Total Reflux Operation)
For the total reflux operation, the material
supply line, top distillate line, and bottom distillate
line are cut off so that all the fluids flow back and
the distillates from the reflux tank H8 and bottom tank
H5 respective ly have target compositions. Valves VI,
V4 and V6 are provided on the respective lines to cut
them off. As illustrated in Fig. r, this operation
strategy requires no additional equipment but simply
the open/close operation of the valves for the reflux
purpose.
(Line Configuration for Circulation Operation)
The circulation operation is an operation strategy wherein
the top and bottom distillates are returned to the
material supply tank H1 and kept within the operation.
For this operation, it is desirable to move to the
total reflux operation when the top and bottom
distillates reach a predetermined composition
(temperature). However, start-up operation may be
effected in the circulation operation until the
distillates reach the desired composition
(temperature). Recycle lines S20 and S21 which run
from a top distillate line S12 and a bottom distillate
line S14 back to the tank H1 are required as
preliminary lines.
As the material supply tank HI, top product tank
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H9 and bottom :product tank H10 are all located on the
ground, pumps :ire needed to return the distillates from
these tanks H9 and H10 to the tank Hl. If the
switching vale<~s SV1 and SV2 are disposed on the
downstream side of the valves V4 and V6,of the
distillate lines S12 and Sl4,and the recycle lines S20
and S21 are branched from the valves SV1 and SV2 shown
in Fig. 8, the distillates would be circulated
back to the tank HI by means of the pumps P3 and P4.
Through the above procedure, the basic plant
design has been completed. It is preferable to
investigate a changing line or by-pass line for inert
gas for the start-up operation and, moreover, to
examine a line configuration for emergency shutdown
operation.
Fig. 9 is the flowsheet of the thus designed
distillation column system shown in Fig. 8 with
reference numerals given to the nodes, processing fluid
and valves. The nodes representing the individual
nodes of the plant components include pipe junction
point, part of a unit, a unit such as a heat exchanger
which has no point to connect to other pipes, a unit
such as a pump which utilizes external force, an
internal node such as a hold-up, a system input node
through which the process fluid or working fluid is
externally supplied to this plant, and a system output
node from which the fluid flows out of the plant. The
process fluid is indicated by reference numeral "Sl" or
the like in contrast with the fluid flowing between the
adjacent nodes. This reference numeral may be also
regarded as an .indication of the fluid passage through
which the fluid flows between the nodes. In some cases
r,
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the "fluid pasaage" means not only a pipe but also a
column unit. 'thus, a feature of the present invention
lies in that the process fluid is associated with the
fluid passage.
A supply :Line SO to the material supply tank Hl is
added. Here, "HO" denotes the system input node, that
is a material reserving tank, and "PO" and "VO"
respective ly indicate a pump and a valve disposed on
the supply line S0. The material reserving tank HO
includes a mobile tank unit such as a tank truck.
Fig. 1 is a schematic block diagram illustrating
the distillation column system designed in the
aforesaid manner. This system comprises a distillation
column D, a reboiler RB, a condenser CD, reserving
tanks, pumps and valves. Since like reference numerals
are used to designate the components corresponding to
the ones shown in the flowsheet of Fig. 9, a detailed
description of those components will be omitted.
The distillation column system according to the
first embodiment is equipped with the plant activation
display apparatus shown in Fig. 2. The display
apparatus displays the plant operation procedure and
the execution taming, so that operators execute the
plant operations, such as the start-up operation, while
monitoring what is on the display.
Configuration of Plant Activation Display Apparatus
The plant activation display apparatus comprises
an electronic control unit (ECU) 40 for controlling the
activation of the entire apparatus, an input device 42,
a displa,v device 44, a printer 46, an external memory
device 48, an I/O interface 50, a drive device 52, and
sensor means 54. The input device 42 serves to input
72465-22
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the plant configuration and a plant activation command
signal when its keys or switches are operated. The
display device tE4 displays the result of computation
done by the electronic control unit 40 or the like on
the screen. Lil~;ewise, the printer 46 prints out the
computation result from the control unit 40. The
external memory device 48 stores computing processes
(program) or the like, which are to be executed by the
control unit 40, The I/O interface 50 controls the
input/output of the control unit 40. The drive device
52 opens or cloy>es valves and drive pumps in response
to a drive signal sent via the I/O interface 50 from
the control unit, 40. The sensor means 54 detects the
hold-up level, column temperature, pressure, line flow
rate, etc., and supplies them to the control unit 40
through the I/O interface 50.
The following is a description of the action of
the plant activation display apparatus.
Preparation of :>eguence Graph
Before describing the action of the plant
activation display apparatus, a description will be
given of how to prepare a sequence graph to be
displayed on the screen of the display device 44 in the
plant activation display apparatus, which is the
fundamental technical concept of the present invention.
(Representation of Fluid Connection and Conditions for
Flow Control)
It is believed that the procedure of the
operations of the chemical plant, especially the start-
up operation procedure, is basically determined by
performing "flow control" and "hold-up control," while
conforming to the conditions for safety and product
F 2037415
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quality. In other words, the fundamental technical
concept of the present invention is based on the ideas
of "flow contrc>1" and "hold-up control."
When the ~~tart-up operation is executed to set the
chemical plant from an initial state to a target state
or steady state, the "flow control" is to control the
state of the fluid in each line or fluid passage
between the adjacent nodes, starting with the system
input node to the system output node, to thereby
establish the target flow state from the initial state.
According to the present invention, how ~o express the
flow of the fluid in the plant is based on the
knowledge that attention being paid to the phase state
of the fluid, the operation procedure can naturally be
represented if the fluid of the same phase is
sequentially tracked from the nodes on the system input
side to those on the system output side.
If the fluid in the same state is tracked from the
nodes on the syatem input side, a change in phase of
the fluid midway inhibits further tracking of the
fluid from that point. This phase change results from
heat exchange with the fluid or a Large change in
pressure on the fluid. If such heat exchange or a
substantial pressure change occurs, the
phase-changed f=Luid is considered to be continuous at
the point of change. In this respect, the phase-
changed fluid i;s tracked forward to the nodes on the
system output side.
with hold-ups provided wherever required in the
plant, the "holo!-up control" is necessary to control
the hold-up quantity for stable plant operations,
particularly for ensuring stable operation timing. The
72465-22
- 2z - 20 374 1 5
"hold-up contro~L" is applied to start and stop
conditions of the valve operation, such as the valve
operation start~~ng when the hold-up quantity of the
fluid flowing into the hold-up reaches a preset
discrimination ~Talue. This discrimination value may
vary according i:o the plant state, taking several
proper values accordingly. For example, a
discrimination value for drive a pump can be set
different from i:he one after the steady state is
reached. In other words, the discrimination value of
the hold-up is considered to be a variable associated
with the necessf~,ry start-up operation time and the
quality control,.
Based on the idea described above, all possible
phase states of the process fluid that flows between
the adjacent nodes in the flowsheet shown in Fig. 9,
are categorized so that all possible fluid connections
a.nd conditions for flow control are given in the table
1 below.
Table
1
SO (0-H -~1-H . L . . PO . V0 )
Sl (1-H ~ 3 . L . . P1 . V1 )
S2 (2 ~ 3 . L . . . )
S 3 ( -~4 . L . . . )
3
S4 (4 ~ 5-H . L . . . )
S5 ( ->6 . L . . . )
5-H
S6 (6 ~ 4 . V+L . +E2 . . )
S7 (4 ~ 3 . V . . . )
S 8 ( -~2 . V . . . )
3
S9 (2 ~ 7 . v . . . )
S 10 ( -~8-H . L . -E 1 . . )
7
20374 15
- 23 -
S11(8-H -~2 . . . P2 . V2 )
L
S12(8-H -~18 . . . P3 . V4 )
L
S13i18 -~9 . . . . SVl(2))
L
SI4(5-H ~ 17 . . . P4 . V6 )
L
S15(17 ~ 10-H . . . . SV2(2))
L
S16(11 ~ 12 . . . . V3 )
L
S17(12 -~13 . . +El . . )
L
S18(14 ~ 15 . . -E2 . . V5 )
V
S19(15 -~16 . . . . )
L
S20(18 -~1-H . . . . SV1(1))
L
S21(17 -~1-H . . . . SV2(1))
L
The follow~~ng is a description of some of what are
indicated by the' above representation of fluid
connections the conditions for and flow control shown
in Table 1.
The process fluid Sl is a liquid L which flows to
the node 3 (feed plate of the distillation column) from
the node 1-H (mf~,terial supply tank H1). The pump P1 is
driven to make i:he liquid flow, which starts only when
the valve V1 is opened.
The proces~~ fluid S3, a liquid L flowing from the
node 3 to the node 4, runs without any external force.
The proces:~ fluid S6 is a mixture of gas and
liquid (L+V) flowing from the node 6 to node 4. Since
the phase of the' fluid S6 changes from the liquid phase
L to the mixed phase (L+V) before or after the node 6,
an external hearing energy +E2 is necessary at the node
6.
The process fluid S10 is a liquid L running from
the node 7 to node 8-H (reflux tank H-8). Since the
fluid S10 changes its phase from the vapor phase V to
2~3~4 15
- 24 -
the liquid phasE~ L around the node 8-H, an external
cooling energy --E1 needs to be provided at the node 8-
H.
The process fluid S15 is a liquid L which runs
from the node 1'? to the node 10-H (bottom product tank
H-10). The fluid S15 starts flowing when the switching
valve SV2 of the node li is set to the state i2).
Table 2
ON conditions
SO [ON <;1-HS] PO VO
.
S1 [ON > 1-HS] P1 V1
.
ss (oN]
s4 [oN]
S5 [ON]
S14[ON ;>5-H$] P4 V6
.
S21[ON SV2(1)
.
S6 [ON > 5-HS] E2
.
S7 [ON]
S8 [ON]
S9 [ON]
S10[ON ] E1
.
S11(ON ;~8-HS] P2 V2
.
S12[ON > 8-HS] P3 V4
.
S20[ON ] SV1(1)
.
S2 (ON]
SO [OFF > 1-HS, > 5-HS, > 8-HS]
Table 2 shows preset conditions under which the
process fluid can be produced, or operating conditions
for valves and pumps. These conditions should be
determined beforehand.
20374 ~5
- 25 -
The condit~_on to permit the process fluid SO to
flow iON condit:~on) is that the hold-up quantity of the
hold-up H1 is smaller than a set value (1-HS). At this
time the pump PO is activated and the valve VO is
opened. When the hold-up quantity of the hold-up H1
becomes greater than the set value (1-HS), and when the
hold-up quantities of the hold-ups H5 and H8
respectively become greater than set values (5-HS) and
(8-H5), the pump PO is stopped to set the process fluid
SO in an OFF stt~te. If it takes much time to prepare
the pumps, the rump FO should be kept operating in an
idling state.
The ON condition for the process fluid S1 is the
hold-up quantity of the hold-up H1 greater than a set
value (1-HS). When the ON condition is satisfied, the
pump P1 is activated and the valve V1 is opened.
The proces:> fluid S3 is always in an ON state,
which means that: when it is supplied to the node 3, the
fluid S3 drops by the force of gravity, thus creating a
fluid flow.
With regard to the process fluid S6, when the
hold-up quantity of the hold-up H5 becomes greater than
a set value (5-fIs), steam is caused to flow to the
reboiler to create the flow of the fluid S6. The
reboiler should be warmed up so that the steam is
supplied to the reboiler on starting the start-up
operation.
Table 3
S15 (ON . '.7 -~ 10 . . SV2I2) . #1]
S13 [ON . l.8 -j. 9 . . SV1(2) . #2]
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- 26 -
Table 3 shows operating conditions for switching
from the start-up operation to the steady-state
operation. When the condition for the transition to
the steady-state operation indicated by "#1" is
fulfilled, the switching valve SV2 is set to the state
(2) so that the process fluid S15 flowing from the node
17 to node 10 is rendered ON. When the condition for
the transition i~o the steady-state operation indicated
by "#2" is fulfp_Iled, the switching valve SV1 is set to
the state (2) so that the process fluid S13 flowing
from the node lei to node 9 is rendered ON. For the _
transition-to-steady-state conditions ~1 and 2, each
composition (temperature) of the bottom and top
distillates should be at a set value (target value).
When the aforesaid fluid connections and
conditions for flow control are prepared, these pieces
of information a.re inputted into the electronic control
unit 40 through the key operation of the input device
42. When a computation start command signal is
inputted to the control unit 40 through the input
device 42 upon completion of the information input, the
control unit 40 prepares a sequence graph based on the
information shown in Tables 1 to 3, In accordance with
the stored computation procedure, a graph is displayed
on the screen of the display device 4=~. Fig. 20
illustrates a sequence graph for the start-up
operation, which is the result of computation done b,y-
the control unit 40 and displayed on the display device
44.
Sequence Graph
The following is a description of the way the
control unit 40 prepares this sequence graph on the
72465-22
_ 2037415
- 2r -
basis of the computation result shown in Fig. I0.
It is easy for one skilled in the art to prepare a
program so that= the control unit 40 runs to obtain the
sequence graph of Fig. 10 on the basis of the
aforementioned fluid connections and conditions for
flow control shown in Tables I to 3, and there are
various ways to prepare the program, so that no
particular discussion will be given to the details of
the program preparation. The feature of the present
invention lies in displaying a sequence graph which
expresses the designed plant configuration, operation
procedure and execution timing in a single flowsheet,
not in how to prepare the computer software.
The sequence graph of the present invention
indicates the individual points of the plant components
by nodes, and shows their layout along the flow of the
fluid in one direction on the screen or downward from
the top of the acreen in this embodiment, successively
tracking the nodes from the system input node to the
system output node on the basis of the phase state of
the fluid. In i~he sequence graph shown in Fig. 10, at
the input node of the body of the distillation column,
there is a singJ_e node 0-H, which corresponds to the
material reserving tank H0. At the output nodes, there
are two nodes 9--H and 10-H, which correspond to the top
product tank H9 and bottom product tank H10. There are
input nodes I=1 a.nd lI as well as output nodes 16 and I3
respective ly in the reboiler and condenser, which
constitute a heat exchanger.
This sequence graph is the contents of Tables 1 to
3 converted into a flowsheet according to the procedure
presented below. First, the control unit 40 tracks the
72465-22
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- 28 -
fluid of the same phase in order from the system input
node to the sysl-,em output node, on the basis of the
input information given in Table 1. More specifically,
with regard to i~he process fluid SO of a liquid phase,
this fluid of a liquid phase L flows from the node f)-H
(the input nodes and reaches the hold-up node 5-H
passing through the nodes 1-H, 3 and 4 in the named
order. The fluud is branched to two directions at the
node 5-H; one pt~.rt becomes the process fluid S14 and
reaches the nodE~ li. At the node 17 or the switching
valve SV2, this fluid becomes either the process fluid
S15 or S21 in ac:cordanee with the switching state of
the valve SV2, reaching the node 10-H or returning to
the input node .l-H accordingly.
The other i'luid branched at the hold-up node 5-H
becomes the process fluid S5 which reaches the node 6.
At the node 6 the fluid S5 changes its phase due to
heating energy I+E2) from the reboiler to have a mixed
phase of the vapor phase V and liquid phase L. When
there occurs he~~t exchange, the process fluid is
considered to be continuous according to the
aforementioned rules. The fluid S6 of the mixed phase
moves from the node 6 to the node 4. At the node 4,
the fluid S6 is divided into two phases. A liquid
portion becomes the aforementioned process fluid S~,
which reaches tree hold-up node 5-H again, a gaseous
portion becomes the process fluid S7, which rises up by
the force of gravity (density difference) and reaches
the node 7 of the condenser passing through the nodes 3
and 2 in the named order. During this period, the
fluid S7 keeps i:he vapor phase, and the flow is
indicated by the broken line in the flowsheet.
20 374 1 5
- 29 -
At the node 7 the heat (-El)of the fluid is
removed by the cooling water, causing the phase
transition from the vapor to liquid. In this case the
process fluid i:~ also considered to be continuous
because of the heat exchange, so that it becomes the
process fluid SLO, reaching to the hold-up node 8-H or
the reflux tank H8. The fluid is divided into two
portions at the node 8-H. One becomes the process
fluid S11 of a =Liquid phase L, which .returns to the
node 3 through i:,he node 2, and the other becomes the
process fluid 512, which reaches the node 18. The
fluid S12 becomes either the process fluid S13 or S20
in accordance with the switching state of the switching
valve SV1, the i_'ormer reaching the output node 9-H and
the latter returning to the input node 1-H.
The steam i'luid S18 of a vapor phase comes from
the input node :'~~4 of the reboiler and reaches the node
15 via the valve V5. This fluid changes its phase here
and reaches the output node 16. The cooling water S16
of a liquid phase from the input node 11 of the
condenser reaches the node 12 via the valve V3. After
heat exchange there, the resultant fluid reaches the
output node 13.
Various synnbols in the sequence graph will now be
explained. The structural nodes are denoted by circles
including ellipses. What is included in the
structural nodes is as described before (see Fig. 9?.
The conditions for hold-up control and various decision
conditions are contained in brackets '' [ ] " . The
decision conditions may additionally include various
conditions, such as the ones for the transition from
the start-up opeeration to the steady-state operation,
2037415
- 30 -
besides the hold-up quantity and the liquid level. It
is to be under:atood that all the possible decision
conditions according to this embodiment are taken into
consideration at the stage of the preparation of Tables
1 to 3, as des<:ribed before.
Although t:he valves are normally closed in the
initial state, the operation sequence may go close
open -~ close ..., depending on the situation.
Therefore, the word or symbol "CLOSE" is added to
indicate the closure of each valve. This symbol can be
displayed with varying brightness on the screen; it may
be dark when the valve is closed, and bright when the
valve is open, for example.
The directions of flow are indicated by the arrows
in Fig. 10, and the broken lines drawn perpendicular to
the flow as if to shield the flow indicate the
activation of valves, heating or cooling, pumps, and
compressors. If every node having a flow which
directly enters this activation and the decision
conditions are marked, the activation can start. For
instance, the first activation appearing as viewed from
the top of the -flow in Fig. 10 indicates the activation
of the valve VO., and the decision condition for opening
this valve is the hold-up quantity equal to or smaller
than a set value 1-HS. If this condition is fulfilled
with the pump FO prepared, every flow directly entering
this activation is marked, allowin~ the valve VO to be
opened. Particularly, when the time-involved valve
operation, such as the opening speed, is important, the
activation may be indicated b.y the double broken line,
with a time condition affixed between the two broken
lines.
72465-22
' 20 3 74 1 5
- 31 -
The aforementioned flow includes the flow of heat
(indicated by the double real line as described before)
and the flow of information in addition to the flow of
a material such as a fluid of a mixed phase. As the
information inc_Ludes information representing that the
decision condition for hold-up control, the decision
condition concerning the process flow, etc., the flow
of information _is indicated by the broken line
connecting the decision condition given in the brackets
"[ ]" and the activation, the arrowhead showing the
direction. Although the material flow and the heat
flow are indicai~ed by the same types of lines as
described before (see Fig. 3), they may be colored
differently or expressed b,y- different lines for
distinction.
The aforementioned marking is made in a manner
such that when t;he decision conditions concerning a
node having a f~~'.ow, the hold-up control, and the
process flow are fulfilled, this node and the decision
conditions are ~_ndicated with an increased brightness
on the screen a~~ aforesaid. Instead of changing the
brightness, color may be changed. Normally, when a
valve is closed, the material flow (heat flow) through
this valve is inhibited. In other words, the mark on
the node, which is associated with the material flow
(heat flow) and is joined to the flow created by the
activation of tH~at valve, disappears. When there is a
recycle loop of a material flow on the downstream side
of the activation associated with the closed valve, the
material flow in the loop may continue in some cases.
In this case, th,e mark on the node in the loop will not
disappear.
20 374 1 5
- 32 -
The aforementioned sensor means 54 always monitors
and checks whether or not the decision condition
concerning the mold-up control and the state of the
process flow is fulfilled. More specifically, the
sensor means 54 always detects the liquid level of a
hold-up or the hold-up quantity, the temperature or
pressure at each position in the distillation column,
the composition of a distillate, etc., and sends a
detection signal_ through the I/O interface 50 to the
control unit, 40,. From this detection signal, the
control unit 40 determines whether or not the decision
conditions associated with the hold-up control and the
process flow are fulfilled.
The following is a description of how to perform
the start-up operation of the plant activation display
apparatus and how to determine the execution timing
while monitorin~; the sequence graph. As the initial
condition, a mai:erial is reserved in the material
reserving tank HO and the hold-up quantity of the other
hold-ups is zero. In addition, the preliminar,y-
operation for the start-up of the pumps and reboiler RB
have already been completed, and the switching valves
SVl and SV2 have been set to the state fll. Also, the
pumps and valves can all be remote ly operated in
response to an ON drive command signal sent to the
drive device 52 from the control unit ~0 through the
switching or ke~r operation of the input device ~2 of
the plant activation display apparatus. It is to be
understood, however, that the pumps and valves may be
also manually operated as needed by operators, or may-
be manually operated for the ON operation and
automatically disabled by the control unit ~0 at the
X037415
- 33 -
time of the OFF' operation or emergency shutdown
operation.
Further, when the activation switch of the
distillation column system is set ON, the hold-up 0-H
and the control condition [< 1-HS] are marked in the
sequence graph on the screen of the display device 44.
The nodes 14 and 11 are also marked and emphatically
indicated. An operator sets the operation switch of the
pump PO ON after confirming the mark indication in the
sequence graph. The valve V5 of the reboiler RB is
opened when the hold-up quantity of the bottom tank H5
reaches a set value. Then, when the valve V3 is
opened, the nodes 11 to 13 of the condenser CD are all
marked. These valves V3 and V5 ma,y be activated at a
preliminary open°ation stage if such an operation is
safe and entail: no problems on the apparatus.
Activating the pump PC also marks the pump node
P C . A s a r a s a 1 t; , a v a r y f 1 o w g o i n g through activation to
the valve VC ha.. been marked, satisfying all the
decision conditions for the valve V0, so that the valve
VO can be opened:. The control unit 40 sends the ON
drive signal through the drive device ~2 to the valve
VO and opens the valve. Consequently, a material fluid
flows from the reserving tank HO to the material supply
tank H1, the hold-up node is emphasized or marked on
the display screen.
The activation concerning the valve VI is held
until a predetermined amount of the material fluid is
supplied to the supply tank HI. At this time, the pump
P1 is idling and is thus marked. tvhen the hold-up
quantity of the tank H1 reaches a set value, the
decision condition is marked and every flow going through
72465-22
2037415
- 3~ -
activation has been marked. Consequently, the control
unit ~0 sends the ON drive signal through the drive
device 52 to the valve V1 and opens the valve. As a
result, a flow t.o the next activation is formed, and
every node up to each activation associated with the
valves V6, V4 and V2 is marked. Actually, because no
flow of the process fluid. S6 by the reboiler RB
substantially occurs unless the hold-up quantity of" the
bottom tank H5 reaches the vicinity of a set value, the
fluid dropping in the bottom tank H5 of the
distillation column is reserved there.
When the hold-up quantity of the bottom tank H5
reaches the set value, the decision condition is
marked. Confirming this mark, the operator activates
the pump P4, marking every- flow going to each
activation assoe:iated with the valve V2, and opening
the valve V6. When the valve V6 is opened, the
switching valve SV2 remains at the state (1) since the
distillation co7_umn system has not reached the steady
state yet. The fluid from the bottom tank H5 therefore
returns to the ~>upply tank H1 through the reflex line
521.
When the hold-up quantity of the bottom H5 reaches
the set value, the valve V6 of the reboiler RB is
opened and heating of the process fluid by steam
starts. The di~~tillate component then reaches the node
7 passing throe~;h the nodes 4, 3 and 2 in the named
order, and is cooled and condensed there by cooling
water. The resulting f.Luid flows in the reflex tank
H8.
The activai:ion associated with the valves V~ and
V2 is held unti7_ the hold-up quantity of the tank 118
2037415
- J ~ -
reaches a set value [8-HS]. When the hold-up quantity
reaches this set value, the pump P3 is activated and
the valve V4 is opened. As a result, part of the
distillate in the reflux tank H8 returns the supply
tank Hl via the switching valve SV1, which is rendered
in the state (1). The pump P2 is activated and the
valve V2 is opened, permitting part of the distillate
of the tank H8 t o return to the top. when the hold-up
quantity of the tank H8 reaches the set value and all
t h a d a c i s i o n c o n d i t i o n s indicate that the hold-up quantities
5-H
and 1-H are equal to or greater than their respective
s a t va 1 ue s , then the valve VO is closed and the apparatus is
ready to shift t;o the steady-state operation in the
circulation system.
The sensor means 5=~ always monitors the
compositions, temperature, etc. of the bottom and top
distillates. When the compositions (temperature or the
like) of the distillates reach target values and the
conditions #1 ar.:d #2 for the steady-state operation are
fulfilled (YES), the associated switching valves SV1
and SV2 are switched to the state (2). As a result,
the top and bottom distillates circulating to the hold-
up node 1-H start being retained in the respective tank
H9 and H10, and the mode shifts to the steady-state
operation.
At the initial stage of the start-up operation,
the process fluid is circulated by the circulation
operation strategy until the compositions of the bottom
and top distillates of the hold-up nodes 5-H and 8-H
reach the target values (temperature), thus shortening
the start-up operation time.
To further ;shorten the start-up operation time,
72465-22
2037415
- 36 -
the valves VI, V4 and V6 may be disabled when the
sensor means 59': detects that the compositions
(temperature, etc.) of the bottom and top distillates
have reached the set values, thus ensuring recycling of
the distillate; of the bottom and top hold-ups H5 and
H8 with the total reflux operation strategy. Also in
this case, when the compositions (temperature, etc.) of
the bottom and top distillates reach the target values,
the valves V1, V4 and V6 are reopened, and the
switching valves SVl and SV2 are set to the state (2),
thus ensuring the transition to the steady-state
operation.
Further, if products are put into the top and
bottom hold-ups H8 and H5 before the start of the
start-up operation, and if the start-up operation is
started according to the total reflux system, the
start-up operation time can be further shortened.
The start-up operation procedure can be described
in brief with r~=ference to the flowchart of Fig. 11.
Various preparation jobs and the initialization of the
control unit 40 are performed (step I). Then, it is
determined whether or not the first decision condition
Gi of the sequence graph is satisfied, and the process
holds until the condition is fulfilled (step 2). When
the decision condition Ci is fulfilled in step 2, the
activation Ai is e:~ecuted (step 3).
The e:~ecution of the activation Ai creates a flow
to the newt activation Ai+1, and the individual nodes
up to the activation Ai+1 in the sequence graph are
marked and emphasized. Then, the control variable _i is
incremented by "1" in step 4. It is then determined
whether or not i_ has reached a predetermined value Ni
72465-22
2U374 15
- 37 -
(step ~1, and the operation returns to step 2 to
determine whether or not the decision condition for the
next activation is fulfilled. 'The individual
activations are sequentially executed in this manner.
When execution of the (?~i - 1)-th activation is
completed, the c>peration advances to step 6 to trait for
the transition-t,o-steady-state conditions #1 and ~2 to
be fulfilled. 4~hen these conditions ~1 and n2 are
fulfilled, the operation for the transition to the
steady state is executed (step 7i, completing the
start-up operation.
Sequence Graph for Shutdown Operation
When the shutdown operation of the distillation
column s,vstem i~~ performed after the steady-state
operation, the aforementioned sequence graph for the
start,-up operation can be used as it is. What should
be considered For the shutdown operation are safety and
the quality of i;he fluid remaining as a hold-up. 'the
shutdocan operation is to inhibit part of the flow
conditions for i~he steady-state operation included in
the sequence graph for the start-up operation. Since
the equipment required for the start-up operation can
be used directl.~-, it may be unnecessary to provide a
particular equipment for the shutdown operation, i.e.,
the structure of the equipment for the shutdown
operation is t~hfy same as the one required for the
start-up operat.p_on.
Thus, the shutdown operation procedure should only
be sequentially executed according to the execution
timing displayed on the screen of the display device
~4, using the sequence graph used for the start-up
operation. In many cases, the shutdown operation
- 2037415
- 38 -
procedure, unlike the start-up operation procedure,
does not create the flow "from material supply to
product."
In the case of the distillation column system of
this embodiment, the valve V1 is closed and the pump P1
is activated to stop the supply of the raw material,
then the valve V5 is closed to cutoff steam which has
been supplied to the reboiler RB. At the same time,
the switching valves SV1 and SV2 are set to the state
(1) to suppress the top and bottom products and
increase the amount of reflux. When the process fluid
is sufficiently cooled down, the valve V3 for supplying
cooling water is closed, thus completing the shutdown
operation.
The operation procedure and e~cecution timing can
be indicated on~~ after another to the operator if the
subsequent activations are sequentially blinked using
the same sequence graph as used for the start-up
operation.
Seguence Graph :Por Emergency Shutdown Operation
In general., since safety has the highest priority
in the emergency shutdown operation procedure,
equipment designed for emergency shutdown is often
added to the plant for safety's sake, and the operation
sequence graph is prepared in accordance with the added
line configuration. The additional equipment may be
one for dischar~;in~' the fluid from the main plant
component or one' for supplying sealing gas for
prevention of explosion. Although the emergency
shutdown operation procedure, in contrast with the case
of the start-up operation, never creates the flow "from
material supply to product," it may be represented by
72465-22
2037415
- 39 -
the same method for the shutdown operation. Although a
line for fluid transportation should be added to the
main process line to supply an additional fluid or
eliminate the process fluid, the additional line
basically can be expressed by the same way as used for
the start-up operation, facilitating the preparation of
the sequence graph. To permit the additional equipment
to forcibly discharge the process fluid, it is
preferable to give particular consideration to the
distinction bet~.~een the node at where the main process
line is ,joined to the discharging equipment, and other
nodes by means of affixing special symbols, coloring or
the like.
The aforementioned plant activation display
apparatus can ensure fully automatic start-up and
shutdown operations if all the pumps and valves are
driven under the control of the electronic control unit
40. That is, the plant activation display apparatus of
the present invention can be used as an automatic
operation apparEitus.
Lse as Simulation Support Apparatus
The plant activation display apparatus according
to the above-de=scribed embodiment of the present
invent.i.on, as applied to a distillation column system,
is effective not; only as an apparatus to inform an
operator of the start-up, shutdown, or emergency-
shutdown operation procedure and execution timing of a
real model, but also as a design support tool to design
a plant in the 7.ight of the operation procedure and the
execution ti.min~;. This plant activation display
apparatus is also effective as a simulation support
apparatus for training operators to how to operate the
2037415
- 40 -
real mode.
To use the plant activation display apparatus as a
simulation apparatus, the sensor means 54 of the plant
activation display apparatus shown in Fig. 2 should
only be replaced with a simulation signal generator,
which generates pseudo signals indicative of status
quantities, such as the flow rate, pressure,
temperature, composition, etc. of the process fluid at
various points in the distillation column, the reboiler
RB and the condenser CD, or in the hold-ups, the
generator being connected to the control unit ~0
through the I/O interface 50. When the pumps and
valves are oper<~.ted, changes in the status quantities
of the process fluid caused by the operation are
estimated and supplied to the control unit 44 in
succession.
Also when the plant activation display- apparatus
is used as the simulation apparatus, as in the
aforesaid case where it is applied to the real model,
the evaluation of the activation performance, such as
the operating ei.-'ficiency of the designed plant, and the
study or learning of the plant operation can be
facilitated by displaying the sequence graphs on the
screen of the display device 44, and operating the
apparatus accorclin.~ to the instructions of the
emphasized activations.
Second Embodiment
The sequence graph displayed on the screen of the
plant activation display apparatus of the present
invention can be also applied to a combined unit which
is formed of a plurality of units. If the basic units
are of high modularity, in particular, the graph can be
72465-22
- 2~ 374 1 5
- 41 -
applied more easily. Since the structure of the plant
corresponds to the procedure of operation, changed
portions of the operation procedure can be cleared up
correspondingly by detecting modified structure
portions necess.&ry for the connection of two units.
The following is a description of a distillation column
system with a heat pump according to a second
embodiment, as an e:cample of the aforesaid arrangement.
In Fig. 12, like reference numerals used to denote the
lines (fluid paasages) of the first embodiment refer to
corresponding fluids.
Line Configuration of Heat Pump
The distillation column system of the second
embodiment is a combined system obtained by connecting
a heat pump HP, which uses water as a working fluid
(heat transfer medium), to the distillation column
system of the first embodiment. Fig. 12 shows a line
configuration~o:E a heat pump unit applied to this
distillation co:Lumn system.
The heat pump HP includes two heat e~cchangers
(side cooler and side heater) SC and SH which are
falling film-type heat e:cchangers. The side cooler SC
removes condensation heat from a process fluid, and
gives the heat i:o the water for use as a working fluid,
thereby vaporizing the water. The side heater SH gives
condensation heat from the working fluid to the process
fluid, thereby evaporating part of the process fluid.
Hold-ups H5~ and H54 for collecting the cast working
fluid are attached to the bottom portions of the side
cooler SC and the side heater SH, respectively. The
heat pump HP is provided with compressors C1 and C2 for
boosting the temperature of the vaporized working fluid
72465-22
- 2037415
- 42 -
and a decompre;>sor V51, besides the heat exchangers.
To increa=~e the wet area of their heat transfer
surfaces, the ~;ide heater SH and the side cooler SC are
provided with a~ process fluid circulation line S44 and
working fluid circulation lines S52 and S53,
respectively. Each combination of circulation pump and
valve P41, V41, and P50, V52, and V53 is arranged in
the individual circulation line.
A line for introducing the working fluid (water)
is required as preliminary equipment for the operation
of the heat pump HP. For example, a fluid injection
pipe S51 is attached to the side cooler SC. The
working fluid is heated to be evaporated by means of
the process fluid in the side cooler SC, and is then
delivered to th~= side heater SH through the compressors
C1 and C2. In the side heater SH, the working fluid is
condensed and collected in the hold-up H54. A pipe S60
for reducing starting load is required for smooth
activation of the compressors C1 and C2. The pipe S60
is provided with a valve V54 which closes the pipe S60
during the steady-state operation. Drain lines S65,
S66 and S67 are provided to be used to remove the
working fluid condensed around the compressors C1 and
C2. Further provided are exhaust lines S61, S62 and
S63 for removing air introduced into the heat pump HP
and a working fluid sprayer (S64, V53? for prevention
of superheating.
Modification of Line Configurations of Distillation
Column & Heat Pump
The heat pump HP is disposed in an intermediate
stage between the condenser CD and distillation column
D of the first embodiment so that the two heat
72465-22
20 37 ~+ 1 5
- ~3 -
exchangers SC and SH are individually in contact with
the column-side process fluid across their respective
heat transfer surfaces. 'Therefore, the distillation
column D and the heat pump HP require a structural
mod:ificati.on for the connection between them. 'table 4
collectively shows the details of ,junctions between the
distil_lat;ion column D and the heat pump HP.
Table 4
Distillation Column Side HP side (phase of fluid)
(phase of fluid)
1) Column top output (Gi ~ SC input (G)
Reflux tank input (L) E- SC output (L)
Condenser input (G) ~ SC output (G)
2) Intermediate stage of
recovery section
Output (L) ~ SH input (L)
Input (L) E SH output (L)
Input (G) E SH output (G)
In consideration of the relationships between the
respective height positions of the two opposite ends of
each connecting line, it is necessary only that a pump
P42 and a valve V43 be arranged in a line S~7 on the
output side of the side cooler SC, a pump P40 and a
valve V40 be arranged in a line S41 on the process-
flu:id input side of the side heater SH, and pipelines
for associated utilities be added, fol.~ use as necessary
transportation apparatuses.
Line Configuration for Start-Up Operation
The following is a description of a necessary line
2374 15
- 44 -
configuration for the start-up operation of the
distillation column system with the heat pump. First,
the circulation system described in connection with the
first embodiment is used, and in this case, piping is
required to return the products from t;he top and bottom
of the column to a material supply tank Hl.
A hold-up 33-H is provided between the top of the
column and the node 7 in addition to the hold-up of
the distillation column system according to the first
embodiment. The hold-up 33-H is used to receive the
process fluid flowing down from the top side of the
distillation column, and deliver it to the side of the
heat pump HP.
Based on this situation, Fig. 13 shows a
structural representation of a distil7_ation column
system modified for the connection of the heat pump HP,
and Fig. 14 shows a structural representation of the
heat pump HP. In these drawings, like reference
numerals used to denote the components of the
distillation column system according to the first
embodiment refer to like or corresponding components.
Preparation of ~~eguence Graph
(Representation of Fluid Connections and Conditions for
Flow Control in Distillation Columnl
Table 5 shows fluid connections and conditions for
and flow control during the start-up operation on the
distillation column side, similar to the ones shown in
Table l, arranged by the same method as the one
described in connection with the first embodiment.
2037415
- 45 -
m ~~ c
SO ( 0-H - 1-H . L . FO . VO )
.
S1 ( 1-H -~3 . L . . P1 . V1 )
S ( 2 - 3 . L . . )
2 .
S3 ( 3 ->30 . L . . )
.
S3' ( 32 -~~ . L . . )
.
S4 i 4 - 5-H . L . . )
.
S5 ( 5-H -~6 . L . . )
.
S ( 6 - 4 . L&V . . )
6 .
S7' ( 4 -~32 . V . . )
.
S7" ( 32 - 31 . V . . )
.
S7"'( 31 -~30 . V . . )
.
S7 ( 30 - 3 . V . . )
.
S ( 3 -~2 . V . . )
8 .
S9 ( 2 -~33-H . V . . )
.
S9' ( 33-H-~i . V . . )
.
S10 (7 -~8-H . L . . )
.
S ( 8-H -~2 . L . P2 . V2 )
11 .
S12 (8-H -~18 . L . P3 . V4 )
.
S13 (18 -~9-H . L . . SV1(21)
.
S14 (5-H -~17 . L . P4 . V6 )
.
S15 (17 -j10-H . L . . SV2(2))
.
S16 (11 -~12 . L . . V3 )
.
S17 (12 -~13 . L . +E1 . . )
S18 (14 -~15 . V . . V5 )
.
S19 (15 -~16 . L . -E2 . . )
S20 (18 -~1-H . L . P4 . SV1(1))
.
S21 (17 -~1-H . L . . . SV2(1))
Table 5 differs from Table 1 only in that fluids
S?', S'7" , Si"', S3', S9, and S9' are added or
modified.
2037~1~
- ~6 -
(Transition to Steady-State Operation)
Switching from the start-up operation to the
steady-state operation on the distillation column side
is achieved i.n the following manner.
When all the hold-ups fulfill their set values
during the start-up operation, the valve V1 is closed
to stop the material supply, and at the same time, the
valves V4 and V6 are closed so that the transition-to-
steady-state conditions #1 and #2 are fulfilled in
accordance with the full reflux system. When the
conditions #1 and #2 are fulfilled, the operation shown
in Table 6 is executed.
m.,,-., ~ c
S13 (18 -~ ~a-H . L . . . SVl(2))
S15 (17 -~ l'.0-H . L . . . SV2(2)?
More specifically, the lines S13 and S15 are
opened, while the lines S20 and S21 are closed. The
transition-to-steady-state conditions #1 and #2 may
alternatively be set so that excesses of the column
bottom and top temperatures over their respective set
values (T1i > Tlis, T18 > T18S) can be discriminated
thereby.
(Representation of Fluid Connections and Conditions for
Flow Control in Heat Pump)
The following is a description of preliminary
operations for the operation of the heat pump HP.
Preliminary Operation 1 (in.jection of working
fluid):
In this operation, a valve V50 of a line S51 i_s
opened, and the working fluid is injected into a hold-
2037415
- 4r -
up H55. When the working fluid is collected to a
required amount, the valve V50 is closed (see Fig.
16A).
Preliminary Operation 2 (heat exchanger
circulation):
In this operation, the pump P50 is actuated, and
the valve V52 is opened to allow the working fluid in
the hold-up H55 of the side cooler SC to circulate.
Also, the pump P41 is actuated, and the valve V41 is
opened t.o allow the working fluid in the hold-up H54 of
the side heater SH to circulate. As t;he working fluid
ci.rcu7_ates in this manner, its wettability on the heat
transfer surfaces increases, so that the heat transfer
efficiency of the system is improved (se<> Fig. 16B).
Preliminary Operation 3 (construction of
compressor circulation line):
This operation should be performed before the
activation of the compressors. The valve V54 is
opened, the discharge side of the compressor C2 is
communicated to the intake-side of the compressor C1,
and the load for starting the compressors is reduced
(see Fig. 16C).
Preliminary Operation 4 (construction of drain
Line):
This operation should be also performed before the
activation of the compressors. A valve V56 on the
discharge side of the first compressor C1 and a valve
V55 on the discharge side of the second compressor C2
are opened to discharge the working fluid (water) from
the compressors into the hold-up H55 (see Fig. 6D)
Preliminary Operation 5 (ventilation):
This operation should be also performed before the
2037415
-4g-
activation of the compressors. Valves V57 and 1'58 a:re
opened, and air in the heat pump HP is discharged by
means of an ejector EJ (see Fig. 16E).
Preliminary Operation 6 (construction of
superheating protection line):
This operation is executed when t:he outlet
temperature of the compressor C2 exceeds a specified
temperature. A valve V53 is opened, and the working
fluid (L) in the hold-up H55 is sprayed into the line
between the compressors C1 and C2 through the aforesaid
circulation line of the side cooler SC',. Thus, the
working fluid is prevented from being superheated (see
Fig. 16F).
These preliminary operation sequence graphs, as
well as the one shown in Fig. 16 (mentioned later), can
be displayed on the screen of the display device 44,
and if necessary, these preliminary operations can be
introduced as decision conditions for the activation
into the sequence graphs. Generally, it is advisable
to complete many of these preliminary operations before
the first activation associated with the heat pump H-P
appears, as shown in the sequence graph of Fig. 16.
Table i shows fluid connections and conditions for
flow control during the start-up operation in the heat
pump and auxiliary lines, arranged in the same manner
as in Table 1.
Table ~ (Process fluid in heat pump HP and flow
conditions in auxiliary lines)
S40 ( 30 -~ 40-H . L . . . )
S41 (40-H =~ 41 . L . . P40 . V40)
S42 ( 41 -> 42-H . L . . . )
r 2037415
- 49 -
S43 (42-H -~43 . L . . P41. )
S44 ( 43 -~41 . L . . . V41
)
S45 f 43 -~32 . V . . . V42
)
S46 f42-H -~43 . L . +E50 . )
.
Table Workin~; fluid inheat pump HP and flow
i (
conditions auxiliary lines)
in
S50 (54-H -~55-H L . -E50 . v51)
. .
S51 f58 -~55-H L . . . V50)
.
S52 (55-H -~56 . L . . P50. V52)
S53 (56 -~55-H L . . . )
.
S54 (55-H -~5i . V . +E51 . )
.
S55 ( 57 -~50 . V . . . )
S56 (50 -~51 . V . . Cl . )
S5 i ( 51 -~52 . V . . . )
S58 (52 -~53 . V . . C2 . )
S59 (53 -~54-H V . . . )
.
S60 (53 -~57 . V . . . V54)
S61 ( 53 -~60 . V . . . V57
)
S62 (59 -j60 . V . . . V58)
S63 ( 60 -~61 . V . . . )
S65 (50 -~63 . L . . . V56)
S66 ( 52 -~.63 . L . . . V55
)
S67 (63 -~55-H . . . . )
L
(Conditions for Transition to Steady-State Operation of
Heat Pump)
The operation mode of the heat pump HP is switched
from the start-up operation to the steady-state
operation as th<~ valve V54 of the circulation line S60
is gradually closed when the working fluid temperatures
in the hold-ups H54 and H55 exceed set values T54S and
2437415
_ ~0 _
T555, respectively (T54 > T54S, T55 > TSbs).
When supplied with the fluid connections and
conditions for flow control shown in Tables 4 to 7, the
electronic control unit 40 creates sequence graphs for
the distillation column and the heat pump in the same
manner as aforesaid. Figs. 15 and 16 show the sequence
graphs for the distillation column D and the heat pump
HP, respectively.
Fig. 17 shows a line configuration of the combined
system obtained by superposing two junctions of the
heat exchangers shown in Figs. 13 and 14. Fig. 18 is a
sequence graph for this combined system, which can be
represented by superposing the .junctions, as in the
case of the sup.=rposition of the line configurations.
This sequence g:caph, which incorporates the sequence
graphs of Figs. 16A to I6F for the preliminary
operation of the heat pump HP, represents the procedure
and execution timing for the start-up operation of the
whole system.
Thus, the sequence graphs of the plant activation
display apparatus according to the present invention
correspond to the line configurations in the operation
procedure and execution timing. Accordingly, modifying
the line configurations and combining the units can be
effected very easily.
In the start-up operation of the combined system,
as described before with reference to Fig. 11, it is
necessary only that activations be successively
executed from the inlet node side, in the same manner
of the first embodiment. The start-up operation of the
heat pump HP is finished by closing the circulation
line 560. In this case, heat exchange between the
72465-22
-~1_ X037415
working fluid ar,~d the process fluid starts before the
line S60 is closed. Thus, the target function or
compressing effect of the heat pump unit can be
fulfilled by cutting off the circulation line S60 ,Then
the working fluid is preheated to a certain
temperature. The sequence graph of Fig. 18 represents
the steps of operation procedure before the transit;ion
to the steady-state operation of the heat pump HP and
the timings therefor, as well as the order of the
operation timings on the heat pump side and on the
distillation column side. In the sequence graphs of
Figs. 15, 16, 16A to 16F, and 18, the display of the
specific decision conditions for the execution of
activation .is omitted. Actually, however, all the
necessary decision conditions are to be described i.n
the brackets ( J.
In the sequence graphs of the plant activation
apparatus according to the present invention, the flow
directions correspond to the time axis. The speed of
the process fluid flowing between the nodes and the
time elapsed before the hold-up quantities attain the
set values can be estimated from simple operational
expressions or empirical values. Shortening time
elapsed for the start-up operation can be facilitated
by arranging the steps of procedure and execution
timing for the start-up operation in a time series
based on the sequence graphs. If the operation times
for the valves and the pumps in the sequence graphs are
fetched and rearranged on the time series basis, for
example, time elapsed for individual steps of the
start-up operation can be more clearly indicated.
Fig. 19 shows the operation times of the valves
- ~ 2037415
- 52 -
after the starting time for the start-up operation of a
positive pilot plant based on the sequence graph of
Fig. I8, that is, the times for the start of individual
activations and transitions to the steady-state
operation, arranged on the time series basis.
The configuration and operating conditions of this
positive pilot plant are as follows:
The distillation column D is a packed column
(column section? with a diameter of 200 mm and height
of 5,000 mm, and a 1-inch mini-cascade ring is used as
a packing, whose packing height is 4,000 mm. The
process fluid to be separated in the column is a
mixture of ethanol and water. As a result of an
experiment, it is ascertained that the theoretical
number of stager corresponding to a plate-column of the
target packed column, including the reboiler RB, is 11.
The material is supplied to a seventh stage
counted from the' column top as a first stage. A side-
cut plate for fe>eding the process fluid to the side
heater SH of the> heat pump HP corresponds to the eighth
plate of the di~~tillation column D. The reboiler RB of
the column D ha,. a heat transfer area of 2.0 m2, and
steam of 2.0 kgfG/cmz is used as a heating utility. In
the reboiler RB, heat exchanges of about 40 kW and 16
kW are made during the start-up operation and steady-
state operation, respectively.
The condenser CD of the distillation column D,
whose heat transfer area is 4 m2, uses water as a
cooling utility. Table 8 shows the principal
specifications of the distillation column of the pilot
plant.
72465-22
2034 ~5
- 53 -
T .. 1. , _ U
Type : Packed co7_umn
Diameter: 200 mm
Height of packed zone: 4,000 mm
Theoretical number of plates: 11
Reboiler hold-up: 70 liter
Reflux tank hold-up: 40 Liter
The heat pump HP, which is of an indirect
compression t,ype~, uses water as a working fluid. The
compressors C1 and C2 are rotary compressors, which are
used in series with each other, enjoying a great
difference in compression temperature. Further, each
compressor is provided with an inverter for load
adjustment.
The two heat exchangers, that is, the side heater
SH and the side cooler SC, which constitute a section
through which hE~at is delivered to or from the
distillation column D, are of a falling-film type.
Thus, these heat, exchangers can satisfactorily exchange
heat energy despite a relatively small temperature
difference from the process fluid. Table 9 shows the
principal specifications of the heat pump of the pilot
plant.
Table 9
Type: Indirect compression type
Working fluid: Water
Compressor type: 2-stage rotary type compressors
Heat exchanger type: falling film type
Heat transfer area of SH: 3.43 m2
Heat transfer area of SC: 5.14 m2
2037415
SH:
Processing fluid hold-up: 20 liter
Working fluid: 7 liter
SC:
Processing fluid hold-up: ? liter
Working fluid: 20 liter
This pilot plant was brought to a stand-by state
for the transition to the steady-state operation of the
distillation co:Lumn when the heat pump HP was switched
to the steady-sl=ate operation, that is, in 246 minutes
after the start of the start-up operation. The whole
system entered t:he steady-state operation in 376
minutes after the start of the start-up operation.
Thus, by operating the plant in accordance with
the sequence graphs displayed by means of the plant
activation display apparatus according to the present
invention, the plant was able to be activated stably
and securely to a target state.
In the first and second embodiment described
above, the start-up operation procedure is composed of
the ideas of "flow control" and "hold-up control," as
the basic concepts, plus "operation mode modification
conditions" and "transition-to-steady-state conditions"
as required. In many cases, it is preferable that the
execution timing is adjusted by
using variables, such as the temperature,
pressure, and composition of the process fluid in a
suitable position, instead of depending solely on the
hold-up state. Further, an operating condition for
avoiding risky operating conditions may- be additionally
used. In any cage, the plant operation can be made
72465-22
20374 15
flexible by adding these conditions to the decision
conditions for the activation.
According t.o the second embodiment, it was
verified that the use of the pilot plant enables a
securer plant ox>eration. Since the completion of the
start-up operation took 376 minutes, however, there is
yet room for improvement in this arrangement.
Thereupon, the operation procedure was improved. Table
shows time elapsed for accumulating desired hold-up
quantities after the valve operation times shown in
Fig. 19.
m~t,n ._ i n
Hl Material supply tank: 5 min.
.
H5 Bottom tank: 20 min.
.
H8 Reflux tanlt: 70 min.
.
H65: Side cooler hold-up: 2 min.
H54: Side heater hold-up: 15 min.
Heat pump preheating time: 80 mi_n.
Stand-by
time
for
transition
to 130 min.
steady-state
operation:
The time elapsed for fluid supply to the bottom
tank H7 at the column bottom can be shortened by
preliminarily supplying the tank Ho caith the bottom
product before the start of the start-up operation. In
this case, it is necessary to additionally use a line
for supplying the bottom tank H5 with the bottom
product.
The time elasped for preheating the heat pump HP
can be shortened if the pump HP is preheated while the
working fluid is being introduced into the side cooler
2037415
- 56 -
SC' as a preliminary operation for the pump. In this
case, the side c:ool.er SC should be additionally
provided with a steam supply line.
The time elasped for fluid supply to the reflux
tank H8 at the column top can be shortened by
preliminarily s~:~pplying the tank H8 with the top
product before the start of the start-up operation.
Also in this ca~~e, it is necessary to additionally use
a line for supplying the reflux tank H8 with the top
product.
When the aforementioned positive pilot plant was
started up after these improvements in lane
configuration and operation procedure, the start-up
operation time required before the start of the steady-
state operation was able to be reduced to 168 minutes.
Fig. 20 clearly shows the operation timing for
each valve. If' the valves are operatE~d not by remote
control but by operators at the ,job site, the
stationing of the operators, valve arrangement, etc.
can be easily achieved in consideration of the
efficiency of tree valve operations at the site. More
specifically, the timing chart of Fig. 20 and the 7_ine
configuration are collated with each other for the
allotment of the individual valve operations to the
operators, or for optimum location of the valves in the
case of a one-man operation. These operations can be
performed with ease because the plant design definitely
corresponds to the plant operation and the timing
therefor, based on the sequence graphs of the plant
activation display apparatus of the present invention.
(Sequence Graph for Shutdo~.rn Operation)
The shutdown operation procedure for the
20 374 1 5
- 5i -
distillation column system with the heat pump HP can be
also decided on the basis of the sequence graph of Fig.
18.
In performing the shutdown operation, the material-
supply and the =_~upply of steam to the reboiler RB are
first stopped. As the steam supply is stopped in this
manner, vapor ceases to be generated from the reboiler
RB. If the heat; pump HP is operating, however, the
process fluid c~~n also circulate, so that the pump HP
is finally stopped.
The shutdo~~rn operation procedure and timing
(operation sequence? can be set in the same manner as
in the case of the first embodiment. Alternatively,
however, these factors may be represented by gradually
lowering the brightness of the activation displayed on
the screen of tl-,e display device 44, using the sequence
graph for the start-up operation.
(Sequence Graph for Emergency Shutdown Operation)
Also in the second embodiment, equipment designed
for emergency shutdown, such as a seal gas supply
system, emergency removal line for the process fluid,
etc., may be added as required to the plant for
safety's sake, in the manner described in connection
with the first embodiment. It is necessary only that
an operation sequence be set in consideration of the
added equipment, as in the first embodiment. Also in
this case, the ~~etivation can be displayed on the
screen of the display device 44 in the same manner as
in the shutdown operation. If the emergenc,v shutdown
equipment is adc'.ed, its operation only requires
emergency shutdown conditions and its operation
sequence to the activation decision conditions.
20374 15
Otherwise, the operation is performed in the same
manner as the shutdown operation.
It is to be understood that the plant activation
display apparatus according to the present invention is
not limited to the distillation column systems of the
first and second embodiments described herein, and that
the invention ma.,y be also applied to various other
chemical plants. There are several methods for
representing sequence graphs for other plant components
as follows.
Fig. 21 shows an evaporator, in which a process
fluid is heated to be evaporated by means of a heat
exchanger' H.EX1 which uses steam as a utility. The
evaporated process fluid flows from the evaporator to a
line S80, while a liquid collected in the evaporator
flows out into a, line 581. Fig. 22 shows its sequence
graph for the evaporator.
Fig. 23 shows a configuration of a self-heat
exchanging reactor, in which a reactive mixed process
fluid reacts and. generates reaction heat. The reactor
R comprises two heat exchangers HEX2 and HEX3. The
heat exchanger H:EX2 uses steam as a heat transfer
medium to preheat the process fluid which reacts in the
reactor R. In the heat exchanger HEX3, the process
fluid heated to high temperature by the reaction heat
generated in the reactor R heats the process fluid
itself flowing into the reactor R. Fig. 2~ shows a
sequence graph for the self-heat exchanging reactor.
The following is an illustration of the wa,y of
representing fluid connections and conditions for flow
control obtained when phase changes are caused at nodes
by crystallization, flash, liquefaction under pressure,
20 374 1 5
- 59 -
or sedimentation, separation.
Crystallization
Table 11
S90 (N1 ~ P~t2 . L . . . )
S91 ( N2 -~~ PJ3 . L+S . -E . . )
Table 11 ir..dicates that a process fluid S90 in the
liquid phase L is cooled to be partial_Iy crystallized
at a node N2, thus forming a process fluid S91
containing portions in the solid phase S and the liquid
phase L.
Flash
Table 12
S92 ( N5 ~ PJ6 . L . . . )
S93 ( N6 -> t~'7 . L . -P . . )
S94 (N6 ~ N8 . V . -P . . )
Table 12 indicates that a process fluid S92 in the
liquid phase L is decompressed to be partially
vaporized at a node N6, thus forming a process fluid
S9~ in the gas ~~hase V and a process fluid S93 in the
Liquid phase L.
Liquefaction under Pressure
Table 13
S96 (N10 -~ N11 . V . . . y
S97 (N11 -~ N12 . L . +P . . )
Table 13 indicates that a process f_Luid S96 in the
gas phase V is pressurized to be condensed at a node
2~37415
N11, thus forming a process fluid S9i in the liquid
phase L.
Sedimentation Separation
Table 1~
S88 (N14 ~ N15 . L+S . . . )
S 8 9 ( N 15 -~ '~i 16 . L . . . )
S90 (N15 -~ N17 . L+S . . . )
Table 14 indicates that a fluid S88 enters a node
N15 in the form of a slurry, whereupon it is divided
into two phases, the liquid phase L and the slurry
phase (L + S). These two divisions emerge from the
node N15 in the form of a fluid S89 and a fluid 590.
Supply of Proce~,s Fluids ~ & B
a chemical plant may be operated in different wars
without changing; its configuration. When process
fluids A and B a.re supplied to a tank 100, as shown in
Fig. 25, the following different methods may have to be
used depending an the processes to be executed.
According to the first supply method, the process
fluid A is first supplied to the tank 100. When the
resulting hold-u.p quantity attains a set value [> 100-
HS], the process fluid B is then supplied to the tank
100. Fig. 26 shows a sequence graph for this case, in
which a hold-up quantity condition [> 100-HS] is added
to an activation condition for a valve V102.
.According to a second supply method, the process
fluids A and B are simultaneously supplied to the tank
100. Fig. 2r shows a sequence graph for this ease, in
which the condition that both of preliminary operations
for the fluids A and B are finished is added to
2037415
- 61 -
activation conditions for valves VI01 and V102. Thus,
the moment the preliminary operations for the process
fluids A and B 2.re both finished, the valves 101 and
VI02 are simultaneously opened. The sequence graph of
Fig. 2i can be rewritten into the one shown in Fig. 2$
according to a conventional method of sequence graph
representation. This sequence graph also indicates
that the valves V101 and V102 are opened in synchronism
with each other.
Although the sequence graphs are displayed on the
screen of the display device ~4 in the embodiments
described above, they may be printed out by means of
the printer ~6. Alternatively, as shown in Fig. 2, the
activation display apparatus may be distributively
connected to a distributed control system (DCS1 49 for
each plant so that the aforementioned sequence graphs
are delivered as required from the central electronic
control unit 40 to the display apparatus in the plant,
thus constituting part of the control system.
