Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS AND APPARATUS FOR TESTING
FL~IDS FOR FO~LING AND ANTIFOULANT
PROTOCOL
The present invention relates to a process and apparatus
for testing fluids, and more particularly, to a process and
apparatus for the in~situ testing and simultaneously moni-
toring and recording of aqueous and non-aqueous fluid systems
for fouling tendencies, and parameters, such as conductivity,
pH, turbidity, corrosion and the like, as well as to the
development of an antifoulant protocol.
The chemical water treatment industry has historically
been involved with reducing or inhibiting the inherent scale
¦ forming or fouling tendencies of natural waters associated
with large industrial cooling water systems. Many of the
foulant components found in water systems originate with the
incoming supply, but some contaminants enter the system from
the local environment or from process contamination.
Fouling is an extremely complex phenomenon. From a
fundamental point of view, it may be characterized as a
combined momentum, heat and mass transfer problem. In many
instances, chemical reaction kinetics is involved, as well as
solubility characteristics of salts in water and corrosion
technology. It has been stated that if the fouling tendency
of a cooling water could be accurately predicted before a
plant is designed and built, significant capital savings
might be realized through more accurate heat exchanger
specifications.
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~sually, it is a normal practice to increase heat
exchanger surface area to overcome losses in performance
caused by fouling deposits with such additional surface area
often accounting for more than half of the actual surface
area of the heat exchanger. When such design practice is
employed with titanium, staninless steel and like expensive
materials of construction, it can be appreciated that capital
expenditures might be significantly reduced if data could be
developed to anticipate and provide for an anti-foulant
protocol.
Fouling of a heat transfer surface is defined as the
deposition on a surface of any material which increases
the resistance to heat transfer. The fouling tendency of a
fluid in contact with a heat transfer surface is a function
of many variables including the components of the fluid,
which in the case of water include, inter alia, crystals,
silt, corrosion products, biological growths, process con-
taminates, etc. Generally, deposits are comprised of a
combination of several of these materials in relationship to,
inter alia, the geometry of the heat transfer surface,
materials of construction, temperature, etc. and thus,
chemical inhibitors to solve the problem of a particular
deposit involves a variety of different chemicals introduced
at varying concentration and at varying times.
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Industry has been relegated to the use of laboratory
simulators or time lapse evaluations of process heat ex-
changers and test heat exchangers with requirement that such
equipment is taken off line, shutdown, opened and inspected
to evaluate fouling problems and antifoulant protocols. In
the case of process heat exchangers, such inspection usually
results in significant plant do~m time and lost production.
Evaluation covers the entire period of process operation and
shows accumulated results, which include system upsets,
process leaks, the loss of chemical feed or human errors.
While the sampling and laboratory testing of fluids permits
evaluation of the fluids, the results of laboratory testing
are tedious and do not provide results of simultaneous
evaluation.
The objects of the present inventions are achieved by
a novel mobile apparatus and process therefor including a
heat transfer test assembly and related conduit and valve
assemblies for connection in fluid flow communication to a
heat transfer apparatus for in-situ testing of the fluid
passing therethrough and including monitoring of recording
apparatus. The heat transfer test assembly includes a heating
member for controlled heat input and thermocouples to measure
the wall temperature of the heating member to permit fouling
determinations at varying flow rates with simultaneous
monitoring and recording thereof together with data, such as
corrosion, pH, conductivity, and the like. In one aspect of
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the present invention, there is generated foulant data
permitting substantially simultaneous implementation of, and
evaluation of an antifoulant protocol on the fluid passing
therethrough and including monitoring and recording apparatus
together with a source of antifoulants for controlled in-
troduction into the fluid to evaluate effecaciousness of the
antifoulant protocol.
Further objects and advantages of the present invention
will become apparent upon consideration of the detailed
disclosure thereof, especially when taken with the accom-
panying drawing wherein like numerals designate like parts
throughout and wherein:
Figure 1 is a cross-sectional elevational view of the
heat transfer test assembly;
Figure 2 is a piping diagram of the novel process
and apparatus of the present invention including the heat
transfer test assembly; and
Figure 3 is a schematic diagram of the process and
apparatus for continuously testing, monitoring and recording
data relative to the heat transfer test assembly as well as
for monitoring and recording data as to corrosion, con-
ductivity, pH, and the like.
Referring now to Figure 1, there is illustrated a
heat transfer test assembly, generally indicated as 10, and
comprised of a tube member 12 and an inner cylindrically-
shaped heating member, generally indicated as 14, formed of a
tube member 16 in which a high resistant heating element 18
is embedded within an insulating matrix 20, such as magnesium
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oxide. The heating mem~er 14 is coaxially-positioned within
the tube member 12 to form an annular fluid flow passageway
22. Symmetrically-disposed in the tube member 16 of the
heating member 14 is a plurality of surface thermocouples 26
generally disposed at positions corresponding to the hour
hand at 3, 6, 9 and 12 o'clock for sensing wall temperature.
The tubular member 12 is formed of any suitable trans-
parent material, such as glass, to permit visual observation
of flow as well as scale formation 24 about the surface of
the heating member 14. The tube member 16 of the heating
member 14 is formed of a metallic material, such as stainless
steel, copper, titanium, mild steel, admiralty metal or the
like, dependent on the fluid to be initially tested by
passage through the test member lO or in the case of existing
units of a like metallic material as that in the unit.
Normally, stainless steel is used for normal cooling water
application whereas admiralty metal is employed for sea water
and brackish water applications.
As more fully hereinafter described, the fouling
tendency of a fluid may be evaluated by the passage of a
fluid through the heat transfer test assembly 10 under
controlled rates of flow and heat output from the heating
element 18 through measurement of temperature drops ~ -i )
between the tube member 16 and the fluid to permit a deter-
mination of the resistance (R) of the scale formation 24
therefor.
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The heat transfer test ~ssembly 10 is positioned
within a piping assembly, generally indicated as 30,referring
now to Figure 2, including an inlet conduit 31 and an anti-
foulant conduit 32 in fluid communication with a container
33 including an antifoulant via the discharge side of a pump
34. The piping assembly 30 includes flow meters 35 and 36, a
rotameter 37 and a flow rate control valve 38. The inlet
conduit 31 is in parallel flow communication with the flow
meters 35 and 36 by conduits 42 and 44 under the control of
valves 46 and 48, respectively. Conduits 42 and 44 are in
fluid flow communication by conduit 50 under the control of
an isolation valve 52 with one end of the rotameter 37,with
the other end of the rotameter 37 being in fluid flow com-
: munication by conduits 54 and 56 with the inlet end of the
heat transfer test assembly 10. Conduit 44 is in fluid flow
communication by conduit 58 under the control of by-pass
valve 60 with conduit 56.
The outlet of the heat transfer test assembly 10 is in
fluid flow communicat~on by conduit 62 and conduit 64 under
the control of an isolation valve 66 via the flow rate
control valve 38 to outlet 68 by conduit 70. Conduit 62 is
in fluid flow commnication with conduit 70 by conduit 72
under the control of a by-pass valve 74. The conduit 70 is
provided with flow cell 76 including a plurality of probes
(not shown) to measure other parameters of the fluid, as more
fully hereinafter discussed.
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The flow meters 35 and 36 are preferably of the venturi
type with each flow meter having a different design rating
of flow rates and are electrically connected via transducers
78 to a differential pressure cell 80 and by lead lines
82 and 84, respectively, to sense the pressure drop across
the flow meters 35 and 36. The piping assembly 30 is pro-
vided with a thermocouple 86 to monitor the bulk inlet water
temperature and with a high temperature cutoff 88.
In order to provide sufficient range of flow velocities,
a plurality of heat transfer test assemblies 10 of differing
diamters may be used for interchangeable insertion into the
piping assembly 30. The flow rate control valve 38 is
preferably of the constant flow type with an internal
pressure equalizer (not shown) to insure flow at the pre-
select value. The rotameter 37 permits visual monitoring and
may be electronically monitored by a differential pressure
cell (not shown).
The piping assembly 30 is integrated or coupled with a
monitoring and recording assembly, generally indicated as 90,
including components of the piping assembly 30, referring now
to Figure 3, disposed on a support structure (not shown) for
positioning within a mobile container (not shown), such as a
trailer, van or the like, for facile movement from location
to location to test fluid passing through a unit, such as a
heat exchanger, reactor or the like, as more fully herein-
after discussed. The container is provided with environmen-
tal capabilities to provide pre-select conditions of tempera-
ture, humidity and the like to insure proper functioning of
the various units of the monitoring and recording assembly.
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The monitoring and recording assembly 90 includes a
power inlet assembly, generally indicated as 92, an analog to
digital coverter 94 and a computer print-out assembly 96.
The power inlet assembly 92 is comprised of a 110 Vac. inlet
connector 98 including transformer 100, a 220 Vac. inlet
connector 102 and a 440 Vac. inlet connector 104 including a
transformer 106 connected by leads 108 to a variable rheostat
110. Generally, 110 Vac. is utilized for the environmental
', capabilities with one of the other power sources utilized in
the monitoring and recording capability. The variable
rheostat 110 is connected by leads 112 to a wattmeter trans-
ducer 114 providing a source of power by leads 116 for the
heating element 18 of the tube member 16.
The wattmeter transducer 114 generates a signal trans-
mitted via lead 118 to the analog-digital converter 94
representative of the power level of the heating element 18
of the tube member 16. The thermocouples 26 and 86 generate
signals representative of a temperature transmitted via leads
120 to a reference junction 122 for transmission via leads
124 to the analog-digital converter 94.
The transducers 78 receives signals generated by the
flow meters 35 and 36 and in turn transmitts a signal via
leads 126 and/or lead 128 to differential pressure cell 80
which generates an analog signal representative of flow rate
transmitted by lead 130 to the analog-digital converter 94.
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The flow cell 76 including a plurality of probes are
connected by leads 132, 134 and 136 to a conductivity monitor
138, a pH monitor 140 and a corrosion monitor 142, respec-
tively, connected to the analog-digital converter 94 by leads
144, 146 and 148 respectively. As known to one skilled in
the art, the analog-digital converter transforms analog
information into digital output data, which in turn is
transmitted by lead 150 to the computer printout assembly 152
for recording in a reference time frame.
In operation, the monitoring and recording assembly 90
disposed on a suitable support assembly and enclosed in a
self-contained environmental container is caused to be
positioned adjacent a unit operation or process, such as a
heat exchanger or delignification digester, respectively,
employing a fluid to be tested, inter alia, for fouling
tendencies to permit evaluation and/or facile treatment to
remedy such fouling tendencies. A source of power is con-
nected to the power inlet assembly 92 and a flexible conduit
placed in fluid flow communication with the unit operation or
process, generally on the up-stream side thereof. The
circulating fluid is caused to flow via conduit 31 into the
piping assembly 30 via either flow meter 35 or 36 by control
of valves 46 or 48, respectively, and thence sequentially
through the rotameter 37 via conduit 50 under the control of
valve 52, through the heat transfer test assembly 10 via
conduits 54 and 56, through the flow rate control valve 38
via conduit 62 and conduit 64 under control of valve 66 and
finally through the flow cell 76 via conduit 70 to be dis-
charged through outlet 68 to waste or to be returned to the
united operation or process.
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During such operational time period, power is supplied
by leads 116 to the heater element 18 of the tube member 16
with the temperature of the wall of the heating member 14
being monitored to obtain an average temperature thereof.
Simultaneously, the bulk fluid temperature is monitored by
thermocouple 86 together with the monitoring of the fluid
velocity to determine what, if any, velocity effects there
are on fouling under given operating conditions. Water
velocity is controlled by the constant flow valve 38 and is
visually monitored by the rotameter 37 concomitant with
electronic monitoring by the differential pressure cell 80
sensing the pressure drop across either flow meter 35 or
36.
The wall thermocouple 26, the bulk water temperature
thermocouple 86, the wattmeter transducer 114 and differen-
tial pressure cell 80 are connected to the analog-converter
94 via reference junction 122 to convert analog electrical
signals to digital output signals which are transmitted for
recordation to the computer printer 96, it being understood
that the computer printer is capable of effecting some
computation to generate calculated data, such as a fouling
factor. Such fouling factor is time related to data from the
conductivity monitor 138, the pH monitor 140 and the corro-
sion monitor 142. In this manner, various data is simul-
taneously collected of factors relating to fouling, etc.
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In the ~ther aspect of the present invention, the
apparatus is caused to be positioned adjacent a unit opera-
tion or process, such as a heat exchanger or delignification
digester, respectively, employing a fluid to be tested, inter
alia, for fouling tendencies to permit evaluation and develop
an antifoulant protocol. During such initial time period,
the apparatus is operated as hereinbefore described to
generate calculated data, such as a fouling factor. Such
fouling factor is time related to data from the conductivity
monitor 138, the pH monitor 140 and the corrosion monitor
142.
Thereafter, the pump 34 is energized for a predetermined
time period or continuously to quantitatively introduce
antifoulant into the piping assembly 30 with concomitant
monitoring of the hereinabove factors together with concomi-
tant generation of fouling data to evaluate the efficacy of
the antifoulant protocol. Monitoring and evaluation of the
antifoulant protocol as well as changes thereto permit the
evaluation of a finalized antifoulant protocol for a given
aqueous or nonaqueous fluid system. Accordingly, the anti-
foulant treated fluid may be returned via the discharge
conduit 70 to the unit operation or unit process thereby
permitting constant evaluation of the antifoulant protocol
for the unit operation or unit process.
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EXAMPLE
Cooling water for a gas processing plant having a pH of
from 7.2 to 7.6 treated with 24 ppms of antifoulant chemicals
including a combination of phosphonates, aromatic glycols and
chelating agents generated a fouling factor of from 240 to
260. In addition to the antifoulant chemicals, there is
introduced 150 ppms of a corrosion inhibitor and 10 ppms of a
microbiocides (on a shock basis to the cooling water).
An antifoulant protocol is developed whereby there is
added 150 ppms of a corrosion inhibitor, 50 ppms of a non-
ionic antifoulant and 50 ppms of a microbiocide together with
a base to alter the range of pH to 8.2 from 7.8. The effects
of the new protocol are determined by continued operation of
the heat transfer test section 10 under like conditions
whereby the resulting fouling factor is from 20 to 25,a ten
fold reduction from that originally observed.
After completion of the development of an antifoulant
protocol protocol, the monitoring and recording assembly 90
is disconnected from the unit operation or process by closing
valves 46 or 48 and disconnecting inlet 31 from the fluid
source. Thereafter, the monitoring and recording assembly 90
may be facilely moved to another location within the plant or
to another plant site.
The process and apparatus of the present invention as
related to the generation of antifoulant protocols is parti-
cularly suited in the development of antifoulant protocols
for once through cooling systems, chemical processing, such
as Kamyr digester, or process water for condensers.
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