Note: Descriptions are shown in the official language in which they were submitted.
~~.~~~~8
APPLICATION FOR PATENT
Inventor: RICHARD H. GARRETT
Title: LIQUID-GAS CONTACTING PUMP DRIVE APPARATUS AND METHOD
Cross Reference To Related Application
This application is rested to Canadian Application 2,1.26,062 fi7.ed June.l6;
1994 and entitled, "Lipoid-Gas Contacting PvmQ Drive Apparatus".
~ackeround Of The Invention
Field Of The Invention
This invention relates to a method and apparatus for powering a pump for
recirculation
of a regenerated fluid, and more particularly to such a method and apparatus
in which the
recirculated fluid is utilized to provide at least a portion of the energy
requirements for powering
the pump.
A gas-liquid contactor vessel is commonly utilized for removing desirable or
undesirable
elements or components from gas miXtures~ such as removing water vapor from
natural 'gas by
contact of the natural gas with a liquid absorber. Gas-liquid contactor
vessels may also be used
in amine-type sour gas treating, absorption type hydrocarbon liquid recovery
plants, and other
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213~1~8
processes. An amine type treater removes hydrogen sulfide and carbon dioxide
from natural gas.
A circulating amine solvent may be utilized as the circulating fluid to remove
sulfur compounds
from the gas stream.
For the removal of water vapor from flowing natural gas, it is desirable to
remove the
water or water vapor from the natural gas before the gas flows into a gas
transmission line. It
has been found that polyethylene glycol (commonly triethylene glycol)
effectively removes
moisture from natural gas when placed in intimate contact with the gas. This
is generally done
in a pressure (contactor) vessel operating at substantially the flowing
pressure of the natural gas,
but this requires that the glycol which is recycled from the contactor through
a reboiler be
injected into the contactor at a pressure slightly higher than the pressure of
the natural gas
flowing in the contactor.
Heretofore it has been the practice to use the driving force of the moisture
laden rich
glycol to operate a fluid motor and associated pump for pumping regenerated
lean glycol back
into the pressurized contacting vessel. For example, U.S. patent no. 4,511,378
shows an energy
exchange apparatus wherein a gear motor is driven by wet glycol and gas to
operate a gear pump
for pumping regenerated dry glycol. In this apparatus, the volume displacement
of the gear
motor is sufficiently greater than the volume displacement of the gear pump so
as to provide
adequate power to overcome friction, head, piping and other losses in the
system in addition to
powering the pump.
Another example is found, in U.S. pate~t;no. 4,427,420 in which an electric
motor,drives,
a separate pump for providing supplemental glycol circulation from the
reboiler to the
pressurized contacting vessel. Each of these arrangements has its particular
drawbacks; in the
-2 -
", 21~~~.~8
wet glycol of the '378 patent, the motor volume must be greater than the pump
volume and the
extra volume of the motor means that gas is used and must be expelled to the
atmosphere or
reclaimed by a low pressure gathering system and recompressed. Some of this
gas can be burned
in the reboiler, but most users prefer not to burn wet gas in the reboiler
because it corrodes the
burner elements, fouls the fire tubes, and is not at all reliable due to
entrained liquids.
The system utilized in the '420 patent utilizes two separate pumps independent
of each
other with each pump receiving only a portion of the dry glycol from the
regenerator. One of
the pumps is driven by a fluid motor and the other pump is driven by an
electric motor to
maintain volumetric balance in the system. While the '420 patent does not vent
natural gas to
atmosphere, many of the recirculating systems being used vent a significant
portion of natural
gas to the atmosphere which results in environmental degradation as well as
wasting valuable
energy in the flared gas. Also, the '420 patent must pump all the volume
required by the
reciprocating piston pump due to its imbalance. This volume must be supplied
at contactor
pressure so an inordinate amount of electric power must be used.
The present invention provides a new and improved apparatus and method which
retains
the principal benefits of the earlier energy exchange unit by recovering
substantial energy from
the system by using as much, of the energy as is available from a given volume
of liquid in the
system before the liquid pressure is reduced to near atmosphere pressure of
the reboiler to drive
a recirculating pump. It avoids the disadvantages of the earlier system
described above in the
'420 patent which requires a separate electric motor and separate pump to
complement the energy
exchange drive powered only by 'the iecirculating liquid. The only electric
power required in
the present invention is to overcome the slight friction encountered in the
pump - motor friction
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CA 02135118 2002-03-14
and associated hydraulic friction in the piping. Aside from the obvious
environmental advantage
of reducing emissions, the present invention also avoids the economic waste
inherent in a system
that vents gas into the atmosphere because that cost, at present day gas
prices, far exceeds the
cost of electricity required to operate a small electric motor.
Accordingly, the present invention seeks to provide a method and apparatus for
the
removal of selected elements from a gas mixture by providing a pump for
recirculation of a
removal fluid through a gas-liquid contactor vessel.
Further, the present invention seeks to provide such a method and apparatus
for the
removal of selected elements from natural gas while utilizing the
recirculating removal fluid to
maximize the energy requirements for powering a pump to pump the regenerated
removal fluid
into the gas-liquid contactor vessel.
An additional aspect seeks to provide an auxiliary drive means operably
connected to the
pump to supplement adequately the power provided to the pump from a fluid
motor driven by
the removal fluid.
SUMMARY OF THE INVENTION
The present invention is a method and apparatus in an improved recirculating
pumping
system for recirculating a removal liquid such as glycol, in a liquid-gas
contactor apparatus, i.e.
using liquid pressure to power a motor to drive a recirculating pump, but with
the added
advantage of supplementing the power preferably with a relatively small
electric drive motor
coupled to the same recirculating pump shaft to add enough additional energy
to offset or
overcome internal friction and/or inefficiencies of the primary pumping
system, thus eliminating
4
213a~~~
the necessity of either a separate electric motor and pump or the necessity of
expending
significant amounts of gas to successfully operate the recirculating pump
system.
Thus, this new invention combines the power conserving advantages of the
energy
exchange pump with the advantages of auxiliary electrical power without the
disadvantages
associated with having two separate pumps and their associated piping and
without using any free
gas. "Free gas" as opposed to "absorbed gas" does not penetrate the inner
structure of a liquid
such as glycol, whereas "absoxbed gas" which includes water vapor penetrates
the inner structure
of glycol or other liquid absorber. The free gas for a natural gas dehydrator
is natural gas.
This new pumping system preferably comprises an energy exchange device using a
hydraulic motor and pump, each having essentially the same volume, with an
additional electric
motor providing just enough additional power to offset the hydraulic motor-
pump friction, head
and hydraulic loss, and/or imbalance, if any, to allow the device to rotate at
the synchronous
electric motor speed: Further, in the event a speed control is used for
varying the flow by
controlling the electric motor speed, a motor speed controller for a small
supplemental motor is
correspondingly smaller and considerably less expensive than a speed
controller for a larger
electric motor.
The present invention is particularly directed to a rotary fluid motor and a
rotary fluid
pump having a drive shaft extending between the rotary pump and motor. A
separate auxiliary
drive means, preferably an electric motor, is operably connected to the drive
shaft to supplement
the power provided by the fluid motor.
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CA 02135118 2004-09-30
The invention in one aspect pertains to a system for removing a predetermined
component of a gas with a liquid absorber wherein there are a contacting
vessel in which the liquid
absorber is in intimate contact with the gas to remove the predetermined
component therefrom, a
treating vessel to receive the liquid absorber with the predetermined
component therein for removal
of the predetermined component from the liquid absorber, a first fluid conduit
from the contacting
vessel to the treating vessel to convey the liquid absorber with the component
therein from the
contacting vessel to the treating vessel and a second fluid conduit from the
treating vessel to the
contacting vessel to convey the liquid absorber without the predetermined
component therein from
the treating vessel to the contacting vessel thereby to provide a regenerated
liquid absorber to the
contacting vessel. A rotary fluid motor in the first conduit is driven by high
pressure liquid
absorber from the contacting vessel and a rotary fluid pump is in the second
conduit to receive from
the treating vessel substantially the entire output of low pressure liquid
absorber from the treating
vessel for pumping to the contacting vessel. A rotary shaft connects the fluid
pump to the fluid
motor for providing a portion of the power to drive the pump for pumping
substantially the entire
output of low pressure liquid absorber from the treating vessel to the
contacting vessel. Auxiliary
drive means independent of the liquid absorber is operably connected to the
pump to provide power
to drive the pump supplementing the power provided by the fluid motor.
Another aspect of the invention provides a power unit for a glycol gas
dehydrator
system in which water and water vapour are removed from natural gas, the power
unit adapted to
be positioned in fluid conduits between a contacting vessel and a glycol
regenerator. The power
unit comprises a fluid motor adapted to be positioned in one of the fluid
conduits to receive high
pressure wet glycol from the contacting vessel and to convey low pressure wet
glycol to the glycol
regenerator. A pump is positioned in another of the fluid conduits to receive
substantially the entire
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CA 02135118 2004-09-30
output of low pressure dry glycol from the regenerator for pumping to the
contacting vessel.
Means connects the fluid motor to the pump for providing a portion of the
power to drive the pump
for pumping substantially the entire output of low pressure dry glycol from
the regenerator to the
contacting vessel and auxiliary drive means not responsive to the glycol is
operably connected to
the pump to provide power to drive the pump for supplementing the power
provided by the fluid
driven motor.
Another aspect of the invention provides a method of removing a predetermined
component of a gas under pressure with a liquid absorber, comprising the
following steps:
circulating the liquid absorber through a contacting vessel for intimate
contact with the gas therein
so that the liquid absorber absorbs the predetermined gas component, providing
a first fluid conduit
between the contacting vessel and a treating vessel for conveying the liquid
absorber and gas
component to the treating vessel for removal of the gas component from the
liquid absorber to
provide a regenerated liquid absorber, providing a rotary fluid motor in the
first fluid conduit driven
by the liquid absorber, providing a second fluid conduit between the treating
vessel and the
contacting vessel for return of the regenerated liquid absorber to the
contacting vessel, pumping
from a rotary pump in the second fluid conduit substantially the entire output
of the regenerated
liquid absorber from the treating vessel to the contacting vessel, connecting
the fluid motor to the
rotary pump for providing a portion of the power to drive the rotary pump,
connecting an auxiliary
drive means to the rotary pump independent of the liquid absorber to provide a
portion of the power
to drive the pump to supplement the power provided by the fluid motor and high
pressure liquid
absorber from the contacting vessel, providing a rotary shaft for the rotary
fluid motor and the
rotary pump and driving the rotary pump from the rotary shaft.
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2135~1~
Brief Description Of The Drawings
Figure 1 is a schematic flow diagram of the method and apparatus of the
present
invention;
Figure 2 is a schematic view of an alternative flow diagram with an
alternative pump
drive apparatus;
Figure 3 is a schematic view of another alternative pump drive apparatus;
Figure 4 is a schematic view of a further alternative pump drive apparatus;
Figure 5 is a schematic view of a pump drive apparatus using a small internal
combustion
motor as an auxiliary power source;
Figure 6 is a schematic view of a typical system utilizing the present
invention and
illustrating a glycol dehydration system;
Figure 7 is a schematic of the electrical circuitry for the system of Figure
6; and
Figure 8 is a schematic of a modification for stopping the fluid pump in the
event of
overspeeding of the fluid motor.
1S
pg~ailed Description
Shown in Figure 1 of the drawings is a schematic view of a typical glycol
dehydrator
system which is illustrative of a system in which the pumping apparatus of the
present invention
is used. The contactor T has fluid connections 10 through which wet gas from a
producing gas
well or other source is introduced into the contactor and an outlet pipe 12
through which
;~ ;, ,,
dehydrated gas flows, i.e. gas from which moisture has been removed by
circulating glycol is
discharged from the contactor. The glycol is introduced into the top of the
contactor T via inlet
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213~~.18
15 and after passing through the contactor in intimate contact with the raw
wet gas is removed
through outlet 16 near the bottom of the contactor. The outlet 16 passes the
moisture laden
glycol to a hydraulic motor M at high pressure and a discharge conduit 20
carries glycol at low
pressure from motor M to the reboiler R where gas and moisture are boiled off
in a conventional
manner at or near atmospheric pressure. Regenerated glycol is then carried
from the reboiler
R to the inlet of the pump P via conduit 18 and pumped back into the contactor
T at high
pressure through inlet 15.
The pump P and the motor M are near equal in volume and are mounted on a shaft
24
which, in the preferred embodiment, extends through the electric motor E. The
electric motor
E, which may include a speed control 25, is large enough to provide the small
amount of power
required to overcome internal friction and other inefficiencies in the pumping
system, piping,
controls, etc. Such a small electric motor and speed control 25 are relatively
inexpensive to
install and operate. Also, in the event a liquid level control is desired, it
need be only a small
controller that is compatible with the near equal volume of liquid passing
through the hydraulic
pump and motor. A bypass line 49 is connected between pump P and reboiler R
and a bypass
valve 54 is provided in line 49 to permit unloading of pump P. When bypass
valve 54 is open,
fluid motor M may by used to start rotation of pump P with glycol being
returned to reboiler R
froira pump P through line 49 and valve 54. When electric motor E is
energized, bypass valve
54 should be closed to allow all of the glycol flow to return to contactor T
through line 15 and
check valve 56. , , ~ , ~ ,
A modified system of the present invention as shown in Figure 2, includes the
primary
hydraulic motor M and pump P which are mounted on offset shaft portions 24A
connected to
2~3a~~~
each other by suitable gear connections (not shown). Additionally, a secondary
fluid motor M-1
provides an auxiliary drive to the primary motor M. The auxiliary motor M-1 is
connected to
the contactor T by a small supply line 30 for supplying fluid (liquid and gas)
to drive the motor
M-1. In this embodiment the primary motor M is supplied motive fluid through
the primary
conduit 16. There is preferably no throttle in the supply conduit 16 that
feeds the motor M,
however there is a throttle control 32 in the smaller line 30 providing
control means to adjust the
amount of fluid. flowing to the auxiliary motor M-1 and thus the amount of
supplemental power
provided to the primary motor M. This arrangement allows the primary motor M
to run
substantially totally on liquid and avoid the losses associated with use of
excess gas. The throttle
valve 32 provides a means to control the speed of the motor M by varying the
flow through
auxiliary motor M-1 and thus the flow rate output of the pump P. Supply line
30 also controls
the liquid level in contactor T without a separate level control.
With the present invention, in each alternative embodiment shown in Figures 3-
5, an
auxiliary power source is added to an energy exchange unit in which the
contactor pressure is
used to drive a primary hydraulic motor to power the pump for recirculating
the glycol through
the gas contacting system. It will be appreciated that a variety of auxiliary
power sources can
be employed to accomplish the purpose and requirements of the present
invention, all within the
scope of this invention as described in the appended claims. Moreover, with
the various
embodiments shown herein, the additional auxiliary power can be applied as
required by
retrofitting supplemental energy, sources to,a preexisting drive motor and
derive the full benefits
of this invention. Particularly in the instance where the entire apparatus is
constructed as a new
unit, the present invention affords the additional advantage of eliminating
the use of the extra
_ g _
~~.~a~.~8
piping and controls which are required in some of the prior art devices and is
applicable to a gear
motor/gump device as well as to a piston type energy exchange pump.
As shown in Figure 3 of the drawings, the pump P and motor M share a shaft 24
and the
auxiliary power source, an electric motor E-1, is mounted on an end of the
shaft 24 extending
beyond the primary motor M. It will be appreciated that space and mechanical
limitations,
particularly in retrofit situations may dictate that the auxiliary power
source be mounted adjacent
either the pump P or motor M, as space allows.
Also, as shown in Figure 4 of the drawings, an auxiliary gas motor G is shown
mounted
on one end of the shaft 24, and in this instance, the gas motor is connected
to a separate source
of low pressure gas (not shown) which is supplied through a pressure regulator
105 from a high
pressure dry gas source which has a meter 106 and a throttle valve 107 for
adjusting the pressure
and flow of the gas to the auxiliary motor.
Another approach is to connect a small gas internal combustion engine M-2 to
the shaft
24 as shown in Figure 5. A bypass line 49 connected between the pump P and
reboiler R, which
is at or near atmospheric pressure provides a means to dump the pump output
and thus unload
the pump P. Bypass valve 54 is provided in bypass line 49. With the bypass
valve 54 open,
the motor M can be used to crank and start the auxiliary engine M-2 as lean
glycol from pump
P may be circulated at low pressure through reboiler R without passing through
the high pressure
contactor. Dry gas is piped to the engine M-2 via conduit 50 from a separate
source such as dry
produced gas from line 12. An adjustable speed control or governor is provided
for engine M-2.
Reference numerals in the embodiments of Figures 2-5 similar to the reference
numerals
of the embodiment of Figure 1 represent similar parts or elements.
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213~~.~~
Referring now to Figure 6, a schematic view of the system for the embodiment
shown
in Figure 3 is illustrated in which various controls are provided for a
typical glycol dehydrator
in which the embodiment of Figure 3 is utilized. Electric motor E-1 is shown
mounted on an
end of shaft 24 extending beyond motor M and forms an auxiliary power source
for powering
pump P. Wet natural gas is introduced within the contactor vessel T through
inlet line 10. Dry
natural gas is discha_Tged from outlet 12 into a suitable transmission line.
High pressure wet
glycol from outlet line 16 drives a gear motor M to rotate the shaft 24 for
driving a rotary gear
pump P. Electric motor E-1 connected to shaft 24 provides a supplemental
source of power to
rotate shaft 24 for powering pump P. A drop in pressure occurs in the glycol
upon exiting motor
M and low pressure wet glycol from outlet line 20 is supplied to reboiler or
regenerator R.
Outlet line 20 has a coil 21 within a heat exchanger 23. Low pressure
regenerated dry glycol
is supplied from reboiler R through outlet line 18 to pump P. High pressure
dry glycol is
pumped from pump P through line 15 to contactor vessel T and is discharged
within contactor
T for absorbing water vapor from the natural gas in contactor T as the liquid
glycol moves
downwardly through contactor T in intimate contact with the natural gas.
Rotary gear pump P
and rotary gear motor M are preferably of the type shown in U.S. Patent No.
4,511,378 but with
the volumetric capacity of gear motor M equal to or less than the volumetric
capacity of gear
pump P.
Outlet line 18 from reboiler R has a coil 19 arranged within heat exchanger
23. Heat
exchanger 23 preheats..wet glycol ;ln coil 2l,,and cools dry glycol in coil 19
of low pressure; line
18 before entering pump P. A block valve 27 is positioned in low pressure wet
glycol line 20
upstream of heat exchanger 23 and block valve 29 is positioned in low pressure
dry glycol line
- 10 -
2~.~~~.1~
18 upstream of heat exchanger 23. A filter or strainer 31 is provided in line
18 downstream of
heat exchanger 23. A relatively small electric motor E-1 may be utilized such
as a motor having
a horsepower (HP) between around '/ HP to 30 HP. Generally the output of motor
E-1 is
around 5% to 40% of the total horsepower required by pump P with the
volumetric capacity of
motor M and pump P being generally equal. The wet glycol for driving gear
motor M has no
appreciable gas therein so no appreciable gas is utilized in the driving of
gear motor M. For
example, a '/x horsepower electric motor may be utilized with an electric
power supply of
between 1 and l lfi amps. As an example, with pump P pumping five gallons per
minute (GPM)
at 400 psi with glycol at a temperature of 216F the auxiliary electric motor E-
1 was operated
with 1.2 amps of electrical power. Under certain conditions, it may be
feasible to provide a
solar source of energy for operation of the electric motor.
Reboiler R is a low pressure heated vessel and has a partition 33 separating a
vessel into
a partially wet glycol reboiler tank section 34 and a dry storage tank section
35. The water
vapor in wet gas is absorbed in the wet glycol entering from line 20 in heated
column 37 and
is flashed off or collected by emission control equipment (not shown). Column
37 may be open
to atmosphere so that steam can escape, or it may be connected to emission
control equipment.
A separate glycol flow measuring device is shown generally at 42 and includes
a
cylindrical transparent measuring container 41 which acts as a gage to measure
the flow rate of
glycol. A vent 39 to atmosphere on measuring container 41 acts to vent air to
atmosphere from
container 41 and has, a removable cap. Air in various conduits during priming
of pump. P ~s
emitted from container 41. A three way diverter valve 43 controls glycol flow
from measuring
container 41. Diverter valve 43 has a manually actuated handle 44 and low
pressure dry glycol
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2~3~i1.~~
from reboiler R is supplied to pump P through line 18 when handle 44 is in the
solid line
horizontal position shown in Figure 6. In the broken line vertical position of
handle 44 shown
in Figure 6, glycol flows from measuring container 41 into line 18 to pump P.
In the 45° degree
broken line portion of handle 44, low pressure dry glycol is supplied
simultaneously both to
container 41 and to pump P from reboiler R.
A connecting bypass line 49 from line 15 has branch lines 48 extending to
reboiler R and
to glycol measuring container 41. A three way diverter valve 46 has a manually
actuated handle
47 for diverting flow through branch lines 48. In the up vertical solid line
position shown in
Figure 6 for handle 47, flow is directed to container 41 through one branch
line 48. In the down
horizontal broken line position of handle 47 shown in Figure 6, flow is
directed to reboiler R
from the other branch line 48, and in the 45° broken line position,
flow is diverted both to
container 41 and reboiler R from bypass line 49. Air in bypass line 49 and
branch lines 48 is
also removed by vent 39 or column 37 depending on the position of handle 47. A
normally
closed solenoid operated valve 51 is provided in connecting bypass line 49 and
a line 53
bypassing valve 51 has a manually operated valve 54 therein thereby to control
flow through
bypass lines 49 and 48, to remove air, prime pump P, and relieve back pressure
on pump P for
ease of start-up.
Graduated indicia is provided on transparent cylindrical container 41 for
visually
indicating the amount of glycol therein. When container 41 is filled with
glycol with handle 44
in a 45° relation, or from valve 54, 46 when pump P is operating,
handle 44 is moved to the
down vertical position to close line 18 and permits flow from measuring
container 41. It may
be desired to determine the glycol flow rate while motor M and pump P are in
normal running
_ a _
21~~~.1~
operation and this can be accomplished by actuation of three-way valve 46 and
three-way valve
43. With handle 44 of three-way valve 43 in horizontal position for normal
operation of motor
M and pump P, handle 47 of valve 46 is in the up vertical position and glycol
flows from line
15 and bypass line 49 into the graduated measuring container 41 when valve 54
is opened.
When the graduated container 41 is filled to a desired level, valve 54 is
closed to stop the supply
of glycol to container 41. Handle 44 of valve 43 is then moved to the vertical
broken line
position shown in Figure 6 and glycol from measuring container 41 then flows
into line 18 with
the flow of glycol from reboiler R to pump P blocked. Pump P and motor M
continue to
operate at the same speed and upon the glycol in container 41 reaching the
zero (0) graduation,
handle 44 is tripped and returned to the up horizontal position to reopen line
18 from reboiler
R. The time for depletion of the glycol from measuring container 41 is
recorded and the flow
rate determined. Thus, a predetermined volume of glycol pumped from measuring
container 41
is timed for accurately determining the flow rate.
Initial Start Up Operation
For a start up operation after pump P and motor M have been shut off for an
extended
.period of time, such as several hours or more, handle 44 of valve 43 is
positioned at the 45 °
position and low pressure dry glycol from reboiler R flows to container 41 and
to pump P. Air
in line 18 is vented from vent 39 of container 41. When container 41 is full,
handle 44 is moved
to the down position to close line ~18. ; ValWe 54 is then opened and any air
in line 15 will be
vented by reboiler R or container 41 depending on the position of valve 46
which is controlled
by manual handle 47. Next, motor M is energized slowly to rotate pump P slowly
with low
213~i11J
pressure glycol in container 41. Reboiler R constantly heats the glycol
therein for flow from line
18 preferably over 380F. When pump P starts, any air in pump P and line 15
will be vented
out to vent 39 of container 41 through bypass line 49 and branch line 48. When
all air is
removed from line 18, 15, 49 and 48 and vented through vent caps 39 of
container 41, the
rotational speed of motor M may be increased, if desired. Next valve 54 is
closed so that the
pressure of glycol in line 15 is increased.
Mea~~rinQ Flow Rate
Flow measuring device 42 may be utilized at any time to measure the flow rate
of glycol.
For measuring the flow rate of low pressure dry glycol being pumped by pump P
through line
18, valve 54 is opened to provide glycol to container 41 until container 41 is
filled to a
predetermined level such'as one (1) gallon while handle 44 is in the up
horizontal position.
Then, valve 54 is closed. Then handle 44 is moved to the down vertical
position with valve 43
blocking fluid flow in line 18 upstream of valve 43. Glycol flows from
container 41 into line
18 downstream of valve 43 to pump P. Pump P thus pumps glycol from container
41 until the
zero (0) graduation is reached at which time handle 44 is tripped and returned
to the up
horizontal position to reopen line 18 from reboiler R. The time for depletion
of one gallon of
glycol from container 41 is recorded and the flow rate determined. Thus, an
accurate
measurement of the flow rate may be timed and visually observed by a
transparent container 41,
and with 'reference to a calibration ohart or formula, the flow rate can be
determined. . It is
apparent also that container 41 may be utilized to add any desired additives
to the glycol by
placing a predetermined amount of a desired additive within container 41 by
removal of the vent
- 14 -
CA 02135118 2004-05-18
cap from vent 39.
A normally closed flow switch 45 in line 18 is open when there is sufficient
fluid flow
to pump P through line 18. If flow of glycol ceases or is less than a
predetermined minimum
flow, switch 45 closes to stop motors M and E-1 as will be explained further
below. Solenoid
valve 51 opens during start up and allows circulation of dry glycol from pump
P to glycol
container 41, or to dry glycol storage tank section 35 in reboiler R depending
on the position of
valve 46. During normal operation after start up, solenoid valve 51 is closed.
Diverter valve
46 is utilized during start up to allow dry glycol from pump P to flow to
reboiler R or glycol
container 41 when either valve 54 or solenoid operated valve 51 is open.
A check valve 56 is mounted in high pressure dry glycol line 15 from pump P to
prevent
any high pressure back flow from contactor vessel T to pump P. Check valve 56
is nee~~ed
particularly during start up. A block valve 58 is positioned in inlet line 15
to contactor T
downstream of check valve 56 to block flow from contactor T and to permit
testing or
replacement of check valve 56. A block valve 59 is provided in outlet line 16
from contacaor
T.
A liquid level control is shown at 61 including a float 63 connected to a
pneumatic pilot
65. A throttle valve 67 is positioned in high pressure wet glycol line 16 and
is responsivf: to
pilot valve 65 for opening in response to float 63 to maintain a constant
level of wet glycol
within contactor T. A low pressure wet glycol branch line 68 extends from
throttle valve 6'1 to
line 20 for return to reboiler R. A suitable throttling motor valve is sold
under Model No. 1-
2220-S14-TGA-12 by Norrisea~l of Houston, Texas.
A control valve shown generally at 70 in high pressure wet glycol line 16 to
gear motor
- is -
CA 02135118 2004-05-18
M has a valve member 71 in line 16 responsive to a diaphragm in diaphragm
chamber 126 and
is held in an open position by the diaphragm under fluid pressure from a low
pressure gas source
72. Valve 82 is a start up control needle valve and block valve 83 is an
isolation valve provided
in lines 16 and 20 on opposed sides of gear motor M. A normally closed
solenoid valve 74 as
shown in Figure 6 vents the diaphragm chamber 126 of control valve 70 to
atmosphere at 7f~ to
maintain valve 70 closed to block the flow of high pressure wet glycol to
motor M. Upon
energizing of solenoid valve 74, low pressure gas is supplied from gas supply
72 through passage
78 of solenoid valve 74 to line 80. The low pressure gas supplied to the
diaphragm chamber 126
moves valve member 71 of valve 70 to an open position to permit the supply of
high pressure
wet glycol to motor M through line 16. Valve member 71 is always maintained in
an open
position during operation of motor M. Upon deenergizing of solenoid valve 74,
solenoid valve
74 returns to the position shown in Figure 6 and fluid from the diaphragm
chamber of control
valve 70 is exhausted to atmosphere thereby resulting in the movement of valve
70 to closed
position blocking the flow of glycol to motor M. A suitable valve 70 is sold
under Model lVo.
1-2220-S 14-TGA-12 by Norriseal of Houston, Texas. Low pressure gas is also
provided to
liquid level control 61 from gas supply 72 through line 73 for maintaining the
proper level of
glycol in contactor T.
OPERATION
In operation for start up and referring to Figure 6, block valves 27, 29 and
83 are open
and three-way valve 43 has its handle 44 positioned at the 45 degrees
intermediate position to
permit dry glycol from reboiler R to flow through line 18, heat exchanger 23
and filter 31 to
- 16 -
CA 02135118 2004-05-18
glycol measuring device 42. Any air in heat exchanger 23 and filter 31 will
escape from glycol
container 41 which is open to atmosphere. Container 41 is filled to about the
half full mark.
Next, handle 44 of three-way valve 43 is moved to a down vertical position to
circulate glycol
for the start up operation. Handle 47 of three-way valve 46 is then positioned
vertically for the
supply of glycol through line 48 into the bottom of glycol measuring device
42. Now, valve 58
is opened with pressure from contactor vessel T blocked by check valve 56.
Then, valve 54 is
opened and if check valve 56 is leaking, liquid from contactor T will flow
into glycol measuring
device 42 through valve 54, line 53, line 49 and line 48. Thus, a visual
observation of glycol
measuring device 42 upon opening of valve 58 will indicate if check valve 56
should be replaced
or repaired. Next, high pressure blocking valve 59 in line 16 at contactor T
is opened with
valves 70 and 82 in a closed position.
Now, referring also to the electrical circuitry shown schematically in Figure
7, power
switch 85 is moved to an on position to supply electrical power from leads L1,
L2 and L3. Push
button switch 87 is then closed to energize relay coil R1 to close contacts at
89 to energize
solenoid valve 74. Push button switch 87 may now be released with contacts 89
remaining
closed. Energizing of solenoid valve 74 effects supplying low pressure gas
from gas supply 72
through passages 73, 78 and line 80 to the diaphragm chamber 126 of motor
control valve 70 for
opening of valve 71. Contacts 91 of coil R1 are also closed upon energizing of
relay R1 thereby
to energize solenoid valve 51 for opening of line 49.
High pressure needle valve 82 in line 16 is now manually opened to supply high
pres-
sure wet glycol, or gas, or gas and glycol, from contactor vessel T to motor M
for slowly rotating
pump P and electric motor E-1 on shaft 24. Low pressure glycol from pump P is
pumped
-17-
~1~3a~~.8
through open bleed valve 54, open solenoid valve 51, line 53, line 49, and
line 48 to glycol
container 41 or dry ~.torage tank section 35 depending upon the position of
three-way valve 46.
Any air in pump P will be purged from container 41 which is open to atmosphere
by vent 39.
If rotation of pump P does not occur, valve 82 is opened further to provide
more power to gear
motor M. Bleed valve 54 is closed upon exhaust of all air from line 18, coil
19, filter 31 and
flow switch 45 through glycol container 41.
Three-way valve 46 is then moved to a down horizontal position to return dry
glycol to
reboiler R and three-way valve 43 is moved with handle 44 in a horizontal
position for the
supply of low pressure glycol to pump P through line 18 from reboiler R. Gear
pump P should
start heating up as hot dry glycol from reboiler R is supplied to gear pump P
through line 18.
The gears and gear housing of gear pump P initially may be heated to unequal
temperatures
resulting in a stoppage of pump P as the hot glycol on the relatively small
gears of pump P may
heat the gears faster than the larger gear housing. However, a continuous
rotation of pump P
will occux when the gears and gear housing obtain thermal equilibrium and at
this time, electric
motor E-1 may be started.
For starting electric motor E-1, push button 92 is pushed to energize relay R2
to close
contacts 93 and 94 for energizing electric motor E-1. Normally closed contacts
95 of relay R2
are opened to deenergize solenoid operated valve S 1 for movement to its
normally closed position
blocking line 49. Since contacts 93 are closed, push button 92 can be
released. The power
supply for electric motor E-1 .is"preferabl,y a three phase 480 volt system.
,Under ,certain
conditions, electric motor E-1 may be of a lower or higher voltage, with
single phase or DC
power applied.
_ 18 _
2~3i~ ~~3
Since solenoid operated valve 51 and bleed valve 54 are closed, the high
pressure dry
glycol from pump P is blocked from returning to reboiler R or flow measuring
device 41 and
thereby increases in pressure to open cheek valve 56 for flow into contactor
T. The flow of low
pressure dry glycol from reboiler R opens contacts 96 of flow switch 45 to
block any signal to
timer T1 as shown in Figure 7. In the event glycol flow in line 18 to pump P
stops or is
reduced below a predetermined amount, contacts 96 will close to start timer T1
for a preset time
such as 1 to 15 seconds as may be set by an operator. When the preset time is
reached, contacts
97 for timer Tl are opened to deenergize solenoid 74 for stopping motors M and
E-1 thereby
to shut down the system. The short time delay provided by timer T1 permits a
small amount of
air to be transmitted in line 18 to pump P without shutting down the system.
To manually shut
down the system at any time, a process stop button 98 may be pushed by the
operator.
When a large temperature differential exists between the hot glycol at a
temperature of
around 225F, for example, and a relatively cold pump, such as 100F for
example, the gears of
gear pump P being of a low mass may expand rapidly beyond the normal
clearance, such as
0.001 inch, between the gears and the relatively high mass gear housing.
Possible damage to
pump P could result if pump P is operated under such conditions. To prevent
operation of motor
E-1 when a temperature differential is above a certain amount, such as a
temperature differential
of over 50F for example, a pair of electrically opposed thermocouples 100 and
102 are provided.
Thermocouple 100 is immersed in hot glycol in suction line 18 to pump P and
thermocouple 102
is positioned in a drilled hole , irl thg metal gear housing, Thermocouples
100 and 102 are
connected in parallel opposed relation to each other and to a transducer 104
which provides a
signal to deenergize relay R3 to open contacts 99 to stop motor E-1. When
motor E-1 is
- 19 -
213~:~18
stopped, flow through line 18 to pump P stops. This allows thermocouple 100 to
start cooling
down and thermocouple 102 begins heating up from the hot glycol that entered
the pump P
before the temperature differential reached or exceeded SOF. Thus, with the
temperature of
thermocouple 100 decreasing and the temperature of thermocouple 102 increasing
the temperature
differential is reduced. The transducer 104 is programmed to have its internal
contacts open
when the differential temperature decreases to a safe differential temperature
of 35F for example.
This opening of internal contacts to transducer 104 deenergizes relay roil R3
allowing contacts
99 to close and restart motor E-1. Again, the differential temperature between
thermocouples
100 and 102 increases and upon reaching SOF, motor E-1 will stop and then
restart at 35F.
Two, three or more such cycles may be necessary to stabilize the temperature
and prevent
possible damage to pump P.
It may be desirable under certain conditions to eliminate the differential
temperature
controller and utilize a second timer (not shown) and a second shut off valve
in series with valve
70 installed between valves 82 and 71 (not shown). In this instance, the
second timer is set at
some predetermined time period, such as 20 seconds, for example.
While a temperature differential transducer 104 and electrical relays have
been illustrated,
it is understood that a suitable electronic, solid state device may be
utilized in place of transducer
104 and the relays responsive to thermocouples 100 and 102 while including a
preprogrammed
temperature differential for providing a suitable output signal to stop motor
E-1 and to restart
motor E-1 at a lower temperature differential. ;Such a solid state device may
be encapsulated in
~~ ~
resin with screw terminals for thermocouples 100, 102 and separate screw
terminals for relay R3
for motor E-1.
_ Zp _
~13~~.~~
It may be desirable under certain conditions to eliminate the timer and
utilize a controller
responsive to a temperature differential over SOF, for example, for stopping
electric motor E-1
and for restarting electric motor E-1 when the temperature differential is
reduced to 35F for
example. The controller would control the energizing and deenergizing of a
solenoid for
stopping and starting motor E-1 and could be set for responding to any desired
temperature
differential. It is noted the deenergizing of electric motor E-1 stops motor M
since the
volumetric displacement of motor M is substantially equal to or less than the
volumetric
displacement of pump P.
A relatively large pressure drop occurs between inlet line 16 to motor M and
outlet line
20 as gear motor M is driven by the high pressure wet glycol from contactor T.
Motor M
normally has a volumetric capacity generally equal to or less than the
volumetric capacity of
pump P so that gear motor M provides a sufficient torque to drive pump P while
overcoming
mechanical and hydraulic friction with either bypass valve 51 or 54 being
open. During some
start up operation, there is no glycol in pump P and the high pressure supply
of glycol through
line 16 to motor M must be controlled so that motor M does not overspeed to
result in possible
damage to pump P. If pump P runs dry for a very short time, no damage to pump
P may occur.
However, overspeeding of motor M may occur at speeds of 5,000 rpm or more and
damage to
pump P at such speeds is likely if the overspeeding occurs for a substantial
period of time while
pump P is dry. It is desirable to provide a control for such an overspeeding
condition.
Refernng to Figure 8, an overspeed device is shown generally at 110 having a
generally
,. ~ ~ ~, , , ,
cylindrical disk or spool 112 mounted on shaft 24 for rotation therewith. A
pair of leaf springs
114 are mounted by screws 116 to the outer circumferential surface 118 of disk
112. Disk 112
- 21 -
'~~ 213 ~ ~ i 8
is mounted for rotation within an outer housing 120 having an extending
plunger 122 for tripping
a bleed valve 124. Bleed valve 124 is connected to a diaphragm operated
control valve 70
through line 128 to the diaphragm chamber 126. Gas is supplied to the
diaphragm chamber 126
from gas supply 129. As shown in Figure 8 with shaft 24 rotating at an
excessive rotational
speed, leaf springs 114 extend outwardly by centrifugal force and contact
plunger 122 to trip
bleed valve 124. Bleed valve 124 exhausts gas from diaphragm chamber 126 to
atmosphere
through line 132. Valve member.71 in line 16 then moves to closed position to
block the flow
of high pressure glycol to motor M through line 16 to stop motor M and pump P.
Upon
correction of the glycol supply to pump P, valve 124 may be manually reset by
lever 133 to
supply gas from gas supply 129 to diaphragm chamber 126 for opening valve
member 71 to
permit operation of motor M.
While a glycol dehydrator system has been illustrated, the present invention
may be
utilized for removing desirable or undesirable elements from other gas
mixtures such as in amine
type sour gas treaters, for example. Amine treaters are used to remove
hydrogen sulfide and
carbon dioxide from natural gas and the circulating fluid or solvent may be an
alkanolamine
diluted with water. An amine unit is positioned upstream from the contactor or
dehydrator and
natural gas from a separator flows into a contactor with lean alkanolamines
flowing into the
upper end of the contactor and rich solvent being discharged from the bottom
of the contactor
for flow to a reboiler or regenerator for conversion into a lean solvent.
Prom the above, it is a arent that the resent invention is rovided to
eliminate the use
P~;. r ~P. P , ~ ,~
of "free" natural gas for driving pump P and preferably utilizes a fluid motor
which has a
volumetric displacement substantially equal to or less than the volumetric
displacement of fluid
2~~~:~18
pump P. The liquid glycol normally has a certain amount of dissolved natural
gas therein
including some water vapor but the "free" gas is separated from the glycol and
does not penetrate
the inner structure of the glycol.
Although the method and apparatus of the present invention have been described
in
connection with several embodiments, it is not intended to be limited to the
specific form set
forth herein, but on the contrary, it is intended to cover such alternatives,
modifications, and
equivalents, as can be reasonable included within the spirit and scope of the
invention as defined
by the appended claims.
