U.S. patent application number 15/592739 was filed with the patent office on 2018-11-15 for method for removing foulants from a heat exchanger through coolant flow control.
The applicant listed for this patent is Larry Baxter, Nathan Davis, Christopher Hoeger, Eric Mansfield, Aaron Sayre, Kyler Stitt. Invention is credited to Larry Baxter, Nathan Davis, Christopher Hoeger, Eric Mansfield, Aaron Sayre, Kyler Stitt.
Application Number | 20180328661 15/592739 |
Document ID | / |
Family ID | 64097104 |
Filed Date | 2018-11-15 |
United States Patent
Application |
20180328661 |
Kind Code |
A1 |
Baxter; Larry ; et
al. |
November 15, 2018 |
Method for Removing Foulants from a Heat Exchanger through Coolant
Flow Control
Abstract
A method for removing a foulant from a heat exchanger is
disclosed. A process fluid, comprising a process liquid and a
fouling component, are provided to a process side of the heat
exchanger. A flow of a coolant to the coolant side is provided by
opening an inlet to the coolant side. The process fluid is cooled,
a portion of the fouling component desublimating, crystallizing,
freezing, condensing coupled with solidifying, or a combination
thereof as a first portion of the foulant onto an outer surface of
the coolant side. The inlet to the coolant side is periodically
closed such that the flow of the coolant slows or stops, warming
the process side, and causing the first portion of the foulant to
sublimate, melt, absorb, or a combination thereof off the outer
surface of the coolant side. The process then returns to the
providing the flow of the coolant step.
Inventors: |
Baxter; Larry; (Orem,
UT) ; Stitt; Kyler; (Lindon, UT) ; Mansfield;
Eric; (Spanish Fork, UT) ; Hoeger; Christopher;
(Provo, UT) ; Sayre; Aaron; (Spanish Fork, UT)
; Davis; Nathan; (Bountiful, UT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Baxter; Larry
Stitt; Kyler
Mansfield; Eric
Hoeger; Christopher
Sayre; Aaron
Davis; Nathan |
Orem
Lindon
Spanish Fork
Provo
Spanish Fork
Bountiful |
UT
UT
UT
UT
UT
UT |
US
US
US
US
US
US |
|
|
Family ID: |
64097104 |
Appl. No.: |
15/592739 |
Filed: |
May 11, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 19/00 20130101;
Y02P 70/10 20151101; F28D 2021/0033 20130101; F23J 2900/15061
20130101; F28D 7/04 20130101; F28D 21/001 20130101; F28D 9/0006
20130101; F28D 9/005 20130101; F28F 27/00 20130101; B01D 5/0015
20130101; F28D 7/16 20130101; B01D 5/0051 20130101; F28F 3/083
20130101; F28F 17/00 20130101; F28F 1/32 20130101 |
International
Class: |
F25J 3/08 20060101
F25J003/08; F28F 17/00 20060101 F28F017/00 |
Goverment Interests
[0001] This invention was made with government support under
DE-FE0028697 awarded by The Department of Energy. The government
has certain rights in the invention.
Claims
1. A method for removing a foulant from a heat exchanger
comprising: providing the heat exchanger comprising a process side
and a coolant side; providing a process fluid, comprising a process
liquid and a fouling component, to the process side; providing a
flow of a coolant to the coolant side by opening an inlet to the
coolant side; cooling the process fluid, a portion of the fouling
component desublimating, crystallizing, freezing, condensing
coupled with solidifying, or a combination thereof as a first
portion of the foulant onto an outer surface of the coolant side;
periodically closing the inlet to the coolant side such that the
flow of the coolant slows or stops, warming the process side, and
causing the first portion of the foulant to sublimate, melt,
absorb, or a combination thereof off the outer surface of the
coolant side; and, returning to the providing the flow of the
coolant step; whereby the foulant is removed from the heat
exchanger.
2. The method of claim 1, wherein cooling the process fluid further
crystallizes, freezes, solidifies, or a combination thereof a
portion of the process liquid onto the outer surface of the coolant
side such that the portion of the process liquid forms a second
portion of the foulant.
3. The method of claim 2, providing the heat exchanger further
comprising a shell and tube style exchanger, plate style exchanger,
plate and frame style exchanger, plate and shell style exchanger,
spiral style exchanger, plate fin style exchanger, or combinations
thereof.
4. The method of claim 3, wherein the inlet to the coolant side
comprises a valve or a pump.
5. The method of claim 4, further comprising removing the coolant
from the coolant side through an outlet from the coolant side when
the inlet to the coolant side is closed.
6. The method of claim 5, wherein the removing the coolant step is
accomplished by pumping the coolant as a liquid from the heat
exchanger.
7. The method of claim 5, wherein the removing the coolant step is
accomplished by boiling the coolant out of the heat exchanger.
8. The method of claim 7, wherein the removing the coolant step is
further accomplished by providing vacuum to the outlet of the
coolant side.
9. The method of claim 5, wherein the heat exchanger further
comprises instruments, the instruments comprising a flow meter on
an inlet of the process side, a temperature sensor on the process
side, a pressure sensor on the process side, or a combination
thereof.
10. The method of claim 9, further comprising providing a
controller that receives signals from the instruments and uses the
signals to control the inlet of the coolant side.
11. The method of claim 10, wherein a change in pressure on the
process side indicates a change in the amount of the foulant, an
increase in the pressure above a threshold triggers the controller
to completely close the inlet to the coolant side, and the pressure
returning below the threshold triggers the controller to completely
open the inlet to the coolant side.
12. The method of claim 10, wherein a change in pressure on the
process side indicates a change in the amount of the foulant, and
an increase in the pressure above a threshold triggers the
controller to close the inlet to the coolant side in proportion to
how far above the threshold the pressure climbs, with the inlet to
the coolant side fully open with the pressure below the first
threshold, and the inlet to the coolant side fully closed above a
high pressure limit.
13. The method of claim 10, wherein an increase in temperature on
the process side indicates an change in the amount of the foulant,
and an increase in the temperature above a threshold triggers the
controller to close the inlet to the coolant side in proportion to
how far above the threshold the temperature climbs, with the inlet
to the coolant side fully open with the temperature below the first
threshold, and the inlet to the coolant side fully closed above a
high temperature limit.
14. The method of claim 1, providing the fouling component further
comprising carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen
dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide,
water, condensed hydrocarbons, or combinations thereof.
15. The method of claim 1, providing the fouling component further
comprising a solid portion comprising particulates, mercury, other
heavy metals, condensed organics, soot, inorganic ash components,
biomass, salts, water ice, other impurities common to a vitiated
flow, producer gases, or other industrial flows, or combinations
thereof.
16. The method of claim 1, providing the process liquid comprising
any compound or mixture of compounds with a freezing point below
the temperature at which the fouling component solidifies.
17. The method of claim 1, providing the contact liquid stream
comprising water, brine, hydrocarbons, liquid ammonia, liquid
carbon dioxide, other cryogenic liquids, and combinations
thereof.
18. The method of claim 1, providing the contact liquid stream
comprising 1,1,3-trimethylcyclopentane, 1,4-pentadiene,
1,5-hexadiene, 1-butene, 1-methyl-1-ethylcyclopentane, 1-pentene,
3,3,3,3-tetrafluoropropene, 3,3-dimethyl-1-butene,
3-chloro-1,1,1,2-tetrafluoroethane, 3-methylpentane,
3-methyl-1,4-pentadiene, 3-methyl-1-butene, 3-methyl-1-pentene,
3-methylpentane, 5-methyl-1-hexene, 5-methyl-1-pentene,
5-methylcyclopentene, 5-methyl-trans-2-pentene,
bromochlorodifluoromethane, bromodifluoromethane,
bromotrifluoroethylene, chlorotrifluoroethylene, cis 3-hexene,
cis-1,3-pentadiene, cis-2-hexene, cis-2-pentene,
dichlorodifluoromethane, difluoromethyl ether, trifluoromethyl
ether, dimethyl ether, ethyl fluoride, ethyl mercaptan,
hexafluoropropylene, isobutane, isobutene, isobutyl mercaptan,
isopentane, isoprene, methyl isopropyl ether, methylcyclohexane,
methylcyclopentane, methylcyclopropane, n,n-diethylmethylamine,
octafluoropropane, pentafluoroethyl trifluorovinyl ether, propane,
sec-butyl mercaptan, trans-2-pentene, trifluoromethyl
trifluorovinyl ether, vinyl chloride, bromotrifluoromethane,
chlorodifluoromethane, dimethyl silane, ketene, methyl silane,
perchloryl fluoride, propylene, vinyl fluoride, or combinations
thereof.
19. The method of claim 1, providing the coolant comprising liquid
nitrogen, ethane, methane, propane, or other refrigerants.
20. A method for removing a foulant from a heat exchanger
comprising: providing the heat exchanger comprising instruments, a
process side and a coolant side, the heat exchanger further
comprising a shell and tube style exchanger, plate style exchanger,
plate and frame style exchanger, plate and shell style exchanger,
spiral style exchanger, plate fin style exchanger, or combinations
thereof, and the instruments comprising a flow meter on an inlet of
the process side, a temperature sensor on an outlet of the process
side, and a pressure sensor on the process side; providing a
process fluid, comprising a process liquid and a fouling component,
to the process side, the process liquid comprising any compound or
mixture of compounds with a freezing point below the temperature at
which the fouling component solidifies, and the fouling component
comprising carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen
dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide,
water, condensed hydrocarbons, or combinations thereof; providing a
flow of a coolant to the coolant side by opening an inlet to the
coolant side, the inlet to the coolant side comprising a valve or a
pump; cooling the process fluid, a portion of the fouling component
and a portion of the process liquid desublimating, crystallizing,
freezing, condensing coupled with solidifying, or a combination
thereof as the foulant onto an outer surface of the coolant side;
receiving signals from the instruments indicating pressure,
temperature, and flow, an increase in the pressure, a decrease in
the flow, or an increase in the temperature indicating an increase
in the amount of the foulant; periodically closing the inlet to the
coolant side when the pressure goes above a pressure threshold, the
temperature goes above a temperature threshold, or the flow goes
below a process flow threshold, such that the flow of the coolant
slows or stops, removing the coolant through an outlet of the
coolant side by providing vacuum such that the coolant boils from
the coolant side and leaves through the outlet of the coolant side,
warming the process side, and causing the foulant to sublimate,
melt, absorb, or a combination thereof off the outer surface of the
coolant side; and, returning to the providing the flow of the
coolant step; whereby the foulant is removed from the heat
exchanger.
Description
FIELD OF THE INVENTION
[0002] This invention relates generally to operation of heat
exchangers. More particularly, we are interested in continuous
operations of heat exchangers for use in foulant removal.
BACKGROUND
[0003] The art of removing condensable vapors from gases, such as
carbon dioxide from combustion flue gas, is a new and growing
field. One of the greatest challenges in the field is heat exchange
in indirect-contact heat exchangers. Cooling of liquids containing
condensable gases can lead to desublimation of gases directly onto
the outside surface of the cooling section of the exchanger,
fouling and eventually blocking the process fluid flow. Shut down,
drainage, and removal can be a significant cost, both from downtime
of the equipment and from startup costs inherent in cryogenic
exchange. The ability to remove foulants and prevent blockage
without shutdown or significant re-cooling costs is required.
[0004] United States patent publication number 8715401, to Baxter
teaches methods and systems for separating condensable vapors from
gases. Condensable vapors, such as carbon dioxide, are separated
from light gases using heat exchangers. The present disclosure
differs from this disclosure in that the only strategy for
preventing fouling of the heat exchanger surface is to provide a
bed of particles on which the vapors can desublimate, minimizing
the amount of desublimation that can occur on the heat exchanger
surface. This disclosure is pertinent and may benefit from the
devices disclosed herein and is hereby incorporated for reference
in its entirety for all that it teaches.
[0005] U.S. patent application Ser. No. 15/425,276, to Baxter, et
al., teaches a method for semi-continuous heat exchange operations
by alternating between heat exchangers. Condensable vapors, such as
carbon dioxide, desublimate onto exchanger surfaces, causing
fouling. The method consists of switching heat exchangers when
fouling occurs in one, allowing the first to have fluids removed
and foulant to melt. The present disclosure differs from this
disclosure in that the procedure requires two heat exchangers and
shuts down the fouled heat exchanger entirely. This disclosure is
pertinent and may benefit from the devices disclosed herein and is
hereby incorporated for reference in its entirety for all that it
teaches.
SUMMARY
[0006] A method for removing a foulant from a heat exchanger is
disclosed. The heat exchanger, comprising a process side and a
coolant side, is provided. A process fluid, comprising a process
liquid and a fouling component, are provided to the process side. A
flow of a coolant to the coolant side is provided by opening an
inlet to the coolant side. The process fluid is cooled, a portion
of the fouling component desublimating, crystallizing, freezing,
condensing coupled with solidifying, or a combination thereof as a
first portion of the foulant onto an outer surface of the coolant
side. The inlet to the coolant side is periodically closed such
that the flow of the coolant slows or stops, warming the process
side, and causing the first portion of the foulant to sublimate,
melt, absorb, or a combination thereof off the outer surface of the
coolant side. The process then returns to the providing the flow of
the coolant step. In this manner, the foulant is removed from the
heat exchanger.
[0007] Cooling the process fluid may further crystallize, freeze,
solidify, or a combination thereof a portion of the process liquid
onto the outer surface of the coolant side such that the portion of
the process liquid forms a second portion of the foulant. The heat
exchanger may further comprise a shell and tube style exchanger,
plate style exchanger, plate and frame style exchanger, plate and
shell style exchanger, spiral style exchanger, plate fin style
exchanger, or combinations thereof. The inlet to the coolant side
may comprise a valve or a pump. The coolant may be removed from the
coolant side through an outlet from the coolant side when the inlet
to the coolant side is closed. The coolant may be removed by
pumping the coolant as a liquid from the heat exchanger or by
boiling the coolant out of the heat exchanger. Vacuum may be
provided to the outlet of the coolant side to increase the rate of
removal of the coolant. The heat exchanger may comprise
instruments, the instruments comprising a flow meter on an inlet of
the process side, a temperature sensor on the process side, a
pressure sensor on the process side, or a combination thereof. A
controller that receives signals from the instruments may be
provided. The controller may use the signals to control the inlet
of the coolant side. A change in pressure on the process side
indicates a change in the amount of the foulant. An increase in the
pressure above a threshold may trigger the controller to completely
close the inlet to the coolant side, and the pressure returning
below the threshold may trigger the controller to completely open
the inlet to the coolant side. The increase in the pressure above
the threshold may trigger the controller to close the inlet to the
coolant side in proportion to how far above the threshold the
pressure climbs. with the inlet to the coolant side fully open with
the pressure below the first threshold, and the inlet to the
coolant side fully closed above a high pressure limit.
[0008] The fouling component may comprise carbon dioxide, nitrogen
oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen
sulfide, hydrogen cyanide, water, condensed hydrocarbons, or
combinations thereof. The fouling component may further comprise a
solid portion comprising particulates, mercury, other heavy metals,
condensed organics, soot, inorganic ash components, biomass, salts,
water ice, other impurities common to a vitiated flow, producer
gases, or other industrial flows, or combinations thereof.
[0009] The process liquid may comprise any compound or mixture of
compounds with a freezing point below the temperature at which the
fouling component solidifies. The contact liquid stream may
comprise water, brine, hydrocarbons, liquid ammonia, liquid carbon
dioxide, other cryogenic liquids, and combinations thereof. The
contact liquid stream may comprise 1,1,3-trimethylcyclopentane,
1,4-pentadiene, 1,5-hexadiene, 1-butene,
1-methyl-1-ethylcyclopentane, 1-pentene,
3,3,3,3-tetrafluoropropene, 3,3-dimethyl-1-butene,
3-chloro-1,1,1,2-tetrafluoroethane, 3-methylpentane,
3-methyl-1,4-pentadiene, 3-methyl-1-butene, 3-methyl-1-pentene,
3-methylpentane, 5-methyl-1-hexene, 5-methyl-1-pentene,
5-methylcyclopentene, 5-methyl-trans-2-pentene,
bromochlorodifluoromethane, bromodifluoromethane,
bromotrifluoroethylene, chlorotrifluoroethylene, cis 3-hexene,
cis-1,3-pentadiene, cis-2-hexene, cis-2-pentene,
dichlorodifluoromethane, difluoromethyl ether, trifluoromethyl
ether, dimethyl ether, ethyl fluoride, ethyl mercaptan,
hexafluoropropylene, isobutane, isobutene, isobutyl mercaptan,
isopentane, isoprene, methyl isopropyl ether, methylcyclohexane,
methylcyclopentane, methylcyclopropane, n,n-diethylmethylamine,
octafluoropropane, pentafluoroethyl trifluorovinyl ether, propane,
sec-butyl mercaptan, trans-2-pentene, trifluoromethyl
trifluorovinyl ether, vinyl chloride, bromotrifluoromethane,
chlorodifluoromethane, dimethyl silane, ketene, methyl silane,
perchloryl fluoride, propylene, vinyl fluoride, or combinations
thereof.
[0010] The coolant may comprise liquid nitrogen, ethane, methane,
propane, or other refrigerants.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In order that the advantages of the invention will be
readily understood, a more particular description of the invention
briefly described above will be rendered by reference to specific
embodiments illustrated in the appended drawings. Understanding
that these drawings depict only typical embodiments of the
invention and are not therefore to be considered limiting of its
scope, the invention will be described and explained with
additional specificity and detail through use of the accompanying
drawings, in which:
[0012] FIG. 1 shows a method for removing a foulant from a heat
exchanger.
[0013] FIG. 2 shows a method for removing a foulant from a heat
exchanger.
[0014] FIGS. 3A-B show a method for removing foulant from a heat
exchanger with reference to an isometric view of a plate and frame
heat exchanger and a side view cross section of plates.
[0015] FIG. 4 shows a method for removing foulant from a heat
exchanger is shown with reference to an isometric view of the
internal components of a plate and tube heat exchanger.
[0016] FIG. 5 shows a method for removing foulant from a heat
exchanger is shown with reference to an isometric exploded view of
a plate and shell heat exchanger.
[0017] FIG. 6 shows a method for removing foulant from a heat
exchanger is shown with reference to a cross-sectional view of a
shell and tube heat exchanger.
[0018] FIG. 7 shows a method for removing foulant from a heat
exchanger is shown with reference to a cross-sectional view of a
u-tube bundle style shell and tube heat exchanger.
[0019] FIG. 8 shows a method for removing foulant from a heat
exchanger is shown with reference to a cutaway isometric view of a
spiral heat exchanger.
DETAILED DESCRIPTION
[0020] It will be readily understood that the components of the
present invention, as generally described and illustrated in the
Figures herein, could be arranged and designed in a wide variety of
different configurations. Thus, the following more detailed
description of the embodiments of the invention, as represented in
the Figures, is not intended to limit the scope of the invention,
as claimed, but is merely representative of certain examples of
presently contemplated embodiments in accordance with the
invention.
[0021] Referring to FIG. 1, a method for removing a foulant from a
heat exchanger is shown at 100, as per one embodiment of the
present invention. A heat exchanger comprising a process side and a
coolant side is provided 101. A process fluid, comprising a process
liquid and a fouling component, are provided to the process side
102. A flow of a coolant is provided to the coolant side 103. The
process fluid is cooled, a portion of the fouling component
desublimating, crystallizing, freezing, condensing coupled with
solidifying, or a combination thereof as the foulant onto an outer
surface of the coolant side 104. The inlet to the coolant side is
periodically closed such that the flow of the coolant slows or
stops, warming the process side, and causing the foulant to
sublimate, melt, absorb, or a combination thereof off the outer
surface of the coolant side 105. The process is then repeated
starting at the coolant step 103.
[0022] Referring to FIG. 2, a method for removing a foulant from a
heat exchanger is shown at 200, as per one embodiment of the
present invention. A heat exchanger comprising a process side and a
coolant side is provided 201. The heat exchanger further comprises
a flow meter on an inlet of the process side, a temperature sensor
on an outlet of the process side, and a pressure sensor on the
process side 202. A process fluid, comprising isopentane and carbon
dioxide, are provided to the process side 203. A flow of liquid
nitrogen is provided to the coolant side through a control valve
204. The process fluid is cooled, a portion of the carbon dioxide
desublimating, crystallizing, freezing, condensing coupled with
solidifying, or a combination thereof as the foulant onto an outer
surface of the coolant side 205. The flow, temperature, and
pressure sensors provide signals indicating flow, temperature, and
pressure, respectively 206. An increase in the pressure, a decrease
in the flow, or an increase in the temperature indicate an increase
in the amount of the foulant. The inlet to the coolant side is
periodically closed such that the flow of the liquid nitrogen slows
or stops 207. An outlet of the coolant side is provided with vacuum
such that the liquid nitrogen boils from the coolant side and is
removed 208. The process side is warmed, causing the foulant to
sublimate, melt, absorb, or a combination thereof off the outer
surface of the coolant side 208. The process is then repeated
starting at the coolant step 204.
[0023] Referring to FIGS. 3A-B, a method for removing foulant from
a heat exchanger is shown with reference to an isometric view of a
plate and frame heat exchanger (PFHE) at 300 and a side view cross
section of plates at 301, as per one embodiment of the present
invention. The PFHE comprises frame 302 holding together plates 304
with process inlet 308, process outlet 310, coolant inlet 312,
coolant outlet 314, and coolant inlet control valve 320. The spaces
between the plates comprise process side 316 and coolant side 318.
Process fluid 330, comprising a process liquid and a fouling
component, is provided to process inlet 308 and passes through
process side 316, where it is cooled against coolant 334. Coolant
334 is passed through coolant inlet control valve 320 and coolant
inlet 312 into coolant side 318 where it cools process fluid 330. A
portion of the fouling component and a portion of the process
liquid desublimates, crystallizes, freezes, condenses coupled with
solidifying, or a combination thereof as a foulant onto process
side surfaces 322. Periodically, coolant inlet control valve 320 is
closed. Coolant 334 drains out of coolant outlet 314, leaving
plates 304 to warm due to process fluid 330. This warming causes
the foulant to sublimate, melt, absorb, or a combination thereof
off process side surfaces 322. At this point, coolant inlet valve
320 is re-opened, starting the cycle again. In some embodiments,
coolant inlet control valve 320 is replaced by a pump. In some
embodiments, the flow direction of coolant 334 is reversed and
coolant inlet control valve 320 is attached to coolant outlet 314,
now coolant inlet 314. In this embodiment, coolant 334 cannot
drain, so vacuum is supplied to the now coolant outlet 312, boiling
off the coolant.
[0024] Referring to FIG. 4, a method for removing foulant from a
heat exchanger is shown with reference to an isometric view of the
internal components of a plate and tube heat exchanger (PTHE) at
400, as per one embodiment of the present invention. The PTHE
comprises coolant side 418 and process side 416. Coolant 434 is
provided to coolant side 418, between plates 404 while process
fluid 430, comprising a process liquid and a fouling component, is
provided to process side 416, inside tubes 402. Coolant 434 cools
process fluid 430 through tubes 402. A portion of the fouling
component and a portion of the process liquid desublimates,
crystallizes, freezes, condenses coupled with solidifying, or a
combination thereof as a foulant onto inside surfaces 422 of tubes
402. Periodically, the coolant feed pump (not shown) is stopped.
Coolant 334 drains and evaporates out of coolant side 418, leaving
tubes 402 to warm due to process fluid 430. This warming causes the
foulant to sublimate, melt, absorb, or a combination thereof off
inside surfaces 422. At this point, the inlet pump is restarted,
starting the cycle again. In some embodiments, the pump comprises a
variable frequency drive, and rather than stopping the coolant feed
pump, the coolant feed rate is lowered until the process fluid 430
can counter the cold from coolant 434, allowing the foulant to be
removed.
[0025] Referring to FIG. 5, a method for removing foulant from a
heat exchanger is shown with reference to an isometric exploded
view of a plate and shell heat exchanger (PSHE) at 500 as per one
embodiment of the present invention. The PSHC comprises shell 502
holding together plates 504 with process inlet 508, process inlet
control valve 524, process outlet 510, coolant inlet 512, coolant
outlet 514, and coolant inlet control valve 520. The spaces between
the plates comprise process side 516 and coolant side 518. Process
fluid 530, comprising a process liquid and a fouling component, is
passed through process control valve 524, inlet 508, process side
516, where it is cooled against coolant 534. Coolant 534 is passed
through coolant inlet control valve 520 and coolant inlet 512 into
coolant side 518 where it cools process fluid 530. A portion of the
fouling component and a portion of the process liquid desublimates,
crystallizes, freezes, condenses coupled with solidifying, or a
combination thereof as a foulant onto process side surfaces 522.
Periodically, coolant inlet control valve 520 is closed and process
inlet control valve 524 is fully opened. Vacuum is applied to
coolant outlet 514 and coolant 534 evaporates out of coolant outlet
514. Process fluid 530 is provided by a process pump (not shown)
which is ramped up to provide a higher flow rate of process fluid
530. The combination of no coolant 534 and faster flow of process
fluid 530 results in warming of plates 504. This warming causes the
foulant to sublimate, melt, absorb, or a combination thereof off
process side surfaces 522. At this point, coolant inlet valve 520
is re-opened and vacuum is stopped, the process pump is returned to
ramped down, and process control inlet valve is returned to its
partially closed state, starting the cycle again.
[0026] Referring to FIG. 6, a method for removing foulant from a
heat exchanger is shown with reference to a cross-sectional view of
a shell and tube heat exchanger (STHE) at 600, as per one
embodiment of the present invention. The STHE comprises shell 602
and tubes 604 with process inlet 608, process outlet 610, coolant
inlet 612, coolant outlet 614, and coolant inlet control valve 620.
The space inside tubes 604 comprises process side 616 and the space
outside of tubes 604 comprises coolant side 618. Process fluid 630,
comprising a process liquid and a fouling component, is provided to
process inlet 608 and passes through process side 616, where it is
cooled against coolant 634. Coolant 634 is passed through coolant
inlet control valve 620 and coolant inlet 612 into coolant side 618
where it cools process fluid 630. A portion of the fouling
component and a portion of the process liquid desublimates,
crystallizes, freezes, condenses coupled with solidifying, or a
combination thereof as a foulant onto the inside of tubes 604.
Periodically, coolant inlet control valve 620 is closed. Vacuum is
provided to coolant outlet 614 and coolant 634 evaporates out of
coolant outlet 614, leaving tubes 604 to warm due to process fluid
630. This warming causes the foulant to sublimate, melt, absorb, or
a combination thereof off the inside of tubes 604. At this point,
coolant inlet valve 620 is re-opened and vacuum is stopped,
starting the cycle again.
[0027] Referring to FIG. 7, a method for removing foulant from a
heat exchanger is shown with reference to a cross-sectional view of
a u-tube bundle style shell and tube heat exchanger (STHE) at 700
and a side view cross section of plates at 701, as per one
embodiment of the present invention. The STHE comprises shell 702
and tubes 704 with process inlet 708, process outlet 710, coolant
inlet 712, coolant outlet 714, and coolant inlet control valve 720.
The space inside tubes 704 comprises process side 716 and the space
outside of tubes 704 comprises coolant side 718. Process fluid 730,
comprising a process liquid and a fouling component, is provided to
process inlet 708 and passes through process side 716, where it is
cooled against coolant 734. Coolant 734, supplied by a coolant pump
(not shown), is passed through coolant inlet 712 into coolant side
718 where it cools process fluid 730. A portion of the fouling
component and a portion of the process liquid desublimates,
crystallizes, freezes, condenses coupled with solidifying, or a
combination thereof as a foulant onto the inside of tubes 704. A
flow sensor (not shown) and a pressure sensor (not shown) are
provided on the pipe feeding process inlet 730. A temperature
sensor (not shown) is provided on the pipe that receives cooled
process fluid 732 out of process outlet 710. These sensors provide
signals indicating flow, pressure, and temperature, respectively.
An increase in the pressure, a decrease in the flow, or an increase
in the temperature indicate an increase in the amount of the
foulant. The coolant pump is periodically stopped and coolant flows
back through the coolant pump such that coolant 734 is removed.
Process side 716 is warmed, causing the foulant to sublimate, melt,
absorb, or a combination thereof off the inside surface of tubes
704. Coolant 734 is then started again, restarting the cycle.
[0028] Referring to FIG. 8, a method for removing foulant from a
heat exchanger is shown with reference to a cutaway isometric view
of a spiral heat exchanger (SHE) at 800 and a side view cross
section of plates at 801, as per one embodiment of the present
invention. The SHE comprises spiraling plates 804 with process
inlet 808 and coolant inlet 812. The space between spiraling plates
804 comprises process side 816 and coolant side 818, alternating.
Process fluid 830, comprising a process liquid and a fouling
component, is provided to process inlet 808 and passes through
process side 816, where it is cooled against coolant 834. Coolant
834, supplied by a coolant pump (not shown), is passed through
coolant inlet 812 into coolant side 818 where it cools process
fluid 830. A portion of the fouling component and a portion of the
process liquid desublimates, crystallizes, freezes, condenses
coupled with solidifying, or a combination thereof as a foulant
onto process side surface 822 of spiraling plates 804. A flow
sensor (not shown) and a pressure sensor (not shown) are provided
on the pipe feeding process inlet 830. A temperature sensor (not
shown) is provided on the pipe that receives a cooled process fluid
out of the process outlet. These sensors provide signals indicating
flow, pressure, and temperature, respectively. An increase in the
pressure, a decrease in the flow, or an increase in the temperature
indicate an increase in the amount of the foulant. The coolant pump
is periodically stopped and coolant flows back through the coolant
pump such that coolant 834 is partially removed. Process side 816
is warmed, causing the foulant to sublimate, melt, absorb, or a
combination thereof off the inside surface of tubes 804. Coolant
834 is then started again, restarting the cycle. In some
embodiments, vacuum is supplied to the coolant outlet while the
pump is shut down and coolant 834 is boiled off.
[0029] In some embodiments, the heat exchanger further comprises a
shell and tube style exchanger, plate style exchanger, plate and
frame style exchanger, plate and shell style exchanger, spiral
style exchanger, plate fin style exchanger, or combinations
thereof. In some embodiments, the removing the coolant step is
accomplished by pumping the coolant as a liquid from the heat
exchanger. In some embodiments, a controller is provided that
receives signals from the instruments and uses the signals to
control the inlet of the coolant side.
[0030] In some embodiments, a change in pressure on the process
side indicates a change in the amount of the foulant, an increase
in the pressure above a threshold triggers the controller to
completely close the inlet to the coolant side, and the pressure
returning below the threshold triggers the controller to completely
open the inlet to the coolant side. In other embodiments, an
increase in the pressure above a threshold triggers the controller
to close the inlet to the coolant side in proportion to how far
above the threshold the pressure climbs, with the inlet to the
coolant side fully open with the pressure below the first
threshold, and the inlet to the coolant side fully closed above a
high pressure limit.
[0031] In some embodiments, the fouling component comprises carbon
dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur
trioxide, hydrogen sulfide, hydrogen cyanide, water, condensed
hydrocarbons, or combinations thereof. In some embodiments, the
fouling component further comprises a solid portion comprising
particulates, mercury, other heavy metals, condensed organics,
soot, inorganic ash components, biomass, salts, water ice, other
impurities common to a vitiated flow, producer gases, or other
industrial flows, or combinations thereof.
[0032] In some embodiments, the process liquid comprises any
compound or mixture of compounds with a freezing point below the
temperature at which the fouling component solidifies. In some
embodiments, the contact liquid stream comprises water, brine,
hydrocarbons, liquid ammonia, liquid carbon dioxide, other
cryogenic liquids, and combinations thereof. In some embodiments,
the contact liquid stream comprises 1,1,3-trimethylcyclopentane,
1,4-pentadiene, 1,5-hexadiene, 1-butene,
1-methyl-1-ethylcyclopentane, 1-pentene,
3,3,3,3-tetrafluoropropene, 3,3-dimethyl-1-butene,
3-chloro-1,1,1,2-tetrafluoroethane, 3-methylpentane,
3-methyl-1,4-pentadiene, 3-methyl-1-butene, 3-methyl-1-pentene,
3-methylpentane, 5-methyl-1-hexene, 5-methyl-1-pentene,
5-methylcyclopentene, 5-methyl-trans-2-pentene,
bromochlorodifluoromethane, bromodifluoromethane,
bromotrifluoroethylene, chlorotrifluoroethylene, cis 3-hexene,
cis-1,3-pentadiene, cis-2-hexene, cis-2-pentene,
dichlorodifluoromethane, difluoromethyl ether, trifluoromethyl
ether, dimethyl ether, ethyl fluoride, ethyl mercaptan,
hexafluoropropylene, isobutane, isobutene, isobutyl mercaptan,
isopentane, isoprene, methyl isopropyl ether, methylcyclohexane,
methylcyclopentane, methylcyclopropane, n,n-diethylmethylamine,
octafluoropropane, pentafluoroethyl trifluorovinyl ether, propane,
sec-butyl mercaptan, trans-2-pentene, trifluoromethyl
trifluorovinyl ether, vinyl chloride, bromotrifluoromethane,
chlorodifluoromethane, dimethyl silane, ketene, methyl silane,
perchloryl fluoride, propylene, vinyl fluoride, or combinations
thereof.
[0033] In some embodiments, the coolant comprises liquid nitrogen,
ethane, methane, propane, or other refrigerants.
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