U.S. patent application number 14/304493 was filed with the patent office on 2015-05-28 for heat recovery vapor trap.
The applicant listed for this patent is Donald C. Erickson. Invention is credited to Donald C. Erickson.
Application Number | 20150144076 14/304493 |
Document ID | / |
Family ID | 53181581 |
Filed Date | 2015-05-28 |
United States Patent
Application |
20150144076 |
Kind Code |
A1 |
Erickson; Donald C. |
May 28, 2015 |
Heat Recovery Vapor Trap
Abstract
A heat recovery vapor trap is provided for removal of vapor
condensate from a container, while preventing any appreciable
escape of vapor, and for achieving beneficial heat recovery from
said condensate prior to temperature degradation associated with
depressurization, whereby useful heating to much higher temperature
is possible. The trap is indirect acting, and is preferably
mechanically actuated by a float.
Inventors: |
Erickson; Donald C.;
(Annapolis, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Erickson; Donald C. |
Annapolis |
MD |
US |
|
|
Family ID: |
53181581 |
Appl. No.: |
14/304493 |
Filed: |
June 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61839095 |
Jun 25, 2013 |
|
|
|
Current U.S.
Class: |
122/456 ;
122/451S; 165/104.14; 165/302 |
Current CPC
Class: |
F28D 21/0012 20130101;
F01K 27/02 20130101; F28B 11/00 20130101; F16T 1/20 20130101; Y02B
30/56 20130101; F28B 9/08 20130101; Y02B 30/566 20130101 |
Class at
Publication: |
122/456 ;
122/451.S; 165/104.14; 165/302 |
International
Class: |
F22B 35/08 20060101
F22B035/08; F28B 9/02 20060101 F28B009/02; F28B 9/08 20060101
F28B009/08; F28B 11/00 20060101 F28B011/00 |
Claims
1. An apparatus for controlling the liquid level in a container
containing saturated vapor and liquid, and for recovering heat from
the liquid discharged from said container by said level control
apparatus, comprising: a. A float actuated mechanical control valve
wherein said float is supported by a liquid level that is in vapor
and liquid communication with said level in said container; b. A
heat recovery heat exchanger having hot and cold ends; c. A first
conduit conveying liquid from said container to said hot end; d. A
second conduit for conveying cooled container liquid from said cold
end to said mechanical float-actuated control valve; and e. A third
conduit for removal of cooled reduced pressure liquid from said
valve
2. The apparatus according to claim 1 wherein said container is
comprised of a steam-heated heat exchanger for a fluid, wherein
said saturated vapor is steam, and additionally comprised of a
feed-effluent heat exchanger for the fluid supplied to and from
said steam-heated heat exchanger, and wherein said heat recovery
heat exchanger is arranged for parallel fluid flow with said
feed-effluent heat exchanger.
3. The apparatus according to claim 1 wherein said float is
contained in said container.
4. The apparatus according to claim 1 additionally comprised of a
housing for said float that is external to said container, plus at
least one fluid conduit connecting said housing to said
container.
5. The apparatus according to claim 1 wherein said valve is
comprised of: a. A rod that rotates inside a cylinder; b. Inlet and
outlet ports in said cylinder that connect to inlet and outlet
fluid conduits of said valve; c. A mechanical connection between
said float and said rod, whereby float movement causes the rod to
rotate; and d. An opening in said rod that aligns with said
cylinder openings at one float position, and misaligns with them at
another.
6. The apparatus according to claim 1 wherein said container is a
desorption column and said saturated vapor is sorbate, and said
liquid is sorbent.
7. The apparatus according to claim 1 wherein said container is a
distillation column.
8. A heat recovery steam trap for a steam heated fluid heat
exchanger, comprised of: a. A condensate level sensing steam trap,
that prevents level buildup in said fluid heat exchanger; b. A
condensate heat recovery heat exchanger; and c. A means for routing
condensate from said fluid heat exchanger sequentially first to
said condensate heat recovery heat exchanger, then to said steam
trap.
9. The apparatus according to claim 8 additionally comprised of a
float for said steam trap that senses said level.
10. The apparatus according to claim 8 additionally comprised of a
level sensor that sends an electronic signal to said steam trap,
which is an electronically-actuated valve.
11. The apparatus according to claim 8 additionally comprised of a
means for splitting said heated fluid into two parallel streams and
routing one stream to said fluid heat exchanger and the other
stream to said condensate heat recovery heat exchanger.
12. The apparatus according to claim 8 additionally comprised of a
second indirect acting steam trap connected to said condensate heat
recovery heat exchanger.
13. An apparatus for removing condensate from a container,
comprised of: a. An indirect acting level control valve for said
container; b. A heat recovery heat exchanger in fluid communication
with said container; and c. A conduit connecting said heat recovery
heat exchanger to said indirect acting level control valve.
14. The apparatus according to claim 13 additionally comprised of
an electronic level sensor, and wherein said valve is an
electronically actuated valve that receives a signal from said
sensor.
15. The apparatus according to claim 13 wherein said valve is float
actuated and additionally comprised of a housing for said valve and
float that is external to said container.
16. The apparatus according to claim 13 wherein said valve and said
float are located internal to said container.
17. The apparatus according to claim 13 wherein said valve is a
float valve comprised of: a. A float; b. A rod that rotates inside
a cylinder; c. Inlet and outlet ports in said cylinder that connect
to inlet and outlet fluid conduits of said valve; d. A mechanical
connection between said float and said rod, whereby float movement
causes the rod to rotate; and e. An opening in said rod that aligns
with said cylinder openings at one float position, and misaligns
with them at another.
18. The apparatus according to claim 13 wherein said container is a
mass transfer column.
19. The apparatus according to claim 13 additionally comprised of a
second indirect acting valve and a second conduit that connects
said heat recovery heat exchanger to said second valve.
20. The apparatus according to claim 13 wherein said heat recovery
heat exchanger is at least partly located inside said container.
Description
[0001] Conventional steam traps decrease the pressure of the
saturated condensate, usually down to the condensate drain pipe
pressure. A decrease in pressure of a saturated liquid represents a
serious degradation of the ability to do useful heating by that
liquid. The pressure reduction yields a two phase saturated mixture
at the lower pressure with a corresponding lower temperature. For
example, consider the use of 100 psig steam (saturation temperature
337 F), used to heat a fluid from 220 F to 300 F. Condensate is
supplied to the steam trap at 337 F. The trap reduces the
condensate pressure to 5 psig, at a saturation temperature of 227
F. With a conventional steam trap, each pound of steam at 100 psig
delivers 881 BTU of useful heating. Conversely, when the condensate
is first used to provide useful sensible heat before being
depressurized, an additional 114 BTU of useful heat can be obtained
from each pound of steam--heat that otherwise ends up as flash
vapor at 5 psig. The vapor temperature at 5 psig (227 F) is too low
to do the required heating, and often that means it is reject heat.
At best it can only be used for low temperature heating, e.g. in a
condensate tank vent condenser. What is needed is a steam trap that
does not depressurize the condensate until after sensible cooling
of the condensate. That is an objective of this invention. The trap
must still maintain the desired liquid level between steam and
condensate, such that condensate does not flood any of the heat
exchange surface.
DISCLOSURE OF INVENTION
[0002] A heat recovery steam trap is disclosed, comprised of a
mechanical float-activated level control valve that controls level
in a container, plus a heat recovery heat exchanger (HRHX). Liquid
condensate removed from said container is first supplied to said
HRHX for cooling, and then supplied to the indirect acting valve
mechanism in said trap for depressurization, and then discharged
into the condensate drain pipe. "Indirect acting" means that the
liquid being depressurized in the trap is not directly from said
container, but is indirectly from the container via said HRHX heat
exchanger. The key advantage achieved is that the fluid being
heated in the HRHX can be heated to a temperature higher than the
saturation temperature corresponding to the condensate drain pipe
pressure (typically equal to the deaeration tank pressure).
[0003] The fluid being heated can be any fluid. If it is the same
fluid as that being heated by the steam, then it is important that
the HRHX be in parallel with another heat exchanger heating the
same fluid, to achieve maximum gain in efficiency.
[0004] The steam trap can either be located externally to said
container (in fluid communication) or internally to said container.
The heat exchanger for sensible cooling of the condensate can be
either an independent dedicated HRHX heat exchanger, or can be a
portion of another heat exchanger, such as the one the trap is
servicing, and including the option of being contained in said
container.
[0005] The disclosed level controlling heat recovery vapor trap may
be used in conjunction with any saturated vapor, i.e. is not
limited to steam.
[0006] The level control mechanism can be other than a mechanical
float, provided that it be capable of achieving the requisite
"indirect acting" function.
[0007] The pressure drop through the HRHX should be low enough on
the condensate side that no appreciable flashing occurs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 depicts a first embodiment of the heat recovery steam
trap, comprised of a mechanical float-actuated indirect acting
level control valve that is located inside the steam-containing
container.
[0009] FIG. 2 illustrates two different applications of the heat
recovery vapor trap, applied in the same apparatus.
[0010] FIG. 3 depicts one preferred configuration of the float
actuated indirect acting level control valve. FIG. 3A is a top
view; FIG. 3B is a cross-sectional view of the rod; FIG. 3C is a
side view with the float in the upmost position; FIG. 3D is a side
view with the float in the lower-most position.
[0011] FIG. 4 illustrates the application of one embodiment of the
heat recovery steam trap to a double effect LiBr absorption
chilling cycle.
[0012] FIG. 5 illustrates applying two heat recovery steam traps to
a double effect LiBr cycle, one on internal condensate and one
external.
BEST MODE FOR CARRYING OUT THE INVENTION
[0013] FIG. 1 illustrates a container 10 wherein a fluid 1 is being
heated by steam via heat exchanger 11. Condensate is discharged
from said container via conduit 14, to a heat recovery heat
exchanger 13, wherein it countercurrently heats fluid 2. Then the
cooled condensate is routed to indirect acting level controlling
steam trap 12. The mechanical float-actuated steam trap 12
maintains the desired zero level of condensate in container 10 by
being located sufficiently below the container that the level in
the trap, controlled by float 15, cannot rise to the container
height. The two fluids may be the same or different.
[0014] FIG. 2 illustrates two simultaneous uses of the heat
recovery vapor trap in the same apparatus. A desorption column 20
is provided for stripping a sorbate from a rich sorbent via
thermally activated multistage vapor liquid contact. The desorber
is reboiled by supplying preheated rich sorbent to a steam heated
reboiler 21. The steam condensate from the reboiler is first routed
in counter current heat exchange 22 with part of the rich sorbent,
then to the valve section of the level controlling trap 23, and
then to the discharge piping 24. Thus both the steam and the hot
condensate are causing the rich sorbent to desorb, and the rich
sorbent is supplied to them in parallel. Although the steam heat
exchanger 25 and the condensate recovery heat exchanger 22 can be
physically separate components, that arrangement would require a
controlled split of the rich sorbent. Hence a preferred arrangement
is to combine both exchange duties in parallel in a single
exchanger 21, as shown. In that way the sorbent split occurs
automatically and inherently. Numerous heat exchanger geometries
are available that permit two hermetically separate fluids on one
side of a heat exchanger, including plate and frame; brazed plate;
opposed slant tube; and triple helix heat exchangers.
[0015] The lean sorbent collects at the bottom of the desorption
column, and must be controllably removed to maintain fixed sorbent
level. That is accomplished by heat recovery vapor trap 26, an
indirect acting level control valve. The bottom liquid is withdrawn
thought heat exchange bundles 27 located on the vapor-liquid
contact trays 28 (e.g. perforated trays). Then it is further cooled
in the rich sorbent preheater 29. Finally it is conveyed to the
valve section of the trap 26, for depressurization.
[0016] This arrangement is useful for any type of desorption: for
example, desorbing ammonia vapor from aqueous ammonia sorbent in an
ammonia absorption refrigeration cycle; or desorbing CO.sub.2 from
a CO.sub.2 scrubbing sorbent in a CO.sub.2 scrubbing cycle. It also
applies to distillation.
[0017] FIGS. 3a, b, c, and d, illustrate one preferred arrangement
for the float-actuated valve section of the vapor trap. A float 30
is connected by a yoke 31 to a rod 32 that rotates in a fixed
cylinder 33. Float movement causes the rod to rotate in the
cylinder. An opening 34 in the rod (e.g. a drilled hole) is
positioned such that when the float is in the up position (high
level, FIG. 3c) the opening aligns with inlet and outlet openings
in the cylinder. That allows liquid to flow in pipe 35 and out pipe
36 thus lowering the level. When the float is in the down position
(low level, FIG. 3d), the opening does not align with the cylinder
openings, and the flow is blocked.
[0018] Hence the rod and cylinder comprise the actual valve, and
the float causes it to actuate responsive to liquid level. Note
that in order to be indirect acting, the valve must have two
connections to outside its container: both inlet and outlet. As is
known in the prior art, the steam trap can additionally have a
vapor purge port for removal of noncondensable gases. The trap may
be located inside a housing 37. Alternatively, the trap may be
located inside the level-controlled container, as in FIG. 1. When
located in its own housing, it requires fluid connections 38 and 39
to reproduce the required level.
[0019] FIG. 4 provides more specific details regarding how the
disclosed heat recovery steam trap can be applied to an absorption
refrigeration cycle in order to achieve about 10% reduction in the
amount of steam necessary to drive the cycle. In this example a
double-effect LiBr absorption cycle is illustrated, comprised of
high temperature generator (HTG), low temperature generator (LTG),
condenser (COND), absorber (ABS), evaporator (EVAP), LiBr pump, and
evaporator water pump. The novel aspect is the treatment of the
steam condensate exiting the HTG steam heat exchanger. The
condensate level is controlled by the level-controlling indirect
acting steam trap 40. The condensate is conveyed first to the float
portion of valve 40 plus to a high temperature heat exchanger
(HTHE) wherein it countercurrently exchanges heat with part of the
LiBr solution enroute to the HTG; then it is conveyed to a low
temperature heat exchanger (LTHE) wherein it countercurrently
exchanges heat with part of the LiBr solution enroute to the LTG;
and then it is conveyed to the mechanical float-actuated level
control valve 40 for depressurization and routing to the condensate
return piping. Steam trap (valve) 40 is located sufficiently below
the HTG that it maintains the desired zero level in the HTG. The
actual level is inside the housing of valve 40. The HTHE and LTHE
are also known as feed-effluent heat exchangers.
[0020] Once again the two condensate heat recovery heat exchangers
can be independent ones, but a preferred arrangement is to combine
them with the HTHE and LTHE that are already present for heat
exchange with returning LiBr, as shown. Also, the same enhancement
can be applied to a single effect LiBr cycle, which does not have
the HTHE.
[0021] FIG. 5 illustrates an additional opportunity to reduce the
driving heat requirement of a double effect LiBr absorption cycle.
This opportunity arises inside the cycle, at the LTG that is being
heated by desorbed vapor from the HTG. The condensate is supplied
to the float side of HRST 41, and to the HRHX (part of the LTHE),
then to the valve side of HRST 41, and finally to COND. There is
still scope for external savings as well with the steam supply HRST
per FIG. 4. An optional alternative configuration is illustrated in
FIG. 5, wherein the indirect-acting level control valve is not a
mechanical float-actuated type. Instead it is comprised of
electronically actuated valve 46, controlled by level sensor 45.
Also, the heat recovery heat exchanger is stand-alone. With that
configuration, to get the full benefit of the higher condensate
temperature, the rich sorbent must be split into two parallel
paths, with only one supplied to the HRHX, e.g. by coordinated
action of valves 43 and 44.
* * * * *