U.S. patent application number 09/847486 was filed with the patent office on 2002-11-07 for process for recovering hydrocarbons from inert gas-hydrocarbon vapor mixtures.
Invention is credited to Dinsmore, Harold L., Fox, Scott J., Lenhart, Melissa G..
Application Number | 20020165419 09/847486 |
Document ID | / |
Family ID | 25300746 |
Filed Date | 2002-11-07 |
United States Patent
Application |
20020165419 |
Kind Code |
A1 |
Lenhart, Melissa G. ; et
al. |
November 7, 2002 |
Process for recovering hydrocarbons from inert gas-hydrocarbon
vapor mixtures
Abstract
An improved process for recovering hydrocarbons from an inlet
inert gas-hydrocarbon vapor mixture is provided. The inlet mixture
is caused to flow through a first bed of solid adsorbent whereby
hydrocarbon vapors are adsorbed on the bed and a residue gas stream
comprised of substantially hydrocarbon-free inert gas is produced.
The hydrocarbon-free inert gas is vented and a second bed of solid
adsorbent having hydrocarbon vapors adsorbed thereon is evacuated
with an ejector operated by a motive liquid. A major portion of the
hydrocarbon vapors is desorbed from the bed and an inert gas and
hydrocarbon-rich vapor mixture commingled with the motive liquid is
produced. The inert gas and hydrocarbon-rich vapor mixture is
separated from the motive liquid and conducted to a point of
additional processing or disposal. The flow pattern of the inlet
inert gas-hydrocarbon vapor mixture is periodically changed whereby
when the bed through which the inlet inert gas-hydrocarbon vapor
mixture is flowing becomes loaded, the inlet inert gas-hydrocarbon
vapor mixture is caused to flow through the bed which has just been
evacuated and the bed loaded with adsorbed hydrocarbon vapors is
caused to be regenerated.
Inventors: |
Lenhart, Melissa G.;
(Haskell, OK) ; Dinsmore, Harold L.; (Tulsa,
OK) ; Fox, Scott J.; (Broken Arrow, OK) |
Correspondence
Address: |
McAfee & Taft
Two Leadership Square
10th Floor
211 N. Robinson
Oklahoma City
OK
73102
US
|
Family ID: |
25300746 |
Appl. No.: |
09/847486 |
Filed: |
May 2, 2001 |
Current U.S.
Class: |
585/810 ;
585/820; 585/823; 585/828 |
Current CPC
Class: |
C10G 5/02 20130101; C07C
7/12 20130101 |
Class at
Publication: |
585/810 ;
585/820; 585/823; 585/828 |
International
Class: |
C07C 007/00; C07C
007/12; C07C 007/14 |
Claims
What is claimed is:
1. An improved process for recovering hydrocarbon vapors from an
inlet inert gas-hydrocarbon vapor mixture comprising the steps of:
(a) flowing said inlet mixture through a first bed of solid
adsorbent having an affinity for hydrocarbon vapors whereby
hydrocarbon vapors are adsorbed on said bed and a residue gas
stream comprised of substantially hydrocarbon-free inert gas is
produced; (b) venting said substantially hydrocarbon-free inert gas
to the atmosphere; (c) evacuating a second bed of solid adsorbent
having hydrocarbon vapors adsorbed thereon with an ejector operated
by a motive liquid whereby a major portion of said hydrocarbon
vapors is desorbed from said bed and an inert gas and
hydrocarbon-rich vapor mixture commingled with said motive liquid
is produced; (d) separating said inert gas and hydrocarbon-rich
vapor mixture from said motive liquid; (e) conducting said inert
gas and hydrocarbon rich vapor mixture to a point of additional
processing or disposal; and (f) periodically changing the flow
pattern of said inlet inert gas-hydrocarbon vapor mixture and
changing the bed of solid adsorbent being evacuated whereby when
the bed through which the inlet inert gas-hydrocarbon vapor mixture
is flowing becomes loaded with adsorbed hydrocarbon vapors, the
inlet inert gas-hydrocarbon vapor mixture is caused to flow through
the bed which has just been evacuated and the bed loaded with
adsorbed hydrocarbon vapors is caused to be regenerated.
2. The process of claim 1 wherein said inert gas is selected from
the group consisting of air, nitrogen and carbon dioxide.
3. The process of claim 1 wherein said hydrocarbon vapor is
selected from the group consisting of gasoline vapors, distillate
vapors, benzene vapor, chlorinated and other hydrocarbon solvent
vapors and alcohol vapors.
4. The process of claim 1 wherein said motive liquid is selected
from the group consisting of glycol, water, petroleum based oils,
hydrocarbon liquids, alcohols and various synthetic fluids.
5. The process of claim 1 which further comprises the step of
introducing a quantity of hydrocarbon-free inert gas into said
second bed while evacuating said second bed in accordance with step
(c) whereby additional hydrocarbons are stripped from said second
bed.
6. The process of claim 1 wherein said motive liquid separated in
accordance with step (d) is recirculated to said ejector.
7. The process of claim 6 wherein said motive liquid is cooled
prior to being recirculated to said ejector.
8. An improved process for recovering hydrocarbon vapors from an
inlet inert gas-hydrocarbon vapor mixture comprising the steps of:
(a) flowing said inlet mixture through a first bed of solid
adsorbent having an affinity for hydrocarbon vapors whereby
hydrocarbon vapors are adsorbed on said bed and a residue gas
stream comprised of substantially hydrocarbon-free inert gas is
produced; (b) venting said substantially hydrocarbon-free inert gas
to the atmosphere; (c) evacuating a second bed of solid adsorbent
having hydrocarbon vapors adsorbed thereon with an ejector operated
by a lean absorbent motive liquid from a separate process or
storage having an affinity for said hydrocarbon vapors whereby a
major portion of said hydrocarbon vapors is desorbed from said bed
and a major portion of said desorbed hydrocarbon vapors is absorbed
in said motive liquid thereby forming a hydrocarbon-rich absorbent
motive liquid and an inert gas-nonabsorbed hydrocarbon vapor
mixture commingled with said hydrocarbon-rich motive liquid; (d)
separating said inert gas-non-absorbed hydrocarbon vapor mixture
from said hydrocarbon-rich absorbent motive liquid; (e) recycling
said separated inert gas-non-absorbed hydrocarbon vapor mixture to
said inlet inert gas-hydrocarbon vapor mixture prior to when said
inlet mixture flows through said first bed of solid adsorbent
wherein hydrocarbon vapors are being adsorbed in accordance with
step (a); and (f) periodically changing the flow pattern of said
inlet inert gas-hydrocarbon vapor mixture and changing the bed of
solid adsorbent being evacuated whereby when the bed through which
the inlet inert gas-hydrocarbon vapor mixture is flowing becomes
loaded with adsorbed hydrocarbon vapors, the inlet inert
gas-hydrocarbon vapor mixture is caused to flow through the bed
which has just been evacuated and the bed loaded with adsorbed
hydrocarbon vapors is caused to be regenerated.
9. The process of claim 8 which further comprises the step of
introducing a quantity of hydrocarbon-free inert gas into said
second bed while evacuating said second bed in accordance with step
(c) whereby additional hydrocarbon vapors are stripped from said
second bed.
10. The process of claim 9 wherein said hydrocarbon-rich absorbent
motive liquid separated in accordance with step (d) is returned to
said separate process or storage.
11. The process of claim 1 which further comprises the additional
process steps of: (g) contacting said inert gas and
hydrocarbon-rich vapor mixture separated in accordance with step
(d) with a lean liquid absorbent whereby a major portion of said
hydrocarbon vapors in said mixture are absorbed in said lean liquid
absorbent; (h) separating the resulting rich liquid absorbent from
the remaining inert gas and non-absorbed hydrocarbon vapors; (i)
conducting said rich liquid absorbent to a point of further
processing or storage; and (j) recycling the remaining inert gas
and non-absorbed hydrocarbon vapors separated in step (h) to said
inlet inert gas-hydrocarbon vapor mixture prior to when said inlet
mixture flows through said bed of solid adsorbent wherein
hydrocarbon vapors are being adsorbed in accordance with step
(a).
12. The process of claim 1 which further comprises the additional
process steps of: (g) contacting said inert gas and
hydrocarbon-rich vapor mixture separated in accordance with step
(d) with condensed hydrocarbon liquid whereby a major portion of
said hydrocarbon vapors in said mixture are also condensed; (h)
separating the condensed hydrocarbon liquid produced in step (g)
from the remaining inert gas non-condensed hydrocarbon vapors; (i)
recycling a portion of said condensed hydrocarbon liquid separated
in step (h) into contact with said inert gas and hydrocarbon-rich
vapor mixture in accordance with step (a); (j) conducting the
remaining condensed hydrocarbon liquid separated in step (h) to a
point of further processing or storage; (k) recycling the remaining
inert gas and non-condensed hydrocarbon vapors separated in step
(h) to said inlet inert gas-hydrocarbon vapor mixture prior to when
said inlet mixture flows through said bed of solid adsorbent
wherein hydrocarbon vapors are being adsorbed in accordance with
step (a).
13. The process of claim 6 which further comprises the additional
process steps of: (g) dividing a lean liquid absorbent into first
and second portions; (h) passing said first portion of said lean
liquid absorbent in heat exchange relationship with said motive
liquid whereby said motive liquid is cooled prior to step (c); (i)
contacting said inert gas and hydrocarbon-rich vapor mixture
separated in accordance with step (d) with said first portion of
said lean liquid absorbent in an absorber whereby a portion of said
hydrocarbon vapors in said mixture is absorbed in said lean liquid
absorbent; (j) contacting the remaining inert gas and
hydrocarbon-rich vapor mixture separated in accordance with step
(d) with said second portion of lean liquid absorbent in said
absorber whereby a second portion of said hydrocarbon vapors in
said mixture is absorbed in said second portion of lean liquid
absorbent; (k) separating the resulting combined rich liquid
absorbent from the remaining inert gas and non-absorbed hydrocarbon
vapors; (l) conducting the resulting combined rich liquid absorbent
from said absorber to a point of further processing or storage; and
(m) recycling the remaining inert gas and non-absorbed hydrocarbon
vapors separated in step (k) to said inlet inert gas-hydrocarbon
vapor mixture prior to when said inlet mixture flows through said
bed of solid adsorbent wherein hydrocarbon vapors are being
adsorbed in accordance with step (a).
14. The process of claim 1 which further comprises the additional
process steps of: (g) passing said inert gas and hydrocarbon-rich
vapor mixture in heat exchange relationship with a cooling medium
whereby a major portion of said hydrocarbon vapors in said mixture
are condensed; (h) separating said condensed hydrocarbon vapors
from the remaining inert gas and non-condensed hydrocarbon vapor
mixture; (i) conducting the separated condensed hydrocarbon vapors
to a point of further processing or storage; and (j) recycling said
remaining inert gas and non-condensed hydrocarbon vapor mixture
separated in step (h) to said inlet inert gas-hydrocarbon vapor
mixture prior to when said inlet mixture flows through said bed of
solid adsorbent wherein hydrocarbon vapors are being adsorbed in
accordance with step (a).
15. The process of claim 14 which further comprises the step of
compressing said inert gas and hydrocarbon-rich vapor mixture prior
to step (g).
16. The process of claim 1 which further comprises the additional
process steps of: (g) conducting said inert gas and
hydrocarbon-rich vapor mixture separated in accordance with step
(d) to a second ejector operated by a motive liquid having an
affinity for hydrocarbon vapors whereby a major portion of said
hydrocarbon-rich vapors is absorbed in said motive liquid; (h)
separating said motive liquid having said hydrocarbon vapors
absorbed therein from the remaining inert gas and non-absorbed
hydrocarbon vapor mixture; (i) conducting said motive liquid having
said hydrocarbon vapors absorbed therein to a point of further
processing or storage; and (j) recycling the remaining inert gas
and non-absorbed hydrocarbon vapor mixture separated in step (h) to
said inlet inert gas-hydrocarbon vapor mixture prior to when said
inlet mixture flows through said bed of solid adsorbent wherein
hydrocarbon vapors are being adsorbed in accordance with step
(a).
17. An improved process for recovering hydrocarbon vapors from an
inlet inert gas-hydrocarbon vapor mixture comprising the steps of:
(a) flowing said inlet mixture through a first bed of solid
adsorbent having an affinity for hydrocarbon vapors whereby
hydrocarbon vapors are adsorbed on said bed and a residue gas
stream comprised of substantially hydrocarbon-free inert gas is
produced; (b) venting said substantially hydrocarbon-free inert gas
to the atmosphere; (c) evacuating a second bed of solid adsorbent
having hydrocarbon vapors adsorbed thereon with an ejector operated
by a motive liquid whereby a major portion of said hydrocarbon
vapors is desorbed from said bed and an inert gas and
hydrocarbon-rich vapor mixture commingled with said motive liquid
is produced; (d) separating said inert gas and hydrocarbon-rich
vapor mixture from said motive liquid; (e) periodically changing
the flow pattern of said inlet inert gas-hydrocarbon vapor mixture
and changing the bed of solid adsorbent being evacuated whereby
when the bed through which the inlet inert gas-hydrocarbon vapor
mixture is flowing becomes loaded with adsorbed hydrocarbon vapors,
the inlet inert gas-hydrocarbon vapor mixture is caused to flow
through the bed which has just been evacuated and the bed loaded
with adsorbed hydrocarbon vapors is caused to be regenerated; (f)
contacting said inert gas and hydrocarbon-rich vapor mixture
separated in accordance with step (d) with a lean liquid absorbent
whereby a major portion of said hydrocarbon vapors in said mixture
is absorbed in said lean liquid absorbent; (g) separating the
resulting rich liquid absorbent from the remaining inert gas and
non-absorbed hydrocarbon vapors; (h) conducting said rich liquid
absorbent to a point of further processing or storage; and (i)
recycling the remaining inert gas and non-absorbed hydrocarbon
vapors separated in step (g) to said inlet inert gas-hydrocarbon
vapor mixture prior to when said inlet mixture flows through said
bed of solid adsorbent wherein hydrocarbon vapors are being
adsorbed in accordance with step (a).
18. The process of claim 17 wherein said inert gas is selected from
the group consisting of air, nitrogen and carbon dioxide.
19. The process of claim 17 wherein said hydrocarbon vapor is
selected from the group consisting of gasoline vapors, distillate
vapors, benzene vapor, chlorinated and other hydrocarbon solvent
vapors and alcohol vapors.
20. The process of claim 17 wherein said motive liquid is selected
from the group consisting of glycol, water, petroleum based oils,
hydrocarbon liquids, alcohols and various synthetic fluids.
21. The process of claim 17 which further comprises the step of
introducing a quantity of hydrocarbon-free inert gas into said
second bed while evacuating said second bed in accordance with step
(c) whereby additional hydrocarbon vapors are stripped from said
second bed.
22. The process of claim 17 wherein said motive liquid is
recirculated to said ejector.
23. The process of claim 17 wherein said motive liquid is cooled
prior to being recirculated to said ejector.
24. The process of claim 17 wherein said motive liquid is a
continuous stream which passes through said ejector only once.
25. An improved process for recovering hydrocarbon vapors from an
inlet inert gas-hydrocarbon vapor mixture comprising the steps of:
(a) flowing said inlet mixture through a first bed of solid
adsorbent having an affinity for hydrocarbon vapors whereby
hydrocarbon vapors are adsorbed on said bed and a residue gas
stream comprised of substantially hydrocarbon-free inert gas is
produced; (b) venting said substantially hydrocarbon-free inert gas
to the atmosphere; (c) evacuating a second bed of solid adsorbent
having hydrocarbon vapors adsorbed thereon with an ejector operated
by a lean absorbent motive liquid from a separate process or
storage having an affinity for said hydrocarbon vapors whereby a
major portion of said adsorbed hydrocarbon vapors is desorbed from
said bed and a major portion of said desorbed hydrocarbon vapors is
absorbed in said motive liquid thereby forming a hydrocarbon-rich
absorbent motive liquid and an inert gas-non-absorbed hydrocarbon
vapor mixture commingled with said hydrocarbon-rich motive liquid;
(d) separating said hydrocarbon rich motive liquid from said inert
gasnon-absorbed hydrocarbon vapor mixture; (e) conducting said
hydrocarbon rich motive liquid to said separate process or storage;
(f) recycling said separated inert gas-non-absorbed hydrocarbon
vapor mixture to said inlet inert gas-hydrocarbon vapor mixture
prior to when said inlet mixture flows through said bed of solid
adsorbent wherein hydrocarbon vapors are being adsorbed in
accordance with step (a); and (g) periodically changing the flow
pattern of said inlet inert gas-hydrocarbon vapor mixture and
changing the bed of solid adsorbent being evacuated whereby the bed
through which the inlet inert gas-hydrocarbon vapor mixture is
flowing becomes loaded with adsorbed hydrocarbon vapors, the inlet
inert gas-hydrocarbon vapor mixture is caused to flow through the
bed which has just been evacuated and the bed loaded with adsorbed
hydrocarbon vapors is caused to be regenerated.
26. The process of claim 25 wherein said inert gas is selected from
the group consisting of air, nitrogen and carbon dioxide.
27. The process of claim 25 wherein said hydrocarbon vapors are
selected from the group consisting of gasoline vapors, distillate
vapors, benzene vapor, chlorinated and other hydrocarbon solvent
vapors and alcohol vapors.
28. The process of claim 25 wherein said motive liquid is selected
from the group consisting of glycol, water, petroleum based oils,
hydrocarbon liquids, alcohols and various synthetic fluids.
29. The process of claim 25 which further comprises the step of
introducing a quantity of hydrocarbon-free inert gas into said
second bed while evacuating said second bed in accordance with step
(c) whereby additional hydrocarbon vapors are stripped from said
second bed.
30. The process of claim 25 wherein said hydrocarbon-rich motive
liquid is cooled prior to step (e).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a process for recovering
hydrocarbons from inert gas-hydrocarbon vapor mixtures, and more
particularly, to an improved process for recovering vaporized
gasoline, distillates, benzene, solvents and the like from a
mixture thereof with inert gas.
[0003] 2. Description of the Prior Art
[0004] In handling multi component and single component hydrocarbon
liquids such as gasoline, inert gas hydrocarbon vapor mixtures are
readily produced which cannot be vented directly to the atmosphere
due to the resulting pollution and fire or explosion hazard. As a
result, a variety of processes have heretofore been developed and
used for removing hydrocarbon vapors from inert gas-hydrocarbon
vapor mixtures whereby the remaining inert gas can be safely vented
to the atmosphere. The removed hydrocarbon vapors are recovered,
processed further or disposed of.
[0005] A particularly suitable prior art process for recovering
hydrocarbons from air-hydrocarbon vapor mixtures and the like is
described in U.S. Pat. No. 5,154,735 issued to Dinsmore et al. on
Oct. 13, 1992. The process comprises the steps of flowing the inlet
air-hydrocarbon vapor mixture through a first bed of solid
adsorbent whereby hydrocarbons are adsorbed on the bed and a
residue gas stream comprised of substantially hydrocarbon-free air
which is vented to the atmosphere is produced. A second bed of
solid adsorbent having hydrocarbons adsorbed thereon is regenerated
by vacuum pumping whereby hydrocarbons are desorbed from the bed
and a hydrocarbon rich air-hydrocarbon mixture is produced. A
substantial portion of the hydrocarbons are recovered from the
hydrocarbon rich air-hydrocarbon vapor mixture produced during the
regeneration. The beds of adsorbent are periodically changed from
adsorption to regeneration and vice versa so that the bed which has
just become loaded with adsorbed hydrocarbons is regenerated, i.e.,
evacuated and stripped of hydrocarbons and the bed which has just
been regenerated adsorbs hydrocarbons. The evacuation of the beds
during regeneration is accomplished in the process of U.S. Pat. No.
5,154,735 by vacuum pumping with a liquid seal vacuum pump. In
order to increase the evacuation, a positive displacement booster
pump connected upstream and in series with the liquid seal vacuum
pump is utilized in combination with the introduction of a
relatively small quantity of hydrocarbon-free air into the bed
being evacuated whereby additional hydrocarbons are stripped from
the bed. The further evacuation accomplished by the booster pump
and air stripping results in the bed being regenerated to a low
hydrocarbon content and in substantially hydrocarbon-free air being
vented to the atmosphere.
[0006] While the above described process utilizing a positive
displacement booster pump in series with a liquid seal vacuum pump
has achieved great commercial success, the cost of the pumps, their
maintenance and their operation are expensive. Thus, there are
needs for improved processes capable of regenerating beds of solid
adsorbent to a very low hydrocarbon content which are less costly
to install, operate and maintain.
SUMMARY OF THE INVENTION
[0007] The present invention provides improved processes for
recovering hydrocarbon vapors from intermittent or continuous inlet
inert gas-hydrocarbon vapor mixtures which meet the needs described
above and overcome the deficiencies of the prior art. The improved
processes of the present invention are basically comprised of the
following steps. An inlet inert gas-hydrocarbon vapor mixture is
flowed through a first bed of solid adsorbent having an affinity
for hydrocarbons whereby hydrocarbons are adsorbed on the bed and a
residue gas stream comprised of substantially hydrocarbon-free
inert gas is produced. The substantially hydrocarbon-free inert gas
is vented to the atmosphere. A second bed of solid adsorbent having
hydrocarbons adsorbed thereon is evacuated with a simple ejector
which is operated by a continuous motive liquid stream whereby a
major portion of the hydrocarbons are desorbed from the bed and an
inert gas-hydrocarbon-rich vapor mixture commingled with motive
liquid is produced. The inert gas-hydrocarbon-rich vapor mixture is
separated from the motive liquid and is processed further or
disposed of. The flow pattern of the inlet inert gas-hydrocarbon
vapor mixture is periodically changed so that when the bed through
which the inlet inert gas-hydrocarbon vapor mixture is flowing
becomes loaded with adsorbed hydrocarbons, the inlet inert
gas-hydrocarbon vapor mixture is caused to flow through the bed
which has just been evacuated and the bed loaded with adsorbed
hydrocarbons is regenerated. The basic processes also preferably
include the step of introducing a quantity of hydrocarbon-free
inert stripping gas into the bed being evacuated whereby additional
hydrocarbons are stripped from the bed and additional inert
gas-hydrocarbon-rich vapor mixture co-mingled with motive liquid is
produced.
[0008] In alternate embodiments of the basic process of the present
invention, the motive liquid can be recirculated through the
ejector or the motive liquid can be a continuous stream which
passes through the ejector only once. In addition, the motive
liquid can be a liquid which has an affinity for the desorbed
hydrocarbon vapor whereby a major portion of the hydrocarbon vapor
is absorbed in the motive liquid as it passes through the
ejector.
[0009] In addition to the above described basic processes, the
present invention provides a variety of additional process steps
which can be utilized in accordance with this invention to liquefy
and recover the desorbed hydrocarbon vapor.
[0010] It is, therefore, a general object of the present invention
to provide improved processes for recovering hydrocarbons from
inert gas-hydrocarbon vapor mixtures.
[0011] Other and further objects, features and advantages of the
present invention will be readily apparent to those skilled in the
art upon a reading of the description of preferred embodiments
which follows when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic illustration of apparatus for carrying
out a basic process of this invention.
[0013] FIG. 2 is a schematic illustration of apparatus for carrying
out another basic process of this invention.
[0014] FIG. 3 is a schematic illustration of apparatus for carrying
out still another basic process of the present invention.
[0015] FIG. 4 is a schematic illustration of apparatus for carrying
out additional process steps for liquefying and recovering the
hydrocarbon vapors produced by a basic process of this
invention.
[0016] FIG. 5 is a schematic illustration of apparatus for carrying
out other additional process steps for liquefying and recovering
the hydrocarbon vapors produced by a basic process of this
invention.
[0017] FIG. 6 is a schematic illustration of apparatus for carrying
out a basic process of this invention as well as other alternate
additional process steps for liquefying and recovering the
hydrocarbon vapors produced by the basic process.
[0018] FIG. 7 is a schematic illustration of apparatus for carrying
out still other additional process steps for liquefying and
recovering the hydrocarbon vapor produced by a basic process.
[0019] FIG. 8 is a schematic illustration of apparatus for carrying
out an alternate form of the additional process steps of FIG. 7 for
liquefying and recovering the hydrocarbon vapor produced by a basic
process.
[0020] FIG. 9 is a schematic illustration of apparatus for carrying
out yet other additional process steps for liquefying and
recovering the hydrocarbon vapor produced by a basic process.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] Referring now to FIG. 1, apparatus for carrying out a basic
process of the present invention is illustrated and generally
designated by the numeral 10. The apparatus 10 is comprised of a
pair of absorbers 12 and 14, each of which contains a bed of solid
adsorbent through which gases can flow. Each of the adsorbers 12
and 14 are closed vessels and include connections on opposite sides
of the beds of adsorbent contained therein, i.e., the adsorber 12
includes inlet and outlet connections 16 and 18 and the adsorber 14
includes inlet and outlet connections 20 and 22. While various
solid adsorbents having an infinity for hydrocarbons can be
utilized in the adsorbers 12 and 14, activated carbon is preferred
in that it is particularly suitable for adsorbing light hydrocarbon
vapors of the type found in inert gas-hydrocarbon vapor mixtures
and for vacuum regeneration.
[0022] An inert gas-hydrocarbon vapor mixture inlet header 24 is
provided connected to a conduit 26 which conducts an inlet mixture
of inert gas and hydrocarbon vapor from a source thereof to the
apparatus 10. The inert gas can be, but is not limited to, air,
nitrogen, carbon dioxide and the like. The hydrocarbon vapor can
be, but is not limited to, gasoline light end vapors, distillate
light end vapors, benzene vapor, chlorinated and other hydrocarbon
solvent light end vapors and alcohol vapors.
[0023] A pair of conduits 28 and 30 are connected to the header 24
and to the connections 16 and 20 of the adsorbers 12 and 14,
respectively. Conventional switching valves 32 and 34, or their
equivalents, are disposed in the conduits 28 and 30, respectively.
A header 36 is connected to the conduits 28 and 30 at points
thereon between the switching valves 32 and 34 and the connections
16 and 20 of the adsorbers 12 and 14. A pair of switching valves 38
and 40, or their equivalents, are disposed in the header 36 and a
conduit 42 is connected to the header 36 at a point between the
switching valves 38 and 40.
[0024] A residue gas header 44 is provided, and a pair of conduits
46 and 48 are connected to the header 44 and to the connections 18
and 22 of the adsorbers 12 and 14. Switching valves 50 and 52, or
their equivalents, are disposed in the conduits 46 and 48,
respectively, and a conduit 54 is connected to the header 44 for
venting substantially hydrocarbon free residue inert gas to the
atmosphere.
[0025] A conduit 56 connected to a source of stripping inert gas
(not shown), which can optionally be heated, is connected to a
inert stripping gas connection 58 in the adsorber 12. A switching
valve 60, or the equivalent, is disposed in the conduit 56. In a
like manner, stripping inert gas is conducted to the adsorber 14 by
a conduit 62 connected to a connection 64 in the adsorber 14. A
switching valve 66, or the equivalent, is disposed in the conduit
62.
[0026] The conduit 42 connected to the header 36 is connected to
the suction connection 70 of a motive liquid ejector 72. The
ejector 72 includes a motive liquid inlet connection 74 and an
inert gas-hydrocarbon-rich vapor mixture-motive liquid outlet
connection 76 which is in turn connected by a conduit 78 to an
inlet connection 80 of an inert gas-hydrocarbon-rich vapor
mixture-motive liquid separator 82. The separated motive liquid
accumulates in the bottom of the separator 82 and is withdrawn
therefrom by way of a connection 84. A conduit 86 connected to the
connection 84 conducts the motive liquid withdrawn from the
separator 82 to the motive liquid inlet connection 74 of the
ejector 72. A motive liquid cooler 88, which can be a shell and
tube heat exchanger, an air cooler, an evaporative cooler or the
like, is disposed in the conduit 86 as is a motive liquid pump 90.
The inert gas and hydrocarbon-rich vapor separated in the separator
82 is withdrawn therefrom by way of an outlet connection 92 and a
conduit 94 connected thereto.
[0027] The motive liquid ejector 72 is operated by the motive
liquid which is pumped into the ejector by the pump 90 by way of
the connection 74. The high velocity flow of the motive liquid
passing through the ejector 72 withdraws inert gas and hydrocarbon
vapors from the adsorber 12 or 14 being regenerated thereby
evacuating the adsorber. The motive liquid can be any suitable
liquid including, but not limited to, glycol, water, petroleum
based oils, hydrocarbon liquids, alcohols and various synthetic
liquids. The motive liquid is continuously circulated from the
separator 82, through the motive liquid cooler 88 and into the
ejector 72 by the motive liquid pump 90.
[0028] The flow pattern of the inlet inert gas-hydrocarbon vapor
mixture is periodically changed as is the bed of solid adsorbent
being evacuated. That is, when the adsorbent bed through which the
inlet inert gas-hydrocarbon vapor mixture is flowing becomes loaded
with adsorbed hydrocarbons, the inlet inert gas-hydrocarbon vapor
mixture is caused to flow through the bed which has just been
evacuated and the bed loaded with adsorbed hydrocarbons is
regenerated.
[0029] The ejector 72 functions as a jet pump to evacuate the
adsorber being regenerated. A particularly suitable ejector (also
referred to as a gas and fluid jet apparatus) for use in accordance
with the present invention is described in U.S. Pat. No. 6,164,567
issued to Popov on Dec. 26, 2000 which is incorporated herein by
reference. The ejector of U.S. Pat. No. 6,164,567 has an increased
capacity and creates a greater depth of vacuum than prior art
ejectors making it particularly suitable for use in the processes
of this invention. The size of the ejector and the flow rate of the
motive liquid through the ejector determine its capacity to
withdraw gases from the adsorbers 12 and 14 and create the required
vacuum therein. Generally, a motive liquid flow rate in the range
of from about 100 to about 1,000 gallons per minute is required for
the processes of this invention.
[0030] The inert gas and hydrocarbon-rich vapor mixture separated
in the separator 82 is conducted by the conduit 94 to a point of
further processing or disposal. Various preferred additional
process steps which can be utilized with a basic process of this
invention for liquefying and recovering the hydrocarbon-rich vapors
are described hereinbelow.
[0031] Referring now to FIG. 2, the apparatus for carrying out a
basic process of this invention utilizing a continuous stream of
motive liquid which passes through the ejector only once is
illustrated. The reference numerals of FIG. 2 are the same as those
used in FIG. 1 except for the motive liquid inlet conduit 98, the
motive liquid pump 92, the optional cooler 94 and the motive liquid
outlet pump 96. That is, a continuous stream of motive liquid from
a separate process or from storage (not shown) is utilized. The
motive liquid enters the apparatus 10 by way of a conduit 98 which
is connected to the motive liquid inlet connection 74 of the
ejector 72. The motive liquid flows through the ejector 72 and
separator 82 only once and is withdrawn from the separator by way
of the outlet connection 84 and a conduit 96 having a pump 92 and
an optional cooler 94 disposed therein. The conduit 96 and pump 92
return the stream of motive liquid to the separate process or
storage facility.
[0032] Referring now to FIG. 3, the apparatus for carrying out
another basic process of this invention is illustrated utilizing
the same reference numerals as those used in FIG. 1. The only
difference in FIG. 2 and FIG. 3 is that the motive liquid used has
an affinity for hydrocarbon vapors (the motive liquid absorbs
hydrocarbon vapors). That is, a continuous stream of a lean
absorbent motive liquid from a separate process or storage facility
is conducted by the conduit 98 to the inlet connection 74 of the
ejector 72. Examples of lean absorbent motive liquids that can be
used include, but are not limited to, gasoline, diesel oil,
naphtha, kerosene and various hydrocarbon solvents and alcohols.
The lean absorbent motive liquid flows through the ejector 72
wherein it causes inert gas and hydrocarbon-rich vapor to be
withdrawn from the adsorber being regenerated into the ejector. As
a result of the contact between the lean absorbent motive liquid
and the inert gas and hydrocarbon-rich vapor within the ejector, a
major portion of the hydrocarbon-rich vapor is absorbed therein.
The resulting hydrocarbon-rich absorbent motive liquid is separated
in the separator 82 and withdrawn therefrom by way of the
connection 84 thereof, the conduit 96 and the pump 92. The pump 92
pumps the hydrocarbon-rich absorbent motive liquid through the
conduit 96 and the optional cooler 94 and returns the hydrocarbon
rich absorbent motive liquid to the separate process or storage.
The inert gas and non-absorbed hydrocarbon vapor separated in the
separator 82 is withdrawn therefrom by way of the connection 92 and
conduit 94. The conduit 94 can be connected to the header 24
whereby the inert gas and non-absorbed hydrocarbon vapor is
recycled to the adsorber 12 or 14 through which the inlet inert
gas-hydrocarbon vapor mixture is flowing.
[0033] Referring now to FIG. 4, apparatus is illustrated for
carrying out additional process steps that can be used for
liquefying and recovering hydrocarbons from the inert gas and
hydrocarbon-rich vapor stream produced by the basic processes
described in connection with FIGS. 1 and 2. The apparatus is
comprised of a condenser column 100 having a packed section or the
equivalent 102, an internal spray nozzle 104 connected to an inlet
connection 106, a condensed hydrocarbon liquid accumulator section
107, a condensed hydrocarbon liquid outlet connection 108, a
non-condensed hydrocarbon and inert gases outlet connection 120 and
an inert gas and hydrocarbon-rich vapor inlet connection 124. The
conduit 94 from a basic process illustrated in FIG. 1 or FIG. 2
conducts inert gas and hydrocarbon-rich vapor to the condenser
column 100. The inert gas and hydrocarbon-rich vapor flowing
upwardly through the packed section 102 of the condenser column 100
is contacted by downwardly flowing condensed hydrocarbon liquid
from the spray nozzle 104. The cool downwardly flowing condensed
hydrocarbon liquid condenses a major portion of the hydrocarbon
vapor in the upwardly flowing inert gas and hydrocarbon-rich vapor
mixture. The resulting condensed hydrocarbons accumulate in the
accumulator section 107 of the condenser column 100 and are
withdrawn therefrom by way of the outlet connection 108. A conduit
110 leads the condensed hydrocarbons to a pump 112 which pumps the
hydrocarbons into and through the conduit 114 connected thereto. A
cooler 116 is disposed in the conduit 114. While the cooler 116 is
illustrated as an air cooler, any suitable form of cooler can be
utilized. A portion of the cooled hydrocarbons flowing through the
conduit 114 is diverted into the conduit 118 with the remaining
recovered hydrocarbons being conducted to storage. The side stream
of hydrocarbons flowing through the conduit 118 passes by way of
the connection 106 into and through the spray nozzle 104 and
contacts the inert gas and hydrocarbon-rich vapor flowing upwardly
as described above. The inert gas and the non-condensed hydrocarbon
vapor remaining pass out of the column 100 by way of the connection
120 into the recycle conduit 122. The recycle conduit 122 returns
the inert gas and non-condensed hydrocarbon vapor to the inlet
header 24 of the basic process illustrated in FIGS. 1 or 2 whereby
it flows into the adsorber through which the inlet inert
gas-hydrocarbon vapor mixture is flowing.
[0034] Thus, the additional process steps for liquefying and
recovering hydrocarbons from the inert gas and hydrocarbon vapor
mixture produced by a basic process of this invention described in
connection with FIG. 4 are comprised of: (1) contacting the inert
gas and hydrocarbon vapor mixture with condensed hydrocarbon liquid
whereby a major portion of the hydrocarbon vapor in the mixture is
also condensed; (2) separating the condensed hydrocarbon liquid
from the remaining inert gas and non-condensed hydrocarbon vapor;
(3) recycling a portion of the separated condensed hydrocarbon
liquid into contact with the inert gas and hydrocarbon vapor
mixture in accordance with step (1); (4) conducting the remaining
separated condensed hydrocarbon liquid to a point of further
processing or storage, and (5) recycling the remaining inert gas
and non-condensed hydrocarbon vapor to the inlet inert
gas-hydrocarbon vapor mixture whereby the remaining inert gas and
non-condensed hydrocarbon vapor flows into the bed of adsorbent
wherein hydrocarbon vapors are being adsorbed.
[0035] Referring now to FIG. 5, an apparatus is shown for carrying
out alternate additional process steps for liquefying and
recovering hydrocarbons from the inert gas and hydrocarbon-rich
vapor mixture produced by a basic process described in connection
with FIGS. 1 or 2. The apparatus is comprised of an absorber column
126 having a packed section or the equivalent 128, an internal
spray nozzle 130 connected to a lean liquid absorbent inlet
connection 132, a rich liquid absorbent accumulator section 135, a
rich liquid absorbent outlet connection 139, an inert gas and
hydrocarbon-rich vapor mixture inlet connection 136 and a recycle
vapor outlet connection 142. The inert gas and hydrocarbon-rich
vapor mixture is conducted to the inlet connection 136 of the
absorber column 126 by the conduit 94. As the inert gas and
hydrocarbon-rich vapor mixture flows upwardly in the absorber
column 126 and through the packed section 128 thereof, it is
contacted by lean liquid absorbent from storage or other location
flowing downwardly in the absorber 126 and through the packed
section 128. As a result, a major portion of the hydrocarbon vapors
in the inert gas and hydrocarbon vapor mixture is absorbed in the
lean liquid absorbent. The lean liquid absorbent is conducted to
the absorber 126 by a conduit 134 which is connected to the lean
liquid absorbent inlet connection 132 and the internal spray nozzle
130. The rich liquid absorbent produced in the absorber 126 is
separated from the inert gas and hydrocarbon vapor mixture therein
and accumulates in the bottom accumulator section 135 of the
absorber 126. The rich liquid absorbent is removed from the
absorber 126 by way of the rich liquid absorbent outlet connection
139, a conduit 140 and a return pump 142. The rich liquid absorbent
is conducted from the pump 142 to storage or other location by a
conduit 146 connected to the discharge of the pump 142.
[0036] Thus, the additional process steps for liquefying and
recovering hydrocarbons from the inert gas and hydrocarbon vapor
mixture produced by a basic process of this invention described in
connection with FIG. 5 are comprised of: (1) contacting the inert
gas and hydrocarbon vapor mixture with a lean liquid absorbent
whereby a major portion of the hydrocarbon vapor in the mixture is
absorbed in the lean liquid absorbent; (2) separating the resulting
rich liquid absorbent from the remaining inert gas and non-absorbed
hydrocarbon vapor mixture; (3) conducting the rich liquid absorbent
to a point of further processing or storage; and (4) recycling the
remaining inert gas and non-absorbed hydrocarbon vapor to the inlet
inert gas-hydrocarbon vapor mixture whereby the remaining inert gas
and non-absorbed hydrocarbon vapor flows into the bed of adsorbent
wherein hydrocarbon vapors are being adsorbed.
[0037] Referring now to FIG. 6, apparatus is illustrated for
carrying out the basic process described in connection with FIG. 1
as well as other alternate additional process steps for liquefying
and recovering hydrocarbon vapors from the inert gas and
hydrocarbon-rich vapor mixture produced by the basic process. The
apparatus of FIG. 1 is shown in FIG. 6 as is the absorber apparatus
illustrated in FIG. 5, both of which include the same reference
numerals as those used in FIGS. 1 and 5.
[0038] The apparatus in FIG. 6 which is in addition to that shown
in FIGS. 1 and 5 includes a conduit 148 for conducting lean liquid
absorbent from storage or other location to a supply pump 150. A
conduit 152 is connected between the discharge of the pump 150 and
the lean liquid absorbent connection 132 of the absorber column
126. A conduit 154 is connected to the conduit 152 downstream of
the supply pump 150 which leads a side stream of lean liquid
absorbent to the motive liquid cooler 88. A conduit 156 is
connected to the motive liquid cooler 88 for removing the lean
liquid absorbent therefrom and conducting it to an inlet connection
158 in the absorber 126 positioned below the packed section 128 of
the absorber 126. A spray nozzle 160 disposed within the absorber
column 126 is connected to the inlet connection 158. A flow control
valve 162 is disposed in the conduit 152 downstream from the supply
pump 150 and the connection of the conduit 154 to the conduit 152.
The flow control valve 162 is used to set the desired flow rate of
lean liquid absorbent to the spray nozzle 130 positioned above the
packed section 128 by way of the conduit 152. A second flow control
valve 163 is disposed in the conduit 154 and is used to set the
flow rate of lean liquid absorbent that flows through the motive
liquid cooler 88 and thereby cools the motive liquid. The resulting
heated lean liquid absorbent flows from the cooler 88 through the
conduit 156, the absorber inlet connection 158 and the spray nozzle
160 below the packed section 128 into the absorber 126.
[0039] Thus, the process steps for liquefying and recovering
hydrocarbons from the inert gas and hydrocarbon-rich vapor mixture
produced by the basic process carried out by the apparatus shown in
FIG. 6 are comprised of the following steps: (1) a lean liquid
absorbent from storage or other location is divided into first and
second portions; (2) the first portion of the lean liquid absorbent
is passed in heat exchange relationship with the motive liquid
whereby the motive liquid is cooled prior to when it enters the
motive liquid ejector; (3) the resulting heated first portion of
the lean liquid absorbent is then utilized to contact the
hydrocarbon rich inert gas-hydrocarbon vapor mixture flowing
through the absorber at a point below the packed section thereof
whereby a first portion of the hydrocarbon vapor in the mixture is
absorbed in the first portion of the lean liquid absorbent; (4) the
second portion of lean liquid absorbent is utilized to contact the
inert gas-hydrocarbon rich vapor mixture flowing upwardly through
the packed section of the absorber whereby a second portion of the
hydrocarbon vapor in the mixture is absorbed in the second portion
of the lean liquid absorbent; (5) the rich liquid absorbent flowing
downwardly in the absorber is separated from the inert gas and
hydrocarbon-rich vapor mixture flowing upwardly therein; (6) the
rich liquid absorbent is removed from the absorber and conducted to
a point of storage or other location; and (7) the remaining inert
gas and non-absorbed hydrocarbon vapor and are removed from the
absorber and recycled into the bed of solid absorbent wherein
hydrocarbon vapors are being adsorbed.
[0040] Referring now to FIG. 7, apparatus is illustrated for
carrying out still other alternate process steps that can be
utilized for liquefying and recovering hydrocarbons from the inert
gas and hydrocarbon-rich vapor mixture produced by the basic
processes previously described and illustrated in FIGS. 1 and 2. In
accordance with the process steps, the inert gas and
hydrocarbon-rich vapor mixture produced by the basic process is
conducted to a non-contact condenser 170 by the conduit 94. The
non-contact condenser 170 is illustrated in the form of a shell and
tube heat exchanger which utilizes a cooling medium such as cooling
water for condensing a majority of the hydrocarbons in the inert
gas and hydrocarbon-rich vapor mixture. As will be understood,
other forms of non-contact condensers using alternative coolants
known in the art can also be utilized. From the condenser 170, the
condensed hydrocarbons, inert gas and non-condensed hydrocarbon
vapor are conducted by a conduit 172 to a separator 174. The
separator 174 includes an inlet connection 176 to which the conduit
172 is attached, a hydrocarbon liquid outlet connection 178 and an
inert gas and non-condensable hydrocarbon vapor outlet connection
180. The condensed hydrocarbons separated in the separator 174 are
withdrawn therefrom by way of the outlet connection 178, a conduit
182 and a pump 184. The pump 184 pumps the condensed hydrocarbons
to storage or other location by way of a conduit 186. The inert gas
and non-condensable hydrocarbons are withdrawn from the separator
by way of the outlet connection 180 and the conduit 144 which
recycles the inert gas and non-condensable hydrocarbons to the
adsorber in the basic process which is adsorbing hydrocarbons from
the inlet inert gas-hydrocarbon vapor mixture.
[0041] Thus, the additional process steps carried out in the
apparatus illustrated in FIG. 7 are comprised of: (1) the inert gas
and hydrocarbon-rich vapor mixture is passed in heat exchange
relationship with a cooling medium whereby a major portion of the
hydrocarbon vapor in the mixture is condensed; (2) the condensed
hydrocarbon vapor is separated from the remaining inert gas and
non-condensable hydrocarbon mixture; (3) the separated condensed
hydrocarbons are conducted to storage or a point of further
processing; and (4) the remaining inert gas and non-condensable
hydrocarbon vapor mixture is recycled to the bed of solid adsorbent
in the basic process wherein hydrocarbon vapors are being
adsorbed.
[0042] Referring now to FIG. 8, the apparatus of FIG. 7 is shown
with the same reference numerals as utilized in FIG. 7 with the
addition of a compressor and a back pressure controller. That is, a
compressor 190 is provided connected to the conduit 94 of a basic
process of this invention. The conduit 94 conducts an inert gas and
hydrocarbon-rich vapor mixture to the compressor 190 wherein the
mixture is compressed. A conduit 192 conducts the compressed
mixture to the condenser 170 wherein a major portion of the
hydrocarbons in the compressed mixture are condensed. From the
condenser 170 an inert gas and non-condensed hydrocarbon vapor
mixture along with condensed hydrocarbons are conducted to the
inlet connection 176 of the separator 174. The condensed
hydrocarbons are withdrawn from the separator 174 by way of the
outlet connection 178, the conduit 182 and the pump 184. From the
pump 184, the condensed hydrocarbons are conducted to storage or
other location by the conduit 186. The inert gas and
non-condensable hydrocarbon mixture exits the separator 174 by way
of the connection 180 and is conducted by the conduit 144 to an
adsorber of the basic process which is adsorbing hydrocarbons from
the inlet inert gas-hydrocarbon vapor mixture. A back pressure
controller 194 is disposed in the conduit 144 for maintaining a
desired higher pressure in the condenser 170 and the separator 174.
The higher pressure brings about the condensation of more of the
hydrocarbon vapors than when the condenser and separator are
operated at a lower pressure.
[0043] Referring now to FIG. 9, apparatus is illustrated for
carrying out yet other additional process steps for liquefying and
recovering hydrocarbons from the inert gas and hydrocarbon-rich
vapor mixture produced by a basic process described in connection
with FIGS. 1 or 2. The inert gas and hydrocarbon-rich vapor mixture
is conducted by the conduit 94 to the inlet connection 198 of a
second motive liquid ejector 200. Lean liquid absorbent motive
liquid from storage or other location is conducted to the motive
liquid inlet connection 202 of the ejector 200. While flowing
through the ejector 200, a major portion of the hydrocarbons
contained in the inert gas and hydrocarbon-rich vapor mixture are
absorbed in the motive liquid. The resulting mixture of rich liquid
absorbent, inert gas and non-absorbed hydrocarbon vapor is
conducted to a separator 210 by way of the ejector outlet
connection 204, a conduit 206 and the inlet connection 208 of the
separator 210. The rich liquid absorbent separated in the separator
210 is withdrawn therefrom by way of an outlet connection 212, a
conduit 214 and a return pump 216. The return pump 216 pumps the
rich liquid absorbent by way of a conduit 218 to storage or other
location. The inert gas and non-absorbed hydrocarbon vapor are
withdrawn from the separator 210 by way of an outlet connection 220
and a conduit 222. The conduit 222 includes a back pressure
controller disposed therein for maintaining a desired higher
pressure in the separator 210 than that produced by the ejector 200
to bring about the condensation of more of the hydrocarbon vapors
than when the separator is operated at a lower pressure. The
conduit 222 recycles the inert gas and non-absorbed hydrocarbon
vapor to the adsorber of the basic process which is adsorbing
hydrocarbons from the inlet inert gas-hydrocarbon vapor
mixture.
[0044] Thus, the additional process steps that can be utilized with
a basic process of this invention carried out in the apparatus
illustrated in FIG. 9 include the steps of: (1) conducting the
inert gas and hydrocarbon-rich vapor mixture produced by the basic
process to a second motive liquid ejector operated by a motive
liquid having an infinity for hydrocarbon vapor whereby a major
portion of the hydrocarbon vapor is absorbed in the motive liquid;
(2) separating the motive liquid having the hydrocarbon vapor
absorbed therein from the remaining inert gas and non-absorbed
hydrocarbon vapor mixture; (3) conducting the motive liquid having
hydrocarbon vapor absorbed therein to storage or other location;
and (4) recycling the remaining inert gas and nonabsorbed
hydrocarbon vapor to the adsorber of the basic process which is
adsorbing the inlet inert gas-hydrocarbon vapor mixture.
Operation of the Apparatus 10
[0045] In operation of the apparatus 10 illustrated in FIGS. 1 and
2 for carrying out the basic processes of this invention, the
switching valves 32, 34, 38, 40, 50 and 52 are operated in a manner
whereby the inlet inert gas-hydrocarbon vapor mixture is caused to
flow through one of the absorbers 12 or 14 while the other of the
absorbers is being regenerated. For example, during a first cycle,
the switching valve 32 is open and the switching valve 34 closed
whereby the inlet inert gas-hydrocarbon vapor mixture flows into
the adsorber 12 by way of the conduit 28, switching valve 32 and
connection 16 of the adsorber 12. Because the switching valve 34
disposed in the conduit 30 is closed, the inlet inert
gas-hydrocarbon vapor mixture is prevented from entering the
adsorber 14. The switching valve 50 disposed in the conduit 46 is
open and the switching valve 52 disposed in the conduit 48 is
closed whereby the residue gas stream produced in the adsorber 12
exits the adsorber 12 by way of the connection 18 thereof, the
conduit 46 and the switching valve 50 and enters the header 44.
From the header 44, the residue gas stream flows through the
conduit 54 from where it is vented to the atmosphere. The switching
valve 38 disposed in the header 36 is closed and the switching
valve 40 disposed therein is open whereby the adsorbent bed within
the adsorber 14 is communicated by way of the conduit 42 with the
ejector 72. The switching valve 60 in the conduit 56 is closed and
the switching valve 66 in the conduit 62 is initially closed.
[0046] During the first part of the cycle when the switching valves
are in the mode described above, the inlet inert gas hydrocarbon
vapor mixture flows through the bed of adsorbent within the
adsorber 12 whereby hydrocarbons are adsorbed on the bed and
removed from the mixture. The residue gas produced which is
comprised of substantially hydrocarbon-free inert gas is vented to
the atmosphere by way of the inert gas vent 54. Simultaneously, the
bed of adsorbent disposed within the adsorber 14 is evacuated by
the motive liquid ejector 72 whereby hydrocarbons are desorbed
therefrom. An inert gas and hydrocarbon-rich vapor mixture is
withdrawn from the adsorbent bed within the adsorber 14 by the
motive liquid ejector 72 and the inert gas and hydrocarbon-rich
vapor mixture commingled with motive liquid are discharged from the
ejector into the separator 82. The separated inert gas and
hydrocarbon-rich vapor mixture is withdrawn from the separator by
way of the conduit 94 and the separated motive liquid is recycled
to the ejector 72 by way of the conduit 86, the motive liquid
cooler 88 and the motive liquid pump 90 (FIG. 1), or the separated
motive liquid is returned to storage or to a separate process by
way of the conduit 96, the pump 92 and the optional cooler 94 (FIG.
2). During the last part of the cycle, after a major portion of
hydrocarbons adsorbed on the bed of adsorbent within the adsorber
14 have been desorbed therefrom by the operation of the motive
liquid ejector 72, the switching valve 66 in the conduit 62 is
opened whereby a quantity of hydrocarbon-free stripping inert gas
flows by way of the conduit 62, the switching valve 66 and the
connection 64 of the adsorber 14 into the adsorber 14. The
stripping inert gas flows through the bed of adsorbent contained in
the adsorber 14 and is withdrawn therefrom by the motive liquid
ejector 72 as previously described. The introduction of a quantity
of stripping inert gas into the adsorbent bed contained within the
adsorber 14 functions to strip additional hydrocarbons from the bed
which were not desorbed therefrom by the operation of the motive
liquid ejector 72, i.e., by the lowering of the pressure exerted on
the bed to the degree of vacuum achieved by the ejector 72.
[0047] After the adsorbent bed within the adsorber 14 has been
fully regenerated and the adsorbent bed within the adsorber 12
loaded with hydrocarbons from the inert gas-hydrocarbon vapor
mixture flowing therethrough, the switching valves are reversed.
That is, the switching valves 32 and 50 are closed, the switching
valves 34 and 52 are opened, the switching valve 38 is open and the
switching 40 is closed. This causes the flow pattern of the inlet
inert gas-hydrocarbon vapor mixture to be changed whereby the
mixture flows through the regenerated adsorbent bed within the
adsorber 14 and the residue gas therefrom to be vented to the
atmosphere. The adsorbent bed within the adsorber 12 is
simultaneously communicated with the motive liquid ejector 72
whereby the bed is evacuated and the switching valve 60 is open
during a latter part of the cycle as described above to strip the
adsorbent bed whereby additional hydrocarbons are desorbed
therefrom. As is well understood by those skilled in the art, the
flow pattern of the inlet inert gas-hydrocarbon vapor mixture and
the bed being regenerated are continuously changed or cycled
whereby when the adsorbent bed through which the inlet vapor
mixture is flowing becomes loaded with adsorbed hydrocarbons, the
inlet mixture is caused to flow into the bed which has just been
regenerated and the bed which is loaded with adsorbed hydrocarbons
is regenerated. The inert gas and hydrocarbon-rich vapor mixture
produced from the bed being regenerated is separated from the
motive liquid and is disposed of or subjected to additional process
steps as described above for liquefying and recovering hydrocarbons
from the inert gas and hydrocarbon-rich vapor mixture.
[0048] The operation of the apparatus 10 illustrated in FIG. 3 is
essentially the same as the operation described above for the
apparatus shown in FIGS. 1 and 2 except that the motive liquid also
functions as an absorbent for the evacuated hydrocarbon vapors, and
the inert gas and non-absorbed hydrocarbon vapor separated from the
hydrocarbon rich absorbent are recycled to the adsorber in which
hydrocarbons are being adsorbed. The lean absorbent motive liquid
utilized is passed through the ejector 72 only once.
[0049] The operation of the various additional process steps for
liquefying and recovering hydrocarbons from the inert gas and
hydrocarbon-rich vapor mixture produced by the basic processes
carried out in the apparatus of FIGS. 1 and 2 will be readily
understood by those skilled in the art from a reading of the
descriptions of such processes given above.
[0050] The hydrocarbon vapor recovery processes described herein
which utilize a motive liquid ejector in lieu of one or more vacuum
pumps are considerably less expensive and less complex as well as
being easier and less expensive to install and operate.
[0051] Thus, the present invention is well adapted to carry out the
objects and attain the ends and advantages mentioned as well as
those which are inherent therein. While presently preferred
embodiments of the invention have been described for purposes of
this disclosure, numerous changes in the arrangement of process
steps and apparatus elements will suggest themselves to those
skilled in the art, which changes are encompassed within the spirit
of this invention as defined by the appended claims.
* * * * *