WO2014088630A1

WO2014088630A1 - Refrigerated vapor recovery system

Info

Publication number: WO2014088630A1
Application number: PCT/US2013/033078
Authority: WO
Inventors: Henry T. HILLIARD, Jr.; Townsend HILLIARD
Original assignee: Hilliard Emission Controls, Inc.
Priority date: 2012-12-04
Filing date: 2013-03-20
Publication date: 2014-06-12
Also published as: GB2512248A; GB2512248B; EP2911770A1; EP2911770A4; GB201412280D0

Abstract

Volatile vapors are removed from a storage vessel by establishing a flow of a stream of volatile vapors from the storage vessel and directing the vapor stream through a heat exchange module for condensing a portion of the vapors in the stream flowing through a cooled heat exchange condensers in the heat exchange module. The uncondensed vapors in the vapor stream are then directed to a carbon adsorption module including a pair of carbon adsorption units. The vapor recovery system also provides a means of desorbing a carbon adsorption unit that approaches its capacity for adsorbing volatile organic molecules and recycling the desorbed vapor stream through a cooled heat exchange condenser to convert the volatile organic material into a liquid state that may be sold as a product or utilized as a raw material rather than being combusted or otherwise disposed of in the atmosphere.

Description

REFRIGERATED VAPOR RECOVERY SYSTEM

STATEMENT OF RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application

No. 61 /797,306 filed December 4, 2012 and entitled "Refrigerated Vapor Recovery System."

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

[0002] This invention relates to the field of purging tanks and vessels and more particularly, to methods and apparatus for using heat exchangers and carbon adsorption tanks to efficiently remove and recover volatile .materials entrained within vapors residing in tanks and vessels.

.DESCRIPTION OF THE RELATED ART

[0003] Volatile liquids, such as benzene, petroleum and the like, are often stored in tanks at bulk terminals, refineries and end-user facilities, and transported in tanks aboard barges or ships, tank trucks and rail cars. All such containers shall be referred to herein as liquid storage vessels. While resident in these liquid storage vessels, volatilization of the liquid occurs leaving residual vapors which must be removed before workmen can be permitted to enter the vessel and before the vessel cm be filled with a different liquid.

[0004] In some cases, such residual vapors are purged by flooding liquid storage vessels with a sufficient volume of water, steam or an inert gas to entrain the vapors and carry them out of the vessel. The resulting mixture of diluted vapors, in many cases, is simply combusted and emitted to the atmosphere and/or the surrounding water supply where they pollute the environment,

[0005] Recently companies have had to minimize the release of volatile materials into the atmosphere during the preparation of storage vessels for maintenance in order to meet environmental standards. One environmentally friendly way to reduce the release of volatile materials into the atmosphere has been to cool and the vapors and to recycle the condensed liquids. [0006] A need exists for .methods for recovering the volatile .materials that are removed .from a storage vessel so that the material may be utilized as a product, or raw material rather than being disposed of.

SUMMARY OF THE INVENTION

[0007] One embodiment of the present invention is a carbon absorption module having: (a) a first carbon absorption unit having a .first inlet in selectable communication with an outlet of a cooled heat exchanger and a first outlet; (b) a second carbon absorption unit having a second inlet in selectable con runieation with the outlet of the cooled heat exchanger and a second outlet; (c) a monitoring device for measuring the concentration of a volatile organic component in an effluent from the first o the second carbon adsorption unit; (d) a first effluent flow path passing from the first outlet through the monitoring device; (e) a second effluent, flow path passing from the second outlet through the monitoring device; (!) an atmospheric discharge outlet i selectable communication with the first and second effluent flow paths; (g) a pump in selectable communication with the first and second effluent flow paths; and (h) a desorption flo path in communication with the pump and the cooled heat exchanger.

[0008] Another embodiment of the present invention is A. carbon absorption module having: (a) a first carbon absorption unit having (i) a first inlet in selectable communication with an outlet of a cooled heat exchanger, (ii) a first flow path for a coolant, and (in) a first outlet; (b) a second carbo absorption unit having (i) a second inlet in. selectable communication with the outlet of the cooled heat exchanger, (ii) a second flow path for the coolant, and (iii) a second outlet, (c) a monitoring device for measuring the concentration of a volatile organic component in an effluent from the first or the second carbon adsorption unit; (d) a first effluent flow path passing from the first outlet through the monitoring device; (e) a second effluent flow path passing from the second outlet through the monitoring device; (f) an atmospheric discharge outlet i selectable communication with the first and second effluent flow paths; if) a pump in selectable communication with the first and second effluent flow paths; and (e) a desorption flow path in communication with the pump and the cooled heat exchanger.

[0009] Yet another embodiment of the present invention is a. method for removing and recovering a volatile organic component from, a vapor stream including the steps of: (a) directing a flow of the vapor stream to a first carbon adsorption unit from a cooled heat exchanger; (b) measuring the vapor stream exiting from the first carbon adsorption unit for the volatile organic component; (c) releasing the exiting vapor stream from the first carbon adsorption unit into the atmosphere if a measured concentration of the volatile organic component is below a desired concentration; (d) diverting the flow of the vapor stream to a second carbon adsorption, unit whenever the measured concentration of the volatile organic component, in the vapor stream exiting from the first carbon adsorption unit, is equal to or greater than, the desired concentration; (e) lowering the pressure in the first carbon adsorption unit to deso.rb the volatile organic component; and (f) directing the desorbed volatile organic component through the cooled heat exchanger to condense a portion of the volatile organic compound.

[0010] Still another embodiment of the present invention is a method for recovering a volatile organic component from a vapor stream comprising; (a) directing the vapor stream from a storage vessel to a heat exchange module having at least one hea exchange condenser; (b) starting a refrigerant flow through at least one heat exchange condenser to cool the condenser; (c) directing the flow of the vapor stream through the heat exchange module, wherein a. portion of the volatile organic component in the vapor stream flowing through the cooled heat exchange condenser is condensed; (d) draining the condensed volatile organic component from the cooled heat exchange condenser; (e) directing the uncondensed vapor stream from the heat exchange module to a first carbon adsorption unit from the cooled heat exchanger to adsorb the volatile organic component; (f) measuring the vapor stream exiling from the first carbon adsorption unit for the volatile organic component; (g) releasing the exiting vapor stream from the first carbon adsorption unit into the atmosphere if a measured concentration of the volatile organic component is below a desired concentration; (h) diverting the flow of the vapor stream to a second carbon adsorption unit whenever the measured concentration of the volatile organic component hi the vapor stream exiting from the first carbon adsorption unit is equal to or greater than the desired concentration; (i) lowering the pressure in the first carbon adsorption unit, to desorb the volatile organic component; and (j) directing the desorbed volatile organic component through the cooled heat exchanger to condense a portio of the volatile organic compound.

[001.1] The .foregoing has outlined rather broadly several aspects of the present invention in. order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed might be readily utilized as a basis for modifying or redesigning the structures for carrying out the same purposes as the invention. It should be realized b those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

BRIEF DESCRI PTION OF THE DRAWI GS

[0012] For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0013] FIG. 1 is a general schematic of a system for removing volatile vapors from a storage vessel

[0014] FIG. 2 A is a more detailed, schematic of the system shown in FIG, 1 showing the volatile vapor .flow from the storage tank through the first heat exchange condenser and then through a refrigerated second heat exchange condenser.

[0015] FIG. 2B is a more detailed schematic of the system shown in PIG. i showing the volatile vapor flow from the storage tank through the second heat exchange condenser and then through a refrigerated first heat exchange condenser.

[0016] FIG. 3 is a sehematie flow diagram of the system shown in FIG. 1 showing the volatile vapor flow from the storage tank through the heat exchange module and then through a carbon adsorption module with two carbon adsorption units,

[0017] FIG. 4 is a schematic for the system, where the coolant used in the heat exchange module is used to selectively cool the carbon adsorption units.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Embodiments of th present invention relate to methods for removing volatile organic vapors from a storage vessel and recovering the volatile organic components (VOCs) from those vapors.

[0019] Storage vessels are used for storing many volatile products such as gasoline, gasoline blending components, diesel, kerosene, solvents, petrochemical s and organic compounds. Before entry into the vessels by personnel assigned t perform maintenance on the empty storage vessel, before the vessel is refilled with a different product, or while the vessel is being filled with a different product the vessel must be purged of the harmful volatile organic components, commonly referred to as VOCs, which were generated while the storage vessel was in use,

[0020] Figure 1 illustrates a general schematic of the refrigerated vapor removal and recovery system 10, In general, a blower 13 suctions a gas source 1 1 (such as air, nitrogen, or carbon dioxide) through a storage vessel .12 to push the volatile vapor stream from within the storage vessel out of the vessel 12 to circulate the vapor stream through a heat exchange module 14. The heat exchange .module 14 will, typically contain a series of heat exchange condensers wherein at least one of the heat ex change condenser is refrigerated.

[0021 J The vapor stream is cooled as it. passes through the refrigerated heat exchange condenser. The volatile organic components in the vapor stream are condensed and drained from the heat exchange condenser into a condensate tank 15 and can be sold a useful product [0022] Generally the majority of the VOCs aire condensed and removed as the vapo stream passes through the heat exchange module 14. However, the vapor stream is then pumped through a carbon adsorption module 16 where w atever VOCs remain in the vapor stream after it leaves the heat exchange module 14 are adsorbed by the carbon adsorption module 16.

[0023] if after the vapor stream passes through the vapor recover system 10, the vapor stream is suitably free of harmful volatile organic components or VOCs the cleaned vapor stream may be released into the atmosphere. However, if an undesirable concentration (i.e., an concentration surpassing an environmentall safe standard) of one or more volatile organic components remains in t e vapor stream, the vapor stream is recycled back throug ihe removal/recovery system 10. The circulation/recircuiation process through the series of heat exchange condensers and carbon adsorption tanks is continued until the vapor stream is suitably free of harmful volatile vapors.

[0024] Figure 2 shows a more detailed schematic of the refrigerated^' vapor recover system 10. While one or more blowers is a preferred apparatus for establishing the flow of the stream of volatile vapors for circulation through the series of condensers within the heat exchange module 14, other apparatus are also suitable, either alone or in combination with a blower such as, for example, rotary compressors, fans, reciprocating compressors, centrifugal compressors, or other vapor pumps known to those having ordinary skill in the art and combinations thereof. The blowers may be driven by electric motors, pneumatic motors, iirrbines or other drivers known to those having ordinary skill in. the art. Preferably, flame arrestors (not shown) may be included on both the suction and discharge of the blower 13 to protect the storage vessel 12 from flashback.

[0025] The stream of volatile vapors from the storage vessel 12 is circulated through the vapor removal system 10 through suitable conduits that connect the storage vessel 12, the vapor pump 13, the heat exchange module 14 and the carbon adsorption module 16. Preferably, metal piping is used such as, for example, carbon steel piping. Alternatively, plastic piping may be useful as well as flexible hose or hose made of woven: metal Material selection for the conduits may be properly selected by one having ordinary skill in the art for each given application.

[0026] HEAT EXCHANGE MODULE

[0027] A preferred embodiment of the beat exchange module 14 is shown .in Figures

2 A and 2B. The illustrated embodiment has a first heat exchange condenser 21 and a second heat exchange condenser 22. Each of the two heat exchange condensers are plumbed such that a refrigerant or coolant can selectably pass through one or both of the heat exchangers at any given time. The preferred coolant for the system, is liquid nitrogen; however othe refrigerants such as ammonia or cold water may also be used. Alternatively, or in combination with the above, a refrigerant or coolant may be used to cool a circulating coolant stream.

[0028] The volatile vapor stream pumped from the storage vessel is typically passed through both of the heat exchange condensers and the refrigerant or coolant is used to cool ihe vapor stream in the second condenser that ihe vapor stream passes through. The refrigerant selected for use is pumped through the second condenser at a temperature equal to or less than the condensing temperature of the known volatile vapors of concern in the vapor stream,

[0029] Although there are a variety of flow paths by which the vapor stream can pass through the first and second heat exchange condensers 21 and 22, Figure 2A and figure 28 each show an example of one flow path. The operation of the pumps, valves, coolant circulation, temperature monitors, pressure monitors, etc. may all be operated manually or by preprogrammed processing units.

[0030] Figure 2A shows the vapor stream pumped from, the storage vessel. 1.2 through an optional inlet knock-out tank 1.9. The suction pump 13 continues to pum the vapor stream into the piping connecting the storage vessel exit to the first heat exchange condenser 21 through open valve 24A. Typically, the refrigerant or coolant is not circulating through the first condenser 21 but is circulating through the second heat exchange condenser 22,

[003 ] Thus, the vapor stream passes through the first condenser 21 and continues toward the second heat exchange condenser 22 through open valves 24B, 24C and 24D. Since the refrigerant is circulating through the second heat exchange condenser 22, the temperature in the second condenser 22 is lower than the temperature of the first heat exchange condenser 21. and is generally lower than the condensing temperature for the VOCs in the vapor stream. Thus, as the vapor stream passes through the second heat exchange condenser 2.2 and is cooled by the refrigerant, condensate from the volatile organic components in the cooled vapor stream will accumulate at the bottom of the second condenser 22.

[0032] The condensate may be drained manually opening the valve 2913 into a condensate collection vessel 15, or alternatively the condensate may be draiiied automatically using a controller thai monitors a liquid level in the condenser to send a signal to open, the valve 2 B and allow the condensate to drain from the second condenser 22 into the condensate collection, vessel 15.

[0033] The flow path illustrated in Figur 2A shows the vapor stream leaving the second heat exchange condenser 22 and passing through open valves 24E and 24F toward the carbon adsorption module 16.

[0034] As the volatile vapors condense in the second heat exchange condenser 22, some of the condensate does not accumulate in the bottom of the condenser but instead freezes within ihe condenser and. plugs a portion of the condenser 22. As the condenser 22 begins to plug the condenser 22. an additional pressure drop is added to the system, thereby reducing the circulation rate of the vapor stream.. As more condensate freezes, the frozen condensaie plugs a greater volume of the condenser until all circulatio is stopped and the system is shut down.

[0035] To prevent shutting down the system due to frozen condensate, the flow path of the vapor stream through the first and second heat exchange condensers .2.1 and 22 is altered. Typically, the direction of the How of the vapor stream is reversed either at preset time intervals (e.g., .10-30 minutes) or whenever the pressure across one or both of the condensers drops to a particular seipoint.

[0036] For example, the vapor flow stream shown in figure 2A. is stopped and the vapor flow stream shown in Figure 28 may he employed. Figure 2B illustrates a vapor stream flow path that pumps the vapor stream into the piping connecting the storage vessel exit to the second heat exchange condenser 22 through open valves 26A, 24C. and 241⁾, The refrigerant or coolant is shut off to the second condenser 22 and the refrigerant begins circulating through the first condenser 21.

[0037] in the flow path shown in Figure 2B, the vapor stream, initially passes into the second condenser 22 from the storage tank 12. The vapor stream is generally warmer than ambient temperature, having been warmed by the blower 1.3, and is wanner than the second heat exchange condenser 22 that contains some frozen condensate. Thus, the warm vapor stream coming from the storage vessel 12 is warm enough to begin, melting the frozen condensate in the second condenser 22. Likewise, the temperature in the second condenser 22 is lower than the temperature of the incoming vapor stream and may condense some of the VOCs entrained in the vapor stream. Any condensate that melts or any vapor condensate wsil accumulate at the bottom of the second condenser 22 and ca be removed b opening valve 298 and allowing the condensate to drain into the condensate collection vessel 15.

[0038] The flow path illustrated in. Figure 2B shows the vapor stream leaving the second heat exchange condenser 22 and passing through open valves 24E and 26B into the first heat exchange condenser 21. Since the refrigerant is circulating through the first heat exchange condenser 21 , the temperature in the first condenser 21 is generally lower than the condensing temperature for the VOCs in the vapor stream. Thus, as the vapor stream passes through the first heat exchange condenser 21 and is cooled by the refrigerant, condensate from the volatile vapors In the cooled vapor stream will accumulate at the bottom, of die first condenser 21.

[0039] The condensate may be drained manually opening the valve 29A into a condensate collection vessel 15, or alternatively the condensate may be drained automatically using a controller that monitors a liquid level in the condenser to send a signal to open the valve 29A and allow the condensate to drain from the first condenser 21 into the condensate collection vessel 15.

0040] The flow path illustrated i Figure 2B shows the vapor stream leaving the first heat exchange condenser 21 and passing through open valves 26C into the carbon adsorption module 16.

[0041] As the volatile vapors condense in. the first heat exchange condenser 21 , some of the condensate will, freeze within the condenser 21 and plug a portion of the condenser .2 L As the condenser 21 begins to plug, an additional pressure drop is added to the system, reducing the circulation rate of the vapor stream containing the VOCs, As more condensate freezes, the frozen condensate plugs a greater volume of the condenser and if the vapor stream is not redirected the frozen condensate might become sufficient to stop all circulation of the vapor stream and the system .

[0042] In order to prevent problems associated with the build up of frozen condensate in one of the condensers, the direction of the flow of the vapor stream is reversed either at preset time intervals (e.g._* 10-30 minutes) or whenever the pressure across one or both of the condensers drops to a particular setpoint,

[0043] For example, an operator of the system may determine whe to switch or reverse the order of the heat exchange condensers in which the vapor stream flows, by monitoring the pressure drop across each of the heat exchange condensers, or across both of the condensers. The monitoring equipment may include pressure transmitters, differential pressure transmitters, pressure gauges or combinations thereof When the pressure drop increases to a predetermined setpoint that indicates one of the heat exchange condensers is becoming plugged doe to frozen condensate, the circulation of the volatile vapor stream is reversed, or switched from the partially plugged condenser to the other condenser.

[0044] The switching from one heat exchange condenser to the other may be made manually or may be accomplished with a controller that i on a timing switch or that monitors the pressure drop and sends a signal to a set of control valves to switch the flow when the pressure dro is at or near the setpoint limit.

[0045] An of the controllers mentioned herein may be digital controllers, analogue controllers or combinations thereof and may be individual controllers suitable for controlling one proces condition or one controller, such as a computer or microprocessor controller capable of controlling and monitoring multiple process conditions, or combinations thereof.

[0046] CARBON ADSORPTION MODULE

[0047] The vapor stream is routed from the heat exchange module 14 to the carbon adsorption module 16. Figures 3 and 4 illustrate a couple of preferred embodiments of the carbon adsorption module 16. The carbon adsorption module shown in Figure 4 ha a first carbon adsorption unit 4.1 and a second carbon adsorption unit 42. Each of the carbon adsorption units contains a carbon adsorption material that reversib!y adsorbs volatile organic- vapor molecules to its surface. [0048] The adsorption of volatile vapors is exothermic and causes the heat to increase in the carbon adsorption units. As the temperature in the carbon adsorption unit increases, the chance of a resulting bed fire in the carbon adsorption unit increases. In addition, as the heat in a carbon absorption unit increases the adsorption of the VOCs becomes less efficient. Thus, the first and second carbon adsorption units 41, 42 are optionally plumbed, as shown i Figure 4, to selectabiy allow the refrigerant or coolant to circulate through the absorption units whenever the temperature in one of the carbon adsorption units increases above a desired limit The preferred temperature for the operation of the carbon absorption unit will depend on the refrigerant or coolani used (preferably nitrogen), the VOCs being absorbed, and the binding coefficient of the carbon absorption unit for the VOCs,

[0049] The first and second carbon adsorption units are plumbed so that the entire first and/or second carbon adsorption unit is flooded with a non-flammable refrigerant or coolant in the case that a bed fire does start. This allows for the quick asphy iatiaiioii of the bed fire. Alternatively the first and second carbon adsorption units are plumbed with piping through the units to allow refrigerant or coolant to be circulated through the piping within the first and/or second carbon adsorption units at a controlled rate.

[0050] As the vapor stream leaves the heat exchange module 1 it passes into one of the carbon adsorption units in the carbon adsorption module 16. If the valve 43 is opened and the valve 44 is closed the vapor will pass into the first carbon adsorption unit 41; whereas if the valve 44 is open and the valve 43 is closed the vapor will pass into the second carbon adsorption unit 42. There are numerous permutations as to how and when each carbon unit may be used to remove volatile organic components from the vapor stream. One example of the use of the first and second carbon adsorption units is discussed below.

[0051] in the example shown in Figure 3, a majority of the volatile vapors will typically have been condensed and recovered in the heat exchange module 14. Thus, there will be fewer volatile vapor molecules to be removed before the vapor stream can be released into the atmosphere.

[0052] As shown in Figure 3, if the valve 44 is closed and the valve 43 is opened the vapor stream passes into the first carbon adsorption, unit 41. At first, all of the volatile organic components will be adsorbed by the first carbon adsorption unit 41 so that the exit flow from, the first carbon adsorption unit 41. can pass through open valve 47 out into the atmosphere. [0053] The vapor effluent from the first carbon adsorption unit 41 Is constantly monitored for the presence of the volatile organic components that are not wanted to be released into the atmosphere. When the presence of one or more of the volatile organic components of concern is first detected, valve 43 and 47 are closed and valve 44 and 48 are opened to divert the vapor stream nto the second carbon adsorption unit 42.

[0054] The vapor stream will be sent to the second carbon unit 42 until its capacity to absorb the volatile organic compounds is reached and the vapor stream is then diverted back to a rejuvenated first carbon adsorption unit 41,

[0055] The carbon adsorption units are rejuvenated by desorhing the volatile organic components from the carbon adsorption unit's surfaces. Desorption is accomplished by applying a. vacuum to, with or without some increase in temperature, the carbon adsorption unit. Since the vaporization of a liquid is endoth.erm.ic and decreases the temperature in the carbon adsorption unit being desorbed, generally the circulation of the refrigerant, or coolant to a carbon adsorption unit Is cut off during desorption of the VOCs and the temperature in the carbon absorption unit is maintained high enough that the absorbed VOCs can be pulled off the carbo absorption unit with a vacuum.

[0056] One embodiment of the desorption of the first carbon adsorption unit 41 includes closing off the inflow of a coolant, such as by closing valve 31 or valve 39. Once the circulation of the coolant to the carbon adsorption unit 41 or 42 has been done, a vacuum is applied to the carbon adsorption unit to be desorbed.

[0057] For example, the desorption of carbon absorption unit 41 involves closing valve 43 and 47 and opening valve 45, A vacuum is applied to the first carbon adsorption unit 41 by engaging the pump 50. The vacuum pump is used to lower the pressure in the carbon adsorption unit 41 to below the vapor pressure of the adsorbed volatile organic components, which causes the volatile organic components to evaporate off the adsorption unit 41 at the temperature that is ambient in the adsorption unit, instead of a higher temperature.

[0058] A simila process is used for the desorption of the second carbon adsorption unit. 42 whenever the vapor stream effluent from the second carbon adsorption unit 42 is detected t contain unadsorhed volatile organic components. Typically, valves 44 and 48 are closed and valve 46 is opened. A vacuum is applied to the second carbon adsorption unit 42 by engaging the pump 50. The vacuum pump is used to lower the pressure in the carbon adsorption unit 42 to below the vapor pressure of the adsorbed, volatile organic components. causing the volatile organic components to evaporate off the adsorption unit 42 at the temperature that is ambient in the adsorption unit, instead, of a. higher temperature. Alternatively, hot air or another liquid that is kept at ambient temperature or warmer is circulated through the refrigerant or coolant flow path through the first and/or second carbon adsorption units to increase the evaporation of the volatile organic components off of the carbon adsorption units,

[0059] Typically, the desorbed vapors are at a higher concentration than when they were initially adsorbed in the carbon adsorption unit 41 or 42. The desorbed vapors or VOCs are then routed to the inlet knock-out tank 19 and hack through the heat transfer module 14. The valve 52 from the storage tank is typically closed while the desorbed vapors are being routed to the knock-out tank 19. The desorbed VOCs are recovered as condensate from the heat transfer module 14.

[0060] CIRCULATION OF REFRIGERANT

[0061 ] The preferred refrigerant or coolant used in the heat exchange module is nitrogen. Typically liquid nitrogen is supplied .from a liquid gas canister 30 shown in Figure 4, such as a cryogenic tank. The refrigerant or coolant is seleetabiy circulated through the first beat exchange unit 21 or the second heat exchange unit 22 as described above. The flow of the refrigerant may be manually controlled, with valves, or with actuators that are controlled by a controller or microprocessor.

[0062] The pressure of the liquid nitrogen inside the heat exchangers is controlled.

Typically, the pressure of the liquid nitrogen at. the inlet of the cooled heat exchanger is maintained at a pressure between 40-50 psi (preferably about 43 psi) and the pressure of the liquid nitrogen on the outlet, ranges between 30-45 psi (preferably about 36 psi).

[0063] When the refrigerant is circulated to the second heat exchange condenser 22, the inlet valve 33 is opened and the refrigerant is pumped into the condenser 22. The refrigerant inlet, valve 33 is typicall closed when the condenser 22 is offline. The circulated refrigerant is typically vented from the heat exchange condenser 22 either to the atmosphere when valve 35 is open and/or to the carbon adsorption units of the carbon adsorption module 36 when the valve 36 is open to assist in maintaining a temperature within, an actively adsorbing unit to prevent bed fires.

[0064] Similarly, when the refrigerant or coolant i circulated to the first heat exchange condenser 21, the inlet valve 32 is opened and the refrigerant is pumped into the condenser 21 , The refrigerant inlet valve 32 is typically closed when the condenser 21 is offline. The circulated refrigerant is typically vented from the heat exchange condenser 21 either to the atmosphere when the valve 34 is open and/or to the carhon adsorption units of the carbon adsorption module 1.6 when the valve 37 is open to assist in. maintaining a temperature within an actively adsorbing unit to prevent bed fires.

[0065] Whenever the ref igerant or coolant is sent: to the carbo absorption module 16 from the second heat exchanger condenser 22, valve 35 is closed to stop the refrigerant from venting to the atmospher and valves 36 and 38 are opened. Similarly, when the refrigerant or coolant is sent to the carbon absorption module 16 from the first heat exchange condenser 21, valve 34 is closed and valves 37 is opened. Valve 31 controls the circulation of the refrigerant or coolant through the first carbon absorption unit 41 and valve 39 controls the circulation of the coolant through the second carbon absorption unit 42.

[0066] ADVANTAGES OF TOE INVENTION

[0067] One advantage of the refrigerated vapor recovery system is that any failure of a. single component in the system does not result in the release of harmful vapors or VOCs to the atmosphere, for example, even if both condensers failed to condense the volatile organic components from the vapor stream due to operator inattention resulting in allowin the condenser temperature to become too high, from mechanical failure of a valve or the blower, running out of refrigerant, or an other cause, the vapors proceed to the carbon adsorption module 16 and stay within the system and are not vented to the atmosphere as may occur in a system that utilizes combustion of the volatile organic components in the vapor stream.

[0068] Another advantage of the vapor recovery system is that the volatile organic components removed from the storage vessel are not combusted, or otherwise disposed of in the atmosphere but rather are converted into a liquid state that may be sold as a product or utilized as a raw material for a process.

[0069] Yet another advantage is that the vapor recovery system allows for multiple cycles of use and reuse with minimum of energy input. For example, the heat exchange module 14 allows for the diversion of the vapor stream from one heat exchange condenser to another heat exchange condenser if a problem develops in one of the heat exchange condensers. Likewise, the system is easily diverted from one carbon adsorption unit to another carbon adsorption unit whenever one carbon adsorption unit needs to be rejuvenated. [0070] The terms "comprising," "including," and "having," as used in the claims and specification herein, shall be considered as indicating an open group that, may include othe elements not specified. The term "consisting essentially of," as used in the claims and specification herein, shall be considered as indicating a partially open group that may include other elements not specified, so long as those other elements do not materially alter the basic and novel character! sites of the claimed invention. The terms "a," "an," and the singular forms of words shall be taken to include the plural form of the same words, such thai the terms mea that one or more of something is provided. For example,, the phrase "a solution comprising a p.hosphoms-containing compound" should be read to describe a solution having one or more phosphorus-containing compound. The terms "at least one" and "one or more" are used interchangeably. The term "one" or "single" shall he used to indicate that one and only one of something is intended. Similarly, other specific integer values, such as "two," are ^•used when a specific number of things is intended. The terms "preferably_*" "preferred," "prefer," "optionally," "may," and similar terms are used to indicate that an item, condition or step being referred to is a option al {not required) feature of the in ven tion,

[0071 ] 11 should be understood from the foregoing description that various modifications and changes may be made in the preferred embodiments of the present invention without departing from its true spirit. The foregoing description is provided for the purpose of illustration only and should not be construed in a limiting sense. Only the language of the following claims should limit the scope of this invention.

Claims

WHAT IS CLAIMED IS:

1. A carbon absorption module having;

(a) a first carbon absorption, unit having a first inlet in selectable communication with an outlet of a cooled heat exchanger and a first outlet;

(b) a second carbon absorption unit having a second inlet in selectable communication with the outlet of the cooled heat exchanger and a second outlet:

(c) a monitoring device for measuring the concentration of a volatile organic component in an effluent from the first or the second carbon adsorption unit;

(d) a first effluent flow path passing from the first outlet through the monitoring device;

(e) a second effluent flow path passing from the second outlet, through the monitoring device;

(f) an atmospheric discharge outlet in selectable communication with the first and second effluent flow paths;

(g) a pu p in selectable communication with the first and second effluent flow paths; and

lh) a desofption flow path in communication with the pump and the cooled heat exchanger.

2. The carbon absorption module of claim 1, further comprising a temperature control, means for controlling the temperature in the first and second carbon absorption units,

3. The carbon absorption module of claim 1 , further comprising a first coolant flow path passing through the first carbon absorption unit and a second coolant flow path passing through the second carbon absorption unit.

4. The carbon absorption module of claim 3, wherein the first and second coolant flow paths are in communication with a third coolant flow path through the cooled heat exchanger.

5. The carbon absorption module of claim 1 , wherein when the first inlet is closed, the first effluent flow path is opened to the pump, and the pump is activated causin the pressure in the first carbon absorption unit to decrease.

6. The carbon absorption module of claim 1, wherein when the second inlet is closed, the second effluent flow path is opened to the pump, and the pump is activated causing the pressure in the second carbon absorption unit to decrease.

7. A carbon absorption module having:

(a) a first carbon absorption unit having

(i) a first inlet in selectable communication with an outlet of a cooled beat exchanger,

(ii) a first flow path for a coolant, and

(iii) a first outlet;

(b) a second carbon absorption unit having

(i) a second inlet in selectabie coinmiraication with the outlet of the cooled heat exchanger,

(ii) a second Slow path for the coolant, and

(iii) a second outlet,

(d) first effluent flow path, passing from the first outlet through the monitoring device;

(e) a second effluent flow path passing from the second outlet through the monitoring device;

(i) an atmospheric discharge outlet in selectable communication with the first and second effluent flow paths;

(f) a pump in selectabie communication with the first and second effluent flow paths; and

(e) a deso.rpt.iott flow path in conimunication with the pump and the cooled heat exchanger.

8. The carbon absorption module of claim 7, wherein the first and. second flow path for the coolant are in selective communication with a flow path for the coolant through the cooled heat exchanger.

9, The carbon absorption module of claim 7, further comprising a temperature control means for controlling the temperature in. the first and second carbon absorption units.

1.0. The carbon absorption module of claim 7, wherein the desorption .flow path passes through a knock-out tank,

1.1. The carbon absorption, module of claim. 7, wherein the cooled heat exchanger is connected to a condensate tank,

12. A method for removing and recovering a volatile organic component from a vapor stream including the steps of:

(a) directing a flow of the vapor stream to a first carbon adsorption unit from a cooled heat exchanger;

(b) measuring the vapor stream exiting from the first carbon adsorption unit for the volatile organic component;

(c) releasing the exiting vapor stream from, the first carbon adsorption unit into the atmosphere if a measured, concentration of the volatile organic component is below a desired concentration;

(d) diverting the flow of the vapor stream to a second carbon adsorption unit whenever the measured concentration of the volatile organic component in the vapor stream exiting from the first carbon adsorption unit is equal to or greater than the desired concentration;

(e) lowering the pressure in the first carbon adsorption unit to desorb the volatile organic component; and

(t) directing the desorbed volatile organic component through the cooled heat exchanger to condense a. portion of the volatile organic compound.

13. The method of claim 12, wherein the first carbon, adsorption unit is cooled during the adsorptio of the volatile organic component.

14. The method of claim 13, wherein a cooiant used to coo! the first carbon absorption unit is the coolant used to cool the heat exchanger.

15. The method of claim 1.4. wherein the coolant Is nitrogen.

1.6. The method of claim 1.2, wherein the desorbed volatile organic component passes through a knock-out tank and an uneooled heat exchanger before passing the desorbed volaiile organic component through the cooled heat exchanger.

17. The method of claim 12, wherein the condensed portion, of the volatile organic component is removed irom the cooled heat exchanger to a condensate tank.

18. The method of claim 12, further including the step of seiectabiy controlling the temperature in the first or second carbon adsorption unit.

1.9. The method of claim 12, ftuther including the step of passing coolant through the first or second carbon adsorption unit to asphyxiate a bed fire,

20. A method for recovering a volatile organic component from a vapor stream comprising:

(a) directing the vapor stream from a storage vessel to a heat exchange module having at least one heat exchange condenser;

fb) starting a refrigerant flow through at least one heat exchange condenser to cool the condenser;

(c) directing the flow of the vapor stream through the heat exchange module, wherein a portion of the volatile organic component in the vapor stream flowing through the cooled heat exchange condenser is condensed;

id) draining the condensed volatile organic component from the cooled heat exchange condenser,

(e) directing the uncondensed vapor stream from the heat exchange module to a first carbon adsorption unit from the cooled, heat exchanger to adsorb the volatile organic component;

(f) measuring the vapor stream exiting from the first carbon adsorption unit for the volatile organic component; (g) releasing the exiting vapor stream from the first carbon adsorption unit into the atmosphere if a measured concentration of the volatile organic component is below a desired concentration;

(h) diverting the flow of the vapor stream to a second carbon adsorption unit whenever the measured concentration of the volatile organic component in the vapor stream exiting from the first carbon adsorption unit is equal to or greater than the desired concentration;

(i) lowering the pressure in the first carbon adsorption, unit to desorb the volatile organic component; and

(]) directing the desorbed volatile organic component through the cooled heat exchanger to condense a portion of the volatile organic compound.

21. The method of claim 20, wherein the heat exchange module contains two heat exchange condensers and a second heat exchange condensers is cooled with refrigerant,

22. The method of claim 20, further comprising the step of seleelab!y cooling the first or second carbo absorption units.

23. The method of claim 20, further comprising the step of controlling the temperature in the first or second carbon absorption units during the absorption of the volatile organic component.

24. The method of claim. 22, wherein the refrigerant is directed to the first or second carbon absorption units from the cooled heat exchange condenser.

25. The method of claim 20, wherein the desorbed volatile organic component passes through, a knock-Out tank and a uneooled hea exchanger before the desorbed volatile organic component, enters the cooled heat exchanger.