Abstract:
An off gas extraction system cleans common sources of off gas, such as storage tanks and polluted soils. Off gas is extracted, followed by compression and condensation. Compression and condensation produce an off gas that can be reintroduced as a treated gas into the off gas source. Alternatively, a regenerative absorber cleans the treated gas by adsorbing residual chemical vapor and concentrates the removed chemical vapors and reprocesses them. If the treated gas is not reintroduced into the off gas source, conventional scrubbers may used on the back end of the system to produce a final exhaust as prescribed by environmental regulation. Methods of accomplishing the same are similarly provided, including novel methods for degassing storage tanks and treating polluted soils to meet current environmental regulations, as well as green technology and sustainability initiatives.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The instant filing requesting grant of Letters Patent claims full Paris Convention Priority from U.S. Provisional Patent Application Ser. No. 61/375,762, as well as PCT/US2010/046232, both filed Aug. 20, 2010 in the name of the present inventor. Both of the referenced applications are expressly incorporated herein by reference, as if fully set forth herein. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to devices and methods for removing contaminated soil vapor. Specifically, the present invention offers for consideration novel vapor recovery systems utilizing compression condensation processes, among other things. 
       SUMMARY 
       [0003]    A vapor recovery system provides superior results to other systems for removing volatile organic compounds and petroleum hydrocarbons from common sources of such pollutants, such as above ground or underground storage tanks and transportable storage tanks. A vapor stream is extracted from a selected source. Depending on the parameters of the selected source and the constituents of concern to be treated, an appropriate technique or combination of techniques including compression, chilling, reheating, condensation, and regeneration, and final treatment are selected. The selected technique or combination of techniques produce liquid condensates and a final vapor stream that is either recirculated back into a source, treated with carbon, thermally or otherwise destroyed, or expelled into the atmosphere. Methods of accomplishing the same are similarly provided, including new ways for characterizing sources of volatile or semi-volatile vapors, optimizing target vapor stream treatment technique selection and processing of the same to achieve cost effective compliance with changing environmental regulations. 
         [0004]    According to a feature of this disclosure, a system for extracting pollutants from a vapor stream is disclosed comprising, in combination: a vapor extraction source, a compressor, a first heat exchanger to condense fluid from off gas and reheat the exhausted off gas, a second heat exchange system to condense fluid from off gas, a regenerative adsorbing unit having at least one regenerative adsorber, and a final treatment step. 
         [0005]    According to another feature, one or many of the first heat exchangers, regenerative adsorbers, and final treatment steps may be eliminated or bypassed based on many factors disclosed herein, including the parameters of the selected source, the constituents of concern to be treated, and the jurisdiction&#39;s environmental regulations. 
         [0006]    According to another feature, the compressor may act by any combination of the following; apply vacuum upon the off gas source, compress the off gas stream, and force the off gas stream through the vapor recovery system. The vacuum applied on the off gas source, the level of compression of the off gas stream, the temperature of compression, the temperature of the compressed off gas exiting the compressor, and the flow rate of the off gas stream through the vapor extraction system can be adjusted to optimize the recovery of contaminants from different sources of vapor and off gas to be treated as known by artisans. 
         [0007]    According to another feature, novel techniques to prevent the accumulation of frozen condensate in the vapor extraction system are disclosed. A method of reheating compressed off gas as it exits a first heat exchange system in order to optimize the functionality of the second heat exchange system is disclosed. 
         [0008]    According to another feature, a regenerative absorber is disclosed comprising, in combination: at least one chamber containing activated alumina, where each chamber has at least one inlet and at least one outlet. The activated alumina is charged with a pollutant at high pressure and the pollutant is unloaded from the activated alumina at low pressure. 
         [0009]    Moreover, further features of this disclosure are disclosed including a method of extracting pollutant from a vapor stream comprising, in combination: selecting optimum flow, compression, condensation, regeneration, and final treatment parameters for the vapor stream to be treated, extracting a vapor stream, compressing the vapor stream to the selected level and temperature of compression, achieving the desired flow rate of the compressed vapor stream, condensing the vapor stream through a series of heat exchangers to form at least one liquefied contaminant in each heat exchanger, reheating the vapor stream prior to at least one heat exchanger in order to optimize the efficiency of that heat exchanger, adsorbing any residual pollutants from the compressed condensed vapor stream with at least one regenerative adsorber to produce a substantially pollutant-free off gas, scrubbing the substantially pollutant-free off gas with a final treatment selected from the list of activated carbon, thermal oxidation, chemical oxidation, reintroduction into the source area, and determining compliance with applicable regulatory requirements. 
         [0010]    Further features of this disclosure are disclosed including a method of extracting pollutant from a vapor stream comprising, in combination; selecting optimum flow, compression, condensation, and recirculation parameters for the vapor stream to be treated, extracting a vapor stream, compressing the vapor stream to the selected level and temperature of compression, achieving the desired flow rate of the compressed vapor stream, condensing the vapor stream through a series of heat exchangers to form at least one liquefied contaminant in each heat exchanger, reheating the vapor stream prior to at least one heat exchanger in order to optimize the efficiency of that heat exchanger, recirculating the substantially pollutant-free off gas to the off gas source, and determining compliance with applicable regulatory requirements. 
         [0011]    Still other features of this disclosure are disclosed including a method for optimizing extraction of pollutant from a vapor stream comprising, in combination: initiating testing to determine contaminants to be addressed at the selected source, determining the optimum flow, compression, condensation, regeneration, and final treatment parameters to treat the source vapor stream so that the vapor extraction flow and chemical recovery rates are optimized, determining the optimum flow, compression, condensation, regeneration, and final treatment parameters to treat the source vapor stream so that the final treatment selected is the most cost effective, cross referencing this preliminary plan to a database of recovery parameters defined by a regulatory authority, executing the plan with a vapor extraction system to recover the contaminants, verifying the nature and quantities of the species of recovered contaminants to form a set of data, and confirming that the data satisfy regulations imposed by a regulatory body. 
         [0012]    Finally according to a feature of this disclosure, there is disclosed a method which comprises; determining a source of at least one vapor stream, recovering at least one contaminant from at least one vapor stream, separating recovered contaminants into at least one subset of contaminants, and recycling the separated recovered contaminants for reuse. 
     
    
     
       DRAWINGS 
         [0013]    The above-mentioned features and objects of the present disclosure will become more apparent with reference to the following description taken in conjunction with the accompanying drawings wherein like reference numerals denote like elements and in which: 
           [0014]      FIG. 1  is a block diagram of embodiments of an off gas treatment system; 
           [0015]      FIG. 2  is a block diagram of embodiments an off gas treatment system including a regenerative adsorber unit; 
           [0016]      FIG. 3  and  FIG. 4  are block diagrams of embodiments of an off gas treatment system with the addition of programmable logistics controller module; 
           [0017]      FIG. 5  is a block diagram of embodiments of vacuum, compression, and flow module; 
           [0018]      FIG. 6  is a block diagram of embodiments of vapor dryer module; 
           [0019]      FIG. 7  is a block diagram of embodiments of a condensation module; 
           [0020]      FIG. 8  is a block diagram of embodiments of a vapor elimination module; 
           [0021]      FIG. 9  is a block diagram of embodiments of refrigeration units; and 
           [0022]      FIG. 10  is a block diagram of a regenerative adsorber module. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    In the following detailed description of embodiments of this disclosure, reference is made to the accompanying drawings in which like references indicate similar elements, and in which is shown by way of illustration specific embodiments in which this disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice this disclosure, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical, functional, and other changes may be made without departing from the scope of this disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of this disclosure is defined only by the appended claims. As used in this disclosure, the term “or” shall be understood to be defined as a logical disjunction and shall not indicate an exclusive disjunction unless expressly indicated as such or notated as “xor.” 
         [0024]    This application incorporates by reference U.S. Pat. No. 7,658,789. 
         [0025]    As used in this disclosure, the term “fluid” shall be understood to mean materials that flow, i.e, gasses, liquids, or plasmas. 
         [0026]    As used in this disclosure, the term “off gas” shall be defined as fluids extracted from contaminated sources and includes soil vapors, previously collected soil vapors, vapors from enclosed sources including tanks, and collected vapors from the production or use of volatile organic compounds, petroleum hydrocarbons, and other volatile vapors. The term vapor is sometimes used herein to be synonymous with the term “off gas” that contains chemical vapors to be recovered. 
         [0027]    In the context of a vapor elimination device, the term “recovery” or “recover” refers to thawing or rewarming a heat exchange module that has been cooled in a prior cycle. 
         [0028]    The industrial revolution marked a radical change to many aspects of society. Industrialized nations became increasingly productive and urbanized. Gasoline and oil production became centralized. Increased pollution resulted. Soil, air, and water carried unprecedented levels of pollutants over the last 200 years. 
         [0029]    Nevertheless, during the middle of the 20th century, social conscience and government sought to eliminate or reduce pollution where possible. The United States government passed strict environmental laws and set aside funds for cleaning polluted natural resources and limiting the emission of carbon dioxide, methane, and volatile vapors into the atmosphere. Similarly, corporations and companies are taking steps to improve the nature and quality of pollutants and to address polluted natural resources. 
         [0030]    The venting of explosive vapors from petroleum and gasoline storage tanks is necessary prior to de-sludging and other maintenance events such as repairing floating deck roofs. Traditionally, pollutants and pollutant vapor trapped in the storage tanks have been vented in order to reduce the concentration of vapors to below lower explosive limits. Venting of these vapors releases large amounts of methane and other green house gasses into the environment. Flaming of these vented vapors reduces the detrimental effect on the environment by reducing the amount of methane introduced into the atmosphere, but is not sustainable when vapor BTU levels begin to decline. Thermal destruction via oxidation, using supplemental fuel supplies to bolster a threshold BTU level and maintain burning, was introduced to remedy this problem. However, vast quantities of carbon dioxide and other damaging emissions are emitted by this process. Moreover, this process uses additional fuels to maintain thermal destruction of volatile vapors. 
         [0031]    Furthermore, storage tanks and other sources contaminated with high levels of predominately petroleum hydrocarbons present a different problem. Common petroleum hydrocarbons such as jet fuels, Stoddard solvent, gasoline, fuel oils, benzene, toluene, ethylbenzene, xylenes, naphthalene, methyl t-butyl ether, aromatic hydrocarbons, and hexane cannot be compressed in a traditional manner due to their explosive properties. In the presence of detectable concentrations of petroleum hydrocarbons, a traditional compression cycle with compression temperatures below 200° Fahrenheit will cause a portion of the petroleum hydrocarbon vapors to turn from gas to liquid phase inside the compression stage of the compressor when the pressure is rapidly increased. The introduction of liquid phase hydrocarbons in the presence of oil will degrade the oil used by the compressor for lubrication and cooling. This disclosure addresses the problem by providing a novel method of preventing the liquefaction of gasses containing petroleum hydrocarbons during compression. 
         [0032]    Because common petroleum hydrocarbons have comparatively lower saturation temperatures and pressures than common chlorinated solvents, the utilization of a vapor extraction system using the high compression levels necessary to process and recover chlorinated solvents may result in unnecessary compression and power consumption when the off gas stream contains predominately petroleum hydrocarbons. This disclosure addresses this problem by providing a novel method of regulating the minimum necessary compression parameters of the off gas necessary to maintain a certain desired flow rate through a determined plurality of heat exchangers, regenerative adsorbers, and final treatment steps. 
         [0033]    The ideal gas law confirms that the state of a gas is determined by its pressure and temperature. Therefore, the ideal gas law holds that as the pressure of an off gas stream increases, the temperature necessary to reach a given saturation rate decreases. When one or more compression devices increase the pressure level of an off gas stream, pollutants in the compressed off gas stream will condense at a higher temperature compared to the same pollutants in an uncompressed off gas stream. This disclosure addresses this problem by providing a novel method of regulating the pressure of the off gas stream through one or more heat exchangers, regenerative adsorbers, and final treatment steps in order to decrease the cryogenic capacity, complexity, and overall size of condensation system used to recover the entrained pollutants. 
         [0034]    As flow rates through the vapor extraction system increase, the rate of chemical recovery through each heat exchanger will increase. At a certain level of increased flow, a given set of heat exchangers will become overloaded with chemical transitioning from gas phase to liquid phase and from liquid phase to solid phase, thus causing blockages in the system, even if it is cycled between refrigeration and thawing cycles. Conversely, if too little a flow of off gas vapors enters through a given set of heat exchangers, the rapid clogging of those heat exchangers with pollutants cooled too rapidly into a solid phase will occur. To overcome this dilemma, this disclosure teaches a novel method for regulating the flow of the vapor extraction system by utilizing different series of heat exchangers. 
         [0035]    Turning now to embodiments illustrated in  FIG. 1 , vapor extraction and recovery system  100  is shown. Vapor extraction and recovery system  100  generally comprises a connection of off gas treatment system  200  to an off gas source  010 . In  FIG. 1 , off gas treatment system  200  comprises a number of subsystems, according to embodiments, including vacuum, compression, and flow module  300 , vapor dryer module  400 , vapor elimination module  500 , and contaminant recovery module  800 . Vacuum, compression, and flow module  300  removes off gas from an off gas source  010 , removes liquid constituents recovered in the off gas removal process, compresses the off gas, and produces flow pressure to move the off gas through vapor extraction and recovery system  100 . Vapor dryer module  400  cools the off gas, removes liquid constituents and substantially all water from the off gas, and reheats the off gas. Vapor elimination module  500  further removes contaminated vapor from the gas and further cools the off gas, producing a substantially dry gas that is free of chemical vapors and routes this gas back to the off gas source  010 . Contaminant recovery module  800  separates condensed and collected chemical constituents by specific gravity, and stores the constituents in one or more storage units. 
         [0036]    According to embodiments illustrated in  FIG. 2 , vapor extraction and recovery system  100  comprises the same core features as vapor extraction and recovery system  100  illustrated in  FIG. 1  with the addition of regenerative adsorber unit  600 . According to these embodiments, vapor dryer module  400  cools the off gas, removes liquid constituents and substantially all water from the off gas, and reheats the off gas. Vapor elimination module  500  further removes contaminated vapor from the gas and further cools the off gas, producing a substantially dry gas as an intermediate result. Regenerative adsorber unit  600  further removes contaminated vapors from the off gas, and routes contaminated gas back to vacuum, compression, and flow module  300 . Also routed from regenerative adsorber unit  600  is an air stream that is substantially free of chemical vapors back to off gas source  010 . This air stream that is substantially free of chemical vapors may be expelled into the atmosphere directly, further scrubbed with granular activated carbon, or directed to further processes. 
         [0037]    According to embodiments and as illustrated in  FIG. 5 , contaminated vapor is removed from off gas source  010  and transferred via inlet conduit  302  into vacuum, compression, and flow module  300 . According to embodiments, liquid (e.g., water) and gas are separated using gas/liquid separator  310  to prevent liquid from entering compressor  330 . Separated liquid is routed from gas/liquid separator  310  via liquid outlet  370 , while gas separated in gas/liquid separator is routed to compressor  330  via gas outlet  303 . According to embodiments, gas/liquid separator  310  may be, for example, a 120 gallon Manchester vertical tank (Manchester Tank, Franklin, Tenn.). 
         [0038]    Gas outlet  303  routes separated gas from gas/liquid separator  310  to compressor  330  (e.g., Quincy model QSI 300 air compressor, 255 cfm at 15″ Hg and 155 psi, 100 horsepower, 3 phase, air cooled 460 volt electric motor). Compressor  330  creates a vacuum that pulls an off gas stream from off gas source  010 . Compressor  330  may be any number of commercially available air compressor systems known to artisans (e.g., Quincy model QSI 370i air compressor, 300 cfm at 15″ Hg and 155 psi, 100 horsepower, 3 phase, air cooled cooled 460 volt electric motor). A person of ordinary skill in the art will know and understand the applicable rotary screw, reciprocating, oil-less, and other compressors to use based on the relevant parameters in the system. Other similar vacuum creation devices may be used depending on the desired gas flow rate, etc., as known and understood by a person of ordinary skill in the art. 
         [0039]    Liquid is moved through liquid outlet  370  with transfer pump  360 , which pumps liquid from gas/liquid separator  310  into initial contaminant recovery tank  810  via liquid conduit  361 . Depending on the source of the off gas stream and prior separation of liquid before entry into inlet conduit  302 , little water will be extracted from off gas source  010 . However, in air sparging or dual phase soil vapor extraction applications, liquid (e.g., water) flow by may occur, necessitating gas/liquid separator  310  to separate the liquid from the gas. 
         [0040]    Transfer pump  360  removes liquid from gas/liquid separator  310 . Transfer pump  360  may be, for example, a centrifugal 120/230 volt ½ horsepower motor pump capable of moving 20 gallons per minute, according to embodiments. Naturally, off gas source  010  that produce large volumes of liquid may require transfer pump  360  that is capable of pumping liquid at a more rapid rate. Similarly, off gas sources  010  producing only nominal amounts of water may be fitted with transfer pump  360  that moves fewer gallons per minute. The exact choice of transfer pump  360  will be known and understood by artisans. 
         [0041]    Initial contaminant recovery tank  810  may be any tank suitable for the purpose of collecting contaminated liquids. As described below, a specific gravity separator may be disposed between transfer pump  360  and initial contaminant recovery tank  810  along liquid conduit  361  to separate each specific contaminant from the other contaminants, according to embodiments. 
         [0042]    As illustrated according to embodiments shown in  FIG. 5 , vacuum created by compressor  330  moves contaminated off gas from gas/liquid separator  310  to compressor  330 . According to embodiments, compressor  330  receives information from programmable logic controller  910  (see  FIGS. 3 and 4 ), including: optimum off gas pressure settings for compressor  330 , optimum temperature for compressor  330  to heat off gas during compression, optimum vacuum pressure for compressor  330  to apply to off gas source  010 , and optimum resulting flow rate from exhaust of compressor  330 . According to embodiments, compressor  330  compresses contaminated off gas to a pressure range between about approximately 75 and 175 psi. According to embodiments, compressor  330  heats compressed off gas to temperature range between about approximately 120 and 235 degrees Fahrenheit. According to embodiments, compressor  330  applies a vacuum on the off gas stream to be extracted from off gas source  010  of between approximately 0 and 20 in. Hg. According to embodiments and depending upon the desired pressure, heat, and vacuum levels, compressor  330  attains an off gas exhaust stream of between approximately 0 and 380 cfm when compressor  330  is a Quincy model QSI 370i air compressor. Compressing off gas containing contaminated vapor concentrates the contaminated vapor for later removal in vapor dryer module  400 , vapor elimination module  500 , and optionally, regenerative adsorber unit  600 . 
         [0043]    After off gas is compressed with compressor  330 , compressed contaminated off gas is routed to aftercooler  350  via conduit  331 , which commences a first round of cooling for the compressed contaminated off gas. According to embodiments, aftercooler  350  is comprised of one or more of an Arrow model AFC 120-1 air to air cooler systems (at 150 psi and 180 scfm), or a similar arrangement with different flow and temperature ratings. As the contaminated off gas is compressed, temperature of gas increases substantially according to the ideal gas law. Aftercooler  350  provides the initial cooling of the compressed contaminated off gas prior to condensation in vapor dryer module  400  and vapor elimination module  500 . According to embodiments, aftercooler  350  cools compressed off gas from approximately 185 degrees Fahrenheit to approximately 90 degrees Fahrenheit. According to other embodiments, programmable logistics controller  910  engages and disengages the cooling fan motor of aftercooler  350  so that the off gas exiting the aftercooler  350  to maintain a constant temperature, for example 100 degrees Fahrenheit. As the compressed contaminated off gas cools inside aftercooler  350 , initial condensation may occur and contaminated vapor may condense to a liquid. The condensate is transferred from aftercooler  350  via aftercooler conduit  355  to initial contaminant recovery tank  810 . According to embodiments, aftercooler conduit  355  may connect into liquid conduit  361  or liquid outlet  370 . 
         [0044]    Turning again to  FIGS. 1-4  and according to embodiments, exhaust from vacuum, compression, and flow module  300  is directed via control valve  402  ( FIG. 1 ) to either vapor dryer module  400  via vapor dryer inlet conduit  403  or to vapor elimination module  500 . Programmable logistics controller  910  operates control valve  402  and determines the direction of the compressed off gas flow. When control valve  402  directs compressed off gas flow to vapor dryer module  400 , the programmable logistics controller  910  will also open control valve  405 , allowing off gas exiting vapor dryer module  400  to enter vapor elimination module  500 . 
         [0045]    According to embodiments, vapor dryer module  400  comprises condensation module  410  and control valves  402 ,  404 . According to embodiments and as illustrated in  FIG. 6 , condensation module  410  is a modified air dryer, such as a ERF- 500A-236 refrigerant air dryer rated at 230 psi for a 35-39° F. pressure dew point, or a similar unit with different flow and temperature ratings. According to embodiments, vapor is first directed to condensation module  410 . 
         [0046]    According to embodiments, condensation module  410  is comprised of air/air heat exchanger  416 , gross water separator  418 , air/refrigerant heat exchanger  420 , and refrigerant unit  450 . In condensation module  410 , the compressed vapor stream is cooled (e.g., from approximately 85° F. to approximately 39° F.) causing condensation of pollutants and water. Condensed liquid pollutant and water from the now-cooled vapor stream is directed to initial contaminant recovery tank  810  via conduit  422 , and the vapor stream is heated to (e.g., to about approximately 75° F.) as it exits condensation module  410 . 
         [0047]    According to embodiments, hot saturated compressed vapor stream from vacuum, compression, and flow module  300  entering condensation module  410  first enters air/air heat exchanger  416 , which cools the air, and gross water separator  418  removes the condensed liquid. The compressed vapor stream enters air/air heat exchanger  416  via vapor elimination conduit  403  where it is pre-cooled by the air discharged from air/refrigerant heat exchanger  420  exiting the condensation module via conduit  421 . Cooled vapor is routed from gross water separator  418  to air/refrigerant heat exchanger  420  via conduit  419 , which further cools the compressed vapor stream. In air/refrigerant heat exchanger  420 , the compressed vapor stream is further cooled (e.g., to about approximately 39° F.), and additional condensed liquid is separated from the vapor stream. Conduit  421  transfers the vapor stream to air/air heat exchanger  416  where it acts as the cooling medium for the previous pre-cooling stage. Air/air heat exchanger  416  also reheats the discharge gas to optimize the temperature of the vapor stream for entry into vapor elimination module  500 . Discharge gas exiting air/air heat exchanger  416  exits condensation module  410  and vapor dryer module  400  via vapor dryer module outlet  404  and to control vale  405 , where the vapor stream is directed to vapor elimination module  500 . 
         [0048]    According to embodiments, when control valve  402  directs compressed off gas flow to vapor elimination module  500 , programmable logistics controller  910  keeps control valve  405  closed, preventing the reversal of flow through condensation module  410 . According to embodiments, vapor elimination module  500  comprises condensation module  510  and control valve  502 , as illustrated in  FIGS. 1-4 . 
         [0049]    According to an embodiment shown in  FIG. 7 , further differentiation of other systems is schematically illustrated, whereby, for example condensation module  510  comprises a heat exchange system for reducing the temperature of the off gas containing contaminated vapor. This module responds to ongoing challenges others have had in dealing with certain volatiles which are not easily converted into the liquid phase. The process causes many chemicals to condense into a liquid, which is subsequently routed to contaminant recovery module  800 . 
         [0050]    According to embodiments, condensation module  510  comprises a plurality of heat exchangers  512   a ,  512   b ,  516   a , and  516   b . Air/air heat exchanger  512  accomplishes initial cooling of compressed contaminated gas. Air/air heat exchanger  512  removes virtually all of the residual water and water vapor in the compressed gas. After initial cooling has occurred in air/air heat exchanger  512 , the compressed contaminated gas is transferred to air/refrigerant heat exchanger  516  via warm vapor conduit  514 . Further cooling of the compressed contaminated vapor occurs in air/refrigerant heat exchanger  516 , causing condensation of the compressed contaminated vapor as the temperature of the gas containing the contaminated vapor drops below condensation point depending on the chemical being condensed. At this stage the compressed gas is virtually dry and free of water and water vapor, according to embodiments. 
         [0051]    Air/air heat exchanger  512  and air/refrigerant heat exchanger  516  work in tandem to heat and cool their respective input and output gasses. The cold output gas from air/refrigerant heat exchanger  516  is routed through air/air heat exchanger  512  via cold vapor conduit  518 . Warm gas incoming to air/air heat exchanger  512  from either aftercooler  350  via control valve  402  or condensation module  410  via control valve  405  is therefore cooled by the cold gas routed into air/air heat exchanger  512  and the cold gas in cold vapor conduit  518  is likewise warmed by warm gas incoming from either aftercooler  350  via control valve  402  or condensation module  410  via control valve  405 . 
         [0052]    According to embodiments shown in  FIG. 8 , air/air heat exchanger  512  and air/refrigerant heat exchanger  516  are disposed in condensation module  510  in a series of two pairs, each pair comprising one air/air heat exchanger  512  and one air/refrigerant heat exchanger  516 . Other configurations with additional air/air exchangers  512  or air/refrigerant heat exchangers  516  are also contemplated. According to embodiments, two Quincy type QSI 370i compressors are used in vacuum, compression, and flow module  300  to apply a vacuum (e.g., 15 in. Hg) on the off gas source  010  and a compression level of (e.g., 155 psi) on the off gas stream causing a resultant flow of compressed off gas sufficient for the pairs of heat exchangers  512 ,  516  (e.g., approximately 500 cfm). 
         [0053]    The compressed off gas flows through vapor condensation module  510  when control valve  402  directs the off gas to condensation module  510 , according to embodiments. Accordingly, the programmable logistics controller  910  activates both heat exchanger pairs  512 ,  516  to work in cycles. During a primary cooling cycle, valves  521 ,  524 ,  526  are open and valves  522 ,  523 ,  525  are closed and refrigerant is delivered to air/refrigerant heat exchanger  516   b . Compressed off gas delivered through either valve  402  or control valve  405  enters module  500  through inlet conduit  452 , and is directed through valve  521 , conduit  452   a , heat exchanger  512   a , conduit  514   a , collection can  561   a,  heat exchanger  516   a,  conduit  518   a , collection can  562   a , heat exchanger  512   a  conduit  552   a , conduit  553 , conduit  452   b , heat exchanger  512   b , conduit  514   b , collection can  561   b , heat exchanger  516   b , conduit  518   b , collection can  562   b , heat exchanger  512   b , conduit  552   b , valve  524 , and conduit  552  when the primary cooling cycle is initiated. Coolant flows from refrigeration units  530 ,  540  into heat exchanger  516   b  via valve  526  when the primary cooling cycle is initiated. Compressed off gas passing through heat exchangers  512   a ,  516   a  is preliminarily cooled to about approximately 15° Fahrenheit by the residual cold temperature of prior cooling cycles. Any frozen condensate in heat exchangers  512   a ,  516   a  from the prior cooling cycle is heated by the comparatively warmer compressed off gas entering said heat exchangers. Initial condensate of the compression off gas forms in heat exchangers  512   a ,  516   a . Condensate is collected in collection cans  561   a ,  562   a  and transported to contaminant recovery module  800 . The preliminarily cooled off gas flows through conduits  552   a ,  553 , and  552   b  and enters heat exchangers  512   b ,  516   b . Compressed off gas passing through heat exchanger  516   b  is cooled to about approximately −45° Fahrenheit as refrigerant flows through heat exchanger  516   b . This cold gas is directed at the return side of heat exchanger  512   b,  where it is warmed to approximately −20° Fahrenheit by the gas flowing through the off gas side of heat exchanger  512   b . Similarly, the approximately 15° Fahrenheit gas flowing through the off gas side of heat exchanger  512   b  is pre-cooled to about approximately 5° Fahrenheit by the cold gas flowing through the return side of heat exchanger  512   b.  Cold gas exiting the return side of heat exchanger  512   b  flows through conduits  552   b ,  552  into module  530 ,  540 . 
         [0054]    Condensate will continue to form as long as refrigerant remains in air/refrigerant heat exchanger  516   b . To remove all condensate, the air/refrigerant heat exchanger pair  512   b ,  516   b  must undergo a thawing cycle to completely liquefy the condensate and remove it, which requires the refrigerant level to be reduced from air/refrigerant heat exchanger  516   b  by closing valve  526 . 
         [0055]    Thus, according to embodiments when two  512 ,  516  heat exchanger pairs are operated in a cycle, air/refrigerant heat exchanger pair  512   b ,  516   b  cools during the primary cooling cycle while the heat exchanger pair  512   a ,  516   a  thaws (i.e., recovers). Once the primary cooling cycle is complete, the respective functions are reversed in what is referred to as the secondary cooling cycle wherein refrigerant is reduced from heat exchanger  516   b  by closing valve  526 , refrigerant is introduced into heat exchanger  516   a  by opening valve  525 , and the heat exchanger pair  512   b ,  516   b  begins to thaw while the heat exchanger pair  512   a ,  516   a  begins to cool. During the secondary cooling cycle, valves  521 ,  524 ,  526  are closed and valves  522 ,  523 ,  525  are open and refrigerant is delivered to air/refrigerant heat exchanger  516   a . Compressed off gas from either control valve  402  or control valve  405  enters module  500  through inlet conduit  452  or inlet conduit  351  and is directed through valve  523 , conduit  452   b , heat exchanger  512   b , conduit  514   b , collection can  561   b,  heat exchanger  516   b,  conduit  518   b,  collection can  562   b , heat exchanger  512   b,  conduit  552   b , conduit  554 , conduit  452   a,  heat exchanger  512   a , conduit  514   a , collection can  561   a,  heat exchanger  516   a,  conduit  518   a , collection can  562   a , heat exchanger  512   a,  conduit  552   a,  valve  522 , and conduit  552  during the secondary cooling cycle. Coolant flows from refrigeration units  531 ,  541  into heat exchanger  516   a  via valve  525  when during the secondary cooling cycle. Compressed off gas passing through heat exchangers  512   b ,  516   b  is preliminarily cooled (e.g., to about approximately 15° F.) by the residual cold temperature of prior cooling cycles. Any frozen condensate in heat exchangers  512   b ,  516   b  from the prior cooling cycle is heated by the comparatively warmer compressed off gas entering the heat exchangers  512   b ,  516   b , thereby thawing the frozen condensate and preparing the heat exchangers for the next cooling cycle. Initial condensate of the compression off gas forms in heat exchangers  512   b ,  516   b . Condensate is collected in collection cans  561   b ,  562   b  and transported to contaminant recovery module  800  via conduit  520 . The preliminarily cooled off gas flows through conduits  552   b ,  554 , and  552   a  and enters heat exchangers  512   a ,  516   a . Compressed off gas passing through heat exchanger  516   a  is cooled (e.g., to about approximately −45° F.) as refrigerant flows through heat exchanger  516   a . This cold gas is directed at the return side of heat exchanger  512   a , where it is warmed (e.g., to approximately −20° F.) by the gas flowing through the off gas side of heat exchanger  512   a . During each cooling, condensate forms and is collected in collection cans  561   a ,  562   a ,  561   b ,  562   b  and moved to contaminant recovery module  800 . Similarly, the cooled (e.g., the 15° F. gas referenced above) gas flowing through the off gas side of heat exchanger  512   a  is pre-cooled (e.g., to about approximately 5° F.) by the cold gas flowing through the return side of heat exchanger  512   a.  Cold gas exiting the return side of heat exchanger  512   a  flows through conduits  552   a,    552  into module  530 ,  540 . 
         [0056]    According to embodiments, refrigerant and warm gas to be cooled by refrigerant are input at the same location and experience parallel flow rather than cross flow. In other words, during one cycle the input of off gas is at one Embodiments employing parallel flow are more rapidly cooled, allowing for shorter cycle times and improving the overall efficiency of the system. According to embodiments, cross flow configurations and parallel flow configurations may be chosen on a case by case basis as would be known to a person of ordinary skill in the art. As used herein, the term parallel flow refers to recovering one heat exchange module while using another heat exchange module for final cooling and condensing, until the heat exchange module either experiences a reduce efficient in air flow, condensation, or temperature, etc., or after a given time period has elapsed. Then the flow of incoming off gas is adjusted for the recovery of the heat exchange module (or another heat exchange module in need of recovery) by using another heat exchange module to do the final cooling. 
         [0057]    Air/refrigerant heat exchanger  516  exchanges heat as would be known to a person of ordinary skill in the art. That is, the refrigerant provides the cooling for the gas. The final temperature range of the gas depends on the coolant used, airflow, and other factors. According to embodiments, if a majority of contaminant condenses in air/air heat exchanger  512 , then gas flow may be increased or cycle time may be decreased as a matter of efficiency. Similarly, where contaminated vapor fails to condense at an efficient rate, gas flow may be decreased or cycle time may be increased to expose gas to refrigerant for a longer period. According to embodiments, the programmable logistics controller  910  selects the proper temperature range and cycle time based on the constituents of concern in the off gas, concentration of those constituents in the off gas, position of control valves  402 ,  404 , pressure of the off gas, and other user-defined parameters. 
         [0058]    According to embodiments, when the heat exchangers cycle, gas flow rate remains constant, but the duration the gas is exposed to the heat exchangers is varied. Thus, according to embodiments, the programmable logistics controller  910  sets a fixed cycle time, for example 30 minutes per pair, when two heat exchanger pairs  512 ,  516  are operated. When the programmable logistics controller  910  detects any decrease in flow rate as measured from a point that is after either of the then-actively-cooling air/refrigerant heat exchangers  516 , the programmable logistics controller  910  will instruct the affected air/refrigerant heat exchanger  516  to cycle into a thawing cycle with its associated air/air heat exchanger  512  while the remaining heat exchanger pair  512 ,  516  continues its cooling cycle, and the programmable logistics controller  910  will simultaneously reset the fixed cycle time. Thus, the flow rate of compressed off gas flowing through any given set of heat exchangers remains constant. 
         [0059]    According to embodiments, programmable logistics controller  910  monitors and controls aftercooler  350  and condensation module  410  so that the compressed contaminated gas exiting aftercooler  350  and condensation module  410  for delivery to condensation module  410  or condensation module  510  is within an optimal temperature range for the chosen condensation cycling. Compressed contaminated gas that is too cold will not effectively warm cold exhaust from air/refrigerant heat exchanger  516  and compressed contaminate gas that is too warm will be inefficiently cooled in condensation module  510  requiring cycle times to be increased to remove a substantial portion of contaminated vapors. Thus, the programmable logistics controller  910  controls the temperature of off gas exiting aftercooler  350  and regulates the flow of that off gas through or around condensation module  410  to provide an optimal compressed contaminated gas temperature to increase efficiency of the system and serves as an optimization step for off gas exiting condensation module  510 . 
         [0060]    For example, condensed off gas leaves compressor  330  at approximately 220° F. and approximately 155 PSI. Aftercooler  350  reduces the temperature from approximately 220° F. to approximately 85° F. As previously described, an initial condensate will be formed as the gas is initially cooled in aftercooler  350 . The initial condensate is transferred to an initial contaminant recovery tank or, according to embodiments, to contaminant recovery module  800 . 
         [0061]    The off gas is transferred from aftercooler  350  to air/air heat exchanger  512  via vapor elimination inlet conduit  351  and a series defined by either control valve  402 , vapor elimination conduit  403 , condensation module  410 , control valve  405 , and vapor elimination conduit  402 . According to embodiments, off gas entering air/air heat exchanger  512  via control valve  402  is cooled from approximately 85° F. to approximately 20° F., as the heat exchange occurs between the gas from aftercooler  350  and the cold gas from air/refrigerant heat exchanger  516 . Further condensate is formed as the gas further cools to approximately 20° F. It is transferred to initial contaminant recovery tank  810  in contaminant recovery module  800  via contaminant recovery module conduit  520 , according to embodiments. Specific gravity separator  808  may be included to separate contaminants by specific gravity and store separated chemical contaminants in multiple contaminant recovery tanks in contaminant recovery module  800 . 
         [0062]    According to the example, off gas entering air/air heat exchanger  512  via control valve  402 , vapor elimination conduit  403 , condensation module  410 , and control valve  405  is cooled from approximately 75° F. to approximately 20° F., as the heat exchange occurs between the gas from aftercooler  350  and the cold gas from air/refrigerant heat exchanger  516 . Further condensate is formed as the gas further cools to approximately 20° F. It is transferred to initial contaminant recovery tank  810  in contaminant recovery module  800  via contaminant recovery module conduit  520 , according to embodiments. Specific gravity separator  808  may be included to separate contaminants by specific gravity and store separated chemical contaminants in multiple contaminant recovery tanks in contaminant recovery module  800 . 
         [0063]    The gas cooled to 20° F. then transfers to air/refrigerant heat exchanger  516  for further cooling to a cold gas from approximately 20° F. to approximately (−50)° F. due to the heat exchange between gas and refrigerant, as known to artisans. As depicted in  FIGS. 8 and 9 , refrigeration unit  531  and refrigeration unit  541  provide refrigerant via refrigerant inlet conduit  532  and refrigerant inlet conduit  542  to air/refrigerant heat exchanger  516  for cooling of the cold gas. To prevent blockages of frozen condensate, gas/gas heat exchanger  512  may be cycled with gas/refrigerant heat exchanger  516 , as would be known to artisans. Thus, prior to freezing up, warmer gas from heat exchanger  512  is used to warm the cold gas in heat exchanger  516 . After cooling, the refrigerant returns to refrigeration unit  531  and refrigeration unit  541  via refrigerant outlet conduit  534   a ,  524   b  and refrigerant outlet conduit  544   a ,  544   b , according to embodiments. At this point in the process, virtually all water vapor has been removed from the off gas, but chemical vapors may remain due to varying dew points and vapor pressures. 
         [0064]    According to another example, the gas cooled to 20° F. then transfers to air/refrigerant heat exchanger  516  for further cooling to a cold gas from approximately 20° F. to approximately (−30)° F. due to the heat exchange between gas and refrigerant, as known to artisans. As depicted in  FIGS. 8 and 9 , refrigeration unit  530  is turned on and refrigeration unit  540  is turned off. In this embodiment refrigeration unit  530  provides refrigerant via refrigerant inlet conduit  532  to air/refrigerant heat exchanger  516  for cooling of the cold gas. To prevent freezing up problems, gas/gas heat exchanger  512  may be cycled with gas/refrigerant heat exchanger  516 , as would be known to artisans. Thus, prior to freezing up, warmer gas from gas/gas heat exchanger  512  is used to warm the cold gas in gas/refrigerant heat exchanger  516 . After cooling, the refrigerant returns to refrigeration unit  530  via and refrigerant outlet conduit  544 , according to embodiments. At this point in the process, virtually all water vapor has been removed from the gas, but chemical vapors may remain due to varying dew points and vapor pressures. 
         [0065]    If the temperature of the off gas exiting the vapor elimination module via conduit  552  must is below about approximately 20° Fahrenheit, the efficiency of regenerative adsorber unit  600  may be degraded. Optimally, the temperature of the off gas entering regenerative adsorber unit  600  is about approximately 60° F. Similarly, when treated off gas exiting vapor elimination module  500  is routed directly back to the off gas source  010 , a this warmer temperature is desired to assist in the volitization of pollutants to be extracted via vacuum, compression, and flow module  300 . As viewed in  FIGS. 8 and 9 , when one or both refrigeration units  530 ,  540  are turned on, off gas exiting the return side of heat exchanger  512  is routed through conduit  552 . Conduit  552  travels through refrigeration units  531 ,  541 . In refrigeration unit  531 ,  541 , off gas from conduit  552  enters heat exchanger  560 . According to embodiments, heat exchanger  560  is a turbo heat exchanger made by Packless Industries. Off gas enters heat exchanger  560  at approximately −20° F., where it is exposed to coils containing warm air of approximately 110° F. from refrigeration condenser  530  or  540  that has entered heat exchanger  560  via conduit  536   a  or  536   b.  The off gas is warmed to approximately 60° F. in heat exchanger  560 , and then exits via conduit  552 . 
         [0066]    According to embodiments, in air/refrigerant heat exchanger  516  final condensation occurs and the condensate is collected after thawing and transferred to contaminant recovery module  800  via contaminant recovery module conduit  520 . The dry cold gas is then transferred to air/air heat exchanger to cool incoming warm gas from aftercooler  350  or vapor chiller module  400  and warm the dry cold gas from air/refrigerant heat exchanger  516  to prepare it for final treatment. According to embodiments, the gas treated by air/refrigerant heat exchanger  516  and routed through air/air heat exchanger  512  is then routed to regenerative adsorber unit  600  to remove residual chemical vapors via regenerative adsorber inlet conduit  652 . 
         [0067]    According to embodiments, multiple condensation modules  510  may be used in parallel or in series to improve efficiency of the condensation process. A person of ordinary skill in the art will understand that each remediation site may require optimization dependant on the particular contaminants at the site, their relative abundance, their vapor pressures, their dew points, and their specific heat of phase conversion. 
         [0068]    This invention&#39;s optimizing improves it from existing systems, with condensation modules  510  used in parallel to provide for greater gas flow through the system. Conversely, condensation modules  510  may be used in series to expose contaminated vapor to subsequent condensation steps in an attempt to remove greater percentages of total contaminants during the condensation step, according to embodiments. 
         [0069]    After the condensation step, residual contaminated vapor typically remains in the gas due to incomplete condensation or chemicals that are not cooled enough or for long enough for condensation to occur. According to embodiments illustrated in  FIG. 10 , high-pressure gas containing residual contaminated vapor is routed to regenerative adsorber module  610  via regenerative adsorber inlet conduit  652 . As shown, two adsorption chambers  660   a ,  660   b  work in tandem to adsorb residual contaminated vapor. During operation, one adsorption chamber  660   a ,  660   b  adsorbs residual contaminated vapor while the other adsorption chamber  660   b ,  660   a  deadsorbs contaminated vapor. The process of desorption regenerates adsorption material  662   a,    662   b  for re-adsorption of contaminated vapor. 
         [0070]    According to an embodiment, an adsorption material  662   a,    662   b  is activated alumina. A person of ordinary skill in the art will readily know and appreciate that other, similar materials may be used in adsorption module depending on the nature of the remediation site, the chemicals involved, and goals of each remediation project. Adsorption by adsorption materials, such as activated alumina, carbon, or resins, occurs at high pressure; desorption occurs at low pressure. Other similar materials and materials specifically suited to adsorption of specific chemicals are expressly contemplated as would be known to a person of ordinary skill in the art. Both adsorption and desorption are relatively temperature insensitive processes, which makes the present system superior for many types of remediation, such as with halogenated chemicals due to the lack of necessity to introduce heat and form strongly acidic byproducts as a result in the desorption process. 
         [0071]    Off gas with residual contamination is introduced to regenerative adsorber module  610  via regenerative adsorber inlet conduit  652 . Disposed between regenerative adsorber inlet conduit and each adsorption chamber  660   a ,  660   b  are inlet valves  654 . Inlet valve  654  control which adsorption chamber  660   a ,  660   b  is adsorbing residual contaminated vapor and adsorption chamber  660   a ,  660   b  desorbing contaminated vapor. During the adsorption process, inlet valve  654  is in an open position allowing off gas containing residual contaminated vapor to enter adsorption chamber  660   a ,  660   b  and contact adsorption material  662   a,    662   b.  During the desorption process, inlet valve  654  is in a closed position to prevent gas from entering adsorption chamber  660   a ,  660   b.    
         [0072]    During the adsorption process, gas containing residual contaminated vapor is forced through adsorption material  662   a,    662   b  in adsorption chamber  660   a ,  660   b . Adsorption material  662   a,    662   b  removes vapor from the gas, including contaminated vapor. As vapor is removed from the gas, adsorption material  662   a,    662   b  charges with contaminated vapor. Gas leaving adsorption chamber  660   a ,  660   b  is therefore substantially, about approximately 99.9%, free of VOCs. Artisans will recognize that one of flow rate of the gas containing contaminated vapor or cycle time will vary from remediation site to remediation site. 
         [0073]    Depending on the types of chemicals being removed, the concentration of the contaminants, the relative amount of contaminated vapor removed in previous remediation steps, for example compression/condensation, and the efficiency of adsorption material  662   a,    662   b  in removing particular vapors from the gas, the parameters within which the system runs will differ. Adsorption material  662   a,    662   b,  surface area of adsorption material  662   a,    662   b,  and other similar variables known to artisans will be evaluated and optimized on a per site basis. In some cases, multiple regenerative adsorption modules  610  will be used in series to accomplish a desired reduction in contaminated vapor passing through vapor elimination module  500 . 
         [0074]    According to embodiments where adsorption material  662   a,    662   b  is activated alumina, adsorption of vapor in gas occurs at high pressure. For example and according to embodiments, cold gas leaving condensation module  510  is at approximately 150 PSI having been compressed prior to entering condensation module  510 . After leaving condensation module  510  and entering regenerative adsorber module  610 , gas pressure is still at approximately 150 psi. 
         [0075]    Referring again to  FIG. 10 , once gas has been exposed to and caused adsorption material  662   a,    662   b  to be charged with contaminated vapor, the exhaust is substantially clean. It escapes through clean exhaust conduit  672 . Disposed on clean exhaust conduit  672  are clean exhaust valves  674 , according to the exemplary embodiment. Generally, at least one clean exhaust valve  674  is disposed along clean exhaust conduit  672  per adsorption chamber  660   a ,  660   b , although multiple clean exhaust valves  674  are contemplated as would be known to artisans. Clean exhaust conduit  672  releases substantially clean gas into vapor stream source  010 , according to embodiments. 
         [0076]    In one embodiment, back pressure regulator  681  is disposed along clean exhaust conduit  672  to maintain a baseline of pressure range of about approximately 130 to 150 psi throughout chemical recovery system  100 . 
         [0077]    According to embodiments, clean exhaust valves  674  shunts a portion of substantially clean gas for the purpose of desorption. When clean exhaust valve  674  is “closed,” it allows a small flow of clean exhaust gas to flow to charged adsorption chamber  660   a ,  660   b  and through charged adsorption material  662   a,    662   b.  This low pressure flow causes adsorption material  662   a,    662   b  to release the contaminated vapors collected in the charging step. These vapors exit through exhaust conduit  670  as inlet valve  654  is closed for charged adsorption chamber  660   a ,  660   b  as the desorption step occurs. 
         [0078]    To that end, clean exhaust valves  674  are configured to shunt a portion of the substantially clean gas into adsorption chamber  660   a ,  660   b  that is desorbing contaminated vapor. Because desorption occurs at lower pressure, a small percentage of the total clean exhaust gas is diverted as a low pressure gas to desorbing adsorption chamber  660   a ,  660   b , while the remaining substantially clean gas continues through clean exhaust conduit  672 . The process of shunting a small percentage of substantially clean gas may be accomplished by partially opening clean exhaust valve  674  or through the use of a multiple valve system, as would be known to artisans. For example, clean exhaust valve  674  may comprise one valve that allows low-pressure substantially clean gas to pass during adsorption chamber&#39;s  660   a ,  660   b  desorption cycle and a separate valve that may be fully opened to allow high-pressure substantially clean gas to escape during the adsorption cycle. The implementation of such a system will be known and understood by a person of ordinary skill in the art. 
         [0079]    Consequently, as one adsorption chamber, e.g.,  660   a , of regenerative adsorber module  610  is being charged with contaminated vapors and exhausting substantially clean exhaust gas, adsorption chamber,  660   b  is being desorbed of contaminated vapors previously collected and contained in adsorption material  662   b.  Desorption occurs as a percentage of the substantially clean gas forming a low pressure flow is shunted into adsorption chamber  660   b . After adsorption chamber  660   a  becomes fully charged, the system is reversed and adsorption chamber  660   b  is charged with contaminated vapors while adsorption chamber  660   a  is desorbed of the previously collected contaminated vapors. 
         [0080]    During the desorption cycle of adsorption chamber  660   a ,  660   b , adsorption material  662   a,    662   b  starts in a state wherein adsorption material  662   a,    662   b  is fully charged with contaminated vapor. As low-pressure substantially clean air is shunted into adsorption chamber  660   a ,  660   b , vapor contained in adsorption material  662   a,    662   b  is released from adsorption material  662   a,    662   b  into the low-pressure substantially clean gas. The resultant gas comprises concentrated contaminated vapor. The gas containing the concentrated contaminated vapor is then routed through exhaust conduit  670  to vacuum and compression module  300  for recompression and rerouting through the compression/condensation process. 
         [0081]    Multiple regenerative adsorber modules  610  may be placed in series or in parallel as a matter of efficiency to ensure adequate removal of particularly difficult contaminants. Moreover, efficiencies of the present system may provide for increased gas flow rates, and thus more rapid remediation of a polluted remediation site, due to increased efficiency of remediation and chemical recovery system  100  over conventional SVE systems. 
         [0082]    Thus, artisans will appreciate that nearly all contaminated vapor from the ground is eliminated by compression/condensation. Vapor that escapes compression/condensation is captured by adsorption material  662   a,    662   b  for reconcentration during the desorption process. The reconcentrated contaminated media will then be more readily condensed out during a second round of compression/condensation owing to the increased concentration of the contaminated vapor, where it would have originally escaped due to the fact that the concentration of contaminated vapor dropped below a critical point where no additional contaminated vapor of a given chemical could be condensed out of the gas. The compression/condensation-adsorption cycle is repeated until the measured volumetric concentration output of contaminant being removed shows the remediation site is substantially clean. 
         [0083]    According to embodiments of a method for the removal of pollutants from a stream of off gas, off gas vapor is processed through a vapor elimination module, said vapor elimination module containing at least one air-to-air heat exchanger and at least one air-to-refrigerant heat exchanger, working in tandem, wherein off gas vapor is condensed in each heat exchanger and removed as a liquid from the vapor elimination module. The off gas vapor stream exiting the vapor elimination module will contain less pollutants than it contained when it entered the vapor elimination module. The nature and concentration of the pollutants, pressurization rate of the off gas stream, refrigerant used, number and size of condensation units used, cooling cycle time, and other factors known to artisans will determine the precise proportion and quantity of pollutants removed as condensed liquid from the vapor elimination module. 
         [0084]    According to embodiments of a method for the operation of a vapor elimination module, the refrigerant flow is decreased to initiate a thawing cycle. The thawing cycle is needed to one or both prevent the freezing of condensate and remove frozen condensate from within both the air-to-air and air-to-refrigerant heat exchangers, especially their inlets and outlets. The thawing cycle is unique in that the air-to-air and air-to-refrigerant heat exchangers work in tandem to warm each other. Warm air flowing into the air-to-air heat exchanger traverses that heat exchanger and enters the air-to-refrigerant heat exchanger, where it warms that heat exchanger. The air exiting the air-to-refrigerant heat exchanger is warm enough to help thaw the air-to-air heat exchanger as it flows through the return side of that heat exchanger. 
         [0085]    According to embodiments of a method for off gas extraction and processing shown in  FIGS. 1-4 , off gas vapor is extracted from an off gas source. These vapors, as previously discussed, contain vapors contaminated with pollutant. The off gas is extracted by means of a vacuum pump, blower, compressor, ring pump, or other device as known by artisans. For example, the off gas is compressed to about approximately 150 psi. The pressurized off gas enters aftercooler  350 , where initial water and pollutant condensate are collected. Thereafter, the pressurized off gas enters condensation module  410 . Condensation module  410  cools the gas further, causing contaminated vapors to condense into a liquid form that may be captured. Condensation module  410  then warms the cooled gas prior to its exit from the drying process. This warming function is integral to the functionality of the condensation process, especially the interaction between the air-to-air heat exchanging condensers and the air-to-refrigerant heat exchanging condensers in the vapor elimination process  500 . Vapor elimination process  500  further cools the gas and causes much of the contaminated vapors to condense into a liquid form that may be captured. The drying and vapor elimination process recovers a large percentage of contaminated vapors from the gas stream. According to embodiments, the gas stream is then: (1) recirculated back to the off gas source, for example a storage tank, to create a closed-loop process; or (2) directed to a regenerative adsorber module  610 , as shown in  FIG. 2 , that further removes any remaining contaminants from the air stream, and then recirculated back to the off gas source, for example a storage tank, to create a closed-loop process. 
         [0086]    Likewise disclosed is a method for optimizing the use of the systems of this disclosures. The optimization method ensures efficient flow. Initially, plans are generated to do this based on the contaminants to be removed and the source of the contaminants. These plans may be directed towards general remediation of a site, to specific contaminants, or according to the directive of a regulatory authority, such as the United States Environmental Protection Agency, or the South Coast Air Quality Management District. Generally, the plan will include use of a degassing system, such as the closed-loop degassing system disclosed herein. Depending on the particular contaminants to be addressed and the source of those contaminants, optimizations of the system will address the particular parameters of the application. 
         [0087]    For example, a railcar tank may be contaminated with difficult to remove contaminants such as vinyl chloride or freon that will be removed inefficiently by a drying and vapor elimination process alone. In these types of cases, for example, the flow of refrigerant through one or more heat exchangers in a vapor elimination module may be increased in order decrease the temperature of the off gas flowing through the heat exchangers to optimize the recovery of liquid phase condensate. Additionally, the freezing and thawing cycles of the vapor elimination module may be varied and optimized based on the plan. Furthermore, a regenerative adsorber module may be added after a vapor elimination module any residual pollutants not recovered as liquid phase condensate. Similarly, decisions may be made to use systems with multiple compression and condensation modules and regenerative adsorber modules in series or in parallel, depending on embodiments. Similarly, the adsorption and desorption of the regenerative adsorber module may be cycled to adjust the system to site conditions, as necessary and according to embodiments. 
         [0088]    In a different example, a degassing site containing a 150 foot diameter above ground storage tank with petroleum hydrocarbon vapors will be efficiently degassed using a compression, vapor drying, and vapor elimination process. Some residual pollutants may still be present in the treated air stream that is returned to the storage tank, but after the degassing process is complete, the concentration of the gasses present in the storage tank will be below safe LEL levels. 
       EXAMPLES 
     Example 1 
       [0089]    An above-ground storage tank at an active refinery site is selected for remediation, wherein the system optimization is conducted to maximize the efficiency of the vapor extraction system and expedite tank degassing. The vapor extraction system targets petroleum hydrocarbon-impacted vapors inside the storage tank. 
         [0090]    One mobile vapor extraction system is installed at the site, adjacent to the storage tank to be treated. The vapor extraction system is rated at 300 scfm capacity. This system draws and processes off gas from the storage tank via a 6 inch diameter flex hose. One end of this flex hose is connected to an adaptation that creates an airtight seal around the open, front access cover of the storage tank. The other end of this flex hose is routed to the vapor extraction system&#39;s vacuum, compression, and flow module. 
         [0091]    As depicted in  FIG. 3 , the vapor extraction and recovery system comprises a vacuum module, a vacuum, compression, and flow module  300 , a vapor dryer module  400 , a vapor elimination module  500 , a contaminant recovery module  800 , and a programmable logistics controller module  900 . The vacuum, compression, and flow module consists of one Atlas Copco Model ZE 375 hp air compressor capable of compressing 310 scfm of off gas to 50 psi while delivering a vacuum of 2 in. Hg. and one specially fabricated stainless steel air-to-air heat exchanger with condensation drain capable of cooling 350 cfm flow at 50 psi. The vapor dryer module consists of one Great Lakes Model ERF-500A-236 refrigerant air dryer, rated for up to 230 psi for a 35-39° F. pressure dew point. The vapor elimination module consists of two pairs of air-to-air heat exchangers and air-to-air heat exchangers working in line. 
         [0092]    The vapor extraction and recovery system delivers recovered, condensed pollutants and water collected from the off gas stream to contaminant recovery module  800 , a series of two interconnected 750 gallon storage tanks. One inlet is present on the first storage tank of the interconnected series of storage tanks. Water delivered to the interconnected series of storage tanks accumulates in this first storage tank, with LNAPL and petroleum pollutants also collecting in this first storage tank and overflowing into the second storage tank of the interconnected series of storage tanks. LNAPL is collected from the second storage tank and the bottom of the first storage tank of the interconnected series of storage tanks and, after the tank degassing is complete, transferred back to the storage tank that was the original source of the off gas stream via a portable transfer pump. The remaining water and trace pollutant is removed for off site disposal. 
         [0093]    While the apparatus and method have been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the disclosure need not be limited to the disclosed embodiments. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures. This disclosure includes any and all embodiments of the following claims.