Abstract:
Embodiments of the invention provide a self-contained unit which is automated for safety and efficiency recovers emissions present as a result of loading volatile organic compositions at marine or land based vessels or terminals. The unit is enclosed for protection of its components from wind, weather and the saltwater marine environment, while including venting for protection against possible vapor build-up. The unit also includes required support services and materials, and also includes structure for protection against transfer of explosion back into the cargo vessel or terminal.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a divisional application of U.S. patent application Ser. No. 12/248,335, filed on Oct. 9, 2008, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to recovery of volatile organic compound (VOC) fluids during loading or unloading from marine vessels, from petroleum production platforms or vessels or other such facility or location. 
         [0004]    2. Description of the Related Art 
         [0005]    Vapor recovery units such as those of U.S. Pat. No. 5,050,603 have been provided to recover volatile organic compound (VOC) emissions during or unloading of barges or other vessels from marine vessels, from petroleum production platforms or vessels or other such facility or location. U.S. Pat. No. 5,050,603 is owned by a related company of the assignee of the present application. U.S. Pat. No. 5,050,603 is incorporated herein by reference. 
         [0006]    Typically, such a vapor recovery unit has been ship or barge mounted and traveled in open marine waters from port to port based on service demands. In such an environment, the unit was continually exposed to the marine atmosphere and elements, such as salt water, rain, wind, wave action and the accompanying corrosive nature they presented. In vapor recovery units of this type, a number of the components, including fluid handling mechanical elements such as vessels, tubing, connections and fittings, as well as control elements such as valves, meters and other instrumentation exposed to the marine atmosphere of an ocean or port environment. Further, the unit and its components have been required by their use and purpose to be present in the hazardous zones created by proximity to oil and gas production. Potential leakage of any VOC vapors from the unit in an already hazardous zone in proximity to oil and natural gas production was a problem and safety concern. Additionally, salt air corrosion of components in the unit and the possible leaking of vapors from the unit were undesirable in order to avoid environmental pollution. 
         [0007]    An additional and separate safety concern was present due to the nature of the VOC fluids being transferred to the vapor recovery unit from a cargo tank of a barge or other transport vessel. Concern was present about the hazardous consequences of an explosion in the event one might occur in the equipment of the vapor recovery unit and then be transmitted back through piping and connections from the vapor recovery unit to the vapor space in a cargo tank of the barge or other vessel from which the vapors were being extracted. In transfer of the explosive vapors which accompany VOC fluids from a cargo space to another vessel such as the vapor recovery unit, the hazard of an explosion in the unit spreading back from the vapor recovery unit into another typically larger vapor space on the vessel was a concern. 
         [0008]    Operation of a vapor recovery system such as that of U.S. Pat. No. 5,050,603 was labor intensive in that it was not automated. The operator was required to be present to run the system 24 hours a day during vapor recovery unit operations. The vapor recovery system required a full time operator to start the system, provide continuous adjustments during operations and shut the system down at the end of vapor recovery operations in connection with a load of oil. The operator was required to have taken specialized training to deal with issues that might arise out of operational problems. Successful operation of the unit was dependent on an operators&#39; detailed knowledge of the process, and equipment settings of the various components. In addition, an operator was required to have mechanical ability to make repairs and adjustments, and instrumentation and control experience, such as record keeping skills in reading and documenting gauge settings and control functions. 
         [0009]    Further, while vapor recovery units according to U.S. Pat. No. 5,050,603 were provided on skids in platform mounted form for mobility purposes, the units were not usable or self-sustaining on arrival at a job site. Outside support was required to be available at the job site in the form of electrical power, compressed air, and diesel fuel, and also of chemicals used in the process, such as methanol. This resulted in additional time and effort having to be spent at the job site in connecting the unit to these required sources and testing these connections during the unit set-up process before the vapor recovery unit was available for use. If the outside support and supplies were not present and available locally at the job site, vapor recovery was typically not available, in the absence of time-consuming prior planning and co-ordination. 
         [0010]    Other systems used in the past for vapor recovery in the oil and chemical industries such as in have included cryogenic gas treatment and recovery by direct refrigeration, light lean oil absorption and activated carbon absorption. 
       SUMMARY OF THE INVENTION 
       [0011]    Briefly, the present invention provides a new and improved mobile apparatus for recovery of volatile organic compound vapor from a vaporous fluid containing volatile organic compounds during transfer from a storage container for pollution reduction. The mobile volatile organic compound (or VOC) recovery apparatus according to the present invention includes a vapor collection safety unit connected in a fluid transfer conduit from the storage container for receiving the vaporous fluid. The vapor collection safety unit contains a shutdown valve responsive to hazardous conditions to block the fluid transfer conduit. A scrubber unit is connected to the vapor collection safety unit and removes corrosive compounds from the vaporous fluid transferred from the storage container. A compressor unit is connected to the scrubber unit to compress the vaporous fluid after removal of corrosive compounds in the scrubber unit. A liquid-vapor separator module is connected to the compressor unit. The liquid-vapor separator module has a liquid outlet for liquids separated from vaporous fluid received from the compressor unit, and a vapor outlet for vapors separated from vaporous fluid received from the compressor unit. A cooler module is connected to the vapor outlet of the liquid-vapor separator module and cools the vapor received into a recovered volatile organic compound liquid and a recovered volatile organic compound vapor. A vapor scavenger unit is connected to the cooler module for utilizing the recovered volatile organic compound vapor. 
         [0012]    The present invention also provides as a separate aspect from that described above a new and improved mobile apparatus for recovery of volatile organic compound vapor from a vaporous fluid containing volatile organic compounds during transfer from a storage container for pollution reduction. The mobile volatile organic compound (or VOC) recovery apparatus according to the present invention includes a scrubber unit connected to the vapor collection safety unit and removing corrosive compounds from the vaporous fluid transferred from the storage container. A compressor unit is connected to the scrubber unit to compress the vaporous fluid after removal of corrosive compounds in the scrubber unit. A liquid-vapor separator module is connected to the compressor unit. The liquid-vapor separator module has a liquid outlet for liquids separated from vaporous fluid received from the compressor unit and a vapor outlet for vapors separated from vaporous fluid received from the compressor unit. A cooler module is connected to the vapor outlet of the liquid-vapor separator module. The cooler module cools the vapor received into a recovered volatile organic compound liquid and a recovered volatile organic compound vapor. A fluid supply is provided in the apparatus for supplying operating fluid for the apparatus. A vapor scavenger unit is connected to the cooler module to utilize the recovered volatile organic compound vapor. 
         [0013]    The present invention further provides as a separate feature from those described above a new and improved mobile apparatus for recovery of volatile organic compound vapor from a vaporous fluid containing volatile organic compounds during transfer from a storage container for pollution reduction. The mobile volatile organic compound (or VOC) recovery apparatus according to the present invention includes a vapor recovery module which includes a scrubber unit removing corrosive compounds from the vaporous fluid transferred from the storage container; a compressor unit connected to the scrubber unit and compressing the vaporous fluid after removal of corrosive compounds in the scrubber unit; and a liquid-vapor separator module connected to the compressor unit. The liquid-vapor separator module has a liquid outlet for liquids separated from vaporous fluid received from the compressor unit, and a vapor outlet for vapors separated from vaporous fluid received from the compressor unit. A cooler module provided as a part of the vapor recovery module is connected to the vapor outlet of the liquid-vapor separator module to cool the vapor received into a recovered volatile organic compound liquid and a recovered volatile organic compound vapor. A vapor scavenger unit of the vapor recovery module is connected to the cooler module for utilizing the recovered volatile organic compound vapor. According to this aspect of the present invention, a platform has the vapor recovery module mounted therewith; and an enclosure is mounted with the platform and encloses the vapor recovery module. 
         [0014]    The present invention further provides as a separate feature from those described above a new and improved mobile apparatus for recovery of volatile organic compound vapor from a vaporous fluid containing volatile organic compounds during transfer from a storage container for pollution reduction. The mobile volatile organic compound (or VOC) recovery apparatus according to the present invention includes a scrubber unit to remove corrosive compounds from the vaporous fluid transferred from the storage container. The scrubber unit has sensors for monitoring process conditions therein and control members connected therewith for controlling fluid conditions therein. A compressor unit is connected to the scrubber unit and compresses the vaporous fluid after removal of corrosive compounds in the scrubber unit. The compressor unit has sensors for monitoring process conditions therein and control members connected therewith for controlling fluid conditions. A liquid-vapor separator module is connected to the compressor unit, and has a liquid outlet for liquids separated from vaporous fluid received from the compressor unit and a vapor outlet for vapors separated from vaporous fluid received from the compressor unit. The liquid-vapor separator module has sensors for monitoring process conditions therein and control members connected therewith for controlling fluid conditions. A cooler module is connected to the vapor outlet of the liquid-vapor separator module and cools the vapor received into a recovered volatile organic compound liquid and a recovered volatile organic compound vapor. The cooler module has sensors for monitoring process conditions therein and control members connected therewith for controlling fluid conditions. A vapor scavenger unit is connected to the cooler module and utilizes the recovered volatile organic compound vapor. The vapor scavenger unit has sensors for monitoring its process conditions and control members connected for controlling fluid conditions. A processor control computer has a stored established set of state point stored therein to establish operating conditions for the apparatus. The processor control computer monitors the sensors and adjusts the control members of the apparatus according to the established operating conditions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The objects, advantages and features of the invention will become more apparent by reference to the drawings appended thereto, wherein like numerals indicate like parts and wherein an illustrated embodiment of the invention is shown. 
           [0016]      FIG. 1  is a schematic block diagram of a vapor recovery unit according to the present invention. 
           [0017]      FIG. 2  is a piping and instrumentation diagram of the vapor recovery unit of  FIG. 1 . 
           [0018]      FIG. 3  is a schematic diagram of a vapor collection safety unit of the vapor recovery unit of  FIG. 1 . 
           [0019]      FIG. 4  is a plan view of the internal layout of the vapor recovery unit of  FIG. 1 . 
           [0020]      FIG. 5  is an isometric view of the vapor recovery unit of  FIG. 1 . 
           [0021]      FIG. 6  is a front elevation view of the vapor recovery unit of  FIG. 1 . 
           [0022]      FIGS. 7 and 8  are side elevation views the vapor recovery unit of  FIG. 1 . 
           [0023]      FIG. 9  is a rear elevation view of the vapor recovery unit of  FIG. 1 . 
           [0024]      FIG. 10  is another isometric view of the vapor recovery unit of  FIG. 1 . 
           [0025]      FIG. 11  is a schematic diagram depicting the arrangement of  FIGS. 11A ,  11 B,  11 C, and  11 D. 
           [0026]      FIGS. 11A ,  11 B,  11 C, and  11 D when arranged as illustrated in  FIG. 11  are an example state point diagram of a vapor recovery unit like that shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    In the drawings, the letter A designates a mobile apparatus according to the present invention for recovery of volatile organic compound vapor from a vaporous fluid containing volatile organic compounds during transfer from a storage container for pollution reduction. The vaporous fluid is typically a hydrocarbon liquid being loaded or unloaded from a storage container, such as a cargo tank. One example of such a cargo tank is a marine vessel, such as a barge or tanker. Another type of cargo tank is a shore-based petroleum tank. It should be understood that the apparatus A may be used with other types of storage containers for bulk storage of hydrocarbons, including those at offshore platforms as well. 
         [0028]    The mobile volatile organic compound (or VOC) recovery apparatus A according to the present invention includes a vapor collection safety unit S connected in a fluid transfer conduit  20  from the storage container for receiving the vaporous fluid. The vapor collection safety unit S contains a shutdown valve  22  ( FIG. 3 ) responsive to hazardous conditions in the apparatus A to block the fluid transfer conduit  20 . In this way, any potential hazard such as fire, flame or incipient explosion in the apparatus A is blocked from passage back to the storage container through the fluid transfer conduit  20 . 
         [0029]    A scrubber unit U ( FIG. 1 ) is connected to the vapor collection safety unit S to remove corrosive compounds from the vaporous fluid transferred from the storage container. A compressor unit C is connected to the scrubber unit U to compress the vaporous fluid after removal of corrosive compounds in the scrubber unit U. 
         [0030]    A liquid-vapor separator module L is connected to the compressor unit U. The liquid-vapor separator module L has a liquid outlet  16  for liquids, at this stage principally water, separated from vaporous fluid received from the compressor unit U. The liquid-vapor separator module L also includes a vapor outlet  26  for vapors, typically principally unliquified hydrocarbons, separated from vaporous fluid received from the compressor unit U. 
         [0031]    A cooler module R is connected to the vapor outlet  26  of the liquid-vapor separator module L and cools the vapor received into a recovered volatile organic compound liquid and a recovered volatile organic compound vapor. As will be set forth, the cooler module R typically takes the form of several sequentially connected cooler stages, each cooling an incoming vapor fluid and separating the incoming vapor into a liquid and a volatile organic compound vapor. A vapor scavenger unit G is connected to the cooler module R for utilizing the recovered volatile organic compound vapor. The utilization may take the form of consumption of the recovered VOC vapors as fuel in an engine or some suitable form of adsorption. In its preferred embodiments, according to the present invention the vapor scavenging unit G is typically a diesel engine adapted to utilize light VOCs as a supplemental fuel which is coupled to either an electricity generator which provides some of the power needed by the apparatus A, or to a hydraulic pump. The present invention also contemplates that the vapor scavenging unit G may take the form of a molecular sieve adsorber capable of absorbing the residual light VOCs. 
         [0032]    The apparatus A also includes a fluid supply F for supplying operating fluid for operation of the other units during vapor recovery operations. When the vapor scavenger unit G takes the form of a diesel engine consuming the volatile organic fluid vapor received from the cooler module R, the fluid supply F includes a fuel supply for the engine. The fluid supply F also includes a supply of coolant supply of coolant fluid for the cooler module R. 
         [0033]    The vapor collection safety unit S, scrubber unit U, compressor unit C, liquid-vapor separator module L, cooler module R, fluid supply F and vapor scavenger unit G take the form of a vapor recovery module M and are mounted on a common platform P of the apparatus. With the present invention, the term “platform” is not restricted to a platform in the sense of a highway flatbed but is intended to include structures for attaching process equipment to a ship or barge or skids after transport by a trailer-type or road transport vehicle over on land. The apparatus A is mounted upon the platform P. As will be set forth, the platform P is typically formed of two separate skid sections, for road transport regulation purposes, which are assembled together to support the apparatus at the job site, whether in a marine vessel or on land. 
         [0034]    According to the present invention, an enclosure E is mounted with the platform P and encloses the vapor recovery module M. The enclosure E is waterproof and weatherproof, being made of steel structure and plates, or comparable materials. The enclosure E is also vented during operations to provide a safe access to operational personnel. The enclosure E also has conventional sensors and associated alarms/indicators suitably placed within it to continuously test the atmosphere, to guarantee the safety of those who enter. 
         [0035]    Tuning now to the vapor collection safety unit S, the shutdown valve  22  ( FIG. 3 ) is a pressure actuated flow control valve of the type furnished with a fail-safe operator, open and closed position limit switches, as well as being capable of manual actuation. The shutdown valve  22  and other instrumentation of the apparatus A is connected to an instrumentation air supply I ( FIG. 1 ). 
         [0036]    A position sensor  22   a  is associated with the shutdown valve, as are pressure/temperature sensors indicated schematically at  22   b  located upstream of the valve  22  on transfer conduit  20 . The sensors  22   a  and  22   b  monitor conditions relating to the apparatus associated with the shutdown valve  22  and provide data readings to the computer K. The pressure actuated shutdown valve  22  is actuated in response to detection of a hazardous condition such as an abnormal or hazardous temperature or pressure in the apparatus A by the computer K to block the fluid transfer conduit  20 . The shutdown valve  22  may also be actuated manually, as noted. 
         [0037]    The vapor collection safety unit S also includes a suitable pressure/temperature sensor  24  located downstream of the valve  22  in conduit  20  to activate audible and visual alarms  26  in response to detection of either low or high conditions pressure conditions in the transfer conduit  22 . The vapor collection safety unit S also includes a cartridge filter  28  to prevent unwanted particles in the conduit from entering the apparatus A and to reduce plugging potential in a detonation arrestor  30  of the vapor collection safety unit S. It should be understood that a basket strainer might also be used, if desired. 
         [0038]    The cartridge filter  28  is provided with a gauge pressure transmitter  28   a  and a differential pressure sensor or transmitter  28   b . The transmitters  28   a  and  28   b  monitor conditions relating to the apparatus associated with the cartridge filter  28  and provide data readings to the computer K. The gauge transmitter  28   a  monitors pressure conditions in the conduit  20  upstream of the filter  28 , while the differential pressure sensor/transmitter  28   b  senses and monitors conditions relating to possible blockage or plugging of the filter  28 . A sample valve  28   c  is also connected to the filter  28  for testing and sampling purposes. 
         [0039]    The detonation arrestor  30  is preferably of the type intended for use with what are known as “Class D Vapors.” The detonation arrestor includes temperature sensors  30   a  and  30   b  on inlet and outlet sides, respectively of arrestor element  30  to monitor conditions relating to the arrestor  30  and provide data readings to the computer K. A differential pressure gauge  30   c  senses and monitors conditions relating to pressure drop across the arrestor  30 . The vapor collection safety unit S also includes a vacuum relief valve  34  connected to the conduit  20  between the cartridge filter  28  and the arrestor  30 . 
         [0040]    The foregoing equipment and components of the vapor collection safety unit S are mounted in a single skid located on the platform P beneath the conduit  20  leading to the scrubber unit U. A conventional control panel  38  ( FIG. 1 ) is provided for operator annunciation and interface, being mounted on the vapor collection safety unit S. The control panel may include at least a horn, a suitable number of strobe lights for annunciation system alarms and emergency push/pull buttons for shutdowns of the apparatus A as required by the process or by any appropriate governmental regulation. 
         [0041]    In vapor recovery with the apparatus A, a direct refrigeration portion of the process occurs in which the VOC emissions first pass from the storage container through the transfer conduit  20  and the vapor collection safety unit S to the scrubber unit U. Scrubber unit U is a suitable form of caustic scrubber where potential corrosive or sulfurous components of the type which may be present in the hydrocarbons in the vapor stream are removed. Flow of the vapor from the storage container and the vapor collection safety unit S through the caustic scrubber is induced by an inline blower  40  ( FIG. 2 ) located downstream of the caustic scrubber U. The blower  40  is fitted with a valve  42  which may be opened by a control mechanism  42   a  in response to the computer K to discharge the vapor through vent  18  to atmosphere in an emergency. Manual operating capability of the valve  42  is also provided. 
         [0042]    From the blower, the scrubbed vapor passes to a compressor  44  which boosts the pressure of the vapor stream to a state point of pressure and temperature established by the process control computer K, as will be set forth. The compressed vapors exiting from the compressor  44  are fed to a liquid-vapor separator  50  of the liquid-vapor separator module L. The liquid stream exiting from a liquid outlet  50   a  at the bottom of the liquid-vapor separator  50  is essentially hot water, free of oil, which may be recycled. 
         [0043]    A vapor outlet  50   b  of the liquid-vapor separator  50  transfers the exiting separated vapor stream through a line  52  so that the separated vapor stream passes through a compressor discharge cooler  54  of the cooler module R, utilizing cooling water from a cooling water supply  55  ( FIG. 1 ) as the cooling medium. The discharge cooler  54  cools the vapor stream to a temperature range established by the process control computer K. A temperature sensor  54   a  and a pressure sensor/transmitter  54   b  are located upstream in the line  52  of the cooler  54  to provide data readings and indications to the process control computer K. 
         [0044]    The cooled vapor stream from the compressor discharge cooler  54  passes through a line  56  to an after cooler knock-out drum  58  of the liquid-vapor separator module L. A temperature sensor  56   a  is located downstream of the cooler  54  to provide data readings and indications to the process control computer K. The cooler knock-out drum  58  is fitted with an oily water drain valve control system  60  including a control valve  62  controlled by the computer K based on readings furnished from a differential pressure transmitter  58   a  to drain hydrocarbon liquids and water through conduit  16  associated with the storage container. 
         [0045]    Vapors exit from an outlet  58   b  at the top of the knock-out drum  58  and travel through outlet  18  to enter a first high temperature chiller  64  of the cooler module R. In the first high temperature chiller module  64 , the entering vapor is cooled with a low pressure refrigerant which is preferably methanol from a methanol or coolant supply unit  68  of the fluid supply F. The vapor is cooled in the chiller  64  to a temperature range established by the process control computer K to produce a vapor-liquid mixture. 
         [0046]    A differential pressure sensor/transmitter (not shown) is connected to the first high temperature chiller module  64  to provide data readings and indications to the process control computer K. A level control valve  66  is controlled by the computer K based on readings from the differential pressure transmitter  64   a  to control fluid levels in the chiller  64 . 
         [0047]    The fluid mixture from the chiller  64  is fed to a cold three-phase knock-out drum  68  which is fitted with a hydrocarbon liquid drain system  70  for recovering liquid hydrocarbons. 
         [0048]    The hydrocarbon liquid drain system  70  includes a differential pressure sensor  72  to provide data readings and indications to the process control computer K and a liquid control valve  74  controlled by the computer K to control fluid levels in the knock-out drum  68 . Liquid hydrocarbons recovered by knock-out drum  68  which are then reinjected into the cargo loading line through a line  76 . 
         [0049]    The vapor portion of the mixture exits from an outlet  68   a  at the top of the three-phase knock-out drum  68  and enters a low temperature chiller  80  where it is cooled by low temperature refrigerant to a temperature range established by the process control computer K. A hydrocarbon liquid drain system  82  includes a differential pressure sensor  84  to provide data readings and indications to the process control computer K and a liquid control valve  86  controlled by the computer K to control fluid levels in the low temperature chiller  80 . 
         [0050]    Upon exiting from the low temperature chiller  80 , the gas passes through a gas-gas exchanger  90  where it is further cooled to a temperature range established by the process control computer K and partially condensed by heat exchange with cold expanded vapors. The liquid from control valve  86  travels to an exchanger  92  which serves as a subchiller for refrigeration vapor, as will be described. Exchanger  92  is also connected to chiller  64  and to low temperature chiller  80 . 
         [0051]    The gas from exchanger  90  then travels to a first low temperature accumulator  100  fitted with a hydrocarbon liquid drain system  102  for liquid hydrocarbon recovery. The hydrocarbon liquid drain system  102  includes a differential pressure sensor  104  to provide data readings and indications to the process control computer K and a liquid control valve  106  controlled by the computer K to control fluid levels in the low temperature accumulator  100 . The residual vapors exit from an outlet  100   a  at the top of the low temperature accumulator  100  and are fed to a turbo-expander  110  which expands the vapor to a pressure established by the process control computer K. Turbo-expander  110  further cools the vapors to a temperature established by the process control computer K causing further vapor condensation. 
         [0052]    The cooled, expanded vapor-liquid mixture from turbo-expander  110  is fed to a second low temperature accumulator  120  fitted with a hydrocarbon liquid drain system  122  for recovering liquefied hydrocarbons for reinjection into the cargo. The hydrocarbon liquid drain system  122  includes a differential pressure sensor (not shown) to provide data readings and indications to the process control computer K and a liquid control valve  126  controlled by the computer K to control fluid levels in the accumulator  120 . 
         [0053]    The cold separated vapor from accumulator  120 , typically now mainly methane, with some ethane, propane and butane, exits from an outlet  120   a  at the top of the second low temperature accumulator  120  and is used as a cooling medium in the gas-gas exchanger  90  before entering an exchanger  128  which serves as a refrigerant subcooler. Vapor from the exchanger  128  after passage through a flame arrestor  132  enters the vapor scavenging unit G at a temperature and pressure established by the process control computer K. 
         [0054]    Typically, the vapor scavenging unit G takes the form of a diesel engine  134  which is also provided with diesel fuel from a diesel fuel tank (not shown) of the fluid supply F. Power generated by the diesel engine  134  is used to drive hydraulic pumps which power the rotating equipment of the apparatus A with the possible exception of the blower  40 , and an electricity generator (not shown) which powers a pump or pumps in the caustic scrubber U; the blower  40 ; and requisite instrumentation and lights for the apparatus A. 
         [0055]    Refrigeration for cooling purposes in the units of the apparatus A is provided by low pressure compressor  140  and high pressure compressor  150  fitted in the conventional manner with ancillary filters, separators, and accumulators associated with such equipment. The compressed refrigerant exiting from the high pressure compressor  150  is fed to a refrigerant condenser  152  via line  154 . The refrigerant condenser  152  is cooled with cooling water. The cooled compressed refrigerant is then fed to a refrigerant accumulator  156  from which it passes via the refrigerant subcooler  128  then via line  160  to the high temperature chiller  64  to provide cooling for the vapor stream. 
         [0056]    Part of the refrigerant exits from the high temperature chiller  64  via line  65  and is routed back to the inlet of the high pressure compressor  150  for recompression and recycling. The remainder of the refrigerant from chiller  64  then flows through line  162  through exchanger  92  to low temperature chiller  80  to provide cooling. The refrigerant exits from chiller  80  through line  85  and is routed through exchanger  92  which serves as a subchiller for refrigeration vapor being returned to the inlet of the low pressure compressor  140 . The low pressure compressor  140  discharges refrigerant in line  142  which routes the refrigerant into the inlet of the high pressure compressor  150 , completing the processing cycle. 
         [0057]    The apparatus A is a complete, self-contained vapor processing plant, and as such weighs about 180,000 pounds when fully loaded with operating fluids. To support this weight and provide a rigid mounting to a barge, the vapor recovery module M is supported by the platform P which is constructed of carbon steel I-beams  200  of suitable size, designed with cross bracing and welded together to form a 20 foot wide by 48 foot long base  202  in the disclosed embodiment. The base  202  is preferably made from two separate skids  203   a  and  203   b , each forty eight feet long, one being eleven feet wide and the other being nine feet wide. This is done to allow for shipping to a barge or other location for installation as each of the two skids of the base  203   a  and  203   b  can be shipped separately and within current transport regulations. 
         [0058]    The skids  203   a  and  203   b  when connected to form the base  202  have a floor  204  ( FIG. 4 ) mounted to form the platform P. The floor  204  ( FIG. 4 ) of the platform is made from a suitable number of carbon steel deck plate members, which are welded together to form an interlocking pattern upon the I-beams  200  of the base  202 . Appropriately located floor drains are installed in the deck plates of the floor  204 , and have threaded couplings that may be plugged when the apparatus A is moved after installation on a barge, or when otherwise necessary. 
         [0059]    The enclosure E is formed from a frame of carbon steel tube members  210  of suitable size and strength that are welded in positions so that they extend upwardly around the perimeter of the base  202 . Cross-members or supports as required are welded as needed for strength and to provide mounting locations for a set of panels or side wall members  214 . The side wall members  214  form side walls on side and end wall segments of the enclosure E. The side wall members  214  are bolted or otherwise mounted to the tube members  210  in order to be removable for maintenance. The junctures of the side panels  214  with the tube members  210  are provided with elastomer seals to prevent water entry or exit and provide protection for the equipment of the apparatus A mounted within the enclosure E. The enclosure E is provided with a suitable number of fore and aft marine doors  216  and  218 , respectively, together with various hinged smaller panels as may be required to be opened during preparation for operation of the apparatus A, or for access to inlet or outlet ports or connection points associated with components of the apparatus A. 
         [0060]    The enclosure E is provided with a roof  220  formed of roof panels  222  mounted above the side wall members with appropriate supports and bracing, if required. The roof panels  222  are sloped and are also removable for maintenance. The sloped roof panels  222  are also removably mounted by bolts to the tube members of the framework of the enclosure E. As with the side wall members  214 , the roof panels  222  are provided with elastomer seals at their mounting with other components of the enclosure E. The tubes  210  of the framework and both the side wall panels  214  and roof panels  222  of the enclosure E are painted with a suitable weather resistant marine epoxy. 
         [0061]    A ventilator fan  230  is mounted in an upper portion  232  of end side panel  214  to draw in and circulate air within the interior of enclosure S, while an outlet vent  234  is mounted in an upper portion  236  of an opposite end side panel to allow outlet circulation of air from the enclosure E. Suitable hoods or canopies  238  are mounted above the fan  230  and vent  234  to prevent entry of rain or other weather elements into the enclosure E. 
         [0062]    The apparatus A is mounted within the enclosure E as a self-supporting and self-contained unit, and provides all its own support services. The generator  138  is installed on a power take off from the diesel engine  134 , allowing supply of the electrical power necessary to support operations of the apparatus A. Diesel fuel in fuel tank  136  and coolant chemicals in coolant supply unit  67  of the fluid supply F are stored in the enclosure E in tanks designed for that purpose. Compressed air is supplied by an onboard air compressor of the instrumentation air system I. These features allow the apparatus A capable of transport or movement from ship to land based operations or the opposite in a short period of time. The required automated functions are located in the enclosure E, eliminating the requirement of a separate and additional remote operations building. 
         [0063]    In the mobile volatile organic compound (or VOC) recovery apparatus according to the present invention the component units of the vapor recovery module M have sensors for monitoring vapor recovery process conditions, including pressure sensors and temperature sensors, and control members including valves for controlling fluid flow and transfer conditions in the apparatus A. The apparatus A also includes a processor control computer K which has a stored established set of state points for the components of the vapor recovery module M to establish operating conditions for the apparatus A. 
         [0064]      FIGS. 11A ,  11 B,  11 C, and  11 D represent an example state point diagram of operating conditions for the apparatus A. The processor control computer K monitors the sensors and adjusts the control members of the apparatus A according to established operating conditions, such as those depicted in the state point diagram of the composite  FIGS. 11A ,  11 B,  11 C, and  11 D. It should be understood that the parameters values of temperature, pressure and the like are given by way of example. The computer K has an associated operator interface panel  250  with operator touch screen for monitoring and control purposes. 
         [0065]    The computer K in a preferred embodiment of the present invention takes the form of a programmable logic controller, such as an ALLEN-BRADLEY™ Model PLC-5, or a programmable automation controller, such as an ALLEN-BRADLEY™ CompactLogix Model L43. The computer K permits user or operator selection of automatic, manual, or maintenance modes of vapor recovery operation. The computer K also permits conventional step sequencer logic for start-up control and provides safety interlocks to meet safety and other regulations. 
         [0066]    It should be understood that other types of process control computers, such as personal computers, microprocessors or process controller may be used, if desired. The computer K receives input data from many sensors associated with units in the apparatus A, analyzes and monitors such data. In addition the computer K contains programmed therein an established set of state points and other parameters to establish operating conditions for the apparatus A. Based on the established set of state points and parameters, as well as the data readings from the temperature and pressure sensors in the apparatus A, the computer K sends signals to mechanical and electrical control members or valves to adjust system operation and efficiency. 
         [0067]    According to the present invention, automation of vapor recovery operations allows for more efficient operations. It also eliminates the need for a full time operator and thus can afford a considerable saving of personnel costs. The computer K also permits independent recording of performance to determine both efficiency of the system and compliance with regulatory mandates. 
         [0068]    In addition, the computer K prevents equipment damage by sensing problems with system operations before a major problem presents itself that could otherwise cause damage to person and property. Further, the computer K monitors and regulates the safety systems present into the apparatus A. 
         [0069]    The control system associated with the computer includes sensors located throughout the unit to monitor a complex set of parameters to tell the logic controller how the system is working. As has been set forth, the state point diagram depicted in the drawings is an illustrative example of established operating conditions. The sensors in the apparatus A involved in vapor recovery operations take the form of pressure transmitters mounted inline, either differential pressure transmitters or gauge pressure transmitters. Also, where desired, conventional visual indicators may be located in the vapor recovery unit in conjunction with the pressure transmitters and elsewhere for operator observation and monitoring. In a preferred embodiment, the sensors are of the type available as ROSEMOUNT™ 3051 S series. 
         [0070]    The differential pressure transmitters previously described herein serve as level controllers, to furnish data readings and direct the computer K to automatically drain a knockout vessel of condensed hydrocarbons or flow more refrigerant into a heat exchanger. The pressure transmitters of the apparatus A monitor process pressure conditions and provide data readings to the computer K for monitoring purposes during vapor recovery operations. The temperature sensors/transmitters of the apparatus A permit monitoring of process temperature conditions, and provide temperature data readings to the computer K for that purpose. In a preferred embodiment, the sensors are of the type available as ROSEMOUNT™ 248. 
         [0071]    The control system of the apparatus A operates under of the computer K, and contains servomechanisms and valve operators to automatically adjust vapor recovery operations based on input values detected by the various pressure and temperature sensors previously discussed. The computer system K has associated with it the control members or mechanisms in the form of valves of the apparatus S as described above. 
         [0072]    An operator interface panel  250  of the computer K displays in real time data about present vapor recovery operations. A preferred display on the operator interface panel  250  takes the form of a piping and instrumentation diagram of the system on a touch screen display. The operator interface panel  250  allows the operator to make manual adjustments to settings and controls as required. The operator interface panel  250  also displays both real time and saved data on current and past operations. 
         [0073]    The operator interface panel  250  allows control of operation of control members such as valves and servomechanisms, such as those described above, to properly control the vapor collection safety unit S, scrubber unit U, compressor unit C, liquid-vapor separator module L, cooler module R, fluid supply F and vapor scavenger unit G of vapor recovery module M The operator interface panel  250  includes an industrial monitor with appropriate software, and mouse and keyboard controls mounted on the front of the panel. It should be understood that a touch screen may be used instead of an industrial monitor. 
         [0074]    If desired, a slave computer unit may also be provided. In such a case, the slave unit can be any suitable computer that capable of receiving signals from the controller of the computer K. Such a slave unit would usually be located in the vicinity of the control center and operator interface panel  250 . 
         [0075]    According to the present invention, the term “volatile organic compounds” (VOC) refers to hydrocarbon or hydrocarbon derived compounds containing from 1 to 12 carbon atoms. 
         [0076]    The term “light VOCs” refers to hydrocarbon or hydrocarbon derived compounds having from 1 to 4 carbon atoms. Further, according to the present invention, the term “light hydrocarbons” refers to C 4  and lighter hydrocarbons. 
         [0077]    The apparatus A is particularly suited for use in the oil and chemicals industry for recovery of volatile organic compounds from a process stream containing such compounds. The mobile volatile organic compound (or VOC) recovery apparatus A according to the present invention meets or exceeds current safety standards for operation in the petroleum industry and marine operations on an oil barge or tanker as defined by United States Coast Guard Regulation and American Bureau of Shipping. 
         [0078]    By enclosing the system in the water-tight, vented enclosure E, the mobile volatile organic compound (or VOC) recovery apparatus according to the present invention meets current regulatory standards, prevent corrosive damage to sensitive equipment by atmospheric elements, and prevent water damage to controls and a safe environment for operators. 
         [0079]    The mobile volatile organic compound (or VOC) recovery apparatus A according to the present invention increases utilization and availability of VOC recovery by allowing a system to be transferred to active equipment and locations that are in current need of such a system. An apparatus according to the present invention eliminate the cost of separately providing at those locations supplies used by the system and support services such as fuel and coolant. 
         [0080]    The mobile volatile organic compound (or VOC) recovery apparatus A according to the present invention includes an automated VOC vapor recovery system to eliminate the constant attention of an operator, reducing labor costs and making the system safer to operate. 
         [0081]    Having described the invention above, various modifications of the techniques, procedures, material, and equipment will be apparent to those in the art. It is intended that all such variations within the scope and spirit of the appended claims be embraced thereby.