Abstract:
Petroleous production is associated with effluents well known to foul lines, nozzles, and containers while consuming substantial energy to assist in both production and remediation. A heat exchanger and manifold system maximizes flows, minimizes changes in flow cross-section, and maximizes heat transfer area, while recycling both water and heat between processes. Dirty regions and clean regions result from scrubbing horizontal exhaust stacks and evaporation of production water in concert to remediate one another, while recycling a significant portion of the energy consumed by each. The heat exchanger relies on a manifold having many layered conduits, each connected to a single layer level of one or more cylindrical conduits in the exchanger. The cylinders of the exchanger themselves are arranged in multiple layers, each layer of a heat exchanger element being connected to a single layer of the manifold. Any shape of cylinder may work, but a right circular cylinder having corrugated sheets spacing the layers may be simple to construct.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/144,665 filed Jan. 14, 2009 and U.S. Provisional Patent Application Ser. No. 61/144,694 filed Jan. 14, 2009, and incorporates by reference the entirety of each thereof. 
    
    
     BACKGROUND 
     1. The Field of the Invention 
     This invention relates to oil and gas production and, more particularly, to novel systems and methods for environmental protection from, and remediation of, production materials and processes. 
     2. The Background Art 
     The production and transportation of petroleum resources, including oil and natural gas, often involves the introduction of emissions of substances considered pollutants into the natural environment. Often the production areas are in locations regarded as being particularly environmentally sensitive. Sources of pollutants include engines, heaters, flares, road surfaces, and production fluids themselves. Production water often contains dissolved solids (e.g., salts) that make it unsuitable for ordinary beneficial (e.g., agricultural, culinary, etc.) use or release directly into the environment. Hauling water to and from the production site usually requires extensive and expensive trucking over roads through environmentally sensitive areas. Similarly, large amounts of waste heat from numerous engines, heaters, burners, flares, or combinations thereof are released into that same sensitive environment. Any company or state with extensive fossil fuel reserves will have much at stake over these issues. 
     What is needed is a system and method to address the issues of effectively mitigating environmental impacts associated with fossil fuel development and production. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the foregoing, in accordance with the invention as embodied and broadly described herein, a method and apparatus are disclosed in one embodiment of the present invention as including a source of combustion exhaust, a substantially horizontal “stack” acting also as a scrubber, and a recovery system. The recovery system may typically include a blower, a cyclone, a condenser, and various heat exchangers. 
     Saline production water is often available in the same location as flares, burners, heaters, engines and compressor stations. Basic design concepts have been developed for using production water to effectively scrub the emissions of volatile organic compounds, unburned hydrocarbons, combustion particulates, and sulfurous oxides. From these combustion sources, systems in accordance with the invention simultaneously put the waste heat from these combustion sources to beneficial use to evaporate production brine, thus reducing the volume of saline production water to be disposed of, in an environmentally responsible manner. 
     In many oil/gas fields, the quantities of waste heat available are not sufficient to process the amount of saline water produced in the same area. In such situations, the same design concepts provide for clean emission-scrubbed combustion of field gas to supplement any waste heat available. An efficient energy recovery system makes evaporation a cost effective way to dispose of the saline water with minimal environmental impact. In addition, the energy recovery system also returns a large fraction of the saline production water as clean distilled water. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: 
         FIG. 1  is a schematic perspective view of one embodiment of an apparatus in accordance with the invention; 
         FIG. 2  is a schematic perspective view of an alternative embodiment of an apparatus in accordance with the invention; 
         FIG. 3  is a schematic perspective view of the embodiment of  FIG. 1  augmented with a bank of heat exchangers; 
         FIG. 4  is a schematic perspective view of an alternative embodiment of an apparatus in accordance with the invention, augmented with heat and moisture recycling heat exchangers; 
         FIG. 5  is a schematic perspective view of the embodiment of  FIG. 4  with double walled scrubber recycling heat and moisture from the heat exchangers; 
         FIG. 6  is an end cross-sectional view of one embodiment of passages of a heat exchanger in accordance with the invention; 
         FIG. 7  is a top quarter perspective view of the heat exchanger of  FIG. 6 ; and 
         FIG. 8  is a side elevation view of the heat exchanger of  FIGS. 6 and 7  assembled with end manifolds. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It will be readily understood that the components of the present invention, as generally described and illustrated herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the system and method of the present invention, as represented here and in the Appendix attached hereto, is not intended to limit the scope of the invention, as claimed, but is merely representative of various embodiments of the invention. 
     Notwithstanding consolidation of multiple wells at a single production site, as well as various waste containment and site restoration, environmental impacts continue from the production of natural gas and oil. Typically, sources of particulate emissions include heaters used to reduced the viscosity of oil. Likewise, various motors or engines designed to run on petroleum byproducts such as “field gas” produce heat and hydrocarbon emissions. Meanwhile, production of small quantities of field gas in oil fields results in gas having to be flared off. Thus, flares and other sources contribute particulate and thermal emissions. The alternative to flaring is to release unburned hydrocarbons into the atmosphere. Even after burning or other remediation methods, unburned volatiles are still often returned into the environment intentionally or accidentally. 
     Heaters typically burn field gas to warm crude oil to reduce its viscosity for better handling. The high viscosity of crude oil is often responsible for high pumping costs. Pumping costs may be reduced by reducing viscosity of the oil. Some crude oil is so thick that it actually behaves as a thixotropic material. Also, as part of the separation process for separating water from oil, gas, or both heaters may be employed. 
     Engines used in oil fields and gas occur in two principal functions. Natural gas typically is compressed to increase the mass flow rate to collection points from the distribution networks at individual oil fields Likewise, crude oil must be pumped or otherwise transported from the well head to a collection point. Some wells produce little enough to transport it on trucks. Others produce sufficient volume to justify pumping from the well head to collection points. From collection points, crude oil may still be trucked or otherwise transported. 
     In any event, pumping requires drive motors. Thus, engines are integral to the transport of crude oil and natural gas. Meanwhile, production of oil requires pumps drawing oil from the earth. Moreover, drilling processes themselves rely on engines. Thus, whether driving a pump, compressor, generator, or drilling rig, engines are a burner of fuels, and a generator of thermal and other emissions. 
     Flares have been reduced in recent years but remain in several circumstances. Typically, if a field produces substantial quantities of natural gas, commercially significant volumes, then collection is developed and an infrastructure is put in place to do so. In other circumstances insufficient quantities may not justify collection and transport. In these circumstances, unsteady or gas may be flared off. Meanwhile, gas production may not be uniform. In such circumstances, periodic gas generation may require flaring. Thus, some amount of flaring of field gas is substantially unavoidable. However, the vision of a tall stack with a large, orange, sooty flame flaring at the top thereof creates public relations issues as well as legitimate environmental concerns. 
     Meanwhile, unburned volatiles existing in the process of producing natural gas and crude oil arise in several circumstances. For example, unburned volatiles may be part of the production water separated from oil and gas products. Meanwhile, various combustion processes (e.g., engines, heaters, etc.) may still pass unburned volatiles through. Unburned hydrocarbons, whether heavy or volatile, can result from heavy molecular chains that are not completely or efficiently broken down and combusted. Likewise, unburned volatiles may simply result from processes and equipment that burn at temperatures and in flow patterns that do not complete combustion of all volatiles. Meanwhile, volatiles can arise from other sources as well. 
     The result is tank batteries, sumps, holding ponds, possible exposure to leaks or breaks in containment structures, and the like. All of these may give rise to the need to handle unburned volatiles. 
     In summary, oil, gas, saline water, (production water), and the like are the typical fluids from oil and gas production. Since evaporation ponds, injection wells, and hauling are all subject to their own difficulties, an apparatus and method in accordance with the invention may augment the disposal of production water. Since containment, hauling, reinjection, evaporation, and the like all have risks and limits, an apparatus and method in accordance with the invention deals with production water at a wide variety of salinity values, net volumes, and so forth. 
     In various embodiments of apparatus and methods in accordance with the invention, production water is used to scrub oil and gas emissions in the field. Meanwhile, waste heat from combustion sources is used in evaporating production water. The production water vapor from evaporation may be dispersed into the atmosphere, or may be re-condensed as distilled water for use in systems that would otherwise not tolerate the water as a saline solution. 
     Referring to  FIGS. 1 and 2 , in one embodiment of an apparatus  10  or system  10  in accordance with the invention, a horizontal remediator  200  may act as an evaporator  200 , as a scrubber  200 , or both. The scubber-evaporator  200  relies on a blower  202  to draw a flow  204  of combustion emissions. Combustion emissions may exist, for example, as an exhaust stream  204  from a flare, a heater, an engine, or the like. A gas burner  206  device or region may hold a flame  207  burning field gas as a heat source or may augment combustion of unburned hydrocarbons (e.g., volatile organic compounds or VOCs) in the exhaust stream  204 , or may serve to do both. 
     Meanwhile, an upstream damper  208  on the flow  204  may be used to regulate the back pressure on the engine, burner, or other source feeding an exhaust stream into the system. A system of nozzles  210  optimized to effect evaporation of water injects an atomized spray  212  of production water (brine, typically) from a feed line  214  into the exhaust stream  204 . The system  10  typically contains salts, and recovers them from the exhaust stream  204  in a cyclone  216 . A blower  202  maintains a draw on the cyclone  216 . Feeding the exhaust stream  204  from a scrubbing “stack”  200 , oriented as a horizontal tube  201  intersecting at the edge of the cyclone  216 , promotes the separation of solids, liquids, or both from the vapor and gases, by the cyclone  216 . 
     In certain embodiments, a burner  206  may be installed as an integral part of the evaporation module  200  in accordance with the invention. In such an embodiment, the burner  206  may be installed in a separate or integrated conduit  218  fed by air flow regulated through a damper  208 . The flow  204  of combustion products is then transported through the conduit  218  to be directly intercepted by atomized sprays  212  of production water. Thereafter, the exhaust products, scrubbed by the liquids, together with the evaporated liquids (now vapors) and precipitated or in trained solids, may be sent into the cyclone  216  for separation. 
     Ultimately, the blower  202  draws the noncondensible gases and the vapors out, exhausting them to the atmosphere or a condenser. Salt as solids, heavy hydrocarbons, other particles scrubbed out, as well as liquids may remain behind, exiting the bottom  219  of the cyclone  216 , such as through a drain  220 , after being separated out by the cyclone  216 . 
     In the cyclone  216 , the flow  204  containing multiple phases such as noncondesible gases, vapors, liquids, and solids, is received as an incoming flow  222 . The incoming flow  222  tends to strike the wall  224  of the cyclone  216 , directing the flow  222  in a circumferential direction centripetal force moves heavier (denser) materials outward  226 , where they may strike the wall  224  and fall downward toward the bottom  219 . Lighter (less dense) materials, more easily accelerated by fluid drag of surrounding vapors and gases, move inward  228 . These less dense, more easily entrained, materials eventually follow a path  230  upward toward an outlet line  232  or conduit  232  evacuating the cyclone  216 . 
     The outlet line  232  feeds into an inlet  234  or inlet portion  234  receiving the noncondensible gases (oxygen, nitrogen, etc.), vapors (water, etc.) from the flow  204 . Thus, the discharge  236  from the blower  202  may pass into the atmosphere or into a device, such as a condenser, for further processing. 
     Not only does the damper  208  provide the opportunity to control back pressure on a heat source such as an engine, heater, flare, or the like, the injection nozzles  210  may be designed to provide repeatedly a cone of spray that will completely cover the cross section of the “stack”  200  formed by the conduit  218 . (The reference numeral  218  refers to conduits generally, and when used with a trailing letter indicates a specific instance thereof.) Thus, by spraying axially along a conduit (forward, backward, or both with respect to the exhaust flow) the flow  204  may pass through several conical curtains of spray  214  that effectively present a barrier across the entire cross section of the conduit  201  of the evaporator  200  or scrubber  200 . Spray  212  direction, velocity, particle size, chemical content, or the like may be optimized for scrubbing, evaporating, or both. 
     In some circumstances, the balance between scrubbing and evaporating may be accomplished by adjusting the length of the scrubber  200  to provide the needed quantity of evaporation as well as scrubbing required. Again, the damper  208  may also be used to optimized flows, balancing back pressure on the burner  206  (or engine, flare, heater, etc.) while also regulating the mixture of dry ambient air mixed into the exhaust flow  204 . 
     A secondary flame  207  or burner  206  for reacting or oxidizing unburned hydrocarbons or volatile organic compounds remaining in an exhaust stream  204  may be operated or installed according to need. If comparatively clean field gas, predominantly natural gas (e.g., methane), is available, the presence of volatile organic compounds may be manageable. By contrast, a diesel engine operating on a well site may release more particulate emissions and unburned volatile or non-volatile organic compounds. Likewise, burning field gas having a higher fraction of larger molecules than does methane, and perhaps some very large petroleum molecules entrained, may tend toward higher levels of volatile organic compounds in the exhaust. 
     Referring to  FIG. 3 , while continuing to refer generally to  FIGS. 1-8 , in one embodiment, a remediator device  200  acting as a scrubber  200 , evaporator  200 , or combination  200 , may also be combined with a recovery module  240 . The recovery module  240  may include one or more condensers  242  to recover water vapor as, effectively, distilled water. A discharge line  244  may send a flow  243  of the recycled condensate to feed the line  214  into the nozzles  210 . In certain embodiments, the condensers  242  may be oriented vertically, so air flows promote a natural chimney-effect buoyancy. For example, air flows  243 , drawn in and used to cool the water vapor and exhaust gases received from the blower  202 , will receive heat therefrom, tending to cause and upwardly rising flow  248  of scrubbed exhaust gases, water vapor, and ambient air as a result of the decreased density thereof out of the system  10 . 
     In certain embodiments, the blower  202  drawing on the cyclone  216  and the scrubber  200  or evaporator “stack” 200  may be configured to raise the pressure in the condensers  242 . Thus, the resulting, reduced, upstream pressure may promote evaporation in the scrubber  200  or evaporator  200 , as well as in the cyclone  216 . The increased pressure in the subsequent or downstream condenser system  242  beyond the blower promotes increased condensation. 
     The flow  243  in the line  244  fed from the condensers  242  is distilled water. Optionally, a makeup flow  249  of water may be required. The makeup flow  249  may pass through the line  245  into the feed line  214  to supply the nozzles  210 . The extent to which the flow  246  from the condenser  242  is insufficient to completely supply the scrubber  200  is driven by the net evaporation of water in the discharge flow  248 , as well as the drained brine exiting the cyclone  216  through the bottom drain  220 . The condensers  242  may be configured modularly in order to best match the flows  222 ,  236 ,  243  throughout the system  10 . 
     In general, flows  246  of ambient air may pass through the inlet  247  into a manifold  248  feeding the condensers  242 . Meanwhile, in a concurrent flow arrangement, passages feeding an exhaust flow  236  from the blower  202  run vertically, adjacent to passages feeding the ambient air flow  246  upward through the condensers  242 . Adjacency may be horizontal in a rectangular, circular, or other configuration. The illustrated embodiment relies on radially concentric, adjacent passages. Thus, cooled exhaust and warmed ambient air form the mixed flows  248  exiting the condensers  242 . 
     Referring to  FIG. 4 , and  FIGS. 1-8  generally, in other alternative embodiments, a heat recovery section  250  or module  250  may be added. The recovery module  250  may be connected by providing manifolds  252 ,  254  on the inlet and outlet ends  256 ,  258 , respectively, of one or more condensers  242  acting as heat exchangers  242 . For example, a counter-flow (or even a cross-flow) heat exchanger  242  may provide ambient air coming into an inlet  260 , passing through the heat exchangers  242 , and continuing onward toward an outlet  262 . 
     As seen in  FIGS. 4 and 5 , in certain embodiments, the outlet  262  may feed into a double-walled conduit  218 . For example, the scrubber  200  may have a double wall as illustrated in order to feed the output flow from the outlet  262  into an outer shell or annulus of the conduit  218 . The outer annulus of the conduit  218 , in turn, empties into the axially central portion of the conduit upstream of and feeding into the flame  207  of the burner  206  thereat. Thus, preheating uses heat and mass flows recaptured by the heat exchangers  242  and recycled into the exhaust flow  24  near the inlet to the scrubber  200 . 
     This ambient air flow  246  passes through one set of channels (e.g., the channels formed by the supporting, corrugated dividers in one annulus of the several concentric annuli) in the heat exchanger  242 . The corresponding heat transfer flow or opposing flow may travel in an opposite direction through radially adjacent annuli flanking the first. This corresponding or opposite flow, when implemented in a rectangular system, may run either parallel to or orthogonal to the channels or overall passages carrying scrubbed exhaust  236  exiting the blower  202 . Leaving the heat exchanger, the discharge  236  becomes an exiting flow  264  issuing from the exhaust outlet  266 . 
     Air and water may be preheated by a condenser  242  acting as a heat exchanger  242  recovering the sensible heat of gases, as well as the potentially substantial latent heat of vaporization out of the distilled water output from the condenser  242 . The outlet  262  passing pre-warmed ambient air into the evaporator  200  may connect to the conduit  201  of the evaporator  200  further upstream along the exhaust flow  204 . In either configuration, significant energy inputs and water (distilled)) may be recovered into the exhaust flow  204 . Thus, a certain portion of the heat may be continually added into the exhaust flow  204 , and yet be re-extracted prior to final exit of the exhaust flow  264  out of the system  10 . 
     Referring to  FIG. 5 , while continuing to refer generally to  FIGS. 1-8 , in other embodiments, waste heat from another device, such as a heater, engine, flare, or the like, outside the system  10 , may not be available. For example, remediation of production water may require burning field gas directly to evaporate water. Thus, in certain embodiments an apparatus  10  in accordance with the invention may burn field gas in a burner  206  creating the hot exhaust flow  204  for the specific purpose of evaporating water to be run through a evaporator  200  and cyclone  216 . Ultimately, the system  10  may condense a portion of the water back to distilled water. 
     By providing heat exchange as in the embodiment of  FIG. 4 , the system  10  may preheat air and water. Heat may be recovered from both the sensible heat recovered from the discharged flow  264  and the latent heat recovered from the condensed distilled water. Pressure increased in the condenser due to pressure from the blower  202  enhances condensation. The pressure drop in the evaporator  200 , due to the draw by the blower  202  demand for input enhances evaporation, as described hereinabove. 
     Referring to  FIGS. 6-7  while continuing to refer generally to certain to  FIGS. 1-8 , in certain embodiments, a condenser  242  may provide a flow of heat, exchanged through concentric cylinders  270  spaced apart. The spacers  272  themselves may take the form of corrugated metal sheets or the like. Thus, the spacers  272  may act as fins while supporting each annulus  274  between adjacent cylinders  240 , forming channels  276  between the fins. 
     Adjacent annuli  274  carry flows in opposite directions for counter-flow heat exchange. Accordingly, excellent thermal contact between the exhaust  236 , with its condensing vapors, and the cooling air receiving heat therefrom may be achieved. A structurally robust configuration results from essentially very thin materials, such as sheet metal, for example. 
     Referring to  FIG. 8 , while continuing to refer generally to  FIGS. 1-7 , such a heat exchanger  242 , using concentric tubular structures  270 , may be interfaced with a manifold  272 ,  274 . Manifolds may be mechanically attached in fluid communication with the condensers  242  at either end. Passages in the manifolds  272 ,  274  each provide access to only periodically occurring (e.g., typically alternating) annular spaces  274 . 
     For example, an ambient air flow  246  may enter an inlet  260  of the manifold  254 . Passing through the channels  276   a , the air is heated by exhaust flows  204  in adjacent annuli  274   a ,  274   b , radially adjacent channels  276 . Adjacency between annuli  274  each with its own set of channels  276  distributed circumferentially therearound, contributes to comparatively high rates of heat transfer therebetween, due to thin annular walls and the fin effect of the spacers  272 . 
     By the time the exhaust flow  264  exits the outlet  266 , it has released most of its heat into the ambient air flow  246 . The exact heat exchange and temperature changes depend upon the specific values of parameters such as thicknesses, hydraulic diameters, lengths, fluid properties, velocities, and so forth controlling heat transfer. 
     Moreover, a significant amount of latent heat from any water vapor condensed therein has also been so transferred. The manifolds  252 ,  254  support distribution and collection of flows into distinct annuli  274  by having each inlet or outlet end of annulus  274  connect to a particular layer  278  of the respective manifold  252 ,  254 . 
     Thus, various apparatus and methods in accordance with the invention may significantly reduce the environmental impact of saline water as well as that of chemical, thermal, particulate, and other exhaust emissions. To the extent that these processes can be balanced, a highly symbiotic relationship may exist between remediation of production water, remediation of organic compositions including VOCs, remediation of rejected heat, and remediation of combustion products. 
     Meanwhile, the tall stack, so familiar, with the flare of a production facility or refinery, may be laid down as a horizontal tube, less expensive to manufacture, easier to maintain, and easier to support. Meanwhile, stacks may have immediate and affirmative back pressure control by attachment of dampers. Meanwhile, scrubbing reduces emissions of volatile organic compounds, oxides of sulfur, particulates, and heat, while recovering heat, distilled water, or both to be recycled from saline production. 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.