Patent Publication Number: US-2012042653-A1

Title: Hydrothermal Power Plant

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation-in-part of and claims the benefit of priority to the international patent application of the same titled filed on Apr. 27, 2010, having application serial no. PCT/2010/US032608, which is incorporated herein by reference. 
     The present application also claims the benefit of priority to the US Provisional patent application of the same titled filed on Apr., 28, 2009, having application Ser. No. 61/173,498, which is incorporated herein by reference. 
    
    
     BACKGROUND OF INVENTION 
     The present invention relates to an improved means of electric power generation via the oxidation of various organic materials in a Supercritical Water Oxidation Reactor (SCWOR). 
     Prior methods of using SCWOR to generate electric power are disclosed in the following U.S. Pat. No. 5,485,728, U.S. Pat. No. 5,000,099 and U.S. Pat. No. 7,640,745, which are incorporated herein by reference. 
     SCWOR have an inherent utility as the most of efficient means to completely oxidize organic waste of all types, including toxic chemical, as well as wet biomass, such as sludge. 
     However, while an SCWOR can also use conventional fuels without creating harmful by-products, other than CO2, the conventional fuels need not be heavily refined and can even be contaminated with water, organic and organo-inter-metallic and metallic compounds. 
     However, prior to the current invention, SCWOR have had poor efficiencies that have not made commercially viable to produce energy. Accordingly, the actual implantation of SCWOR designs in the patent literature is scant and largely in academic research laboratories and government end use to date. 
     Biofuels, in particular ethanol, has gained popularity as an automotive gasoline additive in the US, as well as a direct fuel in other countries. AS ethanol is generally produced from corn or such cane, a significant non-fermentable biomass is created in these processes. These biomasses are sometimes burnt as fuel, but being somewhat wet, are an inefficient and particulate polluting heat source. 
     It would be desirable to utilize mixed biomasses of varying water contents as a fuel with the utmost efficiency to produce power with an entirely clean combustion process, which is producing CO2 as the only gaseous by product, other than water as steam. Achieving such an objective would reduce the dependence on fossil fuels and reduce the overall “carbon footprint” of power production by turning biomass that might otherwise be burnt without generating power into power. In addition, such an improvement in technology would facilitate the clean up and disposal of toxic wastes and allow safe disposal of waste at many manufacturing facilities without the expense and risk of storing and transporting waste. 
     It is therefore a first object of the present invention to provide such a SCWOR of improved efficiency in which moist organic materials can be efficiently combusted without expending additional energy to pre-dry the fuel, and without chemical conversion of the wet fuel into another fuel that is more suitable for combustion in existing combustion apparatus. 
     It is a further object of the invention to provide such power plant in which the SCWOR provides complete combustion without undesirable by-products. 
     It is still another object of the invention to provide such a plant is capable of accept multiple and diverse fuel sources for the recovery of useful energy with high thermal efficiency. 
     SUMMARY OF INVENTION 
     In the present invention, the first object is achieved by providing a power generating plant that comprises a super critical water oxidation reactor (SCWOR) having a feed port for reactants and an exit port for exhaust, a brine separator having an inlet for receiving the exhaust of the SCWOR and at least one outlet for gases, two or more pairs of air compressors and expanders coupled in rotary motion by a common axle, at least one heat exchanger associated with each of said one or more pairs of compressors and expanders, wherein the hot exhaust gas exiting the brine separator enters a first expander, and the cooled exhaust gas exiting the first expander enters a first heat exchanger that cools hot compressed air from the air compressor while reheating the cooled exhaust gas exiting the first expander prior to a second stage of expansion, and the cooled air exiting the heat exchanger enters a downstream compressor stage in said 2 or more pairs of air compressor and expanders, a motor or motor/generator with a rotary coupling to at least one common drive mechanism of the air compressor-expander pairs, wherein the rotary motion of the drive mechanism supplies mechanical power driving the motor generator for both electric power and driving the air compressors. 
     The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of the embodiments thereof taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram the generically discloses the operative principles of the HTPP in a first embodiment. 
         FIG. 2  is a schematic diagram of the power generation system in the HTPP of  FIG. 1 . 
         FIG. 3  is a schematic diagram of a second embodiment of the HTPP. 
         FIG. 4  is a schematic diagram of a third embodiment of the HTPP. 
         FIG. 5  is a schematic diagram of a fourth embodiment of the HTPP. 
         FIG. 6  is a schematic diagram of a fifth embodiment of the HTPP. 
         FIG. 7  is a schematic diagram of a sixth embodiment of the HTPP. 
         FIG. 8  is a schematic diagram of a seventh embodiment of the HTPP. 
         FIG. 9  is a schematic cross-sectional elevation view of a gravity separator for use with any of the above embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 through 9 , wherein like reference numerals refer to like components in the various views, there is illustrated therein a new and improved Hydro-Thermal Power Plant (HTPP) generally denominated  100  herein. 
     In accordance with the present invention,  FIG. 1  illustrates a HTPP  100  that comprises a super critical water oxidation reactor (SCWOR)  110 . At the super critical conditions the organic materials that enter the SCWOR  110  are oxidized, as are described for example in U.S. Pat. Nos. 5,558,783 (issued to McGuinness on Sep. 24, 1996) and 5,384,051 (issued to McGuinness on Jan. 24, 1995), which are incorporated herein by reference. This oxidation reaction generates heat that is used to generate electrical power in the HTTP  100  as described further below. The SCWOR  100  preferably incorporates a permeable-wall or transpiring wall  115 . The SCWOR  110  may be operated at pressures above or below the critical pressure or water. 
     In a currently preferred mode of operation, various combinations of biomass and organic materials are co-injected with water or in an aqueous suspended state into the top of the SCWOR  110  at the injector  1405 . Hot exhaust and reaction products from the SCWOR  110  are controllably cooled in the quench cooler  120  by direct mixing with cooled re-circulated brine that circulates in line  1300  from the bottom of the gravity separator  130 . Gravity separator then received this cooled reaction product from the quench cooler  120  via inlet portal  131 . Thus, the gravity separator  130  receives the output of the SCWOR  100  after passing through the quench cooling section  120 . 
     It should be appreciated that an important aspect of the current invention is the extraction of heat from the hot liquid recirculation stream of the brine in line  1300 . This is both a more efficient way to extract and more effectively deploy heat from gases as proposed in U.S. Pat. No. 5,485,728 (which issued to Norman L. Dickinson on Jan. 23, 1996 for “EFFICIENT UTILIZATION OF CHLORINE AND MOISTURE-CONTAINING FUELS”) and U.S. Pat. No. 5,000,099 (which is a continuation in part of a series of patents to Dickinson), and also enables other routes for heat and energy recovery that would otherwise be lost in a prior art system. Other important and alternative aspects of the invention are described further below. 
     This technology can be applied to all types of pumpable organic sludge and raw biomass slurries. A process using a waste water treatment facility (WWTF) sludge is now described for illustration purposes, as it will be apparent to one of ordinary skill in the art that other sources of organic material can also be used in the same HTTP  100 . For example, many high moisture renewable fuel sources and non-renewable fuel sources such as coal may be used to generate power in the inventive HTPP  100 . Waste water sludge will preferably be taken off the bottom of the existing WWTF gravity thickeners at approx 3% biosolids (BS) concentration. The sludge can be ground as necessary to improve pumpability, and then pumped at low pressure to the HTPP  100 . The sludge is preferably centrifuged to approx 10% biosolids concentration. Filtrate water from the centrifuge is sent back to the WWTF headworks. The concentrated sludge is then pumped to combustor pressure via pump  260 . 
     When the fuel to the SCWOR is sludge it is pre-heated by heater  265  to approx 200° C. before injection into SCWOR  110 , which is preferably a hydrothermal transpiring-wall combustor (such as are disclosed in U.S. Pat. Nos. 5,558,783 and 5,384,051) where it is turbulently combined with a preheated mixture of superheated steam and compressed air. The combustor will normally operate at subcritical pressures (below the critical pressure of water), but may also be designed to operate above the critical pressure of water. Spontaneous oxidation of the sludge occurs upon mixing within the combustor. Superheated reaction products (CO 2 , N 2 , excess O 2 , water vapor and inorganic residuals) exit the bottom of the combustor and enter the quench cooler  120 . 
     The quench cooler  120  partially cools the stream, thereby forming a saturated 2-phase vapor-liquid mixture. This 2-phase stream then enters a gravity or brine separator  130  for separation into liquid and vapor streams. This gravity separator  130  operates below the local saturation temperature of water and will contain what will be referred to as brine, as it contains some dissolved inorganic salts. As shown in the embodiments of FIGS.  1  and  3 - 6 , the hot liquid phase or brine leaves the bottom of the separator  130  at a lower exit portal  132  and then enters the line forming loop  1300 , carrying with it all of the suspended and dissolved inorganic constituents of the sludge. 
     In the embodiment of  FIG. 3-6 , the stream in line  1300  passes through a steam generator  270 , such as a shell &amp; tube heat exchanger for example, before being recycled back to the quench cooler  120  via pump  121 . The steam generator  270  is thus designed to extract useful heat from the liquid brine recirculation loop  1300 . The brine circulation quench pump  121  supports the continued flow of brine in loop  1300 . 
     As shown in  FIG. 3-8 , inorganic solids are continuously removed from the stream of loop  1300  via hydrocyclone filtration at filter  500 , and then removed from the system via blowdown for solids dewatering and disposal at  505 . A hydrocyclone  500  is optionally replaced with a filter or other means known in the art to separate and remove free solids from the liquid in brine recirculation loop  1300 . “Blowdown” refers to a liquid stream leaving the process for disposal. This stream would contain any separated solids from the hydrocyclone or filter, but might only contain dissolved solids to control the total amount of dissolved solids in the brine recirculation loop. This technique is routinely used in steam boilers to prevent total dissolved solids from reaching saturation and precipitating out on the walls of the equipment as scale. The blowdown water containing the dissolved solids is then directed back to the WWTF headworks. This Blowdown is a small percentage of the total flow through the recirculation loop. 
     In the embodiment of  FIGS. 1 ,  3  and  4  the hot vapor mixture of CO 2 , N 2 , O 2  and water vapor exits the 2-phase gravity separator  130  at exit portal  133  and enters a condenser  220 , where the water vapor is condensed and separated from the non-condensable gases. 
     It should be appreciated that the condensed water output from condenser  220  at port  242  is generally free of inorganics and organics; it is essentially distilled water, but may require additional polishing. Such excess condensed water is drained from the process and returned to the WWTF, such as at moisture condenser  240 , via outlet  242 . The remaining condensed water is heated and vaporized for mixing with the compressor air (from compressor  3317 ) via valve  1403 , prior to injection into the SCWOR combustor  110 . Thus, a portion of this condensed water is optionally recycled back to the combustor or SCWOR  110  (via circulation pump  107 ) for liner transpiration via liner  115  at inlet port  1406  (where it is delivered outside the permeable-wall or transpiring wall  115 .) However, the water before returning to the either the injector  1405  or the side port  1406  is preferably reheated by one or more injector trim heaters  1401 . 
     Therefore, two 3-way flow control valves  1402  and  1403  are provided for dividing the total flow of compressed air and transpiration water to separate destinations. Such flow control valves might use multiple 2-way valves instead of a single 3-way valve to achieve same end. Flow control valve  1402  divides liquid transpiration water into two streams. One stream going to the boiler to be vaporized for use in transpiration service and the balance going to the boiler to be vaporized for use in injection/mixing service with the feed. Flow control valve  1403  divides the compressed air into two streams. One stream goes to the reactor annulus at port  1406  for use in transpiration service and the balance going to the feed injector  1405  for injection/mixing with the feed from pump  265 . The injector trim heaters  1401  are also useful in reactor start-up and control. 
     In the embodiments of  FIG. 1-4 , the non-condensable gases are used to generate power in generation train  3000  by being fed to one or more gas expanders wherein they drive a rotary mechanism. Such expanders are generally, but not exclusively turbine devices. As shown in  FIG. 1 , in stage  3300  of train  3000  each of the air compressor stages  3317  are coupled in rotary motion to one or more gas expansion stages  3315  by a common drive mechanism  160 . The exact nature of the drive mechanism will depend on the structure and type of the expander and compressor, which although both are preferably turbine devices, as other types of compressors known in the art can be deployed in the embodiments described herein. One or more of such coupled compressor-expander pairs or stages are arranged in a train of two or more pairs to achieve higher overall compression ratio and expansion ratio than possible with pair. Two or more compressor and expander stages may be coupled in rotary motion at different rotational speeds by means of a common gearbox, as done in integrally-geared compressors known in the art. The cooperative operation of the other stages of train  3000  is shown in more detail in  FIG. 2 . The non-condensable gases leaving the condenser  240  are heated in a pre-heater  3318  by heat from the hot brine recirculation loop  1450  and then reduced to atmospheric pressure via a multi-stage hot gas expander cascade train  3000 . Each stage of the expander cascade drives one of the compressor stages. Should it be desired to recover carbon dioxide from this stream of non-condensable gases, it would best be done upstream of the high-pressure expander preheater at unit  245 , wherein the carbon dioxide by removal is represent by the exciting arrow  246 . 
     The power train  3000  preferably deploys 3 or 4 stages of compression with intercooling, while the expansion likewise requires 3 or 4 stages of expansion with interstage reheat.  FIG. 2  illustrates a preferred aspect of the invention with three separate expander-compressor pairs  3100 ,  3200  and  3300  cascaded in series. In this aspect, heat from each compressor intercooler is used to heat and expand the non-condensable gases upstream of each interstage reheater. This reduces the total preheat required upstream of each stage of expansion, providing more efficient production of energy from the biomass feed. This allows each expander-compressor train to operate more closely to its optimum speed for maximum efficiency. Thus, at least 2 of the 3 coupled expander-compressor pairs  3100 ,  3200  and  3300  have at least one associated heat exchanger  3110  and  3210  (for  3100  and  3200  respectively) that receives the compressor output as a heat source and to increase the enthalpy of the exhaust of the preceding expander in the chain. 
     Thus, in operation the output gas from the first compressor  3117  is fed to the next compressor  3217  in pair  3200 , and the output of compressor  3217  is feed to the next compressor  3317 . An intercooler such as  3110  for compressor-expander pair  3100  cools the gas before the next stage of compression. However, the intercooler receives the cooler exit gas from each expander as the heat transfer fluid such that heat or enthalpy in the gas from compression is transferred to the gas before the next stage of expansion. 
     In addition, the input to the last expander  3115  in coupled compressor-expander pair  3100  is heated first by the output of compressor  3117  via air compressor intercooler  3110 , which acts as a heat exchanger. 
     Further, the input of the second expander  3215  in coupled pair  3200  is heated first by the output of compressor  3217  via air compressor intercooler  3210  that acts as a heat exchanger. 
     In addition, heat from the brine separator  130  liquid effluent stream in line  1300  supplies additional higher temperature heat to the exhaust gases of an expander prior to a first or subsequent expansion stage downstream of s air compressor intercoolers. Thus, preferably as shown each of expanders  3150 ,  3250 , and  3350  are thus associated with heat exchangers  3118 ,  3218  and  3318  which respectively receive either the re-circulating brine, or a heat transfer fluid heated there from, as a heat source to further increase the enthalpy of the exhaust of the preceding expander. 
     The final low-pressure expander-compressor pair  3100  is connected to a motor/generator  3001 . During plant start up from a cold condition motor operation is generally required drive the air compressors. As the system comes up to temperature, the low-pressure expander will gradually supply power to the compressor and eventually produce enough power to generate surplus electric power to the grid. The intermediate-pressure and high-pressure expander-compressor trains  3300  and  3200  may or may not have a connected motor/generator  3002  and  3003  respectively. 
     While U.S. Pat. Nos. 5,485,728 and 5,000,099 similarly use a SCWOR in a power generation scheme they do not appear to teach or suggest the “brine” heat or the heat of compression is used to reheat the expanded gas before it is feed to the next turbine. These patents all refer to preheating the gas before the expander by extracting heat from a hot gaseous stream. The present invention extracts heat from the hot liquid recirculation stream  1300 . 
     Thus, in the present invention the integrated combination of air compression, constant pressure hydrothermal combustion and gas expansion with energy recovery thereby completes a Hydrothermal Brayton Power Cycle. 
     As shown in  FIG. 3-6 , another aspect of the invention is the steam generator  270  located in the hot brine recirculation loop  1300 , which generates steam supplying a conventional steam turbine system  300  for additional power recovery. The steam turbine  314  may drive a dedicated electric generator  312 , or may be connected to the low pressure expander-compressor-motor/generator train via a conventional overrunning clutch. These alternative coupling means are designated  1450  in  FIG. 5-6 . The effluent from the steam powered turbine  314  then enter the steam condenser  311 , which has a water cooling inlet  313 . The steam turbine re-circulation pump  106  is used to return the output of the steam condenser  311  to the heat exchanger  220  that pre-cool that mixture entering the moisture condenser  240 , while a second recirculation pump  105  returns the water exiting this heat exchanger  220  to the steam generator  270 . 
     The total net power produced by the HTPP  100  is roughly evenly split between the expander-compressor cascade  3000  and the steam turbine system  300 . Overall HTPP thermal efficiency is approximately 38% based on higher heating value of the wet feed. Thus, while the present invention will always incorporate a Brayton power generation cycle it may or may not include an optional Rankine (steam) co-generation cycle. 
     In  FIGS. 4 and 6 , an optional steam superheater  400  is disposed at least partially within the SCWOR  110  to further improve the efficiency of the steam turbine system  300 . The superheater  400  acts as a heat exchanger that heats the output of the steam generator  270  before it reaches the steam turbine  314 . 
     In another embodiment of the invention there is a mode of operation whereby a condenser  240  does need not be disposed in the vapor outlet from the brine separator  130  to directly inject the hot vapor mixture into the expander-compressor. These embodiments are illustrated in  FIG. 5  and  FIG. 6  by the optional bypass line  5001  having valves around the condenser  240 , which allows HTPP operation without the condenser in the loop. The reason for condensing and cooling the hot vapor exhaust stream is to cool the gas to facilitate removal of CO 2  from the high-pressure exhaust gas stream, which is most easily done cool. 
     In other aspects of the invention, it may be preferable to provide for in-situ cleaning of the combustor liner and feed injector by injection of a suitable cleaning agent into the feed injector assembly and into the annular space between the pressure vessel wall and permeable liner of the SCWOR  110 . Water treatment systems as known in the art to control corrosion and fouling of process equipment. 
     Further, in the embodiments shown in  FIGS. 5 and 6  a dashed line  166  is intended to illustrate the optional gear box or clutch coupling between the generators  3001  and  312 , or a common shaft to a single generator. 
     It should be appreciated that in alternative embodiments the oxidizer to the SCWOR  1000  may be air, oxygen enriched air, or oxygen. Air separation technology may optionally be installed upstream of the SCWOR  110  to separate air into oxygen-rich and nitrogen-rich streams. The nitrogen-rich stream may optionally be used to drive a gas expander as part of the power generation train  3000 . Such oxidizer or oxygen enriched stream may or may not be mixed with the transpiration water entering at portal  1406 . 
     In power train  3000 , additional motors  3002  and  3003 , may or may not be required at all depending on the application. For example, the motor  3003  might be required for start-up, but then once the system is up to pressure and temperature, the compressor is driven solely by the expander. It is preferable to start the system up without using motors on the higher pressure expander-compressors. A clutch coupling  3116  and  3216 , typically an overrunning clutch, is deployed such that when the expander-compressor comes up to speed it automatically disengages from the motor  3003 , allowing the motor to be switched off. Such clutches are commonly employed in industry. Although a hydrodynamic centrifugal or axial type compressor is shown in the diagram, for smaller plants a reciprocating compressor as known in the art may also be similarly employed in which all stages are driven via a common drive mechanism and motor/generator. Likewise, although hydrodynamic centrifugal or axial gas expanders are shown in the diagram, for smaller flows a reciprocating or other positive displacement type expansion engine may also be similarly employed whereby all stages of expansion may be connected via a common drive mechanism. 
     In other embodiments of the invention the air compressor stages may be driven independently from the gas expander stages. Gas expander stages are capable of generating mechanical power to directly drive electric generators, air compressors, pumps, chillers or any other type of driven equipment. 
       FIG. 7  illustrates yet another embodiment of the invention in which the fluid phase the output of the gravity or brine separator  130  is directed from the bottom thereof at portal  132  through level control valve  706  causing a pressure drop with expansion device or flash drum  701 . The flash drum  701  generates steam and condensed water having some dissolved or suspended solids. In addition, output gas of the SCWOR  110  also exits the gravity separator  130  at the upper portal  133 , and is directed in line  710  toward a system pressure control valve  705 . Line  710  then directs this gas to the input port  3712  of the first or higher pressure expander  3710 , which is mechanically coupled to a second or lower pressure expander  3720 . 
     The low pressure output gas exiting portal  733  of the flash drum  701  is feed to the input port  3722  of the second or lower pressure expander  3720  via line  720 . The lower pressure expander  3720  can also receives at inlet port  3722  the output from exit portal  3711  of the higher pressure expander  3710 , which is mixed into line  720 . As in other embodiments, the rotary mechanical coupling from the expanders  3710  and  3720  drives generator  3710  to produce electric power or other useful energy. It should be appreciated that this embodiment does not require to expanders, as the gas output of either the gravity separator or flash drum can drive a single expander, with the gas output of the other device being used to power an unrelated expander, such as for example in the other embodiments of the invention. 
     U.S. Pat. No. 4,819,437 (issued to Dayan on Apr. 11, 1989), which is incorporated herein by reference, also discloses a process for converting thermal energy to work in which a solution is decompressed, by means of an expansion device, such as a flash drum, in which the exiting vapor mixture is then expanded in a turbine to produce additional work. 
     Liquid output from the bottom of the flash drum  701  will contain a mixture of suspended and dissolved solids. This liquid stream is preferably separated in brine loop  1300 ′ by hydrocyclone filtration at filter  500 , within recirculation or return to loop  1300 ′. The liquid effluent from the solid separator or filter  500  thus returns to the quench cooler  120 , via a brine circulation pump  121 . However, the hot brine may be used in heat exchanger  7401  to pre-heat the feed from pump  260  before it reaches the main heater  265 . loop  1300 ′ returns water back to the gravity separator  130 , preferably by mixing in quench cooler  120  with the direct effluent from SCWOR  110 . 
     It should also be understood that in alternative embodiments of the invention, the output of the SCWOR  110  can be cooled by other means than the quench cooler, with the same effect of the output thereof entering the gravity separator. In such embodiments the output of the gravity circulator can return thereto via the brine circulation loop  1300  or  1300 ′, without the need to enter an equivalent cooling means. 
     Water from the gas streams or steam that drives the expanders can also be returned in a re-pressurized state to the SCWOR  110  as in other embodiments. The low pressure side output at portal  3721  of the low pressure expander  3720  is directed to a moisture condenser  7240 . The condensate there from is stored in a condensate recovery tank  7241 . Liquid condensate is drawn from the bottom of this tank and optionally feed by a pump  261  back to the injector  1405  or between the transpiring wall and inner chamber wall of the SCWOR  110 , but preferably after being re-heated and re-pressurized via the high pressure heaters  707  and  708  respectively. The output of a second feed air compressor  702 , which is driven by motor  703 , is directed toward valve  1407  and  709  to pressurize and drive the water or steam generated by heaters  707  and  708 . 
     The output of fluid from heater  707  is controlled by valve  709  to direct water to the SCWOR chamber or reactor annulus at port  1406  for use in transpiration service. The output of fluid from heater  708  is controlled by valve  1407  to direct water to the feed injector  1405  for injection/mixing with the feed from pump  265 . 
     Make up water is optionally fed to the condensate separator or recovery tank  7241  via port  7012 . The condensate separator or recovery tank  7241  externally vents non combustible exhaust gases at line  7301 . 
     In the embodiment of  FIG. 8 , which is a variant on the embodiment of  FIG. 7 , an optional steam superheater  400  is disposed at least partially within the SCWOR  110  to further improve the efficiency of the generation of electric power at generator  3730 , by pre-heating the gas output of the gravity or brine separator  130  in line  710  before or after it reach pressure control valve  705 . Thus, the output of the gravity brine separator  130  travels via line  411 , and returning to feed the expander  3710  via line  412 . Alternatively, the superheater  400  can receive and pre-heat gas exiting the flash drum  701  that travels in line  720 , as shown by broken lines at  411  and  412 . 
       FIG. 9  illustrates a common and representative structure for a gravity separator  130 . The gravity separator  130  has an inlet port  131  for receiving effluent, such as from the quench cooler  120  of the SCWOR  110 . The influent hits deflection plate  134  which directs liquid downward toward the bottom, where upon prompt gravity separation it can exit via portal  132 . Mist and vapor that expands upward in the separator  130  reaches a mist removal device or water vapor coalesce means  135  situated below the upper vapor exit portal  133 . The mist removal device  135  is optionally a mist mat, vane pack, hydrocyclone and the like, so that liquid from the mist is collected and flows downward, and the vapor phase exits at portal  133 . U.S. Pat. No. 7,654,397 (issued to Allouche on Feb. 2, 201), which is incorporated herein by reference, also discloses the construction of a particular type of gravity separator that separates a liquid phase and a gas phase from a multiphase fluid mixture. 
     While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be within the spirit and scope of the invention as defined by the appended claims.