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WO1992005119A1 - Procede adiabatique d'extraction de dechets aqueux - Google Patents

Procede adiabatique d'extraction de dechets aqueux Download PDF

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Publication number
WO1992005119A1
WO1992005119A1 PCT/US1991/004278 US9104278W WO9205119A1 WO 1992005119 A1 WO1992005119 A1 WO 1992005119A1 US 9104278 W US9104278 W US 9104278W WO 9205119 A1 WO9205119 A1 WO 9205119A1
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WIPO (PCT)
Prior art keywords
stream
waste
reactor
further characterized
oil
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PCT/US1991/004278
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English (en)
Inventor
James F. Grutsch
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Chemical Waste Management, Inc.
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Application filed by Chemical Waste Management, Inc. filed Critical Chemical Waste Management, Inc.
Publication of WO1992005119A1 publication Critical patent/WO1992005119A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8668—Removing organic compounds not provided for in B01D53/8603 - B01D53/8665
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/002—Sludge treatment using liquids immiscible with water

Definitions

  • This invention relates generally to the treatment, dewatering, and detoxifying of contaminated aqueous wastes including wastewaters, slurries, and sludges.
  • the treatment of these contaminated streams has become a national environmental priority, since such streams are being created by so many sources, such as landfills, research, industry, power plants, government and many other chemical, pharmaceutical, biological, plating, and photographic processes.
  • this invention involves a novel process that concentrates solid waste materials and catalytically oxidizes volatile pollutants, both of which are contained in the aqueous wastes that can be treated by this invention. Further, this invention has the capability of providing a useful condensate product.
  • the novel process disclosed herein couples efficient evaporation with gas phase catalytic oxidation.
  • this process can provide for the recapture of distilled quality water that is substantially free of minerals and organics and that may, therefore, be safely returned to rivers and streams or reused in industrial processes.
  • aqueous waste streams such as sewage and animal and human wastes
  • aqueous waste streams has long been a difficult problem because of the difficulties associated with removing the liquids or volatiles that typically comprise the majority of such wastes. More often than not aqueous wastes contain volatile components that if not properly treated would cause massive pollution of the environment.
  • the art has recognized a number of processes for treating aqueous waste, several of which involve evaporation steps to concentrate the solids phase prior to further treatment of the concentrated solids. Treatment of harmful volatile components prior to introduction in the environment is also known to the art. An oxidation process is the most typical of treatment processes for volatilized contaminants.
  • oxidation of organic compounds dissolved in wastewater streams is well known in the art. Both liquid phase and vapor phase oxidation processes are known.
  • industrial fluids such as dyestuf f solutions, can be purified using the process disclosed in U.S. Patent No. 4,279,693 (Kuhnlein et al.). This process involves evaporation of impurities from polluted fluids where approximately 90% of the volatile impurities remain untreated or are subjected to flame combustion at temperatures ranging from 800-lOOOt. A small percentage of the impurities (approximately 10%) may be removed from the non volatiles and destroyed in a catalytic oxidation process.
  • U.S. Patent No. 4,141,829 discloses a two step oxidation process. In the first step a contaminated water stream is subjected to a liquid oxidation process to destroy the majority of the organic substances in the liquid stream. Any volatile organics remaining after the liquid oxidation step are heated and catalytically oxidized in a gas phase reactor.
  • U.S. Patent No. 4,021,500 discloses an improved oxidative dehydration system to catalytically remove dissolved hydrocarbons. A hydrocarbon laden liquid water stream is mixed with an air/steam stream and is contacted with a solid catalyst to yield an effluent of water vapor, carbon monoxide and carbon dioxide.
  • U.S. Patent No. 4,699,720 (Harada et al.) teaches a process for treating wastewater wherein a stream containing suspended solids, ammonia and chemically oxidizable substances is subjected to a liquid phase catalytic oxidation reaction. Separation of the suspended or dissolved solids occurs after the oxidation reaction by employing a reverse osmosis process.
  • U.S. Patent No. 4,632,766 discloses a method of treating wastewater wherein a concentrated "slime" containing water is subjected to a noncatalytic multistage oxidation in the presence of air or oxygen.
  • 3,487,016 teaches the oxidation of organic or inorganic materials in liquid or vapor phase using oxygen-containing gas and a catalyst containing either manganese or lead. Oxidation is performed at low temperatures and at atmospheric or less pressure.
  • U.S. Patent No. 3,804,756 (Callahan et al.) teaches that volatile impurities may be steam stripped from wastewaters and then chemically oxidized with a variety of catalyst formulations, with copper oxide being preferred.
  • VOC volatile organic compounds
  • the present invention presents a novel continuous treatment method for concentrating waste solids and chemically oxidizing volatile contaminants. Further, this invention presents a catalytic oxidation process that can be carried out in the presence of steam at gas phase conditions.
  • This invention is directed toward a novel process for the treatment of aqueous waste streams. More specifically the invention provides a means to convert chemically oxidizable volatile pollutants found in a variety of aqueous wastes to harmless inorganic gases. This process also has the potential to produce a useful condensate product of distilled water quality, free of minerals and dissolved organics.
  • Another object of this invention is to provide a process that specifically is designed to dewater slurries and highly mineralized wastewaters and sludges, especially those containing toxic organic and inorganic compounds which, if treated by conventional treating processes, would be considered hazardous if discharged to surface freshwater receiving streams.
  • a broad embodiment of the invention is directed to a process for dewatering and decontaminating an aqueous waste containing volatile chemically oxidizable pollutants comprising the steps of (a) continuously dewatering the aqueous waste by dispersing a stream of the aqueous waste into a continuous phase comprising oil circulating in an evaporative reactor maintained at a temperature sufficient to volatize water and the chemically oxidizable pollutants; (b) removing from the reactor a first stream comprising a dispersion of dewatered waste and oil and a second stream comprising the volatized chemically oxidizable pollutants and steam; and (c) catalytically oxidizing the second stream in the presence of steam, at gas phase conditions to convert substantially all the chemically oxidizable pollutants, thereby producing a gaseous reaction product comprising substantially steam and incondensible gases.
  • Another embodiment of the invention provides for a process for dewatering and decontaminating an aqueous waste containing volatile chemically oxidizable pollutants comprising, in combination, the steps of (a) continuously dewatering the aqueous waste by dispersing a stream of the aqueous waste into a continuouse phase comprising oil circulating in an evaporative reactor maintained at a temperature sufficient to volatize the chemically oxidizable pollutants (b) removing from the reactor a first stream comprising a dispersion of dewatered waste and oil and a second stream comprising volatized chemically oxidizable pollutants and steam (c) separating the first stream into two separate streams, a slip stream and a recycle stream to facilitate removal of the dewatered waste from the process and to maintain the concentration of the dewatered waste in the evaporative reactor in a steady state conditions, the slip stream having a lower volume compared to the recycle stream and having substantially the same composition as both the recycle stream and the first stream (d) recycling the recycle stream to the
  • Figure 1 is a flow diagram of an embodiment of the invention illustrating the treatment of a municipal sludge that uses a stirred tank evaporative reactor.
  • Figure 2 is a flow diagram of an embodiment of the invention that uses a falling film evaporative reactor.
  • the instant invention is capable of processing a variety of aqueous wastes, including sludges, slurries and wastewaters.
  • this invention can process all forms of municipal sludges, rolling mill sludge, radioactive sludge, harbor or other dredgings, PCB contaminated siudges, alum sludges and oily sludges.
  • slurries and wastewaters that can be treated include wastes from coal tar pits, phosphate slimes, leachates, brine concentrates, chelated chemical cleaning solutions, pharmaceutical waste broths and engineered microorganisms.
  • the solids particle size of the aqueous waste treated should be a maximum of about 1/4 inch. Large particles, such as from garbage, can be ground to size or comminuted by existing techniques, thus making this process applicable to all physical forms of aqueous waste materials.
  • Aqueous waste can be generally characterized as a suspension of solid materials containing a high percentage of water. Many such aqueous wastes are contaminated with volatile chemically oxidizable pollutants comprising both organic and inorganic compounds.
  • the aqueous wastes may contain nonvolatile pollutants.
  • the volatile chemically oxidizable pollutants include compounds, such as alcohols, ketones, esters, aromatic hydrocarbons, chlorinated hydrocarbons, ammoniacal compounds, cyanide and sulfur containing compounds, and a variety of other chemicals that are known pollutants.
  • the nonvolatile pollutants typically comprise minerals, which are broadly defined as any element, inorganic compound or mixture occurring or originating in the earth's crust and atmosphere, including all metals and nonmetals, their compounds and ores. Included in the dissolved solids can be compounds of heavy metals, such as, nickel, zinc, cadmium, mercury, arsenic, and lead.
  • the process of the invention is particularly well suited for the treatment of leachates that emanate from landfills.
  • the complex nature of the constituents of such wastewater streams is illustrated by the following compositional profile of a representative landfill leachate.
  • TDS Total Dissolved Solids
  • the particular aqueous waste to be dewatered and detoxified is dispersed into a nonvolatile continuous phase comprising oil in an evaporative reactor. At least two streams are removed from the reactor, the first comprising an admixture of dewatered and detoxified waste solids and second a vapor phase containing primarily steam and, if present, chemically oxidizable compounds.
  • the oils that are preferred for use in this process include inert, relatively nonvolatile oils or fats, or other oil-like materials, including synthetic oils.
  • Typical oils include motor oil, mineral oil, tallow, other animal fats and vegetable oils, all of which often can be derived directly from the process operation; petroleum oils and their fractions and derivatives including fuel oils, glycerines, glycols and mixtures thereof.
  • the quantity of oil is such that its ratio in the system is in the range of about 10 to about 1 by weight, based on each part of non-fat solid. This ratio refers to total oil, i.e., that added plus that derived from the process for reuse.
  • the unit operation performed in the evaporative reactor necessarily includes an evaporation step and details need not be included herein.
  • Any evaporation design that can dewater and detoxify the solids from a dilute solution of waste solids and produce steam substantially free of dissolved solids can be used in the invention.
  • Examples of known evaporator designs include forced circulation, submerged tube forced circulation, Oslo-type crystallizer, short and long tube vertical, horizontal tube, and falling film.
  • Evaporation may be effected with a stirred tank reactor and in particular by using a back-mix reactor design where the concentration of constituents in the effluent of the reactor is equivalent to that in the reactor.
  • a falling film evaporator is the preferred design for the evaporative reactor.
  • the process conditions for the evaporative reactor include a temperature of the oil of from about lOOt (212°F) to about 130t (266°F) and a pressure from about subatmospheric to about 790 kPa (abs) (100 psig), with most preferred temperature and pressure ranges from about 105°C (221 °F) to about 125t (257°F) and from about atmospheric to about 446 kPa (abs) (50 psig), respectively.
  • Waste solids retention time in the evaporative reactor depends upon the water release characteristics of the solids and may be as little as 0.25 hrs. to as much as 6 hrs., more preferably from about 1 hr to about 4 hrs.
  • the waste solids or dewatered waste that accumulates in the hot reaction oil as a result of the vaporization of water and volatile contaminants from the aqueous waste, are withdrawn from the process in a first stream.
  • the first stream is then split into a recycle stream and a slip stream.
  • the removal of a low-volume slip stream from the evaporative reactor to concentrate the solids eliminates the necessity and cost associated with pumping large volumes of oil throughout the process.
  • the slip stream which comprises an admixture of dewatered solids and oil, is further processed to yield a solid product substantially free of oil and water. Removal of the slip stream is effected by withdrawing the oil and dewatered waste solids from the bottom of the evaporative reactor, removing a low volume of this mixture and returning the balance of the mixture to the top of the reactor.
  • any process that can deoil the dewatered solids may be used.
  • a preferred process involves holding the admixture of dewatered solids and oil in a thickening tank where the solids will settle to form a slurry comprised of about 30 to 40% by weight of solids in oil.
  • This thickened sludge is then washed with a light hydrocarbon, such as pentane, to facilitate extraction of the oil from the solids.
  • the washed solids are then subjected to pressure filtration and further washing with a light hydrocarbon.
  • the resultant filter cake is held at reduced pressure to vaporize any residual light hydrocarbon. Recovered oil and light hydrocarbon are returned to the process for further use.
  • the recovered dry solids may represent a valuable product.
  • the deoiled solid product can be used as a fertilizer, animal feed, or formed into briquets for burning as fuel for the process * or other processes.
  • stabilization is an alternative disposal means, including both physical and chemical stabilization. Any stabilization process known to the art may be used, however, chemical fixation and solidification processes for producing solid wastes suitable for ultimate disposal in landfills or other secure sites are most preferred.
  • stabilizing agents for example, fly ash, asphalts, alkali metal silicates, all forms of cements, pozzolans, gypsum, calcium chloride, kiln dusts, lime, or other known stabilizing agents.
  • the addition of the stabilizing agents can be performed using an in-line or batch process. .After mixing and curing, the mixture forms a solid.
  • the stabilized deoiled solids may then be disposed of following accepted disposal practices. Alternatively, the solid may be used as building materials, as landfill to support buildings, to reclaim coastal lands, or to build levees or dikes.
  • the second stream from the evaporative reactor comprising steam and the volatile chemically oxidizable compounds, is contacted with a solid catalyst in a reaction zone maintained at oxidation reaction conditions.
  • the chemically oxidizable volatile compounds that were volatized when the aqueous waste was contacted with the hot oil are oxidized to produce a gaseous reaction product comprising substantially steam and incondensible gases, primarily carbon dioxide and nitrogen.
  • the second stream typically comprises at least 95 wt% of all of the volatile chemically oxidizable pollutants originally contained in the aqueous waste.
  • the second stream contains at least 96 wt% and more preferably at least 99 wt% of the volatile pollutants present in the aqueous waste.
  • substantially all of the volatile pollutants originally in the aqueous waste are contained in the second stream.
  • substantially all of the volatile pollutants originally present in the aqueous stream are catalytically oxidized in the reaction zone.
  • the second stream from the evaporative reactor contains substantially all of the water originally contained in the aqueous waste fed to the process.
  • the water in the second stream is directed to the catalytic oxidation reactor in the vapor state as steam.
  • the second stream contains significantly more steam than volatile pollutants.
  • the steam-to-organic weight ratio is greater than 2:1. More preferably, the quantity of steam in the second stream is at least 16 times the weight of volatile pollutants contained therein.
  • the volatile pollutant component of the second stream is less than 10% of the total components in the stream.
  • the presence of steam in the oxidation reactor is beneficial to achieving complete oxidation of volatile pollutants. It is believed that the steam directly participates in the oxidation of pollutants either by reacting catalytically, thermally, or through steair. reforming chemistry with partially oxidized compounds. This theory of direct steam participation in pollutant removal could also help explain the apparent lack of a large oxygen effect, since steam is so primarily present. In fact, the oxidation of pollutants can be performed by providing less than the stoichiometric amount of oxygen.
  • each different type of aqueous waste will have a different stoichiometric requirement of oxygen, but because of the high ratio of steam to volatile pollutants present in the reaction zone, high conversions of pollutants are achieved at less than the stoichiometric amount of oxygen.
  • the second stream Prior to the oxidation step the second stream may be compressed by mechanical means or by a steam jet to increase the latent heat value of the second stream.
  • a preferred means to compress the second stream is by compressors powered by steam turbines. These steam turbines can be operated in cogeneration mode using landfill biogas, steam from an incinerator waste heat recovery unit, or other similar source. Energy cost reductions and high cogeneration efficiencies can be realized using steam turbine powered compressors and pumps.
  • the gaseous reaction product that results from the oxidation step may be compressed, in preference to the compression of the second stream, to increase its latent heat value. In either case the latent heat can be used to provide the partial or total heat requirement needed in the evaporative reactor.
  • the catalytic oxidation is performed in a reactor at gas phase conditions using a solid catalyst.
  • the oxidation reaction conditions include a reaction temperature in the range of from about 204 cl C (400°F) to about 1200°C
  • reaction temperature should be maintained in the range from about 371°C (700°F) to about 677°C (1250°F).
  • gas space velocity of the water rich vapor phase stream in the reaction zone is from about 0.1 sec "1 to about 1000 sec "1 , most preferably from about 5 sec " 1 to about 100 sec "1 .
  • the reaction zone pressure preferably is in the operating range of from subatmospheric to about 790 kPa (abs) (100 psig), with a most preferred operating pressure of from about atmospheric to about 446 kPa (abs) (50 psig).
  • the chemically oxidizable compounds in the second stream are catalytically oxidized in the presence of the steam that was formed in the evaporative reactor.
  • the solid catalyst used in the oxidation zone may be selected from any of the known commercially existing oxidation catalyst compositions, or mixtures of known oxidation catalysts, that meet the required standards for stability and activity and that possess a high selectivity for oxidation of volatile organic and inorganic compounds.
  • the active component of the oxidation catalyst is a metal, preferably a nonprecious metal, supported on a solid carrier.
  • the preferred solid carrier is alumina. However, any known carrier may be used, for example, silica, silica-alumina, clay or like materials.
  • the carrier may be in the form of spheres, pellets or extrudates.
  • the amount of active metal on the catalyst is preferably from about 5 to about 50 weight percent, based on the total catalyst weight. More preferably the metal component comprises from about 15 to about 25 weight percent of the catalyst.
  • a preferred oxidation catalyst composition includes chromic oxide and alumina in the form of an extrudate. This preferred catalyst and its method of preparation are more thoroughly described in U.S. Patent No. 4,330,513 (Hunter et al), which is incorporated herein by reference.
  • the oxidation reaction of this invention is exothermic and can cause reaction temperatures to increase to excessive levels.
  • a quench stream may be added to the oxidation reaction zone.
  • a preferred quench medium is the condensate product obtained from the evaporator.
  • additional chemical oxygen can be supplied by any known means, with the injection of air, oxygen enriched air, or O 2 being preferred.
  • This external heat source can be supplied from either direct or indirect sources.
  • Indirect sources include electrical heating and conventional heat exchange equipment.
  • Direct heating includes direct gas fired heating of the second stream.
  • the reactants may be heated by direct fired heat prior to introduction into the oxidation reactor. Any direct fired heating process known to the art may be used.
  • the oxidation reaction step of the invention is capable of catalytically oxidizing a wide range of volatile organic and inorganic compounds, including halogenated organics, organophosphorus compounds, organosulfur compounds and organonitrogen compounds.
  • the gaseous reaction product obtained from the oxidation of such compounds may be highly acidic, containing HC1, PO* SO x and NO x .
  • the acidic nature of the product can have deleterious effects on downstream equipment metallurgy. Neutralization of the acidic gaseous reaction products can prevent corrosion and the eventual destruction of downstream equipment. Any neutralization process known to the art may be used to neutralize the acidic reaction products, including solid scrubbers, liquid scrubbers, or a combination of both.
  • a preferred neutralization method involves the use of a limestone bed located downstream of the oxidation reactor.
  • the inherent alkalinity of limestone will neutralize and remove strongly acidic gases contained in the gaseous reaction stream.
  • multiple limestone beds arranged in series flow may be employed.
  • a preferred type of limestone is dolomitic limestone, which contains a carbonate of calcium and magnesium. The magnesium is better suited to capture volatized borates and arsenates.
  • the limestone bed may also be utilized as a temperature control means when the gaseous reaction product is used to supply the heat of evaporation in the evaporative reactor. Temperature control may be desirable to prevent thermal stress of the reactor. Thermal stress occurs because the gaseous reaction product from the highly exothermic catalytic oxidation reaction can, in some instances, be several hundred degrees higher in temperature than the normal operating temperature of the reactor. Normally it is preferred that the medium used to supply the heat of evaporation be only 5 to 17°C (9 to 30°F) higher than the boiling point of the volatile compounds in the aqueous waste to be evaporated.
  • An alternative means to prevent thermal stress is to quench the gaseous reaction products, preferably using a portion of the condensate product stream.
  • oxidation of the chemically oxidizable compounds in the second stream is preferably performed using a solid supported metal catalyst, it is within the scope of the invention to perform the oxidation step by any catalytic means or combination of means known to the art.
  • the oxidation reaction may be performed by ultraviolet light catalyzed peroxide or ozone oxidation.
  • the composition of the gaseous reaction product exiting from the oxidation reactor comprises substantially steam and incondensible gases, primarily carbon dioxide and N-.
  • the gaseous reaction product can optionally be condensed to produce a useful condensate of substantially liquid water. Condensation can be performed by any method known to the art. One method is to pass the gaseous reaction product through an economizer to utilize its latent heat to effect the evaporation of the volatiles contained in the aqueous waste. Alternatively, the condensation of the gaseous reaction product can be performed in an evaporator while simultaneously utilizing its latent heat to effect the evaporation of the volatiles contained in the aqueous waste.
  • a condensate product stream produced by the process of the invention is comprised of substantially liquid water that is free of minerals and organics and is reusable as a condensate for other processes.
  • the condensate may be directly disposed of to existing surface water receiving streams without the need for additional treatment.
  • the inventive concept of this invention provides the basis for solving important environmental engineering problems.
  • toxic chlorinated organics that are nonvolatile such as certain polychlorinated biphenyl (PCB) congeners
  • PCB polychlorinated biphenyl
  • This invention provides an environment for simultaneous destruction of these PCBs using chemical dehalogenation processes because the heat and the low moisture content is a favorable environment for dechlorination.
  • Any chemical dehalogenation process known to the art may be advantageously used to destroy halogenated nonvolatile organics present in the continuous oil phase.
  • a slip stream of the halogenated organic containing oil dispersion medium is routed to a reactor where the chemical dehalogenation reaction is carried out. After the reaction is complete, all reaction products are routed back to the evaporative reactor. Volatile chlorinated organic fragments are volatized in the evaporative reactor and are completely destroyed when passed over the oxidation catalyst.
  • waste materials containing heavy metals can be processed in this invention by adding oil soluble metal extractants, such as tributyl phosphate, 2-ethylhexyl phosphoric acid, trioctylphosphine oxide, etc. to the continous oil phase.
  • the metal extractants solubilize the metals in the oil and allow for easy extraction from the process.
  • a slip stream of the continuous oil phase is treated to recover the metals and the oil and organic extractant is recirculated to the evaporative reactor.
  • the inventive concept of this process provides a source of high temperature to remove high boiling water residuals. For example, fresh water evaporates at about lOOt (212°F) however, as the water gets more brackish the boiling point can increase substantially.
  • the horsepower for vapor reco pressi ⁇ n evaporation at 212°F is about double when brine is evaporated at 235°F.
  • Using a slip stream of the recirculating continuous oil phase to desuperheat the hot off -gases from the catalystic oxidation provides higher oil temperatures to evaporate this higher boiling water.
  • the evaporative reactor can be operated in a more energy efficient temperature range for evaporting most of the water and evaporation of the much smaller amount of high boiling point water is achieved by using the energy released by catalytic oxidation.
  • FIG. 1 is a flow diagram of one preferred embodiment of the invention illustrating the treatment of municipal sewage or equivalent waste materials.
  • the sewage is carried by line 1 to heat exchanger means 10 where the sewage is heated indirectly with hot gaseous oxidation reaction product carried in line 12.
  • the heated sewage is carried via line 2 to evaporative reactor 3 where it is contacted with hot nonvolatile oil maintained at a temperature in the range from about 240-250°F.
  • the water and other volatile compounds contained in the sewage are vaporized into a mixture of steam and chemically oxidizable compounds and are continuously removed from the evaporative reactor via line 11.
  • the mixture of steam and chemically oxidizable compounds is indirectly heated in heat exchanger means 20, mixed with oxidizing agent introduced through line 14 and contacted with a solid nonprecious metal oxidation catalyst in reactor 13.
  • the amount of oxidizing agent added to the steam and chemically oxidizable compounds will vary depending on the oxygen demand of the chemically oxidizable component.
  • the oxidation reaction that occurs in reactor 13 produces gaseous products that are removed from the reactor via line 12, indirectly heat exchanged in heat exchanger means 20 and 10 and then removed from the process via line 15.
  • An homogenous admixture of oil and dewatered and detoxified waste solids, equivalent to the concentration in the evaporative reactor is removed from the reactor via line 4.
  • Recycle oil from line 22 is added to the admixture in line 4 and indirectly heated in furnace 5.
  • Line 6 recycles the heated admixture of oil and waste solids back to reactor 3.
  • the admixture in line 6 is split to form slip stream 7 and recycle stream 24.
  • Slip stream 7 is a low volume stream having the same composition of the admixture in line 6 and the slip stream is carried to settling tank 8. Volatiles from settling tank 8 are removed via line 9 and combined with the admixture in line 24 prior to recycle to reactor 3.
  • the settled admixture in tank 8 is removed by line 16 combined with a light hydrocarbon as a wash and fed to pressure filter 18.
  • Filtrate 20 comprising oil and light hydrocarbon is removed from the pressure filter via line 20 and carried to flash drum 21 where the light hydrocarbon is vaporized and removed overhead via line 17, condensed and collected in wash tank 23.
  • Recycle oil is removed from the flash drum via 22.
  • the pressure filter produces a filter cake or briquette that is removed via line 19 and subsequently burned as a fuel in furnace 5. Ash product formed in the furnace is removed for disposal via line 23.
  • the aqueous waste to be dewatered and detoxified is carried by line 30 to heat exchanger means 31 where it is heated indirectly with the condensate product stream 37.
  • the heated aqueous waste is carried by line 32 to sump 33 of evaporative reactor 34.
  • a concentrate or slurry of oil and dispersed dewatered waste solids is contained in sump 33. Upon contact with the hot oil in sump 33, water and volatile compounds are vaporized.
  • the slurry of oil and dispersed dewatered waste solids is continuously circulated through lines 35 and 45 to the top of evaporative reactor 34 where water and volatile chemically oxidizable pollutants are recirculated to the heat exchanger section of evaporative reactor 34, where they are heated and vaporized.
  • a slip stream 44 is removed from the slurry in line 35 and treated in a manner similar to that described for the slip stream described in the embodiment illustrated in Figure 1.
  • the steam and chemically oxidizable pollutants generated in the reactor are substantially free of all dissolved solids and are removed from the reactor by line 36.
  • the steam and chemically oxidizable compounds in line 36 are compressed by compression means 39 and returned to line 40.
  • the compressed steam and chemically oxidizable compounds in line 40 are then combined with an oxygen containing stream 41 prior to entering oxidation reactor 42.
  • the degree of conversion of volatile pollutants in the oxidation reactor depends on 1) the degree of contamination of the aqueous waste fed to the process, and 2) the tolerable level of pollutants in the stream ultimately exiting the process. The higher the level of pollutants in the incoming aqueous waste, the greater degree of conversion will be achieved in the oxidation reactor. Similarly, if the level of contaminants allowable in the stream exiting the process is high, then a lower degree of conversion is required in the oxidation reactor.
  • the goal to be accomplished by the oxidation reactor is not the percentage removal of pollutants, but rather is the removal of a sufficient quantity of pollutants such that the discharge stream from the process is not harmful to human health or the environment.
  • the oxidation reactor can achieve at least 95% conversion, and in some instances 99.9+% conversion, of the chemically oxidizable compounds in the second stream.
  • This produces a gaseous reaction product of substantially steam and incondensible gases, primarily carbon dioxide.
  • the gaseous reaction product is removed from the oxidation reactor by line 43.
  • a portion of the gaseous reaction product in line 43 can be used as a preheat means for maintaining the temperature of the reactants entering the oxidation reactor.
  • a steam compressor may be used to compress the gaseous reaction products in line 43 to increase their heat value.
  • Condensation of the gaseous reaction product is accomplished upon introduction of the gaseous reaction product in line 43 to the shell side of the heat exchanger element of evaporative reactor 34.
  • the condensate formed in the heat exchanger is continuously removed through line 37, heat exchanged with incoming aqueous waste and removed from the process via line 38.
  • a laboratory test unit comprising a stirred glass reactor and a reaction product condenser.
  • the glass reactor was operated at atmospheric pressure and was heated externally with an electric heating mantle.
  • the reactor contained approximately 700 ml. of oil, the oil being nonvolatile when heated to 100-125%.
  • aqueous waste was added incrementally to the reactor below the surface of the oil using a metering pump.
  • the waste was added at the rate of about 3 ml./30 sec.
  • Volatiles were collected and condensed using a cold water reaction produced condenser.
  • the condensate was analyzed using gas chromotography techniques. Dewatered waste was extracted from the oil using light hydrocarbon extraction techniques. Results from several test runs are shown below.
  • Thickened reactor oil product solids % 45-52
  • Reactor oil temperature °C 110
  • Feed Composition 20% oil, 35% solids and 45% water Reactor oil temperatures, °C 107 Reactor oil solids at equilibrium, % 15

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Abstract

Procédé d'égouttage mécanique et de détoxification de déchets aqueux, en particulier ceux qui contiennent des polluants organiques et inorganiques volatils chimiquement oxydables. Ledit procédé associe un réacteur à évaporation efficace utilisant de l'huile chaude comme moyen de transfert de la chaleur pour concentrer les déchets solides à une réaction d'oxydation catalytique destinée à convertir les polluants organiques et inorganiques volatils. Un produit condensé peut être obtenu à partir des déchets aqueux selon le procédé décrit. Ledit condensat a la qualité de l'eau distillée et est pratiquement exempt de minéraux et de substances organiques.
PCT/US1991/004278 1990-09-17 1991-06-14 Procede adiabatique d'extraction de dechets aqueux WO1992005119A1 (fr)

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US58366990A 1990-09-17 1990-09-17
US583,669 1990-09-17

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WO1992005119A1 true WO1992005119A1 (fr) 1992-04-02

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PCT/US1991/004278 WO1992005119A1 (fr) 1990-09-17 1991-06-14 Procede adiabatique d'extraction de dechets aqueux

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3716458A (en) * 1970-09-18 1973-02-13 Carver Greenfield Corp Process and apparatus for recovering clean water from dilute solutions of waste solids
EP0354656A1 (fr) * 1988-08-08 1990-02-14 Chemical Waste Management, Inc. Procédé pour le traitement catalytique des eaux usées

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3716458A (en) * 1970-09-18 1973-02-13 Carver Greenfield Corp Process and apparatus for recovering clean water from dilute solutions of waste solids
EP0354656A1 (fr) * 1988-08-08 1990-02-14 Chemical Waste Management, Inc. Procédé pour le traitement catalytique des eaux usées

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