Abstract: Antifoaming agents for use in acid gas scrubbing processes comprising 1-secondary or 1-tertiary alkyl- or 1-cycloalkyl-hexahydro-2-pyrimidinones and 1-secondary or 1-tertiary alkyl- or 1-cycloalkyl-2-imidazolidinones are disclosed.

Abstract: A process for manufacturing synthetic hydrocarbons such as gasoline and/or kerosene from the synthesis of carbon dioxide and hydrogen. The carbon dioxide is obtained from the atmosphere while the hydrogen is obtained during the electrolysis of water. An intermediate fuel, namely methyl alcohol may be stored for use or upgraded to higher heating value hydrocarbons by a catalytic conversion.

Abstract: A process is disclosed for the purification of an inert or non-reacting gas such as lower mono-olefins by the removal of trace amounts of reacting impurities such as carbon dioxide therefrom, comprising passing said gas through an essentially non-aqueous liquid solution of alkali or alkaline earth metal hydroxides and/or weak acid salts and certain selected liquid polyhydric alcohols.

Abstract: A deoxidizer comprises ferrous carbonate having a specific surface area of at least 20 m.sup.2 /g. The ferrous carbonate can be combined with a mixture of a reduced iron powder and a metal halide; or an alkli metal hydroxide and/or an alkline earth metal hydroxide or calcium oxide and/or ettringite. The deoxidizer is used for the deoxidation of a package so as to substitute oxygen by carbon dioxide.

Abstract: In a process of selectively desulfurizing gases which contain hydrogen sulfide and carbon dioxide comprising scrubbing the gases with an aqueous potassium carbonate solution under superatmospheric pressure and at temperatures of about 100.degree. C., regenerating the laden scrubbing solution and recycling the regenerated scrubbing solution, the improvement wherein the gases to be purified are scrubbed with an aqueous potassium carbonate solution so as to maintain a mass ratio of 1.0 to 3.0 vals (gram equivalents) of alkali in the solution per mole of CO.sub.2 and H.sub.2 S in the gases to be purified, the laden scrubbing liquor is subsequently regenerated by being stripped with a gas in which a CO.sub.2 partial pressure above 0.2 bar is maintained, and the so regenerated scrubbing solution is recycled.

Abstract: A process for selectively absorbing H.sub.2 S from gas mixtures which contain CO.sub.2 and H.sub.2 S in a molar ratio of 4:1 or greater and in which the gas flow rate varies substantially. Alkali metal carbonate solutions are used with absorption under pressure and at an elevated temperature and desorption by steam stripping at about atmospheric pressure. The degree of selectivity of H.sub.2 S removal is maintained constant despite substantial variations in the gas flow rate by maintaining a constant stripping steam/gas ratio selected to provide the desired partial pressure of H.sub.2 S in the purified gas and by adjusting the solution/gas ratio to a value in the vicinity of that at which the partial pressure of H.sub.2 S in the purified gas remains at said selected value while the difference between the partial pressures of CO.sub.2 and H.sub.2 S in the purified gas reaches a maximum value, and by then maintaining such solution/gas ratio as the gas flow rate varies.

Abstract: A cyclic urea reaction product forms as a by-product of a hindered amine acid gas scrubbing process and results in an ultimate buildup of the material in the circulating amine scrubbing solution. The buildup of this material has a deleterious effect on acid gas removal rates and accordingly, results in inefficient acid gas removal. In the process of the present invention, the cyclic urea degradation product is removed from the circulating solution by employing a selective precipitation of the cyclic urea followed by filtration. The selective precipitation is carried out by cooling the circulating solution to a particular temperature level such that the cyclic urea comes out of solution while the other components remain in solution.

Abstract: A cellulosic pulp and bleaching process is described. The process integrates two cycles, one is a digestor liquor cycle and the other is a sulfur cycle.The digestor liquor cycle comprises the steps of digesting a fibrous cellulosic feed to form a pulp, separating the pulp and bleaching it in at least one stage with chlorine dioxide, evaporating and burning the remaining waste liquor to form a smelt, dissolving the smelt to form a green liquor and utilizing the green liquor, after recausticizing, as at least a portion of the feed stock for the digestor step.The sulfur cycle of the present invention utilizes a portion of the green liquor of the digestor liquor cycle. The green liquor is carbonated to form a bicarbonate which is then stripped of H.sub.2 S. The H.sub.2 S is converted into H.sub.2 SO.sub.4 and utilized as a feed stock to a chlorine dioxide generator. The chlorine dioxide generator utilizes H.sub.2 SO.sub.4 as feed stock and produces Na.sub.2 SO.sub.4 as a by-product. The Na.sub.2 SO.sub.

Abstract: Acidic gases such as carbon dioxide are removed from a normally gaseous mixture including the acidic component by contacting the gaseous mixture in an absorption zone with an acid absorbing scrubbing solution comprising a basic alkali metal compound and an activator for the compound, during which process at least a portion of the activator is converted to a cyclic urea. The solution is then transferred to the desorption zone to remove at least a portion of the absorbed acidic component. At least a portion of the partially desorbed scrubbing solution containing the cyclic urea is transferred from the desorption zone to a thermal conversion zone maintained at an elevated temperature wherein at least a portion of the cyclic urea is converted back to the activator.

Abstract: A process for manufacturing synthetic hydrocarbons such as gasoline and/or kerosene from the synthesis of carbon dioxide and hydrogen. The carbon dioxide is obtained from the atmosphere while the hydrogen is obtained during the electrolysis of water. An intermediate fuel, namely methyl alcohol may be stored for use or upgraded to higher heating value hydrocarbons by a catalytic conversion.

Abstract: Acidic gases such as carbon dioxide are removed from a gaseous mixture including the acidic component by contacting the gaseous mixture in a scrubbing system with an acid absorbing solution comprising a basic alkali metal compound and an activator, during which process at least a portion of the activator is converted to cyclic urea. At least a portion of the scrubbing solution is transferred to a thermal conversion zone wherein at least a portion of the cyclic urea is converted back to the activator afterwhich the scrubbing solution is returned to the scrubbing system from the thermal conversion zone.

Abstract: An aqueous solution of a zinc salt is used to selectively remove hydrogen sulfide from a gas mixture. An insoluble basic zinc compound is added to the solution to regenerate, or replenish, the salt. A dispersant is added to both decrease the surface tension of the liquid and reduce the degree of hydration of the basic compound, thereby retarding significantly the agglomeration, settling and loss of the basic zinc compound.

Abstract: The invention relates to an absorption desorption composition and process employing said composition for selectively removing acidic gases, particularly carbon dioxide (CO.sub.2) and hydrogen sulphide (H.sub.2 S) from gaseous mixtures, said composition comprising an aqueous solution containing a major proportion of alkali metal salts, potassium carbonate and potassium borate, a minor proportion of a catalytic activator, and a corrosion inhibitor when required, with provision for maintaining the inhibitor in an effective condition and in condition to perform its corrosion reducing function; the process characterized by two stages of absorption and desorption connected in a circulating system for the fluids being processed with suitable temperature and pressure controls, whereby an increased amount of the contaminating gases are removed and corrosive and side reaction difficulties reduced to a minimum.

Abstract: A process for the selective removal of hydrogen sulfide from a gas containing hydrogen sulfide and carbon dioxide wherein said gas is contacted at superatmospheric pressure with an alkali metal carbonate solution, the resultant solution which contains hydrosulfide and bicarbonate is subjected to pressure reduction, the total alkali metal bicarbonate content of the resultant solution is adjusted so that it is at least 55% of the total alkali content of the solution and the said solution is then stripped and recycled to the hydrogen sulfide absorption step.

Abstract: An improved process for removing carbon dioxide from a gaseous feed including carbon dioxide is described. The carbon dioxide is removed from a gaseous feed by contacting the feed in a contacting zone with a scrubbing solution comprising a sterically hindered amine and an alkali metal salt or alkali metal hydroxide, which at least partially absorbs the carbon dioxide. The scrubbing solution subsequently is desorbed and separated into a two-phase liquid system, an upper phase relatively rich in sterically hindered amine and having a relatively high ratio of alkali bicarbonate to alkali carbonate and a lower liquid phase having a relatively low ratio of alkali bicarbonate to alkali carbonate. The lower liquid phase is returned to the contacting zone at a location above that at which the upper liquid phase is returned to the contacting zone.

Abstract: Carbon dioxide containing acidic gases are removed from a normally gaseous mixture by a process comprising contacting the normally gaseous mixture with an aqueous solution comprising (a) a basic alkali metal salt or hydroxide and (b) an activator for said basic salt or alkali metal salt or hydroxide comprising at least one sterically hindered amine.

Abstract: Acidic components are removed from gaseous mixtures by contacting the gaseous mixture with an aqueous solution comprising (1) a basic salt and (2) an activator for said basic salt comprising at least one sterically hindered amine and an aminoacid which is a cosolvent for the sterically hindered amines. The aminoacid serves to prevent phase separation of the aqueous solution at high temperatures and low fractional conversions during the contacting.

Abstract: The foam in acid gas scrubbing solutions created during an acid gas scrubbing process is reduced or eliminated by the addition of certain polyoxyethylene polyoxypropylene block copolymers as defoaming agents. The defoaming agents are particularly effective when the acid gas scrubbing solution contains an amine having a large hydrophobic moiety.

Abstract: Combustion gases containing solids, e.g., gases resulting from regeneration of catalyst contact mass such as used in catalytic cracking of hydrocarbons or resulting from production of other materials or substances, e.g., carbon black, are passed to a separation zone, e.g., a cyclone separation zone in which separation of solids together with a substantial proportion of gases are separated resulting in a gas having a reduced solids content amounting to a tolerable maximum for utilization in an expansion zone, e.g., in a turbine to recover energy therefrom and then into a heat recovery unit or zone, e.g., to produce steam, and then pass to disposal, in one embodiment disposal including a combustion to convert trace amounts of hydrogen sulfide to sulfur dioxide; the solids and gas separated in the cyclone being used for heat recovery and then used as stripping medium to strip hydrogen sulfide from hydrogen sulfide containing fluid, e.g.

Abstract: Waste gases are purged by adding to the gas while it flows through an abser a neutralizing agent together with water and then subjecting the gas to cooling so as to evaporate the added liquid. The adsorption then results in a reaction with the neutralizing agent whereby dry salts are formed which are removed from the process. The temperature of the waste gas is automatically and continuously measured and the volume of the water is adjusted automatically and continously in accordance with the temperature measurements. The amount of waste gases is furthermore automatically and continuously measured, preferably at several places of the process, and the amount of neutralizing agent is continuously and automatically adjusted to the latter measurements so as to obtain always the stoichiometric equivalent for the reaction with the pollutants.

Abstract: High temperature reducing gas is scrubbed of H.sub.2 S and other gaseous sulfur compounds at high temperature (>800.degree. K.) in a highly efficient regenerative process. The scrubbing is effected in at least two sequential stages. The first stage scrubbing medium is a molten salt comprised essentially of molten alkali carbonates, sulfides, and hydroxides. The second stage is optionally either a metallic melt comprised of copper or a second molten salt. The copper melt is regenerated with air. The salt melts are regenerated with steam and/or CO.sub.2. When two or more salt stages are used, they are regenerated stagewise countercurrently to the scrubbing sequence.

Abstract: Certain impure steams, especially those from geothermal sources, are polluted with hydrogen sulfide, ammonia, carbon dioxide, other gases, and finely divided particulate solid matter in a form resembling dust or smoke. These contaminants reduce the efficiency of the steam as a heat transfer fluid, are detrimental to equipment utilizing steam as an energy source, and result in environmental pollution or expensive requirements for limiting the same. By the invention herein so polluted steam is selectively processed in the gaseous state upstream of said equipment to remove hydrogen sulfide therefrom, with or without removing other pollutants, to reduce environmental pollution from effluents thereof, to recover valuable materials therefrom, and to improve the utility of the steam as an energy source.

Abstract: A process for removing gaseous impurities such as CO.sub.2 and/or H.sub.2 S from a gaseous mixture obtained by reacting combustible substances with steam, said steam being produced in boilers fed with water previously purified in degassing columns. The gaseous impurities are removed by means of an absorbent solution and the latter is regenerated in a regeneration column by stripping with steam. The stripping steam necessary for the degassing is delivered, at a pressure at least equal to that in the regeneration column, to the degassing columns and then to the regeneration column. The boiler feed water to be purified is previously heated, by supply of residual heats, to a temperature in the vicinity of the boiling temperature of the absorbent solution in the regeneration column.

Abstract: An improved method for removing a component from a fluid mixture by transport of the component through an immobilized liquid membrane is described. The method includes introducing fresh membrane liquid into a first region of the membrane to effect emission of at least partially deactivated liquid from a second region of the membrane, thereby restoring or maintaining the separation efficiency of the membrane. Also described is an improved packaged membrane system including a plurality of at least partially spaced immobilized liquid membranes disposed in generally parallel surface-to-surface array to define both a first group of flow volumes and a second group of flow volumes alternating between the first group. Screens for spacing apart adjacent membranes are disposed in each of the flow volumes of at least one of the flow volume groups. Frames define the periphery of the flow volumes and flow passages provide separate access to and egress from the flow volumes in the two groups.

Abstract: Antifoaming agents for use in acid gas scrubbing processes comprising 1-secondary or 1-tertiaryalkyl- or 1-cycloalkyl-hexahydro-2-pyrimidinones and 1-secondary or 1-tertiary alkyl- or 1-cycloaklyl-2-imidazolidinones are disclosed.

Abstract: A cyclic urea reaction product forms as a by-product of a hindered amine acid gas scrubbing process and results in an ultimate buildup of the material in the circulating amine scrubbing solution. The buildup of this material has a deleterious effect on acid gas removal rates and accordingly, results in inefficient acid gas removal. In the process of the present invention, the cyclic urea degradation product is removed from the circulating solution by employing a selective precipitation of the cyclic urea followed by filtration. The selective precipitation is carried out by cooling the circulating solution to a particular temperature level such that the cyclic urea comes out of solution while the other components remain in solution.

Abstract: Disclosed are an improved method and apparatus employing at least one immobilized liquid membrane separated from a liquid sweep by a gas-permeable barrier for removing a gaseous component from a gaseous mixture. The improvements include use of one or more liquid-filled passages extending through the gas-permeable barrier to effect diffusive transfer of active carrier species from the liquid sweep into the membrane, thereby maintaining the separation efficiency of each membrane. In a preferred embodiment, the improvements are applied to removal of hydrogen sulfide from mixtures thereof with carbon dioxide as found in gasified coal.

Abstract: A method for hydrolyzing urea in aqueous solutions such as waste-water streams which comprises heating the aqueous solution containing urea in the presence of a catalytic amount of vanadium pentoxide for sufficient time and at sufficient temperatures to effect hydrolysis of substantially all of the urea to ammonia and carbon dioxide.

Abstract: A process for reducing the hydrogen sulfide content of steam, such as steam produced from a subterranean geothermal reservoir, in which the steam is contacted with an aqueous, alkaline solution having a temperature approximating that of the steam to absorb hydrogen sulfide from the steam which is thereafter discharged or utilized in a power generation plant. Hydrogen peroxide is introduced into a cooled portion of the aqueous, alkaline solution to reduce the hydrogen sulfide content thereof and then the aqueous alkaline solution is heated to about the temperature of the steam and recycled into contact with the hydrogen sulfide-containing steam. The temperature of the cooled portion of the aqueous, alkaline solution into which hydrogen peroxide is introduced is such that thermal decomposition of hydrogen peroxide is substantially prevented.

Abstract: A process for removing acid gases such as CO.sub.2 and H.sub.2 S from gas streams using an aqueous alkaline scrubbing solution which is circulated between an absorption and regeneration stage wherein the stripping steam for regeneration is derived at least partly from the hot feed gas to be purified. The thermal efficiency of the process is substantially improved by first heat-exchanging the hot feed gas with the scrubbing solution to raise stripping steam and then heat-exchanging the hot feed gas with water (which is preferably condensate water produced in the scrubbing process) in a second heat exchanger operating under reduced pressure, thus recovering additional low-level heat from the feed gas and producing low-pressure steam which is compressed and then utilized as additional stripping steam.

Abstract: A method for removing sulfur dioxide from flue gases by simultaneous absorption and oxidation in an aqueous absorbent. An enclosed body of an aqueous liquid absorbent for the sulfur dioxide is provided and the flue gas is sparged into an upper portion of the liquid absorbent to form a first zone thereof. An oxygen-containing gas is introduced into a lower portion of the liquid absorbent to form a second zone of the liquid absorbent that is below the first zone of the liquid absorbent and which has an apparent density that is higher than that of the first zone. The oxygen-containing absorbent from the second zone is circulated to the first zone near the point of the flue gas introduction and an alkaline material reactive with the sulfur dioxide in the liquid absorbent is introduced into the body of liquid absorbent thereby fixing the sulfur dioxide in the liquid absorbent in the form of a sulfate. The sulfate is subsequently removed from the body of aqueous liquid absorbent.

Abstract: Hydrogen sulfide is removed from a mixture of gases including carbon dioxide by passing the mixture over an immobilized liquid membrane in intimate contact with a hydrophobic, microporous gas, permeable barrier and absorbing in a liquid solution hydrogen sulfide passing through the membrane. In a sweep of hot carbonate solution, a nearly stagnant boundary layer adjacent the gas permeable barrier absorbs acid gases by reaction and diffusion, maintaining low hydrogen sulfide partial pressure at the outlet side of the barrier. Alternatively, the sweep may comprise an aqueous solution containing a redox agent which converts absorbed hydrogen sulfide into sulfur, or an ethanol amine solution. The apparatus exhibits low permeability to carbon dioxide and high permeability to hydrogen sulfide.

Abstract: Hydrogen sulfide, sometimes referred to as "rotten egg" gas occurs commonly in nature, particularly about oil and gas wells in drilling, completing and working over of wells and is dangerously toxic to workmen and devastatingly corrosive to bore hole casings and drilling equipment. It also contaminates natural gas produced by some wells.Here it has been found that a water soluble zinc ammonium carbonate complex provides nearly quantitative removal of hydrogen sulfide by intimately contacting the carrier thereof with substantially stoichiometric qualities of said complex in aqueous solution.

Abstract: Process for removing gaseous impurities such as CO.sub.2, H.sub.2 S, HCN and SO.sub.2 from a gaseous mixture containing the same, comprising an absorption step in which the gaseous impurities are removed by a scrubbing solution, and a regeneration step in which the exhausted solution is submitted to stripping to remove the inpurities. The regenerated solution is treated with a flow of inert gases to improve the degree of regeneration and extract heat from said solution. The flow of inert gases, containing steam and desorbed impurities, is further enriched in steam supplied from the exterior and the resulting mixture is used as stripping means in the regeneration step.

Abstract: A copper based corrosion inhibitor composition and a method for employing the same to prevent corrosion of metal in contact with acid-gases, i.e., hydrogen sulfide, carbonyl sulfide and carbon dioxide. Copper, or a copper compound and sulfur or a sulfur compound, is maintained in solution in contact with the metal under conditions of operation, particularly the thermal regeneration, which provide copper ions and sulfur atoms, particularly polysulfide moieties at the surface of the metal, e.g. copper sulfide is dissolved in an aqueous alkanolamine, monoethanolamine, solution used as an absorbent for acid-gas removal from sour-gas. The copper and sulfur moieties may be formed in situ or prepared and added in solution. The inhibitor has particular utility in protecting metal surfaces which are subject to corrosion as an incidence of the acid-gas content of either natural or synthetic gases.

Abstract: Certain impure streams, especially those from geothermal sources, are polluted with hydrogen sulfide, ammonia, carbon dioxide, other gases, and finely divided particulate solid matter in a form resembling dust or smoke. These contaminants reduce the efficiency of the steam as a heat transfer fluid, are detrimental to equipment utilizing steam as an energy source, and result in environmental pollution or expensive requirements for limiting the same. Herein so polluted steam is selectively processed in the gaseous state upstream of said equipment to remove hydrogen sulfide therefrom, with or without removing other pollutants, to recover valuable materials therefrom, and to improve the utility of the steam as an energy source. This is done by contacting a flow of the steam with aqueous liquid reactant media consisting essentially of one or more reactive compounds of certain metals which form solid metal sulfide reaction products and which preferably are electropositive with respect to hydrogen.

Abstract: An improved method and apparatus employing at least one immobilized liquid membrane separated from a liquid sweep by a gas-permeable barrier for removing a gaseous component from a gaseous mixture. The improvements include use of one or more liquid-filled passages extending through the gas-permeable barrier to effect diffusive transfer of active carrier species from the liquid sweep into the membrane, thereby maintaining the separation efficiency of each membrane. In a preferred embodiment, the improvements are applied to removal of hydrogen sulfide from mixtures thereof with carbon dioxide as found in gasified coal.

Abstract: A membrane suitable for absorbing a gas component present in a gaseous stream (e.g. carbon dioxide with a hydrogen feed for an alkaline fuel cell) comprises a porous layer of hydrophilic material, both faces of which are covered by a layer of a mixture of 10 to 90 wt.% of a hydrophobic substance and 90 to 10 wt.% of a hydrophilic substance, the hydrophilic portions of the three layers being impregnated with a carbon dioxide hydration catalyst e.g. sodium meta arsenite, at a concentration of 0.1 to 3M and a 2 to 14N alkali metal buffer solution.The gaseous component is absorbed from a gaseous stream containing said component by causing said stream to flow adjacent to a humidified stripping gas having a relative humidity of 0.4 to 0.95, the flows of said stream and said stripping gas being separated by the membrane.

Abstract: Hydrogen sulfide is removed from a mixture of gases including carbon dioxide by passing the mixture over an assembly comprising a pair of immobilized liquid membranes of carbonate/bicarbonate solution separated by a gas permeable barrier of hydrophobic microporous material. Because hydrogen sulfide transport through the membranes is diffusion limited while carbon dioxide transport therethrough is reaction rate limited, the assembly exhibits reduced permeability to carbon dioxide and essentially unchanged high permeability to hydrogen sulfide compared to a single immobilized liquid membrane of thickness equal to total thickness of the membranes in the assembly. Hydrogen sulfide thus passes through the assembly more selectively than carbon dioxide.

Abstract: Novel process for removing polymer from aqueous absorbent solutions used to contact organic gas-containing gas streams comprising the steps of adjusting the polymer-containing aqueous absorbent solutions to a pH of not more than about 8.5, preferably not more than about 7.5, for example, about 6.0 to about 8.5, preferably about 7.0 to about 7.5, and removing the polymer from the resulting solutions by decantation and/or filtration. The novel process is particularly applicable to the system of removing acid gas from hydrocarbon-containing feed gases which contain one or more polymerizable components wherein the feed gas is contacted with an aqueous absorbent solution which absorbs the acid gas and, thereafter, the absorbent solution is stripped to rid it of said acid gas. The adjustment of pH can be accomplished by increasing the acid gas loading in the aqueous absorbent or by adding an acid, preferably one which will not form a heat stable salt with the absorbent. The pH adjustment, e.g.

Abstract: Carbon dioxide containing acidic gases are removed from a normally gaseous mixture by a process comprising contacting the normally gaseous mixture with an aqueous solution comprising (a) a basic alkali metal salt or hydroxide and (b) an activator for said basic salt or alkali metal salt or hydroxide comprising at least one sterically hindered amine.

Abstract: Acidic components are removed from gaseous mixtures by contacting the gaseous mixture with an aqueous solution comprising (1) a basic salt and (2) an activator for said basic salt comprising at least one sterically hindered amine and an aminoacid which is a cosolvent for the sterically hindered amines. The aminoacid serves to prevent phase separation of the aqueous solution at high temperatures and low fractional conversions during the contacting.

Abstract: A gas, formed as a product of a pyrolysis of oil shale, is passed through hot, retorted shale (containing at least partially decomposed calcium or magnesium carbonate) to essentially eliminate sulfur contaminants in the gas. Specifically, a single chambered pyrolysis vessel, having a pyrolysis zone and a retorted shale gas into the bottom of the retorted shale zone and cleaned product gas is withdrawn as hot product gas near the top of such zone.

Abstract: Hydrogen sulfide is removed from a mixture of gases including carbon dioxide by passing the mixture over an assembly comprising a pair of immobilized liquid membranes of carbonate/bicarbonate solution separated by a gas permeable barrier of hydrophobic microporous material. Because hydrogen sulfide transport through the membranes is diffusion limited while carbon dioxide transport therethrough is reaction rate limited, the assembly exhibits reduced permeability to carbon dioxide and essentially unchanged high permeability to hydrogen sulfide compared to a single immobilized liquid membrane of thickness equal to total thickness of the membranes in the assembly. Hydrogen sulfide thus passes through the assembly more selectively than carbon dioxide.

Abstract: A process for hydrolyzing urea in waste water streams which comprises introducing a waste water stream containing urea into a carbon dioxide recovery system such as used in connection with the production of ammonia, and therein hydrolyzing substantially all of the urea in the waste water stream.

Abstract: A process is disclosed for purifying raw gas produced by the gasification of solid fuels under superatmospheric pressure by treatment with gasifying agents containing water vapor and free oxygen. The raw gas contains dust and hydrocarbons and is at a temperature of 400.degree.-700.degree. C as it leaves the gas producer. The raw gas is purified by spraying in at least two scrubbing stages with virtually dustfree, highly dispersed scrubbing water at temperatures of 160.degree.-300.degree. C. In this manner, the gas is cooled to a temperature that is 0.degree.-20 C above the scrubbing water temperature and is saturated with water vapor in the scrubbing stages. Thereafter, the gas is subjected to centrifugal force to increase the relative velocity between gas and water droplets. The scrubbing water which contains dust and tar is withdrawn from each scrubbing stage.

Abstract: Fuel gases such as those produced in the gasification of coal are stripped of sulfur compounds and particulate matter by contact with molten metal salt. The fuel gas and salt are intimately mixed by passage through a venturi or other constriction in which the fuel gas entrains the molten salt as dispersed droplets to a gas-liquid separator. The separated molten salt is divided into a major and a minor flow portion with the minor flow portion passing on to a regenerator in which it is contacted with steam and carbon dioxide as strip gas to remove sulfur compounds. The strip gas is further processed to recover sulfur. The depleted, minor flow portion of salt is passed again into contact with the fuel gas for further sulfur removal from the gas. The sulfur depleted, fuel gas then flows through a solid absorbent for removal of salt droplets. The minor flow portion of the molten salt is then recombined with the major flow portion for feed to the venturi.

Abstract: A hybrid physical-chemical absorbent process using the interrelation between a physical solvent and a H.sub.2 S selective chemical solvent for removal of CO.sub.2 and sulfur containing compounds, principally H.sub.2 S from a mixed gas stream. This process is especially useful in processes such as coal gasification where the incoming stream to the acid gas removal process is at about 1100 psia, 70.degree. F., contains about 15 to 40 mole percent CO.sub.2 at a mole ratio of CO.sub.2 /H.sub.2 S of about 25 to 50. In such cases the product stream contains less than 1 ppm sulfur and less than 3 mole percent CO.sub.2 which is suitable for production of substitute natural gas while the CO.sub.2 atmospheric effluent contains less than 7 ppm sulfur.

Abstract: Improvements in the elimination and recovery of gaseous acid impurities from a gaseous mixture containing them, by an absorbing step, wherein said gaseous mixture is brought into contact with an alkaline absorbing solution and a regeneration step wherein the exhausted absorbing solution is regenerated by steam stripping, said absorption step comprising a main column and a secondary column, the main column operating at a higher pressure and by means of a supply of outside heat, the secondary column operating at a lower pressure and substantially by means of the steam obtained by expansion of the solution regenerated in the main column. The exhausted solution to be regenerated is conveyed firstly in one of the two regeneration columns wherein it is regenerated in an incomplete way, and subsequently into the other column where its regeneration is completed.

Abstract: A process for separating acid gases from gaseous mixtures by absorption in alkaline solutions such as potassium carbonate solution wherin corrosion caused by the absorbing solution is reduced by inclusion therein of an aromatic compound. The aromatic compound has at least one nitro group and at least one hydroxyl group substituted in the same benzene nucleus. The invention is particularly applicable when the absorbent is a potassium carbonate solution activated by arsenic ions.