Abstract: The long term stability of process solutions used in H.sub.2 S-to-sulfur absorption/oxidation process, wherein the incoming hydrogen sulfide-containing gas stream is contaminated with hydrocarbons and/or organic oxygenated compounds and the process is generating an excessive amount of thiosulfate in the process solution, is improved by a method comprising contacting the gas stream and/or the process solution with charcoal to remove both the contamination and at least a portion of the thiosulfate therefrom.

Abstract: The invention provides a process for the selective absorption of chlorine from CO.sub.2 -containing off-gases, which comprises washing the off-gases with an aqueous solution which contains 0.1-10% by weight of NaHCO.sub.3 and 0.01-5% by weight of NaHSO.sub.3.

Abstract: Method of treatment of a hot exhaust gas stream containing acid forming pollutants to produce a scrubbed exhaust and useful or benign by-products. The gas stream is first passed through a heat exchanger and then reacted with an aqueous, alkaline scrubbing solution. After the reaction the solution, now containing dissolved salts with a precipitate of any insolubles, is passed through the heat exchanger wherein it is heated by the gas stream to remove water therefrom, thereby crystallizing the dissolved salts, and wherein it serves to cool and dehumidify the gas stream in a manner to remove heat and collect water therefrom prior to its reacting with the scrubbing solution. Any remaining insolubles are non-toxic or useful, e.g. as cement kiln feed.

Abstract: This invention relates to a CO.sub.2 /H.sub.2 O sorbent comprised of silver oxide, a CO.sub.2 sorption promoter, and a support. Preparation of this sorbent consists of impregnating the support with a silver compound, converting the silver compound to silver carbonate or silver oxide, and further impregnating the support with a CO.sub.2 sorption promoter. Prior to use as a sorbent, the silver carbonate is converted to silver oxide via the application of heat; liberating CO.sub.2 and H.sub.2 O.

Abstract: A process for the complete recovery of NO from the waste gas of ammonium nitrite production, in which gases containing nitrogen oxides are absorbed in a first stage in a solution of ammonium carbonate and/or ammonium bicarbonate to form ammonium nitrite solutions and the resulting waste gas containing carbon dioxide is absorbed in a second stage in an ammoniacal, aqueous solution to form ammonium carbonate and/or ammonium bicarbonate which is returned as such to the first absorption stage, and the waste gas containing carbon dioxide is brought into contact with a sulphuric acid of medium concentration containing from 0.1-5% by weight, preferably from 0.2 to 1.5% by weight of nitric acid before the carbon dioxide is introduced into the second absorption stage.

Abstract: A process for the removal of carbon dioxide, hydrogen sulfide and alkyl mercaptans from a hydrocarbon-containing feed gas:(a) contacting the feed gas with an adsorbent capable of removing hydrogen sulfide and alkyl mercaptans from the feed gas at effective conditions to produce a treated gas having reduced concentrations of hydrogen sulfide alkyl mercaptans;(b) contacting the treated gas with a liquid medium capable of removing carbon dioxide hydrogen sulfide and alkyl mercaptans from the treated gas at effective conditions to produce a product gas having reduced concentrations of carbon dioxide hydrogen sulfide and alkyl mercaptans;(c) contacting a spent absorbent laden with hydrogen sulfide and alkyl mercaptans with a normally liquid fraction at effective desorption conditions to produce a regenerated adsorbent and a regeneration effluent having increased concentrations of hydrogen sulfide and alkyl mercaptans; and(d) utilizing the regenerated adsorbent as at least a portion of the adsorbent in step (a).

Abstract: In a process for cleaning, cleaning a packed column utilized in a gas scrubbing operation wherein the packing is obstructed by solids formed during the scrubbing step, the obstructions are removed in a maximally economical fashion and without interrupting of normal operation. The packed column contains at least n, wherein n>1, superimposed packed beds spatially separated from one another. During cleaning, the lowermost up to maximally the (n-1)th packed bed are flooded with scrubbing agent. Preferably, the packed column is used for scrubbing H.sub.2 S out of a feedgas mixture with an oxidative scrubbing agent wherein sulfur is formed during the scrubbing operation and deposited in the packed beds.

Abstract: Processes for the removal of hydrogen sulphide from gas streams and for the regeneration of spent scrubbing liquor used in an absorber to remove hydrogen sulphide from a gas stream, are disclosed. In the former process, hydrogen sulphide is removed by five-valent oxovanadium which is simultaneously reduced to its four-valent state, the precipitation of which is prevented by having a sufficiently high concentration of total alkalinity present in the scrubbing solution. In the latter process the four-valent oxovanadium is oxidized to its five-valent state, preferably by an oxygen-containing gas, and a suffficently high concentration of total alkalinity is provided in the scrubbing liquor to yield a desired re-oxidation rate of the four-valent oxovanadium.

Abstract: Disclosed are primary sterically hindered aminoacids for use as promoters for alkali metal salts in acid gas scrubbing. The primary sterically hindered aminoacid is selected from 1-amino-cyclopentane carboxylic acid and those represented by the formula: ##STR1## where R.sub.1 and R.sub.2 are independently selected from CH.sub.3, C.sub.2 H.sub.5, and C.sub.3 H.sub.7 ; R.sub.3 and R.sub.4 are independently selected from hydrogen and CH.sub.3 ; and n is 0, 2, or 3.

Abstract: This invention provides a system for simultaneously scrubbing acidic exhaust gases and removing alkali and alkaline earth metal salts from waste dust from a cement plant or the like thereby producing useful products from what would otherwise be wasted. In essence the two wastes are combined in water and the resulting solution and precipitate separated in a tank. The solution is useful both to cool incoming waste gas and as a fertilizer, while the precipitate is suitable as kiln feed stock.

Abstract: Natural gas containing mercury is treated for liquifaction by contacting it with alkali and amine treating units to remove carbon dioxide and hydrogen sulfide. The amine and alkali treating units also contain sulfur in reacted form. This serves to guard downstream equipment against failure of upstream mercury-removing equipment, namely sulfur, on a selected support.

Abstract: The invention relates to a process for the removal of acid gases from gaseous mixtures wherein said mixture is contacted with an aqueous alkaline solution comprising a compound of an alkali metal or ammonia and an alkanolamine-based promoter characterized in that the promoter is a mixture of at least one secondary alkanolamine and at least one N-alkyl-2-aminoethanol, said alkyl radical containing up to 3 carbon atoms.

Abstract: This invention relates to an apparatus and method for simultaneously scrubbing acidic exhaust gases and removing metal salts from alkaline waste dust from a cement plant or the like thereby producing useful products from what would otherwise be wasted. In essence the two wastes are combined in water and the resulting solution and precipitate separated in a tank. The solution is useful both to cool incoming waste gas and as a fertilizer, whilst the precipitate is suitable as kiln feed stock.

Abstract: The present invention is directed to an improved process for the removal of acid gases from gas mixtures which significantly decreases the consumption of heat needed for regenerating the rich alkaline scrubbing solution which is used to remove the acid gases from the gas mixtures. The process comprises passing one portion of the scrubbing solution through a steam stripping section and another portion of the scrubbing solution through a flashing section for regeneration wherein the overhead vapors from the steam stripping section are used to heat and strip the scrubbing solution in the flashing section and heat contained within the regenerated scrubbing solution coming from the steam stripping section is utilized to aid in the regeneration of the scrubbing solution in the flashing section.

Abstract: A process for reducing the formation of dioxins in the incineration of wastes that includes using sodium carbonate or sodium bicarbonate to react with chlorides formed in the incineration process. When sodium bicarbonate is used in the temperature range of 1561.degree. F. to 518.degree. F. a greater porosity is achieved that achieves a high degree of removal of the chlorides thereby preventing their reaction to produce dioxins.

Abstract: The invention relates to a process for the selective removal of hydrogen sulfide from a gaseous stream additionally containing carbon dioxide by contacting the gaseous stream with a polyvalent metal chelate solution for a time sufficient to allow the polyvalent metal chelate to oxidize the hydrogen sulfide to elemental sulfur without allowing the polyvalent metal chelate solution to absorb appreciable amounts of carbon dioxide. The pH of the metal chelate solution should be greater than 7 and the contact time between the polyvalent metal chelate and the gaseous stream is between 0.006 and 0.08 second.

Abstract: The present invention relates to an alkaline salt promoter system which includes an N-aminoalkyl alkylpiperazine, preferably the compound 1-(3-aminopropyl)-2,5-dimethylpiperazine (APDP), an alkali metal salt or hydroxide (e.g., K.sub.2 CO.sub.3) and water. These scrubbing compositions may be used for removing CO.sub.2 from gaseous streams containing CO.sub.2.

Abstract: A process for removing hydrogen sulfide from saturated steam is described whereby the steam and hydrogen sulfide entrained therein are contacted under conditions of turbulent flow with hydrogen peroxide. The effectiveness of the process is improved by simultaneously contacting the steam with a basic reagent such as sodium hydroxide.

Abstract: A method of desulfurizing coke oven gas comprises directing the coke oven gases upwardly and in a hydrogen sulfide scrubber tower, washing the coke oven gases in a cyclic ammonia washing including admixing sulfur compounds containing waste gases and without cooling with ammonia in a degasifying unit which is supplied with ammonia containing water which is advantageously obtained from a tar separator and using the heat content of the waste gases to expel the ammonia from the water, and directing the waste gases laden with the expelled ammonia into the tower. The waste gases advantageously come from a Claus plant process and they are laden with ammonia and they are advantageously directed into the upper portion of the scrubber tower. Ammonia water is circulated in an ammonia circuit from an outlet which is advantageously located in the upper portion of the tower to an inlet which connects to the tower above the outlet.

Abstract: Hydrogen sulfide and/or carbonyl sulfide in a gas which does not substantially contain oxygen can easily be removed from the gas by contacting the gas with an activated carbon containing (1) a copper compound and (2) an alkali metal compound and/or alkaline earth metal compound at a temperature of not higher than 150.degree. C.

Abstract: For the simultaneous absorption and oxidation of hydrogen sulfide, gaseous mixtures substantially free of molecular oxygen are scrubbed in a first stage with an aqueous, alkaline scrubbing agent containing pentavalent vanadium as the oxidizing medium. The hydrogen sulfide is absorbed by the scrubbing agent and oxidized to elemental sulfur with reduction of pentavalent vanadium to tetravalent vanadium. The thus-reduced scrubbing agent is then regenerated in a separate second stage in the presence of an amine promoter by reoxidation of the tetravalent vanadium with molecular oxygen, and reused.

Abstract: Process for the removal of hydrogen sulfide from gas mixtures, particular gas mixtures containing hydrocarbons, wherein the gas mixture is treated with an aqueous solution of a water soluble nitrite such as sodium nitrite, the pH of the aqueous solution being at least 5.5 or greater.

Abstract: An improved system for recovering CO.sub.2 from flue gases containing SO.sub.2 at low CO.sub.2 partial pressure. The system includes the use of K.sub.2 CO.sub.3 as the solvent, regeneration of the solvent, and removal of SO.sub.2 and SO.sub.4.

Abstract: Essentially all of the H.sub.2 S in steam which also contains up to 30 ppmw of CO.sub.2 per ppmw of H.sub.2 S can be scrubbed from the steam with aqueous NaOH or Na.sub.2 CO.sub.3 without consuming more than about 4 mols of NaOH or 2 mols of Na.sub.2 CO.sub.3 per mol of H.sub.2 S and without consuming more than about 0.18 pounds of water per pound of steam scrubbed, if (1) the steam is scrubbed countercurrently in a tower containing a contacting means equivalent to at least 6 theoretical stages, (2) the sulfide species in the tower effluent are completely oxidized to sulfo species and (3) the oxidized effluent--less a bleed stream and plus water and base makeup--is recycled to the tower. If the steam is scrubbed in this manner before being introduced to the turbines in a power plant, the exhaust from the turbines can be vented to the atmosphere without further treatment. The method of the invention is particularly suited for use at the Geysers geothermal "steam" field in California.

Abstract: Hydrogen sulfide is first removed by ammoniacal liquor from coke oven gas in the bottom part of a gas scrubber. In the top part of the scrubber, two consecutively-arranged fine scrubbing stages remove hydrogen sulfide by treating the gases, in the upper stage, with a caustic soda solution or a caustic potash solution. Beneath the upper scrubbing stage is the second fine scrubbing stage fed with a subflow of an aqueous carbonate solution collecting at the outlet of the upper fine scrubbing stage and a subflow of cooled, regenerated carbonate solution discharged from the hydrogen-sulfide/hydrogen-cyanide stripper. From the hydrogen-sulfide/hydrogen-cyanide stripper, a second subflow is admixed with coal liquor for removing fixed ammonia therefrom in a separator. The separator produces water vapor with carbon dioxide vapors that are delivered to the hydrogen-sulfide/hydrogen-cyanide stripper for regenerating the aqueous carbonate washing solution.

Abstract: A gas treating process is disclosed. Hydrogen sulfide and carbon dioxide are removed from a hydrocarbon vapor stream by absorption into an aqueous carbonate solution. Hydrogen sulfide picked up by the circulating carbonate solution is oxidized to produce liquid sulfur, which is withdrawn. The carbonate solution is then stripped to release carbon dioxide and produce the lean carbonate solution used for absorption. By-product thiosulfate formed in the oxidation step is eliminated by reaction with hydrogen sulfide. Metal phthalocyanines are used as the catalyst for the elimination of thiosulfate and for the oxidation of hydrogen sulfide.

Abstract: A system is described for removing CO.sub.2 from the manufactured process gas in an SNG manufacturing plant, the system operating the hot carbonate process wherein hot potassium carbonate solution absorbs CO.sub.2 from the process gas under pressure in an absorber column 1 and is regenerated by pressure reduction and steam stripping in a regenerator column 14 and a reboiler 17 before being returned to the absorber by a circulating pump 7. The system is completely automated and is controlled by a computer so that start-up, running and shut-down of the system is carried out automatically upon initiation by an operator, whereby the system is particularly suited for use in peak load SNG plants.

Abstract: A process is disclosed for treating carbon dioxide-containing gas streams, such as a natural gas, to selectively remove hydrogen sulfide. The process employs an absorption-stripping sequence in which hydrogen sulfide and carbon dioxide are removed from the feed gas. The net overhead vapor of the stripping column is compressed and dried and passed into a fractionation column. Relatively high purity hydrogen sulfide is withdrawn from the bottom of the fractionation column, and the net overhead vapor of the fractionation column is recycled back to the absorption zone.

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. Herein so polluted steam is selectively processed in the gaseous state 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 fluid reactant media comprising one or more reactive compounds of certain metals electropositive with respect to hydrogen. The valuable materials subsequently may be recovered from said media as useful byproducts. The reactant compounds may be recycled.

Abstract: A low melting, eutectic melt salt composition comprising Li.sub.2 CO.sub.3, Na.sub.2 CO.sub.3 and K.sub.2 CO.sub.3, also containing MnCO.sub.3, is disclosed including its use as a melt in the process for the removal of contaminants, e.g., H.sub.2 S, COS and/or fly ash, from gases obtained by partial oxidation/combustion.

Abstract: A novel class of severely sterically hindered secondary aminoether alcohols of the general formula: ##STR1## are prepared wherein R.sub.1 and R.sub.2 are each selected from the group consisting of alkyl and hydroxylalkyl radicals R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are each selected from the group consisting of hydrogen, alkyl and hydroxyalkyl radicals, with the proviso that at least one of R.sub.4 or R.sub.5 bonded to the carbon atom directly bonded to the nitrogen atom is an alkyl or hydroxyalkyl radical when R.sub.3 is hydrogen, x and y are each positive integers ranging from 2-4 and z is a positive integer ranging from 1-4. The compounds are useful in the selective removal of H.sub.2 S from mixtures containing H.sub.2 S and CO.sub.2.

Abstract: The invention relates to a finishing process for the removal of low level concentrations of mercaptans, sulfides and disulfides from a gas stream, especially a natural gas stream. The sulfur compounds are washed from the gas stream with a solution containing hydrogen peroxide, sodium carbonate or sodium hydroxide, and ammonia or an amine.

Abstract: The removal of CO.sub.2 and mixtures thereof with H.sub.2 S from gaseous mixture containing same, is carried out by using an absorbing solution which comprises a first activating substance chosen from aminoacids and primary and secondary ethanolamines, which effects the initial absorption of CO.sub.2 with formation of a carbamate, a second activating substance chosen from As.sub.2 O.sub.3 and its derivatives, secondary ethanolamines and ammonia, which promotes the hydrolysis and decomposition of the carbamate as the latter forms, and a third substance of a basic nature, which effects the quantitative absorption of CO.sub.2 or CO.sub.2 +H.sub.2 S.

Abstract: An improved method for removing malodorous sulfur compounds from flue gases generated in kraft or sodium sulfite pulping operations and the like by the absorption process using green liquor, an aqueous solution containing sodium sulfide and sodium carbonate. The malodorous gas compounds, including hydrogen sulfide, methyl mercaptan, and dimethyl sulfide are preferentially absorbed by the sodium sulfide forming sodium hydrosulfide and methanol. Any sulfur dioxide in the gas is absorbed and neutralized by sodium carbonate. In this method carbon dioxide absorption is minimized and the formation of sodium bicarbonate is limited. Sodium bicarbonate formation is minimized in order to avoid its reaction with sodium hydrosulfide which would then release undesirable hydrogen sulfide during absorption, as well as to forestall the need to increase chemical and lime kiln capacity requirements when the green liquor returned to the kraft recovery process contains excess amounts of sodium bicarbonate.

Abstract: An improved, catalyzed process for the removal of CO.sub.2 from gas mixtures is described using a solution containing 15-40% by weight of potassium carbonate in which the absorption efficiency is enhanced by the addition of sodium or potassium vanadate equivalent to 2 to 10% by weight of V.sub.2 O.sub.5 and sodium or potassium borate equivalent to 1 to 10% by weight of KBO.sub.2 in which the weight ratio of equivalent KBO.sub.2 to equivalent V.sub.2 O.sub.5 is less than 1.5:1. It has been found that use of the described catalysts permits significant reductions in solution circulation rates (up to 45%), which leads to equipment and utility economies.

Abstract: A novel class of di-secondary aminoethers of the general formula: ##STR1## are disclosed wherein R.sub.1 and R.sub.8 are each independently selected from the group consisting of primary alkyl having 1 to 8 carbon atoms and primary hydroxyalkyl having 2 to 8 carbon atoms, secondary alkyl and secondary hydroxyalkyl radicals having 3 to 8 carbon atoms, tertiary alkyl and tertiary hydroxyalkyl radicals having 4 to 8 carbon atoms, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6 and R.sub.7 are each independently selected from the group consisting of hydrogen, C.sub.1 -C.sub.3 alkyl and hydroxyalkyl radicals, with the proviso that R.sub.2, R.sub.3, R.sub.6, and R.sub.7 are C.sub.1 -C.sub.4 alkyl or hydroxyalkyl radicals when R.sub.1 and R.sub.8 are primary alkyl or hydroxyalkyl radicals, and at least one of R.sub.2 or R.sub.3 and R.sub.6 or R.sub.7 are C.sub.1 to C.sub.3 alkyl or hydroxyalkyl radicals when R.sub.1 and R.sub.

Abstract: A process for removing acid gases such as CO.sub.2 and H.sub.2 S from gas streams using a cyclic aqueous alkaline scrubbing solution which is circulated between an absorption and regeneration stage is disclosed. This process is improved by integrating within this cyclic system a process scheme wherein condensed steam having gaseous impurities dissolved therein is recovered from the feed gas and subjected to a pressure below which scrubbing solution regeneration takes place. While maintaining this pressure, the process condensate is heated, boiled and stripped to evolve a vaporous mixture comprising steam and gaseous impurities which are compressed and introduced into the regeneration stage. By this process, useful work is performed by low temperature process streams thereby improving the overall efficiency of the cyclic process.

Abstract: Regenerative process for the purification of a non-reacting industrial gas stream by removal of trace amounts of carbon dioxide therefrom, comprising contacting said gas stream with non-aqueous liquid solution of at least one member selected from the group consisting of: (a) hydroxides and weak acid salts of sodium, potassium, and lithium and (b) specific liquid aliphatic polyhydric alcohol; separating the purified industrial gas from the reaction products of said contacting step including said solution; increasing said reaction products stream to an elevated temperature up to 200.degree. C.; reducing the partial pressure of carbon dioxide in the vapor phase above said reaction product stream; separating carbon dioxide from said reaction product stream; and recycling the treated reaction product stream to said liquid body of said solution for contacting a further quantity of said industrial gas stream.

Abstract: The present invention relates to an alkaline promoter system comprising specific mixtures of nonsterically hindered amino compounds and sterically hindered amino acids and their use in acid gas scrubbing processes. The preferred promoter system comprises a mixture of (i) diethanol amine or 1,6-hexanediamine and (ii) N-secondary butyl glycine or pipecolinic acid.

Abstract: The present invention relates to an alkaline salt promoter system which includes N-secondary butyl glycine and its use in acid gas scrubbing processes.

Abstract: The present invention relates to an alkaline salt promoter system comprising specific mixtures of lower aliphatic mono-substituted alpha amino acids and sterically hindered diamino or triamino compounds and their use in acid gas scrubbing processes. The preferred promoter system comprises a mixture of N-secondary butyl glycine and N-cyclohexyl-1,3-propanediamine or N-cyclohexyl-1, 4-butanediamine.

Abstract: An improved method for removing acidic gases from a gas stream containing the acidic gases is disclosed in which a corrosion inhibitor comprising a mixture of salts of antimony and molybdenum is added to an amine promoted alkaline salt scrubbing solution.

Abstract: The present invention relates to an alkaline salt promoter system comprising specific mixtures of sterically hindered monosubstituted alpha-amino acids and tertiary amino acids and its use in acid gas scrubbing processes. The preferred promoter system comprises a mixture of N-secondary butyl glycine and N-methyl-N-secondary butyl glycine.

Abstract: In the removal of sour gases by scrubbing with an aqueous alkali metal salt solution, e.g. a solution of K.sub.2 CO.sub.3, the circulating scrubbing liquid is gradually contaminated with organic acids, especially formic acid, which in turn ties up K.sup.+ as the formate which is ineffective for scrubbing purposes. To remove the organic acids, at least a partial stream of the circulating scrubbing liquid is subjected to an oxidation step under conditions leading to the oxidation of the salts of the organic acids, thereby liberating the bound alkali metal ions. If the scrubbing liquid contains an oxidizable activator, the latter can be extracted prior to oxidation of the scrubbing liquid and added back subsequent to the oxidation.

Abstract: Acidic gases containing carbon dioxide are removed from a normally gaseous mixture by absorbing CO.sub.2 from the gaseous mixture with an aqueous solution comprising a basic alkali metal salt or hydroxide and an activator or promoter system for the salt or hydroxide which contains (i) at least one non-sterically hindered diamine defined as having both a primary and a tertiary amino moiety wherein the primary amino moiety is attached to a primary carbon atom, and (ii) an amino acid, and desorbing at least partially the absorbed CO.sub.2 from the aqueous solution.

Abstract: Acidic gases containing carbon dioxide are removed from a normally gaseous mixture by absorbing CO.sub.2 from the gaseous mixture with an aqueous solution comprising a basic alkali metal salt or hydroxide and an activator or promoter system for the salt or hydroxide which contains (i) at least one diaminoalcohol of the formula:H.sub.2 N--(CH.sub.2).sub.4 --NRR'wherein R and R' each independently represent a C.sub.1 -C.sub.6 alkyl group and either R or R' or both R and R' have a pendant hydroxyl group, and (ii) an amino acid, and desorbing at least partially the absorbed CO.sub.2 from the aqueous solution.

Abstract: Decarbonation of gases with solutions of alkali metal carbonates and with alkanolamine solutions is improved by exploiting the heat of the vapors exiting the head of the alkanolamine solution regeneration column and also the heat of fluids condensed at the head of the regeneration column for the alkali metal carbonate solution. A very favorable heat balance is achieved and considerable power savings.

Abstract: A fuel gas is desulfurized while hot by contact with a molten alkali salt. The salt is regenerated for further use by contact with a recirculating gas stream. The H.sub.2 S and COS picked up by the recirculating gas stream is scrubbed at low temperature in an aqueous alkaline salt scrub system such as hot potash. H.sub.2 S regenerated from the low temperature alkaline scrub system is subsequently converted to sulfur. By combining both high temperature and low temperature alkali scrubbing in a single dual temperature dual alkali (DTDA) process, the best advantages of both scrub techniques are retained whereas the serious disadvantages of molten salt scrubbing are eliminated.

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 cpolymers as defoaming agents. The defoaming agents are particularly effective when the acid gas scrubbing solution contains an amine having a large hydrophobic moiety.

Abstract: This invention relates to an apparatus and method for simultaneously scrubbing acidic exhaust gases and removing metal salts from alkaline waste dust from a cement plant or the like thereby producing useful products from what would otherwise be wasted. In essence the two wastes are combined in water and the resulting solution and precipitate separated in a tank. The solution is useful both to cool incoming waste gas and as a fertilizer, whilst the precipitate is suitable as kiln feed stock.