Metallgesellschaft Aktiengesellschaft

Chemie Linz Aktiengesellschaft

Paul Wiesner

Hans-Martin Stonner

Fritz Wohler

Alfred Schmidt

Alfred Garber

Hans M Stonner

Gerhard Hochgesand

Alan Sinclair

Heinz Kahles

A condensate which contains cyanide ions, hydrogen sulfide and ammonia is first partly purified by stripping with water vapor and stripped-off gases are then scrubbed with an absorbent. The laden absorbent contains 50 to 300 grams ammonia and 10 to 100 grams hydrogen sulfide and is at a temperature of 70.degree. to 150.degree. C. and has a pH value of at least 9. Sulfur is added to the condensate or the laden aqueous absorbent in a quantity which is at least 0.8 times the quantity that is stoichiometrically required to convert the cyanide ions to thiocyanate ions. The sulfur may be produced from hydrogen sulfide and oxygen, preferably in the presence of an oxidation catalyst. Alternatively, the sulfur may be added to a liquid which contains 10 to 400 grams ammonia and/or ammonium ions per liter so that ammonium polysulfide is formed. That solution is mixed with the liquid that contains cyanide ions.

Process for the treatment of an aqueous condensate

Gas condensates formed from the gases obtained from coal gasification, cokefication, or carbonization are extracted with an acid- and alkali-resistant solvent, e.g. organic esters or ethers, and phenols are thereby removed. The extract is separated into solvent and phenolic phases and the solvent is recycled to the extraction process. The same solvent is used in a greater quantity for a second stage treatment of the gas condensate to preferentially remove tar bases and again the solvent and tar base phases are separated with recycling of the solvent. Residual solvent, acid gases and other volatile components are removed from the gas condensate by distillation and/or stripping with the ammonia and acid gases being separately recovered. The gas condensate is thereafter subjected to biological cleaning, e.g. by a biological oxidation.

Process for reducing biological oxygen demand of gas condensate

The aqueous effluent liquors from gasification or de-gasification of coal are extracted with a water-insoluble solvent and the extract is processed to recover the solvent. The aqueous residue is treated to remove NH.sub.3 in a driving-off column. The invention adds the steps of

Processing aqueous effluent liquors from degasification or gasification

Mono and polyvalent phenols are recovered from gasified coal by scrubbing the phenol-containing gas with water, separating the extracted phenols into a monovalent phenol-rich fraction and a polyvalent phenol-rich fraction and recovering the monovalent phenols separately from the polyvalent phenols by solvent extraction.

Process of scrubbing polyvalent phenols from gas

A process for removing phenols from waste water resulting from the gasification or carbonization of coal and containing CO.sub.2, H.sub.2 S and NH.sub.3, comprising mixing the waste water with a low-boiling organic solvent, separating the mixture into a solvent layer and an aqueous layer, stripping off from the aqueous layer under superatmospheric pressure the vapors of CO.sub.2, H.sub.2 S and organic solvent contained therein, then stripping off from the aqueous layer the NH.sub.3 contained therein leaving a refined aqueous product layer suitable for discharge, scrubbing the stripped vapors under superatmospheric pressure with a portion of the cold refined product to remove organic solvent contained therein, condensing part of the solvent and separating it under superatmospheric pressure, and scrubbing the remaining acid gases still containing ammonia and solvent with recirculated cooled raw phenol to remove the ammonia and solvent.

Removing phenols from waste water

Mono and polyvalent phenols are recovered from gasified coal by scrubbing the phenol-containing gas with water, separating the extracted phenols into a monovalent phenol rich fraction and a polyvalent phenol rich fraction and recovering the monovalent phenols separately from the polyvalent phenols by solvent extraction.

Process of scrubbing polyhydroxy phenols from gas

Pure, concentrated ammonia is recovered from aqueous liquors by stripping off gas water, de-acidifications, scrubbing and withdrawing ammonia from the top of a scrubbing column.

Continuous process for recovering pure, concentrated ammonia

A process for the recovery of pure concentrated ammonia in which the gaseous products of coal gasification or degassing are condensed or are washed with water to produce a phenolic-containing liquid phase (gas water), this liquid is dephenolated by extraction with a solvent, the phenol is recovered from the solvent and the gas is driven from the liquid phase. The gas is washed with circulated phenol and residual solvent is eliminated therefrom after NH.sub.3 is removed by washing.

Process for producing pure concentrated ammonia

Monohydric and polyhydric phenols are removed from waste water together with hydrogen sulfide, free and combined ammonia, by extraction and distillation. The waste water is formed during the degasification or gasification of coal and is subsequently subjected to biological purification. The steps of the process are as follows:

Process for removing monohydric and polyhydric phenols from waste water

Dissolved organic compounds in waste water resulting from coal degassing or gasification processes are removed by extraction with a solvent which is substantially water-immiscible, the solvent residues in the waste water are removed by inert gas scrubbing, and CO.sub.2, H.sub.2 S and NH.sub.3 in the waste water are removed by heating and steam contacting. NH.sub.3 is effectively removed in a steam gas/liquid contacting column by feeding the condensed head product of the column back to the top portion thereof, withdrawing a portion of the condensate from the column at a level intermediate the top and bottom portions of the column, treating the condensate in admixture with waste water containing CO.sub.2, H.sub.2 S and NH.sub.3 in a deacidification gas/liquid contacting column, and feeding the sump product of the deacidification column to the first column at a region below the region at which the condensate is withdrawn but intermediate the top and bottom portions of the NH.sub.3 -removal column.

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Oberursel, Germany

Paul Wiesner