US 5,209,912 AGranted

Process for separating out noxious substances from gases and exhaust gases

AssigneeFTU GmbH

InventorHermann Suchenwirth

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Abstract

A composition for separating out volatile pollutants from gases and exhaust gases consists of calcium hydroxide and water-soluble salts of sulfur-containing compounds, e.g., mercaptans, sulfides, polysulfides, polythionates and thiosulfates, or elementary sulfur which are used in combination with surface-active substances. Possible ways to produce the composition include adding the sulfur-containing compounds to the quicklime during slaking, to the slaking water, or, subsequent to slaking, to calcium hydroxide. The compositions are used for removing the volatile heavy metals, particularly mercury, arsenic, cadmium, thallium, antimony and lead, at temperatures ranging from 20.degree. to 400.degree. C. For this purpose, the composition is blown as powder into the exhaust gas stream, and the resultant products are separated out at fabric filters. Upon addition of surface-active substances, volatile organic pollutants are removed simultaneously with the aforementioned inorganic pollutants.

Claims14

Dependent claims

A process for separating heavy metals from an exhaust gas stream comprising adding a calcium hydroxide composition to the gas stream,

said calcium hydroxide composition comprises a finely divided dry calcium hydroxide, or a finely powdered calcium hydroxide having a water content of 0.1 to 5% by weight, and an effective amount of at least one sulfur-containing compound to remove heavy metals from the gas stream wherein the at least one sulfur-containing compound is selected from among water-soluble salts of sulfur-containing substances, surfaceactive substances on which either water-soluble salts of sulfur-containing substances or sulfur have been applied, or surface-active substances which are mixed with sulfur, wherein the water-soluble salt of a sulfur-containing substance is selected from the group consisting of mercaptans, sulfides, polysulfides, polythionates, and/or thiosulfates while the surface-active substances are selected from the group consisting of active carbon, open hearth lignite coke, activated aluminum oxide, silica gel and/or crystalline silica;
and
separating out the sulfidized heavy metals from the gas stream.

Dependencies are inferred from the claim text.