Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1994-03-28
1995-07-18
Gorgos, Kathryn
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
204129, 473220, 47324301, 473522, 473486, 473437R, 55220, 55222, 55244, 552571, 55268, C25B 102, C25B 124
Patent
active
054338280
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for the removal of hydrogen sulfide and/or carbon disulfide from waste gases. Both compounds occur, alone or in combination, as waste gases of chemo-technical processes, for example, during the manufacture of rayon. They are very noxious agents. Carbon disulfide (CS.sub.2) can cause acute and chronic forms of poisoning, with psychological and behavioral changes, if the patient has been exposed to a concentration between 30 and 120 mg/m.sup.3. For this reason, maximum concentrations of carbon disulfide of only 30 mg/m.sup.3 are allowed for working environment.
Hydrogen sulfide (H.sub.2 S) is similarly poisonous. With concentrations of about 5000 ppm, there is a risk of immediate coma. The presently valid maximum values for hydrogen sulfide are approximately 15 mg/m.sup.3.
SUMMARY OF THE INVENTION
Known methods for the removal of H.sub.2 S and CS.sub.2 rely mainly on the absorption of activated carbon. For the removal of hydrogen sulfide alone, there exist scrubbing processes normally using a caustic soda solution as a scrubbing agent. All these methods are expensive and produce considerable waste waters themselves.
It is, thus, the aim of the invention to present a method of the type mentioned above in which no expensive scrubbing agents are used and no polluting waste waters are produced.
This problem is solved according to the invention by the fact that the waste gases are brought into contact with water and bromine, so that sulfuric acid and hydrobromic acid in an aqueous solution with a bromine proportion of less than 0.5% by weight and possibly carbon dioxide are formed, and that in an electrolytic cell bromine and water are reproduced from said hydrobromic acid.
It is advantageous to subsequently concentrate the sulfuric acid and to lead the waste gases to be cleaned firstly through the sulfuric acid concentrator, which is then fed with the aqueous solution thus formed, so that the latter leaves the concentrator in a vapor state together with the waste gases. If the waste gases are present at a high temperature level, their heat contents can be used, either alone or in combination with an external heat source, for the operation of the sulfuric acid concentrator.
BRIEF DISCUSSION OF THE DRAWINGS
The FIGURE schematically illustrates a hydrogen sulfide and/or carbon disulfide removal process in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
It is known per se that bromine is capable of producing elementary sulfur from sulfur compounds. Examples of such processes are described in U.S. Pat. Nos. 2,809,930 and 3,401,101. Thus, U.S. Pat. No. 2,809,930 concerns the elimination of H.sub.2 S from gasoline. Firstly, H.sub.2 S is separated in a contactor by means of caustic soda, then the caustic soda solution is treated with bromine in a reactor, whereby sulfur is obtained. Surprisingly, the method according to the invention produces sulfuric acid, which can be concentrated and sold.
Further, it is known from Gmelin's Handbuch der anorganischen Chemie, 8th edition 1931, bromine system number 7, page 185, that H.sub.2 S and bromine are converted into S.sub.2 Br.sub.2 and sulfur-free HBr-gas. Of course, the used reagents are pure respectively highly concentrated reagents.
Finally, EP-A-0 171 570 should be discussed, from which the elimination of sulfur dioxide SO.sub.2 from waste gases by means of bromine is known which creates sulfuric acid.
The invention will now be described by means of a preferred embodiment with reference to the sole figure which shows diagrammatically an installation for performing the method according to the invention.
If hydrogen sulfide and carbon disulfide are brought into contact with bromine and water, sulfuric acid and hydrobromic acid are obtained, for example according to the following formulas:
The reaction velocity depends on the diffusion rate of the gaseous components into the gas/liquid boundary layer and can be enhanced by adequate constructive measures at the exchanger colu
REFERENCES:
patent: 2809930 (1957-10-01), Miller
patent: 3401101 (1968-09-01), Keller, Jr.
patent: 4668490 (1987-05-01), van Velzen et al.
Langenkamp Heinrich
van Velzen Daniel
European Atomic Energy Community (EURATOM)
Gorgos Kathryn
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