Chemistry of inorganic compounds – Sulfur or compound thereof – Oxygen containing
Patent
1981-12-24
1984-10-23
Straub, Gary P.
Chemistry of inorganic compounds
Sulfur or compound thereof
Oxygen containing
423533, 423DIG6, 422160, C01B 1714, C01B 1798, C01B 1748
Patent
active
044788088
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the processing of sulphurous gases and more particularly to a method of producing sulphur trioxide.
Known in the art are methods of producing sulphur trioxide by oxidation of sulphur dioxide with subsequent production of sulphuric acid. These methods are performed in contact apparatus with several (most frequently with 4 or 5) adiabatic beds of a catalyst and with built-in or separate heat-exchangers between the beds. The initial gas enters the contact apparatus at a temperature of 20.degree.-100.degree. C. and is heated in the heat-exchangers by the reacted gas up to the temperature of the commencement of the reaction on the first catalyst bed, which is equal to 390.degree.-440.degree. C. The most intensive oxidation takes place on the first bed where the degree of conversion reaches 0.7-0.8 and the gas leaving the catalyst has a temperature of about 600.degree. C. The temperature conditions in the apparatus on all catalyst beds is kept constant. Known methods are used for oxidizing gases with a sulphur dioxide content of 7.5-12 vol.%, these gases being obtained either by burning elemental sulphur or by roasting sulphur-containing ores. ("Spravochnik sernokislotchika" published in 1971, " Khimiya" Moscow, p. 481).
Implementation of such known methods requires complex contact apparatus. The known methods also make possible the production of sulphur trioxide from waste gases, for instance, in non-ferrous metallurgy, with a sulphur dioxide content therein of 3.5-7.0 vol.%, the surface area of heat-exchangers in contact apparatus being considerably increased.
For the oxidation of gases with a sulphur dioxide content of less than 3.5 vol.% constant heat supply is required, for which purpose residual oil or natural gas is used as a fuel.
Gases with a sulphur dioxide content of less than 2.0-2.5 vol.% are generally not processed, since the process becomes uneconomical and the gases are discharged into the atmosphere, thus contaminating and poisoning the environment.
Gases containing more than 12 vol.% of sulphur dioxide are not processed on conventional catalysts because of high and prolonged overheating of the catalyst in the reaction zone (above 650.degree. C.).
It is practically impossible to process by the known methods, without recourse to special measures, waste gases with a variable content of sulphur dioxide in non-ferrous metallurgy when the content varies during short periods of time. It follows from the above that the known methods are technologically complicated and do not allow the processing of gases with low, variable, and high content of sulphur dioxide within a wide range of concentrations both constant and variable with time.
Disclosure of the Invention
It is an object of the invention to provide a method of producing sulphur trioxide which have high technical and economic characteristics and make it possible to process gases having a composition which is either constant or varying with time with a sulphur dioxide content of 0.6 to 15.0 vol.%.
This object is accomplished in a method of producing sulphur trioxide by oxidation of sulphur dioxide in a stationary catalyst bed; in said method, according to the invention, the process is performed with a periodic (every 10-200 minutes) reversal of the direction of the flow of the reaction mixture, containing sulphur dioxide and moving along the catalyst bed, with or a change of the reaction mixture temperature just before entering the catalyst bed from 20.degree.-200.degree. to 350.degree.-600.degree. C. during 10-200 minutes.
Implementation of the process under the above-cited conditions allows the use of simple and cheap contact apparatus of enhanced reliability and decrease of their metal capacity 10-20 times as compared with the known ones. In addition, it becomes possible to process gases with a sulphur dioxide content in a wide range of concentrations, both constant and varying with time. Thus, for instance, gases containing 0.6-2.5 vol.% of sulphur dioxide, ususally discharged into the atmosp
REFERENCES:
patent: 3856927 (1974-12-01), Silveston et al.
Boreskov Georgy K.
Ivanov Alexei A.
Lakhmostov Viktor S.
Matros Jury S.
Volkov Viktor J.
Institut Kataliza Sibirskogo Otdelenia Akademii Nauk SSSR
Straub Gary P.
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