Chemistry of inorganic compounds – Sulfur or compound thereof – Oxygen containing
Patent
1999-01-08
2000-11-28
Griffin, Steven P.
Chemistry of inorganic compounds
Sulfur or compound thereof
Oxygen containing
423529, 423533, C01B 1774, C01B 17775
Patent
active
061531685
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process of producing sulfuric acid from a steam-containing gas mixture, which contains SO.sub.3 and H.sub.2 O in a molar ratio of at least 1:1 and comes from a catalytic SO.sub.2 oxidation with a temperature of 300-600.degree. C.
Many variants of the production of sulfuric acid and details an various process stages, e.g. also on the catalytic SO.sub.2 oxidation, are described in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. A25, pp. 647-664. It is the object of the invention to produce sulfuric acid as inexpensively as possible. This process should allow for making use of the energy of the steam-containing gas mixture, which comes from the catalytic SO.sub.2 oxidation.
In accordance with the invention, this is achieved in the above-mentioned process in that the gas mixture containing SO.sub.3 and steam is passed through a condenser, in which the gas mixture is indirectly cooled by means of a cooling fluid to a temperature of 180-240.degree. C. at the outlet of the condenser, where at least 50% of the theoretically possible sulfuric acid are formed, condensed and discharged, and the cooling fluid, which has been heated to a temperature of at least 130.degree. C., is withdrawn from the condenser, and that an SO.sub.3 -containing gas mixture is withdrawn from the condenser, the gas mixture is brought in contact with concentrated sulfuric acid at a temperature of 60-120.degree. C., and concentrated product sulfuric acid is withdrawn. The cooling fluid used in the condenser may be liquid or gaseous, and it can for instance be cooling water or air.
When the cooling fluid supplied to the condenser is water, steam of 2.5 to 10 bar is generated in the condenser, which steam is a valuable product. This steam can for instance be utilized for operating a turbine, which produces electrical energy. When the indirect cooling in the condenser is effected by means of gas (e.g. air), the energy of the heated gas can also usefully be passed on outside the condenser, and for instance preheated air can be used as combustion air.
Preferably, at least 80% of the theoretically possible sulfuric acid are formed in the condenser, which are withdrawn as condensate. This sulfuric acid usually has a H.sub.2 SO.sub.4 concentration of at least 97 wt-%.
Embodiments of the process will now be explained with reference to the drawing, wherein:
FIG. 1 shows a flow diagram of the process, and
FIG. 2 shows a condenser designed as electrostatic precipitator.
Through line 1, see FIG. 1, SO.sub.2 -containing gas is supplied, e.g. gas from a sulfur combustion or another SO.sub.2 source. Usually, the gas also contains steam and air. The gas in line 1 is treated in a first plant 2 for the catalytic SO.sub.2 oxidation. Plants of this type are known. At a temperature of usually 400-600.degree. C. a gas mixture containing SO.sub.3 and steam leaves the plant 2 via line 3 and is first of all passed through an indirect cooler 4, which serves the pre-cooling of the gas mixture. Usually, the gas mixture in line 3 also contains SO.sub.2. In the cooler 4, the gas mixture is cooled to temperatures of 300.degree. C., so that a condensation does not yet take place. The cooler 4 is expedient for the recovery of energy, but not absolutely necessary.
The steam-containing gas mixture in line 6 has a temperature in the range from 300-600.degree. C. and a pressure of 0.8 to 2 bar. This gas mixture is cooled in the condensers to a temperature in the range from 180-240.degree. C., where sulfuric acid is condensed. The condenser 7 comprises an inlet chamber 7a, a bundle of about horizontal tubes 7b, a supply line 7c for cooling fluid, a cooling fluid chamber 7d, and an outlet chamber 7e. Expediently, the cooling fluid is preheated in the heat exchanger 12, before it enters the condenser 7. The cooling fluid heated in the condenser to a temperature of at least 130.degree. C. and preferably at least 150.degree. C. is discharged via line 9. When water is supplied as cooling fluid through line 7c, steam is generated, which is d
REFERENCES:
patent: 3755549 (1973-08-01), Guth
patent: 3803297 (1974-04-01), Guth et al.
patent: 5118490 (1992-06-01), McAlister
Muller Hermann
Schmidt Georg
Seitz Ekkehart
Dubno Herbert
Griffin Steven P.
Metallgesellschaft Aktiengesillschaft
Myers Jonathan
Vanoy Timothy C
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