Spent sulfuric acid decomposition furnace

Sulfur burning furnace Sulfide mineral smelters and roasters Spent acid decomposition furnace... 

Fig. 5.1. Spent sulfuric acid regeneration flowsheet. H2S04(f) in the contaminated spent acid is decomposed to S02(g), 02(g) and H20(g) in a mildly oxidizing, 1300 K fuel fired furnace. The furnace offgas (6-14 volume% S02, 2 volume% 02, remainder N2, H20, C02) is cooled, cleaned and dried. It is then sent to catalytic S02 + Vi02 —> S03 oxidation and H2S04 making, Eqn. (1.2). Air is added just before dehydration (top right) to provide 02 for catalytic S02 oxidation. Molten sulfur is often burnt as fuel in the decomposition furnace. It provides heat for H2S04 decomposition and S02 for additional H2S04 production. Tables 5.2 and 5.3 give details of industrial operations.

Fig. 5.2. Spent acid decomposition furnace. It is brick lined steel 4 m diameter and 20 m long. The energy for decomposing H2S04(< ) into S02(g), 02(g) and H20(g) and for evaporating water is provided by burning molten sulfur and natural gas with hot air. Industrial details are given in Table 5.2.

Thennal decomposition of spent sulfuric acids to give sulfur dioxide is achieved in a furnace at temperatures around 1,000 °C. Spent acids come from processes where H2SO4 or oleum is used as a catalyst (alkylation, nitration, sulfonation, etc.) or from other processes where H2SO4 is used to clean, dry, and remove water. 

Heat for this reaction is mainly provided by burning molten sulfur and other fuels with preheated air (occasionally oxygen-enriched) and the 02 from Reaction (5.1). A small amount of heat is obtained from oxidizing the spent acid s hydrocarbons. Sulfur burning has the advantages that it increases S02 concentration in decomposition furnace offgas and H2S04 production rate. 

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