Acid pumps, H2SO4 production

The electricity credit for the Table 31.2 acid plant is estimated at 250 kWh/toime of acid produced (100% H2SO4 basis). The acid plant requires 45 kWh/tonne of product acid to run the air blowers, acid pumps, and other utilities. ... 

In an alternative procedure (84), the electrolyte is pumped through the cells at such a rate that the outlet concentration is 50 g/L MnSO and 67 g/L H2SO4. This spent electrolyte is then mixed with equal parts of make-up solution containing 150 g/L MnSO and the mixture returned to the electrolysis step. The electrolysis is continued over a period of days and terrninated when the EMD layer deposited on the anode reaches a specific thickness, usually on the order of 1—3 or 6—8 mm. Following completion of the electrolysis cycle, the entire electrode assembly is removed from the cell for removal of the deposited EMD, either manually or by an automated system (85). The product is repeatedly washed with water to extract the occluded acid (83) and dried at about 85°C in air. 

H2O, I2 and SO2 are fed into a main reaction vessel (R-l), and continuously recirculated, by means of a pump P-1, in a loop where temperature control can be obtained through the cooler (or heater) C-l. Some of the products are intermittently fed to the liquid-liquid separator R-2 where the two acid phases are separated. The upper H2SO4 phase is purified by boiling in R-3, and then decomposed in a quartz cracker containing Fe2C>3 catalyst. 

The product was pumped in a CO2 atm into a 10 liter separator, H O was recycled and the product washed with H2O in a 60 liter column with passing of CO2 to an acidity of 0.001—0.005% H2SO4. The earlier process without CO2 yielded a dark-red to brown product of 0.03—0.05% acidity... 

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