OBTAINING METHOD OF STEAM FOR CONCENTRATING PHOSPHORIC ACID FROM HEAT REMOVED FROM ABSORPTION SYSTEM IN SULFURIC ACID PREPARING APPARATUS

摘要

PURPOSE:To recover the unrecovered and dissipated heat energy and obtain a sufficient heat source, by passing a high-temperature gas containing SO3 through a newly installed high-temperature absorbing column, and then passing the gas through a low-temperature absorbing column. CONSTITUTION:The sensible heat of a high-temperature gas containing SO3 after the completion of the reaction in a converter 6 is recovered by a heat exchanger 9 and an economizer 10 to 220-160 deg.C. The gas is then brought into the countercurrent contact with high-temperature sulfuric acid in a high-temperature absorbing column 11 to absorb the sensible heat of the gas and the heat generated by the condensation and absorption of SO3 by a circulating acid. The discharged gas is then treated with an absorbing column 12 in which sulfuric acid is sprinkled at 75-85 deg.C, and the same operations are carried out in a heat exchanger 13, economizer 14, high-temperature absorbing column 15 and 16 in the same manner as in the apparatus 9-12. The circulating acid heated at a high temperature and concentrated to a high concentration in the columns 11 and 15 is partly fed to a drying column 1 and mostly to a diluting tank 18 where the heat of dilution is generated by the inflow of low-temperature sulfuric acid from the column 1 through a heat exchanger 19 and inflow of the water for adjusting the acid concentration. The resultant sulfuric acid is passed through a heat exchanger 20 and sprinkled from the tops of the columns 11 and 15. Water which received the heat is circulated through an evaporator 22 and the heat exchanger 20 operated at 0.5-20ata, and generated steam is utilized for concentrating phosphoric acid, etc.