Preventing incrustation in recovery of sulfuric acid in titanium dioxide production by pre-concentrating the dilute acid to above 32-45 weight percent

摘要

The dilute sulfuric acid (H2SO4) obtained in the production of titanium dioxide (TiO2) by the sulfate process is pre-concentrated using process heat from 18-28 wt.% to a level in the range from above 32 wt.% up to 45 wt.% before being further concentrated and returned to the TiO2 production. The dilute acid containing 18-28 wt.% H2SO4 and 5-20 wt.% metal sulfates obtained in the production of TiO2 by the sulfate process is pre-concentrated to above 32-45 wt.% H2SO4 by evaporation using process heat before being finally concentrated to 62-70 wt.% and returned to the TiO2 production, the process involving the following conventional steps after the pre-concentration: (i) decomposing the concentrated acid-soaked metal sulfate at 850-1,200 deg C to yield metal oxide and SO2; (ii) pre-cooling to 290-350 deg C; (iii) adiabatically cooling the de-dusted SO2- and metal oxide traces-containing gas to 60-98 deg C by spraying with the dilute acid; (iv) evaporating the resulting pre-concentrated dilute acid; and (v) cooling the SO2-containing gas from the adiabatic cooling step to 30-45 deg C and recycling it to the H2SO4 process.