| 摘要 |
<p>PURPOSE:To recover useful alkali carbonate and H2S by adding a carnon substance to by-product crystals of alkali dithionate, etc, contained in a NOx and SO2 absrobing soln. to thermally reduce the crystals, and allowing CO2 to be absorbed into the resulting aq. soln. of alkali sulfide. CONSTITUTION:Exhaust gas 1 is brought into contact with absorbing soln. 3 contg. an iron-EDTA complex and Na2SO3 in absorption tower 2 to remove NOx and SO2 by absorption. Next part of the soln. to be recycled is fed to crystallization vessel 6 through circulation tank 5 and passed through separator 7 to separate crystals contg. Na2S2O6. 2H2O and sodium sulfate. The crystals are fed to reduction furnace 18 through drier 9, mixed with coal powder, etc., and reduced at above 700 deg.C to form a mixed melt contg. Na2S, which is then supplied to first reformer 28 through cooling and dissolving vessel 22. In reformer 28, CO2-contg. gas 14 is blown to adjust the soln. to pH 9-10. The sonl. is fed to second reformer 31 to be adjusted to pH 8-9, and S is recovered from H2S- contg. gas 33 formed. On the other hand, the slurry in reformer 31 is fed to carbonate separator 34 to separate a cake contg. Na2CO3 and sodium bicarbonate, which then is recycled to tower 2.</p> |
