| 摘要 |
<p>PURPOSE:To conduct wet treatment of exhaust gas at constant operation and at a low cost, by adding lime to the soln. contg. NaOH and having been used for absorbing and removing SOx, NOx contained in exhaust combustion gas in order to separate sulfate group as gypsum, and by reutilizing the soln. liberated from gypsum once again for the treatement. CONSTITUTION:After cooled in a cooling tower 2, exhaust combustion gas from a boiler 1 is passed to an oxidizing-gas mixer 17, where most of the NOx is oxidized to NO2 by addn. of O3, however practically no SO2 is oxidized. The exhaust gas is then led to an absorption tower 4, where it is completely removed of SOx and NOx by treatment with absorbing soln. contg. NaOH and Na2SO3, it is then discharged through a mist separator 7 to the air. A portion of the absorbing soln., which is circulating, is led to an oxidation tank 10, where sulfite group contained in the soln. is oxidized to sulfate group with air, then to a precipitation tank using lime, where lime F is added to the slon., and resulting gypsum B is separated by a filter 24. The filtrate is liberated in a carbonate-precipitation tank 13 from residual C<2+> by addn. of CO2 gas D. In demineralization unit 15, the filtrate is further removed of NaNO3, and is decomposed in a decomposition still 16 into Na2O and N2, the demineralized soln. being mixed and dissolved with Na2O in a mixer 14, and is then returned to the absorbing soln. tank 6 through the carbonate-precipitation tank 13.</p> |
