Study On The Reliability Of Dual-alkali Flue Gas Desulfurization Process And Its Application

In this dissertation, the current state of the flue gas desulfurization (FGD) technology and its application was analyzed. And then the current and future problem of domestic FGD, especially the problem of reliability and disadvantage of dual-alkali FGD system, had been indicated. The reliability of dual-alkali FGD system included scaling in the scrubber and plugging in the pipeline. Therefore, the reliability of dual-alkali FGD system could be improved by studying co-precipitation of calcium sulfite and calcium sulfate, oxidation inhibition and adding seed crystal to the regeneration tank. On the other hand, by using concentrated alkali dual-alkali FGD system instead of diluted alkali dual-alkali FGD system, the reliability of dual-alkali FGD system could be improved. Furthermore, desulfurization efficiency model of concentrated alkali dual-alkali FGD system with a dimensionless factor ε was proposed, which can be used to guide the design and optimize the operations.Experimental results of precipitation of the mixed solution of low concentration calcium sulfate and calcium sulfite indicated that the present of sulfate ion would lead to a great reduction of the concentration of sulfite, which then resulted in an increasing in the concentration of calcium ion. Hence it is necessary to inhibit the oxidation of sulfite ion to prevent the scaling problem.. It was found that co-precipitation phenomenon of calcium sulfite and calcium sulfate happened in the mixed solution of diluted calcium sulfate and calcium sulfite. And a new dissolution equilibrium equation had been presented for this co-precipitation system.In the diluted alkali dual-alkali FGD system, the oxidation of sulfite would lead to low desulfurization efficiency and the increase of the concentration of calcium and sulfate ion. Consequentially, this system was easy to scaling, which would result in a lower reliability. Sodium thiosulfate was introduced to the...