Study On Resource Recovery Processes Of Flue Gas Desulfurization By Ferrous Sulfate

In this paper, resource recovery technology of flue gas desulfurization (FGD) by ferrous sulfate is studied in which better SO₂ removal efficiency is achieved and polymeric ferric sulfate (PFS) is produced. In order to improve the technics feasibility, PFS is confirmed to be the byproduct of FGD. The technics of PFS preparation is studied and the process of FGD by FeSO₄ solution is discussed, where eligible PFS is gained.1. These processes with FeSO₄ as an absorbent, NaClO₃ as an oxidant to remove SO₂ in flue gases and synthesize flocculent agent PFS in the packed absorption column are investigated. The oxidation experiment shows that up to 90% SO₂ removal efficiency is achieved through FGD by FeSO₄ solution in the presence of NaClO₃ even if pH<2. Fe²⁺ is oxided to Fe³⁺ in absorbent continuously. The influence magnitude of each factor on SO₂ removal efficiency is ascertained through pre-experiment and orthogonal experiment. After that the effect of the superficial gas speed, SO₂ inlet mass concentration, absorbent residence time, NaClO₃ additive amount, and total iron molar concentration in the absorbent are further studied as parameters affecting SO₂ removal efficiency from simulated flue gas. Finally, the continuous experiment is conducted in the elected conditions to investigate the variational rules of SO₂ removal efficiency and absorbent pH with reaction time. SO₂ removal efficiencies greater than 91% are achieved with the absorbent which molar ratio of ferric iron to total iron is 0.9 in the continuous experiment.2. The behaves of the FGD absorbent's evaporated concentration and the effect of the concentrated temperature upon the PFS dilute solution's physical and chemical characters were studied. Using water bath to evaporate, the stability of the PFS' characters would be kept well and the liquid PFS production could be prepared excellently. In order to decrease the quantity of the evaporated water for the further drying solidify, the FGD absorbent was continued to be evaporated concentration to increase the total iron concentration up to 17%. The solidify process of the PFS concentrated liquid was studied using room temperature and oven solidify. And the effect of the solidify temperature, stirring frequency, dosage of the crystal seed upon the solidify time and the PFS' physical and chemical characters were also investigated. As a result, the eligible solidify production could be got when the solidify temperature was under 80℃.