Keywords: sulphur removal, flue gas cleanup, air pollution, polymeric ferric sulphate
A process for synthesising polymeric ferric sulphate using sulphur dioxide from coal combustion
We propose a process that uses sulphur dioxide from coal combustion as a raw material to synthesise polymeric ferric sulphate (PFS), a water treatment agent. The process uses sodium chlorate as an oxidant and ferrous sulphate as an absorbent. Sodium carbonate is used as the regulator of the polymerisation process. The major chemical mechanisms in this reaction system include oxidation, hydrolysis, and polymerisation. Oxidation determines sulphur conversion efficiency while hydrolysis and polymerisation control the quality of product. Experiments have shown that the conversion efficiency of sulphur dioxide with ferrous sulphate as an absorbent can be higher than 99% under appropriate process conditions. The temperature of the reaction system is an important factor affecting conversion efficiency of sulphur dioxide. Increasing temperature led to higher conversion efficiencies of sulphur dioxide. The basicity (a polymerisation index for PFS) and total concentration in the PFS can be no less than 10% and 9% respectively, which are appropriate for efficient water treatment processes.