Recovering potassium chloride from calcium chloride - in desulphurisation wash waters, by treating with potassium hydroxide and carbon di:oxide

摘要

Recovery of salts useful as fertiliser comprises conversion of the Ca Cl2 present in recycling wash water of combustion gas desulphurisation units associated with coal-fired power stations, then crystallisation of the salts in concentrators and/or evaporators. The Ca content is pptd. as carbonate using (a) CO2-contg. waste or combustion gases in a KOH-contg. soln. or (b) by adding a stoichiometric amt. of K2CO3 soln.; simultaneously KCl is formed and remains in soln.. The CaCO3 is dewatered in a rotating vacuum filter and the KCl soln. evapd. or crystallised. Opt. after filtration but before conc., other nutrients are added to give a complete fertiliser. KCl is produced from CaCl for which there is little demand. The CaCO3 by-prod. can be recycled to the desulphurisation or sold.