One of our pickling processes in which we use HCl to pre-treat the metal surface and remove unwanted surface impurities like rust etc., generates a considerable quantity of Spent Pickle Liquor (SPL) which primarily consists of Ferrous Chloride.
To make best use of this waste, we intend to convert this SPL into iron oxide. One of the known methods of treatment of this type of SPL is neutralization with Ammonia solution followed by treatment with lime to recover Ammonia. However, this method produces excessive sludge (in this case Calcium Chloride) which creates further challenges and also has slow precipitation kinetics.
The other method is the pyro-hydrolysis. However, this process is very energy intensive and it requires natural gas which makes the whole process very expensive. Moreover it also produces a considerable amount of stack emissions containing HCl, particulate matter & chlorine which are very harmful to the environment and cannot be discharged easily.