payoff period
1.Described in the paper is the cooling-crystallization process adopted by CSST Jintang Branch to produce ferrisulphas from waste sulfuric acid solution. With a total investment of RMB 2.25 million yuan,every year approximately 3,000 tons of ferrisulphas can be produced from the said solution,which means the payoff period of the said investment is expected to be 3～4 years only.
