论文部分内容阅读
In India, Phosphogypsum is currently generated over 7 million tonnes as an industrial waste during phosphoric acid manufacturing in the wet process treatment of natural rock phosphate by sulfuric acid digestion.Phosphogypsum is being disposed into open sandy yards or in ponds close to the plants in the form of slurry made by pumping phosphogypsum with sufficient quantity of water.After percolation and drying, the phosphogypsum is stockpiled for future use.Around 20% of the phosphogypsum generated is used as a set retarder in cement manufacturing.However, still large quantities of phosphogypsum lie unutilized.The proper reuse of phosphogypsum is needed to solve environmental and disposal problems.In present work, a chemical method for making cement from acidic phosphogypsum was investigated.It was found that Phosphogypsum can be decomposed to lime rich material in nitrogen atmosphere and in presence of reducing agents like coal,petroleum coke etc.The liberated lime is used for making clinker in combination with other raw materials simultaneously, which is subsequently converted to cement and the liberated SO2 can be processed further to produce sulfuric acid.In this paper the decomposition of phosphogypsum, intermediate phase development,details of clinker phase formations etc.will be presented along with the strength development and hydration of the cement produced.The cement so produced conforms to the specifications of Indian standard of OPC 33 Grade (IS: 269-2013).