Reverse Research And Process Optimization On The Industrial Production Line For Ammonium Sulfate Byproduct CaCO₃Residue Suspended Decomposition

The calcium carbonate residue which is a byproduct in the production ofammonium sulfate using phosphogypsum has the characteristics of high water content,small particle size and poor mobility. The calcium carbonate residue was heatedtreatment by high solid-gas suspension preheater decomposition-rapid cooling processwhich integrated fast drying, preheating, decomposition and cooling together had beendeveloped by powder engineering research institute.The research institute built thefirst industrial test line for CaCO₃slag resourceful disposal. In the thesis, industrialexperiment production was debugged and a pilot line results were summarizedsystematically. The paper focuses on the process of reverse research and optimization.In this paper, the physical and chemical properties of raw materials wereanalyzed firstly. Then, the process constitutes of the high solid-gas suspensionpreheater decomposition-rapid cooling process line was introduced. The thermalparameters test and analysis of the system, balance calculation and the product qualitytesting confirmed the industrial test lines to achieve the intent of the design anddevelopment. The control point of the production line was obtained and the optimumcontrol parameters of the existing process were determined by debugging. This papernot only formulated detection methods of a decomposition rate of CaCO₃, massfraction and the active, but also provided product quality control system. In thethesis,process reverse research was studied emphatically and wind speed of majorcross-section, the separation efficiency and heat transfer efficiency of preheater and cooler and other internal parameters were obtained.These studies provided referencedata for suspended heat treatment process line development. The main conclusions arelisted in the following:1. The CaCO₃decomposition rate was more than97.7%and the activity of theproduct was high after calcium carbonate residue was heated treatment by highsolid-gas suspension preheater decomposition process which was Low energyconsumption, approximately4402kJ/kg product. The process was ideal process ofdecomposition of CaCO₃residue due to many advantages such as, short calcinationtime, the system temperature distribution is reasonable and small fluctuations, stableoperation, small footprint technology and equipment.2. Inverse calculation results show: single parameter design is reasonable, theseparation efficiency and heat transfer efficiency of preheater and cooler matching wasrational. But the exhaust gas temperature of the system higher due to the actualmoisture content of raw materials is about8%lower than water raw materials used inthe design. It was suggested in the subsequent design and development, if the moisturecontent can be controlled at17%or less, increase a heat exchanger unit should beconsidered. So,there is further improvement room for the system’s production capacity,and energy consumption of unit product can be further reduced.3. The most critical factors that affect the stable operation of the production linewas the water mass fraction and calcium carbonate mass fraction. The great variationdue to site conditions and restrictions of upstream processes. Studies suggest that thesubsequent production process should improve the homogeneity of CaCO₃slag,especially the content of CaCO₃of raw materials, product quality can be guaranteed.