| Evaporation plays a key role in the alumina production process, in which heat of steam with high temperature and high pressure is transferred to the sodium aluminate solution in order to evaporate the redundant water contained in the liquid, and increase the caustic ratio concentration for that the liquid can satisfy the conditions of recycling. Influenced by the change of input parameters in practical production, the concentration of output liquid shows fluctuation. Besides, the delay of the operation on the process caused by the lag of sampling analysis makes it difficult to optimaize and control on evaporation process, and leads to substantial increase of the steam consumption. Therefore, it has important practical significance to research on the dynamic mathematical model of the evaporation process.Taking a four-effect countercurrent falling film evaporation process as the research object, based on mass balance, thermal balance and phase balance, the dynamic mathematical model is established after intensive study on the mechanism of alumina evaporation process. The relationship between the output liquid concentration and the flow of raw material and vapor is formulated by dynamic equations, and the physical parameters are analyzed.Considering the characteristics of long process, large inertia, multiple time-delays, process complexity and time variation of the alumina evaporation process, the control objectives, operation variables and state variables are analyzed and determined, and the multiple time-lagging dynamic mathematical model of the evaporation process of alumina production is constructed.A self-adaptive Runge-Kutta algorithm is proposed to solve the dynamic mathematical model and acquire the concentration of the output liquid of evaporation unit. The comparison between the simulated results and measured values shows that this model can better reflect the evaporation process of alumina production and create conditions for the design of optimal control system. |
PDF Full Text Request