Research On The Control Of Preheating And Precalcining Processes In The NSP Cement Production

The New Suspension Preheater cement production technology has become the main production technology in Chinese cement industry. The core of the New Suspension Preheater cement production technology is the technology of preheating and precalcining system. The stability of the preheating and precalcining processes affects the quality of kiln feed directly, so the research on the control of the preheating and precalcining processes has important significance.Aiming at the control problems of the wind, coal, and raw in the of preheating and precalcining processes, this paper judges the operating mode of the first-order preheating cyclone and the calciner simply, then classifies these operating mode of the calciner, based on the time delay properties of calciner and under multi-operating mode, it obtains the gray forecast union fuzzy control method to realize the stability control on the calciner.The change of raw rate causes the change of the temperature and negative pressure in the preheating and precalcining processes, also affects the requirement for the wind volume. It lets the conditions on the raw rate as the condition when analyses the operating mode on the calciner and the first-order preheating cyclone, also lets the temperature and negative pressure in the preheater as the condition when analyses the operating mode on the calciner. Through comprehensive analyzing it summarizes the five kinds of typical operating modes on the first-order preheating cyclone and the eight kinds of typical operating modes on the calciner normally. According to analyzing the difficulty degree of the control on the calciner under these operating modes, it divides these operating modes on the calciner into two categories which are normal operating mode and special operating mode.The speed change about the high temperature fan is mainly based on the change of the negative pressure in the first-order preheating cyclone in the scene. It temporarily need not do automatic speed change control on the high temperature fan, so only for one of the operating modes on the first-order preheating cyclone, analyses the relationship between the speed change on the high temperature fan and the negative pressure change in the first-order preheating cyclone, proposes that using one-dimensional fuzzy controller to realize the conception about automatic speed control on the high temperature fan, also realizes the automatic change of wind on this condition, provides the reference for the realization of full-automation on cement industry in the future. Based on the control difficulty of calciner which is the time delay properties of calciner, it puts forward the gray forecast method and designs the control scheme based on the two types of operating modes respectively. Under normal operating modes using GM (1, 1) grey forecasting method; Under special operating modes using GM (1, 2) grey forecasting method, these two methods are used to forecast the outlet temperature of calciner, by analyzing the time delay characteristic of controlled object, determines the forecast cycle and control cycle time, then uses the on-site experience and the relationship between the change of outlet temperature of calciner and the coal incremental to obtain the fuzzy control table, finally calculates the feed coal deltas by fuzzy control method.The control scheme of calciner is simulated based on the MATLAB software and the Control Build F software of the Asea Brown Boveri Ltd. Before the simulation it extracts many samples, which are the outlet temperature with various characteristics of the calciner, uses different method to process the initial value, and tests forecast error, according to the forecast results summarizes the optimal method of processing the initial value, obtains the good forecast effect under this method. It creates the OPC client in MATLAB software, realizes communication between the OPC client in MATLAB and the OPC server in Control Build F software,writes operating mode judgment procedure, also the initial value processing and the grey forecast fuzzy controlling procedures in MATLAB software, improves control program by setting virtual set value and gets good simulation result. Simulation results proves the control effect of the method of the gray forecast union fuzzy control on the calciner based on the time delay properties of calciner and under multi-operating mode is better than the conventional control method. After the simulation it uses ADO interface technology, OPC interface technology and SQL server to realize reading and writing of scene data, completes control program based on VC++ software according to MATLAB procedures, so that the control method uses in the scene.