A Research On On-line Simulation, Diagnosis Of Limekiln And Intelligent Control Of Complicated System

Lime calcining is an old technology. About two century ago lime was only used in building construction. With latter-day's development of chemical engineering and metallurgy, the application and consumption of lime are largely increased, and people find that it is very important to study lime calcining process and equipment. In old times, lime was mostly produced by medieval kiln, and mechanization limekiln wasn't used until recent times. With the application of mechanization kiln lime throughput and productivity were doubly increased, and energy expenditure was decreased quickly. But this improvement can't satisfy the increasing requirement of high benefit, low cost and high automatization for chemical engineering, metallurgy, paper making and correlative industries.Lime production is a sequential processes, limekiln itself is a sequential reactor. Raw material and fuel are steadily input, calcium oxide and carbon dioxide are continuously produced. The estimation of production quality formerly depends on the assay of production sample. As there is a serious lag, so the assay result, which is reliable, can't be regarded as presumptive evidence of on-line decision-making control. A limekiln with diameter of four meters and height of twenty one meters is studied systematically in this paper. Based on existing detection system, by equipping necessary on-line detect instrument and collecting enough on-line information in the process of lime production, limekiln hologram monitor is achieved.By applying synthetically the principle of kiln thermal engineering and reaction kinetics, on-line simulation and optimization model and software were worked out. The concentration of carbon dioxide in the exit, "three zone" (warm-up zone, calcinations zone, cooling zone) heights and temperature distribution in kiln could be calculated by on-line simulation system, meanwhile the running historical curves were recorded by the computer which are important evidences for company assessment and management. On the basis of hologram monitor andon-line simulation, combining technical characteristic of limekiln with experiences of engineer and specialized worker, Lime Kiln Status Diagnostic Expert System (LKSDES) was established for the first time to offer on-line guidance for operation. LKSDES can provide multiple functions involving auto alarm, fault interpretation and countermeasure analysis.Based on Neural Network(NN) theory, the author devised a prediction model of quicklime quality with self-organization and self-learning functions. In the system training samples were history data, NN were off-line trained and tested by on-line information. The author found that the average forecasting error is 3.2 percent, thus exact information was offered for manipulation.In the process of lime production, some technical conditions always fluctuate, such as the compositions of raw material, the content of water, the feedrate of charge and the compositions of coke. Many parameters of the model, forming in the process of heat and matter transfer, need be made certain by means of mechanism analysis, hypothesis or experiments. Furthermore, all the state variables should be measured for the operation and management. Based on chaos fuzzy theory, the author adopted system identification method, and studied the interrelation between main control variables and output variables by considering limekiln as a "black-box". By referencing operating knowledge, the author worked out a furnace roof temperature fuzzy controller and an intelligent control system of multi-kiln lime discharging. The former dynamically controlled the roof temperature in the suitable range which was confirmed by simulation and optimization in different working conditions. The latter considered synthetically the complexity of a lime discharging system in the plant, the remarkable nonlinearity, the intense coupling between kilns, the difficulty in detecting important parameters, as well as the fact that only one lime belt system was used by multi-kilns. Then an intelligent control system of material height of limekiln was designed. Based on the chaos theory and the artificial intelligence technology, the intelligent control for the process of calces discharging was realized.The creativeness of the article lies in that the mathematical modelingand on-line simulation are combined to realize the multi-mode kiln status diagnosis and intelligent control of limekiln for the first time.