| Energy conservation and emission reduction have now become the development trend of cement industry.Rotary kiln is one of the facilities whose energy consumption are largest in cement production.During the production process,the raw material is fed into the kiln tail and gradually moves from the kiln tail to the kiln head,which could also be described as from top to bottom,with the continuous rotation of the kiln body.Pulverized coal grated by coal mill is injected from the kiln head into the kiln and then mixed with the kiln air,which burns in kiln to form thermal field and provides heat for the calcination of the raw material.The temperature field in the kiln is evenly distributed into transitional zone,firing zone and cooling zone.And the heat is exchanged by three modes that are radiation,convection and conduction.Rotary kiln can meet the demand of chemical and physical reaction at different stages of clinker formation.The thermal and temperature fields formed during the calcination of the clinker can degrade toxic and waste,and can also solidify the heavy metal,which reduce environmental pollution.There is no available online measurement method for rotary kiln combustion efficiency currently.Off-line measurement method could only use GB/T 26281-2010,Calculation Method of Heat Balance,Heat Efficiency and Comprehensive Energy Consumption of Cement Rotary Kiln,to make material statistics.Using statistical methods to obtain the rotary kiln combustion efficiency is a waste of manpower,resources and time.Its reference significance for the optimal control of rotary kiln is greatly reduced because of the large time delay and it is unable to reflect the running condition of rotary kiln.Therefore,realizing the soft sensor of rotary kiln combustion efficiency which could change the status that the fire in cement production needs to be observed artificially,is of great significance to the optimal control of rotary kiln,the energy conservation and emission reduction of cement industry.In this paper,the 2000T/D cement clinker production line of Jilin Yatai Shuangyang Cement Co.,Ltd is chosen as the research object.Firstly,with the data from DCS,cement clinker rotary kiln combustion efficiency soft sensor original data set is built based on the analysis of rotary kiln structure and cement production process.In the data set,the primary air velocity,secondary air temperature,kiln tail pressure,raw material feeding,coal feeding,kiln tail oxygen concentration,kiln tail carbon monoxide concentration,kiln head pressure,kiln tail flue-gas temperature and kiln tail decomposition rate of decomposing furnace are selected as auxiliary variables and the rotary kiln combustion efficiency is selected as dominant variable.Then the gross errors in the original data set are handled by Grubbs criterion.Finally,the primary air velocity,coal feeding,kiln tail oxygen concentration,kiln tail carbon monoxide concentration and kiln tail flue-gas temperature are chosen to be auxiliary variables with Grey Relational Grade Analysis.Mechanism modeling is not suitable for the measurement of rotary kiln combustion efficiency because of the characteristics of rotary kiln.Therefore,soft sensor models based on BPNN and SVR are built and improved in this paper.BPNN a kind of artificial neural network and SVR is based on statistical study theory.The cement rotary kiln combustion efficiency soft sensor models are verified by simulation and the results show the effectiveness and feasibility.The genetic algorithm is selected to improve the SVR model,which has best soft sensor effect.The rotary kiln combustion efficiency soft sensor software is developed with MFC graphical programming system based on VC++6.0,ADO and OPC.The software is running well during the production process and meets the demand of rotary kiln combustion efficiency soft sensor,which is of certain practical value. |
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