Study On Control System Of Cement Denitration Process

The NO_x emission is accompanied by the inevitable process in cement production,the current our country faces serious air pollution problems,the cement industry emissions of nitrogen oxides is limited more and more strict,the cement enterprises are facing great pressure of environmental protection.The cement industry denitration commonly used SNCR technology,the technology has the advantages of low investment and high efficiency environmental characteristics,but SN CR technology in practical and there are still many problems in the application of denitrification,such as denitrification efficiency is not high,the ammonia consumption,the temperature dependent window suitable and burning system has great influence and so on.At present,China's cement denitration control level is low,the majority of artificial control or conventional PID control can't effectively solve the above problems,to control the concentration of nitrogen oxides is difficult to achieve a stable effect,and ammonia injection regulation is not reasonable,easy to cause the waste of ammonia.In order to reduce the concentration of nitrogen oxides,to ensure the environmental quality standards,and to control the reasonable amount of ammonia injection and reduce the operating costs of enterprises,it is necessary to adopt advanced control technology.With the development of control technology,more and more advanced control technologies,such as predictive control and expert rules,have been applied in industry.The accuracy of the model predictive control requirement is low,the mathematic model with a strong ability to adapt,can effectively overcome the lag problem,eliminate steady-state error,has been applied in the denitration project of thermal power industry,so the predictive control is a good choice of cement denitration control technology.Expert rules have better control effects in complex situations by summarizing the experience of human beings.In this paper,through the analysis of denitrification process of cement,the actual demand and the low emissions and reduce ammonia consumption,analyzes the denitration process itself has the typical characteristics of time delay and transition time is longer and the burning system of large typical problems influence the denitrification process,summarizes the existing denitration control spray the amount of ammonia is regulated is not reasonable,can not effectively overcome the problem of lag and the concentration of nitrogen oxides is not stab le,put forward control scheme combining predictive control and expert rules of cement denitration,and further research according to the scheme,using field data to establish a prediction model of NO_x concentration of ammonia injection volume,according to the theory of DMC predictive controller is designed based on the model of denitrification process,the experience of experts established expert rules,the denitration control is no longer blindly rely on the concentration of NO_x feedback value,the amount of ammonia injection is more forward-looking.Based on the simulation and field debugging,the parameters of the denitration controller are determined,and the simulation results are compared with the PID method.The results show that the control effect of the control is better than the PID control effect.According to the SNCR process and the actual conditions,the design and preparation of ammonia water supply control system,through the statistics and dot table controller and module configuration,PLC ladder programming and PC configuration,to achieve a stable supply of ammonia.In order to improve the precision and improve the ammonia regulation rationality as the concentration of nitrogen oxide control target,control system scheme based on cement denitration process,relying on the existing DCS system in cement plant,ammonia was developed to optimize the structure of control system design,database design and optimization control software development,implementation of the project of cement removal denitrification process control system,detailed introduces the implementation process of the key algorithms and functions of each module.After continuous improvement and debugging of control system,the successful operation of the denitration process of cement,the concentration of nitrogen oxides control stability,low concentration and reasonable and accurate adjustment of the amount of ammonia injection,reduce the operator's labor intensity,improve the control precision of NO_x concentration,reduce the cost of nitrate removal process of cement production,improve the cement enterprise's economic benefit and social benefit.