基于前馈补偿的火电厂脱硝控制系统研究

Research on control system of SCR in thermal power plant based on feedforward compensation

SCR系统具有大延迟、大惯性特性,在磨煤机启/停过程中,传统PID控制方法难以实现喷氨量的准确控制。针对这一问题,在串级控制方法的基础上,通过分析运行数据,选取磨煤机启/停信号构建喷氨量前馈补偿器,提出了SCR系统喷氨量优化控制策略,并通过定值扰动试验、滑压变负荷试验以及磨煤机变工况试验验证了控制系统效果。结果表明,喷氨量优化控制策略解决了磨煤机启/停过程中SCR出口NO_x浓度超标问题,有效提高了SCR系统控制品质,实现了喷氨量的及时、准确控制。优化控制策略具有较好的控制品质,在保证烟气达标排放的同时避免了过量喷氨,SCR系统的动态、静态调节品质全部满足国家相关标准。

SCR system has the features of large delays and inertia which makes it difficult to realize the accurate control of ammonia injection based on traditional PID method during the process of start and stop of coal mill.In view of this problem,start and stop signal was selected by analyzing of operation data to build feedforward compensator for ammonia injection and SCR ammonia injection optimal control strategy was proposed based on cascade control method.The effect of the control strategy was confirmed through constant value disturbance test,variable load test and coal mill load test.The results show that ammonia injection optimal control strategy solves the problem of NOx concentration exceeded discharge standard during the process of start and stop of coal mill,control performance of SCR system is improved and the timely and accurate control of the amount of injecting ammonia is achieved.Optimization control strategy has good performance on the efficiency of denitration and avoiding excessive injection of ammonia.Both of the dynamic and static regulating quality of SCR system could meet the relevant national standards.