炉水磷酸盐多参数协同自动加药控制系统的构置与应用

Configuration and Application of Coordinated Multi-Parameter Automatic Control System for Boiler Water Phosphate Dosing

随着火电厂对汽水品质要求的不断提高,人工调节加药的方式逐渐被自动加药所替代。目前自动加药系统多采用基于单一参数的PID控制,受限于炉水磷酸根监测、加药控制的时滞性,在机组调峰及变负荷运行时不能对磷酸根浓度进行精确调节。针对这一缺陷,提出了炉水磷酸盐多参数协同加药控制方案,其要点是引入炉水的磷酸根含量、p H值、电导率和给水流量4个控制参数,并将炉水p H值、炉水电导率值计算结果与在线监测的炉水磷酸根浓度相互校正,同时结合锅炉给水流量变化情况,采用智能PID控制技术调整磷酸盐加药量。内蒙古某电厂采用该方案对原加药系统进行了改造,实践结果表明,炉水磷酸盐多参数协同自动加药控制系统运行后,炉水磷酸根含量得到稳定控制,p H值为9.40~9.50,电导率为9.5~10.5μS/cm,炉水水质合格率大大提高,为机组安全稳定运行提供了保障。

With the ever-increasing requirements for steam and water quality in thermal power plants, manual dosing has been gradually replaced by automatic dosing. Currently in most automatic dosing systems single-parameter based simple PID control is utilized. However, limited by phosphate monitoring and control delay, this type of control cannot accomplish accurate and immediate regulation of phosphate concentration under peak modulation or variable load conditions. Regarding these problems, this paper proposes a multi-parameter automatic control system for boiler water phosphate dosing. The program introduces the phosphate concentration, pH value, and conductivity of boiler water together with the boiler feedwater flow as the control parameters. The calculation results of pH value and conductivity value of boiler water are corrected with the on-hne monitored phosphate concentration. At the same time, in combination with the boiler feedwater flow changes, the intelligent PID control technique is used to adjust the dosage of phosphate. The program has been implemented in the dosing system innovation project in an Inner Mongolia power plant. The results show that since the commissioning of the multi-parameter automatic control system into operation, the phosphate content has been stabilized with the pH value maintained between 9.40 and 9.50 while the conductivity between 9.5 and 10.5 μS/cm in boiler water. Apparently, the boiler water quality is greatly improved, which ensures the safe and stable operation of the generation unit.