非线性多变量模型预测控制技术及其在聚丙烯装置上的应用

Nonlinear Multivariable Model Predictive Control Technology and its Application in Polypropylene Unit

聚丙烯装置涉及到多个牌号的生产,过程非线性特性强,基于线性模型预测控制算法的APC技术应用在聚丙烯装置这样高度非线性的生产过程中,具有很大的局限性,为进一步提高环管聚丙烯装置的控制和优化水平,以某企业10×10^(4)t/a聚丙烯装置为工业应用背景,首先通过实时计算催化剂进料流量,并构建PID常规控制回路,实现催化剂流量自动控制,为装置实施先进控制奠定了良好的基础;其次基于非线性多变量模型预测控制技术构建了相应的先进控制器,解决控制过程中存在的大滞后、非线性等特点,实现了关键工艺参数的闭环控制和卡边操作。工业应用结果表明:采用所述方法建立的先进控制系统,可以提高聚丙烯装置催化剂计量的准确性,增强装置操作的平稳性,提升产品质量的均匀性,并通过卡边操作,提高装置的处理能力,降低装置的能耗,获取显著的经济效益。

Polypropylene plant involves the production of polypropylene of multiple grades, and its process has strong nonlinear characteristics.The application of APC technology based on linear model predictive control algorithm in the highly nonlinear production process of polypropylene plant has great limitations.In order to further improve the control and optimization of loop reactor polypropylene plant,based on the industrial application of a 100 kt/a polypropylene plant of an enterprise,the catalyst feed flow rate was calculated in real time and the PID conventional control loop was constructed to realize the automatic control of catalyst flow rate,thus laying a good foundation for the advanced control of the plant.Then the corresponding advanced controller was constructed based on nonlinear multivariable model predictive control technology to solve the long time delay and nonlinear characteristics of the control process,thus realizing the closed-loop control and marginal operation of key process parameters.The industrial application results show that the advanced control system established by using this method can improve the catalyst metering accuracy of polypropylene plant,enhance the operation stability of the plant,improve the uniformity of product quality,and improve the processing capacity and reduce the energy consumption of the plant through marginal operation,thus achieving remarkable economic benefit.