一种乙烯精馏塔先进控制系统的开发和应用

Advanced Control System Development and Application of the Ethylene Rectification Tower

乙烯精馏塔是乙烯装置的成品塔之一,对提高乙烯装置的平稳运行率及企业的经济效益有着重要意义。为了稳定乙烯精馏塔操作,提高产品质量,解决测量滞后以及过精馏的问题,提出了基于关键组分软测量的先进控制方案。通过分析影响乙烯精馏塔的关键因素,选择了关键组分软测量模型的辅助变量,仿真比较了PLS方法、RPLS方法以及带遗忘因子的RPLS方法的预测精度,实现了对浓度值进行实时预测,并与相关调节阀组成自动控制回路,实时控制产品质量。基于提出的乙烯精馏塔先进控制方案,开发了关键组分浓度的软测量程序以及自动校正回路,给出了在DCS中的实现过程和先进控制系统的投用方法。分析了新控制系统投用前后的运行情况,验证了所提方案的实施效果,实现了塔顶乙烷、塔釜乙烯浓度的"卡边"操作,保证了乙烯精馏塔的平稳运行。

Ethylene distillation column is one of the products of ethylene plant, which has important significance to improve the stability of ethylene plant and the economic benefit of the enterprise. This paper presents an advanced control scheme based on key components of soft sensor, with the aim of stabilizing the operation of ethylene distillation column, improving the quality of products and solving the problem of measuring time-delay and over-distillation. Through a thorough analysis of key factors that influences the ethylene distillation tower, the instrumental variables of key components for soft measurement model are selected and the concentration of ethane and ethylene can be predicted. Besides, a comparison on prediction accuracy among PLS, RPLS, and RPLS with forgetting factor is also presented. The soft measurement values and the adjusting valves constitute an automatic control loop, and the quality of the products can be controlled. Based on the proposed advanced control scheme of ethylene distillation tower, the soft sensing program and automatic correction of the key components are developed, and the realized process on DCS and the implementation method of the advanced control system are presented. By analyzing the operation results of the new control system, the effect of the proposed scheme is verified. The critical operation of the ethane and ethylene concentration is achieved. It ensures the stable operation of the column and the qualified quality of the products.