空分装置纯化系统的节能控制系统的研究

【作者】 陈亮；

【导师】 刘克平；

【作者基本信息】 长春工业大学 ， 检测技术与自动化装置， 2010， 硕士

【摘要】 空分装置是石化工业中重要的生产设备之一,也是我国节能减排的重要目标对象之一。本文以空分装置中的分子筛纯化系统为研究对象,利用集散控制系统(DCS, Distributed Control System)对分子筛纯化系统切换控制进行改造,实现节能减排的目的。在控制方案的选取上,原有分子筛纯化系统是一个按固定时间切换的开环控制系统,它的2台分子筛吸附器按固定时间交替工作,吸附水分和杂质,消耗了大量的污氮,减少了分子筛的使用寿命。而改造后的控制系统被设计为一个闭环控制系统,不但具有一定的抗干扰能力和自调节能力,而且能够通过系统反馈值(分子筛出口二氧化碳含量)与标准值比较决定是否切换分子筛,既节省了污氮冷吹量,又延长了分子筛的使用寿命。在设备的改造上,采用具有极强抗干扰能力和通信功能的可编程控制器作为控制器。检测仪表采用红外线气体分析仪在线检测分子筛出口二氧化碳含量,通过集散控制系统实现空分装置分子筛纯化系统的自动控制。在控制策略的更新上,由于过程之间存在着较强的相关性,故本文采用部分最小二乘PLS (Partial Least Square)回归法分析少量不相关的量,以达到对整个过程进行控制的目的。根据总的空气压力、空气温度和相关的湿度以及氧化铝和分子筛的厚度等计算氧化铝的最大循环时间和分子筛的最大循环时间,从分子筛纯化系统的历史数据中提炼出统计信息,利用部分最小二乘回归法建立分子筛纯化系统的统计模型,实现对分子筛纯化系统切换控制时间的预测。经过实验和现场运行结果表明,本文所设计的空分装置纯化控制系统实现了分子筛切换的自动控制,有效地降低了能耗,满足了节能控制要求,实现了分子筛纯化系统节能减排的目标。更多还原

【Abstract】 Air separation plant is an important part of petrochemical industry production equipment, is one of the important objectives of Chinese energy conservation and emission reduction. In this paper, the molecular sieve purification system of the air separation plant is researched, the distributed control system is designed to transform the research object and then conserve energy and reduce emission.In selecting the control scheme, the original molecular sieve purification system is an open-loop control system that switching at regularly intervals, and the moisture and impurities are absorbed alternatively by two molecular sieve absorbers of this system, and a lot of waste nitrogen is used, and the life of molecular sieve is reduced. While the closed loop control system designed in this paper has the ability of anti-interference and self-adjust, besides it can decide whether to switch molecular sieve according to the feedback value (the carbon dioxide content at the outlet) and stander value of the system, the amount of waste nitrogen can be reduced and the life of molecular sieve can be extended.In transforming the equipment, the Programmable Logic Controller with strong anti-interference ability and communication function is chosen. The carbon dioxide content at the outlet of molecular sieve is detected on-line by infrared gas analyzer, and molecular sieve is switched automatically according to the carbon dioxide content, so that the automatic control of molecular sieve purification system of air separation device can be implemented.In updating control strategy, due to the close affinity among different processes, a small amount of irrelevant variables is analyzed using partial least-squares regression, in order to control the whole system. The maximum cycle time of alumina and molecular sieve according to the total air pressure, air temperature and relative humidity, besides the thickness of alumina and molecular sieve is computed, the statistic information is extracted from the history data of molecular sieve purification system, and the statistic model of molecular sieve purification system is built using partial least-squares regression, so that the carbon dioxide content at the outlet of molecular sieve purification system can be predicted, and then the switching time of molecular sieve purification system can be controlled.The experiments and result of field operation shows, the automatic control of molecular sieve is realized by the purification system of air separation designed in this paper, the energy consumption is efficiently reduced, the demand for energy control is met, and the object of energy conservation and emission reduction of molecular sieve purification system is realized.更多还原