基于时间Petri网优化设计单杂质间歇过程用水网络

近20年来,间歇过程用水网络的研究得到了人们的广泛关注,并取得了一定的发展。以往对间歇过程的水网络集成研究多采用图解法和数学规划法,图解法无法解决与水质、水量无关的目标或约束,数学规划法计算复杂且较难确定最优解。Petri网具有直观的图形表现能力和严密的数学基础,并且具有强有力的分析技术与手段,非常适合于系统的描述和分析。同时时间Petri网是在Petri网的基础上加入时间因素,可用来建立间歇系统的动态模型。故针对半连续间歇化工过程的单杂质用水网络,本文提出了基于时间Petri网建模的方法,分别对有中间储罐和无中间储罐间歇用水网络进行了研究,首先采用水级联分析法构建了夹点分析通用模型,能够快速准确地确定用水过程的水夹点位置和最小新鲜水需求量。然后根据Petri网的逻辑表述能力、动态传播特性、自主学习机制以及水网络设计原则、水网络综合基本原则和水源匹配规则建立了水网络综合Petri网通用模型,对有中间储罐的情况还确定了中间储罐的位置、数量与容量,实现了单杂质间歇过程用水网络的优化设计。最后对文献中实例进行了研究,得到的夹点位置、新鲜水用量以及用水网络与文献中一致,表明提出的方法是可行和有效的。该方法模型简单、直观,避免了水级联表格的繁复计算,拓展了Petri网在过程领域的应用。

Optimal design of water-using network based on the time petri net in batch process with single contaminant

Nearly twenty years,the study on water-using network in batch processes arouses wide concern and has achieved some development. Formerly,the common approachs for water integration in batch process are the graphic method and mathematical programming,but the objective or restraint irrelevant to water quality and quantity can’t be solved by the graphic method,as for the mathematical with complex calculation,it is more difficult to determine the optimal solution.As the visual graphics performance ability and the strict mathematical basis of Petri net and it’s powerful analytical technique and means,it is very suitable to describe and analyse the system.Meanwhile,the time Petri net, which is defined by adding the time factor to Petri net,can be used to build the dynamic model of the batch system.So a method based on Time Petri net was proposed to design water network in semi-continuaion batch chemical processes with a single contaminant in this paper.The water-using network with/without storage in batch processes is be studied.A common model of pinch analysis,which can be used to rapidly and accurately determine the water pinch point and the minimum amount of fresh water demanded in water-using process,was firstly established using water cascading analysis.Then a synthesis common model of water-using network was built according to the mechanism, logical expression ability,dynamic propagation characteristics of Petri net and principles of designing and matching to realize the optimal design of water-using network with single contaminant.The location,number and capacity of storage was also determined directing at water-using network with storage.In the end,a literature case was studied,the water pinch location,fresh water dosage and the water-using network using the method presented in this paper are consistene with the literature.This demonstrates the validity and advantages of the proposed approach.The model of the approach,which not only can avoid the complicated calculation but also has expanded the Petri net’s application in the field of process system engineering,is simple and intuitional.