基于PLC的化工精馏塔控制系

i基于PLC的化工精馏塔控制系统摘要PLC作为在现在工业中应用最多的控制软件，在化工精馏的控制中也起重要作用。PLC具有非常高的可靠性，并且操作简单，编程简单入手，而且随着工业的发展越来越多并且功能强大的PLC已经被开发出来而且应用逐渐走向成熟。对于化工生产中的精馏过程，具有控制因素复杂，要求的控制指标又必须非常精确，各因素及控制过程的联系非常复杂，功能强大编程简单的PLC非常适合精馏过程的控制。在诸多的控制要素中，温度的控制占据着核心地位，因此我的设计主要是选用合适的PLC，并且选择最能满足工艺要求的过程控制方案来实现化工精馏塔中塔底的温度。我的设计主要任务是是根据一个具体化工精馏塔设计的要求，运用PLC来完成控制。在此设计中要做的具体工作是详细了解精馏塔的工艺过程和它对控制系统的要求，根据精馏塔的要求来进行PLC的选型，过程控制的选择与设计，输入输出量的确定，并且能够画出具体的设计图，还有软件程序的编写。最终要达到的效果是能够编出PLC程序，并且能够在计算机上模拟运行。关键词：化工精馏塔，PLC控制，串级控制，PID算法iiChemicalDistillationColumnControlSystemBasedonPLCAbstractPLCinindustrialcontrolsoftwarehasbecomemostpopularsoftware,alsoplayanimportantroleinchemicaldistillationcontrol.PLCnotonlyhasaveryhighreliabilityandsimpleoperationbutalsohassimpleprogrammingways.AndwiththedevelopmentoftheindustrymoreandmorePLCwhichhashugefactionhasbeendevelopedandgraduallygonetomature.Fordistillationprocessofchemicalproduction,ithascomplexcontrolfactors,requirementsofthecontroltargetsmustbeveryprecise,thefactorsandthecontrolprocessofcontactisverycomplex.Accordingtothesetraits,powerfulPLCissuitablefordistillationprocesscontrol.Inallcontrolfactors,thetemperaturecontroloccupiesthecoreposition,soinmydesign,mymaintaskistoselectthesuitablePLC,andchoosethemostreasonableschemetorealizethechemicalrequirementinthecolumnbottomtemperature.Inmydesign,themaintaskis,accordingtotherequirementsofaspecificchemicalrectificationtowerdesign,tousePLCtoaccomplishcontrol.Inthisdesign,thespecificworkImusttodoistogethangofdetailsaboutdistillationprocessanditsrequirementforcontrolsystem.Accordingtotherequirementoftherectifyingcolumn,tochoosethetypeofPLCaswellasthechoiceofprocesscontrolandthendesignthesystem,todeterminepointsofinputandoutput,andcandrawthedetaileddesigndrawing,andtowritesoftwareprograms.FinallytheeffectwillbetoachievedistobeabletowritePLCprogram,andisabletorunonthecomputersimulation.Keywords:Chemicalrectificationcolumn,PLCcontrol,cascadecontrol,PIDalgorithmII目录第一章绪论...........................................................................................................................................11.1化工精馏塔研究的目的及意义...............................................................................................11.2化工精馏塔的研究现状...........................................................................................................21.3设计主要研究内容...................................................................................................................3第二章系统总体概述...........................................................................................................................42.1精馏工艺简介..........................................................................................................................42.2系统总体结构与设计流程.......................................................................................................52.3串级控制系统的选择...............................................................................................................62.4PID算法的选择........................................................................................................................8第三章硬件的设计.............................................................................................................................103.1PLC机型及安装方式的选择..............................................................................................103.1.1FX2N-48MR-001PLC................................................................................................113.1.2FX2N-4AD特殊功能模块....................................................................................123.2输入输出量的确定................................................................................................................123.3PLC外部结构图.....................................................................................................................133.3.1温度值给定电路.......................................................................................................133.3.2温度流量检测电路...............................................................................................143.3.3输出控制电路..........................................................................................................153.3.4复位电路.................................................................................................................15第四章PLC软件设计.........................................................................................................................174.1编程与通信软件的使用.........................................................................................................174.2程序单元设计........................................................................................................................184.4控制系统控制程序的开发.....................................................................................................204.4.1温度设定...................................................................................................................204.4.2A/D转换功能模块的控制程序.............................................................................204.4.3标度变换程序........