PLC在盐水生产中的应用

随着科学技术日新月异发展,可编程序控制器(简称PLC)已引入化工行业,它功能完善,控制可靠,必将取代传统的继电器控制电路。我厂盐水工段,采用欧姆龙公司C28P控制器,利用容器内液位自然升降,来用浮球液位控制器,实现泵的自控及报警,其效果较好。     

碳化塔液位信号晶体管继电器

碳化塔塔内液位高度的控制直接影响到碳酸氢铵的生产。由于塔内信号电极棒容易附着结晶碳铵和塔内液体具有较大直流电阻以及随着液体浓度变化引起该直流电阻变化,因此直接利用液体与电极棒的接触或断开作为24V信号灯开关来控制信号灯的方法,难于使液位信号准确可靠。最近,我们用晶体管共基电路和共射电路继电器来控制液位信号,实践证明,这种电路继电器安全、灵敏可靠。现将共基电路继电器介绍如下:     

简易精炼铜塔液位自动控制

在批林批孔运动的推动下,我厂电工班的同志,发扬自力更生的精神,土法上马,大胆创新,试制成功了电动式高压液位自动控制器。这种液位自动控制器,结构简单,容易制造,安全可靠,宜于推广。简单介绍如下:工作原理液位自动控制器,由发讯机构和电动执行机构两部分组成。其电器原理、执行机构和发讯器部分见以下各图。发讯电极1和4(图2),分别为高限和低限报警电极,发讯电极2和3,为铜液液位控制电极设,液位在2和3之间波动。当液位徐徐升高,和电极A_2相接触时,继电器L_2通电而动作,其常开触点L_2闭合,交     

蒸发效体液位继电器安装位置地探讨

几乎全国氯碱行业的蒸发效体均采用UQK—02型液位继电器,平均寿命为2个月,其损坏的原因是由于蒸发过程中的高温、强碱、结盐。UQK—02型液位继电器在工作时除外壳外,始终浸泡在高温(80～150℃)、强碱(17％～30％NaOH)中,这     

可编程控制器在磨料制品液压机控制系统中的应用

传统的磨料制品液压机的继电器控制系统需用53个继电器,5个接触器,线路非常复杂,且故障率高.针对这些问题,采用三菱FX2型可编程控制器对原有的继电器控制进行了改造.根据磨料制品液压机需要实现的功能选择相应输入/输出点数的可编程控制器,设计了功能图及液压机运行中主要环节的梯形图.改为可编程控制器控制后,仅用3个压力继电器和5个接触器,外部器件大大减少,可靠性明显增高.     

基于PLC的化工过程液位自动化控制系统设计

在轮胎生产中，硫化罐的液位是质量控制的重要环节，基于可编程逻辑控制器的化学工艺液位自动控制系统是实现高效安全生产的关键，对于确保生产过程的稳定性和安全性至关重要。传统的手动控制方法存在人为误差和效率低下的问题。本文详细介绍了液位控制系统的硬件组成和工作原理，并对液位传感器以及控制算法进行了分析和讨论。针对化工过程中液位控制的需求，设计了新型PLC的自动液位控制系统。分析表明：所设计的系统具有较高的可靠性和稳定性，在液位控制方面具有良好的控制效果。     

大功率交流固体继电器在温度控制中的应用

随着科学技术的进步及工业的发展，特别是微机在工业自动控制中的广泛应用，作为计算机与外界的接口装置，交流固体继电器是比较理想的器件。１　交流固体继电器的结构及工作原理交流固体继电器的内部由输入电路、驱动电路和输出电路三部分组成，如图１所示。图１　交流固体继电器结构简图　　当输入端施加直流信号时，光电器件导通，它驱动可控硅导通，输出端闭合。固体继电器输出部分接有ＲＣ吸收电路，因此加强了电路的可靠性。２　特点（１）使用寿命长。大功率固体继电器是无触点开关，避免了大电流在频繁通过触点后造成触点损坏，提高…     

简易玻璃液位控制器

玻璃液位控制器的发展大致经过了探针式、气动式和光电式三个阶段。当前得到广泛应用的是激光玻璃液位控制器。它是利用经过调制的激光脉冲作为检测手段，然后将光信号转变为电压信号，经放大后控制执行部件，达到稳定玻璃液位的目的。值得注意是这种控制器的电路设计越来...     

模型预测控制的应用研究

针对双容水箱液位控制系统单输入、单输出、时变、非线性、耦合和滞后的特征，以双容水箱液位为被控对象，设计基于状态方程模型的MPC预测控制器，对水箱液位进行控制。仿真结果表明：该控制器可以满足模型多输入、多输出、精确控制、抗干扰、耦合和非线性特征的控制需求，比传统PID控制器有更明显的优势。     

次氯酸钠溶液投加装置

本实用新型涉及次氯酸钠溶液投加装置，它包括稀释罐、液位传感装置和控制器。液位传感装置设置在稀释罐内，液位传感装置的输出端与控制器连接；稀释罐上设有出液管、由控制器控制的进水管、由控制器控制的进药管。本实用新型投加装置能自动对次氯酸钠溶液进行稀释，稀释过程无需人工值守和操作。[第一段]     

压滤机液压系统的技术改造与可靠性研究

综合当前国内外压滤机的发展现状,针对原来压滤机液压系统存在的问题,对液压系统进行简化设计和节能设计,提高其可靠性,降低其能耗。依托PLC及电气元件、硬件和软件的高可靠性设计,使改造后的电控系统具有较高的先进性和自动化程度。运行安全可靠,操作实用简单方便,PLC控制具有常规继电器控制所不具有的优越性。改造后的系统体积小、可靠性高、故障率低、性能价格比高、维护简单方便,提高了设备的利用率。利用PLC控制使系统的柔性大大提高。成功地实现压滤机工业自动化改造与技术提高。     

Decanter Anomaly

A counter‐intuitive decanter level control structure was reported in an earlier article which the aqueous level controller had to use reverse action for stable control. The Aspen model used in this study was the simple Decanter model, which assumes that there are only two liquid phases and pressure remains constant. This article presents results when the alternative Flash3 model is used. The aqueous level controller with direct action works well. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2088–2095, 2013     

Closed-loop automatic tuning of PID controller for nonlinear systems

In this paper, a robust control system is first proposed which is suitable for the control of a class of nonlinear systems. A parallel connection of a relay to a proportional integral derivative (PID) controller collectively forms the robust controller. The relay ensures robust control by providing a high feedback gain, but it also induces a control chattering phenomenon. Instead of viewing chattering as an undesirable yet inevitable feature, the chattering signals are used as natural excitation signals for identifying an equivalent PID controller using the recursive least squares algorithm. No other explicit input signal is required. Analysis is provided on the stability properties of the control scheme. Simulation results for the level control of fluid in a spherical tank using the scheme are presented.     

MMCmicro电动机管理控制器在化工生产中的应用

介绍传统继电器工作中的不足与新型MMCmicro电动机管理控制系统的特点及工作原理,应用于生产中可实现电动机控制的自动化,电机运行稳定,维护成本降低。     

Assessment of controller performance: a relay feedback approach

Assessment of control loop performance is one of the important tasks to be carried out in a plant, regardless of the control strategy. The present work utilizes the shape information from single relay feedback test to assess the performance of a feedback system. The process considered is a typical first-order plus dead time process and the controller used is PI type of controller. An ideal relay is introduced in the feedback loop before the controller. The shape of the relay output characterizes the performance of the controller. The mismatch in the integral time can also be observed from the shape. Based on the shape information, analytical expressions for relay feedback responses are derived and straightforward procedures are evolved to assess the performance of the controller. The proposed scheme assesses the controller performance and computes the new tuning parameters, in case retuning of the controller is necessary. The robustness of the method is also tested for second-order plus dead time as well as for higher order systems. More importantly the present approach employs only one relay test for (1) assessment and (2) retuning of the controller. It provides a reliable way that is compatible even to a non-expert operator to assess the controller performance.     

Process operation near an unstable steady state using nonlinear feedback control

Process performance is sometimes best at an unstable steady state. Following a new control philosophy, stable operation near an unstable steady state can be realized using a relay with hysteresis as a feedback controller. Properly designed, this control scheme produces a stable, small amplitude oscillation in the neighborhood of the desired state. Approximate solutions for such oscillations can be obtained by Tsypkin's method or Describing Function analysis. Comparisons of these solutions with exact simulation results for an example reveal that replacing the relay with the describing function is a major source of error in the approximate analysis.     

The application of chattering-free sliding mode controller in coupled tank liquid-level control system

A chattering-free sliding mode controller (CFSMC) is proposed to realize level position control of liquid level system for two coupled water tanks, as is often encountered in practical process control. The controller is used due to its robustness against large parameter variation, disturbances rejection and reduction in chattering. Experimentation of the coupled tank system is realized in two different configurations: configuration 1 and configuration 2. In configuration 1, the water level in the top tank is controlled by a pump. In 2, the water level in the bottom tank is controlled by the water flow coming out of the top tank. The validity of the proposed controller is verified by means of a practical testing on an experimental liquid level control device.     

硫酸干吸工段的串酸机理分析及自控方案优化

介绍了硫酸干吸工段的串酸机理和自动控制流程。理论分析表明,通过酸的含量和液位参数对干吸的串酸量和产酸量实施自动控制,共有4套可行方案。依据生产的实际情况对各组方案进一步比较和优选后认为,采用其中不同参数间控制关系较为独立且响应最为直接的1套方案组建仪表自控系统效果最好。     

PLANTWIDE CONTROL STUDY OF A VINYL ACETATE MONOMER PROCESS DESIGN

A simulation of a vinyl acetate monomer (VAM) process design was developed and compared with the work of Luyben and Tyreus (1998). Two incremental changes were made to the two main control substructures. Specifically, the two schemes focus on improving the liquid inventory system control and controllability of the azeotropic distillation column. The level control strategy was tested and found to produce a faster response with less oscillatory behavior. Two alternative control techniques for the azeotropic distillation column were tested, a feed-forward model predictive controller and a static feed-forward ratio controller. The model predictive controller results illustrated the large difference between the water composition analyzer sample time and the controller step size. The static feed-forward ratio controller showed excellent disturbance rejection of large feed flow variations to the azeotropic distillation column. Simulation results are presented to illustrate the effectiveness of the new control strategies.     

真空氢气烧结炉电气控制系统的改造设计

介绍了真空氢气烧结炉的性能和电气控制系统在烧结炉中起到的作用,改造了真空氢气烧结炉的电气控制系统。选用欧姆龙PLC为核心控制器进行过程自动控制,详细阐述了电气控制系统的硬件电路设计和软件设计流程。实践应用情况表明,改进的真空氢气烧结炉电气控制系统是可行的。