Control of parallel dry methane and steam methane reforming processes for Fischer–Tropsch syngas

The ratio of hydrogen to carbon monoxide in the synthesis gas required for feeding to the gas-to-liquid Fischer–Tropsch (FT) process to produce liquid transportation fuel is about two. The dry methane reforming (DMR) process feeds carbon dioxide and methane and produces a syngas with a H₂/CO ratio of about unity. The steam methane reforming (SMR) process feeds water and methane and produces a syngas with a H₂/CO ratio of about four. This paper studies the plantwide control of a process with DMR and SMR units operating in parallel to produce FT syngas. The total methane fresh feed is split between the two parallel processes in the appropriate fraction so as to produce the desired H₂/CO ratio in the mixed syngas stream from the process.Both the SMR and DMR reactions are highly endothermic and the reactors are fired furnaces with combustion of fuel providing the endothermic heat of the reactions. Reactor exit temperatures are controlled by manipulating the flowrates of fuel to each furnace, with combustion air ratioed to the fuel. Dynamic reactor models assume tubular SMR and DMR reactors in which heat fluxes are determined by the heat generated in their associated fuel/air combustion reactors.The plantwide control structure effectively handles large 20% disturbances in throughput and large setpoint changes in the desired H₂/CO ratio (1.7–2.3).     

独立、并网双模式户用光伏发电装置的研究与设计

针对户用光伏发电系统的特点和要求进行了系统的研究与设计。系统设计将独立逆变与并网逆变相结合,使系统既可以工作在独立逆变状态,为负载提供正弦交流电源,也可以工作在并网逆变状态,将太阳的能量或蓄电池的能量回馈到电网。本系统采用TI公司32位定点DSP芯片TMS320F2812为控制核心,利用PIC16F877A单片机构成系统的人机操作界面。本文所设计的系统具有完善的保护功能、键盘监控和液晶显示、串口通讯功能,为家庭使用提供了方便。实验结果验证了方案的可行性。     

An optimal control based approach to designing plantwide control system architectures

An approach to designing decentralized plantwide control system architectures is presented. The approach is based on splitting the optimal controller gain matrix that results from solving an output optimal control problem into feedback and feedforward parts. These two parts are then used to design and evaluate decentralized control systems. Results for the application of the methodology to a realistic, 4 by 4 reactor with recycle process are given. For this system, the optimal control based approach suggests feedback pairings that are significantly different than those suggested by the steady state RGA. The approach presented can give an indication if MPC is preferred over a decentralized approach to plantwide control. Comparison of the results produced by the best decentralized plantwide system and a model predictive control system are presented.     

A pulp mill benchmark problem for control: application of plantwide control design

A heuristic for design of plantwide control strategies is introduced and applied to the millwide control of a previously presented pulp mill benchmark. Two control strategies (decentralized control and unit-based model predictive control) are compared according to their capacity to reduce the total error and maximize the operating profits. The control strategies are studied through closed-loop simulations of the process including several disturbances and setpoint changes in the digester, oxygen reactor, bleach plant, recausticizing plant and lime kiln.     

Distributed model predictive control of an experimental four-tank system

A distributed model predictive control (DMPC) framework is proposed. The physical plant structure and the plant mathematical model are used to partition the system into self-sufficient estimation and control nodes. Local measurements at the nodes are used to estimate the relevant plant states. This information is then used in the model predictive control calculations. Communication among relevant nodes during estimation and control calculations provides improvement over the performance of completely decentralized controllers. The DMPC framework is demonstrated for the level control of an experimental four-tank system. The performance of the DMPC system for disturbance rejection is compared with other control configurations. The results indicate that the proposed framework provides significant improvement over completely decentralized MPC controllers, and approaches the performance of a fully centralized design.     

均热炉复杂过程混合模糊控制器的建立

对均热炉工艺过程中由于空/燃比和压力的随机变化而难以稳定炉温的问题进行了研究,并对均热炉的大滞后、多变量工艺过程的特征,提出应用压力前馈通道来预测均热炉炉温变化的超前量,建立了混合的模糊控制器.通过调节空/燃比的修正因子和压力模糊控制器的比例因子,来保证炉温控制主回路的稳定运行.系统的运行结果表明空炉提温曲线、装锭提温曲线和化渣曲线特性具有明显的改善.     

An industrial and academic perspective on plantwide control

The purpose of this paper is to stress the importance of selecting the right plantwide control structure and the need for a formalized approach that can encompass the many issues that arise in plantwide control design. Since the concept of process control design based on a holistic view of the process came about, the variety of procedures and approaches to the design problem has illustrated the difficulty of a unified approach. Using examples, the need and advantages of using a systematic approach based on considering the plant economics are highlighted. The examples deal with disturbance rejection, throughput maximization and economic optimization of plants consisting of parallel units.     

多区域厂房空调系统控制策略的设计与实施

多区域厂房的环境比较特殊,且其空调控制系统存在耦合、时变、滞后等非线性特性.针对厂房的环境特点和空调控制系统的难点,提出了新风量控制、末端送风阀控制和风量协调控制等一系列控制策略.为保障多区域厂房空调在多工况环境下的控制品质和稳定性,运用模糊控制实现风量协调控制,从而满足厂房各区域负荷变化.工程实施结果表明,厂房各区域的温湿度很好地满足了预定要求,从而证明了该控制策略的有效性.     

DCS系统在垃圾焚烧循环流化床电厂的应用

垃圾焚烧发电技术具有高效率处理生活垃圾、节约能源、建设周期短及环保等特点,循环流化床锅炉具有燃烧效率高、适应性强和燃烧强度大等优点,介绍了垃圾发电厂的工艺流程,并详细阐述了DCS控制系统的功能、特点及总线协议在垃圾焚烧热电联产项目的具体应用,最后分析了性能模块在优化电厂机组运行、提高经济效益方面的应用.     

Inventory and flow control of the IGCC process with CO2 recycles

We present control strategies for an Integrated Gasification Combined Cycle (IGCC) power plant with CO₂ recycles. One recycle allows for composition control and is useful when the side objective is to produce synthesis gas for chemicals. The second recycle enables temperature control in the gas turbine by using CO₂ as a diluent. The main advantages of the second recycle are that NO_x is not produced and that CO₂/H₂O separation is significantly easier than CO₂/N₂ separation, which reduces cost if the CO₂ is to be sequestered. Models and control systems are developed using process network theory. We introduce a novel method for controlling quality variables and functions of inventories. Dynamic simulations using MATLAB/Simulink models show the response to step changes in setpoints and disturbances. The inventory control method is derived from conservation laws and the second law and it is applicable to process system models of any degree of complexity. A steady-state sensitivity analysis is performed, examining the effect of changing the temperature and C:O ratio within the gasifier on the power production.     

A decoupled controller for fuel cell hybrid electric power split

The power management of a hybrid system composed of a fuel cell, a battery and a DC/DC power converter is developed. A decoupled control strategy is proposed, aimed at balancing the power flow between the stack and the battery and avoiding electrochemical damage due to low oxygen concentration in the fuel cell cathode. The controller is composed of two components. The first controller regulates the compressor, and as consequence the oxygen supplied to the cathode, via a classic proportional–integral controller. The second controller optimally manages the current demanded by the fuel cell and battery via linear-quadratic control strategy acting on the converter. The closed-loop performance has been tested both in simulation and in real-time simulation using a microprocessor for the controller.     

交叉限幅控制在加热炉中的应用

在炼油生产中,由于加热炉负荷和工况的变化,经常会调整炉温以及出现炉温偏差,为了满足工艺生产的要求,则需要对燃料进行调节。在一般调节过程中,由于温度响应比较慢,且不易稳定。采用交叉限幅控制,可以使燃料和空气达到动态过程的空燃比基本协调一致,从而减少损失,节省燃料。     

基于模糊PID控制器的协调控制系统优化

火力发电厂在我国电力工业中占有主要地位,大型火电单元机组的协调控制对象是一个多变量、强耦合的控制对象,针对此对象设计合适的解耦控制器是急需解决的问题.本文结合以1000MW机组作为具体模型,分别采用常规PID协调控制方式和参数自整定模糊PID解耦协调控制方式对全工况下的协调控制系统进行仿真研究,在线对PID参数进行整定,通过仿真结果进一步比较,可以看出,该方法可以很好的对单元机组协调系统进行控制,并能使控制系统的性能得到完善.     

利用Matlab优选PID参数及其在飞控系统设计中的应用

该文充分利用Matlab中的Simulink工具,对于飞行控制系统的PID参数进行优化,以达到同时保证良好的动态品质特性与充分的鲁棒稳定裕定,给出了完整的设计与分析过程,数字仿真则验证了该方法的有效性。