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1、Batch Process Control,IntroductionSequential and logic controlControl during the batchRun-to-run controlBatch production management,Introduction,Batch operation is very common in the specialty chemical,pharmaceutical and materials processing industriesMultiproduct batch plants produce a range of sim
2、ilar products using the same equipmentBatch control is particularly difficult because there is no steady-state operating point and processes operate over a wide range of conditionsBatch process control systems involve sequencing of different process steps and control during the batchRun-to-run contr
3、ol uses experience from previous batch runs to improve the current runBatch plant scheduling and planning are used to manage the production of different products,Batch Distillation Example,Batch Control Systems,Sequencing and logic sequencing of control steps according to a predefined recipeControl
4、during the batch tracking of predetermined setpoint trajectoriesRun-to-run control end-of-batch measurements are used to improve control of next batchBatch production management planning of production needs and scheduling of product campaigns,Sequential and Logic Control,Control of batch unit operat
5、ions involves the proper sequencing and execution of specific stepsSequential logic can be represented in several ways,such as information flow diagramsInformation flow diagrams can be translated into digital logic diagrams to be executed by programmable logic controllers(PLCs)PLCs can execute seque
6、ncing operations are well as standard PID control algorithmsPLCs are the key control hardware used in batch plants,Batch Sequence Control Example,Control During the Batch,Execution of sequenced operations often involves feedback control of specified outputs Batch control is challenging because there
7、 is no steady-state operating point and processes operate over a wide range of conditionsTracking of predetermined setpoint trajectories is often requiredProcess nonlinearities and model inaccuracies become more pronounced when processes are operated over large regimesSome product properties affecte
8、d during a batch are irreversible once off target,Batch Reactor Control,PI Control of Batch Reactors,Standard PI Controller,PI Controller with Preload,Rapid Thermal Processing,Rapid Thermal Processing(RTP)is semiconductor manufacturing process in which silicon wafers are heated to very high temperat
9、ures(1,200C)on a timescale of seconds.During cooling temperatures must be reduced slowly so the wafer does not break due to thermal shock.Rapid heating and cooling rates are attained with high intensity lamps or lasers.A key challenge in RTP is accurate measurement and control of the wafer temperatu
10、re during a batch cycle.High temperature ramp rates prevent the wafer from coming to thermal equilibrium with the process chamber where temperature is more easily measured.,Gain Scheduled PID Control,PID controllers usually provide satisfactory control near the steady-state operating point where the
11、 controller was designedIf the process is highly nonlinear and/or operates over a large regime a single set of PID tuning parameter may be inadequateRTP processes operate over a very wide range of temperatures and exhibit strong nonlinear behaviorGain scheduling is a simple method to adapt PID contr
12、ollers to nonlinear processesGain scheduling is implemented by adjusting the controller gain according to the current operating pointIMC PI tuning example,Comparison of PID Controllers,Standard PID Controller,Gain Scheduled PID Controller,Run-to-Run Control,Product quality measurements are usually c
13、ollected only at the end of each batch run.Run-to-run control uses quality measurements from previous runs to adjust conditions of the current run.Semiconductor manufacturingControlled variable:film thicknessManipulated variable:heating ratePolymer manufacturingControlled variable:molecular weightMa
14、nipulated variable:chain transfer agent addition rate,Batch Production Management,Many batch plants produce multiple products for multiple customersSpecialty polymers plant:25 products for 100 customersPlanning procedures to optimally order the raw materials,manufacturer the products,and ship the products to customersScheduling procedures to optimally implement the manufacturing plan by scheduling the use of available equipment,Batch Scheduling and Planning,Multiproduct Batch Plant Example,Batch Plant Scheduling Example,Integrated Batch Control Systems,
