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May
02

Applications – Batch Chemical Reactor Control

As mentioned in my previous blogs on the book Control Loop Foundation – Batch and Continuous Processes, the application examples included in Chapter 16 illustrate the various ways single loop and multi-loop control techniques may be used automate plant control. The second workshop exercise in this chapter allows the reader to explore the different features of batch chemical reactor control.

Batch chemical reactors may be used to manufacture a variety of products. Typically the reactor is initially charged (filled) with one or more chemicals, the contents of the reactor are heated to a target temperature and then a metered quantity of one or more reactive chemicals is added to the batch. The feedstock tank and valve manifold used to initially charge the reactor are often shared among multiple reactors. Thus, the timing of the reactor charge must be coordinated by the batch control software. The chemical reaction may be exothermic and thus cooling may be required to maintain the reactor charge temperature at the target temperature. In order to support both heating and cooling, temperature control is implemented as a split-range control loop that adjusts heating and cooling media flow to the reactor shell. The reactor pressure is maintained at setpoint by venting vapors and gases generated by the chemical reaction. The control loops and measurements commonly found on a batch reactor are shown below.

If the cooling requirements exceed what can be provided by the cooling media with the cooling valve wide open, then the batch temperature will exceed the temperature controller setpoint—TC211. If the temperature continues to rise, when the temperature reaches the setpoint of the override controller (TC211A) the feed flow rate to the reactor will be reduced to prevent the temperature from exceeding the override temperature setpoint. If the production of gas and vapor exceeds the capacity of the vent system, then when the pressure reaches the setpoint of the override controller (PC212) the feed flow rate to the reactor will be reduced to prevent the pressure from exceeding the override pressure setpoint. The control module provided for the batch chemical reactor control workshop is shown below.

By accessing the book’s web site, you may complete this batch chemical reactor control workshop using your web browser. The viewer below may be used to see the solution to this exercise.