PCS 7 Unit Template "Stirred tank reactor with Kalman filter" using the example of the Chemical Industry
Continuously stirred tank reactors (“CSTR”) with jacket cooling are widely used in the chemical industry. They are used, for example, in the production of fine chemicals, pigments, polymers, and medicinal products and can be run in batch, semi-batch or continuous operation.
The varying production conditions, the wide operating range, and the nonlinear process dynamics generate special requirements with respect to feedback and feedforward control of batch processes.
Nevertheless to perform an accurate control, online optimization and monitoring of processes require precise knowledge of the status of the respective process at all times. However, only in rare cases it is possible to measure all the states of the reactor comprehensively using real sensor equipment. While some process variables are measured continuously and almost instantaneously with the help of sensors, other variables can often not be determined at all or only with great technical effort. .
The simulation of a dynamic process model in the soft sensor in parallel to the real process allows the reactor, with its thick steel jacket, to virtually become a "transparent reactor". This allows the observation of all modeled inner states of the reactor even if they cannot be registered by measurement equipment.
This application example contains a universal stirred tank reactor that is employed for the production of diverse polymers with different recipes. Here, an extended Kalman Filter serves as a soft filter for the monitoring of the chemical reaction.
The values calculated online by the soft filter can be used to advantage in various ways:
Calculation of the current speed of reaction and the heat released by the exothermic reaction. The reaction exothermicity can be used for feedforward disturbance compensation in temperature control.
Calculation of the monomer mass remaining in the reactor. When the raw material has been used up, the batch can be ended. This way the batch recipe control can be optimized with respect to minimization of batch throughput time.
Calculation of heat transfer from reactor to cooling jacket in order to detect the build-up of deposition (fouling). This information is helpful when planning cleaning cycles.
A stirred tank reactor as part of a process plant
SIMATIC PCS 7 V9.0
Equipment Modules for SIMATIC PCS 7 using the example of the Chemical Industry
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