AdvancedTopic 90 of 100Materials & Chemical
Process control in chemical plants
PID loops regulate temperature, level, flow and composition.
In depth
PID loops control temperature, pressure, level, flow and composition. Strategies: feedback, feedforward, cascade, ratio, split-range, model predictive control. Tuning methods (Ziegler-Nichols, IMC). Interlocks and alarms provide safety. Modern plants use DCS and SIS.
Key points
- Process dynamics with dead time
- Control valve characteristics
- Operator interface
ExampleA reactor temperature loop adjusts coolant flow via a control valve.
Process control keeps temperature, level, flow and composition at their targets, so the plant runs safely, efficiently and to specification.
What is Process control in chemical plants?
PID loops regulate temperature, level, flow and composition.
Why is it important to understand process control in chemical plants?
Process control keeps temperature, level, flow and composition at their targets, so the plant runs safely, efficiently and to specification.
What is a PID controller in a process plant?
A feedback controller that uses proportional, integral and derivative actions to bring the measured variable to its setpoint.
Why is control loop tuning important?
Poor tuning can cause oscillation, slow response or overshoot, which wastes energy and can upset the process.
How is Process control in chemical plants used in practice?
Typical applications include controlling the temperature of a reactor with a jacket and a PID loop, holding the level in a feed tank constant with a valve and keeping the composition of a blended product within limits with analysers.
What should I learn before Process control in chemical plants?
Study "Fluid handling in plants" first (topic 89 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Process control in chemical plants?
Process dynamics with dead time. Control valve characteristics. Operator interface.
Can you give an example of Process control in chemical plants?
A reactor temperature loop adjusts coolant flow via a control valve.
What comes after Process control in chemical plants?
The next topic is "Process safety", which builds directly on this one.
How difficult is Process control in chemical plants?
It is classed as Advanced in Materials & Chemical (topic 90 of 100). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Materials & Chemical.