Quench control is used in applications where cooling of the hot recycle gas is achieved by direct mixing of a cold multi-phase gas/liquid. Quench is commonly used in refrigeration applications as the liquid for quenching is produced by the refrigeration compressor. Simple quench controllers maintain temperature at a given set point using a standard PID loop and are slow to react to fast changes in recycle. This type of control does not account for pressure changes which affect the gas dew point and often have set points that are conservative which leads to excessive quenching.
Advanced quench control leads to efficient operation
The CCC Quench controller uses the saturation curve of the refrigerant gas and suction drum pressure to accurately determining a temperature set point. The set point is configured as an offset from the saturation curve as shown below.
Through coordinated control with CCC Antisurge control, the Quench controller will quickly add quench flow in anticipation of temperature increase when the recycle valve opens rapidly. This prevents large swings in suction drum temperature. In addition, the Quench controller will only add quench when the recycle valve is open which prevents liquid build up.
Some of the key features of the CCC Quench control application include:
- Coordinated control with CCC Antisurge controller
- Feed forward control
- Automatic sequencing of quench valve
- Continuous calculation of temperature set point
- Pre-defined saturation curves for Ammonia, Ethylene, Propylene and Propane
- Remote set point offset to allow for operator adjustment
- Set point offset high and low clamps