Advanced Anti-Surge Control Algorithm for Turbine Driven Centrifugal Compressors

 

Centrifugal compressors are widely used for natural gas transportation by increasing the pressure of the gas. Surge is an inherent phenomenon in a centrifugal compressor, defined as reversal of fluid flow which can possibly damage the machine. Anti-surge control is an important control for safety of the compressor and it can keep the compressor always running in the safe area right to the surge line. In this paper, simulation results of the surge phenomenon occurring in a centrifugal compressor in various conditions such as high header pressure, low suction pressure, start-up and emergency shutdown of the unit are presented and their control strategies are discussed. Dynamic simulation of the centrifugal compressor is carried out in HYSYS. Conventional PID and Advanced (PI plus Recycle Trip) controllers are implemented to check their performance. Advanced controller proves to be superior to simple PID controller in protecting the compressor in severe surge case. Start-up and shut down surge was prevented by fully opening the anti-surge control valve.