Surge protection of centrifugal compressors using advanced anti-surge control system

Arslan Ahmed Amin,Khalid Mahmood-ul-Hasan,Muhammad Taimoor Maqsood

doi:10.1177/0020294020983372

Abstract

Centrifugal Compressors (CCs) are widely used equipment to transport the natural gas over long-distance pipelines from the gas processing facility to end consumers. Surge protection is of vital importance for such compressors to avoid costly damage to machine and production loss due to process interruption. In this paper, the dynamic behaviour of CCs has been studied during four critical scenarios: high header pressure, low suction pressure, startup of the new unit, and emergency shutdown of the unit. The dynamic simulation has been carried out using HYSYS software and validated with an industrial scale CC plant. The advanced Anti-Surge Control (ASC) consists of a split PID control in contrast to conventional PID control. The simulation results demonstrate the superior performance of advanced ASC over a conventional one for the severe surge in the event of high header pressure and low suction pressure. The occurrence of surge during start-up and the emergency shutdown was handled with the full open operation of the Anti-Surge Valve (ASV). The proposed algorithm has proved successful in protecting the compressor during fast transients of the operating point towards the surge limit line. The study is significant for the oil and gas plants and other process industry professionals for designing effective ASC systems.

Highlights

Surge phenomenon in centrifugal compressorsThe pressure of the natural gas is needed to be raised to transport from remote wellhead places to the industrial and commercial regions through pipelines
The results show that the advanced PI + D based Anti-Surge Control (ASC) controller can protect the compressor in severe surge conditions caused by low suction pressure and is proved to be superior over the conventional PID controllers for the safety of Centrifugal Compressors (CCs)
The results show that a properly tuned conventional PID controller can protect the compressor in slow surging conditions caused by high header pressure and low suction pressure

Summary

Introduction

The pressure of the natural gas is needed to be raised to transport from remote wellhead places to the industrial and commercial regions through pipelines. A complete ASC consists of the following components: Surge Detection and Control Algorithm: Surge detection and control algorithm is controlling the compressor protection using discharge and suction transmitters as inputs It calculates the deviation and surge parameter and generates output setpoint for the anti-surge control valve for flow recycle. The severe surge can only be prevented by the rapid opening of the ASV which is possible with high derivative action termed as Recycle Trip Line (RTL) response. SCL has been set at 10% margin from SLL and RTL is set to 5% from SCL.[5,19] In normal and slow low flow conditions, when the operating point crosses the SCL, a PI response is activated by the controller to open the ASV. The term (qr2) reduced flow is employed that is the ratio between differential pressure (DPos) of the orifice plate and (Ps) suction pressure, received from the flow transmitter and suction pressure transmitter respectively

D Pos Ps ð5Þ

Results and discussions

Conclusions