Mitigação de Surge e sistemas de controle de compressores centrífugos.

Abstract

Compression systems are used in the transmission, distribution, exploration, drilling, refining, and production of oil and gas injection. Compression systems used in oil and gás industry are based on high energy consumption compressors (a compression unit of a processing unit of natural gás which promotes compression 85kgf/cm² to 150kgf/cm², consumes on the order of 4,098,566 kWh / month); usually, centrifugal compressors, axial or reciprocating type are used. In this context, the study of control techniques that promote the reduction of energy consumption in compression systems gives rise to a current topic, relevant and with perspective of effective economic impacts. In the case of the centrifugal compressor there is the phenomenon of the "surge" during which there is an increase in energy consumption associated with impairment of the system's structural integrity. The surge is characterized by unstable operation, manifesting itself through pressure and flow fluctuations which may cause mechanical failures. The mitigation of the surge problem avoids the presence of unwanted mechanical oscillations that may compromise the structural integrity of compression units and thus increases the operational safety. The use of control techniques provide adequate performance, allow the maximization of energy efficiency and, consequently, reduce energy costs, thereby reducing the production cost. The centrifugal compressor control system using recycle valve to mitigate the surge problem. In general, these control laws do not exploit the speed control of the compressor driver. The design of the actuator control law gives rise to a subsystem that contributes effectively to reducing the compression system power consumption. However, there are few studies which explain the energy consumption in compression systems. Thus, from the centrifugal compressor model, this paper proposes to evaluate and develop models of cascaded solutions capable of performing capacity control, and anti-surge control, differently from that used in the industry, integrating yet, the valve control loop recycle.