Method and apparatus for composition based compressor control and performance monitoring

摘要

A method and apparatus controls a compressor, where the compressor inlet gas may contain water and/or non-aqueous liquid. The method includes the steps of measuring temperature at the compressor inlet and/or outlet side, measuring pressure at the compressor inlet and outlet side in order to determine a compressor pressure ratio, measuring fluid mixture density at the compressor inlet and/or outlet side, measuring individual volume fractions of gas, water and non-aqueous liquid at the compressor inlet and/or outlet side, measuring fluid velocity at the compressor inlet and/or outlet side, and determining individual flow rates of gas, water and non-aqueous liquid on the basis of the measured individual volume fractions of gas, water and non aqueous liquid and the fluid velocity at the compressor inlet and/or outlet side.

主权项

1. A method for surge protection of a compressor with an inlet and outlet side, wherein an inlet gas flow or stream of the compressor comprises time-varying amounts of water and/or non-aqueous liquid, by continuously or discontinuously measuring and/or determining various parameters of the fluids passing through said compressor, the method comprising the steps of:
a) measuring temperature at the compressor inlet and/or outlet side, b) measuring pressure at the compressor inlet and outlet sides in order to determine a compressor pressure ratio, c) measuring fluid mixture density at the compressor inlet and/or outlet side, d) measuring individual volume fractions of gas, water and non-aqueous liquid at the compressor inlet and/or outlet side, e) measuring fluid velocity at the compressor inlet and/or outlet side, f) determining individual flow rates of gas, water and non-aqueous liquid on the basis of the measured individual volume fractions of gas, water and non-aqueous liquid and the fluid velocity at the compressor inlet and/or outlet side, g) based on the determined individual flow rates of gas, water and non-aqueous liquid, determining an actual fluid mixture total volumetric flow rate of gas and liquid at the compressor inlet and/or outlet side, and h) on the basis of the determined compressor pressure ratio and the determined actual fluid mixture total volumetric flow according to steps a-g, controlling a recirculation valve position of at least one recirculation valve arranged between the inlet and outlet side of said compressor in order to ensure that the compressor does not enter into a surge regime; wherein a compressor performance is determined on the basis of the measured fluid mixture total density and determined parameters such as gas composition, gas and liquid properties and by means of a polytropic head equation:YTP=nTPnTP-1·[p2ρH⁢⁢2-p1ρH⁢⁢1]where YTP reflects that the equation is valid also for two-phase flow, and where ρH1 is the inlet bulk density of the gas and liquid mixture, ρH2 is the outlet bulk density of the gas and liquid mixture, p1 is the inlet pressure, p2 is the outlet pressure, and nTP is determined by:nTP=ln⁡(p2p1)ln⁡(ρH⁢⁢2ρH⁢⁢1)and where a compressor efficiency is then calculated according to:ηTP=YTPhTP⁢⁢2-hTP⁢⁢1where hTP2 (n=2) and hTP1 (n=1) are defined as:
hTPn=βGn·hGn+βCn·hCn+βnonAn·hnonAn+βWn·hWn where β is the mass fraction of each of the gas (G), condensate (C), non-aqueous liquid (nonA) and water (W) phases present in the flow at the inlet (n=1) and outlet (n=2).