Method and apparatus for composition based compressor control and performance monitoring

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 side 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 and 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 and/or the measured temperature and/or the measured fluid mixture density at the compressor inlet and/or outlet side 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.