Abstract: Liquid injection into the interstage steam flow in a multi-stage compressor is controlled by calculating a saturation temperature of the fluid in the interstage and then controlling the liquid flow to reduce the incoming fluid temperature to a value a predetermined amount above the saturation temperature. In one embodiment, the fluid temperature is measured at the downstream end of the interstage conduit after it has been reduced by liquid injection. This measured temperature is used to compare with the calculated saturation temperature to determine whether to increase or decrease the liquid injection flow. In another embodiment of the invention, the fluid temperature is measured upstream of the liquid injection point.

Abstract: A steam generation system employing a flash tank feeding low-pressure steam to a compressor controls surges in the compressor by calculating the amount of steam generated based on the temperature change and flow of water passing through the flash tank and modulates the flow rate in order to maintain the steam flow above a surge limit. If increasing the water flow rate is incapable of producing enough steam to avoid surges, a recycle control recycles steam from the output of the compressor back to the flash tank. A further embodiment of the invention permits using an auxiliary source of low-pressure steam to augment the steam produced in the flash tank while maintaining the total steam flow at a level sufficient to avoid surges. The steam flow may alternatively be derived from the differential pressure between outlet and inlet of the compressor.