Modeling of Multistage Air-Compression Systems in Chemical Processes

A systematic modeling method is proposed to predict the overall efficiency and power requirement of a multistage air-compression system consisting of a multistage compressor, a multistage expander, and an electric motor/generator. First, under a lack of measurements at the interstages of the multistage compression system, a calculation method of the overall efficiency is developed based on thermodynamic compression and expansion equations. Then, the prediction structure of the overall efficiency and actual power consumption/generation rate of the compression system is presented, where either partial least-squares models or artificial neural network models can be employed to predict unknown state variables and the overall efficiency, which are, in turn, used to predict the actual power consumption/generation rate based on compression and expansion equations. Finally, to verify the proposed modeling method, it is applied to two industrial compression systems of a terephthalic acid manufacturing process, and...