Energy recovery in oil refineries by means of a Hydraulic Power Recovery Turbine (HPRT) handling viscous liquids

Chemical plants like oil refineries involve energy intensive processes. Several energy efficiency interventions are being performed in oil refineries to meet the latest emission targets, but few of them are related to the energy recovery from process liquids. In this paper, an energy recovery study of an Italian oil refinery is presented: specifically, a Hydraulic Power Recovery Turbine (HPRT), coupled with the shaft of the feed pump used in the same process, is used to replace a Pressure Reducing Valve (PRV). The machine is installed in the H2S removal process and it exploits the Selexol® solvent. A new model that predicts the Best Efficiency Point (BEP) of the HPRT in turbine mode when handling liquids different from water is discussed and validated through operational BEP data. The HPRT supplies 349.3 kW to the feed pump, leading to a yearly electric energy recovery of 2966 MWh and a maximum PayBack Period (PBP) close to 9 years considering the installation, the Carbon Dioxide Equivalent (CDE) allowances and both operational and maintenance costs. The obtained PBP is quite high, but the installation costs would be fairly lower if the HPRT is already considered in the design phase of the chemical process.