Power Recovery in Plants & Refineries | Energy Conservation
Various processes run at elevated pressures, enabling the opportunity for power recovery from the pressure in the flue gas. In gas industry, gas treating units using absorption-stripping mechanism exhibits good application of power recovery using hydraulic pumps or other means for integration for the reduction of power consumption in this important process in any gas plant having gas treating units.
The major application for power recovery in the petroleum refinery is the fluid catalytic cracker (FCC). However, power recovery can also be applied to hydrocrackers or other equipment operated at elevated pressures. Modern FCC designs use a power recovery turbine or turbo expander to recover energy from the pressure. The recovered energy can be used to drive the FCC compressor or to generate power.
Power recovery applications for FCC are characterized by high volumes of high temperature gases at relatively low pressures, while operating continuously over long periods of time between maintenance stops (> 32,000 hours). There is wide and long-term experience with power recovery turbines for FCC applications. Various designs are marketed, and newer designs tend to be more efficient in power recovery. Recovery turbines are supplied by a small number of global suppliers, including UOP and GE Power Systems, for instance.
Many refineries around the world have installed recovery turbines. In a retrofit application in a refinery in US to replace an older power recovery turbine to enable increased blower capacity to allow an expansion of the FCC, the re-rating of the FCC power recovery train led to power savings of 22 MW.
Power recovery turbines can also be applied at hydrocrackers. Power can be recovered from the pressure difference between the reactor and fractionation stages of the process. In another application in US the oil refinery installed a 910 kW power recovery turbine to replace the throttle at its hydrocracker, operating at 160 bar. The power recovery turbine produces about 7.3 million kWh/year (assuming 8000 hours/year), and the investment was only to $1.2 million.
In gas processing power recovery units now represents an important opportunity for energy efficiency optimization.