ORC, Screw Expander
In oil refineries and chemical plants, there exist large amount of hot fluids. The typical hot fluids include the hot medium water for the process, the condensed hot water, the hydrofining diesel and the hydrofining gasoline etc. These hot fluids from the process have the temperature above 95Â°C typically, and they need to be cooled down to the temperature required by the process. Â The air cooling and/or water cooling are used to cool these fluids, and the large amount of thermal energy is wasted in addition to the power and water consumptions. The thermal energy in the hot fluids can be recovered by ORC (Organic Rankine Cycle) to generate power. At the same time the hot fluids can be cooled down to the required temperatures, and thus the power and the water, which are consumed to cool the hot fluids, can be saved. The author applied single stage and cascaded ORC to recover the thermal energy in the hot fluids in refineries and chemical plants, and at the same time to cool the hot fluids to the required temperatures. For the hot fluids with large flow capacities and high required temperature drops, cascaded ORC systems are used to increase the thermal efficiency. In this paper, the author presented two ORC application cases in refineries: a single stage ORC power plant with a screw expander is used to cool down the hydrofining gasoline from the process, which properly is the first case in the world that the hot hydrofining gasoline enters the ORC directly, and a cascaded ORC power plant with screw expanders is used to cool down the hot medium water from the refining process. For the hot medium water application, the author compared the thermal efficiencies for both the single stage and cascaded ORC systems. For the same flow capacity and the same temperature drop of the hot medium water, the thermal efficiency of the cascade ORC is 13.2% higher than the single stage ORC.