There are generally three types of expansion machines in expansion refrigeration systems, namely low-pressure expansion machines, medium pressure expansion machines, and liquid expansion machines.
For a certain type of gas expander, the higher the volumetric flow rate of the working fluid, the higher the efficiency. General flow rate 8000Nm ³ The efficiency of the low-pressure expander mentioned above is 85-88%, and the flow rate is less than 3000-8000Nm ³ The efficiency will be as low as 70-80%.
Medium pressure expansion machines generally use one imported and one domestically produced (backup). Air volume 8000Nm ³/ The efficiency of imported expansion machines above h is 82-91% (4 points less at the boosting end); The efficiency of domestic expansion machines is 78-87% (5 points less at the boosting end).
Before starting the expansion machine, it is necessary to first blow (remove impurities in the piping system and the volute of the expansion machine), then pass the sealing gas (normally provided by the boosting end), and then carry out external and internal circulation of the oil system. After completing the interlock test, it can be started. After passing the cold test, it can be cooled and tightened; Cold start requires starting the fuel tank heater, which is not required after normal operation. At this point, the cold and hot bearings have been balanced.
The essence of a liquid expander is to use the pressure head of a high-pressure liquid to perform hydraulic work (at the same time, the enthalpy of the liquid decreases, but compared to gas, it is far different). Generally, for compressed air separation equipment above 40000 levels, a liquid expander can be used instead of a high-pressure liquid air throttle valve. Its advantage is to use the liquid expansion mechanism for cooling and expansion power generation to achieve energy-saving goals, which can generally achieve energy savings of about 2%, but its investment can reach millions of yuan.
