Process for precooling, expanding and liquefying natural gas

Abstract

The invention discloses a process for precooling, expanding and liquefying natural gas. The process includes (a), compressing nitrogen at two stages, then cooling the compressed nitrogen by the aid of coolers, and precooling the cooled compressed nitrogen in multi-stream heat exchangers; (b), expanding the nitrogen by the aid of turbo expanders and filling backflow to heat exchangers; (c), secondarily expanding the nitrogen by the aid of the turbo expanders and sequentially filling backflow to the heat exchangers; (d), compressing and pressurizing propane by the aid of propane compressors; (e), enabling the pressurized propane to flow through water coolers; (f), performing cooling and depressurization to generate a gas phase and a liquid phase, filling the gas phase and the liquid phase into the multi-stream heat exchangers and precooling the natural gas and high-pressure refrigerants by the aid of the multi-stream heat exchangers; (g), cooling the natural gas by the heat exchangers at first; (h), depressurizing and cooling the cooled natural gas by the aid of throttle valves to generate a gas phase, and storing the remaining liquid phase in liquefied natural gas storage tanks; (i), filling the gas phase as backflow gas into the heat exchangers to provide cooling capacity for the heat exchangers, reheating the backflow gas and using the reheated backflow gas as regenerated gas for purifiers for pre-treating the natural gas. The process has the advantages that the natural gas can be quickly liquefied, and power consumption and the cost are low.

Description

technical field [0001] The invention relates to a natural gas precooling expansion liquefaction process. Background technique [0002] The main component of liquefied natural gas is methane, which is recognized as the cleanest energy on earth. Colorless, odorless, non-toxic and non-corrosive, its volume is about 1 / 600 of the same volume of gaseous natural gas, and the weight of liquefied natural gas is only about 45% of the same volume of water. The manufacturing process is to first purify the natural gas produced in the gas field, and then transport it by liquefied natural gas ship after a series of ultra-low temperature liquefaction. After burning, the air pollution is very small, and the heat is released, so liquefied natural gas is good. [0003] Liquefied natural gas is natural gas that becomes liquid after being compressed and cooled to its boiling point (-161.5 degrees Celsius). Usually, liquefied natural gas is stored in a low-temperature storage tank at -161.5 deg...

AI Technical Summary

Problems solved by technology

[0006] Foreign liquefaction devices are large in scale, complex in process, multi-equipment, and high in investment. They basically adopt cascade refrigeration and mixed refrigerant refrigeration processes. At present, both types of devices are in operation, and the newly put into production design is mainly the mixed refrigerant refrigeration process. , the main purpose of the research is to reduce the energy consumption of liquefaction