Ultralow temperature processing method and ultralow temperature processing device for liquefied natural gas (LNG) equipment

The invention discloses a method for conducting low temperature processing by utilizing liquefied natural gas (LNG), that is, low temperature gaseous natural gas produced during vaporization of the LNG is utilized to cool work pieces to be processed under an air isolated condition, and the gaseous natural gas already absorbing heat is used as fuel of a natural gas engine, so that dynamic of low temperature processing can be directly provided. According to the method, the LNG absorbing energy during vaporization is fully utilized to provide an ultralow temperature processing environment, and the gaseous natural gas of the LNG is directly used as a transmission medium, so that cooling media are avoided from being lost and the method has the advantages of energy conservation and environmental protection; and meanwhile, the processing and manufacturing environment and the working environment of LNG equipment are consistent, thereby facilitating the stability of the low processing temperature. A device implementing the method comprises an LNG storage tank, a vaporizer, a buffer storage tank, the natural gas engine, a transmission device, a vacuum pump, a sealing box body, a processing unit, a thermal insulating pipeline, stop valves, connecting switches, a pressure gauge and a safety valve.