The invention disclose a full-
liquid air separation device using the cold energy of the
liquefied natural gas (LNG), comprising an air compressing and pre-cooling
system, an air purifying
system, an air separating
system and a
nitrogen circulating system capable of recycling the cold energy of the LNG which has the pressure of 8.0MPa or higher. The
nitrogen circulating system capable of recycling the cold energy of the LNG comprises a
nitrogen compressor, a wound tube
heat exchanger and a gas-liquid separator; the
gaseous nitrogen coming out of the gas separating system is made to enter the wound tube
heat exchanger to exchange heat with the LNG and then is compressed by the nitrogen compressor to have higher pressure; the
liquid nitrogen coming out of the wound tube
heat exchanger is separated into
gaseous nitrogen and
liquid hydrogen; the
liquid nitrogen coming out of the gas-liquid separator is separated into two branches, wherein one
branch of the
liquid nitrogen is fed in the air separating system to be used as the return liquid of a lower
tower to involve in the rectification of the lower
tower and to be made to carry the cold energy in the air separating system, and the other
branch of the liquid nitrogen is discharged as the liquid nitrogen product; the
gaseous nitrogen coming out of the gas-liquid separator is made to enter the wound tube heat exchanger and reheated to the temperature of the inlet of the nitrogen compressor and then made to enter the nitrogen compressor to circulate. Compared with the prior
air separation device of the same scale, the full-
liquid air separation device can save the
electric energy of more than 50 percent and the consumed water of more than 90 percent.