The invention discloses a method and a device for preparing liquid CO2 (carbon
diode) by cold energy of LNG (
liquefied natural gas). The method comprises the following steps of pumping the LNG into a tube of a shell-and-tube
heat exchanger, releasing the potential heat of the LNG in the tube of the shell-and-tube
heat exchanger, cooling and liquefying the lower-temperature gaseous CO2, sending the gasifying byproduct of the LNG as a cold source into a multi-strand flow plate fin type
heat exchanger, cooling the raw CO2, then sending into a CO2 compressor, cooling the outputted high-pressure and high-temperature CO2, raising the temperature of the LNG, and gasifying the LNG into the normal-temperature
natural gas with the temperature of 10-20 DEG C; sending the cooled CO2 into a shell of the shell-and-tube heat exchanger, dividing the liquid CO2 flowing from an outlet of the shell of the shell-and-tube heat exchanger into two branches, sending one
branch into a liquid CO2
storage tank, and sending the other
branch into a
dry ice machine to prepare
carbon dioxide ice. The method has the advantages that the gradient utilization of the cold energy of the LNG is realized, and the
utilization rate of the cold energy of the LNG is high; the preparation pressure of the liquid CO2 and the
carbon dioxide ice is decreased to 0.6-1.0MPa by the cold energy of the LNG, the gaseous CO2 at the inlet of the compressor is cooled to the temperature of -40 to -30 DEG C, and finally the effect of saving the energy by more than 58% is realized in comparison with the effect of the common low pressure method.