Device and method for manufacturing liquefied natural gas and hydrogen-rich products out of high methane gas

The invention relates to a device and method for manufacturing liquefied natural gas and hydrogen-rich products out of high methane gas. The device comprises a mixed refrigerant compressor refrigerating system, a precooling system, a liquefying cold box system and a nitrogen compressor system. The method comprises a mixed refrigerant cycle process, a high methane gas liquification and separation process and a nitrogen refrigerant cycle process. Low-temperature hydrogen-rich gas and nitrogen-rich gas generated by rectifying towers and low-temperature nitrogen evaporated out of liquid nitrogen on the outer portion of a condenser are used for undercooling the liquid nitrogen before the liquid nitrogen enters a condensing evaporator, thereby being different from traditional undercooling of the liquefied natural gas; heat exchange curves of cold fluid and hot fluid in the whole heat exchanger process are better matched, the temperature difference of heat exchanger cold ends is smaller, heat exchange efficiency is