Device for preparing synthesis ammonia raw material gas and LNG through liquid nitrogen wash and preparing method thereof

The invention discloses a device for preparing synthesis ammonia raw material gas and LNG through liquid nitrogen wash. The device comprises a first-order heat exchanger (1), a second-order heat exchanger (2), a third-order heat exchanger (3), an MR compressor unit (4), a liquid nitrogen wash tower (5), a tower top condenser (6), a tower top separator (7) and an LNG rectifying tower (8). A pipeline M (23) is connected with a pipeline Q (28), a mixer (35) is connected between the pipeline M (23) and the pipeline Q (28), and the mixer (35) is connected with a regulating valve II (32). The inlet end a of the liquid nitrogen wash tower (5) and the inlet end n of the tower top condenser (6) are both connected with a pipeline P (27). The top end of the LNG rectifying tower (8) is connected with the inlet end g of the tower top condenser (6). The invention further discloses a preparing method. The device for preparing the synthesis ammonia raw material gas and the LNG through liquid nitrogen wash and the preparing method thereof have the advantages that the synthesis ammonia raw material gas can be prepared, hydrocarbon such as methane in the synthesis gas can be efficiently utilized and recycled so that the LNG can be prepared, and environmental protection benefits and economic benefits are greatly increased.