Integrated plate-fin heat exchanger

The utility model discloses an integrated plate-fin heat exchanger which comprises a closed reactor main body of a plate-fin heat exchanger structure, and the reactor main body sequentially comprises a pre-cooling section, a main heat exchange section and a supercooling section from top to bottom; two paths (a first expansion air channel and a second expansion air channel) which are completely symmetrical are arranged in the pre-cooling section and can be switched according to needs. According to the utility model, the resistance of low-pressure nitrogen and waste nitrogen in the three devices, namely the precooler, the main heat exchanger and the subcooler, which are connected through pipelines can be reduced, the cross section is reduced, meanwhile, the pipelines among the three devices are reduced, the piping is simple, and the space of the cold box is saved. The utility model has the advantages that two independent precoolers are combined on one main heat exchanger, so that the number of equipment is redu