Method and system for recovering Fischer-Tropsch synthesis tail gas

The invention provides a method and a system for recovering Fischer-Tropsch synthesis tail gas. The recovery method comprises the following steps: decarburizing and dehydrating Fischer-Tropsch synthesis tail gas oil washing dry gas in sequence, and then carrying out first precooling, first gas-liquid separation, second precooling and second gas-liquid separation to obtain a second gas phase and C5 and above hydrocarbons; then carrying out first graded refrigeration, third gas-liquid separation, second graded refrigeration and fourth gas-liquid separation to obtain a fourth gas phase and a cooling liquid phase; performing liquid nitrogen washing on the fourth gas phase to obtain H2; and carrying out catalytic conversion on the cooling liquid phase to obtain H2 and CO. According to the invention, the oil washing dry gas obtained after the Fischer-Tropsch synthesis tail gas is subjected to low-temperature oil washing treatment is subjected to a tail gas treatment process flow consisting of a plurality of procedu