Method for producing biodiesel through combination of tubular reactor and fixed bed reactor

The invention relates to the field of biofuel production, and discloses a method for producing biodiesel by combining a tubular reactor and a fixed bed reactor, which comprises the following steps: (1) in the presence of hydrogen, introducing a grease raw material into the tubular reactor for first hydrotreatment to obtain a hydrotreatment effluent I; (2) in the presence of hydrogen, introducing the hydrotreating effluent I into a fixed bed reactor for second hydrotreating to obtain a hydrotreating effluent II; (3) carrying out separation I on the hydrotreating effluent II to obtain a liquid hydrocarbon material flow, water and a gas material flow; (4) in the presence of hydrogen and a hydroisomerization catalyst, at least part of the liquid hydrocarbon material flow is subjected to a hydroisomerization reaction, and a hydroisomerization reaction effluent is obtained; and (5) carrying out separation II on the hydroisomerization reaction effluent to obtain the biodiesel. The method provided by the invention is