The invention concerns a device for producing liquid hydrocarbons by Fischer-Tropsch synthesis on solid catalyst particles in a three-phase bed reactor, said device being equipped with at least one filter cartridge mounted in a filtering zone inside said reactor, said filter cartridge comprising: a filter for separating the filtrate of the solid catalyst particles, a cylindrical casing, and inner element having the shape of a hollow cylinder open at its ends and mounted substantially coaxial relative to the longitudinal axis of the casing, an annular chamber delimited by the casing and the walls of the inner element, said chamber being designed to collect the filtrate, and a discharge conduit for said filtrate, wherein the walls of the inner element of the filter cartridge are at least partly formed by the filter of the cartridge.