For carrying out the Fischer-Tropsch synthesis of heavy paraffins starting from syngas (CO + H-2), a multi-stage bubble column slurry reactor design is carried out. The advantages of this reactor configuration with respect to a conventional slurry reactor design, consisting of one well-mixed stage, are (a) increased syngas conversion, and (b) increased reactor productivity. The multi-stage bubble column construction requires installation of additional cooling surface area in order to keep the exothermic reaction within the desired temperature limits.