they move from the feed to the product end of the shell a layer of fischer tropsch catalyst is applied to the outside of the heat transfer tubes 1 before they are sealed inside the shell 2 also shown is a gas liquid separator 7 for separating the gas and liquid leaving the reactor via outlet nozzle 5 and a liquid product pump 8 synthesis gas enters through inlet nozzle 3 and passes from side to side due to the baffles 4 as it moves down the shell 2 gas and liquid produced by the fischer tropsch catalytic reactions eventually reach the end of the shell and leave through exit nozzle 5 the product gas and liquid are separated in a separator vessel 7 a portion of the liquid is pumped with liquid product pump 8 and recycled to the feed gas and reenters the shell through the inlet nozzle 3 heat transfer fluid is fed to the inside of the heat transfer tubes 1 via nozzle 9 and exits via nozzle 10 the flow rate temperature and pressure of the heat transfer fluid are controlled to achieve the desired level of heat removal other embodiments can be described as variations of fig3 as follows the reactor is placed in a horizontal orientation or at an incline the liquid product leaving the liquid product pump 8 is separated into fractions using distillation absorption or some other method and a portion of one or more fractions is recycled to the inlet nozzle 3 a portion of the gas product leaving the gas liquid separator 7 is recycled back into the reactor.