Apparatus and method for conducting a fischer-tropsch synthesis reaction

Abstract

In order to avoid fouling (precipitation of solid matter on cold surfaces) in heat-exchangers down-stream of the gas outlet of a Fischer-Tropsch reactor, the reactor gas stream containing hydrocarbon products that are solid at lower temperatures is fed into a liquid wash tank. Condensation of heavy oil in the liquid wash tank is effected by feeding an evaporable light oil into the liquid wash tank. Heavy oil is recovered as a bottom product from the liquid wash tank while a gaseous product is taken out of the liquid wash tank as the top product. The light oil is obtained from the wash tank top product.

1 . A process for recovering condensable products contained within an outlet gas stream from a Fischer-Tropsch reactor, comprising the steps:
 conveying a Fischer-Tropsh reactor gas stream to a condensation and separation unit;   subjecting the F-T gases to direct heat exchange in the condensation and separation unit against a stream of evaporable hydrocarbon liquid, thereby cooling the F-T gases;   condensing higher boiling components in the F-T gases;   separating the condensed higher boiling components from gaseous components; and   removing a gaseous fraction and a condensed higher boiling fraction;   wherein at least a portion of the evaporable hydrocarbon liquid stream is obtained from subsequent processing of the gaseous fraction obtained in the removing step.   
     
     
         2 . A process as claimed in  claim 1 , wherein the reactor gas stream is pre-cooled in order to produce a mixture of gaseous and liquid components before it is conveyed to the condensation and separation unit. 
     
     
         3 . A process as claimed in  claim 2 , wherein the pre-cooling comprises indirect heat exchange between the reactor gas stream and a syngas feed stream to the reactor. 
     
     
         4 . A process as claimed in  claim 1 , wherein one or more operating parameters are controlled in order to avoid condensation of water in the condensation and separation unit. 
     
     
         5 . A process as claimed in  claim 1 , wherein the gaseous fraction obtained from the removing step is subjected to a first separation step wherein the gaseous fraction is separated into a gas phase, a liquid hydrocarbon phase and an aqueous phase. 
     
     
         6 . A process as claimed in  claim 5 , wherein prior to the first separation step, the gaseous fraction is subjected to a cooling step to form a stream of gas and liquid products. 
     
     
         7 . A process as claimed in  claim 5 , wherein at least a portion of the liquid hydrocarbon phase from the first separation step constitutes the evaporable hydrocarbon liquid conveyed to the separation unit. 
     
     
         8 . A process as claimed in  claim 5 , wherein the gas phase from the first separation step is subjected to a second separation step wherein the gas phase is separated into a gas phase, a liquid hydrocarbon phase and an aqueous phase. 
     
     
         9 . A process as claimed in  claim 8 , wherein prior to the second separation step, the gas phase from the first separation step is subjected to a cooling step to form a second stream of gas and liquid products. 
     
     
         10 . A process for conducting a Fischer-Tropsch synthesis reaction to produce Fischer-Tropsch wax which comprises supplying H 2  and CO to a Fischer-Tropsch reactor, conducting the process set out in  claim 1 , and removing a wax product stream from the reactor. 
     
     
         11 . A process as claimed in  claim 10 , wherein the reaction is carried out in a slurry bubble column reactor, and wherein the H 2  and CO are supplied to a slurry in the reactor, the slurry comprising catalyst in suspension in a liquid including the reaction products of the H 2  and CO, the catalyst being maintained in suspension in the slurry at least partly by the motion of the gas supplied to the slurry. 
     
     
         12 . A process as claimed in  claim 11 , wherein a reaction temperature is in the range of 190-250° C. and a reaction pressure is in the range of 10-60 bar. 
     
     
         13 . A process as claimed in  claim 11 , wherein a H 2 /CO ratio of the gases supplied to the Fischer-Tropsch synthesis reactor is in the range of 1.1 to 2.2. 
     
     
         14 . A process as claimed in  claim 11 , wherein a superficial gas velocity in the reactor is in the range of 5 to 60 cm/s. 
     
     
         15 . A process as claimed in  claim 11  wherein, the product of the Fischer-Tropsch synthesis reaction is subsequently subjected to post-processing. 
     
     
         16 . A process as claimed in  claim 15 , wherein the post-processing is selected from de-waxing, hydro-isomerisation, hydro-cracking, and combinations thereof. 
     
     
         17 . An apparatus for recovering condensable products contained within an outlet gas stream from a Fischer-Tropsch reactor, comprising
 a Fischer-Tropsch reactor;   a condensation and separation unit;   a gas/liquid separator;   a line arranged to convey a Firscher-Tropsch reactor gas stream to the condensation and separations unit;   a condensed higher boiling fraction outlet from the condensation and separation unit;   a gaseous fraction outlet line from the condensation and separation unit arranged to convey at least a portion of the gaseous fraction to the gas/liquid separator; and   a recycle line arranged to convey evaporable hydrocarbon liquid from the gas/liquid separator to the condensation and separation unit, thereby subjecting the reactor gas stream to direct heat exchange in the condensation and separation unit against the stream of evaporable hydrocarbon liquid.   
     
     
         18 . The apparatus as claimed in  claim 17 , wherein the condensation and separation unit is a liquid wash column. 
     
     
         19 . The apparatus as claimed in  claim 17 , wherein the reactor is a slurry bubble column reactor. 
     
     
         20 . The apparatus as claimed in  claim 17 , wherein the gas/liquid separator is a liquid flash tank. 
     
     
         21 . The apparatus as claimed in  claim 17 , further comprising a heat exchanger facilitating indirect heat exchange between the reactor gas stream and a syngas feed stream to the reactor. 
     
     
         22 . The apparatus as claimed in  claim 17 , further comprising a second gas/liquid separator arranged to receive a gas stream from the first gas/liquid separator. 
     
     
         23 . The apparatus as claimed in  claim 22 , wherein the second gas/liquid separator is a liquid flash tank.