Chemistry of hydrocarbon compounds – Miscellaneous process – e.g. – indeterminate modification of a...
Reissue Patent
1998-08-13
2001-06-12
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Miscellaneous process, e.g., indeterminate modification of a...
C422S219000, C422S227000, C585S922000, C585S924000, C502S034000, C518S700000
Reissue Patent
active
RE037229
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and a means for improving the operation of a hydrocarbon synthesis process and the distribution of catalyst in a reactive slurry comprising catalyst in hydrocarbon synthesis product and synthesis process feed gases in slurry phase reactors used in said process. Catalyst circulation is improved and catalyst distribution in said reaction slurry is made more uniform by the presence of substantially vertical conduit means in the reaction zone of the hydrocarbon synthesis process. The downcomer is a substantially vertical conduit means, open at both ends, is fully submerged in the reaction slurry, the bottom end of which substantially vertical conduit means is near the bottom of the reaction zone of the reaction process and the top end of which is topped by gas disengaging means and is below the top surface of the reaction slurry in the reaction zone of the reaction process. For simplicity the substantially vertical conduit means will hereafter be referred to as a downcomer or downcomers. The downcomer circulates the catalyst and liquid slurry from the top of the slurry back down to the bottom of the slurry, helping to prevent stagnant zones by stimulating such catalyst and liquid circulation in the reaction slurry. Such movement also promotes more uniform catalyst utilization and more uniform catalyst aging in the process while reducing the back mixing of the synthesis process feed gases. It also promotes a more uniform temperature within the reaction zone with consequent better utilization of heat transfer area.
BACKGROUND OF THE INVENTION
Slurry reactors are well known for carrying out highly exothermic, three phase, catalytic reactions. Usually called “bubble columns” these reactors have a liquid phase in which solid catalyst particles are dispersed or held in suspension by a gas phase bubbling through the liquid phase, thereby creating a slurry. These reactors provide improved heat transfer characteristics for the exothermic reaction, and the bubbling gas maintaining the catalyst dispersed in the liquid phase.
Bubble column reactors typically have a multiplicity of tubes suspended within a shell-type housing, the tubes being filled with a heat transfer medium, e.g., boiling water, which absorbs the heat generated by the exothermic reaction occurring on the shell side of the tubes in the main body of the housing.
Alternatively the reactor can be of a similar multi-tube design housed in a common shell-type housing as previously described but wherein the gas and liquid are passed through the multiple tubes which function as the reactor tubes, with effluent being removed from the upper ends of the reactor tubes and heat transfer fluid is passed through the space along the outside surfaces of the reactor tubes. The reactor tubes can be either multiple individual tubes with spaces between adjacent tubes, or multiple bundles of tubes with spaces between adjacent bundles of tubes.
Likewise the entire cross section of the reactor vessel may have a plurality of shafts disposed within it, the bottoms of said shafts being located above the reaction gas inlet but extending a distance above the top surface of the reaction slurry into the gas disengaging spaces so as to create multiple single columns of standing, non-circulating liquid with catalyst suspended and dispersed in said standing liquid. The reaction zone therefore has multiple single columns, said columns having a common bottom reaction gas introduction zone and a common upper gas disengagement space. To insure proper control of the exothermic process additional tubes can be inserted into or between the multiple single columns to function as heat exchangers.
It would be an advance if, in whatever configuration the reaction vessel may take, catalyst within the reaction vessel could be more uniformly distributed and circulated so as to insure more even catalyst aging in the course of the reaction, more effective use of the catalyst by insuring a higher probability that the maximum amount of available catalyst is in the reaction zone to promote the reaction by eliminating stagnant zones of uncirculating, standing catalyst and to provide a more uniform dispersion of catalyst throughout the reaction zone.
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Behrmann William C.
Mauldin Charles H.
Pedrick Larry E.
Exxon Research and Engineering Company
Griffin Walter D.
Simon Jay
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