Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By addition of extraneous agent – e.g. – solvent – etc.
Reissue Patent
1998-08-13
2001-02-06
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Purification, separation, or recovery
By addition of extraneous agent, e.g., solvent, etc.
C208S188000, C208S950000, C423S650000, C518S702000, C518S705000
Reissue Patent
active
RE037046
ABSTRACT:
FIELD OF INVENTION
This invention relates to a process of recycling condensate from a hydrocarbon or alcohol synthesis, wherein the condensate comprises water and orgaic compounds such as oxygenates, alcohols, and hydrocarbons, which comprises contacting the condensate with a hot gaseous mixture, preferably comprising CH
4
and steam, to strip organic compounds and steam from the condensate; recovering a gaseous stream comprising the organic compounds; and separately recovering the purified liquid water of the condensate.
BACKGROUND OF THE INVENTION AND PRIOR ART
Carbon monoxide and hydrogen may be reacted over a suitable catalyst to produce hydrocarbons and oxygenated compounds (such as aldehydes and alcohols) containing one or more carbon atoms. Perhaps the best known of such processes is the Fischer-Tropsch process which involves the catalytic hydrogenation of carbon monoxide to produce a variety of products ranging in size and functionality from methane to higher alcohols. The methanation reaction was first described by Sabatier and Senderens in 1902. The later work of Fischer and Tropsch dealing with higher hydrocarbons was described in Brenstoff - Chem. 7, 97 (1926).
The product stream of a Fischer-Tropsch reaction or hydrocarbon synthesis will in general comprise hydrocarbon wax and a condensate. This condensate will typically comprise water and such compounds as hydrocarbons, alcohols, and other oxygenates; water being the predominate component. The desired heavy hydrocarbon product generally can be separated by sedimentation from the remaining liquid phase or condensate. The separation is not necessarily complete, though, and often the condensate will have present in it some of the lower molecular weight hydrocarbons and oxygenates in the liquid phase. This contaminated condensate is of little or no commercial value The oxygenates are known to cause corrosion while the hydrocarbons may cause foaming. Thus, the condensate is normally passed to a water treatment facility where it undergoes typical water treatment steps, such as anaerobic digestion and biological oxidation, in order to remove the contaminants from the clean water.
It is known in the art to recycle the original condensate from a hydrocarbon synthesis or alcohol synthesis to a process where that condensate can be used as a supplemental reactant in the feedgas, thereby enriching the feedgas. European Patent Application No. 168892 discloses the recycling of organic products of a Fischer-Tropsch, methanol or oxo synthesis as a supplement to the feedgas to a steam reforming reaction. The recycled products increase the product yield and thermal efficiency of the steam reforming reaction.
The need exists in the art for a process of stripping the organic compounds or contaminants from the recycled condensate to produce a purified water stream, thereby eliminating the need for the complex and expensive water treatment processing while at the same time producing a stream of oxygenates, steam, and other organic compounds for use as a reactant in a feedgas to some other process, particularly a synthesis gas generation process.
SUMMARY OF THE INVENTION
The present invention is directed at the purification of a typical condensate stream from a hydrocarbon synthesis or alcohol synthesis process. The condensate typically comprises water and contaminants, such as lower molecular weight hydrocarbons (after the desired heavier hydrocarbons have been separated), alcohols, and other oxygenates; water being the predominate component. The condensate is contacted with a hot gaseous mixture comprsing a light hydrocabon gas, preferably comprising CH
4
, and steam. The hot gaseous mixture strips the contaminants from the condensate leaving a stream of purified, clean water. The purified water has had about 80-90% of the contaminants removed. One advantage to this invention is that it provides an easy and cost saving process for purifying the condensate from synthesis processes without the need for expensive water treatment facilities.
In the above process, the contaminants are stripped from the condensate as a gaseous stream comprising lower molecular weight hydrocarbons; alcohols; other oxygenates; a light hydrocarbon gas, preferably comprising CH
4
; and steam. Preferably, this light hydrocarbon gaseous stream, preferably CH
4
-containing, is used as feedgas to a synthesis gas (CO/H
2
) generation process or to any other process with suitable reictant requirements.
The invention also relates to a method of producing heavy hydrocarbons comprising reacting CO and H
2
over a catalyst at reaction conditions; separately recovering the heavy hydrocarbons from the condensate; contacting the condensate with a hot gaseous mixture preferably comprising CH
4
and steam to strip the condensate of any contaminants such as lower molecular weight hydrocarbons, alcohols, and other oxygenates; recovering a gaseous stream comprising the contaminants, CH
4
, and steam; and converting the CH
4
-containing stream to CO and H
2
. Preferably, the CH
4
-containing gaseous stream is converted to synthesis gas (CO/H
2
) by a catalytic fluidized bed synthesis gas generation process or any combination of steam reforming and partial oxidation reactions with heat integration between the reactions. The CO and H
2
produced may then be used as feedgas in producing the heavy hydrocarbons.
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Brennstoff-Chem. 7, 97, Apr. 1926.
Carlson Edwin D.
Hildinger Henry W.
Exxon Research and Engineering Company
Griffin Walter D.
Simon Jay
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