Patent GB-1189610-A (GB)
Title: Recovery of Carbon.
IPC: B01D12/00
Filed: 1968-11-19
Abstract: 1,189,610. Purifying fuel gas. TEXACO DEVELOPMENT CORP. 19 Nov., 1968 [4 Dec., 1967], No. 5746/68. Heading C5E. [Also in Division C1] The unconverted particulate carbon in an effluent gas stream, as produced by the partial oxidation of a hydrocarbon fuel in the production of a synthesis gas comprising CO +H2, is recovered by scrubbing all of said carbon from the effluent stream with acidic water which is defined as water having an acidity sufficient to prevent the formation of a system upsetting emulsion, thus forming a dispersion of particulate carbon in such water, separating the cleaned gas, then mixing the acidic watercarbon dispersion with a light hydrocarbon liquid so as to form a two-phase system, one phase being a light hydrocarbon liquid-carbon slurry containing entrained acidic water, and the other a clarified acidic water containing as impurity a fractional amount of the light hydrocarbon liquid, and separating the two phases. The pH of the acidic water may be in the range 4.5 to 7 and such water may be prepared by introducing acetic, formic, carbonic, HC1, H 2 SO 4 , boric or phosphoric acid into the scrubbing zone. Preferably the entrained water is removed from the light hydrocarbon-carbon slurry and the slurry recycled as make to the process producing the effluent gas stream. The clarified aqueous phase may be treated in a vaporizing zone to remove its hydrocarbon contaminant, and the acidic water so purified returned to the scrubbing zone. If desired, the light hydrocarbon liquid/carbon slurry may be mixed in a second zone with a heavy hydrocarbon liquid, and the resulting mixture distilled when a mixture of light hydrocarbon and acidic water is taken overhead and a bottoms slurry of heavy hydrocarbon liquid and carbon withdrawn. The overhead mixture may be recycled to extract further carbon from the dispersion of carbon in acidic water, the bottoms slurry being recycled as make to the synthesis gas generator. Additional amounts of watersoluble acid may be added to the distillation step to avoid the formation of emulsions which upset the system. If desired, air may be excluded from the system which is therefore maintained in a deaerated condition and all feed streams except the raw gaseous effluent from the gas generator may be treated to scavenge oxygen therefrom, e.g. by adding hydrazine or sodium sulphide. The raw gaseous effluent may be mixed with a first stream of acidic water in a turbulent mixing zone, the resulting dispersion separated from the accompanying gas which is then washed by direct countercurrent contact with a second stream of acidified water. Alternatively the raw effluent from the gas generator is quenched using acidified water which produces a stream of raw gas containing a reduced amount of carbon, which raw gas stream is then introduced into a turbulent mixing zone where it is contacted with acidic water to remove all its remaining carbon content. The effluent from this mixing zone may be then introduced into a zone where the purified gas and the carbon dispersion produced are separated, the purified gas then entering a washing zone where it is washed with further acidic water. The carbon particles in the acidic water dispersion are said to possess structure, have a particle size of 70 millimicrons and have a surface area of 600 to 800 m2/gm.