GB883579A - Improved hydrocarbon conversion process - Google Patents

Abstract

<PICT:0883579/III/1> <PICT:0883579/III/2> Carbon is deposited from a gaseous or vaporous hydrocarbon on to resistance-heated carbon-containing particles, e.g. coal or coke, in a moving or fluidised bed of the particles. The hydrocarbon may be methane or naphtha. The methane may be in the form of natural gas or refinery tail gas which has been scrubbed to remove hydrogen sulphide and carbon dioxide. Direct or alternating current may be used. The hydrocarbon is preferably passed in counter-current to a moving bed of coke particles, a portion of the coke product, e.g. 75-80%, being recycled. In the decomposition of methane, 35-70 lb., preferably 42-56 lb., of coke per 1000 cu. ft. of product hydrogen may be recycled. The bed may move upwards or downwards. In the former case a screw or piston feeder may be employed. The reaction temperature may be 1800 DEG -3000 DEG F., preferably 1900 DEG -2500 DEG F. The voltage drop may be 0,1-1000 volts, preferably 3-10 volts, per inch. The moving bed may have a density of 40-75 lb. per cu. ft. The pressure in the reaction chamber may be 65 p.s.i.g. 30 K.W.H. per 1000 cu. ft. of methane may be consumed. The contact time may be 0,5-20 sec., preferably 2-5 sec. The coke particles may have a diameter of 0,05-10 inch, preferably 0,18-0,4 inch. A portion of the circulating coke may be subjected to size reduction or may be replaced by fresh coke. Reduction may be effected by the use of jets of hydrogen or methane in the reaction chamber or by impact against a target in a separate vessel. A portion of the hot product hydrogen may be recycled and mixed with the feed hydrocarbon. A liquid hydrocarbon may thereby be vaporised. Heat may be transferred from product gas to feed hydrocarbon by the circulation of metallic or ceramic beads, sand, or graphite. The product may have a resistivity of 0,030-0,036 ohms per inch and a particle density of 110 lbs. per cu. ft. As shown in Fig. 1, a hydrocarbon feed is admitted to a reaction chamber 10 from a conduit 19 and optionally from a conduit 20, "grinding" gas, e.g. hydrogen or methane, may be admitted from a conduit 23, and product gas is withdrawn from a conduit 21. Coke is passed from a pressurised bucket lift 16 via a storage hopper 26 to the top of the reaction chamber 10, is electrically heated therein by means of a plurality of anodes 14 and cathodes 15, a portion of the product coke is withdrawn through conduit 24 and the remainder is recycled to bucket lift 16 via conduit 25, in which it is cooled by means of a water spray 27. Fresh coke may be added or recycled coke may be withdrawn via conduit 18. In a fluidised bed process the coke particles may have a size of 20-100 mesh and the bed may have a density of 40-60 lbs. per cu. ft. As shown in Fig. 3 a fluidised bed of coke particles is maintained in a reaction chamber 100 by the addition of feed hydrocarbon through line 114 and optionally through 116 and fluidising gas, which may be methane, hydrogen or an inert gas, through line 112. A portion of the product coke is removed through conduit 115 while the remainder is reduced in size by means of the fluidising gas. Feed hydrocarbon is pre-heated in chamber 102 by passage in countercurrent to granular solid which has been heated in chamber 101 by passage in countercurrent to the product gas. The cooled solid is recycled to chamber 101 via lift 103. Fine coke particles are removed from the product gas after passing through chamber 101 in a cyclone separator 108.