GB883751A - A continuous process for the thermal decomposition of a gaseous or vaporous hydrocarbon to coke and hydrogen - Google Patents

Abstract

<PICT:0883751/III/1> In a continuous process for the thermal decomposition of a hydrocarbon at the surface of heated coke in a fluidized or moving bed to deposit carbon on the coke and produce hydrogen, a portion of the coke is recycled to the process after preheating by passage downwards through a burner vessel first in the freely falling state, and then as a moving bed, in countercurrent to air injected into the vessel both above and below the moving bed so as to form carbon monoxide by partial oxidation of the coke in the moving bed and burn the carbon monoxide above the bed without substantial oxidation of the carbon in the freely falling state. The air may be preheated by indirect heat exchange with the combustion product gas. The hydrocarbon may be preheated by indirect heat exchange with the product hydrogen gas to 1000 DEG F. in a conventional tubular gas heater or to 2000 DEG F. in a regenerative system in which coke particles are recycled between heat absorption and recovery vessels. The hydrocarbon may be in the form of natural gas, naphtha or refinery tail gas from which hydrogen sulphide, oxygen, carbon monoxide and carbon dioxide have been removed. The hydrocarbon-decomposing coke particles may have a particle size of 1/16 -1 inch, preferably 1/4 inch, the moving bed may have a depth of 1/2 -6 feet, preferably 1-2 feet, and the coke particles may fall freely for 10-90 feet, preferably 30-50 feet. The coke particles may be heated to 2000 DEG 3000 DEG F., preferably 2400 DEG F., in the burner vessel. As shown, coke particles are recirculated to a burner vessel 20 from a line 6, a cracking vessel 5, lines 8 and 10, an air lift 14, a storage hopper 15 and a line 16. Air is injected into a moving bed 19 in vessel 20 from a line 25 and above the bed from a line 24, and combustion product gases are removed from the vessel via a line 26. The enlarged coke particles from vessel 5 are reduced in size in line 8 and the fines are removed as product through line 9. The product hydrogen passes from cracking vessel 5 via line 7 to a heat recovery vessel 28 up which it passes in countercurrent to coke particles which are recycled to the vessel via line 3, hydrocarbon preheat vessel 2, line 29, bucket lift 30, line 31, hopper 32, and line 33. The hydrocarbon passes to cracking vessel 5 via line 1, preheat vessel 2 and line 4. Conditions in the various vessels are specified.