GB793517A - Cracking hydrocarbons to produce lighter hydrocarbons and/or fuel gases - Google Patents

Abstract

Hydrocarbons such as high-boiling petroleum oils and low-temperature carbonization tars are cracked by contacting the material with hot particles of refractory solid in a reaction vessel containing a mixing mechanism comprising two <PICT:0793517/III/1> <PICT:0793517/III/2> <PICT:0793517/III/3> shafts rotating in the same direction and having disposed thereon devices which free the mixing mechanism from excessive deposits of coke. The coke formed on the particles is preferably burned off by fluidizing them in air in a transfer line; the reheated particles are then separated from the combustion gases and returned to the reaction vessel. The shafts 31, 32 may be fitted with paddles 33, 34 (Fig. 6) or with lenticular bodies 51 (Fig. 9). The particles, which should preferably have a grain size betwene 0.5 and 2 mm. may comprise coke, sand, alumina, fireclay, or metallic silicates. The particles may be made of, or coated or impregnated with, catalytic substances. The reaction, which is preferably carried out in the presence of steam, may be effected between 600 DEG and 900 DEG C. to produce low-boiling fractions; or it may be effected at 1000-1500 DEG C. to produce heating gas comprising carbon monoxide and hydrogen. Air is added to the hydrocarbon feed when it is desired to produce a gas mixture suitable for ammonia synthesis. Products rich in olefines, diolefines, benzene and acetylene can be obtained when the reaction-period is kept short by rapidly cooling the vapours leaving the reaction vessel. In Fig. 1, contact particles at 950 DEG C. flow as a compact mass through ceramic-lined pipe 5 into mixing mechanism 1. The liquid hydrocarbon, together with steam if desired, is preheated to 300 DEG C. by heat-exchange with the vaporous products or with hot combustion gases leaving separator 3, and is then introduced into the mixing mechanism through line 4. About 30 to 80 parts by weight of contact particles are used per part of feed. The mixing mechanism comprising two rotating, water-cooled shafts on which forwardly-curved paddles of sheet metal are mounted. The vaporous products are quenched with water spray in cooler 14. They are cooled to 400 DEG C. if they are to be used to preheat the feed or the combustion air, or the feed water; but they are quenched to 50 DEG C. if no after-reaction is allowable. The contact particles discharged from reaction vessel 1 flow into container 9. The particles, which now have a temperature of 500 DEG C., say, then pass through pipe 7 into line 2, up which they are conveyed by air introduced through pipe 10. The coke is burned off the particles in line 2 and they are reheated to 950 DEG C. The combustion gases are separated from the reheated particles in separator 3. The hot gases are used to raise steam in boiler 13. They may also be used to preheat the air introduced through line 10. Furnace 15 is employed, if required, to supplement the heat obtained by combustion of the deposited coke, or if this coke is to be utilized in another manner. If an after-treatment of the vaporous products is to be effected, they may be passed to a second reactor instead of to cooler 14; alternatively the vapours may be re-introduced into reactor 1 at a position between the ends, or they may be introduced into container 9. Specification 793,518, [Group XII], is referred to.