GB650487A - Improvements in or relating to the conversion of hydrocarbons by thermal treatment - Google Patents

Abstract

Non-aromatic hydro-carbons are subjected to cracking followed by aromatization by passing the feed in parallel through a number of straight tubular-reactors, each reactor having an initial portion of high "surface <PICT:0650487/IV (b)/1> <PICT:0650487/IV (b)/2> to volume" ratio and a following portion of low "surface to volume" ratio, arranged in a furnace heated by hot gases flowing through it in the same direction as the hydrocarbons, and introducing a blanket of cooler gases into the furnace at or close to the plane passing through the junctions of the two different portions of the reactors. Petroleum naphtha or kerosene is fed through pipes 39 (Fig. 1) into vaporizers 21; and the vapours are passed through pipes 38 into reactors 14 which may be packed with metallic catalyst or with ceramic material, at a pressure between 1 and 3 atm. (gauge) and with a space velocity between 0.2 and 0.6 litres of liquid-hydrocarbon per hour per litre of reactor volume. Reactors 14 are arranged along each of the longer sides of furnace 10 (see also Fig. 2), which is fixed by burners 11 to give a temperature of 800 DEG to 900 DEG C. at the top of the furnace. Each reactor comprises a tube 15 of 3 inch diameter passing into a tube 16 of 10 inch diameter. A blanket of flue gases from the furnace. cooled to a temperature of 300 DEG to 400 DEG C., is introduced from duct 17 into the furnace through staggered jets 18, 19 so as to reduce the furnace-temperature to about 700 DEG C. from the zone of the jets down to the bottom. The gases leave the furnace through flue 12; and are cooled by passing them through vaporizing-chamber 20, or through chamber 24 which contains low-pressure steam-boiler 25, or through both. Chambers 20 and 24 are connected to ducts 33 and 17 by a system of ducts 28 to 31 having dampers 34, 35, 36, and a fan 32. The chambers are also connected to a stack (not shown) by duct 37. The quantity and temperature of the cooling gases introduced into the furnace through jets 18, 19, are controlled by means of the duct and damper system. The products leaving reactors 14 (aromatic hydrocarbons and olefin-containing gases) pass, after quenching by p means 45, through pipes 42 into off-take pipe 44. Specifications 552,216, 575,383 and 650,485 are referred to.ALSO:<PICT:0650487/III/1> <PICT:0650487/III/2> Hydrocarbons are subjected to catalytic or non-catalytic conversion in two stages, the first stage being endothermic (e.g. cracking) and the second stage being thermo-neutral or slightly exothermic (e.g. aromatization), by passing the feed in parallel through a number of straight tubular - reactors, each reactor having an initial portion of high "surface to volume" ratio and a following portion of low "surface to volume" ratio, arranged in a furnace heated by hot gases flowing through it in the same direction as the hydrocarbons, and introducing a blanket of cooler gases into the furnace at or close to the plane passing through the junctions of the two different portions of the reactors. The cooling gases may comprise a portion of the flue gases from the furnace, which have been cooled, e.g. by vaporizing the hydrocarbon-feed. Petroleum naphtha or kerosene is fed through pipes 39, Fig. 1, into vaporizer 21; and the vapours are passed through pipes 38 into reactors 14, which may be packed with metallic catalyst or with ceramic material, at a pressure between 1 and 3 atm. (gauge) and with a space velocity between 0.2 and 0.6 litres of liquid-hydrocarbon per hour per litre of reactor-volume. Reactors 14 are arranged along each of the longer sides of furnace 10 (see also Fig. 2), which is fired by burners 11 to give a temperature of 800 DEG to 900 DEG C. at the top of the furnace. Each reactor comprises a tube 15 of 3 inch diameter passing into a tube 16 of 10 inch diameter. A blanket of flue gases from the furnace, cooled to a temperature of 300 DEG to 400 DEG C., is introduced from duct 17 into the furnace through staggered jets 18, 19 so as to reduce the furnace-temperature to about 700 DEG C. from the zone of the jets down to the bottom. The gases leave the furnace through flue 12; and are cooled by passing them through vaporizing-chamber 20, or through chamber 24 which contains low-pressure steam-boiler 25, or through both. Chambers 20 and 24 are connected to ducts 33 and 17 by a system of ducts 28 to 31 having dampers 34, 35, 36, and a fan 32. The chambers are also connected to a stack (not shown) by duct 37. The quantity and temperature of the cooling gases introduced into the furnace through jets 18, 19, are controlled by means of the duct and damper system. The products (aromatic hydrocarbons and olefin-containing gases) leaving reactors 14 pass, after quenching by means 45, through pipes 42 into off-take pipe 44. Specifications 552,216, [Group IV], 575,383 and 650,485 are referred to.