GB755463A - Improvements in method and apparatus for thermolytic and pyrolytic gas generation - Google Patents

Abstract

<PICT:0755463/III/1> A process for thermally cracking normally liquid hydrocarbons to obtain fuel gases and liquid products comprises passing a first stream of heat transfer pebbles, initially at a temperature sufficiently high to cause thermal cracking of the hydrocarbons and preferably at 1400 DEG -1600 DEG F., as a compact downwardly moving bed through a first contacting zone; passing a second stream of heat transfer pebbles, initially at a temperature low enough to cause condensation of a portion of the reaction products from the thermal cracking and preferably at 750 DEG -800 DEG F. or temperatures between 600-1000 DEG F., through a second contacting zone a portion of which is in open communication with the first zone, the hydrocarbons being contacted with the pebbles of the first zone and the products of the reaction are passed through the pebbles of the second zone thereby to condense on these pebbles some of the tars and gums in the reaction products. As shown in the drawing heat transfer pebbles, for example hard carbon balls of 1/4 -\ba3/4 inches in diameter, are fed from a heater 15 to the upper portion 12 of a first contacting zone, to the lower portion 11 of which hydrocarbons are fed through a preheater 40 and 41 from a tank 37. The products of reaction pass through a gap in the wall 10 dividing the first and second contacting zones and into the stream of pebbles descending through the second zone 17 Uncondensed reaction products are withdrawn through line 55 and are separated into gaseous and normally liquid components in a fractionating column 62. Heavy botvy bottoms are sent by line 64 to the upper portion 12 of the first contacting zone and preferably are also in part circulated through line 55 via line 73 to keep line 55 clear of deposits. Pebbles to the zone 17 are supplied from a hopper 18 in which they are heated or cooled to bring them to the desired temperature. Pebbles from both zones are collected in the device 23 which controls the rate of flow of the pebbles through each zone. All the pebbles are returned to a receiver 27 by a gas lift in line 26 and are then fed in their correct proportions to heater 15 and hopper 18. The pebbles in heater 15 may be heated by combustion of the carbon deposited on the pebbles or by combustion of a fuel gas the flue gases are, after cooling in cooler 57, used for the gas lift in line 26. The rates of flow of the pebbles are controlled such that the pebbles leaving both zones are "dry" and preferably such that the products leaving the second zone are at the temperature of the incoming pebbles and the pebbles leaving the second zone are at the temperature of the first zone at the point where the two zones are in open communication. Alternatively the flow of pebbles in the second zone is increased over the flow which gives the above temperature conditions. The cracking stock may be any heavy hydrocarbon such as Bunker-C fuel oil, tars, light oils or other petroleum products. Employing a Bunker-C fuel oil and with a temperature of 1550 DEG F. in the chamber 11 a fuel gas of about 1000.B.Th.U. is obtained.