GB713977A - Improvements in or relating to fluidised bed processes for the conversion of hydrocarbons - Google Patents

Abstract

<PICT:0713977/III/1> In endothermic processes for converting hydrocarbons by introducing a hydrocarbon fluid into a reactor 5 in the lower part of which is maintained a dense fluidized bed 3 of catalytic or inert contact material, a stream of contact material is withdrawn at 9, mixed with a stream of heat-carrier particles in line 11, being heated thereby, the contact material and heat carrier are separated at 13, as shown by elutriation with steam introduced at 6, the contact material returned to the reactor and the heat carrier taken by line 16 to a heating zone 18 which as shown is a transfer line burner. After reheating the heat carrier solids are returned by stand-pipe 11 to the mixing zone at the base of the pipe. The pipe 16 acts as a depressurizer for the heat carrier, thus avoiding pressure reducing valves and consequent attrition. The heat carrier solids should have a standpipe density of 30-200 pounds per cubic foot and may be metal, metal oxides, ceramic particles, silica or carborundum. The heat carrier may be physically or chemically conditioned to promote combustion in the burner by using high surface area metals and/or by using a combustion catalyst comprising chromium or copper &c. coated on a base material such as sponge iron, alumina or silica gel. Fuel for the burner 18 may be gas supplied at 20, part of which may be burned in an auxiliary burner 23, or large coke particles from the reactor allowed to remain with the heat carrier solids. Part of the reheated solids may be returned to the burner by line 28. A coking process is described in which a crude residuum of boiling range in excess of 900 DEG F., which may be cut back with naphtha, is preheated to 700 DEG F. and injected by line 1 into reactor 5 maintained at a temperature between 800 and 1400 DEG F. and pressure between 25-300 p.s.i.g. The reactor contains coke or other inert particles of 40-300 microns in diameter in an amount between 0.1 and 10 pounds per pound per hour of feed. A dense fluidized bed is maintained by steam introduced at 6. The hydrocarbon residence time is 5-50 seconds. Coke is continuously withdrawn at 9 and mixed with stainless steel shot of 200-500 microns diameter at 1000-2000 DEG F. in line 11. The shot and reheated coke are separated in elutriator 13 by the steam and the coke returned directly or via an intermediate zone to the reactor. In the mixing zone 11 additional products are released from the coke resulting in a dry coke product with a reduced agglomeration tendency part of which may be withdrawn as product from the upper part of elutriation zone 13. Such coke may then be heated still further by shot from line 11 in a separate zone. The feed may be introduced above the bed instead of into the bed as shown, and fresh feed may be added to the mixing line 11 or elutriator 13 or mixed with recycle coke in a separate zone. In addition to coking, the operations of hydroforming, the catalyst being heated by contact with metal shot independently of the normal catalyst circulation, thermal cracking, vis-breaking, sulphur recovery and dehydrogenation are referred to.