Patent GB-839806-A (GB)
Title: Recovery of finely divided solids
IPC: B04C5/081
Filed: 1958-06-10
Abstract: <PICT:0839806/III/1> Oil to be cracked is supplied by a pipe 162 to a line 158 to which is also supplied hot regenerated catalyst such as silica-alumina, silica-magnesia, silica-alumina-magnesia, or acid-treated bentonitic clay.  The particle size of the catalyst ranges from 10-150m , the bulk of the particles lying in the range 20-80m , and 10-30% by weight of the particles lying in the range 10-40m  to ensure good fluidization.  The oil-catalyst mixture enters a fluidized bed 168 within a reactor 150.  In the reactor the temperature lies between 850-1050 DEG  F., the catalyst-to-oil weight ratio lies between 5-20, and the weight of oil per hour per weight of catalyst lies between 0.5-60.  Cracked vapours rising from the bed are separated from catalyst particles in cyclones 176, 188, the vapours finally discharging through a pipe 202 and the particles being returned to the bed.  During cracking catalyst is removed from the reactor and is fed by a line 214, together with air supplied by a pipe 216, to a fluidized bed 220 in a regenerator 152.  Gases rising from the bed 220 are separated from catalyst particles in cyclones 226, 230, the particles being returned to the bed to pass eventually through a stand-pipe 164 into the line 158.  In a hydroforming process (see Group IV (b)) the catalyst such as alumina-molybdena, alumina-platinum or alumina chromia has a particle size distribution which is the same as that of the catalyst used for cracking.  A specified alumina molybdena catalyst containing about 9% molybdena consists of 10 wt. per cent of 20-40m  particles, 72 wt. per cent of 40-80m , and 18 wt. per cent over 80m .ALSO:A reactor 10 is supplied with hot regenerated catalyst particles through a line 14, naphtha at 750-1050 DEG  F. and at 100-750 p.s.i. through a line 24, and hydrogen or hydrogen containing gas at 1050-1200 DEG  F. by a line 34.  The catalyst such as alumina-molybdena, alumina-platinum or alumina-chromia has a particle size ranging from 10-150 m , the bulk of the particles lying in the range 20-80 m , and 10-30% by weight of the particles lying in the range 10-40 m  to ensure good fluidization.  Hydrogen and naphtha vapours rising from the fluidized bed 36 formed within the reactor are separated from catalyst particles in cyclones 46, 56, 66, the particles returning to the bed and the gas and vapours being discharged by a pipe 78 to fractionating <PICT:0839806/IV (b)/1> means.  Some of the excess hydrogen produced in the reactor is removed from the gases leaving the fractionating means to form a hydrogencontaining gas of about 40-80% by volume of hydrogen which is recycled to the reactor. During reforming catalyst withdrawn from the reactor by a line 82 is mixed with air from a pipe 92 and fed to the fluidized bed 98 of a regenerator 12. Gases rising from the bed 98 are separated from catalyst particles in cyclone separators 105, 107, 109, the particles being returned to the bed to eventually pass to the line 14.ALSO:Fine particles are removed from particle laden gas by directing the gas through cyclones arranged in series, the inlet velocity of the last cyclone being at least 50% greater than that of the first cyclone. The increase in inlet velocity may be obtained by using a last cyclone which is smaller than the first, or by introducing steam or a gas into the pipe connecting the penultimate and last cyclones.  The series of cyclones may be arranged within reactors for reforming or cracking hydrocarbons, or in the cokers of such apparatus.  Each cyclone has a dip leg extending into a bed of a fluidized catalyst, the leg discharging on to a shield.  The Specification describes a series of cyclones in which the velocity at the inlet of the last cylone is less than 50% greater than that of the first cyclone. Dimensions of cyclones having tangential inlets are given.