Patent GB-1532224-A (GB)
Title: Collection and recovery of thermal carbon black
IPC: C09C1/48
Filed: 1976-06-22
Abstract: 1532224 Thermal carbon black JONES GAS PROCESS CO Ltd 22 June 1976 [27 June 1975] 27307/75 Heading C1A A method of collection and recovery of thermal carbon black, produced in a generator in a heat and make cyclic process by pyrolysis of liquid or gaseous hydrocarbon feedstock comprises passing the pyrolysis products of the "make" period and the products of combustion of the heating period through the same bag filtration unit after controlled cooling, separate outlet paths being provided downstream of the filter unit for the filtered "make" gas free of carbon black and the filtered combustion products gas from the heating period, and directing the "make" gas and combustion products gas to their respective outlets in accordance with the timing of the heating and making cycles. The control means may comprise diverting valves whose operation is co-ordinated with the changeover between the heating and making parts of the cycle, suitably by utilizing a gas density sensitive means which responds to variations in the density of the gas passing through the bag filtration unit corresponding to the "make" and combustion product gases. Such valves may be operated after a period from the changeover of the heating and making cycles corresponding to the predicted time for the gases to travel from the generator to the diverting valves. Desirably, the controlled cooling of the gases is effected by injection of coolant into the gases, the amount of coolant injected being controlled by gas temperature sensing means, the filtered make gas is further cooled and dehumidified before being passed to its respective outlet and thence to storage means and the filtered combustion products are vented to atmosphere. Black is preferably discharged from the filter unit only while inert combustion product gases are passing therethrough. In apparatus as shown, thermal carbon black is produced by pyrolysis of a liquid or gasesous hydrocarbon feedstock in an alternating flow generator 10 having two similar chambers 12, 14 containing refractory checkerwork acting as a heat reservoir, taking up heat during the heating period and giving up heat to pyrolyse the feedstock during the making period, and seprated by a partition 10, with a transfer passage 18 at the bottom. Feedstock enters at inlets 20, 22, and air at inlets 24, 26 supplied through common supply line 32; 28, 30 are product outlets which come together in a common conduit 34. The alternate air and feedstock inlet passages and products outlet passages are controlled by valves, operated by control system 35, so that only one of the air or feedstock inlet passages and one of the products outlet passages is open at a time, and while air or feedstock is being supplied to one chamber the products are being taken from the other chamber. Incoming air is warmed, and the outgoing products gas cooled, by passage through heat exchanger 38, water being injected into the common products passage 34 at 40 and at 42, to bring the products to a suitable temperature before passing to bag filter unit 44, where the black is separated, while the gaseous products flow through outlet 46 which branches into separate conduits 48, 50 controlled by valves 52 so that the gases are diverted into one or other of the branches 48, 50. Carbon black is retained in filter unit 44 by valve 56 during the "make" part of the cycle and let out during the combustion part of the cycle, entering hopper 58 through valve 56. Rotary valve 60 controls the outlet of the hopper 58, and feeds carbon black into one end of a screw 62, which is also supplied at 72 with a small amount of carbon black originating from the washing unit for the dehumidifying and cooling units. Slurry from the washing unit is fed via conduit 66 to vacuum rotary filter 68, clean water retained therefrom at 70, and the filter cake containing carbon black delivered at 72. The combined carbon black supply is then fed to pelletizer 74 and the resulting pellets to layer 76 and hence to storage hopper 78. Unpelletized carbon black powder emerging from the dryer passes through conduit 80 to bag filter 82, whence clean carbon black is returned through rotary air lock 84 to screw 62. As both the "make" products and "heat" products are passed through the same bag filter unit 44, the filter unit is maintained at its correct temperature using a single carbon black generator, without the need to have two generators working as a pair, and the system is accordingly applicable to the production of thermal black from liquid hydrocarbon cracking where the two parts of the cycle are of unequal duration, as well as to gas cracking where the two parts can be equal: