Patent GB-854097-A (GB)
Title: Rotary furnace installations and method of processing charges therein
IPC: B01J6/00
Filed: 1959-02-25
Abstract: 854,097. Rotary furnaces. SAEMAN, W. C. Feb. 25, 1959, No. 6541/59. Class 51 (2). [Also in Group XIII] In a method of thermally fusing granular solids or heat treating solids, or gases, a rotary furnace 10, Fig. 1, receives a lining 56 of non- bonded granular material which will not melt in the furnace heat or react chemically with the charge to be processed by centrifugal action of the furnace substantially about its horizontal, longitudinal axis. Flanges 16, 18 laterally confine the lining and the furnace shell 12 is chain driven by a motor 53, Fig. 2, to rotate on rollers 28, 30 at sufficient speed to maintain the lining in position against the shell 12. The granular charge material c to be fused, which is .introduced into the furnace through a shoot 64, is carried to the top of the shell 12 as at 68 until gravity compels it to cascade transversely across the furnace as at 70. The furnace is heated by the flame F of a burner 60 and the charge c cascades towards the flame as the furnace is slightly inclined to the horizontal where it fuses in the hot zone about the flame F. In starting the process a portion of the charge c is allowed to fuse on to the lining 56 as an impervious solid bowl 76 with constrictions 78, 80. The molten charge material f, Fig. 3, is scooped from the bowl to which it adheres by an adjustable funnel 84 which may be cooled by circulating water through conduits 90, 92 and a passage 94, or be heated by an auxiliary burner to maintain a passage for the melt. To aid the adherence of the molten material f to the bowl 76 its temperature may be lowered to increase its viscosity by directing cool air thereon through conduits 100 or by introducing cool charge material thereto. In a modification, Fig. 4 (not shown), the furnace which has a lining maintained in position by centrifugal force but no fusion bowl or discharge funnel, is adapted for heating a gas or gases, e.g. petroleum gases. In another modification, however, in which the furnace is substantially as in Fig. 4, the cascading solids, which act as heat transfer solids to the gas or gases, do not melt at the chosen temperature in the furnace but cascade in countercurrent to the gas or gases to be processed and absorb a maximum amount of heat by the time they reach the vicinity of the flame to lose to the cooler gas which is introduced behind the burner. A further modification comprises a preheating and a fusion furnace 172, 174, Fig. 5, respectively, wherein a granular charge to be fused is first fed into the preheating furnace which is inclined to cascade transversely therethrough in counter flow to hot combustion products from a burner 226 in the fusion furnace which products are introduced into the preheating furnace through a conduit 242. The linings of the furnaces are held in position by centrifugal force as in the previous embodiments. The heated granules are transferred through a shoot 244 to the fusion furnace which is driven independently of the preheating furnace at a quicker rate to cause the entire melt to adhere to and travel with the lining 234 to assure adequate drainage of molten material by a scoop 236 from the fusion furnace regardless of the rate of delivery of the preheated granules. In a further embodiment, Fig. 6 (not shown), a furnace for preheating and fusing a granular charge is substantially similar in operation to that described with reference to Fig. 1, but the peripheral wall is divided into cylindrical sections, wherein that of larger diameter comprises a fusion chamber and that of smaller diameter a preheating chamber. The methods are described as being adapted for the defluorination of natural phosphates by fusion to produce phosphatic fertilizers, or for the decomposition of calcium sulphate to yield sulphur dioxide and for the furnace described with reference to Fig. 4, for the direct fixation of nitrogen or for heat treating petroleum gases to produce ethylene and acetylene.