Patent GB-167195-A (GB)
Title: An improved process of producing decolorizing carbon
IPC: C01B32/336
Filed: 1919-06-11
Abstract: 167,195. Sauer, J. N. A. June 11, 1919. Carbon.-Relates to a. continuous process for the manufacture of " decolourizing-carbon. " The raw or partlycarbonized material is passed through a retort or a series of associated retorts, and while therein, and without removal from the system, is subjected to zones of increasing temperature which may be classified generally as, -. a preliminary distillation zone, a carbonizing zone, and a final zone of intense heating; and it is an essential condition that, in this final zone, endothermic reactions which would prevent the attainment of the requisite high temperature within the mass, are avoided, for example, by ensuring that the carbonization is completed in the preceding zone and that no gas or only inert gases such as chlorine and ammonia are introduced, and that any gases or vapours evolved or produced in the preceding zone are either deflected from the final zone or cnly enter therein after being rendered inert by passage through a sufficient height of material. If partly carbonized material is employed, the preliminary distillation may be carried out in a separate apparatus; when, however, raw carbonaceous material such as wood or peat. is used then it is a feature of the process that ammonia and other condensible products arising from destructive distillation can be recovered from the primary zone by reason of the separation of the several stages, and to facilitate the recovery of such products :gases such as carbon dioxide or steam may be introduced; the gases produced in the other zones may also be collected and suitably utilized, for example, if combustible, for heating the retort or retorts. In the case of wood, peat or like raw material, the temperatures maintained in several zones are, -primary distillation zone, 300-600‹ C. ; carbonizing zone, 1000‹ C; final-burning zone, 1500‹ C. The wood or other material to be carbonized may be used in its raw condition and in the dry or wet state, or it may first be treated with steam or water or with acid, alkalies or solutions such as those of calcium, magnesium, or zinc chlorides, lime, or starch, which materials serve either as mineral spacing-agents or for the evolution of gases during carbonization, etc.; or these materials and others such as calcium carbonate and chloride of lime may be added in the dry state; and during the process there may be introduced air, steam, carbon dioxide or monoxide, hydrogen or chlorine. The finished product is cooled out of contact with the air, and is finally disintegrated in a ball mill. The apparatus employed may consist of three vertical retorts, corresponding to the three zones mentioned above, superimposed and separated by valves or sluices; each retort is provided with inlets and outlets for gases or vapours, and is surrounded by a separate heating-chamber, in the lowest of which the gases from the carbonization and final-heating zones are burnt, the hot gases being them passed through the upper chambers in succession so as to obtain the desired :zones of increasing temperature as the material falls. Or a single undivided retort or shaft 1, Fig. 2 may be used, in which case the combustion chamber 21 is arranged at the lower part of the shaft, and is supplied with gases withdrawn through apertures 16 at the side of the shaft and formed in a partition 13 extending for a part of or the entire height of the shaft; the gases and vapours evolved in the preliminary distillation zone are withdrawn through a branch 7; the perforations 16 may be covered by a slide (not shown) and the duct behind the partition accommodates a pipe 14 for the introduction of gas. Or the partition may be omitted, the gas being then introduced through a pipe passing through a tubular duct in the brickwork of the furnaces, and the gases for heating the retort being withdrawn through pipes inserted at the intermediate and hottest zones. With such an arrangement the preliminary distillation may be carried out in a separate retort isolated by a sluice or valve. A plant is illustrated in Fig. 6 in which the preliminary distillation is carried out in an upper sheet iron or steel retort 2 provided with a charging-hopper 6 and an outlet 7 leading to a main 31, and communicating by means of a slide 5 with a lower retort 1 of firebrick &c., in which the carbonization and final heating is effected; the retort has an inlet 8 for superheated steam or gas, and an outlet 9 for retort gases which are led to a combustion chamber 21 surrounding the lower end and hottest zone 4 of the retort; the hot gases pass to a chamber 29 surrounding the carbonization zone 3, thence through a flue 24 to a chamber 11 surrounding the distillation retort or chamber 2, from there to a recuperator 26 for preheating the air for combustion, and finally to a superheater 27 for the steam; from the recuperator the air flows through ducts 28 and is further heated, and the steam, on its way to the inlet 8, is further superheated by passage through pipes 30 by means of a damper 33 part of the hot combustion gases may be passed direct to the recuperator 26.