GB902674A - System for baking carbonaceous products or the like - Google Patents

Abstract

902,674. Heat-treating carbon electrodes; gas-fired furnaces. SWINDELL-DRESSLER CORPORATION, and ALUMINUM CO. OF AMERICA. Feb. 24, 1959 [Feb. 28, 1958], No. 6303/59. Classes 51 (1) and 51 (2). Carbonaceous products, such as electrodes for use in aluminium production, are heat-treated in a tunnel furnace without saggers or lateral supports. The electrodes, on tracks 17 having close-fitting machined ends, move into a preheating zone, Fig. 3, from an entry part with a door at each end and a pipe for the supply of an inert purging gas. Pipes 34 traversed by hot gases from the heating chambers of subsequent sections provide heat, and side-plates 52 on the trucks 17 dip into condensed tarry products given off as the electrodes are heated, which collect in troughs 51 at the sides of benches 29. At the entry end, the condensate escapes through holes in the troughs to a trough 48 in the bottom of the furnace, where it is kept liquid by a steam coil 50 and removed from an outlet 49. The space below the trucks is kept cool by nozzles delivering cool inert gas toward the entry at the beginning of a second preheating section, and by cooling pipes in the second preheating and heating sections. The second preheating section has heating chambers 36, Fig. 4, left-hand part, formed by loosely interlocking tiles on the side benches 29. Combustible gases given off by the electrodes are drawn in to chambers 36 by air jets 68, Fig. 6, and supply fuel for the preheating section. In the following section, burners in heating chambers 39, Fig. 4, right-hand part, raise the electrodes to the maximum temperature. The walls of chambers 39 are formed of hollow tiles 40, which may have holes 82 so that the interior of each tile acts as a flue. The tiles fit together loosely so that deposits on the outside of chambers 39 may be burnt off by gases issuing from the chambers. In the final section of the furnace, the electrodes are cooled by air pipes, some of which may supply heated air for combustion. The heating chambers 36, 39 communicate through a restricted, dampered passage and the pressure in the chambers 36, 39 is controlled by means of suction fans connected to collecting drums for the combustion products so as to be slightly below and slightly above the pressure in the furnace proper, respectively. The gases having a high oxygen content from the preheating combustion chambers 36 are fed through the preheating pipes 34 and discharged, while the gas from the chambers 39 are arranged to be sufficiently inert to be used in curtain jets, roof jets, under-car jets or as purge gases for the entry and exit sections. In the sections having combustion chambers, sand seals are formed at the sides of the trucks.