GB782426A - Improvements relating to the production of calcium carbide - Google Patents

Abstract

<PICT:0782426/III/1> In the process for the production of calcium carbide by reacting lime or limestone with carbon under heat in a shaft furnace, a solid fuel rich in carbon is continuously supplied to a combustion zone or zones in the hearth of the furnace where combustion is maintained by means of a blast or blasts rich in oxygen to provide the heat necessary for the reaction, and lime or limestone, for reacting with unburned carbon is supplied continuously, in excess of that corresponding to the reaction equation CaO+3C--> CaC2+CO , to an adjacent zone or zones, and the formed molten carbide, contaminated with free lime, is caused during tapping to flow laterally beneath the combustion zone, or at least one of the combustion zones, in contact with carbon in such zone, and sufficiently slowly to cause the greater part of the free lime to be converted to carbide under the radiant heat from the combustion zone. The lime or limestone may be mixed with carbon. The process may be carried out in a furnace of the type described in Specification 755,397, [Group XII], where the charging space 2 is alternately filled with coke fuel and lime or lime/coke mixture in molar ratio CaO : C, say 1/2 . Coke is fed, on lowering closing member 4, with hopper 6 in position shown, into bunker space 8 between sheet iron wall 1 of the furnace and wall 7 of inner bunker space 9, whence it passes continuously round wall 16 enclosing free space 15 into lower section of shaft having a firebrick lined hearth 12 and slag pit 11, and is burnt by oxygen-enriched air or oxygen/steam mixture injected through tuyeres 13. Lime or lime/coke mixture is fed from space 2, with hopper 6 turned through 180 degrees, into inner bunker space 9, whence it passes continuously into lower section of the shaft. The lime melts and reacts with coke, when it is surrounded by the combustion zones of the coke bed around the tuyere outlets, at, say, 2200-3000 DEG C., and the molten carbide collects in slag pit 11, whence it is tapped through one or more holes 14, after being subjected to radiant heat from the combustion zones due to the downward inclination of tuyeres 13 for a sufficient time to permit lime present in the molten carbide to react with coke also present. Combustion gases collect in space 15 and are withdrawn through pipe 10 without contacting the bulk of the fuel. Alternatively, coke may be fed to bunker space 9 and lime or lime/coke mixture to space 8, with consequent lengthening of tuyeres 13 into centre of the furnace and adjustment of tap hole position. In an alternative apparatus (Fig. 2, not shown), having three shafts connected to a common hearth, coke is fed to the two outside shafts and lime/coke mixture to the centre shaft.