GB1218982A - A method for carrying out heating processes in long kilns and a long kiln for carrying out the method - Google Patents

Abstract

1,218,982. Tunnel kilns. SVENSKA METALLVERKENS UGNS A.B. 1 Feb., 1968 [3 Feb., 1967], No. 5113/68. Heading F4B. A method of heat treating ceramic goods in tunnel kilns having pre-heating 11, burning 12 and cooling 13 sections, is characterized in that a part of the kiln space is divided in its longitudinal direction into relatively long sections separated by relatively short sections by controlling the removal and supply of gas from and to said part of the kiln space, a counterdirectional flow of gas being maintained in adjacent relatively long sections in said part of the kiln space, the gas removed from at least one of the relatively long sections being passed through a circulation system wherein the gas is modified with respect to its temperature and/or composition. As shown, the cooling section 13 is divided into relatively long and short sections. In operation, gases from a final cooling zone 18 are conveyed by means of a fan 17 in a conduit 19 to the rear of section 10 to dry the bricks, the 'after-dried' bricks entering the preheating section 11 in counterflow to hot gases comprising hot air and products of combustion, these gases arriving from two recirculation zones 21, 22 situated in the cooling section 13 via conduit 23, and also from the firing section 12 situated behind the section 11. The bricks after passing through the firing section 12 enter the cooling section 13, said section 13 being subdivided into three zones, the relatively long recirculation zones 21, 22 and the final cooling zone 18, said zones forming three separate gas flow zones. In the zones 21, 22 newly supplied cooling gas is introduced via conduits 36, 47, respectively, a gas flow corresponding to the newly supplied gas flow being led away from the recirculation system through conduits 38, 49, respectively, into the conduit 23. Arranged in the conduits leading to the various sections are valves, e.g. 26, by which the pressure drop in the sections can be controlled. This control is suitably effected automatically on receipt of a signal sent from means, e.g. 27, which senses the pressure at some suitable portion of the associated section.