Indirectly heated tunnel furnace - esp for ceramics, heated recirculated gas giving uniform temp distribution

摘要

Indirect heating is used by circulated gas which is heated to the desired furnace temp; the gas is introduced into the furnace at high speed from a space between two furnace vaults; the lower vault has a number of perforations or slots through which the gas enters the furnace from the inter. space, while above and flanking the upper vault and its adjacent insulating brick-work, there is a further wall cavity or space into which cool air is introduced, under a pressure which is pref. = the pressure between the two vaults. The high pressure required between the double vault arrangement for producing high speed circulation within the furnace, is thus achieved, without escape of gas as a result of a pressure gradient from the furnace; this possible escape is resisted by the blanket of air in the external cavity.