Flue pressure control for tunnel kilns

A method of operating a tunnel kiln in which green carbon articles are baked in the ware space of a baking zone by heat produced by the combustion of fuel in chambers adjacent the baking zone, and having walls that separate the chambers from the ware space, the combustion chambers being connected in fluid communication with flues extending lengthwise of the kiln and adapted to remove products of combustion from the chambers, the flues having a pressure gradient that extends lengthwise of the flues and combustion chambers, the method comprising the steps:

• baking carbon articles in the baking zone such that hydrocarbon gases are produced from an organic binder in the articles, which gases contact the surfaces of the walls of the combustion chambers facing the carbon articles, the temperature of said surfaces being such that the hydrocarbon gases tend to crack on the surfaces and leave deposits of coke on the surfaces;
• and
• controlling the pressure gradient within the flues and the pressure in the ware space such that a pressure differential between the combustion chambers and the ware space is effected that causes products of combustion to flow into the ware space from the combustion chambers in amounts sufficient to burn and consume coke deposits without burning the carbon articles;
• the step of controlling the pressure gradient in the flues including the placing of exhaust stacks in fluid communication with the flues at locations in the combustion chambers of the flues.