"During the first 20 years of this century, many types of waste burners were designed. Some were designed for complete combustion, some for low initial cost, and others for low maintenance. ...

The steel-jacketed, brick-lined, cylindrical burner was perhaps the most common type. A shell made from steel plates was lined with common brick and firebrick ...   Foundations were made of brick or concrete, and often consisted of a central core several feet in diamter and an outer base on which the burner rested. There were grates between core and base. Fuel dropped from about 40 feet onto the central core. The top of the burner was covered with a 3 by 3 mesh, 14-gauge wire screen. The base area was from 3.5 to 5.5 square feet per 1000 board feet of mill output. Exteriors were often painted or tarred to prevent corrosion. Maintenance costs were high because the brick-work had to be replaced annually.

Some steel, water-cooled burners were used which had no brick lining but, instead, had a watertight steel jacket surrounding the inner shell, which was from 12 to 15 inches thick. These burners were constructed in all sizes up to 50 feet in diameter and 115 feet in height. Paint and asphalt were used to protect the outer surface. Very few were built, however, because of high construction and maintence costs.

Open pit fires were used then, as they sometimes are today. These consisted of a semicircular screen or wall rising 20 to 30 feet on the side of the fire toward the mill.

Brick shell burners were cylindrical and similar to brick-lined shell burners, except that they were shorter. Steel straps were placed around them for support.

An air-cooled burner was placed on the market in 1916. It had a conical base and a cylindrical stack without any brick lining. The foundation was a concrete wall 1 foot thick and extending 2 feet above the grate level. The framework was made of structural steel and iron pipe, with an outside covering of medium-weight steel plates rivited together. The conical shape place the base of the burner farther away from the fire, and air circulation cooled it. These burners cost 40 to 50 percent less than brick-lined steel burners.

This was the beginning of the tepee burner commonly in use today. Most builders have abandoned the cylindrical stack and now construct burners which are conical from base to screen.

Most tepee burners have two screens at the top - a flat, horizontal screen and a hemispherical one. Tangential openings at the base to supply overfire air to the fire have been used for many years. Underfire air is usually supplied by one or two blowers to cones or burner grates. Some burners are elevated to provide tunnels below the grate level to admit underfire air.

The practice of building prefabricated burners has been developed since 1946. These are built in sections, running from the base tot he screens. The structural framework is on the outside, with the plates on the inside. The burners are raised into place on location and bolted together in a short time. They can be dismantled easily, transported, and re-erected at another location."


Source:    U.S. Environmental Protection Agency, 1976, "Combustion of Wood Residue in Conical Wigwam Burners"m EPA 340/1-76-002, February 1976.