DescriptionAmCyc Brick - Hoffmann's Annular Brick Furnace (side).jpg	English: Woodcut/drawing of an annular brick furnace (side view), designed by Friedrich Hoffman.
Date	published 1879
Source	The American Cyclopædia, v. 3, 1879, p. 267 (Fig. 1, top).
Author	unknown artist/Friedrich Hoffman, designer
Permission (Reusing this file)	Public domainPublic domainfalsefalse This work is in the public domain in the United States because it was published (or registered with the U.S. Copyright Office) before January 1, 1929. Public domain works must be out of copyright in both the United States and in the source country of the work in order to be hosted on the Commons. If the work is not a U.S. work, the file must have an additional copyright tag indicating the copyright status in the source country. Note: This tag should not be used for sound recordings.PD-1923Public domain in the United States//commons.wikimedia.org/wiki/File:AmCyc_Brick_-_Hoffmann%27s_Annular_Brick_Furnace_(side).jpg

Description:

A large annular chamber, with openings at the sides for the reception of the bricks, is constructed with a central chimney, and with removable divisions for separating the annulus into different parts. When the furnace is filled with unburnt bricks heat is applied to one division, the smoke and hot air escaping into the adjoining one, which is the next to be burnt, the air for maintaining the combustion being received through the compartment last burned, whereby the bricks in it are cooled. Each compartment of bricks or other articles is thus burned in turn, the waste heat of the burning compartment continually drying the compartment before it, and taking all the heat of the one behind. The letters a a mark the circular arched furnace, furnished with doors, b b. Flues, c c, lead to the circular chamber e e, surrounding the chimney, d. Valves of cast iron are made to close at pleasure the orifices of the flues. Movable sluices in the dividing walls allow of communication to be made or closed between the chambers; h h are plugs through which the coal, in powder, is introduced, undergoing calcination.