CALCINE KILN.
The quantity of " chamotte " or calcine required in a fire brick works depends largely on the nature of the clay in use and the proportion of tiles and blocks made. If the supply of calcine required is of a limited character, lumps of raw clay may be placed in each kiln ; but in cases where more calcine is necessary than this method will supply, it is advisable to make provision for the demand by the erection of a calcine kiln. This form of kiln is simple in construction, being erected some what after the plan of a lime-kiln, and worked in a similar manner; that is, the kiln is always kept filled. When the calcine at the bottom of the kiln is sufficiently burned, it is drawn out, the remainder settling down, leaving a vacancy at the top, which is filled with a further supply of lump clay, so that the calcining process is one of regular feeding and draw ing out of the clay. In Figs. 127, 128 and 129 is shown a calcine kiln. The kiln is 5 feet in diameter, and 15 feet from the bottom to the cone or stack. The base has four fire-holes 18 inches wide, and fitted with 3-feet grates. Letters d and c represent the feeding and discharge doors, the clay being con verted into calcine as it gradually descends from the height of the door d to the door c.
The calcine kiln should be built as near the mill-room as possible, and connected with the clay bank by a trestle at a line level with the feeding door d, so that the loaded cars may be run directly up to the door. Where there is no accommo dation for thus conveying the clay to the calcine kiln, a hoist or inclined plane would be necessary. The kiln being in close proximity to the machinery, this could be done at small expense.
In order to secure a regular draft in burning the calcine, the clay should all be thrown into the kiln in lump form, fresh from the mine, so that it is not air shaken and liable to break up when discharged from car to kiln, as the small clay would have a tendency to check the draft.
A calcine kiln of the size shown illustrations would produce ten tons of good calcine each day. A smaller kiln with three fire-holes would work equally as well, of course yielding a less quantity of calcine.