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          Clay brick making machine-Brick machine-Baoshen brick making machine

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          Clay brick manufacturing process Part four

          Firing

          Down-draught kilns consist of a rectangular space with a barrel-vaulted roof and a slotted or per Bricks are fired at temperatures between 1 000? and 1 200?C, depending on the clay. Light-coloured clays usually require higher firing temperatures than dark-coloured ones. Of the many known types of ceramic kilns, four types were used in South Africa: the Down Draught kiln, The Hoffman-type Transverse Arch kiln (T.V.A.), the Tunnel kiln and Clamp kiln. However, the Down Draught type of kilns have been discontinued because of their uneconomical firing procedure (labour, coal etc.).

          Down-draught kilns consist of a rectangular space with a barrel-vaulted roof and a slotted or per forated floor open to flues below. Green bricks (40 000 to 100 000 at a time) are stacked in the kiln. Fires are lit in fireboxes along the sides and the hot gases fire up to the cur ved roof, down through the bricks and from there to the chimney stack. Fires are fuelled by coal, gas or oil. When the desired temperature has been reached, the temperature is maintained for a specific period and the fires are then allowed to die. The kiln cools down, the fired bricks are removed and another batch of green bricks is placed in the kiln for firing.

          Firing in the T.V.A. kiln is continuous. Each day, green bricks are placed, in cleared chambers, in front of the fire and fired bricks are removed from behind it, with two or three adjacent wickets being kept open for this purpose. When a chamber is full, the wicket is bricked up and fuel (coal, oil or gas) is fed in among the bricks through holes in the crown or roof of the kiln.



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          免费做暧暧暖免费观看日本

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