Hoffman Kiln

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The Hoffman kiln is a kind of the kilns used in various branches of the ceramic industry. The kiln invented by a person of the same name in 1856 and is currently used in brick, clay, pottery, and refractory industries. This kiln is in the category of continuous kilns. In this kiln, the products are fixed and the fire is movable.

The Hoffman kiln is a long tunnel that is made in the form of a ring or ellipse, dividing it into chambers. The Hoffman kiln chambers are connected by channels or doors embedded in the separating walls of the chambers. Each room also has an outlet door that is used for loading and unloading the kiln. The size of the Hoffman kiln is expressed by these doors; for example, a 34-door kiln is a kiln with 34-chambers, and each door connected to a brick-making chamber (or other products). The place where the fuel sprays are located is also on the roof.

How to Bake Products in the Hoffman Kiln

In the Hoffman kiln, the products are heated by the heat of the other chambers. Before being cooked directly by the fire. This is called the pre-warming. This heat, along with the exhaust gas from the firing chamber, travels through the embedded valves and enters the next rooms, and preheating the products in them. While in a room, the baking operation is ongoing, in the opposite chamber (farthest room), unloading and loading operations are ongoing. This is done by using a door that holds the chamber out of the oven. During loading, cool air also enters the kiln, which is sucked in by the fire in the firing chamber and travel through the ventilation holes between the chambers. So the air moves out of the rooms where the baking process has already taken place and cools the finished hot products.

Thus, there are two air flows in the Hoffman kiln ring. 1st, the air flowing out of the firing chamber in the first semicircle that pre-warm the next chambers. 2nd, the air flowing in from the outside of the semicircle, into the firing chamber that cools the previous rooms.

When the firing operation is completed in the firing room, in the opposite room of the Hoffman ring, the loading operation is completed and the door is closed. At this point, the burners are transferred from the rooftop to the next chamber rooftop. And the front door of this room (finished firing room) will be opened for unloading and loading again.

Types of Hoffman Kilns

Hoffman kilns are made in several different types:

• Ring kiln
• Zig-zag klin
• Bocks kiln
• Harrizon kiln

But usually, the ring kiln is called the Hoffman kiln.

Another type of brick kiln is the tunnel kiln.