The term ‘Kiln’ is normally used when referring to high temperature treatment of non-metallic materials in various industries like in the ceramic, cement (cement rotary kiln), lime (lime kiln) etc. whereas, when melting at high temperature is involved the term ‘Furnace’ is used as in steel manufacture (Blast Furnace, Basic Oxygen Furnace, Ladle Furnace), glass industries (Glass Melting Tank Furnace) etc. More about the meaning and function of a furnace and kiln has been dealt in one of our previous article: The Function of a Furnace (Kiln) used in Ceramic Industries [Read]. Here we shall discuss about the different criteria used for classifying a kiln or furnace.
Furnaces may be classified broadly:
(a) According to the nature of heating medium -
(1) Fuel fired furnace, (2) Electrically heated furnace.
(b) According to the form and shape of the space to be heated -
(1) Shaft kiln, (2) Crucible furnace, (3) Rotary kiln, (4) Hearth furnace, (5) Tunnel kiln,
(6) Muffle furnace, (7)Tank furnace etc.
(c) According to the process taking place -
(1) Ceramic (2) Metallurgical (3) Non-metallurgical etc.
(d) According to the products obtained -
(1) Lime kiln (2) Cement kiln (3) Copper smelter (4) Glass tank furnace (5) Gold furnace etc.
(e) According to the method of handling and firing the materials in its passage through the furnace -
(1) Direct fired (2) Indirect fired (3) Batch type firing (Intermediate, Periodic)
(4) Continuous type firing.