United States Gypsum Company

Daniel J. Milligan

George E. Rowland

Michael L. Cloud

George E Rowland

Michael L Cloud

Daniel J Milligan

A method and apparatus is disclosed for the continuous calcining of gypsum material in a high-efficiency, refractoryless kettle preferably heated by a multiple series of separate immersion tube burner coils, each coil operating within a specific calcining zone inside the kettle. The lowest, i.e., initial, burner tube coil is formed with a low profile to permit use of a small initial gypsum charge, and hence, a quick kettle start-up cycle. That low profile initial burner design also helps keep the agitator motor's load at a minimum during cycle start-up. Due to the immersion tube burner coil construction, no refractory structure for the kettle is required. Also, no separate hot pit structure is required, as the kettle is used to merely hold the material being calcined and no residual heat is present. A relatively thin kettle can be constructed, as it need only withstand relatively low operating temperatures. The kettle's staged, interiorly-disposed burner tube coils act to directly transfer burner tube heat to the kettle's contents, and the coils exhaust exteriorly of the kettle. The present calcining method and apparatus permits substantially improved tonnage output of calcined material, for a kettle of a given size. A modification to the present apparatus includes structure for recovering and recycling a portion of the spent burner gases, and also separate structure for forced aeration air, both preferably for introduction through the kettle bottom. One alternate embodiment concerns a differently-shaped kettle design. Another alternate embodiment concerns a modified kettle which uses a single immersion burner tube coil to provide the total heating of the kettle's contents, for use in certain calcining applications.

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Naperville, IL, United States of America

George E Rowland