Kilns direct -heat rotary

The barium sulfide solution is produced by dissolving fused barium sulfide in water. The barium sulfide is obtained by reducing an intimate mixture of crushed barite (ca. 1 cm lumps) with petroleum coke according to Equation (3) in a directly heated rotary kiln at 1200-1300°C ... 

A furnace is a device (enclosure) for generating controlled heat with the objective of performing work. In fossil-fuel furnaces, the work appHcation may be direct (eg, rotary kilns) or indirect (eg, plants for electric power generation). The furnace chamber is either cooled (waterwaH enclosure) or not cooled (refractory lining). In this article, furnaces related to metallurgy such as blast furnaces ate excluded because they ate coveted under associated topics (see... 

The zinc salt and BaS solutions are mixed thoroughly under controlled conditions (vessel geometry, temperature, pH, salt concentration, and stirring speed, see (a) in Fig. 20). The precipitated raw lithopone does not possess pigment properties. It is filtered off (b2) and dried (c) ca. 2 cm lumps of the material are calcined in a rotary kiln (d) directly heated with natural gas at 650-700 °C. Crystal growth is controlled by adding 1-2 wt% NaCl, 2 wt % Na2S04 and traces of Mg2 + (ca. 2000 ppm), and K+ (ca. 100-200 ppm). The temperature profile and residence time in the kiln are controlled to obtain ZnS with an optimum particle size of ca. 300 nm. 

The rotary dryers (direct-heat dryers and kilns) are controlled by indirect means, e.g., by measuring and controlling the gas temperatures in their two ends, whereas shell temperature is measured on indirect calciners, and steam pressure and temperature as well exit gas temperature and humidity are controlled on steam-tube dryers. It is not possible to achieve control by measuring the product temperature because not only this is difficult but also its changes are slowly detected, although the product temperature is used for secondary controls. 

J. K. Brimacombe and A. P. Watkinson. "Heat transfer in a direct fired rotary kiln Part 1. Pilot plant and experimentation," Met Trans. B, 9B, 201-208, 1979. 

In this treatment sulfur is oxidized to sulfur dioxide and mercury is vaporized. For direct heating a multiple-hearth furnace may be used or alternatively a rotary kiln. These latter furnaces are operated at about 350°C at the charging head and 750°C at the discharge end. In the indirect heating system, two concentric tubes are utilized. 

The effect of heat capacity of the thick refractory wall on the heat transfer of directly fired rotary kilns is taken into account with the semi-empirical expressions derived by Vaillant [12] for the evaluation of the temperatures of the covered and uncovered wall together with a heat balance over the wall for evaluation of the heat loss, Vioss environment. The convective and... 

Clay Activation. The clay is heated to about 700 °C to destabilize the kaolinite structure by removing hydroxyl ions as water. This can be either a batch process with the clay in crucibles in a directly fired kiln, or a continuous process in a tunnel kiln, rotary kiln, or other furnace. 

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