Push-Type Furnace

Hydrogen has to be applied in large excess, which guarantees a fast flow over the powder layer. The excess depends on the desired grain size (smaller for coarse and higher for fine powder). The range is somewhere between 2.5 and 40 times stoichiometric. 

Multitube furnaces (14 to 18 tubes arranged in two rows) are frequently in use today. A photograph of an industrial aggregate is shown in Fig. 5.26. The boat material, in most cases, is an iron alloy high in Ni and Cr (Inconel). More seldom, because of the high price, boats are made of TZM (molybdenum alloy with Ti, Zr, and C) or pure tungsten. 

The furnaces are either gas fired or electrically heated in three or four separate zones. Furnace temperatures range between 600 and 1100 °C. For smaller and mediiun W grain 

FIGURE 5.26. Push-type leduction fiimaces. By courtesy of Wolfram Bergbau- und Huttenges. m.b.H., Austria. 

The reduction is commonly carried out in one stage. Alternatively, a two-stage reduction sequence can be applied instead. In this case, the first reduction stage takes place at lower temperature (500-700 °C formation of brown oxide, WO2) and the second stage at 600-1100 °C (formation of tungsten metal). 

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In iadustrial production of titanium carbide, pure (99.8%, with minor impurities of Si, Fe, S, P, and alkahes) titanium oxide [13463-67-7] Ti02, iu the dry or wet state is mixed iu 68.5 31.5 ratio with carbon black or finely milled low ash graphite. The dry mixture is pressed iato blocks that are heated iu a horizontal or vertical carbon-tube furnace at 1900—2300°C hydrogen that is free of oxygen and nitrogen serves as protective gas. In the vertical push-type furnaces, the Hberated CO itself provides protection. 

Industrial Production. TBO is formed by calcination of APT under slightly reducing conditions. The conversion can be performed either in multitube push-type furnaces or in... 

TABLE 5.9. Push-type Furnace Reduction Conditions and Capacities for Different Grain Sizes"... 

Scrap oxidation is performed either in push-type or in rotary furnaces. Also, multihearth roasting furnaces are employed. 

FIGURE 9.5. Push-type carburization furnaces used for conventional powder carburization (maximum temperature 1650 °C). By courtesy of Wolfram Bergbau und Hiittenges.m.b.H, Austria. 

When constructing a laminar flow hood, the filter size must be precisely fitted with a high pressure fan. All fans are rated by the manufacturer according to the volume of air (CFM or cubic feet per minute) they can push past materials of specified resistance. The type of high pressure fans needed in a laminar flow hood are usually of the squirrel cage type ("furnace blowers"). 

Both furnaces are fed by the same type of system, utilizing a charging hopper and a hydraulic ram. The ram pushes the solid waste into a primary combustion... 

Thus, the slag formed on the open hearth charge is quite frothy. It is pushed off the pool of molten steel beneath it with a type of hoe, once or twice during the process. Blast furnace metal melts at about 1,130°C, whereas pure iron, more... 

Oxidation-Reduction of Heavy Metal Turnings. Heavy metal turnings can be easily oxidized by air at about 800 °C. The layer height in this step is critical, because if it exceeds a certain limit then local overheating (exothermic reaction) can cause melting. The oxidized product is subsequently milled and screened and, finally, it is reduced in hydrogen atmosphere at 900-1000 °C in the same type of push-t5q)e furnaces used for W-powder production. 

The battery has a pusher side and a coke side. On the pusher side of the battery there is a large machine, with an extendable ram used to push the coal converted to coke at the end of the coking cycle, from the slot-type ovens. The coke exits the ovens on the coke side of the battery, through a coke guide and into a quench car. The hot coke in the quench car is then water-cooled in a quench tower. Coke is a necessary component for the production of iron in a blast furnace. 

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