Furnaces and ovens

Industrial process furnaces and ovens Mechanical powertransmission equipment, n.e.c. General industrial machinery and equipment, n.e.c. Electronic computers Computer storage devices Computer terminals Computer peripheral equipment, n.e.c. Calculating and accounting machines, except electronic computers Office machines, n.e.c. ... 

Steel sheets are aluminized by a hot-dip process similar to galvanizing. The principal applications for such a product are furnaces and ovens, automobile mufflers, and other equipment requiring heat and corrosion resistance. When a sheet which has been coated with aluminum by a hot-dip process is exposed to a temperature over l,000°F (538aC). the aluminum forms an iron-aluminum alloy which is heat- and corrosion-resistant. 

Many experiments have shown that combustion of petroleum fuels is cleaner and more eflBcient if small water droplets are dispersed in the oil by ultrasonic, hydrodynamic, or chemical techniques (21). The presence of the water leads to a lower generation of nitrogen oxides and to less soot, probably because of lower combustion temperatures and better fuel atomization. The most tested system is a mechanical one for furnaces and ovens produced by the French oil company, ELF (22). 

Zircon is also used to make bricks in high-temperature furnaces and ovens. These furnaces and ovens are used to work with molten metals. Zircon bricks are ideal for such ovens because they reflect heat and are not destroyed by high temperatures. 

In higher temperature furnaces, the interradiation from hotter solid surfaces to cooler surfaces tends to self-correct minor nonuniformities. For example, in batch furnaces and ovens, the door end and back end incur the greatest heat losses. In one instance it was found that in an 1100 F (593 C) oven, a 150°F (83°C) differential was sufficient to level out the temperatures from center to each end. However, in a 2250 F (1232 C) furnace, only a 70°F (39°C) difference was necessary to level out the temperatures (because of the 4th power effect in the Stefan-Boltzmann radiation... 

Unless otherwise specified in this book, furnaces and ovens are assumed to be direct fired. Indirect-fired units use radiant tubes or muffles to protect the load from contact with the poc. 

Refractory materials can be melted, spun, and blown into fiber strands similar to wool or blanket insulations. They are used in many medium- and low-temperature furnaces and ovens furnaces, and for outer layers in multilayered refractory walls. Because of all their small air spaces, they are much better insulators than solid refractories, but they are more fragile, less durable, and more difficult to install so that they do not settle, shrink, or otherwise lose their good insulating property. Many of the suggestions in a later section on insulation installation can apply to fiber refractory installation. 

Whenever unvented combustion occurs iadoors or when venting systems attached to combustion units malfunction, a variety of combustion products win be released to the iadoor environment. Iadoor combustioa units include nonelectric stoves and ovens, furnaces, hot water heaters, space heaters, and wood-burning fireplaces or stoves. Products of combustion include CO, NO, NO2, fine particles, aldehydes, polynuclear aromatics, and other organic compounds. Especially dangerous sources are unvented gas and kerosene [8008-20-6] space heaters which discharge pollutants directly into the living space. The best way to prevent the accumulation of combustion products indoors is to make sure all units are properly vented and properly maintained. 

The carbonization by-products are usually refined, within the coke plant, into commodity chemicals such as elemental sulfur (qv), ammonium sulfate, benzene, toluene, xylene, and naphthalene (qv) (see also Ammonium compounds BTX processing). Subsequent processing of these chemicals produces a host of other chemicals and materials. The COG is a valuable heating fuel used mainly within steel (qv) plants for such purposes as firing blast furnace stoves, soaking furnaces for semifinished steel, annealing furnaces, and lime kilns as well as heating the coke ovens themselves. 

Sihca bricks are used extensively in coke ovens, the roofs and walls of open-hearth furnaces, and the roofs and sidewalls of glass tanks and as linings of acid electric steel furnaces. Although sihca brick is readily spalled (cracked by a temperature change) below red heat, it is very stable if the temperature is kept above this range and for this reason... 

Various methods of heating are required in the analytical laboratory ranging from gas burners, electric hot plates and ovens to muffle furnaces. 

Silica bricks are used extensively in coke ovens, the roofs and walls of open-hearth furnaces, and the roofs and sidewalls of glass tanks and... 

Use of regenerators is limited to large steel-melting furnaces for example, an open-hearth furnace, and by-product coke ovens with fuel combustion systems only. 

T3. Tigerschoid, M., and Ilmoni, P. A., Proc. AIME Blast Furnace Coke Oven Raw Mater. 9, 18 (1950). 

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