High-temperature furnaces

The same properties that make molybdenum metal effective in high temperature furnace appHcations make it useful as support wires for tungsten filaments in incandescent light bulbs and as targets in x-ray tubes. 

Spent Sulfuric Field. Spent sulfuric acid recovered from petrochemical and refinery processes can be fed to a high temperature furnace at 870—1260°C, where it is transformed kito sulfur dioxide, water, and other gaseous products. After suitable scmbbkig and drykig, the gases are passed to a conventional contact sulfuric acid plant (263). 

When radiating and receiving surfaces are not in parallel, as in rotary-ldln devices, and the sohds burden bed may be only intermittently exposed and/or agitated, the calculation and procedures become veiy complex, with photometric methods of optics requiring consideration. The following equation for heat transfer, which allows for convective effects, is commonly used by designers of high-temperature furnaces ... 

The green cokes were calcined by placing a weighed amount of green coke into an alumina tube. The tube was fitted with end caps to allow for a constant purge of nitrogen. The alumina tube was then inserted into a high-temperature furnace and the temperature raised to about 1000°C for a period between 30 and 60 minutes. The furnace was turned off, cooled to room temperature, and the product recovered to determine the calcined coke yield. 

Over the past decades, advances have been made that reduce environmental impacts of coal burning in large plants. Some arc standard and others experimental. Limestone (mainly calcium carbonate) scrubber smokestacks react with the emitted sulfates from the combustion and contain the chemical products, thereby reducing the release of SO., into the atmosphere by a large factor (of ten or more). Pulverization of coal can also allow for the mechanical separation of some sulfur impurities, notably those in the form of pyrites, prior to combustion. Currently deployed—with more advanced versions in the development stage—are various t yies of fluidized bed reactors, which use coal fuel in a pulverized form, mixed with pulverized limestone or dolomite in a high temperature furnace. This technique reduces sulfate release considerably. There are... 

Molybdenum shows good corrosion resistance to zirconia up to 2000° C but above about 1200°C, zirconia becomes electrically conductive and thus care must be taken in the design of high temperature furnaces using zirconia... 

The principal applications of the outstanding stability of platinum and its alloys at high temperatures lie in their use as materials of construction for equipment to handle molten glass and as electrical resistance windings for high-temperature furnaces. 

Support materials were prepared by blending the fine power as stated in the later part of this case study. PVA was used as the binder. The organic macromolecule was used to create sufficient pores in the material when bumed out after a solid strong support was formed. Drying was performed in a high-temperature furnace. The shape and thickness of the support were based on the mass of the material and the way it was moulded. 

Heating elements for high temperature furnaces. Coating for fusion reactors. 

Inorganic carbonate is removed by acid addition, evaporated at fairly low temperature to a dry sea salt residue, and the residue combusted to carbon dioxide in a high-temperature furnace. 

Van Hall et al. [100] inject a 20 litre sample into a high-temperature furnace at 950 °C containing catalyst to promote oxidation of carbon compounds to carbon dioxide, which is then passed into a non-dispersive infrared analyser. The carbonate interference can be determined by passing an acidified portion of the sample through a low-temperature furnace [101-103]. 

Apart from the reactions described above for the formation of thin films of metals and compounds by the use of a solid source of the material, a very important industrial application of vapour phase transport involves the preparation of gas mixtures at room temperature which are then submitted to thermal decomposition in a high temperature furnace to produce a thin film at this temperature. Many of the molecular species and reactions which were considered earlier are used in this procedure, and so the conclusions which were drawn regarding choice and optimal performance apply again. For example, instead of using a solid source to prepare refractory compounds, as in the case of silicon carbide discussed above, a similar reaction has been used to prepare titanium boride coatings on silicon carbide and hafnium diboride coatings on carbon by means of a gaseous input to the deposition furnace (Choy and Derby, 1993) (Shinavski and Diefendorf, 1993). 

The horizontal temperature distribution in various furnaces was measured around a circle of 15 mm

heating elements could be seen in the temperature distribution curves of the high temperature furnaces which is connected with geometry. At 1000 °C the differences are within the order of several degrees. 

FIGURE 10.1. Apparatus used to grow silicon-based self-aligned nanostructures and nanowires. A quartz tube was placed in a high temperature furnace (shown here). Ar, H2 and CH4 selectively flowed through the tube. 

The catalyst is necessary to ensure that the components react with reasonable speed, bnt unfortnnately, the reaction does not always proceed to completion. For this reason, two or three stages are nsed, with sulfur being removed between the stages. For analysts it is valuable to know that carbon disulfide (CS2) is a by-product from the reaction in the high-temperature furnace. The carbon disulfide can be destroyed catalytically before it enters the catalytic section proper. Generally, the Clans process may remove only about 90% of the hydrogen sulfide in the gas stream, and as already noted, other processes, such as the Beaven process, SCOT process, or Wellman-Lord process are often used to recover additional sulfur. 

An intrinsic, exothermic water-gas shift reaction occurs in the steam reformer reactor. The combined reaction, steam reforming and water gas shift, is endothermic. As such, an indirect high temperature heat source is needed to operate the reactor. This heat source usually takes the shape of an immediately adjacent high temperature furnace that combusts a small portion of the raw fuel or the fuel effluent from the fuel cell. Efficiency improves by using rejected heat from other parts of the system. Note that the intrinsic water-gas shift in the reactor may not lower the... 

Air-staged burners Low-NO air-staged burners for firing gas (or oil) are shown in Fig. 24-28. A high-performance, low-NO, burner for high-temperature furnaces is shown in Fig. 24-32. In this design, both air-staging and external flue-gas recirculation are used to achieve extremely low levels of NO emissions (approximately 90 percent lower than conventional burners). The flue gas is recirculated by a jet-pump driven by the primary combustion air. 

FIG. 24-32 Low-NOx burner with air-staging and flue-gas recirculation for use in high-temperature furnaces. Hauck Manufacturing Company. Developed and patented by the Gas Research Institute.)... 

Boron nitrate (B + N —> BN) is a white powder used to line high-temperatures furnaces, to make heating crucibles, for electrical and chemical equipment, for heat shields on spacecraft nosecones, and to make high-strength fabrics. 

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