Thermal processing equipment

Some types of thermal processing equipment, such as a Banbury, are designed to perform the preliminary mixing before the extrusion step. In this case, a weighed-out formula batch is directly added to the feed throat of the equipment. 

Routine monitoring indicates that typical exposures at the point of thermal process equipment feed range from a low of 0.10 mg/m3 to a high of 2.93 mg/m3 (total dust). The average exposure level over a 5-year period may be about 0.71 mg/m3. 

In the newest plants, the sealed mixing chamber would be directly connected to the feed throat of the thermal processing equipment before it is opened. When the vessel is emptied, it is again closed and sent to a special equipment wash bay for cleaning. This enclosed system virtually eliminates dust emissions throughout the thermal encapsulation process. 

Purge resin generated by thermal processing equipment clean-out is a nonhazardous material that is either reentered into the production process or sold to plastics recyclers. However, small quantities of this material do end up in a facility s routine trash and ultimately ends up in a solid waste landfill. 

K-H. Lee, T. P Merchant, and K. F. Jensen, Simulation of Rapid Thermal Processing Equipment and Processes, in J. C. Gelpy et al. (eds.), Rapid Thermal and Integrated Processing II, 303, pp. 197-209, Materials Research Society Symposium Proceedings, MRS, Pittsburgh, 1993. 

Process Va.ria.tlons. The conventional techniques for tea manufacture have been replaced in part by newer processing methods adopted for a greater degree of automation and control. These newer methods include withering modification (78), different types of maceration equipment (79), closed systems for fermentation (80), and fluid-bed dryers (81). A thermal process has been described which utilizes decreased time periods for enzymatic reactions but depends on heat treatment at 50—65°C to develop black tea character (82). It is claimed that tannin—protein complex formation is decreased and, therefore, greater tannin extractabiUty is achieved. Tea value is beheved to be increased through use of this process. 

The thermal stabiUty of epoxy phenol—novolak resins is useful in adhesives, stmctural and electrical laminates, coatings, castings, and encapsulations for elevated temperature service (Table 3). Filament-wound pipe and storage tanks, liners for pumps and other chemical process equipment, and corrosion-resistant coatings are typical appHcations using the chemically resistant properties of epoxy novolak resins. 

Adiabatic Reaction Temperature (T ). The concept of adiabatic or theoretical reaction temperature (T j) plays an important role in the design of chemical reactors, gas furnaces, and other process equipment to handle highly exothermic reactions such as combustion. T is defined as the final temperature attained by the reaction mixture at the completion of a chemical reaction carried out under adiabatic conditions in a closed system at constant pressure. Theoretically, this is the maximum temperature achieved by the products when stoichiometric quantities of reactants are completely converted into products in an adiabatic reactor. In general, T is a function of the initial temperature (T) of the reactants and their relative amounts as well as the presence of any nonreactive (inert) materials. T is also dependent on the extent of completion of the reaction. In actual experiments, it is very unlikely that the theoretical maximum values of T can be realized, but the calculated results do provide an idealized basis for comparison of the thermal effects resulting from exothermic reactions. Lower feed temperatures (T), presence of inerts and excess reactants, and incomplete conversion tend to reduce the value of T. The term theoretical or adiabatic flame temperature (T,, ) is preferred over T in dealing exclusively with the combustion of fuels. 

The absence of corrosion, coupled with the fact that scale and other deposits appear to be dislocated by thermal cycling, result in a finish on tantalum heating surfaces that is as good as the original, even after 20 or 30 years in service, and also ensure that good heat-transfer properties are maintained throughout the life of the equipment. The use of tantalum for process equipment also ensures freedom from contaminations of the product. 

The Cluster Tool Concept. A recent trend in semiconductor equipment is the integration of two or more functions, such as CVD, PVD, etching, stripping, or rapid thermal processing, in one piece of equipment the so-called cluster tool. A continuous vacuum can be maintained, a feature which reduces the handling and contamination problems, increases the overall throughput, improves the process control, and generally lowers the cost. 

Light sources are often expensive, especially if made of thick-walled quartz as in high-pressure mercury lamps, and delicate, so that equipment costs may be high compared to thermal processes. 

Results for thermal expansion coefficient of liquids are presented for major organic chemicals. The results are especially helpful in the design of relief systems for process equipment containing liquids that are subject to thermal expansion. 

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