Large industrial

The extremely unusual physical properties of the rare earths are the reason for a number of industrial appHcations where no other element can suffice. Furthermore, although RE chemical properties are rather similar to those of the alkaline earths, some specific properties have pushed the rare earths into large industrial developments. 

However, packaged boilers have a limited size range. Thus, field-erected boilers are stiU required for most large industrial and utiUty iastakations. 

Economy of time and resources dictate using the smallest sized faciHty possible to assure that projected larger scale performance is within tolerable levels of risk and uncertainty. Minimum sizes of such laboratory and pilot units often are set by operabiHty factors not directly involving internal reactor features. These include feed and product transfer line diameters, inventory control in feed and product separation systems, and preheat and temperature maintenance requirements. Most of these extraneous factors favor large units. Large industrial plants can be operated with high service factors for years, whereas it is not unusual for pilot units to operate at sustained conditions for only days or even hours. 

Oil having characteristics that make it unsuitable for further use or economic recycling. This material may be usable as a fuel in large industrial furnaces, such as cement kilns. 

Industrial Uses. Large industrial faciUties, particularly those using cyclone boilers or fluidized-bed boilers, are potential markets. In addition, several vendors of small- and medium-sized industrial energy and steam faciUties are marketing units capable of using I DE. As the availabiUty of I DE expands with new producers entering the market, it is hoped that the industrial use of I DE will also expand (7). 

For by-product coke ovens, it is general practice to blend two or more types of coals that have complimentary technical as well as economic characteristics. Because most by-product coke plants are located near the large industrial users of the coke and by-products, coals usually have to be transported from the coal mines to the coke plants. Thus coal blends are designed on integration of coke quaUty needs, by-product quaUty needs, coal costs, transportation costs, impacts of productivity, and impacts on the coke ovens themselves. The physical behavior of coal blends during coking can damage coke ovens. 

The system shown in Fig. 11-75 is direct expansion where diy or slightly superheated vapor leaves the evaporator. Such systems are predominantly used in small applications because of their simplicity and light weight. For the systems where efficiency is crucial (large industrial systems), recirculating systems (Fig. 11-77) are more appropriate. 

Economics Microfiltratiou may be the triumph of the Lilliputians nonetheless, there are a few large-industrial applications. Dextrose plants are veiy large, and as membrane filtration displaces the precoat filters now standard in the industry, very large membrane microfiltratiou equipment will be built. 

Large industrial operations with on-site needs for electricity and heat in the form of process steam, direct heat, and/or space heat. 

Figure 2.3.1 (Wachtel, et al, 1972) shows the ARCO reactor that tried to simulate the real reaction conditions in a fluid cracking unit. This was a formal scale-down where many important similarities had to be sacrificed to get a workable unit. This unit was still too large for a laboratory study or test unit, but instead was pilot-plant equipment that could still give useful empirical results Since this serves a very large industry, it may pay off to try it, even if it costs a lot to operate.

Tubular (side combustors). These designs are found on large industrial turbines, espeeially European designs, and some small vehieular gas turbines. They offer the advantages of simplieity of design, ease of maintenanee, and long-life due to low heat release rates. These eombustors may be of the... 

With each succeeding year in the 1950s and 1960s there was a swing away from coal and vegetable sources of raw materials towards petroleum. Today such products as terephthalic acid, styrene, benzene, formaldehyde, vinyl acetate and acrylonitrile are produced from petroleum sources. Large industrial concerns that had been built on acetylene chemistry became based on petrochemicals whilst coal tar is no longer an indispensable source of aromatics. 

The United States generates about 20 million metric tons of nitrogen oxides per year, about 40% of which is emitted from mobile sources. Of the 11 million to 12 million metric tons of nitrogen oxides that originate from stationary sources, about 30% is the result of fuel combustion in large industrial furnaces and 70% is from electric utility furnaces. 

In large industrial installations, the latter is the most common arrangement. The burner has a profile plate that controls the rate of combustion air. The warm air delivery fan may be either centrifugal or axial. 

A number of general methods and methods particularly suited to and needed for ventilation in large industrial rooms are presented in the previous sections. They differ in complexity of effort and accuracy of results and therefore are applied at different stages of the design process. 

---