Plants, portable batch

A mobile source of air pollution can be defined as one capable of moving from one place to another under its own power. According to this definition, an automobile is a mobile source and a portable asphalt batching plant is not. Generally, mobile sources imply transportation, but sources such as construction equipment, gasoUne-powered lawn mowers, and gasoline-powered tools are included in this category. 

Portable batch plants have also been built to melt and blend composites on-site. These are useful for larger applications where multiple batches of composite are required. One such unit, built and maintained in Canada, consists of two steam-heated vessels mounted on a common skid. They can be used to convert sulfur into composites or to melt preblended composite delivered to the site in solid form. The vessels have capacities of 1500 and 800 gal. The pump and manifold system has a dual function to transfer sulfur and composite to and from the vessels or to spray-apply composite directly from the tanks via heated hoses. 

Access to the canal was reasonably good so the Canadian portable batch plant described earlier was used to make the composite and to spray-apply it to the canal. The batch plant, an electrical generator, and a steam boiler were placed on a 40-ft flatbed trailer. The trailer remained stationary while the composite was prepared and sprayed but was moved periodically between batches. 

The oscillatory baffle reactor/oscillatory flow reactor (OBR/OFR) types are seen as for niche applications, where one wants to convert a long residence time batch process to a continuous one. In the case of biodiesel, Dr Harvey indicates that a conversion could be carried out in 10 minntes, compared to 1-6 hours in continnons indnstrial processes. One variant is shown, by means of a flow diagram, in Figure 10.20, while Figure 10.21 shows components of the OFR. The aim is to make the plant portable so that it will fit into a standard shipping container. The unit could be sold worldwide to, for example, formers to produce their own fuel locally. 

Batching and mixing plants encountered in construction work vary over a wide range. The plants may be large-capacity, fully automatic plants with several stationary mixers they may be small portable, manually operated... 

The sodium reduction of titanium tetrachloride was actually carried out as early as 1939 in Germany, and about 670 kg was produced by the Deutsche Gold and Silber Scheideanstalt, during the 1939-45 war. The process, now obsolete, involved reduction in a molten bath of 50 per cent sodium chloride and 50 per cent potassium chloride at 800°C in an atmos phere of hydrogen. The reactors consisted of expendable welded sheet-iron cylindrical vessels, 50 cm diameter by 70 cm deep and 2 mm thick. These rested loosely in a stout iron crucible, fitted into a gas-fired furnace. A portable stirrer was used to agitate the reactor contents. Approximately 20 kg batches of titanium were reduced by distilling 85 kg of titanium tetrachloride at a controlled rate into a melt of 15 kg sodium chloride and 15 kg of potassium chloride, covered with a layer of 46 kg of molten sodium. The titanium sank to the bottom of the molten salts, and at the end of the reaction was recovered from the crushed solidified melt by leaching with dilute hydrochloric acid, in a ceramic-lined vessel. It was finally washed in water and dried at a moderate temperature. The same plant was also used for the production of zirconium metal by the sodium reduction of potassium fluorozirconate (KaZrF ]. 

---