Clean processing

Technologies to minimize resource consumption, to promote waste recovery and to develop clean processes and products... 

The cleaning process proceeds by one of three primary mechanisms solubilization, emulsification, and roll-up [229]. In solubilization the oily phase partitions into surfactant micelles that desorb from the solid surface and diffuse into the bulk. As mentioned above, there is a body of theoretical work on solubilization [146, 147] and numerous experimental studies by a variety of spectroscopic techniques [143-145,230]. Emulsification involves the formation and removal of an emulsion at the oil-water interface the removal step may involve hydrodynamic as well as surface chemical forces. Emulsion formation is covered in Chapter XIV. In roll-up the surfactant reduces the contact angle of the liquid soil or the surface free energy of a solid particle aiding its detachment and subsequent removal by hydrodynamic forces. Adam and Stevenson s beautiful photographs illustrate roll-up of lanoline on wood fibers [231]. In order to achieve roll-up, one requires the surface free energies for soil detachment illustrated in Fig. XIII-14 to obey... 

All glassware should be scrupulously clean and, for most purposes, dry before being employed in preparative work in the laboratory. It is well to develop the habit of cleaning all glass apparatus immediately after use the nature of the dirt will, in general, be known at the time, and, furthermore, the cleaning process becomes more difficult if the dirty apparatus is allowed to stand for any considerable period, particularly if volatile solvents have evaporated in the meantime. 

Another quaHty control problem of multipurpose plants is the clean out for a product change. A test for residual cleaning solvents in the ppm level is a necessity. The best vaHdation of the cleaning process is to develop an analytical method that is able to find the previous product in the new product at a level of not more than 1 ppm. Tests should be mn on at least the first three batches. 

Properties. The properties of char products from two possible coal feeds, a low sulfur Western coal, and a high sulfur Midwestern coal, are shown in Table 11. The char derived from the low sulfur Western coal may be direcdy suitable as plant fuel, with only minor addition of clean process gas to stabilize its combustion. Elue gas desulfurization may not be required. Elue gas from the combustion of the char derived from the high sulfur Illinois coal, however, requires desulfurization before it may be discharged into the atmosphere. 

Conventional coal cleaning processes can remove about 50% of pyritic sulfur and 30% of total sulfur. For northern Appalachian region coals it has been shown that a greater sulfur reduction can be achieved by applying physical coal cleaning to finer size coals (Table 3) (8). 

R. E. Hucko and co-workers, "Status of DOE-sponsored Advanced Coal Cleaning Processes," ia R. R. K1 impel and P. T. Luckie, eds.. Industrial Practice of Fine Coal Processing, SME, Inc., Littieton, Colo., 1989. 

Fig. 4. Process flow diagram for aluminum enameling showing (a) enamel preparation and application, and (b) metal preparation, where the cleaning processes A, B, and C represent primarily sheet D, primarily castings and E, aluminized steel (11).

Particulate matter contributes to the soiling of fabrics. The increased frequency of washing to remove dirt results in more wear on the fabric, causing it to deteriorate in the cleaning process. 

The centrifugal fuel-cleaning process consists of mixing 5-10% water with the oil plus an emulsion breaker to aid the separation of water and oil. Then a mixer dispenses the wash water into the oil stream to aid the impurities in forming a water solution. The centrifuges then separate this water from the... 

Used for small duties, clean process, and only infrequent cleaning required. Vaporization is usually less than 30%, but less than 15% if the fractionator pressure is below 50psig. The viscosity of the reboiler feed should be less than 0.5 cp. Put a butterfly valve in the reboiler inlet piping. This type is used in nearly 100% of chemical plant thermosyphon applications (70% of petrochemical). 

In the factory processes the sticklac is first passed through crushing rollers and sieved. The lac passes through the sieve but retains the bulk of the woody matter. The sieved lac is then washed by a stream of water and dried by a current of hot air. A second mechanical cleaning process removes small sticks which have not been removed in the earlier roller process. The product, seedlac, now contains 3-8% of impurities. 

J. Knoth, H. Schwenke, P. Eichinger in M. Heyns, M. Heuris, P. Mertens (eds.) Ultra-Clean Processing (UCPSS 94, IMEC), ACCO Leuven 1994, p. 107. 

As we learn from Sims s reviews, many other improvements have been made to superalloys and to their exploitation in recent decades. Solid-solution strengthening, grain-boundary strengthening with carbides and other precipitates, and especially the institution, some twenty years ago, of clean processing which allows the many unwanted impurities to be avoided (Benz 1999) have all improved the alloys to the point where (McLean 1996) the best superalloys now operate successfully at a Kelvin temperature which is as much as 85% of the melting temperature this shows that the prospect of significant further improvement is slight. 

The precautions for the use of perchloroethylene conespond with those for trichloroethylene (Table 5.52). The dry cleaning process, and its safety measures comprise ... 

A typical formula would consist of 18-28 parts of SBS rubber, 50-60 parts of an aliphatic/aromatic tackifier with about 15-30% aromaticity (for long open time), and 15-30 parts of a white oil or a very clean process oil. Formulations are designed to maximize open time, while maintaining adequate heat resi.stance (maintenance of bond strength upon aging at 40-55 C — warehouse conditions). 

---