Processing drying

Dry bead process Dry-cell batteries Dry chemistry Dry-cleaning Dry cleaning fastness Dry-cleaning fluid Dry-cleaning solvent Dryers... 

The shell-molding process, introduced in the United States in 1948, is an important market for phenoHc resins. In the original process, dry sand and powdered resin (6—8%) are blended. However, because of the high binder content and the difficulty in obtaining a uniform mix, precoating methods were developed. 

Mixing of latex compounds is accompHshed by stirring ingredients into the latex in the form of water solutions, dispersions, or emulsions. Although the mbber softeners needed to process dry mbber are not necessary for latex, use of emulsified softeners or polymeric plasticizers in natural or synthetic latex compounds provides lower modulus in the finished products. This reduces hand fatigue and increases touch sensitivity in dipped mbber gloves. Mineral oils are also used as an economy. 

Early Synthesis. Reported by Kolbe in 1859, the synthetic route for preparing the acid was by treating phenol with carbon dioxide in the presence of metallic sodium (6). During this early period, the only practical route for large quantities of sahcyhc acid was the saponification of methyl sahcylate obtained from the leaves of wintergreen or the bark of sweet bitch. The first suitable commercial synthetic process was introduced by Kolbe 15 years later in 1874 and is the route most commonly used in the 1990s. In this process, dry sodium phenate reacts with carbon dioxide under pressure at elevated (180—200°C) temperature (7). There were limitations, however not only was the reaction reversible, but the best possible yield of sahcyhc acid was 50%. An improvement by Schmitt was the control of temperature, and the separation of the reaction into two parts. At lower (120—140°C) temperatures and under pressures of 500—700 kPa (5—7 atm), the absorption of carbon dioxide forms the intermediate phenyl carbonate almost quantitatively (8,9). The sodium phenyl carbonate rearranges predominately to the ortho-isomer. sodium sahcylate (eq. 8). 

Another modification to the vertical coke oven process, dry quenching of the coke as first developed in the GIS (13), started becoming of interest in the 1960s and has continued to grow steadily. Using dry quenching, the coke is discharged into a hot car and is quickly transported and dumped into a... 

Dry-Throwaway Processes. Dry-throwaway systems were the precursor of processes that removed SO2 iu the ductwork, eg, the BCZ and IDS processes. Here, however, the device is a spray chamber similar to the wet scmbbers such as the three modules of the Colstrip iastallation (Fig. 12). Into the upper portion of the chamber a slurry or clear solution containing sorbent is sprayed. Water evaporates from the droplets, the sorbent reacts with SO2 both before and after drying, and the dry product is removed ia a downstream baghouse or ESP (72). Unfortunately, dry scmbbiag is much less efficient than wet scmbbiag and lime, iastead of the much less expensive limestone, is required to remove SO2 effectively. Consequentiy, a search has been conducted for more reactive sorbents (72—75). 

E. M. Cook and H. D. DuMont, Process Drying Practice, McGraw-Hill, Inc., New York, 1991. 

L. P. Posati and M. L. On, Composition of Foods, Fairy and Ejpr Products, Fam-Processed-Dried, Agriculture Handbook No. 8-1, USDA Reseaicli Service, Washington, D.C., Nov., 1976. 

Driers are used in the forest products industry to lower the moisture content of the wood product being processed. Drying of dimension lumber gives it dimensional stability. This type of drying is done in steam kilns and is a batch process. No appreciable pollutants are released. 

Hydrochloric acid may conveniently be prepared by combustion of hydrogen with chlorine. In a typical process dry hydrogen chloride is passed into a vapour blender to be mixed with an equimolar proportion of dry acetylene. The presence of chlorine may cause an explosion and thus a device is used to detect any sudden rise in temperature. In such circumstances the hydrogen chloride is automatically diverted to the atmosphere. The mixture of gases is then led to a multi-tubular reactor, each tube of which is packed with a mercuric chloride catalyst on an activated carbon support. The reaction is initiated by heat but once it has started cooling has to be applied to control the highly exothermic reaction at about 90-100°C. In addition to the main reaction the side reactions shown in Figure 12.6 may occur. 

The drying a chemical substance is not a simple process. Drying a mass of finely divided solid particles carrying 30 to 40% water, for example the rate of evaporation is constant and high as long as the surfaces exposed are wet. After the surface is dry, the water in the interstices must make its way to the surface, a process of diffusion that is slower than evaporation from a wet surface the rate will then drop. This second part of the process must be modified according to the case with which the material crumbles as it dries, exposing new surfaces. 

Lampinen, M. J. and Toivonen, K., Application of a Thermodynamic Theory to Determine Capillary Pressure and Other Fundamental Material Properties Affecting the Drying Process, DRYING 84, Springer-Verlag, 228-244, 1984. 

Pre-heating a product in an industriai process Drying mait... 

Although implants are rather easily fabricated, problems have occurred in instances when care is not taken in maintaining an ultradry processing environment. It is extremely important to thoroughly dry the bulk polymer and the bioactive agent, usually at ambient temperature under vacuum, prior to processing. Dry nitrogen... 

Resist stripping- Both wet and dry removal processes are used at this step in processing. Dry ashing removes the bulk of the photoresist and wet stripping removes remsuning residues. 

During fermentation and subsequent drying, the unfermented wet beans lose about 65% of their weight. The reduction of moisture halts the enzymatic processes. Drying is complete when the moisture content reaches about 6% and the beans readily break into pieces called nibs. 

Finally, a novel process has been described for efficient photoconversion of low-grade organic materials such as waste biomass into polyesters. In this process, dry biomass has been thermally gasified which resulted in gas mixtures composed primarily of CO and H2. Photosynthetic bacteria photoassimilated components of the synthesized gas into new cell mass. Under unbalanced culture conditions, when growth was limited by several nutrients, up to 28 % of the new biomass was found to be poly(3HB) [37]. 

Mica is available in a variety of grades and finds application as a semi-reinforcing filler and more often as a processing dry lubricant owing to its flake-like structure. It is also used as a dusting agent. 

PTT polymer pellets must be dried to a moisture level of <30 ppm, preferably in a close-loop hot air dryer, to avoid hydrolytic degradation during melt processing. Drying is carried out with 130 °C hot air with a dew point of < -40 °C for at least 4 h. Because of the faster crystallization rate, PTT pellets are already semicrystalline after pelletizing, and do not require pre-crystallization prior to drying as with PET. The dried polymer is extruded at 250-270 °C into bulk continuous filaments (BCFs), partially oriented yam (POY), spin-draw yam (SDY) and staple fiber. 

Two manufacturing processes, dry and wet, are in competition leading to some significantly different properties, particularly for the impact resistance ... 

The atmospheric load is delivered to the sea surface via two processes dry and wet deposition. Dry deposition is mostly gravitational when winds weaken, solid particles fall to the sea surface. Wet deposition involves incorporation into a raindrop that falls to the sea surfece. Particulate trace elements can become entrained in raindrops and thereby carried to the sea surfece. Along the way, some of the trace elements can dissolve. Gaseous trace elements, such as mercury, can also be dissolved directly into raindrops. Thus, rainwater can contain dissolved trace metals. 

Uses. Manufacture of fluorocarbons for refrigerants, aerosol propellants, plastics purifying antibiotics solvent photographic processing dry cleaning... 

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