Drier, secondary

Cobalt. There is no U.S. mine production of cobalt. Refining of imported nickel—cobalt mattes has not occurred since the mid-1980s. About 1600 t of secondary cobalt was recycled from scrap by 13 faciUties in the United States representing - 22% of total U.S. consumption. The price of the metal was around 44/kg. Most is imported from Zaire and Zambia. Increasing quantities are coming from Russia. Historically, the price of cobalt has been quite volatile and dependent on the pohtical environment in those countries. Cobalt is used in superaHoys, 40% catalysts, 14% paint driers, 11% magnetic alloys, 10% and cemented carbides and other uses, 16%. 

Tray, Truck, and Tunnel Driers In order to accelerate drying, the closet is factory-built with tight walls. It forms a box, and the air is passed by means of a fan over a radiator or over finned tubes and then over the trays. A portion of the air escapes at the discharge opening the remainder is reheated and recirculated. An amount of new air equivalent to the volume discharged is admitted at the fan. Secondary heating tubes are placed in the path of the air to restore their temperature and heat content. In the tray drier, shallow pans 2 ft by 3 ft by 2 in. deep, for example, are placed on a rack, forming part of the drier. In the truck drier, the rack is on wheels, and the whole may be wheeled in and out of the drier. There may be one or several trucks to each drier, and each truck may have twelve, sixteen or more levels for trays. 

In modem boilers, both FT steam spaces and WT steam drums incorporate various devices to promote the effective separation of steam from water and the production of dry steam. These devices include horizontal separators and baffle plates in the steam/water space, and chevron driers, cyclone separators, and secondary steam scrubbers in the steam space. Older or simpler boiler designs with steam release velocities of below 3 ft/s (0.9 m/s) may rely solely on the natural separation of steam from water. 

Constipation can be due to primary and secondary causes (Table 18-1). Primary or idiopathic constipation is typified by normal-transit constipation, slow-transit constipation, and dyssynergic defecation. In the normal-transit type, colonic motility is unchanged and patients tend to experience hard stools despite normal movements. In the slow-transit type, motility is decreased leading to infrequent harder, drier stools. In dyssynergic defecation (also known as pelvic floor dysfunction), patients have lost the ability to relax the anal sphincter while coordinating muscle contractions of the pelvic floor. Some causes of secondary constipation are listed in Table 18-1. 

I) Raw material. (2) Acid water. (3) Primary steam. (4) Secondary steam. (5) Vapor of 5.5 % furfural. (6) Demineralized water. (7) Cake to drier. (8) Reactor condensate. (9) Waste water. (10) Low boilers. 

Desiccation, under drier conditions (RH < 30%), will lead to increased cross-linking of the chains in the amorphous zones through secondary bonding, and brittleness. The overt results are shrinkage and loss of flexibility. As the... 

In chemical process control the variable that is most commonly inferred from secondary measurements is composition. This is due to the lack of reliable, rapid, and economical measuring devices for a wide spectrum of chemical systems. Thus inferential control may be used for the control of chemical reactors, distillation columns, and other mass transfer operations such as driers and absorbers. Temperature is the most common secondary measurement used to infer the unmeasured composition. 

Thomas, D. B. and Pratt, D. J. (1967). Bush control studies in the drier areas of Kenya. IV. Effects of controlled burning on secondary thicket in upland Acacia woodland. /. Appl. EcoL 4, 325-335. 

Since we are here concerned mainly with pharmaceutical and, especially, biopharmaceutical freeze-drying, processing costs are of secondary importance. Care must however be taken that limited freeze-drying capacity does not give rise to production problems. Thus, where the total drier capacity threatens to become the limiting factor in the production cycle, the best remedy is to examine whether, and how the cycle length might be reduced, commensurate with the maintenance of an acceptable product quality. This is a problem to which we shall return several times. 

The secondary and through driers are of a group of metals, including lead, zirconium, calcium and cerium, which assist the drying of the lower layers of the paint film by mechanisms which are not fully understood, but probably involve interactions of the metal with carboxyl (and perhaps hydroxyl) groups in the film-former. Because lead is a cumulative poison, permissible levels of lead in household paints have been reduced so much that paint manufacturers now formulate paints of this type without the use of any added lead at all. 

Cobalt leads to more rapid drying at the surface of the film than in the lower layers. If the surface dries first, it will buckle or shrivel when the rest of the film contracts as it hardens. For this reason, secondary driers are usually added with cobalt to accelerate the drying of the bulk of the film. The presence of calcium accelerates the loss of unsaturation in the film. When the levels of the two types of drier are balanced , shrivelling does not occur. Manganese is less pronounced in its surface bias, but is also used with secondary driers. 

For applications involving electricity generation, the steam generators deliver superheated steam to the turbines, eliminating the need for steam drams, driers and steam separator equipment. Since the secondary pressure is less than the primaiy pressure, the steam generator tubes will operate under compression, which provides added resistance to stress-induced corrosion cracking. 

Limestone is homogeneous in chemical composition, mainly containing calcium carbonate, with varying amounts of magnesium (dolomites) and clay (Marschner, 1995 Lugo et al., 2001). On limestone bedrock a variety of calcium-rich soils develop, particularly the rendzinas. Climatic differences determine variations in ion accumulations in the upper soil layers. In drier climates, rapid evaporation causes water-soluble salts to accumulate at the surface. In more hmnid regions, rainfall leaches out both nutrients and calcium carbonate leading to a secondary acidification . 

Lead driers have traditionally been the most common, although toxicity concerns now severely restriet their use. Lead is a secondary drier as its sole function is to catalyze oxygen uptake. This and its relatively low reactivity make it a good through drier. For this reason it was widely used in combinations with primary driers in the past. It is still used where toxicity and atmospheric sulfide staining do not rule it out. Caleium soaps have been used with lead driers to improve lead solubility and low temperature drying. 

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