Dry processing method

Although the retention of selective fission products in fissile materials may not adversely affect the performance of fuel in a reactor, the intensity of the gamma radiation is such that the fissile material must be handled, transferred, and fabricated remotely. As a result, it is both technically difficult to divert the fissile material and fabricate a weapon, and nearly impossible to do so without detection. The levels of residual radioactivity in the product of some of the pyrochemical or dry processing methods is close to that found in spent unreprocessed fuel and hence the reprocessed product presents a risk to proliferation only trivially less than that of spent fuel. Pyrochemical and dry processing methods can be used that will... 

Pyrochemical processing methods may offer unique advantages over more conventional aqueous methods with respect to meeting nonproliferation goals. Some pyrochemical processes are intrinsically proliferation resistant because the process is incapable of producing a weapons-usable product without significant alterations. The product also can be sufficiently radioactive that it is physically difficult to divert. These features warrant the examination of pyrochemical and dry processing methods under current nonproliferation policies. 

Manufacturing of medium-density fiberboards (MDFBs) from hngo-ceUulosic fibers has been increasing in recent years [113-115]. Structural fiberboards are being made from wood, other plant materials, and wastepaper. They are classified by density and can be prepared by dry or wet processes. These boards fall into two main categories high density (hardboard) fiberboards and MDFBs. The fiberboards are prepared by the dry process method, whereas the wet process method is apphed to both hardboards and low density insulation boards [103]. 

The manufacture of MDF, with a few exceptions, dupHcates the manufacture methods for dry-process hardboard, described at length hereia. One exception to it is that most MDF is made ia the medium-density range, 640—800 kg/m although small amounts are made at lower or higher densities. Second, the vast majority of MDF is made with UF resia adhesives with resia requhemeats ia the 7—11% range, and wax is usually added at the 0.50—0.75% level. A small amount of exterior-grade MDF is made with isocyanate resia. 

Production of net-shape siUca (qv) components serves as an example of sol—gel processing methods. A siUca gel may be formed by network growth from an array of discrete coUoidal particles (method 1) or by formation of an intercoimected three-dimensional network by the simultaneous hydrolysis and polycondensation of a chemical precursor (methods 2 and 3). When the pore Hquid is removed as a gas phase from the intercoimected soHd gel network under supercritical conditions (critical-point drying, method 2), the soHd network does not coUapse and a low density aerogel is produced. Aerogels can have pore volumes as large as 98% and densities as low as 80 kg/m (12,19). 

OC-Hemihydrate. Three processing methods are used for the production of a-hemihydrate. One, developed in the 1930s, involves charging lump gypsum rock 1.3—5 cm in size into a vertical retort, sealing it, and applying steam at a pressure of 117 kPa (17 psi) and a temperature of about 123°C (6). After calcination under these conditions for 5—7 h the hot moist rock is quickly dried and pulverized. 

Efforts have also been made to overcome compHcated processes. Methods to reduce the number of steps or to use new starting materials have been studied extensively. l-Amino-2-chloro-4-hydroxyanthraquinone (the intermediate for disperse red dyes) conventionally requires four steps from anthraquinone and four separation (filtration and drying) operations. In recent years an improved process has been proposed that involves three reactions and only two separation operations starting from chloroben2ene (Fig. 2). 

Flue gas desulfurization may be carried out using either of two basic FGD systems regenerable and throwaway. Both methods may include wet or dry processes. Currently, more than 90% of utility FGD systems use a wet throwaway system process. Throwaway systems use inexpensive scrubbing mediums that are less costly to replace than to regenerate. 

Freeze-drying, like all drying processes, is a method to separate liquid water from a wet solid product or from a solution or dispersion of given concentration. However, the main difference is that the liquid water is separated by solidification (i.e., the formation of ice crystals) and subsequent vacuum sublimation instead of evaporation. This allows a drying at subzero temperatures which can be advantageous in case of heat-sensitive products. There are two general applications... 

Frit may be milled dry or wet. The long established dry process is used for cast iron baths and for chemical plant. Vitreous enamel application by a dry electrostatic method is being used on an increasing scale. In these cases, the frit is milled alone, or with inorganic colouring or refractory additives. This is achieved in cylinders using balls of porcelain, steatite or more dense alumina, or with pebbles of flint, to produce a fine powder of predetermined size. 

The old dry process enamelling of cast iron (baths etc.) is no longer widely used. The method consisted of sieving finely powdered frit onto the preheated casting and inserting the casting back into a furnace at about 900°C to produce the smooth finish. 

Volatile There are plastics that contain small quantities of material that boil at processing temperatures, or they may be contaminated by water absorbed from the atmosphere. These volatiles may cause bubbles, a scarred surface, and other defects. Processing methods of removing volatiles are used such as drying materials to be processed, vented plasticator barrels, etc. (Chapter 7, OTHER BEHAVIOR, Drying Plastic). 

Another processing method has been termed the solventless. process. In this method, a premix is made from NC fibers plus liquid NG and minor ingredients dispersed in water. The paste is centrifuged and air-dried. The remaining ingredients are tumble-blended and then calender-rolled into sheets called carpet rolls . These are then extruded into finished pellets or cylinders... 

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