Batch casting

In laboratory operations, batch casting with a mobile doctor blade and stationary carrier are used. Plate glciss is usually used as a carrier. Tape drying can take place on the support by electric heaters placed imder the support. If only partial drying occurs, the tape, with or without the support, is placed in an oven to complete the dr5dng. Tapes of 0.5 m wide, 2 m long and 1-2 mm thick can be obtained. 

Fig. 9. Batch process for cast-composite polymer-based propellants. QC = quality control.

The slag is batch tapped into a receiving room where it is cooled and broken up for disposal. The metal buUion is tapped from the furnace periodically via a siphon into 2-t cast-iron molds. Typical buUion content from an electric furnace in wt % is Sb, 13—18 Sn, 1—2 As, 0.5—1 Cu, 0.3—0.4 and Ni, 0.05—0.1. The balance is lead. 

Three bulk polymerization processes are commercially important for the production of methacrylate polymers batch cell casting, continuous casting, and continuous bulk polymerization. Approximately half the worldwide production of bulk polymerized methacrylates is in the form of molding and extmsion compounds, a quarter is in the form of cell cast sheets, and a quarter is in the form of continuous cast sheets. 

Distillation. This is the point at which refining begins and was the first method by which petroleum was refined. Originally, distillation (qv) involved a batch operation in which the stiU was a cast-iron vessel mounted on brickwork over a fire and the volatile materials were passed through a pipe or gooseneck which led from the top of the stiU to a condenser. The latter was a coil of pipe, or a "worm" (hence the expression worm end products), immersed in a tank of miming water. 

Calcined alumina is a reactive powder used to make synthetic grain. It also may be used as a bonding or fine component in batched refractory mixes, as a raw material for molten cast refractories, or for refractory casting sHps. 

Pure zirconium tetrachloride is obtained by the fractional distillation of the anhydrous tetrachlorides in a high pressure system (58). Commercial operation of the fractional distillation process in a batch mode was proposed by Ishizuka Research Institute (59). The mixed tetrachlorides are heated above 437°C, the triple point of zirconium tetrachloride. AH of the hafnium tetrachloride and some of the zirconium tetrachloride are distiUed, leaving pure zirconium tetrachloride. The innovative aspect of this operation is the use of a double-sheU reactor. The autogenous pressure of 3—4.5 MPa (30—45 atm) inside the heated reactor is balanced by the nitrogen pressure contained in the cold outer reactor (60). However, previous evaluation in the former USSR of the binary distiUation process (61) has cast doubt on the feasibHity of also producing zirconium-free hafnium tetrachloride by this method because of the limited range of operating temperature imposed by the smaH difference in temperature between the triple point, 433°C, and critical temperature, 453°C, a hafnium tetrachloride. 

Vacuum-Shelf Dryers Vacuum-shelf diyers are indirec t-heated batch diyers consisting of avacuumtight chamber usually constructed of cast iron or steel plate, heated, supporting shelves within the chamber, a vacuum source, and usually a condenser. One or two doors are provided, depending on the size of the chamber. The doors are sealed with resihent gaskets of rubber or similar material (Fig. 12-49). 

Continuous mix — direct cast Continuous mix — transport to cast 300-gallon vertical batch 150-gallon vertical batch Continuous mix - transport to cast (processing 3 dissimilar formulations per week)... 

To study reaction kinetics, cement batches of total mass 300 g were prepared using ingredients measured to the nearest 0-1 g. Mixing was carried out for 10 minutes using a kitchen blender, after which specimens were cast in slabs 10 x 10 x 1-2-1-5 cm in polyethylene moulds. When the setting reaction had proceeded to a sufficient extent and viscosity had risen to give a reasonably stiff paste, a small portion was removed, placed on a glass microscope slide and immediately examined by X-ray diffraction. The remainder of the sample was allowed to set. 

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