Pellet drying process

In many cases drying operations are critical to the production of successful commercial catalysts. Close control of the drying process is necessary to achieve the proper distribution of the catalyst precursor within the pore structure of the support. Drying also influences the physical characteristics of the finished catalyst and the ease with which subsequent pelleting or extrusion processes may be carried out. 

Other pigment blacks and the rubber blacks are compacted by granulation. Two processes are used dry and wet pelletization. Dry pelletization is a simple, energysaving method, but it does not work with all types of carbon black. It is mainly used for color blacks. Dry pelletization is carried out in rotating drums, where the powdery carbon black rolls to form small spheres. 

Portland cement clinker emerges from a dry process kiln as rounded pellets, or from a wet process kiln as irregularly shaped lumps, in either case typically of 3-20 mm dimensions. Typical clinkers are greenish black, the colour being due to ferrite phase that contains Mg (Ml8) in the absence of Mg , they are buff. Reducing conditions in the kiln typically produce clinkers that are yellowish brown, especially in the centres of the lumps, where less reoxidation has occurred. Light colours can also arise from underburning. 

The system utilized in Figure 3.13 for HIPS can also be used to produce a solution polymerization ABS. This type of ABS is used in non-glossy applications. The glossy ABS is usually produced in an emulsion process in which emulsified polybutadiene latex is grafted and agglomerated and blended with a continuous phase of SAN. This blended material is then dried and pelletized. This process is not cost competitive with the continuous solution polymerization, but it produces a product with a superior balance of properties that commands a premium price. 

The processing of the raw materials is different for plastic clays and lumpy shale. Plastic clays are crushed, ground, mixed, partially dehydrated and then formed into pellets of different sizes on a granulation table or similar apparatus before being thermally treated (half-wet process). Lumpy raw materials, such as shale, are only ground and, if necessary, classified (dry process) before thermal treatment. Adjustment of the bulk density of the final product to the required value is carried out during the subsequent thermal treatment. 

In the dry process, introduced by Allied Chemical Corp., the uranium concentrate is pelletized and directly reduced with hydrogen to uranium(IV) oxide at temperatures between 540 and 650°C in a fluidized bed reactor. Hydrofluorination to uranium(IV) fluoride proceeds in two fluidized bed reactors connected in series. After fluorinating the uranium(IV) fluoride formed in a production unit consisting of a flame-reactor and a fluidized bed reactor, the uranium(Vl) fluoride produced is purified in a two stage pressure distillation process. This distillative purification process is necessary, because, in contrast with the wet process, no purification is carried out in earlier stages. 

Cylindrical internal reflectance infrared spectroscopy presents many advantages over conventional infrared techniques for the study of aquatic humic and fulvic materials. Samples can be studied in their natural state and in the aqueous environment from which they are isolated. Sample alterations due to drying and exposure to high pressures in the pellet forming process are avoided. In addition. 

The AIROX (Atomics international Reduction Oxidation) process is being developed to reprocess spent uranium oxide-based fuel. It is a cyclic oxidation-reduction process that employs only gaseous and solid materials no liquids are used. Hence, this process is often referred to as a dry process which simultaneously declads and pulverizes the fuel. Pulverization permits release of volatile fission products and comminutes the fuel for reenrichment and recycle. It also provides gaseous access to unreacted fuel in the center of the pellet. 

Basic process steps in the production of ROEMMC fuel pellets are DRYING of the wet raw material, SIZE REDUCTION of the dry material, and DENSIFICATION of the dry, fine material. The thermal energy for the drying process is derived from the combustion of fines separated from the dry, fine material. The only external energy input to the production of pellets is electrical. The hardware embodiment of these processes is described in these paragraphs, as employed in the Stillwater, Minnesota, plant. This plant was designed to have an output production rate of 150 tons per day, continuous operation. 

Overall, the spectra of the humic substances recorded in the aqueous state are comparable to those measured by the conventional KBr pellet technique on dried samples. However, FTIR allows the samples to be observed in their native wet state and avoids the shifts in chemical equilibrium which must necessarily accompany the drying process. More detailed information on the ionization of the carboxylic acid functional groups could be obtained by measuring the spectra of the aqueous samples over a wide range of pH values. FTIR may also provide a tool for investigating the kinetics of metal-humic interactions and other reactions of humic substances in the aqueous state. 

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