Cooling belt

Several plants employ cooled-belt flakers. These consist of flexible steel belts, ca 1-m wide and up to 50-m long, that have short mbber skirting at the edges. Molten pitch flows from a thermostatically controlled tank over a weir to give a flat thin sheet on the belt, which is cooled from below by water sprays. At the end of the belt, the solid pitch is broken up by rotating tines. The pitch flakes are drained and transported to a covered storage silo by belt conveyor, during which time the surface moisture evaporates. 

Since the binder systems are solid at room temperature, they can be produced by the existing methods used for powder coafingsd Solid resins, pigments, photoinitiators, and other additives are premixed, then melted and dispersed in an extruder at 100 to 130°C (212 to 266°F). The molten blend is then squeezed into a thin ribbon between chilled rolls. This ribbon is further cooled to near room temperature on a water-cooled cooling belt. The cooled ribbon is broken first into flake and then ground into a fine powder ready for use. The process is illustrated in Figure 7.15. 

Under this term are known devices in the form of rotary drums for prepg various substances in the form of small scales (flakes). Such drums, known as flakers are used in the manuf of TNT. Flaking can also be done by using water-cooled belts, such as in the Stengel process for making flaked Ammonium Nitrate. This process is briefly described in this Encycl, Vol 1, p A315-R. 

As shown in Fig. 14.20, the discharged product cools and hardens on a cooling belt and is cut in a strand pelletizer. Alternatively, it can be cut directly at the nozzle by a head pelletizer and cooled in a vibrating screen. 

In the sizing operation, the medicated lozenges are collected as they leave the cooling belt and transferred to a series of counterrotating rollers separated via caliper adjustment. The sizing operation removes all oversized and undersized lozenges, ensuring uniformity. 

Hot-melt extrusion also requires other components to be scaled up in size as the extruder is scaled up in size. Typical components include multiple powder and liquid feeders, a chiller, a take-off cooling belt unit, and a control panel(s). Proper sizing of all components to achieve control of the process at each step is critical, especially because of the interrelationship of individual component feeds into the extruder and the resulting quality of the final extrudate. Variability on inputs translates into product variability on output from the extruder owing to its continuous principle of operation. 

Jones BT, Glick MR. Mignardi MA. et al. 1988. Determination of polycyclic aromatic hydrocarbons in cooked beef by low-temperature molecular luminescence spectrometry using a moving sample cooling belt. Appl Spectrosc 42(5) 850-853. 

The cresols are charged into the kettle and heated to 95°C, the catalyst is added and dissolved, and the formaldehyde is added over several hours to complete the exothermic reaction. The kettle is then heated to above 160°C and vacuum is drawn. Water and unreacted p-cresol are stripped off, residual oxalic acid decomposes to carbon dioxide, and only molten novolac resin remains in the kettle. The product is poured onto a cooling belt, and crushed. ... 

The Sandvik continuous cooled belt crystallizer (Figure 8.25) may be considered as an alternative to the rotary cooled drum. The underside of the steel belt is sprayed with cooling water to provide a controlled temperature gradient along... 

Drop the batch on a heated roll mill, cut into a continuous strip and convey on an air-cooled belt to a dicer or feed to an extmder attached to an underwater pelletizer or a strand die, conveyer belt and a dicer. If mbber level is high, then the pellets may stick together. In such instances one can dust the pellets with a small amount of dusting agent. One can also use a two roll stuffer to feed the molten blend to the single-screw extruder. 

Online processing of extrudates Cooling belt, pelletization, milling, and chillers Calendaring or direct shaping of materials such as films, implants, or tablets Downstream processing of the extrudates... 

The standard cooling belt is carried out as a stainless steel conveyor while the cooling is done by pharma air (Fig. 15). The belt swings at the entry to deposit the warm product with maximum contact surface. This allows short belts even for high temperature differences between extrudate entry and product outlet. 

Phenol resins, both resols and novolacs, are exclusively made in batch processes. In the production of novolacs, molten phenol is charged into the heated and stirred reaction tank together with the weak acidic catalyst (for estample, oxalic add). At 95°C, the aqueous formalin solution is slowly added, while the reaction heat is removed through distillation of water at slightly diminished pressure. When all the formaldehyde has reacted, the water is distilled off and the reaction with the excess phenol is continued at higher temperature (140-160°C). When the desired viscosity is reached, the excess of unreacted phenol is removed by distillation as well. The molten resin is let down onto a cooling belt, and broken into small glassy lumps. 

In cases where the resins are to be supplied in a solvent anyway, azeotropic distillation can be used to remove the water more efficiently and at lower temperatures. Figure 16.3 describes the reactor design for polyester resin production, which can also be applied to alkyd resin production (see Section 16.5). The product resin can be either cooled and discharged via a cooling belt in case a solid delivery form is required, or thinned with solvents. 

Sulfur forming was invented to allow the transportation of solid sulfur with less risk than broken. The earliest sulfur forming was flake or slate sulfur. Liquid sulfur is poured onto a water-cooled moving belt to produce a sheet or ribbon of sulfur, which falls off the belt and breaks into chips, called slate. In the mid 1950 s, Texas Gulf Sulfur was experimenting with slate sulfur. A plant was installed at their Chacahoula mine. One of the earliest sulfur slate-forming plants was installed by Pemex of Mexico in 1953 the unit contained a water-cooled belt... 

The extruded strands are cooled in a water bath or preferably with a cooling belt to a temperature that they can be chopped in the pelletizer. If the strand is too hot entering the pelletizer the pellets will smear and deform. K the strand is too cold entering the pelletizer, shards will break off the strand during the cutting process due to the brittle nature of the material. A strand temperature near 100 °C is usually suitable for palletizing SPS formulations. To avoid excessive fines, care should be taken to keep the cutter knife sharp and maintain rotor-bed knife gap on the pelletizer. 

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