Bottom Spray System

The Wurster bottom spray system has also been used successfully to coat particles as small as 100 microns. Attempting to coat smaller particles may result in the same difficulties as discussed in the previous segment. Batch capacities range from a few hundred grams to approximately 600 kg. Because fluidization quality is affected by batch size, at least 50% of the volume outside of the partition should be occupied by the uncoated product. Finished product batch size (for fine and intermediate particles) can be determined by the following equation . 

Almost all particle-separating devices can be converted into wet scrubbers by adding liquid spraying systems. Three types of commonly used scrubbers are the spray chamber, cyclonic scrubber, and venturi scrubber. Figure 7.18 shows a simple spray chamber in which water is sprayed through a series of nozzles into a settling chamber. The dust-laden gas is fed from the bottom of the chamber and exits from the upper portion of the chamber. 

This example examines the design of a water-spray system that is used for the mitigation of anhydrous ammonia in the event of an accidental release. The NH3 tank is capable of storing 35 m3, it is 11 m in length and is cylindrical in shape lying in the horizontal plane. The base of the tank is surrounded by a protective dike or a bund. All piping connections are at the bottom of the tank. This is shown in Figure 4.4. 

Bottom-spray film coating is accomplished by means of the Wurster system, originally developed by Dr. D.E. Wurster (Wurster 1959). A scheme of the bottom-spray fluid bed is given in Figure 16.4. 

FIG. 21-170 Niro Precision Granulation process. Agglomeration in bottom-spray draft tube fluid-bed granulation. Scale-up is accomplished by replicating draft tube geometry. Courtesy Niro Fharma Systems.)... 

Figure 372. Schematic representations of the product handling sections of three fluidized bed coaters. (a) Top spray, (b) tangential spray (rotary fluid bed coater), (c) bottom spray (Wurster coating system)...

Fig. 5.13 Sketch of the material processing section of a bottom spray fluidized bed coater (Wurster coating system) [B.71]...

Top spray. In the top spray system, the coating material is sprayed downward on to the fluid bed such that as the solid or porous particles move to the coating region, they become encapsulated. Top spray fluid-bed coaters produce higher yields of encapsulated particles than either bottom or tangential sprays. 

The containment is equipped with sumps to collect the water of the primary circuit and of the ECCS water storage tank after a LOCA in order to recirculate the water in the second phase of the accident. The openings of the containment bottom plate are covered with a screen which is intended to prevent debris penetration to the suction of the ECCS and containment spray system. 

The WWER-1000 plants are equipped with ECCS and containment spray systems that have a similar design basis and similar basic configuration as in western PWRs. These systems have 3 100% redundancy with the exception of the ECCS water storage tank which is common to all subsystems. The same tank serves as a containment sump. The tank is located under the containment and has open connections to the containment through the bottom plate. Each of the three safety system trains has one suction line from the ECCS water storage tank to the residual heat exchangers and further to the low pressure safety injection, high pressure safety injection and spray pumps. The suction line is equipped with one containment isolation valve. 

Early extractor designs based on solvent percolation were basket-type extractors in which flaked seeds were placed in baskets with perforated bottoms. These systems looked like an enclosed bucket elevator. The baskets were supported by endless chains in a sealed housing and continuously raised and lowered at a slow rate (1 revolution/h). Each basket was filled with flaked seeds by an automatic feed hopper at the top. As the basket started descending solvent is sprayed over the baskets. The spent flakes in baskets ascended to the top of the housing on the opposite side of the feed hopper. At the top baskets were automatically inverted and spent seeds were discharged into a hopper, from which they were transferred to a meal desolventizer on a conveyor belt. Basket type extractors were bulky and hard to maintain. The newer extractor designs are horizontal and rotary type. The design principle for horizontal extractors is similar to the basket-type extractors but the baskets rotate in a... 

Sepro Conta.iner, The Sepro container consists of a collapsible plastic bag fitted into a standard three-piece, tin-plated container such as a 202 X 214, 202 x 406, or 202 x 509 can. The product is placed within the bag, and the propellant is added through the bottom of the container, which is fitted with a one-way valve. There is no limitation on the viscosity of the product but compatibiUty with the plastic bag must be considered. A free-dowing hquid can be dispensed either as a stream or a fine spray, depending on the type of valve employed. A viscous material is often dispensed as a stream. This system has been used for caulking compounds, postfoaming gels, and depilatories. 

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