Pneumatic conveyer system

Rotary V lve Feeders. Devices known as rotary valve feeders are commonly used for circular or square configured outlets. These are particularly useful when discharging materials to a pneumatic conveying system where a seal is required to prevent air flow through the hopper outlet. The discharge rate is set by the speed of rotation of the vanes or pockets of the valve. 

The capacity of a pneumatic-conveying system depends on (1) produc t bulk density (and particle size and shape to some extent), (2) energy content of the conveying air over the entire system, (3) diameter of conveying hne, and (4) eqmvalent length of conveying hue. 

Hopper Trucks These trucks are used to transport by highway a wide variety of materials. Vehicle types range from the open-dumping kind to the closed type. Most common is the type that unloads by pressure differential into its own pneumatic-conveying system, which is temporarily connected to a storage silo. On this type of truck, the unloading of 18,100 kg (40,000 lb) of produces takes about 1 h, sometimes less. 

NFPA 650 Standard for Pneumatic Conveying Systems for Handling Combustible Particulate Solids, 1998 edition. National Fire Protection Association, Quincy, MA. 

Gerchow, Frank J., How to Select a Pneumatic Conveying System, Chemical Engineering, February 17, 1975. 

Perkins, Don E., Wood, Jim E., Design and Select Pneumatic Conveying Systems. Hydrocarbon Processing, March 1974. 

These are mainly pneumatic conveying systems, in which impurities and solid waste, but also materials or goods, are transported by air flows. The systems categories are low-pressure, medium-pressure and high-pressure systems, depending on how heavy the impurities are that the system will transport. 

Example of Calculating the Pressure Losses in a Pneumatic Conveying System 1353... 

Reprinted from M. Lampinen, Calculation Methods for Determining the Pressure Loss of Two-Phase Pipe Flow and Ejectors in Pneumatic Conveying Systems, Acta Polytechnica Scandinavica, Mechanical Engineering Series No. 99, published by the Finnish Academy of Technology, Helsinki, 1991. 

With the aid of this equation the pressure loss in a pneumatic conveying system can be calculated. All we need to know are the velocity difference between gas and solid particles,... 

Now, when these three parameters are known, Eq. (14.126) can be used for calculating the pressure losses in pneumatic conveying of wood chips in any other conditions. Also the pressure-loss curves for planning pneumatic conveying systems for wood chips can now be drawn. Figures 14.17 and 14.18 present examples of these. Similar curves can now be drawn for any pipe diameter D and for any air velocity by solving Eq. (14.126) numerically according to Fig. 14.16. 

We study a pneumatic conveying system shown in Fig. 14.19 for the conveying capacity = 27.3 kg/s. The material conveyed is wood chips, for which the parameters (14.133)-(14.135) are valid. 

Calculating the Pressure Loss of an Ejector in a Pneumatic Conveying System... 

As another example of calculation and dimensioning of pneumatic conveying systems we consider an ejector shown in Fig. 14.20. In fluidized bed combus tion systems a part of the ash is circulated with the hot flue gas. The task of the ejector, is to increase the pressure of the circulating gas to compensate the pressure losses of the circulation flow. The motivation for using an ejector, rather than a compressor, is the high temperature of the flue gas. The energy... 

TABLE 14.2 Computed Pressure Losses in the Pneumatic Conveying System Shown in Fig. i4.l9... 

The essential difference in dimensioning an ejector for pneumatic conveying systems comes from the acceleration term of the solids, Eq. (1Ai37). 

TABLE 14.3. Calculations for an Ejector of a Pneumatic Conveying System, According to Fig. 14.20... 

Ash sluice pump Make-up water pump Pneumatic conveying system Conditioned ash conveyor Submerged ash conveyor... 

The separation step requires (1) application of a force that produces a differential motion of the particles relative to the gas, and (2) sufficient gas-retention time for the particles to migrate to the collecting surface. Most dust-collections systems are comprised of a pneumatic-conveying system and some device that separates suspended particulate matter from the conveyed air stream. The more common systems use either filter media (e.g., fabric bags) or cyclonic separators to separate the particulate matter from air. 

A pneumatic conveyer system consists of a long tube or duct to carry air at high velocities, an induced draft fan to propel the air, a suitable feeder for addition and dispersion of particulate solids... 

In a pneumatic conveying system, air or some other gas is used to transfer solids from one place to another. These systems are entirely enclosed, hence the product loss is small, contamination is minimized, and the problem of dust emission to the atmosphere is greatly reduced. There are many different systems only a few will be presented here. 

CV-603 B-601 B-602 2 Aluminum Ductwork for pneumatic conveying systems, v 2000 ft Blowers, cast iron. BHP =15... 

Rotary valves have been specified for the receivers of the vacuum pneumatic conveying systems (RV-601 and RV-602) and for the feeders (RV-40 1) and receivers (RV-501) of the positive-pressure system transferring powder from the dryers to the extruders. Perry72 gives some recommended sizes for rotary valves. The power required by all these valves will probably not exceed 2 kw and will be ignored. 

---