Pneumatic controllers conveying

The principle of discontinuous conveying allows a simple design but reaches boundaries when it comes to conveying heights of more than 30 m and distances of 100 m. With the combination of two receiver vessels and if the pneumatic control is switched to the twin mode a continuous vacuum in the conveying line is maintained (Figure 17.14). Alternatively a rotary valve can be used. 

Selves, T. P., Barnes, R. N., and Reed, A. R., The Use of Flow Diverting Air Injection to Actively Control the Split Ratio of Pneumatically Conveyed Particulate Materials, 5th Int. Conf. on Bulk Materials Storage, Handling and Transportation, IEAust. Proc, 1 263-271, Newcastle (1995)... 

Advances in quality control requirements for rubber compounds have demanded that special care is exercised in the weighing of the various fillers and critical small volume powders necessary for the formulation. Ingredient weighing systems are available which can be tailored to the specific requirements of individual factories. Additional components can include conveyors, bagging units and pneumatic conveyance systems. 

The NORIT Porta-Powdered Activated Carbon (Porta-PAC) dry injection system pneumatically conveys an adjustable amount of powdered activated carbon (PAC) from bulk bags into the flue gas streams of incinerators for mercury and dioxin emission reductions. PAC is metered using a volumetric feeder into a pneumatic eductor where moving air transfers the carbon to the injection point. A series of interlocks control the operation of the unit and allow local or remote operation and monitoring of the unit. This technology is commercially available. All information is from the vendor and has not been independently verified. 

Control fluidization of powder. Beware of processes, such as pneumatic conveying, that increase the potential for the material to become aerated. 

The advantages of a pneumatic conveying system are that there are few mechanical parts, there is a clean controlled environ-... 

Figure 12-97 shows a traditional spray dryer layout with a cone-based chamber and roof gas disperser. The chamber has two-point discharge and rotary atomization. The powder leaving the chamber bottom as well as the fines collected by the cyclone is conveyed pneumatically to a conveying cyclone from where the product discharges. A bag filter serves as the common air pollution control system. 

Close-up of the pneumatic conveying facilities used in the operation of the dry scrubber for plant-wide control and recycling of volatile flourides. 

A physical-chemical interaction through adsorption of the gas on the solid surface, which affects the resistance to breakage, attrition and abrasion. Thus the properties of the suspending gas have to be taken into account, or controlled, not just in the obvious applications where gas clearly plays a part like fluidization or pneumatic conveying but also in the not-so-obvious ones like grinding and discharge of powders from hoppers. 

Rotary, star valve feeder used especially as solids feeders for dilute-phase pneumatic conveying to provide an air lock and to feed solids. Seal/wear depends on Ap and abrasiveness of powder. For pressure systems keep Ap <80 kPa for vacuum systems Ap <40 kPa. Provide an air vent to take the air loss away from the gravity flow of the solids and to control the filling of the star. 

Balls collecting at the bottom of the preheater in an appropriately dimensioned boot are stripped of shale particles by elutriating gas. Under ideal conditions, the largest shale particles that can be readily elutriated from between the pellets are about half the size ot the pel lets. In practice the separation is more efficient when the ball/shale size ratio is 4-5. Balls drop by controlled flow into a transport line where they are pneumatically conveyed to the shale heat recovery section. 

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