How to divide a Pneumatic Conveying Stream

Pneumatic Conveying Lines

How to divide a Pneumatic Conveying Stream

Splitter for continuous distribution of bulk solid material during pneumatic conveyance - dimensioning, calculation, operating behaviour. Worldwide, a great number of so-called splitters are in operation as elements of pneumatic conveying lines, in order to continuously distribute the conveyed bulk material to several receiving stations. These splitters have taken an important position within the pneumatic conveying systems and are applied in different designs. But there is not much literature available dealing with the phenomenon “splitter”, and providing assistance regarding application possibilities, dimensioning, selection and experiences during operation. The available literature mostly deals with answers to specific questions, like for example pressure losses in various ramifications, etc.
(ed. wgeisler - 31/5/2017)
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Fig. 9: Equivalent circuit diagram splitter (fourfold)             

In this arrangement the following applies:

Changes in resistance have a direct effect on the changes of throughput (of current). However, in most cases this effect is not desired. A small “trick” to avoid this is to connect an additional resistance in series (see Fig. 10).

Fig. 10: Equivalent circuit diagram splitter                                                                


In case the additional resistance is chosen big enough, differences in pipe resistance can be neglected. It is obvious, however, that the voltage has to be increased to keep the throughput.

Here the following applies:


4   Examples of Operating Plants

Examples of executed plants are dense phase splitters for pulverized coal out of a pressure vessel and a dilute phase splitter in the co-firing of animal meal. Both are applications from the power plant sector, but can similarly be found in the chemical industry.

4.1  Dense Phase Splitter from a Pressure Vessel

Fig. 11 shows the arrangement of a plant which supplies 2 x 6 pulverized coal burners in dense phase mode with a loading factor of 20 to 35 kg solids per kg air. The performance per string lies at approximately 1200 kg of coal per hour. The inner diameter of the individual conveying lines is 35 mm. These pipe strands can be switched on and off individually.

Fig. 11: Multiple dosing system for coal dust                                                                                             

4.2  Dilute Phase Splitters for the Conveyance of Animal Meal

The plant shown in Figs. 12 (layout) and 13 (detail photo) directly conveys meat- and blood-meal from a silo-truck to the boiler. The material can be conveyed relatively easily, which is partly also due to the relatively even particle from. In order to keep the required velocities in the burner pipes, a considerable amount of additional air was injected into the lower area of the splitter. The injection is done tangentially (by now it is done from both sides to avoid a tilted position), in the lower part of the splitter.

Fig. 12: Block diagram animal meal splitter                                                                                     

The above figure clarifies the arrangement of the plant. The air is lead twice to the truck (cover and propellant air) and once to the fourfold splitter (additional air). The amount of air is divided in such a way, that the desired output of 4 x 2,5 t/h is achieved. The pressure in the truck is kept deliberately low, so that the desired performance is achieved.                    

(Unfortunately) Fig. 13 only shows the lower part of the splitter. In addition to the pipelines leaving the splitter four more single pipes, which are served from so-called interchangeable silos, can be seen.

Fig. 13: Picture of the splitter with connections for single  
pipes and additional air                                     

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