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Home > News > The pipeline system of the pneumatic conveying system

The pipeline system of the pneumatic conveying system

Author£ºniasi Date£º2013-8-1 11:32:56 Source:en.dgniasi.cn

The pipeline system of the pneumatic conveying system 

The pneumatic conveying system is widely used in the raw material conveying, dust removing, etc. Due to the delivered materials, such as the solid particles and dust, etc. that the screening workshop transport, they have the characteristics of high density, high hardness, sharp angle, high speed of conveying medium. The pneumatic conveying pipeline, especially the pipe bend's wear situation is very serious, which has affected the continuity of industrial production and safety.The solution of the wear problem of  gas-solid two phase flow such key part has great significance to save raw materials. It is a powerful embodiment of saving energy and reducing consumption.

Classification and characteristics of the pneumatic conveying system: there are many ways to the classify the pneumatic conveying system, such as classified according to the material-gas ratio, the features of the material-gas two-phase fluid mechanics, the features of the material-gas two-phase movement, the device characteristics, etc.

 

There are two main categories: classify them according to the conveying equipment. Its basis from the state of the air pressure in the pipeline, the other is a classification of the material flow state in pipeline, based on the phase diagram, pipeline gas solid flow state, the throughput and the material-gas ratio per unit time.

(1). According to the conveying device characteristics, the pneumatic conveying can be divided into negative pressure type, positive pressure type and hybrid type.

 (a) the  negative-pressure pneumatic conveying

Negative-pressure conveying system is motivated by the negative pressure difference with the outside that the air suction device formed. With the existence of pressure difference.The outside air is inhaled into the pipeline, at the same time the material will be brought into the pipeline along with the movement. After reaching the finish line, the material will be separated from the air and be collected.After purification,the air will go back into the atmosphere or be recycled.The negative-pressure conveying system is mostly used for the centralized conveying, namely the directional to a centralized one, such as the workshop dust removal, grain warehousing, etc. The advantage of the negative pressure conveying  is that it can effectively collect  the material and it will not enter into the atmosphere.It is especially important for toxic materials pneumatic conveying, but because of the influence of vacuum degree, the transmission distance will be limited by some certain factors.Generally.the limits of the system pressure declination is o. 044 mpaf71. 

(b) positive pressure conveying 

The positive pressure conveying is the pneumatic conveying system that is first put to use.It is also the most basic form of the pneumatic conveying system. The positive pressure conveying  uses the blower of the system's starting point  to pass into the compressed air into the pipeline, using pipeline pressure difference between the starting point and the end point, making the air flows  in the pipe, and drive materials move. In the positive pressure conveying system, the material is delivered by the feeding device into the conveying system.At the end delivery, the material and air are separated.Compared to the negative-pressure pneumatic conveying system, the positive pressure conveying system transmission distance is longer than the other. The positive-pressure conveying system is suitable for distributed conveying, namely one point to multipoint transmission.In the pipeline, the material can separate  the transmission medium depending on the material gravity at any discharging point

(c) the hybrid type pneumatic.conveying  

Hybrid transmission system is the system combining the positive-pressure conveying system and negative-pressure conveying system in the same delivery system. It combines the characteristics of the positive-pressure and the negative-pressure conveying system,.Thus,it can be used in the complex conditions.


(2) According to the material-gas ratio, the pneumatic conveying system can be divided into dilute-phase pneumatic conveying, dense-phase dynamic pressure pneumatic conveying, dense phase static pressure pneumatic conveying and tube type pneumatic conveying.

(a) dilute phase pneumatic conveying
The characteristics of the dilute phase pneumatic conveying are: high air flow velocity in the conveying system, material remains at the suspension state, big void fraction. The material conveying  mainly relies on the kinetic energy of the air velocity. Dilute phase pneumatic conveying speed is usually 12 ~ 40 m/s, the material- air quality ratio is on average of 1 ~ 5, no more than 15.

(b) phase dynamic pressure pneumatic conveying

The  air velocity  of the dense phase dynamic pressure pneumatic conveying is generally between 8 to 15 m/s. In the dense phase dynamic pressure conveying, the material are densely distributed in the pipe, relying on the air kinetic energy to transport. This kind of gas deliver units are divided into:high pressure compression conveying, high vacuum suction conveying and fluidization conveying.There is a big changinrange of the material-gas ratio of the dense phase dynamic pressure conveying with high pressure and high vacuum.

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