Pneumatic Conveying

pneumatic conveying

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A pneumatic conveying system refers to a material handling technology that transfers different bulk materials to a specified location. The process may use airflow as the conveying medium, with air being one of the most commonly used mediums. A properly designed conveying system should be efficient, practical, and economical for transporting bulk materials to one or more destinations.

As an efficient and flexible material conveying technology, the pneumatic conveying system allows for the conveying of a wide range of materials such as feed, cement, starch, powdered sugar, and so on.

It can be categorized into dilute-phase conveying and dense-phase conveying based on the density of materials in the pipeline.

Application of pneumatic conveying system

The Pneumatic conveying system can meet the transportation of various powder materials and tiny particles. Therefore, pneumatic conveying systems are used in many industries.

The food packaging industry is one of the sectors that relies on pneumatic conveying equipment to meet the high hygiene standards required.Pneumatic conveying systems are used to transport various food products, including rice, cereals, sugar, salt and animal and pet food.

The pharmaceutical industry relies on pneumatic conveying systems to transport products without contamination. Quite literally, pharmaceutical manufacturers have a real need for the suction capacity of vacuum conveying systems.

It is well known that there is a hazard that arises from exposure of some chemical products. To avoid it, pneumatic conveying systems provide the chemical industry with a medium to ensure that its products meet environmental standards without cross-contamination.

Three Types of Pneumatic Conveying Systems

Pneumatic conveying systems are normally classified based on their operating principle into dense phase conveying and dilute phase conveying. Also considering the difference between suction and pressure conveying, it is further divided into positive pressure pneumatic conveying and negative pressure pneumatic conveying, where the material runs under pressure or vacuum.

Dense phase pneumatic conveying includes: dense phase vacuum conveying(dense phase negative pressure conveying) and dense phase positive pressure conveying.

Dilute phase pneumatic conveying includes: dilute phase vacuum conveying(dilute phase negative pressure conveying) and Dilute phase positive pressure conveying

Hybrid pneumatic conveying refers to the conveying method that combines pressure conveying and suction conveying, and is suitable for conveying viscous materials over long distances.

Dilute Phase Conveying

Dilute phase conveying, also known as air suspension pneumatic conveying, is the most common method of conveying materials. Dilute phase conveying uses large volumes of air and lower pressures than dense phase systems to transport materials. These materials are typically transported through the system at higher velocities while suspended in air. During the process, it is important to sustain the proper air conveying velocity.

Dense Phase Conveying

dence phase conveyer and vacuum conveying

dense phase conveying

In concentrated phase conveying, positive-pressure pneumatic conveying, where the material is extruded under sufficient pressure, referred to as dence phase conveyor; and suction conveying under negative-pressure vacuum, referred to as vacuum conveyor.

Dense phase conveying uses high pressures and low gas volumes to move material along a pipe. Materials with low flowability are not suitable for this system because they may cause high friction in the system. Instead, Instead, the high flowability material is transported through the pipe with air in a variety of modes at low speeds and high differential pressures.

The difference between dilute phase and dense phase conveying systems.

Dilute phase pneumatic conveying system uses compressed gas as kinetic energy to convey materials suspended in the gas stream along the pipeline. The material in the conveying process will form a gas-solid two-phase mixture with the gas.

Applicable materials: powder, granular and other dry materials with good flowability.
Advantages:
   (1) Due to the lower material bulk density and the formation of a gas-solid two-phase mixture, the gap between the material is larger to effectively avoid pipeline clogging in conveying.
   (2) Faster conveying speed as more gas and less material, suitable for shorter conveying distance.
   (3) Simple equipment structure without excessive valves and with low maintenance costs.
Disadvantages: lower conveying efficiency, and risk of material wear due to high flow velocities.

Dense-phase pneumatic conveying systems transport denser materials at relatively low velocities to the discharge point by the pressure difference created in the pipeline.

Applicable Materials: commonly used for conveying bulk materials with large particle size such as coal, ore and so on.
Advantages:
   (1) Dense-phase conveying system meets the conveying demand of high-flow conveying and long conveying distance.
   (2) Stable conveying as less gas and more material, so less wear on the materials.
   (3) Low energy consumption and dust pollution emissions, and more friendly to the environment.
Disadvantage: pipe blockage may occur due to high material density.

In a word, it is necessary to choose the appropriate pneumatic conveying system for your application according to the characteristics of the material and the use requirements. Further considerations include conveying distance, conveying flow rate, investment cost and many other factors to develop customized technical solutions. What’s more, no matter which system is chosen, the parameters of pneumatic conveying need to be adjusted according to the actual situation, to avoid blockage and abrasion, and to improve the stability of the system.