Learn about pneumatic conveyors

10-03-2022 1.046

Pneumatic conveyors can move dry, fine materials by using differential pressure and air flow, typically compressed air or nitrogen.

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What is Pneumatic Conveyor?


Pneumatic conveyors can move dry, fine materials by using differential pressure and air flow, typically compressed air or nitrogen. The material is completely enclosed in ducts, where the difference in pressure on either side causes the flow of the product. This pressure differential can be accomplished through increasing or decreasing the pressure on either side of the tube, where the addition of a blower will melt the fine powder. A push system (also known as a positive pressure system) can push materials from one inlet to many outlets, and a pull system (negative pressure) can pull material from multiple inlets to one outlet.

It is also possible to have push-pull combinations in the same system if desired, but these will increase costs. Pneumatic conveyors have fewer parts than other conventional conveying systems and are best suited for small, dry, low bulk density products such as wheat, sugar, cement powder, sand and other products. other aggregates.
 

 

Application of pneumatic conveyor


The main applications of pneumatic conveyors are burners, metal powder conveying, recycling and any similar use case where dry powders, granules, flakes and bulks are needed. They are a versatile option for designers to move products, as the carriageway can be bent around existing equipment and is relatively small. They have a lower investment cost than other types of conveyors but are generally less efficient, as more energy is required to keep the blowers and suction machines running.

They also transfer material much faster and without any loss, but there is a risk of clogging and further wear on the system. So while not as popular as belt conveyors, pneumatic conveyor technology can handle aggregates that were once too difficult to move without loss.
 

Types of pneumatic conveying systems


The types of pneumatic conveyors are determined based on the type of material that can be moved and their source of airflow. The three main types of pneumatic conveyors are dilution, solid phase and semi-solid conveyors, where each can be controlled by pressure or vacuum. This section breaks down each of these categories to show where each performs best, as well as their notable features. Note that these distinctions are kept generic and do not include manufacturer-specific types.
 

- Diluted compressed air conveyor


Dilution pneumatic conveyors are a common system for non-fragile materials and perform high-speed, low-pressure air flows to boil fine particles. The material is loaded into a hopper, where an air movement machine then delivers it through the conveyance line to its destinations at high speed. They can be dilution pressure conveyors or dilution vacuum conveyors.

Pressure conveyors work best with powders that have a small density and can move particles over long distances, while vacuum conveyors are best suited for packaging materials under pressure and are intended for short distances. . Dilution vacuum conveyors also reduce the risk of internal material contact, which is useful for chemical and hazardous applications. In both cases, dilution pneumatic conveyors are used to transport light, non-abrasive, non-fragile materials such as flour, carbon, powdered chemicals, etc. They require little space and are a cheap and efficient method of transporting large quantities.
 

- Dense phase pneumatic conveyor


Dense phase pneumatic conveyors are the opposite of dilution conveyors, as they use high pressure and low velocity to move fragile products. The material is loaded into a pressure vessel, where high pressure forces the material into the transport path to its destinations. The product should not boil in the air stream, and instead the system assumes "pulsation", sometimes with the help of air nozzles. As a result, the dilution conveyor is much slower than dilution varieties but also easier on the material. Dense phase pressure conveyors gently convey smaller particles over long distances, while solid phase vacuum conveyors can do the same thing but over much shorter distances. Common applications of concentrated phase pneumatic conveyors are to move bulk, abrasive products such as sugar, salt, etc.
 

- Semi-solid phase pneumatic conveyor


Semi-solid phase pneumatic conveyors are the midpoint between the last two types of pneumatic conveyors and, therefore, have the qualities of both. Both are pressurized and have air movement, which allows them to transport non-fragile materials smaller than 0.25 in at medium velocities where only part of the material is boiled in air. Semi-solid pneumatic conveyors tend to be chosen when solid or thin conveyors are idle, as they provide some increased speed but still protect the material through the system. They work well with abrasive materials, and can convey them at a fast rate
 

Specifications and selection criteria


It would be helpful to provide some basic specifications to your supplier if you are interested in pneumatic shipping. This section briefly explains some important values ​​and provides several methods for determining the right pneumatic conveyor for your project. Note that the selection process for pneumatic conveyors is difficult and this list is only a basic overview of the most important values.
 

- Distance, flow rate and pipe design


It is necessary to know the distance your material will travel, the desired flow rate and the shape of the desired setup. There is more mathematical analysis in this type of conveyor than most others, so the more information you can bring in, the better. Variables like pipe size, pipe length, product density, air flow rate and many others affect the efficiency of a pneumatic conveyor, so detail the numbers. the estimated amount of bends, inlets and exits in the system, as well as your material characteristics. Also, if you're not sure what you'll need, always review your application and determine your end goal. How many products do you want to ship in a certain period of time? Your provider can help you work backwards and determine the necessary values ​​needed for what you are trying to accomplish.
 

- Filters, fans, vents and guards


If your product is too dusty, can create bubbles, or is toxic, the right filter should be used to protect both personnel and the system itself. Improper filtration can lead to a number of nasty problems, including repair and replacement, so be sure to have a sufficient number of filters and vents to keep the system in good working order. Fan selection depends on the material, the length of the conveyor and will also affect the life of the conveyor, so use only the minimum velocity needed to move your product. Again, all of these specifications are closely related, so it can be frustrating to find the right quality blend, but safety and effectiveness should always be a priority. 
 

- Controls and special considerations


Pneumatic conveyors can be controlled via closed feedback or another control system, so make sure your supplier knows if your applications require this. Also, make sure the system has adequate measuring equipment that will allow troubleshooting in the event of a failure. The functionality of these conveyors is highly dependent on the material they are transporting, so make sure you know the working characteristics of your materials, as well as potential variation between batches of the same. material. Any other specifications specific to your project should be made available to your supplier, who will have the best information on what will and will not work. There are also always other options if pneumatic conveyors don't seem right, so don't hesitate to ask about other processing technology.