When it comes to bulk material handling, there are various mechanical devices that are used to apply energy into material in order to induce flow. There are also indirect methods for conditioning bulk material that essentially condition the material’s atmosphere within a pneumatic conveying system. By controlling the temperature and humidity inside the convey line and introducing dry air to the system, moisture can be prevented from accumulating (and allowing product to stick to surfaces like filters, walls, pipes and receivers).
The characteristics of a particular material will warrant what could be best utilized to accomplish flow. In this AZO blog post, we’ll cover three different methods for inducing flow for bulk material — dehumidification, aeration and specifically utilizing pneumatic impactors.
Conditioning by dehumidification alters the amount of moisture a material absorbs
When humidity is a particular concern (like with many processes in the baking industry), conditioning the environment through dehumidification can make it more suitable for longer-term storage. If product begins to build up in the pneumatic conveying system, introducing a dehumidifier will help bring the relative humidity inside the system to an acceptable level where the material isn’t absorbing moisture out of the air. As a bonus, oftentimes a dehumidifier can be added to an existing system if such problems arise.
Conditioning by aeration injects air to create ‘fluidization zones’
Vibration causes some types of powders to densify. By itself, this may not cause concern, but compaction is another matter altogether. Once materials have trouble flowing because of compaction, aeration (also known as “fluidization”) then offers a suitable conditioning option. Certain types of aeration devices inject air that vibrates an inner flexible membrane to create fluidization zones around the cone and sweep the hopper wall. This can be particularly useful for material that has become stagnant within a silo. Yet another type of aeration device uses a diffuser to emit fluidizing air into the material.
It should be noted that only materials that respond well to fluidization should be conditioned by devices in this way. Typically, dry powders and fine powdered material are prime candidates to be conditioned by air pads, air-jet nozzles, fluidization devices and turbo cones.
Aeration pads from AZO
Most of these devices can all accomplish the same function and ensure the hygienic transfer of materials, but turbo cones are used to promote flow for difficult flow-resistant finely divided materials. In other words, for products that are exceptionally difficult where vibration will impact them and aeration will help move them, turbo cones are particularly applicable. In certain special situations, both aeration and vibration are utilized.
What makes the difference for turbo cones? Rather than having localized fluidization zones (where the pads are located), 100% of the hopper surface is permeable and an active fluidizing cone. Materials like Diatomaceous Earth or Ti02 are perfect examples of materials that would likely require a turbo cone. Utilizing such a device for the aeration of materials that are relatively free-flowing is simply unnecessary.
Pneumatic impactors perform “de-dusting” to dislodge material
While there are also innovations such as material vibrators that provide vibration to the walls of a hopper in order to discharge material, an “impactor” performs the function of “de-dusting.” This is a process mostly implemented in scaling operations. Once material has been weighed to a particular weight and the scale is being discharged, an impactor would strike a hopper to ensure that residual material is not left in the hopper.
Impactors can be used in concert with material vibrators as well. The final bit of dust clinging to a hopper wall or even a filter (oftentimes in conjunction with a pulse jet) is typically knocked loose by an impactor. Whether a scaling operation incorporates a receiver, hopper, mixer or liquefier, an impactor can ensure that a weighed amount of material does indeed get captured in the next step of a process.
A new, free guide from AZO further elaborates on various mechanical devices that are used to apply energy into material in order to induce flow. “Flow and Functionality: Determining The Proper Discharge Aids For Your Bulk Material Handling Process” contains pertinent information about many machines that are often used in concert with each other (as well as flow agents) to overcome the friction between material and the wall of storage vessels.
If you find that you have any other conveying queries, you can always feel free to speak to an AZO specialist. We have more than seven decades of experience in handling raw materials and shaping ingredient automation along the way. Contact our sales team for any questions on how to help your plant and processes run smoothly.