Anyone working in the bulk solids processing industry knows that powdered materials can be incredibly challenging to work with for a litany of reasons; powdered materials are difficult to handle, present health and sanitation issues, and are challenging to store.
Agglomeration, or particle size enlargement, provides a means of processing such materials into granules for easier and cleaner handling, a more manageable production environment, and improved storage qualities. The benefits achieved when a producer chooses to agglomerate powder do not stop there, however; many producers are surprised to discover the myriad of other advantages they can gain by opting to agglomerate their powder product.
Agglomerate Powder for These Potential Benefits
While not all benefits are applicable in every setting, the following benefits are often made possible through powder agglomeration:
Improved Flowability
A lack of flowability is one of the most common reasons for which producers decide to agglomerate a powdered material or product. The rheology of powders, while varying from one material to the next, makes powder generally less flowable than a granular product.
When powder is agglomerated, however, particularly by wet granulation (also known as tumble-growth or agitation agglomeration), flowability is greatly improved.
Greater flowability lends several advantages to any production setting, including a more consistent product, higher process efficiency, reduced downtime, and more.
Simplified Handling & Transportation
As anyone who has handled them can attest, materials in powder form present several complications when it comes to handling and transporting the material. Although all materials differ in the extent to which they cause dust issues, powdered materials inherently present a number of problems associated with dust.
A dusty material is easily picked up and moved by wind or a nearby exhaust gas outlet, making handling, transport, and deposition incredibly challenging, particularly when conducted outdoors. In some cases, fugitive dust can also be a liability.
Further, most powders are generally light enough that simply moving through a transition point such as a transfer chute or onto a conveyor can cause substantial dust issues for the surrounding environment.
By agglomerating powder, the material’s bulk density is typically increased. Even a small increase in bulk density is enough to keep material from becoming airborne and contaminating the surrounding area. As a granular product, the material can now move through transition points, be dumped into trucks, and the like, with minimal dust generation.
More Effective Metering
Metering or dosing becomes especially challenging with a powdered material, in large part because of its lack of flowability, but for other reasons as well. In settings where precise quantities of material are essential, a dusty material can make production and product quality goals almost impossible to meet.
Since granules are more flowable than a powdered material, agglomerating powder into granules significantly improves the ability to meter exact quantities.
Cleaner Production Environment
The propensity for powder particles to become airborne makes controlling them incredibly difficult. Thus, production settings working with powdered materials are often coated with a layer of dust that seems to permeate every nook and cranny – equipment motors and mechanical components included. This not only creates a potentially hazardous work environment, but it can also reduce equipment efficiency and overall longevity.
As with handling and metering, increasing the bulk density and size of powders through agglomeration significantly reduces their potential to become airborne. This substantially reduces the amount of dust and buildup occurring in and around the production environment, promoting a cleaner, healthier, and more efficient work area, while also helping to prolong equipment life.
More Marketable End Product
The many challenges associated with a dusty material make powdered products unattractive to consumers and therefore more challenging to market and sell.
By simply converting the powder to granules that are dust-free or generate minimal dust, the product is perceived as a higher-value product and can be sold at a premium.
Mitigation of Product Lost as Dust
During processing, handling, and transportation, the amount of product lost as dust may seem negligible, but adds up quickly when working with the tonnages associated with bulk solids. Consider that if a product worth just $20 per ton lost even 1% to dust, the operation would lose $2,000 per month (at a rate of 10,000 tons per month), equating to a loss of $24,000 per year.
While product loss will never be 100% preventable, it can be significantly reduced through powder agglomeration, again because the product is much less prone to becoming airborne and dispersing.
Improved Product Storage
All materials have different properties that influence their storability. However, powders are generally less storage-friendly, because they have a tendency to cake, particularly when the material is hygroscopic; during storage, the material picks up moisture from the air, which causes crystal bridges to form between particles, resulting in caking. Caking may or may not be severe, but it can cause product loss, require reprocessing, and may even be a danger to employees.
Caking can still occur if powder is agglomerated, but the potential for it is significantly reduced. When a powder is agglomerated into granules, there is much less surface area contact between particles, reducing the number of places where crystal bridges can form.
Controllable Particle Characteristics
Perhaps one of the most significant advantages to powder agglomeration is the ability to control particle characteristics. This benefit may or may not be of value depending on the application, but offers an array of opportunities when taken advantage of.
The properties that can be controlled may differ depending on the specific material and the agglomeration equipment used, but typically include:
- Bulk density
- Particle size distribution
- Product formulation
- Porosity
- Moisture content
- Green strength
- Dry crush strength
- Attrition
- Flowability
Segregation Prevention
Segregation is a problem all too familiar to those working with bulk solids, occurring when particles of varying sizes or densities naturally separate into like particles.
Bulk solids are frequently provided as a blended product, or a product made up of many different components. Even if a manufacturer thoroughly blends the disparate parts into a homogeneous mixture, the variation in sizes and densities will cause the particles to segregate over time throughout handling and storage.
Particle segregation is problematic because it creates a non-homogeneous mixture, which, depending on the product, can translate to uneven results, flowability challenges, inadequate dosing, and more.
By agglomerating powdered components into granules of similar size and density, agglomeration removes the potential for segregation to occur.
Enhanced Downstream Performance
While agglomeration is often used with the intent to improve downstream performance, it may be an unanticipated benefit in some cases. Agglomerated material often performs better in furnaces and kilns, though this is dependent on the specific thermal processing goals. Since flowability is improved, downstream processing may occur more smoothly, or avoid clogging issues associated with a powdered material.
Additionally, the minute void spaces within granules produced via tumble-growth agglomeration often lend improved performance in applications such as adsorbents, soil amendments, and more.
Added Value
Oftentimes, material is considered as having little-to-no value simply because of the form it’s in. This is frequently the case with process byproducts and waste materials. By agglomerating the powder, its usability greatly improves, making it more acceptable for use as a filler for concrete or building products or other applications.
Conclusion
Powdered materials are challenging to work with, presenting numerous problems in the form of production issues, lost product, difficult handling, and so much more. Through agglomeration, however, these issues are resolved, with a few added benefits along the way.
FEECO is a leading provider of tumble-growth (agitation) agglomeration technology, offering agglomeration testing services, custom equipment, and full system supply. If you’re looking to agglomerate a powder material, contact us today!