During process development in the FEECO Innovation Center, manufacturers are often targeting a set of parameters to ensure their product handles and performs as desired. Meeting this specific set of properties gives manufacturers control over how their product looks, feels, and behaves during commercial use.
The Innovation Center uses a variety of particle tests throughout process development to ensure product meets specification. What follows are some of the most commonly performed particle tests, why they are necessary, and how they are carried out.
Particle Tests Performed in the FEECO Innovation Center
While this list covers the particle tests most commonly conducted in the Innovation Center, it’s important to note that a range of other tests can be carried out as well, such those important to producers in targeting granular fertilizer properties.
Attrition Testing
An attrition test is used to determine the amount of degradation that will occur during product handling- that is, the amount of product that will break down into fines. As one can imagine, it is desirable to target the least amount of attrition possible, as attrition results in product loss, dust problems, and more.
Testing for attrition during product development can help technicians make adjustments to the process, such as a formulation change, or modification of binder concentration, in order to minimize the potential for attrition.
Attrition testing is carried out in a specialized machine that simulates the conditions under which granules rub against each other and degrade during handling. On-size pellets are put into the machine, agitated, and then measured to see what portion of the sample is still on-size.
Crush Strength
Crush strength tests are used to determine the strength of a granule, or in other words, how much pressure it takes to crush the granule completely. A low crush strength indicates that it takes little pressure to break pellets during normal handling, while a high crush strength indicates a stronger product that can withstand more handling without premature degradation.
Target crush strength is an important characteristic in creating a pellet that will perform as needed, particularly in the fertilizer industry where the product must be strong enough to withstand handling, baggage/storage, transportation, and even spreading without breakage. Yet, the pellets must still be capable of breaking down under standard field conditions.
Crush strength tests are performed on a single pellet, using metal plates to apply increasing pressure to the pellet.
Green/Wet Crush Strength
Green/wet strength tests are the same as crush strength tests, but are performed on a wet pellet prior to drying, instead of on a finished dry pellet.
Pellets need a certain amount of strength to withstand the number of drop points during processing, such as when moving from one conveyor to another. Green/wet strength tests are carried out to confirm that the newly formed granules can withstand the required process handling.
Compression
Similar to crush strength, compression tests look at how granules behave under stress, but as a whole, instead of just as a single pellet.
Compression is important when it comes to materials required to withstand heavy loading. A common example of this can be found in the proppant industry.
Proppants must be able to endure extreme amounts of pressure to hold open rock fissures, allowing natural gas or oil to flow out. If proper strength were not attained, proppants would crush under pressure, defeating their purpose. They would also subsequently clog veins to the main wellbore, inhibiting extraction.
Technicians in the Innovation Center use a controlled product amount and a hydraulic press to perform compression tests: Material is placed in a cylinder. A smaller, solid cylinder is placed on top of the pellets inside the larger cylinder. The smaller cylinder is then pressed onto the granules at a specified rate of pounds per square inch to determine their compression strength.
Particle Size Distribution (Sieve Analysis)
Particle size distribution, or PSD, is a measurement of the quantity of material that falls into each size range within a given sample. Most manufacturers require a specific PSD in order to meet different processing, handling, and application objectives.
Sieves are used to measure particle size distribution. For this reason, the test is also commonly referred to as a sieve analysis.
This test is especially important in determining what percentage of on-size pellets are produced in an agglomeration process, as well as the amount of over- and under-size particles the process yields.
Bulk Density
The bulk density of a product is essential for a number of reasons. First, it is necessary in sizing equipment according to material and processing needs (i.e. tons per hour of production). Further, certain products may require a specific bulk density for a variety of reasons, such as packing or shipping purposes, consumer use, or otherwise.
Bulk density is measured by taking a container of known volume, filling it with granules, and then weighing it. The weight/volume reveals the material’s bulk density.
Particle Shape & Surface Quality
Particle shape is crucial in many industries where the end product will go directly to market.
Many companies and industries want spherical or oblong particles, whereas other customers request something different to match their needs. While agglomerate shape can be determined simply by viewing the final product, it can be evaluated in greater detail using a microscope.
FEECO’s state-of-the-art microscope and software program captures detailed particle images, allowing technicians to evaluate the agglomerate shape, in addition to surface quality and other features that can’t be seen with the naked eye. This in-depth view provides tangible confirmation that a process is producing the specified granule properties.
Solubility
Also referred to as a dissolving test, solubility tests indicate how a material will dissolve in water. These tests often require nothing more than a simple beaker of water, and, of course, the product to be tested. Several items are recorded and analyzed during solubility testing, including:
- Time
- Temperature
- If the material dissolves
- How much of the material dissolves
These tests are extremely valuable for fertilizer and soil amendment products, ensuring that the product breaks down at the optimal rate under standard field conditions. In addition, solubility tests are useful in testing how well coating agents perform.
Flowability
Flowability tests reveal how agglomerates move, or “flow,” as a unit. Flowability is an essential indication of how well material will move through processing, feeding, and handling equipment. A material with poor flowability is likely to cause challenges such as poor feeding, clogged equipment, and process upsets, so maximizing flowability is often a top priority for manufacturers.
Flowability is measured simply by pouring material onto a makeshift chute positioned at various angles, and observing how the material moves from point A to B. During these tests, technicians are specifically looking at the angle-of-repose: the steepest angle, from 0-90°, of descent in relation to the horizontal surface to which the material can be piled without falling.
Moisture Content
The moisture content of a product is another essential measurement in process development. In drying a granular product for example, not meeting the target moisture content could result in product caking, mold growth, or other problems. A moisture content above that which is specified also inflates shipping costs, because the producer is essentially paying to ship water. For these reasons, reaching a target moisture range, or even an exact percentage, is required for most products.
FEECO uses a moisture analyzer to record the amount of free moisture present in particles. The analyzer uses heated coils to withdraw moisture from the agglomerate sample, tracking the initial moisture content, the temperature and duration of the heat, and the final moisture content.
Conclusion
The ability to test these and other properties is critical not only in ensuring a product meets specified parameters, but also in helping technicians to make process adjustments during process development testing. In other words, by analyzing a sample at various stages of processing, technicians are able to fine-tune process variables and make the necessary adjustments to consistently meet product quality requirements. This data then provides the framework necessary for scaling up the process and designing the commercial-scale equipment.
For more information on testing in the FEECO Innovation Center, contact us today!