Particle Size Reduction A Comprehensive Guide for Increased Efficiency

Particle size reduction techniques are used in nearly every industry to enhance efficiency and not just to augment flowability. For the food and beverage industry sector, particle size reduction aids in making solutions that include dissolved materials. Particle size reduction also makes extracting valuable materials from ores easier in mining and mineral processing industries. In the pharmaceutical sector, reducing particle size helps with dosing and mixing applications while improving active ingredients' bioavailability. Reducing particle size also amplifies drying applications because it exposes more surface area. Whatever the purpose, particle size reduction is a key process that is essential in making so many products.

Factors Influencing Efficiency in Particle Size Reduction Operations

Regardless of the type of manufacturer or product being made, one of the most basic processing activities in the industry involves reducing a material’s particle size. Reduction processes may differ depending on the sector and exact application. Still, it’s crucial for crushing ores in mining operations, grinding grains for flour, or reducing active pharmaceutical ingredients to a fine powder for medications. Though the equipment and methods may differ, particle size reduction is a cornerstone of many industries.

Some common particle size reduction methods include: 

• Crushing: This means reducing material used by sectors like construction and mining, exploiting the force of compression to diminish particle size; reduction equipment like impact crushers and jaw crushers apply pressure to crush material.
• Cryogenic particle size reduction: This method entails bringing materials to very low temperatures until they become brittle; this allows materials to break up more easily and is used for materials particularly sensitive to heat. 
• Grinding: For precision particle size reduction via grinding, abrasive and shear forces break material down; machinery used for this type of particle size reduction includes grinding mills.
• Homogenization: This method is used in the food and beverage industry to ensure consistency. It involves reducing particles within a fluid, resulting in smooth and uniform mixes. This technique is used to produce milk, peanut butter, and other emulsions containing fat or oils.
• Micronization: The term micronization usually refers to reducing average particle diameters to the micrometer range but can also describe further reduction to the nanometer scale. Common applications include producing active chemical ingredients, foodstuff ingredients, and pharmaceuticals. These chemicals need to be micronized to increase efficacy.
• Milling is a general term that means subjecting material to mechanical forces to reduce particle size; reduction machinery like rod mills, hammer mills, or ball mills is used to pulverize, grind, or crush material for a wide variety of applications and industries. 
• Pulverization: This broad category describes how crushers, impact mills, and grinding mills reduce coarser materials into powder; particle size reduction is often used in the chemical processing and pharmaceutical sectors.
• Shredding: This process involves cutting or tearing material, and it is often used in waste management and recycling operations to reduce particle size. Pulverizers are commonly used to recycle scrap metal, paper, and old tires.
• Ultrasonic particle size reduction: This entails using sound waves to break down materials; pharmaceutical and nanotechnological applications will sometimes use this method.

Choosing the best technique for particle size reduction entails understanding the properties of the materials, how they’re processed, the conditions under which they’re processed, and the type of machinery used to process them. These aspects of material processing, in turn, affect the quality of the end product and the efficiency of the process, both of which are, in turn, altered by the equipment used to reduce particle size. Reduction methods also require nuance, as techniques for one manufacturer may not work for another due to differences in materials, manufacturing conditions, processing limitations, and equipment.

Properties of Materials

Material properties help determine the best type of particle size reduction equipment for a specific processing application. For example, studies on material properties have shown that moisture content in ingredients for animal feed affects the minimum amount of energy needed to ensure the necessary particle size reduction. Lower moisture content makes the material more brittle, making it easier to break down. The properties of materials influence how they react during processing, affecting the efficiency of an operation.

Material characteristics manufacturers should consider include: 

• Abrasiveness: Hard materials like minerals are abrasive, while the processing of abrasive materials affects the lifespan of machinery used for particle size reduction.
• Brittleness: These materials are more brittle, responding well to impact forces for shattering to finer sizes with greater capacity.
• Bulk density: Certain products that remain aerated can have a lower bulk density in powder form due to the amount of air or void space between particles. These products also tend to be more fluid.
• Fracture toughness: Refers to the amount of force required to break apart material.
• Hardness: The higher the hardness, the more energy it takes to break down a material. 
• Moisture content: The moisture content of a material affects material properties like hardness, toughness, and viscosity of a material, which in turn affect how they interact with machinery and how sticky and free-flowing it may be.
• Temperature sensitivity: Certain materials degrade when reduced, so particle size reduction techniques sometimes require minimizing temperatures.
• Viscosity: Materials with higher moisture content are more viscous, leading to machinery clogging, increased heat during operation, and reduced efficiency.

Understanding the difference between a material’s toughness and hardness is important. Some softer materials are tougher than harder materials. For example, glass is easier to break than rubber because glass is less tough but more brittle. Toughness is often a factor in the pharmaceutical sector when dealing with medications that include fibrous ingredients, whose moisture content also affects how readily they break down.

While moisture content matters, depending on the type of bulk material, processing should be done when either dry or wet rather than damp. For materials to be ground when dry, a moisture content of under 5 percent is advisable, whereas for wet grinding, moisture content should be over 50 percent. To prevent agglomeration of a material, which commonly happens when too much moisture is present in the material, manufacturers will sometimes use surfactants to improve the efficiency of the particle size reduction process.

Operational & Environmental Factors 

To help determine the most efficient design for material processing systems, numerous operational and environmental factors must be evaluated to understand how they affect particle size. Reduction machinery needs to be chosen according to the techniques that ought to be applied to achieve the desired production capacity and throughput. Certain particle size reduction methods better suit smaller-scale production, while others work better when processing in bulk. Most equipment manufacturers will have various sizes for their machines that suit larger, smaller, or midsized production runs.

Additionally, the equipment used must consistently break down the material, as the quality of the final product can be impacted by its particle size. Reduction equipment should be big enough to handle the estimated feed rates, though these machines shouldn’t be so large that they’re underutilized either. Temperature and humidity within a facility also affect a product’s uniformity, as heat and moisture can cause certain materials to degrade. However, high temperatures are sometimes required for high-moisture and viscous materials.

Specific types of material processing equipment must also take into account numerous factors. For example, systems involving ball mills must consider the number, material type, and dimensions of grinding media, as these appreciably affect particle size. In turn, reduction equipment like jet mills must adequately control pressure levels to break down materials optimally. The type of equipment affects the particle reduction methods applied, which can affect the quality of the end product. Conditions within a facility may also affect efficiency, such as residue from product clogging equipment, which is why many systems require specialized rotary airlock valves to control dust during production. 

In addition to controlling quality, manufacturers dealing with bulk materials must meet certain regulatory requirements and industry standards. While many of these relate to health and safety, complying with environmental regulations has become increasingly important over the last half-century. While the impact of climate change has driven manufacturers towards choosing more energy-efficient solutions, sustainability has also proved economically beneficial, as it’s led to reduced energy use and waste, resulting in cost savings. 

Processing Parameters

Bulk material handling isn’t just about engineering machines to break down different materials by particle size. Reduction methods based on material science look to mathematical functions to describe how different materials behave under certain forces and conditions. Much research has been done to build machines to efficiently process the materials needed to make products for modern society. This research continues, extending to evaluating processing parameters.

Processing efficiency is affected by milling speed, for example, as speeds that are either too fast or too slow often reduce efficiency. Though longer processing times will usually result in finer particles, the efficiency of a process will eventually decrease to a point where overgrinding and waste occur. The longer it takes to process a material, the more energy is required to reach a certain particle size range. Reduction machinery works most efficiently when it operates within a sweet spot that applies sufficient energy for processing while not so much that it wastes energy and causes premature wear.

Three laws apply to particle size reduction equipment used when designing material processing systems. These laws govern energy use and efficiency in relation to the specific proportion, surface area, and surface-to-volume ratio of a material’s particles. Yet manufacturers must also consider particle size distribution, especially for certain products, as this can affect the uniformity and effectiveness of the end product. This is expressed using the Gaudin-Schuhmann equation, explaining why softer materials normally produce more fines.

Design of Particle Size Reduction Equipment & Systems

Material processing equipment and systems design involve mathematical formulas and commonsense engineering to achieve the appropriate particle size range. Reduction of material often works more efficiently when done in stages, though for products that require very fine particles, a single stage is often more desirable. As such, it’s important that manufacturers carefully consider the type of machinery they use for particle size reduction, as certain mills and other processing equipment are more efficient for specific applications.  

Screen area also plays a role. This is especially important when breaking down agricultural material like cereals, often processed using hammer mills. The ratio of screen area to HP for a given machine can result in more efficient, cooler grinding. H. Where size reduction dictates smaller screens, an air-swept mill can be more efficient and keep the product cooler. An air-swept pneumatic circuit can also convey the material to another part of the process while providing a pneumatic means for conveying less dense materials like powders.

How material is broken down will also affect the efficiency of the process. The design behind grinding mechanisms affects particle size, with reduction equipment using attrition, compression, impact, and shear for different materials and applications. Material scientists and mechanical engineers study the designs of such machinery to determine the most efficient way to reduce particle size. Reduction efficiency might increase by changing the angle at which hammers impact the product entering the grinding chamber, which may lessen the processing time required. Hammer speed can also factor into particle size, as a speed reduction will result in a higher proportion of coarse particles.

The design of machines used for particle size reduction goes beyond these mechanisms for breaking down materials. It encompasses how materials flow through systems and machines, looking at optimal pathways for products and minimizing dead zones where the product isn’t properly processed. Feeding and metering systems must be considered in the overall processing system to produce a consistent product and reduce waste. Efficiency in design shouldn’t remain static, however. Innovation and flexibility should always be continuous, with scientists, engineers, and machine operators collaborating to adapt equipment to increase efficiency for specific applications and industries.

Maintenance & Particle Size Reduction

The design of equipment used in processing operations should include an effective preventive maintenance program, as equipment maintenance greatly affects the efficiency of reducing particle size. Reduction machinery should be regularly cleaned and lubricated to clear blockages and reduce friction, increasing processing efficiency. Worn components should be replaced once they affect production efficiency, if not before, and keeping a stock of critical parts on hand will limit downtime.  

Prater Particle Size Reduction Equipment

At Prater Industries, we pride ourselves on the efficiency of our equipment. Using the expertise and ingenuity of Prater’s engineers, we offer some of the world's most efficient designs for handling and processing materials. We also design our machines for easy cleaning, maintenance, and repair to keep production lines running.  

Prater’s equipment for particle size reduction applications includes: 

• Air classifying mill: Combining air classification with a dual-stage grinding mill, Prater’s air classifying mill provides a single-unit design that uses space and energy more efficiently.
• G-Series full-screen hammer mill: Able to provide markedly uniform particle size reduction, Prater’s G-series hammer mills bring energy efficiency to high-capacity bulk material processes.
• Lump breakers: More reliable and efficient than any competing lump breaker on the market, this machine optimizes operating efficiency and lowers operating costs while enhancing quality; additionally, adding a Prater lump breaker to a material processing system will make downstream operations more efficient.
• Mega Mill hammer mill: Operating with greater efficiency and lower airflow than conventional hammer mill designs, Prater’s Mega Mill requires minimal energy to operate while also engineered to need little maintenance to reduce downtime.
• M-Series fine grinders: Able to achieve incredibly tight particle size distribution, our fine grinders are suited for resins, sugars, and other heat-sensitive materials and are incredibly efficient.

We invite you to read the case study below to learn more about how Prater’s equipment and teams help manufacturers in real-world situations. For more information on our products and services, contact us today.

Efficiency in Recycling

A global recycling company contacted Prater Industries to help them solve a problem. They came to us due to our company’s expertise in particle size reduction. An end user who separated certain materials from microchips approached the recycler to see if they could help them develop a more efficient way to extract them. Their current processing machinery limited their ability to salvage material, as the slow process only allowed for low throughputs. The metals they sought to recover fused at higher temperatures, further complicating the process.

Efficient Recovery of Valuable Metals through Enhanced Processing Technology

Prater needed to find a way to make the recovery of these valuable metals more efficient while limiting heat buildup. Samples were sent to Prater’s testing facility, where engineers tested processing in controlled conditions. Their best outcome came from Prater’s full-screen G-6 hammer mill. The G-6’s greater efficiency allowed full use of the screen to improve output while not increasing energy consumption. Wider rotors enabled flexibility in hammer arrangements, while the machine’s robust design made it capable of operating 24/7. Both the recycler and end-user were pleased with the solution, which allowed them to expand their operations.