Selecting the Right Industrial Grinder for Your Application

Industrial grinders are available in different sizes, and designs. These machines are used in bulk material processing across chemical, food, mining, and pharmaceutical industries. They mainly help in classifying and reducing the particle size of various materials. Understanding the different types of industrial grinders is crucial to choosing the right one for your application.

Choosing the Best Industrial Grinder for an Application

Material handling operations use industrial grinders to reduce particle size, making additional processing easier and creating a more uniform distribution of particle sizes. These grinders help break down bulk materials, making them more suitable for downstream processing, storage, or transport. They also improve the efficiency of material handling systems, enhance product quality, and ensure smooth material flow throughout processing.

Examples of the tasks industrial grinders perform in material handling systems include: 

• Break down materials into more manageable sizes, as is the case when condensing scrap metal in recycling operations, grinding grains for flour, and pulping wood chips during paper production.
• Preparing ground ore, powdered chemicals, or other such materials for shipping enhances flowability and reduces bulk.
• Shredding waste products in recycling or waste management operations to make them easier to reuse or lessen disposal costs, including agricultural waste, recycling rubber from worn tires, or reducing debris from construction sites.
• Texturing bulk materials to achieve certain properties for the end product, such as coarser aggregates for construction or fine powders for cosmetic products.

There are several different types of industrial grinders, each designed to handle specific applications better than others. Within each category, there are various iterations of industrial grinders, many of which are customized for specific purposes.

Types of Industrial Grinders

There are very few industries that process bulk solids without industrial grinders. Though the type may differ, mechanical grinding of materials to reduce the size and increase the surface area of their particles can often significantly alter properties. These modifications, in turn, result in increased processing speeds and lower temperatures of materials during specific handling activities.

Industrial grinders are generally categorized into these types: 

• Attrition mills: Though generally producing less output than other industrial grinders, attrition mills typically are used for processing heat-sensitive materials due to the lower temperatures they generate.
• Ball mills: These industrial grinders are widely used for separating valuable minerals within ore-producing rock and altering material properties, mixing and reducing materials into powdered form.
• Impact mills: These general-purpose industrial grinders are used for a diverse range of applications and come in multiple configurations, including classifier mills, fine-grinding mills, hammer mills, and pin mills.
• Jet mills: Used to produce extremely fine powders, jet mills are used in the production of cosmetics, industrial powders, pesticides, pharmaceuticals, pigments and powdered coatings.
• Roller mills: Industrial grinders of this sort are typically used for processing grains and minerals, with certain types of roller mills utilized for crushing more brittle material.

There are variations on all these industrial grinders, which are normally tailored to the exact application for which they will be used.

Attrition Mills

These mills utilize two metal disks for grinding, typically with one disk rotating while the other remains stationary. Certain types instead are configured with two mobile disks that rotate in diverging directions. Attrition mills receive material at the point where the disks are positioned, flinging material outwards and through the disks to a discharge point once particles attain the necessary size. The centrifugal force produced by this action assists in attaining a narrow particle size range.

Characteristics of attrition milling include: 

• Cleaning: Most attrition mill designs offer easy access to internal areas for cleaning and other maintenance.  
• Cryogenic milling: These mills can be used for reducing cryogenic or chilled materials. 
• Feeding: Multiple feeding configurations are available for these industrial grinders.
• Grinding plates: Normally, the configuration of attrition mills keeps the outer stator disk stationary, while the inner runner disk rotates, with the spring pressure on the grinding plate adjustable to ensure material uniformity during milling.
• Size reduction: Producing particles ranging from 100 to 10 mesh (149 to 2000 microns), particle size is adjusted by altering the gap between the mill’s dual disks.
• Temperature control: Efficient control of temperature during processing can be achieved with these mills.
• Throughput: The horsepower ratio to throughput achieved is higher than many other industrial grinders.

Attrition milling techniques can finely grind a wide array of materials, making them useful for a plethora of applications. They’re used for finishing, grinding, and scrubbing non-metallic minerals like graphite, for example, or even to wash soil. Vertically positioned attrition mills are often used for processing metals and alloys that contain bauxite, copper, iron, lead, molybdenum, nickel, and zinc. Additional applications include mixing cement and pulp for paper, while they’re also useful for generating nanoparticles from ceramics. 

Ball Mills

Industrial grinders in this class use spherical media to blend and grind material. These “balls” come in various sizes, both impacting and attritting material to reduce it, often to extremely fine particle sizes. Horizontally positioned, the mill’s drum contains balls that fill about half its volume and, as it turns, these grinding media are carried to the top of the drum before tumbling back to the drum’s center. These industrial grinders also can mill either dry or wet materials.

Characteristics of ball milling include:

• Cylinder: Grinding occurs within a hollow cylindrical shell that rotates around an axis that’s either horizontal or gently sloped.
• Grinding media: These industrial grinders use balls usually made from stainless or other steel, rubber, or ceramics. Their quantity, density/ weight, and dimensions affect the milling process.
• Lining: Materials resistant to abrasion, like manganese steel or rubber, line the hollow shell.
• Product size: Ball milling can reduce material to particle sizes as small as 152 mesh (100 microns).

Factors like the feed rate, speed at which the cylinder turns, time spent within the mill, and type of grinding material all affect the ball milling process. These industrial grinders are useful for a wide array of materials, such as ceramics, coal, ores, paints, pharmaceutical ingredients and pigments. They are also used for scientific research, working well for cutting-edge processes that involve creating ultrafine and even nano-sized particles. Ball mills are additionally seen as an important element for making future iterations of biodiesel and other biofuels that utilize microalgae, as they can break down cells more quickly than other types of industrial grinders.

Impact Mills

Impact mills are industrial grinders that use rigid force from hammers or similar implements to break down material mechanically. Most impact mills are fed through the top and discharge through a screening mechanism at the bottom of the machine once particles reach a suitable size. Commonly used types of impact mills include hammer mills, lump breakers and pin mills.

Characteristics of impact milling include:

• Classification: Depending on the type of impact mill, implements like classifying wheels, screens or sieves usually help classify material as it’s discharged.
• Grinding area: Normally cylindrical or shaped like a disk, material is contained within this grinding zone until reduced to a specific particle size.
• Housing: Generally, these industrial grinders feature a housing that’s either welded, hinged or with a design resistant to shock due to pressure.
• Internal components: Normally, wear plates or other critical components are easily interchangeable to ensure less downtime.
• Maintenance: Impact mills tend to be one of the easiest industrial grinders to keep clean and maintain.
• Rotor: These industrial grinders feature a rotor that operates at high speeds, to which implements of varying shapes are connected.
• Temperature-sensitive capabilities: Certain impact mills can have their grinding chamber designed to handle material that’s sensitive to temperature extremes.  
• Vibrations: Many impact mills feature a belt drive that protects the drive motor to compensate for the machine’s vibrations during operation.

Generally, these industrial grinders are used for crushing more brittle materials with Mohs-hardness ratings up to 3. Impact mills are used in the chemical processing, cosmetics, food processing, recycling and pharmaceutical industries, among others. They’re also used for breaking down agglomerated materials, such as when treating boiler ash received from incinerators.

Jet Mills

Instead of using mechanical means for reducing material, industrial grinders in this category use a stream of compressed gas – normally air or steam – that moves at high speed to help grind materials. The pressurized gas causes particles to collide with each other and the mill’s interior surfaces, creating a fine powder. Though air classification mills also use a pressurized airstream to grind materials, jet mills require additional equipment to classify materials by particle size.  

Characteristics of jet milling include: 

• Components: Unlike many other industrial grinders, jet mills don’t use mechanical implements that will wear out over time.
• Cross-contamination: As these mills utilize no mechanical components, they present little risk of causing contamination to product.
• Dry production: Jet mills are only used with dry materials that don’t require dehydration or other types of drying.
• Low temperatures: Jet mills are often used for heat-sensitive materials due to their lower grinding temperatures.
• Particle size reduction: Capable of reducing particles to submicron levels, they work well for abrasive, brittle and hard materials.
• Uniformity: Able to produce particles that are uniform in size to enhance certain material properties.

Jet mills help streamline production by combining grinding with collection processes. These industrial grinders are used for processing a wide variety of materials for multiple industries. They’re used within the cosmetics sector, particularly for facial products as the powders they produce have a lustrous and silky finish. The lower chance of cross-contamination in the pharmaceutical industry makes them ideal for producing active ingredients for medications. The agricultural sector uses jet mills, as they more finely grind pesticides and herbicides, so less active ingredients are needed. Chemicals, clays, coatings, paints, pigments, and other powdered materials are also produced with jet mills, including heat-sensitive materials like ceramics, dyes, fluorescent powders, silica, and toner.

Roller Mills

Industrial grinders that use cylindric rolling implements operating in pairs that move in opposing directions or against flat plates are known as roller mills. They compress bulk materials, crushing and grinding them to achieve various textures, with the gap between two rollers or a roller and plate determining fineness. Roller mills produce less dust than impact mills like hammer mills and generate uniformly sized particles. However, these industrial grinders aren’t suitable for fibrous materials or for coarse grinding, and they also require more operator attention and greater expense to operate.

Characteristics of roller milling include: 

• Consistency: Product produced via roller milling is consistent in quality and texture.
• Cost: Generally, roller milling is an inexpensive means for reducing products.
• Dust: Milling with these industrial grinders produces very little dust.
• Efficiency: For certain applications, like flour milling, roller mills can produce large amounts of product while generating little waste.
• Energy use: Compared to other industrial grinders, roller mills use up to 50 percent less energy than other techniques.
• Low heat: Produces less heat than other milling techniques, so it works well for heat-sensitive materials.
• Particle size: These industrial grinders can produce consistently uniform materials while yielding narrow particle size distributions. The gap between the roller and grinding surface can be adjusted to control material particle size.
• Speed: The rollers on these industrial grinders can be adjusted to rotate at varying speeds.  

Roller mills are widely used for processing agricultural and food products, especially for reducing grains like wheat and barley into fine flours, while also producing products like grits and cornmeal from corn. Feed manufacturers also use these industrial grinders to produce fodder for poultry and livestock. Additionally, roller mills can be used for a host of other materials, including ceramics, chemicals, fertilizers, glass, gravel, limestone, ores, and plastic resins. Such industrial grinders are sometimes used for reducing scrap metals and alloys in recycling operations as well.

Industrial Grinders from Prater for Fine Grinding Applications

Prater Industries makes several different types of industrial grinders, including two models used to produce finely ground material. Both these industrial grinder designs produce materials down to a fineness of 400 mesh (37 microns) in a highly efficient fashion, while also supporting narrow particle size distributions. Just like other Prater industrial grinders and material handling equipment, these fine grinders also allow for quick access to their internals to permit easier maintenance and repairs.

Prater’s industrial grinders for producing finely ground material are: 

• 10-Bar fine grinders: These industrial grinders are made to process materials that are more prone to explosions, such as the case when grinding sugars from 4X to 12X in a single process; providing shock resistance for pressures up to 10-bar in metric (equivalent to 145 pounds per square inch), these specialty industrial grinders are well-suited for products needing tight particle size distributions that are also sensitive to heat.
• M-series fine grinders: Prater’s M-series industrial grinders offer greater capacity, improved dust control, and precision control over particle size distributions, along with safety features standard with other Prater equipment.

To learn more about these and our other industrial grinders, along with our other products and services, contact the material handling experts at Prater today.