The pugmill mixer, also commonly referred to as a paddle mixer or pug mill, is widely employed in a variety of processes transversing many industries. Flexibility in mixing, agglomerating, and conditioning make the capabilities of the pugmill mixer applicable to a wide range of bulk solids.
The unique medium-shear action imparted by the pugmill mixer, combined with its robust build, is an ideal fit for working with materials that can be challenging and require high torque to work through. This continuous industrial mixer is often chosen for the combination of benefits it can offer, which makes it ideal for tough materials:
- High capacity (500 lb/hr – 250 TPH)
- Heavy-duty construction for withstanding rigorous processing
- High torque for better combating tramp material, sludge-like consistency, and lumps
- Customizable for various settings and demands
- Kneading and folding action for thorough mixing of tough materials
- Effective combination of solid and liquid feed components
- Usable as a stand-alone device or as part of a larger agglomeration setup
While the pugmill mixer is only one of many industrial mixers available on the market and is widely utilized across industries, the qualities listed above have resulted in it becoming an irreplaceable tool in some processes…
Animal Feed Granulation
A number of agricultural processing applications require the robust capabilities of the pugmill mixer – one of which is the production of animal feed; pugmill mixers have become the center of production of Mono-Calcium Phosphate (MCP) and Di-Calcium Phosphate (DCP) feed products.
In this setting, the pugmill mixer, coupled with a vertical high-speed mixer, is used to complete the reaction between phosphoric acid and calcium carbonate (limestone), mixing of recycle, and granulation of the intended product. The chemical reaction in this process necessitates a thorough mixture of feedstock components to ensure a complete reaction and uniform end product.
The medium-shear kneading motion that the pugmill mixer imparts is highly effective at creating a homogeneous mixture of components and granulating that mixture to achieve a uniform product.
In addition to the mixing motion, the pugmill mixer is also essential in this application because its robust build is capable of withstanding the constant motion of the corrosive and abrasive feedstock components. Paddles can be fabricated of special steels or faced with special materials to deter corrosion or decrease wear. The paddles are easily replaced when needed as well.
Additional resources on the pugmill mixer in animal feed granulation:
- Article: Processing Phosphates for use in Animal Feed
- Project Profile: Animal Feed Granulation
Fertilizer Production
The production of fertilizers is highly diverse, with many techniques available. The pugmill mixer, more often referred to as a pug mill in this setting, is often utilized in the production of such products in order to thoroughly mix liquid raw materials, solid raw materials, and recycle before a rotary drum or disc pelletizer, or to simply mix and roughly agglomerate the material into a homogeneous end product.
The pugmill mixer can be used for both organic and inorganic applications, from manure to traditional NPK products, and everything in between.
Here again, the kneading and folding over motion used by the pugmill mixer makes it essential in producing a homogeneous mixture of liquid and solid feed materials for fertilizer production. Similarly, the mixer is able to withstand the often-corrosive nature of the feedstock components involved in fertilizer production.
Additional resources on the pugmill mixer in fertilizer granulation:
- Article: Types of Organics Granulation Systems
- Project Profile: Manure Granulation Plant
Fly Ash Conditioning
Pugmill mixers are also widely used in the energy industry for conditioning coal and coal ash products – most notably, fly ash.
Fly ash is a powdery by-product of coal-fired power generation. Fly ash has some opportunities for beneficial reuse, but is otherwise landfilled. Whatever its destination, the dusty substance requires conditioning to reduce dust and make handling easier. While pin mixers are frequently used for processing materials in powder form, the pugmill mixer is chosen in this setting for two reasons. First, it offers a higher capacity compared to pin mixers; second, the kneading and folding motion that occurs in a pugmill mixer offers a reduced potential for wear compared to the intense spinning action of a pin mixer.
Pugmill mixers “condition” the fly ash with water in order to promote rough, de-dusted agglomerates that are more easily handled and won’t become windblown upon deposit.
A novel application uses the pugmill mixer to blend fly ash with another coal-fired energy by-product: FGD scrubber sludge.
The sludge-like consistency of the material resulting from flue gas desulphurization makes handling and landfilling the material a challenge. The pugmill mixer can be used to blend the dusty fly ash with the wet sludge to increase the handling properties of both materials for improved handling and deposition into landfill.
Additional resources on the pugmill mixer’s use with fly ash:
- Project Profile: Pugmill Mixers for De-dusting Fly Ash
Copper Concentrates Smelting
Due to the coarse, heavy, and abrasive nature of metals and minerals, pugmill mixers are often the equipment of choice in this industry as well, particularly when it comes to smelting copper concentrates.
In the smelting process, pugmill mixers mix and condition copper concentrates along with flux, reverts, matte recycle, dust recycle and often water (as a binder) in preparation of the smelter. This creates a homogeneous mixture of the varying feedstock components and causes rough agglomeration. The agglomeration helps to prevent the otherwise dusty materials from becoming entrained in the smelter’s process gas, while the homogeneous mixture helps to ensure maximum recovery.
Pugmill mixers are the equipment of choice in this setting for their robust build, high torque, and high throughput. They have become so critical in processing copper concentrates and maximizing recovery that producers will often purchase two mixers at a time – one as a backup in the event of an issue or maintenance requirement.
Additional resources on processing copper concentrates with a pugmill mixer:
- Article: The Role of the Pugmill Mixer in Processing Copper Concentrates
- Project Profile: Pugmill Mixers for Copper Concentrates
Iron Recovery from Steel Mill Waste
Pugmill mixers have become a critical component in steel production as well.
Dust and scale are produced in excess quantities during the steel making process. Despite being a by-product, however, these materials still contain a significant amount of iron that must be recovered.
Iron dust is fed to the blast furnace in the form of briquettes so it does not become entrained and carried out. The briquetting process requires a uniform feedstock to produce briquettes with the desired specifications, but the abrasive nature of the by-products requires a device that can withstand the rigorous demands.
Once again, the pugmill mixer is ideally suited for this application. After drying in a rotary dryer, the dry by-products are mixed with a binder in a pugmill mixer, creating a uniform mixture that promotes optimal briquetting. The by-products can then be reintegrated back into the process so no iron goes to waste.
Additional resources on processing steel mill waste with a pugmill mixer:
Project Profile: Pugmill Mixers for Processing Steel Mill By-Products
Conclusion
The pugmill mixer serves various industries in need of a robust industrial mixer capable of homogeneously mixing solid and liquid feed components. However, the high-capacity, high-torque capabilities of this mixer, combined with its robust construction, makes ita necessity in processing challenging materials such as fertilizers, fly ash, copper concentrates, and steel mill by-products.
FEECO engineers and manufactures custom pugmill mixers for all of the applications discussed here, and more. Our pugmill mixers are highly customizable and are designed with a variety of features that make them a long-term, reliable solution despite a demanding production setting. For more information on our pugmill mixers, contact us today!