Rotary Drum Granulator

Table of Contents

What is Rotary Drum Granulator?

A rotary drum granulator is used in industrial processes to agglomerate or granulate bulk solids for downstream processing, easier handling, and improved performance. 

It works by tumbling material in a rotating drum, typically in the presence of a binder, which causes the fines to become tacky and allows them to pick up additional fines, forming agglomerates in a process referred to as coalescence. 

The tumbling action helps to round the agglomerates and create a homogenous mixture. 

Rotary drum granulators are commonly used in the fertilizer industry and can be used for both hot and cold granulation.

Rotary Drum Granulator Process Flow Chart (4)

Basic Composition and Equipment Lists of Rotary Drum Granulator

A rotary drum granulator is a moulding machine commonly used in the fertilizer industry to turn materials into specific shapes. It applies to both hot and cold granulating. 

It is used to mass produce low, medium, and high-concentration compound fertilizers. 

The granulation ratio of a rotary drum granulator is up to 70%, making it very suitable for large-scale fertilizer production plants. 

The machine works by tumbling material in the presence of a liquid binder to encourage granule formation and growth. 

Feed material and binder are constantly fed through the rotating drum, and the rolling action, combined with the stickiness from the binder, causes fines to collect together into larger granules or particles with a more uniform shape. 

The machine requires a feeding and offtake system to convey material. 

Other machines that can work with the rotary drum churning granulator include a compost fertilizer machine, crush machine, fertilizer mixer, rotary drier, rotary cooler, and other miscellaneous equipment.

Rotary Drum Granulator Process Flow Chart (3)

Structures of Rotary Drum Granulator

A rotary drum granulator is a rotating cylinder inclined horizontally to facilitate material transportation through the drum. The drum is usually equipped with a dam ring to minimize the back-spill of the inlet material. 

The granulation loop of a typical rotary drum granulation process consists of a rotary drum granulator, a granule classifier (screens), and a roll crusher. 

The interior of the rotary granulator machine is designed to be adhesion-proof, so no materials will be attached to the inner wall during granulation, making it easy to maintain with less cost. 

The essential bracket supports the whole machine, which has huge strength and high friction in the rotating process. With it, granulation will take place. 

A rotary drum granulator is a moulding machine that can make the material into a special and qualified shape. It is one of the key fertilizer equipment in compound fertilizer production lines. 

The granulation ratio of a rotary drum granulator is up to 70%, making it very suitable for large-scale fertilizer production plants.

Rotary Drum Granulator Process Flow Chart (1)

Application of Rotary Drum Granulator

Rotary drum granulators are commonly used in fertilizer to turn materials into specific shapes. They apply to both hot and cold granulating. 

They are used to mass produce low, medium, and high-concentration compound fertilizers. 

The granulation ratio of a rotary drum granulator is up to 70%, making it very suitable for large-scale fertilizer production plants. 

The machine works by tumbling material in the presence of a liquid binder to encourage granule formation and growth. 

The resulting larger granules or particles have a more uniform shape, making them easier to handle and process downstream. 

Rotary drum granulators are versatile and can do both cold and heated granulation. They are cost-effective and consume relatively low energy while working. 

The special design of the interior of the rotary granulator machine is adhesion-proof, making it easy to maintain with less cost.

Raw Materials for Rotary Drum Granulator

The raw materials for a rotary drum granulator are typically powdery fertilizer materials that can be turned into specific granules. The machine is commonly used in fertilizer and applies to hot and cold granulation. 

It is suitable for large-scale production of low, medium, and high-concentration compound fertilizers. The granulation ratio of a rotary drum granulator is up to 70%, making it very suitable for large-scale fertilizer production plants. 

The machine works by tumbling material in the presence of a liquid binder to encourage granule formation and growth. 

The resulting larger granules or particles have a more uniform shape, making them easier to handle and process downstream. 

The humidity of the powdered raw materials should be consistent with that of the rotary granulator. 

To ensure consistency, small amounts of materials such as steam, nitrogen solution, phosphoric acid, ammonia, calcium slurry, or phosphate ammonia slurry can be added.

Features of Rotary Drum Granulator

The features of a rotary drum granulator include its ability to turn powdery fertilizer materials into specific granules, making it one of the primary pieces of equipment used in the fertilizer industry. 

It applies to both hot and cold granulating. It mass produces low, medium, and high-concentration compound fertilizers. 

The granulation ratio of a rotary drum granulator is up to 70%, making it very suitable for large-scale fertilizer production plants. 

The machine works by tumbling material in the presence of a liquid binder to encourage granule formation and growth. 

The resulting larger granules or particles have a more uniform shape, making them easier to handle and process downstream. 

The interior of the rotary granulator machine is adhesion-proof, making it easy to maintain with less cost. The machine consumes relatively low energy while working, making it a cost-effective choice. 

The rotary drum is large in size, so it can deal with a lot of materials simultaneously.

Rotary Drum Granulator Process Flow Chart (3)

Advantages of Rotary Drum Granulator

The rotary drum granulator is a highly efficient and cost-effective solution for fertilizer production. 

Its unique design and advanced technology offer several advantages over other granulating methods. 

The granulator is easy to operate and maintain, making it a popular choice for small and large-scale fertilizer manufacturers. 

It offers excellent control over the size and shape of the granules, ensuring consistent quality every time. 

The granulator is also highly versatile and can produce various fertilizers, including organic and inorganic varieties. 

In addition, it is environmentally friendly and can help reduce the carbon footprint of your manufacturing process.

Rotary Drum Granulator (7)

Production Process of Rotary Drum Granulator

The production process of rotary drum granulators is highly efficient and reliable for producing high-quality fertilizer. 

It starts with preparing raw materials, which are then fed into the drum and mixed with a binder and water. 

The drum rotates, and as it does so, the material is gradually formed into small granules. 

The granules are then dried and cooled to ensure their stability and long shelf life. The entire process is automated, making it easy to operate and maintain. 

It is also highly customizable, allowing you to adjust the parameters to meet your specific production requirements. 

With a rotary drum granulator, you can produce high-quality fertilizers with ease and confidence.

Rotary Drum Granulator Process Flow Chart (2)

How Does Rotary Drum Granulator Work?

The rotary drum granulator efficiently processes materials into uniformly sized granules. Its large steel drum rotates slowly, tumbling and rubbing the feedstock against abrasive discs. These discs break up clumps and crush the material into small pellets.

As the granules tumble, they polish against each other, smoothing edges and rounding shapes. Smaller fins help further classify sizes. The finely cracked granules exit the drum as a consistent, flowable product.

This simple but ingenious design handles materials that jam other equipment. The rotary action creates minimal dust and allows the safe handling of damp or reactive products. 

The result is high-quality granules for various applications, from fertilizer to sandblasting media. With durable construction and adjustable controls, rotary drum granulators have operated for decades, helping businesses thrive sustainably and economically.

Working Principle of Rotary Drum Granulator

A rotary drum granulator works by continual tumbling and abrasion. As the heavy steel drum slowly spins, the feedstock material tumbles within, grinding and crushing against itself. Positioned at an angle within the drum are abrasive discs that further pulverize any Large pieces.

The tumbling action causes the material to round, smooth and polish the granules. Small fins lining the drum help classify the granules by size as they tumble. 

Larger granules continue grinding against smaller ones until they reach the target size range. This particle-on-particle grinding results in higher throughput than jaws or hammer mills.

The rotary motion also prevents clogs since the material keeps moving. Damp or cohesive materials that would jam other equipment can process smoothly. 

The gentle crushing helps minimize damage to fragile or irregularly shaped feedstock. Multiple drums or larger drums allow high volume production of efficiently sized granules for various applications like soil conditioners, kitty litter, sandblasting media, etc.

A rotary drum granulator delivers high-quality, consistent granules sustainably and affordably through its innovative and low-maintenance design. 

With more than 30 years of field-proven performance, rotary granulators continue evolving to better serve diverse industries and applications.

What Capacities Can a Rotary Drum Granulator Accommodate?

Rotary drum granulators come in various capacities to suit different needs. Small granulators can process under 1 ton per hour, perfect for trials or niche applications. Mid-sized models handle 5 to 30 tons per hour, which is ideal for most commercial operations. Large industrial granulators can churn through 100 tons or more per hour for massive volume production.

No matter the size, rotary granulators have maintained efficient, low-maintenance performance for decades. Larger drums mean more material can tumble and grind at once. Multiple drums in series or parallel configurations can multiply throughput for high-demand applications.

Some granulators also feature integrated or standalone pollution control equipment like cyclone collectors, baghouses or bin vents to safely handle dusty materials. Volume flexibility, durability and optional features allow businesses to start small and scale up as their operations grow over many years.

Rotary drum granulators demonstrate how simple, proven technologies can tackle even the biggest challenges. Their continual tumbling action and minimal fines generation translate to economies of scale, lower costs and increased sustainability – benefits that resonate in every capacity. 

From lab to industrial, rotary granulators accommodate capacities and capabilities for the most demanding processing needs.

Is Rotary Drum Granulator Customizable?

Rotary drum granulators offer ample opportunities for customization. Their versatile and modular design lends itself well to modifications for diverse materials and applications. Customers can specify drum diameters, lengths and quantities to achieve any throughput target. Abrasion and classification systems, including different disc configurations and fin types, can also vary.

Additional features include replaceable drum liners for easy cleanup, steel or rubber lining for added durability, variable speed controls for optimal processing, overload protection systems, dust collection connections, and locking casters for portability. Pollution control equipment like baghouses or cyclones can be integrated or added separately.

Many manufacturers also provide custom options like dedicated bulk loading chutes, gear motors instead of standard V-belts, magnets or metal detectors integration, and the ability to process hazardous or at-risk materials. Every custom aspect helps tailor a rotary granulator to safely and efficiently handle unique requirements.

Whether modifying existing design or engineering one-of-a-kind solutions, rotary granulator builders have the experience and capability to deliver custom equipment for even the most demanding applications. 

With many years of field service supporting custom solutions, end-users can feel confident in operating and maintaining equipment that perfectly fits their specific operational needs and processing constraints. 

Customization strengthens the partnership between manufacturer and customer.

Is Rotary Drum Granulator Batch or Continuous?

Rotary drum granulators typically operate on a continuous feeding principle rather than in batches. They feature open tops or bulk-loading chutes that allow constant additions of feedstock material at a controlled rate. 

This steady feeding matches or exceeds the continuous output of granulated products from the discharge. Continuous processing prevents interruptions in material flow for charging and discharging, which could reduce throughput.

However, some rotary granulators do offer batch processing capabilities or hybrid approaches. These include:

•Dedicated batch loading chambers that accept an entire batch before releasing it to the drum. This works well for very uniform feedstock.

•Valves, gates or other flow control systems to synchronize batch addition with drum rotation. They prevent over/underloading for optimal performance.

•Drum liners containing an entire batch can then be discharged as one unit. This enables processing materials that would be damaged by constant tumbling.

•Operating multiple drums in series, where one drum acts as a surge hopper to feed downstream drums continuously for higher continuous production.

•Custom designs for specific batch-oriented processes like coating, drying, agglomeration, and granulation.

While continuous feeding suits most applications, batch capabilities provide greater flexibility and suitability for certain materials. 

The option is there for those who need it. Both methods can produce high-quality granules through the tumbling, grinding action of the rotary drum.

Types of Rotary Drum Granulator Fertilizer Pellets

Rotary drum granulators produce fertilizer pellets in various compositions and grades. The most common types include:

Straight or simple granules

Made from a single nutrient source like urea, ammonium sulfate or potassium chloride. Easy to produce but limited use.

NPK compound granules

Contain nitrogen, phosphorus and potassium for balanced, complete fertilizer. Produced by separately granulating and mixing multiple nutrient materials.

Micronutrient granules

Supplemented with micronutrients like boron, iron, manganese, molybdenum or zinc, depending on crop needs.

Slow or controlled release granules

Nutrients are released gradually for longer-lasting effectiveness. Produced using wax or polymer coatings during granulation.

Polyon granules

They are extremely dense and durable for application in difficult conditions. Higher production cost but reduced ammonia volatilization and less mess.

Coated or compounded granules

Nutrients combined with other additives such as pesticides, inhibitors, pigments or perfumes for speciality uses. Require close control during production to maintain product integrity.

Organic or natural granules

Made from natural, organic materials such as manure, alfalfa meal, soybean meal or blood meal. Gaining popularity due to sustainability and soil health benefits. It may require adjustments to the granulation process.

Rotary drum granulators provide flexibility to produce many fertilizer granules tailored for specific applications, effectiveness levels, user preferences and crop requirements. 

With the right process controls and mix of materials, fertilizer pellets can achieve optimal performance at the lowest environmental impact.

fertilizers produced by Rotary Drum Granulator (2)

How to Make Rotary Drum Granulator Fertilizer?

Here are the key steps to make rotary drum granulator fertilizer:

Select nutrient materials

Choose nitrogen (N), phosphorus (P) and potassium (K) sources such as ammonium sulfate, urea, single superphosphate and potassium chloride to provide the desired NPK ratios for your fertilizer. Micronutrients can also be added.

Grind or pulverize the materials

Run the raw materials through a hammer mill, jaw crusher or another grinder to produce uniform and finely divided particles. This improves granulation and nutrient release.

Compound the nutrients

Mix the ground N, P and K materials in the proportions required for fertilizer grade. You can also premix multiple nutrients together. Add micronutrients and any coatings at this stage.

Granulate the compounded powder

Feed the powder into a rotary drum granulator at a rate allowing even and efficient tumbling and granulation. Moisture content should be around 10-12% for best results.

Apply granulation aids (optional)

Adding a granulation aid such as bentonite clay or vegetable oil helps reduce dust, improves granule roundness and strength, and allows for higher hardness.

Control granule size

Adjust the drum rotation speed, abrasion systems, mesh screen size over the discharge and fine classifier settings to produce granules in your desired size range. Must meet product specifications.

Coat granules (optional)

Applying a coating such as a polymer latex or paraffin wax for controlled or slow-release fertiliser. Carefully monitor the coating rate to avoid damaging larger granules. Curing time may be required.

Packaging and shipping

Transfer the finished granules to storage bins or bags for packaging, loading and shipping to distributors, retailers or end users. Follow standard safety practices.


Sample and test the finished fertilizer product for guaranteed analysis, pH level, granule properties and other specification traits before wide release. Make any necessary adjustments to the formula or process.

Quality assurance

Continue testing random samples throughout production to ensure consistent quality, effectiveness and safety. Follow all regulations regarding fertilizer composition, labelling and distribution.

How to Produce Round Granules in Rotary Drum Granulator?

Here are some tips to produce round granules in a rotary drum granulator:

Use granulation aid

Adding a granulation aid such as bentonite clay, vegetable oil, or wax helps bind materials together and round out granules during tumbling. Start with a small amount, around 0.5-2% of the total mass. You can always add more, but too much aid will reduce fertility.

Adjust drum speed

Lowering drum speed allows more time for granules to polish and round out during tumbling. Around 10 to 25 RPM is typical for most materials. Higher speed produces more fine dust and angular granules. Slow, longer tumbling results in smoother, rounder granules.

Add steamed material

Feeding steamed or pre-heat treated material into the drum helps bind the total mix during granulation. The heat will soften the material, allowing granules to fuse together more easily. Start with around 10% steamed material and adjust up or down based on results.

Use durable materials

Granulation and rounding work best when starting with materials that can withstand the tumbling action without excessive crushing or breakdown. Choose materials with higher hardness, less friability and more uniform particle size. Fragile or dusty materials will not round out well.

Adjust drum liner and classifier

A drum liner and multi-deck classifier help control material exposure time and size classification within the drum. More liner coverage or smaller classifier openings will allow more granules to round out before discharge. Less liner or larger openings speed up processing but reduce granule roundness.

Tumble at a lower capacity

Running the granulator at lower feed rates means materials have more time tumbling and contact time for rounding out granules. Reduce feed rate by 10-30% and monitor granule roundness and hardness. Higher capacity will produce more fine, dusty and angular granules due to less tumbling time.

Cure granules (if coating)

For coated granules, proper curing is key to developing roundness and hardness. Curing allows the coating material to fully bind to the granule surface and core. Follow the recommended cure time, temperature and humidity for your specific coating to achieve optimal roundness, sphericity and durability.

With practice and adjustment, you can optimize your rotary drum granulator to produce round, premium fertilizer granules that meet all quality and productivity targets. Strong granules mean a superior product, higher value and customer satisfaction.

How to Batch and Ratio Raw Materials for Producing Fertilizer Particles?

Here are some tips for batching and rationing raw materials to produce fertilizer particles in a rotary drum granulator:

Determine the NPK ratios

Choose the nitrogen, phosphorus and potassium nutrient levels in the finished fertilizer. Express them as pounds of actual nitrogen (N), phosphorus pentoxide (P2O5) and potassium oxide (K2O) per ton of fertilizer. These will guide your material ratios.

Select nutrient sources

Choose nitrogen sources like ammonium nitrate or urea, phosphorus sources like triple superphosphate, and potassium sources like potassium chloride. Consider clay, sulfate and ammonium forms for various crops and soils.

Batch materials by weight

Use a truck-mounted scale, conveyor scale or loss-in-weight feeder to batch materials by weight. Start with smaller batches as you determine the ideal ratios. Weight is the most accurate measurement for consistent nutrition.

Adjust for differences in nutrient content

Account for the percentage of actual N, P2O5 and K2O in each nutrient material. Materials with higher percentages will require less weight to achieve the same nutrition level. Calculate ratios on an actual nutrient basis.

Mix a test batch

Once you have an initial ratio estimate, mix a small test batch to analyze the nutrient levels. Send a sample to a testing service or lab to ensure the NPK ratios meet your targets before scaling up production. Make adjustments as needed to the ratios for the next test batch.

Accommodate additive levels

If micronutrients, coatings, inhibitors or other additives are included, determine the target additive rate as a percentage of the total nutrient materials. Then adjust the main material weights to achieve that rate in the final fertilizer. Add additives after the main materials have been thoroughly mixed.

Record and compare ratios

Track the ratios used for each batch and analyze the results. Look for differences in nutrient levels, granule properties, cost, and field performance. Refine ratios over time to optimize the formula for your needs and resources. Have the formula tested regularly to ensure consistent, guaranteed nutrient levels.

Consider blender rights

Determine the formula and ratios allowed if purchasing pre-made raw materials and blender rights. Stay within the rights specifications to avoid legal issues. You can make minor adjustments to suit your needs, but they shall not exceed the allowed ranges.

Calibrate often

Frequently calibrate equipment to measure and batch materials like loss-in-weight feeders, volumetric feeders, weigh hoppers, and conveyor scales. Even small inaccuracies can significantly impact the nutritional quality and performance of the finished fertilizer over large production volumes.

These tips will help you achieve the ideal ratios and customize fertilizer formulas in your rotary drum granulator to meet agricultural demands precisely.

How to Grind Fertilizer Granules to Powder?

Here are some tips for grinding fertilizer granules to powder:

Select grinding equipment

The three main options for grinding fertilizer granules are:

› Hammer mill

Aggressive grinding, can produce fines, good for most fertilizers. Looks for cooled hammer mills for amending purposes.

› Jaw crusher

Course grinding produces larger particle sizes than a hammer mill. Good for preliminary size reduction before a hammer mill. Use oscillating or gyratory jaw crushers.

› Roller grinder

Fine grinding produces smaller particles than a hammer mill with fewer fines. Produces a uniform, flake-free powder. They are more expensive than hammer/jaw crushers.

Determine the target powder size

The size of the powder depends on how you will use it. Finer powder around 100 mesh or less is needed for top dressing, foliar feeding or amendment. Coarser powder around 20-60 mesh suits bulk blending into fertilizer or livestock feed.

Control humidity

Feed the granules at the proper moisture level, around 10-15%, for best results. Too wet will ball up; too dry will not grind efficiently. Add moisture with a spry nozzle as needed.

Adjust settings

For hammer mills, increase hammer speed and decrease screen size to produce a finer powder. For jaw crushers, increase the jaw gap to allow larger particles through. For roller grinders, increase roller pressure and speed. Make adjustments in small increments to avoid damage.

Reduce fines

Install dust collection equipment to minimize airborne fines, improving safety, equipment and powder quality. Cyclones, baghouses and bin vents all work well for fertilizer grinding operations.

Consider agglomeration

Agglomeration may be needed after grinding for some fertilisers to prevent dust-off before application. Use a binding agent such as clay, starch, molasses or polymers to help particles stick together into granules. Apply with a spray system as powder moves through the equipment.

Test and analyze powder

Collect random powder samples and have them tested by an independent lab to ensure that guaranteed nutrient levels meet specifications before sale or use. Analyze for nitrogen, phosphorus, potassium, pH level and other nutrients/properties as needed. Make any necessary adjustments to the formula or grinding process to bring powders into compliance.

Follow all safety procedures

Grinding fertilizer materials generates dust that may be irritating or explosive under certain conditions. Implement and enforce all recommended dust control, containment and personal protective equipment practices. Safety should be the top priority for any fertilizer grinding operation.

How to Mix Fertilizer Powder and What's the Mixing Process?

Here are some tips for mixing fertilizer powder and the general process:

Select powdered ingredients

Choose nitrogen (N), phosphorus (P2O5) and potassium (K2O) sources that have been ground into a powder with similar particle size for even mixing. Powders must also have similar flow characteristics to blend thoroughly without clumping. Test various powders before attempting large-scale mixing.

Determine the formula ratio

Decide on the NPK ratio for your custom fertilizer formula. Express it as pounds of actual N, P2O5 and K2O per ton of fertilizer. These ratios will guide how much each powder should add for a balanced, high-performance fertilizer. Higher N for foliar feed, higher P or K for bloom or root growth.

Batch ingredients by volume or weight

Use a calibrated volumetric feeder, weigh hopper or loss-in-weight feeder to ensure accurate and consistent batching for each production run. Batch to achieve the ideal NPK ratio in the final mixed formula.

Mix a test batch

Once you have estimated batch amounts for each powder, run a small test batch through your mixer. Analyze a sample of the mixed powder to ensure actual NPK levels meet your formula targets before scaling up production. Make adjustments to batch amounts as needed for the next test batch.

Add any additives

If including micronutrients, coatings, inhibitors or other supplements, determine the additive target rate per cent, then adjust main powder batch amounts to achieve that rate. Add additives after the base powders have been thoroughly mixed.

Calibrate equipment often

Volumetric feeders, weigh hoppers and other equipment used to batch powdered ingredients should be calibrated frequently, ideally before each production run. Small variances can significantly impact nutritional quality and product performance, especially over large volumes.

Record and compare results

Track the amounts of each powder used for every batch and analyze the results. Look for differences in nutritional levels, granule properties or performance that could affect quality or cost-effectiveness. Make incremental adjustments to continue optimizing the formula over time based on results.

Test and analyze for compliance

Collect samples of the final mixed powder and have them tested by an independent lab to verify that guaranteed nutrient levels meet product specifications before sale or use. Any levels outside compliance require addressing before releasing to market.

Follow safety procedures

Powder mixing and transfer operations generate dust that may irritate or become airborne, creating hazards if proper containment is not practised. Implement and enforce all recommended measures, including dust collection, personal protection equipment, containment barriers and respiratory guidelines. Safety should be the top priority.

What's the Granulating Process for Producing Fertilizer Particles?

The granulating process for producing fertilizer particles typically follows these main steps:

Select fertilizer powder ingredients

Choose nitrogen (N), phosphorus (P2O5) and potassium (K2O) powders that have been ground to a similar particle size and flow ability for even mixing and granulation. Pilot testing of different powders is recommended before large-scale production.

Determine the formula ratio

Decide on the NPK ratio you want in the finished granules. Express it as pounds of actual N, P2O5 and K2O per ton of fertilizer. Higher N for foliar feed, higher P or K for bloom or root growth. These ratios guide how much of each powder to add.

Batch powder ingredients

Use a calibrated volumetric feeder, weigh hopper or loss-in-weight feeder to batch each powder by volume or weight. Aim for the ideal ratios in your fertilizer formula. Test a small batch to ensure actual levels meet targets before large-scale production. Make adjustments as needed.

Add any additives (optional)

If including micronutrients, coatings, inhibitors or other supplements, determine the target additive rate as a % of the total powder mix. Then adjust the main powder batch amounts accordingly. Add additives after the base powders have been thoroughly combined.

Condition and granulate the powder

Spray the powder with water or another Conditioner to help bind the particles together. Add enough to allow the powder to form granules but not become muddy. Then feed the conditioned powder into a granulator, drum mixer, pellet mill or prill tower for granulation.

Test and analyze granules

Collect samples of the finished granules and have them tested by an independent lab to verify that guaranteed nutrient levels meet product specifications before sale or use. Any levels outside compliance require addressing before releasing to market.

Packaging and shipping

Transfer the fertilizer granules to bags, bins or bulk containers for packaging, storage, shipping and sale to distributors, wholesalers or end users. Be sure the packaging allows for breathability to prevent clumping.

Safety procedures

Granulation and material transfer operations generate dust that may irritate or become airborne, requiring proper containment. Implement and strictly follow all recommended measures, including dust collection, personal protection equipment, good housekeeping practices and respiratory safeguards. Safety must be the top priority.

Rotary Drum Granulator Process Flow Chart (5)

How to Separate Qualified And Unqualified Fertilizer Particles?

There are several methods for separating qualified and unqualified fertilizer particles:


Uses mesh screens of different sizes to separate particles by diameter. Particles too large or too fine pass through the wrong screen size. Screens can be static, vibratory or gyratory for varying efficiency. Common screen sizes for fertilizer are 10/20, 20/40 and 40/80 mesh (2000- 420 microns).

Air classification

Blows lighter, smaller particles away from the mainstream using adjustable airflow. Allows very precise control to split particles to tight size ranges based on material density and shape differences. Often considered the most effective method but also the most expensive.

Magnetic separation

Uses strong magnetic fields to pull ferromagnetic particles out of the stream, leaving the non-magnetic particles. Works for separating ferrites and other magnetic minerals. Requires magnetic material to be present in the unqualified particles.

Electrostatic separation

Charges particles using friction or induction, then applies an electric field to deflect particles in different trajectories based on charge. Allows separation of particles by density, shape, size, moisture and other properties impacting charge ability and mobility. Requires properly conditioning the material to allow even charging.

Density separation

Uses mediums of different densities like water, kerosene or lithium heteropolytungstate solutions to separate particles based on relative density. Lighter particles float while denser particles sink to different depths. Most effective on fairly uniform particle size distributions. Requires determining appropriate solution densities for your materials.


Uses high-speed streams of gas, liquid or other abrasive media to grind away fines and soft or loose particles, leaving harder, purer particles. It can scrub or polish certain particles to tighten size distribution and increase purity before final separation. Generates a significant fine powder byproduct that requires collection and disposal.

Gravitational settling

Simple separation based solely on particle size and density difference using the force of gravity. Larger, denser particles settle out of suspension faster than smaller, lighter particles. Least expensive method but limited in efficiency and ability to produce tight cuts. Works best on nearly uniform, nearly mono-sized distributions.

The specific or combination of methods used will depend on your materials, equipment, efficiency and budget needs. Pilot testing at a small scale is the best way to determine optimal separation for your fertilizer production process. 

How to Process The Qualified Fertilizer Granules After Screening?

Here are some common processing steps for qualified fertilizer granules after the screening:

Coating (optional)

Applying wax, polymer or other materials can help control the release rate of nutrients, prevent dust-off, and improve granule hardness and durability. Coatings are applied as a spray, dip or melt using equipment specifically designed for coating fertilizer granules. Proper coating curing is required to develop cohesion between the coating and granule.

Pelletizing (optional)

Intense pressure can compress granules into round nutrient-dense pellets. Pellets often have controlled-release coatings. Pelletizing improves handling properties and reduces dusting/separation during bulk transfer and application. Requires a pellet press, roller compactor or another pellet mill for processing.

Agglomeration (optional)

A binding agent like bentonite or molasses can help loose granules stick together into stronger granule clusters or “super-granules”. Agglomeration improves durability for applications requiring free-flowing, dust-free granules. The binding agent is applied as a spray and allowed to develop cohesion between granules. Curing is typically not required.

Micronutrient incorporation (optional)

Adding micronutrients helps ensure your fertilizer provides complete nutrition. Micronutrients are typically added as powders or dust and mixed/coated onto the granules. Testing is needed to verify even incorporation at the ideal rate for your formula and application method. Omitting micronutrients may require testing with and without to determine actual effects on crop growth or soil health.

Testing and analysis

After further processing, an independent laboratory should test random samples of the qualified granules to verify that the analysis meets guaranteed levels and product specifications before final sale or use. Any deviations require reformulation, reprocessing or withdrawal from sale until the product is fully compliant.

Packaging and shipping

Transfer the fertilizer granules to bags, bins, bulk trucks or another packaging for shipping to distributors and end users. Ensure packaging is properly rated for the contents and meets all regulations regarding product containment, water resistance, tear strength, labelling and hazardous materials shipping.

Safety procedures

Continue following all recommended safe practices to prevent hazards from dust, product contact or spills/leaks during further processing, packaging and transfer operations. Safety should remain the top priority across all fertilizer production activities.

How to Dry The Qualified Fertilizer Granules?

Drying fertilizer granules helps improve several key properties before final processing and sale. Here are some common methods for drying fertilizer granules:

Convection drying

Blowing warm air over the granules at relatively low pressure removes moisture through evaporation. Can reach high Throughputs using multiple blowers and static, fluidized bed or deep bed drying systems. Requires moderate temperatures around 130-170 F to avoid cooking the granules. Best for small- to medium-size granules.

Conduction drying

Placing the granules in direct contact with heated surfaces develops an even temperature throughout the bed, allowing moisture to dissipate from the centre and edges. Uses heated drums, trays, plates or endless belt conveyors. It can reach higher temperatures than convection without the risk of scorching. Requires periodic raking or turning of the granule bed for uniform drying. Best for medium- to large-size granules.

Vacuum drying

Reducing pressure around the granules allows moisture to vaporize and be removed at lower temperatures. Uses an airtight chamber under vacuum to speed drying while minimizing heat exposure. Prevents overheating delicate granules or volatile nutrients. It can achieve very low residual moisture content but at a slower rate and higher energy cost due to the equipment required. Best for heat-sensitive granules, coatings or micronutrients.

Solar drying

Exposing granules to direct sunlight provides radiant energy to evaporate moisture. Requires clear sunny days, frequent raking and may take significantly longer than other methods. Has zero energy costs but is subject to weather dependence and the inability to control temperature. Only suitable if other drying equipment is unavailable or for minor drying needs. Not ideal for volatile materials.

Hybrid drying

Combining multiple methods, such as blowing warm air over a moving bed (convection/conduction) or reducing pressure around a fluidized bed (vacuum/fluidized bed), improve efficiency over a single method alone. Hybrid systems are often more flexible, producing higher quality at lower cost but requiring more complex and expensive equipment. Pilot testing is important to determine the optimal hybrid for your needs.

Drying fertilizer granules improve handling/flowability, reduces dusting, allows for other processing like coating/pelletizing, and helps prevent caking during storage.

Samples should be tested before and after drying to ensure no significant changes in nutrient analysis or other properties. Proper drying is crucial to producing a premium, high-performance fertilizer product.

How to Get The Dried Granules Cooled?

There are several methods for cooling dried fertilizer granules:

Allow natural cooling

Letting the granules cool on their own after drying allows the temperature to gradually decrease through heat dissipation to the surrounding environment. This passive cooling method requires little additional equipment. Still, it results in a slight, uneven temperature decrease across the granule bed which can lead to overcooling or moisture reabsorption on the surface before the centre cools. Only suitable for small loads and when other cooling methods are unavailable.

Forced convection cooling

Blowing air over the granules at the minimum required velocity helps speed up natural cooling by enhancing heat transfer through convection. Uses the same or different fans/blowers as drying. Allows faster, more even cooling than natural cooling alone but at a higher energy cost. Good for larger operations or sensitive materials.

Fluid bed cooling

Passing air downward through a fluidized granule bed using a porous plate or grid cooler improves heat transfer for quicker cooling. The upward air flow prevents overcooling problems common to natural/convective cooling. Requires finely-tuned air flow and distribution for optimal performance. Most rapid and even method but also the most expensive and complex. Best for heat-sensitive materials, coatings or moisture-sensitive granules.

Direct contact cooling

Bringing granules into contact with cooled surfaces, like chilled steel trays, belts or rollers, cools them extremely quickly through conduction. Although easy to implement, direct contact risks overcooling outer granule layers before inner portions have finished cooling, potentially damaging temperature-sensitive materials. Usually only suitable for short-duration cooling of granules at the end of processing.

Batch cooling

Collecting a single “batch” of granules after drying and allowing them to cool together in an enclosed area helps retain heat within the batch, speeding cooling while reducing overcooling risks. The mass and insulation provided by the granules themselves help create a more even temperature decrease. Simple but limited throughput and flexibility between product runs compared to continuous cooling methods.

Hybrid cooling

Combining multiple methods, such as fluid bed cooling with batch or convection cooling with direct contact, can balance efficiency, cost and quality for optimal results. Hybrid systems provide flexibility and high performance at an affordable price but tend to require more complex equipment. Pilot testing different hybrids is important to determine the best approach for your particular drying process and materials.

How to Make Your Fertilizer Particles More Colorful?

Here are some tips for making fertilizer particles more colourful:

Add pigments or dyes

Pigments are powdered inorganic materials like iron oxides that provide colour, while dyes are organic liquids or powdered colourants. Add pigments/dyes directly to the fertilizer materials before grinding, mixing and granulating. Start with a small amount, around 1-5% by weight, and mix thoroughly for an even colour throughout. Add more for deeper, darker shades. Test colourfastness before large-scale production.

Incorporate brightening agents

Adding optical brighteners, also known as fluorescent whitening agents, helps make colours brighter and more vivid. They work by absorbing invisible UV light and re-emitting visible blue light. Around 0.01-0.5% is typically adequate for fertilizers. Fluorescent dyes can also be combined with standard colour dyes and pigments.

Use colour-coated particles

Apply colour pigments or dyes as a spray-on coating after granulation. Allow the coating to develop by tumbling, agitation or airflow before screening for an even coat. Coatings provide custom colours without changing the core nutrient formulation. They can wear off more easily during handling and application than masterbatch colouring.

Blended colouring

For tiered or graduated shading, start with a brighter base colour, then add darker shades incrementally and re-mix after each addition until reaching your target depth. Test colour in between mixes to ensure the hue remains consistent. This method allows subtle colourations not possible with a single concentrated pigment dose.

Fluorescent colours

Fluorescent pigments and dyes absorb invisible UV light and re-emit visible colours when exposed to UV or black light. They provide brighter, more vibrant shades than standard colourants for the same weight percentage. Fluorescent colours are more visible and eye-catching, aiding in product recognition and marketing. UV safety goggles are recommended for production personnel working with fluorescent pigments.

Metallic colours

Add powdered aluminium, copper, magnesium or titanium to the fertilizer during processing for a lustrous metallic sheen. Metallic pigments provide metallic-looking colour and light-reflective qualities. They are more expensive than standard pigments but help your fertilizer stand out. Test for colourfastness, pH balance and other property changes before large-scale use.

How to Pack your Fertilizer Particles Automatically?

Here are some options for automatically packing fertilizer particles:

Bulk bag filling

Filling large 1-2 ton woven polypropylene bags allows for economical bulk storage and shipping. Bag filling equipment includes weighing hoppers, volumetric feeders, spouts and bag holders. Automated bag tie-off seals the bag once filled to your specifications. Bulk bags require a crane or forklift for handling/movement.

Bagging equipment

Bulk particle flow is fed into a bag opening at the bottom of a vertical form-fill-seal bagging machine. Bag material is fed from a roll and cut to your bag size before filling and sealing. These provide high-speed, continuous packaging. Bagged fertilizer can be stacked/palletized for easy warehousing and shipping.

Box filling

Filling cardboard, plastic or wood boxes allows displaying attractively-packaged fertilizer products on store shelves. Box materials, sizes and closures (taping, stapling, lidded) will depend on your product and market. Box filling equipment includes volumetric feeders, vibratory feeders, scoops and sealers. Stacked boxes offer convenience but reduced density storage versus bulk bags.

Bag-in-box packaging

A bladder bag is placed inside a corrugated cardboard box. The flexible inner bag is filled with fertilizer through an opening, then a spigot and tap are attached as a spout for dispensing. When closed, it has the storage ability of a bag but dispensing and visibility of a boxed product. Bags can be swapped for different products to minimize packaging waste.

Loose filler spout

For bagged products, a loose filler spout attaches to the top opening and extends downward, allowing product to flow in but seals off for dispensing through a spigot at the end. This increases fill rate, reduces spills and allows for a wider range of bag sizes/materials than traditional open bag filling approaches. Spouts can be adjustable or offer multiple dispensing options.

Volumetric/loss-in-weight feeders

These metered feeders provide precise, consistent volumetric or loss-in-weight dosing of fertilizer into packages to control nutrient analysis and guarantee product specifications with each package produced. They help achieve uniform, balanced and trusted product quality essential for brand reputation and customer loyalty.

Different Fertilizer Shapes Produced by Rotary Drum Granulator

A rotary drum granulator can shape fertilizer particles into prills, pellets, granules, agglomerates, and coated granules. 

Prills are small, round beads with a smooth surface and high surface area for rapid nutrient release. 

Pellets are oval or cylindrical, larger than prills, and release nutrients more slowly. 

Granules are intermediate in size between prills and pellets with irregular cubic shapes and moderate surface area. 

Agglomerates are clusters of smaller granules fused together with lower surface area than granules within but higher than pellets. 

Coated granules are standard granules coated with materials to control nutrient release, reduce dustiness, and provide color. 

Rotary drum granulators produce prills, granules, and agglomerates with moderate residence time and an abrasive drum surface. 

Pellets require higher residence time and a pelletizer for additional compaction. Coating is applied as a spray-on after granulation.

fertilizers produced by Rotary Drum Granulator (1)

What is the Price of A Rotary Drum Granulator

The price of a rotary drum granulator varies depending on capacity, drum size, material, complexity, automation, brand, and additional features. 

Larger capacity granulators cost more, as do wider and longer drums made of stainless steel or porcelain enamel. 

Simple smooth drums for prilling are the least expensive, while abrasive drums for agglomeration or pelletizing add cost. 

Fully automatic granulators with programmable logic controllers, sensors, and automated material handling tend to cost significantly more than manual granulators. 

Well-known reputable brands are typically on the higher end, while less established brands may offer lower prices. 

Additional features like dust collection and variable speed control can increase the price by 5-20% or more. 

Expect to budget at least $200,000 to $500,000 or more for a new industrial fertilizer granulator with modest automation and complexer drums/materials. 

When buying, getting quotes from multiple suppliers, comparing specifications carefully, and negotiating the best deal is advisable.

Quality Control of Rotary Drum Granulator

Quality control is essential to ensure consistent, optimal performance, and high-quality fertilizer granules in rotary drum granulators. 

Key areas of quality control include material input monitoring, process parameter control, granule testing, force feedback control (optional), troubleshooting, preventive maintenance, documentation, auditing, and training. 

Monitor materials fed into the granulator inlet to maintain consistent formulation and other properties affecting granulation. Tightly control drum speed, residence time, feed rate, and other adjustable granulator parameters. 

Regularly collect granule samples to test for size, shape, nutrient analysis, moisture content, hardness, and other properties. Some granulators use force feedback control to detect abnormalities in material flow. 

Develop procedures to diagnose and fix problems quickly and implement preventive maintenance schedules. Document all procedures, testing results, parameter adjustments, maintenance activities, problems, and solutions implemented. 

Provide necessary training for all personnel involved in operating, maintaining, or overseeing the granulator. Competent, well-trained staff are essential to successful quality control.

How to Clean Rotary Drum Granulator

Proper cleaning of a rotary drum granulator is necessary to maintain its optimal performance and produce high-quality fertilizer granules.

 Cleaning tips include shutting down and locking out power, dismantling and removing transitions, scraping stuck-on material, sweeping or vacuuming, compressed air blowdown, wiping down interior surfaces, cycling detergent solutions, rinsing, and drying. 

Remove any product spouts or other components attached to the granulator drum or frame to ensure thorough cleaning. Scrape off large chunks of dried or baked-on product before sweeping or vacuuming loose debris. 

Use high-pressure air to remove any remaining dust and fines from the granulator. Wipe down all interior surfaces, including the drum, with a degreaser or detergent solution. 

For stuck-on messes, use a thick detergent solution and abrasive brushes on specific problem areas. Rinse with clean water and run short cycle runs to spin out excess moisture. 

Use air knives, heaters, dryers or leave to air dry until all parts are fully dry before the granulator is opened again to prevent product contamination.

Maintenance Work of Rotary Drum Granulator

Regular maintenance is crucial for a rotary drum granulator to ensure optimal performance, efficiency, safety, and equipment lifespan. 

Key maintenance tasks include lubrication of all moving parts, tension checking of drive belts and chains, alignment checking of multiple drive motors, shafts, and pulleys, replacement of worn or damaged seals, cleaning of screens and outlets to prevent material backups, regular inspection and replacement of bearings and bushings, safety checks of all switches, guards, alarms, and markings, following a structured preventative maintenance schedule, and periodic repair or overhaul for larger granulators or heavy use. 

Proper maintenance helps minimize unplanned downtimes and optimizes productivity and quality between servicing. 

Regular overhaul schedules can prevent major damage or downtimes and double the equipment lifespan if performed properly.

How to Use a Rotary Drum Granulator to Make Your Own Fertilizer Pellets?

To make fertilizer pellets using a rotary drum granulator, select a drum with an abrasive surface such as knurled steel, rubber, or perforated steel. 

Increase the residence time by adjusting the drum rotation speed or decreasing the feed rate to allow granules to pelletize together for at least 30-60 seconds. 

Spraying granules with a binding agent such as molasses, lignin sulfonate, or starch slurry helps accelerate pellet formation and produces stronger pellets. 

Screen and regrind oversized pellets to produce a uniform pellet size range suitable for your product. Cooling pellets is optional but important when producing soft pellets or using temperature-sensitive binding agents. 

Regularly collect samples of the pellets to check size, hardness, nutrient analysis, and other specifications and make adjustments to optimize pellet quality. 

Passing the pellets through an industrial roller press after the granulator can provide additional compaction for demanding applications. 

Cool and package the pelleted fertilizer properly to prevent softening or damage during packaging and shipping operations.

Preparation Steps To Operate Rotary Drum Granulator Safely And Efficiently

To operate a rotary drum granulator safely and efficiently, lock out power and check all safety devices before preparation. 

Clear the workspace, check hose and chute positioning, and establish initial feed rates and drum rotation speeds. 

Check lubricants and tension drive components to prevent excess noise, vibration, friction, and durability issues. 

For critical runs, collecting samples for testing can ensure specifications are met before full-scale production. 

Lock out power after each use to prevent unexpected startup that could cause injury.

Why People Want to Invest in Rotary Drum Granulator

Investing in a rotary drum granulator has several benefits, including increased production capacity for large-scale operations, consistent quality with tight control of process parameters and materials, improved handling with less material loss and waste, enhanced product value with premium pricing over raw or irregular materials, reduced material waste with minimized production of undesirable fines or off-spec products, automatic and efficient operation with minimal manual intervention, improved safety with fully enclosed automated equipment and proper guarding, and reduced energy usage with efficient electric motors, drives, controls, and insulation. These benefits lead to higher output and profits, customer trust and loyalty, higher efficiency and cost savings, boosted profit margins, improved safety and risk management, and lower carbon footprint and utility costs.

How to Become a Compound Fertilizer Manufacturer?

To become a compound fertilizer manufacturer, develop a fertilizer formula by determining the nutrient analysis, release properties, and other specifications needed for the target customer base and local soil/crop conditions. 

Source raw materials that meet agricultural standards and establish supply contracts for continuity. Invest in durable, high-volume manufacturing equipment like blenders, granulators, coaters, drying systems, and packaging lines. 

Set up facilities with covered storage, dust collection systems, weigh rooms, testing labs, bagging equipment/storage, and shipping areas. Obtain proper business licenses/registrations and environmental/pollution control permits. 

Implement thorough quality control procedures for testing incoming raw materials, in-process, and finished products. 

Build a brand and marketing strategy to sell compound fertilizers through wholesale distribution, retail sales, private labeling, or a mix. 

Stay up-to-date with advancements in raw materials, manufacturing equipment, quality testing methods, formulas, release technologies, and application techniques to improve efficiency, reduce costs, and develop new specialized blends/products to maintain customer loyalty and business growth.

How To Choose The Rotary Drum Granulator?

When choosing a rotary drum granulator, consider the capacity and throughput, drum size, surface, materials, automation level, additional features, brand and reputation, and costs. 

Determine the required hourly granulation capacity and select a granulator that is 20-50% larger than the initial needs to allow for future growth. Choose a drum size that balances your needs and constraints for granule size and quality. 

Pick a drum surface that achieves the desired granule type, size, and strength. Balance material cost and longevity versus needs. Consider the automation level needed versus cost constraints. 

Add features that provide value. Choose a high-quality granulator that fits your budget while still meeting essential needs. 

Lower costs by choosing a smaller size, less automation or starting with a simpler model and adding features over time.

Rotary Drum Granulator (28)


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Frequently Asked Questions

The price of a rotary drum granulator can vary significantly depending on the size, materials, features, brand and other factors, but you can generally expect to pay between $200,000 to $1 million or more for a new industrial rotary drum granulator.

A rotary drum granulator creates uniform granules by tumbling and rubbing materials together in a rotating horizontal drum. The key components include the drum, drive and power, feed inlet, granule discharge, raw material, and optional binders.

The drum has an abrasive, perforated, or smooth inner surface and determines how aggressively materials are tumbled and rubbed together.

An electric motor powers the drum rotation, and the feed speed controls the residence time of material in the drum.

Granules are discharged at the other end of the drum, and screens or traps can separate them by size.

Raw materials can include fertilizer chemicals, lime, sulfate, or prilled urea, and binders like molasses can be sprayed to help granules stick together.

Retention time in a rotary drum granulator impacts granule size and quality.Wider and longer drums provide more area and longer retention time.

Slower drum speeds and slower feed rates result in longer retention times.Adding binding agents can stick granules together even with shorter retention times.

Materials with finer particle size, dustiness, and less cohesion require slower speed and longer retention time.

Retention times range from 30 seconds to several minutes, with 1-5 minutes common for average-sized granules.

Monitor granules closely to determine the optimum retention time and speed settings for the best quality and strength.

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