As the global fertilizer industry continues to focus on production efficiency, energy consumption, product quality, and environmental compliance, manufacturers are looking for granulation technologies that can deliver more consistent results with lower operating costs.
One technology attracting increasing attention is Ammoacid granulation. Unlike conventional steam-based granulation, this process uses the exothermic reaction between sulfuric acid and ammonia directly inside the granulator bed. The resulting ammonium sulfate slurry provides both a liquid binding phase and reaction heat, allowing chemical agglomeration and thermal energy generation to take place within the same process.
This approach can improve granulation efficiency while reducing the dependence on external heat sources. When properly engineered, it can also support flexible fertilizer formulations, lower recycle loads, and improved overall production economics.
1. How Does Ammoacid Granulation Work?
The basic principle of the Ammoacid process is relatively straightforward: sulfuric acid and ammonia react inside the granulator, producing ammonium sulfate while releasing significant heat.
Instead of relying primarily on steam to provide moisture and heat for particle formation, the chemical reaction itself becomes an important part of the granulation process.
This creates two major differences compared with traditional rotary drum steam granulation:
- Internal heat generation: Reaction heat supplies part of the thermal energy required during granulation.
- Chemical binding: The ammonium sulfate slurry generated during neutralization helps bind fertilizer particles together.
In a properly controlled system, the granulation temperature can be maintained around 80–90°C, promoting dissolution and recrystallization of soluble fertilizer salts.
Compared with conventional processes, this can increase the pelletizing rate, reduce material circulation, and lower energy requirements. Depending on the formulation and operating conditions, pelletizing rates can reach approximately 60–90%, while energy consumption may be reduced by around 20–30%.
The actual performance, however, depends on raw materials, formulation, equipment configuration, and process control.
2. Dilute Acid and Liquid Ammonia Buried-Pipe Technology
One of the important process considerations in Ammoacid granulation is how sulfuric acid and liquid ammonia are introduced into the granulator.
Rather than relying on concentrated acid or conventional pipe-reaction arrangements, the process uses a dilute-acid and liquid-ammonia buried-pipe configuration.
Controlled Chemical Reaction
Medium-concentration sulfuric acid, typically around 50–80%, and liquid ammonia are separately metered into the rolling material bed.
The liquid ammonia rapidly vaporizes and reacts with the acid within the material layer, generating ammonium sulfate slurry and reaction heat.
Accurate metering is essential because the acid-to-ammonia ratio directly affects process stability and final fertilizer characteristics.
Reduced Side Reactions
Using a more controlled dilute-acid environment can help reduce undesirable reactions with potassium chloride and minimize ineffective acid consumption.
It can also help reduce the generation of HCl-containing exhaust compared with less controlled process configurations.
Better Equipment Protection
The buried-pipe arrangement keeps ammonia injection within the material bed and can reduce direct exposure of sensitive equipment surfaces to corrosive gases and materials.
Combined with suitable lining and corrosion-resistant components, this can contribute to longer equipment service life.
3. Two-Stage Drying and Two-Stage Cooling
High-nutrient compound fertilizers can be difficult to dry. Removing moisture too quickly may damage the particle surface, while insufficient drying can increase the risk of caking during storage.
To address this issue, a staged thermal treatment process can be used:
Primary Drying → Primary Cooling → Screening → Secondary Drying → Secondary Cooling → Finished Product
The purpose is not simply to remove as much moisture as quickly as possible. Instead, the process separates initial drying from final moisture control.
Primary Drying: Protecting Granule Structure
The first drying stage removes surface moisture while maintaining a controlled outlet moisture level.
For example, moisture may initially be maintained around 2.0–2.5% rather than being reduced immediately to the final target.
This can help reduce surface cracking and roughness caused by excessive or uneven dehydration.
Screening Before Final Drying
After primary cooling, the material is screened. Qualified particles proceed to secondary drying, while oversize and undersize materials can be managed through the appropriate recycle or crushing system.
This allows the final drying stage to focus on particles that already meet the required size range.
Secondary Drying: Final Moisture Control
The second drying stage provides more controlled moisture removal, allowing the finished fertilizer to reach a lower and more stable moisture content.
Depending on the fertilizer formulation, the process can target approximately:
- ≤0.6% moisture for certain high-nitrogen products
- ≤0.8% moisture for certain single-chloride formulations
- ≤1.2% moisture for certain double-chloride formulations
Actual specifications should be established according to the product formula, raw materials, and applicable standards.
4. Environmental Control and Ammonia Recovery
Environmental management is another critical part of a modern fertilizer production line.
Ammoacid granulation can generate ammonia-containing exhaust from the granulator as well as dust-containing exhaust from drying, cooling, screening, and conveying systems.
A comprehensive treatment system can combine dry and wet collection technologies.
Ammonia Recovery
Ammonia-containing granulator exhaust can be treated through a combination of Venturi scrubbing and packed-tower absorption.
A circulating dilute sulfuric acid solution captures ammonia and converts it into ammonium sulfate-containing liquor.
With appropriate system design, ammonia recovery rates can reach approximately 98.5%, while treated exhaust can be controlled to a target ammonia concentration of around 30 mg/Nm³ or lower, subject to operating conditions and applicable regulations.
The recovered ammonium sulfate liquor can then be returned to the fertilizer production process.
Dust Removal
Drying and cooling exhaust typically contains fertilizer dust. A multi-stage system can combine:
Compound Baffle Deduster → Cyclone Deduster → Wet Scrubber
Such a configuration can achieve overall dust removal efficiency of approximately 99.5% under suitable operating conditions.
Recovered dry material can be returned to the granulator, while scrubber liquid can be reused in the preparation of dilute acid. This approach supports internal resource circulation and can significantly reduce wastewater generation.
5. DCS Automation for Stable Production
Modern fertilizer plants require more than mechanical equipment. Process control has a direct influence on production stability and product consistency.
A Distributed Control System (DCS) can connect raw material feeding, acid and ammonia addition, granulation, drying, cooling, screening, coating, conveying, and other processes into one coordinated control platform.
Intelligent Batching and Granulation
Based on the selected fertilizer formulation, raw material moisture, recycle rate, and online process measurements, the control system can calculate appropriate feeding rates.
It can coordinate the addition of:
- Raw materials
- Sulfuric acid
- Liquid ammonia
- Steam
- Water
This helps maintain the required granulation conditions and reduces fluctuations caused by manual adjustment.
Automated Coating and Dusting
Finished fertilizer can be treated with anti-caking or coating agents according to the product flow rate.
Automatic proportional dosing helps provide more consistent surface treatment across the production stream.
Crusher and Silo Interlocking
Crusher operation can also be linked to oversize-material silo levels. The system can automatically start or stop crushing equipment according to material accumulation, helping reduce unnecessary energy consumption and manual intervention.
6. Key Equipment in an Ammoacid Granulation Line
A complete production system requires coordinated equipment across several process stages.
| Process Section | Main Equipment | Key Function |
|---|---|---|
| Raw Material Processing | Pre-crusher, electronic belt scale | Provides suitable raw material fineness and accurate feeding |
| Ammoacid Granulation | Dedicated ammoniation granulator | Integrates mixing, reaction, granulation, and particle polishing |
| Drying & Cooling | Rotary dryer and cooler | Controls product moisture and temperature |
| Screening | Trommel screen | Separates qualified, undersize, and oversize particles |
| Environmental Control | Baffle deduster, Venturi scrubber | Removes dust and recovers ammonia |
| Material Conveying | Bucket elevator, belt conveyor | Transfers materials between process sections |
| Iron Removal | Electromagnetic separator | Removes ferrous contamination and protects downstream equipment |
Granulator Design
The dedicated ammoniation granulator can be divided into different functional zones for mixing, reaction, granulation, and polishing.
Special anti-clogging nozzles and suitable internal lining materials help maintain stable operation in a chemically aggressive environment.
Under appropriate operating conditions, the system can achieve a high pelletizing rate and produce relatively smooth, strong granules. A target granule strength of around 25 N can be achieved for suitable formulations.
Drying and Cooling Equipment
Rotary dryers and coolers can be fitted with specially arranged lifting flights to improve material distribution and reduce wall sticking.
Uniform material movement helps improve heat transfer while reducing excessive particle breakage.
Screening System
Trommel screens equipped with self-cleaning elastic elements can reduce blockage and minimize the need for manual cleaning.
For products with a target size of approximately 2–4 mm, screening efficiency can be optimized to achieve a finished-product pass rate of around 90% or higher, depending on material characteristics and screen configuration.
Corrosion-Resistant Conveying
Because fertilizer production involves corrosive materials, material selection is important throughout the conveying system.
For example, PP polypropylene elevator buckets and acid-resistant, tear-resistant conveyor belts can be used where appropriate to improve durability and reduce contamination risks.
7. Iron Removal and Product Purity
Ferrous contamination can damage equipment and affect finished fertilizer quality.
A multi-stage magnetic separation arrangement can therefore be installed at key locations, such as:
- Raw material inlet
- After crushing
- Before finished-product storage
This provides multiple opportunities to remove metal particles before they can enter sensitive equipment or reach the finished product.
8. Production Flexibility and Operating Performance
A well-designed Ammoacid fertilizer production line can be configured for a range of compound fertilizer products.
Typical system characteristics may include:
- Annual design capacity: approximately 150,000–300,000 tons per line
- Potential production output: up to approximately 120% of design capacity under optimized conditions
- Continuous operation: designed for extended production campaigns exceeding 30 days
- Product flexibility: suitable for selected chloride-, sulfate-, urea-, high-N, and high-K formulations
- Formula changeover: approximately 2 hours under suitable production conditions
- Power consumption: approximately 16–26 kWh/ton for typical products
- Steam consumption: relatively low compared with conventional steam-dependent granulation systems
These figures should be treated as engineering targets rather than universal guarantees. Actual performance depends on fertilizer formulation, raw material properties, production capacity, and plant configuration.
9. Business Value for Fertilizer Manufacturers
The value of Ammoacid granulation is not limited to the granulation equipment itself. A properly integrated production line can influence several areas of plant economics.
Lower Production Costs
Internal reaction heat, reduced recycle ratios, lower energy demand, and the ability to use economical nitrogen sources can contribute to lower production costs.
Under specific raw material and market conditions, the technology can provide meaningful cost savings per ton.
Better Product Quality
Controlled granulation and staged drying can produce fertilizer with:
- Higher granule strength
- More consistent particle size
- Lower residual moisture
- Better appearance
- Improved storage characteristics
- Reduced caking tendency
Reduced Manual Intervention
DCS automation and automated material handling reduce repetitive manual operations. This can lower labor requirements and make process control less dependent on individual operator experience.
Improved Environmental Performance
Ammonia recovery, dust collection, and internal reuse of recovered materials can help reduce emissions and waste while supporting compliance with increasingly strict environmental requirements.
Conclusion
Ammoacid granulation technology provides an alternative approach to conventional steam granulation by integrating chemical reaction, heat generation, and particle formation within the granulator.
The combination of dilute-acid liquid-ammonia injection, staged drying and cooling, ammonia recovery, multi-stage dust removal, and DCS automation can create a highly integrated compound fertilizer production system.
For manufacturers, the potential benefits extend from improved pelletizing efficiency and product quality to lower energy consumption, greater formulation flexibility, reduced manual intervention, and stronger environmental performance.
Ultimately, the success of an Ammoacid fertilizer project depends not on a single machine, but on the coordination of process design, equipment selection, automation, environmental control, and raw material management. A properly engineered turnkey system can provide fertilizer producers with a more efficient and flexible platform for long-term production.
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