OVERVIEW
Ammonium sulfate fertilizer is a widely used nitrogen and sulfur fertilizer containing:
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Nitrogen (N): ~21%
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Sulfur (S): ~24%
It is valued for supplying ammoniacal nitrogen and water-soluble sulfur, making it especially suitable for alkaline soils, sulfur-deficient soils, and sulfur-loving crops. Ammonium sulfate is produced through several industrial routes, depending on raw material availability and plant integration.
RAW MATERIALS USED
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Ammonia (NH₃)
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Sulfuric acid (H₂SO₄)
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Process water
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Optional additives (anti-caking agents, conditioners)
CHEMICAL REACTION
The production of ammonium sulfate is based on a neutralization reaction:
2 NH₃ + H₂SO₄ → (NH₄)₂SO₄
This reaction is exothermic and forms ammonium sulfate solution or crystals.
MAIN PRODUCTION PROCESSES OF AMMONIUM SULFATE
1. DIRECT NEUTRALIZATION PROCESS (MOST COMMON)
Process Description
Ammonia is directly neutralized with sulfuric acid to produce ammonium sulfate solution, which is then crystallized and processed into fertilizer form.
Main Steps
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Controlled feeding of sulfuric acid
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Ammonia injection and neutralization
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Formation of ammonium sulfate solution
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Concentration of solution
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Crystallization
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Solid-liquid separation
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Drying, cooling, and packaging
Advantages
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Simple and efficient
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High product purity
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Widely used in fertilizer plants
2. BY-PRODUCT RECOVERY PROCESS
Ammonium sulfate is recovered as a by-product from other industries.
Common Sources
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Coke oven gas treatment
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Caprolactam production
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Steel and chemical industries
Process Description
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Ammonia-rich gas or solution reacts with sulfuric acid
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Ammonium sulfate solution forms
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Crystallization and drying follow
Advantages
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Low production cost
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Utilizes industrial waste streams
3. GYPSUM CONVERSION PROCESS
(Used in integrated fertilizer plants)
Process Description
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Ammonium carbonate reacts with gypsum (CaSO₄)
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Produces ammonium sulfate and calcium carbonate
Characteristics
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Less common
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Requires solid-liquid separation steps
CRYSTALLIZATION AND SOLID FORMING
Crystallization
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Concentrated solution is cooled
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Ammonium sulfate crystals form
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Crystal size controlled by cooling rate
Drying and Cooling
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Removes residual moisture
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Improves storage stability
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Prevents caking
FINAL PRODUCT FORMS
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Crystalline ammonium sulfate
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Granular ammonium sulfate
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Powdered ammonium sulfate
Granular forms are preferred for mechanical spreading and blending.
QUALITY CONTROL PARAMETERS
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Nitrogen content (%)
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Sulfur content (%)
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Moisture level
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Particle size distribution
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Bulk density
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Caking tendency
APPLICATION AREAS
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Cereals (wheat, rice, maize)
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Oilseeds
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Sugar crops
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Vegetables
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Pasture and forage crops
Particularly effective in alkaline and calcareous soils.
ADVANTAGES OF AMMONIUM SULFATE FERTILIZER
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Supplies both nitrogen and sulfur
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Improves protein content in crops
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Acidifying effect benefits alkaline soils
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Low nitrogen loss compared to nitrate fertilizers
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Compatible with many NPK blends
STORAGE AND HANDLING
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Store in dry, ventilated conditions
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Protect from moisture
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Use anti-caking treatment for bulk storage
SUMMARY
Ammonium sulfate fertilizer is produced mainly by the neutralization of ammonia with sulfuric acid, followed by crystallization, drying, and finishing steps. Its dual nutrient content (N and S), soil-acidifying nature, and stable performance make it an important fertilizer in modern agriculture.
