Urea Fertilizer

Fertilizer terminals handle urea in tonnages where a handling decision becomes a civil engineering one.

Caking

Above its critical relative humidity urea takes up water, and each humidity cycle builds solid bridges between prills.

• Dehumidified storage, or at least controlled ventilation that does not import humid air.
• Coated product where the supplier offers it.
• Limited storage height and residence time, since pressure accelerates caking.

Breaking a cake in a warehouse is done with machines, and the operation is both costly and hazardous.

Dust and attrition

Prills break at every transfer, and the dust is a visible emission as well as a product loss.

Cascade chutes and telescopic loading spouts with extraction contain the material column, which is more effective than filtering the resulting plume.

Corrosion

Damp urea and its decomposition products attack carbon steel and some coatings.

Material selection, drainage that prevents ponding and regular washdown of structures protect the asset.

Segregation and blending

Bulk blends of urea with other fertilizers separate by size and density during handling, which changes the nutrient ratio the farmer receives.

Matching particle size across blend components matters more than the blender itself.

What to establish before buying equipment

• Humidity profile in the store across the year.
• Prill or granule strength and the fines generated at design drop heights.
• Materials of construction for every damp contact surface.
• Loading rate and the dust control method at ship or truck.

Urea is strongly hygroscopic and that governs the store.

It takes up moisture above a fairly low humidity, and prills then stick together into a solid mass. Warm humid air is the worst case, which is exactly what a closed shed in summer provides.

• Seal and condition; ventilation with untreated air makes it worse, not better.
• Expect caking in the surface layer first, where the humid air reaches.
• Handle gently: broken prills cake faster than intact ones.

Gentle handling and dry air are the design.

Prills break at every impact, and the dust that results is both a loss and the fraction that cakes. Low drop heights and generous chutes do more for a urea plant than extra capacity.

• Cascade chutes and low drop heights.
• Dry conveying air with a stated dew point.
• Corrosion-aware materials; urea solutions attack some steels.

Urea itself is low hazard, and the issues are dust, decomposition products and housekeeping.

• Dust capture at transfer points.
• Awareness that heated urea gives off ammonia, which matters in a fire.
• Keep it separate from incompatible materials in storage.