From Rock Phosphate to DAP Production: A Complete Step-by-Step Guide

Diammonium Phosphate (DAP) is one of the most widely used phosphate fertilizers in the agricultural industry. It provides high concentration of nitrogen and phosphorus (18-46-0) to the crop. However, the journey from raw geological deposits to the uniform granules found in a farmer's spreader is a complex engineering feat. It requires robust rockphosphate to DAP production system to convert natural phosphate ore into valuable fertilizer products. Mastering the process of rock phosphate to DAP production requires a deep understanding of chemical molarities and a suite of robust industrial machinery.

This guide explains the complete rock phosphate to DAP production process step by step, while introducing the advancedDAP fertilizer machinery solutions provided by LANE Heavy Industry.

The Raw Materials: The Foundation of DAP

Before the machinery begins to turn, three primary ingredients must be managed:

1. Rock Phosphate: The source of phosphorus (P2O5).
2. Phosphoric Acid: Created by treating rock phosphate with sulfuric acid.
3. Ammonia (NH3): The source of nitrogen.

The goal of rock phosphate to DAP production is to chemically bond two molecules of ammonia to each molecule of phosphoric acid.

Step 1: Phosphate Rock Mining and Beneficiation

Phosphate rock is extracted from sedimentary or igneous deposits before they are crushed and ground. raw ore contains only 15–25% P₂O₅. Before it can be used it must be beneficiated through washing, screening, and flotation to rise the concentration to 28–38% P₂O₅. The beneficiated rock is dried and stored in silos, and ready for acidulation. LANE supplies the primary crushing and grinding equipment like RaymondMill, ball mills, and classifiers engineered to handle the abrasive nature of phosphate rock with minimal downtime.

Step 2: Sulfuric Acid Production (Integrated Plant)

Phosphate rock cannot be directly converted to fertilizer without first reacting it with sulfuric acid. Large DAP complexes often include an on-site. Large DAP complexes often include an on-site sulfuric acid plant that burns elemental sulfur to produce SO₂, converts it to SO₃, and absorbs it in water to yield concentrated sulfuric acid (typically 98%). LANE can integrate this section into the overall line, ensuring seamless material flow from acid production to the phosphoric acid reactor.

Step 3: Wet Process Phosphoric Acid (WPA) Production

The beneficiated Phosphate is fed into a reactor where it reacts with sulfuric acid under controlled temperature and agitation. The chemical reaction produces phosphoric acid (as a slurry) and calcium sulfate (phosphogypsum) as a byproduct. The slurry passes through a tilting-pan or belt filter to separate the gypsum, yielding weak phosphoric acid at 26–32% P₂O₅. LANE’s WPA systems feature acid-resistant reactors (lined with carbon brick and acid-proof tiles), high-efficiency tilting-pan filters with automated cloth washing, and fume scrubbing to capture fluorine gases. Recovery rates consistently exceed 96%.

Step 4: Phosphoric Acid Concentration

The weak acid is concentrated via forced-circulation evaporators operating under vacuum. Bringing the acid to 40–54% P₂O₅ is critical for the ammoniation step ahead. LANE provides energy-efficient evaporator bodies with enhanced heat transfer surfaces and liquid-vapor separators that minimize entrainment, ensuring the acid meets the strict solids and fluorine limits required for DAP production.

Step 5: Pre-Neutralization

Concentrated phosphoric acid is pumped to a pre-neutralizer vessel where gaseous ammonia is sparged into the liquid. The reaction produces a hot slurry of monoammonium phosphate (MAP), releasing significant heat. Temperature is maintained at 115–130°C to prevent crystallization and manage the ammonia-to-phosphoric acid mole ratio at around 1.4:1. a carefully controlled intermediate state before the second ammoniation. LANE’s pre-neutralizer tanks are fabricated from 316L stainless steel with high-turbulence agitators to ensure complete reaction and uniform slurry density.

Step 6: Granulation (DAP Formation)

The MAP slurry, together with recycle fines from the screening circuit, enters a rotary drum granulator. The drum’s internal rubber lining prevents caking and protects against corrosion. LANE’s granulator design incorporates steam injection to elevate the bed temperature, reducing post-granulation moisture and boosting balling efficiency to around 70%. Rotational speed and drum inclination are adjustable to tune granule size.

Step 7: Drying

Wet DAP granules, typically containing 2–3% moisture, pass into a rotary dryer fired by a hot air generator. Inlet drying gas temperatures are controlled below 350°C, with the product temperature kept under 90°C to avoid ammonia loss and thermal decomposition. LANE’s dryers feature advanced flight designs for uniform cascading, maximizing heat transfer while minimizing fuel consumption. Exhaust gases are treated in cyclones and wet scrubbers to recover dust and ammonia.

Step 8: Cooling

Dried granules exit the dryer at elevated temperatures and must be cooled to near ambient before storage. A rotary cooler uses ambient air to bring the product down to below 40°C. This prevents caking during storage and protects downstream screening equipment. The cooler air is also dedusted before release.

Step 9: Screening and Crushing

The cooled product is screened on double-deck vibrating screens to separate on-size granules (typically 2–4 mm). Oversize granules are crushed in a chain mill or roll crusher and returned, along with undersize fines, to the granulator as recycle material. This closed-loop sizing circuit pushes the plant’s granulometric efficiency above 95%. LANE’s screens are robust, corrosion-resistant, and designed for 24/7 operation.

Step 10: Coating and Packaging

On-spec DAP granules are treated with an anti-caking coating (e.g., amine-based liquid sprayed in a rotary coating drum) at a dosage of 1–2 liters per ton. Coated product is conveyed to storage bins or bagging lines. LANE supplies automated bagging systems that fill, weigh, and seal 25–50 kg bags, with palletizing options for bulk distribution.

FAQ

1. What is the main raw material for DAP production?

The primary raw material is phosphate rock.

2. What is the formula of DAP?

DAP formula is (NH4)2HPO4.

3. What machinery is required for DAP production?

Main machines include crushers, reactors, granulators, dryers, coolers, screens, and packaging systems.

4. Is rock phosphate to DAP production profitable?

Yes, due to strong global fertilizer demand and high market value.

For more details, please feel free to contact us.

Henan Lane Heavy Industry Machinery Technology Co., Ltd.

Email: sales@lanesvc.com

Contact number: +86 13526470520

Whatsapp: +86 13526470520