Erosion-Corrosion Laws of 100ZJ-60 Slurry Pump in Phosphogypsum Transport: Phosphoric Acid Crystallization and Particle Size Distribution Analysis

Introduction

Phosphogypsum is the main solid waste generated in wet-process phosphoric acid production. For every ton of phosphoric acid, about 4-5 tons of phosphogypsum are produced. Phosphogypsum slurry consists of gypsum crystals (CaSO₄·2H₂O), unreacted phosphate rock particles, residual phosphoric acid, and various impurities. It is characterized by high concentration, sharp particles, strong acidity, and a tendency to crystallize. In phosphogypsum transport, slurry pumps face the dual challenge of corrosion and wear – phosphoric acid accelerates chemical corrosion, while gypsum crystals and phosphate particles cause severe abrasive wear. Their synergistic effect significantly shortens wear part life compared to conventional tailings service.

The 100ZJ-60 is a high-flow model in the ZJ series (100mm discharge, 600mm impeller diameter), designed for flows of 150-400 m³/h and heads of 30-70 m. It is widely used in phosphogypsum disposal and tailings transport in the phosphate chemical industry. However, field feedback indicates that impellers and liners suffer severe wear, scaling, and even perforation after only 2,000-3,000 hours, leading to sharp efficiency drops and high maintenance costs.

Based on sieve analysis and crystal morphology studies of phosphogypsum slurry, Hebei Xingou Machinery Equipment Co., Ltd. has identified the synergistic effect of phosphoric acid crystallization and particle size distribution on wear part erosion. This article systematically analyzes the erosion-corrosion laws of the 100ZJ-60 pump in phosphogypsum transport, providing material selection and operational guidance.

1. Composition and Characteristics of Phosphogypsum Slurry

Phosphogypsum slurry is a complex solid-liquid two-phase medium with the following main components and characteristics:

Phosphogypsum slurry is characterized by high solids concentration, irregular particle shapes (needle/plate), strong acidity, and a tendency to crystallize on metal surfaces. These properties together determine that the erosion-corrosion behavior of the 100ZJ-60 pump differs significantly from conventional mineral slurries.

2. Particle Size Distribution and Wear Patterns

2.1 Field Sieve Analysis

Hebei Xingou Machinery performed sieve analysis on a phosphogypsum slurry sample from a phosphoric acid plant:

Key findings:

• About 60% of particles are in the 44-150 μm range, which is most aggressive for cutting wear.

• Needle‑shaped gypsum crystals in the 44-74 μm range have cutting capability 2-3 times higher than spherical particles.

• Coarse particles >150 μm (unreacted phosphate rock, quartz) cause local impact and embedding, accelerating pitting.

2.2 Effect of Particle Morphology

The needle‑like morphology of gypsum crystals is a primary cause of severe wear. In high‑velocity zones of the 100ZJ-60 pump (blade inlet edge, discharge corner, volute tongue), the needle‑shaped crystals impact the metal surface at high angles, producing grooves and micro‑cutting that accelerate material removal.

3. Effect of Phosphoric Acid Crystallization on Wear Parts

3.1 Crystallization Mechanism

Residual phosphoric acid in the slurry can precipitate phosphate crystals (e.g., iron phosphate, calcium phosphate) inside the pump casing, impeller flow passages, and pipelines due to temperature changes, evaporation, or supersaturation. These crystals are hard and adhere strongly, gradually forming scale layers on metal surfaces.

3.2 Synergistic Effect of Crystallization on Wear

Key conclusion: Phosphoric acid crystallization is not merely a scaling problem; the “scale formation → spalling → wear” cycle significantly increases material loss. Field statistics show that in severe crystallization conditions, impeller life is reduced by over 40% compared to predictions based solely on particle wear.

4. Wear Location and Failure Mode Analysis

Based on failed parts statistics from 100ZJ-60 pumps in phosphogypsum service, wear distribution shows distinct location characteristics:

Typical failure sequence: Pitting at blade inlet edge due to particle impact and acid corrosion → increased surface roughness → accelerated cutting wear → blade thinning → repeated scale spalling at discharge corner → eventual perforation or fracture.

5. Material Selection and Optimization Recommendations

5.1 Performance of Different Materials in Phosphogypsum Service

Recommended solution:

• For phosphogypsum slurry (pH 2-4, containing needle crystals), the high‑chrome Cr30 impeller + acid‑resistant rubber lining combination offers the best cost‑performance. The rubber lining provides acid resistance and cushioning against needle crystal impact, while the high‑chrome impeller resists cutting wear.

• If quartz content exceeds 5%, apply chrome carbide hardfacing (65 HRC) on the blade inlet edge and discharge corner.

• For extreme high‑concentration, highly corrosive conditions, silicon carbide lined pumps are an option, but with higher initial cost.

5.2 Structural Optimization Measures

6. Maintenance Recommendations

Conclusion

The 100ZJ-60 slurry pump in phosphogypsum transport faces synergistic erosion-corrosion caused by phosphoric acid crystallization and cutting wear from needle‑shaped gypsum crystals. Particle size analysis shows that 44-150 μm needle crystals are the primary contributor to cutting wear; phosphoric acid crystallization further accelerates material loss through a scale formation‑spalling‑wear cycle. Hebei Xingou Machinery Equipment Co., Ltd. recommends the high‑chrome Cr30 impeller + acid‑resistant rubber lining combination, along with thickening the blade inlet edge, polishing flow passages, and regular scale removal, which can extend wear part life by 2‑2.5 times.

For material selection tailored to your specific phosphogypsum conditions or on‑site wear diagnostics, please contact Hebei Xingou Machinery‘s technical team.