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Comparison of polyaluminum chloride produced by different processes
There are significant differences in raw materials, cost, product purity and application fields of Polyaluminum Chloride (PAC) with different production processes. The following is a comparative analysis based on the production process:
- Classification according to drying process
- Drum drying method
Raw materials: aluminum ash, aluminum slag, coal gangue, minerals and other low cost raw materials.
characteristic ：
- Natural precipitation type: more impurities, high water insoluble matter (>2%), low aluminum content (about 24-28%);
- Plate and frame filter type: after mechanical filtration, impurities are reduced, aluminum content is increased (up to 28%), water insoluble matter is low.
Application: mainly used in industrial sewage treatment, low cost but general quality.
- Spray drying method
Raw material: high purity aluminum hydroxide or bauxite.
Features: high aluminum content (>29.5%), very low water insoluble matter (≤0.3%). Fast dissolution speed, colorless and transparent solution, salt base degree is controllable (about 50%).
Applications: drinking Water Treatment, precision manufacturing and other high requirements fields.
- Classification according to raw materials and reaction process
- Acid solution one-step method (metallic aluminum method)
Raw materials: aluminum chips, aluminum ash and other waste.
Features: simple process, low cost, but the product contains heavy metal impurities, poor stability.
Representative process: primary cell method, high efficiency but still corrosion problems.
- Alkali dissolution method
Raw materials: bauxite, sodium aluminate.
Features: the product is pure (less heavy metals), but the process is complex, high cost, need to adjust pH value.
- Neutralization method
Process: aluminum chloride and sodium aluminate are prepared step by step, and then mixed and neutralized.
Features: less impurities, high aluminum content and salinity (up to 85%), but higher cost.
- Alum hydroxide acid dissolution method
Raw material: high purity aluminum hydroxide.
Features: Suitable for the production of high purity PAC (such as white PAC), but requires high temperature and pressure, energy consumption is large.
- Mineral acid dissolution method (such as bauxite, coal gangue)
Process: crushing, roasting, acid dissolution and adjusting the base degree.
Features: raw materials are cheap (such as coal gangue), but the product is high in iron content, mostly used for low-end sewage treatment.
- Comparison of core indicators
| Process type | Aluminum content (Al₂O₃) | Salinity (B%) | water-insoluble | pigment | applicable scene |
| spray-drying process | ＞29.5% | ≈50% | ≤0.3% | White/transparent | Drinking water, precision industry |
| Roller drying-plate and frame filter | ≈28% | 70-85% | lower | yellow | Municipal sewage and general industrial water |
| Roller drying-natural sedimentation | 24-26% | 50-80% | ＞2% | Brownish / grey | Low requirements for industrial sewage treatment |
| One-step acid dissolution method (aluminum ash) | ＜28% | Volatility is high | tall | Dark yellow/brown | Ordinary industrial wastewater |
| Aluminum hydroxide acid dissolution method | ＞30% | Adjust to 90% | Very low | white | Food, medicine and other high purity fields |
- Suggestions for process selection
- High-end fields (drinking water, pharmaceuticals): spray drying or aluminum hydroxide acid dissolution are preferred to ensure low heavy metals and high purity.
- Municipal/industrial sewage treatment:
- Medium water quality: plate and frame filter drum process (high cost performance);
- High phosphorus/hazardous metal wastewater: neutralization method or alkaline dissolution method (salinity> 80%, strong adsorption).
- Low cost scenario: acid dissolution one-step method or coal gangue acid dissolution method, but impurities need to be monitored.
Tip: After the salinity exceeds 80%, the improvement of purification effect slows down, and the balance between cost and efficiency is needed.
The quality of low-end raw materials can be improved by optimizing the process (such as two-step acid dissolution and adding calcium aluminate powder).
