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Dec 23, 2024
In the wet-process phosphoric acid production, phosphate rock reacts with sulfuric acid to generate phosphoric acid solution (dilute phosphoric acid) and by-product dihydrate calcium sulfate crystals (phosphogypsum). The belt filter uses a belt filter cloth as the filtration medium to efficiently separate solid phosphogypsum from the liquid phosphoric acid solution in the reaction slurry. Its performance directly affects:
1. Production efficiency (filtration rate, capacity)
2. Product quality (clarity of phosphoric acid)
3. Resource recovery rate
4. Operating costs (energy consumption, filter belt replacement frequency)
5. Environmental compliance
1. Chemical Corrosion Resistance
The filter belt must withstand strong acids such as phosphoric acid, sulfuric acid, and fluosilicic acid, as well as potential fluorides, without swelling, degradation, or significant loss of strength.
2. Anti-Clogging Performance
Phosphoric acid slurry contains gypsum crystals, colloidal silica, and fluorides that can easily clog filter pores. The filter belt should have a specialized weave structure (e.g., monofilament, multifilament, satin weave) and surface treatment (e.g., calendering, coating) to minimize clogging.
3. High Strength and Dimensional Stability
The filter belt must endure vacuum suction, filter cake weight, mechanical tension, and high pressure in the squeezing zone. It should exhibit excellent tensile strength, abrasion resistance, and low thermal shrinkage.
4. Good Cake Release Properties
The filter cloth surface should be smooth or specially treated to ensure that the formed cake can be easily and completely removed by scrapers or rollers in the discharge zone, reducing residue and improving efficiency.
5. Optimized Air & Water Permeability
While meeting the required filtrate clarity, the filter belt should maximize air and water permeability to achieve higher filtration speeds.
6. Long Service Life
Under harsh operating conditions, the belt filter cloth should have an extended service life to reduce replacement frequency and production costs.
Therefore, selecting the appropriate filter belt material, structure, and precision based on specific process conditions (acid concentration, temperature, particle characteristics, etc.) and maintaining it properly are crucial for the stable, efficient, and economical operation of phosphoric acid production plants.
