Principle: use gravity to make the phosphating slag natural precipitation at the bottom of the pool, the supernatant is discharged. Applicable scene: slag volume is small, treatment requirements are not high occasions. Advantages: low cost, simple operation. Disadvantages: low efficiency, need to be left for a long time, slag water content is high.
How many filtration types of phosphate slag produced in phosphate production?
Author: Robby
In phosphate production, the filtration of phosphate slag (mainly composed of phosphate precipitation, metal ion residue, etc.) is a key link in wastewater treatment or slag recycling. Common filtration methods mainly include the following, according to the scale of treatment, the amount of slag, cost and environmental requirements to choose the appropriate method:
1. Natural sedimentation method
Principle: use gravity to make the phosphating slag natural precipitation at the bottom of the pool, the supernatant is discharged.
Applicable scene: slag volume is small, treatment requirements are not high occasions.
Advantages: low cost, simple operation.
Disadvantages: low efficiency, need to be left for a long time, slag water content is high.
2. filter press filtration
Plate and frame filter press:
Through high pressure to slag liquid squeezed between the filter plate, the formation of filter cake.
Advantages: low water content of the cake (up to 30% ~ 50%), large capacity.
Disadvantages: high investment in equipment, the need for regular replacement of filter cloth.
Chamber filter press:
Similar to plate and frame type, but better sealing, suitable for fine particle slag.
3. Vacuum filtration
Rotary drum vacuum filter:
Filter cloth covered drum in the vacuum adsorption under the separation of slag.
Advantages: continuous operation, high degree of automation.
Disadvantages: complex equipment, suitable for medium-scale processing.
Belt vacuum filter:
Solid-liquid separation is achieved through conveyor belt and vacuum suction, suitable for slag with high water content.
4. centrifugal filtration
Centrifuge (such as decanter centrifuge):
Use centrifugal force to quickly separate solid-liquid phase.
Advantages: high efficiency, suitable for fine particles.
Disadvantages: high energy consumption, high maintenance costs.
5. Membrane filtration technology
Microfiltration/Ultrafiltration membranes:
Phosphate slag particles are intercepted through the pore size of the membrane.
Advantages: high filtration precision, can recover useful components.
Disadvantages: the membrane is easy to contaminate, need frequent cleaning, high cost.
6. Simple mechanical filtration
Filter bag / cartridge filtration:
The slag liquid through the filter bag or cartridge to intercept the solid.
Advantages: simple equipment, suitable for small-scale or pretreatment.
Disadvantages: manual cleaning, limited capacity.
7. Chemical precipitation + filtration
First add flocculants (such as PAC, PAM) to make the slag cohesion into large particles, and then with the above filtration method.
Advantages: improve filtration efficiency, reduce the water content of filter cake.
Suggestions
Small scale/intermittent production: natural sedimentation + filter bag filtration.
Medium and large scale continuous production: filter press or vacuum filtration (balance between efficiency and cost).
High-precision recycling needs: membrane filtration + centrifugation combination.
Strict environmental protection areas: need to be combined with chemical precipitation to ensure that the wastewater meets the standards.
Practical applications may need to combine a variety of methods, and consider the subsequent treatment of phosphate residue (such as hazardous waste disposal or resource utilisation).