Candle filters, a type of high-efficiency solid-liquid separation equipment, are widely used in industrial filtration.
Core Features
**High Efficiency and Energy Saving:** Possessing a large filtration surface area, it can quickly separate solid-liquid mixtures, improving filtration efficiency and reducing energy consumption.
**Sealed and High-Precision:** The cylinder is tightly sealed, ensuring no leakage during production. Suitable for handling liquids of various viscosities and solid contents, especially suitable for materials prone to clogging and requiring fine filtration.
Main Structure
**Filter Cartridge Assembly:** The core component, composed of a porous tube and filter cloth. The porous tube provides a supporting structure, ensuring the filter cloth withstands pressure without deformation during filtration. The filter cloth directly undertakes the filtration task; its material and pore size determine the filtration accuracy. Common materials include synthetic fibers such as polypropylene, polyester, and nylon, as well as metal fibers. Different materials are suitable for different chemical environments and filtration requirements.
**Outer Shell:** The main structure of the equipment, typically made of stainless steel (such as 304 or 316L), possessing good corrosion resistance and strength, and capable of withstanding pressure and temperature changes during filtration.
Auxiliary System: Equipped with a feeding/discharging system, a slag removal system, and a backflushing/cleaning interface, etc., to realize the entire process of material feeding, filtration, slag removal, and filter element regeneration.
Working Principle: Based on a pressure-driven filtration mechanism, it mainly consists of three stages:
Filtration Start-up: The suspension to be filtered enters the filter under pressure (usually pumped). The feeding distribution system ensures that the suspension flows evenly to each candle filter element, ensuring a consistent filtration load for each element.
Filter Cake Formation and Growth: The liquid in the suspension passes through the filter cloth on the surface of the filter element, and solid particles are trapped on the surface of the filter cloth, gradually forming a filter cake layer. Initially, the filter cake layer is loose, but as particles accumulate, it gradually compacts, and its internal pore structure becomes a filtration barrier, trapping particles larger than the pore size, achieving liquid clarification. As the filter cake layer thickens, the filtration resistance increases, and the filtration rate decreases.
Backflushing and Cake Removal: When the filtration pressure reaches a preset value or the filtration rate decreases to a certain level, the backflushing system is activated. Backflushing media (such as compressed air, nitrogen, etc.) blows backward from the inside of the filter element, generating shear force that causes the filter cake to detach from the filter cloth surface. The detached filter cake is discharged through the bottom discharge port, and the filter then enters the next filtration cycle.
Applications: Candle filters offer significant advantages in desalination filtration of polyether polyols. Compared to bag filters, plate and frame filters, and centrifuges, their advantages lie in their adaptability to high-viscosity systems, desalination precision, and continuous production capabilities:
Comparison with bag filters: Adaptable to high-viscosity systems, using pressure filtration + filter element backwashing regeneration, maintaining stable throughput in high-viscosity systems, eliminating the need for frequent shutdowns to replace filter media, and allowing for longer continuous operation cycles.
Comparison with plate and frame filters: Higher desalination precision, with filter element precision reaching 1~5μm, effectively trapping micron-sized salt crystals, ensuring polyether conductivity meets industry standards, and improving product purity.
Compared to centrifuges: Lower product loss and greater safety; closed-loop pressure filtration eliminates solid-liquid entrainment issues, resulting in higher product yield; the entire process is sealed, avoiding safety hazards such as solvent leakage and explosion.
Compared to self-cleaning filters: More suitable for fine salt particles; uniform filter element pores provide stronger retention stability for micron-sized salt crystals; and the residual polyether impurities after desalination are more controllable.
Candle filters achieve continuous, high-precision, and low-energy-consumption solid-liquid separation through the high-efficiency filtration and backflushing regeneration technology of candle filter elements. They have significant advantages, especially in the fine filtration of high-viscosity, high-solid-content materials, making them a key piece of equipment for improving product quality and production efficiency in industrial production.
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