Purity Beneath the Filter Cloth —— Application of Horizontal Vacuum Belt Filters in Iron Phosphate Production

In the new energy materials industry chain, lithium iron phosphate FePO ₄ ) is lithium iron phosphate ( LiFePO ₄ ) The key precursor for cathode materials, its purity, particle morphology, and moisture control directly determine the performance and lifespan of lithium batteries.
From raw material reaction to drying and packaging, the entire production process relies on one critical step. —— Solid-liquid separation Meanwhile, in this stage, the selection and design of industrial filter cloths and filtration meshes often determine the filtration efficiency, product purity, and economic viability of the process.

In the lithium iron phosphate production line, the horizontal vacuum belt filter ( Horizontal Vacuum Belt Filter, HVBF ) has become mainstream equipment. With its continuous operation, high vacuum, automatic cleaning capabilities, and excellent washing efficiency, it has emerged as a critical enabler for achieving high-purity production in the battery materials industry. At the heart of all this lies —— Filter cloth 。

I. The Core Challenges of the Iron Phosphate Filtration Process

Iron phosphate is a powder obtained by reacting iron salts (such as ferrous sulfate or ferrous chloride) with phosphoric acid, resulting in a precipitate that is subsequently washed, filtered, and dried. The filtration process exhibits the following typical characteristics:

1. The particles are extremely fine and easily clog the filter cloth.
   Iron phosphate particle sizes are mostly concentrated in 1 to 5 Between micrometers, some reaction byproducts are even smaller, forming a fine, mud-like slurry that easily builds up into a dense layer on the filter cloth surface, thereby reducing the flux.
2. Washing requirements are high, with low tolerance for impurities.
   Product purity is typically required. FePO ₄ Content >98% , while impurity ions ( Na ⁺ 、 Cl ⁻ 、 SO ₄ ² ⁻ ) The content must be controlled within ppm Level, thus requiring multi-stage spray scrubbing.
3. The slurry has poor fluidity and high vacuum filtration load.
   Due to its large specific surface area and high viscosity, the slurry encounters significant resistance during vacuum filtration, placing a heavy load on the filter cloth. Drainage Channel and Structural Support Set extremely high expectations.
4. Continuous operation and prominent automatic cleaning needs
   Battery material companies operate at a fast pace with high levels of automation, requiring filter cloths that are… High durability combined with excellent regenerative performance , ensuring long-term operation without belt changes.

Therefore, the filter cloth suitable for iron phosphate filtration is not only “ The Selection of Materials ” , and even more so, a complete set Systems Engineering for Structure, Weaving, and Process Control 。

II. The Working Mechanism of Horizontal Vacuum Belt Filter Machines

A horizontal vacuum belt filter is a type of Continuous Vacuum Filtration Equipment It consists of a filter belt, vacuum box, fabric system, spray cleaning device, and discharge system.
Its operational process can be summarized into five stages:

1. Fabric : The post-reaction iron phosphate slurry is evenly distributed onto the running filter cloth via a distributor.
2. Vacuum Filtration : The vacuum system creates negative pressure beneath the filter cloth, rapidly drawing the liquid away while retaining the solid particles to form a filter cake.
3. Filter cake washing : Multiple-stage cleaning via the spray system removes impurity ions from the mother liquor.
4. Filter cake dewatering and discharge :The filter cake is removed by air blowing or scraping and then enters the subsequent drying process.
5. Online Filter Cloth Cleaning : The filter cloth undergoes high-pressure water spraying in the return zone, completing the regeneration and cleaning process for reuse.

Throughout the entire process, The filter cloth serves as both a filtration medium and a transport carrier, as well as a liquid-discharge channel. , its structural design plays a decisive role in determining the filtration rate, the moisture content of the filter cake, and the washing efficiency.

III. Structural Design of Filter Cloth Dedicated for Iron Phosphate Filtration

Xiamen Xiamen Xiadias CITIUS With extensive experience in the field of battery material filtration, we have developed [product/technology] specifically tailored to address the fine-particle and high-viscosity characteristics of lithium iron phosphate slurry. High-precision, multi-layered composite structure filter fabrics and filtration mesh series , its structural features are as follows:

1.  Double-layer heterogeneous weaving, balancing retention and flux.

The surface of the filter cloth is made with High-density monofilament weaving , with uniform aperture and stable distribution, effectively retaining fine iron phosphate particles;
At the bottom level, it employs Open-structured support fabric , forming a smooth channel for fluid drainage.
The double-layer structure enables the filter cloth to maintain high filtration accuracy while still delivering excellent liquid drainage performance.

2.  Smooth surface design, with excellent filter cake release properties.

The filter cloth features a正面 Leveling Treatment Or Long-term Node Organization Structure , reducing particle embedding and adhesion, enabling the filter cake to be smoothly detached without breaking or leaving residues, thereby significantly enhancing discharge efficiency.

3.  Enhanced Edge and Anti-Drift Structure

Given the continuous operation characteristics of horizontal belt conveyors, the filter cloth edges are reinforced with stitched-in fibers and equipped with anti-deviation features. “ Conduction Band Layer ” , ensuring operation under tension No discounts, no deviations. , extending the service life.

4.  Excellent regenerative cleaning performance

The back of the fabric features a high-pressure and chemically resistant design, enabling it to withstand high-pressure water cleaning performed on-site.
After hundreds of cycle tests, the filter cloth's air permeability decay rate was less than 10% , maintaining high-throughput operation over the long term.

5.  Customizable weaving

Depending on the slurry concentration, vacuum level, and target moisture content of each production line, Xiamen Xiadias CITIUS Custom aperture options available ( 1 to 50 Micrometer-level filter cloth solutions, tailored in thickness and structure, achieve an optimal balance between filtration and washing efficiency.

IV. Practical Application Performance and Process Benefits

In applications across multiple lithium iron phosphate cathode material companies, Xiamen Xiadias is employed. CITIUS After the filter cloth of the horizontal vacuum belt filter is treated, significant technical and economic benefits have been achieved:

• Increased filtration rate 25~40% : Vacuum suction filtration is smooth, shortening the slurry filtration time;
• The moisture content of the filter cake is reduced to 18~22% : Subsequent drying energy consumption reduced by approximately 10%；
• Enhanced Filter Cloth Lifespan 30% The above : The fabric boasts a stable structure and excellent fatigue resistance;
• Filter cake peeling efficiency improved : Residual amounts are reduced, leading to more stable material discharge;
• Online Cleaning Recovery Rate >90% : Maintain long-term stable flux and minimize downtime for maintenance.

Some users have reported that even during continuous operation, the system... 1000 Hours later, the filter cloth still maintained stable vacuum suction and liquid-discharge efficiency, demonstrating exceptionally high operational reliability.

V. Functional Synergy of Industrial Filter Fabrics and Filter Meshes in the System

In the iron phosphate filtration system, filter cloths are often used in combination with filter meshes:

• Upper filter cloth Responsible for particle retention and filter cake formation;
• Lower filter mesh Provides mechanical support, ensures uniform vacuum distribution, and guarantees smooth liquid drainage.

This combined design makes the filter's overall performance more balanced:
It can both prevent the filter cloth from deforming, collapsing, or overstretching, and ensure a uniform pressure distribution in the vacuum zone, thereby avoiding “ Localized vacuum failure ” This leads to uneven thickness of the filter cake.
Xiamen Xadias CITIUS The industrial filter mesh is made from high-strength polyester monofilaments woven together, offering excellent tensile strength and superior dimensional stability. It perfectly matches the main filter cloth, creating a seamless integration. “ Double-layer composite drainage system ” , enhancing the vacuum utilization efficiency of the equipment and ensuring uniformity of the filter cake.

6. Green Manufacturing and Trends in Technological Evolution

As the new energy materials industry moves toward “ High-purity, low-carbon, and intelligent ” Moving in the right direction, filtration equipment and filter cloth technologies are also continuously innovating:

1. Micro- and nanoscale pore structure control
   Through advanced weaving and post-processing technologies, we achieve controllable pore size distribution and customizable retention curves, enabling more precise filtration for nanoscale iron phosphate products.
2. Surface Functionalization Modification
   Through plasma treatment, PTFE Coating or hydrophilic treatment enhances the filter cloth's anti-fouling and hydrophobic properties, reducing the risk of scaling.
3. Intelligent Monitoring and Digital Operations
   The new belt filter machine can be equipped with tension, misalignment, and air permeability monitoring systems, enabling real-time visualization of the filter cloth condition and providing data support for predictive maintenance.
4. Renewable and Environmental Protection Direction
   Recyclable, low-energy-consumption filter cloth materials are becoming a trend; Xiamen Xiadias CITIUS Currently under development Recyclable Polyester-Based Composite Filter Cloth , to reduce the carbon footprint of chemical production.

VII. Conclusion: The Essence of Filtration, the Soul of Manufacturing

In the manufacturing process of lithium iron phosphate, filter cloth is not just a layer of fabric—it’s a sophisticated engineering feat.
It bridges the gap between chemical reactions and material quality, while also reflecting the precision level of industrial manufacturing.

Xiamen Xiamen Xiadias CITIUS Through long-term research on weaving structures, fluid dynamics, and solid-liquid separation mechanisms, we will “ Industrial filter cloth ” From passive media to proactive technology solutions.
At the filtration site where vacuum and crystals coexist, a high-performance filter cloth not only boosts production line efficiency but also sets new standards for material purity within the industry.

Filtering is not just separation—it’s also the fundamental logic behind creation.
In the wave of new energy materials, The combination of a horizontal vacuum belt filter and high-performance filter cloth , is reshaping the boundaries of chemical separation processes for iron phosphate —— Even the entire lithium battery industry chain —— Providing a more efficient, cleaner, and smarter solution.