Filter Cardboard in Modern Plate and Frame Filtration

In the realm of industrial solid-liquid separation, the relationship between the filtration equipment and its media is fundamental to process efficiency and final product quality. Nowhere is this synergy more critical than in applications utilizing filter cardboard. This article from Yuwei Filtration explores the technical correspondence between this versatile depth filter medium and the equipment designed to use it, specifically focusing on the cardboard filter press and the cardboard plate filter. 

What is Filter Cardboard?

Filter cardboard is not simply paper; it is a specialized depth filtration medium manufactured from a blend of cellulose, diatomaceous earth, and perlite. This composition creates a rigid, porous sheet capable of retaining particles, colloids, and even microorganisms throughout its matrix, not just on the surface. Its primary functions are clarification, polishing, and microbiological stabilization of liquids. The choice of filter cardboard grade depends on the desired filtrate clarity and the nature of the particles to be removed, making it a critical variable in the filtration equation.

The Cardboard Filter Press

The equipment designed to utilize filter cardboard is engineered to provide the necessary mechanical support, pressure, and flow distribution for effective depth filtration. In this configuration, the filter press acts as the housing and pressure system, while the filter cardboard performs the actual separation. Here is how this critical correspondence between medium and machine works:

Plate and Frame Design with Filter Cardboard

A standard plate and frame filter press consists of alternating plates and frames. When adapted for filter cardboard, this design is utilized to support the medium effectively:

• Loading the Medium:

Sheets of filter cardboard are placed over the faces of the plates, covering the drainage areas. The frames, which are hollow in the center, create the chambers where the unfiltered liquid accumulates.

• Sealing and Pressure Application:

The plates, frames, and filter cardboard sheets are compressed together by a hydraulic or manual closing mechanism. This compression creates a sealed system where the edges of the filter cardboard are clamped, preventing any bypass of unfiltered liquid.

• Filtration Process 

Unfiltered liquid is pumped into the frames under pressure. The pressure forces the liquid to pass through the filter cardboard on either side of the frame. As the liquid travels through the depth of the filter cardboard sheet, solids are trapped within its matrix. The clarified filtrate then travels through drainage channels on the surface of the plates and exits the machine.

• Outcome

The result is a highly polished filtrate, with the filter cardboard acting as both the clarifying agent and the final barrier. This setup is particularly valued in industries like beverage (wine, beer, juice) and pharmaceuticals for achieving brilliant clarity and stabilization.

Medium and Machine

The effectiveness of the filtration process hinges on the correct pairing of the filter cardboard with the equipment. This correspondence involves several key factors:

• Mechanical Support: The plates in a cardboard plate filter must provide uniform support to prevent the filter cardboard from cracking or collapsing under pressure. The drainage patterns on the plates are designed to match the flow characteristics of the cardboard.
• Sealing: Proper gasketing or seating mechanisms are essential to ensure that unfiltered liquid cannot bypass the filter cardboard and contaminate the clean filtrate. This seal integrity is a hallmark of well-designed equipment.
• Pressure and Flow: The filtration system must operate within the pressure limits of the filter cardboard. While a robust medium, excessive pressure can compact its structure, reducing flow rate and filtration efficiency. The equipment, whether a cardboard filter press or a dedicated plate filter, must be equipped with proper controls to manage this.
• Application-Specific Pairing: A coarse grade of filter cardboard might be used for pre-filtration in a cardboard filter press, while a finer grade is employed in a downstream cardboard plate filter for final polishing. The choice of equipment dictates which grades of filter cardboard can be effectively utilized.

For industries demanding high-purity filtrates, the combination of filter cardboard with specialized equipment like the cardboard filter press and cardboard plate filter represents a pinnacle of separation technology. The success of the operation depends on understanding that the filter cardboard is not just a consumable, but an integral component of a precisely engineered system. By matching the correct grade of filter cardboard with appropriately designed plates and controlled pressure, operators can achieve consistent, high-quality results essential for their final product.