A Guide To The Filtration Methods Of Syrup Filter Press

Syrup filter press generally refers to the Cardboad filter press used for depth filtration of syrup. In some cases, the membrane filter press in syrup filtration systems specifically used for filtering cane juice is also called a syrup filter press.

Cardboad filter press

Membrane Filter Press

Cardboad filter press for Syrup Filtration

The cardboad filter press (plate filter/plate and frame filter) uses cardboad as the filtration medium and serves as the core equipment in the syrup depth filtration stage. They primarily process:

• Raw syrup after evaporation and concentration (60-65°Bx)
• Refined sugar remelt syrup: Serving as the final filtration step before syrup enters the crystallizers, their core objective is the deep removal of submicron-sized suspended impurities, ensuring syrup purity meets crystallization requirements

Filter Press for Coarse Filtration of Sugarcane Juice and Syrup

Filter presses (mainly membrane filter press) are often used in the syrup filtration process for clarifying and filtering sugarcane juice and decarbonizing syrup.

1. Mainstream applications of sugarcane juice clarification processes

   • Treat the slurry mixture after lime sulfur fumigation to separate solids from liquids.
   • The dryness of the filter cake is reduced to 35-40% through secondary pressing, followed by filter cake washing to replace sugar and reduce sugar loss.

2. Auxiliary application of sugar syrup decarbonization

   • Suitable for solid-liquid separation following granular activated carbon decolorization processes.

Next, we will focus on the specific functions of cardboad filter press. For more information on filter presses for sugarcane juice filtration, please refer to this article:How Membrane Filter Presses Work in Sugarcane Juice Filtration？

What Is the Role of a Syrup Filter Press in Syrup Production?

Cardboad filter press are primarily used in the sugar industry for the depth filtration stage of sugar syrup, particularly for concentrated sugar syrup (also known as crude syrup) after evaporation and for the final purification of refined sugar syrup. It serves as the final critical filtration process before the syrup enters the crystallization tank, with the objective of producing sugar syrup that is nearly free of suspended impurities and highly pure. The following are the specific functions of cardboad filter press:

• Removal of fine suspended solids: Intercept extremely fine insoluble impurities (typically less than 10 microns, and sometimes as small as 1-2 microns) remaining in coarse syrup. If these impurities enter the crystallization tank, they can act as nucleation sites or adhere to crystals, leading to uneven crystallization, small crystal size, poor color, difficulty in honey separation, and adversely affecting the whiteness, turbidity, and ash content of the finished sugar.
• Reduce turbidity and color value: Effectively remove colloidal substances and some pigment polymers that cause syrup turbidity, improving the light transmittance and purity of the syrup.
• Improving crystallization efficiency and product quality: Pure syrup promotes the formation of large, uniform crystals, increasing crystallization rates and sugar recovery rates, and ultimately resulting in high-quality white sugar or refined sugar.

Key Factors in Choosing the Right Filtration Equipment

In the sugar industry, selecting syrup filtration equipment requires comprehensive consideration of multiple factors, including process objectives, material characteristics, economic viability, and operational/maintenance requirements. As syrup filtration is a critical step in sugar production, the following analyzes key equipment selection points from a filtration demand perspective.

1. Solid-liquid separation of sediment and syrup

   • Membrane Filter Press: Suitable for high-pressure dewatering scenarios. They significantly reduce filter cake moisture content (down to 30-40%) via membrane squeezing, thereby enhancing sugar recovery efficiency.
   • Chamber Filter Press: Suitable for conventional solid-liquid separation. However, the dryness of the filter cake is lower than that achieved with membrane presses. They are often used in small-to-medium scale production.

2. Decolorization process:

   • Activated carbon decolorization: Utilizes filter presses for carbon removal, intercepting activated carbon particles and recovering sugar liquor. This requires fine filter cloth with an aperture ≤20μm.
   • Ion exchange decolorization: Relies on dedicated ion exchange equipment. Colourants are adsorbed by resin, eliminating the need for a solid-liquid separation step.

3. Clarification and Staged Filtration Scheme

   • Coarse Filtration Stage: Employs bag filters for the rapid removal of large particulate impurities (>50μm), protecting downstream equipment.
   • Fine Filtration Stage: Diatomaceous earth filter → Bag filter → Cardboad filter press.