Coal Based Granular Activated Carbon

What is Coal-Based Granular Activated Carbon?

Coal-Based GAC is a form of activated carbon specifically made from coal (typically bituminous or sub-bituminous) and processed into coarse, granular particles rather than a fine powder. These particles are generally larger than 0.4 mm, making them ideal for use in fixed-bed filters and reactors.

The "granular" form gives it a high surface area internally, while also creating void spaces between particles that allow fluid to pass through with minimal pressure drop. This is a key difference from powder, which is designed for mixing and settling.

How is it Made?

The process is similar to other activated carbons but optimized for coal:

1. Raw Material Selection: High-grade coal is pulverized and mixed with a binder.

2. Briquetting & Pelletizing: The coal-binder mixture is formed into specific shapes (pellets, briquettes) to create the desired granular size and mechanical strength.

3. Carbonization: The shaped coal is heated in an oxygen-deficient furnace at high temperatures (600-700°C) to drive off volatile components and create a fixed carbon structure.

4. Activation: The carbonized material is then exposed to an oxidizing agent (usually steam) at 800-1100°C. This process "etches" the vast network of micropores and mesopores, creating the enormous surface area.

5. Screening: The final product is screened and sorted into specific particle size distributions (e.g., 8x20, 12x40 mesh) for different applications.

Key Characteristics

• Pore Structure: Coal-based GAC typically has a mix of micropores and mesopores. This makes it exceptionally good at adsorbing a wide range of contaminants, from small molecules to larger organic compounds.

• High Hardness & Abrasion Resistance: Coal-based carbons are known for their mechanical strength and durability, which is critical in systems where the carbon is constantly subjected to pressure, backwashing, and movement. This results in less dust and lower losses.

• High Density: Provides more adsorption capacity per unit volume in a filter bed.

• Natural Affinity for Organics: It is particularly effective at removing chlorine, chloramines, and a wide spectrum of organic chemicals.

Primary Applications of Coal-Based GAC

This type of carbon is the workhorse of industrial and municipal filtration. Its main advantage over powder (PAC) is that it can be used in a contained filter bed for continuous, large-scale treatment.

1. Water & Wastewater Treatment

• Municipal Drinking Water Purification: Used in fixed-bed filters to remove:

  • Disinfection Byproducts (DBPs) like trihalomethanes (THMs) and haloacetic acids (HAAs).

  • Natural Organic Matter (NOM) that causes color, taste, and odor.

  • Pesticides and Herbicides from agricultural runoff.

  • Chlorine and Chloramines.

• Industrial Wastewater Treatment: Treats water from chemical plants, pharmaceutical manufacturers, and food processing facilities by adsorbing toxic organic compounds, solvents, and dyes before discharge or reuse.

2. Air & Gas Purification

• Volatile Organic Compound (VOC) Control: Used in vapor-phase filters in manufacturing plants, paint spray booths, and printing facilities to capture solvent vapors.

• Odor Control: Installed in ventilation systems of wastewater treatment plants, composting facilities, and industrial sites to remove hydrogen sulfide and other odorous gases.

• Landfill Gas Recovery: Purifies methane gas extracted from landfills so it can be used as an energy source.

3. Food & Beverage Industry

• Decolorization: Used to remove color impurities from products like sugar syrups, corn sweeteners, and citric acid.

• Purification: Used in the final polishing stages of products like spirits and edible oils to ensure purity and remove off-flavors.

4. Other Specialized Applications

• Groundwater Remediation: Used in Pump-and-Treat systems to remove industrial solvents (e.g., TCE, PCE) and petroleum products from contaminated groundwater.

• Catalyst Support: Its large surface area makes it an excellent support material for catalysts in various chemical processes.

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