activated carbon rotary kilnEV Charger AC Wall Mounted Charging Pile

Chemical process activated carbon making machine

The advantages of chemical activated carbon kilns are their lower operating temperature and higher production rate.

Activated carbon making machine 439

Raw materialPine, fir, birch
ActivatorPhosphoric acid
Automation PLC
capacityCustomizable

BRIEF INTRODUCTION

Chemical method is a common method for producing activated carbon, which has high activation effect and low production cost. Phosphoric acid, as a chemical activator, plays a key role in the production of activated carbon, which can significantly improve the pore structure and surface area of carbon, thereby enhancing its adsorption performance.

PROCESS

The raw material is crushed into sawdust ≤ 4mm. Then it enters the dryer to dry the moisture to 10-15%. The dried sawdust is screened to screen out particles > 4mm.

The raw material and phosphoric acid are mixed and stirred in the specified ratio. The sawdust has a large specific surface area and can be moistened in a short time.
The mixed material is sent to the activation furnace. The material goes through the following stages.
Low temperature stage (100–200°C): phosphoric acid dehydration and initial carbonization of the raw material.
High temperature stage (400–600°C, usually 450–550°C): phosphoric acid catalyzes oxidation reaction to form microporous and mesoporous structures. The activated carbon after activation enters the washing tank for water washing to clean the phosphoric acid in the activated carbon.

Phosphoric acid undergoes the following changes during the whole process:

Low temperature stage (100–200°C): dehydration and esterification Physical changes:
Liquid phosphoric acid (H₃ PO₄) penetrates into the raw material (such as sawdust) and is evenly distributed through capillary action.
Water gradually evaporates, the concentration of phosphoric acid increases, and a viscous liquid film is formed to wrap the cellulose fibers.
Chemical changes:
Dehydration reaction: Phosphoric acid releases H⁺, which reacts with the hydroxyl group (-OH) in cellulose to form phosphate ester (cellulose-OPO₃ H₂)
and removes water:
Cellulose-OH + H₃ PO₄ → Cellulose-OPO₃ H₂ + H₂O Cellulose-OH + H₃ PO₄ → Cellulose-OPO₃ H₂ + H₂O
Ester bond formation: destroys the crystalline structure of cellulose, making it easier to pyrolyze, and fixes the carbon skeleton through cross-linking to prevent excessive shrinkage.

Medium temperature stage (200–400°C): decomposition and cross-linking Physical changes: Phosphoric acid is partially dehydrated to form condensed acids such as pyrophosphoric acid (H₄ P₂O₇) and polyphosphoric acid (H₅ P₃O1₀). The raw materials begin to carbonize, and volatile organic matter (such as tar) is inhibited by phosphoric acid, reducing pore blockage. Chemical changes: Acid-catalyzed cracking: Phosphoric acid accelerates the pyrolysis of cellulose and lignin, generating CO, CO₂ and small molecular organic matter to form initial pores. Cross-linking stability: Phosphoric acid forms P-O-C bonds with the carbon skeleton, enhancing the mechanical strength of the carbon structure and preventing pore collapse at high temperatures. 3. High temperature activation stage (400–600°C): oxidation and pore formation Physical changes: Phosphoric acid is further dehydrated and partially converted into metaphosphoric acid (HPO₃) and phosphorus oxides (such as P₂O₅). The carbon skeleton is etched by phosphoric acid, and a large number of micropores and mesoporous structures are generated.

Chemical changes:
Oxidation reaction: Phosphoric acid acts as an oxidant to promote the oxidation of carbon to generate CO₂ and expand the pores:
C + H₃ PO₄ → CO₂↑ + H₂O + phosphate C + H₃ PO₄ → CO₂↑ + H₂O + phosphate
Template effect: Phosphoric acid and its condensation products occupy space during the carbonization process, leaving pores after washing (similar to “sacrificial template”).

Cooling and washing stage: residue and recovery Phosphoric acid residue:
Undecomposed phosphoric acid remains in the activated carbon pores in the form of H₃ PO₄ or phosphate (such as K₃ PO₄, Na₃PO₄).
Acid recovery:
Phosphoric acid is recovered by water washing (the recovery rate can reach more than 80%).

Finished activated carbon can be added to screening equipment, crushing and grinding equipment according to the customer’s particle size requirements to reach the customer’s finished product size requirements and then enter the packaging machine for packaging.

Product Advantages

What are the advantages of chemical activation?
High carbon yield, the ratio of raw materials to activated carbon products can reach 2.5-3.5:1
High quality of finished products, low ash content
Why should the raw materials be dried before adding chemicals?
Because dry impregnation only requires mixing and stirring, it is suitable for continuous production.
Wet impregnation takes 2-4 hours.
Why choose phosphoric acid to impregnate sawdust raw materials?
Mild process conditions and low energy consumption
Low temperature activation, the activation temperature is usually 400-600 °C, which is much lower than the physical activation method (800-1000 °C), greatly reducing energy consumption.
No pre-carbonization is required, chemical activation and carbonization are completed in one step, simplifying the process and shortening the production cycle.
Highly controllable pore structure, rich micropores and mesopores

Phosphoric acid etching forms developed micropores (<2nm) and mesopores (2-50nm), which are particularly suitable for liquid phase adsorption (such as decolorization, water treatment).
By adjusting the phosphoric acid concentration, impregnation ratio and activation temperature, the pore size distribution can be directional controlled (for example, high concentration

phosphoric acid is more likely to generate mesopores).

Excellent product performance High specific surface area
The specific surface area can reach 1000-2000 m²/g, and the adsorption capacity is large.
Rich surface chemical properties
The phosphoric acid residue forms oxygen-containing functional groups (-COOH, -OH) and phosphorus groups (-PO₃), which enhances the adsorption capacity of polar molecules (such as heavy metal ions, ammonia).
High mechanical strength
The cross-linking effect of phosphoric acid stabilizes the carbon skeleton and reduces the problem of powdering during use.
High production efficiency Short activation time
Usually 1-1.5 hours to complete the activation, while the physical activation method may take longer.
High yield
Low carbon loss, raw material conversion rate can reach 30-40%
Wide application field Water treatment
Highly efficient adsorption of organic matter, heavy metals (such as arsenic, lead) and dye decolorization.
Food and medicine
Decolorization and purification of sugar solution and edible oil, drug carrier (residual phosphoric acid must be strictly controlled).
Environmental protection
Volatile organic compounds (VOCs) adsorption, flue gas desulfurization and denitrification.

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