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Activated Carbon Plant

It is industry proven and worldwide recognized that the multiple hearth furnaces are the best tool to produce high grade activated carbon and they have the highest efficiency as well with very little carbon loss (Efficiencies as high as 95% could be attained) . More than 400 multiple hearth furnaces are installed worldwide and half of them are dedicated to activated carbon production and regeneration of spent carbon. Calgon, Norit and Chemivron use widely those furnaces for producing activated carbon.

Basics of thermal activation of carbon
Activated carbon can be made from a wide range of source materials, such as coal, coconut shells , wood etc. The material is often carbonized then activated in a high temperature environment to produce an extensive network of pores. These pores provide sites for the adsorption of chemical contaminants in gases or liquids.

The activation of carbon is carried out at high temperatures (up to 1000°C) with steam for gasification of a part of the fixed carbon as per the following reactions :

C+H2O >> H2 + CO
C+CO2 >> 2CO

The gasification process can be manipulated to produce desired characteristics in the product..

The gasification phase is influenced by the following parameters, that also determine the quality of the final product.

  1. chemical nature and concentration of the oxidizing gases
  2. temperature of reaction
  3. length of the activation and rate of reaction
  4. nature of the raw material

Description of  a Typical Installation
At this stage , we have made the assumption that the coconut shell is carbonized and its content on volatile matters is approximately 20%. The carbonized product would go through the following processing steps :

  • Grinding: The raw material is ground to the size distribution that is required. (between 1 an 3 mm depending on the use)
  • The Activation: The product is carried to the top of the furnace through a bucket elevator. The furnace has a diameter of approximately 6 meters and 7 hearths. The furnace is essentially composed by a cylindrical shell (carbon steel) supported by  steel or concrete legs. The total height of the furnace is approximately 15 meters.
    See the MHF for full description of the furnace.
    Each hearth is supplied with minimum 3 gas burners . There is a steam injection foreseen also on each hearth. An automatic control of the burners and the temperature on each hearth is supplied.
  • Cooling of Activated Carbon: The activated carbon is cooled down at the furnace exit thru water or indirectly via heat exchangers.
  • Storage and Packing: The activated carbon is transported via a conveyor or pumping system to the screening equipment . From there it fills the silos of different size distribution. The bags are filled from the bottom of the silos.

Advantages of Multiple Hearth Furnaces
The activation of the carbon, requires a control of the gaseous atmosphere and un good distribution of the air. It is necessary that all air is burned in gaseous phase and that it does not reach the carbon bed. From their design , the multiple hearth furnaces are the ideal equipment for producing activated carbon.

  • They are completely sealed , preventing parasite air from entering the furnace and burning the carbon, thus reducing the efficiency of the furnace.
  • It easily allows the introduction of combustion and activation products at different points of the furnace. Their introduction at different points , allows to control the reaction rate, and avoid to have a maximum rate of activation at the product entry as is the case with a rotary kiln.
  • It allows to have the desired temperature profile and reduce carbon losses.
  • Multiple hearth furnaces have a big flexibility of operation. They can use for carbonisation, activation and regeneration in continuous operation.

Estimated Investments
Our plants come at different sizes from 50 tons per month to 1000 tons per month.

    The furnace includes:
  • Refractory parts
  • Metallic parts (steel shell and platforms)
  • Gas burners and auxiliary piping around the furnace
  • Raw material storage silo (15 m3)
  • Extractor and raw material conveyor from storage silo to top of the furnace
  • Chute and double sealed valve at furnace top inlet
  • Activated carbon discharger and quenching device.
  • Staircases, access ladders and floors around the furnace
  • Fans, ducting, motors and mechanical equipment
  • PLC - and electrical cabinets.
    The rough schedule for the erection of a 200 MT plant is as follows:
  • Engineering and fabrication of equipment: 8 to 10 months 
  • Packing and transportation : +/- 2 months
  • Mounting on site: 6 to 8 months
  • Drying, testing , heating up and start up : +/-2 months

Questions before you request a quotation

Question 1 : Should the raw material be carbonized? If no, what are its characteristics, humidity, dry weight percentage of the volatile material, carbon, ash content and size distribution. Should we envisage the carbonization only for the activated carbon production or other uses as well ?If yes; what are the characteristics of the carbonised coconut shells? Humidity, dry weight percentage of the volatile material, carbon, ash content and size distribution

Question_2: What is the desired quality of the activated carbon and for which applications? Iodine number :  Methylene Blue :  Benzene absorption :  Bulk density Other indexes?  Size distribution or mesh range?

Question 3: Have you already conducted activation tests? If yes what are the results and under which conditions?

Question 4: Do you need an heat recuperator at the exhaust fumes? If yes what are the characteristics of the steam to be produced?

Question 5: Do you have a boiler water treatment on site? If yes , what are boiler water characteristics? If no, should we include it in the quotation?

Question 6: What are the local restriction as to the dust emissions? Should we foresee exhaust fumes washing?

Question 7:  What is the climatical data ?

Question 8: What is the desired length of exploitation of the factory, and the desired daily tonnage to be produced?

Question 9: Do we have on site the following utilities: cooling water, steam, instrument air, natural gas?

Sketch of plant