PRODUCTION

Black Opal Group manufactures and deliver activated carbon for their worldwide customers from own associated factories in India, China and Indonesia.

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Coconut activated carbon: India

 

Our coconut activated carbon facility in India is the largest in the region with annual production capacity of 30 million pounds of carbon. BO group factories pursues uncompromising quality standards in all the stages of its process and operation activities. For this a meticulous quality control program is operated throughout the entire process from the selection of the raw material to the final quality assurance prior to shipment. Our craving for uncompromising quality starts at the selection of raw material itself. Charcoal is sourced from selected outlets after rigorous quality inspections. Careful control of the activation process in the presence of a stringently controlled flow of steam allows the carbon specifications to be readily altered to suit a wide range of specific requirements. Our factories employ state-of-the-art equipment and technology and supported by highly qualified and skilled technicians, 'no-compromise' quality control is their top priority. Specially designed crushing and screening machines assure a great degree of control over particle size to precisely meet the application-specific mesh size range requirements of our customers. Quality of IndoCarb coconut carbon products has been extensively tested and acclaimed by all major industry leaders and various reputed laboratories around the world.

 

Method: Steam Activation   

Steam activated carbons are produced in a two-stage process. Firstly the coconut shells in the form of lumps, is carbonized to convert coconut shells to char or charcoal by a process called pyrolysis, which is the chemical decomposition of the shell by heating in the absence of oxygen. For this stage temperatures usually do not exceed 700°C. Carbonization reduces the volatile content of the source material to less than 20% creating a carbonaceous mass full of tiny pores.

 

In the second stage, this carbonized base material is activated at high temperature (1,100°C/2,012°F) in steam. The chemical reaction between the carbon and steam takes place at the internal surface of the carbon, removing carbon from the pore walls and thereby enlarging the pores. The steam activation process allows the pore size to be readily altered and carbons can be produced to suit specific end-sues. For an example, the pore structure has to be opened up more for the adsorption of small molecules from a solution, as in water purification, than for the adsorption of large colour molecules in sugar decolorization. Activation temperature and the amount of activation time are important to create the internal pore networks and to impart certain surface chemistries inside each particle. In essence, the total activation process gives carbon its unique adsorption characteristics.

 

Output from the rotary kiln is further processed in the postproduction plant where it is crushed and screened to different sizes and to remove fines and dust to meet the specifications for granular activated carbons. To produce powdered activated carbons, the carbon granules are further ground using a gentle pulverizing action.

Coal activated carbon: China

 

Our Coal base Activated Carbon is manufactured from a selected grade of bituminous through thermal activation. Coal base Activated Carbon consists of more mesopores and macropores which is suitable for adsoption of large molecules. Coal base Carbon is widely used for surface/municipal water treatment and total organic compound removal due to its unique pore structure. Coal made from bituminous or anthracite is pulverized and sized by extrusion and/or briquetting. Selective binders are added at this stage to prepare the raw material for carbonization.  Carbonization involves thermal decomposition of the carbonaceous material, eliminating non carbon species and producing a fixed carbon mass and rudimentary pore structure. This process is usually carried out in rotary kilns at temperatures below 800o C in a continuous stream of inert gas. The resulting carbonaceous product is once again sized and ready for activation. The activation process is carried out at temperatures in excess of 1,000o C in vertical retort furnaces (SLEP) for approximately 36 hours depending on the quality required. Anthracite coal activated carbon possesses a finer pore size distribution than bituminous coal activated carbon.  Post activation processes can include additional crushing and sizing, acid washing, de-dusting and de-magnetization.    

Wood Activated Carbon: Indonesia

 

Chemical activation is the method used in general for the production of activated carbon from sawdust, wood or peat. The starting material is impregnated with the activating agent in the form of a concentrated solution usually by mixing. This results in the degradation of the cellulosic material. The chemical impregnated material is then extruded and pyrolyzed in a rotary kiln between 400o and 600o C in the absence of air. The pyrolyzed product is cooled and washed to remove the activating agent, which is recycled. On calcination, the impregnated chemicals dehydrate the raw material, which results in charring and aromatization of the carbon skeleton and the creation of a porous structure. The most widely used activating agents are phosphoric acid and zinc chloride. The common feature of these activating agents is that they are dehydrating agents, which influence the pyrolytic decomposition and inhibit the formation of tar. They also decrease the formation of acetic acid and methanol and enhance the yield of the carbon. Chemical activation is usually carried out at temperatures between 400o and 800o C. When zinc chloride is the activating agent, the optimum temperature is about 600o and 700o C.  These temperatures are lower than needed in the physical activation process and therefore the development of a porous structure is better in the case of chemical activation. The pore size distribution in the final product is determined largely by the degree of impregnation, the larger the degree of impregnation, the larger the pore diameter of the carbon.

 

Chemically activated carbons, however, have a lower purity than specifically acid-washed steam activated carbons as they contain small amount of residual phosphate. This chemical activation process mostly yields a powdered activated carbon. If granular material is required, granular raw materials are impregnated with the activating agent and the same method is used. The granular activated carbons produced have a low mechanical strength, however, and are not suitable for many gas phase uses. In some cases, chemically activated carbon is given a second activation with steam to impart additional physical properties.

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