Begg Cousland Envirotec work with Active Char Products Ltd who is a premium exporter of Activated Carbons to Europe , USA, Africa, Middle East and South East Asia from their 100% Export Oriented Unit facility in Kerala, India. Over 20 years of experience and with an annual capacity of 16,000 tons Active Char Carbon makes them one of the leading manufacturer of Activated Carbons in India and one of the largest manufacturers globally in terms of coconut shell carbon production. They are represented in Europe by AC CARB Ltd.in UK.
Activated Carbon is used in various industries like Oil and Gas refining, Food Processing Units, Edible Oil and Beverages Treatment, Pharmaceutical and Medicinal Applications, Military Applications, Solvent Recovery Plant, , Air Purification and Treatment, etc.
Begg Cousland Envirotec will design systems incorporating the active carbon material for air purification and other applications.
Activated carbon is a non-graphite form of carbon which could be produced from any carbonaceous material such as coal, lignite, wood, paddy husk, coir pith, coconut shell, etc. Activated carbon manufactured from coconut shell is considered superior to those obtained from other sources mainly because of small micropores structure which renders it more effective for the adsorption of gas/vapour and for the removal of impurities and pollutants.
The activated carbon is extensively used in the refining and bleaching of vegetable oils and chemical solutions, water purification, recovery of solvents and other vapours, recovery of gold, in gas masks for protection against toxic gases, in filters for removing pollutants, in cigarette filters to reduce the poisonous components,
Steam activation and chemical activation are the two commonly used processes for the manufacture of activated carbon. However coconut shell based activated carbon units are adopting the steam activation process to produce good quality activated carbon.
Activated carbon adsorbs. The chemical process of absorption is commonly compared to a sponge soaking up water. The water is fully integrated into the sponge, not being limited to the surface area. Differently, adsorption is a process whereby molecules stick to the inner surface area only. As mentioned above, activated carbon has a large surface area due to being a porous material. The unwanted substance sticks to the surface area of the carbon particles.
Adsorption is a surface phenomenon while Absorption is a whole body phenomenon.
Carbons capacity for chemicals depends on many things. The molecular weight of the chemical being removed, the concentration of the chemical in the stream being treated, other chemicals in the treated stream, operating temperature of the system and polarity of the chemicals being removed all affect the life of a carbon bed.
– Coal (lignite, sub-bituminous, bituminous, peat and anthracite
– Wood (hard wood, soft wood and bamboo).
– Coconut shell charcoal
– Petrochemical derivatives like Pitch, Phenol Formaldehyde and other resins
– Any carbonaceous material
Coconut Shell Activated Carbon: The best quality of activated carbon is produced from Coconut shells. PROS: They have the highest hardness. Maximum micropores suitable for air and water filtration. Lowest impurity content ( Ash). And it is produced from naturally occurring raw material and has the lowest environmental impact.
CONS: Usually the most expensive of all the carbons because of the raw material availability is limited. Production and pricing prone to environmental conditions in the tropical countries. Not suitable for colour and odour removal as these particles are usually larger and need a higher proportion of Macropores
Wood Activated Carbon: usually sold in powdered form. Most commonly used in Pharmaceutical and Food applications.
PROS: They have the largest percentage of Macropores highly suitable for Decolourisation applications.
CONS: As the name says we need to cut down trees to make these carbons. The common process is to make the activated carbon using a chemical activation process which is highly polluting. China is the largest producer of this type of carbon in the world.
Coal Activated Carbon: 70% of the world Activated Carbon is dominated by this raw material
PROS: Large availability, highly developed mesopores usually give a higher rate of adsorption in some special applications. Tend to be priced lower than coconut usually.
CONS: Highest content on impurities. Inconsistency in quality as the raw materials tends to be varying quality. Not an Environmentally friendly production process (china closed down more than 200 activated carbon plants in the last 5 years)
– Surface area of activated carbon
– Pore size of carbon
– Solubility of solute in aqueous solution
– Size of activated carbon particle
– Concentration of solute in solution
– Temperature of solution
Activated carbon is physically characterized by the Particle Size Distribution of the Grain sizes of the Carbon particles. This is usually mentioned following the Taylor Series Mesh. A Mesh conversion to Millimeters or Microns can be made available on request.
By 8 x 30 mesh carbon we mean that, if we screen the carbon on a standard mesh screen setup, 90% of the particles will remain within the 8 and 30 meshes.
Determination of the pore size distribution of an activated carbon is an extremely useful way of understanding the performance characteristics of the material. The International Union of Pure and Applied Chemistry (IUPAC) defines the pore size distribution as:
Micropores: r < 1 nm
Mesopores: 1 < r < 25 nm
Macropores: r > 25 nm
The macropores are used as the entrance to the activated carbon, the mesopores for transportation, and the micropores for adsorption.
• Hardness – An important factor in system design, filter life and product handling. There are large differences in the hardness of activated carbons, depending on the raw material and activity level. Coconut Is one of the hardest naturally occurring raw material.
• Bulk Density -Should be carefully considered when filling fixed volumes as it can have considerable commercial implications.
• The backwashed and drained density will show a lower value due to the water film between the particles of activated carbon.
• Particle size distribution – The finer the particle size of an activated carbon, the better the access to the surface area and the faster the rate of adsorption kinetics. In vapour phase systems this needs to be considered against pressure drop, which will affect energy cost. Careful consideration of particle size distribution can provide significant operating benefits.
• Moisture of the product.-Lower the moisture content means you are getting more carbon for the money paid
• Ash content.Measure of the impurities other carbon present in the material. This is indicative of the purity of carbon. Coconut carbon has the lowest value of ash in a natural state.
• Powdered activated carbon; particle size 1-150 μm
• Granular activated carbon, particle size 0.5-4 mm
• Extruded activated carbon in pellet or spherical shape, particle size 0.8-4 mm
Based on naturally occurring raw materials with a highly crystalline form and extensively developed internal pore structure, activated carbons are excellent adsorbents for use across a wide range of contaminants. They are comparatively low in cost and are effective adsorbents in air, liquid and gaseous phase applications. They are also re-usable after reactivation, non-hazardous and safe to use.
Once granular carbon is saturated or the treatment objective is reached, it can be recycled, by thermal reactivation, for reuse. Reactivation involves treating the spent carbon in a high temperature reactivation furnace to over 800 °C. During this treatment process, the undesirable organics on the carbon are thermally destroyed. Recycling by thermal reactivation is a highly skilled process, to ensure that spent carbon is returned to a reusable quality.
Both are process in which the life of the activated carbon can be extended. Reactivation is a physical and chemical process where the carbon is subjected to usually temperatures of above 800 °C to regain majority of the activity by removing the impurities on the activated carbon. This cannot be done at site as it requires specialized machinery and pollution control measures. Whereas Regeneration is an in situ recovery of some of activity of the carbon by using steam, or high pressure air purging to remove some of the impurities; to give a slight extension of the carbon life.
ASTM-American Standard Testing Method ( this is most commonly accepted standard of testing globally) AWWA -American Water Works Association .
ANSI/NSF Standard – American National Standard Institute/ National Sanitation Foundation
EN – European Norm
Many carbons preferentially adsorb small molecules. Iodine number is the most fundamental parameter used to characterize activated carbon performance ( primarily in the water treatment industry). It is a measure of activity level (higher number indicates higher degree of activation), often reported in mg/g (typical range 500–1,200 mg/g). It is a measure of the micro pore content of the activated carbon (0 to 20 Å, or up to 2 nm) by adsorption of iodine from solution. It is equivalent to surface area of carbon between 900 m²/g and 1,100 m²/g. It is the standard measure for liquid phase applications.
Depending on the industries and the kind of applications there have been different standard measurement methods or test procedures used for measuring the activity or Level of adsorption. Here are some of the major ones:
CTC(Carbon Tetra Chloride activity) – Measurement of the porosity of an activated carbon by the adsorption of saturated carbon tetrachloride vapour. This was the most commonly followed test for the longest time. But since CTC was banned globally, other tests have achieved higher prominence. But even today most of the older specifications and applications notes and even most of the tenders still use this as a reference when they talk about activated carbon. This test is highly relevant for the Vapour Phase adsorption
Iodine number Discussed above. It is the standard measure for liquid phase applications.
Molasses number or molasses efficiency is a measure of the mesopore content of the activated carbon (greater than 20 Å, or larger than 2 nm) by adsorption of molasses from solution. A high molasses number indicates a high adsorption of big molecules (range 95 – 600).
Caramel dp (decolorizing performance) is similar to molasses number. This is the measure of macro pore structure, it is less than 500A.
Both these figures are important in the food and Pharmaceutical industry as it is important for decolorizing/deodourising performance of activated carbon.
Methylene Blue number or MB value Some carbons have a mesopore (20 Å to 50 Å, or 2 to 5 nm) structure which adsorbs medium size molecules, such as the dye Methylene blue. Methylene blue adsorption is reported in gm/1kg (range 110 – 400 gm/kg).
The Butane activity this test method is a measure of the ability of an activated carbon to adsorb butane from dry air under specified conditions. Usually used in the solvent recovery application specifications, and also when the carbon is used in air filtration application like cabin air filters. The butane activity is an indication of the micropore volume of the activated carbon sample. A typical value is 7 – 15 gm/100ml.
We are able to improve the adsorption power of activated carbon by depositing certain chemicals on the surface of activated carbon. The Impregnate can be either a Metal, a metallic salt, a Organic Complex, etc. all depending on the type of performance improvement we want from the carbon.