Activated carbons production

In addition to surface area, pore size distribution, and surface chemistry, other important properties of commercial activated carbon products include pore volume, particle size distribution, apparent or bulk density, particle density, abrasion resistance, hardness, and ash content. The range of these and other properties is illustrated in Table 1 together with specific values for selected commercial grades of powdered, granular, and shaped activated carbon products used in Hquid- or gas-phase appHcations (19). 

Table 1. Properties of Selected U.S. Activated Carbon Products ...

Specifications. Activated carbon producers furnish product bulletins that Hst specifications, usually expressed as a maximum or minimum value, and typical properties for each grade produced. Standards helpful in setting purchasing specifications for granular and powdered activated carbon products have been pubHshed (33,34). 

Production capacity was almost equally spHt between powdered and nonpowdered activated carbon products. Powdered activated carbon, a less expensive form used in Hquid-phase appHcations, is generally used once and then disposed of. In some cases, however, granular and shaped products are regenerated and reused (35). In 1990 production capacity for granular and shaped products was spHt with about two-thirds for Hquid-phase and one-third for gas-phase appHcations (37). 

Western Europe has seven manufacturers of activated carbon. The two largest, Norit and Chemviron (a subsidiary of Calgon), account for 70% of West European production capacity, and Ceca accounts for 13% (42). Japan is the third largest producer of activated carbon, having 18 manufacturers, but four companies share over 50% of the total Japanese capacity (43). Six Pacific Rim countries account for the balance of the world production capacity of activated carbon, 90% of which is in the Philippines and Sri Lanka (42). As is the case with other businesses, regional markets for activated carbon products have become international, lea ding to consoHdation of manufacturers. Calgon, Norit, Ceca, and Sutcliffe-Speakman are examples of multinational companies. 

Source references for frequentiy used test procedures for determining properties of activated carbon are shown in Table 4. A primary source is the Jinnual Book ofyimerican Societyfor Testing and Materials (ASTM) Standards (61). Other usehil sources of standards and test procedures include manufacturers of activated carbon products, the American Water Works Association (AWWA) (33,34), and the Department of Defense (54). 

Activated carbon products used for decolorizing food products in Hquid form must meet the requirements of the Tood Chemical Codex as prepared by the Pood Nutrition Board of the National Research Council (63). 

J. W. Hassler, Jictivated Carbon Chemical Publishing Co., Inc., New York, 1963, pp. 1—14. A comprehensive account of the development and use of activated carbon products to about 1960. 

Activated carbon is an amorphous solid with a large internal surface area/pore strucmre that adsorbs molecules from both the liquid and gas phase [11]. It has been manufactured from a number of raw materials mcluding wood, coconut shell, and coal [11,12]. Specific processes have been developed to produce activated carbon in powdered, granular, and specially shaped (pellet) forms. The key to development of activated carbon products has been the selection of the manufacturing process, raw material, and an understanding of the basic adsorption process to tailor the product to a specific adsorption application. 

Table 4. Properties of selected activated carbon products. Reprinted from [11], copyright (c) 1992 John Willey Sons, Inc., with permission.

The current requirements have led to the development of pellet shaped activated carbon products specifically for automotive applications. These pellets are typically generated as chemically activated, wood-based carbons. 

Derbyshire, F., Jagtoyen, M. and Thwaites, M., Activated carbons - production and applications. In Porosity in Carbons, ed. J.W. Patrick, Halsted Press, New York, 1995, pp. 227 252. 

Material safety data sheets on activated carbon products, available from the manufacturers, 1991. 

Activated carbons [171-182] are amorphous materials showing highly developed adsorbent properties. These materials can be produced from approximately all carbon-rich materials, including wood, fruit stones, peat, lignite, anthracite, shells, and other raw materials. The properties of the produced adsorbent materials will depend not merely on the preparation technique but as well on the carbonaceous raw material used for their production. Actually, lignocellulosic materials account for 47% of the total raw materials used for active carbon production [178],... 

Super-heated water vapor has been widely used in many industrial processes such as heat-exchange process and drying, and has also been used in the activation process for activated carbon production. Recently, the super-heated water vapor has been utilized in food industry for production of instant food and drying of vegetables and tea leafs. The characteristics of the super-heated water vapor [3] are (1) it can heat the materials without oxidation because it does not contain oxygen and carbon dioxide, (2) drying speed becomes much faster than super-heated air due to heat emission of water molecules, and (3) waste gas is easily recovered by condensing. 

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