Carbonates production

Human activity, particularly in the developing world, continues to make it more difficult to sustain the world s biomass growth areas. It has been estimated that tropical forests are disappearing at a rate of tens of thousands of hm per year. Satellite imaging and field surveys show that Brazil alone has a deforestation rate of approximately 8 x 10 hm /yr (5). At a mean net carbon yield for tropical rain forests of 9.90 t/hm yr (4) (4.42 short ton /acreyr), this rate of deforestation corresponds to a loss of 79.2 x 10 t/yr of net biomass carbon productivity. 

Fig. 2. Overall schematic of solid fuel combustion (1). Reaction sequence is A, heating and drying B, solid particle pyrolysis C, oxidation and D, post-combustion. In the oxidation sequence, left and center comprise the gas-phase region, tight is the gas—solids region. Noncondensible volatiles include CO, CO2, CH4, NH, H2O condensible volatiles are C-6—C-20 compounds oxidation products are CO2, H2O, O2, N2, NO, gaseous organic compounds are CO, hydrocarbons, and polyaromatic hydrocarbons (PAHs) and particulates are inerts, condensation products, and solid carbon products.

T. J. Carbone, "Production Processes, Properties, and Apphcations for Calcined in High-Purity Aluminas," in L. D. Hart, ed., Jilumina Chemicals Science and Technology Handbook, The American Ceramic Society, Columbus, Ohio, 1990. 

Many plants outside of North America pfill or granulate a mixture of ammonium nitrate and calcium carbonate. Production of this mixture, often called calcium ammonium nitrate, essentially removes any explosion hazard. In many cases calcium nitrate recovered from acidulation of phosphate rock (see Phosphoric acid and the phosphates) is reacted with ammonia and carbon dioxide to give a calcium carbonate—ammonium nitrate mixture containing 21 to 26% nitrogen (23). 

One commercial process for producing sodium sulfide is as a by-product of barium carbonate production (see Barium compounds). Barite ore, BaSO, is reduced with carbon at 800°C to produce cmde barium sulfide (black ash), which is then leached to dissolve the barium sulfide in solution. The solution is then reduced using sodium carbonate to produce barium carbonate, leaving a weak sodium sulfide solution as the by-product. The sodium sulfide solution may then be concentrated and flaked or crystallized. 

After precipitation is complete, the slurry is pumped to vacuum dmm filters where a nearly complete Hquid-soHds separation is accompHshed. The hquid is dilute sodium sulfide solution, which is concentrated by evaporation to a flaked 60 wt % sodium sulfide product. The filter cake is a 60 wt % strontium carbonate soHd which is fed to a carbonate dryer. After drying, the strontium carbonate product is cooled, ground, and screened for packaging. 

Losses are kept to a minimum by carbonation of the mother Hquor with CO2 and recycle of the carbonated product back to the leach system. From acid solutions, uranium is usually precipitated by neutralization with ammonia or magnesia. Ammonia gives an acceptable precipitate, for which compositions such as (NH 2(U02)2S04(0H)4 were calculated. The ammonium salt is preferred if the product is to be used ia the manufacture of... 

Most barium compounds are prepared from reactions of barium carbonate [513-77-9] BaCO, which is commercially manufactured by the "black ash" process from barite and coke ki a process identical to that for strontium carbonate production. Depending on the co-product, soda ash and/or carbon dioxide are also consumed. 

The use of calcium carbonate in paint, paper, and plastics make up the principal part of the market. In the paper industry calcium carbonate products find two uses as a filler in the papermaking process and as a part of the coating on paper. 

Carbon Blacks. Carbon blacks are occasionally used as components in mixes to make various types of carbon products. Carbon blacks are generally prepared by deposition from the vapor phase using petroleum distillate or gaseous hydrocarbon feedstocks (see Carbon, carbon black). 

Anthracite. Anthracite is preferred to other forms of coal (qv) in the manufacture of carbon products because of its high carbon-to-hydrogen ratio, its low volatile content, and its more ordered stmcture. It is commonly added to carbon mixes used for fabricating metallurgical carbon products to improve specific properties and reduce cost. Anthracite is used in mix compositions for producing carbon electrodes, stmctural brick, blocks for cathodes in aluminum manufacture, and in carbon blocks and brick used for blast furnace linings. 

Synthetic Resins. Various polymers and resins are utilized to produce some specialty carbon products such as glassy carbon or carbon foam and as treatments for carbon products. Typical resins include phenoHcs, furan-based polymers, and polyurethanes. These materials give good yields of carbon on pyrolysis and generally carbonize directly from the thermoset polymer state. Because they form Httle or no mesophase, the ultimate carbon end product is nongraphitizing. 

D. J. Page, Industrial Graphite Engineering Handbook, Union Carbide Corp., Carbon Products Division, New York, 1991, Section 5B.02.03. 

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). 

Active Carbon" under "Carbon" in ECT 1st ed., VoL 2, pp. 881—899, byj. W. Hassler, Nuchar Active Carbon Division, West Virginia Pulp and Paper Co., and J. W. Goet2, Carbide and Carbon Chemicals Corp. "Activated Carbon" under "Carbon" in ECT 2nd ed., VoL 4, pp. 149—158, by E. G. Doying, Union Carbide Corp., Carbon Products Division "Activated Carbon" under "Carbon (Carbon and Artificial Graphite)" in ECT 3rd ed., Vol. 4, pp. 561—570, by R. W. Soffel, Union Carbide Corp. 

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. 

As in the case of the chloroformates, most of the carbonate production is used captively and production figures are not available. However, from pubHshed data, the 1991 price (fob works) of commercial carbonates was 3.08/kg for both dimethyl (DMC), dmms, tmcHoad and diethyl (DEC), tankwagon (89). 

Carbon black from oil is the main competition for the product from coal, which is used in filters. Carbon for electrodes is primarily made from petroleum coke, although pitch coke is used in Germany for this product. The pitch binder used for electrodes and other carbon products is almost always a selected coal tar pitch. 

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