Coal calcium distribution

Table VIII. Calcium Distribution in Selected Coals...

Laser-microprobc mass spectrometry has an unusually high sensitivity (down to 10 g), is applicable to both inorganic and organic (including biological) samples, has a spatial resolution of about I pm, and produces data at a rapid rate. Some typical applications of laser-microprobe mass spectrometry include determination of Na/K concentration ratios in frog nerve fiber, determination of the calcium distribution in retinas, classification of asbestos and coal mine dusts, determination of fluorine distributions in dental hard tissue, analysis of amino acids, and study of polymer surfaces. ... 

Occurrence. Carbon is distributed very widely in nature as calcium carbonate (limestone). Coal, petroleum and natural gas are chiefly hydrocarbons. Carbon is found as carbon dioxide in the atmosphere of the earth and dissolved in all natural waters. The atmosphere of Mars contains 96% C02. It is plentiful in the sun, stars, comets and the atmospheres of most planets. 

For comparison with Tables I and II, Table lit gives the range and typical values of the mineral distributions observed in bituminous coals by the CCSEM and Mossbauer techniques, derived from studies of perhaps a hundred different bituminous coal samples in this laboratory. Some obvious differences in mineralogy are apparent. In addition to the difference in calcium dispersion and abundance already noted, it is seen that certain minerals common in bituminous coals, such as Fe-bearing clays (illite and chlorite) and siderite, are virtually absent in the low-rank samples of Tables I and II. Conversely, minerals such as barite (BaSO ), apatite (Ca5(P0 )30H), and other Ca, Sr phosphates are rather uncommon in bituminous coals. 

Chloride minerals are rarely found in coal in the form of solid species because of high solubility of sodium, calcium and trace metal chlorides in coal strata waters. The "inherent" water content of coal is related to its porosity and thus the moisture content of lignite deposits can exceed 40 per cent decreasing to below 5 per cent in fully bituminous coals (11). Chlorides, chiefly associated with sodium and calcium constitute the bulk of water-soluble matter in British bituminous coals (12). Skipsey (13) has found that the distribution of chlorine coals was closely related to the salinity of mine waters. Hypersaline brines with concentrations of dissolved solids up to 200 kg m occur in several of the British Coalfields. 

Figure 6. The effects of three chemical additives on product coal particle size distribution while milling at constant conditions, (O) No Additives (A) 2 Ibs/ton Calcium Hydroxide (D)...

The convection pass cools the flue gas and entrained particulate matter from about 1145 K (1600°F) to below 645 K (700°F). For bituminous coal with a combustion temperature of 1115 K (1550°F), a recycle ratio of 2.5 (mass rate of particulate recycle to coal feed rate) increases combustion efficiency to over 97 percent from around 90 percent without recycle. For a bituminous coal containing 3 percent sulfur, 90 percent sulfur capture is achieved with limestone as sorbent at a calcium-to-sulfur (Ca/S) molar ratio of 2.3 and a recycle ratio of 2.5. A Ca/S molar ratio of over 3.4 is required when there is no recycle. The recycled material also enters the bed through T nozzles, one per 7 m (72 ft ) of bed floor area. A means of distributing the particulate flow from the multiclones to the feed lines and overcoming the... 

On the other hand, a heterogeneous mixture is one in which different compounds and/or substances are mechanically blended together and create a nonuniform distribution of substances. This is the case for concrete. Concrete is usually made by mixing cement, limestone or granite, and water, just to name a few concrete components. Limestone is made up of calcium carbonate (CaCOj), which is decomposed to calcium oxide, releasing CO in the process. Recently, the use of recycled materials to make concrete has gained popularity. Hy-ash, a by-product of coal-fired electric... 

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