Minerals moisture content

The specific heat of coal (Table 7.2) usually increases with its moisture content (Figure 7.1), decreases with carbon content (Figure 7.2), and increases with volatile matter content (Figure 7.3), with mineral matter content exerting somewhat less influence. The values for the specific heats of various coals fall into the general range 0.25 to 0.37, but as with other physical data, comparisons should be made only on an equal (e.g., moisture content, mineral matter content) basis. 

Wide variations in soil resistivity can be found within a given geographic area, as documented in Table 10.15. The wide range of values shown results from differences in moisture content, mineral content, and temperature. 

The same moisture content of the produced cake can be obtained in shorter dewatering times if higher pressures are used. If a path of constant dewatering time is taken, moisture content is reduced at higher pressures with a parallel increase in cake production capacity. This is an advantage of pressure filtration of reasonably incompressible soHds like coal and other minerals. 

A variation to the top-feed dmm filter is the dual dmm filter which uses two dmms of the same size in contact with each other and rotating in opposite directions. The feed enters into the V-shaped space formed on top of the two dmms and the cake that starts forming initially contains coarser particles due to the settling which takes place in the feed zone. This is beneficial to the clarity of the filtrate because the coarser particles act as a precoat. Erom the point of view, however, of the final moisture content of the cake the stratification of the soHds in the cake may lead to somewhat wetter cakes. Utilization of the area of the dmms is poor since there are dead spaces under the two dmms. The primary appHcation of the dual dmm filters is in dewatering coarse mineral or coal suspensions at feed concentrations greater than 200 kg/m. ... 

The KDF Filter. The KDP filter (Pig. 23) (Amafilter, Holland) is based on the same principle as disk filters. It was developed for the treatment of mineral raw materials, like coal flotation concentrates or cement slurries, and can produce a filter cake of low moisture content at very high capacities, up... 

Volatilization. The susceptibility of a herbicide to loss through volatilization has received much attention, due in part to the realization that herbicides in the vapor phase may be transported large distances from the point of application. Volatilization losses can be as high as 80—90% of the total applied herbicide within several days of application. The processes that control the amount of herbicide volatilized are the evaporation of the herbicide from the solution or soHd phase into the air, and dispersal and dilution of the resulting vapor into the atmosphere (250). These processes are influenced by many factors including herbicide application rate, wind velocity, temperature, soil moisture content, and the compound s sorption to soil organic and mineral surfaces. Properties of the herbicide that influence volatility include vapor pressure, water solubility, and chemical stmcture (251). 

Drying. In many cases, the high moisture content of young coals dictates significant drying (qv) before use. In some cases, partial removal of mineral matter, especially water-soluble species, is desirable. 

More recendy, the molten caustic leaching (MCL) process developed by TRW, Inc. has received attention (28,31,32). This process is illustrated in Eigure 6. A coal is fed to a rotary kiln to convert both the mineral matter and the sulfur into water- or acid-soluble compounds. The coal cake discharged from the kiln is washed first with water and then with dilute sulfuric acid solution countercurrendy. The efduent is treated with lime to precipitate out calcium sulfate, iron hydroxide, and sodium—iron hydroxy sulfate. The MCL process can typically produce ultraclean coal having 0.4 to 0.7% sulfur, 0.1 to 0.65% ash, and 25.5 to 14.8 MJ/kg (6100—3500 kcal/kg) from a high sulfur, ie, 4 wt % sulfur and ca 11 wt % ash, coal. The moisture content of the product coal varies from 10 to 50%. 

Although filtratioa rates can be much faster with flocculants, the final cake moisture is often higher ia a flocculated cake (60—63). Ia coatrast, usiag flocculants optimized for filtration, coal, and other mineral slurries can be dewatered to moisture contents significantly lower than the untreated cake (64—68). The advantages of rapid filtration rates can also be preserved. Flocculants that provide better filtration tend to form floes having the foUowiag characteristics (65) ... 

Capillary Flow Moisture which is held in the interstices of solids, as liquid on the surface, or as free moisture in cell cavities, moves by gravity and capiUarity, provided that passageways for continuous flow are present. In diying, liquid flow resulting from capiUarity appUes to liquids not held in solution and to aU moisture above the fiber-saturation point, as in textiles, paper, and leather, and to all moisture above the equiUbrium moisture content at atmospheric saturations, as in fine powders and granular solids, such as paint pigments, minerals, clays, soU, and sand. 

Example 4 Calculation of Sample Weight for Surface Moisture Content An example is given with reference to material with minimal internal or pore-retained moisture such as mineral concentrates wherein physically adhering moisture is the sole consideration. With this simphfication, a moisture coefficient K is employed as miiltipher of nominal top-size particle size d taken to the third power to account for surface area. Adapting fundamental sampling theory to moisture sampling, variance is of a minimum sample quantity is expressed as... 

Mineral composition, permeability, and porosity, grain-size distribution, in-situ density, moisture content... 

Major emphasis in studies of N-nitroso compounds in foods has been placed upon volatile nitrosamines, in part because these compounds are relatively easy to isolate from complex matrices by virtue of their volatility. Procedures utilizing atmospheric pressure or vacuum distillation have been used by most investigators, with variations of the method of Fine e al. (2) being among the most popular. This procedure employs vacuum distillation of a mineral oil suspension of the sample with optional addition of water to improve nitrosamine recovery from low moisture content samples (6) The usual approach to prevention of nitrosamine formation during analysis involves adding sulfamic acid or ascorbate to destroy residual nitrite at an early stage of sample preparation. 

Soils and vadose zone information, including soil characteristics (type, holding capacity, temperature, biological activity, and engineering properties), soil chemical characteristics (solubility, ion specification, adsorption, leachability, cation exchange capacity, mineral partition coefficient, and chemical and sorptive properties), and vadose zone characteristics (permeability, variability, porosity, moisture content, chemical characteristics, and extent of contamination)... 

Decreased soil phosphatase activity and total P in aboveground plant biomass Increased microbial P mineralization (approx. 0.8 mg P kg-1 day1) and immobilization (approx. 6 mg P kg-1 day1) with higher moisture content No effect on soil phosphatase activities, plant P concentrations, or N/P ratios No effect on colonization of roots with mycorrhizae... 

Abiotic organic reactions, such as hydrolysis, elimination, substitution, redox, and polymerization reactions, can be influenced by surfaces of clay and primary minerals, and of metal oxides. This influence is due to adsorption of the reactants to surface Lewis and Br nsted sites. Temperature and moisture content are the most important environmental variables. Under ambient environmental temperatures, some reactions are extremely slow. However, even extremely slow transformation reactions may be important from environmental and geochemical viewpoints. 

The dissociation of water coordinated to exchangeable cations of clays results in Brtfnsted acidity. At low moisture content, the Brrfnsted sites may produce extreme acidities at the clay surface-As a result, acid-catalyzed reactions, such as hydrolysis, addition, elimination, and hydrogen exchange, are promoted. Base-catalyzed reactions are inhibited and neutral reactions are not influenced. Metal oxides and primary minerals can promote the oxidative polymerization of some substituted phenols to humic acid-like products, probably through OH radicals formed from the reaction between dissolved oxygen and Fe + sites in silicates. In general, clay minerals promote many of the reactions that also occur in homogenous acid or oxidant solutions. However, rates and selectivity may be different and difficult to predict under environmental conditions. This problem merits further study. 

El-Amamy, M. M., and T. Hill, Hydrolysis kinetics of organic chemicals on montmorilIonite and kaolinite surfaces as related to moisture content , Clays and Minerals, 32,67-73 (1984). 

Bituminous coal is a dense coal, usually black, sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke. The moisture content of bituminous coal is usually less than 20% by weight. The heat content of bituminous coal ranges from 21 to 30 million Btu/ton on a moist, mineral-matter-free basis. 

Earth resistance depends on the type of soil, its mineral composition, moisture content, and temperature. Table 5.2 provides the resistivity of various types of soils Table 5.3, the effect of moisture on soil resistivity and Table 5.4, the effect of temperature on soil resistivity. The information contained in the tables is used to illustrate the effect of various natural factors on soil resistivity. Table 5.5 shows the changes in earth resistance by using multiple ground rods. Note that, to realize the full benefits of multiple rods, the rods should be spaced an adequate distance apart. 

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