Coal reflectance distribution

Figure 3. Reflectance distribution of macerals in tymcal coals with the same maceral contents but of different ranks ( liptinite (Uj vitrinite inertinite)...

Pieces of coal are mixtures of materials somewhat randomly distributed in differing amounts. The mineral matter can be readily distinguished from the organic, which is itself a mixture. Coal properties reflect the individual constituents and the relative proportions. By analogy to geologic formations, the macerals are the constituents that correspond to minerals that make up individual rocks. For coals, macerals, which tend to be consistent in their properties, represent particular classes of plant parts that have been transformed into coal (40). Most detailed chemical and physical studies of coal have been made on macerals or samples rich in a particular maceral, because maceral separation is time consuming. 

Optical microscopy is another method that has been used to determine the distribution of minerals in coal. This method is based on the detailed microscopic examination of polished or thin sections of coal in transmitted and/or reflected light. In principle, observing several of its optical properties, such as morphology, reflectance, refractive index, and anisotropy, makes identification of a mineral type possible. 

The volume percent of physical components of coal is used as an aid in the characterization of coal for use in carbonization, gasification, and combustion processes. To determine the volume percent of the physical components of coal (ASTM D-2799), the components in a representative crushed coal sample (ASTM D-2797) are identified under a microscope according to their reflectance, other optical properties, and morphology. The proportion of each component in the sample is determined by observation of a statistically adequate number of points and summing those representative of each component. Only area proportions of components are determined on a surface section of a sample. However, the area and volume proportions are the same when the components are distributed randomly throughout the sample. 

Currently, global hydrogen production is 48% from natural gas, 30% from oil, and 18% from coal water electrolysis accounts for only 4%. The distribution of production reflects the effects of thermodynamic constraints on economic choices of the four processes for obtaining hydrogen, partial combustion of natural gas in a natural gas combined cycle power plant offers the most efficient chemical pathway and the greatest off-take of usable heat... 

As an aid in establishing the analytical problems, published data were compiled and reviewed for coal combustion and waste incineration (1 ). Important conclusions drawn from this review were 1) only a limited number of organic components had been identified in the effluents 2) the identified components reflected analytical capabilities and interests rather than a true distribution 3) reliable quantitative data were not available and 4) the data base was insufficient for predicting the probable environmental effects associated with the combustion of coal. 

According to the New York Times (11/7/07), the actual average "wholesale" costs of one kWh of electricity in 2007 in the United States was as follows Pulverized Coal - 5.7c, Nuclear - 6.4c, Coal Gas - 6.6c, Natural Gas - 7.3c, Wind - 9.6c, Biomass - 10.7c, Solar Thermal -12.0c. These numbers do not yet reflect the coming carbon charges, nor do they reflect transportation and distribution costs required to... 

Pittsburgh, like Essen and Newcastle, became a great industrial center just because of the rich coal veins in the area. So the chance distribution of elements in the earth millions and billions of years ago is reflected in our maps and history books today. 

More recent studies suggest that the distributions of methylated naphthalenes and phenanthrenes reflect the dilution of the components in the bitumen inherited from diagenesis by addition of components with different distributions generated from kerogen (Radke et al. 1990 Killops et al. 2001). The effects of this dilution process are probably more noticeable in coals because their larger adsorption capacity tends to delay oil expulsion to a greater extent than in marine shales. 

Thus the properties of quicklime from a given kiln reflect the average properties of individual lumps, each of which has experienced a particular time-temperature history. Fig. 15.8 compares the distribution of particle densities for a light-burned quicklime from an annular shaft kiln, with a mean apparent density of 1.66 g/cm with that of a solid-burned quicklime from a coal-fired traditional shaft kiln with a mean apparent density of 2.15 g/cm. Table 15.4 presents some typical... 

---