Coal content

Approximately 8 percent unconverted coal content, determination by difference. Direct determination. eInsufficient solubility in pyridine. 

Table 4.13 Estimated amounts of fossil carbon in the crust (after Kempe 1979 Tissot Welte 1984 Ward 1984 Kvenvolden 1998 Falkowski et al. 2000).Approximate conversions to carbon basis assume densities of 0.8 tnT3 for conventional oils, 0.9tm 3 for heavy oils, 0.65 kgnT3 for gas, and corresponding C contents of 85, 80 and 75% coal content of 80% C (dmmf) 10% ash and 5% moisture...

FIGURE 6-22 Response of density signal to change in coal content of slurry. 

Many research were focused on the effect of fly ash, siUca fume and granulated blast furnace slag addition on the concrete freeze-thaw resistance. All these additions improve the freeze-thaw resistance, as compared with the concrete from Portland cement, however, on condition that all these eoncretes are air entrainment [80], Freeze-thaw resistance of concrete with fly ash ean be lowered in the case when it has high coal content. The limit value, increased recently to 9% (according to the European standard EN 197-1 2002/A3 2007), is too high and the 5% level should be maintained, as it was reeommended by the elder directives (previous standard EN 197-1 2002). The effeet of non-eombusted coal on the appUcabilily of fly ash is diseussed in details in Seet 7.4. 

Code Coal Content Content Yield Total Micropore ... 

Pollutant distributions between char, tar, and gases are expected to be a function of pyrolysis conditions and, hence, are process-dependent. Khan developed models to predict the distribution of sulfur in the products based on pyrolysis data for 32 different coal samples devolatilized in a fixed-bed reactor. It was observed that the total sulfur content in the pyrolysis products at 500 C could be correlated with the total sulfur (weight percent of original coal) content. The relationships are as follows ... 

Fuel switch. The choice of fuel used in furnaces and steam boilers has a major effect on the gaseous utility waste from products of combustion. For example, a switch from coal to natural gas in a steam boiler can lead to a reduction in carbon dioxide emissions of typically 40 percent for the same heat released. This results from the lower carbon content of natural gas. In addition, it is likely that a switch from coal to natural gas also will lead to a considerable reduction in both SO, and NO, emissions, as we shall discuss later. 

Fuel switch. Fuel switch from, say, coal to natural gas reduces the CO2 emissions for the same heat release because of the lower carbon content of natural gas. 

The composition of coal tar varies with the carbonization method but consists, largely, of mononuclear and polynuclear aromatic compounds and their derivatives. Coke oven tars are relatively low in aliphatic and phenolic content while low-temperature tars have much higher contents of both. 

Coals (the plural is deliberately used because coal has no defined, uniform nature or structure) are fossil sources with low hydrogen content. The structure of coals means only the structural models depicting major bonding types and components relating changes with coal rank. Coal is classified, or ranked, as lignite, subbituminous, bituminous, and anthracite. This is also the order of increased aromaticity and decreased volatile matter. The H C ratio of bituminous coal is about 0.8, whereas anthracite has H C ratios as low as 0.2. 

When a suitable reaction involving the analyte does not exist it may be possible to generate a species that is easily titrated. Eor example, the sulfur content of coal can be determined by using a combustion reaction to convert sulfur to sulfur dioxide. 

QIGNITE AND BROWN COAL] (Vol 15) Recycled-content mandates... 

The key to understanding dewatering by air displacement is the capillary pressure diagram. Figure 6 presents an example typical for a fine coal suspension there is a minimum moisture content, about 12%, called irreducible saturation, which cannot be removed by air displacement at any pressure and a threshold pressure, about 13 kPa. 

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... 

The KDF filter was first tested in prototype on a coal mine in northern Germany. It was installed in parallel with existing vacuum filters and it produced filter cakes consistendy lower in moisture content by 5 to 7% than the vacuum filters. Two production models have been installed and operated on a coal mine in Belgium. The filter is controlled by a specially developed computer system this consists of two computers, one monitoring the function of the filter and all of the detection devices installed, and the other controlling the filtration process. The system allows optimization of the performance, automatic start-up or shut-down, and can be integrated into the control system of the whole coal washing plant. 

The test results reported show the advantages of pressure filtration quite clearly, ie, the dry cake production capacity obtained with the test soHds (coal suspensions) was raised 60 or 70% and the final moisture content of the cake reduced by as much as 5 to 7% by increasing the pressure drop from 60 to 200 kPa. Further increases in the operating pressure bring about less and less return in terms of capacity and moisture content. 

Environmental considerations also were reflected in coal production and consumption statistics, including regional production patterns and economic sector utilization characteristics. Average coal sulfur content, as produced, declined from 2.3% in 1973 to 1.6% in 1980 and 1.3% in 1990. Coal ash content declined similarly, from 13.1% in 1973 to 11.1% in 1980 and 9.9% in 1990. These numbers clearly reflect a trend toward utilization of coal that produces less SO2 and less flyash to capture. Emissions from coal in the 1990s were 14 x 10 t /yr of SO2 and 450 x 10 t /yr of particulates generated by coal combustion at electric utiUties. The total coal combustion emissions from all sources were only slightly higher than the emissions from electric utiUty coal utilization (6). 

The chemical characteristics of biomass vary over a broad range because of the many different types of species. Table 8 compares the typical analyses and energy contents of land- and water-based biomass, ie, wood, grass, kelp, and water hyacinth, and waste biomass, ie, manure, urban refuse, and primary sewage sludge, with those of cellulose, peat, and bituminous coal. Pure cellulose, a representative primary photosynthetic product, has a carbon content of... 

Cmde gas leaves from the top of the gasifier at 288—593°C depending on the type of coal used. The composition of gas also depends on the type of coal and is notable for the relatively high methane content when contrasted to gases produced at lower pressures or higher temperatures. These gas products can be used as produced for electric power production or can be treated to remove carbon dioxide and hydrocarbons to provide synthesis gas for ammonia, methanol, and synthetic oil production. The gas is made suitable for methanation, to produce synthetic natural gas, by a partial shift and carbon dioxide and sulfur removal. 

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