Brown coal composition

Because of the wide variation in composition and properties of brown coal (see Table 3), efficient combustion of these fuels caimot be accomphshed by a single system. The moisture content limits combustion efficiency because some chemical energy is required to convert Hquid water to steam in the flue gases. The steam then increases the dew point of the gases, requiring higher temperatures to avoid condensation in the stack. For fuels up to 25% moisture content, 80% efficiency can be achieved. As the moisture content increases to 60%, the efficiency decreases to 70% and efficiency continues to decline about another 1% for each additional 1% moisture to 70%. 

Goal Constitution. Chemical composition studies (35,36) indicate that brown coals have a relatively high oxygen content. About two-thirds of the oxygen is bonded carboxyl, acetylatable hydroxyl, and methoxy groups. Additionally, unlike in bituminous coals, some alcohoHc hydroxyl groups are beheved to exist. 

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. 

Montan wax is obtained by solvent extraction of certain types of lignite or brown coal. It has a dark colour when not treated, but it is lighter when refined. Its chemical composition includes esters of C22 C32 acids (53%), free acids (17%), free alcohols (1 2%), ketones (3 6%) and terpenoids (20 23%) [85]. 

Brown coal, 6 703 classification, 6 712 composition, 6 720t origin, 6 704... 

Conversions between 42-68% were obtained for supercritical water extraction of Victorian brown coals at 380°C and 22MPa, considerably higher than using toluene under the same conditions. The conversions obtained with a bituminous and a sub-bituminous coal were much lower. Pressure had a marked effect on both the conversion and the extract composition, whereas temperature had only a slight effect. Considerably higher conversions were achieved using dilute sodium hydroxide rather than water. The composition of the products is discussed. 

Figure 2. Extract composition for water (and toluene) extractions of brown coals at 380°C and 22MPa.

Figure 1. Schematic composition of the brown coal structure.

Rhenish brown coal has an average ash content of about 4 % (mf), a volatile matter of about 52 % (maf) and a lower heating value of 25.6 MJ/Kg of coal (maf). The final analysis of the coal under maf conditions shows the following average composition ... 

CORRELATIONS BETWEEN PETROGRAPHICAL STRUCTURE, CHEMICAL COMPOSITION AND REFINING BEHAVIOUR OF RHENISH BROWN COAL... 

The lithotype profile was investigated in greater detail with the product composition of the different brown coals being reported in Tables 1 and 2. A distinct decrease in the total concentration of detectable oxidation products occurs with darker lithotypes (Table 1). This result is consistent with increasing aromaticity (Figure 2) and the preferential attack on aromatic structures by the pertrifluoroacetic acid reagent. The total destruction of the tertiary structure within the brown coal lithotypes is evidenced by their low yield of insoluble products (Residue) which is primarily composed of mineral matter. 

Product Composition of Brown Coal Lithotypes Pertrifluoroacetic Acid Oxidation Mixtures... 

Chemical composition of waste plastic cracking products depends on shares of the individual polymers (PE, PP, PS) in the feed and process parameters. This fact decides the technological application of the final products. Important products of the cracking process, both petroleum fractions and waste plastics, are coke residues. Coke residue yield increases considerably, up to 10 wt%, in cracking of municipal and industrial waste plastics since they contain various inorganic impurities and additives. It can be applied as solid fuel, like brown coal. In the fluid cracking the solid residue is continuously removed from the process by combustion in a regenerator section. 

Coal Used. The coal tested was Morwell brown coal from Victoria, Australia. Its composition on a dry basis is shown in Table I. This coal contains over 60% moisture as mined. It was ground wet to 80% less than 25 mesh and used in the wet state (60% moisture). 

Some brown coals may contain up to 30% humic acid. Typical compositions are shown in Table 2. Bituminous coal contains no humic acids. 

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