Coal lignite

Properties. Pilot-unit data indicate the EDS process may accommodate a wide variety of coal types. Overall process yields from bituminous, subbituminous, and lignite coals, which include Hquids from both Hquefaction and Flexicoking, are shown in Figure 14. The Hquids produced have higher nitrogen contents than are found in similar petroleum fractions. Sulfur contents reflect the sulfur levels of the starting coals ca 4.0 wt % sulfur in the dry bituminous coal 0.5 wt % in the subbituminous and 1.2 wt % sulfur in the dry lignite. 

Humic acids are alkaH-extractable materials and total humic acid content is a term that refers to the humic acid content of coal that has had its carboxylate cations removed with sodium pyrophosphate. Values for some typical AustraHan brown coals range from 24—92% (13). Treatment of lignitic coals with mineral acid to release the alkaH and alkaline cations may dissolve up to 20% of the coal. The naturally moist coals are slightly acidic and have a pH of 3.5—6.5. 

Analysis. Analyses of a number of lignitic coals are given in Table 3. Figure 1, a distribution plot of 300 U.S. coals according to ASTM classification by rank, indicates the broad range of fixed carbon values (18). According to the ASTM classification, fixed carbon for both lignite and subbituminous coals has an upper limit of 69%, but in practice this value rarely exceeds 61%. 

The moisture content of freshly mined lignitic coals can be as high as 73%, but it is usually 30—65%. The more mature, consoHdated coals have lower moisture contents and thus a higher heating value. Figure 2 shows moisture and ash contents, as well as net heating values for lignitic coals from the world s principal deposits (19). 

The importance of a coal deposit depends on the amount that is economically recoverable by conventional mining techniques. The world total recoverable reserves of lignitic coals were 3.28 x 10 metric tons at the end of 1990 (3), of which ca 47% was economically recoverable as of 1994 (Table 4). These estimates of reserves change as geological survey data improve and as the resources are developed. 

Hard coal is more important ia most of the western European countries with the exception of Austria and Italy. No lignitic coal production was iadicated ia 1989 for the Netherlands, Denmark, Belgium, Sweden, Norway, and the United Kingdom (24). 

Other Regions. In AustraUa, Victoria has the largest reserves, although smaller ones occur in southern AustraUa, western AustraUa, Tasmania, and Queensland (28). The main deposit consists of many thick seams in about 500 km of the Latrobe Valley. The YaHourn coal field provides most of the fuel. The top coal seam is 65 m thick and is covered with 13 m of overburden. Most of this coal is used for electric power generation. It is very moist (55—72%), but has less than 5% ash. The lignitic coal found in South AustraUa is, for the most part, too deep for economic recovery. However, some of the better deposits are mined for power generation. 

Seam thicknesses and depths vary tremendously. The most favorable deposits have shallow overburdens and thick seams that cover large areas. Acceptable stripping ratios, ie, overburden thickness to coal thickness, depend on the quaHty of the fuel. Ratios up to 10 1 have been used for bituminous coals, but lower ones are required for lignitic coals because of the lower heating value per unit weight. 

The lignitic coals of the northern United States tend to have low sulfur contents, making them attractive for boilet fuels to meet sulfur-emission standards. However, low sulfur content coals have impaired the performance of electrostatic precipitators. The ash of these coals tends to be high in alkaline earths (Ca, Mg) and alkaUes (Na, K). As a result, the ash can trap sulfur as sulfites and sulfates (see Airpollution control methods). 

The CO2 Acceptor process, also developed under AGA/DOE sponsorship, by the ConsoHdation Coal Co., uses steam to gasify lignitic coal. Heat is supphed by the exothermic reaction between CO2 and calciaed dolomite [17069-72-6]. The dolomite is calciaed ia a separate fluidized bed. This process operates ia a 40 t/d pilot plant, but there are no plans for commercialization as of this writing. 

Monta.n Wax. An important product of the direct extractive treatment of lignitic coals is montan wax [8002-53-7]. The term montan wax or Bergwachs refers strictiy to the material obtained by solvent extraction of suitable German brown coals. The generic term for similar materials is montana wax. The small quantities made outside Germany are usually referred to as montan, prefixed by the country of origin (see Waxes). 

R. A. Durie, ed.. The Science of Victorian Brown Coal Structure, Properties and Consequencesfor Utilisation, Butterworth Heinemann, Oxford, 1991. An excellent reference not only for Victorim Brown Coal, but for lignitic coals of the world. 

Charcoal briquet production from all sources in-cluding wood, bark, lignite, coal, and agricultural residue. 

Lignite coal polymer GPC Appl. Biochem. Biotech. 24/25, 889 (1990)... 

Methanation Section Test Conditions. To date, the HYGAS pilot plant has been operated with Montana lignite coal feed. This lignite is a low sulfur (usually less than 1 wt % ) coal which has good reactivity for hydrogasification. The coal is nonagglomerating (thus eliminating the need for pretreatment), and it represents the lowest rank of U. S. coals that are available for conversion to substitute natural gas. 

In run 19, where considerable carbon monoxide conversion was obtained in both stages, the recycle ratio was 1.48 scf recycle gas per scf feed gas. Recycle ratios in the other tests varied from 1.14 to 1.30. The design recycle ratio is 1.67 for lignite coal feed with hydrogen/steam synthesis gas. 

Black coal. Black coal ranges from Cretaceous age (65 to 105 million years ago) to mid-Permian age (up to 260 million years ago). They are all black some are sooty and still quite high in moisture (sub-bituminous coal). A common name for this coal in many parts of the world is "black lignite. Coals that get more deeply buried by other rocks lose more moisture and start to lose their oxygen and hydrogen they are harder and shinier (e.g., bituminous coal). Typical energy contents are around 24 to 28 MJ/kg. These coals generally have less than 3% moisture, but some power stations burn coal at up to 30% ash. 

Lignitic coal, classification by rank, 6 711t Lignocellulose, 5 367-368 10 295 Lignocellulose-based raw materials,... 

Figure 8.7 PCDD/F I-TEQ (pg/g) values of flue gas after the combustion of lignite coal, solid waste, and PVC in the samples without inhibitor and 19 different compounds used with a 10% inhibitor of the fuel. (From M. Pandelova et al.. Environ. Sci. Technol, 2005.)...

Mobile phase spectra of Blind Canyon coal look rather similar to Beulah-Zap lignite coal with regard to the peaks at m/z 324, 342, 424. Alkylsubstituted naphthalenes components are clearly separated and the other dominant peaks at m/z 310, 324, 342, 356 are believed to originate from triterpenoid aromatization (26). The mass spectra of Blind Canyon coal, which contains 11% resinite, illustrate the importance of depositional environment as well as of rank in determining the components in the mobile phase. 

Lewiston-Stockton coal contains the least amount of alkylsubstituted naphthalenes in the mobile phase among six coals except Beulah-Zap lignite coal from the fact that Figure 6a represents only 0.03% of TIL In contrast, Pittsburgh 8 coal appears to contain the largest amount of alkylsubstituted naphthalenes. Lewiston-Stockton coal also appears to contain steranes in the mobile phase as represented by homologous series of m/z 232, 246, 260. 

The 2003 ACGIH threshold limit valuetime-weighted average (TLV-TWA) for bituminous or lignite coal dust is 0.9mg/m as respirable particulate a TLV-TWA of... 

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