Sub-bituminous coal

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. 

As volatile matter in the coal increases to as much as 40% of the coal (dry and ash-free basis), increasing amounts of oils and tars are released. However, for coals of higher volatile content, the quantity of oils and tars decreases and is relatively low in the sub-bituminous coals and in lignite. 

H-Coal, A Future Energy Source, "H-Coal Special Issue, 1 Energy Countdown Eccles and DeVaux, "Current Status of H-Coal Commercialization " "H-Coal Plant Sets February Restart Using Western Sub-Bituminous Coal," Energy Insider, February 1982, 5, p 1,... 

The main purpose of magnesia addition to a limestone wet scrubbing system is to facilitate high S02 removal. For a wet scrubber that cleans flue gas from a utility coal-fired boiler, the scrubber inlet gas S02 concentration is typically about 700 ppm by volume per one weight percent sulfur in the fired coal. For sub-bituminous coal having only 0.7 weight percent sulfur content, the inlet S02 concentration is about 500 ppm, and, for example, the outlet S02 has to be less than 50 ppm to achieve 90 percent removal. In order to avoid serious inhibition of mass transfer because of S02 back-pressure, the equilibrium S02 partial pressure should be about four or more times lower than the actual S02 partial pressure in the gas. Thus, Figure 3 indicates that for this low-sulfur coal system, the scrubber inlet pH should be at least 5.5, and the outlet pH at least... 

Figure 1. M2x pyrograms of a brown coal (R30) (A), its extracted residue (B), and samples of Collie (C) and Amberley (D) sub-bituminous coals. Analytical data in Table I.

The fuel burned in the present experiments was a Utah sub-bituminous coal containing 10.16 percent ash. Its properties are summarized in Table I. 

Lignite (Brown Coal). A brownish-black coal in which the alteration of vegetable matter has proceeded further than in peat, but not as far as in sub-bituminous coal. There is no sharp distinction between these three materials, but in general, lignite is denser, darker in color, and contains more C than peat. Lignite consists of w 9—12, vol comb matter 31—38, fixed C 27—43, and ash 5-20% (Ref 3)... 

Praharaj, T., Powell, M. A., Hart, B. R. Tripath y, S. 2002. Leachability of elements from sub-bituminous coal fly ash from India. Environment International, 27, 609-615. 

Bituminous Coat. Coal that ranks between sub-bituminous coal and semibituminous coal and that contains 15-20% volatile matter. It is dark brown-to-black in color and bums with a smoky flame. Bituminous coal is the most abundant rank of coal and is commonly Carboniferous in age. The most common synonym is soft coal. 

Sub-bituminous Coal. A black coal intermediate in rank between lignite and bituminous coals, or in some classifications, the equivalent of black lignite. It is distinguished from lignite by higher carbon content and lower moisture content... 

The sub-bituminous coals are further classified in terms of their calorific value ... 

Sub-bituminous A Coal—A type of sub-bituminous coal having 10,500 or more, but less than 13.000 Btu per pound (5838-7228 Calories/kg). 

Lignite Coal. A brownish-black coal that is intermediate in coalihcalion between peat and sub-bituminous coal consolidated coal with a calorific value less than 8,300 Btu per pound (4615 Calories/kg), on a moist, mincial-matter-free basis. Synonyms include brown lignite and brown coat. Further classifications of lignite are made on the basis of calorific value ... 

During the Cretaceous period which dates back approximately 100 million years. Deposits include the predominately bituminous and sub-bituminous coal beds in the Rocky Mountain Province, extending in large, separated regions from central Montana into northeastern Arizona and northwestern New Mexico. 

During the Tertiary period which dates back approximately 65 million years. Deposits include the sub-bituminous coal and lignite beds in the Great Plains Province, which includes northeastern Wyoming, eastern Montana, western North Dakota, and northwestern North Dakota. 

Tests on the activity of LP-produced Fe-based nanopowders for liquefaction of a sub-bituminous coal under high (688 K, 1 h of reaction) and low (658 K, 0.25 h of reaction) severity conditions have been reported.38 The catalysts tested were Fe7C3 (92 m2 g 1 (BET), particle size = 17 nm (XRD))and Fe XS (42 m2 g 1 (BET), particle size = 14 nm (XRD).38 For comparison, a commercial superfine iron oxide catalyst (SFIO, supplied by Mach I, Inc.) whose major phase has been identified in one study as y-Fe20339 (surface area = 195 m2 g 1 (BET), particle diameter = 3 nm (XRD)) and in other study as the ferrihydrite40 was also evaluated under similar conditions. The coal liquefaction experiments were carried out in 50 cm3 horizontal microautoclave reactors loaded with 3 g of sub bituminous Black Thunder coal and 5 g of tetralin used as hydrogen donor. Catalyst loadings of 0.7% and 1.4% of as-received coal... 

Samples Preparation. The coal liquids were derived from the catalytic liquefaction of Pittsburgh Seam bituminous and Wyoming sub-bituminous coals. The analysis of these coals is given in Table I. The coals were liquefied in a bench-scale catalytic unit using cyclone overhead product as recycle solvent to insure that the liquid products were derived from the coal and not the solvent. The product streams from... 

Direct Zinc Chloride Hydrocracking of Sub-bituminous Coal and Regeneration of Spent Melt... 

The present paper presents batch autoclave data on the direct hydrocracking of a single sub-bituminous coal from the Powder River basin of southeastern Montana. Comparative data were also obtained with the Pittsburgh Seam bituminous coal that was used in the previous work (I). Data on the regeneration of simulated spent melts from such an operation are also given in a continuous bench-scale, fluidized-bed combustion unit. 

Attempts to run with the sub-bituminous coal at the above mild conditions without a vehicle were not successful because a high viscosity mix formed which made temperature control very poor and yielded erratic results. 

The addition of a hydrogen-donor solvent to the sub-bituminous coal at these mild conditions, appears to assist in melting the coal to permit access of the molten halide catalyst. 

The total liquid yield, i.e.y C4 through MEK soluble hydrocarbons at these mild conditions, is almost as high with the sub-bituminous coal... 

If the temperature and pressure are increased, then a vehicle is no longer necessary even with the sub-bituminous coal. A series of experiments was carried out without a vehicle using a hydrogen partial pressure of 205 atm and at temperatures ranging from 370° to 427°C. The zinc chloride/moisture free (MF) coal feed ratio and the reaction time were held constant at 2.5/1 and 60 min, respectively, in these runs. 

We believe, based on the results just presented and on other results, that fluid-bed combustion provides a workable process for regenerating zinc chloride from direct hydrogenation of western sub-bituminous coals. Other work not presented here indicates that the process can also be applied successfully to melts from direct hydrogenation of eastern bituminous coals. The process is restricted, however, to coals having relatively low sodium and potassium contents so that economically prohibitive amounts of chlorine are not lost to these alkali metals. Lignites are the major type of coal that would be ruled out by the above restriction. 

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