Volatile yields from bituminous coal

Some methane is manufactured hv the distillation of coal. Coal is a combustible nick formed from the remains of decayed vegetation. Ii is ihe only rock containing significant amounls of carbon. The elemental composition of coal varies between 60% and 95% carbon. Coal also contains hydrogen and oxygen, with small concentrations of nitrogen, chlorine, sulfur, and several metals. Coals are classified by the amount of volatile material they contain, that is. by how much of Ihe mass is vaporized when the coal is healed to about 900 C in the absence of air. Coal that contains more than 15% volatile material is called bituminous coal. Substances released from bituminous coal when it is distilled, in addition to methane, include water, carbon dioxide, ammonia, benzene, toluene, naphthalene, and anthracene In addition, the distillation also yields oils, tars, and sulfur-containing products. The non-volatile component of coal, which remains after distillation, is coke. Coke is almost pure carbon and is an excellent fuel, However, it may contain metals, such as arsenic and lead, which can he serious pollutants if ihe combustion products are released into the atmosphere. 

Figure 7. Effects of pressure and coal particle size on yields of total volatiles, tar plus hydrocarbon liquids, all hydrocarbon gases, and methane, from bituminous coal pyrolysis. Heating rate = 1000°C/sec. Temperature = 1000°C. Isothermal holding time = 2-10 sec. Particle diameters, ixm C) 74 (X) 297-833 (O) 833-991 (14).

It has been known for some time that the yields of desirable products from coal liquefaction can be enhanced by dispersing the hydrogenation catalyst into the coal. For example, in the liquefaction of a high volatile bituminous coal, the total conversion to tenzene-soluble material, the asphaltene (hexane-insoluble), and oil yields were all enhanced when the catalyst was impregnated into the coal rather than mixed with the coal as a dry powder (2). In that work, impregnated salts of iron. 

The rank of coal (maturity) is an important factor that affects PAH emissions from residential combustion. PAH emission from various coals is found to have a relationship with their volatile contents, and the complete combustion of coals with a high volatile content is more difficult to achieve. Bituminous and sub-bituminous coals with high volatile content yield more PAHs when burned at low temperatures, such as residential combustion, while anthracite coal containing very little volatile matter can burn more completely and emit PAHs with a mass that is three orders of magnitude lower than bituminous coal. Smoky coal, which is burned as fuel for cooking and heating in unvented homes, produces combustion emissions composed primarily of parent PAHs and alkylated PAHs. 

Low sulfur fuel oils were prepared from a high volatile bituminous coal by hydrogenation under high temperatures and pressures. At a coal conversion of 80%, the ratio of oiU to-gas yields was about three, and 23% of the coal sulfur was contained in the oil. Sulfur content of the oil, however, remained the same at different coal conversion levels. The data obtained in the semi-continuous, dilute phase hydrogenation system showed that the whole oil can be directly used as a fuel oil where 1% sulfur is tolerated. Fuel oils containing 0,5 and 0,25% sulfur were produced by desulfurization of the whole oil, A preliminary economic evaluation indicated that low sulfur fuel oils can be produced from coal by hydrogenation at a manufacturing cost of about 5-6 per barrel. 

When the concentrates of macerals of a high-volatile bituminous coal were irradiated with 6-J pulses from a ruby laser the total gas yield varied directly with volatile matter (13.4—55.4 rtiaf%) of the macerals273). Major gases evolved were H2, CO and C2 H2 their relative concentrations varied little among the macerals. 

Bituminous coals are those richest in volatile matter and make the best coking and gas coals. In high-grade coke, the volatile content of the coal ranges from 25 to 30%. The sulphur content is higher for second-grade coke. Coking coals may yield from 50% to 80% coke. 

In contrast to the results obtained with bituminous coals, the weight-loss curve of subbituminous coal exhibited no peak instead, it reached a plateau in Figure 2. From 800° to 1000°C the volatile yield remained level at about 42 wt % of the coal. Beyond this region the production of volatiles increased sharply. The fact that the devolatilization curve of subbituminous A coal differs distinctly from those of bituminous coals indicates a need for further study of other subbituminous coals and lignites. Low rank materials such as these are of interest in coal gasification because their reserves are abundant and because they are situated in deposits with shallow ground cover. 

In general terms, lignite and anthracite coals appear to contain much lower proportions of the volatile organic componnds (10) than the bituminous coals, although alkaline extraction of lignite (and bituminous coal) will yield organic acids of various types that can be characterized. On the other hand, the hexane-soluble portion of the pyridine extracts that were obtained at 50°C (120°F) from coal (carbon content 83.6% w/w) have been identified as alkylated chrysenes as well as alkylated picenes in addition to a mixture of C2g, C29, and C30 paraffins. There were also indicates of the presence of an alicyclic or methyl-substituted five-ring (cat-condensed) system as well as l,2,5,6-dibenzanthracene(s) (Table 10.1). 

The yield of volatile matter in this process is a function of the coal type and ranges from approximately 20% w/w of the coal for a low-volatile bituminous coal to somewhat more than 55% w/w of the coal for a high-volatile C bituminous coal subbituminous coals may not show a volatile matter peak with increasing temperature. In addition to tarry products, the rapid pyrolysis of coal produces gases such as hydrogen, methane, and carbon monoxide as well as lesser amounts of hydrocarbons. Pyrolysis of coal is generally defined as the thermal decomposition of coal in the absence of air or other added substances. 

Where MVY is maximum volatile yield (percent), and VMpj is volatile matter measured in a standard proximate analysis. The r for this equation is 0.945, over a suite of 10 fuels ranging from fresh sawdust to petroleum coke and including lignite, PRB, western bituminous, Illinois basin, and Pittsburgh seam coals. Using this equation the maximum... 

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