Rapid subbituminous coal

North America.. In the United States, lignite deposits are located in the northern Great Plains and in the Gulf states. Subbituminous coal is found along the Rocky Mountains. The western half of North Dakota has about 74% of the nation s resources, Montana 23%, Texas 2%, and Alabama and South Dakota about 0.5% each. The lignite resources to 914 m represent 28% of the total toimage of all coal deposits in the United States. The lower cost and low sulfur content have contributed to rapid growth in production. 

Flash hydrogenation is a short residence time (1 to 10 sec) gas-phase, non-catalytic process in which pulverized coal is rapidly heated (20,000-30,000° C/sec) in hydrogen to obtain liquid and gaseous hydrocarbons directly. Experiments were conducted in a 2 lb/hr, 1 ID x 8 ft long downflow tubular reactor in the range of 500° to 900°C and 500 to 3000 psi H2 pressure for North Dakota Lignite and New Mexico subbituminous coal (L). The ultimate analyses of these coals are given in... 

Yields of Preasphaltenes and Asphaltenes. Subbituminous coal is converted very rapidly to soluble products in tetralin at 427°C. Figure 1 shows the yields of THF-soluble but pentane-insoluble, benzene-soluble and pentane-soluble products vs. reaction time. These fractions correspond respectively to a mixture of preasphaltenes and asphaltenes, asphaltenes and oils. Of the 78% ultimate yield of THF-soluble products based on the dry coal containing 8.6% ash, 55-60% are formed within 5 to 10 min of reaction time. By 35 min of reaction time, conversion of coal to soluble products is essentially complete. In contrast to the extremely rapid process of conversion of the parent coal to preasphaltenes, the further degradation of preasphaltenes occurs only very gradually, the yield of asphaltenes increasing from 10 to only 25% over a 1-hr reaction time. 

Figure 2. Devolatilization of subbituminous coal by rapid heating...

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. 

Coals were devolatilized at rates comparable with those encountered in combustion and gasification processes. Rapid pyrolysis was attained with pulse-heating equipment developed for this purpose. This technique permitted control of the heating time and the final temperature of the coal samples. Subbituminous A to low volatile bituminous coals were studied. All bituminous coals exhibited devolatilization curves which were characteristically similar, but devolatilization curves of subbituminous A coal differed markedly. The products of devolatilization were gases, condensable material or tar, and residual char. Mass spectrometric analysis showed the gas to consist principally of H2, CHh, and CO. Higher hydrocarbons, up to C6, were present in small quantities. 

Interferon induction by influenza virus in monkey kidney (LLC-MKj) cell monolayers pre-treated with coal dust was inhibited in relation to coal rank (Hahon 1983). Maximal inhibition of viral interferon induction was noted with high rank coal and the degression of this activity was related to coal s position in the carboniferous series anthracite, bituminous, subbituminous, lignite, and peat. Adsorption of poly(4-vinylpyridine-M-oxide) to bituminous coal dust from the Pittsburgh seam, Cambria County, Pa., not only occurred at a more rapid rate than to cell monolayers, but also less polymer was required to pretreat coal dust than cell mono-layers to achieve comparable amelioration of interferon production (Hahon 1976). 

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