Subbituminous rank

Moscow wood is more similar to coalified wood of subbituminous rank than it is of coalified wood of lignite rank, assuming that its lignin was originally similar to lignin in Cretaceous or younger woods. 

Long), are shown in Figure A. Construction lines like OAB suggest that the coals were around subbituminous rank before intrusion in the complete sequence of seams in the coal measures there might have been a range of rank from high rank lignitous to subbituminous, or subbituminous to very low rank bituminous. 

This classification does not include a few coals, principally nonbanded varieties, that have unusual physical and chemical properties and that come within the limits of the fixed-carbon or calorific value of the high-volatile bituminous and subbituminous ranks. All of these coals either contain less than 48% dry, mineral-matter-ffee fixed carbon or have more than 15,500 moist, mineral-matter-free British thermal units per pound. 

Huminite/vitrinite macerals are derived from humic substances, the alteration products of lignin and cellulose. Huminite refers to macerals in lignite and subbituminous rank (see the following) coals (S korovd et al, 2005), and vitrinite to maceral of bituminous and anthracitic ranks. 

CP/MAS NMR study of Baganuurcoal, Mongolia Oxygen-loss during coalification from lignite to subbituminous rank. 2010 82 37-44. 

Coals (the plural is deliberately used because coal has no defined, uniform nature or structure) are fossil sources with low hydrogen content. The structure of coals means only the structural models depicting major bonding types and components relating changes with coal rank. Coal is classified, or ranked, as lignite, subbituminous, bituminous, and anthracite. This is also the order of increased aromaticity and decreased volatile matter. The H C ratio of bituminous coal is about 0.8, whereas anthracite has H C ratios as low as 0.2. 

Conversion of carbon in the coal to gas is very high. With low rank coal, such as lignite and subbituminous coal, conversion may border on 100%, and for highly volatile A coals, it is on the order of 90—95%. Unconverted carbon appears mainly in the overhead material. Sulfur removal is faciUtated in the process because typically 90% of it appears in the gas as hydrogen sulfide, H2S, and 10% as carbonyl sulfide, COS carbon disulfide, CS2, and/or methyl thiol, CH SH, are not usually formed. 

The tiansition from a choice of multiple fossil fuels to various ranks of coal, with the subbituminous varieties a common choice, does in effect entail a fuel-dependent size aspect in furnace design. A controlling factor of furnace design is the ash content and composition of the coal. If wall deposition thereof (slagging) is not properly allowed for or controlled, the furnace may not perform as predicted. Furnace size varies with the ash content and composition of the coals used. The ash composition for various coals of industrial importance is shown in Table 3. 

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%. 

Aromaticity of coal molecules increases with coal rank. Calculations based on several models indicate that the number of aromatic carbons per cluster varies from nine for lignite to 20 for low volatile bituminous coal, and the number of attachments per cluster varies from three for lignite to five for subbituminous through medium bituminous coal. The value is four for low volatile bituminous (21). 

Fig. 11. Effect of coal rank on furnace sizing (constant heat output) (82), where W = width, D = depth, and h and H are the heights indicated. A represents medium volatile bituminous B, high volatile bituminous or subbituminous C, low sodium lignite D, medium sodium lignite and E, high...

In absolute terms, the quantities of reactor solids found in various processes do vary considerably. The rate of accumulation is related to several factors, such as coal characteristics, recycle solvent quality and reactor design. However, it can be stated in general terms that liquefaction of low rank coals (sub-bituminous C and lignites) does result in higher rates of accumulation of solids than do similar operations with bituminous coals. For example, during normal operations of the SRC-I pilot plant at Wilsonville, Ala., it has been found that the amount of solids retained varies from about 0.2-0.5 wt.% (moisture-free) for bituminous coals to 1.0-1.9 wt.% (moisture free) for a subbituminous C coal (Wyodak) (72). Exxon also reports much larger accumulations for lignites and subbituminous coals than those found for bituminous coals (73). 

Subbing formulations, gelatin in, 12 444 Subbituminous coal, 6 703 classification by rank, 6 1 lit defined, 6 829... 

The phenol, the cresol isomers, and the dimethylphenols, major pyrolysis products in e Moscow wood sample, are probably also derived frt>m lignin precursors that have been altered through coalification reactions. Hatcher [fr] have shown that an increase is observed in the relative proportion of phenols and cresols as rank of coaHfred wood samples increases to subbituminous coal. Comparing the distribution of pyrolysis products from the Moscow wood to that of other coalified wood samples of Hatcher allows us to deduce that the... 

Coals covering a range of rank downwards from low-volatile bituminous were examined in solvent-free catalytic hydrogenation over the temperature range 300-400°C and for reaction times up to 60 min. The work discussed here specifically Involved four coals which were obtained form the Penn State Coal Sample Bank. These were a subbituminous coal PSOC-1403, and three hvAb bituminous coals, PSOC-1168, PSOC-1266 and PSOC-1510. 

Over the initial period of conversion, it was also observed that only small quantities of light hydrocarbon gases were produced. The liberation of carbon oxides, principally CO2, was more facile. For both subbituminous and bituminous coals, the yields of CO2 realised at 300 C were significant, although much higher for the lower rank coal (8.9). 

The proof of the influence of time on the rank of coal can be found in the following comparison Kuyl and Patijn (13) have described subbituminous... 

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