A comparative study of extracts from liquid-fixed products of deoxidated in different degree coals J and G, and mixed materials on their basis has been conducted. The results of gas-chromatography-mass-spectrometry allow to suppose that caking is connected not only with the end-of-centration of polycyclic aromatic hydrocarbons in alifatical and aromatic fractions of neutral oil..
Coking is the most large-scale industry of coal thermic processing. Coal must possess a number of specific properties, among which the main thing is caking. Indispensable condition of caking coal is its ability of transition during the heating to a plastic state. At one stage of thermal degradation of coal are formed substances in liquid-floating state. Together with the solid residue and gas-shaped products of degradation, they form a complex system that it is plastic coal mass, which is a heterogeneiting system and formed from coking coal at a temperature of 350 °C, consisting of continuously changing with increasing temperature of different solid, liquid (non-volatile) and steam (fixed) products.
The nature of the coal components providing their transition in a tough fluid, plastic state, is not investigated enough. The currently used methods for characterizing the plastic mass can't permit to solve this problem since they are based on the determining of thickness of the plastic layer and its viscosity, the resistance rate of the metal plate is loaded in the coal and other physical properties [2]. At the same time in the 20-th of the last century, Fischer and other researchers have suggested that the answer to this phenomenon should be found by extracting and studying products of coals dissolution in organic solvents.
The aim of this research paper is a comparative study of the composition of the extracts of liquid non-volatile products (LNP) of thermal filtration of gas and coals deoxidated in different degree, as well as their charge, in order to identify the compounds responsible for the sintering process. Mark J is an indispensable component of the base coke production, and the Mark G is a component of low caking (Table 1).
| Mine | Mark of coal plast |
Type | Technical analysis, % | Elemental analysis, % daf | |||||
| Wa | Ad | Sdt | Vdaf | C | H | O+N | |||
| Central | G, k7 | a | 2,2 | 5,2 | 1,22 | 36,0 | 85,1 | 5,11 | 8,71 |
| Dimitrova | G, l1 | b | 2,1 | 4,4 | 2,49 | 38,7 | 83,8 | 5,34 | 9,50 |
| Zasyadko | J, l4 | a | 1,4 | 2,6 | 1,09 | 31,6 | 87,8 | 5,16 | 7,00 |
| Zasyadko | J, k8 | b | 0,8 | 2,7 | 2,81 | 31,7 | 87,3 | 5,23 | 7,20 |
The experimental part
The following standard methods of research are used in this paper: method thermal filtration (GOST 17621–89), technical (GOST 11014–89, 11022–95, 2059–95, 6382–91) and elemental (GOST 2408.1–95) analysis.
The separation into components LNP was performed in the following way: the water was removed, then asphaltenes, carbenes, carboids were separated. The substance soluble in hexane was separated into a base-carboxylic acidies, phenols, neutral oil by sequential treatment with 10 % H2SO4, 3 % NaHCO3, 5 % NaOH. The neutral oil was chromatographed on silica gel using as eluent hexane, benzene or acetone and subsequently recovered paraffinic-naphthenic, aromatic and polar hydrocarbons. The neutral oil extracts coal by gas-chromatography-mass-spectrometry is studied in this paper.
Figure 1 presents a comparative composition of the main combinations defined in fractions of neutral oils studied coals.
Figure 1 shows that the content of alkanes in gaseous coals of various types of reduction is by 42–46 %, and it is 10 times bigger than the content
of these compounds in the fatty coals. The content of the charge coal alkanes ranging from 31–43 % depending on the gas content of coal %. Biphenyl content
in coal gas is up to 1 %, but the type of fat a
is 13,63 %. The content of fatty biphenyl type b
is 2
times lesser — 7,72 %. In the charge-holding biphenyls is up to 1 %. Essential components are connected with the number of rings from 1 to 5,
most of which are alkyl-substituted.
Figure 1 — The comparative composition of the basic compounds of neutral oils, extracted from coal and LNP of coals and batches deoxidated in dif-ferent degree
The comparison of LNP exit, the concentration of PMC in it and the result of GC-MS for the pair of fatty and gas coals (Table 2) all this allow us to conclude that sinterability is associated primarily with the presence of LNP PAH, anthracenyl, fluorenyl, phenanthrenes and biphenyls which are presented mainly in the form of alkyl compounds containing 1–4 substituents.
It is known from the literature that the stability of radicals depends on the spatial effects and delocalization of the unpaired electrons in the system of polyconjugation.
Previously, it is shown that caking coal is associated with the presence of high concentrations LNP PMC [3]. These data are consistent with well known views that the PMC coals are stably free radicals of aromatic nature. In the condensed system of unpaired rings the electron is stabilized by resonance energy. This increases the stability of the PMC with the increasing of polyconjugation system.
| Coal | Ga | Gb | Ja | Jb | |
| N, spin/g x 10-17 in LNP | 38,5 | 1,8 | 114,9 | 159,9 | |
| Exit and composition of LNP, % |
Exit of LNP | 12,44 | 4,28 | 21,33 | 39,28 |
| Absolute content of components in the neutral oil ofLNP, % |
Alkylated PAH | 8,40 | 11,92 | 13,95 | 20,14 |
| Total PAH | 10,23 | 13,12 | 15,57 | 21,47 | |
| Alkylated benzene-fluorenyl, fluorenyl (R = 1 ÷ 3) |
5,73 | 0,51 | 3,61 | 2,27 | |
| Total fluorenyls | 6,71 | 0,57 | 3,61 | 2,27 | |
| Alkylated anthracenes + phenanthrenes (R = 1 ÷ 4) |
6,76 | 3,72 | 16,70 | 12,62 | |
Total anthracenes + phenanthrenes
| 7,07 | 4,07 | 18,83 | 13,50 |
|
Taking into account the connection between the emission and the concentration of PMC LNP in them, and the results of GC-MS of neutral oils, it can be argued that the formation of the plastic layer in the mesophase radicals formed by following types: diphenylmethyl, fluorenyl, fenilnaftil, phenoxy and others. Number of fluorenyl radical of fenilnaftil type based on alkyl-substituted anthracenes, phenanthrenes Gb is significantly lower than other coals. The comparison of the substitution's degree of given radicals indicates that it is significantly lower in comparison with Gb to Ga — fenilnaftalines, anthracenes, and phenanthrenes, it is possible to assume that Gb radicals are less stable.
Table 3 presents a comparison of LNP emission concentration with PMC results of GC-MS for batches deoxidated in different degree.
The results of analysis show that the proportion of charge extracts Ja + Ga 70/30 differ by 6 % lower yield of nonvolatile liquid products with PMC lower concentration and lower alkylated PAH content of almost two times compared with the batch of Jb + Ga 70/30.
| Coal | Ja + Ga | Jb + Ja | |
| N, spin/g x 10-17 in LNP | 43,1 | 114,4 | |
| Exit and composition of LNP, % |
Exit of LNP | 20,71 | 26,19 |
| Absolute content of components in the neutral oil of LNP, % |
Alkylated PAH | 3,93 | 10,70 |
| Total PAH | 6,03 | 14,33 | |
| Alkylated benzene-fluorenyl, fluorenyl (R = 1 ÷ 3) |
9,27 | 9,80 | |
| Total fluorenyls | 10,47 | 13,00 | |
| Alkylated anthracenes + phenanthrenes (R = 1 ÷ 4) |
5,65 | 4,9 | |
Total anthracenes + phenanthrenes
| 5,98 | 5,13 |
|
Although it is the significant increase in content of fluorene in LNP batches extracts, especially in charge Jb + Ga, where the rate increased by 2–4 times compared with extracts of raw coals.
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