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Autor: Dmitriy Dedovets

Theme: Research of the influence metamorphism stage on overmolecular coal organization

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Efficient coal use is impossible without clear understanding of its structure and characteristics dependable on the structure.

One of the methods, by means of which the study of coal structure is done, is x-ray structured analysis.

The sense of method lies in fact that x-ray radiation with fixed intensity and wavelength known to researcher is passed through a sample revolving with determined angular velocity. While passed the sample x-ray is subjected to diffraction and accordingly its intensity on output will be different, in contrast with source ray. This intensity is recorded with the help of a special counter and the graph of intensity dependence on the angle of the sample tumbling is built. The given graph is called diffractogram or x-raygram. It is necessary to note that there is another way of carrying out this experiment, when the sample under investigation remains at rest but the counter moves with fixed velocity around it. The given way has recently been the most wide-spread. With the help of number of transformations with the received diffractogram and the further calculation using known formula the structure parameters of coal sample under investigation are defined.

Interesting problem from our point of view is not only to study the construction a separate coal sample but first of all to trace the changes in coal structure in the processes as metamorphism and pyrolysis. And if study of the coal structure change in the process of metamorphism is more interesting from academic point of view, but knowledge how the coal is transformed in the process of pyrolysis is important for optimization of the coking process, which is practically not investigated now.
To trace, the influence of metamorphism process on coal structure, a lot of coal samples of different grades were taken, commencing from brown and finishing anthracites.
The method of diffractogram receiving was the following:

1. All coal samples were scanned in filtered copper radiation (CuKα = 0,15418 nm) on DRON-3 under alike mode: accelerating voltage - U = 30 kW; the current on turbine - I = 23 mA; the intensity of the count - 1000 mm/sec; the velocity of the moving the counter - 2 /min; the velocity of the tractor of the diagram tape - 600 mm/hour; the operating slots were the same in all experiments.
2. Scanning of all coal samples was done under the same angle range (2θ°) from 6° to 110°
3. The used velocity of counter moving (2 /min) is the most optimum for amorphous materials.

The received x-raygrams were scanned, digitized (tabulation was done i.e. diffractogram was presented in the form of the table of angles and intensities of the resulting x-ray radiation corresponding to them). Data of digitization was processed by the program, designed by us, and parameters of coal structures were received. The results of calculus are presented in table 1.

Table 1 – Overmolecular organization parameters of researched coal samples

№	Coal sample (mark, layer)	Cdaf	d002	Lc	La	Lc/La	h/l	Cг	n
1	BC, Novomirgorodskiy	65,4	0,413	1,44	5,16	0,28	0,67	0,18	4,49
2	BC, Konstantinovskiy	66,8	0,395	1,55	4,09	0,38	0,57	0,26	4,93
3	BC (Poland)	71	0,413	1,39	5,44	0,26	0,86	0,18	4,38
4	BC, Kansko-Achinskiy	74,3	0,395	1,49	3,66	0,41	0,87	0,25	4,79
5	Дl2	76,2	0,413	1,22	4,46	0,27	0,67	0,16	3,95
6	Дl4	79	0,404	1,37	4,21	0,33	0,99	0,20	4,40
7	Гl3	82,2	0,395	1,51	4,12	0,37	1,67	0,25	4,84
8	Гl1	82,7	0,363	2,51	4,14	0,60	3,09	0,89	7,90
9	Жm2	87,4	0,349	3,55	3,20	1,11	1,44	2,53	11,18
10	Кk8	88,6	0,349	3,96	3,47	1,14	4,38	2,81	12,33
11	ОСl6	88,9	0,349	4,05	4,39	0,92	5,73	2,88	12,60
12	Тh8	90,3	0,342	5,75	2,82	2,03	7,14	7,70	17,78
13	Аh8	93,7	0,349	3,73	7,58	0,49	6,42	2,65	11,69

As it has been shown in the researches, gradual reduction of the nuclear-between distance d002 is occurred in metamorphism process. It is the greatest in the lowmetamorphazed brown coal and the least in the anthracite. The correlation factor between carbon contents in sample Cdaf and nuclear-between distance d002 is equal to r = -0,891 i.e. it is significant for given number of coal samples ( rtable = 0,661 for f = 13 - 1 = 12).

It is important to note the increase in the amount of ranked layers in a pack and, thicknesses of the pack during increase metamorphism degree. This phenomenon in the aggregate with nuclear-between distances reduction is possible to be explained by coal structure order increasing, its similarity to graphite crystalline structure. Package size decreases because the lateral aliphatic fragments are chipped off from aromatic circles during increase of metamorphism degree. Simultaneously this gives the aromatic kernel the chance to become denser which leads to nuclear-between distances decrease and unification into higher packages.