Bondaletova Victoria

Faculty of ecology and chemical technology

Speciality: Chemical technology of fuel and carbon materials

Theme of master's work:

Possibilities of optimization of coal blends on the basis of the Donetsk coal

Scientific adviser: doctor of chemical sciences, professor Butuzova Ludmila

Abstract

Introduction

Actuality of the topic. Index of sulfur is one of the key index of quality in determining the suitability of coal for different use, primarily in the processes of semi-coking and coking. Sulfur affects the quality of coke, as in the smelting it passed into iron goes making it brittle, and steel received from it is - red-brittle. The raw material base of Donbass as well as Ukraine in whole is characterized by low content of sulfur coals of such grades as C, F, OC and other coals. The composition of the coals let use them in coal blends and obtain coke of the specified quality. Existing methods of preparation and desulphurization of coal concentrates, as well as the introduction of new technologies in the coking process at this stage of industrial development can solve this problem only partially [1]. In this connection, the task of ensuring the required quality of coke in the existing coal resources base is very urgent. It is possible to realize with elaboration of rational variants compilation with the inclusion of coal blends of coals of different genetic types of reconstruction. It is planned to study the effect of the additions of various carbon-containing compounds on the caking behavior of the coal blends and the processes of redistribution of sulfur in the pyrolysis products. Now, the reduction rates of coal is not paid sufficient attention, however, it affects significantly on the behavior of coal in the coal blends in the process of thermal destruction, the output of the plastic layer which is responsible for caking. More complete knowledge about the structure of sulfur coals will allow more effectively to use them.

The object of this study is the coals of the Donetsk Basin grades of F and G, the blends on their base with various combinations of components low-reduced (Flrc, Glrc) and reduced (Grc, Frc) types.

The aim of researching is to investigate the possibility of forming coal blends with a high content of sulfur components and the minimum share of caking coals.

Supposed scientific novelty of this work is the optimization of coal blends content reducing the sulfur content of coal by introducing carbon-containing additives.

Experimental

In this work you can find the researching of the yield of liquid, gaseous and solid products of pyrolysis of isometamorphic pairs of coal of different types on reconstruction by using the thermal filtering method. The advantages of this method:

1) for thermal destruction in a centrifugal field the destruction products do not come into a secondary interaction;

2) this is the only method that allows to separate liquid non-volatile components from the coal plastic mass.

The batch of coal blends weighing 6g is placed into the receiver, which is the glass vessel and covered with a filter mesh. On this mesh we download a sample of coal. After that the coal is covered with a circle of filter paper, which then it is layed by a sheet of asbestos. Then, the vessel is placed in the porcelain socket and then into the tubular furnace, which provides heat to 600^оC for 12 minutes [2].

The essence of this method, intended for studing the caking coal is that a plastic system test caking coal is filtered through a metal grid under the action of centrifugal forces of intensifying the rheological processes runoff in many times. When applying the centrifugal field, liquid non-volatile components of plastics, with high fluidity are forced to pass through a layer of coal and then through the mesh filter in the receiver, but the formed hard (high viscosity) residua of the thermal destruction of coal retained on the grid. Volatile products of thermal destruction of coals (gases and vapors) under its own pressure as education are removed from the loading cartridge to the atmosphere [3].

To investigate we used coals of the Donetsk Basin of Zentralnaya (Glrc), Dimitrova (Grc), Zasyadko (Flrc, Frc) mines.

Table 1 shows the characteristics of the coal.

Table 1 – Characteristic of initial coals

As it can be seen from the table, coal reduced type («rc») have higher sulfur content comparing with low-reduced coals. The results are shown in Table 2.

Table 2 - There is the output of products from gas and fat coals of different genetic types of reduction and blends based on them, %

The obtained data show that at each stage of metamorphism, types of reduction have a different effect on the yield of products, that is why each brand nuds a separate study. Type of reduction affects significantly on output of liquid mobile products which are responsible for caking. Thus, the reducted gas coal has of the output of the liquid phase in 3-4 times lower, and the reduced fat, coal on the contrary, has an the output of liquid mobile products in 25% higher than their isometamorphic couples. The output of the solid residue from the Grc increases on 8%, and of Frc decreases almost on 19%. The output of steam and gas phase from the gas coal is practically unchanged, the output of the reduced fat coal is decreadsed on 6% in comparing with low-reduced coals.

Then, we study classical coal blend with a ratio of 70:30 fat coal to gas coal. Blends were prepared with different combinations of low-sulfur and sulfur components. The obtained data shows that the combination of coal grades Frc and Glrc is optimal, because it gives the highest yield of liquid mobile products. In comparing with the blend Flrc+Grc the output liquid mobile products is increasing almost in 16%. This picture shows that we can not take into account the type of reduction.

Then, in the laboratory the various options for the above pointed blend: were compiled and analyzed, differing in ratio of coal grades Frc and Glrc in order to establish the optimum composition. Also we calculated a theoretical yield of the products on the rule of additivity on the formula:

S=a*W(a) + b*W(b),

where S - the yield of products,%;

             a, b - the yield of products of the components of the blends,%;

             W (a, b) - the contents of these components in the blends, the portions.

The results are presented in Table 3. Table 4 presents a theoretical yield of products calculated by the rule of additivity.

Table 3 - The output of products at different ratios of coals and brands Frc and Glrc, %

Table 4 - Theoretical yield of products, calculated by the rule of additivity, %

As we can see from the table, the experimental data on the yield of products are not additive to the theoretically calculated. It is evidence of chemical interaction between components of the blend. The graph shows dependence of the output liquid mobile products from the ratio of components.

From these data we can conclude that:

- there is interaction between components of the blends, which has a minimum at 50:50 and a maximum at 40:60;

- for blends, containing more than 50% of coal Frc, interaction leads to decreasing of the yield of liquid mobile products by increasing the yield of solid residue in comparing with theoretically calculated;

- for blends, containing less than 50% of coal Frc, interaction leads to of decreaseing of the yield of liquid mobile products, but to a greater extent by increasing the yield of gaseous products.

Conclusions

It is found that the blend with a ratio of components Frc:Glrc = 50:50 is optimum in terms of getting liquid mobile products. When this ratio is:

- the yield of products is close to the output obtained with a ratio of 70:30;

- sulphur in the coke will be considerably less, because of high proportion of low-sulfur coal Glrc.

Next I am planning to study the composition of the blend by the extraction method and gas chromatography-mass spectrometry, and also to investigate the effect of various additives on the redistribution of sulfur in the pyrolysis products in selected blend.

List of references

1. Маковский Р.В., Семковский С.В., Бутузова Л.Ф. Исследование шихт на основе сернистых углей. Охорона навколишнього середовища та раціональне використання природних ресурсів/ Збірка доповідей VIII Міжнародної наукової конференції аспірантів і студентів. Т. 2 - Донецьк: ДонНТУ, ДонНУ, 2009. - с. 168-169.
2. ГОСТ 17621-72. Угли каменные. Метод определения выхода жидкоподвижных продуктов из пластической массы угля.
3. Бирюков Ю.В. Термическая деструкция спекающихся углей. – М.: Металлургия, 1980. – 120 с.