Reproducibility of plastic measurements: The need to modify State Standard GOST 1186-87

A very important characteristic of coking coal is its clinkering ability, i.e., its ability to form a nonvolatile solid residue, consisting of disparate grains, on heating in specific conditions. The clinkering ability of the coal is determined by the properties of its plastic mass. Various methods may be used to evaluate the plastic-ductile properties of the coal. However, since the 1930s, the main method used to evaluate the clinkering properties of coal, within the nations of the former Soviet Union, has been the Sapozhnikov-Bazilevich plastometric method, because it provides more information than competing approaches. For the same reason, the thickness of the plastic layer, which is one of the parameters determined by this method, is used for coal classification in State Standard GOST 25543-88 (Lignite, Coal, and Anthracite: Genetic and TEchnological Classification) and its Ukrainian counterpart DSTU 3472-96 (Lignite, Coal, and Anthracite: Classification). This explains the strict requirements on the accuracy and reliability of the plastometric characteristics.     

Use of laser interferometers for measuring displacements of the surfaces of tested objects

A mathematical model and the results of the numerically simulated procedures of measuring displacements of tested objects’ surfaces with the use of laser interferometers are presented. Promising measurement techniques are substantiated, and recommendations for their use are given.     

Convergence and reproducibility in State Standard GOST 1186-87

Factors affecting plastometric measurements for coal are considered. The need to revise State Standard GOST 1186-87 is discussed.     

Effect of the conditions of sintering of sodium-reduced tantalum powders on their characteristics

The effect of the granulation and heat treatment of sodium-reduced tantalum powders with a specific surface area of 2.5–3.6 m²/g on the bulk density, the powder flow time, and the specific surface area of the powders and the specific capacitance of the anodes made of them is studied. It is shown that heat treatment of a granulated powder in vacuum at 1100°C or in a mixture with magnesium at 800°C makes it possible to achieve the required powder flow time.     

Relation between the maximum moisture content of coal and its porous structure

Seven coal samples and two anthracite samples are subjected to technical, petrographic, and elementary analysis. The maximum moisture content and total pore volume (for water) in the samples are determined. There is a linear relation between the maximum moisture content and total pore volume. The corresponding correlation coefficient is 0.99, and the coefficient of determination is 98.1%. The relation of the coal porosity with the yield of volatiles and the carbon content in the coal’s organic mass (characterizing its metamorphic stage) is assessed. The corresponding correlation coefficient is 0.86–0.98, while the coefficient of determination is 73.8–95.6%.     

Determining deformation and strength of a filling mass during stoping by the inverse problem solving

The authors have developed a method for quantitative estimation of filling mass deformation and strength characteristics in the course of stoping at sheet ore deposits by the in situ measurements of relative displacements of points at the mined-out stope boundary. The article also analyzes the structure of objective functions of the formulated inverse coefficient problems for the elastic-plastic rock deformation model, and examines their solvability.     

Ignition temperature of coal 3. Multicomponent coal mixtures

The ignition temperature of three-component mixtures is determined. The mixtures contain coal of different metamorphic development, in various proportions. It is found that the actual ignition temperature differs from the values calculated on the basis of the sum rule; the actual ignition temperature is lower. A formula is derived for predicting the ignition temperature of three-component and multicomponent mixtures.     

Lignite oxidative desulphurization: notice 3—process technological aspects and application of products

International Journal of Coal Science & Technology - The study reviews the process of oxidative desulphurization of high-sulphur Ukrainian lignite, which was performed by coal treatment using...     

Oxidation of coal in industrial conditions. 1. Kinetics of natural oxidation

In the light of research on the artificial oxidation of coal in the laboratory, earlier results on the natural oxidation of coal in open storage at different coke Ukrainian plants are analyzed. On the basis of the kinetics of coal oxidation in natural conditions, the need to correct existing standards for open storage is evaluated. Since the dependence of the degree of oxidation d _o on the storage time is sigmoid, the results are analyzed on the basis of the Avrami-Erofeev equation for the kinetics of heterogeneous reactions. The constants of that equation and the rate constants of oxidation are calculated for enriched coal of different ranks (G, Zh, K, and OS) in summer and winter. The influence of the degree of metamorphism on the rate constant of natural oxidation in summer and winter is mathematically described. On the basis of the Avrami-Erofeev equation, limiting open-storage times for the coal are established. The earlier limiting storage times must be corrected.