The process leading to spontaneous combustion of lignite from the Kansk-Achinsk basin used for subsequent carbon activation

An increased fire hazard of lignite drives the need to study its propensity to self-combust resulting from possible self-heating, which eventually leads to its ignition. Coals formed by low-grade metamorphism are subject to these dangerous processes to a greater degree. Availability, large reserves and low cost of these natural coals, as well as appropriate physical and chemical properties make them indispensable in carbon activation. Activated carbons, in turn, are employed for carrying out various processes in hydrometallurgy; for removing impurities of inorganic and organic origin from industrial wastewater; for purifying industrial gases. Moreover, activated carbons are used in medicine and other economic sectors. In this study, we determined the kinetic parameters characterising the fire hazard associated with spontaneous combustion of lignite during its treatment in the course of carbon activation. Lignite from a well-known large Irsha-Borodino deposit of the Kansk-Achinsk basin was selected as the object of study. Dispersity was chosen as the main physico-chemical parameter, since its value has a significant impact on the creation of hazardous conditions for self-heating of dispersed materials. In order to choose a research procedure, an analysis of known methods for evaluating the propensity of dispersed substances to spontaneous combustion was performed. Spontaneous combustion of lignite was studied using an improved method of calorimetry, allowing investigation of this process in terms of materials dispersity. The rate of heat release during spontaneous combustion of lignite, as well as the main kinetic parameters (effective activation energy and pre-exponential factor), were determined. The obtained values of the kinetic parameters show that a decrease in the dispersity and consolidation of crushed lignite particles (Irsha-Borodino deposit, Kansk-Achinsk basin) significantly raises the propensity of these coals to self-heating and eventual spontaneous combustion. The obtained results can be used for developing measures aimed at reducing the fire hazard involved in lignite processing technologies employed in the course of carbon activation. Compliance with specific recommendations on controlling the self-heating process and resulting spontaneous combustion can be achieved by forecasting conditions for the increase of coal temperature through controlling kinetic parameters.

spontaneous combustion, lignite, kinetic parameters, calorimetry

1. Agroskin A.A. Khimiya i tekhnologiya uglya [Chemistry and technology of coal]. Moscow: Nedra Publ., 1969, 237 p.

2. Leonov S.B., Elshin V.V., Dudarev V.I., Randin O.I., Oznobikhin L.M., Domracheva V.A. Uglerodnye sorbenty na osnove iskopaemykh uglei [Carbon sorbents based on fossil coal]. Irkutsk: Irkutsk State Technical University Publ., 2000, 268 p.

3. Eremina A.O., Golovina V.V., Ugai M.YU., Rudkovskii A.V., Stepanov S.G., Morozov A.B. Carbon adsorbents from brown coal of the KanskAchinsk basin. Sovremennye naukoemkie tekhnologii. 2004, no. 2, pp. 55. (In Russian)

4. Kol'tsov K.S., Popov B.G. Samovozgoranie tverdykh veshchestv i materialov i ego profilaktika [Spontaneous combustion of solids and materials and its prevention]. Moscow: Khimiya Publ., 1978, 160 p.

5. Kuznetsov P.N., Maloletnev A.S., Ismagilov Z.R. Influence of the Properties of Fossil Coal on Its Tendency to Self-Ignition. Khimiya v interesakh ustoichivogo razvitiya 2016, vol. 24, no. 3, pp. 335–346. (In Russian)

6. Gorshkov V.I., Korol'chenko I.A. Investigation of spontaneous combustion processes. Part I. Pozharnaya bezopasnost'. 2008, no. 1, pp. 68–77. (In Russian)

7. Tursenev S.A., Kibirev A.G. Thermal spontaneous combustion of embankments and sediments of solid dispersed materials. In: Ekologiya, ekonomika, energetika. Mezhvuzovskii sbornik nauchnykh trudov. Vyp. X. «Pozharnaya, promyshlennaya i ehkonomicheskaya bezopasnost'» [Ecology, Economy, Energy. Release X. «Fire, industrial and economic security»]. St. Petersburg: Sintez Publ., 2009, pp. 68–71. (In Russian)

8. Hebden D., Stroud H.J.F. Coal Gasification Processes. In: Chemistry of Coal Utilization. Ed. by M. Elliot. New York: Wiley-Interscience Publ. 1981, pp. 1599–1752.

9. Kashiwagi T. A radiative ignition model of a solid fuel. Combustion Science and Technology. 1973, vol. 8, issue 5, pp. 225–236. DOI: 10.1080/00102207308946646

10. Tognotti L. Self-heating and spontaneous combustion of coal and carbonaceous materials: a method for prediction and prevention. Riv. Combust. 1993, no. 26, pp. 61–62.

11. Butkin V.D., Demchenko I.I. Problems of processing and complex use of Kansko-Achinsk coals. Gornaya promyshlennost'. 2001, no. 1, pp. 3–8. (In Russian)

12. Saranchuk V.I. Okislenie i samovozgoranie uglya [Oxidation and spontaneous combustion of coal]. Kiev: Naukova dumka Publ., 1982, 166 p.

13. Kiselev Ya.S. Thermal spontaneous ignition of dispersed carbon materials with a non-uniform surface. Fizika goreniya i vzryva. 1973, no. 1, pp. 124–127. (In Russian)

14. Weinberg F.J. The significance of reaction of low activation energies to the mechanism of combustion. Proceeding of the Royal Society. Ser. A. 1955, vol. 230, no. 4, pp. 331–342.

15. Amel'chugov S.P., Bykov V.I., Tsybenova S.B. Spontaneous combustion of brown-coal dust. Experiment, determination of kinetic parameters, and numerical modeling. Combustion, Explosion, and Shock Waves. 2002, vol. 38, issue 3, pp. 295–300.