Journal of Environmental Biology

CO₂ emission of coal spontaneous combustion and its relation

with coal microstructure, China

Haiyan Wang*, Chen Chen, Tao Huang and Wei Gao

Faculty of Resources and Safety Engineering, China University of Mining and Technology (Beijing), Beijing-100 083, China

*Corresponding Author?s E-mail: whyhyp@163.com

Publication Data

Paper received:

28 January 2015

Revised received:

08 April 2015

Accepted:

06 June 2015

Abstract

Coal spontaneous combustion is widely distributed all over the world. CO₂ is the main greenhouse gas emitted by coal spontaneous combustion. In the present study characters of CO₂ emitted by 10 typical Chinese coal spontaneous combustion and the influence of raw coal functional group on CO₂ was studied. CO₂ already exists under normal temperature as coal exposed in atmosphere. Under low temperature, the quality of CO₂ released by coal spontaneous combustion is relatively small, but tends to increase. And corresponding with it, the oxygen consumption amount is also small. At medium temperature, the oxygen consumption increases rapidly and CO₂ mass release rate begins to increase rapidly. Then, CO₂ release rate increase rapidly under relatively high temperature (higher than 673K). Over 873K, concentration of O₂ is 6% and release rate of CO₂ tends to be steady. It also concluded that mass ratio of CO to CO₂ (CO/CO₂) during coal spontaneous combustion was lower than 0.10 at low temperature. And then, it increased rapidly at medium temperature and reached to top at about 673K. At 673-873K, the ratio decreased again, and did not decrease evidently at about 873K. At temperature higher than 873K, the ratio was about 0.13. During the whole testing temperature range, CO/CO₂ was not be higher than 0.26, lower than 0.2. This means that release rate of CO₂ was much higher than CO during the whole process of coal spontaneous combustion. Moreover, the gas release quantity of CO₂ is positively related with carbonyl content in raw coal. Carbonyl and carboxyl were both material basis of CO₂.      

 Key words

Coal, Functional group, Greenhouse gas, Mass release rate, Spontaneous combustion 

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