Experimental study on the thermal properties of coal during pyrolysis, oxidation, and re-oxidation

Study on the characteristics of coal spontaneous combustion during the development and decaying processes

A new kind of compound material—foamed gel composed of compound foaming agent (CFA) and high water absorbency gel (HWAG) and formed by physical and mechanical stirring—for controlling the spontaneous combustion of coal in coal mine was researched and developed. It makes use of the all-around properties of foam and gel to control the spontaneous combustion of coal in coal mine. The composition, preparation, and controlling mechanisms of foamed gel were analyzed. To optimize the characterizations of the foamed gel, the optimal CFA concerning foaming ability and mixed ratios of single foaming agents, mass concentration, and salt-resistance performance as well as the optimal HWAG concerning optimal synthesis parameters, Fourier transform infrared spectroscopy, thermogravimetric property, and foam stability were analyzed. Meanwhile, characterizations including microstructure and controlling spontaneous combustion of coal of foamed gel were studied. The results were best when the mass fraction of compound of modification alkyl polyglucoside (APG) and sodium dodecyl sulfate (SDS) is 0.9%, the mixed ratio of APG versus SDS is 4:1, the mass fraction of HWAG is 0.4%, and methylenebis acrylamide concentration, ammonium persulfate concentration, and mass fraction ratio of soluble starch:acrylic acid of HWAG synthesis are 0.05%, 0.5%, and 1:10, respectively. This is the ideal foamed gel. The success preparation of foamed gel and the microstructures differences between CFA and foamed gel are confirmd by the microstructures analysis results of CFA and foamed gel simultaneously. Moreover, foamed gel can effectively seal air leakages, prolong moisturizing time of coal, markedly enhance cooling effect on coal of moisture, and efficaciously reduce the rate of coal oxidation reaction and the heating rate to control the spontaneous combustion of coal in coal mine.

Research and development of foamed gel for controlling the spontaneous combustion of coal in coal mine

The effect of oxygen concentration on the non-isothermal combustion of coal

As a harmful gas in underground coal mine, CO seriously threatened the safety of miners. Currently, the spontaneous combustion of residual coal in goaf is generally considered as the main source of underground CO. CO gas is also widely used as an indicator gas in fire prediction in mines. However, high concentrations of CO are also detected in some mines without spontaneous combustion of coal. Therefore, in the paper, with four ranks of coal, we studied other two potential CO sources: crushing and oxidation at ambient temperature. The more completely crushed coal produces more CO. The concentration of generated CO is inversely proportional to moisture content in coal. Therefore, the addition of water can inhibit the generation process of CO during the crushing process of coal. Lignite with low metamorphic grade can be oxidized to produce CO at ambient temperature (25 °C), and anthracite with high coal rank can be only oxidized to produce CO at 60 °C. Infrared spectra indicated that the coal with rich aliphatic hydrocarbons and oxygen-containing functional groups are more susceptible to oxidation at room temperature. Moreover, the smaller particle size of coal is more beneficial to the oxidation at ambient temperature to generate CO. CO generation during coal oxidation is also closely related to the ventilation rate.

Sources of underground CO: Crushing and ambient temperature oxidation of coal

Experimental Study on Characteristic Parameters of Coal Spontaneous Combustion

Fire development is influenced by many factors, such as oxygen concentration, external radiation, and the inclination angle of the combustible material. This article examines the effect of these fa...

Flame Spread on Inclined Wood Surfaces: Influence of External Heat Flux and Ambient Oxygen Concentration

The Influences of Key Factors on the Consequences Following the Natural Gas Leakage from Pipeline

To simulate the release consequence, a modified Gaussian plume model considering plume rise and ground roughness is proposed and discussed. Based on it, a case of toxic ammonia release is presented, in which spatial concentration distribution of ammonia is predicted and expressed as a concentration contour map. The maximum downwind and crosswind distance as well as area of each influenced zone area corresponding to the toxic criteria are simulated in detail. And the difference between this modified model and the traditional model is compared further. Finally, the effects of influencing factors involved in the modified model are also analyzed carefully.

Hongya Zhu

Papers

Experimental Study on Characteristic Parameters of Coal Spontaneous Combustion

Flame Spread on Inclined Wood Surfaces: Influence of External Heat Flux and Ambient Oxygen Concentration

The Influences of Key Factors on the Consequences Following the Natural Gas Leakage from Pipeline

The Simulation of Release Consequence with a Modified Gaussian Plume Model