Xiaoxing Zhong

Controlling coal fires using the three-phase foam and water mist techniques in the Anjialing Open Pit Mine, China

Coal fires are a serious environment, health, and safety hazard throughout the world. They damage the environment, threaten the health of people living nearby, burn away non-renewable coal, and result in significant economic losses. In this paper, the characteristics of the ignition and propagation of coal fires are illustrated first. Semi-enclosed environments (loose zones and abandoned roadways) favor the ignition of coal fires. The “upper fire” is pointed out to be prevalent and difficult to be controlled. Furthermore, the advantages and disadvantages of several commonly used techniques for controlling coal fires are analyzed. The three-phase foam and water mist techniques are believed to be effective in controlling coal fires, especially the “upper fires” in loose zones and abandoned roadways, respectively. Then, the three-phase foam coal fire extinguishing system is improved, and the water mist coal fire extinguishing system is developed. Finally, these two techniques are applied to control coal fires in the Anjialing Open Pit Mine. The results show that the three-phase foam and water mist techniques control coal fires efficiently and ensure the safe production of the mine as well as the security of personnel and equipments. Most importantly, this study provides a valuable method for the control of other coal fires.

The effects of poly(ethylene glycol) on the low-temperature oxidation reaction of coal as monitored using in situ series diffuse reflectance FTIR

In situ series diffuse reflectance FTIR was used to study the effects of poly(ethylene glycol) as a potential chemical additive inhibiting coal oxidation process at low temperatures. Two coals with different volatile content and, different ash percentages were examined following treatment with 5 wt% poly(ethylene glycol) 200. The surfaces of samples both with and without the additive were analyzed at temperature up to 200 °C in air using in situ diffuse reflectance FTIR. The results showed that poly(ethylene glycol) 200 is capable of inhibiting the oxidation of aliphatic moieties such as methyl and methylene groups, and also reducing the quantity of surface hydroxyl groups through reactions that form more stable ether linkages, thus improving the thermal stability of the coal. A mechanism by which the additive interacts with the coal surfaces is proposed.

In-situ Series Diffuse Reflection FTIR Used in Studying the Oxidation Process of Coal

A comparison of in-situ series diffuse reflection Fourier transform infrared and non-series Fourier transform infrared in studying the conversion of functional groups in the process of coal oxidation is studied. It is found that non-series Fourier transform infrared could not monitor the changes of functional groups precisely while in-situ Fourier transform infrared can. In-situ Fourier transform infrared was also used to monitor the oxidation processes of low ranks of coal at low temperatures (30–220°C) and a series data was obtained. The variation regularity of six main functional groups was discussed and found that in-situ Fourier transform infrared would make it possible to reveal the mechanism of coal oxidation.

GPR Simulation for the Fire Detection in Ground Coal Mine Using FDTD Method

As the radar wave is a kind of electro-magnetic wave and the spread of the wave accords with Maxwell equation, the wave field simulation method has been used in forward simulation of ground-penetrating radar (GPR) profile. The finite-difference time-domain (FDTD) scheme for simulation is derived from the Maxwell’s curl equations. The method is applied to simulate the (GPR) profile of fire detection in ground coal mine. The numerical results show that this method is correct and feasible.

Oxygen consumption and chemisorption in low-temperature oxidation of sub-bituminous pulverized coal

ABSTRACT Studying the effect of oxygen in coal oxidation is very important for understanding and controlling coal spontaneous combustion. However, the oxygen effect is not very easy to determine clearly due to the large effect of heat source on coal oxidation in temperature rising experiments. Here, focused on sub-bituminous coal, the oxygen effect was separated from coal oxidation by continuously measuring FTIR spectra of coal with respect to varying temperatures and under oxygen and nitrogen. The active groups’ real-time changes of coal oxidation, thermal treatment and oxygen effect were measured. The carboxylic ester and carboxyl units are the main functional groups that increase with temperatures increasing under oxygen and nitrogen, while the other functional groups decrease in quantity. The oxygen effect promoted the consumption of aliphatic hydrocarbons and hydroxyl groups and also promoted the formation of oxygen-containing groups (except hydroxyl). Four characteristic temperature stages involved in the oxygen effect and their key functional groups were identified. Simultaneously, the relationship of oxygen consumption and chemisorption in oxygen effect was analyzed. The starting temperature of oxygen chemisorption is between 50 and 60°C. The maximum contribution of oxygen effect was observed in methyl and methylene groups. These results are important for chemical control of coal spontaneous combustion. The oxidation of aliphatic hydrocarbon should be controlled before oxygen chemisorption. The value of oxygen consumption between 70 and 80°C can be measured accurately due to the constant chemisorption rate, which help to identify the tendency for spontaneous combustion. These results will help in better understanding of the reaction mechanism of coal oxidation, especially the oxygen effect.

Detection, extinguishing, and monitoring of a coal fire in Xinjiang, China

Coal fire is a global catastrophe. Xinjiang suffers the most severe coal fire in China and even in the world. Coal firefighting work has been being conducted for decades in Xinjiang. In this paper, coal fire detection, extinguishing, and monitoring approaches that were derived from coal firefighting experience are introduced in detail by taking the Fifth Fire Area (FFA) of the Heshituoluogai coal fire for instance. We first introduce the geology and fire situation in the FFA. Before developing efficient strategies to extinguish it, magnetic and self-potential methods are adopted to delineate the extent of the fire. A composite index is proposed to better indicate the fire. The comprehensive coal firefighting method is illustrated in detail, which consists of surface cooling, excavation and leveling, borehole drilling, borehole water injection and grouting, and loess backfill. The subsequent temperature and CO monitoring records show that the fire is extinguished successfully without burnback. The methodology presented here provides guidance and reference for putting out other coal fires around the world.

PLS Regression on Wavelet Transformed Infrared Spectra for Prediction of Coal Contents

Study on multivariate calibration for infrared spectrum of coal was presented. The discrete wavelet transformation as pre-processing tool was carried out to decompose the infrared spectrum and compress the data set. The compressed data regression model was applied to simultaneous multi-component determination for coal contents. Compression performance with several wavelet functions at different resolution scales was studied, and prediction ability of the compressed regression model was investigated. Numerical experiment results show that the wavelet transform performs an effective compression preprocessing technique in multivariate calibration and enhances the ability in characteristic extraction of coal infrared spectrum. Using the compressed data regression model, the reconstructing results are almost identical compared to the original spectrum, and the original size of the data set has been reduced to about 5% while the computational time needed decreases significantly.