Botao Qin

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.

Preparation and Stability of Inorganic Solidified Foam for Preventing Coal Fires

Inorganic solidified foam (ISF) is a novel material for preventing coal fires. This paper presents the preparation process and working principle of main installations. Besides, aqueous foam with expansion ratio of 28 and 30 min drainage rate of 13% was prepared. Stability of foam fluid was studied in terms of stability coefficient, by varying water-slurry ratio, fly ash replacement ratio of cement, and aqueous foam volume alternatively. Light microscope was utilized to analyze the dynamic change of bubble wall of foam fluid and stability principle was proposed. In order to further enhance the stability of ISF, different dosage of calcium fluoroaluminate was added to ISF specimens whose stability coefficient was tested and change of hydration products was detected by scanning electron microscope (SEM). The outcomes indicated that calcium fluoroaluminate could enhance the stability coefficient of ISF and compact hydration products formed in cell wall of ISF; naturally, the stability principle of ISF was proved right. Based on above-mentioned experimental contents, ISF with stability coefficient of 95% and foam expansion ratio of 5 was prepared, which could sufficiently satisfy field process requirements on plugging air leakage and thermal insulation.

Thermal analysis of Vitamin C affecting low-temperature oxidation of coal

Simultaneous thermal analysis was used to study the influence of Vitamin C as possible chemical additive inhibiting coal oxidation process at low temperature. Some oxidation characteristics of Vitamin C affecting the coal oxidation were investigated at different heating rates. The TG-DSC data show that the impact of Vitamin C on coal oxidation process can be directly evaluated using ignition temperature and critical temperature. Comparison with the effect of water on coal oxidation shows that Vitamin C is more efficient than water. However, the blank experiment conducted with inert α-Al2O3 also suggests that Vitamin C can decompose at about 200 °C, which limits the usage of Vitamin C on inhibiting coal oxidation.

Fly ash suspensions stabilized by hydroxypropyl guar gum and xanthan gum for retarding spontaneous combustion of coal

ABSTRACT This study evaluated the potential application of hydroxypropyl guar gum (HPG) and xanthan gum (XG) (HPG/XG weight ratio 1:1) to stabilize highly concentrated fly ash suspensions (FAS) (300 g/L) used for retarding spontaneous combustion of coal. The rheological behaviors of FAS were measured with different HPG/XG mixture concentrations including 1.2, 1.4, 1.6, 1.8, and 2 g/L, respectively. The effects of concentrations on the static stability of FAS were investigated to determine the optimal concentration. It was found that increasing HPG/XG concentration was beneficial to the viscoelasticity of FAS as evidenced by higher elastic modulus (G′), and FAS can be stabilized over 72 h when HPG/XG concentration increased to 1.6 g/L. Retarding spontaneous combustion experiments indicated that FAS significantly elevated the crossing point temperature of coal and reduced the carbon monoxide during low-temperature oxidation, efficiently retarding spontaneous combustion of coal.

Aqueous clay suspensions stabilized by alginate fluid gels for coal spontaneous combustion prevention and control

We have developed aqueous clay suspensions stabilized by alginate fluid gels (AFG) for coal spontaneous combustion prevention and control. Specially, this study aimed to characterize the effect of AFG on the microstructure, static and dynamic stability, and coal fire inhibition performances of the prepared AFG-stabilized clay suspensions. Compared with aqueous clay suspensions, the AFG-stabilized clay suspensions manifest high static and dynamic stability, which can be ascribed to the formation of a robust three-dimensional gel network by AFG. The coal acceleration oxidation experimental results show that the prepared AFG-stabilized clay suspensions can improve the coal thermal stability and effectively inhibit the coal spontaneous oxidation process by increasing crossing point temperature (CPT) and reducing CO emission. The prepared low-cost and nontoxic AFG-stabilized clay suspensions, exhibiting excellent coal fire extinguishing performances, indicate great application potentials in coal spontaneous combustion prevention and control.