Investigation of the Suppression of Methane Explosions by N2/CO2 Mixtures in Different Proportions.

To characterize the inerting effect of N2/CO2 mixtures containing various proportions on methane-air explosions, a series of experiments were conducted in a 20 L spherical vessel under the normal temperature (25 °C) and normal pressure (101 kPa). Six concentrations (10, 12, 14, 16, 18, and 20%) of N2/CO2 mixtures were selected to analyze the suppression of methane explosion by N2/CO2 mixtures. The results indicated that the maximum explosion pressure (p max) of methane explosions was 0.501 MPa (17% N2 + 3% CO2), 0.487 MPa (14% N2 + 6% CO2), 0.477 MPa (10% N2 + 10% CO2), 0.461 MPa (6% N2 + 14% CO2), and 0.442 MPa (3% N2 + 17% CO2) in the presence of the same N2/CO2 concentration, and similar decreases in the rate of pressure rise, flame propagation velocity, and production of free radicals were observed. Therefore, with the increase of CO2 concentration in the gas mixture, the inerting effect of N2/CO2 was enhanced. Meanwhile, the whole process of the methane combustion reaction was affected by N2/CO2 inerting, which was mainly attributed to heat absorption and dilution of the N2/CO2 mixture. N2/CO2 with a greater inerting effect leads to lower production of free radicals under the same explosion energy and a lower combustion reaction rate at the same flame propagation velocity. The findings of the current research provide references for the design of safe and reliable industrial processes and the mitigation of methane explosions.

Investigation of thermal behavior and hazards quantification in spontaneous combustion fires of coal and coal gangue.

To explore the thermal behavior and hazard during the spontaneous combustion fires (SCFs) of coal and coal gangue (CG), the characteristics of heat release and thermal transfer during the SCFs of coal and CG were tested. The results indicate that coal contains more combustibles and aromatic hydrocarbons, while CG possesses higher contents of ash and inorganic silicate. Coal has a stronger heat release capacity, while CG owns a smaller specific heat capacity, a larger thermal diffusivity and a greater thermal conductivity. Thus, CG performs better with respect to heat transfer. The apparent activation energy of coal is larger in the endothermic stage, whereas that of CG is more notable in the exothermic stage. Based on heat release and heat transfer performance, hazardous zones during the SCFs of coal and CG were identified, and the combustion growth index was established to quantify the hazard of SCF disasters. The results show that the hazard is determined by both heat release and thermal transfer capacities. Coal or CG with a combustible component of 31.3 %, which not only releases massive heat but also transfers heat quickly, corresponds to the most considerable hazard of SCF disasters.

Oxidation Characteristics of Functional Groups in Relation to Coal Spontaneous Combustion.

To investigate and better understand the mechanism of coal spontaneous combustion, the distributions, evolution, and oxidation characteristics of functional groups in different coal samples were characterized using in situ Fourier transform infrared (FTIR) and electron paramagnetic resonance (EPR) experiments. The macroscopic characteristics of coal spontaneous combustion in relation to functional groups were also analyzed using the thermogravimetric/differential scanning calorimetry-FTIR coupling technique. The experimental results indicated that -OH was the most active groups of coal spontaneous combustion. It not only could react with the absorbed oxygen spontaneously but also found to be the main product of the chemisorption. Consequently, -OH was believed to contribute most both for the loss and increase of coal mass during the process of spontaneous combustion. Aliphatic hydrocarbons were the main components to form -C-O-O• and could be further oxidized into C=O. However, reactions between aliphatic hydrocarbons and oxygen were nonspontaneous. EPR experiments suggested that the tendency of coal spontaneous combustion acutely depended on the stability and survival time of free radicals. The more the stable and longer survival time of free radicals are, the lower the tendency of coal spontaneous combustion is.

Effects of Atorvastatin on Conservative and Surgical Treatments of Chronic Subdural Hematoma in Patients.

OBJECTIVE: To investigate effects of atorvastatin on conservative and surgical treatment of patients with chronic subdural hematoma. METHODS: A retrospective analysis was performed of 109 patients (including 3 outpatients) with chronic subdural hematoma at Northern Jiangsu People's Hospital from April 2014 to October 2015. Patients' gender, age, Glasgow Coma Scale score, symptoms, history of antiplatelet or anticoagulant use, hematoma location, volume of hematoma, operation methods, and application of atorvastatin and its duration were recorded. Prognostic indicators including changes in hematoma volume and neurologic status were extracted. Statistical methods were conducted to evaluate drug efficacy. RESULTS: Seven conservative patients received atorvastatin for 1-6 months (range, 3.57 ± 1.72 months). The volume of hematomas was ± 4.49 mL to 11.40 ± 4.46 mL (P > 0.05) after 1 month's atorvastatin treatment. Hematomas disappeared after 6 months in all 7 patients. In surgical patients, gender (P = 0.797), age (P = 0.063), Glasgow Coma Scale score (P = 0.216), history of antiplatelet or anticoagulant (P = 0.350), volume of hematoma after admission (P = 0.896), location (P = 0.282), and operation methods (P = 0.832) were nonsignificantly associated with follow-up groups, but atorvastatin was significantly associated with follow-up results (P = 0.045). CONCLUSIONS: Atorvastatin has preliminarily been proved to be safe and effective for chronic subdural hematomas in both conservative and surgical patients and can provide a drug treatment strategy for neurosurgeons.