Papers by Keyword: Oxygen Concentration

Abstract: As the selective non-catalytic reduction denitration(SNCR denitration) was used in cement decomposition furnaces under the high concentration cement raw materials and complex flue gas composition , the denitration efficiency is poor and the reducing agent is largely consumed.In order to meet the more stricter requirements of environmental protection, there is an urgent need to improve the denitration efficiency of SNCR and reduce the escape of reducing agentsin order to prevent the unnecessary waste caused by excessive use of reducing agents and secondary atmospheric pollution.Therefore, studying the effect of cement raw materials and O₂ concentration on SNCR process is very important. In this paper, the initial concentration of NO and the ammonium to nitrogen ration (C_NH3/C_NO) was 800ppm and 1.5, respectively. The effects of cement raw material and oxygen concentration on the reaction process of NH₃+NO+O₂ in the temperature range of 750°C -1100°C were investigated by means of denitration rate, in Situ DRIFTS analysis.The results demonstrate when O₂ concentration was 5% and denitration temperature was 950°C, the deNOx rate reached a maximum of 89.64%, which due to O₂ promoted NH₃ and NO to react with O₂ to produce N₂ and H₂O. However,under the effect of cement raw material, O₂ can promote NH₃ which was adsorbed on the surface of cement raw material to react with O₂ and produce NO and H₂O, and the reaction of oxidation of NH₃ is dominant, therefore, the denitration reaction is inhibited. .When O₂ concentration was 5% and temperature was 850°C, the deNOx rate reached a minimum value of -109.09%. the high concentration cement raw material and flue gas composition reduce the denitration efficiency of cement kiln.

Abstract: To integrate circuits into the organic light emitting diode displays, it is necessary to fabricate polycrystalline silicon (poly-Si) based thin-film transistors (TFTs) on the glass substrates. In this work we investigated the correlation between the electrical characteristics and the poly-Si morphology of the excimer laser annealed (ELA) TFTs in ultralow oxygen concentrations (~ ppm). The main feature of ELA poly-Si films is the protrusion at grain boundaries that makes the film surface rough. The surface roughness increases with an increasing oxygen concentration during the laser annealing and degrades the TFT characteristics in the on-state as well as the breakdown voltage of the gate insulator, while the off current is independent of process conditions. This result is attributed to the increased oxygen incorporation in the film in the case of an ELA process. Since oxygen increased the defect density in the polysilicon bandgap, controlling the oxygen concentrations in the process chamber helped to improve the performance of the ELA poly-Si TFTs. Based on these results, we discuss the relationship between performance of active matrix organic light emitting display panels and oxygen concentrations during ELA.

Abstract: The paper considers the influence of melting technology and out-of-furnace treatment on the nature and amount of nonmetallic impurities in rail steel. The dependence of the nature of nonmetallic impurities on oxygen concentration in steel is stated. The paper demonstrates the influence of oxygen concentration on rail metal quality.

Abstract: Oxygen impurity in Germanium single crystals has been characterized using Fourier transformed infrared spectrometry. The crystals were grown by Czochralski method in an argon atmosphere. The oxygen concentration in crystals was determined on optical density from the absorption band at 843 cm⁻¹. It was established that oxygen dissolved concentration in Germanium is variable from 0,2·10¹⁶ to 1,3·10¹⁶ сm⁻³. The oxygen band maximum shifts toward 856 cm⁻¹ when its concentration increases under the influence of annealing in the oxygen containing atmosphere with ≤ 10⁻³ Па.

Abstract: In order to study “three zones” of goaf spontaneous combustion with U+L ventilation mode working face. Numerical simulation is used to simulate the distribution law of “three zones” of goaf spontaneous combustion in case of different distance between crossheading and working face, and different air quantity. Research suggests that the “three-zones” of spontaneous combustion has great influence with different distances and different supplied air volume.

Abstract: We conducted a numerical simulation of oxygen concentration in goaf using Comsol4.3b when the air volume in working face ranges from 500 m³/min to 900m³/min. The result show that with the air volume increasing the oxygen concentration boundary of 18% move to deep goaf in a small scale, while the boundary of 8% move to deep goaf in a large scale and show an exponential relationship, in other words air volume change greatly affect the 8% boundary. The boundary of maximum air leakage and air leakage 0.004% all display an exponential relationship with air volume. But the movement scale of air leakage boundary 0.004% is small. The width of oxidation zone increases obviously with air volume increasing and the relations formula is L_max= 100.4ln (Q)-25.55ln (Q)-410.4. Draw a conclusion that in ventilation management air volume should be reduced appropriately in order to reduce the width of oxidation zone and slow the speed of moving to deep goaf, thus control spontaneous combustion in goaf.

Abstract: Combustion behavior of indigenous lignite in oxygen-enriched conditions was investigated by using thermogravimetric analyzer (TGA). Combustion tests were carried out in different oxygen concentration (21%O₂/79%N₂, 30%O₂/70%N₂, 40%O₂/60%N₂, 50%O₂/50%N₂, 60%O₂/40%N₂, 70%O₂/30%N₂). Then get the characteristic temperatures. . The model-fitting mathematical approach was used to evaluated the kinetic triplet (f (α),E,A) through Gorbatchev method. The combustion stages were divided into the early combustion stage and the later combustion stage. The calculation showed that the kinetics parameters higher in the early combustion stage than that in the later combustion stage.

Abstract: High temperature proton exchange membrane fuel cells (HT-PEMFCs) have been drawing much attention due to their easy water management and other advantages. A three-dimensional non-isothermal transient model of HT-PEMFCs with phosphoric acid doped polybenzimidazole (PBI) membrane is developed in this study. The inlet relative humidity (RH) is considered for the membrane conductivity in the model. The effect of inlet RH on the transient response of the cell is discussed and the results show that the increase of inlet RH had positive effect on cell performance but negative effect on transient response.

Abstract: For diesel particulate filter (DPF) drop-to-idle uncontrolled regeneration, a regular regeneration is initiated following a vehicle stop while the engine switches to idle. The increase in oxygen concentration and the decrease in exhaust flow rate can result in a sharp exotherm in the filter and high temperature to damage the substrate. In this paper, control solutions for the idle thermal protection of the filter was proposed and validated experimentally. At high idle speed of 2200rpm, increasing exhaust gas recirculation (EGR) combined with intake throttling was a practical way to reduce available oxygen content to control the exothermal reaction rate. A much lower peak temperature was obtained for safe DPF regeneration during idle. The research would provide based information for optimizing the regeneration management strategy in order to avoid DPF failure in real world operation.

Abstract: To elevate the air flow rate in vent pipes of semi-aerobic landfill, promote oxygen transmit into waste and methane mitigation, a wind-driven cowl was fixed on one of the two semi-aerobic landfills’ vent pipe. With the aim of figuring out the influence of cowl on the spatial distribution of oxygen under different climates, wind speeds were set at 3 m/s, 5 m/s, 7 m/s and 0 m/s sequentially. Oxygen concentrations and temperatures were recorded once a week. Data from experimental results indicated that oxygen concentrations went up along with the height above the bottom of landfill after deducting the oxygen transported by leachate collection pipes. Average oxygen concentrations except the surface layer were 3.5%, 4.2%, 3.8%, 3.0% for S-A with cowl and 2.9%, 3.4%, 3.7%, 3.0% for S-A under the wind speeds of 3 m/s, 5 m/s, 7 m/s, 0 m/s, respectively. Meantime, the aerobic radius in S-A with cowl were 0.84 m, 1.01 m, 0.87 m, 0.62 m and 0.76 m, 0.84 m, 0.87 m, 0.65 m in S-A. The effect of the cowl on oxygen transmission maximized at the wind speed of 5 m/s. It is clearly that wind energy can be better used on enhancing the ventilation in vent pipe and expanding aerobic radius after application of cowl.