共查询到19条相似文献,搜索用时 187 毫秒
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宏观煤岩分类及燃烧反应动力学参数 总被引:1,自引:1,他引:0
本文将神木、西山煤用重液分离法分为亮煤、暗煤和无机矿物质三种宏观煤岩类别并进行了燃烬实验。实验结果表明,显微组分存在形式的不同导致厂其在各宏观煤者类别中纯度的较大差异;宏观煤岩类别间燃烧反应动力学参数的明显差异要求对原有的将煤粉视为物理、化学性质均匀的颗粒的燃烧模型进行改进。 相似文献
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本文针对煤粉燃烧SCT模型中的氧气可达比表面积,进行了不同煤种的TG实验和N2/BET比表面积的测试,研究了煤粉燃烧过程中不同温度下比表面积在不同孔径下与燃尽度和燃烧速率的相关性,研究表明:煤粉在燃烧过程中的平均孔径大于3~11 nm时,该孔径以上的累积比表面积与燃尽度有很好的相关性;高阶煤的氧气可达比表面积在反应过程中逐渐增加,而低阶煤的氧气可达比表面积在反应过程中的变化不是很显著;通过大量的实验说明,不是所有的比表面积在反应过程中都发挥作用,而氧气可达比表面积可以很好地反映燃烧速率的变化. 相似文献
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Christopher R. Shaddix Ethan S. Hecht Cristina Gonzalo-Tirado Brian S. Haynes 《Proceedings of the Combustion Institute》2019,37(3):3071-3079
Apparent char kinetic rates are commonly used to predict pulverized coal char burning rates. These kinetic rates quantify the char burning rate based on the temperature of the particle and the oxygen concentration at the external particle surface, inherently neglecting the impact of variations in the internal diffusion rate and penetration of oxygen. To investigate the impact of bulk gas diffusivity on these phenomena during Zone II burning conditions, experimental measurements were performed of char particle combustion temperature and burnout for a subbituminous coal burning in an optical entrained flow reactor with helium and nitrogen diluents. The combination of much higher thermal conductivity and mass diffusivity in the helium environments resulted in cooler char combustion temperatures than in equivalent N2 environments. Measured char burnout was similar in the two environments for a given bulk oxygen concentration but was approximately 60% higher in helium environments for a given char combustion temperature. To augment the experimental measurements, detailed particle simulations of the experimental conditions were conducted with the SKIPPY code. These simulations also showed a 60% higher burning rate in the helium environments for a given char particle combustion temperature. To differentiate the effect of enhanced diffusion through the external boundary layer from the effect of enhanced diffusion through the particle, additional SKIPPY simulations were conducted under selected conditions in N2 and He environments for which the temperature and concentrations of reactants (oxygen and steam) were identical on the external char surface. Under these conditions, which yield matching apparent char burning rates, the computed char burning rate for He was 50% larger, demonstrating the potential for significant errors with the apparent kinetics approach. However, for specific application to oxy-fuel combustion in CO2 environments, these results suggest the error to be as low as 3% when applying apparent char burning rates from nitrogen environments. 相似文献
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煤粉燃烧火焰辐射光谱实验研究 总被引:1,自引:0,他引:1
针对煤粉燃烧辐射光谱问题,利用光纤光谱仪对煤粉平面火焰炉实验装置煤粉燃烧火焰辐射光谱进行了测量,详细分析了煤粉辐射光谱特征,并基于普朗克辐射传热定律,通过对光谱仪波长响应特性的标定,得到火焰绝对辐射强度随波长的分布情况,进而利用最小二乘法获得火焰温度与辐射率参数,由此提出基于煤粉燃烧火焰辐射光谱测量的火焰参数测量方法。利用该方法对不同燃烧条件下煤粉燃烧参数进行测量,开展了不同燃烧参数下煤粉火焰辐射光谱实验研究,研究结果表明:煤粉燃烧火焰辐射在200~1 100nm波段具有较强且连续的光谱特征,基于普朗克辐射定律与最小二乘法可实现煤粉燃烧火焰温度与辐射率的测量;煤粉燃烧火焰辐射光谱在590,766,769和779nm附近可见明显的Na和K等碱金属痕量元素原子光谱发射谱线,并且这些原子谱线的出现与火焰温度有关;随着煤粉浓度的提高,虽然燃烧温度变化不大,但由于火焰辐射率的增加,造成辐射光谱强度的大幅提升。这对锅炉煤粉燃烧优化具有重要参考价值。 相似文献
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Lin Li Lunbo Duan Zhihao Yang Zhenkun Sun Changsui Zhao 《Proceedings of the Combustion Institute》2021,38(4):5485-5492
Pressurized oxy-fuel combustion of coal in fluidized bed (FB) holds the potential to realize low-cost CO2 capture. However, the fundamental study in this manner is still rare due to the difficult access to the pressurized oxy-FB combustion tests. In this work, the experimental study of single char combustion was firstly conducted in a visualized pressurized FB combustor under various operating conditions. Then an experimentally verified particle-scale char combustion model was developed to reveal the dependence of char combustion on parameters. Results showed that the char conversion was accelerated with the increase of pressure, mainly due to the high oxygen diffusion and char gasification. The gasification played a non-negligible role in pressurized oxy-fuel combustion, especially under high oxygen concentration and bed temperature. Increasing oxygen concentration and bed temperature not only promotes the char oxidation rate and particle temperature, but also increases the gasification rate and the share of char conversion via gasification, resulting in shortening the burnout time of char. In addition, a higher fluidization number lowered both the burnout time and peak temperature of char particle, due to the simultaneous improvement of mass and heat transfer. The influences of char size and fluidization number on char gasification conversion ratio are very weak. In addition, the quantitative analysis of the influence of different operating parameters on the combustion process was obtained by model sensitivity analysis. 相似文献
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Khalid Hadi Ryo Ichimura Genya Hashimoto Yu Xia Nozomu Hashimoto Osamu Fujita 《Proceedings of the Combustion Institute》2021,38(3):4131-4139
This study aims to clarify the effect of fuel ratio of coal on the turbulent flame speed of ammonia/coal particle cloud co-combustion at atmospheric pressure under various turbulence intensities. High-fuel-ratio coals are not usually used in coal-fired thermal power plants because of their low flame stability. The expectation is that ammonia as a hydrogen-energy carrier would improve the ignition capability of coal particles in co-combustion. Experiments on spherical turbulent flame propagation of co-combustion were conducted for various coal types under various turbulence intensities, using the unique experimental apparatus developed for the co-combustion. Experimental results show that the flame speed of co-combustion with a low equivalence ratio of ammonia/oxidizer mixture for bituminous coal case was found to be three times faster than that of pure coal combustion and two times faster than that of pure ammonia combustion. On the other hand, the flame speed of co-combustion for the highest-fuel-ratio coal case is lower than that of the pure ammonia combustion case, although the flame propagation can be sustained due to the ammonia mixing. To explain the difference of tendencies depending on the fuel ratio of coal, a flame propagation mechanism of ammonia/coal particle cloud co-combustion was proposed. Two positive effects are the increases of local equivalence ratio and the increases of radiation heat flux, which increases the flame speed. In opposite, a negative effect is the heat sink effect that decreases the flame speed. The two positive effects on the flame speed of co-combustion overwhelm a negative effect for bituminous coal case, while the negative effect overcomes both positive effects for the highest-fuel-ratio coal case. The findings of the study can contribute to the reduction of solid fuel costs when the ammonia is introduced as CO2 free energy carrier and can improve the energy security through the utilization of high-fuel-ratio coals. 相似文献
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Kenji Yamamoto Tomoya Murota Teruyuki Okazaki Masayuki Taniguchi 《Proceedings of the Combustion Institute》2011,33(2):1771-1778
Large eddy simulation (LES) is applied to a pulverized coal jet flame ignited by a preheated gas flow. The simulation results are compared to experimental data obtained for the inlet stoichiometric ratios of 0.14, 0.22, and 0.36. An accurate and computationally inexpensive devolatilization model suitable for combustion simulation in LES is proposed and incorporated into the LES. The numerical results of gas temperature and coal burnout on the centerline show good agreement with the experimental data. Two kinds of lift-off heights are introduced to verify the combustion simulation. One is the height from the primary nozzle exit to the starting point of the growing flame region. The other is the height from the primary nozzle exit to the starting point of the continuous flame region. The calculated results of the two lift-off heights show good agreement with the experimental data. In contrast to LES, the standard k–ε model overestimates the lift-off heights because it calculates time-averaged temperature which does not contain information about local flame structure. The stoichiometric ratio in the gas phase at the starting point of the growing flame region is found to be independent of the inlet stoichiometric ratio in the range from 0.14 to 0.36. 相似文献
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煤焦颗粒燃烧过程中,灰膜形成显著影响其燃烧特性。因此,本文借助高温沉降炉研究了61~75,75~90和90~125μm三种粒径黄陵烟煤在1273和1673 K温度下的燃烧特性与灰膜形成比例;借助扫描电镜(SEM)详细观测空心微珠颗粒内部结构,提出灰膜比例计算公式,并分析温度,粒径和碳转化率对灰膜比例的影响。结果表明,高温下大部分灰分在焦炭烧尽阶段以灰膜形式存在。灰膜比例随温度和碳转化率增加而增加,随煤粉粒径增大而减小。高温下灰分用于形成灰膜比例相对较高,这为煤焦燃尽阶段的低反应性提供了合理的解释。煤焦颗粒动态燃烧过程中灰膜形成比例随燃烧工况变化而变化。该研究为煤焦颗粒燃烧动力学模拟灰膜比例选择提供了关键数据支撑。 相似文献