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对O2/N2, O2/CO2和O2/H2O三种气氛下CH4燃烧特性及主要污染物生成进行了数值模拟,将出口O2浓度作为污染物排放的协同考虑因素,提出了基于O2/H2O气氛燃烧置换天然气水合物的新技术方案,比较了3种燃烧气氛对甲烷燃烧温度、燃烧速率、污染物(NOx和碳黑)生成量及燃烧效率等的影响. 结果表明,相较于O2/N2和O2/CO2气氛,O2/H2O气氛下燃烧温度最低、燃烧速率最高、污染物生成量最少、燃烧效率最高、出口O2浓度最低. 确定了与传统燃烧温度分布特征曲线相匹配的浓度配比为32vol% O2/68vol% H2O. 基于模拟研究结果,提出了一套O2/H2O燃烧技术与开发天然气水合物联产的技术新思路. 相似文献
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在水平管式炉上研究了O2浓度、CO2浓度、温度及石灰石添加等各参数对O2/CO2气氛下徐州烟煤和龙岩无烟煤燃烧过程中SO2/NO排放特性的影响。结果发现,O2/CO2气氛下,烟煤和无烟煤燃烧SO2/NO的析出规律与空气气氛下不同,同等O2浓度下析出量比空气气氛下小。O2/CO2气氛下,随着O2浓度的提高,烟煤和无烟煤SO2/NO排放量均增大;随着CO2浓度的升高, SO2/NO排放量均减小。O2/CO2气氛下,石灰石添加对SO2排放的抑制作用低于空气气氛下;石灰石添加对NO的排放有一定减排作用。对煤灰的元素分析显示O2/CO2燃烧对SO2的抑制主要是由于煤灰的自固硫能力增强,而对NO的减排作用则是促进燃料N向其他含N气体的转换。 相似文献
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O2/CO2气氛下煤燃烧SO2/NO析出特性 总被引:2,自引:0,他引:2
在水平管式炉上研究了O2浓度、CO2浓度、温度及石灰石添加等各参数对O2/CO2气氛下徐州烟煤和龙岩无烟煤燃烧过程中SO2/NO排放特性的影响。结果发现,O2/CO2气氛下,烟煤和无烟煤燃烧SO2/NO的析出规律与空气气氛下不同,同等O2浓度下析出量比空气气氛下小。O2/CO2气氛下,随着O2浓度的提高,烟煤和无烟煤SO2/NO排放量均增大;随着CO2浓度的升高, SO2/NO排放量均减小。O2/CO2气氛下,石灰石添加对SO2排放的抑制作用低于空气气氛下;石灰石添加对NO的排放有一定减排作用。对煤灰的元素分析显示O2/CO2燃烧对SO2的抑制主要是由于煤灰的自固硫能力增强,而对NO的减排作用则是促进燃料N向其他含N气体的转换。 相似文献
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采用热力工况与实际煤粉炉相近的沉降炉实验装置,制备了不同环境气氛下(O2/N2及O2/CO2气氛)、不同燃尽率的煤焦试样,并采用低温氮吸附仪和扫描电子显微镜测定了其孔隙结构和表面形貌。结果表明,在相同的操作条件下,相同O2浓度的O2/CO2气氛下煤焦的燃烧速率较慢、燃尽率较低,各试样的孔比表面积和比孔容积均较小。两种气氛下燃尽过程孔结构参数(SBET和VBJH)均呈减小趋势,且在孔径变化较明显的区域内(<5 nm)在CO2气氛下煤焦的孔径分布较小且与煤种相关。SEM图像显示CO2气氛下的煤焦表面致密,孔隙较少,其定性结果与N2吸附法的定量测量结果吻合较好。 相似文献
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对O2/CO2气氛中甲烷预混水蒸气燃烧特性及主要污染物生成进行了数值模拟研究,在加湿燃烧的基础上提出一种全新的清洁燃烧方式,即在保证甲烷流量一定时,通过改变入口处水蒸气的质量分数,研究水蒸气预混比Rf(0, 0.1, 0.2, 0.3, 0.4和0.5)对燃烧流场、燃烧组分和污染物浓度的影响。结果表明,随Rf增大,燃烧反应速率上升、燃烧效率提高且污染物排放量降低。模拟所得甲烷预混水蒸气的最优气氛为81%CH4/19%H2O,提出了一种高效节能的O2/CO2气氛下水蒸气预混CH4燃烧与烟气余热梯级利用方案。 相似文献
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O_2/CO_2燃烧技术是燃烧后捕集和存储CO2的有效方法之一,研究CO2氛围的煤粉燃烧特性对于明确煤粉着火特性和锅炉温度场分布至关重要。本文运用FLUENT软件非预混燃烧模型对O_2/CO_2气氛下二维通道内煤粉燃烧过程进行数值模拟,针对两种典型Ⅲ类烟煤抚顺/水城煤种进行模拟,研究不同氧分压下煤粉燃烧的温度场分布,结果表明:在氧分压2%到20%范围内,随着氧分压的增加,由于有更多的O_2与煤粉反应,温度场分布高温区域有逐渐减小的趋势。在30%氧分压下,温度场分布高温区域变大,这主要是火焰温度过高,辐射区域较大的缘故。 相似文献
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利用滴管炉研究了O2/N2、O2/CO2和O2/CO2/NO气氛下煤燃烧过程中NOx的排放特性。实验结果表明,在O2/N2和O2/CO2气氛下,高温或高O2浓度均使NO排放量增加。O2/CO2气氛下NO排放量比O2/N2气氛下NO排放量低大约30%~40%。在O2/CO2/NO气氛下,温度不同时,O2浓度变化对NO排放量的影响规律不同,对循环NO降解的影响规律也不同。高温不利于循环NO降解。随停留时间的延长NO排放量出现两个峰值。 相似文献
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Hao LIU Hong Yao Xing Yuan Xiaojie Xu Yibo Fan Takashi Ando 《Chemical Engineering Communications》2013,200(8):991-1011
Based on experiments on desulfurization, CaSO4 decomposition, and a system approach using theoretical analysis, efficient in-furnace desulfurization in O2/CO2 combustion was investigated. The influence of combustion conditions and sorbent properties on system desulfurization efficiency was clarified. The global desulfurization efficiency was found to increase with O2 purity. The global desulfurization efficiency in a dry recycle was higher than that in a wet recycle. The global efficiency of in-furnace desulfurization decreased with initial O2 concentration. As the temperature increased, the global desulfurization efficiency increased first and then decreased due to the decomposition of CaSO4. In the temperature range investigated, the global desulfurization efficiency in O2/CO2 coal combustion was much higher than that of conventional coal combustion in air. The global desulfurization efficiency decreased with sorbent size. When the particle radius decreased to one quarter, the global desulfurization efficiency doubled, becoming as high as 80%. The global desulfurization efficiency was very different among the three sorbents investigated, whether in O2/CO2 combustion or in conventional air combustion. The global desulfurization efficiency increased in the order of Ca(OH)2, scallop, and limestone in O2/CO2 combustion, but in the order of scallop, Ca(OH)2, and limestone in conventional air combustion. Nevertheless, all three sorbents demonstrated much higher desulfurization efficiency in O2/CO2 combustion than in conventional air combustion. 相似文献
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在热重分析仪上对焦作无烟煤焦和云浮烟煤焦O2/CO2条件下燃烧特性进行研究。确定在不同温度下不同煤焦O2/CO2燃烧的特征。利用随机孔模型(RPM)表征两种煤焦反应速率与碳转化率的关系,同时与未反应缩核模型(Model Ⅰ)和混合模型(Model Ⅱ)的拟合结果进行比较。研究表明,在不同反应条件下,随机孔模型具有最佳的拟合效果,相关系数都在0.986以上。比较RPM、ModelⅠ和Model Ⅱ计算结果发现,焦作无烟煤焦的O2/CO2等温燃烧的活化能比云浮烟煤焦的高,且同一煤种燃烧反应温度越高反应速率常数越大。由于随机孔模型的结构参数ψ可以很好地表现孔结构变化对煤焦燃烧反应的影响,因此随机孔模型能更加准确地描述煤焦O2/CO2燃烧特征。 相似文献
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Experimental investigation of the combustion of an air-dried Victorian brown coal in O2/N2 and O2/CO2 mixtures was conducted in a lab-scale drop-tube furnace (DTF). In situ diagnostics of coal burning transient phenomena were carried out with the use of high-speed camera and two-colour pyrometer for photographic observation and particle temperature measurement, respectively. The results indicate that the use of CO2 in place of N2 affected brown coal combustion behaviour through both its physical influence and chemical interaction with char. Distinct changes in coal pyrolysis behaviour, ignition extent, and the temperatures of volatile flame and burning char particles were observed. The large specific heat capacity of CO2 relative to N2 is the principal factor affecting brown coal combustion, which greatly quenched the ignition of individual coal particles. As a result, a high O2 fraction of at least 30% in CO2 is required to match air. Moreover, due to the accumulation of unburnt volatiles in the coal particle vicinity, coal ignition in O2/CO2 occurred as a form of volatile cloud rather than individual particles that occurred in air. The temperatures of volatile flame and char particles were reduced by CO2 quenching throughout coal oxidation. Nevertheless, this negative factor was greatly offset by char-CO2 gasification reaction which even occurred rapidly during coal pyrolysis. Up to 25% of the nascent char may undergo gasification to yield extra CO to improve the reactivity of local fuel/O2 mixture. The subsequent homogeneous oxidation of CO released extra heat for the oxidation of both volatiles and char. As a result, the optical intensity of volatile flame in ∼27% O2 in CO2 was raised to a level twice that in air at the furnace temperature of 1273 K. Similar temperatures were achieved for burning char particles in 27% O2/73% CO2 and air. As this O2/CO2 ratio is lower than that for bituminous coal, 30-35%, a low consumption of O2 is desirable for the oxy-firing of Victorian brown coal. Nevertheless, the distinct emission of volatile cloud and formation of strong reducing gas environment on char surface may affect radiative heat transfer and ash formation, which should be cautioned during the oxy-fuel combustion of Victorian brown coal. 相似文献
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《Fuel》2005,84(7-8):833-840
Pulverized coal combustion in air and the mixtures of O2/CO2 has been experimentally investigated in a 20 kW down-fired combustor (190 mm id×3 m). Detailed comparisons of gas temperature profiles, gas composition profiles, char burnouts, conversions of coal–N to NOx and coal–S to SO2 and CO emissions have been made between coal combustion in air and coal combustion in various O2/CO2 mixtures. The effectiveness of air/oxidant staging on reducing NOx emissions has also been investigated for coal combustion in air and O2/CO2 mixtures. The results show that simply replacing the N2 in the combustion air with CO2 will result in a significant decrease of combustion gas temperatures. However, coal combustion in 30% O2/70% CO2 can produce matching gas temperature profiles to those of coal combustion in air while having a lower coal–N to NOx conversion, a better char burnout and a lower CO emission. The results also confirm that air/oxidant staging is very effective in reducing NOx emissions for coal combustion in both air and a 30% O2/70% CO2 mixture. SO2 emissions are proved to be almost independent of the combustion media investigated. 相似文献
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利用TG-DTG法和DTA法研究了无烟煤催化燃烧时燃点的变化情况,结果表明Fe2O3可使无烟煤的燃点降低。基于无烟煤燃点的形成原因和催化热解过程,研究了催化热解过程中热解转化率、热解气组成、半焦表面结构的变化情况,结果表明Fe2O3促进了无烟煤的热解,热解转化率、热解气的组成明显变化,热解气热值增加。催化热解产生的半焦表面形貌粗糙,颗粒细碎,比表面积大。由于热解过程直接影响到点燃过程,因此通过催化热解的研究,可知催化燃烧过程中均相燃烧(热解气燃烧)提供给异相燃烧(半焦燃烧)的热量高于非催化燃烧。同时催化热解所得半焦的吸附氧气能力强,在低温时吸附氧气的速率较快,缩短了达到点燃时所需氧气浓度的时间,进而降低了无烟煤的燃点。 相似文献
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Pulverized coal injection (PCI) is employed in blast furnace tuyeres attempting to maximize the injection rate without increasing the amount of unburned char inside the stack of the blast furnace. When coal is injected with air through the injection lance, the resolidified char will burn in an atmosphere with a progressively lower oxygen content and higher CO2 concentration. In this study an experimental approach was followed to separate the combustion process into two distinct devolatilization and combustion steps. Initially coal was injected into a drop tube furnace (DTF) operating at 1300 °C in an atmosphere with a low oxygen concentration to ensure the combustion of volatiles and prevent the formation of soot. Then the char was refired into the DTF at the same temperature under two different atmospheres O2/N2 (typical combustion) and O2/CO2 (oxy-combustion) with the same oxygen concentration. Coal injection was also performed under a higher oxygen concentration in atmospheres typical for both combustion and oxy-combustion. The fuels tested comprised a petroleum coke and coals currently used for PCI injection ranging from high volatile to low volatile bituminous rank. Thermogravimetric analyses and microscopy techniques were used to establish the reactivity and appearance of the chars. 相似文献
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《Fuel》2007,86(12-13):2008-2015
CO2/O2 combustion of pulverized coal is one of the promising new technology in order to reduce the emission of CO2 and NOx from coal combustion furnaces. However, several experiments with pulverized coal burners show that temperature and stability of pulverized coal flame is reduced in this condition. CO2 has distinctive thermodynamic and optical property compared with that of other gas, and it is important to know the effect of CO2 on the flame stability of pulverized coal. In this study, effect of CO2 on flame propagation velocity of pulverized coal clouds were studied experimentally using micro-gravity condition, and also numerically considering detailed radiation heat exchange using Monte Carlo method.Experiments were made by using spherical chamber with inner diameter of 200 mm. Micro-gravity condition was used in order to achieve uniform pulverized coal cloud in a chamber. Flame propagation velocity was measured from the photographic image of the flame front by using high speed camera. Results show that flame propagation velocity of pulverized coal cloud in CO2/O2 mixture gas decreases to about 1/3–1/5 of that in N2/O2 mixture gas at the same oxygen concentration. By using Ar/O2 mixture gas, it is revealed that thermal diffusivity of gas seems to have a large effect on flame propagation velocity. From the numerical analysis using Monte Carlo method, effect of absorption of radiation by CO2 gas is proven to be relatively small compared with that of thermodynamic property especially for heat capacity of CO2. Consequently, it is clarified that reduction of flame stability in CO2/O2 combustion is mainly due to the larger heat capacity of CO2 gas. 相似文献