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With horizontal bias combustion burners, experiments have been carried out on a 670 t h?1, corner‐fired, pulverized‐coal fired boiler burning bituminous coal. At 200 MWe load, the furnace excess O2 remains stable. The different horizontal fuel biases are obtained by changing the tilt angle of all the Louvre enrichers' regulating blades. The tilt angles of the blades are 0, 15, 24, 32°; the result is that the enriching ratios of the fuel‐rich primary air increase from 2.2 to 2.6 at No. 2 corner, and from 1.2 to 4.2 at No. 3 corner. The gas temperature increases in the burner region. The application of the horizontal bias combustion burners results in a reduction in NOx formation from 545.7 mg Nm?3 (O2=6%) to 287.9 mg Nm?3, and a substantial reduction in carbon in ash content from 5.24 to 2.48%. The boiler operated stably at a load of 80 MWe without auxiliary fuel oil. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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利用Fluent软件对1台900 MW四角切圆燃烧锅炉在不同负荷下炉内燃烧过程进行了数值模拟,分析了负荷变化对炉内流动和传热的影响规律.结果表明:在高负荷工况下运行时,炉内燃烧充分且稳定,但是炉内火焰更容易冲刷水冷壁,可能发生局部结渣现象;在低负荷工况下运行时,炉内火焰充满度较差,切圆燃烧的稳定性显著下降,炉膛水冷壁灰污表面温度也相应降低,水冷壁表面结渣的倾向弱化,沿高度方向水冷壁吸热不均匀性增大.由于该锅炉的低NOx燃烧器采用了分离燃尽风,使得高温区扩展,火焰中心高度比采用有关标准推荐的方法计算所得结果高4~5 m. 相似文献
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为提高1 000 MW超超临界四角切圆燃煤锅炉低负荷工况(300 MW)燃烧稳定性,在一次风中掺混不同比例氢气和氧气,采用数值模拟方法对比分析了低负荷掺混氢氧前后炉膛平均温度场和CO体积分数等参数。研究结果表明:一次风掺混氢氧加强了低负荷工况下的火焰温度,进而提升炉内整体平均温度,改善低负荷燃烧不稳定现象;掺混5%体积分数的氢气,主燃区炉内截面平均温度达到1 603 K,比初始工况平均温度高了37 K;掺混8%~15%体积分数的氢气,随着氢气燃烧产生水份比例增高,炉膛截面平均温度逐步降低;掺混5%体积分数的氢气和10%体积分数的氧气,主燃区炉内截面平均温度达到了1 696 K,比只掺混5%体积分数的氢气平均温度提高了93 K,比初始工况平均温度提高了130 K,此工况是该四角切圆锅炉低负荷下改造后较为理想的工况。 相似文献
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分析了煤粉燃烧过程NOx的形成机制和特点,研究了减少NOx生成量的基本途径和分级燃烧的基本原理,并进行了数值分析。在乌拉山电厂100MW煤粉炉上进行了分级燃烧改造,将以轴向空气分级和径向空气分级为核心的现代低NOx燃烧技术引入了传统的煤粉炉燃烧系统中,考察了炉膛轴向和径向分级风,过量空气系数,锅炉负荷等因素对炉内NOx形成的影响。NOx排放浓度降低了250-500mg/m^3(干烟气,70%O2)。 相似文献
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本文采用数值分析技术对大容量切圆燃烧锅炉改变燃烧器二次风反切风量以及反切风位置时的炉内流场特性进行了全三维模拟和研究,研究结果表明在燃烧器上部二次风采用反切布置的情况下.无量纲数XJ在1左右时炉膛出口残余旋转较小,炉内气流湍动混合较好,炉内气流运动稳定;研究亦表明反切风位置对炉内流场影响较大。同时,对7个电厂13台大型锅炉进行了改造效果统计,验证了数值分析的结论。 相似文献
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目的观察经股动脉行介入诊疗术后股动脉穿刺点应用股动脉止血贴(V+PAD)的临床效果。方法应用随机排列表随机入选80例行冠状动脉介入诊疗的患者,其中偶数应用止血贴共40例作为试验组,奇数应用徒手压迫不使用止血贴共40例作为对照组。所有患者均签订知情同意书。观察两组的按压时间、止血后穿刺点的处理、患者卧床姿势、下床活动时间、患者的舒适度、出院前穿刺点并发症情况。结果两组患者年龄、性别构成比、激活凝血时间和血压差异均无统计学意义(P<0.05),但试验组和对照组的压迫时间分别为(7.9±0.5)min和(19.8±5.1)min,卧床时间分别为(6.1±5.0)h和(23.9±0.2)h,两组间差异均有统计学意义(P值均<0.01)。试验组所有患者在拔管后即刻均采用床头抬高30°卧位,1h后将床头抬高90°,常压包扎,不制动,所有患者舒适度明显提高。试验组有1例比较肥胖的女性发生假性动脉瘤,其余入选患者在住院期间均未出现穿刺处并发症。结论股动脉止血贴止血迅速,效果确切,患者舒适度明显提高,减轻了医护人员的工作量,可以在临床大规模推广应用。 相似文献
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The behavior of heat transfer and emissions in a semi-industrial 300 kWth natural gas fired furnace with three pairs of regenerative flameless oxidation burners was studied. The furnace offers unique possibilities for varying burner positions and firing modes (parallel and staggered). The operational behavior of two burner configurations have been compared regarding emissions (NO, CO) and temperature uniformity, for both parallel and staggered firing mode. Additionally, the flue gas O2 percentage (excess air ratio) and the cycle time have been varied. Parallel firing mode results in a higher temperature uniformity ratio in the furnace and in a lower NO emission. CO emission did not vary much between parallel and staggered mode. 相似文献
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在实验室的卧式煤粉炉中,对中心大速差射流是否能降低NOx排放量进行了实验研究。实验表明:中心大速差射流不仅能明显降低NOX排放量,而且可使煤粉提前着火,从而提高了煤粉燃烧的稳定性。该方法若用于煤粉锅炉的最上一层的燃烧器,则可望在降低NOX排放量的同时不影响锅炉的燃烧效率。 相似文献
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《International Journal of Thermal Sciences》2000,39(8):833-841
This paper presents the results of experimental researches on nitrogen oxide emissions from coal-fired boilers. Two Chinese lean coals have been fired in two full scale boilers (1 025 t · h −1 ) and in a pilot scale test furnace (Drop-Tube Furnace) to study the influence of nitrogen content in coal on nitrogen oxide emission. The nitrogen oxide emission was found to correlate well with the fuel nitrogen content. The test results of the drop-tube furnace and the single burner furnace with three Chinese coals show that the staged combustion can greatly reduce the nitrogen oxide emission. Identical trends in nitrogen oxide emission as a function of the volatile matter of the coals have been obtained under different combustion conditions. The principle of low nitrogen oxide emissions of the wide range burner (biased combustion or internal air staging) and the cases with over fired air port (furnace air staging) is introduced in this paper. In addition, the influence of excess oxygen content on nitrogen oxide emission has been tested in the utility boilers and test furnaces. 相似文献
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《International Journal of Heat and Mass Transfer》2006,49(1-2):421-426
To develop low-pollution burners, the effect of a coal concentrator on NO formation in swirling coal combustion is studied using both numerical simulation and experiments. The isothermal gas–particle two-phase velocities and particle concentration in a cold model of swirl burners with and without coal concentrators were measured using the phase Doppler particle anemometer (PDPA). A full two-fluid model of reacting gas–particle flows and coal combustion with an algebraic unified second-order moment (AUSM) turbulence-chemistry model for the turbulent reaction rate of NO formation are used to simulate swirling coal combustion and NO formation with different coal concentrators. The results give the turbulent kinetic energy, particle concentration, temperature and NO concentration in cases of with and without coal concentrators. The predicted results for cold two-phase flows are in good agreement with the PDPA measurement results, showing that the coal concentrator increases the turbulence and particle concentration in the recirculation zone. The combustion modeling results indicate that although the coal concentrator increases the turbulence and combustion temperature, but still can remarkably reduce the NO formation due to creating high coal concentration in the recirculation zone. 相似文献
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Technological development of furnaces over conventional melting methods of diesel or gas‐fired furnaces is necessary. These furnaces have large amount of heat losses and hence their thermal efficiency is very low. Moreover, these furnaces do not produce good quality melt because of the chances of embedment of impurities from after‐combustion gases and agitation. The time required for melting in such furnaces is more. Also, insulation is not provided and there are heat losses which increase the time of melting. An electric resistance heating furnace is developed which overcomes all the problems associated with the fuel‐fired conventional furnace. The thermal efficiency of this developed furnace is found to increase quite drastically up to 85%, which is by about 33% more than conventional furnace; while reducing the operating cost of furnace. This benefits industry overall by profit of 70% and certainly can replace the existing conventional fuel‐fired furnaces. 相似文献
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炉内燃烧器区热态准等温旋转气流上翘特性的模型分析 总被引:1,自引:0,他引:1
在对四角切圆锅炉炉膛、燃烧器结构进行简化后,通过对炉内热态准等温旋转气流上翘特性进行数学推导,获得了不同上翘程度下燃烧器区热态准等温气流的旋转流量和旋转动量,并进一步了解和掌握了实际燃烧电站锅炉内热态非等温气流的旋转特性。 相似文献
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Simulation of combustion in spark-ignition engine fuelled with natural gas-hydrogen blends combined with EGR 总被引:1,自引:0,他引:1
Jie Wang Zuohua Huang Bing Liu Xibin Wang 《Frontiers of Energy and Power Engineering in China》2009,3(2):204-211
A numerical simulation of the influence of different hydrogen fractions, excess air ratios and EGR mass fractions in a spark-ignition
engine was conducted. Good agreement between the calculated and measured incylinder pressure traces as well as pollutant formation
trends was obtained. The simulation results show that NO concentration has an exponential relationship with temperature and
increases sharply as hydrogen is added. EGR introduction strongly influences the gas temperature and NO concentration in the
cylinder. The difference in temperature will lead to even greater difference in NO concentration. Thus, EGR can effectively
decrease NO concentration. NO concentration reaches its peak value at the excess air ratio of 1.1 regardless of EGR mass fraction.
The study shows that natural gas-hydrogen blend combined with EGR can realize a stable combustion and low NO emission in a
spark-ignition engine. 相似文献
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