无烟煤与贫煤的混煤NOx排放特性的实验研究

利用小型煤粉燃烧试验台对贫煤、无烟煤及其3种配比的混煤进行了实验研究,分析了上述煤种在不同配风下NOx的生成规律,并对其燃尽特性进行了研究,提出实现混煤高效低污染燃烧的过量空气系数范围.     

一维火焰炉中混煤燃烧氮析出特性的试验研究

在一维煤粉燃烧试验台上,对贫煤掺混不同煤种的混煤在一维火焰燃烧过程中氮的析出特性进行了试验研究.结果表明:煤中析出氮主要以NO存在,NO2生成量很少;贫煤掺混不同煤种在相同工况下燃烧时氮释放差别较大,掺配比、氮存在形态对氮析出产物的形式和浓度有较大影响;混煤燃烧氮析出曲线一般具有双峰结构,混煤析出氮与组分单煤的加权平均有一定差异,氮析出量与混煤掺烧比例有关.     

五彩湾煤燃烧特性的试验研究

对五彩湾煤与乌东煤2种煤种及3种不同掺烧比例的混煤分别进行了物理化学特性分析、煤粉气流着火温度测试、一维火焰炉中燃烧与结渣试验以及200kW沾污试验台的沾污性能试验,并对各种混煤的着火、燃尽和结渣性能进行了评定.利用专家系统对试验煤样的主要特性进行了最终评价,并结合2种沾污性能判别指标对煤灰的沾污性能进行了验证,给出推荐的设计煤种和校核煤种.结果表明:混煤具有严重结渣倾向;五彩湾煤具有严重的沾污倾向,而乌东煤为低沾污倾向煤种,通过掺烧乌东煤可以减轻五彩湾煤的沾污;推荐选用五彩湾煤与乌东煤的掺烧比例为7∶3和5∶5的混煤1和混煤3分别作为设计煤种和校核煤种.     

无烟煤与烟煤的混合煤燃烧特性与结渣特性研究

本文介绍某电厂３００ＭＷ锅炉燃用阳沁无烟煤与黄陵烟煤组成的混合煤的燃烧与结渣特性。由此确定等效挥发份及混煤的最佳掺烧比例。并用大型燃烧试验炉热态试验结果验证。     

不同煤种混煤燃烧时NO_x生成和燃尽特性的试验

在一维沉降炉上对无烟煤、贫煤、烟煤及其混煤的燃烧特性进行了研究,分析了不同因素对NOx排放量的影响,并讨论了不同过量空气系数、掺混比及一、二次风比例对燃尽率的影响,试验结果表明：当烟煤的掺混比例为25％,NOx的排放量较低,混煤燃烧时沿程分析结果表明,煤种特性的不同导致NOx排放时有不同的峰值。     

混煤燃烧特性的热重试验研究

对不同配比下由烟煤、无烟煤和褐煤掺混得到的混煤的燃烧性能进行了热天平试验研究，对不同配比下混煤的活化能进行了计算，并根据活化能与着火温度随掺混比的变化规律对混煤的着火特性进行了探讨;此外根据不同掺混比下煤样的试验数据，从阿累尼乌斯定律出发，提出了表征煤在着火后燃烧速度和燃烧稳定性指数HF，对不同配比下煤的HF进行了计算，并据此对混煤的稳燃及燃尽性能进行了研究。图11表2参5     

超临界W火焰锅炉燃用劣质燃料燃烧优化研究

针对W火焰锅炉运行中热效率偏低问题,对燃用的烟煤、石油焦、越南无烟煤等主要煤种开展配煤掺烧,以降低燃料成本、提高锅炉效率。从燃用煤质适应性分析、W火焰锅炉燃烧过程数值模拟和混煤掺烧优化试验3方面,研究了石油焦和越南无烟煤不同掺混比例下热解和燃烧过程特性,制定了掺烧策略并通过燃烧过程模拟研究和掺烧优化试验找到了合适的配煤掺烧方法,解决了锅炉效率低、飞灰含碳量较高、锅炉排烟温度高等问题,实现了节能降耗、提高经济效益的目的。     

混煤在一维火焰燃烧过程中氮析出特性研究

对贫煤与不同煤种组成的混煤在一维火焰燃烧过程中氮的析出特性进行了试验研究。结果表明:在相同工况下,贫煤掺混不同煤种燃烧时氮的析出特性差别较大,掺配比、氮存在形态对混煤中氮的析出产物形式、浓度有较大影响,在试验基础上找出了混煤燃烧过程中氮的析出规律,对混煤污染物控制,优化燃烧有一定的指导意义     

磨煤方式对混煤燃烧特性的影响分析

通过不同磨制方式制取煤样,利用同步热分析系统对掺入劣质煤或优质煤的混合燃料进行燃烧特性试验研究,用着火温度、可燃性指数、燃烧稳定性指数和燃尽特性指数考察了混磨/分磨方式对劣质煤和优质煤掺烧的影响规律。试验结果表明:磨制方式对不同煤种掺烧影响不同;对掺烧优质煤的混煤燃烧特性影响较大,两种磨制方式着火特性和稳燃特性间差异不随比例增加而明显变化,燃尽特性随比例增加而增大;对掺烧劣质煤的混煤燃烧特性影响较小,当掺入比例达到25%时才表现出明显的影响。     

电厂锅炉混煤燃烧技术应用现状及分析

为降低发电成本,拓宽煤炭供应渠道,国内各燃煤发电厂相继开展了锅炉非设计煤种的掺烧试验研究。首先介绍了电厂锅炉混煤掺烧常见的三种方式,分析了这三种混煤掺烧方法的优缺点,然后介绍了国内电厂掺烧烟煤、褐煤、无烟煤的情况;分析了目前电厂锅炉掺烧烟煤、褐煤、无烟煤时所存在的问题,并提出了一些切实有效的技术措施;最后分析了混煤燃烧对锅炉运行的影响,指出需要对燃烧混煤时锅炉性能的变化、掺烧经济性等问题做深入研究。     

The effect of air staged combustion on NOx emissions in dried lignite combustion

Experiments were carried out in a multi-path air inlet one-dimensional furnace to assess NOx emission characteristics of the staged combustion of BRXL lignite and its dried coals. The impact of moisture content, multiple air staging, pulverized coal fineness and burnout air position on NOx emissions under deep, middle and shallow air-staged combustion conditions. Moreover, the impact of blending coals on NOx emissions was investigated in this paper. The unburned carbon concentration in fly ash was also tested. Experimental results based on the combustion of BRXL lignite and its dried coals show that NOx emissions can be reduced drastically by air-staged combustion. NOx emissions reduce with the increase of the air that is staged and the distance between the burner and burnout air position. Dried coal of BRXL lignite emits a smaller amount of NOx than that of BRXL lignite. However, the dried degree of BRXL lignite is closely related to R₉₀ fineness. Dried coal with optimal moisture content yields least NOx emissions. When deep or middle staged combustion was adopted, the application of multi-staged combustion is conducive to NOx reduction. However, when shallow staged combustion was adopted, NOx emissions are higher in multi-staged combustion than that in single-staged combustion with M_S = 0.54. Thus, the existence of a certain concentration of O₂ in reduction zone would significantly reduce NOx emissions. The blending coals that dried coals of BRXL lignite were blended with bituminous coals emit a larger amount of NOx than that of the dried coal alone. NOx emissions decrease with the increase of the proportion of dried coal in the blending coal. Moreover, the unburned carbon concentration in fly ash of dried coal in staged combustion is lower than that of BRXL lignite in staged combustion. On the whole, the dried coal of BRXL lignite is conducive to NOx reduction in staged combustion.     

NOx and H2S formation in the reductive zone of air-staged combustion of pulverized blended coals

Low NO_x combustion of blended coals is widely used in coal-fired boilers in China to control NO_x emission; thus, it is necessary to understand the formation mechanism of NO_x and H₂S during the combustion of blended coals. This paper focused on the investigation of reductive gases in the formation of NO_x and H₂S in the reductive zone of blended coals during combustion. Experiments with Zhundong (ZD) and Commercial (GE) coal and their blends with different mixing ratios were conducted in a drop tube furnace at 1200°C–1400°C with an excessive air ratio of 0.6–1.2. The coal conversion and formation characteristics of CO, H₂S, and NO_x in the fuel-rich zone were carefully studied under different experimental conditions for different blend ratios. Blending ZD into GE was found to increase not only the coal conversion but also the concentrations of CO and H₂S as NO reduction accelerated. Both the CO and H₂S concentrations inblended coal combustion increase with an increase in the combustion temperature and a decrease in the excessive air ratio. Based on accumulated experimental data, one interesting finding was that NO and H₂S from blended coal combustion were almost directly dependent on the CO concentration, and the CO concentration of the blended coal combustion depended on the single char gasification conversion.Thus, CO, NO_x, and H₂S formation characteristics from blended coal combustion can be well predicted by single char gasification kinetics.     

链条炉区段烟气再循环对锅炉运行及NOx排放特性影响的工业试验研究

针对一台采用尽早配风方式的29MW链条炉进行分区段烟气再循环对锅炉运行及NOx排放特性影响的工业试验。在挥发分析出及燃烧区段煤层下的一次风室混入再循环烟气将有效强化该区段煤层燃烧,降低该区段煤层以上燃烧空间的氧浓度,控制及消减挥发分N向NOx的转化,同时降低了穿过该区段煤层一次风的氧浓度,抑制焦炭N向NOx转化,NO消减效果最高达到25%。在焦炭燃烧区段煤层下的一次风室混入再循环烟气,能够降低穿过床层气流的氧浓度,抑制焦炭氮向NO的转化过程,该区段烟气再循环低氮效果有限,最大降幅9%。再循环烟气可以替代部分一次风,以维持足够的风室风压,进而降低穿过煤层气流的O2浓度,从而强化链条炉区段燃烧特性的低氮特征,实现链条炉的NOx减排。随着工业锅炉NOx排放指标的不断提高,烟气再循环作为一项有效的前置低氮环节,能有效降低整个低氮系统的投资,进而取得较好的经济性。     

Comparison of nitrogen oxide emissions from boilers for a wide range of coal qualities

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.     

大型亚临界无烟煤电站锅炉的开发设计

本文介绍哈尔滨锅炉厂有限责任公司开发设计的３００ＭＷ亚临界循环无烟煤锅炉的技术特点和运行业绩。着重论述耿保证低挥发份煤种的着火、稳燃、燃尽和防止炉膛结焦、降低不投油稳燃负荷、减少ＮＯｓ排放量所采取的有效技术措施。特别是在燃烧器设计中,采用了哈锅与清华大学联合开发研制的,并获得国家创造发明专利金奖的“双一次风通道自稳式燃烧器”,该燃烧器具有明显的低负荷稳燃特性和综合性能,使大型无烟煤锅炉的设计达到了     

稀燃条件下甲醇汽油发动机燃烧和排放特性的试验研究

在一台汽油缸内直喷(GDI)增压发动机上,研究了稀燃条件下燃用不同甲醇汽油混合燃料的燃烧特性和排放特性。试验结果表明:稀燃条件下,随混合气浓度逐渐变稀,当量燃油消耗率呈现出先降低后升高的趋势,并且随着甲醇比例的增加,当量燃油消耗率增加,但均低于原机。在混合气逐渐变稀的过程中,燃烧时缸压峰值和燃烧温度总的变化趋势是逐渐降低,而燃烧持续期和循环变动率逐渐升高。稀燃条件下,CO排放量逐渐降低,碳氢化合物排放呈先降低后增加的趋势。NO_x排放量总的变化趋势是先增大后逐渐降低,随着甲醇体积分数的增加,NO_x的排放量逐渐降低,且3种甲醇、汽油混合燃料的NO_x和CO排放量都低于汽油燃料。     

混煤煤质及燃烧特性研究

针对混煤的煤质特性和燃烧特性开展实验研究,以指导燃煤电站科学合理的燃用混煤。研究结果表明,混煤的元素分析、工业分析及发热量满足质量加权平均,但混煤的可磨性和灰熔融特性不满足加权平均,低灰熔点煤中掺烧高灰熔点煤能显著提高混煤灰熔点,改善锅炉燃烧过程中的结渣问题,混煤灰熔点变化受到单煤灰成分的影响。热重实验分析表明,混煤的剧烈燃烧阶段与单煤存在明显差异,混煤的燃烧特性介于参与掺混的单煤之间,但不满足线性叠加,其燃烧过程存在着不同程度的交互作用。混煤的着火特性接近于易燃煤,而燃尽特性与难燃煤相近。除此以外,随着氧浓度的降低,混煤的燃烧特性明显变差,易燃煤对氧浓度的变化更加敏感。