流化床中高水分煤的燃烧与排放试验研究

通过在一小型流化床中进行高水分煤的燃烧与排放的试验研究，表明水分含量和空气－燃料比对于高水分煤的燃烧与排放有较大影响。随着水分增加，流化床床温下降，ＮＯｘ、ＳＯｘ排放量也下降。空气－燃料比存在一最佳值，这时床温最高，而偏离此值，床温下降，随着空气量的增加，ＮＯｘ、ＳＯｘ排放量也增加。当空气－燃料比变化时，燃烧干煤与燃烧高水分煤有着类似的试验结果。     

煤的挥发份组分对NOx和SOx排放的影响

在煤的燃烧过程中，ＮＯＸ和ＳＯＸ的形成大部分来源于挥发份的燃烧。对于不同的煤种，其挥发份的含量和组分是不同的。本文专门研究了煤的挥发份在富氧燃烧条件下，不同挥发份组分对ＮＯＸ和ＳＯＸ形成与排放的影响。通过基于化学反应动力学机理的模型计算发现，在不同组分的挥发份燃烧过程中，ＮＯＸ和ＳＯＸ的形成规律相似，但在煤的含氮量和含硫量相同的条件下，ＮＯＸ和ＳＯＸ的排放量受挥发份组分的影响较大，其排放量与燃料的     

煤焦特性及其NO2生成影响因素的实验研究

在流化床上进行了两种煤的热解及焦炭的燃烧实验，研究了煤种，粒径，热解条件对煤焦性质对Ｎ２Ｏ转化率的影响。研究结果表明：除粒径外，煤种和热解条件都对煤焦中Ｎ的Ｎ２Ｏ转化率有明显影响。     

流化煤燃烧中氮氧化物的生成机理

在一个流化床反应器和一个固定床反应器中研究了流化床煤燃烧中Ｎ２Ｏ及ＮＯｘ生成的机理。发现流化床煤燃烧中Ｎ２Ｏ和ＮＯｘ主要来自于煤中的氮，即挥发分氮和焦炭氮，部分ＮＯｘ来自于空气中的Ｎ２。     

循环流化床煤燃烧过程中N_2O_NOx的排放研究

在一个循环流化床热态试验台上,研究了煤燃烧过程中氮氧化物（ＮＯｘ和Ｎ２Ｏ）的生成过程,测试了其沿床层高度方向的浓度变化。试验发现,沿炉膛向上,Ｎ２Ｏ浓度不断增加而ＮＯｘ迅速减少,在炉膛出口处Ｎ２Ｏ达到最大值,且排放量远大于ＢＦＢ。作者对其原因进行了分析,同时研究了运行参数对Ｎ２Ｏ及ＮＯｘ排放的影响。     

燃煤流化床中N2O及NOx排放特性的试验研究

在一直径为１００ｍｍ的小型燃煤流化床反应器中试验研究了床温、过量空气系数和煤种对Ｎ２Ｏ及ＮＯｘ排放特性的影响。结果表明，随床温增加，Ｎ２Ｏ排放量减小，而ＮＯｘ排放量增加。降低过量空气系数能同时减少Ｎ２Ｏ和ＮＯｘ的排放量；且过量空气系数对Ｎ２Ｏ排放的影响与煤种有关。燃用含氮量高的煤，Ｎ２Ｏ和ＮＯｘ的排放量也高。燃料氮转化为Ｎ２Ｏ、ＮＯｘ的转换率与煤种有关，其中最主要的是挥发份含量。     

煤焦特性及其N_2O生成影响因素的实验研究

在流化床上进行了两种煤的热解及焦炭的燃烧实验,研究了煤种、粒径、热解条件对煤焦性质及Ｎ２Ｏ转化率的影响。研究结果表明：除粒径外,煤种和热解条件都对煤焦中Ｎ的Ｎ２Ｏ转化率有明显影响。     

流化床煤燃烧中氮氧化物的生成机理

在一个流化床反应器和一个固定床反应器中研究了流化床煤燃烧中Ｎ２Ｏ及ＮＯｘ生成的机理。发现流化床煤燃烧中Ｎ２Ｏ和ＮＯｘ主要来自于煤中的氮,即挥发分氮和焦炭氮．部分ＮＯｘ来自于空气中的Ｎ２．挥发分氮主要以两种形式ＨＣＮ和ＮＨ３均相反应生成Ｎ２Ｏ和ＮＯｘ;焦炭氮则以多种多相反应方式生成Ｎ２Ｏ和ＮＯｘＮ２Ｏ与ＮＯｘ的消减机理有很大的区别。Ｎ２Ｏ主要通过为氢原子和氧原子的还原的反应、床层中各种固态物质的催化还原及自身的热分解而减少。ＮＯｘ则通过在固态物质催化下与ＣＯ、Ｈ２、ＮＨ３和焦炭的反应而减少。     

煤粉燃烧过程中NOx生成的数值模拟

本文提出用有限反应速率２阶矩封闭模型来模拟湍流对煤燃烧过程中ＮＯｘ生成的影响。     

煤燃烧过程中燃料型NOx的生成与控制研究

建立了对煤中燃料型ＮＯｘ的生成和定量测定的研究模式,在不同温度下测定了几种动力用煤的燃料型ＮＯｘ,测定结果表明,在高温下快速燃烧,可有效抑制燃料型ＮＯｘ的生成。     

Co-firing of Thai lignite and municipal solid waste (MSW) in a fluidised bed: Effect of MSW moisture content

Co-firing investigation of a high-moisture-content municipal solid waste (MSW) with Thai lignite have been performed in a laboratory-scale fluidised bed to study the effects of MSW moisture content on the combustion and emission characteristics of major gaseous pollutants. In this study the comparison of 35%- and 60%-moisture MSWs were tested. The results show that the bed temperature in the case of 35%-moisture content is higher than for in case of 60%-moisture content due to the difference of physical properties of the fuel. The combustion efficiency for the case of 35%-moisture MSW is higher than that for 60%-moisture MSW due to higher bed temperature at lower waste moisture content. The synergistic effect of the co-firing of lignite with MSW reduces the emission of CO leading to increase in combustion efficiency. CO concentration for the case of 35%-moisture content is generally lower, and is much less sensitive to the level of excess air. Both the concentration values of SO₂ and the fuel-S converted are lower for lower moisture content waste, particularly at high mass fraction of waste. The fuel mixture with low-moisture in waste gives higher fuel-N conversion to NO whereas the fuel-N conversion to N₂O is higher for higher moisture content waste, particularly at high excess air.     

Emissions from a conical FBC fired with a biomass fuel

The results of experimental tests conducted on a conical fluidised bed combustor (FBC), firing mixed sawdust of some Thai woods, are discussed. The concentration profiles for major gaseous emissions (CO, NO_x and CO₂), as well as the temperature and O₂ profiles along the combustor height, were obtained for various operating conditions (fuel feed rate and excess air) for three “fixed” bed heights (20, 30 and 40 cm). The influence of fuel quality (through varying the fuel's moisture content) on the formation of gaseous emissions was also studied. Both CO and NO_x axial profiles were found to have an extreme (maximum) in the active combustion zone. The effects of FBC load and excess air, as well as fuel moisture, on the CO_max were found to be very strong. The NO_x,max was less affected by the combustion conditions, approaching 1.5–3 times the NO_x values at the combustor outlet. The influence of the sand's bed height on the rate of gaseous emissions was found to be minor. The dependencies of the CO and NO_x emissions (i.e. concentrations in the waste flue gas) on the FBC operating conditions are shown for different values of fuel's moisture content.     

生物质燃油燃烧CO和NO排放特性试验研究

以小桐子油、地沟油、小桐子生物柴油、地沟油生物柴油和0号柴油为燃油,研究了其在炉窑内的燃烧排放特性。结果表明:随着油压的增大,燃烧生物质燃油和柴油时,烟气中CO浓度逐渐降低,NO浓度逐渐升高;随着过量空气系数的增大,烟气中CO浓度呈现先减小后增大的趋势,NO浓度变化趋势则相反;在最佳过量空气系数下,烟气中CO浓度最低、NO浓度最高,生物柴油能明显降低CO的浓度,从最高970 mg/m~3 降低到181 mg/m~3 ,但提高了NO的浓度;随着生物柴油混合比例的增大,烟气中CO的浓度逐渐降低。     

在线乳化燃油燃烧烟气排放特性的试验研究

为进一步控制燃油设备的排放污染,采用自制的在线乳化燃油燃烧系统,对不同含水量和过量空气系数共15个工况下的乳化油进行了燃烧试验,并进行定量分析。试验结果表明:乳化燃油含水率和过量空气系数对烟气污染物排放量有很大影响。随着乳化油含水量的增多,NO浓度不断降低;含水量达到5%时,SO_2浓度最低;含水率达到10%时,烟尘浓度最低;含水量达到20%时,NO_2浓度最低,H2浓度达到最高,同时排烟温度达到最高;CO、CO_2浓度随含水量不同变化不大。过量空气系数越大,总体上烟气污染物浓度越低,而排烟温度反而越高。综合各试验工况,当含水率为20%,过量空气系数为1.3时,为最佳排烟工况,NO_x浓度较乳化前降低31%,SO_2降低28%,烟尘浓度降低了57%。     

Combustion and emission characteristics of a swirling fluidized-bed combustor burning moisturized rice husk

Burning of rice husk in a swirling fluidized-bed combustor (SFBC) was the focus of this experimental study. Swirl motion of a fluidized bed in this combustor was induced by an annular spiral distributor of primary air and also promoted by tangential injection of secondary air into the bed splash zone. “As-received” rice husk was moisturized with the aim to control NO emission from the combustor. The SFBC was tested at a constant fuel feed rate (of about 80 kg/h) for six fuel-moisture contents (from 8.4% to 35%). In each test series for the particular fuel quality, excess air was ranged from about 20% to 80%. Radial and axial profiles of temperature and gas concentrations (O₂, CO and NO) were plotted for different fuel options and operating conditions with the aim to study pollutants formation and reduction in different regions of the SFBC. With increasing the fuel-moisture content, the emission of NO from the combustor apparently reduced, while the emission of CO was adjusted at a quite low level due to the effects of secondary air. An effective least-cost control of both NO and CO emissions and high (over 99%) combustion efficiency are achievable when firing moisturized rice husk in this SFBC.     

Experimental investigation of the primary combustion zone during staged combustion of wood-chips in a commercial small-scale boiler

In this work the primary combustion zone of a modified, commercial, small-scale boiler was investigated during staged combustion of wood-chips. Experimental research on thermal conversion of biomass in fixed beds is necessary to supply reliable data for gas phase combustion model validation and optimization. Furthermore, scruting of pollutant emission formation and combustion efficiency enhancement can be conducted. Two different fuel moistures were used while the primary combustion zone of a small-scale boiler was investigated as a function of the primary air ratio. The combustible products leaving the fuel layer were analyzed under continuous operation by an extractive method. This approach is new in the field of small-scale biomass combustion research and considers the strong coupling between the products leaving the fuel bed and the heat fluxes emitted by the flame of the secondary combustion zone. Additionally, fine particulate matter emissions were quantified to study the effect of varying primary air ratio and different fuel moisture on particulate formation. Results show that the primary air ratio and the fuel moisture have a significant influence on the primary combustion products composition, on the fuel bed behavior and on fine particulate matter emissions. At low primary air ratios, tars constitute a significant part of the heating value of primary combustion products. The smallest amount of particulate emissions was found at low primary air ratio and low fuel moisture. Experimental data was validated with an elemental balance, which showed perfect accordance.     

Effects of operating conditions and fuel properties on emission performance and combustion efficiency of a swirling fluidized-bed combustor fired with a biomass fuel

This work reports an experimental study on firing 80 kg/h rice husk in a swirling fluidized-bed combustor (SFBC) using an annular air distributor as the swirl generator. Two NO_x emission control techniques were investigated in this work: (1) air staging of the combustion process, and (2) firing rice husk as moisturized fuel. In the first test series for the air-staged combustion, CO, NO and C_xH_y emissions and combustion efficiency were determined for burning “as-received” rice husk at fixed excess air of 40%, while secondary-to-primary air ratio (SA/PA) was ranged from 0.26 to 0.75. The effects of SA/PA on CO and NO emissions from the combustor were found to be quite weak, whereas C_xH_y emissions exhibited an apparent influence of air staging. In the second test series, rice husks with the fuel-moisture content of 8.4% to 35% were fired at excess air varied from 20% to 80%, while the flow rate of secondary air was fixed. Radial and axial temperature and gas concentration (O₂, CO, NO) profiles in the reactor, as well as CO and NO emissions, are discussed for the selected operating conditions. The temperature and gas concentration profiles for variable fuel quality exhibited significant effects of both fuel-moisture and excess air. As revealed by experimental results, the emission of NO from this SFBC can be substantially reduced through moisturizing rice husk, while CO is effectively mitigated by injection of secondary air into the bed splash zone, resulting in a rather low emission of CO and high (over 99%) combustion efficiency of the combustor for the ranges of operating conditions and fuel properties.     

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。     

微富氧条件下煤粉燃烧及NO生成特性的研究

利用热重分析技术对微富氧条件下煤粉的燃烧特性进行了研究,并与富氧条件下煤粉的燃烧特性进行了对比,利用固定床测定了燃煤NO的生成规律,分析了反应气氛和煤种的影响．结果表明：随着氧体积分数增加,微富氧条件下煤粉的燃烧向低温区移动,综合燃烧特性指数S逐渐增大;在相同的氧体积分数下,由于N2和CO2的物性差异,煤粉的微富氧燃烧特性优于富氧燃烧特性,但当氧体积分数升高到40％时,两种气氛的燃烧特性差别不大;反应气氛和煤种均对燃料氮的转化率影响显著;氧体积分数升高或N2的参与会使反应温度上升,影响燃料氮的转化率;煤的挥发分和元素氮的质量分数也会影响燃料氮的转化率．