循环流化床中石油焦与煤混合燃烧NO排放特性

在一座0．5MWt循环流化床热态试验台上进行了石油焦与煤混合燃烧试验,研究了烟气中NO的排放特性,对于石油焦与煤不同燃料配比,不同锅炉运行参数,如一次风率、过量空气系数、床温和Ca／S比等对烟气中NO排放浓度的影响规律进行了研究。试验表明对纯焦而言,其NO排放浓度较其他混合燃料要高得多,当燃料中焦煤比增大时,NO的排放浓度降低,对不同焦煤比的燃料,随一次风率增大,NO的排放量增加;随过量空气系数的增大,NO的排放浓度增大;随着运行床温的提高,NO排放浓度升高。     

高含水菌渣流化床燃烧NOx、SO2排放特性

采用流化床反应器,研究了高含水抗生素菌渣直接燃烧的NO_x、SO₂排放特性。结果表明,增加过量空气系数,NO_x排放浓度升高,SO₂排放浓度降低;升高燃烧温度,NO_x及SO₂排放浓度均升高;随着燃料含水率的增加,NO_x及SO₂排放浓度均呈现先降低后升高的趋势。空气分级燃烧能有效降低NO_x排放,二次风率增加,NO_x排放浓度显著降低;当二次风率为3/7时,NO_x排放浓度较传统燃烧降低50%。添加CaCO₃进行炉内脱硫,实验结果显示：随钙硫摩尔比（Ca/S）增加,SO₂排放浓度下降,当Ca/S 3时,SO₂排放浓度降低到25 mg·m^-3以下,脱硫效率超过99%。     

流化床燃烧石油焦N2O排放特性

通过在一小型流化床试验台上进行石油焦的燃烧试验 ,阐述了N2 O和NO形成与分解机理 ,模拟研究了N2 O的排放特性 .采用不同程度脱去挥发分的石油焦颗粒 ,研究脱挥发分的程度对N2 O形成的影响 ,脱挥发分的温度越高 ,即脱挥发分的程度越高 ,石油焦氮形成N2 O的量越少 ,这表明石油焦挥发分氮形成N2 O量高于相应石油焦焦炭氮燃烧产生的N2 O量 .燃料燃烧过程中 ,NO形成比较均匀 ,而N2 O形成比较复杂 ,燃料氮向NO的转化率随脱挥发分温度升高而增加 ,而向N2 O的转化率则有一临界脱挥发分温度点 .     

富氧富水蒸气条件下燃烧高氮燃料的NOx排放特性

在富氧富水蒸气条件下,研究了富含氮的燃料白酒糟在流化床中燃烧时NO_x的排放特性。结果表明,在过量空气系数1.2条件下,水蒸气和O₂对NO_x的生成相互影响。当O₂浓度低于约35%时,向燃烧气中加入水蒸气能抑制NO_x生成,使烟气中NO_x的排放浓度和燃料N转化为NO_x的转化率降低;而当氧气浓度高于约35%时,加入水蒸气促进了NO_x生成,表明提高氧气浓度使得氧化作用起到主导地位。NO_x生成量随温度的升高先增加后减少,在较高氧气浓度下,NO_x生成量随温度升高而降低的转折点发生在较低的温度;燃烧气氛中添加水蒸气延迟了转折点的发生,使转折点发生在较高温度。     

燃煤增压流化床氧化亚氮排放特性的试验研究

在小型增压流化床内研究增压流化床内Ｎ２Ｏ和Ｎ煌排放特性,研究运行条件对Ｎ２Ｏ和ＮＯ排放量的影响,包括压力、氧浓度以及床层温度对Ｎ２Ｏ和Ｎ排放量的影响。结果表明,在增压燃烧的条件下,随着床温的增加Ｎ２Ｏ的排放量减少得很快,而床温对Ｎ煌排放影响很小,这一结果与常压下的结果不同;随着氧浓度的增加,Ｎ２Ｏ和Ｎ煌排放量均增加,但Ｎ２Ｏ增幅不如ＮＯ强,ＮＯ的排放量随着压力的增高有明显的降低,在氧浓度较低的条件     

循环流化床燃烧中NOx及SO2排放特性试验研究

总结了在国电热工研究院1MWthCFBC试验台上进行的工程煤种和石灰石及烟煤在循环流化床燃烧试验中NOx及SO2排放特性,重点分析了床温、Ca/S,排烟氧量等因素对NOx及SO2排放特性的影响。     

循环流化床燃烧在高过剩空气下的NOx排放

提出了借助循环流化床在高过剩空气系数下燃烧的技术提供高温空气的新构思。搭建了循环流化床燃烧热态试验台,完成了循环流化床燃烧在高过剩空气系数下的NOx排放特性试验,结果表明:循环流化床在高过剩空气系数下燃烧温度分布均匀,燃烧稳定性好;过剩空气系数增大,氮氧化物排放增加;提升管二次风高度的增加和还原区系数的减小有利于控制氮氧化物的排放水平和减少煤中的N向NOx的转化比。在过剩空气系数为1.6、还原区系数为0.72和二次风高度为1 500 mm时,循环流化床NOx排放为339 mg/m3,煤中的N向NOx转化比为21%。循环流化床高温空气NOx的浓度对燃料高温燃烧NOx排放的影响需要进一步研究。     

煤焦燃烧生成NO的特性研究

对小屯煤焦中氮的存在形态进行了X射线光电子能谱(XPS)分析。并对小屯煤焦在模拟分解炉中NO释放特性进行了实验研究,考察了气氛、温度、生料对焦炭氮释放特性的影响。研究结果表明:小屯煤焦中氮主要以吡咯五元环形式存在;氧气体积分数对NO的生成速率有明显影响;在无生料催化下,生成量基本随温度的升高而加大,但是,当生料存在时,生成量随温度的升高而减少;生料的加入大大加速了NO的生成速率和生成量,表明生料对NO生成有显著的催化作用。焦炭氮转化为NO的几率主要由2个互相竞争的反应决定:包括N的氧化反应和NO的还原反应。     

O2/CO2气氛下不同煤质NO排放规律及燃烧特性

为减少电厂锅炉燃煤燃烧带来的NO等有害气体排放,结合华电节能减排目标与要求,在模拟实际燃煤燃烧环境的情况下,设置燃煤燃烧试验装置,并以无烟煤(SH)和烟煤(DT)作为研究对象,分别探讨上述两种燃煤在不同气氛、不同氧气浓度、不同温度下的NO排放特性,并分析两种燃煤在不同气氛下燃烧的着火温度和燃烧特性指数等.结果表明,在O...     

模拟分解炉中煤焦燃烧生成NO的特性

对国内水泥行业中几种煤焦在模拟的分解炉中NO生成特性进行了研究,考察了煤种、温度、生料对焦炭氮的释放特性的影响,探讨了焦炭氮在工业分解炉中的释放机理.研究结果表明,不同煤种的NO生成特性有较大的不同;温度对NO的生成特性也有明显的影响,基本随温度的升高而加大,但有时也有下降现象;生料的加入大大加速了NO的生成速率和转化率,表明生料对NO生成有显著的催化作用.工业分解炉中产生的NO主要来源于燃料NO,焦炭氮转化为NO的概率主要有两个互相竞争的反应决定：包括N的氧化反应和NO的还原反应.     

Fluidized bed pyrolysis of distilled spirits lees for adapting to its circulating fluidized bed decoupling combustion

Distilled spirits Lees, rich in cellulose, water and N element, are difficult to burn efficiently and cleanly in grate chain stock boiler. The circulating fluidized bed decoupling combustion (CFBDC) was therefore proposed to burn the distilled spirits lees efficiently and with low-NOx emission. The pyrolysis behavior of the distilled spirits lees was investigated in a fluidized bed reactor for optimizing the pyrolysis conditions of the pyrolyzer in CFBDC. The results showed that the distilled spirits lees began to devolatize at 250 °C and at 350–450 °C the tar yield reached its maximum of about 16.3 wt.% (dry base). The chemical oxygen demand (COD) value of the condensed liquid reached its maximum of about 50,000 mg/L at 450 °C. With raising temperature the pyrolysis gas tended to contain more CO and H₂ and less CO₂. The functional groups H-O, aliphatic C-H, aromatic ring, C=O and C-O were all presented in the char generated at low-temperatures, while only the C-O group was identified for the char from the pyrolysis at 650 °C. The article suggested that the pyrolysis for the CFBDC was better around 500 °C so that certain volatiles could remain in the char to sustain stable combustion.     

A simplified model of nitric oxide emission from a circulating fluidized bed combustor

A simplified mathematical model leading to a closed form of solution is developed for estimation of nitric oxide emission from a coal fired circulating fluidized bed (CFB) furnace. The furnace is divided into two sections: a lower section below and an upper section above the secondary air injection level. Reactions in the cyclone and the return leg are neglected. Furnace dimensions, coal feed rate, coal composition and furnace temperature are inputs to the model which was validated against several pilot scale and commercial units. Experimental results from two pilot plants and two commercial power plants agree with model predictions. A sensitivity analysis was carried out using the model to examine the effect of different operating parameters and coal properties on the overall NO emission from the furnace. It was found that excess air and furnace temperature are most important factors influencing the NO emission level. The primary to secondary air ratio influences the NO emission level reasonably. Properties of coal are other factors which affect the NO emission to a large extent. The model, though it invovles some simplification, predicts the overall emission of NO with a level of accuracy accepted in commercial operation.     

煤在富氧流化床燃烧条件下汞的析出及形态分布

目前有关于富氧气氛下流化床燃烧汞的形态转化特性的报道还不是很多,因此本文开展了富氧气氛下煤种对汞形态转化特性的影响的实验研究。采用流化床作为实验设备,选用徐州烟煤和淮北烟煤作为实验燃料,研究了空气气氛下不同温度和不同煤种对汞析出规律的影响,富氧气氛下煤种对汞形态转化规律的影响,并深入分析了相应的汞氧化机理。研究结果表明：在空气气氛下,温度的增加会促进汞的氧化,煤中的含硫量对汞的氧化也有影响;在富氧气氛下,徐州烟煤燃烧产生的气态总汞浓度高于淮北烟煤燃烧产生的气态总汞浓度,徐州烟煤的Hg²⁺（g）的分布率也比淮北烟煤的Hg²⁺（g）的分布率高出16%左右,因为徐州烟煤中高含硫量会影响Hg²⁺（g）的分布率;富氧气氛下徐州烟煤的Hg²⁺的分布率低于空气气氛下的,而淮北烟煤的Hg²⁺（g）分布率则与之相反,这与两种煤中硫含量的不同有关。     

NOx emission from a 71 MWe pressurized fluidized bed combustor

Flue gas NO_x concentration was measured at the outlet of gas turbine (the inlet of de-NO_x catalyst) of a 71 MWe pressurized fluidized bed combustor. The effect of operating parameters on NO_x emission was approximated by assuming a linear combination of three independent parameters, concentration of O₂ in the flue gas, SO₂ removal efficiency, and dense bed temperature. Sensitivity factors for different type of coals were obtained. The relationship between the sensitivity factors and fuel ratio (fixed carbon/volatile matter ratio) was obtained. NO_x emission was well approximated by the present approximation, even for coals/coal mixtures that were not used to determine the sensitivity factors. NO_x emissions for coal/coal mixtures and combustor operation under fly ash recycle conditions can be predicted approximately from the equation derived from other coals under conditions without fly ash recycle.     

Effects of fuel type and operating conditions on SO2 emission in fluidized bed combustion

The SO₂ emission from six fluidized bed combustors was examined. Approximately 71.5% of the fuel sulphur was found to be emitted as SO₂ in sorbent-free tests. General observations on the effects of Ca/S molar ratio, limestone size and recycle systems are presented. The effects of limestone type and superficial velocity were found to be insignificant, as was the effect of bed temperature in the range 800-950°C. In tests with fine solid and liquid fuels, circulating FBC's were found to provide significantly better sulphur capture than bubbling FBC's.     

循环流化床锅炉烟气污染物排放测试及特性分析

针对额定蒸发量分别为240 t/h和450 t/h的2台循环流化床锅炉(分别记为U1和U2),在100%BMCR负荷条件下,根据行业试验规范进行了现场测试,分析了循环流化床锅炉主要烟气污染物的排放特征、设备协同脱除效率及环境效益。测试结果表明:污染控制设备的协同脱除作用使得循环流化床锅炉具有清洁高效的特性,U1锅炉的烟尘、SO_2、NO_x、Hg、NH_3及SO_3排放浓度分别为13.1、16.0、71.4、5.6×10(-3)、1.7、1.6 mg/m~3,U2锅炉上述指标排放浓度分别为4.8、10.4、95.7、4.9×10~(-3)、0.4、0.6 mg/m~3。2台锅炉的SO2排放绩效分别为0.085 8、0.040 1 g/k Wh,NO_x排放绩效分别为0.370 1、0.354 4 g/kWh。故只须对烟尘和NO_x进行控制削减,就能达到现行的超低排放标准。     

Mixing and combustion in a shallow coal-limestone fluidized bed combustor

A model based on the Monte Carlo approach was developed to simulate the mixing and combustion behavior of a shallow coal-limestone fluidized bed combustor. The model involved the coupling of two sub-models: a combustion sub-model based on the two-phase concept of fluidization and a mixing sub-model based on our previously developed dynamic mixing model. The combustion sub-model considered both the volatile and char combustion. It assumed that the combustor consisted of three distinct phases, i.e., jet, bubble and emulsion, with combustion occurring only in the emulsion phase. The mixing sub-model considered the upward or downward movement of a coal particle in the bed as being governed by certain probability laws; these laws were, in turn, affected by the bubbling hydrodynamics. In all, the combustor simulation model took into consideration the effects of coal feed rate, coal size distribution, limestone size, air flow rate and combustor temperature on the combustor behavior. The simulation results included the dynamic response of coal concentration profile, coal size distribution, coal particle elutriation rate as well as the mixing status between the coal and limestone particles.     

Modelling of NO and N2O emissions from biomass-fired circulating fluidized bed combustors

A model for NO and N₂O emissions from biomass-fired circulating fluidized bed (CFB) combustors has been developed and evaluated in this study. All the model parameters were chosen for a typical woody biomass-pinewood chips. Both drying and devolatilization of biomass particles were modelled with limited rates, which were selected from the literature based on woody biomass fuels. The partition of fuel-nitrogen between volatiles and char was also specifically chosen for pinewood based on available experimental data from the literature. Volatile nitrogen was assumed to consist of NH₃, HCN and N₂ with the distribution between three species as input parameters to the model. Twenty-five homogenous and heterogeneous global chemical reactions were included in the model, of which 20 reactions represents the global fuel-nitrogen reactions. Both gaseous and solid phase were assumed to be in plug flow. The model has been applied to the modelling of a 12 MW_th CFB boiler. The predicted N₂O emissions were always less than 5 ppmv for pinewood combustion, which was consistent with the experimental results. The predicted NO emissions increased with the total excess air of the riser and the fuel-N content while the predicted percentage conversion of fuel-N to NO decreased with increasing fuel-N content. The NO emissions were also predicted to decrease with increasing primary zone stoichiometry. These predictions agree with the experimental results. The predicted NO emissions decreased slightly with increasing bed temperature, whereas experiments showed that NO emissions slightly increased with bed temperature for birch chips combustion and did not change with bed temperature for fir chips combustion. Sensitivity analyses reveal that the reaction between NO and char is the key reaction to determine the NO emissions.     

气固流化床中声发生机理及在工业装置中的应用

利用声测量技术,结合频谱分析,建立了颗粒碰撞的声波频率模型,可定量描述声波主频随颗粒粒径、弹性模量和密度的变化规律.通过改变流化颗粒的粒径、弹性模量参数和密度,发现声波主频与频率模型计算值之间的最大偏差为8.3%,说明声波主频可以代表颗粒在壁面的碰撞频率.讨论了热态和冷态条件下声波主频之间变化规律,通过对弹性模量参数的校正,声测量技术可以用于预测工业装置中物料的平均粒径变化,并将该模型应用于线性低密度聚乙烯、高密度聚乙烯和双峰聚乙烯工业生产装置中的平均粒径测量,发现与传统的取样筛分方法所得测量结果十分接近.同时,发现当系统产生聚合物颗粒结块时,声波主频将急剧降低,声波频谱的能量分布将明显集中增大,这可作为判断流化床稳定运行的一个判据.