不同稀释剂对燃气锅炉NOx排放及燃烧稳定性的影响

结合试验与数值模拟,对比分析了过量空气、烟气、水蒸气3种稀释剂对天然气锅炉扩散燃烧过程中的NO_x排放及燃烧稳定性影响。结果表明:随着稀释剂吸热功率的增加,NO_x生成量减少。添加等同吸热功率的过量空气、烟气、水蒸气时,NO_x生成量依次减少,在3种稀释剂吸热功率达到250 k W时,NO_x生成水平分别为78,30,20 mg/m3;继续增加稀释剂添加量,燃烧稳定性变差。采用烟气再循环技术,在燃烧稳定极限点的NO_x排放浓度随过量空气系数增大先下降后保持不变;而采用加湿燃烧技术,在稳定极限点的NO_x排放度随过量空气系数升高而升高。     

烟煤层燃炉颗粒物的生成特征与管理控制

以95台中小型燃烟煤层燃炉(≤70MW)的燃料特性分析数据和颗粒物(PM)排放实测数据为基础,利用统计分析方法,研究了锅炉出力、过量空气系数、燃煤灰分含量对燃烧过程中PM初始排放浓度的影响,分析了燃煤锅炉PM排放现状,讨论了我国中小型燃煤锅炉PM排放管理控制的潜力和可行性。结果表明,在锅炉运行负荷≥80%的条件下,PM初始排放浓度随过量空气系数和燃煤灰分含量的增加略有增大,而与锅炉出力无关;在用烟煤层燃炉PM排放浓度基本上能够满足国家现行污染物排放标准规定的排放限值要求;有96%的锅炉所采用的除尘装置的除尘效率大于80%;与其他国家相比,目前我国对于中小型燃煤锅炉PM的排放控制还处于中等水平,建议在国家层面上适时提高燃煤锅炉颗粒物的排放限制。     

燃BMF锅炉烟气监测过量空气系数取值探析

阐述了锅炉中燃料燃烧时过量空气系数及其对污染物排放浓度的影响。指出BMF是固体燃料,其过量空气系数取值,应按燃煤固体燃料值为1.8。提出了减少排放烟气中过量空气系数实测值的途径。     

中小型烟煤层燃炉NOx排放因子的研究

以86台中小型烟煤层燃炉(额定出力≤65 MW)的燃料特性和NO_x排放实测数据为基础,采用统计分析方法,分析了锅炉出力、过量空气系数、燃煤挥发分〔w(挥发分)〕和燃煤含氮量〔w(N)〕对NO_x排放因子的影响,研究了NO_x排放因子的确定方法. 结果表明:中小型烟煤层燃炉基于燃料消耗量、低位发热量和燃煤w(N)的NO_x排放因子EF_C,EF_H和EF_N的平均值分别为3.87 g/kg,185.01 ng/J和0.47 kg/kg;锅炉出力对NO_x排放因子没有显著影响;NO_x排放因子随燃煤w(挥发分)增高而降低;随过量空气系数和燃煤w(N)增大,NO_x排放因子的EF_C和EF_H增高,而EF_N并不受影响.      

煤粉锅炉掺烧石油焦燃烧污染物排放特性的研究

对煤粉锅炉掺烧石油焦的污染物排放特性作了较详细的研究.煤焦粉的细度对燃烧性能影响很大,因而间接地影响NO_x,SO₂排放;煤焦掺混比以及煤、焦各自的含氮、硫量对NO_x,SO₂排放影响明显;烟气中SO2的浓度随过量空气系数α的增大而减少,过量空气系数α在1.3～1.4之间时,烟气中NO_x的浓度最高.现场调试结果与实验室试验结果基本一致.实际应用中应综合考虑煤焦粉细度、煤焦掺混比以及煤焦中含氮、硫量对其燃烧特性以及NO_x,SO₂排放的影响,以确定合适的细度及煤焦掺混比投入生产运行中.      

我国中小型燃煤锅炉SO2排放特征与控制对策

 基于87台中小型燃烟煤层燃炉(£70MW)的燃料特性分析数据和SO2排放实测数据,研究了锅炉出力、过量空气系数、燃煤硫含量对燃烧过程中SO2初始排放浓度的影响,分析了燃煤锅炉SO2排放现状,讨论了我国中小型燃煤锅炉SO2排放管理控制的潜力和可行性.结果表明,在锅炉运行负荷³80%的条件下,SO2初始排放浓度与燃煤硫含量之间具有显著的线性相关性,与锅炉出力和过量空气系数无关;分别有94%和87%的实测锅炉可以满足国家现行排放标准规定的第I和第II时段SO2最高允许排放浓度.     

1000 MW燃煤锅炉宽负荷区炉内结焦和飞灰含碳量分析

针对1台1 000 MW四角切圆塔式燃煤锅炉,研究煤粉粒径和锅炉负荷对炉内水冷壁结焦和飞灰含碳量的影响。利用FLUENT软件平台,对炉内燃烧进行了三维稳态数值模拟,并对结焦程度和结焦原因进行了详细分析。结果表明:在选定的50%、75%、100%3种负荷下,水冷壁的结焦程度和飞灰含碳量均随煤粉颗粒粒径的增大而增加。在选定的25,40,60,80,100,120μm 6种平均煤粉粒径下,水冷壁的结焦程度和飞灰含碳量均随锅炉负荷的降低而增加。针对锅炉低负荷下结焦严重和飞灰含碳量过高问题,应用广义回热技术,提高一次风、二次风温度,从而提高煤粉颗粒温度和燃烧效率,可以很大程度上解决该问题。该研究结果可为燃煤锅炉运行实践、设计以及改造提供依据。     

城市混合垃圾组分及其燃烧产物特性分析

对混合垃圾自然组分、物性及燃烧产物特性进行了实验研究。结果表明 :城市混合垃圾中无机物、水分、灰分含量较高 ,热值较低 ;燃烧产物中烟气的主要成分是 N2 、CO2 、H2 O、O2 ,以及少量 CO、HCl、NOx、SOx、H2 S等 ;灰渣的主要成分是 Si O2 、Al2 O3、Ca O、Ca SO4等。随着过量空气系数的增大 ,呈现 CO、HCl、SOx、H2 S减少 ,NOx 增加的趋势 ;随着温度的升高 ,CO、H2 S逐渐减少 ,HCl、SOx、NOx 增加 ;适宜的城市混合垃圾燃烧温度应在 80 0～ 1 0 0 0℃     

废轮胎热解富芳烃油燃烧温度与烟气污染物排放特性

清洁燃烧是各类有机固废热解油高效能源化利用的主要途径。全钢废轮胎热解油产物中芳香烃含量约占30%,其热值及黏度与柴油相似,但闪点偏低,仅为20℃。在自建燃烧炉膛中进行燃烧实验,研究了废轮胎热解油的燃烧温度及烟气排放特性。实验发现,当过量空气系数为1.3时,热解油燃烧温度最高;当过量空气系数为1.4时,烟气中CO浓度降至0;NO_x浓度随着过量空气系数增大而升高;过量空气系数超过1.3后,SO₂浓度大幅降低。喷射油压提升可提高燃烧温度,使热解油燃烧更加充分,同时可降低烟气中CO浓度,促进热力型NO_x生成。当压力由1.5 MPa升至1.75 MPa时,燃烧温度、CO浓度与NO_x浓度变化幅度最大。喷嘴喷孔直径增大会使雾化锥角增大,燃油雾束更易展开与空气接触反应,CO浓度随之降低;同时雾化锥角的增大可减小喷雾贯穿距,缩短火焰长度,减少烟气在高温区的停留时间,降低NO_x浓度。     

1025t/h四角切圆煤粉炉内空气过量系数对NO生成的影响

文章采用计算流体力学软件Fluent数值模拟了1 025 t/h四角切圆煤粉炉内的湍流扩散燃烧,分析了空气过量系数对炉内烟气速度、烟气温度和氮氧化物组分的影响。结果表明:空气过量系数会对炉内流场的空气动力学特性和温度场分布均匀性产生显著影响。煤粉炉膛最佳空气过量系数为1.07,此时炉内温度场、速度场和浓度场的分布可使燃烧中间产物HCN和NH_3较好的将燃料型NO还原为N_2,来充分发挥空气分级燃烧降低NO排放的功效。     

Pollutant emission characteristics of rice husk combustion in a vortexing fluidized bed incinerator

Rice husk with high volatile content was burned in a pilot scale vortexing fluidized bed incinerator. The fluidized bed incinerator was constructed of 6 mm stainless steel with 0.45 m in diameter and 5 m in height. The emission characteristics of CO, NO, and SO2 were studied. The effects of operating parameters, such as primary air flow rate, secondary air flow rate, and excess air ratio on the pollutant emissions were also investigated. The results show that a large proportion of combustion occurs at the bed surface and the freeboard zone. The SO2 concentration in the flue gas decreases with increasing excess air ratio, while the NOx concentration shows reverse trend. The flow rate of secondary air has a significant impact on the CO emission. For a fixed primary air flowrate, CO emission decreases with the secondary air flowrate. For a fixed excess air ratio, CO emission decreases with the ratio of secondary to primary air flow. The minimum CO emission of 72 ppm is attained at the operating condition of 40% excess air ratio and 0.6 partition air ratio. The NOx and SO2 concentrations in the flue gas at this condition are 159 and 36 ppm, which conform to the EPA regulation of Taiwan.     

Emissions of SO2, NO and N2O in a circulating fluidized bed combustor during co-firing coal and biomass

This paper presents the experimental investigations of the emissions of SO2, NO and N2O in a bench scale circulating fluidized bed combustor for coal combustion and co-firing coal and biomass. The thermal capacity of the combustor is 30 kW. The setup is electrically heated during startup. The influence of the excess air, the degree of the air staging, the biomass share and the feeding position of the fuels on the emissions of SO2, NO and N2O were studied. The results showed that an increase in the biomass shares resulted in an increase of the CO concentration in the flue gas, probably due to the high volatile content of the biomass. In co-firing, the emission of SO2 increased with increasing biomass share slightly, however, non-linear increase relationship between SO2 emission and fuel sulfur content was observed. Air staging significantly decreased the NO emission without raising the SO2 level. Although the change of the fuel feeding position from riser to downer resulted in a decrease in the NO emission level, no obvious change was observed for the SO2 level. Taking the coal feeding position R as a reference, the relative NO emission could significantly decrease during co-firing coal and biomass when feeding fuel at position D and keeping the first stage stoichiometry greater than 0.95. The possible mechanisms of the sulfur and nitrogen chemistry at these conditions were discussed and the ways of simultaneous reduction of SO2, NO and N2O were proposed.     

O2/CO2气氛下氮反应机理的研究

选取CH4、O2、CO2、Ar、NO、NH3，等气体，作为混合气和煤粉一起送入一维沉降炉内，以模拟O2／CO2气氛下煤中燃料氮、循环NO以及二者的相互作用对NO排放的影响，结果显示，在还原性气氛下NH3、HCN、CH4、CO与循环NO间的反应是NO排放下降的主要因素，且煤焦与NO的异相反应、吸附反应对NO的降解效果要明显高于氧化性气氛，同时，CO2体积分数的增加使得燃料中氮的氧化率升高，循环NO的降解率下降；氧化性气氛下随CO2体积分数的增加，燃料中氮的氧化率也增加，但循环NO的降解率升高．当CO2体积分数不变时，其对NO降解的作用随循环NO体积分数的增加愈加明显，在循环NO也不变且CO2体积分数较低时，随过量空气系数的增加，循环NO的降解率下降，而CO2体积分数较高时则出现相反情况。     

Simulation of temporal and spatial change of N2O emissions in the Yangtze River Delta

A biogeochemical model(DNDC) is combined with a plant ecological model to estimate N2O emission from rice paddy fields in the Yangtze River Delta region. The model is driven by local meteorological, soil, and physiological data and is validated for 1999 and 2000 at a site in the region, which showed that the simulated N2O emissions agree fairly well with the observed data. This adds some confidence in the estimated N2O emissions during 1950 and 2000 in the Hangzhou Region. A significant correlation between the N2O emissions and the population for the Hangzhou Region is found, which is due to a combination of increased application of fertilizers and cultivated area.Such a correlation can not be established for the whole Yangtze River Delta region when the data of both urban and rural are as areincluded. However, when the data from the heavily urbanized areas are excluded, a significant correlation between population and N2O emissions emerges. The results show clearly that both the temporal and the spatial N2O emissions have significant positive relationship with population under traditional farming practice. These results have implications for suitable mitigation options towards a sustainable agriculture and environment in this region.     

Temporal and spatial variations of air pollution across China from 2015 to 2018

This study investigated concentrations of PM_2.5, PM₁₀, SO₂, NO₂, CO and O₃, and air quality index（AQI） values across 368 cities in mainland China during 2015–2018. The study further examined relationships of air pollution status with local industrial capacities and vehicle possessions. Strong correlations were found between industrial capacities（coal, pig iron, crude steel and rolled steel） and air pollution levels. Although statistical and ...     

大气例行点位常规监测污染物的相关性分析及防控措施研究

根据济南市历下区5个大气例行监测点位2015年上半年PM2.5、PM10、SO2、CO、NO2、O3逐小时浓度的监测数据,通过SPSS软件对各项污染物的相关性进行分析得出:CO与PM2.5、PM10、SO2、NO2强相关性出现次数最多,表明CO排放源是引起颗粒物污染的主要原因之一.对监测点位周边2 km范围内机动车尾气和餐饮燃煤两项污染源进行排放量估算得出:机动车尾气CO、NOx、PM2.5和PM10年排放量分别为388.18吨、111.18吨、4.35吨和4.72吨;餐饮燃煤CO、SO2、NOx年排放量分别为36.0吨、24.0吨和9.6吨.因此,控制CO排放源对改善济南市大气环境质量至关重要.     

沼泽湿地CO2、CH4、N2O排放对氮输入的响应

利用静态暗箱-气象色谱法，选取小叶章沼泽化草甸进行野外原位试验，研究氮输入对沼泽湿地CO2、CH4和N2O等3种温室气体排放的影响,结果表明：氮输入对沼泽湿地CO2和CH4排放有明显影响，其季节排放总量分别是对照处理的1.3和2.5倍，但对CO2和CH4的季节变化模式无明显影响；氮输入对N2O的排放强度和季节变化模式均有显著影响,CO2排放通量与5cm深土壤温度存在显著的正相关关系，与地表温度和1.5m气温存在指数关系，而CH4和N2O排放与温度之间没有显著的相关性．在20、100和500年时间尺度上氮输入处理的CH4和N2O全球增温潜势（GWP）分别比对照处理增加了150％、150％和80％，表明氮输入在长、短时间尺度上都是增强CH4和N2O的温室效应的。     

中国水泥工业节能减排效果分析及对策研究

根据水泥工业大气污染物排放的数学模型;测算2005年-2011年中国水泥工业二氧化碳(CO2)、氮氧化物(NO2)、二氧化硫(SO2)、颗粒物(PM)和氟化物(F)等污染物排放量,分析节能减排的效果并提出解决问题的对策。结果表明:水泥工业CO2排放量逐年增长,并且与水泥产量和单位产品综合能耗呈线性关系;原料煅烧和能源利用过程CO2排放量分别占56%和44%;单位水泥产品CO2排放强度由0.68 t·t-1下降到0.58 t·t-1,相当于每年节约标准煤682×104t、减少CO2排放共计1.03×108t。NO2排放量分别是SO2、PM、F的4、7、160倍。发展新型干法技术、建设烟气脱硝装置、协同处置固体废物是水泥工业未来节能减排的发展方向。     

废物管理活动中N_2O产生及排放研究进展

N_2O是一种重要的温室气体,并且对臭氧层有严重的破坏作用,因而在全球气候变化研究中受到广泛关注。随着人类活动的加剧,全球废物排放量呈上升趋势,且废物管理活动中产生的N_2O显著增加了全球温室气体的排放。废物管理活动中N_2O排放源主要包括废水处理、动物粪肥管理及生活垃圾处理处置系统。目前对废物管理活动中N_2O排放缺乏全面认识,文章综述了废物管理活动中N_2O排放机理及产生规律,指出应加强废物管理活动中N_2O减量化方向的研究。     

农业废弃物对土壤中N_2O、CO_2释放和土壤氮素转化及pH的影响

用一种丹麦农业土壤作为供试材料，在室内培养条件下探讨了施用４种常见农业废弃物（猪粪泥浆、牛粪泥浆、黑麦秸秆、小麦秸秆）对土壤中Ｎ_２Ｏ、ＣＯ_２释放和土壤氮素转化及ｐＨ的影响。试验结果表明，施用４种农业废物均会明显增加Ｎ_２Ｏ、ＣＯ_２释放量。培养２周后，土壤中Ｎ_２Ｏ的释放量分别为：猪粪＞牛粪＞黑麦秸秆＞小麦秸秆；ＣＯ_２的释放量为：黑麦秸秆＞小麦秸秆＞牛粪＞猪粪。施用４种农业废物均会显著促进ＮＯ_３－Ｎ的转化和ＮＨ_４－Ｎ、ＮＯ_２－Ｎ的累积。施用４种废物均会改变土壤ｐＨ，其中施用秸秆的２个处理中ｐＨ显著降低，但施用牲畜粪便的２个处理中ｐＨ则稍微升高。