糠醛渣在流化床中燃烧特性的试验研究

介绍了糠醛渣生物质燃料的工业分析,临界流化程度,着火温度,与煤掺烧时的烧结特性,灰成分分析以及热天平分析,重点研究了糠醛渣燃烧后灰成分析及热重分析,解释了没有烧结的根本原因在于,糠醛渣燃烧后形成的灰中,钾盐主要以硫酸盐物质存在,熔点较高所致,试验发现,糠醛渣中氯含量较高,燃烧后灰中氯含量很低,说明主要以HCl气体析出,同时糖醛渣中含有呋喃甲醛,当然烧不充分时将会产生多氯二苯并呋喃（PCDFs－二恶英）,提出合理的燃烧温度及停留时间,试验结果为设计流化床糠醛渣锅炉奠定了基础。     

流化床垃圾焚烧炉中NOx的排放特性试验研究

在哈尔滨垃圾发电厂流化床垃圾焚烧炉上进行NOx的排放特性试验研究,得到了垃圾特性、燃烧温度、烟气中氧浓度、尿素喷射量等因素对排烟中NOx排放浓度的影响规律.试验结果表明,随着垃圾中有机物含量及燃烧温度的增加,NOx排放浓度增加;随着烟气中氧浓度(＜7%～8%)的增加,NOx排放浓度也相应增加,进一步增加空气量,NOx排放浓度开始缓慢下降.在850～900℃下喷尿素水溶液进行脱氮试验研究,发现NOx排放浓度不但没有降低反而比不喷尿素时增高,说明尿素中的有机氮被氧化为NOx,造成总NOx排放浓度增加.在正常燃烧工况下,排气中NOx浓度一般小于150mg/m3.此研究结果对流化床垃圾焚烧炉运行具有指导作用.     

循环流化床中糠醛渣与煤混燃特性的试验研究

在炉膛尺寸为150 mm×150 mm×2 500 mm的循环流化床燃烧试验台上进行糠醛渣与煤的混燃试验,研究其燃烧特性、尾部飞灰及烟气排放特性。研究表明:糠醛渣掺混质量比例为10%-50%的混合燃料在循环流化床中均可稳定燃烧;随着糠醛渣的掺混比例增加,炉膛上部温度升高,尾部飞灰含碳量下降,而颗粒排放浓度升高;随着流化风速增加,炉膛上部温度升高。密相区的温度升高,CO排放浓度下降,SO2、NOx排放浓度上升;糠醛渣的掺混比例增加,CO排放浓度上升,SO2、NOx排放浓度下降。     

棉秆流化床燃烧的成灰特性和床料选择

介绍了山东某地棉秆的物理、化学特性,在0.2MWth试验装置上研究了棉秆流化床燃烧时不同床高的温度分布,利用ICP技术对灰的元素成分进行了分析,发现棉秆流化床燃烧时部分碱金属以挥发态析出,其中钾元素析出比例最大.飞灰中碱金属成分含量较高,对流受热面的沾灰可能性很大.该文中重点对棉秆流化床燃烧时两种床料:石英砂和高铝矾土的烧结特性进行了研究,通过使用SEM/EDX对两种床料燃烧前后微观结构和元素成分的变化进行了对比,结果发现石英砂床料颗粒表面形成了低温共熔混合物,烧结非常严重,并最终影响到正常流化,高铝矾土床料经长时间运行没有发现烧结现象,因此,棉秆流化床燃烧选择弱酸性的高铝矾土床料为宜.试验结果为棉秆流态化燃烧锅炉设计和运行提供了理论基础.     

粉煤流化床燃烧中N_2O的生成特性

粉煤流化床 (PC- FB)是一项燃烧效率高 ,同时实现炉内脱硫 ,低 NOx 和 N2 O排放的新型高效、清洁煤燃烧技术。在一座 0 .3MW的试验台上 ,研究了其 N2 O生成与分布特性 ,包括床层温度 Tb、流化速度 U0 、二次风率 R2 ,PC- FB流化床燃烧区 (FBCZ)出口氧浓度 O 2 、钙硫比 (Ca/S)对 FBCZ出口 N2 O浓度的影响 ;以及各层二次风份额(R2 i% )及悬浮空间燃烧区 (FCZ)的温度分布与炉内 N2 O浓度分布的关系。     

棉秆在流化床中的燃烧特性

介绍了棉秆的物理、化学特性,30～50 mm棉秆和床料混合物的临界流化速度,以及棉秆热解、燃烧的热重试验结果,重点研究棉秆流化床燃烧时的温度分布,并利用ICP技术对灰组成进行了分析,得出棉秆流化床燃烧时碱金属的析出特性.分析表明,棉秆着火温度低,挥发分析出速度快,部分碱金属流化床燃烧时以挥发态析出,其中钾元素析出比例最大,飞灰中碱金属成分含量较高,对高温对流受热面的沾灰可能性很大.     

玉米秆在流化床中燃烧特性的初步研究

对玉米秆与弱酸性床料的混合流化特性进行了研究,结果表明,长度为20～50mm玉米秆与一定粒径分布的床料,当质量配比为1%,流化数N=3～6时,能较均匀地混合流化,但N>6后,混合的均匀度有所下降.根据热重试验结果可以看出玉米秆着火温度低,挥发份析出速度快,并容易燃尽.在0.2MWth流化床试验台上研究发现,当N>6时,玉米秆和床料分层严重,密相区温度在820℃以下,当N=3～6时,密相区温度能达到设计要求,说明冷态试验结果能够指导热态运行,玉米秆流化床燃烧时流化风速不能太大.经过24h热态试验后,床料没有出现烧结现象,利用XRF技术分析发现玉米秆灰中碱金属含量较高,高温对流受热面的沾灰可能性较大.     

循环流化床锅炉燃用巴基斯坦塔尔褐煤试验研究

在3 MW循环流化床锅炉(CFB)燃烧试验台上开展巴基斯坦塔尔褐煤燃烧特性、沾污特性、排放特性等试验研究.试验结果表明:巴基斯坦塔尔褐煤为高水分、高挥发分、低灰分、低灰熔点、低热值褐煤,极易着火、易燃尽;煤中碱金属含量较高,存在较强沾污风险;石灰石纯度高、活性好,脱硫效果明显;通过合理的控制相关运行参数,可控制较低的S...     

油页岩半焦在流化床内的燃烧特性研究

为了实现油页岩半焦的鼓泡流化床燃烧,构建炉膛尺寸150 mm×150 mm×2 500 mm的流化床试验台,研究了油页岩半焦的燃烧特性和烟气中污染物的排放特性。研究表明:低热值半焦可以在鼓泡流化床中稳定燃烧;随密相区温度的升高,烟气含氧量及燃料停留时间降低,SO_2与NO_x排放浓度增大;床层高度比(指床层高度与炉膛本体高度比)为0.16时,烟气含氧量及燃料停留时间有最大值;密相区温度升至900℃时,飞灰与底渣的含碳量达到稳定值,且飞灰浓度最低;鼓泡流化床燃烧的典型工况:流化风温取400℃,床层高度比取0.16,炉内密相区温度取900℃。     

运行调整对循环流化床锅炉NOx排放影响分析

在300 MW循环流化床锅炉上进行了运行调整对NOx排放影响分析,考查了燃烧温度、过剩空气系数、空气分级、Ca/S等因素对NOx排放的影响.试验结果表明：燃烧温度与过剩空气系数对NOx的排放浓度影响显著;空气分级燃烧对NOx的排放浓度有一定影响,但影响相对有限;过大的Ca/S易导致NOx排放浓度的增加.     

竹园污泥焚烧污染物排放特性的试验研究

选取上海竹园污泥,将原始污泥样品分为全干污泥、均匀干化污泥(含水率10%)和干湿混合污泥(含水率20%,干湿污泥质量比例为10∶3)三种样品,分别送入小型流化床焚烧炉中焚烧。试验研究了全干污泥在750℃、850℃、950℃三个工况下的燃烧特性,并研究了均匀干化污泥和干湿混合污泥在850℃工况下的燃烧特性。研究发现,上海竹园污泥在小型流化床焚烧炉中燃烧时,排放的主要常规污染物包括CO、SO2、NOx、HCl等以及二噁英和Cd、Hg、Pb等重金属。不同燃烧温度和含水率对污染物的排放有一定影响,提高燃烧温度,CO、SO2、NOx、HCl等的排放基本呈现出下降趋势,而烟气中Pb的排放随着温度上升而升高,相同燃烧温度下含水率升高能降低二噁英的排放总量,随着含水率的提高飞灰中重金属含量有所降低,而底渣中重金属含量呈上升趋势。     

A comprehensive study on NOx emission and fuel nitrogen conversion of solid biomass in bubbling fluidized beds under staged combustion

Despite the relatively low emissions in fluidized-bed combustion, NOx emission for biomass combustion is still a major concern because of increasingly stricter regulations. To realize NOx emission behavior in fluidized beds comprehensively, the effects of bed temperature, excess oxygen, staged combustion, and flue gas recirculation (FGR) are investigated in this study. In particular, three different types of operation are applied in staged combustion to find out the key parameter. The results indicate that NOx emissions increase with both bed temperature and excess oxygen, in which the influence of excess oxygen is greater than the other. Lowering bed temperature by water addition seems to be able to simultaneously reduce NOx emission and agglomerate formation, especially for fuels with high nitrogen content, but the pros and cons should be considered. The results in staged combustion infer that the residence time is much more critical than the stoichiometry in the bed. As for FGR, its impact appears to depend on the type of fuel. The correlation between NOx emission behavior and fuel characteristics is also scrutinized; it is concluded that the fuel-N conversion to NOx is essentially related to some features of fuels.     

流化床启动过程中底料磨损行为研究

以国内首台自主研发的65t/h低倍率油页岩循环流化床锅炉底料灰为研究对象,在小型流化床试验台上考察了流化风速、流化时间和床层温度等因素对底料磨损程度的影响,据此建立了二阶磨损模型.结果表明：流化状态下页岩灰的磨损先后经历快速衰减和稳定磨损2个阶段,页岩灰在流化床内的质量保持率呈指数衰减趋势;随着流化风速增大,床层温度升高,磨损相对加剧;二阶磨损模型能够很好地描述流化床内页岩灰质量的变化规律.     

Combustion of hydrogen in a bubbling fluidized bed

The combustion of hydrogen in a hot, bubbling bed of quartz sand fluidized by air has been studied for the first time, by injecting hydrogen just above the distributor, via six horizontal fine tubes of Cr/Ni. Overall the fluidizing gas was oxygen-rich, with the composition varying from nearly stoichiometric to very lean mixtures. With the bed initially fluidized at room temperature, combustion (after ignition by a pilot flame) occurs in a premixed flame sitting on top of the bed. When the sand warms up, combustion becomes explosive in bubbles leaving the bed, exactly as with a hydrocarbon as fuel. However, in contrast to hydrocarbons, it is clear that when the bed reaches 500-600 °C, heat is produced both above the top of the bed (because of H₂ bypassing the bed) and very low down in the bed. In fact, with hydrogen as fuel, the location of where bubbles ignite descends abruptly to low in the sand; furthermore, the descent occurs at ∼500 °C, which is ∼100 K below the ignition temperature predicted by well-established kinetic models. However, the kinetic models do reproduce the observations, if it is assumed that the Cr/Ni hypodermic tubes, through which the fuel was injected, exert a catalytic effect, producing free H atoms, which then give rise to HO₂ radicals. In this situation, kinetic modeling indicates that bubbles ignite when they become sufficiently large and few enough to have a lifetime (i.e. the interval between their collisions) longer than the ignition delay for the temperature of the sand. The amounts of NO found in the off-gases were at a maximum (24 ppm), when the bed was at ∼500 °C for λ=[O₂]/stoich[O₂]=1.05. The variations of [NO] with [air]/[H₂] and also temperature indicate that NO is produced, at least partly, via the intermediate N₂H. In addition, the air-afterglow emission of green light (from NO+O→NO₂+hν) was observed in the freeboard, indicating the presence there of both NO and free atoms of oxygen for 1.05<λ<1.1.     

油页岩及半焦混合燃烧的燃尽特性

油页岩是一种高灰分、高挥发分、低热值的劣质燃料,不适合通常的燃烧方式,而将其作为循环流化床锅炉燃料是适宜的.采用收缩核模型对油页岩燃烧过程进行理论分析,通过在自行搭建的流化床试验台上对桦句油页岩及半焦混合燃烧燃尽特性进行试验研究.分析了不同床层温度、流化速度、混合比等因素对燃尽规律的影响.结果表明:提高床层温度,增大流化速度和混合比,有助于减少燃尽时间;整个燃烧过程更接近于化学动力控制.     

煤灰对流化床氮氧化物排放影响的试验研究

在流化床试验台上分别燃烧典型烟煤和褐煤,测量加入煤灰和煤灰中无机矿物质（CaO、MgO、Fe2O3、Al2O3、CaSO4、MgSO4）前后N2O和NO排放质量浓度的变化,研究煤灰对流化床氮氧化物排放的影响及其主要活性成分.结果表明：煤灰能降低N2O排放质量浓度,提高NO排放质量浓度;燃料氮向NOx的总转化率随着灰分质量分数的增加而提高;煤灰中影响氮氧化物排放的主要活性成分为CaO、Fe2O3和MgO.     

Case studies––Problem solving in fluidized bed waste fuel incineration

Fluidized bed combustion technology has been widely used as the new, flexible, multi-fuel boiler for waste combustion and energy recovery from low grade fuels. However, problems such as low thermal efficiency, high emissions, bed agglomeration etc. are still encountered in the operation of fluidized beds. Valuable experiences were gained from two case studies recently conducted regarding wastes combustion in industrial scale fluidized beds.In the first case, the performance of a fluidized bed combustor for energy recovery from oil sludge was evaluated during the commissioning trials. Apart from the sludge characterization and bed material analysis, the combustion efficiency, solid flow balance and on stack emission of CO, SO_x and NO_x were investigated, as well as the fluidization quality. Although the system was operated with good combustion efficiency (>99.9%), sulfur dioxide emission (>1000 ppm) was found to be substantially higher than the allowable discharge limit. It was recommended to increase the limestone feed rate in order to meet the SO₂ emission standard, and subsequently, installation of a cyclone is suggested to remove the potentially significant increase in ash and fine particles.The second case study focused on the bed agglomeration observed in a fluidized bed incinerator where a burning blend of three wastes (i.e. carbon soot, biosludge and fuel oil) is involved. To understand the mechanisms and related chemistry, several analytical approaches are employed to identify the bed materials (fresh sand and degrader sand) and the clinkers formed from full scale incinerator tests. The formation of clinker is believed to follow the mechanism of partial melting and/or reactive liquid sintering. The effects of temperature and blending ratio are tested in a muffle furnace. Carbon soot is believed to be more susceptible than the other two fuels. Thermodynamic multi-phase multi-component equilibrium (TPCE) calculations predict that the main low melting point species are predominant under the oxidizing condition, suggesting that reducing conditions might be favorable to restrain bed agglomeration. This study provides valuable information for better understanding of the chemistry related to clinker formation; it also helps in developing methods for control and possible elimination of the bed agglomeration problem for the design fuels.     

Development of a low-temperature two-stage fluidized bed incinerator for controlling heavy-metal emission in flue gases

This study develops a low-temperature two-stage fluidized bed system for treating municipal solid waste. This new system can decrease the emission of heavy metals, has low construction costs, and can save energy owing to its lower operating temperature. To confirm the treatment efficiency of this system, the combustion efficiency and heavy-metal emission were determined. An artificial waste containing heavy metals (chromium, lead, and cadmium) was used in this study. The tested parameters included first-stage temperature and system gas velocity. Results obtained using a thermogravimetric analyzer with a differential scanning calorimeter indicated that the first-stage temperature should be controlled to at least 400 °C. Although, a large amount of carbon monoxide was emitted after the first stage, it was efficiently consumed in the second. Loss of the ignition values of ash residues were between 0.005% and 0.166%, and they exhibited a negative correlation with temperature and gas velocity. Furthermore, the emission concentration of heavy metals in the two-stage system was lower than that of the traditional one-stage fluidized bed system. The heavy-metal emissions can be decreased by between 16% and 82% using the low-temperature operating process, silica sand adsorption, and the filtration of the secondary stage.     

620t·h-1循环流化床锅炉提效 及低NOx改造的实践

针对国产620 t·h-1循环流化床锅炉效率及NOx排放浓度不能达到性能保证值的现状,分析了锅炉的热损失情况以及NOx排放浓度与平均床温等参数间的规律,得出排烟热损失及固体未完全燃烧热损失过大、平均床温偏高、因风帽磨损引起的流化质量下降是造成锅炉效率及NOx排放浓度超性能保证值的主要原因.在此基础上提出了提高空预器吸热量、降低床温、提高流化质量的改造思路,对改造思路逐项分析,得出了回转式空预器改造、加长水冷屏和屏式过热器以及风帽改型等具体改造措施.对改造后参数作了分析,并提出改造完成后可能出现的热风管磨损及浓相区上移等问题.通过改造实现了锅炉提效和减排的目标.