生物质锅炉对流受热面积灰冷态模拟实验研究

燃用生物质的CFB锅炉的尾部受热面上容易出现严重的积灰问题,严重影响换热并可能导致停炉等问题。惯性碰撞是引起生物质锅炉积灰的主要机理,而温度通过影响灰中熔融质所占的比例,进而影响积灰程度。采用加热熔融的石蜡与循环灰的混合物来模拟真实的高黏性飞灰,并搭建了冷态积灰实验台。发现石蜡与循环灰的熔融物可以快速地黏附在受热面上,大大缩短了实验时间。通过图像处理得到沉积厚度随时间的变化情况,沉积过程的生长趋势与真实生物质积灰实验一致。在冷态下实验发现,随着熔融质比例、烟气速度、颗粒粒径的增加,积灰程度呈上升趋势,为生物质锅炉的设计和运行提供了一定的参考依据。     

锅炉除灰剂的除灰原理及其使用

<正> 一凡固体或液体燃料在锅炉内燃烧,其受热面和烟道上都会粘结烟灰,甚至结渣。受热面上有了积灰和结渣,会使传热恶化、排烟温度升高、热效率降低、能耗增加;更有甚者是,因受热面积灰后还往往加速管壁的腐蚀,影响锅炉的正常运行,严重时得停炉清渣。以往由人工打焦块、定期停炉清积灰,这不仅劳动强度大、效率低,而且不安全;对锅炉(在运行中)受热面上的积灰,则是用蒸汽或压缩空气吹除,这需耗蒸汽和动力,同时吹     

五彩湾煤在O2/CO2燃烧条件下的积灰特性

锅炉燃用准东煤极易发生严重的受热面积灰结渣等问题,制约了新疆准东地区煤炭资源的大规模利用。在一维沉降炉燃烧与积灰试验系统上,研究了准东五彩湾煤的积灰特性,分析了稀释气体种类、O_2/CO_2燃烧中氧浓度对飞灰沉积的影响。结果表明:在21%氧浓度下,与稀释气体为N_2相比,稀释气体为CO_2时得到的沉积灰颗粒之间黏连现象不明显,积灰倾向较弱; O_2/CO_2燃烧条件下,随着氧浓度提高,五彩湾煤的积灰倾向加重,细散灰颗粒减少,球形灰颗粒比例增加,灰颗粒的黏连现象加重。SEM-EDS分析结果表明:O_2/CO_2燃烧中随氧浓度的提高,沉积灰中的块状灰颗粒表面缩孔及凹坑增多,且灰颗粒表面黏附了白色细散絮状灰,Na和Cl的富集加重,这是造成高氧浓度燃烧受热面积灰加剧的重要原因;稀释气体种类对五彩湾煤积灰倾向的影响研究中,稀释气体为N_2(空气燃烧)时,Na和Cl含量明显高于稀释气体为CO_2(O_2/CO_2燃烧)时的含量。此外,燃烧稀释气体为N_2的沉积灰中还出现了Ca和S元素的富集,高温下CaO与硅铝酸盐发生反应生成低温共熔体,这也是空气燃烧时积灰较O_2/CO_2燃烧严重的重要原因。XRD分析结果在一定程度上佐证了EDS的分析结论,灰分中CaSO_4、NaCl等低熔点物质的富集导致了空气燃烧工况和O_2/CO_2高氧浓度燃烧工况积灰的加剧。燃烧的颗粒温度差异是导致O_2/CO_2燃烧和空气燃烧积灰特性不同的主要原因,也是造成不同氧浓度下O_2/CO_2燃烧积灰特性差异的主要原因。煤燃烧的颗粒温度较高时,煤粉着火、燃烧性能得到改善,更高的颗粒温度会导致烟气中出现更多的熔融灰,灰颗粒表面出现熔融相进而增强了灰表面的黏性,加剧积灰现象。     

垃圾焚烧系统换热表面的积灰生长与控制研究进展

焚烧是我国处理城市生活垃圾的重要方式，能够实现城市生活垃圾的减量化、无害化和资源化利用。由于城市生活垃圾水分高、盐分多、热值低，导致垃圾焚烧炉普遍面临严重的积灰问题，这不仅为垃圾焚烧炉的安全运行带来隐患，还严重影响垃圾焚烧发电厂的经济效益。本文综述了垃圾焚烧炉受热面积灰生长的研究现状，介绍了垃圾焚烧炉受热面积灰生长的机理，分析了飞灰粒径、烟气流速、烟气温度、换热面温度等对垃圾焚烧炉受热面积灰生长特性产生影响的因素。在燃煤锅炉和生物质炉积灰结渣的现有积灰模型基础上，需要结合垃圾炉的积灰实验数据发展可以预测垃圾焚烧炉积灰结渣问题的模型。针对垃圾焚烧炉受热面积灰严重的现象，本文提出了设备改进、工艺优化、使用添加剂和涂层技术抑制积灰生长的一系列方法。最后总结了当前的重点研究内容，提出了建立能够准确预测垃圾焚烧炉积灰生长的模型，开发新的有效减轻垃圾焚烧炉换热面积灰的涂层等今后开展研究的方向，为垃圾焚烧电厂的合理运行提供了参考建议。     

锅炉清灰剂的生产和应用

<正> 以固体或液体为燃料的锅炉在燃烧时,其受热面和烟道都会粘附烟灰。烟灰的成分及其量随着燃料的种类、燃烧状况、附着部位的构造和表面温度不同而不同。灰垢的附着对锅炉热效率有很大影响。据有关部门测算,积灰的导热系数只有钢的0.2％,受热面积灰达0.1mm时,管子的吸热量减少15～20％;积灰0.4mm,降低40％。因此,如何及时消除锅炉受热面上的积灰,是重要的节能课题。我厂在调查了解辽宁、上海、南京等单位生产锅炉清灰剂的基础上,结合我省燃料     

生物质对呼盛褐煤灰熔融特性的影响

灰熔融特性对煤与生物质共气化意义重大。为探索生物质对褐煤灰熔融特性的影响规律, 向呼盛褐煤中分别加入不同质量比例的花生壳、玉米秸秆和松木屑, 采用ALHR-2型智能灰熔点测定仪对混合灰样的灰熔点进行了测定, X射线荧光仪(XRF)和X射线衍射仪(XRD)分析了灰熔融特性变化的原因。结果表明生物质能够在一定程度上降低呼盛褐煤的灰熔融温度, 这与生物质灰分含量以及混合灰样化学组成有关, 且生物质掺混比例与混合灰熔融特征温度呈现非线性关系;莫来石的生成和消失使花生壳与呼盛褐煤混合灰样和玉米秸秆与呼盛褐煤混合灰样的灰熔融特征温度出现了波动;高熔点硅线石含量的降低、低熔点钙长石含量的增加、以及低熔点白榴石和斜辉石的生成导致了松木屑与呼盛褐煤混合样灰熔融特征温度降低。     

电厂锅炉受热面积灰机理及其预防

电站锅炉检验时常发生积灰,怎样做好积灰面积预防与处理得到了重视。结合实践研究,就电厂锅炉受热面积灰机理及其预防方法进行简要分析,排除安全隐患从而保证电站锅炉稳定运营。     

含盐焚烧锅炉积灰防治措施

为解决含盐废弃物焚烧锅炉受热面积灰问题,从积灰形成机理、积灰危害以及结构设计上的积灰防范措施3个方面优化含盐焚烧锅炉的设计,并提出了积灰的防治措施。     

混合生物质燃料循环流化床锅炉受热面结焦机理研究

某75 t/h生物质循环流化床锅炉长期燃用混合燃料(桉树皮、木尾、木板、竹子和工业合成板),在实际运行过程中高温过热器和低温过热器区域结焦严重。考虑到不同生物质燃料特性的差异性,了解混合生物质燃料燃烧中壁面的结焦机理尤为迫切。研究了5种生物质燃料的灰成分和灰熔点特性,并对该循环流化床锅炉结焦严重的高温和低温过热器受热面区域的结焦和积灰样品进行物理和化学特性表征。研究结果表明:该锅炉所燃用的生物质燃料中,竹、木尾和木板的钙和钾含量高,灰中CaO含量在30%左右,K_2O含量在10%以上;桉树皮硅和铝含量高,灰中SiO_2含量高达62.4%;工业合成板与木尾含有较多的氯元素,灰中氯含量分别为0.670%和0.865%。5种生物质除竹和工业合成板灰熔融温度较低外,其余生物质灰熔融温度高,软化温度在1 200℃以上。过热器区域的结焦呈分层结构:高温过热器焦样的外层较硬,中层包含白色的KCl晶体和飞灰颗粒,外层以及飞灰颗粒均以Ca_2Al_2SiO_7、SiO_2、KCl、Ca_2MgSi_2O_7等为主;低温过热器焦样外层的灰成分与高温过热器侧焦样的组分相同,但白色中层的KCl晶体含量更高,其同烟气中KCl蒸气的冷凝析出密切相关。     

烟气横掠管束外表面的积灰特性

针对石灰线生产中烟尘易沉积,烟气换热器表面积灰的问题,为开发具有自清灰功能和扩展受热面的高效传热元件,对粉尘物理、化学和外部工作过程特性进行研究,通过采用扫描电子显微镜及XRD等仪器,研究灰的粒径分布、外观形貌及化学成分等物理化学特性,并对管束外表面积灰特性进行实验研究,结果表明：石灰线粉尘粒径较大,颗粒结构紧密,表面有大小不一的孔,易产生物理沉积形成松散积灰;灰样浓度的增大会导致积灰量增加,相同时间内灰样浓度越高积灰量越大,顺风面更易产生积灰现象;烟气流速较大时,积灰量很快达到稳定,烟气流速的增加会导致迎风面积灰量减少,背风面积灰量增加,存在最佳的烟气流速使飞灰颗粒在管道表面的沉积量最小;增加横向节距、减少纵向节距有利于减少积灰量。     

Ash deposition behavior of upgraded brown coal in pulverized coal combustion boiler

Ash with a low melting point causes slagging and fouling problems in pulverized coal combustion boilers. Ash deposition on heat exchanger tubes reduces the overall heat transfer coefficient due to its low thermal conductivity. The purpose of this study is to evaluate the ash deposition for Upgraded Brown Coal (UBC) and bituminous coal in a 145 MW practical coal combustion boiler. The UBC stands for Upgraded Brown Coal. The melting temperature of UBC ash is relatively lower than that of bituminous coal ashes. Combustion tests were conducted on blended coal consisting 20 wt.% of UBC and 80 wt.% of bituminous coal. Before actual ash deposition tests, the molten slag fractions in those coal ashes were estimated by means of chemical equilibrium calculations. The calculation results showed the molten slag fraction for UBC ash reached approximately 90% at 1523 K. However, that for blended coal ash decreased to 50%. These calculation results mean that blending UBC with bituminous coal played a role in decreasing the molten slag fraction. This phenomenon occurred because the coal blending led to the formation of alumino-silicates compounds as a solid phase. Next, ash deposition tests were conducted using a practical pulverized coal combustion boiler. A water-cooled stainless-steel tube was inserted in locations at both 1523 K and 1273 K in the boiler to measure the amount of ash deposits. The results showed that the mass of ash deposition for blended coal did not greatly increase, compared with that for bituminous coal alone. Therefore, appropriately blending UBC with bituminous coal enabled the use of UBC without any ash deposition problems in practical boilers.     

燃煤工业锅炉黏性积灰和露点腐蚀耦合机理

通过现场实验研究了燃煤工业锅炉的黏性积灰和露点腐蚀耦合机理,在现场测试了不同壁面温度（90、80、70、60、50和40℃）下20^#碳钢实验段的积灰和腐蚀特性,然后利用XRF、XRD和SEM-EDS对灰样和金属试样进行了系统理化分析。结果表明,当壁面温度低至70℃时,H₂SO₄开始在壁面上冷凝并沉积,引起黏性积灰和露点腐蚀。随着壁面温度的降低,实验段上的积灰量和腐蚀层厚度不断增加。当壁面温度降至40℃时,HCl开始在壁面上冷凝并加重积灰和腐蚀。烟气中的飞灰可以通过吸附冷凝的酸液并与其反应来减少壁面的黏性积灰和露点腐蚀。燃煤工业锅炉的低温受热面宜控制壁面温度在70℃以上,以减少酸液冷凝造成的黏性积灰和露点腐蚀。     

Development of a modeling approach to predict ash formation during co-firing of coal and biomass

The scope of this paper includes the development of a modelling approach to predict the ash release behaviour and chemical composition of inorganics during co-firing of coal and biomass. In the present work, an advanced analytical method was developed and introduced to determine the speciation of biomass using pH extraction analysis. Biomass samples considered for the study include wood chips, wood bark and straw. The speciation data was used as an input to the chemical speciation model to predict the behaviour and release of ash. It was found that the main gaseous species formed during the combustion of biomass are KCl, NaCl, K₂SO₄ and Na₂SO₄. Calculations of gas-to-particle formation were also carried out to determine the chemical composition of coal and biomass during cooling which takes place in the boiler. It was found that the heterogeneous condensation occurring on heat exchange surfaces of boilers is much more than homogeneous condensation. Preliminary studies of interaction between coal and biomass during ash formation process showed that Al, Si and S elements in coal may have a ‘buffering’ effect on biomass alkali metals, thus reducing the release of alkali–gases which act as precursors to ash deposition and corrosion during co-firing. The results obtained in this work are considered to be valuable and form the basis for accurately determining the ash deposition during co-firing.     

循环灰条件下1-甲基萘催化裂解的实验研究

热解气化过程中 ,促进焦油的裂解使之转化为高热值煤气 ,对高挥发分劣质煤和生物质燃料的清洁高效利用具有重要的意义 .在固定床反应器上 ,以石英砂和两种烟煤在循环流化床锅炉上燃烧形成的循环灰为床料 ,实验研究了焦油中含量较高的 1 -甲基萘的裂解反应 ,测定了反应动力学参数 .结果表明 ,与石英砂条件下相比 ,循环灰促进了 1 -甲基萘的裂解 ,反应活化能降低 ,裂解气体的总产率提高     

Deposition behaviour of model biofuel ash in mixtures with quartz sand. Part 1: Experimental data

Model biofuel ash of well-defined size and melting properties was fed into an entrained flow reactor (EFR) to simulate the deposition behaviour of commercially applied biofuel mixtures in large-scale boilers. The aim was to obtain consistent experimental data that can be used for validation of computational fluid dynamics (CFD)-based deposition models. The results showed that while up to 80 wt% of the feed was lost to the EFR wall, the composition of the model ash particles collected at the reactor exit did not change. When model ashes were fed into the reactor individually, the ash particles were found to be sticky when they contained more than 15 wt% molten phase. When model ashes were fed in mixtures with silica sand, it was found that only a small amount of sand particles was captured in the deposits; the majority rebounded upon impact. The presence of sand in the feed mixture reduced the deposit buildup by more than could be expected from linear interpolation between the model ash and the sand. The results suggested that sand addition to model ash may prevent deposit buildup through erosion.     

煤粉炉和循环流化床锅炉飞灰吸附汞动力学及其吸附机制

在固定床吸附反应器内对两台300MW等级燃煤发电机组循环流化床锅炉和煤粉锅炉飞灰样品进行气相零价汞吸附实验,通过改变实验工况研究温度、入口汞浓度和入口气体流量对飞灰汞吸附能力的影响。采用颗粒内扩散模型、准一阶和准二阶动力学模型、耶洛维奇（Elovich）模型对实验数据分别进行拟合,从动力学的角度探讨两种锅炉飞灰对气相零价汞吸附的影响机制以及两种锅炉飞灰与气相零价汞之间吸附动力学行为差异。结果表明：相同工况下循环流化床锅炉飞灰汞吸附过程的穿透时间和平衡吸附量远大于煤粉锅炉飞灰。吸附温度为150℃时,两种锅炉飞灰对气相零价汞的平衡吸附量最大。由于外扩散阻力随气体入口流量的增加而减小,入口汞浓度的增加可提高传质推动力,飞灰对汞的吸附得以增强。动力学分析表明飞灰的零价汞吸附由外扩散、内扩散和表面化学吸附共同控制,其中表面化学吸附是该吸附过程中的控制步骤;准二阶动力学模型和Elovich动力学模型更适合于描述该吸附过程。相同实验条件下,循环流化床锅炉飞灰吸附过程拟合所得的颗粒内扩散系数、准一阶动力学常数和初始吸附速率均大于煤粉锅炉飞灰。