CFB垃圾焚烧炉烟道沿程烧结积灰的特性

使用扫描电镜、能谱、粉末X射线衍射等测试手段，分别对循环流化床（CFB）垃圾焚烧炉尾部烟道沿烟气流程不同受热面的烧结积灰进行了微观结构、元素和物相组成的分析对比，对Ca、S型烧结积灰的机理进行了讨论。结果表明，CFB垃圾焚烧炉受热面烧结积灰主要由亚微颗粒熔融团聚而成，烟气温度越高烧结积灰结构越致密。形成烧结积灰的主要元素是Ca、S等，600℃左右对流受热面积灰中Ca、S的富集达到最大。松散积灰中Si、Al是主要的成分，Ca、S也仍保持较高的水平。烧结积灰的物相组成主要是CaSO4，还有少量低熔点的钙的硅酸盐，化学反应烧结和传质作用的强化是积灰固化的重要原因。图3表1参13     

钾对生物质燃烧过程积灰的影响

对生物中钾的赋存形式及其沉积过程进行分析得出钾含量高且反应性高是影响积灰形成的关键因素。研究了钾对飞灰特性的影响以及烟气中钾浓度对积灰的影响,研究结果表明,钾促进了积灰的形成。钾促进积灰形成的主要途径是:钾与硅酸盐结合形成低熔点化合物促进灰粒间的烧结;钾沉积在飞灰颗粒的表面增加了飞灰的表面粘性。最后介绍了几种减轻钾对积灰形成的影响的方法。     

高岭土粒径对新疆煤积灰行为及烧结特性的影响

针对燃烧新疆煤面临严重的沾污结渣问题,添加高岭土添加剂是缓解该问题的有效途径。结合沉降炉积灰实验和固定床烧结实验对不同粒径高岭土的防控性能与机理进行研究。结果表明：高岭土通过自身的稀释作用和与煤中矿物的交互作用两方面共同改变新疆煤的成灰特性,进而影响积灰行为与烧结特性;细高岭土虽然通过交互作用可以有效抑制碱性物质气相沉积,但添加剂自身的稀释作用导致成灰粒径较小,更易在初始阶段形成积灰;在两方面的综合作用下,细高岭土和粗高岭土对初始阶段积灰生长的防控效果相近;此外,添加细高岭土后更小的成灰粒径分布促进灰烧结程度的发展,不利于沉积物的吹灰清除。     

高碱灰渣烧结反应的化学热力学平衡计算

针对高碱灰渣烧结特性进行化学热力学平衡反应计算,并与试验结果进行了比较.计算采用FactSage 5.2计算软件中的Equilib模型.计算结果显示高碱灰渣的强烧结特性主要是由大量黝方石、蓝方石、霞石、无水芒硝等较低熔点的钠基复合盐造成.计算结果与试验分析物相基本一致,表明化学热力学反应平衡分析方法是研究灰渣烧结特性的有效手段.     

准东煤循环流化床气化过程中的矿物质转化行为特性

基于0.25,t/d高碱煤热化学转化热态试验台,利用X射线衍射(XRD)、扫描电镜-X射线能谱(SEMEDX)和电感耦合等离子体-原子发射光谱(ICP-AES)等手段,研究了准东天池木垒煤在煤气化过程中的矿物质转化行为.结果表明,天池木垒煤中含有大量Ca和Na,且主要分别以CaSO_4和NaCl的形式存在,其他矿物质元素多以硅铝酸盐矿物形式存在;在煤气化过程中,Na的硅酸盐是引起底渣聚团的主要原因,K、Mg、Fe、Ca等元素组成的低温共熔体和复合硫酸盐对聚团起低温助熔剂的作用;挥发的Na会在飞灰颗粒表面富集,导致尾部受热面出现积灰沾污现象,同时飞灰中有富Ca絮状物生成.     

添加物对钛酸铝性能的影响

本研究采用工业和矿物原料合成钛酸铝,探讨了各种添加物对钛酸铝烧结性能、抗弯强度、热膨胀系数和稳定性的影响,同时利用XRD分析了材料的物相组成。结果表明,添加物的引入能在不提高钛酸铝热膨胀系数的情况下获得具有较高强度的稳定钛酸铝。     

富磷添加剂对生物质燃烧中积灰结渣和腐蚀作用的探析

文章探讨了富磷添加剂对生物质燃烧过程中锅炉受热面积灰、结渣和腐蚀的作用机理,分析了其作用效果,考察了燃烧温度、燃烧气氛、生物质种类、Ca/K摩尔比、P/K摩尔比等主要因素对作用效果的影响规律。结果表明,富磷添加剂可以将烟气中的碱金属(主要是钾)和氯元素固定于底灰中,生成高熔点化合物,减轻碱金属熔融结渣和氯腐蚀。同时,添加剂改变了灰的物理和化学性质,使灰松软不易烧结,从而有效减轻了生物质燃烧过程中锅炉受热面的积灰、结渣和腐蚀。     

氧化钙添加剂对烟气中汞分布的影响

在一个大气压下,273．15～l273．15K温度范围里,采用化学热力平衡分析方法研究了煤燃烧过程中CaO和HCl对痕量元素汞的形态及分布的影响。化学热力平衡分析结果表明,在煤燃烧的最高温度区域里,单质汞是汞的主要形式。随着在烟气中温度的降低,单质汞将发生化学反应而生成二价汞的化合物,其中主要是HgCl2(g);预测结果还表明氯元素的增加可以增强汞元素的蒸发、排放,而CaO(s)对汞元素在烟气中的行为特性的影响不大。尽管化学热力平衡分析结果与实验结果之间存在较大差异,但是通过与实验结果的比较,仍可以推断CaO(s)主要是通过减少灰粒表面积或改变飞灰矿物学和形态学特性影响烟气中汞元素分布特性。     

炉内燃烧温度对准东煤灰熔融特性影响的实验研究

当炉内燃烧温度为950℃、1 150℃和1 350℃时,改变炉膛出口氧体积分数,分别设置为2.0%~2.5%、4.0%~4.5%和6.5%~7.0%,在准东煤沾污结焦实验台上进行实验,并收集沾污段的飞灰进行可燃物化验、电子扫描电镜扫描和X射线荧光光谱仪检验等分析.结果表明:炉内燃烧温度升高会使煤粉表面烧结性更强,阻碍了氧气向煤粉内部的扩散,导致飞灰可燃物质量分数增大;钠元素在950~1 150℃存在某种形式的快速释放,而钾元素则不会;炉内燃烧温度越低,煤灰熔融温度越低,结渣性越强,但这不是引起炉内沾污积灰的主要原因;炉膛出口氧体积分数的变化对飞灰成分和碱金属析出的影响较小.     

炉排_循环床垃圾焚烧炉过热器结渣现场实验

为研究焚烧炉过热器内的飞灰沉积、沾污和结渣的原因及影响因素,在260 t/d炉排-循环床垃圾焚烧炉过热器区域安放结渣实验采样段,利用SEM/EDX、XRF和XRD等方法分析了积灰和渣的成份和形态。研究表明:管束的几何结构对结渣有重要的影响,受热管越细越容易结渣。高温过热器渣层上的颗粒排列紧密,呈砖形,长度约2～5μm,物相组成为CaSO4、石英、SiO2、Ca2SiO4等。垃圾焚烧炉结渣主要是由粘结性颗粒撞击管壁所致。     

添加剂对垃圾焚烧炉飞灰熔融特性的影响

将SiO2、CaO和Al2O3按不同比例与垃圾焚烧炉飞灰均匀混合,对混合后试样的熔融特性进行实验研究。结果表明:当添加剂加入量在15%左右时,试样的灼烧减量基本趋于稳定,添加量过高或过低试样灼烧减量波动均很大。适量(15%左右)的加入3种添加剂时,SiO2可使试样达到更好的熔融效果,CaO不利于试样的熔融,Al2O3可提高试样的硬度和致密性。添加剂对熔融试样的重金属分布有显著影响,添加SiO2、CaO均能促使Cr、Ni固溶在熔融体中,且SiO2含量增加有助于As的挥发;而CaO可抑制As挥发。Al2O3除对Ni固溶有正面影响外,对Cr、As、Cu的固溶有负面影响。     

Effects of leaching and additives on the ash fusion characteristics of high-Na/Ca Zhundong coal

Considering the intensive application of Zhundong coal and its serious slagging during combustion in pulverized coal fired boilers, the effects of water leaching and different dosages of additives (Na₂CO₃, CaO, SiO₂, and kaolin) into the leached coal on ash fusion characteristics were studied using sintering tester, X-ray Fluorescence, and X Ray Powder Diffraction. After leaching, the contents of Na₂O, K₂O, CaO, MgO, SO₃, and Cl decreased, whereas the contents of SiO₂ and Fe₂O₃ increased. As a result, the slagging and fouling index of Basic/Acid ratio decreased from 1.6 in the raw coal ash to 1.1 in the leached coal ash, and alkali-induced slagging was reduced. However, the decreased ash fusion temperatures (AFTs) of the leached coal worsen the melt-induced slagging. Detailed analysis on the effects of ash compositions on the AFTs by additions of Na₂CO₃, CaO, SiO₂, and kaolin additives into the leached coal showed that Na₂CO₃ and SiO₂ improved the formation of low-melting Na₂SO₄ and Na₂SiO₃, and thus decreased the AFTs; However, overdosed Na₂CO₃ (for instance 9 wt%) improved the formation of relative high-melting Na₄Al₂Si₂O₉ and thus increased the AFTs. Overdosed SiO₂ as a high-melting contaminant also increased the AFTs. Similar with the function of overdosed SiO₂, CaO in the ash of leached coal was excess, and the AFTs increased with increased CaO dosage. Kaolin, which decomposed as high-melting mullite and cristobalite, caused an elevation of the AFTs. Therefore, water leaching decreased the AFTs of Zhundong coal and consequently worsen melt-induced slagging, lime and kaolin additives increased the AFTs effectively, but Na₂CO₃ and SiO₂ additives showed ‘V’ shaped functions on the AFTs. These general results are useful for the pretreatment of Zhundong coal during combustion and alleviating slagging.     

准东煤灰与液态排渣煤粉炉耐火材料的烧结特性

采用TGA-DSC分析确定了准东煤灰和其混合灰样(不同质量比的准东煤灰和耐火材料)燃烧过程中的特征温度,并分别采用XRD和FSEM-EDS对不同特征温度段灰样进行矿物识别和形貌、能谱分析,得到了原灰与混合灰的烧结温度、灰中主要矿物的转化和熔融过程,并对比了不同耐火材料含量的煤灰熔融温度;在此基础上提出了耐火材料构型的极...     

Design of solid biofuels blends to minimize the risk of sintering in biomass boilers

Biomass with high concentration of alkali/alkaline and silica components can lead to slagging/fouling, and sintering of the ash deposits, causing corrosion and erosion of the boilers. There are several methods to predict bed agglomeration such as slagging/fouling indexes. However, these indexes are developed to be used for coal ashes, which shows a different behaviour than biomass fuels. The aim of this work was to determine the suitable percentage of different species found in biomass blends in order to reduce the risk of slagging and sintering. We studied the ash behaviour of 24 blended biomass samples using two slagging indexes: the alkali index, and the % of bases in ashes index, and we validated these two indexes with the Bioslag test, and with the Hardness Index (%D₁). There is low risk of slagging in most of the samples, as well as a low sintering risk. However, some samples present moderate risk of sintering possibly due to SiO₂. The Bioslag test and the %D₁ test support our results. Samples showing risk of sintering exceed 25% of the total accumulated ash weight percentage ac%_1P>25%, and show a hardness of %D₁ > 0.7. These validations can be considered as useful tools for estimating slagging and sintering of woody biomass fuels in domestic pellet boilers.     

准东煤灰熔融特性试验研究

将神华准东煤（神华煤）和天池能源准东煤（天池煤）与碱沟煤按照不同质量掺混比进行混合并制得灰样,将NaCl、CaO、Al2O3和SiO2按不同添加比例加入神华煤和天池煤并制成灰样,对上述混合灰样的熔融特性进行研究.结果表明：碱沟煤掺混2种准东煤后,随着准东煤质量掺混比的增大,混合灰各个灰熔点特征温度先降低后升高;随着灰样中Na含量增加,准东煤灰样的变形温度显著降低,软化温度、半球温度和流动温度先降低后趋于不变;当灰样中Na含量达到一定比例后,NaCl对准东煤灰熔融特性的影响明显减弱;CaO对准东煤灰熔点的影响较复杂,可以降低也可以提高灰熔点;随着Al2O3添加比例的增加,准东煤灰熔点先升高后急剧降低;随着SiO2添加比例的增加,神华煤灰样的变形温度先升高后降低,而天池煤灰样的变形温度逐步升高,其他3个特征温度均逐渐降低.     

Characterization and productivity of cassava waste and its use as an energy source

This study sought to quantify and characterize cassava waste as fuel. The wastes from three cultivars were collected to study and were divided into three distinct parts of the cassava plant: seed stem, thick stalks, and thin stalks. Physical and chemical analyzes were carried out to determine the elemental composition of the waste: volatile matter; fixed carbon; ash; moisture; lignin; cellulose; hemicellulose; ash composition and higher heating value were determined. We conducted a thermogravimetric analysis in oxidizing and inert atmospheres to study the behavior of the waste as fuel. The root productivity obtained ranged from 7.7 to 13.0 t ha⁻¹ yr⁻¹ on a dry basis (db), and the ratio between waste and roots varied from 0.36 to 0.91. The physical and chemical properties of cassava waste are analogous to those of woody biomass regarding the elemental composition, the higher heating value, and thermogravimetric analysis. Ash content varied from 2.5% to 3.5%, reaching around 6.0% in samples unwashed. Approximately 60% of the ashes are alkali oxides, especially P₂O₅, K₂O, and CaO, which have low melting points. The alkali index calculated suggests that there is a strong tendency that the combustion process leads to ash fouling and the formation of ash deposits.     

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.     

Slagging tendencies of wood pellet ash during combustion in residential pellet burners

Ash related problems have more than occasionally been observed in pellet burners during the last years. These problems can lead to reduced accessibility of the combustion systems as well as bad publicity for the market. The objectives of the present work were to; (i) evaluate how different raw materials for pellets affect the accessibility of the existing burner equipment, (ii) determine which of the ash forming element(s) that could be responsible for the deposit/slagg formation and, (iii) estimate the critical slagging temperature for the different raw materials. Stored and fresh materials from sawdust, logging residues and bark were used as raw material in three different pellet burners. The results showed that the slagging properties were relatively sensitive to the variations in total ash content and ash forming elements of the fuel. It is therefore recommended that ash rich fuels like bark and logging residues should not be used in the existing residential pellet burners. Both fuel and burner type affected the amounts of ash deposit produced. The degree of sintering (i.e. the strength of the deposits) was mostly affected by the fuel composition. Subsequent controlled sintering test of the produced deposits/slags showed critical slagging temperatures of about 850–900 °C for stored bark and about 1000 °C for fresh bark and stored and fresh materials from sawdust and logging residues. The results further indicated that the Si-content in the fuel correlated (relatively) well to the sintering tendencies in the burners. Chemical equilibrium models were used to interpret the experimental findings, and good quantitative agreements between modelling and experimental results were generally obtained.     

城市垃圾焚烧飞灰物理化学性质及重金属风险分析

对7种城市垃圾焚烧飞灰的物理化学性质进行了详细表征。针对飞灰中重金属成分复杂的特点对重金属含量、形态分布和浸出毒性进行了分析,并进行了风险评估指数和风险指数计算。飞灰的化学组分和晶相结构分析显示,城市垃圾焚烧飞灰中含有大量的CaO、CaSO₄、SiO₂、Al₂O₃、NaCl和KCl等化合物,具有资源化利用的潜力。但同时飞灰中含有大量的重金属,其中Pb和Cd的生态风险高,浸出毒性高于飞灰直接处理和处置要求。研究结果表明,垃圾焚烧飞灰需进行处理至达到一定要求后才能进行资源化利用。     

焦炭体系下添加剂对CO2重整CH4特性的影响

利用固定床试验装置,以SiO2、MgO和CaO为添加剂,在焦炭体系下进行了CO2重整CH4活性的试验研究,并分析了反应温度和CaO含量对重整反应的影响.利用热重分析仪和扫描电镜分别对重整过程中焦炭失重和反应后焦炭微观形貌进行研究,探讨了反应机理.结果表明:加入SiO2后,制得的焦炭催化活性降低,加入CaO和MgO后,制得的焦炭催化活性提高,且CaO优于MgO;温度对重整反应影响显著,随着温度升高,反应气转化率增加;CaO添加剂含量控制在15%~20%之间对反应速率的提高较合适,且CaO的添加使焦炭失重速率也有所提高.