水煤浆燃烧炉内固体残留物的微观分析

以不同特性煤浆的炉内燃烧固体残留物为研究对象，对取自炉内不同部位及沉积于硅碳棒和灰污探针上的典型燃烧灰的化学成分、矿物组成、元素分布及微观结构等进行分析研究。结果表明，水煤浆灰样中含Al、Fe、Ca的化合物和矿物的质量分数高于黑液浆，Na、K、S、Cl的情况与此相反。Fe的富集是造成水煤浆沾污结渣的根本原因。Na和Fe是引起黑液浆沾污结渣的主要矿物元素，Na的作用比Fe更大。黑液浆灰样中含有大量的霞石和硫酸钠等低熔融温度富钠化合物，Na是引起沾污结渣的根源。微观分析结果与实际燃烧状况是一致的，黑液浆结渣特性强于水煤浆，并且二者的灰沉积机理是不同的。     

不同反应气氛下准东高钠煤中钠的迁移转化与积灰特性

为了获得循环流化床工艺下不同反应气氛对准东高钠煤中钠的迁移转化与积灰特性的影响,在0.4t/d循环流化床实验装置上开展了相同床温(950℃)下的新疆沙尔湖高钠煤的气化(还原性气氛)与燃烧(氧化性气氛)实验研究。结果表明,气化和燃烧气氛下飞灰与积灰中Na主要以NaCl的形式存在;气化比燃烧更容易将Na、Cl固留在底渣和飞灰中,相应的进入气相中的Na、Cl更少;燃烧气氛下,部分NaCl会被烟气中的SO_2硫化,生成稳定性更高的Na_2SO_4并冷凝在飞灰和积灰棒表面,燃烧过程中产生的飞灰粒径更细,积灰更严重;沙尔湖煤燃烧与气化过程中存在HCl对金属壁面的腐蚀。     

黑液水煤浆主要矿物元素在炉内的迁移和沉积行为研究

为了研究黑液水煤浆的灰沉积机理,采用沿烟气行程从实验炉不同部位抽取空间灰粒和提取相应位置炉壁灰渣样相结合的方法,并与常规水煤浆相对比,研究了各主要矿物元素（Na、K、Si、Al、Fe、Ca）在烟气流中的迁移趋势和沉积特性。并且通过X射线衍射（XRD）和扫描电镜（SEM）等分析从微观角度进行了验证。结果表明,与常规水煤浆不同的是,Na、Si、Al的迁移和沉积是引起黑液水煤浆沾污结渣的主要矿物元素,灰沉积物中主要包括无水芒硝、霞石等低熔融温度富Na物相,而Fe的沉积是次要因素。     

准东煤流化床气化飞灰的理化特性研究

采用灰熔点测定仪、X射线荧光光谱仪、扫描电镜和热重分析仪等方法,研究了准东煤流化床气化飞灰的灰熔融特性、物理结构和化学组成及气化反应活性。结果表明,准东煤与其流化床气化飞灰中Si O2、Fe2O3、Na2O和Ca O等矿物质含量存在显著的差异,但飞灰的灰熔点与原煤无明显差异。准东煤气化飞灰具有较宽的粒径范围,呈现双峰分布特征,且不同粒径区间飞灰的元素含量存在显著差异。提高气化温度,有利于提高飞灰的气化反应活性。准东煤流化床气化飞灰石墨化程度比煤焦要高,但其孔隙结构更为发达,含有丰富的中孔和中大孔,使得飞灰的气化反应活性高于煤焦。可通过提高气化温度、循环再气化的方法提高气化效率。     

生物质气化发电厂灰渣中微量元素的分布与富集规律

采用电感耦合等离子体发射光谱仪,研究了生物质气化发电厂灰渣中元素As、Al、Br、Ca、Cd、Cl、Cr、Cu、F、Fe、Ga、K、Mg、Mn、Na、Ni、P、Pb、S、Si、Sr、Ti、Zn在气化器底灰、淋洗器灰和旋风分离器灰中的质量分数,并分析了这些元素在不同粒径3种灰渣中的分布规律。结果表明,大部分极易挥发的元素,如卤族元素、碱金属元素主要在淋洗器中存在,表明了它们在飞灰颗粒中的富集。旋风分离器灰在灰渣中所占比例为10%左右,以粗灰为主,灰中Fe、Si、Ni、Pb、Zn、Cr、Cd为多;表明了此灰中重金属元素积累。在气化炉底灰中以K、S、Mn、Cu为主。元素随颗粒物粒径大小和元素性质的不同,呈现不同的富集规律。     

化学沉积Ni–Fe–P合金的冲蚀特性研究

采用扫描电镜、能谱仪、X射线衍射等方法,研究了化学沉积Ni–Fe–P合金的组成和结构,并对其冲蚀性进行了研究。结果表明,随着镀液中硫酸亚铁浓度增大,化学沉积Ni–Fe–P镀层中的铁含量增大,磷含量下降。化学沉积Ni–Fe–P镀层的腐蚀电位比化学镀Ni–P镀层的腐蚀电位高。在3.5%(质量分数)Na Cl溶液组成的悬浮液冲击下,碳化硅颗粒粒度为124μm时,镀层质量损失出现最大值,随着悬浮液流速的增大镀层质量损失增加。     

对戈尔德施密特的“地球化学”的几点意见

戈尔德施密特是近代地球化学的奠基人之一,生前对于变质岩和煤灰等中元素的分布情况,曾经进行过比较系统的研究工作。在个别元素(如钪)的地球化学方面以及稀土类元素在矿物中的配分方面也都有一些独到的见解和出色的研究成果。他曾经根据冶炼过程中所观察到的元素的分别富集现象,提出了关于地球内部物质组成的假说,并将已知的元素进行了地球化学分类;以后又从原子构造(主要是电子层结构)及     

卷心菜和芹菜中的17种元素测定

采用微波消解法处理卷心菜和芹菜样品,并用ICP-AES法测定这两种蔬菜中的17种微量元素Ca,Mg,K,Na,P,Zn,Fe,Cu,Mn,Al,Se,Cr,Ni,Cd,As,Pb,Hg。结果表明,两种蔬菜中均含有丰富的矿物元素Ca,Mg,K,Na,P,芹菜中的矿物元素更高,也存在少量能调节人体生理机能的有益微量元素Zn、Fe、Mn、Al、Cu、Ni,除了卷心菜中Hg含量超标外,其它有害重金属元素均属国家食品安全卫生标准之内。     

煤中痕量元素在循环流化床锅炉中的迁移行为与富集特性

对天津市某电厂循环流化床(CFB)锅炉燃用的原煤及燃烧产物底灰、飞灰、细飞灰(≤50 μm)进行痕量元素含量的测定,分析了Be、Zn、Hg、V、Cr、Mn、Co、Ni、Cu、As、Se、Cd、Pb 13种痕量元素在燃烧过程中的迁移行为,揭示了痕量元素在CFB锅炉中的分配、富集特性。结果表明,CFB锅炉中,较低的炉温对于痕量元素的迁移富集产生了较大的影响。由相对富集系数得知,Be、V、Co、Se在底灰中耗散,在飞灰中富集,Zn、Mn倾向于在底灰中富集,元素Cd、Pb、Ni、Cu挥发性较强,在底灰和飞灰中均是耗散。As受钙氧化物影响,挥发性表现并不明显。Hg在底灰和飞灰中相对富集系数均很低,表明Hg在整个燃烧过程中以气态形式排放;Hg、As、Se、V、Cr、Mn、Co、Ni、Cu、Zn、Pb均有向小颗粒物中富集的趋势。根据相对富集系数以及研究的13种元素在低温CFB锅炉中的迁移行为,将这些元素分为三类:A类(E_R<0.1),主要是以气态形式排放元素Hg;B类(0.1R≤0.85),较易挥发元素As、Be、Ni、Cu、Se、Cd、Pb、Co、V;C类(E_R>0.85),主要残留在固体产物中元素Zn、Mn、Cr。     

激光剥蚀电感耦合等离子体质谱小激光斑束线扫描定量分析技术

采用激光剥蚀-扇形磁场电感耦合等离子体质谱(LA-SF-ICP-MS)技术建立了小激光斑束(15μm)线扫描定量分析方法。对比了硅酸盐矿物LA-ICP-MS分析中不同激光进样模式(点剥蚀和线扫描)对于元素信号强度和分馏效应的影响。小激光斑束点剥蚀分析元素信号强度随时间下降明显,并且剥蚀过程中元素深度分馏效应影响明显。深度分馏效应主要是由于各元素倾向于富集在不同粒径颗粒中,而不同大小颗粒在剥蚀坑附近发生冷凝沉淀的几率差异造成。实验结果表明,相对于内标元素Ca,Na、K、Cr、Co、Cd和U等元素富集在更小颗粒中;Cu、Zn、V、Mn、Fe、Ni、Tl、W、Rb、Cs等元素与Ca富集行为相似;Al、Y、Sc、Zr、Nb、Hf、Ta、Th和REE等元素易进入大颗粒中。线扫描分析具有高且稳定的元素信号强度,分析过程中剥蚀行为一致,不受深度剥蚀效应的影响。采用双剥蚀池结构进样系统研究单脉冲激光剥蚀信号结构,不同元素信号强度降低至50%需0.8~1.2 s;降低至20%需1.2~1.6 s;降低至背景值需2~3 s。本研究通过优化仪器参数降低信号叠加作用的影响,在均质和非均质样品(榍石)线扫描分析中,获得了准确的元素含量和元素比值。线扫描定量分析技术可有效降低激光斑束(≤15μm),相对于采用线扫描元素强度分布研究,数据更加直观,可表现元素比值的变化特征。通过调整激光斑束大小和扫描速度可在不同分辨率尺度下全面了解矿物中元素的分布特征。     

燃煤飞灰中铁质微珠的显微结构及其组成研究

选用我国三个典型燃煤煤种的电厂飞灰中铁质微珠,进行显微结构与物相组成等方面的研究。揭示出铁质微珠中存在空心微珠、子母珠和实心微珠三种显微颗粒类型,在这些显微颗粒表面可识别出以微粒状和八面体自形晶两种方式存在的赤铁矿和磁铁矿析晶;元素分析表明,燃烧褐煤电厂铁质微珠主要由Fe、Ca、Al、和Si元素组成,燃烧烟煤和无烟煤的电厂铁质微珠主要由Fe、Al和Si元素组成;物相分析发现,Fe在铁质微珠中以四种存在形式：Fe3O4、α-Fe2O3、γ-Fe2O3和Fe3+-玻璃相。这些物相在三个电厂飞灰中呈现出不同的分布特征,反映出不同的燃煤煤种在锅炉中燃烧温度的差异。随着温度的升高,Fe3O4先氧化为γ-Fe2O3,或γ-Fe2O3与Fe3O4的固熔体,然后再转变为α-Fe2O3,当温度超过 1 400 ℃时,Fe2O3又转化为Fe3O4。     

粉煤灰物化性质对单质汞吸附性能的影响

在固定床实验台上考察了三种不同来源粉煤灰对单质汞的吸附性能,采用X射线荧光光谱仪、X射线光电子能谱仪、激光粒度分析仪、扫描电子显微镜等对不同粉煤灰的物化性质进行了表征,并探讨了物化性质对汞吸附性能的影响。结果表明,粉煤灰对汞的吸附包括物理吸附和化学吸附;粉煤灰中未燃尽碳是影响粉煤灰汞吸附性能的重要因素之一,其中,表面C元素与Ti、Si等元素(M)相互作用形成的"C-M"化学键促进了单质汞的氧化,同时粉煤灰中含有的无机化合物Fe₂O₃等也对单质汞的氧化有促进作用;增大比表面积和减小孔径,及适中的颗粒粒径均有利于提高粉煤灰单质汞吸附性能。     

Removal of phosphate from aqueous solution by zeolite synthesized from fly ash

Fifteen Chinese fly ashes were converted hydrothermally into zeolites, and phosphate immobilization capacity (PIC) of the synthesized zeolites and the corresponding raw fly ashes were determined using an initial phosphate concentration of 1000 mg/L. Results showed that there was a remarkable increase in PIC (from 1.2 to 7.6 times) following the synthesis process. Fractionation of immobilized phosphorus indicated that Fe+Al-P increased most significantly and consistently among all the phosphorus fractions following the conversion of fly ash to zeolite. The PIC and Ca+Mg-P were closely related to Ca content (with r values of 0.9683 and 0.9651, respectively) rather than Mg content (with r values of 0.3920 and 0.3212, respectively). The r values of PIC and Fe+Al-P with Fe content (with r values of 0.4686 and 0.6385, respectively) were higher than those with Al content (with r values of -0.7857 and -0.3770, respectively). Although calcium and iron components were mainly involved in phosphate immobilization, there was no significant change of Ca and Fe content following the conversion of fly ash to zeolite. Increase in dissociated Fe(2)O(3) and specific surface area probably accounted for the enhancement in PIC of synthesized zeolites compared with corresponding fly ashes. The PIC value of zeolites showed a significant correlation with dissociated Fe(2)O(3) (r=0.6186). The specific surface area increased 26.0-89.4 times as a result of the conversion of fly ash to zeolite. The maximum removal of phosphate occurred within different pH ranges for zeolites which were synthesized from high, medium and low calcium fly ashes and this behavior was explained by the reaction of phosphate with calcium and iron components.     

The hydraulic activity of high calcium fly ASH

Cementitious mixtures with so-called high calcium fly ash show better strength parameters as compared to the ones with conventional siliceous fly ash. This practical feature is the consequence of improved hydraulic activity. Differential thermal analysis and thermogravimetry were used, together with the other methods, to evaluate the reactivity of high calcium fly ash in mixtures with cements. This type of fly ash exhibits hydraulic properties (setting and hardening on hydration) and durability, after hardening, in the presence of water. The so-called pozzolanic activity is the feature of high active silica containing fly ash while the hydraulic activity is related to the high calcium ones. However, the chemical and phase composition is variable and related to the particle size. The hydraulic/ pozzolanic properties are strongly improved by additional grinding (specific surface increase).     

Size-based analysis of incinerator fly ash using gravitational SPLITT fractionation, sedimentation field-flow fractionation, and inductively coupled plasma-atomic emission spectroscopy

Fly ash has been regarded as hazardous because of its high adsorption of toxic organic and/or inorganic pollutants. Fly ash is also known to have broad distributions of different chemical and physical properties, such as size and density. In this study, fly ash emitted from a solid waste incinerator was pre-fractionated into six sub-populations by use of gravitational SPLITT fractionation (GSF). The GSF fractions were then analyzed by sedimentation field-flow fractionation (SdFFF) and ICP–AES. SdFFF analysis showed the fly ash has a broad size distribution ranging from a few nanometers up to about 50 µm. SdFFF results were confirmed by electron microscopy. Inductively coupled plasma–atomic emission spectroscopy (ICP–AES) analysis of the GSF fractions showed the fly-ash particles contain a variety of inorganic elements including Ca, Si, Mg, Fe, and Pb. The most abundant in fly ash was Ca, followed by Si then Mg. No correlations were found between trace element concentration and particle size.     

DTA study of the chlorination of fly ash and bauxite in the presence of carbon

The chlorination processes of fly ash and bauxite in the presence of carbon were studied by means of a gas-flow type DTA, X-ray analysis and SEM observation, and the reactivity of Al-compounds as their constituents was compared. In the case of fly ash, the exothermic peak due to the formation of AlCl₃ (mainly) and FeCl₃ appeared at about 790–920°C. The reactivity of Al estimated from the DTA peak temperature depended on the particle size, carbon content and preparation temperature of fly ash, and was much lower than that of bauxite. Fractional conversion of Al was about 60–70%, when fly ash (?300 mesh) was heated up to 900°C in Cl₂ at 5°C min^?1 of heating rate. In the case of bauxite, two exothermic peaks due to the chlorination of Fe and Al appeared at about 270 and 490°C, respectively. The chlorination of Al was completed at 550°C under the above conditions.     

医疗垃圾焚烧飞灰中OCDD/OCDF的球磨机械化学法降解试验研究

利用机械化学法进行含二噁英废弃物的无害化处置,是一个值得关注的研究领域.本研究以去除大部分二噁英及其它有机成分的医疗垃圾焚烧飞灰作为反应基质,添加了八氯代二噁英和呋喃(OCDD/OCDF)后,在自行研制的行星式球磨试验装置上进行了球磨机械化学法降解试验研究.实验球磨两种飞灰分别采自某回转窑热解流化多段焚烧系统和某简易固定床焚烧系统的医疗垃圾焚烧炉布袋除尘器,其中对于简易固定床焚烧处置的飞灰,OCDD和OCDF分别减少了64.7%和63.6%,氯化度由6.86降至5.53.两种飞灰处理后,平均粒径大幅缩小,比表面积、孔容积显著增加,CaCO3强度显著减弱.实验证实飞灰本身的某些组分(CaCO3等)在球磨机械化学处理过程中起到类似氧化钙(CaO)的脱氯还原剂作用,且机械化学法降解二噁英的效果显著.研究结果对实际医疗垃圾焚烧飞灰中二噁英类污染物的脱除具有指导意义.