数字全息在线测量煤粉粒度分布

煤粉粒度是燃煤电厂的重要指标,在线测量煤粉粒度能够即时指导锅炉优化运行,对节能减排具有重要意义。搭建了一套模拟一次风粉管道的煤粉粒径在线测量的装置,解决了传统取样方法堵塞和测量实时性差的问题,并设计实验研究数字全息在线测量煤粉粒度的可行性和可靠性。实验结果表明,数字全息在线测量煤粉粒度分布曲线与激光粒度仪的测量曲线趋势一致,平均粒径相对误差为5.6%,表征粒度分布的关键参数d₅₀和d₉₀的相对误差均低于2%,满足工业应用的需求。数字全息技术对稀释前后不同浓度的煤粉粒径关键参数的测量相对误差均低于7%,稀释前后的煤粉粒度的数量分布和体积曲线的趋势一致,验证了数字全息技术在线测量煤粉粒度分布的可靠性,为整体测量装置的开发奠定了基础。     

级配粒度对宁东煤成浆性影响的研究

以宁东煤为研究对象,采用正交试验法进行了煤粉粒度分布对水煤浆成浆性能影响的分析研究。自制了不同颗粒区间的煤粉,并将各种粒径的煤粉配制成相同浓度的水煤浆,以水煤浆的黏度和流动性作为试验指标,探讨了不同粒度级配对宁东煤成浆性的影响。采用超声衰减粒度仪进行了粒度分布测定,并得到了分布曲线。试验结果表明:双峰级配的煤粉粒度级配合理,大颗粒和小颗粒之间相互填充,煤粉堆积效率达到最大,煤粉空隙中的水量最小,表现为浆体的黏度低、流动性好。     

粒度级配对神府煤成浆性能的影响

为提高神府煤制备水煤浆的成浆性能,分析了神府煤的原煤性质,说明神府煤的成浆指标为11.55,属于很难成浆煤种。对不同粒度级配的干基煤样进行粒度分析,通过粗、细煤粉单独制浆实验和不同粒度级配煤粉的成浆性实验,研究了不同粒度级配对水煤浆成浆性的影响。结果表明:经过级配的干基煤样具有双峰粒度分布特征,适宜制浆;粗煤粉不能单独成浆,细煤粉单独制浆的最大成浆浓度为61%;粗细煤粉质量比约为1∶2时,水煤浆具有较好的流动性和稳定性,最大成浆浓度可达63.8%,此时水煤浆黏度为1000 mPa·s,符合工业水煤浆制备标准,说明合理的粒度级配可降低水煤浆黏度,增强流动性及稳定性。     

煤粉燃烧率与粒度组成的研究

试验研究不同煤种燃烧率和煤粉粒度组成关系。研究表明烟煤存在最佳燃烧率的粒度组成值。当考虑到磨煤能量消耗,无论是烟煤还是无烟煤,都有合适的粒度组成范围,根据研究结果推荐值是将煤粉-0．074mm比例定为60％-80％。同时也初步探讨了煤粉燃烧率与镜质组反射率之间的关系,得到了一些有益的结果。     

水煤浆粒度测试技术研究

介绍了筛分法和激光粒度仪2种测量水煤浆粒度分布方法的测量原理,并用2种方法对2个煤粉样品进行了测量。结果表明,筛分法与激光粒度仪测试样品粒度分布结果存在一定偏差,而测量原理、取样环节、颗粒形状和测量条件都是导致结果偏差的主要因素,其中除取样环节可最大限度减小人为误差,其他因素均不可人为避免,因此2种测量结果均可为水煤浆技术领域中的科研生产提供参考。     

磨制煤粉粒度组成及其质量分布关系研究

为认识磨制煤粉的粒度特性及灰分、硫分矿物质在各粒度级的分布状况,选取西山煤电公司等三个产地的原煤和内蒙五虎山洗精煤共四个样品,采用小型球磨机在相同条件下分别进行了制粉实验,通过对磨制煤粉的粒度特性进行测试分析,证实了磨制煤粉的粒度组成均符合Rosin-Rammler粒度特性方程;该方程的参数k和b分别反映了煤样的可磨性和磨粉产品的细度,洗精煤的k值明显高于原煤,各粒度级的灰分和硫分实验结果表明:粗粒级煤粉的灰分均较高,而硫分在各粒度级中的分布同煤种有关,缺乏普遍规律可循.     

我厂不同在线粒度分析仪的调试和维护

水泥的质量与工程质量有着密切的关系，尤其是水泥的粒度（颗粒级配）对最终混凝土商品的耐久性、适用性、强度，以及其施工性和经济性都起着重要影响。不仅水泥的粒度，水泥生产过程中的煤粉和生料的粒度也对水泥生产有着重要的影响。传统的勃氏比表面积法和筛析法可以获得水泥（生料、煤粉）整体粗细和部分不同粒径段的信息；现代激光粒度分析仪能够24 h连续工作，就像安装在生产线上的一双眼睛，可以对生产现场管道中水泥、生料、煤粉颗粒的粒度分布以及变化趋势作全天连续的实时追踪和监控，是先进水泥企业日常分析物料颗粒级配的利器。     

分形理论对煤粉粒度和孔隙的表征

介绍了分形理论的定义,说明自相似性和标度不变性是分形的2个重要特征。从粒度分形规律和煤粉研磨超细化分形2个方面对煤粉超细化分形进行了研究,说明煤粒研磨过程中,绝大部分能耗用在小颗粒的研磨上,颗粒表面分形维数越大,研磨能耗越高,颗粒形状越不规则,能耗越大。详细介绍了气体吸附法、压汞法和扫描电镜图像法3种测定煤粉孔隙分形维数的方法,阐述了煤粉粒度和孔隙的分形规律及国内外相关研究现状,着重说明了煤粉的研磨、高效燃烧、煤粒与孔隙发育程度的关系及煤粒孔隙的特点与瓦斯存在形式的关系。最后提出了煤粉粒度和孔隙的研究方向。     

电厂煤粉粒度特征及其对煤粒燃烧的影响

采用MS2000激光粒度仪分析了电厂炉前煤粉粒度分布特征，磨煤造成了显微组分的分离与富集，镜质组有向粗粒度富集的趋势，惰质组有向细粒度富集的趋势．较粗粒径煤粉（212μm～75μm）特别是212μmn～150μm粒度段所占比例对炉内煤粉燃烧效率的影响最大．虽然镜质组有向粗粒度富集的趋势，但最粗粒煤粉因颗粒太粗，在炉内短暂加热时间内来不及迅速燃烧；而较细粒煤粉则因磨煤引起惰质组向细粒度富集而影响其燃烧效率．所以，在理论分析和实验研究粒度对煤粒燃烧特性的影响时，应考虑磨煤造成的显微组分分离与富集所引入的干扰和煤自身煤岩特征的差异．     

粒度分布对宁东羊场湾煤制水煤浆性能的影响

为了提高宁东地区煤的成浆性能,通过调整煤粉成浆的粒度分布,研究了粒度分布对水煤浆成浆性能的影响。实验证明,采用双峰级配,且小于200目煤粉占50%时,制得的水煤浆质量分数达到61.7%,比甲醇厂实际工况中水煤浆最大质量分数提高3%。     

Dispersion polymerization of n‐butyl acrylate

The dispersion polymerization of n‐butyl acrylate (BA) was investigated using alcohol/water mixtures as the dispersion medium, 4,4′ ‐azobis‐(4‐cyanopentanoic acid) as the initiator, and polyvinylpyrrolidone (PVP) as the stabilizer. The effects of polymerization parameters, such as the alcohol/water ratio in the medium and the type and concentration of the polymeric stabilizer, on the resulting particle size and size distribution were studied. The final particle size and the stability of the dispersion system were found to be greatly influenced by the type of alcohol used in the mixture; that is, methanol or ethanol, even though the apparent solubility parameters are almost the same for the two types of mixtures. Poly(butyl acrylate) particles with controlled size and size distribution (monodisperse), and gel content were successfully prepared in a 90/10 methanol/water medium. It was found that the particle size decreased with increasing initiator concentration. This is the opposite of what was previously reported in the dispersion polymerizations of styrene and methyl methacrylate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2692–2709, 2002     

不同炉型潞安煤灰理化及酸/碱溶解特性

对潞安煤经循环流化床、煤粉炉和气化炉处理后得到的煤灰进行了化学组成、矿物组成、特征基团、粒径分布、比表面积及微观形貌等理化性质的对比研究,并考察了其在酸浸和碱浸过程中Al^3+,Si^4+,Fe^3+,Ca^2+,K^+和Ti^4+等离子的溶解特性。结果表明:不同炉型潞安煤灰中铝、钙、硫等元素的含量有明显的差异;矿物组成包括晶相的鳞石英、方石英、莫来石、硬石膏及非晶相的偏高岭石、假莫来石、无定型二氧化硅等;相比较而言,气化炉灰中铝硅酸盐矿物结构更加不稳定。循环流化床灰颗粒呈具有一定孔洞结构的不规则状,而煤粉炉灰和气化炉灰均为光滑球形颗粒,循环流化床灰的粒径>煤粉炉灰的粒径>气化炉灰的粒径,循环流化床灰的比表面积>气化炉灰的比表面积>煤粉炉灰的比表面积。在HCl溶液中,Al^3+,Fe^3+,Ca^2+,K^+,Ti^4+的溶出率均较高;在NaOH溶液中,仅Si^4+和K^+的溶出率较高。不同炉型潞安煤灰中各元素的溶出率具有较大差异,主要与其矿物组成、结构稳定性、粒径和比表面积等相关。     

透射电镜在不同分散条件下测定纳米铁粉的粒度和分布

以纳米铁粉为研究对象,以不同有机溶剂为分散介质,采用超声振荡、分散剂等分散技术,利用透射电镜(TEM)测定了纳米铁粉的粒度及粒度分布,初步探讨了不同分散技术对纳米铁粉分散的影响。确定了最佳的测定条件,以乙醇为分散介质,分散剂OP-10的分散效果最佳,测定的纳米铁粉的外观为圆球型,平均粒度为32．9nm,粒度分布区域为20-40nm。     

Ultrafine comminution of dental glass in a stirred media mill

A systematic study on the comminution of amorphous glass particles with complex composition (seven constituents) to produce nanoparticles has been performed in a high-energy stirred media mill. The influence of solids loading, dispersion stabilisation via pH and addition of dispersants on particle size was investigated in aqueous suspensions. Further, the effect of using 2-propanol and benzyl alcohol as dispersion media on the particle size and morphology is presented and compared to the aqueous system. The specific surface area of the product powder was analysed by the BET method, the secondary particle size was determined by static light scattering and the morphology was investigated by SEM and TEM. Dispersion viscosity and stability was measured using rotational viscosimetry and zeta-potential measurements, respectively. The results show that the solids loading plays a central role in the comminution efficiency, where lower loadings lead to finer particles after a given milling time. Stabilisation of the aqueous powder dispersion by adjusting the pH or by adding a dispersant did not result in an enhanced milling efficiency in terms of fast reduction of the particle size. The smallest glass nanoparticles with a primary particle size were achieved by a two-step comminution process. The particles were irregularly shaped when milled in water, however, when processed in 2-propanol and benzyl alcohol, they had a plate-like geometry.     

氧化石墨烯对棉秆皮纤维素气凝胶球结构影响

采用超声分散法将纳米氧化石墨烯（GO）分散到二甲基亚砜中，再与棉秆皮微晶纤维素（MCC）和氯化1-丁基-3-甲基咪唑（BmimCl）溶解液混合，通过垂直悬滴法制备醇凝胶球，用超临界二氧化碳干燥法制备棉秆皮纤维素/氧化石墨烯（MCC-GO）气凝胶球。采用粒径分布软件和SEM、TG、FT-IR设备对材料的形貌结构进行表征。结果表明：当MCC占BmimCl质量百分比为3%时，纤维素醇凝胶球成型效果最好，平均粒径大小为2.78mm；随着GO占MCC质量百分比的增加，醇凝胶球的平均粒径变化不明显，均匀程度降低，确定系数R2由0.9985降低到0.8897；气凝胶球平均粒径随着GO质量分数的增加而先增大后减小，粒径均匀程度降低，确定系数R2由0.9915降低到0.6864，当GO质量分数为6%时，MCC-GO气凝胶球平均粒径最大为1.79mm，体积收缩率最小为57%；GO的添加增大了气凝胶内部孔隙，改变了孔结构，提高了MCC气凝胶球的热稳定性和吸附能力。     

Formation and dispersion of ropes in pneumatic conveying

In this study, the solid flow nonuniformities which develop in lean phase upward flow in a vertical pneumatic conveying line following a horizontal-to-vertical elbow were investigated. Laboratory experiments were conducted in 154 and 203 mm I.D. test sections using pulverized-coal particles (90% less than 75 μm) for two different 90° circular elbows having pipe bend radius to pipe diameter ratios of 1.5 and 3.0. The experiments covered a range of conveying air velocities and solids mass loadings. Experimental measurements of time-average local particle velocities, concentrations, and mass fluxes were obtained using a fiber-optic probe which was traversed over the cross-section of the pipe. The measurements indicate a continuous rope-like structure forms within the elbow. The rope maintains its continuous structure until it disintegrates into large discontinuous clusters at downstream locations. Comparisons of the results of CFD simulations of turbulent gas-particle flow and time-average experimental data were used to explain rope formation and dispersion. The CFD simulations, based on the Lagrangian particle-source-in-cell method, predict a denser particle rope as the nondimensional radius of curvature (R/D) is increased, agreeing with trends in experimental data. The individual effects of secondary flows and turbulence on axial dispersion of the rope were studied computationally and the results show both mechanisms are important.     

低温可逆热敏示温微胶囊的粒径控制及结构

采用界面聚合法制备了以CoCl2为芯材、聚乙烯醇为壁材的可逆热敏示温微胶囊,系统研究了乳化剂用量、内水相与油相用量比、搅拌速度、内乳液加入方式对微胶囊粒径的影响,并对微胶囊的结构和形貌进行了表征. 结果表明,当Span-80/Tween-80含量为5%(w)、水油体积比为0.2、转速为1200 r/min、内乳液采用逐步滴加方式加入外水相中时,制备的微胶囊粒径均一,平均粒径为12 mm,分散性好.     

Particle size analysis of plasticized PVC dispersion resins using the photometric centrifugal sedimentation method

There are many known methods for determining the particle size distribution of PVC dispersion resins. Most of these methods require that the resin be in an aqueous medium. PVC dispersion resins are used primarily in a plasticizer medium. The shearing action that takes place when the resin is mixed in plasticizer and the subsequent solvating action of the plasticizer affect the particle size distribution of the dispersion resin. It is advantageous to be able to determine the particle size distribution of the plasticized resin since it can affect various properties such as rheology, gloss and foam quality. It is the purpose of this paper to show that a fast zonal sedimentation technique can be used to analyze the less than 20 μ particle size fraction of a dispersion resin after it has been mixed in a plasticizer system. This can be accomplished in less than 90 minutes. This technique can be used to relate particular dispersion resin properties to the particle size distribution of the resin. The method can also be used as a quality control test.     

单分散二氧化硅微球的制备与表征

通过Stober法合成了单分散的二氧化硅微球,系统地研究了反应条件对成球粒径及单分散性的影响,通过透射电子显微镜对其进行了表征。随着氨水和正硅酸乙酯浓度的提高,生成的二氧化硅微球的粒径逐渐减小。而温度升高的条件下则会形成粒径较小的微球,溶剂粘度的升高也会增大形成的微球的粒径。另一方面,向反应体系中加入电解质可以有效地增大球的粒径,从而为制备微米级的二氧化硅微球提供了一种简单有效的方法。研究了相关的反应机理,根据这些反应条件的变化可以确定制备不同粒径单分散二氧化硅微球的条件。     

The influence of the ionic concentration, concentration of the polymer, degree of neutralization and chain extension on aqueous polyurethane dispersions prepared by the acetone process

There are many variables in the preparation of aqueous polyurethane (PU) dispersions. Chemical and compositional variables such as carboxylic acid concentration, concentration of the polymer, degree of pre/post-neutralization of the carboxylic acids and chain extension that all impact solution properties such as particle size and viscosity. Another variable is the method by which the dispersion is prepared; two primary methods are currently employed in industrial manufacture, the prepolymer mixing process and the acetone process. This study evaluates the impact of the chemical variables on a given PU dispersion formulation prepared by the acetone process. Changes in carboxylic acid concentration, degree of pre/post-neutralization and chain extension were found to have the expected impacts on dispersion solution properties. Increased ionic concentration, and degree of pre-neutralization led to lower particle size and higher viscosity, increased degree of chain extension led to larger particle size and lower viscosity, increased post-neutralization increased both particle size and viscosity, and increased concentration of the polymer led to a viscosity increase without any change in particle size.