Effects of calcium chloride and sodium chloride on the flotation removal of unburned carbon from coal fly ash

The effects of calcium chloride and sodium chloride on the coal fly ash flotation were investigated by studying the surface properties of coal fly ash. X-ray photoelectron spectroscopy and scanning electron microscopy showed the presence of many lime particles in the coal fly ash, which, together with Ca(OH)₂(s), could be adsorbed on the rough surface of unburned carbon particles. The flotation results indicated that calcium chloride reduced the performance of unburned carbon removal from the coal fly ash, whereas sodium chloride increased froth stability thereby improving the flotation performance.     

电厂锅炉飞灰含碳量测量模型

目前广泛采用微波技术进行在线测量电厂飞灰含碳量,现场使用过程中飞灰成分变化对仪器的测量精度有严重影响。利用RBF神经网络对影响飞灰成分的多维数据和微波功率进行融合,建立电厂锅炉飞灰含碳量测量模型。该模型能够避免飞灰种类变化对飞灰含碳量测量结果的影响,提高了飞灰含碳量的测量精度。     

No removal in the selective catalitic reduction process over Cu and Fe exchanged type Y zeolites synthesized from coal fly ash

The nitric oxide (NO) removal capacity of ion-exchanged zeolite Y obtained from coal combustion fly ash was evaluated in this work. Zeolite Y was exchanged either with Cu²⁺ or Fe²⁺ to obtain two different catalysts for the selective catalytic reduction of NOx from flue gas.

The selective catalytic reduction experiments were carried out at temperatures ranging from 50°C to 350°C, water content 0% and 5% and 5% O₂. In the absence of water, a total conversion of NO is obtained at 200°C for both zeolites, but important differences were found between zeolites LY-Cu and LY-Fe in the reduction of NO at temperatures lower than 200°C, and especially in the presence of water, that could be attributed to the different temperatures at which active species Cu²⁺ and Fe³⁺ are available for both ion-exchanged zeolites at the studied conditions. The greater surface area of zeolite LY-Cu can also contribute to its higher activity.     

Graphite materials prepared by HTT of unburned carbon from coal combustion fly ashes: Performance as anodes in lithium-ion batteries

The behaviour as the potential negative electrode in lithium-ion batteries of graphite-like materials that were prepared by high temperature treatment of unburned carbon concentrates from coal combustion fly ashes was investigated by galvanostatic cycling. Emphasis was placed on the relation between the structural/morphological and electrochemical characteristics of the materials. In addition, since good electrode capacity retention on cycling is an important requirement for the manufacturing of the lithium-ion batteries, the reversible capacity provided by the materials prepared on prolonged cycling (50 cycles) was studied and the results were compared with those of petroleum-based graphite which is commercialized as anodic material for lithium-ion batteries. The graphite-like materials prepared lead to battery reversible capacities up to ∼310 mA hg⁻¹ after 50 cycles, these values were similar to those of the reference graphite. Moreover, they showed a remarkable stable capacity along cycling and low irreversible capacity. Apparently, both the high degree of crystallinity and the irregular particle shape with no flakes appear to contribute to the good anodic performance in lithium-ion batteries of these materials, thus making feasible their utilization to this end.     

降低流化床水煤气炉飞灰含碳量的方法与实验研究

介绍了降低流化床水煤气飞灰含碳量的方法及实验研究结果。实验研究包括在现场进行的飞灰停留时间的冷态实验以及在实验室进行的飞灰反应性的实验。     

MMT对煤燃烧飞灰含碳量和NOx排放的影响

在一维沉降炉上对神混l号煤样添加MMT后燃烧的飞灰含碳量和NOx排放特性进行了试验研究,并对其燃尽率进行了分析.试验结果表明:所用沉降炉设计合理,添加MMT后,煤燃烧的飞灰含碳量和NOx排放同时降低.与原煤相比,最大降低量分别为18.39％和14.29％.原因是MMT的含锰燃烧产物能够促进C的氧化,同时还能作为催化剂促...     

Coal chars recovered from fly ash as promising electrocatalysts for oxygen reduction reaction

The endless and dramatic increase of global energy demand makes it imperative to develop sustainable, affordable, and efficient materials to act as electrocatalysts in the clean energy technologies. Electrocatalysts based on coal chars are promising materials as they can be considered as value-added by-products from coal combustion contributing to industrial ecology and circular economy. Therefore, herein we report the application of three sets of coal char (char concentrates before and after carbonization and demineralized and graphitized char concentrates) obtained from four different countries (Portugal, Romania, Poland, and South Africa) as oxygen reduction reaction (ORR) electrocatalysts. All electrocatalysts presented moderate ORR activity with some showing selectivity for the indirect two-electron process while others for a mixed regime between the two- and four-electron process. Still, the positive results obtained are better or in some cases comparable to commercial graphene. Moreover, all electrocatalysts presented good tolerance to methanol poisoning. More importantly, the results of this study demonstrate that pristine coal chars are promising materials to prepare efficient ORR electrocatalysts which will be of great importance in the near future.     

300MW电站锅炉飞灰含碳量过高的分析及优化

分析某300MW电站锅炉飞灰含碳量过高的原因,并提出了增设卫燃带,一次风集中布置,合理配比一、二次风,调整煤粉细度,调整出口氧量等优化措施,经改造取得满意效果。     

Activated carbons derived from fly ash and their electorchemical performances in supercapacitors

煤炭气化过程中产生大量飞灰,其中仍然含有未被利用的炭.以飞灰为前驱体,经浮选脱灰,化学活化制备活性炭.考察了制备条件对活性炭性能的影响.结果表明:①碱炭比升高,总孔容和微孔容积增加,中孔含量降低;②碱炭比越高,比电容越大,但大于2∶1后,比电容没有显著提高;③浮选脱灰的电化学性能得到提高;④在大电流密度下充放电仍然保持较高的比电容并且具有优异的循环使用性能.     

Numerical study on reduction of NOx and unburned carbon in micronized coal reburning

Three dimensional numerical simulation of bituminous coal reburning in a full-scale tangentially fired boiler was conducted with CFD method to study the effects of reburn zone length, the height of reburn nozzles, the stoichiometric ratio in reburn zone, the reburn fuel fraction and the reburn coal fineness on NOx reduction efficiency and unburned carbon in fly ash. The results indicate that the NOx reduction efficiency reaches the largest value when the relative height of reburn nozzles is about 0.21 and the stoichiometric ratio is between 0.8 and 0.9 in reburn zone; NOx reduction efficiency increases with reburn zone length, reburn fuel fraction and the decrease of reburn coal particle size; the smaller the coal particle size is, the better the burnout performance of coal is.     

前后墙对冲燃烧锅炉降低飞灰含碳量的燃烧调整试验

分析了浙江浙能长兴发电有限公司3号锅炉飞灰含碳量升高的原因,指出磨煤机研磨能力下降、煤粉过粗、煤粉浓度分配不均匀以及局部缺氧燃烧等是主要原因;介绍了针对巴威DRB-XCL旋流燃烧器的特点,通过采取调整燃烧器调风盘、内、外二次风叶片角度以及提高炉膛氧量等措施,从而降低锅炉飞灰含碳量2%~3%,解决了3号炉飞灰含碳量高的问题,提高了机组运行的经济性。     

“无废城市”背景下粉煤灰资源化利用途径研究进展

随着“无废城市”建设工作的推进,粉煤灰造成的土地和环境的污染问题急需解决。粉煤灰由于物理和化学性质特殊,可当作一种潜在的资源,因此如何合理利用粉煤灰成为众多企业的研究重点。介绍了粉煤灰的性质、分类和成分,并探讨了粉煤灰在多个领域的应用。比较了粉煤灰主要利用途径的优缺点和应用前景,并通过分析得出：附加值较高的利用途径,其处理成本也较高,粉煤灰的消纳量较少,存在的问题也较多,而且大多数研究尚处于实验室阶段,还未实现工业化利用。最后,针对如何提高粉煤灰的资源化利用率提出了相应的措施和建议。     

Effect of ball milling on the thermal conductivity and viscosity of Indian coal fly ash nanofluid

The present study investigates the effect of ball milling on thermal conductivity and viscosity of stable nanofluid of fly ash from Indian coal. The particle size of fly ash decreased from micron size to 89, 55.5, and 11.5 nm with reduction by 55, 90, and 434 times, respectively, due to ball milling for 30, 40, and 60 hours. The surfactant Triton X-100 was used to attain stability of 0.1% and 0.5% volume concentration of fly ash nanofluid. The samples were characterized by using scanning electron microscopy, dynamic light scattering, and zeta potential analysis. The outcome reveals that the thermal conductivity of fly ash nanofluid increases with temperature, volume concentration, and reduction in particle size. A maximum enhancement in thermal conductivity of 11.9% with 11.5-nm nanofluid sample and 5.4% with 89-nm nanofluid sample for 0.5% concentration at 60°C is observed. The viscosity of fly ash nanofluid increases with concentration and varies inversely with particle size and temperature. A difference of 1.6% in viscosity is observed between the values obtained with 11.5 and 89 nm nanofluid samples for 0.5% concentration at 30°C.     

Mercury capture by native fly ash carbons in coal-fired power plants

The control of mercury in the air emissions from coal-fired power plants is an ongoing challenge. The native unburned carbons in fly ash can capture varying amounts of Hg depending upon the temperature and composition of the flue gas at the air pollution control device, with Hg capture increasing with a decrease in temperature; the amount of carbon in the fly ash, with Hg capture increasing with an increase in carbon; and the form of the carbon and the consequent surface area of the carbon, with Hg capture increasing with an increase in surface area. The latter is influenced by the rank of the feed coal, with carbons derived from the combustion of low-rank coals having a greater surface area than carbons from bituminous- and anthracite-rank coals.     

燃煤锅炉飞灰含碳量的BP神经网络模型

燃煤锅炉是复杂的多变量系统,其飞灰的含碳量形成机理复杂,不能用简单的数学公式估算。现场实炉测试这些数据具有工作量大,测试工况有限等缺点;燃煤锅炉运行参数及燃料特性等因素影响着飞灰的含碳量,其相互耦合,导致分析数据过程困难。神经网络建模将燃煤锅炉视为黑箱,应用该方法可以良好的描述其输入输出之间的黑箱特性,因此,人工神经网络应用广泛。利用燃煤锅炉试验数据,采用3层BP(back propagation)神经网络构建了锅炉飞灰的含碳量排放特性模型。通过锅炉的实测数据验证,该BP神经网络对飞灰含碳量相对预测误差在0.19%~0.50%,预测效果良好。测试结果表明,建立的神经网络预测模型可以准确逼近验证样本数据,也能够较好的逼近非验证样本数据,具有良好的泛化能力。     

降低循环流化床飞灰含碳量的探析

飞灰含碳量高是循环流化床锅炉燃烧效率低的主要原因,通过分析影响飞回含碳量的因素,得出降低飞灰含碳量的方法。     

The effect of coarse gangue particles during the coal flotation process

It is well known that fine gangue particles play an important role in contaminating the concentrate during coal flotation process. However, the contamination behavior of coarse gangue particles in the concentrate has been neglected in the past. In this paper, the contamination behavior of coarse gangue particles in the concentrate during coal flotation process was investigated using a mixture of coarse gangue particles and low ash coal particles at a proportion of 1:1. The size fraction of coarse gangue particles was 0.5–0.25 mm. The size fraction of low ash coal particles was 0.5–0.25, 0.25–0.074, and ?0.074 mm, respectively. The results of XRD showed that coarse gangue particles were composed of quartz, pearl clay, kaolin, mica, and dickite. The results of contact angle measurements showed that the contact angle of coal particles was about 89° while that of gangue particles was only 30°. The results of flotation tests indicated that the contamination behavior of coarse gangue particles in the concentrate during the coal flotation process cannot be neglected.     

防渗材料对粉煤灰析出物吸附特性研究

采用标准测定方法 ,通过吸附动力学试验、静态吸附试验测定两种防渗材料 :黄土状亚粘土和石灰改性粘土对粉煤灰浸出液中主要污染组分的吸附特性 ,结果表明 :后者对污染物的吸附比前者好     

基于改良BP神经网络的生物质锅炉飞灰含碳量预测模型研究

针对生物质锅炉飞灰含碳量较高的问题,文章提出了基于主成分分析法(PCA)或Garson算法与普通LM-BP神经网络相结合的两种生物质锅炉飞灰含碳量预测模型。这两种模型通过对负荷、燃烧室烟气温度、烟气含氧量等17个原始输入变量进行降维得到新输入变量,再进行训练建模,提高了模型精度。利用我国某生物质电厂飞灰含碳量的实测数据对模型进行检验,检验结果表明,LM-Garson-BP神经网络的MAPE为2.09%,MSE为0.11,MAE为0.25,泛化能力最强,稳定性最好。     

Physiochemical and leaching characteristics of fly and bottom ash

Bottom ash and fly ash are the by-products of coal in thermal power plants. They are the combustion wastes and contain many elements that may harmful to the environment. The present study investigates the physiochemical, mineral, and leaching characteristics of an Indian coal ash (bottom ash and fly ash). From the characterization of bottom ash and fly ash, it is found that the ash samples are enriched predominantly in silica, alumina, and iron oxides. A series of leaching experiments have been performed to analyze the tracing elements of metal at the different liquid to solid ratio (L/S). The L/S varies from 20:1 to 80:1. From the leaching results of the fly ash and bottom ash data, it is observed that the tracing elements of Mn, Mg, Cr, Zn, Ni, Pb, Fe, and Cu are the most abundant elements, while Hg, Mo, and Co are the least abundant elements.