Reaction behaviour of Al_2O_3 and SiO_2 in high alumina coal fly ash during alkali hydrothermal process

The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morphology of the solid samples obtained by different alkali hydrothermal treatments as well as the leaching ratio of SiO2 to A1203 in alkali solution. The results showed that with the increase of the hydrothermal treating temperature from 75 to 160 ~C, phillipsite-Na, zeolite A, zeolite P, and hydroxysodalite were produced sequentially while the mullite and corundum phase still remained. Zeolite P was massively formed at low-alkali concentration and the hydroxysodalite was predominantly obtained at high-alkali concentration. By the dissolution of aluminosilicate glass and the formation of zeolites together, the leaching efficiency of SiO2 can reach 42.13% with the mass ratio of A1203/SIO2 up to 2.19：1.

Extraction of aluminum by pressure acid-leaching method from coal fly ash

Aluminum was leached out from coal fly ash by pressure acid-leaching method. The effects of coal fly ash size, sulfuric acid concentration, reaction time and reaction temperature on extraction efficiency of aluminum were investigated comprehensively. The phase and morphology of coal fly ash and solid residues after reaction were analyzed by XRD, SEM and IR. The optimal technological conditions for extracting aluminum from coal fly ash were eventually confirmed that coal fly ash with size of 74 μm and sulfuric acid with concentration of 50% are mixed in pressure reaction kettle to react for 4 h at 180 ℃. Under the optimal conditions, the extraction efficiency of aluminum can reach 82.4%.

Steam gasification reactivity of a high-sodium coal fly ash obtained from a pilot scale CFB gasifier

Circulating fluidized bed （CFB） gasification has several advantages for the utilization of low rank coals. However, the carbon content of fly ash is usually very high, which greatly infuences the gasification efficiency. The purpose of this research is to investigate the gasification reactivity of a high-sodium Zhundong （ZD） coal fly ash obtained from a pilot-scale 2.5 t/d CFB gasification system. The experiments were carried out in a thermogravimetric analyzer with steam as gasification agent, and fast pyrolyzed ZD char was also investigated as a reference sample. The results show that increasing temperature accelerates the gasification rate both for fly ash and ZD char. Fly ash has higher gasification rate at the initial gasification stage. On the contrary, ZD char has higher reaction rate even at higher carbon conversion stage. Via distributed activation energy model, the average activation energy of ZD char and fly ash is calculated to be 94.4 and 91.2 kJ/mol, respectively. The integrated model study reveals that the reaction order of ZD char is about 0.74, whereas the reaction order of fly ash decreases from 1 to 0.59 when temperature increases from 900 to 1050 ℃. The gasification reactivity of ZD coal fly ash is quite different with literature research on those fly ashes with rarely little catalytic elements in coal ashes. The interesting results are related with the unique properties of ZD coal fly ash and the transformation of sodium during gasification process.

Microstructure and properties of mullite-based porous ceramics produced from coal fly ash with added Al_2O_3

Using coal fly ash slurry samples supplemented with different amounts of Al2O3, we fabricated mullite-based porous ceramics via a dipping-polymer-replica approach, which is a popular method suitable for industrial application. The microstructure, phase composition, and compressive strength of the sintered samples were investigated. Mullite was identified in all of the prepared materials by X-ray diffraction analysis. The microstructure and compressive strength were strongly influenced by the content of Al2O3. As the Al/Si mole ratio in the starting materials was increased from 0.84 to 2.40, the amount of amorphous phases in the sintered microstructure decreased and the compressive strength of the sintered samples increased. A further increase in the Al2O3content resulted in a decrease in the compressive strength of the sintered samples. The mullite-based porous ceramic with an Al/Si molar ratio of 2.40 exhibited the highest compressive strength and the greatest shrinkage among the investigated samples prepared using coal fly ash as the main starting material. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Trends and advances in the development of coal fly ash-based materials for application in hydrogen-rich gas production:A review

Coal fly ash(FA),a valuable industrial solid residue generated from coal combustion,is composed of various metal oxides and has a high thermal stability.Given that the coal-based energy will continue to account for a significant portion of global electricity generation in the coming years,the lack of effective management strategies exacerbates the threat of FA wastes to the surrounding environment and human health.For a sustainable development,green and renewable hydrogen economy and CO_(2)capture efforts provide appealing opportunities to valorize FA as catalysts and/or sorbents due to their appealing physicochemical properties.Hydrogen applications along with carbon neutrality are potential strategies to mitigate climate change crisis,but high processing costs(catalysts/sorbents)are challenging to realize this purpose.In this context,the utilization of FA not only enhances industrial competitiveness(by reducing manufacturing costs),but also provides ecologically friendly approaches to minimizing this solid waste.This state-of-the-art review highlights a wide-ranging outlook on the valorization of FA as catalysts and sorbents for hydrogen-rich gas production via conventional/intensified processes(CO_(2)/H_(2)O reforming,ammonia decomposition,hydride hydrolysis).The fundamental physicochemical characterizations and hazards/utilization of FA,which significantly affect the FA's utilization in various fields,are first introduced.The influence of several factors(like FA types and catalysis/sorption operation conditions)on the activity performance of FA-based materials is then discussed in detail.This critical review aims to open the window to further innovative ideas regarding the application of different FA residues in other catalytic and sorption processes.

Utilization of Coal Fly Ash for the Production of Glass-ceramics With Unique Performances: A Brief Review

Coal fly ash is an industrial by-product generated during the combustion of coal for energy production. Due to the increasing annual consumption of coal power and the serious potential environmental threats of coal fly ash, a considerable amount of research on the utilization of coal fly ash has been undertaken worldwide. Vitrification seems to be one of the most promising options for reusing this industrial waste. This paper presents a short overview of the production of unique high performance glass-ceramics using coal fly ash as a raw material. A detailed description of the methodologies for the synthesis of glass-ceramics from coal fly ash and the principal crystal phases, corresponding property and possible usage of those materials are introduced. Investigations revealed that converting coal fly ash into high performance glass-ceramic materials is a promising new approach to improve the utilization of this industrial by-product. This conversion not only alleviates the problems with disposal but also converts a waste material into a high value-added marketable commodity.

中高灰炼焦煤生产高品质83焦的应用实践

为了降低配煤成本,云煤能源安宁分公司使用低价格的中高灰炼焦煤。由于配量过大,导致焦炭CSR严重下降,在总结经验和小焦炉试验的基础上,采用合适的配煤比,消化了库存的中高灰炼焦煤,焦炭CSR达到≥66.0%的要求。

水溶液隔膜电解除铁

在用高铝粉煤灰盐酸法制备氧化铝的过程中,粉煤灰中的铁会随酸性浸出液进入氯化铝溶液.为了低成本降低氯化铝溶液中铁杂质的质量分数,提出了在水溶液中电解除铁的方法.除铁实验中使用双室隔膜电解槽,对初始条件为pH值2.0,Fe^(2+)质量分数0.25%的FeCl_(2)溶液进行循环电解,研究了几种常见金属阴极板上单质铁的析出效果.结果表明:使用钛、铁、锡、铜、铅5种金属电极均可在5 h电解后达到90%的除铁率,溶液中亚铁离子的质量分数降低至小于0.03%.

煤泥分级浮选工艺的研究

为了解决煤泥混合浮选工艺中分选粒度范围过宽、高灰细泥夹带污染精煤,导致浮选精煤灰分高、尾煤灰分低,严重影响精煤产品质量的问题,采用正交试验、小筛分、分步释放浮选实验方法,对影响浮选效果的因素进行深入的探讨,提出了分级浮选工艺:用分级旋流器组进行浮选入料粗、细煤泥分级,<0.125mm细煤泥采用新型旋流微泡浮选柱-快速双隔膜压滤机处理,0.5～0.125 mm粗煤泥采用原有的浮选机-过滤机处理,实现粗、细煤泥高精度分选和高效脱水.结果表明:应用分级浮选工艺,浮选精煤灰分下降了1.08%,尾煤灰分提高了9.51%,精煤回收率提高了0.73%.

CaO含量对高钠煤灰熔融特性的影响

为研究CaO含量对高钠煤灰熔融特性的影响,配制了不同CaO含量的高钠合成灰并对灰熔融温度(AFTs)进行了测试,利用Fact Sage 7.0提供的热力学数据库对灰熔融过程进行了模拟,分析不同CaO含量的高钠合成灰的矿物质变化,利用X射线衍射(XRD)、扫描电子显微镜(SEM)对合成灰的矿物质组成及微观形貌进行了研究。结果表明,随着CaO含量的增加,灰熔融温度先降低后提高。添加CaO同时影响含钙矿物质与含钠矿物质的存在形式与相对含量。在1 000℃下,含钙矿物质由钙长石依次转化为钙铁榴石、硅灰石、钙黄长石、硅钙石和原硅酸钙,含钠矿物质由钠长石转化为霞石。二元相图和似三元相图的结果表明,液相线温度随CaO含量的变化趋势与灰熔融温度相同。对本研究中的煤种,当CaO含量高于40%时,可以有效提高灰熔融温度。

山西“两高”煤灰分对石灰石助熔机制影响的研究

以山西"两高"煤为研究对象,考察了洗选改变灰分对添加助熔剂Ca CO3的影响。研究发现,随着洗煤灰分的降低,煤灰中二氧化硅含量及硅铝比(Si/Al)降低,煤灰流动温度降低至液态排渣气流床气化所需温度时,Ca CO3的添加比例与洗煤高温下生成的矿物质种类及其含量相关,经过洗选降低灰分后的FH与SH洗煤,通过添加一定比例的助熔剂Ca CO3,高温下煤灰渣类型由结晶渣变为玻璃体渣,排渣温度范围宽,能够很好地满足气流床气化液态排渣的要求,洗选与添加Ca CO3助熔剂配合使用的方式,可以有效调控山西"两高"煤灰流动性质。

MgO含量对高钠煤灰熔融特性的影响

为研究MgO含量对高钠煤灰熔融特性的影响,配制了不同MgO含量的高钠合成灰并对灰熔融温度进行了测试。利用Fact Sage 7.0提供的热力学数据库建立了SiO_2-Al_2O_3-Fe_2O_3-CaO-MgO-Na_2O多元体系,模拟不同MgO含量的高钠合成灰的熔融过程。使用X射线衍射(XRD)和扫描电子显微镜(SEM)对合成灰的矿物质组成及微观形貌进行了研究。结果表明,随着MgO含量的增加,灰熔融温度先降低后升高。当MgO质量分数由0增加到5%时,高温下灰中生成大量低熔点的透辉石,透辉石会与霞石等矿物质形成低温共熔体,导致灰熔融温度降低。进一步增加MgO含量,高温下灰中生成镁黄长石、镁橄榄石和镁硅钙石等高熔点矿物质,使灰熔融温度升高。二元相图和似三元相图的结果表明,全液相温度随MgO含量的变化趋势与灰熔融温度相同。对本研究中的煤种,当MgO质量分数为30%时,可以有效提高灰熔融温度并抑制熔融液渣的生成。

锅炉飞灰含碳量异常偏高的试验研究

通过锅炉冷态试验、常用煤种和异常煤种的热态调整试验,排除了可能引起某125MW机组飞灰含碳量异常(最高达14%)的结构及运行因素;常用煤种和异常煤种的常规指标接近,但其燃尽特性明显较常用煤种差;对异常煤种进行颗粒分离并分别进行工业分析,发现异常煤种由煤矸石、烟煤、无烟煤混合而成,无烟煤的含量达31.56%;对各颗粒分别进行热重分析,并与异常煤种TG-DTG曲线进行比较发现,烟煤、无烟煤的快速失重点分别与异常煤种的两个快速失重点相对应,进一步证明异常煤种主要由烟煤和无烟煤掺配而成。大量无烟煤的掺入导致燃尽困难,即为锅炉飞灰含碳量异常偏高的原因所在。

高铝煤混燃飞灰电除尘特性的试验研究

我国部分地区的煤燃烧后飞灰的铝含量高达45%以上,严重影响了飞灰的电除尘性能,实际测定其飞灰比电阻达到了1012Ω.cm以上,使电除尘器效率明显下降。采用高铝煤与其它煤种按不同比例混配后在高温炉中燃烧,并测定燃烧后飞灰的粒径、比电阻等特性;对电除尘效率进行建模计算,在保证对锅炉燃烧热效率影响不大的情况下,找出最佳混配比例,使混燃后高铝煤灰的物化特性得到改善,从而提高电除尘效率。

烟气汞浓度监测吸附管离线采样方法的拓展应用

将吸附管离线采样方法应用于美国EPA Method 30B标准允许外的高温、高灰条件下的汞浓度及形态监测试验研究,以拓展该方法的应用范围。试验结果表明:当采用吸附管采样法测量烟气总汞,且控制低流速采样并采用防尘罩时,该方法可以应用于湿法脱硫除尘前等粉尘浓度较高的场合,由粉尘引起的误差小于1%,但该方法不适用于高粉尘浓度的极端条件;在空气预热器前的高温位置,通过加设风冷套管并控制采样枪插入深度,可以保证吸附管温度处于合适的温度水平,从而保证测量的准确性;在烟囱入口等低粉尘浓度区域,测得的元素汞的比例与Hg-CEMS基本一致,尤其是湿法脱硫后的测试数据一致性良好,而干法脱硫后的采样测试结果略显偏低;但在高粉尘浓度区域,测得的元素汞比例则可能严重偏低。

P204从高铝粉煤灰硫酸浸液中萃取除铁

主要针对高铝粉煤灰酸浸液中铁铝萃取分离性能进行研究,通过模拟高铝粉煤灰酸浸液(C(Al^(3+))=37.1 g/L,C(Fe^(3+))=5.1 g/L),采用P204+260^(#)溶剂油萃取体系,对组成液中铁铝进行萃取分离,系统研究了P204体积分数、温度、反应时间、溶液初始pH值、相比V_((O))∶V_((A))等因素对萃取和反萃的影响,得出以下结论:在有机相为40%P204+60%260^(#)溶剂油,温度为60℃,反应时间为20 min,水相pH值为0.4,相比V_((O)):V_((A))为1∶1的条件下,模拟酸浸液中铁的萃取率可达93.24%,铝的萃取率为2.3%。当反萃采用5 mol/L的盐酸溶液,相比V_((O))∶V_((A))为1∶3时,经过10 min的反应,铁的反萃率可达92.96%。

高灰细泥细粒煤浮选技术进展

我国是世界上最大的煤炭生产和消费国。随着采煤机械化程度的提高,原煤粒度越来越细且灰分很高,导致高灰细泥细粒煤的分选成为选煤界的一大难题。文章针对高灰细泥细粒煤的分选现状,综述了一些比较典型的用于高灰细泥细粒煤浮选的技术,并指出了高灰细泥细粒煤分选的发展方向。

液固流化床分级与分选联合工艺的研究与应用

为了解决液固流化床在粗煤泥分选过程中入料粒度范围过宽、高灰细泥进入溢流污染精煤导致的粗精煤灰分偏高,严重影响液固流化床分选效果和精煤产品质量的问题,提出了液固流化床分级与分选联合工艺,即采用液固流化床对粗、细煤泥进行分级,溢流的细煤泥采用浮选处理,底流的粗煤泥进入第二台液固流化床分选,从而使粗、细煤泥均实现了高精度的分选。液固流化床分级与分选联合工艺在梁北选煤厂的生产实践中取得了良好效果,使入料中高灰细泥减少了80.32%,粗精煤灰分下降了2.43个百分点。

晋城矿区“三高”劣质煤资源开发与利用探讨

介绍了晋城矿区"三高"劣质煤资源的基本特征及开发利用现状;分析了"三高"劣质煤的燃烧及气化特性,剖析了灰熔聚气化技术在生产运行中存在的一些深层次问题;提出了"三高"劣质煤资源规模化开发利用的相关对策措施。