Role of mineral matter in the chemical reactivity of coal

Previous work showed that the solvent extraction yield of coal increased as a result of chemical reactions such as formylation, reductive acylation, acylation, amidomethylation, alkylation, reduction and depolymerization. In the work described in this Paper, dmmf coal obtained after demineralization with mixed HF-HCI acids was used for solvolytic extraction studies after depolymerization, alkylation, acylation, amidomethylation, reductive acylation and reduction reactions. In comparison with the original coal, mineral matter free coal showed less increase in extractability as a result of these reactions indicating that mineral matter present in the original coal was acting as a promoter for these reactions.     

Effect of demineralization process on the liquefaction of Turkish coals in tetralin with microwave energy: Determination of particle size distribution and surface area

The effects of solvent/coal (S/C) ratio and demineralization on the solubilization of Turkish coals (Tunçbilek, Muğla-Yatağan, Beypazarı lignites and Zonguldak bituminous coal) in tetralin by microwave energy have been investigated. Particle size distributions and the surface area of the coals decreased with demineralization. For the investigation of the effect of the S/C ratios with values of 8/1, 10/1 and 12/1, the coal samples were heated by microwave energy for 20 min. The result indicated that the optimum S/C ratio was 8/1. The effect of microwave heating period was investigated at this value and the heating period was changed from 5 to 20 min at 5-min intervals. It was found that THF solubles yields of original coals were higher than those for demineralized coal except for Muğla-Yatağan lignite.     

Effect of leaching high sulphur subbituminous coal by potassium hydroxide and acid on removal of mineral matter and sulphur

The effect of leaching coal samples from Boragolai and Ledo collieries of Makum coal fields, Assam, situated in north eastern region of India with potassium hydroxide solution alone at 95 and 150 °C as well as followed by mild acid on demineralization and desulphurization was investigated. Potassium hydroxide alone leads to 2-19% demineralization and 16-30% desulphurization of the coal samples at 95 °C. Demineralization of the coals decreases to 1-11 and desulphurization increases to 26-43% on increasing the temperature to 150 °C. The decrease in demineralization is due to increased precipitation of potassium aluminosilicates. Demineralization of the coal may be enhanced to 28-45 and 39-68% and desulphurization to 22-35 and 34-53% at 95 and 150 °C, respectively, by leaching the potassium hydroxide treated coal with 10% hydrochloric acid which decomposes the potassium aluminosilicates to certain extent. The treatment almost completely remove the inorganic and up to 37% organic sulphur from the coal samples.     

微波场中高含铁量煤矸石酸浸制备氧化铁的研究

研究了微波场中酸浸高含铁量煤矸石制取Fe2O3,探索了煅烧时间、煅烧温度、酸浸温度、酸浸时间、微波功率、HCl质量分数、煤矸石粒度对Fe2O3浸出率的影响。结果表明,在固液比1∶3条件下,煅烧时间为120 min,煅烧温度为700℃,酸浸温度为105℃,酸浸时间为30 min,微波功率为500 W,HCl质量分数为20%,煤矸石粒度为0.1753 mm,Fe2O3的浸出率可达39.36%。与传统方法相比,在大大节省时间的同时,改善了操作环境。制备的Fe2O3样品有较好的应用价值。     

Effect of the alkylation of brown coal and peat on the composition and properties of humic acids isolated from them

The effect of alkylation with alcohols in the presence of a mineral acid on the yield of humic acids from brown coal and peat was studied. A change in the ratio between the phenol and carboxyl groups of humic acids depending on the conditions of brown coal and peat alkylation was shown. An increased biological activity of humates obtained from the alkylated materials was noted.     

Ultra clean coal production by microwave irradiation pretreatment and sequential leaching with HF followed by HNO3

The goal of this project was to develop and test an innovative coal cleaning process to reduce the ash content of coal and produce ultra clean coal (UCC). Coal samples that were prepared from concentrates of Iran's Zirab and Tabas coal preparation plants were found to have initial ash contents of 8.31 and 10.36%, respectively. These coals were demineralized with the combination of microwave irradiation pretreatment and dual acid leaching processes with HF followed by HNO₃ in a batch reactor. For samples that were microwaved and leached with HF, the reduction in ash ranged from 22 to 76% and from 22 to 82% for Zirab and Tabas coal samples, respectively, depending on leaching conditions. Microwave irradiation pretreatment had a positive effect on demineralization with HF, especially for the coarse size fractions. For the fine size fractions, reduced leaching times were found to enhance the effect of microwave irradiation. The microwave-irradiated, HF-leached product was leached further using a 1.4 M HNO₃ solution at a leaching temperature of 65 °C to remove fluoride sediments and pyritic sulfur. The ash content of the Zirab coal was reduced from 2.57 to 0.69% by leaching with the HNO₃ solution for 1 h. The ash content of the Tabas coal was reduced from 2.44 to 0.39% by leaching with the HNO₃ solution for 3 h. The results show that microwave irradiation can be considered as a pretreatment process in the chemical leaching of coal to produce UCC.     

Stepwise extraction of brown coal from the Sergeevskoe deposit

The mechanism of the stepwise dissolution of coal was investigated. It was found that the step-by-step demineralization of extraction residues facilitated the quantitative extraction of bitumoids and their acid constituents. The acids were separated in accordance with bond types, and the individual composition of the resulting fractions was analyzed. It was established that more than a third of the organic matter of the test coal has aliphatic nature.     

Effect of demineralization and catalyst addition on N2 formation during coal pyrolysis and on char gasification

Six coals with different ranks and different ash contents have been used to study the effect of demineralization on N₂ formation during coal pyrolysis. Chars obtained after pyrolysis have been also gasified with carbon dioxide at 1000 °C to investigate the influence of the demineralization on char gasification reactivity. The pyrolysis results show that the demineralization by acid washing drastically changes N₂ formation profiles and decreases nitrogen conversion to N₂ for low rank coals; on the other hand, the demineralization has little effect on N₂ formation for high rank coals. Addition of 0.5 wt% Fe promotes N₂ formation from the demineralized coals, but the catalytic effect depends on the coal type. It is found that the Fe remarkably promotes N₂ formation from the demineralized low rank coals, but the effect is much smaller for high rank demineralized coals. These observations suggest that the existing state of Fe-containing minerals and added Fe catalyst is important for catalytic N₂ formation during coal pyrolysis. Gasification results show that the demineralization lowers char gasification reactivity not only for low rank coals but also for high rank coals.     

煤中砷的超声波和微波辐照氧化脱除研究

用超声波和微波辐射法在氧化反应体系下,对晋源煤进行了脱砷的研究,主要考察了煤浆浓度、煤的粒径、处理时间、氧化剂的浓度、超声波功率以及溶液酸度等因素的影响.实验结果表明:超声波和微波结合氧化剂可得到较好的脱砷效果,砷的脱除最高可达90 %以上.在各影响因素中,煤浆浓度越低、氧化剂的浓度越高、酸度越大和超声波的功率越大,脱砷的效果越好.     

微波辅助下N1-乙氧基羰基甲基-5-氟尿嘧啶的绿色合成

在微波辐射下,以氯乙酸和乙醇为原料,合成氯乙酸乙酯,再以氯乙酸乙酯和5-氟尿嘧啶为原料合成了重要的医药中间体N1-乙氧基羰基甲基-5-氟尿嘧啶。通过改变溶剂、微波辐射功率、辐射时间、碱,确定了最佳的反应条件,并讨论了这些因素对反应的影响。在以水为溶剂、辐射功率250 W、辐射时间7 m in的最佳条件下,快速、绿色合成了N1-乙氧基羰基甲基-5-氟尿嘧啶,收率达90%,是一种绿色、简便、有效的合成新方法。产物结构经1H NMR,13C NMR和质谱确证。     

Reductive alkylation of Illinois No. 6 coal in liquid ammonia

The reductive alkylation of Illinois No. 6 coal was investigated using alkali metals and alkyl halides in liquid ammonia. Potassium is the most effective reducing agent and butyl iodide is the most effective alkylating agent for the preparation of coal alkylate that is soluble in tetrahydrofuran. The overall yield of soluble product is often improved through the reaction of the tetrahydrofuran-insoluble portion of the initial reaction products with an alkylating agent in the presence of tetrabutylammonium hydroxide. The infrared spectra of these materials suggest that the phase transfer agent catalyses the esterification of residual carboxylic acid functions. The intermolecular interactions between such acid groups and acceptor groups markedly restrict the solubility of the coal alkylate. The gel permeation chromatograms of the soluble reaction products are essentially featureless with only modest maxima at short and long elution volumes. The proton and carbon nuclear magnetic resonance spectra of the reductive methylation products, prepared using methyl-¹³C iodide, suggest that carbon alkylation exceeds oxygen alkylation and that the alkylation of phenolic groups is the dominant O-alkylation reaction. The spectra also suggest that fewer ethers are cleaved in the reaction in liquid ammonia than under the conditions of the Sternberg reaction.     

Microwave heating of coal for enhanced magnetic removal of pyrite

Amenability of Aşkale coal to desulfurization by magnetic separation following microwave heating was investigated. The coal was subjected to magnetic separation at 2 T following the treatment in a microwave oven at 850-W power and 2.45-GHz frequency. The increase in magnetic property by microwave heating at 850 W and 2.45 GHz was not sufficient to enhance the removal of considerable amount pyritic sulfur from the coal by magnetic separation at 2 T. Pyritic sulfur content was reduced by 37.46%. With the addition of 5% magnetite, which is an excellent microwave absorber mineral, microwave heating was enhanced and pyritic sulfur content of coal was reduced by 55.11%, by magnetic separation at magnetic field intensity of 2 T following the microwave heating. In addition, 21.54% decrease in ash content and 20.39% increase in calorific value also resulted.     

超超临界燃煤机组的锅炉补给水工艺的比较

对汉川三期工程和蒲圻二期工程两个超超临界燃煤机组的锅炉补给水系统的工艺进行了比较。得出两种工艺均能满足出水水质要求,一级除盐+混床运行操作及管理相对复杂,维护量较大,且对环境有一定的污染,但经济上综合年费较低;二级反渗透+混床除盐系统占地小、安装方便、运行操作及控制相对简单,环境污染较小,但综合年费较高。     

煤催化微波热解技术及其碳基吸波催化剂研究进展

微波技术与煤热解技术结合而成的煤微波热解技术可高效地治理传统煤热解技术中环境污染高和资源利用效率低的难题,为低变质煤的清洁高效利用和分级提质利用提供了新的思路。煤催化微波热解技术能有效改善热解升温特性和产物分布,从而受到较多学者的关注。本文从低变质煤催化微波热解技术发展历程着手,概述了国内外煤催化微波热解研究技术进展,通过加入Fe、Co、Ni和Cu等金属化合物或焦炭、活性炭等碳材料作为吸波剂,能显著增强煤对微波的吸收能力,提高热解升温速率、产物收率及产物质量,而有些金属化合物在微波热解反应中不仅起到吸波作用,还具有催化作用。碳基吸波催化剂作为一种性能优越的煤微波热解催化剂,具有优越的电磁和吸波性能、较好的催化性能和高经济性等优点,本文在煤催化微波热解技术研究现状的基础上,对碳基吸波催化剂进行了较为详细地分析,概述了碳基吸波催化剂的碳基体和催化活性组分的研究进展,对比了3种常见碳基吸波催化剂制备方法的优劣势。最后,总结了碳基吸波催化剂在研发过程中存在的难题,并展望了低变质煤催化微波热解技术的应用前景。     

煤的表面处理及润湿性研究

煤炭是一种具有大分子网状结构的有机岩石,表面润湿性是其工业应用的重要物性参数。通过原煤及分别经过偶联剂和烷基化处理的煤样表面润湿性的定,对煤表面润湿性进行了初步研究,结果表明,分别经过偶联剂处理和烷基化处理的煤样,其润湿性有一定程度的改善,使煤样表面发生了改性,烷基化反应后煤样的红外测试结果也证明了这一点。     

Fast tailoring of the acid–base properties in the NaX zeolite by cesium-exchange under microwave heating

NaX zeolite can show an acidic or basic behaviour depending on the degree of ion-exchange of sodium by cesium cations. The acid–base properties of the X zeolite are tunable by means of the cesium-exchange degree. This allows X zeolite to be prepared according to the needs of any determined reaction. Moreover, the cesium-exchange is carried out in a short period of time (5 min) when microwave radiation is used as the heat source. In addition, microwave heating decreases the volume of the ion-exchange solution. Only one cesium-exchange (28 cesium atoms per unit cell) under microwave heating was enough to annul the acid behaviour of the NaX zeolite in the toluene alkylation.     

Peculiarities in methanol action during liquefaction of different coal type

The peculiarities in methanol action during liquefaction of coals having different origin and rank were investigated. When liquefying sapropelic coals, the action of methanol does not differ from that of toluene. In the case of humic coals, methylation of aromatic fragments takes place and methylated liquid products are produced. The degree of alkylation increases with decrease in coal rank. The alkylation of model coal substances and some polyaromatic hydrocarbons was small. It was concluded that during coal liquefaction, reactive coal intermediates are subjected to alkylation.     

酸洗脱灰对准东次烟煤结构和反应活性的影响

研究酸洗脱灰过程对煤的化学结构和反应活性的影响对煤的清洁高效利用十分重要。采用HCl-HF-HCl和HF-HNO₃-HCl两种方法对准东次烟煤进行处理,利用傅里叶红外光谱对原煤及其酸洗处理得到的脱灰煤进行结构表征,并用微型流化床多阶段气固反应分析仪对煤粉样品燃烧反应性进行分析。结果表明,酸洗处理可使煤中灰分含量降低到0.2%以下,脱灰煤中OH和COOH附近的吸收峰强度显著增强,脂肪侧链变短,芳香环上取代基减少。HF使得煤中硅铝类矿物质被大量脱除,HNO₃会与煤中有机物发生硝化反应,导致部分含氧官能团含量进一步增加。当温度在600和700℃时,脱灰煤燃烧反应性与原煤相比显著降低,但随着温度升高至800和900℃,脱灰煤与原煤的反应性差距变小。     

洗煤过程中煤结构的变化

选用山西阳泉无烟煤、东北贫煤、云南小龙潭褐煤,通过洗煤制取煤样,低温灰化并采用XRF进行灰成分分析,结合傅里叶红外光谱法对煤结构进行分析,而且引入了红外参数来反映整个分子结构的变化。研究发现:水洗对煤中的矿物质脱除效果不明显,主要脱除的是可溶性物质,而酸洗主要脱除的是晶态SiO2,但是还有部分物质不能被脱除;随着煤阶的增加,煤中的矿物质与煤分子结构结合更紧密。煤化程度越低,煤结构中的基团越复杂,煤化程度高的煤中,谱图比较规律,在指纹区中,更能反映洗煤对煤结构的影响。对红外参数的分析说明了贫煤和无烟煤中脂肪度都很低,且主要以芳环碳骨架为主,而褐煤中存在很多支链结构。     

Improvement of grinding characteristics of Indian coal by microwave pre-treatment

The influence of microwave pretreatment on the grindability of high-ash Indian coal was investigated. Scanning electron microscope analysis characterized the micro fractures in microwave treated coal samples, which may be due to the thermal stress cracking resulting from the microwave pretreatment. X-ray diffraction analysis showed that the microwave treated coal had a higher peak compared to the untreated coal indicates that the crystallinity increased with the microwave exposure time. The calculation of the Hardgrove grindability index indicated an increase in the ease of grinding or an increase in the grindability index of the microwave treated coal. Bond grindability tests showed that the work index decreased 15.4% after a microwave exposure time of 120 s. Grindability tests showed that the microwave treated coal ground much more rapidly initially than the untreated coal, with the specific rate of breakage (S₁) increasing by an average of 15%. The results showed that the rates of breakage of both microwave untreated and treated coal samples were dependent on particle size.