热提质褐煤预氧化后自燃特性变化及其自由基原位分析

针对不同温度热提质褐煤新鲜样及其自然环境中储存一定时间后的预氧化样,利用订制的自燃测定实验装置测得各样品的自燃倾向性差异,采用X-band电子自旋共振波谱仪进行自由基动态原位分析,研究预氧化对热提质褐煤自燃特性的影响。结果表明,热提质温度升高,新鲜样的自燃倾向性降低。但随着储存时间延长,105~500℃热提质褐煤发生预氧化,自燃倾向性不同程度地增加,400℃热提质后的预氧化样与原煤一样易自燃。在自燃氧化过程中,与新鲜样不同,预氧化样的吸氧量增加,自由基浓度也增加。预氧化不仅使热提质褐煤自由基增加;且在自燃的加速氧化阶段后期,不断产生自由基,维持氧化自热升温。而400℃热提质褐煤新鲜样在自燃氧化初期消耗大量小分子自由基,损失达80%,因不能持续产生活性自由基难以维持自燃氧化反应进行。     

煤粉收集器在褐煤提质工艺中的运用

煤粉收集器作为褐煤煤粉的收集设备,在褐煤提质工艺中扮演着安全生产和烟尘排放治理的双重角色,是褐煤提质工艺中的关键一环。本文通过介绍煤粉收集器的特点及在褐煤提质工艺上的应用实例,对煤粉收集器在褐煤煤粉收集的安全应用方面存在的问题予以揭示,并提出改进建议。     

碱／碱土金属盐对提质褐煤自燃倾向的影响

利用煤着火点测定仪和热重仪对添加碱／碱土金属盐制的提质褐煤着火点、燃烧特性进行分析,研究碱／碱土金属盐对其着火点、燃烧特性的影响。研究表明,碱／碱土金属盐对提质褐煤着火点有影响,按对抑制作用大小排序：MgCl2〉CaCl2〉Na2CO3〉K2CO3;碱／碱土金属盐对提质褐煤燃尽段有促进作用,可以有效降低碳在灰分中的残余。     

褐煤水热提质研究进展

为实现褐煤水热提质的工业化应用,分析了水热提质对煤质的影响,综述了水热提质改善水煤浆泵送特性,脱除煤中有害物质,实现废水治理等应用现状,最后阐述了水热提质连续化装置的研究进展。褐煤水热提质可同时脱水、脱氧,解决褐煤远距离运输及自燃问题,提高利用效率;水热提质同时还可脱除煤中潜在的有害元素,提高褐煤成浆性;水热提质的废水问题可结合水热气化方法或废水制浆解决。提出应加快管道式褐煤水热工业化装置的开发,对褐煤水热提质联合水煤浆气化或燃烧发电的经济性进行分析,加快实现褐煤水热提质的工业化步伐。     

褐煤提质技术现状

阐述了褐煤在运输、储存、利用中存在的问题,指明了褐煤提质技术对合理利用褐煤资源的重大意义;综述了褐煤提质工艺成型技术现状并对褐煤提质技术的发展前景进行了展望。     

浅析褐煤提质现状

褐煤提质可有效提高褐煤的质量及扩大褐煤的用途。针对国内褐煤提质技术的发展现状进行了分析,介绍了现在比较热的褐煤提质工艺,并对国内褐煤提质技术的发展趋势进行了探讨。     

浅析褐煤提质现状

褐煤提质可有效提高褐煤的质量及扩大褐煤的用途。针对国内褐煤提质技术的发展现状进行了分析,介绍了现在比较热的褐煤提质工艺,并对国内褐煤提质技术的发展趋势进行了探讨。     

褐煤提质技术发展现状及分析

分析褐煤储量和褐煤性质的基础上,提出了褐煤提质的必要性。介绍了国内外褐煤主要提质技术,分析了这些技术的利用状况及优缺点,并提出了褐煤提质新工艺。     

褐煤提质前后成浆特性的研究

褐煤是煤化程度最低的煤种,为泥炭在适度压力下转变而成,煤化程度低,用作气化原料存在许多缺陷,如高水分、高灰分、熔点变化大、机械强度低、热稳定性差、煤气粉尘含量大、料层透气性差等。但将褐煤提质后制备高浓度水煤浆,再通过水煤浆气化加以利用是褐煤利用的一个新途径。本文通过对褐煤原煤和提质型煤成浆特性的研究,通过级配试验、添加剂试验、成浆浓度试验等,得出褐煤经提质后成浆性可以得到很大的提高,为褐煤应用拓宽了应用领域。     

褐煤提质技术开发现状及分析

分析褐煤储量和褐煤性质的基础上,提出了褐煤提质的必要性。介绍了国内外褐煤主要提质技术,分析了这些技术的利用状况及优缺点,重点介绍了国内褐煤提质的主要示范项目,并对褐煤利用方向提出了一些建议。     

干燥褐煤的自燃与爆炸特性试验研究

为抑制褐煤堆放时发生自燃与煤粉爆炸,利用自燃装置试验台和煤粉爆炸试验台,对褐煤及其干燥到不同水分的干燥煤进行试验研究,分析其自燃特性和爆炸特性。结果表明,对于自燃特性而言,褐煤水分减少10%,耗氧速度增加约0.17%/min,粒径减小一个等级,耗氧速度增加约0.11%/min;对于爆炸特性而言,褐煤水分减少5%,平均煤粉爆炸下限质量浓度约降低0.015 kg/m~3,温度每升高10℃,平均煤粉爆炸下限质量浓度降低约0.03 kg/m~3;总体而言,随着干燥程度的加深,褐煤自燃、爆炸特性均增强,危险性增加。     

热重分新法对不同粒度煤自燃过程特征温度的研究

选用3种煤分别制得3种粒度的试样。采用非定温测量法进行TG分析,得到相应的TG／DTG曲线,选定煤自燃过程中的6个特征温度,并确定其温度界限,分析不同粒度煤样特征温度的变化并总结规律。结果表明,高位吸附温度和着火温度基本保持不变,其余4个特征温度的变化规律不尽相同。     

乌拉盖褐煤热解特性及反应动力学参数研究

为获得较好的褐煤半焦制备工艺参数,研究了不同制备条件(热解终温、升温速率、原煤粒径、热解气氛)下制得的乌拉盖褐煤半焦的燃烧性能和燃烧动力学参数。结果表明,热解终温对半焦品质的影响最大,热解升温速率、原煤粒径和热解气氛对半焦燃烧特性的影响不显著。热解终温由350℃升至600℃时,反应指数RI由235℃升至292℃,半焦着火性能变差;燃尽指数Cb由4.68升至6.15,半焦燃尽性能变差;爆炸指数Kd由2.54降至0.46,半焦爆炸倾向性变低;反应活化能由44.4 k J/mol升至63.4 k J/mol,半焦燃烧动力学特性变差。热解终温为520℃时制得的半焦反应指数、燃尽指数、爆炸指数和反应活化能分别为265℃,5.34、0.80和53.2 k J/mol,属于易着火、易燃尽、中等爆炸燃料,燃烧特性良好。     

硫化矿石堆氧化自燃全过程特征综述与分析

针对能产生自燃内因火灾的典型硫化矿石类型,介绍了其堆积、氧化自热、着火及燃烧各阶段的特征,分析了氧化自燃发生的原因和发展过程,并探讨了影响硫化矿石自燃的各种因素及其作用机理.在此基础上,澄清了对硫化矿山火灾防治有重要指导意义的自燃发火初期的概念及其征兆识别方法,可为现场硫化矿山自燃火灾的早期识别与防治提供指导.     

Investigation of combustion reactivity and NO emission characteristics of chars obtained from the devolatilization of raw and partially dried lignite

In an attempt to achieve the clean and efficient utilization of lignite, drying pre-treatment was performed in this study before lignite combustion. The combustion reactivity and NO emission characteristics of the partially dried lignite samples in the char combustion stage were investigated by means of TG and isothermal combustion tests, and the reactivity could be summarized as the following order: L1>L0.5>raw>L3>LT>L5 (chars obtained from the devolatilization of the raw and partially dried coals at 378 K for 0.5, 1, 3, 5, and 120 minutes) and the NO conversion ratio of L1 was the lowest. When the moisture content in the coal particles was relatively high (19.68%-35.84%), the drying treatment could increase the combustion reactivity and inhibit NO emission in the char combustion stage; When the moisture content was within a relatively low range (0.17%-19.68%), the moisture removal had negative effects on the reactivity and NO emission in the char combustion stage. The surface behaviour and microstructure of the raw coal char and chars derived from the partially dried coals were clarified by temperature programmed desorption/reduction (TPD/TPR) and Raman spectroscopy. The results illustrated that L1 derived from L_c1 (19.68%) was the most reactive sample with the largest amount of C(O) on the particle surface. There were also more reactive aromatic structures in L1 than other samples. Compared with direct combustion or excessive drying treatment, lignite should be dried to a certain degree (19.68%) for optimized lignite combustion.     

新桥硫铁矿矿石自燃特征及综合防治措施

通过新桥硫铁矿－230m中段6次自燃火灾事故调查和矿岩自燃倾向性以及现场堆矿实验研究,系统阐述了硫化矿石氧化自热到自燃整个过程的特征规律,并针对火灾提出了一系列防灭火技术措施,特别指出了硫化矿自燃初期征兆的识别方法,对硫化矿山火为预防和综合治理有重要指导意义。     

Air and oxy-fuel combustion characteristics of biomass/lignite blends in TGA-FTIR

Pyrolysis and combustion behavior of indigenous lignite, olive residue and their 50/50 wt.% blend in air and oxy-fuel conditions were investigated by using thermogravimetric analyser (TGA) combined with Fourier-transform infrared (FTIR) spectrometer. Pyrolysis tests were carried out in nitrogen and carbon dioxide environments which are the main diluting gasses of air and oxy-fuel environment, respectively. Pyrolysis results of the parent fuels and the blend show that weight loss profiles are almost the same up to a temperature of 700 °C in these two environments, indicating that CO₂ behaves as an inert gas in this temperature range. However, further weight loss takes place in CO₂ atmosphere at higher temperatures due to CO₂-char gasification reaction which leads to significant increase in CO and COS formation as observed in FTIR evolution profiles. Comparison between experimental and theoretical pyrolysis profiles of the blend samples reveals that there is no synergy in both atmospheres. Combustion experiments were carried out in four different atmospheres; air, oxygen-enriched air environment (30% O2-70% N₂), oxy-fuel environment (21% O₂-79% CO₂) and oxygen-enriched oxy-fuel environment (30% O2-70% CO₂). Replacing N₂ in the combustion environment by CO₂ causes slight delay (lower maximum rate of weight loss and higher burnout temperature) in the combustion of all samples. However, this effect is found to be more significant for olive residue than lignite. Elevated oxygen levels shift combustion profiles to lower temperatures and increase the rate of weight loss. Combustion profiles of olive residue/lignite blends lie between those of individual fuels. Comparison between experimental and theoretical combustion profiles and characteristic temperatures of the blend samples indicates synergistic interactions between the parent fuels during co-combustion of olive residue and lignite.     

水泥行业用煤的燃烧特性评价及统计分析

本文通过热重分析检测煤炭燃烧特性,在已积累的大量数据基础上,对水泥行业用烟煤和无烟煤的煤烧特性各项指标统计分析,并对各项参数给出了参考数值：（1）烟煤着火温度范围在390～620℃,平均值在430℃左右;燃烧烈度范围0.3～2.7 mV/（mg·min）,平均值1.18 mV/（mg·min）;燃尽时间范围12～37 min,平均值18 min;(2)无烟煤着火温度范围在430～650℃,平均值558℃左右;燃烧烈度范围0.6～2.3mV/（mg·min）,平均值1.58mV/（mg·min）;燃尽时间范围10～30min,平均值13min。将燃烧特性参数进行赋分和排位,在数据库中求得分位值,绘制煤炭燃烧特性排位图,为生产用煤配煤提供技术指导和控制要求。     

Evolution mechanism of active groups and thermal effects of Chinese lignite in low-temperature oxidation

Abstract

The evolution of active groups at low temperature was examined using Chinese lignite by infrared technology and X-ray photoelectron spectroscopy (XPS). The results showed that the hydroxyl, aliphatic ether, methylene, and methyl groups played important roles in the low-temperature oxidation of lignite below 200?°C. Carbonyl and carboxyl groups were important intermediates. Thus, a multi-step evolution mechanism involving the hydroxyl, aliphatic ether groups, and alkane was reasoned to describe the low-temperature oxidation of lignite. In addition, according to the oxidation kinetics experiment and the evolution laws of the active groups, the ratios of the reaction lines were determined considering the accuracy of thermal effects. The thermal effects and the heat release intensities of each temperature interval were obtained based on the evolution mechanism and the reaction ratios. The shortest spontaneous combustion period of lignite was calculated and compared with the experimental value, which proved that the reasoned evolution mechanism of the active groups and the calculations of the thermal effects were reliable.