Speciation and thermal transformation of sulfur forms in high-sulfur coal and its utilization in coal-blending coking process:A review

The utilization of high-sulfur coal is becoming more urgent due to the excessive utilization of low-sulfur,high-quality coal resources, and sulfur removal from high-sulfur coal is the most important issue. This paper reviews the speciation, forms and distribution of sulfur in coal, the sulfur removal from raw coal,the thermal transformation of sulfur during coal pyrolysis, and the sulfur regulation during coal-blending coking of high organic-sulfur coals. It was suggested that the proper characterization of sulfur in coal cannot be obtained only by either chemical method or instrumental characterization, which raises the need of a combination of current or newly adopted characterization methods. Different from the removal of inorganic sulfur from coal, the organic sulfur can only be partly removed by chemical technologies;and the coal structure and property, particularly high-sulfur coking coals which have caking ability,may be altered and affected by the pretreatment processes. Based on the interactions among the sulfur radicals, sulfur-containing and hydrogen-containing fragments during coal pyrolysis and the reactions with minerals or nascent char, regulating the sulfur transformation behavior in the process of thermal conversion is the most effective way to utilize high organic-sulfur coals in the coke-making industry.An in-situ regulation approach of sulfur transformation during coal-blending coking has been suggested.That is, the high volatile coals with an appropriate releasing temperature range of CH_4 overlapping well with that of H2 S from high organic-sulfur coals is blended with high organic-sulfur coals, and the C–S/C–C bonds in some sulfur forms are catalytically broken and immediately hydrogenated by the hydrogencontaining radicals generated from high volatile coals. Wherein, the effect of mass transfer on sulfur regulation during the coking process should be considered for the larger-scale coking tests through optimizing the ratios of different coals in the coal blend.     

微波场中长焰煤与焦煤共热解实验研究

对王家沟(WJG)长焰煤和焦煤(JM)两种原料煤进行了微波共热解实验研究,考察了两种煤配比不同时热解产物的收率及成分变化.结果表明,微波热解条件下,随着混煤中JM比例的增大,焦油收率在逐渐减少,而固体焦的灰分含量与硫含量逐渐增加.SEM照片也表明,固体焦表面的微孔结构越来越多,微孔的边界越来越清晰.煤气中CO2,CO,CH4和CnHm含量在3 min以前随热解时间的延长均逐渐增加,随后逐步减少.随着混煤中JM配比的增大,热解煤气中CO2和CO含量逐渐减少,但CH4和CnHm含量在3 min以前变化不是很明显,在3 min~15 min区间逐渐增加.     

生物质与聚合物、煤共热解研究进展

综述了近几年来生物质与其它物质如煤和聚合物共热解的研究进展。通过对生物质、煤和聚合物的单独热解以及同煤和其它聚合物共热解的大量文献报道结果进行比较发现:生物质与许多聚合物共热解具有协同作用,可以降低液体产物的含氧量,提高热解液相产率等。显示出生物质与某些聚合物共热解比单独热解具有一定的优势;并比较了煤和生物质共热解产生的现象,得到煤和生物质共热解难以产生协同作用。本文作者结合现阶段的研究成果,提出生物质与煤采用两步法热解工艺的思路,使生物质材料的氢有可能转移到热解煤的产物中,以改善煤热解过程中液体的性质,对今后生物质与煤及聚合物共热解的研究方向提出了自己的建议。     

生物质与煤共热解研究现状

综述了近年来国内外煤与生物质共热解的研究现状。当生物质与煤共热解过程中存在协同反应时,能够将生物质中的氢有效地转移到煤热解过程中,改善煤热解过程中产物的性质,提高煤的热解效率。后续对生物质与煤共热解的研究可以考虑适当的方法,如添加合适的催化剂等来促进协同反应的发生。     

煤与稻壳共热解热重分析及动力学

利用热重分析仪对长焰煤和稻壳分别单独及按不同掺混比例进行热质量损失实验研究。通过比较煤与稻壳共热解热质量损失曲线和计算得到的理论曲线发现,添加稻壳对共热解过程有促进作用,在不同的稻壳掺混比例下,共热解过程质量损失率和最大质量损失速率均较理论值有不同程度的增大,推测稻壳掺混对共热解存在促进作用,促进作用与稻壳掺混比例不成线性关系。对煤与稻壳及共热解过程进行动力学分析,获得了反应活化能和频率因子,分析计算热解动力学参数表明共热解过程存在动力学补偿效应。     

柠条与低阶煤共热解特性初探

为研究柠条与低阶煤共热解特性及相互作用,利用热重分析仪研究了不同煤种和不同混合比例条件下,柠条与4种内蒙古盛产低阶煤的共热解。结果表明：不同煤种与柠条共热解相互作用趋势只在中温区表现不同,混合比例对共热解相互作用的大小有影响,对整个过程的相互作用趋势无影响。由作用率Δα的计算值得柠条与煤共热解过程的作用效果可分为4个阶段：在柠条剧烈失重温度段对应为第一、二阶段,先为煤粉抑制柠条挥发分的析出,后为柠条挥发分促进煤的热解;第三阶段,为柠条焦炭热解温度段,柠条焦炭与煤相互作用,受煤品种的影响,柠条与煤共热解为协同或抑制作用;第四阶段,为共热解过程的高温段,柠条灰分中的矿物质促进煤的热解。     

有机固体废弃物与煤共热解基础研究

利用分析热天平等仪器,通过TG技术对榆林长焰煤、济源焦煤、焦作无烟煤等3种不同煤化程度的煤及固体废弃物(塑料)在不同热解速度、不同混合比例下的热解实验研究。结果表明,煤与塑料共热解的影响因素很多,包括升温速度、煤化程度、混合比例、热解终温等。     

微负压系统中煤与橡胶共热解的协同作用

在热重分析仪及自制的微负压煤热解实验装置上,对陕北烟煤、橡胶及两者的混合物进行了实验研究。结果表明,煤与橡胶共热解时存在协同效应,并且随着热解温度增加,协同效应逐渐增强。橡胶是共热解反应的供氢物质,同时橡胶热解产生较多的甲烷,有利于煤中大分子的裂解,可提高煤热解的焦油收率。在热解温度为800℃时,任意橡胶质量分数的煤与橡胶混合物共热解的焦油收率均比线性叠加值高,当橡胶质量分数为20%时,协同作用最为显著。     

固定床烟煤与木屑共热解的协同反应性研究

在自制的固定床反应装置上对木屑和烟煤以及两者的混合物进行了热解特性研究,考察了木屑与烟煤在不同掺混比例和热解终温下的共热解反应特性。研究结果表明:协同作用发生的程度与热解反应条件有关,烟煤与木屑共热解的协同反应性不仅体现在气、液产物收率方面,同时对气体组成也有显著影响;因木屑灰分中的碱金属化合物对热解焦油的催化裂解作用,使得共热解反应在较高热解终温和较低木屑掺混比条件下表现出更为显著的协同作用;在木屑掺混比(木屑质量分数)为25%、终温540℃条件下,热解气产率的协同值达到22.6%,焦油产率协同值为-27.3%;H自由基与烟煤热解产生的自由基结合成CH4等烃类气体或转移到焦油组分,是一种重要的协同作用机理。     

生物质和煤共热解特性及催化剂对热解的影响

为研究生物质和煤程序升温共热解特性及相互作用,利用热天平和管式炉反应器对白松木屑和五彩湾烟煤的共热解特性及催化剂对生物质和煤共热解的影响进行了研究,并考察了共热解半焦的孔结构特性。结果表明：不同比例的生物质和煤在共热解过程中,两者基本保持了各自的热解特性,由于生物质和煤的主要热解阶段温度相差较大,共热解过程中没有发生明显的协同作用。生物质和煤共热解半焦产率实验值大于计算值,当生物质质量分数从75%减少至25%时,半焦产率实验值与计算值之间的差值从0.81个百分点增加到1.07个百分点。橄榄石和载镍橄榄石（NiO/olivine）的添加促进了共热解反应发生的深度。载镍橄榄石催化剂添加（原料和催化剂质量比1：1）的条件下,共热解碳转化率提高了0.5%~5.1%,随着混合物中生物质比例的增加,催化剂的催化效果更加明显。     

炼焦煤尾煤热重动力学分析及热解产氢

基于热重分析和固定床热解实验,研究了升温速率和温度对高矿物质含量的炼焦煤尾煤热解特性的影响. 尾煤热解过程可分为室温至400, 400~600及600~950℃三个阶段. 尾煤与焦煤热解曲线基本吻合,尾煤热解特征温度略向高温区推移. 采用Coats-Redfern积分法拟合计算了尾煤热解的动力学参数,得出反应活化能为22.6~66.2 kJ/mol,热解过程可用3个二级反应描述. 30 g尾煤固定床实验结果表明,氢气在低于400℃析出很少,400~600℃缓慢析出,之后随温度升高析出增加,600℃后大量析出,900℃左右达到最大析出量. 终温950℃时,30 g尾煤热解产气4300 mL,氢气产量1722 mL;焦煤产气7950 mL,氢气产量2716 mL. 尾煤热解富氢气体产量达焦煤热解气产量的54%,具有较高的再利用价值.     

Co-pyrolysis as a method of upgrading some products of coal processing

Co-pyrolysis was investigated as a method of upgrading various products resulting from coal processing. Co-pyrolysis of vacuum residue (VR) with coal extraction products as well as with primary tars from flash pyrolysis leads to a considerably enhanced yield of liquid products. It has been established that superheated steam and increased outgassing rate, favour the yield of liquid products. The proportion of the ingredients in the mixture as well as the quality of the VR also have a definite effect. The excess yield of liquid products in co-pyrolysis of coal extraction products was 8–23 wt%, depending on operating conditions and the composition of the mixture. The flash co-pyrolysis of primary tars yielded a 1.5–15.9 wt% surplus of liquid products depending on the mixture composition. Products originating from co-pyrolysis of these raw materials with VR are characterized by relatively high atomic hydrogen to carbon ratio, usually not less than 1.5 and the total abscence of asphaltenes. Generally, co-pyrolysis of VR with various products of coal processing is comparable with hydrogenation in the light of good yields of liquid products.     

低阶煤与浒苔低温共热解过程分析及动力学

采用自行设计低温干馏装置对不同配比的低阶煤（LRC）和浒苔（EN）进行低温干馏实验,发现在浒苔配入量为30%时,焦油的产率达到最大值11.39%,比煤单独热解提高了28.61%,比理论加权值提高了8.87%。对低阶煤、浒苔及浒苔配入量为30%的混合样进行热重分析,发现低阶煤与浒苔共热解时在240～750℃段存在明显的协同效应,且其相对最大值达18.5%。动力学分析表明,混合热解时活化能与指前因子之间存在补偿效应,两者混合使反应活性增大,反应速率降低,协同作用主要表现在使共热解反应活性增大。     

煤半焦和沙柳炭混合物恒温共热解作用的研究

采用先混合原沙柳和煤粉再制焦的次序,利用热重分析法研究了4种煤半焦和沙柳炭混合物的恒温共热解作用。从胜利煤的变温热解中,选定恒温共热解的温度400、500和600℃来研究温度对沙柳炭和胜利煤半焦混合物共热解作用的影响,结果显示400和600℃表现为协同作用,500℃表现为抑制作用,通过分析选择600℃作为恒温共热解温度。在600℃时,研究了沙柳炭与不同种类煤半焦在不同掺混比例下的恒温共热解,显示沙柳炭对挥发逸出能力较强或较低的煤半焦(霍林河煤和准格尔煤)均表现为抑制作用,对挥发分逸出能力中等的煤半焦(胜利煤和宝日希勒褐煤)表现为协同作用;受煤种的影响,掺混比例对共热解的作用效果大小无固定的排序。     

炼焦过程中硫元素迁移规律研究

以华北地区的峰峰低硫肥煤和山西中硫焦煤为原料,利用1 kg热解试验装置进行模拟炼焦试验,并对所得焦炭、煤焦油和煤气产品中硫元素形态和质量进行测定,揭示了炼焦煤中硫元素的迁移规律。结果表明:两种炼焦煤挥发分差别不大,硫元素迁移规律基本相同;炼焦过程中,不但原料煤中硫酸盐硫得以保留,还有其它形态硫经过复杂的热解化合反应生成新的硫酸盐硫;无机硫中的黄铁矿硫和有机硫中的脂肪硫、硫醚、硫醇等在炼焦过程中以H2S形式转移到煤气中,转移效率一般低于50%;原料煤中黄铁矿硫含量越高,H2S的转移率也越高;其他噻吩硫等在炼焦过程中不分解,留在焦炭中。     

高温再热对依兰煤低温干馏产物及结焦行为的影响

研究了依兰六级煤低温干馏气在高温二次加热过程中的裂解和结焦行为,分析了干馏气体产率、焦油产率的变化和加热器内的结焦情况。煤低温干馏终温600℃,干馏气二次加热温度600℃～750℃。研究表明,二次加热造成干馏产物中气体产率显著增大,焦油产率降低,加热器内存在结焦现象。提高二次加热的温度和延长气体在加热器内的停留时间,加剧了干馏气中烃类分子的裂解、缩聚和结焦,进一步降低了油品收率,并造成油品密度增大。温度对干馏产物中有机大分子裂解行为的影响更为显著,而停留时间和干馏气中烃类产物的浓度对缩聚反应的影响更大。     

神木烟煤与桦甸油页岩的共热解特性

采用热重分析仪和固定床反应器研究了神木烟煤和桦甸油页岩的混合共热解特性及协同作用机制. 结果表明,神木煤与桦甸油页岩混合共热解的失重率高于计算值,表明二者在热解和挥发分逸出过程中存在相互作用,促进了挥发分释放,减少了半焦生成. 煤与油页岩的协同作用可增加热解油收率、降低半焦和水收率. 油页岩与煤质量比为1:1时,所得油收率最高,为9.84%,比计算值提高8.8%. 共热解有助于提高轻质油含量和收率,油页岩与煤质量比为1:4时,轻质油含量超过80%,收率约为7.5%,比计算值分别提高了8%和11.2%,表明添加少量油页岩可明显提高热解油品质. 共热解过程中油页岩产生的富氢组分及自由基能抑制煤热解产生的芳香族化合物的聚合反应,促进芳烃向产物油转化,提高热解油的收率和品质.     

Co-pyrolysis of polymethyl methacrylate with brown coal and effect on monomer production

Pyrolysis capillary gas chromatography has been applied to the study of the co-pyrolysis of polymethyl methacrylate (PMMA) with Slovakian brown coal with the aim of finding pyrolysis conditions yielding a maximum amount of methyl methacrylate (MMA). Effects of pyrolysis temperature and PMMA-coal weight ratios were investigated. Capillary gas chromatography coupled with mass spectrometric detector (cGC-MS) was used for MMA identification. The highest yield of MMA in the pyrolysate was obtained at 750 °C. The optimal PMMA-coal weight ratio for maximum MMA production lies in the interval 0.5 mg PMMA and 0.6-0.8 mg brown coal with an MMA yield of 64%. Coal addition to the sample affects species recombination in gaseous phase, augments MMA production at higher temperatures and eliminates degradation products of PMMA and coal pyrolysis. Different conversion diagrams are characteristic for thermal degradation of single PMMA and in the mixture with coal. Detailed mechanism of synergetic effects arisen during co-pyrolysis are not yet known. It was also found that lower pyrolysis temperatures are more suitable to study degradation mechanism and kinetics while higher temperatures are more applicable for identification purposes. MMA decomposes completely at 900 °C.     

Co-pyrolysis of bituminous coal and biomass in a pressured fluidized bed

An experimental study on co-pyrolysis of bituminous coal and biomass was performed in a pressured fluidized bed reactor. The blend ratio of biomass in the mixture was varied between 0 and 100 wt%, and the temperature was over a range of 550–650 °C under 1.0 MPa pressure with different atmospheres. On the basis of the individual pyrolysis behavior of bituminous coal and biomass, the influences of the biomass blending ratio, temperature, pressure and atmosphere on the product distribution were investigated. The results indicated that there existed a synergetic effect in the co-pyrolysis of bituminous coal and biomass in this pressured fluidized bed reactor, especially when the condition of bituminous coal and biomass blend ratio of 70:30(w/w), 600 °C, and 0.3 MPa was applied. The addition of biomass influenced the tar and char yields and gas and tar composition during co-pyrolysis. The tar yields were higher than the calculated values from individual pyrolysis of each fuel, and consequently the char yields were lower.The experimental results showed that the composition of the gaseous products was not in accordance with those of their individual fuel. The improvement of composition in tar also indicated synergistic effect in the co-pyrolysis.     

基于正交实验的低阶粉煤与玉米芯微波共热解研究

生物质协助低阶粉煤微波热解可改善热解产物的分布和特性,尤其是油气收率和品质。采用四因素四水平正交实验法研究了微波功率(420 W,280 W,700 W,560 W)、热解时间(30min,20min,10min,40min)、玉米芯粒径(0.250mm~0.420mm,0.177mm~0.250mm,0.841mm~1.680mm,0.420mm~0.841mm)和玉米芯添加量(10%,40%,30%,20%,质量分数)对低阶粉煤与玉米芯微波共热解中焦油收率的影响,对比分析了低阶粉煤、玉米芯单独微波热解和微波共热解的升温特性和产物特性。结果表明:影响焦油收率由主到次的因素分别为玉米芯添加量、微波功率、玉米芯粒径、热解时间。在本实验参数范围内,正交实验得到的最佳工艺条件为:微波功率700W、热解时间40min、玉米芯粒径0.841mm~1.68mm、玉米芯添加量40%,此时的半焦和气体产物收率分别为51.22%和32.17%,焦油收率达到最大,为8.85%。与低阶粉煤单独微波热解相比,微波共热解生成的焦油中轻油含量提高了11.89%,而杂原子化合物含量降低了7.09%,实现了热解焦油的轻质化和高品质化。