超细煤粉快速热解动力学特性实验研究

采用居里点裂解器及气相色谱仪研究了3种超细煤粉的快速热解特性。实验发现:超细煤粉挥发分的快速热解释放主要发生在升温阶段,烟煤与无烟煤挥发分中焦油的质量分数均最大,其中烟煤焦油释放量占挥发分的质量分数达到50%以上,高于无烟煤。烟煤气态挥发分中CO质量分数最大,达到40%以上,其次为CO2,然后依次为CH4、其他碳氢化合物CnHm,H2。无烟煤的CO,CO2,CH4释放质量分数基本相当,H2质量分数与CnHm接近。根据热解产物的释放数据,采用单方程反应模型计算出了煤粉升温速率、热解频率因子及活化能,为进一步研究超细煤粉的着火及燃烧提供了理论基础。     

磷-胺-醛树脂型阻燃剂处理落叶松的热分析及其动力学

将落叶松用一系列磷-胺-醛树脂型阻燃剂进行阻燃处理,所得阻燃落叶松采用热分析、锥形量热研究其热解行为,用氧指数、剩炭率、热释放速率、总热释放量等参数表征它的阻燃性能,并用Broido方程计算落叶松的动力学参数. 结果发现,阻燃落叶松氧指数、剩炭率增加,热释放速率、总热释放量降低,表明经阻燃剂处理的落叶松燃烧性降低. 落叶松经阻燃剂处理后,热解活化能降低很多,表明阻燃剂对落叶松热解具有催化作用,其主要热解阶段在低于300℃进行. 在此温度下,落叶松热解主要发生脱水、重排交联炭化反应,产生水、CO及CO2、固体残渣,可燃性气体大大降低,达到降低落叶松燃烧性的目的.     

利用TG-FTIR研究造纸黑液碱木质素的热解机理

采用热重-傅里叶红外光谱（TG-FTIR）联用的分析方法对造纸黑液碱木质素的热解失重特性和产物生成特性进行了研究。结果表明：碱木质素热解失重过程可分为3个阶段,其中200~500℃是碱木质素主要的热解挥发阶段,反应符合一级反应动力学模型,利用Coats-Redfern动力学模型计算得出不同升温速率下热解主反应的表观活化能为39.3~43.1 kJ/mol。FTIR的实时分析结果表明：碱木质素热解的气态产物主要有H₂O、CO₂、CO、CH₄、甲醇、酚类和N₂O;产物中的CH₄、甲醇、酚类和N₂O主要在300~500℃区间内释放,随着热解温度的升高,这些气态产物在420℃附近集中释放,且产量达到最大。     

流化床煤燃烧过程不同气氛下的气态氮释放特征

利用微型流化床反应装置,结合快速过程质谱仪,在850~940℃操作温度下,研究了三种不同粒度分布烟煤和无烟煤在热解、气化和燃烧反应条件下四种主要气态氮产物HCN、NH₃、NO和NO₂的释放规律。结果表明,微型流化床可以实时检测挥发分氮和焦炭氮的动态释放序和类型,热解、气化和燃烧反应气氛的改变主要影响HCN和NH₃的释放量。热解产物的气态氮主要是来自于挥发分,燃烧反应的HCN和NH₃的释放量与温度有明显关系,而气化反应的各类气态氮释放量随温度变化波动不大。煤颗粒尺寸和温度变化对烟煤和无烟煤中各类气态氮释放量产生影响比较复杂,其中NH₃的释放特性是区分挥发分N释放和半焦N释放的重要特征。     

吐哈盆地褐煤的热解和燃烧特性及动力学分析

吐哈盆地褐煤的热解和燃烧特性研究利于煤的清洁高效利用及煤炭地下气化的开展,为探究吐哈盆地褐煤煤粉颗粒的热解特性和燃烧特性及动力学特性,通过热重实验、热解特征指数计算、综合燃烧指数计算及动力学软件Kinetics Neo模型拟合法,研究了煤粉在不同升温速率(5℃/min, 10℃/min, 20℃/min)和不同粒径(大于0.8 mm, 0.2 mm～0.6 mm,小于0.1 mm)下分别在氮气气氛中的热解特性和空气气氛中的燃烧特性,获得了不同条件下煤粉颗粒热解和燃烧过程的动力学参数。结果表明：升温速率升高有利于煤粉颗粒热解和燃烧,显著提升了热解和燃烧性能;煤粉颗粒粒径增大有利于煤粉热解,不利于煤粉燃烧;不同粒径煤样热解和燃烧焦产率没有明显区别,粒径增加对于挥发分释放的影响不大;热解与燃烧过程中活化能与指前因子分别在一次热解阶段和干燥挥发阶段较高,说明在这两个阶段反应速率较慢,单位时间内化学反应程度较高。     

TG-FTIR研究污泥掺混废轮胎共热解特性

采用热重-红外联用(TG-FTIR)分析污泥与废轮胎混合热解特性。研究发现,污泥与废轮胎混合热解可弥补单污泥热解存在的不足;随着废轮胎掺混比例增加,热解特性指数逐渐增加(由8.54E-14增加到2.24E-12)。利用Coats-Redfern法研究热解反应动力学发现,在第一阶段(168~600℃),不同混合比例的样品热解过程适合的反应级数不同;在第二阶段(600~1 200℃),所有样品的热解均符合3级反应规律。FTIR分析表明,热解主要生成H_2O、CO_2、CO和CH_4等物质;其中CO在750℃之后的析出主要是由CO_2与焦炭的反应产生。     

添加KNO_3对Al与CO_2热反应特性及点火燃烧性能的影响

采用热分析仪和可视化管式炉研究了添加KNO3对纳米铝粉在CO2气氛中的热反应特性和点火燃烧特性的影响.结果表明,随KNO3添加量增加,纳米铝粉着火点降低.添加1%和5%(?)KNO3可分别使着火点温度降低18.3和37.9℃,并使燃烧特性指数增加,但增加程度逐渐降低.添加KNO3可加速纳米铝粉在CO2气氛中的点火过程,使铝粉氧化反应更剧烈.添加KNO3后纳米铝粉的燃烧产物中除有大量?-Al2O3与少量单质Al外,还存在部分?-Al2O3.     

高硫煤泥燃烧过程中的汞排放特性

通过固定床程序升温汞脱附试验系统对所选高硫煤泥中汞排放特性进行在线监测,并利用热重分析仪对煤泥热解和燃烧特性进行研究,结合试验所得热解和燃烧特性参数,采用分布活化能模型,进行动力学分析。结果表明：煤泥的热解和燃烧过程可分为3个阶段,非等温条件下,随着升温速率增加,热解过程在高温区发生,最大失重率提升,对应峰值温度偏移,产生热滞后,利于挥发分析出;在煤泥热解过程中少量氧气的参与,抑制挥发分的析出,在7% O₂条件下综合热解特性参数值D最大。热解性能随CO₂浓度升高而得到改善;煤泥燃烧性能随升温速率的增加而得到加强,其活化能随转化率变化呈现“U”型趋势分布;煤泥中无机汞化合物主要为HgCl₂、α-HgS、HgSO₄以及硅铝酸盐类结合汞,总汞释放主要范围对应200~600℃;煤泥中汞释放量随O₂浓度增大,CO₂气氛条件下,随着CO₂浓度增加,总汞释放量逐渐增大。     

白肋烟热解特性及其动力学

采用TG-DTG-DSC热分析联用技术研究了不同产地白肋烟的热解燃烧行为及其动力学,结果表明,从室温加热到800℃,不同产地的白肋烟热解燃烧过程均经历4个热失重过程,但温度范围不同,且每个阶段的质量和热量变化均不同,样品的主要反应发生在138~583℃内. 采用Coats-Redfern法对不同产地的白肋烟样品4个热失重阶段进行了动力学计算,结果表明,第I与第II阶段机理函数相同,而第III与第IV阶段机理函数相同;燃尽阶段的活化能明显比其他阶段的活化能高. 采用特殊收集装置收集4个热失重阶段的粒相产物,对其有害产物和致香成分的定量分析结果表明,不同产地的白肋烟样品在热解不同阶段产生的有害物质和致香成分的量有所不同,但大部分有害物质和致香成分在第II热失重阶段产生,且产生的量相对较大.     

生物柴油热解的TG-FTIR联用研究及动力学参数计算

利用热重(TG)-傅里叶变换红外光谱(FTIR)联用对生物柴油的热解及气体产物的释放特性进行了研究,并通过非预置模型法的Vyazovkin算法和Avrami理论计算了生物柴油热解的活化能和反应级数等动力学参数。生物柴油在554~773K区间存在失重率约为87.59%的失重阶段,伴随的热解气体产物主要包括CO2、H2O、CH4和其他有机化合物,其中主要气相产物析出规律一致,但浓度存在差异。随着升温速率的提高,生物柴油的热解向高温区移动。同时,生物柴油的热解呈现多段特性,在不同转化率区间,动力学参数变化较大,活化能为100.48~151.14kJ/mol,反应级数为1.21~1.24。     

Effects of Ca-based additives on desulfurization during coal pyrolysis

The effects of different Ca-based additives on the sulfur removal of coals during pyrolysis up to 900 °C have been studied in a fixed-bed reactor. It was found that Ca(OH)₂ and CaO were quite effective to capture the sulfur-containing gases, 95% of the sulfur evolved from untreated coal was retained in the char by the use of additives. Both the tar yield and the sulfur content of the tar decreased with addition of Ca-based additives. The effect of Ca(OH)₂ was better than that of CaO due to its higher activity, but CaCO₃ had little effect because of its higher decomposition temperature (−900 °C) than the peak temperature range (400–500 °C) of sulfur-containing gases emission. There is remarkable sulfur retention effect with Ca(OH)₂ prepared by impregnation and ultrasonic treatment due to the higher dispersion in coal particles than by simple mechanical mixing. The ultrasonic treatment is the best method with regard to the lowest SO₂ release during the char combustion. XRD results showed that the sulfur captured by Ca-based additives during pyrolysis turned into CaS. FeS detected in pyrolysis char without additives disappeared in chars with additives, which indicated that CaO could react with FeS through solid-solid reaction. When the chars with calcium-additives were burned in fixed bed reactor, they gave out less SO₂ than the raw coal added with same additives. The best total desulfurization efficiency could reach to about 85%.     

内热式回转炉煤热解工艺的焦油产率与性质研究

研究了３ｋｇ／ｈ内热式回转炉煤热解工艺实验装置的热解温度、热解时间、煤粒度、煤气燃烧的空气过剩系统对焦油产率的影响,用正态分布函数模拟了初次焦油产率随热解温度的变化,用韦布乐分布函数模拟了焦油二次裂解率随气相温度的变化,对比了四种煤的焦油产率,分析了热解温度对焦油元素组成、馏分组成、中性油族组成等的影响。     

Kinetik der Kohlen-Pyrolyse als Grundlage für die Auslegung technischer Reaktoren

Kinetics of coal pyrolysis as a foundation for the design of technical reactors . The pyrolysis of coal is understood to mean its thermal decomposition at temperatures above 300°C, affording tar and char. It is the basic process underlying coking and the starting reaction of combustion, gasification, and hydrogenation. In addition, pyrolysis offers a means of converting coal into gases and liquids in a ?third way”? besides gasification and hydrogenation. In order to establish a basis for the design of relevant technical reactors, the kinetics of coal pyrolysis has been investigated as a function of temperature and rate of heating and recently of pressure under inert gases and hydrogen. In particular, the rates of formation and the yields of liquid and gaseous products and the alteration of the solid matter have been examined under pressures ranging from 1 to 100 bar and at rates of heating between 0.05 and 1 000 K/s. It is shown how product formation can be controlled by these parameters and how the experimental data can be applied to reactor design.     

Vacuum pyrolysis of Prince Mine coal, Nova Scotia, Canada

Preliminary results are given on thermal decomposition characteristics of a high volatile A bituminous coal from Eastern Canada using vacuum pyrolysis experiments (pressure 2–200 mm Hg) over the temperature range 322–1000 °C. The objectives of the study were to determine the optimum temperature range for the formation of coal tar and to study the influence of reaction temperature on the nature of the solid residues. Significant decomposition reactions start at 300–400 °C and the optimum temperature range for the production of coal tar was 450–600 °C. The major gaseous products H₂S, CO₂ and CH₄ are formed up to 600 °C. Above 600 °C the coal decomposes mainly into CO and H₂. The solid residues are characterized by volatile matter content, calorific values and elemental analysis. The volatile matter content decreases rapidly from 322 °C and stabilizes at reaction temperatures > 750 °C. The 15% VM level, a minimum requirement in coal combustion processes, was reached at 500 °C. The changes in calorific values do not show any significant trend up to 600 °C, but decrease markedly above 600 °C. From the preliminary results vacuum pyrolysis is regarded as an effective process in which valuable coal tar by-products can be obtained from coal prior to its combustion.     

The effect of steam on pyrolysis and char reactions behavior during rice straw gasification

Steam gasification of biomass can generate hydrogen-rich, medium heating value gas. We investigated pyrolysis and char reaction behavior during biomass gasification in detail to clarify the effect of steam presence. Rice straw was gasified in a laboratory scale, batch-type gasification reactor. Time-series data for the yields and compositions of gas, tar and char were examined under inert and steam atmosphere at the temperature range of 873-1173 K. Obtained experimental results were categorized into those of pyrolysis stage and char reaction stage. At the pyrolysis stage, low H₂, CO and aromatic tar yields were observed under steam atmosphere while total tar yield increased by steam. This result can be interpreted as the dominant, but incomplete steam reforming reactions of primary tar under steam atmosphere. During the char reaction stage, only H₂ and CO₂ were detected, which were originated from carbonization of char and char gasification with steam (C + H₂O→CO + H₂). It implies the catalytic effect of char on the water-gas shift reaction. Acceleration of char carbonization by steam was implied by faster hydrogen loss from solid residue.     

氧气浓度对K2CO3催化无烟煤和石墨燃烧的影响

采用综合热分析仪研究不同氧气浓度下K2CO3催化无烟煤和石墨燃烧的特性,考察了氧气浓度对催化燃烧机制的影响. 结果表明,K2CO3提高了燃烧反应和氧气扩散速率,但对燃烧速率的提高幅度大于对氧气扩散速率提高幅度,延长了无烟煤燃烧过程的平台时间. 氧气浓度由21%增加到100%时, K2CO3催化无烟煤着火温度降低幅度由37.7℃增至78.1℃,催化石墨着火温度降低幅度由204.8℃增至233.6℃. 煤燃烧初期K2CO3使燃烧活化能下降,氧气浓度高于40%时,燃烧由扩散向反应控制转变;燃烧后期活化能低于40 kJ/mol,燃烧受扩散控制. 石墨在燃烧初期K2CO3使燃烧活化能下降,但氧气浓度增加并未改变燃烧控制步骤,燃烧受反应控制;燃烧后期氧气浓度由21%增加到100%时, K2CO3催化石墨燃烧活化能由39 kJ/mol增至110 kJ/mol,燃烧由扩散控制向反应控制转变.     

熔盐添加剂对玻璃离子交换和增强的影响

在工业纯KNO3中分别添加KOH,K3PO4,K2CO3,K2SiO3与Al2O3的混合物,研究了熔盐添加剂对浮法玻璃离子交换和增强的影响.用电子探针测试了玻璃表而的K+浓度;测定了样品的表面应力、弯曲强度和显微硬度.结果表明:上述添加剂町以增加离了交换层深度,缩短离子交换时间,明显提高玻璃的力学性能,其增强效果与分析纯KNO3的增强效果相当,甚至比后者好:在交换温度为450℃下,玻璃交换层厚度大于29μm,玻璃的力学性能为:表面应力>480MPa,弯曲强度>400MPa.显微硬度为6.49GPa.     

钙基添加剂对煤慢速和快速热解行为的影响

在固定床反应器上对淮北煤(Hub)进行热解实验,测定了气体、焦油和焦炭的产率、主要气体的累积释放量以及苯、甲苯和二甲苯(BTX)产率,旨在考察2种常见钙基添加剂CaCO3和Ca(OH)2对煤慢速和快速热解的影响。在慢速热解情况下,无论CaCO3还是Ca(OH)2都使焦炭产率明显降低,气体产率上升,焦油产率有所下降,BTX产率增大,但Ca(OH)2的作用较强。在快速热解情况下,钙基添加剂使焦油产率略有下降,气体和焦炭产率略有增大,但增加不明显。由此表明,钙基添加剂在慢速热解时对焦油二次裂解及对煤焦分解的作用较大。