燃烧反应动力学研究进展

化学反应动力学是燃烧过程分析的重要工具。燃烧微观反应过程、复杂反应机理、燃烧实验测量和湍流燃烧数值模拟等方面的研究工作已经取得了长足进步。本文主要介绍燃烧反应动力学研究方法,包括电子结构方法、燃烧反应热力学和速率常数的计算方法、燃烧详细机理构建和简化、反应力场分子模拟以及燃烧中间体测量、燃料点火延迟和光谱诊断等方面的研究现状。燃烧反应动力学具有很强的应用背景,燃烧过程化学物种的反应速率计算是湍流燃烧数值模拟的一个中心任务。由于燃烧反应网络的高度复杂性,我们对燃烧机理的认识还远不清楚。化学反应和湍流相互作用研究的深入、燃烧反应动力学和计算流体力学的协同发展,将对新燃料设计、燃烧数值模拟、发动机内流道流场结构的准确描述产生深远影响。     

乙烯装置裂解炉管焦炭燃烧特性的研究

齐鲁石化公司乙烯厂是我国最先引进计算机控制下蒸汽 空气在线烧焦技术的乙烯厂 ,在线烧焦使其过程自动化程度大大提高 ,裂解炉没有升降温过程 ,延长了裂解炉管的使用年限[1～ 5] 。但裂解气盘管管径较小 ,易于堵塞 ,烧焦时间稍短 ,管壁上的焦炭就燃烧不完全 ,目前在线烧焦时间还需 70ｈ～ 80ｈ。为了进一步缩短烧焦时间 ,节约能源 ,提高炉子运行周期 ,必须对乙烯装置裂解炉管焦炭的微观结构及燃烧过程进行深入研究 ,以提出进一步加快烧焦速度的办法 ,满足工业生产的需要。本研究采用国内某乙烯厂裂解炉管焦炭为实验原料 ,研究了焦炭的微观…     

Magnesium boride sintered as high-energy fuel

Boron was chosen as fuel owing to its excellent thermodynamic values for combustion. The difficulty of the boron in combustion is the formation of a surface oxide layer, which postpones the combustion process, reducing the performance of the rocket engine. In this paper, magnesium boride was sintered as high-energy fuel as a substitute for boron. The combustion heat and efficiency of magnesium boride and boron were determined using oxygen bomb calorimeter. The combustion characteristics of magnesium boride were investigated by thermal analysis, chemical analysis, XRD, and EDS. Results show that the combustion performance of magnesium boride are better than that of amorphous boron in oxygenated environments. The evaporation of magnesium in magnesium boride combustion process prevent the formation of a closed oxide layer, leading to higher combustion efficiency.     

生物质炭燃烧特性与动力学分析

利用小型固定床反应器对棉杆和木屑进行了炭化制焦实验,利用热重分析仪对制得的生物质炭进行氧化实验.基于综合反应速率方程推导了生物质炭氧化过程气固反应机理,并对热重实验结果进行拟合计算.实验结果表明,随着制焦炭化温度的升高,生物质炭的着火温度和燃尽温度升高,燃烧特性指数S减小;棉杆炭综合燃烧性能优于木屑炭.棉杆炭在低温段和高温段燃烧的反应机理不同,低温段燃烧反应的机理是片状内扩散反应机理,高温段燃烧反应的机理是球形界面化学反应机理.木屑炭的反应机理是球形界面化学反应机理.拟合计算求得的活化能并不能反映出生物质炭进行燃烧反应的难易程度.     

煤系高岭岩中固定碳燃烧动力学特性

煤系高岭岩中可燃矿物与不可燃矿物的共生组合增加了可燃矿物燃烧的复杂性,研究这类"燃料"的燃烧特性对充分利用煤矸石资源有积极的意义。参照FCC催化剂结焦燃烧机理,基于一系列假设,建立了煤系高岭岩中固定碳燃烧反应模型—未反应收缩核模型。采用空气气氛下等温热重法研究了煤系高岭土中固定碳的燃烧反应。研究表明,低于700℃,反应的控制步骤是煤系高岭岩中固定碳燃烧界面化学反应。通过对非均一颗粒体系的未反应核收缩模型计算分析,获得煤系高岭岩中固定碳燃烧反应动力学参数,活化能(E)为100.12kJ/mol,频率因子(A)为2.27×106s-1。     

两相流中煤粉的燃烧机理及动力学特征

利用微型流化床动力学分析仪研究了两相流条件下无烟煤粉的燃烧反应机理和动力学特征,并与热重法所得结果进行比较分析。结果表明,当温度大于850℃时,煤粉燃烧机理发生了变化,燃烧气态产物的生成比例也随之改变;当气速大于0.10 m/s时,气体扩散限制基本被消除,煤粉燃烧反应速率主要受界面化学反应控制;煤粉燃烧反应速率随着氧气分压的增大呈幂函数形式增长,且氧气分压对煤粉静置燃烧的影响更加显著。煤氧两相流燃烧的表观活化能与静置燃烧相比降低了49 kJ/mol,相同温度条件下两相流燃烧的界面化学反应阻力也明显小于热重法测试结果。     

Challenges and perspectives of combustion chemistry research

In the past decades, combustion chemistry research grew rapidly due to the development of combustion diagnostic methods,quantum chemistry methods, kinetic theory, and computational techniques. A lot of kinetic models have been developed for fuels from hydrogen to transportation fuel surrogates. Besides, multi-scale research method has been widely adopted to develop comprehensive models, which are expected to cover combustion conditions in real combustion devices. However, critical gaps still remain between the laboratory research and real engine application due to the insufficient research work on high pressure and low temperature combustion chemistry. Besides, there is also a great need of predictive pollutant formation model. Further development of combustion chemistry research depends on a closer interaction of combustion diagnostics, theoretical calculation and kinetic model development. This paper summarizes the recent progress in combustion chemistry research briefly and outlines the challenges and perspectives.     

煤-焦炉气共热解半焦燃烧动力学特性研究──燃烧模型的建立及其表观活化能动态描述

采用热重分析方法（ＴＧＡ）对煤－焦炉气共热解半焦燃烧动力学特性进行研究,建立了半焦燃烧动力学模型,采用新的数学处理方法,实现了表观活化能在半焦燃烧过程中的动态描述及平均表观活化能的求取。分析结果表明,表观活化能在半焦燃烧过程中呈“两头高、中间低”的“钟”型动态分布,其变化范围为：４７～９５ｋＪ／ｍｏｌ,其中主要燃烧失重阶段（转化率为２０％～８０％）的表观活化能较低且变化幅度较小,约为４７～６０ｋＪ／ｍｏｌ,在燃烧转化率为４０％左右出现最低活化能约４７ｋＪ／ｍｏｌ。同一半焦燃烧过程中,表观活化能与燃烧速率动态分布具有良好的对应关系,即较大燃烧速率对应着较低表观活化能,这说明表观活化能的大小直接体现了半焦燃烧反应活性的高低     

O2/CO2气氛下煤焦燃烧实验研究

在热重分析仪上进行了不同气氛下徐州烟煤及其煤焦的燃烧实验,分析了O₂浓度、CO₂浓度和颗粒粒径等参数对其燃烧特性的影响;并对其进行了燃烧动力学分析。结果表明,气氛对煤和煤焦开始脱挥发分的时间影响不明显,但对其燃烧速率和燃尽时间影响很大;高浓度CO₂使煤焦的燃尽时间延长。气氛没有改变煤焦的燃烧反应动力学机理。O₂浓度提高、CO₂浓度降低和煤粉细化均可改善燃料的燃烧特性,但对煤焦的改善程度比对烟煤的小。扫描电镜（SEM）结果显示,同等O₂浓度下O₂/CO₂气氛较空气气氛煤灰表面孔隙结构更丰富。     

煤质特性对CeO2催化煤粉燃烧的影响

利用酸洗法和燃烧法分别得到煤中的有机物（脱灰煤粉）和煤灰,研究了煤变质程度、显微组分、煤灰含量等煤质特性对CeO₂催化煤粉燃烧的影响。研究发现,变质程度对CeO₂催化煤粉燃烧具有明显的影响,变质程度越高的脱灰煤粉燃点降低越多,燃速提高越快。其催化燃烧顺序为褐煤<烟煤<无烟煤。同时研究发现,CeO₂对神华烟煤两种主要显微组分的燃烧没有明显的催化作用。煤灰对脱灰煤粉燃烧也有催化作用,对人工煤而言,当煤灰含量低于18%时,煤灰与CeO₂具有协同作用。煤灰的质量分数为6%时,煤灰与CeO₂的协同作用最强,之后随着煤灰增加协同作用逐渐变弱;当煤灰的质量分数超过18%时,协同作用消失,CeO₂的催化作用消失。说明煤灰含量超过18%时,CeO₂的催化作用被抑制。     

Evaluation of the suitability of sampling on Tenax TA and polydimethylsiloxane for the analysis of combustion gases

Two sorbents commonly employed for air sampling were selected for the evaluation of their suitability for the analysis of combustion gases namely Tenax TA as adsorbent and polydimethylsiloxane (PDMS) as absorbent. Target compounds were selected among the gaseous combustion products of polyurethane foam and fire-retarded polystyrene. The combustion gases were generated by burning test materials in the flame of a Bunsen burner. Gaseous combustion products were sampled simultaneously with the two sorbents using a two-way adapter, thereby exposing each sorbent to the same combustion gas atmosphere. Special attention was given to the deterioration encountered in the Tenax TA performance upon repeated combustion gas exposure, limiting its use for sampling reactive atmospheres.     

The fire-retarding effect of inorganic phosphorus compounds on the combustion of cellulosic materials

The pyrolysis and combustion of cellulosic substances treated with MAP and DAP have been studied using thermal analysis, flame spread tests and a specifically designed apparatus for smoldering combustion test. The samples used were: cotton string, cotton fabric and pure cellulose powder. Diammonium Phosphate (DAP) and Monoammonium Phosphate (MAP) can reduce the combustion and pyrolysis maximum mass loss temperature, decrease the initial pyrolysis temperature and considerably increase mass residue. Moreover, MAP and DAP reduce the flaming combustion rate of cellulosic materials and completely inhibit smoldering combustion. This study can facilitate a better understanding of the mechanism of pyrolysis and combustion of fire-retarded cellulosic materials.     

Nonlinear theory of combustion stability in liquid rocket engine based on chemistry dynamics

Detailed models of combustion instability based on chemistry dynamics are developed. The results show that large activation energy goes against the combustion stability. The heat transfer coefficient between the wall and the combust gas is an important bifurcation parameter for the combustion instability. The acoustics modes of the chamber are in competition and cooperation with each other for limited vibration energy. Thermodynamics criterion of combustion stability can be deduced from the nonlinear thermodynamics. Correlations of the theoretical results and historical experiments indicate that chemical kinetics play a critical role in the combustion instability.     

煤炭自燃防火及灭火技术研究进展

综述了近年来煤炭自燃防火及灭火技术和方法的研究现状;简单概括了煤炭自燃机理、过程、基本规律及必备条件,分析了各种煤炭自燃防火及灭火技术的优缺点,进而总结了其存在的问题,并就其发展趋势和后续研究方向提出了建议.     

不同液化条件下生物质残渣的燃烧特性研究

对锯屑在不同液化条件（溶剂、气氛、温度、催化剂）下所得液化残渣在热天平上进行了燃烧特性研究，通过比较液化残渣燃烧的三个特征温度，着火点ti、燃烧峰温tp和燃烬温度tb，分析了液化条件对残渣燃烧特性的影响。同时通过热重曲线所得数据探讨了液化残渣燃烧过程的动力学，并计算了活化能和频率因子 。结果表明，不同溶剂下所得液化残渣的燃烧特性显著不同，以四氢萘为溶剂所得液化残渣具有较好的燃烧特性；不同气氛下所得残渣的燃烧特性没有明显的不同；350℃下所得液化残渣的燃烧特性要好于300℃下所得液化残渣的燃烧特性；由于催化剂的影响，加入1%Mo后降低了所得液化残渣的燃烧特性；液化残渣的燃烧反应符合两段一级反应动力学。     

空气污染组分H2O和CO2对乙烯燃烧性能的影响

超燃冲压发动机在高空工作时, 以高温高速纯净空气作氧化剂使燃料燃烧. 但在地面实验中, 高温空气往往通过燃烧加热方式获得, 从而使空气包含了H2O和CO2污染组分. 本文用电阻加热来流空气并添加污染组分的方法, 研究了燃烧室模型中乙烯的燃烧状态和壁面压力受污染组分的影响. 用化学反应动力学模拟的方法, 在绝热刚性反应器模型中用H2O和CO2取代空气中的N2, 研究了污染组分对点火延迟和燃烧温度的影响, 并从链反应机理的角度讨论了实验和动力学模拟结果.     

颗粒油页岩燃烧及含硫杂质的转化

对抚顺、茂名及约旦颗粒油页岩在热重分析仪(TGA)上进行了燃烧研究,考察了抚顺及茂名颗粒油页岩在模拟流化床快速升温条件下的燃烧性能并与恒温燃烧作了对比。结果表明,升温速度提高时,失重率(即燃烧速率)明显加剧。文中还对含碳酸盐及含硫量高的约旦颗粒油页岩在燃烧过程中硫的转化进行了研究。X射线衍射分析表明,它在燃烧过程中有较强的自脱硫能力。通过对该油页岩燃烧过程中热量的有效利用问题的讨论,认为在流化床内燃烧此类含碳酸盐较高的油页岩时宜采用短停留时间的炉型。     

旋流煤粉燃烧的一维综合数值模拟

发展了综合考虑气－固两相旋流流动，气相燃烧，颗粒相变与燃烧及两相辐射传热的旋流煤粉燃烧－维数学模型，给出了气－固两相能量方程中颗粒相就源项的计算表达式，应用这一模型对涡旋燃烧炉环形通道内多组工况的旋流气体燃烧和煤粉燃烧进行了数值模拟，计算得到的炉内温度分布和燃烧效率与实验数据基本相符，表明本文建立的模型可用于旋流煤粉燃烧的一维综合数值模拟。     

制革、造纸和湖泊污泥燃烧特性的研究

利用热重分析法对城市湖泊污泥、制革污泥,以及两种造纸污泥进行了实验研究,并分析了污泥的燃烧特性。结果表明,四种污泥都具有高挥发分、高灰分、低热值的特点。污泥的燃烧分为挥发分燃烧和固定碳燃烧两个阶段,除了制革污泥在两个阶段失重份额相当外,湖泊污泥和造纸污泥的挥发分燃烧阶段失重都超过燃烧总失重的70%,表明挥发分是污泥中的主要可燃成分,而且挥发分和燃烧过程温度范围比较宽。污泥的挥发分燃烧DTG峰有明显的多峰叠加现象,表明污泥的挥发分析出组分较为复杂。运用Coats-Redfern积分法进行动力学分析后表明,大部分污泥的燃烧过程为二级反应,污泥燃烧的活化能较低。     

Effect of Combustion Improver on Combustion Behavior of Cigarette Paper by Simultaneous TG/DSC Detection

Combustion behavior of cigarette paper containing different content of combustion improver was investigated in order to provide direct experiment data to elucidate lower components in cigarette smoke caused by combustion improver in cigarette paper. The content of the combustion improver was denoted as "organic" potassium index and determined by atomic absorption spectroscopy and ionic spectroscopy. The combustion process obtained by simultaneous thermal analysis was divided into four stages: weight loss due to loss of absorbent water, decomposition of the cellulose, the oxidation of the cellulose char and decomposition of calcium carbonate. Combustion improver reduced the temperature of cellulose decomposition 3–12 K and contributed to oxidation of the cellulose char. Ignition point was gained and reduced 3–8 K by combustion improver. Above results were further verified by samples from two other cigarette paper factories. Mechanism of lower components in cigarette smoke by the combustion improver in cigarette paper was discussed.