Detection of natural oxidation of coking coal by TG-FTIR—mechanistic implications

The natural oxidation/weathering of coal continues to be a subject of interest both scientifically and industrially, in part due to the complexity of the molecular processes at hand as well as to the commercial implications involved. It is widely recognized that coking can be adversely affected by weathering whereas, combustion processes appear to be enhanced as result of oxidation.Combustion techniques are commonly used in the analysis of coal, and organic compounds in general, for the determination of elemental hydrogen, carbon and nitrogen. For oxygen, the method in common practice involves the determination by difference from directly determined values for moisture, ash, sulphur, hydrogen, carbon and nitrogen. This has led us to consider the use of thermogravimetry coupled to gas analysis by infrared spectroscopy (TG-FTIR) to measure organic oxygen in coal directly. Although this technique, developed by Solomon and coworkers, has been extensively used by our group and others, it appears not to have been considered for this particular purpose.Recently, we have shown that TG-FTIR is capable of measuring all the organic oxygen in both fresh and oxidized coal by simultaneous measurement of the three main oxygen-containing gases H₂O, CO and CO₂ evolved during rapid pyrolysis. This gives us a way of measuring quantitatively the oxygen introduced into the coal matrix during oxidation and at least a partial capability of establishing oxygen speciation.We have found, using TG-FTIR, that the early stages of coal oxidation results in the appearance of O-containing functional groups not present in the original coal. The nature of these functional groups is directly related to the oxidation reaction mechanism. These results will be presented and discussed in detail.     

A TG-FTIR investigation on the co-pyrolysis of the waste HDPE,PP, PS and PET under high heating conditions

The present study relates to the investigation of degradation of polymers such as HDPE, PP, PS and PET individually and in mixed forms. Eleven different mixture combinations were analyzed via TG Analysis to determine their degradation behavior individually and in mixed forms. FTIR analysis of the raw polymers was performed to investigate the presence of different functional groups in the sample. Online TG-FTIR analysis was performed to investigate the functional groups present in the volatiles fractions during single component pyrolysis and the interaction of polymers during co-pyrolysis was analyzed, compared and reported. Also, a real-world post consumer mixed waste was also analyzed and compared. During the co-pyrolysis of HDPE with PP and PS, the degradation of PP was delayed whereas PS reduced the degradation temperature of HDPE. In the case of degradation of PS with PP and PET, the increase in degradation temperature was reported whereas, in the case of PET and HDPE mixture, the degradation temperature of HDPE was reduced. During the interaction of PP and PET mixed degradation, PET degradation temperature was delayed. During the FTIR analysis a large amount of alkanes, alkenes, aromatics groups were observed during the degradation of HDPE, PP and PS whereas in case of PET the presence of oxygenated groups is observed. During the mixed degradation, the presence of PET in the sample caused the formation of oxygenated groups by reducing the absorption intensity of other groups or by disappearing the groups. Compounds such as benzoic acid, CO and CO₂ was detected during the degradation of PET whereas in other polymers a large amount of methane or methylene group is observed. Overall during the degradation of mixed polymer mixture presence of PET played a vital role in the formation of light gas fractions. Even though a numerous investigation on co-pyrolysis of polymers were available, there is still not sufficient information of interaction of polymers with each other, especially with PET. This article attempts to fill this gap.     

煤沥青与石油沥青共混改性及其热解特性

考察了不同添加量的煤沥青四氢呋喃萃取物(THFS)对石油沥青的改性,随着THFS添加量的增多,改性沥青针入度降低,软化点升高,延度下降,参照英国标准(BSI BS—3690)得出最佳添加量为8%。利用TG-FTIR、FTIR对改性沥青进行了表征,结果表明:THFS、改性沥青的失重率大于基质沥青70的失重率; THFS在700～900cm^-1处芳香烃类的透射峰强度明显强于基质沥青与改性沥青;沥青老化后在2953cm^-1和1377cm^-1(—CH₃)、1461cm^-1和2924cm^-1(—CH₂—)处透射峰逐渐增强;1600cm^-1(C=O和苯环C=C)透射峰逐渐增强;沥青热解半焦中的脂肪烃类物质含量较少,主要以高度缩合的稠环芳香烃类物质为主;沥青在老化过程中主要发生了氧化、裂解、加成、聚合、缩合等反应。     

TG-FTIR在煤灰研究中的应用 ——真实煤灰和模拟灰受热气体释放规律比较

我国的煤炭种类多, 煤灰组成千变万化, 从中找到明确的矿物转变规律并非易事。为探索用模拟灰替代真实煤灰开展高温转变规律研究的可行性, 依据镇雄煤(ZX)煤灰化学成分, 利用FeS₂矿物和Fe₂O₃、SiO₂、Al₂O₃等分析纯化学试剂配制模拟灰, 测试灰熔融温度, 并借助热重红外联用(TG-FTIR)技术比较ZX真实煤灰和模拟灰在氮气气氛下升温过程中的质量变化及气态产物组成。结果表明, 模拟灰的流动温度接近ZX煤灰的流动温度, 最大相差49℃。当温度大于770℃时, 含有FeS₂的模拟灰与真实煤灰的TG-DTG曲线变化趋势一致。FTIR谱图显示两者释放的气体种类相同, 1080℃左右都产生SO₂气体, 此时的硫来源于黄铁矿的部分氧化产物FeS_x。含有FeS₂的模拟灰在高温下的变化更接近真实煤灰。     

热重-红外联用分析垃圾衍生燃料的热解特性

利用热重红外分析仪(TG-FTIR)研究了两种不同垃圾衍生燃料(RDF)的热解特性。研究发现,尽管两种RDF的来源不同,但却具有相似的热解特性,其热解过程主要分为3个阶段:生物质组分(220～430℃)、塑料类物质(430～520℃)以及无机碳酸盐(>650℃)的分解。利用Coats-Redfern法,求得了RDF热解前两个阶段的表观动力学参数,计算结果表明高温段的反应活化能要高于低温段。通过FTIR对RDF热解析出的气体进行了在线分析,发现两种RDF热解过程中的气相产物析出规律基本一致,析出的气体主要包括H₂O、CO₂、CO以及CH₄等烃类。HCl在低温阶段(230～400℃)即析出完毕。相比之下,NH₃开始析出的温度较高(260℃),并且整个析出温度范围较广,高温下仍有少量析出。SO₂在热解条件下仍有相当量的生成,其析出主要集中在300～600℃的温度范围内。     

柠檬酸的热解特性

使用热失重/傅里叶变换红外联用( TG-FTIR)技术研究了柠檬酸的热裂解特性,测定并比较了不同氧气浓度下柠檬酸的热重(TG)和微商热重(DTG)曲线,以及柠檬酸热解气相产物相对含量和生成规律,探讨了柠檬酸可能的热解机制.结果表明:①柠檬酸的热解气相产物主要有CO2,CO,H2O,酸酐和酮类物质.CO2是气相产物中相对含量最高的物质,CO最低;水最早出现在气相产物中,酸酐是最后存在于气相产物中的物质;②柠檬酸可能有2种主要热解途径:先脱水后脱CO2的酸酐生成模式和主要脱CO2的酮生成模式.在热解初期,2种模式同时发生,氧气浓度的增加有利于酮的生成.在较高温度下,主要以酸酐生成模式为主.     

基于TG-FTIR的生物油重质组分热解特性研究

和用热重红外技术在线分析了3种生物油重质组分模型化合物(丁香酚、3,4.二甲氧基苯甲醛、左旋葡聚糖)在10,20,30℃C/min升温速率下的热解特性.热重试验结果表明:酚类物质最易热解,其次是醛类物质,再次是糖类物质;提高升温速率有利于热解反应的进行,但对最终失重量无影响.红外检测数据表明:左旋葡聚糖的热解分为两段,前段主要为脱水反应,生成醛等小分子物质,后段遵循醛类物质热解的机理,主要产物为小分子的不饱和烃类和CO_2,并伴随有少量的醚和H_2O生成.     

城市生活垃圾典型组分燃烧特性的TG-FTIR研究

利用热重分析和傅立叶变换红外光谱法(TG-FTIR)联用分析了城市生活垃圾的典型组分(大米饭、PVC、PS、煤炭)的燃烧特性,定性得到了燃烧过程中的排放产物。结果表明,厨余类垃圾水分较高,300℃左右挥发分快速析出燃烧,燃烧产物中含有烃类、CO、乙酸类物质,垃圾热值较低;PS类燃料挥发分较高,在350℃左右迅速失重,燃烧产物中含有烃类、氢气、多聚物、苯乙烯等物质。此外,对其中3种单质垃圾进行了混合燃烧试验,混合样品的氧化过程可以看作单组分的简单叠加。     

利用热重-红外联用对生物质热解特性研究

采用热重-红外(TG-FTIR)联用技术研究不同升温速率对生物质热解特性影响。以氮气为载气,在室温和600℃区间,以3种升温速率(10,30,50℃/min)对生物质试样(麦秆)进行热解实验,确定了生物质起始分解温度,热解失重主要发生在快速热解阶段,升温速率越高,热解起始温度和失重速率越大;热解气体通过FTIR分析结果表明,热解初始阶段的气态产物主要是水蒸气和少量的CO及CO2,随着温度的升高,热解的主要气态产物变为CO、CO2、CH4以及小分子烃类。     

调质对钙基固硫剂固硫效果影响的TG-FTIR研究

针对目前燃中固硫技术普遍存在的钙转化率较低、固硫效果不理想的问题,以不同的调质剂分别浸渍CaO,然后把调质后的CaO以添加和不添加Fe2O3助剂两种形式与高硫煤在模拟空气中燃烧,采用TG-FTIR的测试方法对固硫效果进行定性分析.实验结果表明,将钙基固硫剂分别用2%的NaCl、2%的Na2CO3、50%的乙醇和25%的乙酸溶液浸渍后与煤混燃,经TG-FTIR在线分析,得出用50%的乙醇浸泡后CaO的固硫效果较好,其烟气红外3D图上,SO2峰的高度最低,调质剂的固硫效果依次为:50%乙醇＞2%NaCl＞25%Na2CO3＞2%的Na2CO3;在加入助剂Fe2O3后,经50%乙醇浸渍过的CaO固硫效果显著提高,固硫率达到97.42%.