用热分析研究树皮的热解动力学参数

对影响热天平热解实验结果的一些主要因素进行了分析,由此选择了合适的实验条件,并对３种树皮的热解特性进行了实验。通过选择热解反应机理方程,采用积分法求得到了３种树皮的热解动力学参数。     

用热分析技术研究树皮的热解动力学参数

对影响热天平热解实验结果的一些主要因素进行了分析,由此选择了合适的实验条件,并对３种树皮的热解特性进行了实验。通过选择热解反应机理方程,采用积分法求解得到了３ 种树皮的热解动力学参数     

生物质与煤共热解特性研究

选取4种典型生物质样品(麦秆、稻秆、木质素、造纸废液颗粒),将生物质样品与煤分别以1∶9、3∶7、5∶5的重量比例掺混。采用热重分析法,在相同升温速率下,对各掺混样品进行热解实验,探讨了生物质与煤热解特性的差异以及它们共热解时生物质对煤热解过程的影响。研究表明,生物质与煤的热解特性差异很大:生物质热解温度低,热解速度快,而煤相对热解速度慢,热解温度高;在生物质与煤混合热解时,总体热解特性分阶段呈现生物质和煤的热解特征;将各生物质样品与煤混合热解的实际微分曲线与按比例折算后曲线进行比较,得出实际微分曲线与折算曲线基本吻合,即生物质对煤的热解无明显影响。     

峰值分析法在聚乳酸热解特性研究中的应用

建立了一种利用热重微分曲线上的特征点以分析热解动力学的研究方法,该方法利用峰温度、峰高和峰值转化率来确定动力学参数。理论证明了峰特征点和动力学参数之间的关系;并通过聚乳酸热解动力学的实验研究,验证了该关系式的合理性。结果表明,聚乳酸的表观活化能为264.35kJ·mol~(-1),表观指前因子为7.89×10~(21)s~(-1),反应级数为0.9415。另外,理论DTG与实验值结果拟合效果良好。     

不同升温速率下水煤浆的热解特性分析

采用日本岛津(SSHIMADZU)公司生产的DTG-60H型热重-差热分析仪研究了胜利制浆厂水煤浆在不同升温速率下的热解特性,所采用的升温速率为20℃/min、30℃/min和50℃/min,气体为99.999%的N2,吹扫气体流量为100 ml/min.水煤浆的颗粒粒度分布用德国SYMPA公司SUCELLGL型激光粒度分析仪用湿式方法测得.根据实验数据计算了不同升温速率下水煤浆的热解动力学参数,分析了水煤浆热解特性.结果表明:随着升温速率的增大,水煤浆热解的失重份额和活化能增大,热解特性趋好,放热更集中.     

城市污泥和煤混燃特性的热重分析法研究

利用热重分析法对某城市污泥和某煤种及其两者混合物的着火温度、活化能及综合燃烧特性等参数进行了研究。试验结果表明,混合试样和煤相比其活化性能得到了提高,着火温度提前,综合燃烧性能下降。在混燃过程中,煤和城市污泥基本上保持了各自的挥发分析出特性,煤的燃烧表现得更为明显。     

生物质废弃物热解特性的热重分析研究

采用热重分析方法,以氮气为载气,在室温和973K之间,以三种升温速率(10,20,30K/min)对三种生物质废弃物试样(稻秆、稻壳和白松木屑)进行热解实验。确定了起始分解温度D。采用了生物质整体热解分区、生物质化学组分热解分区、活化热解与消极热解分区等三种热解分区方法进行分析。由于三种试样化学成分的差别导致热解特性的差异。得到了三种试样热解动力学参数。     

实验条件对煤热解特性影响的分析

采用TG-FTIR联机实验方法．对不同煤样进行了热重分析．同时对煤样的析出产物进行红外光谱实时跟踪检测；研究不同升温速率和试样用量对煤热解过程TG、DTG曲线以及实时跟踪红外光谱分析的影响．为掌握煤的热解特性、提高煤的有效利用提供依据。     

神华煤液化残渣的热解特性

在TGA/SDTA851热重分析仪上,以N_2为载气,在气体流速为20 mL/min,升温速率分别为20℃/min、40℃/min、60℃/min和80℃/min,终温1100℃的条件下,进行了煤液化残渣的热解特性研究实验,得到了不同升温速率下神华煤液化残渣热解的TG和DTG曲线,表明神华煤液化残渣的热解是分两步进行的．在低温段主要是神华煤液化残渣中挥发性的气体溢出引起热解失重,在低温度段180～450℃,挥发分迅速释放;高温段则主要是一些高分子有机质的热解过程．此外,研究了粒径对热解特性的影响．研究发现,随着粒径的增加,残渣的最大挥发分释放速率逐渐减小,而最大挥发分释放速率对应的温度逐渐增加．利用Freeman-Carroll法得到煤液化残渣的动力学参数,为煤液化残渣的有效和经济利用提供理论依据．     

煤热解燃烧气体产物的热重-红外联用分析

利用热重分析仪对煤的热解过程进行实验研究，并使热解后煤中的固定碳在模拟空气状态下充分燃烧。同时利用联机的傅立叶变换红外光谱仪对气体产物(烟气)进行实时红外光谱跟踪分析，研究煤在热解燃烧过程中烟气的排放规律以及升温速率、试样用量对烟气红外光谱的影响。     

Kinetic modeling and simulation: Pyrolysis of Jatropha residue de-oiled cake

An improved kinetic model based on thermal decomposition of biomass constituents, i.e. cellulose, hemicellulose and lignin, is developed in the present study. The model considers the independent parallel reactions of order n producing volatiles and charcoal from each biomass constituent. While estimating the kinetic parameters, the order of degradation of biomass constituents is also checked and found to be matching with the order of degradation reported in the literature. The results of thermo-gravimetric analysis of Jatropha de-oiled cakes are used to find the kinetic parameters. The experimental runs are carried out using a thermo-gravimetric analyzer (TGA 4000, Perkin Elmer). TGA study is performed in a nitrogen atmosphere under non-isothermal conditions at different heating rates and the thermal decomposition profiles are used. The model is simulated using finite difference method to predict the pyrolysis rate. The corresponding parameters of the model are estimated by minimizing the square of the error between the model predicted values of residual weight fraction and the experimental data of thermogravimetry. The minimization of square of the error is performed using non-traditional optimization technique logarithmic differential evolution (LDE).     

桦甸油页岩燃烧过程的热重分析

本文介绍桦甸油页岩热重分析的研究结果，采用全自动光电分析天平进行了桦甸油页岩的ＴＧ、ＤＴＧ和ＤＴＡ分析，研究结果表明 ，桦甸油页岩在３５０－５５０℃之间是挥发份的主要析出区间，在６００－８５０℃区间主要的放热反应区间。     

玉米秸秆热解特性及其动力学研究

用热重分析方法研究了玉米全秸秆、秸皮和玉米叶的热解失重过程和热解特性.结果表明:3种原料的热解过程相似,分为预热解、主热解和碳化3个阶段,且均在340C左右达到最大失重速率;玉米全秸秆的热解特征指数最大,挥发分析出特性最好,其次是秸皮和玉米叶;采用不同反应级数n进行动力学拟合发现:n=2时的热解动力学拟合效果较n=1好,同时玉米全秸秆的动力学参数均最大,玉米叶最小,即全秸秆需要最多的热量才可以热解,但开始热解后其热解过程也相对更容易进行.     

混煤燃烧特性的实验研究

选择武钢高炉混煤喷吹的某种烟煤和某种无烟煤为研究的煤源,对不同混合比例的混煤燃烧进行了实验研究。利用差热天平的TG—DTG—DTA热分析,探讨了烟煤不同掺混比对混煤的燃烧特性的影响规律和合适的烟煤掺混比例,阐明了烟煤掺混高炉喷煤技术经济指标的改善作用。     

褐煤干燥及热解机理研究现状

单个大颗粒褐煤干燥、热解机理的研究对于褐煤提质技术的开发具有重要的理论与实际意义,可用于该过程的数值计算与优化研究.对于单个大颗粒褐煤而言,在干燥、热结过程中内部存在较大的温度、水含量及挥发分含量的梯度,所涉及到的科学问题为多孔介质传热与传质问题.文中主要针对褐煤的干燥机理、热解机理及堆积态干燥过程机理进行了详细的文献调研.     

煤的加压热解试验研究

运用热分析仪器研究固体热分解特性和反应动力学是目前较为流行的方法。本文在自制的加压热重分析仪上，研究了在惰性气体（Ｎ２）环境下，压力（１０１ｋＰａ～１３１７ｋＰａ）对煤的热解过程的影响规律，测得了不同压力下煤粒挥发份的析出过程，以及煤粒粒径对煤热解时挥发份析出过程的影响。同时，在前人的基础上得出了煤加压热解动力学方程，并以此建立了加压煤热解模型。利用该模型进行了分析计算，其计算结果与实验结果符合得很好。     

Pyrolysis pretreatment of biomass for entrained-flow gasification

The biomass for entrained-flow gasification needs to be pretreated to significantly increase its heating value and to make it more readily transportable. The pyrolysis pretreatment was conducted in a lab scale fixed-bed reactor; the reactor was heated to elevate the temperature at 5 °C/min before holding at the desired pyrolysis temperature for 1.5 h a fixed time. The effects of pyrolysis temperature on the yield, composition and heating value of the gaseous, liquid and solid products were determined. The pyrolysis removed most oxygenated constituents of rice straw while significantly increased its energy density. Meantime, it changes the physical properties of biomass powders. The results show that the angle of repose, the angle of internal friction of semi-char decrease obviously; the bulk density of semi-char is bigger than that of biomass. This could favor the feeding of biomass. Considering yield and heating value of the solid semi-char product and the feeding problem, the best pyrolysis temperature was 400 °C. The results of this study have confirmed the feasibility of employing pyrolyzed biomass for entrained-flow gasification; they are useful for the additional studies that will be necessary for designing an efficient biomass entrained-flow gasification system.     

煤热解研究的分析方法

为了让更多的科研工作者了解煤热解试验仪器及其分析方法,对热重-差热、红外、气相色谱、质谱等仪器分析方法的特征性能进行了综述,重点描述了其在原煤、半焦、焦油、热解气体等分析研究中的应用,同时简要介绍了一些先进的联合分析法在煤热解研究中的应用。另外还对热重分析仪(瑞士METTLER-TOLEDO公司生产TGA/SDTA851e热重/同步差热分析仪)、傅立叶变换红外光谱仪(Nicolet公司生产的5700型)、气相色谱仪(5975MSD)、质谱仪(6890GC)进行了介绍。     

Effect of heating rate on the pyrolysis yields of rapeseed

The pyrolysis yields of rapeseed were investigated applying thermogravimetric analysis technique. The pyrolysis experiments were performed up to 1273 K at heating rates of 5, 10, 20, 30, 40 and 50 K/min in a dynamic nitrogen flow of 40 cc/min. Effects of heating rate on the mass losses from the rapeseed were examined using the derivative thermogravimetric analysis profiles. This study showed that important differences on the pyrolytic behavior of rapeseed are observed when heating rate is changed. At the lower heating rates, the maximum rates of mass losses were relatively low. When the heating rate was increased, maximum rates of mass losses also increased. These variations were interpreted by the heterogeneous structure of biomass. Heating rates also concluded to affect the shape of the peaks. Increase in the heating rate shifted the main peak on the DTG profile to the lower temperatures. At low heating rates, there is probably resistance to mass or heat transfer inside the biomass particles. However, increase in heating rate overcame these restrictions, and led to higher conversion rates. The final pyrolysis temperatures were also affected from the variation of the heating rate. Activation energy values were first increased and then decreased depending on the heating rates.     

Pyrolysis characteristics of bio-oil fractions separated by molecular distillation

Molecular distillation was used to separate bio-oil into a light fraction, a middle fraction and a heavy fraction. The chemical composition of the three fractions and the crude bio-oil was analyzed by gas chromatography coupled with mass spectrometry (GC–MS). The diversity of the components reflected the complexity of the bio-oil and the necessity for fractionation. The pyrolysis characteristics of the bio-oil fractions were determined with a thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG–FTIR). The weight loss of components was in agreement with the chemical composition. The light fraction evaporated fastest with the formation of water, CO₂, hydrocarbons and alcohols. The heavy fraction had the slowest rate of decomposition and the highest char residue yield due to the presence of phenols and saccharides, and the pyrolysis products included CO₂ and alcohols or phenols, which was similar to the middle fraction except the formation of water and formic acid. The release of CO or methane, evidence of a secondary reaction, began at ∼450 °C in the pyrolysis of the light and middle fractions.