微波诱导市政污泥热解实验的热重分析

通过TG-DSC实验,研究微波辐射对污泥热解特性的影响,与污泥-生物质混合热解特性作对比,并利用Coats-Redfern积分法计算出污泥热分解反应的表观活化能、反应级数及指前因子.结果表明,在辐射剂量为10 W/g、20 W/g和25 W/g的条件下,污泥TG实验的失重率分别提高了4.6％、5.7％和1 1.6％;热解反应的活化能分别降低了19.2 kJ/(mol·K)、2.6 kJ/(mol·K)、12.7 kJ/(mol·K),平均降低了24％,反应级数略有变化.在10 K/min升温速率下,添加质量分数为5％的木屑或麦秆,污泥热解失重率分别为4.7％和8.9％.     

印染污泥与木屑混燃特性及动力学

采用综合热重分析法,在不同升温速率及印染污泥与木屑不同比例混合条件下,对印染污泥、木屑及其混合物的燃烧特性进行了研究.结果表明,印染污泥的热重曲线存在4个明显的失重峰,分别与水分的析出、两个挥发分的析出以及固定碳的燃烧阶段相对应.混合试样燃烧过程中,污泥和木屑基本保持各自的挥发分析出特性,其燃烧曲线位于污泥和木屑燃烧曲线之间,且混合试样微熵热重曲线的变化趋势与组成比例较大的成分DTG曲线变化趋势较为接近.污泥与木屑混合后其综合燃烧特性指数SN有所增大,说明挥发分含量越高对应的燃烧特性越好;采用积分法(Coats-Redfern方程)计算得到各阶段燃烧反应的机理方程及相应的活化能参数,分析表明单一印染污泥燃烧的活化能较低,活化能的大小与试样的燃烧阶段是相对应的.     

锡林浩特褐煤燃烧特性热重分析

利用热重分析仪获得了升温速率分别为10 K/min、30 K/min、50 K/min和70 K/min下锡林浩特褐煤的燃烧失重特性曲线,计算了着火温度、燃尽温度、最大失重速度等燃烧特性参数。采用Coats-Redfern法计算出反应动力学参数:活化能E和频率因子A。结果表明,随着升温速率升高,其着火温度降低,燃尽时间增加。     

利用分布活化能模型研究木材的热解和燃烧机理

在热天平上考察了三种木材在不同气氛和升温速率下的热解行为,并利用分布活化能模型研究了三种木材的热解动力学.结果表明:在空气气氛下,热失重分为三个阶段,失重率为500/~6000/时,三种木材的活化能值都在110~250 kJ/mol,且非单调增加;在氮气气氛下,热失重分两个阶段,失重率在1000/~8500/时,三种木材的活化能值都在165~230 kJ/mol,且呈“W”形变化.活化能的分布函数,反映了木材在热解、气化、燃烧过程中不同阶段的反应活性变化规律,有助于了解木材的热解和燃烧机理.     

煤热解动力学的单一反应模型和分布活化能模型比较

利用程序升温热重技术研究了宝日希勒褐煤和包头烟煤热解的失重过程,比较分析了单一反应模型和DAEM对其动力学分析的适应性。单一反应模型仅需一条失重曲线就可以获得动力学参数,但一般需要对失重曲线进行分段处理,且只能得到某一温度范围内活化能的平均值。Miura积分法可以在DAEM的应用中不需事先假设活化能分布的形式和频率因子为定值,由至少3条不同升温速率下的失重曲线直接得到煤热解的活化能分布和频率因子的值。Miura积分法的结果表明,宝日希勒褐煤和包头烟煤热解的活化能随着失重率的升高而增大,活化能分布于250～400kJ/mol的区间。频率因子先随活化能的升高而增大,而当活化能大于300kJ/mol时,频率因子趋于水平。DAEM能描述非等温热解自低温到高温的全过程,对煤种和升温速率变化有宽广的适应性。     

生活垃圾和农林废弃物混合燃烧特性及动力学分析

为解决生物质和城市生活垃圾有效再利用问题,以城市生活垃圾中的高热值组分比例为基础制备模化垃圾,并与锯末按6种比例混合制成复合燃料。利用热重法分析复合燃料的燃烧特性并计算综合燃烧特性指数S。采用Coats-Redfern法对各样品进行动力学分析,根据不同温度区间分段求取活化能结果相关系数高。结果表明:燃料中锯末含量的增加会使着火点提前,燃尽温度推后,综合燃烧特性指数S增大,活化能降低,从而有利于复合燃料的燃烧。综合分析表明复合燃料中锯末与模化垃圾的最优比为8∶2,综合燃烧特性指数S为9.71×10~(-8)min~(-2)·K~(-3),活化能为53.26 kJ/mol。     

城市污水污泥成型燃料燃烧动力学特性研究

利用热分析方法研究污泥、煤、稻草,以及三种原料三种不同配比情况下的污泥成型燃料的燃烧特性,分析试样燃烧的TG-DTG曲线,得出各个试样的着火温度、可燃性指数、燃烧特性指数和燃烧动力学参数。结果表明,掺入煤和稻草有利于改善污泥的燃烧特性;不同配比的污泥成型燃料,挥发分含量越高,越容易着火和燃尽;采用积分法(Coats-Redfern方程)计算得到各阶段燃烧反应的机理方程及相应的活化能参数,污泥成型燃料的燃烧过程的第一阶段符合2级反应,第二阶段符合0.5级反应。     

基于分布式改良Coats-Redfern法的梧桐叶燃烧动力学研究

采用热重分析法分别研究梧桐叶及其热解炭、水热炭在不同升温速率下(10、20、30℃/min)的燃烧特性,采用分布式改良Coats-Redfern积分法分析其燃烧动力学,编程计算出拟合度最佳的反应级数n和活化能E,并与Coats-Redfern法分析结果进行对比。结果表明:梧桐叶及其水热炭燃烧差热重量分析法(DTG)曲线呈4个峰,热解炭呈3个峰;升温速率为20℃/min时,相对于梧桐叶,其热解炭综合燃烧特性指数下降85%,水热炭下降18%,表明水热炭更适合用作燃料;样品燃烧过程中活化能分布均呈N型,低温燃烧区活化能较高,高温燃烧区活化能较低。     

玉米秸秆热解反应动力学的研究

利用热重分析法(TG)对粒径为0.28~0.60mm的玉米秸秆在5、10、20、30℃/min 4种不同升温速率下的热解反应动力学进行了研究。结果表明,秸秆的热解过程分为4个阶段,主要反应阶段在287~400℃之间,随着升温速率的增加,主要反应区间略有增加。Ozawa法计算出的玉米秸秆活化能(E)值在153~160 kJ/mol范围内,KAS法得出的玉米秸秆活化能集中在147~157 kJ/mol之间。用微分法Achar方程、积分法Coats-Redfern方程,将41种常用的固体反应动力学机理函数一一代入,再根据热分析动力学三因子求算的比较法得出玉米秸秆热解过程符合Mampel Power法则,并给出机理函数的微分形式和积分形式,反应级数为2,本研究为生物质热解装置的设计及参数优化提供了科学依据。     

稻壳燃烧特性与动力学模型的研究

采用热重分析仪,在空气气氛下对稻壳的燃烧热失重状况进行了研究,并分析了四种升温速率（5,10,20,50℃／min）对燃烧特性指数的影响。利用Coats-Redfern模型,Freeman—Caroll模型和Flynn—Wall-Ozawa模型分别计算了稻壳燃烧的活化能及频率因子。实验表明：随着升温速率的升高,燃烧性能得到良好改善,但反应起始温度和终止温度由于受热滞后性影响,向高温区偏移使着火温度升高。模型计算结果表明：稻壳燃烧的表观活化能较低,升温速率对活化能的影响并不明显,Coats—Redfern模型、Freeman-Caroll模型可用于估算,Flynn—Wall—Ozawa模型可作为重要数据参考。     

不同粒径棉花秆粉末压制成型颗粒燃烧动力学特性

为掌握不同粒径棉花秆粉末压制的成型颗粒燃烧的动力学特性,开展不同粒径粉末的热重分析,并将粉末压制为质量相当的成型颗粒,开展成型颗粒燃烧失重实验,并采用等温热分析的双对数方法进行动力学分析。结果表明:棉花秆粉末粒径较大时,灰分也较高,在较低温度下燃烧可形成骨架,有利于挥发分和氧气的扩散,促进燃烧速率。压制成型颗粒时,棉花秆粉末粒径越小,粉末间结合越紧密,压制的成型颗粒密度越大,相同条件下的燃烧失重速率明显降低,表现活化能从77.71 kJ/mol逐渐降至69.44 kJ/mol。成型颗粒的高温燃烧过程可分为2个阶段,首先是水分和挥发分全部析出,而后为焦炭燃烧阶段。燃烧温度可显著加快水分和挥发分的析出速度。     

Thermogravimetric kinetic analysis of Nannochloropsis oculata combustion in air atmosphere

The thermal behavior of Nannochloropsis oculata combustion in air atmosphere were investigated by performing experiments on STA PT1600 Thermal Analyzer at heating rates of 10°C/min, 40°C/min and 70°C/min and range of temperatures from room temperature to 1200°C. The kinetic parameters were evaluated by using Kissinger and Ozawa methods. The result showed that Nannochloropsis oculata combustion occurred in five stages. Started with initial devolatilization, the main thermal decomposition and combustion process, transition stage, the combustion of char and the last stage was the slow burning reaction of residual char. In line with increasing heating rate, the mass loss rate increased as well, but it delayed the thermal decomposition processes toward higher temperatures. The average activation energy at the main thermal decomposition stage and the stage of char combustion were approximately 251 kJ/mol and 178 kJ/mol, respectively.     

Combustion characteristics of Turkish lignites at oxygen-enriched and oxy-fuel combustion conditions

Combustion and oxy-fuel combustion characteristics of two Turkish lignites (Orhaneli and Soma) were investigated by Thermogravimetric Analysis (TGA) method. Experiments were carried out under oxygen-enriched air and oxy-fuel combustion conditions with 21, 30, 40% oxygen concentrations. Three heating rates of 5, 10, and 20 °C/min were considered and the isoconversional kinetic methods of FWO, KAS, and Friedman were employed to estimate activation energies. The uncertainty assessment in obtaining the activation energy values was also considered. The obtained results indicated that the combustion of volatiles at both air and oxy-fuel conditions were approximately identical. However, at air combustion conditions, the decomposition of CaCO₃ took place at temperatures above 700 °C. This decomposition process was independent of the oxygen concentration and took place when the temperature reached to a certain threshold. The decomposition of CaCO₃ did not accomplish in oxy-fuel conditions as far as the temperature was higher than 900 °C. Combustion in oxy-fuel conditions had higher activation energy values comparing to conventional combustion atmosphere. The activation energy values were approximately unchanged at the start of combustion regardless of oxygen concentration or combustion atmosphere at about 165 kJ/mol and 150 kJ/mol for Orhaneli and Soma lignites, respectively. The apparent activation energies were higher at elevated oxygen concentrations. The uncertainties values related to FWO method were lower than KAS and Friedman methods. The calculated average uncertainty values were found to be at the range of 5–15% for most of the cases.     

酒糟非等温热解动力学研究

酒糟气化是酒糟高效利用的一种方式。文章对酒糟的热解行为进行了热重分析研究。在高纯氮气的保护下,将10 mg酒糟分别以10,20,30 K/min的升温速率线性升温到923 K。结果显示,酒糟热分解的主要阶段为453～743 K,试样的大部分失重发生在该区域,失重率达67%以上。使用Coats-Redfern模型拟合方法分析酒糟的热解过程,确定了反应的动力学参数。在此阶段,酒糟热分解的级数为2.1级,表观活化能为69.31 kJ/mol,指前因子为4.92×105min-1。此热解动力学模型可以为酒糟的热化学转化有效利用提供基础数据。     

沼渣热解动力学、热力学分析及热解产物特性研究

采用热重分析（TG）分析沼渣的热解特性,研究沼渣的热解动力学并计算指前因子A、焓变ΔH、吉布斯自由能ΔG、熵变ΔS等热力学参数。进一步考察温度对沼渣热解产物分布与性质的影响。其热解过程可分为3个失重阶段,其中第2阶段为主要失重阶段,采用Flynn-Wall-Ozawa（FWO）法、Friedman法和Kissinger-Akahira-Sunose（KAS）法计算的平均活化能分别为410.00、471.32和420.01 kJ/mol,热力学参数计算结果表明沼渣热解过程具有稳定的能量输出。沼渣热解油的产率随温度上升先增加后降低。气体产物的高位热值（HHV）从400 ℃时的6.82 MJ/Nm³增加到700 ℃时的8.54 MJ/Nm³。红外光谱（FTIR）、拉曼（Raman）光谱表明热解温度升高生物炭结构的有序性增加。     

Thermochemical treatment of E-waste from small household appliances using highly pre-heated nitrogen-thermogravimetric investigation and pyrolysis kinetics

The EU directive on waste of electrical and electronic equipment (WEEE) 2002/96/EC has set a goal of recovering 70–80% in terms of materials and energy. Nowadays, thermal cracking (pyrolysis) of such waste streams is receiving renewed attention, due to the energy and material recovery that can be achieved and therefore the sustainable waste management. However, it still lacks the kinetic background which is of great importance for a successful design of thermochemical processes. In this study the kinetic parameters of WEEE (originating from small household appliances) pyrolysis using highly pre-heated nitrogen under six different heating rates (1–2.5 K/s) have been estimated using a combination of model-free and model fitted methods. Even though WEEE is heterogeneous material, similar behavior at each of the six different heating rates applied was observed. The activation energy of the pyrolysis process determined with two different model-free methods gave comparable results. Pre-exponential factor and reaction order were determined using the Coats-Redfern method. The estimated kinetic parameters for the WEEE pyrolysis are: E = 95.54 kJ/mol, A = 1.06 × 10⁸ and n = 3.38.     

Co-solvent ethanolysis of chicken waste: Optimization of parameters and characterization of biodiesel

Fatty acid ethyl ester (FAEE) was developed from chicken waste. A blend of chicken fat and waste chicken oil was used as a feedstock for FAEE preparation via alkali-catalyzed transesterification with ethanol assisted by a co-solvent. Hexane was used as the co-solvent. The influences of alkali catalyst type and concentration, ethanol/blend molar ratio, hexane/ethanol volume ratio, temperature, time, and type of co-solvent on the yield of FAEE were investigated. The best yield of FAEE (96.94%~96.78% w/w ester content) was obtained at 0.75% KOH w/w, 8:1 ethanol/blend molar ratio, 1.5:1 hexane/ethanol volume ratio, 60°C temperature, and 60 min of reaction. The fuel properties of FAEE produced as well as its blends with petro diesel were within the range of those prescribed by ASTM D 6751 standards, indicating its suitability as fuel for combustion engines. It was concluded that the presence of co-solvent increased the yield of FAEE and enhanced its properties compared to FAEE produced via non-solvent processes. The process was found to follow first-order kinetics, and the activation energy was found to be 13.31 kJ/mol.     

A modified temperature integral approximation formula and its application in pyrolysis kinetic parameters of waste tire

A modified temperature integral approximation formula was proposed to calculate the kinetic parameters of tire pyrolysis. The relative error percentage of our formula was less than 0.02% at the range of 5 ≤ u ≤ 80. In order to validate our formula, the kinetic parameters of waste tire pyrolysis in a Thermogravimetric Analyzer (TG) were calculated according to different temperature integral approximation formula. The results demonstrated that the coefficient of the experimental TG and simulated TG from our formula was higher than that from Coats-Redfern method. The active energies of tire pyrolysis were 33.03 (120–300°C), 72.30 (300–420°C), and 50.83 kJ/mol (420–500°C).     

稀薄氨气的燃烧特性及动力学研究

文章通过稀薄氨气在固定床反应器中的燃烧,研究了反应温度、停留时间、氨气浓度和氧气浓度对低浓度氨气燃烧特性的影响,并描述了氨气在氧气过量条件下在陶瓷蜂窝蓄热体中燃烧的动力学过程。研究结果表明:提高反应温度、延长停留时间以及增大氧气浓度和氨气浓度均可以提高NH3转化率,氧气浓度过高会促进NO生成;当反应温度为740~770℃、氨气浓度为1%、氧气浓度为15%时,氨气在陶瓷蓄热体中燃烧的活化能为253.56 kJ/mol;与氨气在自由空间内的燃烧相比,氨气在陶瓷蜂窝蓄热体中主要发生表面燃烧反应。