污水污泥热解和燃烧特性的实验研究

采用热分析的方法研究了2种污泥的热解和燃烧特性。实验结果表明,热解和燃烧都可以划分为3个阶段。第1阶段是水分析出阶段。第2个阶段是污泥失重的主要阶段,燃烧失重是由于有机物的分解燃烧和固定碳的燃烧引起,热解失重是由于有机物的分解引起。第3阶段中,燃烧过程失重主要是无机物引起,热解过程失重是由于无机物和残余有机物引起。在燃烧和热解主要阶段(第2阶段)内,污泥燃烧的反应速率总体上大于热解的反应速率。污泥热解和燃烧在第2和第3阶段是放热过程。     

城市污水污泥热解特性及动力学研究

采用热重分析仪与傅里叶红外光谱仪对城市污水污泥进行实验,考察了反应过程及逸出气体产物,求解了热解表观动力学参数。研究表明,污泥样品在N2、CO2和N2+O2气氛中分别发生的热解、气化和燃烧反应,反应过程的特征参数不同;在N2中主要热解温度范围为200~560℃,反应过程在600℃基本完成;随着升温速率增加,热解最大失重速率提高;污泥样品在N2中的热解过程依次析出H2O、CO2、CH4和CO等气体;污泥样品热解不同反应阶段具有不同反应机理和动力学参数,表观活化能在60~100 kJ/mol范围内。     

纤维素热解的TG-FTIR分析

以生物质主要组分纤维素为原料,在热重-红外光谱联用仪上对纤维素分别以5,10,20,40℃/min的升温速率进行了热解实验研究,考察了纤维素的热解特性及轻质气体析出规律。结果表明:较高的升温速率能促进热解反应的进行,升温速率可作为影响最大热解失重速率对应温度(Tp)的一个重要因素,Tp会随着升温速率的增大而升高;纤维素热解过程中,热解气体的最大析出峰都对应于给定升温速率下的DTG失重峰;4种主要轻质气体(H2O,CO,CO2和CH4)均表现为双峰特性,且CO气体在热解后期的析出规律与CO2,H2O和CH4气体的析出规律不同;不同官能团键的断裂和重整,致使小分子气体组分和析出量的差异很大,热解过程中,羰基(C=O)和醚键(C-O-C)的断裂对CO2的生成影响显著;在低温区间CO的析出主要源于C-O-C的断裂,而在高温区间二芳基醚的分解则是CO产生的主要原因;CH4气体的析出主要由甲氧基(CH3O-)的伸缩振动引起。     

生物油热解及燃烧特性分析

对由木粉热解所得的生物油样品分别进行了氮气与氧气气氛下不同升温速率的热重分析试验.结果表明:生物油的热解分为两个阶段,第一阶段为生物油中低沸点有机物的挥发以及各组分间反应生成各类产物的过程,第二阶段为各种重组分的裂解过程;生物油的燃烧分为3个阶段,即前期的挥发与裂解和最后焦炭的燃烧过程.提高升温速率使氮气气氛中生物油样品的初始失重温度、失重峰值温度及对应的最大失重速率均有所增大,且在较高升温速率(20℃min)下,较少含炭残余物形成.随升温速率升高,生物油着火温度提高,最终失重率无变化.最后根据热重数据对热解与燃烧各段反应进行了动力学拟合.     

麦秆酶解残渣热解特性及动力学分析

对比分析了麦秆及其酶解残渣的基础物化特性,利用热重−红外联用技术研究了酶解残渣的热解反应过程及其主要气体产物的析出特性,并用混合反应模型计算了酶解残渣热解过程的表观动力学参数。结果表明,麦秆酶解残渣是一种富含木质素的高灰分、低热值的生物质原料,与麦秆原料相比,其热解过程相对平缓,主要失重温度区间为200℃ ~ 800℃,最大失重峰为350℃,与木质素的热解特性相近;提高升温速率可以使酶解残渣热解反应剩余产物质量明显减少,最大失重速率提高;热解主要气体产物中CH4析出的温度区间为400℃ ~ 700℃,CO和CO2在380℃、450℃和650℃都存在析出峰。动力学分析结果表明,酶解残渣热解过程在低温区（200℃ ~ 350℃）和高温区（350℃ ~ 800℃）分别遵循一级和二级反应动力学规律。     

用TG-FTIR技术研究染料残渣热解污染物的排放特性

用热重分析仪（TG）研究了典型高热值危险废弃物——染料残渣的热解过程,分析了在程序升温下的热解失重变化情况;同时用红外光谱仪（FTIR）对热解气态产物进行实时跟踪检测分析,研究了热解产生的CO2、CO、SO2、HCN等各种气体浓度随时间（热重温度）的变化。此种废弃物热解过程中,SO2的排放在较低温度（257℃附近）就出现高峰。热解中还出现了一个短暂的有毒气体氰化氢析出峰,可将该温度段热解气体在有氧环境下燃烧使之分解破坏后排放。可以考虑绝氧干馏燃前脱除污染物的焚烧方法。     

采用热重与红外光谱联用研究玉米秸秆热解

采用热重与红外光谱联用技术(TG—FTIR),在升温速率为20℃/min下,对玉米秸秆各部分(秸秆皮、秸秆瓤、叶子及苞叶)的热解产物及析出过程进行了实验研究。实验结果表明,玉米秸秆各部分的热解产物主要为CO2、CO、CH4、H2O,同时含有少量的丙酸类物质;秸秆皮和秸秆瓤热解气体的析出呈单峰形状,而叶子和苞叶热解气体的析出呈双峰形状;玉米秸秆各部分的热解最大失重率对应的热解温度约为360～371℃,相差较小;对玉米秸秆的同一部分,主要热解产物的最大失重率对应的热解温度基本相同。     

小麦秸秆热解产物逸出特性TG-FTIR研究

以小麦秸秆为研究对象,采用热重一傅里叶变换红外光谱(TG-FTIR)联用技术和分布活化能模型(DAEM),考察升温速率对其热解产物逸出特性的影响,计算热解过程的动力学参数。研究结果表明:随着升温速率的增大,小麦秸秆热解的起始温度和最大失重温度均向高温侧移动,最大失重速率增大,半纤维素热解的肩状峰逐渐出现;热解活化能E介于155~286 kJ/mol之间,指前因子k_0的数量级介于10~(14)~10~(23)之间;热解产物以H_2O、CO_2、CO、CH_4、甲酸和苯酚为主;主要产物的最大吸光度随升温速率的增大而增大,最大吸光温度向高温侧移动。     

城市污泥热解特性及热解过程中Pb、Cd迁移特性

以城市污泥为研究对象,考察了其在不同升温速率下的热解特性、热解反应动力学特征以及重金属Pb和Cd在热解过程中的迁移规律。通过热解失重曲线图得出,污泥的热解过程可分为水分析出阶段、挥发分析出阶段和半焦分解阶段。提高升温速率会导致污泥的失重量减少,挥发分最大失重速率增加。根据Coats-Redfern积分法计算结果得到,挥发分析出的第1阶段和第2阶段的反应级数分别为1和2,且不同升温速率下挥发分析出的第1阶段和第2阶段下的活化能总体上变化不大。通过管式炉热解实验可知,在热解温度为400、500、600和700℃范围内,重金属Pb和Cd的残留率随热解温度的升高均表现为先上升后下降的规律。Cd的残留率在热解温度为500和700℃时分别达到最高(41.64%)和最低(2.92%),而Pb的残留率随温度变化不大,均为93%以上。热解温度为400~500℃,Cd和Pb挥发较少。     

坝上地区莜麦秸秆热解特性研究

为实现高寒坝上地区农作物秸秆高效清洁燃烧,文章选取典型莜麦秸秆作为研究对象,通过混合气体模拟烟气燃烧过程中的热解气氛环境,采用热重分析仪研究空气和N2,CO2,O2不同比例组成的混合气体氛围下热失重特性以及升温速率对其影响,采用AKTS软件进行动力学分析。结果表明：莜麦秸秆热解过程可分为干燥（30～140℃）、挥发（140～370℃）、炭化（370～900℃）3个阶段;气体氛围主要影响热解的炭化阶段,对干燥和挥发阶段影响较小;升温速率影响挥发和炭化阶段,升温速率越快,反应速率越大;当热解气氛为15%O2-5%CO2-80%N2混合气体（气体2）时,热解过程所需活化能最少,平均活化能为139.86 kJ/mol。研究结果可为高寒坝上地区生物质秸秆能源化利用提供一定理论依据。     

Combustion characteristics of a swirling inverse diffusion flame upon oxygen content variation

The combustion characteristics of a swirling inverse diffusion flame (IDF) upon variation of the oxygen content in the oxidizer were experimentally studied. The oxidizer jet was a mixture mainly composed of oxygen and nitrogen gases, with a volumetric oxygen fraction of 20%, 21% and 26%, and liquefied petroleum gas (LPG) was used as the fuel. Each set of experiment was conducted with constant oxygen content in the oxidizer. When the oxygen was varied, the changes in flame appearance, flame temperature, overall pollutant emission and heating behaviors of the swirling IDF were investigated. The swirling IDFs with different oxygen content in the oxidizer have similar flame structure involving a large-size and high-temperature internal recirculation zone (IRZ) which favors for thermal NO formation, and the thermal mechanism dominates the NO production for the swirling IDFs. The use of nitrogen-diluted air (with 20% oxygen) allowed the IDFs to operate at lower temperature with reduced NO_x formation, compared to the case of air/LPG combustion (with 21% oxygen). Meanwhile, an increase in CO emission is observed. With oxygen-enriched air (26% oxygen), the increase in temperature and EINO_x under lean conditions is more significant than under rich conditions. With 26% oxygen in the oxidizer stream, the IDF produces: (1) a shorter and narrowed navy-blue flame ring located closer to the burner exit, (2) highly luminous yellow flame extending into the central IRZ and above the blue flame ring, (3) a low CO emission, especially under lean conditions, (4) an increase in temperature at low Ф while a decrease in temperature at high Ф, and (5) an increase in EINO_x at all Ф. The heating test using the swirling IDFs in flame impingement heat transfer reveals that the heating rate can be monotonically increased as oxygen content in the oxidizer jet increases under the lean condition (Ф = 1.0). The oxygen enrichment does not contribute to the heating rate under the rich condition (Ф = 2.0), because for the non-premixed combustion of an IDF, the enrichment in oxygen means a lower oxidizer jet Reynolds number and thus less complete combustion occurs as a result of reduced amount of entrained ambient air.     

The influence of temperature and heating rate on the slow pyrolysis of biomass

The slow pyrolysis of biomass in the form of pine wood was investigated in a static batch reactor at pyrolysis temperatures from 300 to 720°C and heating rates from 5 to 80 K min⁻¹. The compositions and properties of the derived gases, pyrolytic oils and solid char were determined in relation to pyrolysis temperatures and heating rates. In addition, the wood and the major components of the wood—cellulose, hemicellulose and lignin—were pyrolysed in a thermogravimetric analyser (TGA) under the same experimental conditions as in the static batch reactor. The static batch reactor results showed that as the pyrolysis temperature was increased, the percentage mass of solid char decreased, while gas and oil products increased. There was a small effect of heating rate on product yield. The lower temperature regime of decomposition of wood showed that mainly H₂O, CO₂ and CO were evolved and at the higher temperature regime, the main decomposition products were oil, H₂O, H₂, hydrocarbon gases and lower concentrations of CO and CO₂. Fourier transformation infra-red spectroscopy and elemental analysis of the oils showed they were highly oxygenated. The TGA results for wood showed two main regimes of weight loss, the lower temperature regime could be correlated with the decomposition of hemicellulose and the initial stages of cellulose decomposition whilst the upper temperature regime correlated mainly with the later stages of cellulose decomposition. Lignin thermal decomposition occurred throughout the temperature range of pyrolysis.     

陕西主要动力煤种燃烧特性的热天平研究

为了研究分析陕西主要煤种的燃烧特性,采用德国NETZSCH STA-409PC型热重分析仪分析了样品质量、升温速率、粒径对煤粉燃烧特性的影响。实验结果表明,随着粒径的减小,神木烟煤的燃烧性能先增强后变弱,粒径75～90μm左右燃烧特性最好。升温速率、样品质量对煤粉的燃烧特性也有影响。随着升温速率的提高,煤粉的着火温度升高,最大失重速率增大,最大失重速率对应的温度升高;随着质量的增加,煤粉的着火温度略有降低,燃尽温度却逐渐增大,最大失重速率明显增大,放热效应的最大温度点逐渐增大,并且煤粉挥发分燃烧低温放热与固定碳燃烧高温放热有一定的分期。     

污泥热解油的燃烧特性及动力学模型

利用热重分析(TG)对污泥热解油的燃烧特性进行了研究,污泥热解油的燃烧过程分为两个阶段.第1阶段为轻质有机物挥发后与氧发生均相燃烧,第2阶段为难挥发有机物与氧发生非均相燃烧,其中第1阶段燃烧反应是其失重的主要原因.分析了升温速率对燃烧特性的影响,发现增大升温速率有利于燃烧.对燃烧过程中烟气的排放规律进行了红外分析(FTIR),从另一角度印证了热重分析的结果.根据热重曲线建立动力学模型,分别对不同升温速率下燃烧过程的两个阶段进行动力学参数计算.活化能的变化趋势再次表明提高升温速率有利于污泥热解油的燃烧.     

Production of waste tyre oil and experimental investigation on combustion,engine performance and exhaust emissions

In this study, waste tyre was pyrolyzed at different conditions such as temperature, heating rate and inert purging gas (N₂) flow rate. Pyrolysis parameters were optimized. Optimum parameters were determined. The main objective of this study was to investigate combustion, performance and emissions of diesel and waste tyre oil fuel blend. Experimental investigation was performed in a single cylinder, direct injection, air cooled diesel engine at maximum engine torque speed of 2200 rpm and four different engine load including 3.75, 7.5, 11.25 and 15 Nm. The effects of waste tyre oil on combustion characteristics such as cylinder pressure, heat release rate, ignition delay (ID), combustion duration, engine performance were investigated. In-cylinder pressure and heat release rate increased with waste tyre oil fuel blend (W10) with the increase of engine load. In addition, ID was shortened with the increase of engine load for test fuels but it increased with the addition of waste tyre oil. Lower imep values were obtained because of the lower calorific value of waste tyre oil fuels. Maximum thermal efficiencies were determined as 28.27% and %25.12 with diesel and W10 respectively at 11.25 Nm engine load. When test results were examined, it was seen that waste tyre oil highly affected combustion characteristics, performance and emissions.     

Thermal analysis and kinetics of coal during oxy-fuel combustion

The pyrolysis and oxy-fuel combustion characteristics of Polish bituminous coal were studied using non-isothermal thermogravimetric analysis. Pyrolysis tests showed that the mass loss profiles were almost similar up to 870℃ in both N_2 and CO_2 atmospheres, while further mass loss occurred in CO_2 atmosphere at higher temperatures due to char-CO_2 gasification. Replacement of N_2 in the combustion environment by CO_2 delayed the combustion of bituminous coal. At elevated oxygen levels, TG/DTG profiles shifted through lower temperature zone, ignition and burnout temperatures decreased and mass loss rate significantly increased and complete combustion was achieved at lower temperatures and shorter times. Kinetic analysis for the tested coal was performed using Kissinger-Akahira-Sunose(KAS) method. The activation energies of bituminous coal combustion at the similar oxygen content in oxy-fuel with that of air were higher than that in air atmosphere. The results indicated that, with O_2 concentration increasing, the activation energies decreased.     

Thermogravimetric-Mass Spectrometric Study of the Pyrolysis Behavior of Shenmu Macerals Under Hydrogen and Argon

The pyrolysis characteristics of macerals separated from Chinese Shenmu coal were systematically investigated using TG-151 pressurized thermobalance coupling with mass spectrometer under 0.1 MPa of Ar and H₂, heating rate of 10°C/min and final temperature of 900°C. The TG/DTG results showed that vitrinite always had a higher volatile matter yield, larger maximum rate of weight loss, lower temperature of the maximum rate of weight loss than inertinite. Inertinite showed high response to the external hydrogen, especially at a higher temperature. The gases evolved during thermogravimetric analysis of macerals were analyzed on-line by mass spectrometer for the relative intensity of H₂O, C₁–C₄, and C₆H₆. An obvious difference in evolution curves could be observed. The content of all gases evolved from vitrinite was higher than those from inertinite in both atmospheres. The amount of H₂O and light hydrocarbons was higher in H₂ than that in Ar, indicating the hydrogenation of oxygen-containing functional groups and free radicals formed during pyrolysis. The evolution curves of H₂O and CH₄ had different peak distributions and evolution temperatures under H₂ and Ar, suggesting the different reaction mechanism during pyrolysis in different atmosphere. The evolution curves also revealed the different structural characteristics among vitrinite, inertinite and the parent coal.     

FTIR–PCFC coupling: A new method for studying the combustion of polymers

Gases released from pyrolysis and partial combustion of various polymers (low-density polyethylene, polystyrene, poly(parabromostyrene), pure and flame-retarded polypolyamide 6, cellulose, and chloroprene) were studied using a new coupling between Fourier transform infrared spectrometry (FTIR) and pyrolysis combustion flow calorimetry (PCFC). Combustion in PCFC was monitored by modifying the combustion temperature between 600 and 900 °C. Decreasing the combustion temperature in PCFC leads to partial combustion and the evolution of CO, but also of methane, acetylene, or ethylene when temperature is very low. The evolution of these gases depends also on the polymer and on the presence of a flame inhibitor, demonstrating that flame inhibition can be studied using this method. A correlation between FTIR–PCFC and FTIR–cone calorimetry coupling was attempted via the CO/CO₂ ratio. The first results show that an “isoconversion temperature” in the cone calorimeter test may be estimated. Polar gases such as chlorinated or brominated gases are not fully observed using this method due to possible adsorption in the transfer line before they reach the FTIR gas cell.     

Optimum conditions for a natural gas combined cycle power generation system based on available oxygen when using biomass as supplementary fuel

Due to the higher oxygen content and lower heating value, the amount of biomass required in a combined cycle, where it is used as supplementary fuel, to meet a given energy demand is such that the biomass consumes almost all of the oxygen remaining from gas turbine combustion process under certain conditions. This situation requires additional air for biomass combustion thus reducing the cycle efficiency and the net work output rate while increasing CO₂ emissions. Three conditions at which the oxygen is completely consumed are identified based on alterations in net fuel utilization. The first condition is linked to fuel utilization, which is observed to be significantly affected by variations in temperatures at three locations in the combined cycle (air temperature entering the gas turbine combustion chamber, gas turbine inlet temperature and HRSG inlet temperatures). The second condition relates to the characteristics of the feedstock (oxygen content of the biomass and heating value of natural gas). The heat loss due to combustion of natural gas and biomass is the third condition that affects oxygen availability. The current work assesses these conditions in order to identify the proper condition at which no additional air is required for supplementary firing of biomass.     

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。