低变质煤微波热解数值模拟研究

采用COMSOL Multiphysics软件对低变质煤微波热解过程进行了数值模拟分析,研究了微波功率、热解时间和煤样位置对微波炉腔体内电场和煤样温度场的影响,以模拟最优工艺条件进行热解实验,并对产物收率和组成进行了表征分析。结果表明:微波功率和煤样位置对腔体内电场和煤样温度场影响十分明显;热解时间对腔体内电场几乎没有影响,而对煤样温度场影响较大。微波腔体中电场强度、煤样的升温速率和热解终温都随微波功率的增大而增大。在腔体中心靠近波导3 cm的位置(-3 cm)时,煤样处在高温区域的面积最大,热解终温最高。数值模拟低变质煤微波热解的最优工艺条件为微波功率700 W、热解时间1 800 s和煤样处于-3 cm位置。在此条件下进行热解实验,其产物兰炭、煤焦油、热解水和煤气的收率(质量分数)分别为70.25%,3.99%,5.31%和20.45%,其中,煤焦油中轻质油含量为37.43%(质量分数),煤气中"富氢"气体组分含量为53.02%(体积分数)。     

次烟煤与高硫焦煤共热解相互影响及动力学研究

为了研究次烟煤与高硫焦煤共热解过程中的相互作用,选取资源相对丰富的水峪高硫焦煤(SC)作为主炼焦煤样,伊宁次烟煤(YC)为配入煤样,通过热重分析技术对2种煤样及其不同配比混煤的热解行为进行了研究,并通过计算动力学参数分析热解过程的动力学特性。结果表明,由于变质程度的不同,煤样SC和YC单独热解的行为差异明显;混煤共热解的失重率随着YC掺入比例的增加而增大,但共热解行为并非SC和YC热解特性的简单加和。动力学分析表明,2种煤及其混煤在不同热解反应阶段的动力学参数不同,各热解阶段的活化能和指前因子数值的大小顺序均随YC掺入比例的增加呈规律性变化,但并非单种煤热解活化能和指前因子数值的简单加权平均,混煤的热解行为是2种原煤相互作用的结果。     

过渡金属硝酸盐浸渍对和丰煤表面形貌及热解行为的影响

采用SEM和FTIR技术分析浸渍过渡金属硝酸盐的脱灰和丰煤样(DC)的表面结构变化特征,利用TG-MS和固定床研究煤样的热解和气体逸出行为,探讨金属组分对半焦结构和焦油组成与品质的影响。结果表明:浸渍Fe~(3+),Ni~(2+(和Co~(2+)的硝酸盐后,煤样表面疏松并重构,热解半焦产率增加,焦油产率下降,其中在Fe组分的作用下,焦油产率比DC热解焦油产率低53.71%。Fe~(3+)有利于CO和CO_2的生成。XRD结果表明:Ni盐经由分解为NiO和还原生成Ni的过程来影响煤样的热解行为,而Fe和Co的作用形态主要为Fe_2O_3和Co_3O_4。在Ni和Co组分的催化作用下,半焦的不饱和度增加。与DC热解焦油相比,Fe,Ni和Co组分均可增加焦油中的轻质组分含量,促进沸点高于300℃的长链烷烃分解,使得C≥17组分含量分别比无金属组分作用时降低23.12%,11.90%和18.59%。     

半焦基催化剂裂解煤热解产物提高油气品质

利用上段热解下段催化的两段固定床反应器,针对府谷煤研究了半焦和半焦负载Co催化剂对煤热解产物的催化裂解效果。结果表明,半焦和半焦负载钴对热解产物催化裂解后,热解气收率增加,焦油收率降低,但焦油中沸点低于360℃的轻质组分含量提高,轻质焦油收率基本保持不变或略有增加。与煤在600℃直接热解相比,在热解和催化温度均为600℃,采用煤样质量20%的半焦为催化剂时焦油中轻质组分质量含量提高了约25%,轻质组分收率基本不变,热解气体积收率增加了31.2%;在热解温度600℃,催化温度500℃时,采用煤样质量5%的半焦负载钴催化剂,焦油中轻质组分质量收率和含量分别提高了约8.8%和28.8%,热解气体积收率增加了21.5%。煤热解产物的二次催化裂解的总体效果是将焦油中重质组分转化为轻质焦油和热解气。     

垃圾衍生燃料与褐煤共热解特性及动力学模型比较

以城市生活垃圾(municipal solid waste,MSW)的典型组成为样本基础,配制具有稳定物理化学性质的垃圾衍生燃料(refuse derived fuel,RDF).通过升温速率控制,探究不同升温速率对垃圾衍生燃料与褐煤共热解的影响;采用Coats-Redfern模型法以及Friedman,Flynn-WallOzawa(FWO)和Kissinger-Akahira-Sunose(KAS)无模型法,得到RDF与褐煤共热解反应动力学参数.结果表明:Coats-Redfern模型中,升温速率为10℃/min时,对应生物质组分及塑料类高分子聚合物热解阶段活化能最低;生物质组分及塑料类高分子聚合物热解阶段最优拟合级数分别为0.5和1.5;随着级数的增长,活化能与级数呈正相关关系.按照Friedman,FWO及KAS无模型法拟合的结果,转化率为α=0.1,α=0.2~0.6,α=0.7~0.9的共热解反应过程具有相似的动力学特性及反应机理.     

生物质与煤共热解特性研究

采用热重分析的方法对三种生物质(花生壳、木屑、核桃壳)和煤样在高纯N2气氛下,按照一定升温速率(20 K/min)分别进行单独热重实验及不同掺混比例生物质与煤样进行共热解实验。结果表明:生物质与煤进行共热解时,随着生物质添加量的增加,样品的失重速率增加,且热解的开始温度向低温区平移并大大缩短了热解所需的时间。     

煤红外快速热解过程中床层对二次反应的影响

针对煤快速热解研究中样品添加量少(mg级)、焦油收集难等问题,本研究利用压片法制备微薄厚度(mm级)的煤层,并采用红外加热装置考察大添加量(g级)、微薄煤层的快速热解特性。对比堆积煤样和不同煤压片厚度(1.5~3 mm)与个数(1~2)的压片煤样热解特性发现,压片煤层热解过程的二次反应受到明显抑制,焦油产率急剧增加,在1000℃时达9.96%,为格金分析的1.5倍,实现油气产量的同步增长。模拟蒸馏分析发现,堆积状态下焦油以沥青质为主,而微薄煤层制焦油含大量轻油、酚油、萘油、洗油和蒽油。GC-MS和FTIR分析表明,随煤层厚度和个数的减少,焦油组分和含量提高,芳香烃类和含氧官能团吸收增加,进一步验证煤快速热解过程中煤层厚度对焦油产率和品质的影响,揭示在二次反应充分抑制下煤高温热解的初级反应特性。     

不同热解终温对化产品收率的影响

为了研究不同热解终温对低阶煤热解产品产率及性质的影响,在750,800,850℃的热解温度下,利用1 kg热解和化产品回收装置对煤样进行了模拟热解实验研究。结果表明:3个温度所得兰炭都属于V-1级和FC-1级,750℃时兰炭产率、Vd均较高。气相产物中,H2和CO含量均较高,3个温度中的H2产量均大于40.00%,且850℃含量最高;CO则在750℃时取得最大值(17.14%)。最后对热解化产品的组成及收率进行了分析测定。为了更好地指导生产,对化产品收率及性质的预测应在理论研究的基础上,结合模拟热解实验研究。     

半焦催化裂解原位煤热解焦油的研究

在两段固定床反应器内考察了不同半焦对府谷煤热解产物的催化裂解效果。结果表明,不同半焦对煤热解产物催化裂解后,焦油收率降低,但焦油中沸点低于360℃的轻质组分质量分数明显增高。与煤在600℃直接热解相比,在热解和催化温度均为600℃时,采用煤样质量20%的半焦为催化剂时催化效果最好,其中轻质焦油收率基本不变,焦油中轻质组分质量分数提高了25%。半焦的表面结构和灰分都对煤热解产物的催化裂解有一定效果。在比表面积较低时,半焦中的灰分对原位煤热解焦油的裂解作用比较明显;随着比表面积的增加,灰分的影响越来越弱,半焦表面结构的影响越来越明显。     

寻甸褐煤的催化多段加氢热解过程

利用热重技术对寻甸褐煤的催化多段加氢热解过程进行了研究,考察了不同的催化剂制备方式对该过程的影响,并在固定床上研究了产物的分布和焦油组成.结果表明：催化剂的存在明显增加了自由基的生成及其被氢化饱和的速率,从而导致了总转化率的提高;与不加催化剂相比,当Mo负载量为0.2%时, 350 ℃的停留过程使转化率从26%激增到50%;不同Mo负载量下的停留对加氢热解过程中的低温峰和高温峰的影响不同;经超声处理催化剂制备的煤样,其加氢热解在任何温度下的转化率均高于用电磁搅拌制备的结果,而且热解温度越高其效果越明显;超声负载催化剂的多段催化加氢热解的总转化率远远高于通过电磁搅拌制备的煤样;催化条件下的多段加氢热解过程改变了产物的分布,并明显提高了焦油中轻质组分的含量,苯类、酚类和萘类收率分别增加了42%、37.8%和115.4%.     

Laser and furnace pyrolyzed organosilazane-based glass/ZrO2 composite coating system—A comparison

The laser pyrolysis of a ceramic coating system composed of an organosilazane (Durazane 1800) with monoclinic ZrO₂ and glass particles as fillers was investigated. The samples were produced by spray coating on pre-treated stainless steel substrates and subsequently pyrolyzed by Nd:YV0₄ laser radiation (λ =1064 nm). The interaction of laser radiation with the polysilazane-based glass/ZrO₂ coating system led to formation of semi-crystalline dense coatings with a thickness up to 20 μm in a short time.Laser pyrolyzed ceramic coatings were characterized and compared with furnace pyrolyzed coatings. The microstructure of the coatings was investigated by scanning electron microscopy (SEM). Additionally the corrosion resistance and mechanical properties, such as hardness, adhesive strength and the tribological behaviour have been investigated. Ceramic coatings generated by laser pyrolysis showing promising mechanical properties, a super-hydrophobic surface as well as a high corrosion resistance.     

基于FUSION模型的碳基固废热解产物产率预测

低温热解是清洁转化碳基固废、实现汇碳和减排的成熟有效方法之一。通过建立预测碳基固废热解产物产率的数学模型可以极大缩短科研探索时间,优化调控热解反应过程。本研究以80组热解实验数据为样本,首先对神经网络（ML）、支持向量机（SVM）和线性回归（LR）模型进行训练和测试,分析机器学习的有效性,然后将三种模型通过算法融合,建立具有自适应性的FUSION模型。最后,利用实验数据对该模型进行进一步的训练和测试,形成适合预测碳基固废热解产物的数据模型。融合模型能够有效解决单一模型在预测碳基固废热解产物分布过程中,受热解交互作用影响,预测精度波动的问题。同时,该模型预测值精度较高,预测值与实验值的相对误差<2%。     

Measuring the Size Distribution of Atmospheric Organic and Black Carbon Using Impactor Sampling Coupled with Thermal Carbon Analysis: Method Development and Uncertainties

A method for determining the mass size distribution of organic and black carbon (OC and BC) in atmospheric aerosols is introduced. The method relies on a particle sampling with 2 parallel size-segregating devices, a 12-stage Small Deposit area low pressure impactor (SDI) and a virtual impactor (VI), and the subsequent analysis of the samples with thermal and thermal-optical methods, respectively. The method development revealed that SDI is, like other sampling methods, susceptible to serious sampling artifacts and OC pyrolysis during thermal analysis. However, some of the SDI's limitations can be overcome by parallel VI measurements. The good correlation between the SDI and the VI data for most of the samples collected here indicates that under most conditions, the lack of the pyrolysis correction for the SDI samples does not cause significant errors in the OC/BC split. Valuable features of this method are that it offers a good size resolution in both sub- and supermicron size fractions, indicates if there has been serious positive or negative artifacts for OC during sampling, reveals if the samples have been affected by OC pyrolysis during thermal analysis, and provides semiquantitative means by which the OC and BC size distributions can be corrected for the samples being affected by OC pyrolysis. Application of the method to real atmospheric samples is demonstrated, and the major areas requiring further research and/or method development are identified.     

Microkinetics of high-temperature pyrolysis

High-temperature pyrolysis of various classes of polymers have been discussed. For the non-carbonizing polymers it was shown that polymer structure can affect the pyrolysis characteristics. Data on the high-temperature pyrolysis of some polypropylene samples with different crystallinity have been presented. Modification of the standard method allowing one to obtain kinetic data from the single experiment was discussed. A kinetic model for the degradation of char-forming polymers in conditions of high-temperature pyrolysis has been suggested. It has been supposed that pyrolysis of carbonizing polymers proceeds in some (two in present work) parallel stages with different activation energies, temperatures and pyrolysis rates. Questions of the applicability of the suggested model to describe the various types of charring systems have been discussed. High-temperature pyrolysis for a number of epoxy resin-based polymeric compositions have been investigated. Kinetic parameters of the pyrolysis have been computed. © 1998 John Wiley & Sons Ltd.     

挥发分-半焦交互反应对生物质热解半焦特性的影响

挥发分-半焦交互作用是生物质热化学利用过程普遍存在的现象。为了解析交互反应对生物质热解半焦特性的影响,利用一阶固定床/流化床反应器及快速热裂解仪进行实验。针对挥发分-半焦交互反应,对碱金属和碱土金属（AAEM）元素的析出特性展开了研究,同时分析了交互反应对生物质热解半焦反应活性的影响。结果表明在700~900℃范围内,交互反应的存在使得热解成焦率较无交互反应下有所提高。热解过程中交互反应导致了单价K元素析出量增加,对二价Ca/Mg元素的析出影响较小。挥发分-半焦交互反应的存在使得半焦反应活性对温度的敏感度降低,随温度的升高其反应速率的下降幅度变缓。     

Potassium catalysis in the pyrolysis behaviour of short rotation willow coppice

Short rotation willow coppice (SRC) and a synthetic biomass, a mixture of the basic biomass components (cellulose, hemicellulose and lignin), have been investigated for the influence of potassium on their pyrolysis behaviours. The willow sample was pre-treated to remove salts and metals by hydrochloric acid, and this demineralised sample was impregnated with potassium. The same type of pre-treatment was applied to components of the synthetic biomass. Characterisation was performed using thermogravimetric analysis with measurement of products by means of Fourier transform infrared spectroscopy (TGA-FTIR) and pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). A comparison of product distributions and kinetics are reported. While the general features of decomposition of SRC are described well by an additive behaviour of the individual components, there are some differences in the magnitude of the influence of potassium, and on the products produced. For both SRC and the synthetic biomass, TGA traces indicate catalytic promotion of both of the two-stages of biomass decomposition, and potassium can lower the average apparent first-order activation energy for pyrolysis by up to 50 kJ/mol. For both SRC and synthetic biomass the yields and distribution of pyrolysis products have been influenced by the presence of the catalyst. Potassium catalysed pyrolysis increases the char yields markedly and this is more pronounced for synthetic biomass than SRC. Gas evolution profiles during pyrolysis show the same general features for both SRC and synthetic biomass. Relative methane yields increase during the char formation stage of pyrolysis of the potassium doped samples. The evolution profiles of acetic acid and formaldehyde change, and these products are seen in lower relative amounts for both the demineralised samples. A greater variation in pyrolysis products is observed from the treated SRC samples compared to the different synthetic biomass samples. Furthermore, substituted phenols from lignin pyrolysis are more dominant in the pyrolysis profiles of the synthetic biomass than of the SRC, implying that the extracted lignins used in the synthetic biomass yield a greater fraction of monomeric type species than the lignocellulosic cell wall material of SRC. For both types of samples, PY-GS-MS analyses show that potassium has a significant influence on cellulose decomposition markers, not just on the formation of levoglucosan, but also other species from the non-catalysed mechanism, such as 3,4-dihydroxy-3-cyclobutene-1,2-dione.     

主要垃圾组分热解动力学模型的优化及比较

引言 垃圾热解技术是近年来备受关注的热点技术这是因为该技术是在隔绝空气的还原性条件下完成的,产生的酸性气体、二(口恶)英等污染物很少另外,热解产物(包括可燃气体、焦油和焦炭)既可以储存,还可以进入下一级燃烧室,在低空气比下燃烧.     

Metal-insulator transition in iodinated amorphous conducting carbon films

In this work, the effect of iodine incorporation on the electrical conductivity, magnetic susceptibility (χ) and magnetoresistance (MR) of amorphous conducting carbon (a-C) films has been discussed. Variation in conductivity of a-C films depends on the sample preparation conditions and iodine concentration. Evidence of metal-insulator (M-I) transition as a function of pyrolysis temperature is observed for iodinated (a-C:I) samples. The temperature dependent magnetic susceptibility of a-C:I sample shows a Curie behavior at low temperatures. The positive magnetoresistance is observed for all the samples irrespective of the conduction regimes. This is accounted by the electron-electron interaction in the a-C:I system.     

小分子烃类蒸汽热裂解自由基机理模型研究方法的探讨

由于热裂解存在反应时间短、自由基数量多、浓度小,且不同原料产生的不同自由基之间、反应深度较大时管壁处于高温和停留时间所生成的不同自由基与主流体间的相互作用会随时改变反应路径,并影响到产物分布,因此造成了用实验方法研究单体烃热裂解反应机理的困难。将Materials Studio软件与Aspen Plus软件相结合来研究单体烃热裂解的自由基反应机理,并通过对乙烷热裂解一次反应机理、乙烷和丙烷混合热裂解相互作用机理、动力学数据准确性对比及正已烷空间位阻的影响,对研究方法进行了论述。结果表明,数值模拟的理论方法与实验方法相比,可以深入了解实验研究不可能达到的一些机理细节问题,如果将实验研究和模拟研究相结合,可避免目前动力学模型研究中的各种假设,提高机理模型研究的准确性,为工业生产预测提供高精度的机理模型。     

The pyrolysis of extracted solids from oxidized kraft black liquor after lignin precipitation

A laboratory investigation of the possibilities for the reduction of odor from Kraft mill stack gases by lignin precipitation from oxidized Kraft black liquor and subsequent pyrolysis of the filtrate solids has been carried out. Samples of oxidized black liquor were acidified with sulphuric acid and the lignin precipitate extracted. The extraction scheme indicates that > 90% w/w of the sodium in the original black liquor samples can be retained in the filtrate after lignin removal at final pH 2.0. The evaporated filtrate solids containing the bulk of the black liquor inorganic chemicals were pyrolyzed and the evolved hydrogen sulphide, methyl mercaptan and dimethyl sulphide monitored by gas-chromatography. Gas-chromatograph traces displaying the increase and decrease of methyl mercaptant evolution levels on pyrolysis of the filtrate solids to increasing temperatures are shown. A thermogravimetric technique was used to investigate the decomposition rates of the extracted samples and these rates correlated with the levels of sulphur gases evolved on pyrolysis. Heats of combustion were determined by bomb calorimetry. Sulphur losses from the filtrate solids and the Kraft black liquor total solids are compared. The results show a significant decrease in the evolution of organo sulphur gases from samples of ligninextracted black liquor solids in comparison with original total solids samples, an increase in the level of hydrogen sulphide evolution however, presents a problem.