城市污泥耦合锯末共热解特性及动力学分析

为实现城市污水污泥与锯末共热解的工业应用,利用热重分析仪对污泥耦合锯末共热解过程进行了实验与理论研究,揭示了锯末添加比例、升温速率对污泥热解特性的影响,并基于Coats-Redfern法,结合20种常见固体热解机理函数确定了污泥耦合锯末共热解过程最优热解动力学模型。结果表明:锯末相比污泥具有更低的表观活化能,最大失重速率是污泥的4倍;锯末的添加使得热重分析(TG)曲线向下偏移,最大失重速率明显增大,挥发份析出特性变强;随着升温速率的增大,固态残渣增加,最大失重速率减小,不利于热解反应的进行;按7∶3比例混合的污泥锯末耦合热解微分热重分析(DTG)曲线峰前(230~350℃)表观活化能为38.81 k J/mol,最优动力学模型为D_5-3D扩散模型;峰后(350~500℃)表观活化能为29.93 k J/mol,最优动力学模型为C~2-化学反应模型。     

污泥与木屑共热解特性研究

文章采用污泥、木屑为原料,在氮气气氛下进行热重实验,研究了升温速率和木屑添加量对污泥与木屑共热解特性的影响规律,并进行动力学分析。研究结果表明:随着升温速率的增加,样品挥发分析出阶段向高温方向移动,最大失重速率增加;随着木屑添加量的增加,样品总失重量及最大失重速率均显著增加。动力学分析认为:污泥热解的反应机理为三维扩散,机理函数为Z-L-T函数;污泥与木屑共热解的反应机理为成核和生长,机理函数为Avrami-Erofeev函数。污泥热解活化能为287.29～390.57 kJ/mol,污泥与木屑共热解活化能为170.16～277.05 kJ/mol,木屑的加入降低了污泥的热解活化能。     

纤维素的加压热解特性及动力学研究

利用加压热重仪对纤维素进行了热重分析实验,获得了不同升温速率(5,10,20 K/min)和不同压力(0.1,0.5,1,1.5,2 MPa)条件下的热重曲线TG和失重速率曲线DTG,并通过热分析数学方法获得了热解动力学参数。结果表明,在各压力条件下,提高升温速率,纤维素主热解区间均往高温区移动,热解略有加深;在各升温速率条件下,增大压力,主热解区间均往低温区移动,热解时间缩短,剩余残渣百分比增大;在同一升温速率下,随着压力的增大,热解活化能增大,且升温速率越大,活化能随压力增大越明显;在同一压力下,随着升温速率的提高,热解活化能增大,且压力越大,活化能随升温速率增大趋势越明显;在各条件下热解活化能和指前因子存在着较好的补偿效应。     

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。     

煤催化热解过程动力学的研究

由ＷＲＴ－２型热天平测定上海市工业用煤在添加不同类型催化剂（或氧化剂）时的热解曲线，由此确定不同催化剂添加量时的热解动力学参数（表观活化能Ｅ，频率因子Ｋ０，反应级数ｎ），并根据动力学参数的变化规律建立催化热解模型。试验结果表明：催化剂可促进煤热解过程的发生，但不能使挥发份产量提高；氧化剂的效果不如催化剂；热解过程中，热重微分曲线上的峰值点所对应的温度Ｔｍａｘ可作为判断催化剂效能的特征参数；Ｔｍａｘ     

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。     

城市污水污泥的热解动力学特性研究

采用差示热天平获得上海程桥污水处理厂污泥的TG、DTG曲线，对干燥污泥的热解行为及其动力学规律采用热重分析法进行了研究。实验结果表明：干燥污泥的热解过程中有2个失重速率比较高的区域，这2个区域以挥发分的析出为主。通过热重分析法，求解了这2个区域的化学反应动力学参数——频率因子A和活化能E，对其反应机理进行了分析。     

CO2/N2气氛下煤粉热解气化特性研究及动力学分析

采用热重分析仪在CO_2/N_2气氛下对煤粉进行了非等温热解气化实验研究,分析了程序升温速率和CO2浓度对煤粉热解、气化特性的影响,并采用Coats-Redfern法、FWO法和KAS法对煤粉热解、气化过程进行了动力学分析。实验结果表明:在CO_2/N_2气氛下,随着程序升温速率的升高,热解和气化反应速率均增大,表观活化能均减小。在CO_2/N_2气氛下,CO2不会影响煤粉的热解过程,而对气化过程有决定性影响,CO2浓度越高,气化反应速率越大,表观活化能越大。在CO_2/N_2气氛中煤粉气化反应的表观活化能E和表观指前因子A之间具有动力学补偿效应。在相同气氛下,煤粉气化反应的表观活化能随转化率的增大而减小。     

氢氧化钾催化木屑热解特性影响研究

为了考察钾盐催化剂对生物质热解特性的影响,实验以木屑为原料,采用浸渍方法加入不同质量KOH,干燥和粉碎后进行热重和热解实验。实验中使用热重分析仪对样品进行热重实验,采用Starink法进行动力学分析,使用自行搭建的固定床热解炉研究热解温度和KOH添加量对木屑热解的影响。热重结果表明,加入KOH后热解温度降低,改变了木屑热解路径,降低了热解失重速率。动力学分析结果表明,加入KOH后使木屑主要热解区间表观活化能降低。热解实验结果表明,加入KOH后,木屑热解产物中热解油产率降低,热解合成气和半焦产率增加。热解产物经分析发现,加入KOH后,热解合成气中氢气含量显著增加,热解油品质有所改善,低KOH添加量对半焦孔隙结构影响较小,高KOH添加量使半焦的孔隙更加发达。     

市政污泥与木屑共热解特性及动力学分析

采用热重分析法对市政污泥、木屑及其不同比例的混合样品热解特性进行了分析,研究了升温速率和混合比例对热解过程的影响。对污泥和木屑进行单独热解时,木屑比污泥的反应活性更高;随着升温速率的增大,二者的挥发分析出指数D均有增大,但升温速率对污泥挥发分析出的影响更大;污泥与木屑共热解改善了污泥热解过程的综合热解释放特性,有利于热解反应的进行;随木屑添加比例的增加D值呈指数增长,在木屑添加比例为80%时,D达到最大值118.18×10-8,但仍低于理论值141.67×10-8,说明存在竞争作用。文章采用FWO(Flynn-Wall-Ozawa)和Starink方法,分别计算木屑添加比例为80%的共热解表观活化能。当转化程度α为0.1～0.8时活化能变化较小,α为0.9时活化能分别突增到761.64,786.12 kJ/mol。这说明共热解过程可分为150～520℃和520～1 000℃两个温度阶段,与污泥单独热解相比,降低了转化率达到90%时的终温。     

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。     

Devolatilization Characteristics of Shenmu Coal Macerals and Kinetic Analysis

The pyrolysis of Shenmu coal macerals was performed in TG151 thermobalance. The volatile matter evolved in primary and secondary devolatilization and devolatilization kinetics were studied. The volatile matter evolved during primary devolatilization is the major part of the total volatile matter, especially for vitrinite. The percentage of volatile matter evolved during primary and secondary devolatilization suggested that inertinite have higher thermal stability. Though the heating rate can affect the percentage of volatile matter evolved during primary and secondary devolatilization, the order of volatile matter in all the temperature range is the same: vitrinite > parent coal > inertinite. The kinetic analysis of devolatilization using distributed activation energy model (DAEM) shows that the activation energy existed relatively large error at the conversion of initial 10% and final 10%. And the conversion of 10% to 90% was used to describe the variation of activation energy during pyrolysis. The activation energy of vitrinite appeared a minimum of about 50% conversion, but that of inertinite always increased as pyrolysis went on, indicating the different structure and chemical composition between them. Inertinite has higher activation energy and lower pyrolysis rate than vitrinite.     

稻壳和褐煤热解特性的初步研究

利用TG-DSC联用分析稻壳与褐煤热解过程中热失重规律及吸放热情况,结果发现,稻壳的热失重率较大,共热解失重过程相当于二者单独热失重过程的叠加。通过DSC曲线分析稻壳与褐煤热解过程的吸放热量显示,与二者单独热解过程不同的是共热解在高温热分解阶段须吸收大量的热量。利用气相色谱分析不同温度下稻壳与褐煤热解气体产物各组分比例,并与热失重过程相对应分析气体产物变化规律,结果发现,H2和CH4气体组分变化规律相同;与褐煤热解相比,稻壳热解气体产物中CO气体组分较多。总体而言,共热解产物是二者单独热解产物的简单加和,但共热解过程吸放热量变化却显示二者存在热量交换和相互影响。     

污水污泥热解过程的能量平衡与反应热分析

依据能量守恒定律,通过分析污水污泥热解过程的能量利用、耗散和回收情况,提出了污泥热解制取三相产物处理系统的能量平衡模型,分析计算了污泥热解反应热,并利用回收率和耗能比对热解处理系统的耗能状况进行了评价.结果表明:能量利用过程中总存在能源的耗散,减少能耗的主要方式是尽可能提高产物的能值、降低热消耗和废弃的能量;在不同的热解工况下,热量损失的差别明显,热解停留时间长、升温速率慢、热解温度高均会导致输入能量和热损失增大;能耗评价也验证了热解技术能够回收更多的能量,可以获得更大的能耗比.     

High temperature steam gasification of wastewater sludge

High temperature steam gasification is one of the most promising, viable, effective and efficient technology for clean conversion of wastes to energy with minimal or negligible environmental impact. Gasification can add value by transforming the waste to low or medium heating value fuel which can be used as a source of clean energy or co-fired with other fuels in current power systems. Wastewater sludge is a good source of sustainable fuel after fuel reforming with steam gasification. The use of steam is shown to provide value added characteristics to the sewage sludge with increased hydrogen content as well total energy. Results obtained on the syngas properties from sewage sludge are presented here at various steam to carbon ratios at a reactor temperature of 1173 K. Effect of steam to carbon ratio on syngas properties are evaluated with specific focus on the amounts of syngas yield, syngas composition, hydrogen yield, energy yield, and apparent thermal efficiency. The apparent thermal efficiency is similar to cold gas efficiency used in industry and was determined from the ratio of energy in syngas to energy in the solid sewage sludge feedstock. A laboratory scale semi-batch type gasifier was used to determine the evolutionary behavior of the syngas properties using calibrated experiments and diagnostic facilities. Results showed an optimum steam to carbon ratio of 5.62 for the range of conditions examined here for syngas yield, hydrogen yield, energy yield and energy ratio of syngas to sewage sludge fuel. The results show that steam gasification provided 25% increase in energy yield as compared to pyrolysis at the same temperature.     

松木锯屑在N2和CO2气氛下的热解特性研究

对松木锯屑在N2和CO2气氛下的热解反应进行了分析,分别运用Ozawa法和Coats-Redfern法求得松木锯屑在N2气氛下的反应活化能与适合的机理函数。试验结果表明:在CO2和N2气氛下,松木锯屑热解过程分为干燥、热解预热、热解和高温煅烧4个阶段。随着升温速率的提高,热解曲线向高温一侧移动;较之在N2气氛下的热解过程,松木锯屑在CO2气氛下热解完成后的残余质量更少,由此可推断:CO2气氛有利于热解产生更多的气体产物。     

Pyrolysis behaviors of oilfield sludge based on Py-GC/MS and DAEM kinetics analysis

In this work, the effect of heating rate (10, 20, 50 and 100 K min^?1) on oilfield sludge pyrolysis was studied on thermogravimetric analyzer (TG) and the pyrolysis kinetics was investigated by means of the distributed activation energy model (DAEM). The TG/DTG curves of oilfield sludge pyrolysis are shifted to higher temperatures evidently as the heating rates increase and the intensity of DTG peak is increased with the increase of heating rate. The pyrolysis process of oilfield sludge could be divided into two stage. Kinetics analysis by DAEM revealed that the activation energy (E) decreased from 99.54 to 44.19 kJ mol^?1 in the conversion ratio range of 0.1–0.2, and then E raised up to 184.63 kJ mol^?1 with increase of the conversion ratio. In addition, Py-GC/MS experiments were performed to investigated the types of products and their proportions in pyrolysis process of oilfield sludge at different pyrolysis temperature (758, 943 and 1193 K) and the corresponding mechanism for oilfield sludge pyrolysis was briefly discussed. Cracking depth of oilfield sludge can be significantly improved by increasing pyrolysis temperature, and the light molecule weight of hydrocarbons (C₄C₁₀) increased with the increase of pyrolysis temperatures. Moreover, the increase of pyrolysis temperature was also conducive to the decrease of the polycyclic compounds. However, there is an abrupt increase of aromatics yields (14.69%) when temperature is up to 1193 K. The change of content of gasoline and diesel range hydrocarbons in pyrolysis products of oilfield sludge with pyrolysis temperature was also discussed.     

城市固体废弃物热重分析及热解动力学研究

对城市垃圾典型组分（塑料、橡胶、果皮、织物、纸板等）进行热重分析及热解动力学研究。热重分析结果表明，塑料组分开始分解的温度较高，但分解速率最快；橡胶组分开始分解反应的温度相对较低，且分解速率相对较慢。果皮、织物和纸板类以纤维和木质类物质为主要成分，其热解特性较为相似。热解动力学研究表明，橡胶的热解活化能最高，最难分解，且热解符合二维扩散机理；塑料的热解相对较容易，符合一维扩散机理。而果皮、织物和纸板类的活化能较低，它们的热解符合体积缩小机理。     

Catalytic pyrolysis of microalgae to high-quality liquid bio-fuels

The pyrolytic conversion of chlorella algae to liquid fuel precursor in presence of a catalyst (Na₂CO₃) has been studied. Thermal decomposition studies of the algae samples were performed using TGA coupled with MS. Liquid oil samples were collected from pyrolysis experiments in a fixed-bed reactor and characterized for water content and heating value. The oil composition was analyzed by GC-MS. Pretreatment of chlorella with Na₂CO₃ influences the primary conversion of chlorella by shifting the decomposition temperature to a lower value. In the presence of Na₂CO₃, gas yield increased and liquid yield decreased when compared with non-catalytic pyrolysis at the same temperatures. However, pyrolysis oil from catalytic runs carries higher heating value and lower acidity. Lower content of acids in the bio-oil, higher aromatics, combined with higher heating value show promise for production of high-quality bio-oil from algae via catalytic pyrolysis, resulting in energy recovery in bio-oil of 40%.     

逐级萃取对准东煤的热解特性影响

为探究洗煤对准东煤热解特性的影响机理,采用逐级萃取法对准东煤进行洗煤处理。利用热重分析仪对比研究了洗煤对准东煤热解的影响规律,结合煤样热解前后样品的微观结构分析了洗煤对准东煤热解过程的作用机理,并采用分布活化能模型对煤样的热解反应动力学参数进行了计算。结果表明:脱除与煤中有机质结合的矿物质可以使煤样中产生大量新的多孔结构;洗煤会影响煤孔隙结构与官能团结构,导致煤样在热解初始阶段与热缩聚阶段失重量与失重率减少,主热解阶段失重量与失重率增大,并有利于煤焦微晶结构向石墨化进程演化;分布活化能模型可以较好地描述煤样的热解过程,随着洗煤程度的加深,活化能的分布曲线f(E)极大值对应的活化能由265.32升高至377.20 kJ/mol,说明热解反应活化能的主要分布区间向活化能较高的区域移动。