防火密封胶热分解动力学研究

利用热重-差热分析仪研究了防火密封胶在空气氛围下不同升温速率的热解特性规律。研究结果表明:在空气氛围下,随着升温速率的增大,防火密封胶的各阶段热解起始温度和终止温度都向高温方向移动。防火密封胶在空气氛围下热解分为三个阶段:第一阶段为主要失重阶段;第二阶段由于有炭层的形成,所以失重较小;随着温度的升高,热量的积累,最后冲破了炭层,致使燃烧热分解的第三阶段发生。通过采用Kissinger法、Flynn-Wall-Ozawa法和Starink法计算了防火密封胶的活化能E,其平均活化能分别为111.970、111.950和106.442 kJ/mol,结果基本一致。     

生物质炭化原料选择及需热量分析

从生物质原料的工业分析结果和木质素含量两个角度出发,分析了二者对生物质炭化的影响.对生物质炭化原料进行选择,认为木材类生物质适合作为生物质炭化的原料,可加强对树木枝条、锯末及薪炭林的炭化;为实现生物质炭化的工业化,还应设计利用烟气余热等热源来热解生物质的换热器,这项设计需知道生物质热解需热量.运用热重-差示扫描(TG-DSC)同步热分析仪对选用的木屑进行热解实验并利用DSC曲线对木屑炭化需热量进行分析.结果表明,木屑炭化终温为500℃时(初始温度为40℃),需热量为491kJ/kg.提出DSC曲线在工业用热解换热器传热设计和校核中的应用方法.     

酸性糠醛残渣热解实验及热解炭性能研究

为解决糠醛渣的堆放及资源的合理利用,以糠醛渣为研究对象,分别在同步热分析仪及管式炉上进行热解实验研究,主要考察热解终温、升温速率、碳酸钠含量对糠醛渣热解产物分布及热解炭性能的影响。同步热分析仪分别以10—40℃/min的升温速率升高到850℃(10℃/min添加碳酸钠);管式炉上以10℃/min的升温速率到达热解终温300—600℃。结果表明:热重分析确定热解失重过程为干燥段、挥发分逸出段、热解炭化段3个阶段,确定主要热解温度区间为300—600℃。添加碳酸钠后抑制水分的析出,失重变化率峰值变大,表明碱金属钠盐促进纤维素的分解。随着热解温度的升高热解碳的p H值逐渐增大,热解温度为400℃时达到最高的亚甲基蓝脱色率44.4%。热解炭可进一步用于活性炭染料吸附。     

热降解动力学方法研究ABS的降解机理

在空气气氛下,采用热重分析(TGA)研究了不同升温速率下丙烯腈-丁二烯-苯乙烯共聚物（ABS）的热降解过程,分别使用Flynn-Wall-Ozawa法和Kissinger法对降解过程进行动力学分析。结果表明,ABS降解包含2个阶段,350~450 ℃之间发生降解反应,同时伴有交联反应,降解活化能（Ea）在200 kJ/mol左右,转化率在80 %~90 %时发生炭化反应,Ea提高到262.81 kJ/mol;500~600 ℃之间是残炭的氧化,Ea降低到130 kJ/mol左右,炭层稳定性较差。ABS的降解过程反应级数为0.946,降解受到随机成核与生长机理控制,降解在ABS基体内进行,而不是表面,所以降解气体燃烧不完全,易产生黑烟和熔融滴落。     

葵花杆的热解特性及热解产物分析

为充分利用生物质葵花杆,采用同步热分析仪以升温速率为影响因素对葵花杆的热解特性进行研究,利用Coats-Redfern积分法计算主要阶段热解动力学参数,并采用气相色谱/质谱联用仪对热解产物进行了定量分析.研究结果表明:葵花杆的热解过程可分为预热干燥、主要热解及炭化3个阶段;随着升温速率的增大,葵花杆热解的TG曲线向高温...     

升温速率对稠油氧化特征影响的实验研究

为了研究升温速率对稠油氧化过程中的影响,采用热重分析仪和差示扫描量热仪对不同升温速率下的稠油氧化特征进行了研究。结果表明:升温速率越快原油失重速率曲线向高温侧轻微移动,原油氧化反应速率加快,燃料沉积阶段时间变短,导致了燃料沉积阶段裂解反应不充分。在采用Coats-Redfern方法对原油氧化动力学参数进行计算时发现,升温速率对反应机理函数的选取并无影响,但各氧化阶段活化能的计算结果呈现差异性。分析DSC曲线显示,升温速率加快,原油氧化放热量增加,特别在高温氧化阶段增加尤为明显。因此,说明升温速率对稠油氧化过程有较大的影响。     

沥青球在流化床反应器中氧化不熔化及后续炭化行为的研究

用流化床反应器对沥青球进行了氧化不熔化处理,考察了不同温度下沥青球的氧化行为及其后续炭化行为。采用热重分析仪、傅里叶变换红外光谱仪、元素分析仪及扫描显微镜对氧化沥青球和炭化球进行了表征。结果表明:流化床反应器强化了沥青球氧化不熔化的传热和传质过程,在0.21 m/s的临界流态化气速下,以0.5℃/min快速升温至300℃进行沥青球的不熔化处理,得到具有良好表面形貌和球形度的氧化沥青球及其炭化球,极大改善了沥青球制备过程中氧化不熔化的耗时、耗能问题。     

采用同步热分析仪研究氰酸酯固化过程

采用Q600型同步热分析仪研究了氰酸酯的热固化过程,确定了固化工艺参数,根据Kissinger及Ozawa方程分别计算出固化活化能,并通过红外光谱法得到不同固化阶段氰酸酯的转化率。结果表明,氰酸酯可以在同步热分析仪炉内固化,固化工艺条件为:229℃/2 h+269℃/4 h+313℃/2 h,固化活化能分别为76.31 kJ/mol和81.70 kJ/mol,CE单体转化率为97.43%,固化过程中失重为8.5%。利用同步热分析研究氰酸酯固化过程是可行的。     

磷石膏脱水反应动力学研究

利用Netzsch STA 409PC型TG-DSC同步热分析仪,在升温速率分别为2.5,5.0,10,20℃/min的条件下对磷石膏脱水进行测试,研究其动力学和反应机理。结果表明,磷石膏脱水分为2步进行,产物分别是CaSO4.0.5H2O和CaSO4。2步脱水都遵循Avrami-Erofeev方程,脱水速率受晶核的形成及生长控制,活化能分别为97.67 kJ/mol和92.63 kJ/mol。利用得到的动力学方程对磷石膏在不同温度下的脱水过程进行模拟计算,结合工业上采用磷石膏制备建筑石膏的工艺和控制问题进行了讨论和分析。     

农业废弃物葵花秆热解过程几种动力学模型结果比较

利用同步热重分析仪考察了不同升温速率下葵花秆的热失重行为并进一步研究了其热解特性,根据热重数据采用四种热分析动力学模型:Friedman法、Doyle法、Flynn-wall-Ozawa(F-WO)法和DEAM法研究了葵花秆的热分解动力学,估算出热解反应的表观活化能。结果表明:葵花秆的主要失重区间为200~400℃,随着升温速率的提高,葵花秆热解的初温度升高,热解向高温方向移动。同时四种方法获得的葵花秆活化能值分别为519.1kJ/mol,235.33kJ/mol,223.8kJ/mol和224.9kJ/mol。采用Friedman法得到的活化能值高于其它三种方法。葵花秆热解是包含了分子键能断裂的一系列复杂、连续反应过程。     

生物质半焦燃烧特性实验研究

为了提高生物质秸秆利用率,以小麦秸秆和玉米秸秆为研究对象,在400、450℃的炭化温度下制备了小麦秸秆和玉米秸秆半焦。采用TG-DTA热分析联用技术研究了升温速率、氧浓度对半焦反应动力特性的影响,建立了反应动力学模型,获得了不同工况下的频率因子及活化能。实验结果表明：活化能随着升温速率的变大及氧浓度的提高而略微减小;频率因子受升温速率以及燃烧氛围影响较大,氧气浓度越高则频率因子越大;升温速率越快则频率因子越大。     

稻秆慢速热解的需热量及动力学分析

应用热重-差式扫描(TG-DSC)同步热分析仪进行稻秆的热解实验,通过对DTG和DSC曲线的对比分析,详细探讨了稻秆的基本热解过程;以440 K为临界温度,将实验曲线转换为干稻秆DSC曲线,升温速率β为10,15,20和30 K/min时,干稻秆的热解净热效应分别为878,836,770,841 kJ/kg;采用Coats-Redfern积分法进行动力学分析,基于典型固态反应动力学机理模型,按最小二乘法原理确定A2模型为最佳动力学机理模型。结果表明,随着升温速率的增加,稻秆试样的活化能增加。同时,稻秆热解符合2段机理模型。     

The effect of steam on pyrolysis and char reactions behavior during rice straw gasification

Steam gasification of biomass can generate hydrogen-rich, medium heating value gas. We investigated pyrolysis and char reaction behavior during biomass gasification in detail to clarify the effect of steam presence. Rice straw was gasified in a laboratory scale, batch-type gasification reactor. Time-series data for the yields and compositions of gas, tar and char were examined under inert and steam atmosphere at the temperature range of 873-1173 K. Obtained experimental results were categorized into those of pyrolysis stage and char reaction stage. At the pyrolysis stage, low H₂, CO and aromatic tar yields were observed under steam atmosphere while total tar yield increased by steam. This result can be interpreted as the dominant, but incomplete steam reforming reactions of primary tar under steam atmosphere. During the char reaction stage, only H₂ and CO₂ were detected, which were originated from carbonization of char and char gasification with steam (C + H₂O→CO + H₂). It implies the catalytic effect of char on the water-gas shift reaction. Acceleration of char carbonization by steam was implied by faster hydrogen loss from solid residue.     

规模化连续生物质炭化设备的评价及产品分析

针对目前国内生物质废弃物热解炭化设备规模化生产中存在着生产设备运行不稳定、秸秆炭化产率低、副产品回收利用难等问题,采用稻壳和玉米秸秆成型颗粒为原料,研究其在该套规模化连续生物质炭化设备中长时间连续炭化情况,从而系统分析了该生物质炭化设备的适用性和稳定性。该设备由炭化单元、气体分离单元和出炭单元组成,炭化单元采用双层套筒结构,内层为炭化室,外层为燃气加热室,将生物质炭化产生的高热值生物质气回收后燃烧加热实现热解炭化过程的连续运行。实验结果表明：该生物质炭化设备设计合理,可满足不同原料炭化,可实现稻壳和玉米秸秆颗粒的长时间连续稳定炭化,炭化产能可达到490 kg/h,炭化温度控制在500℃左右,生物质炭的得率在37%以上,热解后固、液、气三相分离完全,气体得到循环利用。     

秸秆的自加热及自燃特性研究

针对秸秆堆积储存和制粉过程中的自燃问题,采用杜瓦瓶自加热装置对稻草(RS)、麦秸(WS)、玉米秸秆(CS)堆积储存的自加热过程进行研究,并考察含水量对自加热的影响;同时,采用慢速升温的热重分析方法对3种秸秆的低温氧化特性进行研究.自加热实验结果显示:3种秸秆的自加热过程遵循相同的规律(均分为诱导期、温度上升期和温度下降...     

PERFORMANCE OF A PRESSURIZED TWO-STAGE FLUIDIZED GASIFICATION PROCESS FOR PRODUCTION OF LOW-BTU GAS FROM COAL CHAR

A two-stage pressurized fluidized-bed gasification process has been developed to produce low-heating value gases from coal char. The reactor was 0.075 m id. and 1.4 m long, and gasification experiments were conducted under pressures up to 790 kPa and at temperatures up to 1323 K. A partition disc was used to divide the fluidized bed into two stages, using the first stage as a partial combuster and gasifier and the second stage as a gasifier. The disc was designed to control compositions of coal char particles in both stages so that the heat required for the endothermic gasification reaction in the second stage can be provided by the heat of combustion in the first

For conditions examined here, the disc with an opening ratio of 40° was found to give optimum distribution of the char particles in both stages without ash agglomeration. It was also shown that all oxygen gas was completely consumed within the first stage

The heating value of the product gas increased with the char feed rale. However, there may be an oplimum Teed ratio of char and sand-particles since the higher char feed rate causes more frequent ash agglomeration as well as less carbon conversion     

Heats of combustion of high temperature polymers

The heats of combustion for 49 commercial and developmental polymers of known chemical structure were determined using an oxygen bomb calorimeter according to standard methods. The experimental results were compared with thermochemical calculations of the net heat of combustion from oxygen consumption and the gross heat of combustion from group additivity of the heats of formation of products and reactants. The polymers examined were thermally stable, char forming thermoplastics and thermoset resins containing a significant degree of aromaticity and heteroatoms including — nitrogen, sulphur, phosphorus, silicon, and oxygen in linear and heterocyclic structures. The gross and net heats of combustion calculated from polymer enthalpies of formation and oxygen consumption thermochemistry were within 5% of the experimental values from oxygen bomb calorimetry. The heat released by combustion per gram of diatomic oxygen consumed in the present study was E=13.10±0.78 kJ/gO₂ for polymers tested (n=48). This value is indistinguishable from the universal value E13.1 kJ/gO₂ used in oxygen consumption combustion calorimetry. Published in 2000 by John Wiley & Sons Ltd.     

Characteristics of fast pyrolysis of biomass in a free fall reactor

Fast pyrolysis of four kinds of biomass (legume straw, tobacco stalk, pine sawdust and apricot stone) was conducted in a free fall reactor. Interest is focused on hydrogen-rich gas production. The experimental results verify the occurrence of the in-situ steam reforming of tar, the steam gasification of char and the water–gas shift reaction with the primary pyrolysis of the biomass at higher heating rate in the free fall reactor. These reactions influence greatly the products' distribution and dry gas compositions in fast pyrolysis, especially at higher temperature. The pyrolysis is mass and heat transfer controlled for biomass particle size of above 0.20 mm but kinetically controlled in the case of particle size smaller than 0.20 mm. Biomass composed of higher cellulose and hemicellulose favors hydrogen-rich gas production in fast pyrolysis than that composed of higher lignin. The pyrolysis characteristics of each type of biomass can be explained according to its chemical compositions.     

过程参数对纤维素水热碳化的影响

生物质废弃物是当今世界上的第四大能源,传统的焚烧处理方式不仅会污染环境,还会浪费能源。水热碳化是一种高效的废弃生物质资源化技术。考察了反应温度和停留时间对纤维素水热碳化碳分布的影响,并对碳化物的物理化学特性、微观结构进行了研究,以及从反应机理角度进行解释。结果表明,原料中的碳大部分都保留在了碳化物中,占71%～75%,其余部分被转移至液相和气相。随着温度和时间的增大,碳化物的产率降低,热值升高,O/C原子比降低。SEM显示当温度达到220℃时,碳化物表面开始形成微球结构,且随着温度和时间的增大,微球结构均一性、分散度越来越好。FTIR表明碳化物表面生成羟基和羰基等官能团,水热碳化过程中会发生脱水和芳香化反应。