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1.
综合流动和传热的废轮胎回转窑热解模型   总被引:1,自引:0,他引:1  
废轮胎在回转窑内的热解主要受到气-固相流动、传质和传热及化学反应动力参数等因素的影响。在对回转窑 内固体颗粒运动、传热传质进行分析的基础上,结合对轮胎热解反应动力学的研究,发展了综合流动、传热的废轮胎回转 窑热解模型,可计算得到回转窑内热解的温度分布、物料转化率、产物得率等。模型计算结果与试验结果吻合较好。  相似文献   

2.
The thermal decomposition of post-consumer samples of a carbonated water bottle made of poly(ethylene terephthalate), PC-PET, was examined by linear temperature programing under an argon atmosphere to determine its mass loss kinetics. A simple kinetic model, called the first order pseudo single-component model, was used. The total weight-loss of each sample assumed to be in two periods, with each period corresponding to a one step decomposition of the PC-PET to volatiles. Three methods for determining the kinetic parameters by thermal gravimetric analysis were examined: differential analysis at a constant heating rate (differential), temperatures of a given conversion at a number of heating rates (isoconversional), and the maximum rate at multiple heating rates (peak temperature). The latter two multiple heating rates methods results were comparable to each other but they were not in agreement with the results from the differential method. The results of the differential method were insensitive to the heating rate and consistent with kinetics data reported in the literature for PET.  相似文献   

3.
Atmospheric pressure plasma arc (APPA) cleaning is a newly developed method of metal surface cleaning. In this paper, a mathematical model of reactive kinetics in the metal surface contaminant cleaning using APPA has been developed. Based on the analysis of APPA cleaning mechanism and the feature of cleaning interface, a governing equation was established with heat transfer equation and energy conservation on the moving interface. Using fourth-order Rounge-Kutta method, above equation was solved and removal percentages of the cleaning contaminant at different time were obtained. In virtue of reactive kinetics theory, a reactive kinetics model of metal surface cleaning using APPA was established on the base of above calculation results. Afterwards, reactive kinetics parameters such as activation energy and pre-exponential factor were calculated. Cleaning lubricant was taken as an example, the results indicated that predictive values of lubricant removal percentages gotten from this established reactive kinetics model show good consistent with experimental data at the same time. Furthermore, the ambient temperature on the cleaning lubricant surface affects the removal rate strongly. The removal rate increases with the increase of the ambient temperature. To avoid the damage of metal substrate surface because of higher temperature and ensure the removal rate of the lubricant, the appropriate temperature which lies between the lubricant decomposition temperature and damage temperature of metal substrate under given calculation conditions should be determined.  相似文献   

4.
Combustion is directly related to energy conversion and the environment. Gas-phase chemical reactions such as thermal decomposition, oxidation and recombination play a critical role in combustion processes. Here we review six applications of synchrotron vacuum-ultraviolet (VUV) photoionization mass spectrometry (PIMS) in fundamental studies of combustion chemistry. These applications range from the use of flow reactors to probe elementary reaction kinetics, studies of pyrolysis in plug-flow reactors and oxidation in jet-stirred reactors, studies of spatial evolution of species concentrations in premixed and non-premixed flames, product distributions in pyrolysis of biomass, and analysis of polycyclic aromatic hydrocarbon (PAH) formation. These experiments provide valuable data for the development and validation of detailed chemical kinetic models. Furthermore, some additional potential applications are proposed.  相似文献   

5.
用傅利叶变换红外光谱仪研究了湖南晨溪地开石热分解前后的红外光谱,加热反应后原矿粉红外光谱在3620.73、3695.34cm-1处的地开石羟基伸缩振动吸收峰和在916.06、1009.33cm-1处的羟基弯曲振动吸收峰都消失,表明其质量失重为羟基脱水.在298~1123K,用TG DTA综合分析仪研究了地开石在程序升温下的热分解行为.结果表明,在600~1000K,其质量损失为13.7%,与理论计算的脱水量相近.根据TG DTG曲线上的基础数据,联合运用积分法(Coats Redfern方程、HM方程、MKN方程)和微分法(Achar方程)对地开石脱水反应过程进行了非等温动力学研究,结果显示,地开石热分解反应的机理函数为F2,求得反应的动力学参数:反应级数为2.1,表观活化能为131.62kJ/mol,指前因子为108.3s-1.作为一种验证方法,使用Ozawa方程对不同升温速率TG曲线上相同分解率处的绝对温度进行线性回归分析,求出的表观活化能值为133.07kJ/mol,此值不仅与上述各种方法的表观活化能值相近,也与确定机理函数时的表观活化能值相近.说明实验求得的动力学参数在很大程度上是可靠的.  相似文献   

6.
Thermophysical properties of intumescent fire-retardant (IFR) materials are important input parameters to simulate the pyrolysis process of IFR materials in fire scenarios. In this article, the effects of the thermophysical properties on pyrolysis of IFR materials are simulated based on a pyrolysis model of IFR materials. The selected thermophysical properties here are the specific heat capacity of the virgin material, thermal conductivity of the virgin material and char layer, heat of decomposition, density of virgin material, intumescent temperature, and surface emissivity of virgin material and char layer. Simulated mass loss rates (MLR) for the IFR materials at an incident heat flux of 50 kW/m2 are investigated for the varied thermophysical parameter values. The results show that changes in these property values can affect the pyrolysis behavior of materials profoundly. Comparison with experimental results indicates that the simulations of MLR are in reasonably good agreement with the experiments.  相似文献   

7.
采用增强壁面函数的标准k-ε模型对超临界R134a水平圆管内冷却换热进行了模拟研究.分析了管内不同截面上流体温度、速度和湍动能的分布情况及对应关系。研究了质量流量和浮升力对换热系数的影响。结果表明,流体速度随着温度的降低而减小,并且最大速度处对应着最高温度和最小湍动能.换热系数随着质量流量的增加而增大,其峰值出现在准临界温度附近。浮升力在似液体区的影响较大,对流体换热起到增强的效果。  相似文献   

8.
利用热重-傅里叶变换红外光谱联用方法研究添加CaO对麦秆热解过程和挥发份析出特性的影响.热重和红外光谱分析均表明添加CaO后麦秆热解旱现两个明显的失重和挥发份析出阶段,而纯麦秆热解则只有一个.CaO在第一阶段不但能够吸收CO2,而且能够降低甲苯、苯酚和蚁酸等焦油类物质的产生,使得该阶段失重率和最大失重速率随CaO添加量增加而减小.CaCO3的煅烧分解是添加CaO麦秆热解第二阶段产生的原因,该阶段失重率和最大失重速率随CaO添加量增加而增大.研究结果表明,在采用生物质为原料的零排放系统中添加CaO有利于捕获CO2和减少焦油物质的产生,系统的气化温度应适当降低以防止CaCO3的煅烧分解.  相似文献   

9.
The range of the characteristic decomposition rates of dihydride molecule radicals adsorbed by the silicon surface in the temperature interval 450?C700°C is experimentally found for a number of kinetic models. A relationship between the rate of silicon atom incorporation into a growing crystal and the characteristic rate of disilane molecule pyrolysis on the silicon surface is found. The temperature dependence of the rate of disilane fragment decomposition on the silicon surface is nonmonotonic, and its run depends on temperature conditions. It is shown that the temperature dependence of the molecular decomposition rate on the growth surface is described by a superposition of two activation curves with various activation energies. The activation energies depend on the peculiarity of interaction between the molecular beam and the silicon surface when the filling of surface states with hydrogen is low and high.  相似文献   

10.
Biomass combustion in pulverized-fuel boilers is a growing way to produce electricity from a renewable source of energy. Slagging and fouling limit however the reliability of the units that were initially designed for coal combustion. Computational Fluid Dynamics (CFD) codes aiming at studying those phenomena include simplified models of biomass particle pyrolysis, of which the pertinence has already been questioned for the typical conditions of interest. A comprehensive model has been developed to investigate pyrolysis of particles in pulverized-fuel boilers, with sizes ranging from 17 μm to 2.5 mm. The detailed model accounts for internal heat conduction, internal gaseous convection, moisture evaporation and particle shrinkage. It includes a competitive, multi-component kinetic scheme, improved for high temperatures. The discrepancy between the simplified models integrated in most CFD applications and the detailed simulations is highlighted. The simplified isothermal models underestimate pyrolysis time for the largest particles. Moreover, such models delay and shorten the volatiles release. The flame lengths, the local temperature fields and the pollutant emissions might be importantly impacted in global combustion simulations. Apparent kinetic parameters have been derived from the detailed simulations. Their use in existing simplified models improves the behavior of the biomass particles during pyrolysis, and offers therefore an efficient alternative to the integration of complex pyrolysis models in CFD codes.  相似文献   

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