共查询到20条相似文献,搜索用时 15 毫秒
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J. C. Jones B. F. Gray H. Rahmati 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,53(4):383-387
A novel piece of apparatus is described which simulates rigorously the ‘infinite slab’ in traditional thermal ignition theory. The apparatus was applied to shavings of a particular type of wood, and the results are shown to be consistent with those from more conventional experiments using basket heating. 相似文献
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J. C. Jones H. Rahmati T. D. H. Do 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,54(4):317-318
Wood shaving samples were heated in both cubic baskets and in a previously described system realising the conditions of the ‘infinite slab’ in thermal ignition. Results from the two sets of experiment were found to be totally consistent with each other. 相似文献
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Experiment study of the altitude effects on spontaneous ignition characteristics of wood 总被引:1,自引:0,他引:1
This paper has studied the influence of ambient pressure and oxygen content on spontaneous ignition of wood by conducting contrastive experiments with wood slab exposed to high temperature radiation at two different altitudes. The measurement of mass loss, time to ignition, and surface temperature of wood are carried out. Results show that mass loss rate of wood at high altitudes (3650 m) is higher than the one at low altitudes (50 m), while ignition delay time of the sample at high altitude is shorter. The surface temperatures at the time of ignition in the two different places are both close to each other, which indicates that the pressure did not affects the ignition temperature. The theoretical analysis on the phenomenon of different ignition behavior of wood in these two altitude environments has been presented. 相似文献
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Marc Janssens 《火与材料》1991,15(4):151-167
The physical phenomenon of piloted ignition of a material is described. A number of mathematical models of this phenomenon are presented in order of decreasing complexity. The most sophisticated models include gas-phase phenomena. Simple models neglect all chemical effects and are purely thermal. The most commonly used criteria for piloted ignition are discussed. Correlations used in piloted ignition studies from the past 40–50 years are summarized. Many investigators have been successful in correlating piloted ignition data of wood using a simplified thermal model in combination with a critical surface temperature criterion. Emphasis of this review is therefore on this approach. The paper concludes with a detailed analysis of various factors affecting piloted ignition of wood. Some of the factors are related to the experimental conditions, others are associated with the characteristics of the material. 相似文献
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The results of studies of the thermal transformations of granulated wood biofuel performed by thermogravimetry and differential scanning calorimetry in an atmosphere of argon at heating rates of 5, 10, 20, and 30 K/min are reported in this paper. The results of the analysis were used for the determination of the preexponential factor and activation energy of the thermal decomposition of wood biofuel based on the Kissinger, Kissinger–Akahira–Sunose, and Ozava–Flynn–Wall isoconversion model-free methods. The values of activation energy for the release of volatile substances in the course of the thermal decomposition of wood granules varied in ranges of 87–250 and 76–242 kJ/mol. 相似文献
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Venkatesh R.Pai Vernekar Josyula R. Mohana Rao Balisagar K. Subba Rao Mandayam A. Tirunarayanan 《Fuel》1982,61(7):634-638
A study of the thermal decomposition and ignition of coal as functions of pelletizing pressure and dwell time has revealed that: (1) ignition and thermal behaviour are related to the apparent density of the pelletized coal; (2) for a given apparent density of pelletized coal, the ignition temperature is related to the rate constants of thermal decomposition. Isothermal decomposition in air at 550 °C has been shown to fit the Avrami-Erofeev equation for three-dimensional growth of nuclei. 相似文献
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Conclusions A generalized mathematical model of heating of materials in a layer with thermal decomposition of them taking into consideration in the interrelationship the heat and mass exchange and kinetic rules of the production operations has been developed. A Fortran computer program used for production heat-exchange equipment has been developed on the basis of the model.Translated from Ogneupory, No. 6, pp. 37–41, June, 1987. 相似文献
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On the basis of experimental data on the ignition temperatures of pure nitrous oxide flow with p=0.3–4.1 MPa, and using the criterial equation given by the ignition theory of Ya. V. Zeldovich, we have computed the reaction order and the Arrhenius parameters for the process of thermal decomposition of N2O. For p>0.7 MPa, we find good agreement with the established values recommended in the literature. Lower values of the effective activation energy are found for lower N2O pressures; this is due to the influence of a heterogeneous catalytic surface.Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 6, pp. 81–86, November–December, 1991. 相似文献
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Dekui Shen Rui Xiao Mengxiang Fang Wanki Chow 《Korean Journal of Chemical Engineering》2013,30(1):228-234
The pyrolysis and ignition of wood is of great importance to understand the initial stage of combustion, helping control the occurrence and spread of unwanted building and forestry fires. The development of a thermal-balanced model is introduced for examining the analytical relationship between the ignition time and external heat flux. The critical heat flux, one of the important fire-retardant characteristics of combustible solid, is determined from a correlation study between the ignition time and external heat flux. One of the thermal-balanced integral models, considering the effect of surface heat losses, average absorptivity and moisture content, is employed to give the prediction of surface temperature rise, ignition time and ignition temperature of the Aspen. The results show that the model readily and satisfactorily predicts ignition temperature and ignition time of wood with different moisture contents. 相似文献
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The thermal behaviour of a multipass process gas heater has been investigated using the zone method of analysis, with the aim of estimating the accuracy of previous predictions based on an extended two-flux model of the radiation field. Process gas, furnace gas, tube surface and refractory surface temperature distributions predicted by the two methods are found to agree well with each other and with the limited experimental data available for the heater. Good agreement is also found between the radiative flux densities calculated using the two-flux model and the zone method. Due to the well established accuracy of the zone method of analysis, the closeness of the two sets of predictions indicates that the two-flux model should prove extremely useful in assessing the thermal effects of changes in design or operating conditions in process gas heaters, particularly because of its computational simplicity compared with the zone method. 相似文献
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Many municipal waste combustors use preheated primary air in the first zone to dry the waste. In most cases the preheat temperature does not exceed 140 °C. In previous experiments it is found that at temperatures around 200 °C, in some circumstances, self- or spontaneous ignition can be achieved. Using preheated air can be a powerful tool to control the ignition and combustion processes in a waste combustion plant. To use this tool effectively, the influence of the preheated air on the fuel bed needs to be well understood. The present work is done to investigate in a systematically way the spontaneous ignition behaviour of a packed bed heated with a preheated air stream. Experiments on a lab scale packed bed reactor are carried out for various fuel types. Because MSW is an highly inhomogeneous fuel, wood and char are used as model fuels. To include the inhomogeneous character of MWS, also experiments are carried out with RDF. Parameters such as primary air flow velocity and temperature, addition of inert material, moisture content of the fuel (wood chips) and particle size (char) have been changed to see their effect on the spontaneous ignition temperature and on the minimum air temperature needed for ignition. The spontaneous ignition temperature is defined as the bed temperature at which a transition takes place from a negligible or slow fuel reaction rate to a rapid oxidation of either the volatiles or the solid fuel without an external source such as a spark or a flame. The minimum or critical air temperature is defined as the lowest air temperature at which ignition can be obtained. It is found that the type of fuel has influence on the ignition temperatures. Besides both the critical air temperature needed for the spontaneous ignition and the spontaneous ignition temperature increase with an increase in the primary air velocity (between 0.1 and 0.5 m/s) and increasing the added inert fraction (between 0 and 40 wt%), irrespective of the fuel type. The effect of air flow velocity and temperature and also the effect of inert on both the critical air temperature and the spontaneous ignition temperature can be explained qualitatively by using Semenov’s analysis of thermal explosions. Semenov’s theory is quantitatively applied to predict the spontaneous ignition and the critical air temperatures for wood. 相似文献
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The theromo-oxidative decomposition, flash ignition and burning of high-impact polystyrene containing the flame-retardant system decabromodiphenyl oxide + antimony trioxide was investigated using the Setchkin apparatus combined with mass spectrometry. The time dependences of the release rate of the main products into the gas phase during decomposition and burning showed that the flame-retardants markedly influence these processes. It was found that the retardants used exhibit an acceleration of the polymer degradation and that the efficiency of inhibition in the gas phase depends on the atomic ratio antimony: bromine. 相似文献
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玻璃纤维增强塑料(GFRP)因其良好的热绝缘性能和力学性能,在高能物理和核物理实验领域被用来制作支撑设备,而高能物理和核物理实验会对其支撑设备产生一定的γ和中子辐照,为保证GFRP支撑设备在γ辐照条件下的结构稳定性,需研究辐照对其热分解性能的影响。结果表明,GFRP在氮气氛围中的热分解可分为3个阶段;GFRP失重率随辐照剂量的增大而增大;辐照使GFRP的活化能增加,Friedman法计算得出平均活化能由辐照前的96.1 kJ·mol-1增加到200 kGy辐照后的116.6 kJ·mol-1,Flynn-Wall-Ozawa(FWO)法计算得出平均活化能由辐照前的107.6 kJ·mol-1增加到200 kGy辐照后的125.4 kJ·mol-1。扫描电镜对微观形貌观察发现辐照后环氧树脂与玻璃纤维结合度降低,差示扫描量热法分析得出辐照使环氧树脂进一步固化反应。 相似文献