DETERMINATION OF KINETIC CHARACTERISTICS OF SOLID FUEL.

V. Chmel, I. Novikova
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Abstract

The combustion process begins with the ignition of the fuel - bringing it to the auto-ignition temperature, which is one of the important components of the kinetic characteristics of the fuel. Fuel ignition does not occur immediately - but after a certain period, during which activation energy is accumulated: heat or active centers, depending on the mechanism of the process - thermal-kinetic or chain-kinetic, sufficient to overcome the potential barrier. At the same time, the period of reaching the self-ignition temperature is the induction period of this reactive system: for self-ignition or the ignition time during ignition. The purpose of the work is to substantiate the kinetic characteristics of the fuel: self-ignition temperature and induction period, methods of their experimental determination for solid fossil fuels and biomass waste. According to the methodology, an installation was created for the experimental determination of the self-ignition temperature and the induction period of solid fuel in the layer. Studies of such fuels as anthracite, hard coal, buckwheat husk, millet, oats, flax husks, birch wood, peat, and paper showed the dependence of the self-ignition temperature on the degree of metamorphosis and volatiles. With an increase in the degree of metamorphism and a decrease in volatiles in solid fuel, the self-ignition temperature increases. However, the self-ignition temperature does not depend on the size of its particles, their number in the layer and the temperature of the oxidizer. The above allows us to conclude that the self-ignition temperature depends only on the conditions of heat exchange (accordingly, on aerodynamics), and the absolute value of the auto-ignition temperature for an infinite space, in the absence of a jet stream, is a constant value, and only then, in the presence of heat exchange (with velocity gradients) , takes one or another value. It was found that the induction period depends only on the initial temperature of the process, the induction period decreases with increasing temperature. This is due to the more intensive transfer of heat to the fuel particles due to the increase in the temperature gradient and the acceleration of the development of the oxidation reaction. The induction period, as shown by the conducted experiments, does not depend on the size of the particles. This can be explained only by the fact that the rate of thermal destruction of the fuel is close to the rate of its heating. The burning time of coal particles, on the contrary, depends on the size of its particles. Expressions for determining the autoignition temperature and the induction period were obtained based on the processing of the results of the conducted experiments. The results of the work can be used in combustion technologies, in which self-ignition of fuel is one of the main components of the process - it ensures combustion in the self-ignition mode of fuel when in contact with an oxidizer.
固体燃料动力学特性的测定。
燃烧过程从燃料点火开始,使其达到自燃温度,这是燃料动力学特性的重要组成部分之一。燃料点火不是立即发生,而是经过一段时间,在此期间,活化能积累:热量或活性中心,取决于过程的机制-热动力学或链动力学,足以克服势垒。同时,达到自燃温度的时间即为该反应体系的诱导期,即为自燃或着火时的着火时间。这项工作的目的是证实燃料的动力学特性:自燃温度和诱导期,以及固体化石燃料和生物质废物的实验测定方法。根据该方法,建立了一个装置,用于实验测定层内固体燃料的自燃温度和诱导期。对诸如无烟煤、硬煤、荞麦壳、小米、燕麦、亚麻壳、桦木、泥炭和纸张等燃料的研究表明,自燃温度与变质程度和挥发物有关。随着变质程度的增加和固体燃料中挥发物的减少,自燃温度升高。然而,自燃温度并不取决于其颗粒的大小,它们在层中的数量和氧化剂的温度。以上可以使我们得出结论,自燃温度仅取决于热交换条件(相应地,取决于空气动力学),并且在没有急流的无限空间中,自燃温度的绝对值是一个恒定值,只有在存在热交换(具有速度梯度)时,才取一个或另一个值。结果表明,诱导期仅与工艺初始温度有关,随着温度的升高,诱导期逐渐减小。这是由于温度梯度的增加和氧化反应发展的加速使热量更密集地传递到燃料颗粒。所进行的实验表明,诱导期不取决于颗粒的大小。这只能用燃料的热破坏率接近其升温率这一事实来解释。相反,煤颗粒的燃烧时间取决于其颗粒的大小。在对实验结果进行处理的基础上,得到了自燃温度和引燃周期的确定表达式。这项工作的结果可以用于燃烧技术,其中燃料自燃是该过程的主要组成部分之一-它确保燃料在与氧化剂接触时以自燃模式燃烧。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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