SYNTHESIS OF SILICON CARBIDE BY FUEL-RICH COMBUSTION IN CERAMIC SURFACE BURNER

多孔陶瓷表面燃烧器是沿多孔陶瓷板表面形成火焰的燃烧器，其可燃性在宽等效比区域内具有极限。如果甲烷-氧混合物能在相当富燃料的当量比下在高温下燃烧，二氧化硅就可以转化为碳化硅。本文提出了一种将表面燃烧器应用于碳化硅燃烧合成的方法，并从根本上探讨了其可行性。获得以下知识：1)表面燃烧器采用陶瓷蜂窝组装，可燃性极限试验未观察到闪回现象。2)燃烧器的富燃料燃烧当量比达到3.0，但烟灰产生明显。3)在小于1.5 w的等效比下，附着在蜂窝表面的火焰较薄，而在小于1.5 w的等效比下，附着在蜂窝表面的火焰长度增大，且随着等效比的升高超过1.5，火焰长度增大。4)基于31种元素的化学反应动力学模型进行了分析。分析结果表明，在高于2.0的等效比下，二氧化硅的组成和温度满足炭化反应所需的条件。在燃烧器的富燃料火焰中，研究了一块石英玻璃，在平板上合成了一层碳化硅薄膜。然而，由于与燃烧热负荷相比，辐射热损失较大，样品无法保持反应所需的足够高的温度，因此XRD分析无法检测到产物。这意味着实现这一过程的一个关键因素应该是减少与燃烧热负荷相比的辐射热损失。这一事实意味着实现这一目标的一个关键因素应该是减少板坯的辐射热损失并保持温度。少

The porous ceramic surface burner, in which flame is formed along the surface on a porous ceramic plate, has flammability limit in wide region of equivalence ratio. If the combustion of a methane-oxygen mixture at high temperature can take place under a fairly fuel-rich equivalence ratio, silicon dioxide may be converted to silicon carbide. In the present study, an application of the surface burner to the combustion synthesis of silicon carbide was proposed and the possibility was investigated fundamentally. The following knowledge was obtained : 1) The surface burner was assembled by using ceramic honeycomb and flashback was not observed from the test of flammability limit. 2) The fuel-rich combustion of the burner achieved up to 3.0 in equivalence ratio, but soot generation became significant. 3) The thin flame attached on the surface of honeycomb in less equivalence ratio than 1.5 while the length of the flame attached on the surface of honeycomb in less equivalence ratio than 1.5 w … More hile the length of the flame was enlarged with elevation of the equivalence ratio beyond 1.5. 4) The chemical reaction kinetic model was analyzed on the basis of the elementary reactions with 31 species. The analytical result showed that the composition and temperature satisfied the condition required for the carbonizing reaction of silicon dioxide in the higher equivalence ratio than 2.0. 5) A piece of quartz glass was examined to synthesize a film of silicon carbide on the slab in the fuel-rich flame of the burner. However the production was not detected by XRD analysis because the sample could not maintain sufficiently high temperature necessary for the reaction due to large radiant heat loss compared with the combustion heat load. The fact means that a key factor for realizing this process should be to reduce the radiant heat loss compared with the combustion heat load. The fact means that a key factor for realizing should be to reduce the radiant heat loss from slabs and maintain temperature. Less