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Development of Characterizing System for Surface Structure and Interaction between Fine Particles at High Temperature Conditions with Special Atmosphere

特殊气氛高温条件下表面结构和细颗粒间相互作用表征系统的开发

基本信息

批准号：
10555262
负责人：
KAMIYA Hidehiro
金额：
$ 7.81万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2001
项目状态：
已结题

项目摘要

To characterize the increasing mechanism of cohesive behavior of ash powders at elevated and high-temperature conditions, two type of adhesion force testing system at high temperature were developed. The modified ash powders were prepared from fine pure amorphous silica powder coated and heat-treated on the surface with 0.5 wt% sodium and/or potassium and the cohesive behavior and deformation properties were determined. In the high-temperature range above 800 ℃, since a rapid increase of tensile strength and plastic rupture deformation occurred in both the natural ash samples and the model ash powder samples prepared from alkali metal and pure silica powder, it is suggested that the coating alkali metal reacted with the amorphous silica phase and formed a small amount of low-melting-point eutectic materials, such as K_2O・4SiO_2. Since these eutectic materials formed a small amount of liquid phase at inter-particles at about 800 ℃. To reduce the liquid bridge force at high temperature conditions, two methods were developed in this research. One is the high temperature chemical reaction by the addition of fine CaO powder with fine coal powder during coal combustion process to reduce such liquid bridge formation at high temperature condition. Another approach is the coating of ultra-fine carbon powder or the addition of coarse kaoline particle with ash particle to increase the surface distance and to decrease the wettability of liquid phase on ash particles. Both approaches is useful to reduce the adhesion behavior of ash particle at high temperature conditions.

为了研究灰粉在高温和高温条件下粘结性能的增强机理，研制了两种高温粘结力测试系统。用0.5wt%的钠和/或钾对超细无定形二氧化硅粉进行表面包覆和热处理，制备改性灰粉，并测定其内聚行为和变形性能。在800 ℃以上的高温范围内，由于天然灰样和碱金属与纯硅微粉制备的模型灰粉样的抗拉强度迅速增加，并发生了塑性断裂变形，推测包覆碱金属与无定形硅微粉相发生反应，生成了少量的低熔点共晶物质，如K2 O·4SiO 2。由于这些共晶材料在800 ℃左右在颗粒间形成少量液相。为了减小高温条件下的液桥力，本研究开发了两种方法。一种是通过在煤燃烧过程中添加细CaO粉末与细煤粉的高温化学反应来减少这种高温条件下的液桥形成。另一种方法是在灰颗粒表面包覆超细碳粉或加入粗高岭土颗粒，以增加灰颗粒与液相的表面距离，降低液相对灰颗粒的润湿性。这两种方法都有助于减少高温条件下灰粒的粘附行为。