| Popis: |
For many decades, the world has been facing a major problem involving the significant increase in energy consumption and CO2 gas emissions. The cement industry is one of the top five contributors to this crisis. In the production of cement, the raw material must be heated to temperatures as high as 1450oC. Unfortunately, 40% of this energy is lost from heat energy, and approximately 20% of this lost energy is through heat transfer from the refractory lining and kiln shell. This thesis addresses this problem by developing a high emissivity coating to be applied to the refractory lining in the upper transition zone of the cement rotary kiln. The function of this coating is to absorb and re-emit the heat back inside the rotary kiln, which will lead to energy savings. In other words, the same amount of cement will be able to be produced using less energy. As a result, mixing CeO2 with AlH6O12P3 and sintering at 1300oC produces a coating having an emissivity of 0.8 in the infrared range, which is double the emissivity of uncoated refractory bricks. The reason that this coating provides high emissivity in the infrared range is that the infrared represents heat energy and the presence of CeO2 in the coating has a high thermal activation, which leads to high lattice vibration and polaron absorption. Although this coating has been proven to possess a high level of emissivity and has the potential to provide energy savings when used at high temperatures, it has shown a poor behaviour when it is in an alkaline environment. Therefore, further improvement of its alkaline corrosion resistance is needed. Moreover, experiments on abrasion resistance and thermal shock resistance are also required to confirm if this coating will survive the harsh environment of a cement rotary kiln. Open Access |
