熱交換鋼管玻璃基塗層研究

Abstract

近日，能源使用與日遽增，其主要來源仍然以燃燒石化原料為基礎。然而燃燒石化原料會生成一些像SO2、SO3、NO2、H2O和HCl等化合物，當這些具腐蝕性的酸性物質與冷卻端的金屬接觸時，會發生冷凝作用（形成鹽酸、硝酸、硫酸等），導致腐蝕的發生。熱交換器是在石化行業中常見的一個設備，因此如何防止腐蝕的發生非常重要，耐酸的玻璃基鍍層將是一個很好的方法。 本論文著重於兩部分。一為商用玻璃鍍層的分析，並探討其與鋼管間結合的機制；另一部分則是藉由增加結晶度以及添加碳化矽粉末在塗層中來增加熱傳性能。結果顯示，商業化玻璃鍍層的成分以矽氧化物加上鹼金族氧化物為主，而鈷及鎳氧化物的添加對於釉料和底材的結合至關重要，在界面處發生反應來產生不平整的接合面，提供足夠鎖合力。針對熱傳導性質的提升，結果發現提高結晶度，晶粒並沒有完全連續而是分散在各個小區域，成效不佳；碳化矽顆粒添加對於熱傳性質有所提昇，但需要使用鎳層前處理來降低界面阻抗，10%碳化矽的添加可讓商用鍍層熱傳值提升近40%之多，大幅改善了玻璃熱傳不好的性質。 本論文另外利用光學顯微鏡、SEM、TEM、X射線繞射儀，電子微探分析儀，DSC和TGA熱差熱重分析，來做鍍層性質、表面和橫截面的研究。並且制定檢測流程來測試玻璃鍍層的實用性。

Recently, the use of energy is increasing and the main source of energy is still burning fossil-based raw materials. However, the burning of fossil will produce exhausts such asSO2, SO3, NO2, H2O, and HCl. When the exhausts contact with the metal on the cooling side, acidic substances are formed by condensation, including HCl, HNO3, and H2SO4, and corrosion occurs. Heat exchanger is a common equipment in the petrochemical industry. How to prevent the corrosion of heat exchanger is very important. The acid-proof glass-based coating will be a good candidate to protect heat exchanger steel tubes from corrosion. This study focuses on two parts. One is to analyze the glass-based coating on a commercial heat exchanger steel tube so as to gain better understanding on the mechanism of bonding between the glass coating and steel substrate. The other part is to improve the heat transfer properties of the glass coating by increasing the degree of crystallinity and adding SiC powders in the glass-based coating. The results show that the commercial coating is mainly composed of silicon oxide and alkali oxide, while the presence of cobalt and nickel oxide is critical to bond the glaze to the steel substrate. Reaction occurs at the interface to generate uneven surface, which provides sufficient mechanical locking force. The degree of crystallinity has little effect on the heat conductivity because crystalline grains are dispersed in an amorphous matrix. In contrast, the addition of silicon carbide particles in the glass matrix improves heat transfer properties when a nickel layer pretreatment is employed to reduce the interfacial resistance. The presence of 10 wt% silicon carbide powders in a commercial glass coating results in approximately 40% increase in the heat conductivity. Finally, this thesis develops a testing procedure to evaluate the performance of a glass coating on heat exchanger steel tubes for the petrochemical industry, including optical microscopy, SEM, TEM, XRD, EPMA, DSC, and TGA to characterize the microstructure and defect of the glass coating.