Comparison of corrosion-resistant materials for flues, chimneys, desulfurization, and dust removal

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Flue ducts, chimneys, desulfurization systems, and dust removal systems present challenges in terms of corrosion protection. Corrosion-resistant materials are required to have high temperature resistance, resistance to acids and alkalis, excellent corrosion resistance, water and moisture resistance, wear and impact resistance, a smooth surface that does not easily develop cracks, a favorable coefficient of expansion, and resistance to peeling. Therefore, when selecting such materials, a thorough evaluation and strict inspection are necessary to ensure reliable corrosion protection for flue ducts, chimneys, desulfurization systems, and dust removal systems, allowing for long-term use. Based on a comparison of the corrosion-resistant materials used for flues, chimneys, desulfurization systems, and dust removal systems in China at present, a simple analysis is as follows: (1) Fiberglass-reinforced plastic (FRP) for corrosion protection: Corrosion-resistant materials made of fiberglass have a smooth inner surface, making it difficult for deposits to form; they are also wear-resistant, acid-resistant, and have good heat resistance. However, the disadvantages of fiberglass-reinforced plastic for this purpose include a low elastic modulus, poor long-term temperature resistance, susceptibility to aging, and low interlayer shear strength. Overall comparison score: 0.9 points (2). Coating corrosion resistance: The anti-corrosion coatings for flue gas use materials such as silicon carbide, boron nitride, and fine-grained aluminum oxide as fillers. These coatings are resistant to high temperatures, as well as acids and alkalis; they have a high coefficient of expansion, good adhesion, excellent wear resistance, a smooth surface, impact resistance, and are less prone to cracking. They are particularly resistant to the corrosion caused by fluorine in flue gas. They are easy to apply, but their price is relatively high. Overall comparison score: 0.93 points (3). For rubber-based anti-corrosion materials, silicone rubber and polyurea are commonly used in the domestic market; however, these products are not resistant to high temperatures, though they have excellent waterproofing and acid-resistant properties, which makes them unsuitable for long-term use in environments with high temperatures. Overall comparison score: 0.7 points (4). Corrosion resistance provided by glass flake coatings: Since the main filling material in glass flakes is SiO2, these materials have excellent heat and acid resistance as well as high hardness; however, their adhesion is poor, and they tend to peel off in sheets. Commonly used products in the market include foam glass bricks and glass flakes. Overall comparison score: 0.83 points (5). Acid-resistant mortar for corrosion protection: Acid-resistant mortar has good temperature and acid resistance, as well as a certain level of adhesion and a long service life; however, it has poor waterproofing and moisture-proofing properties, is prone to absorbing moisture from smoke leading to crumbling and peeling, and is susceptible to cracking in extremely cold conditions. Overall comparison score: 0.85 points (6). Corrosion resistance of mullite: Mullite features uniform expansion, excellent thermal shock stability, a high load softening point, low values of creep at high temperatures, high hardness, and good resistance to chemical corrosion. However, it is prone to cracking during analysis, its corrosion and water resistance are reduced, it has a large mass, and it is difficult to bond. Overall comparison score: 0.7 points (7). Stainless steel corrosion resistance: it can withstand high temperatures, as well as acids and alkalis; however, its wear resistance is poor, its surface is smooth which results in low friction, it has good impact resistance. Yet its welds are prone to corrosion, it is difficult to shape, and its cost is high. Overall comparison score: 0.8 points. In summary, when comparing various materials used for flues, chimneys, desulfurization, and dust removal applications as well as those with corrosion resistance, flue gas anti-corrosion coatings score high in terms of all performance aspects and offer a good cost-performance ratio; they are therefore the preferred materials for such applications in the future. Currently, in China, there is only one company that produces flue gas anti-corrosion coatings, namely Beijing Zhisheng Weihua Chemical Co., Ltd. The ZS-1041 flue gas anti-corrosion coating produced by this company is widely used in power plants, steel mills, oil and petrochemical industries, metallurgy, shipbuilding, pharmaceuticals, and the chemical industry, to provide corrosion protection for flues, chimneys, desulfurization equipment, and dust removal equipment. Overall, its anti-corrosion effectiveness is quite notable.