Anti-corrosion technology of magnesium hydroxide desulfurization tower: economic competition between 316L stainless steel and ceramic coating
1. Anti-corrosion demand and material selection logic
In the magnesium hydroxide wet desulfurization process, the internal environment of the desulfurization tower has the triple characteristics of strong corrosion, high wear and temperature change impact. The slurry soaking area at the bottom of the tower is corroded by alkaline media and undissolved magnesium hydroxide particles, and the top of the tower is corroded by acidic gas condensate. Although the traditional glass flake mortar solution is low-cost, its poor temperature resistance and easy hardening and shedding defects have made it difficult to meet the continuous production needs of modern industry.
As a new generation of anti-corrosion technology, 316L stainless steel and ceramic coating compete in the desulfurization industry with "metal corrosion resistance" and "inorganic protection" as their core advantages respectively. The difference in cost structure between the two reflects the deep competition between material properties and engineering economy-the former exchanges high initial investment for long-term stability, and the latter uses precision technology to achieve protection under extreme working conditions.
2. Analysis of material properties and cost anchor points
1. "Metal defense line" of 316L stainless steel
316L stainless steel forms a dense oxide film in magnesium hydroxide slurry with the alloy ratio of chromium, nickel and molybdenum, which can withstand a wide range of corrosion environments. Its smooth surface characteristics can reduce the circulation resistance of the slurry and reduce energy consumption losses. However, the premium of molybdenum element has pushed up the material cost, and the welding process requires argon arc welding and pickling passivation, which further increases the complexity of construction.
2. "Inorganic fortress" of ceramic coating
The hardness of alumina and silicon carbide-based ceramic coatings is far higher than that of stainless steel, and the wear resistance is increased by 5-8 times, and the risk of galvanic corrosion is completely avoided. Its non-metallic properties perform well in highly corrosive media containing Cl⁻ and SO₄²⁻. However, the investment in precision equipment for plasma spraying or laser cladding processes makes the construction cost account for more than 70% of the total investment.
3. Cost comparison of the whole life cycle
1. Initial investment comparison
The plate procurement cost of 316L stainless steel is dominant, and the initial investment of the same specification desulfurization tower is about 1.5-2 times that of the ceramic coating solution. Although the unit price of ceramic coating materials is low, it requires a carbon steel substrate and precision spraying equipment, and the comprehensive cost is still competitive.
2. Economic comparison of operation and maintenance
Maintenance cycle: 316L lining is maintenance-free for an average of 8-10 years, and ceramic coating requires partial repair every 5 years;
Energy loss: 316L has low surface roughness, and the slurry circulation energy consumption is 15%-20% lower than that of ceramic coating;
Loss of shutdown: Ceramic coating repair requires longer downtime, and the capacity loss is significant.
3. Residual value recovery potential
The recovery value of 316L scrap plates can reach 40% of new materials, while the residual value of carbon steel of ceramic coating substrate is less than 10%. In the scrapping stage of equipment, the residual value income of 316L can offset part of the initial cost gap.
4. Scenario-based selection strategy
1. 316L is preferred for ship desulfurization
Ocean-going ships are limited by space and are difficult to maintain frequently, and the temperature in the cabin fluctuates violently. The low-temperature brittle fracture resistance of 316L is better than that of ceramic coatings, and its overall welded structure can better resist the impact of hull deformation.
2. Thermal power desulfurization tends to ceramics
The dust content of flue gas in coal-fired power plants is high, and the wear resistance of ceramic coatings is prominent. Actual measurements show that no scouring marks were found in the ceramic coating area, while uniform corrosion occurred in the adjacent 316L area.
3. Coking/metallurgical mixed solution
The composite structure of "bottom 316L + top ceramic" is adopted, which not only uses 316L to resist slurry wear, but also gives play to the gas phase corrosion protection advantages of ceramic coatings, and the comprehensive cost is reduced by 15% compared with the single material solution.
V. Technological evolution and cost reconstruction
1. Material innovation and cost reduction
Low-molybdenum stainless steel: By replacing part of the molybdenum element with nitrogen alloying, a new type of molybdenum-saving steel is developed, and the material cost can be reduced by 25%;
Nano-ceramic coating: The ultra-thin nano-coating is prepared by the sol-gel method, and the construction efficiency is increased by 3 times, and the unit area cost is reduced by 40%.
2. Process innovation and efficiency improvement
Modular prefabrication: 316L lining is prefabricated in the factory and assembled on site, shortening the construction period by 60%;
Intelligent monitoring: IoT sensors monitor the corrosion rate in real time, optimize the maintenance cycle and reduce the maintenance cost.
3. Low-carbon benefit upgrade
Precise control makes the utilization rate of magnesium hydroxide exceed 95%, and the purity of the by-product magnesium sulfate reaches 99%, which can be directly used in the fields of agriculture and building materials, and the carbon trading income increases by 15%.
In the corrosion battlefield of magnesium hydroxide desulfurizer, the cost game between 316L stainless steel and ceramic coating is far from over. The former relies on the process maturity of metal materials to stick to the main market, and the latter relies on the performance ceiling of inorganic materials to open up high-end fields. With the high-quality development of the environmental protection equipment manufacturing industry, anti-corrosion solutions that are both economical and reliable will become the industry standard. Enterprises need to make accurate choices in this material revolution based on working conditions, cost tolerance and sustainable development needs.