Reason for using CS at the bottom of the regeneration tank

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The primary reason for using carbon steel (CS) at the bottom of regeneration tanks is its sufficient corrosion resistance under specific operating conditions as well as its cost-effectiveness; as long as temperature and stress conditions are properly controlled, carbon steel can be safely used in alkaline environments. The operating conditions are relatively mild: the bottom of the tank remains below the liquid level for an extended period, resulting in minimal temperature fluctuations; this prevents the evaporation and concentration of alkali solutions, thus avoiding the risk of alkali embrittlement caused by high concentrations of alkali. When the temperature of the alkaline solution is kept below 46°C, the corrosion rate of carbon steel in static alkaline solutions is low, and its structural stability remains good. Stress can be eliminated through heat treatment: the biggest risk with carbon steel is that welding residual stresses may cause alkaline embrittlement. After stress elimination through post-weld heat treatment (PWHT), carbon steel can effectively prevent cracking in low-temperature alkaline environments, meeting the requirements for long-term operation. There is a clear cost advantage: the bottom area of the tank is large, and using 304 stainless steel would significantly increase the cost of the equipment. While ensuring safety, the use of carbon steel can significantly reduce material costs, in line with the principles of engineering economics. Therefore, under conditions of low temperature, no evaporation, and stress relief, carbon steel is a suitable choice for the bottom of regenerative tanks.