Material selection for flue gas containing HCl in GGH tubes
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There is an existing GGH heat exchanger; the flue gas outside the tubes contains 100233 mg/Nm3 of HCl gas and 1637 mg/Nm3 of HBr gas, while the clean flue gas inside the tubes contains 10 mg/m3 of HCl gas and 10 mg/Nm3 of HBr gas. Currently, it is planned to use fluoroplastic steel pipes, with a PFA membrane on the outside to prevent corrosion. But can carbon steel be used for the metal core of the pipe? Are 10mg/m3 HCl and HBr gases highly corrosive? The net moisture content of the flue gas inside the pipe is 7.91% (by volume)
Choosing fluoroplastic steel pipes is appropriate, as the PFA membrane exhibits excellent corrosion resistance to HCl and HBr. Carbon steel is not highly corrosive at HCl and HBr gas concentrations of 10 mg/Nm3, but it can still corrode when exposed to an environment containing water vapor over a long period of time. Therefore, it is better to consider using materials with better corrosion resistance, such as stainless steel or carbon steel coated with an anti-corrosion layer. .
The net moisture content of the flue gas inside the pipe is 7.91% (on a volume basis). Is this moisture content considered high? Is it feasible to use 316L for the base tube? Net flue gas temperature inside the tube: 40℃
A water content of 791% (by volume) is likely an incorrect value; it may have been entered by mistake. Under normal circumstances, the water content does not exceed 100%. If it is assumed that the moisture content is relatively high, corrosion will increase under such humid conditions. 316L stainless steel has good corrosion resistance due to the presence of molybdenum, enabling it to resist pitting and crevice corrosion caused by chlorides; therefore, it is feasible to use 316L stainless steel as the base tube in an environment with a temperature of 40°C and low concentrations of HCl and HBr gases. However, a final decision still needs to be made based on the actual operating conditions and cost considerations. .
In this type of heat exchanger, with the original flue gas on the outside of the tubes and clean flue gas inside, it is feasible to use a fluorine-based coating on the outside of the tubes for corrosion protection; however, using carbon steel or stainless steel inside the tubes does not yield good results. Since the medium inside the pipe is commonly referred to as low-temperature wet flue gas, both carbon steel and stainless steel materials will be corroded by this low-temperature wet flue gas. Therefore, it is recommended that for such heat exchange tubes, carbon steel tubes be used, with polymer materials applied to their inner and outer surfaces to achieve a better corrosion-resistant effect.
According to the operating conditions of the GGH heat exchanger specified in the design, the heat from the raw flue gas is used to heat the flue gas that has been purified in the desulfurization tower, bringing its temperature to around 90 degrees. It is recommended to use a heat pipe heat exchanger for better results. This method only provides corrosion protection for the outer wall of the tube bundle, making the painting process simpler.
Thank you so much for Mr. Wang’s guidance :)
Hello, the moisture content is 7.91% (7.91% by volume), not 791%
The GGH heat exchangers we provide to our customers are all graphite heat exchangers, and they deliver excellent performance.
It’s probably the flue gas after wet washing, right? It is highly corrosive; anti-corrosion measures are absolutely necessary. Heat pipes, fluoroplastic heat exchangers, and so on can be considered