When stopping acid production and using cold blowing directly, scarring occurs on the catalyst at the bottom of the first layer
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When shutting down the acid production unit, thermal purging must be carried out first to blow away all SO2 + SO3 from the catalyst, before proceeding to cold purging. However, there are also factories that cannot carry out direct cold blowing because the preheater and electric furnace cannot be put into use. After cold blowing, there is primarily a layer of pulverized scabs at the bottom, along with a layer where the catalyst turns green at the bottom. To date, 2 cases have been identified in the aforementioned situation, but an explanation cannot be provided at the moment; everyone is welcome to share their opinions.
Analysis: Cold air (containing SO2) flows downward through a layer; upon reaching the middle and lower parts of this layer, it is heated. The cold air (containing SO2) is heated to its ignition temperature, during which SO2 is converted into SO3. Further on――at the bottom of one layer, once there’s powdering and scarring, I can’t continue: L