How long can a catalytic reaction suffer from bed fouling with internal heat generation that isn’t removed?

In fact, the temperature drop in the bed is caused by the following factors: 1. The backflow rate of air within the bed layer； 2. Main air or pressurized serial quantity ； 3. The heat extraction amount of the heat extractor. If the bed is blocked or the actual material level does not cover the heat exchanger, it has little impact on the heat exchanger; what’s important is to estimate the approximate position of the material level after the bed is blocked, in order to determine whether the steam inside affects this heat exchanger. I have 600,000 tons of coaxial capacity; the pressurized air flow is maintained at 3,500 cubic feet per hour. The main fan is kept running, but the actual airflow rate is low, at around 1,500 cubic feet per hour. Within three hours, the bed temperature drops from 700 degrees to 580 degrees. To restore normal operation, sulfurizing fuel is used to maintain the bed temperature at 700 degrees, after which the bed is allowed to rest again.