In some top-fired reformers flue gas can be found to be flowing upwards between the outside tube rows and the furnace wall. This has been proven by injecting the powder from dry powder fire extinguishers into the furnace peepholes on several reformers. These furnaces are found to have a tube wall temperature variation across the furnace and will have difficulty with furnace balancing. The effect is described, the results of computational fluid modeling to validate and understand the effect is reported, and some options are reviewed which can rectify the problem.
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