Effect of Process Conditions On Film Temperature in Fired Heaters

Variation in process conditions in fired heaters arise due to multiple circumstances, of these, percentage of excess air, throughput and inlet temperature are the most recurrent. Film temperature is an important parameter to be observed during the operation of this type of equipment due to its influence in the development of coke on the heat transfer walls. The consequence of the building up of a fouling layer is the reduction of the thermo hydraulic performance which introduces additional expenses and eventually forces plant shut down for maintenance. In this work, an assessment of fired heaters performance is carried out at a fixed outlet temperature and pressure. Results show that plant throughput variation demand higher firing rates with the largest impact on film temperatures. Increased percentage of excess air also demands higher firing rates; however it does not show a strong impact on film temperatures. Finally the effect of inlet temperature appears not to shift the local film temperature profile from its original condition.