Correcting Improper Performance of Direct Fired Heaters
By Babak Maghbooli and Afshin Bakhtiari Tarahan Naftoon Arya Engineering Co. Hamidreza Najafi Farayand Sabz Engineering Co. |
Occasionally, direct fired heaters that have operated satisfactorily for long periods of time subsequent to startup develop operating problems that do not allow for operation at design conditions, as specified in the manufacturers API data sheets for the heater.
Performance that may be guaranteed, or otherwise specified by the supplier would include the type and characteristics of the feedstock processed, the heater duty, inlet and outlet temperatures and pressures, heat flux, tube-metal temperature and any other process conditions that are measurable by instrumentation provided with the heater or calculable through the use of the heater instrumentation data.
In many cases, operators cannot identify the cause of an operating problem by simply comparing the specified data and faulty data obtainable from the heater instrumentation. For example, although the measured tube-metal temperatures demonstrate no significant increases, an unexpected pressure drop may occur in heater passes because of internal fouling, mainly caused by coke formation. In many cases, operators are unable to achieve the design heater duty and overall thermal efficiency, while the cause of faulty performance is unknown to them. Most of these cases may be due to faulty…