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From: atc/nc cat
Category: Safety
Date: 06 Jan 2005
Ideally and considering the premise that capital cost is out of the equation, I would suggest you address all the DCU equipment and its appurtenances to be able to attain the project goal of DCU revamp increase to 120% capacity. If your project is seriously considering a third heater, I would suggest that it be sized to give 60 to 65% maximum continuous heater load rating. Likewise I would not run the three (3) heaters continuously with different load or firing rate. From my own vantage point, I would run two (2) heaters during normal operation and have the other heater as active standby heater for emergency and/or for heater decoking. Bear in mind that when a heater is running at its minimum load it will not be very efficient and fouling rate may be worst compare to other heater running at its normal design condition. Also, you may encounter a situation wherein you may end up running with one heater or shutdown the entire three (3) heaters one at a time more often and may not support your goal to have continuous operation of the DCU unit. You could have a better heater performance curves and performance records when heaters share load equally. Based on the above, I advocate that the new heater be sized to 60~65% and the other existing heaters be upgraded to have same capacity as the new one. Operate the DCU unit using two (2) heaters at a time. Staggered or established the proper heater decoking schedule. In this way you can be assured of 100% ~ 120% DCU capability and/or maximum DCU production possible. VTY, atc/nc cat