INVESTIGATION OF BULGING BEHAVIOR OF COKE DRUM -A PRACTICAL ANALYSIS OF BULGING UNDER COMPLEX QUENCH CONDITIONS

ABSTRACT Coke drums undergo cyclic operations typically in the temperature range from room temperature to about 500°C (930°F). During quenching, the coke drum is inevitably subjected to a rapid drop in temperature because cooling water is injected directly into the coke drum through the bottom inlet nozzle. The temperature profile on the shell surface is uneven during quenching, and can vary in each cycle of the quenching operation. Such a complicated thermal profile induces large strains in the shell portion of the coke drum, and eventually causes damage like bulging and/or cracking. INTRODUCTION Coke drums in oil refineries are designed to upgrade and convert petroleum residuum into liquid and gas product streams leaving behind a solid concentrated petroleum coke. Coke drum diameters range from 4 to 9.8meters (13 to 32') with the straight side being around 25meters (82'). Usually the drum is fabricated from more than 25mm (2") thickness of chromemolybdenum low alloy steel and is clad internally with 2.8mm (7/64") of stainless steel for protection against sulfur corrosion. The outside of the drum is insulated with around 10cm (4") of fiberglass insulation. The authors have investigated the bulging behavior of the coke drum by the thermal elastic-plastic FE-analysis, considering the existence of the overmatch welds and uneven temperature field during quenchin