Working Process Numerical Simulation And Life Evaluation Of Coke Drum

Delayed coking is major oil refining process and the coke drum is the key equipment of the delayed coking so the safe operation of coke drum is a essential factor of the petroleum refining industry's development. In the paper, the causes of cracking and bulging of the coke drum was analyzed through the process simulation. The influence law of the operating cycle and the cooling water temperature to coke drum's stress and deformation was analyzed. Use strain range method assessed the residual life of coke drum.Using the ANSYS finite element analysis software simulated the temperature field and the coupling field of the coke drum's working process. The data of top and bottom field surveying temperature linear fitted along the highly direction acted as thermal analysis boundary conditions, as the boundary temperature is a composite function about time and height, dynamic thermal boundary problem during the coke-forming and water-cooling stages was solved. Element birth and death technology was used for simulating the coke-forming process. Analysis showed that coke drum's temperature rises steadily during preheat and steam-cooling stages. In coke-forming stage, mixed-phase interface gradually rise up. When the drum wall contact with the interface its temperature will rising dramatically. Temperature change rate is high and the trend of thermal gradient variation is complex during water-cooling stage.The gravity, temperature periodic changes, operating pressure and the presence of coke were all considered in the coupling field simulating. The results show that thermal stress is the root cause of the high stress for coke drum during the work process. The coke constrains the deformation of the tower wall, this aggravated the stress state of the coke drum's lower part, the resulting welds cracking occur. Temperature distribution and variation of the coke drum is non-uniform along the axial direction. It is this difference caused bulging deformation of coke drum after several years running.Coke drum's failure mode is low cycle thermal fatigue. In the paper, notched cylindrical specimens were used for low cycle thermal fatigue test. A function based on the Manson-Coffin equation was fitted for life assessment of coke drum. This function considered time factor of the actual cycle and the experiment cycle. Structural numerical simulation result was used to obtain the remaining life of the coke drum.