Coke bed structure in a delayed coker Original Research Article

The porous structure of the coke bed in a delayed coking reactor is investigated in order to understand how flow channels are formed and how the cooling water distributes during the quench stage of the reactor cycle. Tomography, gas expansion, pycnometry and mercury injection are performed in an attempt to associate the bed characteristics with the development of thermal stresses and bulges in the reactor walls. The study has revealed the permeability of the coke to be very low because flow is defined by small pore sizes, in spite of the presence of some larger empty spaces. These can only be accessed through small pores and therefore remain nearly isolated. As a consequence, the water distribution during the cooling stage is mainly defined by the channel structure revealed by the pilot plant studies of Ellis and Hardin. Such a structure is developed during the filling stage of the cycle and the operation has no control of this process.