Studies On Coke Cooling Process In Coke Drum

On the basis of the multidimensional transient heat transfer differential equation, two-dimensional transient heat transfer governing equation in the cylindrical coordinate was derived. Fully implicit discretion equation of inner nodes and discretion equation of boundary nodes by means of additional source term method were built up, too. The solution of algebraic equations was also accomplished with the help of alternating direction implicit and tridiagonal matrix method.Taking cokes in coke drum as the research object, a simplified middle-channel model was built up. Then the mathematical model established in this paper was numerically analyzed using finite volume method. Visual Basic 6.0 was used to program to calculate the temperature fields of cokes in coke drum. The object-oriented programming language was used in the development of this program. According to the fact that the exothermic amount of coke is equal to the heat absorption amount of water, combined with the maximum evaporation point and the flux range of condensated water, the model of boiling heat transfer was selected from three exothermic models. The model of boiling heat transfer takes the process of water vaporization and heat transfer into consideration. The influence of grid number, coke properties and boiling heat transfer coefficient on the temperature fields, exothermic amount of cokes and vaporization amount of water was analyzed in the model of boiling heat transfer. The results showed that it is necessary to take the discrepancy of coke vaporization ability at different space and time into consideration. The time step, grid number in radical and axial direction especially in radical direction have an apparent influence on the initial vaporization amount of water. Among the parameters of coke properties, the influence of coke thermal conductivity on the vaporization amount of water is more apparent than coke heat capacity and density. However, the influence of boiling heat transfer coefficient and water bulk temperature is little. Additionally, if the diameter of coke drum is extended from 6m to 8.8m, the capacity of vent system will be raised about 13%; if the diameter is extended to 9.4m, the capacity will be raised about 15%.