Abstract: The simulation of various types of transport processes is reviewed, Using the centered difference mothod, the mathematical model of a rotary drying process is transformed into a numerical model which is expressed by a couple of nonlinear bi-tridiagonal matrix systems with split boundary conditions. As a result of the designed algorithm, the numerical solution is accurately obtained, and the process is simulated on a digital computer. Thus, tile Douglas algorithm is successfully extended to the process with boundary values of two discontinuities at both ends. Tests demonstrate that the presented method is flexible and efficient for extension to more complicated systems.