JAYCOR has developed a computer code for modeling fluid flows containing agglomerating particles, with the goal of providing a method for optimization and scale-up of certain coal gasification reactors. The physical and chemical processes modeled in the computer code range from fluid and particle flow with heat transfer, to pyrolysis, mixing, and agglomeration of the coal. The initial effort has been directed toward a simulation of the Westinghouse Electric Corporation's devolatilizer unit, which uses a draft tube and fluidized bed for devolatilizing coal, while limiting the agglomeration of the coal particles. The simulation code is flexible and can easily be adapted to study the behavior of other reactors.