In this paper a detailed dynamic mathematical model of a plant for the production of low density polyethylene (LDPE) is derived. Besides the main part, a tubular reactor, the plant comprises compressors, heat exchangers and material recycles. The dynamic model for the overall system consists of differential, partial differential and algebraic equations. For the numerical solution with the simulator DIVA, this system is transformed into a system of differential and algebraic equations. For the transformation an adaptive finite difference scheme is used. With this mathematical model, the influence of the reactor wall and the influence of the material recycles on the plant dynamics is studied. In particular, it is shown that the reactor wall due to its high thermal capacity dominates the time constant of the stand alone reactor. By closing the material recycles the time constant is significantly increased. In addition, the recycles give rise to intricate nonlinear behavior. (c) 2006 Elsevier Ltd. All rights reserved.