Detailed steady-state simulation of tubular reactors for LDPE production: plug flow versus cascaded CSTR model

This paper compares two approaches for simulating the steady state of tubular reactors for the production of LDPE, i.e., the plug flow and the cascaded CSTR approach. In principle, both strategies should yield similar predictions. However, numerical discretization issues related to, e.g., the large-scale and complex system of equations with various time scales needed to model this polymerization, may lead to serious discrepancies. First, this paper gives a condensed overview of the detailed model, i.e., the reaction mechanisms, the balance equations and the physical, transport and thermodynamical properties. Then, the two simulation approaches are discussed and the intrinsic differences are unraveled. Finally, the influence of discretization during integration is studied in simulation. Although this aspect is crucial to ensure accurate steady-state simulations, it is in practice too often overlooked.