Development of PP Melt Index Inferential Model
The melt index (MI) is an important quality specification in polypropylene (PP) production industries. Accurate online measurement of MI becomes vital in PP quality control. A new MI inferential model is proposed by using macro heat of reaction (MHR) as a key factor in MI correlation. MHR is calculated from a dynamic propylene polymerization model. The proposed MI model is validated by plant data and the prediction error is less than 5%. Simulations are performed by three different MI inferential models. The results show that the proposed model has least errors in various operation conditions. The MI model could be used as online soft sensor model or MI control
Optimal Grade Transitions in a Gas Phase Polyethylene Reactor
Using gas-phase technology many grades of polyethylene can be produced in a single reactor. For a series of three polyethylene products, model-based dynamic optimization is used to determine optimal grade changeover policies. Optimal manipulated variable profiles are determined for hydrogen and butene feed rates, reactor temperature setpoint, gas bleed flow, catalyst feed rate, and bed level setpoint. It is shown that large transitions in melt index are hampered by slow hydrogen dynamics, and that the time required for such a transition can be reduced by manipulating the temperature setpoint and the bleed stream flow. Reduction of the bed level and catalyst feed rates during changeovers can significantly reduce the quantity of off-specification polymer produced. It is demonstrated that melt index and density are not sufficient to characterize the properties of polymer produced during grade transitions, and that the shape of the cumulative copolymer composition distribution is very sensitive to the grade changeover policy used. Optimal transition policies should not be implemented without feedback control. Disturbances and model mismatch can result in product property trajectories which deviate significantly from the nominal optimal trajectory.
The EU Legal Framework for the Enforcement of Consumer Law
The European Union (EU) is special in that it is a multi-level system in which, principally, consumer law can be adopted at the EU level but it is enforced at the level of the Member States. Nevertheless, the EU has over time developed an ever denser legal framework for the enforcement of consumer law by the Member States. It is this legal framework that this contribution focuses upon.