(72d) Dynamic Simulation for Poly-Ethylene Process By PC-SAFT Model

Current applications for polyethylene plant simulation, especially for Operator Training Simulators (OTS), safety features analysis in dynamic, as well as ethylene compressor control mechanism, require both model accuracy and simulation performance. However this cannot be achieved without proper selection of the thermodynamic model. Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) ^[1] has been well established through its accuracy in modeling monomer solubility into polymer solutions, and hence placed itself as an excellent candidate for model accuracy of polyethylene plant simulation.

Questions for PC-SAFT come from the performance and reliability of the density solutions on vapor/liquid phase at extreme conditions such as high temperature and high pressure ^[2]. Here, we present a state of the art implementation and modification of PC-SAFT through DYNSIM, a dynamic simulation tool by Schneider Electric that achieves both model accuracy and simulation performance, with which clients can apply to execute various tasks in both steady state and dynamic analysis over the entire plant.

Detailed information for the implementation and modification of PC-SAFT would be discussed in the scopes of

•             Super-linear approach when previous rigorous solution had been converged; 

•             Pseudo-density extrapolation near and over super-critical region

Demonstration by DYNSIM simulation with PC-SAFT at key regions of polyethylene plant would be displayed, followed by the potential upstream and chemical plants’ applications.

[1] J. Gross and G. Sadowski, “Perturbed-Chain SAFT: An Equation of State Based on a Perturbation Theory for Chain Molecules”, Ind. Eng. Chem. Res. 2001, 40, 1244-1260

[2] Privat R., R. Gani  and J-N. Jaubert, “Are safe results obtained when the PC-SAFT equation of state is applied to ordinary pure chemicals?”, Fluid Phase Equilib. 2010, 1, 76-92.