No abstract

An empirical model has been developed for the successful prediction of the melt index (MI) during grade change operations in a high density polyethylene plant. To efficiently capture the nonlinearity and grade-changing characteristics of the polymerization process, the plant operation data is treated with the recursive partial least square (RPLS) scheme combined with model output bias updating. In this work two different schemes have been proposed. The first scheme makes use of an arbitrary threshold value which selects one of the two updating methods according to the process requirement so as to minimize the root mean square error (RMSE). In the second scheme, the number of RPLS updating runs is minimized to make the soft sensor time efficient, while reducing, maintaining or normally increasing the RMSE obtained from first scheme up to some extent. These schemes are compared with other techniques to exhibit their superiority.

No abstract

A chemical heat pump, based on the reversible reaction couple of the i‐propanol‐acetone system, was investigated experimentally. The endothermic dehydrogenation of i‐propanol occurred at 80°C with a Raney nickel catalyst suspended in the liquid phase. The unreacted i‐propanol was separated from gaseous products in a condenser. The exothermic hydrogenation reaction of the acetone was performed at 200°C and 1atm, in the presence of the Raney nickel catalyst. The positive value (ΔG) of the change of Gibbs free energy can make the dehydrogenation reaction of i‐propanol rather difficult. This problem can, though, be overcome by the continuous removal of gaseous acetone and hydrogen products from the reaction medium. The dehydrogenation rate equation of i‐propanol was obtained as V = 0.1 Cp/(1 + 7.0 CA). The gas phase hydrogenation reaction of acetone was performed in an exothermic tubular reactor. In order to estimate energy efficiency, a simulation of the separation stage was performed. Based on these experimental and simulation results, the optimal design specifications for the chemical heat pump were determined. The maximum hydrogenation of acetone was obtained when the mole ratio of acetone to hydrogen was 4.0. Energy efficiency was increased when the conversions of hydrogenation and dehydrogenation increased.

No abstract