Polyethylene Terephthalate Reactors Research Articles

In vitro toxicity studies of novel solar water disinfection reactors using the E-screen bioassay and the Ames test

Abstract Solar water disinfection (SODIS) is a cost-effective point of use method for disinfecting water, usually in a 2 L polyethylene terephthalate (PET) plastic bottle. To increase the volume of water disinfected, three novel transparent reactors were developed using PET in 25 L transparent jerrycans, polymethyl methacrylate (PMMA) in tubular solar reactors capable of delivering >20 L of water and polypropylene (PP) in 20 L buckets. In vitro bioassays were used to investigate any toxic substances leached from the plastic reactors into disinfected water as a result of exposure to sunshine for up to 9 months. The Ames test was used to test for mutagenicity and the E-screen bioassay to test for estrogenicity. No mutagenicity was detected in any sample and no estrogenicity was found in the SODIS treated water produced by the PMMA reactors or the PP buckets. While water disinfected using the PET reactors showed no estrogenicity following exposure to the sun for 3 and 6 months, estrogenicity was detected following 9 months' exposure to sunlight; however levels detected were within the acceptable daily intake for 17β-estradiol (E2) of up to 50 ng/kg body weight/day.

Multiobjective Optimization of Industrial Processes Using Elitist Multiobjective Differential Evolution (Elitist-MODE)

Multiobjective optimization (MOO) refers to solving more than one-objective optimization problems simultaneously to attain a set of solutions, i.e., the Pareto front. In this study, an elitist strategy of multiobjective differential evolution (Elitist-MODE) algorithm is used to find the Pareto optimal solutions for a set of multiobjective test problems [POL (unconstrained), CONSTR-EX (constrained), and TNK (constrained)] and two-industrial engineering process problems, namely, styrene reactor and polyethylene terephthalate reactor (PET). A detailed analysis is reported for the test problems and real-world industrial problems, and the obtained Pareto fronts are compared with the Pareto front obtained using MODE and MODE III algorithms. Simultaneous maximization of selectivity and yield (for the styrene reactor) and simultaneous minimization of acid- and vinyl-end group concentrations (for the PET reactor) are considered. A detailed analysis of obtained Pareto fronts with respect to the set of decision variables for the individual industrial study is reported. It is observed that the improved strategies of MODE algorithms in general converge to the true Pareto front both for the test problems (constrained/unconstrained) and complex industrial problems. It is also suitable for solving the problems having disconnected Pareto front.

Hybrid multi-objective differential evolution (H-MODE) for optimisation of polyethylene terephthalate (PET) reactor

Multi-objective evolutionary algorithms (MOEAs) are used to solve the optimisation problems with more than one objective to be optimised simultaneously having conflict among each other. Due to the limitations of traditional deterministic algorithms to handle complex and nonlinear search space, several EAs are developed in the recent past. The multi-objective differential evolution (MODE) algorithm is already tested and found to be a reliable algorithm due to their ability to handle non-linear problems efficiently. Though MODE is accurate in terms of converging to the global Pareto front, traditional method has their advantage in terms of speed. We combined these two algorithms and developed hybrid strategy of MODE thus, achieving both accuracy and speed. Hybrid MODE (H-MODE) algorithm is applied on multi-objective optimisation of industrial wiped film polyethylene terephthalate reactor. The results of the present study are compared with those obtained using MODE algorithm. Smooth and well diverse Pareto optimal front is observed with a much faster speed using H-MODE.

Modelling of polyethylene terephthalate reactors—X. A comprehensive model for solid-state polycondensation process

A new comprehensive model for solid-state polycondensation (SSP) of polyethylene terephthalate (PET) has been developed, which interprets a number of hitherto unexplained observations. Degradation and other side reactions which were neglected in the earlier models for SSP process of PET are included. The diffusivity changes due to crystallisation of PET, the true influence of nature of carrier gas and the increase in the reactive chain end group mobility due to the change in the free volume in the presence of an inert gas have been considered. The model predictions have been validated with experimental data reported in the literature. The model can be used for a quantitative prediction of the influence of a variety of parameters on the degree of polymerisation as well as side products formation. The model correctly brings out the true influence of the carrier gas which had remained unexplained so far. It also suggests additional directions for improving the SSP process.

Optimization of the transesterification stage of polyethylene terephthalate reactors

AbstractThe tranesterification step of the polyethylene terephthalate (PET) formation consists of several side reactions in addition to the main ester interchange, transesterification, and polycondensation reactions. The side reactions considered in this work are acid end group, acetaldehyde, diethylene glycol, water, and vinyl end group formations. The objective function of the batch esterinterchange reactor is assumed to consist of maximizing the conversion and simultaneously minimizing the formation of side products. The control vector iteration procedure has been used to optimize the esterinterchange reactor and the temperature‐time profile that gives the best performance has been found. It is found that the reactor should be operated at a high temperature initially to obtain high conversion of dimethyl terephthalate (DMT) first, but then it should be lowered to reduce the formation of side products.

Solution of final stages of polyethylene terephthalate reactors using orthogonal collocation technique

AbstractThe formation of polyethylene terephthalate (PET) has been modeled to have reactions with monofunctional compounds, redistribution, and cyclization reactions in addition to the usual polycondensation step. In the final stages, the overall polymerization is mass‐transfer controlled and solution of the reactor performance equations have been determined through the orthogonal collocation technique. This technique is found to be considerably more efficient for PET reactors compared to the finite difference method; the use of ten collocation points gives results which are close to the exact solution.

Modeling of polyethylene terephthalate reactors: 7. MWD considerations

AbstractA mathematical model has been developed to compute the molecular weight distribution (MWD) in the polyethylene terephthalate (PET) manufacturing process. Unlike the previous efforts, this model takes into account the influence of side reactions and various interchange reactions on MWD. The process of blending of molten polyester chips has also been simulated with a view to calculate the equilibrium MWD as well as the time required to reach the equilibrium MWD. The1 significance of the results has been discussed in terms of industrial operations involving PET polymerization and PET blending.

Simulation of cyclics and degradation product formation in polyethylene terephthalate reactors

The second stage of a batch polyethylene terephthalate (PET) reactor with a kinetic scheme consisting of side reactions like thermal degradation, redistribution, cyclization and reaction with monofunctional compounds (cetyl alcohol), in addition to the major polycondensation step, has been simulated. The cyclization equilibrium has been shown by Semlyen for various cyclic compounds to be chain-length-dependent 1. Mass balance for various side products and the polymer, PET, have been carefully worked out and the resulting set of differential equations have been solved for the molecular weight distribution ( MWD) of the polymer. It is found that the cyclization reaction has considerable effect on the polydispersity index of the polymer even though the total quantity of cyclic compound is no more than 5%. The effect of variation of temperature and initial concentration of monofunctional compound was found to have little influence on the polydispersity index of the polymer. Since the removal of the condensation product does not become diffusion-controlled till the average chain length of the polymer reaches the value of 30, the reaction mass can be assumed to attain a uniform ethylene glycol concentration for a given applied vacuum and can be determined by the vapour-liquid equilibrium relation. The fractional level of ethylene glycol concentration, [ G] (≡ [ EG] [ P 1] 0 ) , has been taken as a parameter and the MWD results were found to vary the redistribution rate constant with sensitivity increasing with decreasing [G]. It was shown that the importance of the redistribution reaction is increased when the cyclization reaction also occurs.