Agnes Szanyi

Novel hybrid separation processes for solvent recovery based on positioning the extractive heterogeneous-azeotropic distillation

The solvent recovery is often the separation of highly non-ideal mixtures. The separation and recovery of quaternary solvent mixtures coming from printing and medicine factories are investigated. The components of the six quaternary mixtures studied in form of heterogeneous and homogeneous azeotropes of minimum boiling point. The mixtures can be categorised into three groups according to their VLLE behaviours. After studying their behaviours, three novel hybrid separation processes based on the extractive heterogeneous-azeotropic distillation, a special kind of new distillation, are developed and recommended for each group of solvents. In the novel processes, beside the extractive heterogeneous-azeotropic distillation, ordinary distillations and phase separation units are also used utilising the fact that the combination of such units, the hybrid processes, offer a higher variety of the possibilities for the separation of highly non-ideal mixtures. The separation processes are verified experimentally and the agreements between the simulated and measured data prove to be rather favourable. A strategy is recommended for the use of the novel hybrid processes developed according to the VLLE behaviour of the non-ideal quaternary mixtures.

Environmental and economic comparison of waste solvent treatment options

The sustainable development and consumption need more efficient use of natural resources. As a consequence, the use of industrial solvents demands their recovery instead of end-of-pipe treatment. It is not always clear, however, which treatment alternative should be applied. Based on an industrial case study, the environmental and economic evaluation and comparison of the treatment alternatives of a non-ideal solvent mixture containing azeotropes is investigated for determining the preferable option. For the recovery of the industrial solvent mixture, two different separation alternatives are evaluated: a less effective alternative and a novel design based on hybrid separation tools. An end-of-pipe treatment alternative, incineration, is also considered and the split of the solvent mixtures between recovery and incineration is investigated. The environmental evaluation of the alternatives is carried out using ‘Eco-indicator 99 life-cycle impact assessment methodology’. Economic investigation is also accomplished. The economic features clearly favour the total recovery, however, the environmental evaluation detects that if a recovery process of low efficiency is applied, its environmental burden can be similar or even higher than that of the incineration. This motivates engineers to design more effective recovery processes and reconsider the evaluation of process alternatives at environmental decision making.

Separation of Process Wastewater with Extractive Heterogeneous-Azeotropic Distillation

Abstract The application of vapour-liquid equilibria-based separation alternatives can be extraordinarily complicated for the treatment of process wastewaters containing heterogeneous-azeotropic. Despite dissimilar successfully tested methods for separation, there is possibility to get better distillation method by enabling the separation of more and more specific process wastewater. Extractive heterogeneous-azeotropic distillation (EHAD) is a new advance in treatment of fine chemical wastewater showing special features to cope with the treatment of highly non-ideal mixtures. This method combines the worth of heterogeneous-azeotropic and extractive distillations in one apparatus without addition of any extra materials. The study of the separations of ternary component process wastewater from the fine chemical industry shows both in the modelled and experimental results that EHAD can be successfully applied. The measured and modelled compositions at extreme purities, that is, close to 0% or 100%, can be different because of the inaccuracies of the modelling. This highlights the paramount importance of the experiments if special extra-fine chemicals with almost no impurities, e.g. of pharmacopoeial quality are to be produced by special distillation technique. This study expands the application of EHAD technique, this new field is the separation of process wastewaters.

Intensification of a Solvent Recovery Technology through the Use of Hybrid Equipment

Abstract In printing companies often different four-component-mixtures (mixture 1: ethanol, ethyl acetate, isopropyl acetate, and water, mixture 2: ethanol, ethyl acetate, methyl-ethyl-ketone, and water) arise as waste. The recovery of the individual components is complicated by the highly nonideal feature of the mixtures, namely several binary and ternary azeotropes are formed by the components. Based on the synthesis procedure proposed by Rev et al. (1994) and Mizsey et al. (1997), new separation processes using hybrid separation techniques are developed followed up the vapour-liquid-liquid equilibrium behavior of the mixtures. The first process (ternary-cut-system) splits mixture 1 into two ternary mixtures which are separated later in subsequent units into components of the prescribed purity (∼95%). This technology needs, however, seven distillation columns and two extractors. The second separation process is based on two coupled columns and a three-phase-flash (two-column-system) which can cope with the separation of both mixtures into binary mixtures and the binaries can be easily separated further with conventional methods. Both processes are using extra water addition for the necessary separation. These processes are experimentally also verified (Mizsey et al., 1997, Raab, 2001). A third integrated separation process is developed with evolutionary steps merging the extractor and distillation units, designed for the ternary-cut-system, into integrated extractive distillationprocess using water as extractive agent (integrated-system). The integrated-system can separate both mixtures into components of the prescribed purity and consists of only four distillation columns. Beside the simpler separation structure the energy consumption is also investigated and compared with the other two processes. The use of this innovative solvent recovery process makes the reduction of the number of processing units possible and operating costs can be significantly reduced compared to the other non-integrated separation technologies.

Evaluation of the accuracy of modelling the separation of highly non-ideal mixtures: extractive heterogeneous-azeotropic distillation

Abstract The distillation based separation can be extremely complex if highly non-ideal mixtures are to be separated. In spite of different successfully applied unit operations there is still possibility to improve distillation technique and widen its toolbar. A new improvement in this area is the introduction of the extractive heterogeneous-azeotropic distillation (EHAD). This unit operation includes the merits of the extractive and heterogeneous-azeotropic distillations in one unit without an extra material addition. In spite of the complexity of this unit operation it can be efficiently applied and complex separation technologies can be simplified with its application. The separations of ternary and quaternary mixtures from the fine chemical industry show both in the modelled and the experimental results that the extractive heterogeneous-azeotropic distillation is an efficient tool of this area. Demonstrating the accuracy of EHAD, the separation of methanol–ethyl-acetate–water and ethanol–ethyl-acetate–water mixtures are examined and the EHAD is compared with conventional distillation techniques. These separation processes are rigorously modelled and optimized with dynamic optimization method in professional flowsheeting environment. The objective function is the total annual cost but the energy consumption is also investigated. The modelling results are verified with laboratory experiments, too. It can be concluded that the extractive heterogeneous-distillation is a capable method for the separation of these highly non-ideal mixtures.

Enhanced separation of highly non-ideal mixtures with extractive heterogeneous-azeotropic distillation

ABSTRACT The distillation based separation can be extremely complex if highly non-ideal mixtures are to be separated. In spite of different successfully applied unit operations there is still a possible way to improve the distillation technique and widen its toolbar. A new improvement in this area is the development of the extractive heterogeneous-azeotropic distillation (EHAD). This unit operation includes the merits of extractive- and heterogeneous-azeotropic distillations in one unit without extra material addition. Our work supports EHAD features with successful experiments compared with modelling and comparison with other separation structures proving that the application of EHAD makes the separation of extremely non-ideal mixtures possible on an easy, powerful, energy saving, and cost efficient way.