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Laponite nanodiscs are low cost synthetic silicate clay with extreme hydrophilic behavior. Therefore, laponite can be used to enhance pervaporation membranes’ performance. Poly(vinyl alcohol), (PVA)/laponite pervaporation membranes were fabricated via simple exfoliation method of the nanoclay in the polymer solution followed by chemical crosslinking using glutaraldehyde (GA). The fabricated membranes were employed to study the pervaporation desalination performance when treating reverse osmosis (RO) concentrated brine solution. The effect of nanofiller concentration on membrane properties, as well as the water diffusion coefficient through the membrane, swelling measurements was investigated. The highest rejection of ∼99.98% was achieved using 7 wt% laponite nanocomposite membrane at 40 °C with a flux of 31.2 kg/m2 h. Increasing the feed concentration resulted in a decrease in water flux, whereas the salt rejection was negligibly changed. The influence of the operating temperature and feed salt concentration on the desalination performance 7 wt% laponite nanocomposite membrane (PVA7) were obtained at different temperatures in the range between 30 °C and 70 °C and feed concentration up to 100,000 ppm the temperature profile is expressed by Arrhenius relationship.

This study investigates the formic acid-mediated hydrothermal carbonisation (HTC) of microalgae biomass to enhance green hydrogen production. The effects of combined severity factor (CSF) and feedstock-to-suspension ratio (FSR) are examined on HTC gas formation, hydrochar yield and quality, and composition of the liquid phase. The hydrothermal conversion of Chlorella vulgaris was investigated in a CSF and FSR range of −2.529 and 2.943; and 5.0 wt.% – 25.0 wt.%. Artificial neural networks (ANNs) were developed based on experimental data to model and analyse the HTC process. The results show that green hydrogen formation can be increased up to 3.04 mol kg−1 by applying CSF 2.433 and 12.5 wt.% FSR reaction conditions. The developed ANN model (BR-2-11-9-11) describes the hydrothermal process with high testing and training performance (MSEz = 1.71E−06 & 1.40E−06) and accuracy (R2 = 0.9974 & R2 = 0.9781). The enhanced H2 yield indicates an effective alternative green hydrogen production scenario at low temperatures using high-moisture-containing biomass feedstocks.

Pervaporation (PV) has shown great promise in water desalination technology. In this work, Laponite XLG – Poly (vinyl alcohol) (PVA-Lap) mixed matrix membranes (MMMs) were fabricated to investigate the elaboration of desalination of high-salinity water by pervaporation. The influence of Laponite content on the morphology, chemical structure and hydrophilicity of the membranes was investigated. In addition, salt transport properties in the membranes were observed. Moreover, the effect of different Laponite content in the PVA matrix on the desalination performance was observed at temperatures from 40 °C to 70 °C and feed solutions with up to 10 wt% NaCl. The prepared MMMs showed higher hydrophilicity and roughness of the surface and higher mechanical stability. The higher water flux of 58.6 kg/m2 h with a salt rejection over 99.9% was achieved using 2 wt% Laponite XLG MMMs desalinating 3 wt% aqueous NaCl solution at 70 °C. The salt permeability in the membrane was lower by two orders of magnitude than that of water. The water/salt selectivity increased, while the water permeability decreased, with increasing of Laponite content in the membrane.

This study examines the light factorial optimization of Chlorella vulgaris microalgae cultivation under different wavelengths and light intensities. RGB light-emitting diodes were applied on microtiter plate and lab scale stirred tank photobioreactors. One-way ANOVA and response surface methodology were adopted to investigate the effects on biomass productivity. The highest biomass productivity is found at 243.5 and 96.8 μmol photon m−2 s−1 in case of red and blue color intensities, respectively. Scaled-up fermentation in stirred tank photobioreactors shows that changing light intensity and aeration settings result in differing biomass productivity and composition. The effects of targeted cultivation are investigated on hydrothermal gasification (HTG) which is carried out in tubular reactor system at 550 °C, 30.0 MPa and average 120 s residence time. It is found that the fermentation of microalgae under optimized light factor levels results in higher H2 yield compared to unoptimized light intensity levels. Throughout the HTG process high H2 yield is achieved (4.38–9.34 mol kg−1) without using any catalyst, which indicates that the efficiency of downstream processing can be increased already at the cultivation stage.

In the separation industry the extractive heterogeneous-azeotropic distillation (EHAD) is a new and powerful innovation, that is capable of making the separation of highly non-ideal mixtures feasible and economical. In the last years there has been much attention paid to the separation of the minimum boiling homogeneous azeotropes. Although maximum boiling azeotropes are fewer in numbers than the minimum boiling ones but their separation is more complicated but it could be solved with the EHAD, too. Since EHAD is not limited to the separation of minimum boiling azeotropes, the separation of the maximum boiling azeotropes is studied in this work. Our work is motivated by industrial problems because there are such maximum boiling azeotropes in the liquid wastes of the fine chemical industry. The separation of highly non-ideal Water–Acetone–Chloroform–Methanol and Water–Ethyl Acetate–Chloroform–Ethanol quaternary mixtures are investigated and optimized in professional flowsheet simulator environment. Total Annual Costs are also determined. The purity requirement is 99.5 m/m% for Chloroform and the bottom product should be as clear as possible in water so that less liquid organic waste has to be incinerated. It is also an important merit of the EHAD that the chemicals in the distillate can be usually reused supporting sustainability. Different solutions for the separations supplemented with heat integration are examined. On the basis of the computer simulations and the experimental verification it can be concluded, the first time on the literature, that the separation efficiency of EHAD is superior also for the separation of the maximum boiling azeotrope mixtures.

Different research works demonstrate that the pervaporation can replace the distillation or deliver better solutions. It should be, however, accepted with criticism. In our case study, isobutanol-water separation is studied since it is increasingly important in the field of biofuels and process wastewater treatment. There are many options for the separation and they differ in their efficiency, economic features, robustness, development level and environmental impact. Five separation structures are investigated using distillation, both organophilic and hydrophilic pervaporations and hybrid separation units consisting of distillation and pervaporation including heat integrated solutions. The different alternatives are modelled in professional flowsheeting environment. Life cycle assessment, energy evaluation and Multi-Criteria Decision Analysis (MCDA) based on PEST (Political, Economic, Social, and Technological) analysis are completed to evaluate and compare the five alternatives. The feed stream to be separated has the composition of 7 wt% isobutanol 93 wt% water that corresponds to the mixture of the phase split due to the limited solubility. Two product purities are considered, 98.8 and 99.9 wt%. In case of distillation processes, heat integration is also considered, that is, the feed is preheated with its bottom flow. Heat integration significantly improves the efficiency of the distillation and makes it for practically a competitive alternative. The best efficiency can be obtained with heat integrated hybrid separation, that is, the combination of distillation and pervaporation. The pure pervaporation that is the combination of organophilic and hydrophilic pervaporation can be efficient only at sloppy product purities because of the modest separation factor of the organophilic pervaporation membranes. In case of sharp separations, the organophilic pervaporation can be an equally applicable solution as the azeotropic distillation for isobutanol-water separation.

Hybrid separation materials intended for the hydrophobic pervaporation process with a new type of fillers were generated. Membranes based on poly(ether block amide) (Peba 2533) containing two organic fillers: 4-(trifluoromethyl)-N-(pyridine-2-yl)benzamide (denoted as F1) and 4-(dimethylamino)-N-(pyridine-2-yl)benzamide (denoted as F2) were fabricated. Novel materials were systematically characterized from the material point of view and subsequently applied in the pervaporative separation of binary water-organic mixture. The correlation between the type (e.g. hydrophobicity) and amount of the filler on the membrane performance has been discussed. The pervaporation performance was assessed for ethanol/water mixture containing 5 wt% ethanol at temperatures ranging from 30 °C to 60 °C. The separation factor (β), thickness normalized total and partial permeate fluxes (Jt,N and Ji,N), and thickness normalized Pervaporation Separation Index (PSIN) were utilized for evaluation of the process. The best efficiency in recovery of ethanol from a mixture containing 5 wt% of ethanol was found for the membranes containing 2.5 wt% of F1 (membrane denoted as PF1-2.5) and 10 wt% of F2 (membrane denoted as PF2-10). The incorporation of the organic fillers improved the pervaporation performance of the PEBA membrane, regarding both permeate flux and separation factor. The highest normalized flux of 28.9 μm kg m-2h−1 and separation factor of 4.6 was achieved at 60 °C, using PF1-2.5 in contact with 5 wt% ethanol as feed.

Carbon dioxide emission, one of the core cause of global warming and other threats of nonreversible environmental effects, is in focus today. Among the several methods of CO2 emission mitigation, post-combustion carbon capture (PCC), based on absorberdesorber systems with amine absorbents, is one of the promising alternatives. The major anthropogenic CO2 point sources are power plants, natural gas extraction units, oil refineries, cement factories, biogas plants, etc. As these CO2 sources can be treated with a PCC absorber-desorber system, then these two units should cope with various conditions. To maintain a desired high removal efficiency, the capture unit must work in flexible conditions. The aim of this study is to evaluate the influence of the extent of the absorption of carbon dioxide on the overall performance of the acid gas removal process, considering that, generally, as the amount of removed CO2 increases, the separation becomes more challenging. In this work a verified computer based process model for the absorber-desorber system is used. Aspen Plus® professional flowsheet simulator is used for this purpose. Attention is paid on the proper operating parameters of a PCC absorber-desorber system for the case of increasing the CO2 capture efficiency up to 99%. As alternative solutions for these cases different scenarios are considered: • the increase of the capacity of a classic configuration of an absorber-desorber system; • the introduction of a second absorber column as extending the absorption column height; • the possible use of two absorbers and two desorbers working in series. This work deals with the detailed study on maximizing CO2 removal efficiency while maintaining the minimal energy consumption for the absorbent regeneration section.

CO2 is the primary greenhouse gas (GHG) due to its large quantity of anthropogenic emission. In this work the amine based carbon capture process and the CO2 storage, called Carbon Capture and Storage (CCS) is analysed from different viewpoints. PESTLE (Political, Economic, Social, Technological, Legal and Environmental) analysis of the CCS alternatives (Fossil based, Improved process, Renewable based) is investigated in detail and the alternatives are also compared with the uncontrolled CO2 release using Life Cycle Assessment (LCA) methods. Life cycle inventory data is set up and analysed with four life cycle impact assessment methods. In order to conclude the comparison of CCS and the uncontrolled release of CO2 a Multi-Criteria Decision Analysis (MCDA) is also applied with Multi Attribute Value Theory (MAVT) method. Our results show that applying process improvement and renewable energy sources (e.g., biogas) for absorbent regeneration result in a CCS technology of much smaller environmental and social impacts, and therefore the CCS technology becomes more favorable than the uncontrolled release.

Converting carbon dioxide to fine chemicals such as methanol using electrolytic hydrogen could be an efficient way of renewable energy storage. The conversion of CO2 to methanol is a rather complicated multistep process which is usually performed catalytically in gas phase. However, the aqueous phase conversion of CO2 is also feasible in certain conditions. Thus, a catalyzed-like water enhanced mechanism of CO2 hydrogenation to methanol has been designed and studied by using the highly accurate W1U composite method. The initial reactant mixture was CO2 + 6H + 8H2O + H3O+, where the hydrogen atoms are added one-by-one to mimic the catalytic effect of a metal surface. The presence of water and H3O+ further enhance the reaction by lowering the reaction barriers. By computing the thermodynamic properties of the reaction mechanism, it was found that the highest relative energy barrier in the most preferred pathway is 212.67 kJ/mol. By taking this into account, the energy efficiency of the pathway has been calculated and it was found to be equal to 92.5%.

The work is motivated by an industrial separation problem, that is, isobutanol removal from aqueous mixture. To complete this goal a hybrid separation system of organophilic–hydrophilic pervaporation system is designed applying Sulzer PERVAP™ 4060 and 1510 membranes and investigated to obtain information about the separation of isobutanol–water mixture. The aim of research is to rigorously model and optimize this novel hybrid process. Permeation fluxes, permeances, selectivities and separation factors are experimentally determined for this hybrid system. The pervaporation separation index (PSI) and selectivity data are compared with those of other membranes published in the literature and it is found that PERVAP™ 4060 has the highest PSI value and its other parameters are also among the best. Our experimental data are evaluated with the pervaporation model of our improvement and it is found that the model can be applied also for both organophilic and hydrophilic pervaporations. The hybrid separation system is rigorously modelled with ChemCAD and optimized with the dynamic programming optimization method. The objective function of the hybrid system is the total annual cost but its energy consumption is also investigated. It can be determined that this hybrid process, that is, the combination of organophilic and hydrophilic pervaporations is capable for the separation of isobutanol and water and it can become the alternative of distillation based separation. Considering our results it can be assumed that the combination of the organophilic and hydrophilic pervaporations opens new horizons for the membrane processes.

This study investigates enhanced biogas production via co-Hydrothermal gasification (co–HTG) of wet Chlorella vulgaris biomass and hydrochar (HC). Hydrothermal carbonization was applied to valorize struvite containing waste microalgae stream into solid bio-fuel with improved combustion properties. The effects of HC quality and mixing ratio are investigated on biogas yield, composition and carbon conversion ratio. The results show that the application of blending components promotes H2, CH4 formation and selectivity in hydrothermal gasification. The total co-HTG gas yield is increased from 19.13 to 46.95 mol kg - 1 at 650 °C and 300 bar by applying 5 wt% HC blending concentration and reduced level of volatile matter content (24.61 wt%). The obtained high hydrogen, methane yields and carbon conversion ratio (19.49, 2.98 mol kg - 1 , 82.31%, respectively) indicate effective hydrothermal upgrading potentials in case of wet and waste biomass feedstocks.

The energy and raw material supplies are crucial issues in our societies. The possible solution of these issues can be coupled with the storage alternatives of renewable energy. The chemical way of energy storage can be quite different but we follow the Supplement of Natural Gas concept since this delivers a high storage capacity solution. The chemical way of energy storage is based on the carbon dioxide hydrogenation. It is in agreement with the theory of the circular economy so that the carbon emission is reduced with the concept of Carbon Capture and Utilization (CCU). In this work the reaction system of the carbon dioxide hydrogenation is studied thermodynamically applying the tool of quantum chemistry. The aim of the study is to support the carbon dioxide transformation alternatives of industrial scale, that is, the CCU. It is determined that the methane production has the highest thermodynamic efficiency where the methanol production is the second in the ranking. These thermodynamic efficiencies are 14.4% for methanol and 44.4% for methane. Both alternatives have, however, advantages since the methane can be introduced directly into the natural gas network and the methanol has the highest volumetric energy content. Both molecules can be transformed into different kind of raw materials, see e.g. methanol economy. At the selection, however, other, practical points of view should be also considered where industrial experiences and circumstances are to be also taken into account. Having recognized the need to deal with the reduction and utilization of carbon dioxide emission (CCU), the University of Miskolc established the “Environmental Carbon Dioxide Partnership”. It has several industrial partners having significant carbon dioxide emission and therefore experience in this issue. The experts of the partnership help to solve emission problems and the carbon dioxide utilization, based on the theoretical and practical results and experiences of the Partnership. This thermodynamic investigation supports the development of the Partnership to carry out the most efficient CCU method.

Processes applied for the capturing of carbon-dioxide from industrial gases are in the focus of the reduction of green-house gas emission. The highest amount of anthropogenic CO2 is emitted in flue gas form but with varying gas composition according to the source and the circumstance of the combustion of fossil fuel. A typical method for such CO2 capturing is an absorber–desorber system where the absorbent is quite frequently 30 wt% aqueous monoethanolamine (MEA) solution. The aim of our work is to setup an adequate and verified computer based process model that is capable for the rigorous simulation and analysis of the treatment of various flue gases, evaluating the purification of different types of flue gases to see the environmental aspect and further possible process improvements. For the verification of the absorber–desorber model, measured data are applied. The data are obtained on an existing absorber–desorber system of pilot plant size for the cases of two different test gases of different compositions. It is shown and explained why the equilibrium stage model is not accurate in such cases but the non-equilibrium stage assumption, that is, the rate based modeling is suitable. Modeling explains the reasons of why the operation with less absorbent need higher energy for the operation than the optimal one and shows the effect of carbon footprint of the energy demand achieved with various fuels used for desorber heating.

The work is motivated by an industrial environmental problem, that is, methanol removal from aqueous mixture. In order to complete this goal, organophilic pervaporation of methanol/water mixture through commercially available Sulzer PERVAP™ 4060 and 2211 membranes are investigated to obtain information about the removal of methanol. The experimental results are obtained at different feed concentrations (0.05–20 m/m% methanol) and temperatures (50–70 °C). Permeation fluxes, permeances, selectivities and separation factors are determined. The separation factors are modest but it proves to be greater in the case of PERVAP™ 4060 than 2211 membrane but it decreases with the methanol feed concentration. On the contrary, the total flux is higher in the case of PERVAP™ 2211 and it increases with feed methanol concentration and temperature. Our experimental data are evaluated with the pervaporation model ( Valentinyi et al., 2013 . Chem. Eng. Res Des. 91, 174–183) of our improvement and it is found that the model can be applied also for this organophilic case. Long-time experiment shows that the membranes of the current selectivity values are not capable for the entire removal of methanol from an aqueous mixture and the membrane development work should be continued in this area, too. However, if methanol removal is needed to solve the motivating this problem, then rectification can be recommended as a reliable solution in this case, too.

This work investigates the techniques used in evaluating distillation structures from lean manufacturing point of view. Oil & gas industry has already started adopting lean manufacturing principles in different types of processes from information flow to processing technologies. Generally, energy costs are the most important factors in processing hydrocarbons. Introducing flexibility desired by lean principles to the system may conflict energy efficiency of the system. However, this does not mean that the economic optimum is the energetic optimum. Therefore all possible changes due to temporarily stopped or not fully utilised plants have to be investigated, resulting in a large amount of cases that have to be evaluated. For evaluation exergy analysis can be used as it involves all energy types, and evaluation is straightforward. In this paper plain distillation structures are investigated, and the boundaries of the systems are set up according to the status of the site. Four component case studies are presented that show that the very same distillation structure can be more or less efficient depending on the status of the industrial site. It is also shown that exergy analysis used with different boundaries on the same system can show flexibility of the system and reveals potentials.

Pervaporation is proved to be a commercially viable membrane separation process by this time. However, to become a widely applied process in the industry it is of crucial importance to develop membrane properties, process and module design as well as proper modelling in professional software environment. In this work a pervaporation model improvement of the basic solution–diffusion model ( Rautenbach et al., 1990 ) is recommended and tested on experimental data. The reason behind this improvement is that the transport coefficient cannot be considered as constant assumed in the basic model in a wide concentration range. The change of the transport coefficient is considered as an exponential function of the composition of permeating compound. This exponential dependency is assumed by the authors after investigating the shape of the flux curves measured in a wider feed concentration range. The accuracy of this improved model is experimentally tested with the pervaporation of isobutanol–water, n-butanol–water, and ethanol–water mixtures on commercial hydrophilic composite membranes. This model improvement gives accurate and reliable data for a wide range of feed concentration proving that the assumption of practically constant transport coefficient cannot be applied. Therefore the use of this improved model in professional flowsheeting software packages is more reliable and reasonable than the application of the basic model for the design and operation of pervaporation, or a more effective hybrid separation system including pervaporation.

The increasing price of energy, the security of supply, the reduction of green house gases, and the scarcity of oil and gas urge the use of more and more renewable energy. An important renewable energy source is the biomass which can be applied for heat, electricity, and transportation fuel production. The heat and electricity production are the so called “direct utilisation” alternatives and the transportation fuel production alternatives are the “indirect utilisation” alternatives of biomass energy. If efficient land use is considered, the alternatives can be compared on the basis of the utilisable energy produced from the biomass per hectare. It is shown that the bioethanol production from corn has about 89–99% less energy production capability than that of the direct utilisation alternatives. The cellulosic type bioethanol production technologies, since these partially directly utilise the biomass energy, have better energy utilisation potential, that is about 40–50% of direct alternatives.

In this work, our methodology proposed earlier for the modelling of pervaporation is applied. The modified Rautenbach model is selected again, as an integral part of our methodology. The applicability of the methodology is investigated in the case of ternary mixtures: the connections between the model parameters of the binary and ternary mixtures are studied. For the possibility of comparison the widely investigated water—ethanol as binary and water—ethanol—2-propanol as ternary mixture. involved a PERVAP 2210 PVA/PAN composite membrane are chosen. The parameters of the model are capable to describe the system simultaneously the function of temperature and in the range of feed mixture 0.5–10 wt.% water. For the parameter estimation, the mathematical software GAMS© (GAMS Development Corporation, 2005) is used. The defined number of the model parameters and feed mixtures are applied in our user added subroutine of the ChemCAD© (5.1.3 Professional, 2001) chemical process simulation software. The comparison of measured, modelled and simulated data shows that the parameters of the most permeating component (water) can be taken from either the binary or the ternary measurements. This new result can help to reduce experimental work and improve modelling work. The simulations show high accuracy of the modelling of pervaporation based on the parameters obtained from experimental data.

Copper rejections of a nanofiltration (NF) and a reverse osmosis (RO) membrane are investigated with coppersulfate and copper-nitrate solutions as test wastewaters. The copper content of the solutions represents the typical copper ion concentration of process waters from a textile coating plant, i.e. 2 kg/m3. Experiments are performed with the test solutions on a bench-scale cross-flow membrane filtration apparatus with acid resistant flat sheet membranes. The active membrane area is 28 cm2. Isotherm experiments at 25°C are carried out. The applied conditions (e.g. pressure or pH) are in the applicable range of parameters. Permeate flux, conductivity, pH, and copper concentration of the permeate are measured to determine the membrane characteristic and rejection. The transport through the membrane is modeled in the function of time with the solution–diffusion model and in the function of yield with the modified osmotic pressure model. Modeled data is then compared to the experimental data. This comparison shows a good agreement between the measured and the modeled fluxes. Finally, the effect of anion composition on permeate flux is also studied using copper-sulfate and -nitrate at a constant copper content of 2 kg/m3. However, no influence of the anions on the permeate flux and copper rejection can be observed.

A simulation tool is developed in order to support the operation of an industrial scale hybrid distillation–pervaporation system that is used to regenerate isopropanol. Laboratory-scale experiments were carried out to determine the parameters of a semi-empirical solution–diffusion membrane transport model that is used for the modelling of the pervaporation transport. Isotherm experiments were made at three different temperatures (60, 80, 90°C) using a hydrophilic flat sheet membrane (PERVAP 2210, Sulzer Chemtech). The permeate fluxes and compositions were measured at different constant feed compositions. The parameters of the applied transport model were fitted to the experimental data. For simulating the pervaporation apparatus, an earlier developed user added pervaporation module within the ChemCad software package was applied. The user added module and the fitted transport model parameters were used for the simulation of our measured laboratory-scale data. Simulation of the industrial scale distillation pervaporation hybrid system was also carried out. The simulated and measured data were compared.

Although sulphur emissions (mainly as SO2) have been continuously decreasing over the last 20 years in most western industrialized countries, localized SO2 problems still exist in conjunction with strong local emission, meteorological, and topographical factors. In this study, the effect of supplementary installed flue gas desulphurization (FGD) units at high-capacity power plants on regional air pollution in the Carpathian Basin is investigated. The dispersion and accumulation of the SO2 air pollutant are studied with the regional three-dimensional on-line atmosphere-chemistry model REMOTE. The changes in the SO2 air pollution are investigated by parallel simulations in a case study, where the single modified parameter is the SO2 emission rate. The results show that FGD units significantly reduce the horizontal and the vertical dispersion of the emitted SO2, and its transboundary transport, too. Beside the SO2 removal efficiency, the dispersion and accumulation also depend on the seasonal weather conditions. During winter, the dispersion and accumulation are higher than in other seasons. Due to this phenomenon, higher SO2 removal efficiency is needed to guarantee similar air quality features like in the other seasons.

The rigorous modelling of pervaporation, especially in professional software environment, plays a high practical importance if hybrid separation processes containing membrane units are to be designed. In this work a methodology is recommended and presented for such design problems. This methodology consists of the following steps: laboratory pervaporation experiments, estimation of the parameters needed for the modelling of the pervaporation, and finally the double verification of the parameters. The parameter estimation is handled as a mixed integer nonlinear programming (MINLP) problem and professional flowsheeting simulator is also applied in the double verification step. Following this methodology, reliable parameters of the pervaporation needed for rigorous modelling can be determined. The pervaporation module with the reliable parameters in professional software environment enables the design of complicated separation processes, e.g., hybrid separation processes containing pervaporation.

Design of novel hybrid processes is performed for the industrial recovery of tetrahydrofuran (THF) from two different highly non-ideal mixtures. The novel hybrid processes combine the advantages of batch and/or continuous distillations, extractive distillation, and pervaporation for efficient separation of highly non-ideal mixtures. Pervaporation, used for the final dewatering of the THF, is the last step in the separation technologies and carried out with available industrial technology (Sulzer Chemtech GmbH, Batch pervaporation BP models, PERVAP ® 2210 membrane type). It is necessary, however, to design a proper pre-separation process of the mixture to be pervaporated and coordinate its operation with the pervaporation unit. Since methanol is also present in one of the mixtures, its behaviour during pervaporation is also investigated. It shows that since the methanol is able to permeate the membrane, it should be separated in the pre-separation process. The vapour–liquid equilibrium data indicate that with extractive distillation it becomes possible to break the THF—methanol azeotrope and the appropriate application of pervaporation makes the further reduction of the recovery costs possible. The total annual costs of the novel hybrid separation processes range between 10.3 and 54% of that of the old technology based on chemical dewatering. The THF loss decreases to the 7.5 and 17% of that of the old technology and shows that pervaporation is also a powerful tool for the application of the principles of the sustainable development and consumption.

Ternary systems, which contain flammable gas, inert gas and air, were studied in order to give the user an evaluation of the ISO 10156 calculation method for the flammability of gas mixtures. While in Part 1 of this article the fire potential of flammable gases was the focal point, the influence of inert gases on the flammability of gas mixtures was studied in Part 2. The inerting capacity of an inert gas is expressed by the dimensionless K value, the so-called "coefficient of nitrogen equivalency". The experimental determination of K values is demonstrated by using explosion diagrams. The objective of this study was to compare the estimated results, given by ISO 10156, with measurements of explosion ranges based on the German standard DIN 51649-1, given by CERN and CHEMSAFE. The comparison shows that ISO 10156, Table 1, supplies conservative K values, which can be regarded as safe in all cases. Nevertheless, in a number of cases ISO underestimates the inerting capacity, so that non-flammable gas mixtures are considered flammable.

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.

Four different alternatives of mobile power train developments (hybrid diesel, fuel cell operating with hydrogen produced on a petrochemical basis, methanol reformer-fuel cell system, gasoline reformer-fuel cell system), are compared with the gasoline internal combustion engine (ICE), for well-to-wheel efficiencies, CO 2 emissions, and investment costs. Although the ICE requires the lowest investment cost, it is not competitive in well-to-wheel efficiencies and less favourable than the above alternatives for CO 2 emissions. The hybrid diesel power train has the highest well-to-wheel efficiency (30%), but its well-to-wheel carbon dioxide emission is similar to that of the fuel cell power train operated with compressed hydrogen produced on a centralised petrochemical basis. This latter case, however, has the advantage over the hybrid diesel power train that the carbon dioxide emission is concentrated and easier to control than the several point-like sources of emissions. Among the five cases studied only the on-board reforming of methanol offers the possibility of using a renewable energy source (biomass).

Methanol is considered as a renewable energy source for fuel processor–fuel cell systems. The determination of the kinetics of methanol autothermal partial oxidation can be simplified if the problem is divided into subproblems. As a first step, the kinetics of methanol decomposition (Me) are studied. To describe this subproblem, a reaction system consisting of four reactions is assumed. The reactions are: Me, dimethyl ether (DME) formation, steam reforming, and water gas shift (WGS) which are studied on a commercial copper containing catalyst (5 wt.% copper on alumina). The dehydration of methanol to DME is a second order reaction and essentially provides an excess of water over the whole reactor allowing first order kinetic assumptions for steam reforming and WGS. The WGS reaction proves to be slow, compared to the other reactions, and equilibrium limited. The activation energies (kJ/mol) are estimated: Me 76 (±4%), DME formation 117 (±2%), steam reforming 81 (±7%), WGS 50 (±25%). Turnover frequencies for Me are estimated based on copper surface areas determined by the nitrous oxide pulse reduction method. At 220°C, values of 0.05 s−1 are estimated compared to a literature value of 0.019 s−1 at 200°C.

Direct separation sequence without, with forward, and with backward energy integration, indirect separation sequence without, with forward, and with backward energy integration, sloppy separation sequence without (preflash system), with forward, with backward, and with double energy integration, and thermally coupled sloppy separation sequence (Petlyuk system) are compared with short-cut and rigorous modelling. Based on theoretical considerations and economically evaluated rigorous case studies for ternary mixtures it is demonstrated that in the most cases the Petlyuk system is not superior to the energy integrated configurations even in energy savings. According to the energy consumption of sharp separation determined by short-cut methodology, all the sloppy sequence structures are equivalent. According to the energy losses determined by short-cut methodology, derived here, the energy-integrated structures win almost everywhere in the studied conditions that include a range of relative volatility ratios and the whole feed composition triangle. According to rigorously simulated and optimised results, together with controllability studies, the advantageous application of the thermally coupled (Petlyuk) systems is constrained to a very small range of relative volatility ratio, feed composition, and price structure. This small range is situated somewhere around balanced relative volatility ratio A/B to B/C, small amount of the middle component B, balanced presence of the two swing components A and C in the feed, and high energy costs to investment costs ratio or slow depreciation rate.

Separation of a ternary mixture by different distillation schemes was simulated rigorously at steady state. Conventional schemes, heat integrated schemes, and the fully thermally coupled structure (Petlyuk system) have been optimized over total annual cost including two different regional utility price systems (high and low utility prices): The results show that price ratios have considerable effect on the savings and consequently on the optimal schemes. Using low utility price the number of actual trays is reduced and the reflux ratios will be increased. At extreme high utility prices the Petlyuk system can be justified as one of the best schemes in savings, but not against the sloppy forward heat integrated scheme. The maximum savings in total annual cost in both cases are about 28%.

Dehydrogenation of methylcyclohexane to toluene is studied by modelling and experimentally in two fixed bed reactor systems in the laboratory and pilot plant scale. Kinetic and transport parameters are estimated and measured. Interstage membranes for hydrogen separation are used to improve efficiency and exceed equilibrium conversion by 1–12%. The complexity of modelling the laboratory scale necessitates a pseudo-homogeneous two-dimensional model to compensate for radial gradients giving satisfactory agreement between simulated and measured data. The pilot plant scale system is simpler to model, a pseudo-homogeneous one-dimensional model describes the system with good accuracy. The highest yield achieved in the pilot plant scale system is 98%.

Two energy integrated distillation schemes for the separation of three different ternary mixtures of four typical feed compositions have been rigorously investigated and compared to the best conventional two-column distillation scheme. The two energy integrated schemes are: the heat integrated two column system and the fully thermally coupled distillation column (FTCDC), also known as Petlyuk column. The comparison of the energy savings and the total costs of the investigated schemes show that the heat integrated two column scheme is economically always better than the conventional scheme. The FTCDC shows considerable energy savings in several cases, however, it can be competitive with the heat integrated two column system only in those rare cases where the concentration of the middle component is high, the split between the first and second components is harder than the split between the second and third components, and the separation is not too sharp (Annakou and Mizsey, 1996). The rigorous economic study is supported by controllability studies for the two energy integrated distillation schemes. Degrees of freedom analysis and steady-state multivariable control structure synthesis tools show that both investigated schemes can be controlled by conventional decentralised control structures, however, in the case of the heat integrated two column scheme heuristics and also the steady-state control indices show that the interaction among the control loops is less than in the case of the FTCDC. The dynamic simulations of the two energy integrated schemes without and with the most promising control structures support the steady-state analysis. They also demonstrate that in the case of the control of the FTCDC due to the significant interaction among the control loops detuning of the controllers is necessary. Higher overshoots, longer settling time and more sluggish behaviour are expected compared to the heat integrated two column system.

The effects of the recycle of mass or energy on the control of chemical processes are studied. The recycle can be considered analogous to a feedback and significantly changes the characteristics of the process. The study on simple transfer function models indicates that the recycle loop gain strongly and time constant of the recycle unit somewhat less strongly influence the behaviour and the controllability of the process. Higher time constants of the recycle, the use of large surge tanks, and the control of the recycle unit of smaller time constants improves the range of stability. Two case studies, the distillation train of the manufacture of styrene and a simple reactor-distillation column system, demonstrate that chemical processes with internal recycle can usually be controlled with decentralised control structure with individually tuned controllers. The case studies also show that in the case of the control structure design the connections of the different units should be considered and the control of the recycle unit is also important.

In this work a propylene-propane splitter assisted by a heat pump of the vapour recompression type is investigated by rigorous methods. Two schemes, a single compressor scheme and a double compressor scheme in parallel arrangement, are scrutinised and compared to the conventional stand alone column. The investigation includes parametric study, operability assessment and an estimation of the role of heat pump in minimising flue gas emissions. The parametric study of the influences of the column top pressure and the pressure lift of the heat pump on the economics shows, for both schemes at the optimal conditions, practically the same annual total cost, which is about 37% cheaper than the conventional stand alone column. The operability of the system is investigated by degrees of freedom analysis and steady state controllability parameters. The operability considerations show that in the case of the double compressor scheme, the column pressure can be independent of the threshold temperature of the condenser. Thus the column pressure can be determined to satisfy the optimum separation parameters. Due to this operability reason, the double compressor scheme is preferred to the single compressor scheme. The heat pump share in reducing flue gas emissions is estimated. It is found that about 60% of the flue gas emissions can be minimised when using a heat pump.

The influence of relevant parameters on the economics of distillation plants involving distinct heat pump cycles is scrutinised and the results are compared to conventional and integrated schemes. On the basis of the COP , energy costs and efficiencies, simple expressions are proposed for preliminary economic analysis and design of heat pump assisted distillation. The influence of heat pump type, purity requirement, column pressure drop, feed rate, energy cost, relative volatility etc. on the energetic aspects and economic range of application is presented. Heat pumps can be economical substitutes for conventional distillation process design whenever direct refrigeration or chilled water are required for condensation and for separating close boiling mixtures in columns of small pressure drop. A design strategy for selecting the most economical distillation system, considering different types of heat pump structures (vapour recompression, bottom flash, closed cycle, absorption cycle), is proposed, based on pinch technology, primary energy rate, energy cost factor and estimated payback time of excess capital. The strategy is demonstrated by industrial case studies.

The waste minimisation in the chemical industry has shifted from the end-of-pipe treatment to the elimination of wastes at the source as well as environmentally sound internal recycling. Several systematic strategies based on the hierarchical process design have been developed and used in the practice. In the case of a chemical company that consists of several processes or plants it is necessary to co-ordinate the waste minimisation incentives on the company level. The main goal is to utilise the waste of a plant in another plant that is to design closed-cycle processing. This article describes a systematic two level procedure for the reduction of the global emission of a chemical company.

The task of synthesizing optimal total flowsheets with energy integration usually represents a large combinatorial problem. In order to reduce the search space, an efficient bounding strategy is presented for synthesizing energy integrated total flowsheets with distillation-based liquid separation systems. The strategy utilizes a predictor-based ordered search technique and can be attached to the conceptual design of chemical processes. The strategy is based on computing lower bounds of the utility and investment costs for the feasible process alternatives. Beside optimizing the column matches the integration of heat pumps with separation system is also considered. The outlined procedure exploits the advantages of both major approaches, i.e. the hierarchical and algorithmic design.