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Total ammoniacal nitrogen (TAN) occurs in various wastewaters and its recovery is vital for environmental reasons. Forward osmosis (FO), an energy-efficient technology, extracts water from a feed solution (FS) and into a draw solution (DS). Asymmetric FO membranes consist of an active layer and a support layer, leading to internal concentration polarization (ICP). In this study, we assessed TAN recovery using a polymeric thin-film composite FO membrane by determining the permeability coefficients of NH4+ and NH3. Calculations employed the solution–diffusion model, Nernst–Planck equation, and film theory, applying the acid–base equilibrium for bulk concentration corrections. Initially, model parameters were estimated using sodium salt solutions as the DS and deionized water as the FS. The NH4+ permeability coefficient was 0.45 µm/s for NH4Cl and 0.013 µm/s for (NH4)2SO4 at pH < 7. Meanwhile, the NH3 permeability coefficient was 6.18 µm/s at pH > 9 for both ammonium salts. Polymeric FO membranes can simultaneously recover ammonia and water, achieving 15% and 35% recovery at pH 11.5, respectively.

Nanofiltration can be used as the last step in the purification of the biomolecules that are present in many industrial by-products, such as biological protein hydrolysates. The present study explored the variation in glycine and triglycine rejections in binary solutions with NaCl at different feed pHs with two nanofiltration membranes: MPF-36 and Desal 5DK with molecular weight cut-offs of 1000 and 200 g mol−1, respectively. First, water permeability coefficient showed a n-shaped curve with feed pH, which was more evident for the MPF-36 membrane. Second, membrane performance with single solutions was studied and the experimental data were fitted with the Donnan steric pore model with dielectric exclusion (DSPM-DE) to explain the variations of solute rejection with feed pHs. Glucose rejection was assessed to estimate the membrane pore radius of the MPF-36 membrane, and a pH dependence was observed. For a tight membrane (Desal 5DK), glucose rejection was close to unity and the membrane pore radius was estimated from the glycine rejection in the feed pH range from 3.7 to 8.4. Glycine and triglycine rejections showed a pH-dependence with a u-shaped curve, even for the zwitterion species. In binary solutions, glycine and triglycine rejections decreased with NaCl concentration, especially in the MPF-36 membrane. Triglycine rejection was always higher than NaCl rejection and it was estimated that triglycine can be desalted using a continuous diananofiltration the Desal 5DK membrane.

With the growing environmental awareness, renewable energy sources that can replace crude oil are being in-depth studied. One of these is the bio-oil, a renewable energy source that can be obtained from biomass pyrolysis. It is characterised by the fact that its components include ketones, furans, and phenols. Among the ketones, cyclopentanone, 2-butanone, and 2,3-butanedione are the most significant, as they are useful for producing fine chemicals. The first objective of the present study is the design of a suitable separation process for the mixture composed of cyclopentanone, 2-butanone, and 2,3-butanedione, considering the presence of an azeotrope between the 2-butanone and 2,3-butanedione. For this purpose, the enhanced distillation method of pressure-swing distillation is used. To the best of our knowledge, this technique has not been applied before for this particular separation, as existing studies consider the mixture as ideal and do not take into account the presence of the azeotrope. Therefore, the separation process becomes simpler. The second objective is to optimise the aforesaid process. Given the combination of real and integer variables, the high dimensionality of the problem and the constraints on the variables, it has been decided to apply a genetic algorithm as an optimisation method. The optimised variables are the number of stages and reflux ratios of the columns, the molar flow rate of the recirculation stream and the pressure of the high-pressure column. The genetic algorithm is implemented in MATLAB ® programming language, and rigorous simulations are performed using Aspen Plus ®. The optimised variables and compositions of all streams are determined; the results of the overall heating services are 12,788 kW, and cooling services are 12,512 kW for 100 kmol/h of the crude feed. By improving the process of compound separation from pyrolysis bio-oil, the present study contributes to the use of renewable resources such as biomass instead of crude oil to produce valuable chemical compounds.

There is growing emphasis on developing green composites as a substitute for oil-based materials. In the pursuit of studying and enhancing the mechanical properties of these composites, tensile tests are predominantly employed, often overlooking the flexural properties. This study focuses on researching the flexural properties of abaca-fiber-reinforced bio-based high-density polyethylene (BioPE) composites. Specifically, composites containing 30 wt% of abaca fiber (AF) were treated with a coupling agent based on polyethylene functionalized with maleic acid (MAPE). The test results indicate that incorporating 8 wt% of the coupling agent significantly improved the flexural strength of the composites. Thereafter, composites with AF content ranging from 20 to 50 wt% were produced and subjected to flexural testing. It was observed that flexural strength was positively correlated with AF content. A micromechanics analysis was conducted to evaluate the contributions of the phases. This analysis involved assessing the mechanical properties of both the reinforcement and matrix to facilitate the modeling of flexural strength. The findings of this study demonstrate the feasibility of replacing oil-based matrices, such as high-density polyethylene (HDPE), with fully bio-based composites that exhibit comparable flexural properties to their oil-based counterparts.

Composite materials containing natural reinforcement fibers, generally called biocomposites, have attracted the interest of both researchers and manufacturers, but the most environmentally advantageous combinations include a bio-based matrix, as well. With this in mind, a poly(lactic acid) (PLA) matrix was reinforced with natural fibers from hemp, both untreated strands (UHSs) and soda-bleached fibers (SBHFs). The preparation of the subsequent fully bio-sourced, discontinuously reinforced composites involved kinetic mixing, intensive single-screw extrusion, milling, and injection molding. Up to a fiber content of 30 wt%, the tensile modulus increased linearly with the volume fraction of the dispersed phase. Differences between SBHFs (up to 7.6 Gpa) and UHSs (up to 6.9 Gpa) were hardly significant (p = 0.1), but SBHF-reinforced composites displayed higher strain at failure. In any case, for the same fiber load (30 wt%), the Young’s modulus of PLA/hemp biocomposites was greater than that of glass fiber (GF)-reinforced polypropylene (5.7 GPa), albeit lower than that of PLA/GF (9.8 GPa). Considering all the measurements, the contribution of each phase was analyzed by applying the Hirsch model and the Tsai-Pagano model. As a concluding remark, although the intrinsic tensile modulus of SBHFs was lower than that of GF, the efficiency of those natural fibers as reinforcement (according to the rule of mixtures) was found to be higher.

The nanofiltration performance of three commercial membranes was analyzed by the Steric Pore Model (SPM) and the extended Nernst–Planck diffusion equation inside membrane pores. The model was completed with the equation to predict the concentration polarization, and the mass transfer coefficient was determined by considering the presence of a feed spacer. The model parameters that characterized the performance of the membrane were the hydrodynamic coefficient, which accounts for the possible variations in solute size and membrane pore radius, the effective membrane thickness, and the water permeability coefficient. All experiments were conducted at fixed feed pH of 6. The rejections of uncharged solutes (glucose for membranes with a high molecular weight cut-off (MWCO) and glycerol and ethylene glycol for membranes with a low MWCO) allowed the model parameters to be determined. We found that glycerol and ethylene glycol overestimate the membrane pore radius due to their ability to interact with the membrane matrix. Therefore, the rejection of glycine as a small amino acid was explored to characterize the membranes with low MWCO since these molecules do not interact with the membrane matrix and have an almost zero charge at pH values between 4.5 and 6.5. Based on the experimental rejections, it was stated that glucose and glycine could be separated by these membranes operating in continuous diafiltration mode.

Heat exchangers are present in most industries as they allow the recovery of thermal energy, making processes more profitable and environmentally sustainable. The design of classical heat exchangers is performed based on well-established semi-empirical equations, e.g. Double Pipe Heat Exchangers (DPHE). Those semi-empirical equations are very susceptible to geometry changes, as well as flow conditions at the entrance of the heat exchangers. Semi-empirical correlations are based on simplifying assumptions such as constant fluid properties along the heat exchanger. A design solution to this issue is Computational Fluid Dynamics (CFD), which is widely used for the design of novel heat exchanger geometries saving experimentation time and cost. To the best of our knowledge, CFD results have not been tested against the classical semiempirical equations. Before facing future complex geometries, the proper CFD model options are identified and validated against classical equations. In this study, this analysis is performed for the case of a classical DPHE. Series of CFD simulation results are critically compared with classical for DPHE. Different turbulence models and wall treatments are tested, as well as fully developed velocity profiles at the entrance of the heat exchangers, obtained by iteration. Results show that CFD codes are able to predict and model the flow in DPHE reliably, with the same accuracy as classical correlations. CFD simulations are found to differ from semi-empirical correlations up to 0.87 % in the case of pressure drop and 7.1 % in the case of heat transfer. Consequently, CFD simulations with proper setup parameters are a good choice for assessing novel configurations. Reliable novel heat exchange configurations assessment is compulsory for heat exchange network revamping in restricted space industrial scenarios and opens novel opportunities for higher heating and cooling services savings.

Energy hotspots for the production of vanillin from Kraft lignin are identified and process improvements are proposed and rigorously simulated. The hotspots identified and addressed are related to the flowrate of methanol used as solvent and recycled in the process. Several alternative process designs containing fewer distillation columns and able to reduce the overall energy consumption are proposed. Recycling aqueous methanol, a distillation column is not required and the overall energy consumption is halved compared to the available literature (i.e. 42 %). In addition, based on a literature review and the screening of suitable solvents used for the liquid-liquid extraction of vanillin from the main product stream, the use of aliphatic alcohols such as hexanol is proposed as an optimal and underexplored solution. Their physicochemical properties allow for the elimination of the acidification step that takes place during the feed preparation stage at the beginning of the process. In this way, the process design can be simplified further. Two distillation columns are not required and the overall energy consumption of the process is reduced to 23% compared to previous studies. The proposed Kraft-lignin-based vanillin production process improvements contribute to the development and competitiveness enhancement of biomass-based vanillin production processes, which are currently in need of further refinement compared to the more mature petrochemical-based processes, but at the same time have the potential to be more sustainable, cleaner and energetically efficient.

Vanillin is an important building block for the chemical, pharmaceutical and food industries, with potential to become a key intermediate for bio-polymers. Vanillin nowadays is mostly produced from non-renewable petro-based resources as raw materials. A plausible process design to recover vanillin from an acidic oxidation of Kraft lignin in an hydroalcoholic mixture is available from recent literature, but it has yet to be improved before becoming a competitive one capable of substituting the petrochemical route. The alcohol used in the reaction is methanol. Following the reaction step, the process requires a flash drum and five distillation columns, most of the energy consumption being due to methanol recovery and recycle for which three distillation columns are employed. The first aim of the present study is to simulate and quantify the energetic costs and environmental impact of the proposed process design, while studying possible improvements to the principal energetic hotspots identified in the literature.Through rigorous simulations, it is shown that this base case design can be improved and the train of distillation columns simplified. Through the use of alternative designs, one of the distillation columns used to separate methanol from water coming from the vapour phase of the flash drum can be eliminated. An energy consumption of only 43 % relative to the base case scenario is achieved this way. The second aim of this work is to perform simulations of suitable solvents used for liquid-liquid extraction of vanillin from the main stream, taking into account both the energetic efficiency and the environmental impact of each one, and to classify them accordingly. Specific emphasis is put on the study of the performance of aliphatic alcohols such as hexanol, as their physicochemical properties allow for the elimination of the acidification operation in the pre-reactor feed preparation stage. This is important because it avoids the technological problems related to lignoacid precipitation that follows an acidification step and has the potential to reduce energy consumption greatly, as fewer columns would be needed. Rigorous simulations show that an energetic consumption reduction of 78 % relative to the base case design is achieved when using hexanol as the solvent in an aliphatic-alcohol-specific process design, improving the energy efficiency of both the currently used industrial methods and the commonly studied alternatives based on non-aliphatic alcohol solvents.

Greenhouse gas footprint of fuels is due to both the burning fuel and its production process. Bioethanol is a sustainable biofuel but it is obtained diluted in water and its dehydration consumes large amounts of energy. Heterogeneous azeotropic distillation is a well-known suitable option for dehydration of bioethanol (separation of ethanol from water). Many entrainers for this process are studied in literature but unfortunately, there is no critical comparison in terms of the corresponding process efficiency. The distillation efficiency assessment is necessary as it has a great impact on the energy consumption and sustainability of bioethanol production. The process scheme and entrainer are screened following a fast-to-rigorous procedure: feasibility checking using the infinite/infinite analysis, screening based on the Distillation Sequence Efficiency (DSE) method and rigorous simulation using AspenPlus®. Different process schemes are assessed taking into account also that some gasoline additives, used as entrainers, could remain in bioethanol, which is to be included in the gasoline formulation. Some examples of commonly used ethers as gasoline additives are methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), diisopropyl ether (DIPE) and tert-amyl methyl ether (TAME). The study shows that when the entrainer is a gasoline additive, collecting the distillation product as a mixture of ethanol and additive consumes 27 % less energy than collecting pure ethanol. Performing the ethanol dehydration and gasoline additive mixing together in the same process leads to a 27 % decreasing of CO2 emissions.

Most of the distillation processes deal with multicomponent mixtures, existing a great quantity of distillation sequences for this process. The sharp splits available for an ideal ternary mixture are the direct and the inverse distillation sequence scheme in which the compounds are separated in two different columns. There are non-sharp splits in which all the compounds are separated in a single distillation column that can incorporate a side column. Unfortunately, to choose non-sharp splits schemes, there is no heuristic that can provide information about the recommended cases, e.g. a single distillation column in which the intermediate boiling compound is collected by a side stream at the required purity or by other possibilities, such as the use of a side stripper or a side rectifier. The literature about this subject is very scarce, and many times when the non-sharp splits are used, no comparison with the sharp split alternatives is provided. Therefore, the cases for which the literature suggests the use of side columns are further studied, e.g. BTX (Benzene, Toluene, Xylene) mixtures separation. For many case studies, the results obtained show that the energy savings achieved, due to the use of side columns, are not significantly higher than the best sharp split process schemes. However, these results do not discard that for some other situations; the side column could be the most advantageous case. Usually, it is considered that when the desired purity of the main product in a stream is reached, the impurities proportion do not affect significantly the energy consumption, and for most of the systems, this is true. However, for a mixture with a molar composition of 10 % isopentane, 10 % pentane and 80 % hexane (mol), when split in the respective compounds at a purity of 95 % (mol), very different energy requirements are depicted depending on the proportion of isopentane and hexane, present in the pentane stream obtained in a direct sequence process . The rigorous simulation results illustrate that almost 60% of the energy required to separate the above-mentioned mixture is saved when the pentane stream carries a mixture of isopentane and hexane. In addition, the environmental impact has been analyzed for each case studied, being reduced in the same way as the energy consumption does.

Process intensification and selection of the most efficient chemical process provides resources conservation and decreases the energy consumption to minimize CO2 emissions. Distillation Sequence Efficiency (DSE) method is extended to chemical processes also considering the reactors to provide a very simple and useful process design tool. A minimum amount of input data and computation power is required for a fast screening providing a basis for other more rigorous methods, i.e. including a cost assessment. The method considers, in a rough approach but at very early stages of process design, three factors related to environmental impact resources conservation and catalyst costs. The input data required is the vapour-liquid equilibrium represented by a proper thermodynamic model and some other predictable basic thermodynamic data. As it is an early stage approach, the reactor outputs can be assumed at chemical equilibrium minimizing the free Gibbs Energy. The 8/8 analysis is used to check the feasibility and calculate the stream flow rates and compositions. The distillation column output streams are at boiling point, and therefore the input data for the DSE method is available, which quantifies the process efficiency and therefore it is related to its environmental impact. A resources conservation factor, considering reactant losses, relates the product quantity generated to the amount that could be generated. A catalyst cost factor, considering catalyst deactivation, relates the feed raw materials to the system with the total feed stream to the reactor. ETBE (Ethyl Tert-Butyl Ether) production process is used as a case study. According to the results, the best alternative is the intensified process, i.e. reactive distillation, followed by the process proposed in the BREF. Other five alternative process schemes values are all in agreement with Recker et al. (2015) cost assessment results. However, there is disagreement between methods only in one case due to catalyst cost.

Nowadays, more than 1 Mt of cyclohexanol is produced each year by the direct hydration of cyclohexene according to the patented Asahi process proposed in 1990. The Asahi process involves a reactor and a separation system to recover the reactants back to the reactor and collect the pure product. The non-reacted water is recovered in a decanter and the non-reacted cyclohexene in a distillation column. Nowadays, many processes have been successfully intensified, combining several unit operations into a single unit providing savings in units, piping and often also in energy due to the synergies generated. Examples of these synergies are: the continuous removal of products push forward the reaction to total conversion overcoming the chemical equilibrium limitations; the catalyst placed in the rectifying section of the column becomes protected from heavy compounds that could poison or deactivate the catalyst; the enthalpy of reaction is directly used in the separation; the boiling point of the mixture avoids hot spots that could damage the catalyst, etc. Although its advantages, it is not widely used in the industry and further study on intensification providing further successful examples are required. The present study shows by rigorous simulation with Aspen Plus V9.0 that the Asahi process is a good candidate to be intensified in a single unit. The rigorous simulation results show that cyclohexanol is collected with a molar fraction purity of 0.9999 at the bottoms of a hybrid reactive distillation column with 11 equilibrium stages operated at total reflux, i.e. total conversion of reactants. The water is fed at the top to stage 1 and the cyclohexene on stage 3, both in equimolar flow rate. The catalyst is only placed in these three stages at the column top. A side stream from stage 6 is fed to a side decanter, where the aqueous phase is recycled to the column top (stage 1) and the organic phase to the next bottom stage, i.e. stage 7. As in the Asahi process, a great excess of water is present to push the reaction equilibrium forward. Hence, the molar ratio of water recycled vs feed to the system is of 125. The reboiler duty is 197 kJ/mol of cyclohexene, and the condenser duty is 564 kJ/mol cyclohexene due to the exothermic reaction. Therefore, a novel intensified process scheme for cyclohexene hydration is proposed.

In this study, experimental analysis on the compressive strength of multi-leaf thin-tile masonry is presented. A compressive strength test was carried out on thin-tile, mortar and 48 specimens with two- and three-leaf thin-tile masonry. The results obtained were compared with literature on brick masonry loaded parallel to a bed joint. Based on the results of this study, the failure mode presented the first crack in the vertical interface; this crack grew until the leaf was detached. From this point until collapse, lateral buckling of the leaves was generally observed. Therefore, the detachment compressive strength value was considered relevant. Up to this point, both masonries exhibit similar stress–strain behavior. The experimental values of the detachment compressive strength were compared with the values calculated from the equation generally used in the literature to evaluate the compressive strength of brick masonry. From the results obtained, the following conclusion can be drawn: This equation is only suitable for tree-leaf thin-tile masonry but with more relevant influence on the compressive strength of the mortar. This study concluded that only three-leaf specimens behave similarly to brick masonry loaded parallel to a bed joint. Finally, whether the failure mode was due to shear or tensile stresses in the vertical thin-tile-mortar interface cannot be identified.

Distillation is the most widely used separation process for liquids separation in the industry. Even when the volatilities of the mixture are not favorable, then enhanced distillation is used. Extractive distillation is the enhanced distillation most widely used that consists in introducing a large flow rate of a third compound called extractive agent with a high boiling point that it is collected at the column bottoms and recovered in another column and reused again. Some heuristics are available for distillation column design, e.g. the optimum reflux is around 1.2 to 1.35 times the minimum reflux (or 1.1-1.2 times for refrigerated systems). Unfortunately, there is not a similar heuristic to determine the optimum extractive agent flow rate. Based on a literature review of rigorous simulations of extractive distillation processes, a heuristic is proposed that indicates that the optimum extractive distillation flow rate is which provides a Distillation Sequence Efficiency at 78 % of its maximum value. The maximum value is calculated assuming infinite flow rate of extractive agent. The Distillation Sequence Efficiency is a shortcut method available for distillation columns sequencing.

Nowadays the ventilation design of enclosed spaces is still based on the number of air renewals per hour. This coarse approach was developed in the past but nowadays is a fast and simple computational exercise to determine where and when the Threshold Limit Value (TLV) is surpassed. A rather superficial Computer Fluid Dynamics (CFD) analysis is able to provide insights that are useful to propose measures to keep the pollutants concentrations at safe levels. As illustrative example, the contaminants’ level inside a factory is simulated, both in steady and unsteady state, for risk and health assessment to determine the contaminant levels reached as consequence of the normal operation or in case of a sudden release. The case study is based on an example related to the ventilation of a printing factory for which there are field measurements available in literature. Two pollutants are emitted separately; one continuously during operation and the other only sporadically during cleaning. A good agreement is obtained between the simulations and previous field measurements. This case is an example that a design fulfilling the legislation according to the air renewals tabulated can surpass the threshold limit value in practice. The main conclusion is that the legislation should be based on CFD results instead of general tabulated values, as in some cases the ventilation could be too oversized and in others may result insufficient.

A novel surrogate model useful for designing CO2 absorption columns is provided to describe the vapour-liquid equilibrium of CO2 in a flue gas or biogas and aqueous monoethanolamine (MEA). The surrogate model is adjusted with experimental data and compared with dedicated software for electrolyte mixtures, i.e. OLI®. The assessment of CO2 partial pressure is conducted at different MEA concentrations, temperatures and loading of CO2/ MEA in the liquid phase. The OLI® model is in good agreement with the experimental data when MEA concentration is between 15 to 30 % wt, as well as for high MEA concentrations (between 45 and 60 % wt) at 60 °C. However, for temperatures above 80 °C, the model is in agreement with experimental data only when the load of CO2 in the liquid phase exceeds the range from 0.25 to 0.30 (usual industrial operating range is from 0.2 to 0.4). A point not addressed in experimental data in literature is the presence of MEA in the vapour phase, which overcomes the recommended values from health safety point of view at 100 °C. The presence of MEA in biogas could produce NOx. The influence of inert gas (CH4) on the equilibrium is considered to check the model suitability for biogas enrichment. The novel surrogate model provides a good regression of all the experimental data in the operating region and it is validated using Pareto diagrams.

Due to its high biocompatibility, bio-degradability, and low cost, cellulose finds application in disparate areas of research. Here we focus our attention on the potential applications of cellulose nanofiber in cement-based materials for the building sector. We first describe the chemical/morphological composition of cellulose fibers, their process and treatment, the characterization of cement-based composites, and their flexural strength. In recent research in this field, cellulose has been considered in the form of nano-sized particles, i.e., cellulose nanofibers (CNF) or cellulose nanocrystals (CNC). CNF and CNC are used for several reasons, including their mechanical and thermal properties, their extended surface area and low toxicity. This study presents some potential applications of lignocellulosic micro/nanofibers (LCMNF) in cement-based composites in order to improve flexural strength. Samples were made with 0.5-1.0-1.5-2.0 wt% of LCMNF obtained from pine sawdust, CEM I (Portland) and a 1:3 cement-water ratio. The composites were then tested for flexural strength at 7, 14, and 28 days and the evolution of flexural strength was assessed after water immersion during 72 h. Scanning electron microscopy was employed to visualize the bond between LCMNF and the cement matrix. Results showed that LCMNF improved the flexural strength of the composite in all the dosages used.