Process Intensification Techniques Research Articles

Conceptual methods for synthesis of reactive distillation processes: recent developments and perspectives

AbstractReactive distillation (RD) is a process intensification technique that offers major advantages over conventional technologies by enabling the integration of reaction and separation into a single apparatus. This integration introduces and exploits complex interaction between mass transfer, chemical reaction and hydrodynamics within an RD column; however, these complexities can hinder the adoption of RD by industry. Many approaches have been developed by the scientific community to advance understanding and to expedite the initialization of RD design at the conceptual level. This paper critically discusses recent developments in conceptual methods for synthesizing RD processes. This review paper is the first to consider the range of available approaches for assessing the technical feasibility, controllability, economic viability, and sustainability of RD units by taking into account various configurations in which RD is treated as a new unit operation, and as part of process synthesis in a different way of designing processes based on functions. The review also addresses complex configurations, such as advanced RD technologies. Special attention is paid to process modeling and simulation as well as to education. Knowledge gaps to be filled by further research are indicated. © 2024 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

A new hybrid reactive-extractive distillation configuration for ternary azeotropic separation with intensification opportunity

The concept of reactive-extractive distillation (RED) is not new and has gained significant attention as an innovative approach for separating azeotropic mixtures. Presently, there have been at least 18 studies on RED, exploring variations such as triple column RED (TCRED), double column RED (DCRED), and their intensified configurations like dividing-wall DCRED (DW-DCRED) or side-stream DCRED (SS-DCRED). However, a major drawback observed in all existing intensified RED studies is the inability to achieve energy savings, which contrasts with the outcomes of most conventional distillation system studies. To address this, we propose a new alternative configuration called extractive-reactive distillation (ED-RD) by rearranging the column sequence in DCRED. The ED-RD configuration achieves a substantial 7 % reduction in the total annual cost (TAC) compared to DCRED, primarily due to a reduced number of stages and the utilization of relatively cheaper low-pressure steam in the extractive distillation column (EDC). Furthermore, the intensified thermally coupled ED-RD (TC-ED-RD) configuration demonstrates superior performance, achieving an impressive 21 % reduction in TAC compared to the proposed ED-RD configuration, mainly driven by a significant decrease in total reboiler energy consumption. Overall, the TC-ED-RD configuration excels with a remarkable 28 % reduction in total reboiler energy consumption and a 27 % decrease in TAC compared to DCRED. This reflects the potential of incorporating process intensification techniques to the proposed configuration to achieve substantial energy and cost savings, in contrast to the limitations observed in the conventional RED systems.

CO2 utilization for ammonia removal in skim latex: Processing and rubber properties

An innovative CO2 utilization approach for skim rubber production was developed in this research. Traditionally, skim rubber is produced using a substantial amount of concentrated sulfuric acid to coagulate the rubber particles. Before acid addition, ammonia removal process is required to reduce the volume of acid used. This process, however, involves large operating area, long processing time, environmental issues, and health hazards. To minimize those drawbacks, as a process intensification technique in this study, CO2 microbubbles were applied as a feedstock to reduce the ammonia and hence the volume of acid addition. The properties and microstructure of skim rubbers produced via CO2 microbubbles (MBSL) were investigated in comparison with those produced by traditional processes. The MBSL exhibited smooth surface texture with enhanced tensile strength and thermal stability. Utilization of CO2 as a sustainable feedstock to coagulate skim latex has a potential for not only diminishing the limitations caused by traditional processes but also highlighting an environmental-friendly and cost-effective process with improved product properties.

Biodiesel production using microreactor with integrated microheater through multi-objective optimization approach

Microreactor is one of the process intensification techniques which uses reaction dimensions below millimeter size and have greater yield within lesser reaction time and a high heat transfer rate due to their high surface to volume ratio. To develop energy efficient reactors, microheater is chosen as the heating source for microreactor which consume less power than the conventional heating elements. Using response surface methodology (RSM) and artificial neural network (ANN) the effects of the biodiesel process variables was analyzed: catalyst concentration (0.5–2.5 wt.%), reaction temperature (35–55 °C), flow rate (5–25 mL/min), oil to methanol molar ratio (1:6–1:18), and power supplied to the microheater (15–35 W). To observe more than set limit, Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) and VIKOR were used to evaluate the optimum conditions. Under the optimum conditions of 20 mL/min flow rate, 45 °C reaction temperature, 1.5 wt.% catalyst concentration, 1:9 oil to methanol molar ratio, and 20 W power supplied, the maximum biodiesel yield for microreactor with microheater is 91.1 %. Using ultrasonic mixing additionally for microreactor with microheater had maximum yield of 94.4 % under the optimum conditions.

Innovation in natural rubber latex coagulation using CO2 microbubbles

Traditionally, acids have been employed in the production of raw rubber sheets. Using concentrated acids to coagulate natural rubber latex has led to issues such as subpar product quality and the generation of a significant volume of acidic latex serum waste. In contrast, opting for weak acids results in increased production costs. To address these limitations, this research adopts an innovative approach that leverages CO2 microbubbles as a process intensification technique. CO2 was bubbling into a bubble column filled with fresh natural rubber latex and closely monitored the pH and coagulation percentage over time. The physical and mechanical properties of the solid rubber products were characterized, in comparison with the products gained from conventional techniques. The use of CO2 microbubbles yielded shorter processing times and reduced the generation of acidic waste serum. Notably, this approach also led to significant improvements in key properties such as initial Wallace plasticity (P0), plasticity retention index (PRI), nitrogen content, and biodegradability in soil of the rubber samples. Interestingly, the utilization of CO2 as a feedstock highlights its role in promoting a sustainable process. This innovative approach not only minimizes environmental impact but also results in the production of value-added rubber products with enhanced properties.

Impact of thermal and nonthermal process intensification techniques on yield and quality of virgin coconut oil

Virgin coconut oil (VCO) is valued for its nutraceutical potential. The focus of this research was to assess the effect of selected thermal and nonthermal pre-treatments on the yield and quality of subsequently wet-extracted VCO. The fresh coconut cream was subjected to microwave heating (450 W, 2 min), ohmic heating (180 V, 5 min), ultrasonication (350 W, 10 min), or a pulsed electric field (40 kV cm−1, 12.32 min). The thick cream was separated, and VCO was obtained after a freeze–thaw process. The highest VCO yields (>93%) were observed in the cases of ultrasonicated and pulsed electric field-treated samples. A range of oil quality parameters, total phenolic content, and antioxidants were evaluated. Further, the fatty acid composition of all oils was studied. Observations from this research indicate that ultrasonication pre-treatment resulted in the best VCO yield and quality.

Dehydration of Isopropanol: A Comparative Review of Distillation Processes, Heat Integration, and Intensification Techniques

The dehydration of isopropanol (IPA) is a crucial process in numerous industries, and the optimization of its efficiency and economic viability is essential. This review provides a comprehensive analysis and comparison of various distillation processes, heat integration (HI) strategies, and process intensification (PI) techniques employed for IPA dehydration. The advantages, limitations, and applicability of distillation processes, such as extractive distillation, heterogeneous azeotropic distillation, and pressure swing distillation, are discussed. In addition, this review explores the potential of HI techniques to optimize energy consumption and reduce operating costs of IPA dehydration processes. PI techniques, including thermally coupled arrangements and dividing wall columns, are examined for their ability to improve the process efficiency and sustainability. It is crucial to conduct thorough evaluations, as well as energy and economic analyses, when choosing the appropriate distillation process, HI approach, and PI technique for specific IPA dehydration applications. This review emphasizes the potential for improving the energy efficiency, product purity, and cost-effectiveness of IPA dehydration through the integration of advanced distillation processes and PI techniques.

Utilizing an ultra-sonication process to optimize a two-step biodiesel production from Karanja oil.

Currently, biodiesel is produced from non-edible oils, which have various poisonous and un-saponifiable components; therefore, it is harmful and unfit for humans. Biodiesel replaces petro-diesel fuel, which can be used as additives or substitutes for diesel engines. The novelty of the present study is to optimize the process parameters of a two-step (esterification and transesterification) process for biodiesel production using high free fatty acid (FFA) containing Karanja oil (Pongamia pinnata oil), with the ultrasound (US) process intensification (PI) technique, which is carried out for the first time. In the first step, a reduction in the initial FFA concentration of 11.06% was achieved through optimization of the esterification process using response surface methodology (RSM)-supported central composite design (CCD) method in which methanol:oil molar ratio of 6:1 and 60°C reaction temperature kept as fixed parameter, whereas H2SO4 catalyst loading (0.5-1.5w/w%) and reaction time (15-45min.) were varied. The FFA value is reduced to 1.56% under the optimal condition (32.8min reaction time and 1.14 w/w% of catalyst loading). The second step of optimization of the transesterification of esterified oil was performed by applying RSM supported Box-Behnken design (BBD) method with varying independent parameter ranges such as the molar ratio (A), CH3OK catalyst loading (B), and reaction time (C) with the range of 6:1-9:1 (methanol: oil), 0.5-1.5 w/w%, and 10-30min., respectively. A biodiesel yield of 98.16% was obtained under optimal conditions of a molar ratio of 7.6:1, catalyst loading of 0.98 w/w%, a reaction time of 20.6min., and a reaction temperature of 60°C (constant). Superior optimization results were observed than the conventional stirring method. The biodiesel's estimated characteristics were discovered to be within ASTM criteria and suitable for blending with diesel fuel.

Understanding the impact of reactive holdup on process intensification in the design of reactive distillation column

The commercial viability of reactive distillation as a front-runner industrial process intensification technique is limited by slow reactions. It is because the diameter established by the vapor-loading method restricts large holdup volumes (or catalyst amount) to accomplish the essential conversion. However, placing a large amount of catalyst on column trays necessitates either a high tray weir height (limited to excessive column pressure drop) or a large column diameter. This study aims to investigate an alternative design approach by increasing the column diameter beyond that required for vapor loading to retain a large holdup volume. Several combinations of tray weir heights and column diameters were studied and demonstrated through case studies for three industrial processes, and their optimal designs have been reported. High catalyst holdup volume enhanced energy efficiency and overcame hydraulic limitations despite requiring large diameter vessels. These design configurations with optimized catalyst holdup also resulted in improved process economics. Fabricating a wide column diameter is a good conservative engineering procedure considering safety aspects and better design control.

Control of new energy‐intensified triple column extractive distillation using feed split technique

AbstractBACKGROUNDHere, we investigated the control performance of extractive distillation intensified with ‘feed split’ (FS) technique – a process intensification technique that has not been widely applied to extractive distillation. Today, only a handful of studies have been reported on this topic, with only one focusing on the control performance and reporting the significant trade‐off between the steady‐state and dynamic performances. Nonetheless, the previous control study was based on the complex double column FS configuration. Recently, a new triple column FS configuration was reported (Sep. Purif. Technol. 2022 (297) 121467), but its control performance was not investigated. Hypothetically, the triple column FS configuration is less complex and does not involve any column integration and thus, may demonstrate a better dynamic performance. This study analyzed the control performances of the triple column FS configuration and the conventional configuration for the binary azeotropic separation of tetrahydrofuran and ethanol.RESULTSTwo types of control structures were examined for both configurations, i.e., the basic temperature control structure and the different feed forward temperature control schemes. The best control structure from each configuration is compared and findings showed that the conventional configuration provides better controllability performance.CONCLUSIONOur results suggested that the conventional configuration can bring the product qualities closer to their setpoint, while providing a lower transient deviation. © 2023 Society of Chemical Industry (SCI).

Techno-Economic Analysis of Upgrading Corn Stover-Based Acetone, n-Butanol, and Ethanol to Higher Ketones and Alcohols: Fuels or Fine Chemicals?

Acetone–butanol–ethanol (ABE) fermentation is a traditional industrial exploitation with a history of 100 years and the second largest fermentation industry in the world, second only to bioethanol fermentation. However, low ABE concentration in the fermentation broth, a complex separation process, and high separation cost are the bottlenecks of the biobutanol industry. Therefore, developing an efficient and energy-saving ABE upgrading process gives another approach to the reindustrialization of ABE fermentation, even with the completeness of fossil resource-based products. Here, we report on a coupling salting-out catalytic process intensification technique in which acetone was alkylated with ethanol and 1-butanol by Pd/C + K3PO4, and the higher ketone and alcohol products were separated by the salting-out effect of K3PO4. The higher ketones and alcohols were experimentally obtained with >70% mass fractions at 200–250 °C under the fermentation-derived H2 atmosphere and can be used as fuel precursors or fine chemicals. Aspen Plus was employed to simulate corn stover-based biobutanol production and the upgrading process through a series of analyses on raw materials cost, capital cost, operating cost, product selling prices, net present values, and sensitivities. A comparison between fuel precursors and fine chemicals was carried out, and fine chemicals turned out to be the preferred choice if the selectivity of the products and further purification process could be optimized. The results of a sensitivity analysis show that the ABE concentration process is one of the most energy-intensive processes. Reducing the costs of raw materials is one strategy to improve the completeness of ABE fermentation.

On the green hydrogen production through gasification processes: A techno-economic approach

Green hydrogen rises in the world energy scenario as one of the most promising non-carbon-based fuels capable of replacing fossil fuels. Biomass gasification is emerging as a cleaner and sustainable process of producing green hydrogen. Green hydrogen can be obtained by resorting to different biomass gasification processes. Moreover, techno-economic studies are essential to determining the viability of these processes and are missing in the literature. The novelty of this study is the identification of the gasification process that produces the highest hydrogen yields and the presentation of the viability conditions for three gasification plants aiming to produce green hydrogen. The methodology followed is based on the development of three models of biomass gasification processes (conventional, plasma, and supercritical water) in Aspen Plus® to estimate maximum hydrogen yields through a parametric study. The economic study was conducted based on economic indicators (net present value and payback) to assess the viability of each gasification process for green hydrogen production. The results suggest that supercritical water gasification is the most suitable process for hydrogen production, with hydrogen yields of 0.844 Nm3/kgbiomass. Hydrogen yields of 0.828 Nm3/kgbiomass, and 0.758 Nm3/kgbiomass were achieved for the conventional gasification and plasma gasification processes, respectively. From the economic assessment, it was concluded that none of the gasification processes are viable under the determined optimal operating conditions. A sensitivity analysis, however, revealed that conventional gasification is viable for steam-to-biomass ratios <3. Process intensification techniques were applied, revealing that supercritical water gasification can be viable for feed concentrations between 15 and 25%. A minimum selling price of 7 €/kg, 10 €/kg, and 13 €/kg were obtained for green hydrogen generated by the conventional, supercritical water, and plasma gasification processes, respectively. The results obtained in this study are of paramount importance for the hydrogen economy. However, this research should be supplemented by further intensifying the gasification processes in order to bring green hydrogen production costs down to a more competitive level.

Flow and mixing characteristics of gas-liquid slug flow in a continuous Taylor-Couette flow reactor with narrow gap width

This work experimentally investigated flow characteristics and mixing properties of the two-phase flow in a continuous Taylor-Couette flow reactor (CTCR) with narrow gap width. In the device with a gap width of 0.5 mm, to the authors’ knowledge, the narrowest gap width device ever studied in CTCR systems, the present study revealed that slug flows with alternating gas and liquid phases, as observed in microchannels, appeared in a certain flow regime. This slug flow appeared mainly in the region of low rotational Reynolds and axial Weber numbers. The non-dimensional effective diffusion coefficient Deff/uL [-] of slug flow was also measured by a tracer response method. Deff/uL in the slug flow was on the order of 10−6 and it has been successfully found that ideal plug flow mixing characteristics could be achieved under this flow condition. Since the intensified and controllable mixing in the liquid phase due to Taylor vortex motion induced by the inner cylinder rotation is expected to be much better than the mixing in the liquid phase of slug flows in microchannels, this flow is expected to be one of the process intensification techniques that will outperform the performance of the conventional microreactors with microchannels.

Performance assessment of the co-gasification for sustainable management of municipal solid waste: Moroccan Case

In the quest of virtuous energy system, clean energy production poses important environmental, social, and financial challenges. Among the potentially useful energy carriers, hydrogen emerges as a serious alternative to fossil fuels. Hydrogen is a clean energy vector whose use is likely to undergo significant development in the medium and long term. This article describes the current situation of municipal solid waste generation and management in Morocco. Additionally, a co-gasification plant model for hydrogen production from municipal solid waste and biomass blends was developed in Aspen Plus. A parametric analysis was carried out to study the effect of various parameters such as the temperature of gasification and the steam to feedstock ratio on syngas composition. The main findings show an increase in hydrogen molar fractions for higher temperatures (optimal values being achieved for ∼750 °C) and steam to feedstock ratios ≥1.2. The present model of the co-gasification plant could be further improved by adding a water–gas-shift reactor. This process intensification technique can contribute to the production of sustainable alternatives to the actual predominant fossil-based fuels.

CFD–DEM modeling of autothermal pyrolysis of corn stover with a coupled particle- and reactor-scale framework

Autothermal operation of fast pyrolysis is an efficient process-intensification technique wherein exothermic oxidation reactions are used to overcome the heat-transfer bottleneck of conventional pyrolysis. The development of accurate, reliable modeling toolsets is imperative to generating a deeper understanding of biomass autothermal pyrolysis systems to support scale-up and industrial deployment. This modeling effort describes the development of single-particle and reactor models which incorporate detailed reaction schemes and simultaneous exothermic oxidation reactions. The particle-scale model was parameterized for corn stover feedstock with particle morphology, density, ash content, and biopolymer composition, all of which impact the emergent conversion characteristics during pyrolysis. Results were then used to parameterize a reactor-scale autothermal pyrolysis model, which was developed using a coarse-grained computational fluid dynamic–discrete element method. The simulation results compared well with experimental results, with the predicted bio-oil, light gas, and biochar yield within 3.0 wt% of the experimental yields. Further analyses were performed to test the influence of equivalence ratio, biomass injection position, and particle size distribution on autothermal pyrolysis. The analysis of the physio-chemical properties of the fluid and solid phase inside the reactor and at the reactor outlet help reveal important process interactions of autothermal pyrolysis.

Supercritical fluid reactive deposition: A process intensification technique for synthesis of nanostructured materials

Supercritical fluid reactive deposition (SFRD) is a promising process intensification technique for synthesis of a wide variety of nanostructured materials. The enhanced mass transfer characteristics of supercritical fluids (SCFs) coupled with high solubilities of reducing gases in SCFs provide many advantages related to equipment size and time minimization over conventional techniques. Among SCFs, the emphasis has been placed on supercritical CO2 (scCO2) which is non-toxic, cheap and leaves no residue on the treated medium. Moreover, in SFRD, multiple processes such as dissolution, adsorption, reaction, and purification are combined in a single piece of equipment which is an excellent example of process integration for process intensification. In this review, the fundamental thermodynamic and kinetic aspects of the technology are described in detail. The studies in the literature on synthesis of a wide variety of nanostructured materials including supported nanoparticles, films, and ion-exchanged zeolites by SFRD are reviewed and summarized. The applications of these materials as catalysts and sensors are described. The review hopes to lead to further studies on further development of this technology for a wide variety of applications.

Process intensification and control strategies in cooling crystallization: Crystal size and morphology optimization of α-PABA

This study explores the process intensification techniques and process control strategies on the product properties optimization. α-PABA, a long needle-like shape, can cause problems for the downstream processing. This study proposes ultrasound technique, supercooling control (SSC), and temperature cycling (TC) technologies to optimize the morphology and crystal size distribution of α-PABA. Firstly, the solubility and metastable zone of α-PABA in ethanol solvent are measured to determine the operational range. Next, the concentration calibration model is established to correlate the solubility with the ATR-FTIR intensity and temperature qualitatively. Furthermore, the process improvement techniques and control strategies are introduced to optimize the products. The ultrasound intensification contributes to produce the uniform crystal seeds. The SSC is benefit for the crystal growth, and can reduce the L/D ratio of the crystal product. While, TC is an efficient tool to eliminate the fine crystals. Moreover, the combination of ultrasound, SSC, and TC technology can show a significant improvement on the product particle aspects. The L/D ratio, crystal size, crystal morphology can show different degree of improvement under the combination techniques. At last, the outlook and perspectives on the process analytical technology are developed.

Continuous flow synthesis of Butyl Levulinate using a microreactor –RTD and kinetic studies

Levulinic acid (LA) is produced abundantly from biomass processing, it serves as an eminent precursor for the synthesis of a variety of levulinate esters used as fuel additives. One such additive is Butyl Levulinate (BL) which possess excellent fuel blending properties. With the advent of process intensification techniques like microreactors higher conversions of value added chemicals and API's (Active Pharmaceutical Ingredients) can be achieved in lesser time. In the present work a Residence Time Distribution (RTD) study was performed on a microreactor to probe into non-idealities existing within the system. The microreactor system was then used to study the synthesis of Butyl Levulinate by varying the catalyst loading and residence time. In the microreactor 89.19% conversion of levulinic acid was obtained at 35% (mole) catalyst loading and 2 ​min space time, the mole ratio and temperature were fixed at 1:8 (LA:butanol) and 60 ​°C. Whereas, under similar conditions in a batch reactor LA conversion of 40.54% was achieved after 50 ​min.

A Novel Spherical Crystallization Method Using Pickering Emulsions

Spherical crystallization is a promising process intensification technique, where surfactant is an important ingredient in formulation but needs to be used carefully due to toxicological reasons. This work proposes to adopt colloidal particles stabilized Pickering emulsions for spherical crystallization, in order to eliminate or reduce the surfactant use. A representative system is selected for study, where silica nanoparticles are prepared to stabilize emulsions and evaporative crystallization of ibuprofen is carried out. Depletion attraction is exploited to improve the Pickering emulsion stability for better confining on crystallization with two depletants PEG and PVA tested. Crystal products from the emulsions prepared with silica nanoparticles and the non-ionic surfactant Tween 20 are compared. The results show that depletion attraction is helpful for producing stable Pickering emulsions with high dispersed phase fraction and mono-dispersed ibuprofen spherical agglomerates. Silica nanoparticles contribute to reduced induction time by boosting heterogeneous nucleation and mitigate secondary agglomeration possibly by steric effects.

Evaluation of mechanical vapor recompression in the reactive distillation of the N-butanol esterification process

The process of producing esters is usually performed through esterification in a reactor followed by a distillation column to separate the products. However, this design limits the reagent conversion. Reactive distillation is an alternative to get around this issue as it allows greater reagent conversions in reactions limited by chemical equilibrium. It is one of the most famous process intensification techniques. On the other hand, mechanical vapor recompression has been used to recycle waste heat to improve efficiency of conventional distillation columns. In this context, this work evaluated the inclusion of a mechanical vapor recompression system in a reactive distillation process to obtain n-butyl acetate via n-butanol esterification with acetic acid. Systems with and without recompression were simulated in an Aspen Plus™ environment. The addition of recompression resulted in a reduction of 33.65% in the annual cost of the process, while not significantly affecting the purity of the desired product and the reagents’ conversion. From an environmental point of view, the mechanical vapor recompression system adoption resulted in a 12.69% reduction in CO2 emissions, contributing positively to meeting the requirements of the environmental regulations.