Multifunctional Reactor Research Articles

Two-stage conversion of syngas and pyrolysis aqueous condensate into L-malate

Hybrid thermochemical–biological processes have the potential to enhance the carbon and energy recovery from organic waste. This work aimed to assess the carbon and energy recovery potential of multifunctional processes to simultaneously sequestrate syngas and detoxify pyrolysis aqueous condensate (PAC) for short-chain carboxylates production. To evaluate relevant process parameters for mixed culture co-fermentation of syngas and PAC, two identical reactors were run under mesophilic (37 °C) and thermophilic (55 °C) conditions at increasing PAC loading rates. Both the mesophilic and the thermophilic process recovered at least 50% of the energy in syngas and PAC into short-chain carboxylates. During the mesophilic syngas and PAC co-fermentation, methanogenesis was completely inhibited while acetate, ethanol and butyrate were the primary metabolites. Over 90% of the amplicon sequencing variants based on 16S rRNA were assigned to Clostridium sensu stricto 12. During the thermophilic process, on the other hand, Symbiobacteriales, Syntrophaceticus, Thermoanaerobacterium, Methanothermobacter and Methanosarcina likely played crucial roles in aromatics degradation and methanogenesis, respectively, while Moorella thermoacetica and Methanothermobacter marburgensis were the predominant carboxydotrophs in the thermophilic process. High biomass concentrations were necessary to maintain stable process operations at high PAC loads. In a second-stage reactor, Aspergillus oryzae converted acetate, propionate and butyrate from the first stage into L-malate, confirming the successful detoxification of PAC below inhibitory levels. The highest L-malate yield was 0.26 ± 2.2 molL-malate/molcarboxylates recorded for effluent from the mesophilic process at a PAC load of 4% v/v. The results highlight the potential of multifunctional reactors where anaerobic mixed cultures perform simultaneously diverse process roles, such as carbon fixation, wastewater detoxification and carboxylates intermediate production. The recovered energy in the form of intermediate carboxylates allows for their use as substrates in subsequent fermentative stages.

Application of rotating cone reactor for continuous biodiesel production: Effect of cone geometry and optimization of operating variables through response surface methodology (RSM)

The work developed a rotating cone reactor (RCR) as a promising multifunctional reactor for continuous biodiesel production from refined palm oil (RPO) homogeneously catalysed by NaOH. The effects of rotating cone geometry, rotational speed, catalyst amount, and reactant feed flow rate on FAME yield were investigated. Response surface methodology (RSM) and the Design Expert software were used to optimize the operating variables. The grooved cone surface was found to play an important role in increasing FAME yield. The model predicted a maximum FAME yield of 96.9 % at the process conditions of NaOH loading of 0.602 wt.% of oil, a feed flow rate of 298 mL/min, and a rotational speed of 751 rpm. It provided a high yield efficiency of 1.324 × 10−3 g/J and a high productivity of 0.715 mol/min at a very short residence time of 2 – 3 s. This resulted in a significant reduction in transesterification time, suggesting that the RCR is a promising multifunctional reactor for economical continuous biodiesel production.

Experimental PSA reactor for methanol-enhanced production VIA CO2 hydrogenation

Methanol synthesis via catalytic CO2 hydrogenation has emerged as one of the main ways to valorize CO2. The main problem is that the methanol synthesis reaction is thermodynamically controlled, and there is a parallel endothermic reaction, reverse water gas shift (RWGS), so low methanol production ratios are achieved.In this scenario, process intensification, particularly multifunctional reactors where reaction and separation occur simultaneously, is of great interest. Sorption-enhanced reaction processes (SERP) technologies are widely used in equilibrium-controlled processes to increase reagent conversion through selective product removal.Various authors have proposed SERP processes for CO2 hydrogenation to methanol, but most of them are simulations studies and it is difficult to find experimental data. The aim of the work is the experimental study of the CO2 conversion and selectivity to methanol of a SERP process based on a four-step PSA reactor. The process has been carried out with a commercial Cu/ZnO/Al2O3 catalyst and commercial 3A zeolite as adsorbent.Conversions beyond the equilibrium have been achieved in the SERP process, even complete conversion of CO2 at 50 bar, 250 °C, and 300 °C. In the cyclic process, high CO2 conversions far from equilibrium are achieved in all the range of temperatures, 200–300 °C. The best results of methanol yield are achieved at 250 °C and 50 bar, followed closely by 200 °C. It is worth mentioning that methane is detected in the transitory state at 300 °C and 50 bar. Also, the purge step has been studied, concluding that it is necessary for adsorbent regeneration, improving CO2 conversion in the cyclic steady state.

A cyclic sorption-reaction process for continuous synthetic methane production from flue gas and green hydrogen

In the scope of Power-to-Methane processes, green H2 and CO2 (captured from flue gas, for instance) can be catalytically converted to CH4 (or synthetic natural gas), an easily stored and distributed energy vector. From the perspective of process intensification, the CO2 capture (by sorption) and conversion can be performed in the same multifunctional reactor, thus requiring fewer operational units and potentiating the synergy between the exothermic methanation and the endothermic CO2 desorption. In this regard, two reactors were individually packed with alternating layers of two commercial materials, a CO2 sorbent (K-promoted hydrotalcite) and a methanation catalyst (Ru-based), and tested to carry out a cyclic sorption/reaction process. The feed during the sorption stages consists of a synthetic flue gas stream containing 15 %vol. of CO2 balanced in N2. In the reactive regeneration stage, the inlet is pure H2, which reacts with the previously sorbed CO2, producing CH4. The two sorptive reactors were operated in parallel and out of phase until a cyclic steady-state was reached. The employed materials showed no signs of deactivation during over 150 h of time on stream. The performance of the cyclic unit was tested under different operating conditions, in a parametric study that assessed the influence of each variable on several performance indicators like CH4 productivity and CH4 purity. The study was carried out at atmospheric pressure and centered on a reference experiment in which a CH4 productivity of 1.12 molCH4·kgcat–1·h−1 and a purity of 60.8 % were obtained, using 200 mLN·min−1 of synthetic flue gas (15 %vol. CO2) and 100 mLN·min−1 of H2, at 350 °C and a switching time of 30 min. Nevertheless, all performance indicators could be improved in other operating conditions (CH4 purity up to 71.6 % and CH4 productivity up to 1.32 molCH4·kgcat–1·h−1).

Modeling and Optimization of Mass and Heat Flux Profiles in a Multifunctional Reactor for CO2 and H2 Valorization to Dimethyl Ether

Dimethyl ether is one of the future synthetic fuels in the 2025–2050 energy mix. This work presents a detailed numerical optimization approach for a multifunctional reactor for the direct synthesis of dimethyl ether from CO2 and H2, with a specific focus on the methodological aspect that can be used as a guide to help or evaluate the development of innovative technological strategies. An innovative approach based on the dynamic optimization of the mass and heat flux profiles is applied for the intensified configuration, coupling simultaneously the reaction, heat exchange, and membrane separation (R–E–M). Several degrees of freedom and optimization strategies (mono- and multi-objective/deterministic and stochastic) are addressed. The energetic criterion is evaluated, namely, the total heat power exchanged. Optimization results highlight the performance improvement potentialities offered through the optimal exploitation of the synergy between these elementary functions. Simulation results show that the kinetic inhibition caused by water can be overcome and that a water-free process output is achievable, enabling an economic gain due the removal of a postreaction separation (water/methanol). The heat flux optimization provides more flexibility for mass transfer. Up to 95 and 98% in DME yield and CO2 conversion have been obtained per single pass for optimal theoretical heat- and mass-transfer flux profiles, respectively, within a multifunctional reactor. The results are obtained for the reactor inlet temperature and pressure of 518.15 K and 70 bar, respectively.

Influence of heat-transfer resistances in an optimized multifunctional reactor

This work presents a detailed model for the implementation of the dimethyl ether (DME) direct synthesis from CO2 and H2 in an intensified equipment. The effect of heat-transfer resistances within a multifunctional reactor is studied. Considering these resistances has demonstrated their influence on the temperature profile, hence, their role for both catalyst activity and membrane stability: a higher hot spot of about 20 °C is obtained within the first reactor segments.Based on a proper methodology, optimization approaches are proposed for the optimal heat management and water separation. Considering these heat-transfer resistances influences the optimal heat flux and water separation profiles, thus the optimized reactor design. Up to 80% in DME yield per single pass can be achieved proving the synergy between functions for process improvement. Simulation results demonstrate the strong DME yield dependence on the extracted water profile as well as on the heat flux profile exchanged with the coolant.

Olive Mill Wastewater Valorization through Steam Reforming Using Multifunctional Reactors: Challenges of the Process Intensification

Olive oil mill wastewater (OMW) is a polluting stream derived from the production of olive oil and is a source of environmental pollution; this is relevant in many countries around the world, but particularly in all the Mediterranean region where major producers are located. In this effluent, several pollutants are present—namely, sugars, fatty acids, and polyphenols, among others. Nowadays, to reduce the pollutant load, several treatment techniques are applied, but these technologies have numerous cost and efficiency problems. For this reason, the steam reforming of the OMW (OMWSR) presents as a good alternative, because this process decreases the pollutant load of the OMW and simultaneously valorizes the waste with the production of green H2, which is consistent with the perspective of the circular economy. Currently, the OMWSR is an innovative treatment alternative in the scientific field and with high potential. In the last few years, some groups have studied the OMWSR and used innovative reactor configurations, aiming to improve the process’ effectiveness. In this review, the OMW treatment/valorization processes, the last developments on catalysis for OMWSR (or steam reforming of similar species present in the effluent), as well as the last advances on OMWSR performed in multi-functional reactors are addressed.

Influence of Hydrodynamic Conditions on Precipitation Kinetics of Barium Sulfate in a Multifunctional Reactor

In this paper, the influence of hydrodynamic conditions in Kenics static mixer, which acts as a multifunctional reactor, on precipitation kinetics of barium sulfate is investigated. The investigated range of the Reynolds number varied between 500 and 5000, which covered both laminar and turbulent flow regimes. In all experiments, the relative supersaturation was maintained at the constant level (σ = 205). The obtained precipitate was collected and used for crystal size distribution (CSD) determination. On that basis, the kinetic parameters of the process were calculated using the mixed suspension mixed product removal (MSMPR) mathematical model of the process. It was found that for the whole investigated range of Reynolds number, the mixing conditions were satisfactory. CSD analysis showed that in the laminar regime, a clear tendency in crystal behavior could not be noticed. However, during the analysis of the turbulent regime, the presence of a critical Reynolds number was noticed. Above this value, there is a change in the flow pattern, which results in a change of kinetic parameters (B, G), as well as manifests in a form of a decrease in the value of mean diameters of crystals. The flow pattern change is caused by the geometry of the reactor’s inserts.

Modeling and simulation of a steam-selective membrane reactor for power-to-methanol

The hydrogenation of CO2 to methanol is currently receiving increased attention following the deployment of Power-to-X processes. In this exothermic reversible reaction, the CO2 conversion is strongly limited by the thermodynamic equilibrium and the offer of commercial catalysts is mostly limited to Cu-based materials. Therefore, available options for improving methanol production consider either process design and optimization and/or using multifunctional reactors that provide advantageous features compared to conventional reactors, despite additional complexity. In this work we have modeled and simulated a membrane reactor (MR) featuring steam removal for shifting the reaction equilibrium to the products side and thus not only improving the CO2 conversion but also contributing to the increase of catalyst life span and representing a reliable alternative for heat removal. For this purpose, the proposed model for the MR considered the properties of a hydrophilic sodalite (SOD) membrane and the kinetics of a Cu/ZnO/Al2O3 catalyst. A split feed strategy has been devised to tackle poor membrane selectivity in the temperature range of interest. At 270 °C and 50 atm, the split feed allowed increasing the methanol yield up to 18%, while an ideal membrane (i.e., infinitely selective to steam) up to 31% (both in relative terms), when compared to a traditional reactor. Moreover, using the MR with the SOD membrane in the referred conditions it was obtained a permeate outlet stream containing only reactants and steam, therefore easily recyclable.

Olive mill wastewater valorization through steam reforming using hybrid multifunctional reactors for high-purity H2 production

The main purpose of this study was to assess the benefits of different hybrid multifunctional reactors (sorption-enhanced reactor (SER), membrane reactor (MR) and sorption-enhanced membrane reactor (SEMR)) comparatively to a traditional reactor (TR) for H2 production through the steam reforming of olive oil mill wastewater (OMWSR). In all reactor configurations, an in-house prepared Ni-Ru/Ce-SiO2 catalyst was used, combined in the SERs with a potassium-promoted hydrotalcite-based sorbent to capture CO2. Additionally, in the MR and SEMR configurations, a commercial Pd-Ag membrane was utilized to separate H2 from the reaction medium.It was verified an increase in both the H2 production and catalyst stability using the SER (during the pre-breakthrough of CO2) in comparison with the TR. However, a higher enhancement of the H2 yield was observed using the SEMR (again during the pre–breakthrough period), which was less pronounced after the saturation of the sorbent (i.e., in the MR), due to the effect of the H2-selective membrane only. Furthermore, pure H2 can be obtained in the permeate side of the membrane reactors (in the absence of sweep gas).It was also demonstrated that the use of such multifunctional reactors (and particularly the SEMR) in the steam reforming of real olive mill effluents allows reducing drastically the pollutant load of these streams, while economically valorizing this waste with the production of green H2.

A Compact, Self-Sustaining Fuel Cell Auxiliary Power Unit Operated on Diesel Fuel

A complete fuel cell-based auxiliary power unit in the 7.5 kWe power class utilizing diesel fuel was developed in accordance with the power density and start-up targets defined by the U.S. Department of Energy. The system includes a highly-integrated fuel processor with multifunctional reactors to facilitate autothermal reforming, the water-gas shift reaction, and catalytic combustion. It was designed with the help of process analyses, on the basis of which two commercial, high-temperature PEFC stacks and balance of plant components were selected. The complete system was packaged, which resulted in a volume of 187.5 l. After achieving a stable and reproducible stack performance based on a modified break-in procedure, a maximum power of 3.3 kWe was demonstrated in a single stack. Despite the strong deviation from design points resulting from a malfunctioning stack, all system functions could be validated. By scaling-up the performance of the functioning stack to the level of two stacks, a power density of 35 We l−1 could be estimated, which is close to the 40 We l−1 target. Furthermore, the start-up time could be reduced to less than 22 min, which exceeds the 30 min target. These results may bring diesel-based fuel cell auxiliary power units a step closer to use in real applications, which is supported by the demonstrated indicators.

Viability and Colony Morphology Variation of Rhodococcus rhodochrous CNMN-Ac-05 in the Presence of Magnetite Nanoparticles

In recent decades the use of nanotechnologies in the remediation of xenobiotic substances has proven its effectiveness, but not its safety. Nanoparticles often accumulate in the remedied environment, having, over time, toxic effects on living organisms. In this context, research on the vital activity of microorganisms and their interaction with nanoparticles is of major importance. Aim of the research was to determine the influence of Fe3O4 nanoparticles, obtained by different ways (laboratory method and synthesis in the reactor) on the viability and colony morphology of Rhodococcus rhodochrous CNMN-Ac-05 strain. Methods. Encapsulated magnetite (Fe3O4) nanoparticles were synthesized by chemical co-precipitation method, using iron(II) sulfate and iron(III) chloride in the presence of poly-N-vinylpyrrolidone, used as a stabilizer. Fe3O4 SR (Synthesis in the Reactor) was produced in the multifunctional reactor VGR-50, at the same conditions. Cell biomass was determined on the spectrophotometer by the optical density at 540 nm,with subsequent recalculation to cell dry weight according to the calibration curve. The cell dry weight was determined by gravimetric method. The morphological features of the rhodococci colonies were described according to the standard microbiological method. Results. It was established that magnetite nanoparticles in concentrations of 1–100 mg/L were not toxic to the R. rhodochrous strain, had a positive effect on the viability of rhodococci by stimulating the growth of biomass, regardless of their concentration and the method of their synthesis. In the presence of Fe3O4 nanoparticles the population dissociated to S1, S2, R1, R2 forms, and S-R type of colonies, while the basic morphological features of R. rhodochrous colonies corresponded to type S1. Conclusions. The optimal concentration of magnetite nanoparticles, which stimulated the growth and development of R. rhodochrous was 25 mg/L for Fe3O4 and 50 mg/L Fe3O4 SR. At all concentration of Fe3O4 nanoparticles the main colony morphotype of the rhodococci was smooth S1-type; the new types of colonies represented only 0.1–0.6% of the population, and the lowest degree of variability corresponded with the highest colony-forming units index.

A conceptual evaluation of a new multifunctional reactor containing glycerol steam reforming and nitrobenzene hydrogenation

In this work, the process intensification has been applied through simultaneous heat and mass transfer. A new multifunctional reactor for the co-production of hydrogen and aniline has been proposed. The heat required for the endothermic process (glycerol steam reforming) is provided by the exothermic process (hydrogenation of nitrobenzene to aniline). Additionally, all the required hydrogen for the aniline manufacture process is provided by a portion of the obtained hydrogen from the glycerol steam reforming via the membrane side. The achieved results of the glycerol steam reforming process have been compared with the conventional data. Acceptable improvement can be seen in the performance of the reformer, in which the conversion of glycerol and yield of hydrogen have improved by around 32% and 6.5%, respectively. Also, the conversion of nitrobenzene displays an adequate number of 81.74%. Furthermore, a parametric analysis is accomplished to evaluate the performance of the reactors. Finally, the order of locations in the offered configuration has been reversed to investigate its effect on the simulation. The arrangement manipulation contributed to increasing the conversion of glycerol from 53.28% to 56.96 %, hydrogen yield from 4.83 to 4.89, and around 2.71% reduction of nitrobenzene conversion.

CFD simulation of creeping flows in a novel split-and-recombine multifunctional reactor

Various mixing processes deal with the blending of viscous fluids at low Reynolds numbers. Some of the emerging trends rely on the use of either active or passive microstructures to achieve this task when highly viscous or fragile fluids are employed. The compactness of such mixers remains, however, a major challenge due to the long residence times required to achieve the desired outcome. Split-and-Recombine (SAR) mixers are a promising solution since they rely on a multi-lamination process to perform a series of baker’s transforms on the concentration profile.The current work is a numerical study that describes the hydrodynamic and mixing performance of a new topology of SAR mixers. This mixer is characterized by a double separation and recombination aimed at increasing the mixture homogeneity in a shorter distance. For this purpose, a finite element solver is used to compute the pressure drop, friction factor, concentration profile, and segregation scales for a viscous fluid in the creeping flow regime. The results are compared against two commonly used SAR mixers in the open literature. The findings show that the newly proposed mixer exhibits a superior performance through a better mixing quality at a lower energy consumption requirement.

Development of Carbonization and a Relatively High-Temperature Halogenation Process for the Removal of Radionuclides from Spent Ion Exchange Resins

This study investigated a two-step thermochemical treatment process consisting of carbonization and halogenation for the removal of radionuclides from spent cation-exchange resin (CER). Based on a thermal analysis of cation-exchange resins, we propose a two-step thermochemical treatment process involving the conversion of spent CER into pyrocarbon and then the removal of radioactive elements from the carbonized CER by converting them volatile halides at very high temperatures. The proposed process mainly consists of a carbonization and halogenation reactor, a UHC (unburned hydrocarbon) combustor, and wet scrubber. A step-by-step experimental and numerical optimization study was conducted with the carbonization and halogenation reactor and the UHC combustor. The optimum operating conditions could be established based on the results of a thermal analysis of the CER, a nonisothermal kinetic analysis, a numerical modeling study of a plug flow reactor (PFR)-type combustor, and a thermodynamic equilibrium analysis of a system consisting of a mix of carbonized CER and halogenation gas. The results of this study present detailed design of a novel multifunctional reactor and operating conditions of a bench-scale carbonization and halogenation process. Basic performance tests using CER doped with nonradioactive Co and Cs, indicated as Cs-137/134 and Co-60/58, were conducted under the optimized conditions. The results of these tests showed that the novel thermochemical process proposed in this study is a viable process that effectively removes radioactive elements from spent CER.

A review of catalyst and multifunctional reactor development for sustainable biodiesel production

A review of catalyst and multifunctional reactor development for sustainable biodiesel production

Metal–organic framework derived NiS2 hollow spheres as multifunctional reactors for synergistic regulation of polysulfide confinement and redox conversion

Distinctive NiS2 nanocages with hollow sphere structures can effectively suppress the “shuttle effect” and accelerate the redox kinetics of polysulfides.

A review of domestic and foreign experience of steel treatment in CCM tundishes

The modern steelmaking facilities melt as a rule a semi product, which is further subjected to various processes of refining in steel ladle. Recently an additional treatment of the metal in CCM tundish became widespread in the domestic and foreign practice. A tendency of transforming tundish into a multifunctional metallurgical reactor was noted, since more and more technological operations are transferred in it, including alloying, stirring, various methods of heating, modifying and removal of nonmetallic inclusions. Examples of comprehensive utilization of a bloom CCM tundish at some Japanese plants of Kobe Steel in Kakagava presnted, at which the metal is filtered when going through holes in the two partitions thus effectively removing nonmetallic inclusions. New variants of metal blowing off in the tundish by inert gas developed by domestic specialists considered, including a technology for metal blowing off by an inert gas and a facility for the inert gas supply through the stopper of the tundish. Supply of inert gas through the stopper results in efficiency increasing of degassing and nonmetallic inclusions removal as well as submerged nuzzles service time increase, which is particularly important at casting of steels with high content of aluminum. Examples of solutions of metal treatment in tundish by cored and aluminum wire given. Schemes of cored wire introduction into tundish and liquid steel treatment in a CCM mold considered. Considerable attention was given to the problem of metal temperature control in tundish, including by an electric arc, induction and plasma heating. List of domestic and foreign plants presented, implemented facilities of steel plasma heating in the CCM tundish. It was noted, that steel chemical heating in tundish can be applied at unforeseen problems arising at casting.

Process Intensification through Directly Coupled Autothermal Operation of Chemical Reactors

Summary Autothermal operation of a chemical reactor involves coupling exothermic and endothermic chemical reactions for the purpose of thermal management without resorting to external energy sinks or sources. Often this is accomplished through regenerative or recuperative heat exchange between spatially or temporally separated exothermic and endothermic reactions. However, it is also possible to directly couple these reactions simultaneously within the same reactor volume, eliminating the heat-transfer bottleneck that characterizes much of chemical manufacture. It is not widely recognized that directly coupled autothermal operation allows dramatic process intensification. This perspective defines autothermal operation and contrasts it with conventional heat transfer for thermal management of chemical processes. The intensification and cost savings that can be achieved are quantified, and the implications to modular chemical process intensification are presented. Guidelines are proposed for designing directly coupled autothermal processes. Diverse examples are presented. Several challenges to expanding the field are critically discussed.

Analysis of reactor–separator processes for polymeric and oligomeric degradation products with controlled molar mass distributions

Integration of reaction and separation is attractive in production of biobased oligomers and short polymers from polysaccharides and proteins via catalytic degradation. The challenge lies in controlling the molar mass distribution. Theoretical analysis for process integration is performed for conventional CSTR, a multifunctional reactor, and reactor-separator-recycle processes. Closed-form solutions for the mass balance equations are obtained for coupled serial-parallel first-order reactions. The influence of the separators’ cut-off range and sharpness on the feasible operating parameter range and process performance is visualized. It is found that a membrane reactor may be less productive than a CSTR if total concentration is limited. An additional separator to recycle the solvent significantly improves purity and productivity. Solvent recycling decouples the feed rate and the residence time of the product molecules. To maximize purity and productivity, no product molecules should be retained in the reactor whereas the recycled solvent can be impure.