Honeycomb Reactor Research Articles

Investigation of a Novel Thermochemical Reactor for Medium- and Low-Temperature Heating Applications in Buildings

This research paper investigates a novel triangular honeycomb thermochemical energy storage reactor for low- and medium-temperature applications in buildings, emphasizing its potential to enhance sustainable heating. Using a validated 3D numerical model, the reactor’s performance is analyzed in depth across various configurations, focusing on key parameters such as energy storage density, pressure drop, internal air flow distribution, and round-trip efficiency. Results show that the reactor achieved an energy storage density of 872 kJ/kg and a round-trip thermal efficiency of 41.51% under optimal conditions. Additionally, the triangular honeycomb reactor (30°, 60, and 90°) configuration achieved the highest temperature lift of 48.7 °C. In a feasibility analysis for residential heating in northern China, the reactor with 30°, 60°, and 90° angles required 24.91% less volume to meet daily heating demands compared to other configurations. This study contributes valuable insights for the development of efficient, low-carbon heating solutions for low- and medium-temperature applications in buildings, offering interesting advancements in the field of thermochemical energy storage technology.

Maximizing thermal performance in triangular honeycomb thermochemical reactors: Structural and operating parameter studies

Using thermochemical energy storage methods to store energy is increasingly vital for boosting the share of renewable energy in consumption within buildings and industries. This entails harnessing off-peak excess renewable energy, such as electricity or waste heat energy, for storage purposes. While previous research emphasizes the importance of improving reactor performance, comprehensive analysis of the new honeycomb reactor designs is lack. Innovative advancements in maximizing thermal performance within triangular honeycomb reactors are elucidated in this study. This study employs a validated 3-D model to explore the effects of these parameters on heat and mass transfer within a triangular honeycomb reactor. By investigating structural and operational parameters, a novel equilibrium is achieved, amplifying heat exchange efficiency and channeling thermal energy with unprecedented precision. Through a rigorous examination of reactor air velocity distribution, air temperature lift, and outlet air absolute humidity, this research unveils pivotal insights into enhancing reactor efficacy. Notably, the study identifies that increasing the channel thickness by 1.2 times, resulting in energy storage density of 463 kJ/kg. This innovation positions triangular honeycomb reactors at the forefront of sustainable energy management, offering a potential solution for decarbonization such as storing industrial waste heat and harnessing surplus off-peak electricity in buildings.

Honeycomb reactor: a promising device for streamlining aerobic oxidation under continuous-flow conditions.

We report on the high potential of a honeycomb reactor for the use in aerobic oxidation under continuous-flow conditions. The honeycomb reactor is made of porous material with narrow channels separated by porous walls allowing for high density accumulation in the reactor. This structure raised the mixing efficiency of a gas-liquid reaction system, and it effectively accelerated the aerobic oxidation of benzyl alcohols to benzaldehydes under continuous-flow conditions. This reactor is a promising device for streamlining aerobic oxidation with high process safety because it is a closed system.

Optimal design of novel honeycomb photocatalytic reactors for numerical analysis of formaldehyde degradation by CFD modeling

As an alternative to the investigation of photocatalysts, it is a potential approach to enhance the photocatalytic performance of the novel photocatalytic reactor by optimizing its geometric structure and reaction conditions. In this work, five different honeycomb photocatalytic reactors with a deflector and a porous airflow distribution plate were designed and a numerical simulation was performed based on computational fluid dynamics (CFD). The simulation results showed that a huge vortex appeared near the entrance of the original model and the velocity distribution inside the reactor was non-uniform, whereas these shortcomings could be effectively overcome when using the 45° deflector model (S-4) compared to the other models. Compared to S-1, the photocatalytic conversion rate of formaldehyde for S-4 was boosted by 7.29% at a flow velocity of 0.04 m s−1. In addition, it was found that the photocatalytic conversion rate of formaldehyde increased from 55.45 to 94.73% when the velocity decreased from 0.04 to 0.01 m s−1, and the photocatalytic removal rate of formaldehyde decreased from 94.73 to 70.05% as the relative humidity varied from 20 to 70%. Furthermore, when the irradiance increased from 45 to 265 mW cm−2, the photocatalytic conversion rate of formaldehyde improved by 10.78%. Overall, this work contributes to the design of the novel honeycomb reactor to acquire the optimized construction of the photocatalytic reactor.

Numerical study on the heat and mass transfer in charging and discharging processes of a triangular honeycomb thermochemical energy storage reactor

• A triangular honeycomb reactor has been designed and experimentally investigated. • A 3-D numerical model of this reactor has been developed and validated. • Relationships between heat transfer and mass diffusion are determined. • The thermal efficiency of triangular honeycomb reactor can achieve around 20% Adsorption heat storage based on porous adsorbents attracts considerable attention for the high energy storage density and long storage duration compared to sensible and latent heat storage methods. However, one of the critical challenges is the poor heat and mass transfer performance of thermochemical reactors. This study presents a triangular honeycomb reactor using zeolite 13X-H 2 O working pair and investigates the heat and mass transfer performance. To do this, a three-dimensional transient heat and mass transfer model has been built in COMSOL to simulate the adsorption and desorption processes of the new reactor. A detailed numerical model and the corresponding modelling methods are critical to the investigation while most of the recent studies are based on one-dimensional and two-dimensional models. The model has been experimentally validated thoroughly to a close agreement in both adsorption and desorption processes (mean sum of percent errors of 0.6% to 8.91% for air temperature and relative humidity). The reactor thermal efficiency from the simulation and experiment are 19.57% and 21.93%, respectively, which are achieved by the fast and controllable charging and discharging performance along with the reduced air pressure drop benefited from the reactor design. To add value of the charging and discharging details, this study also presents the contour diagrams with detail discussions for the air velocity, temperature, water concentration, and heat and mass flux variations of the triangular honeycomb channel during desorption and adsorption processes. The results show that the side of triangle channel has larger and stronger moisture desorption in a charging process and stronger moisture adsorption in a discharging process than that of the triangle corner areas.

Numerical analysis of solar chimney power plant integrated with CH4 photocatalytic reactors for fighting global warming under ambient crosswind

Methane's global warming potential (GWP) is much larger than carbon dioxide and contributes significantly to global warming. Solar chimney power plant (SCPP) integrated with photocatalytic reactors can capture and remove atmospheric methane, and generate electrical power without fossil energy consumption simultaneously. In this paper, the performance of the flow characteristics, the CH4 removal, the CO2 emission reduction, and the power generation were analyzed for the SCPP integrated with different types of photocatalytic reactors under ambient crosswind (ACW). The results revealed that the SCPP integrated with a honeycomb reactor was more stable for the degradation of CH4 than that with a plate reactor. With an increase in ACW, the removal rate of atmospheric CH4 was reduced to a constant value of 0.41 g/s for the honeycomb reactor and 0.11 g/s for the plate reactor. The SCPP integrated with a honeycomb reactor achieved a maximum power generation of 88.31 kW, which was 1.63 times than that of the conventional SCPP when G = 857 W/m2 and ACW = 0 m/s. In addition, the improved SCPP could reduce CO2 emissions by 85.04 kg/h when G = 857 W/m2, ACW = 0 m/s, and △P = 320 Pa.

Computational investigation of the hexagonal honeycomb adsorption reactor for cooling applications

Adsorption cooling is a sustainable technology, since it can utilize solar energy or waste heat, while employing substances without ozone depletion and global warming potential. The adsorption reactor design is determinant for the system performance. An underexplored geometry hitherto – the hexagonal honeycomb adsorption reactor – was numerically investigated. An in-house, validated, three-dimensional computational model based on unstructured meshes was employed. The Specific Cooling Power (SCP) and Coefficient of Performance (COP) were quantified for several geometrical and operational parameters. The cell inradius creates a dichotomy between SCP and COP, being 218.9 W/kg˙s and 0.356 for 1 mm, while being 80.4 W/kg˙s and 0.606 for 6 mm. The cell height influences prominently the SCP, being 159.5 W/kg˙s and 86.1 W/kg˙s for 5 mm and 30 mm, respectively. The fin thickness impacts mostly the COP, being 0.599 and 0.364 for 0.5 mm and 3 mm, respectively. Higher COP is achieved for higher evaporator, lower adsorption and lower condenser temperatures. Higher SCP is achieved for lower adsorption and condenser, and higher evaporator and desorption temperatures. Shorter cycles result in high SCP and low COP, whereas the inverse occurs for longer cycles. Aluminum heat exchanger yields 7.7% higher COP than copper. The results are discussed from a physical, as well as, an engineering perspective. • Hexagonal honeycomb reactor studied in the context of adsorption cooling. • Quantification of COP and SCP under various geometrical and operational parameters. • Geometrical and operational parameters are determinant for the reactor performance. • Adaptive cycle duration is highly useful for the regulation of system performance. • Aluminum heat exchanger yields 7.7% higher COP than copper.

Numerical Investigations on the Transient Heat and Mass Transfer of Triangular Honeycomb Reactor

Numerical Investigations on the Transient Heat and Mass Transfer of Triangular Honeycomb Reactor

The Efficiency of Pd Addition and Sr Substitution on La1−xSrxMnO3 to Remove Ventilation Air Methane in a Catalytic Flow Reversal Reactor

Ventilation air methane (VAM) is the main cause of greenhouse gas emissions in coal mining. Catalytic flow reverse reactor (CFRR) is widely used in VAM to mitigate methane emissions. In this study, palladium (Pd) and La1−xSrxMnO3 were used as catalysts in a CFRR. Different types of catalysts were prepared by loading La0.8Sr0.2MnO3, La0.9Sr0.1MnO3, and 0.1%Pd-La0.9Sr0.1MnO3 on a cordierite honeycomb reactor coated with γ-Al2O3 to compare their performances. In addition, this study compared the performance of the three catalysts in an 800 °C reactor based on different methane inlet concentrations, inlet speeds, and conversion times. The results showed: (1) 0.1% addition of Pd increased methane conversion. (2) La0.8Sr0.2MnO3 had higher efficiency at lower methane inlet concentrations, whereas La0.9Sr0.1MnO3 was more efficient at higher methane concentrations. This study demonstrates that a higher Sr loading is worth implementing only when the methane concentration of VAM is lower than 0.6%. (3) To achieve a higher methane conversion efficiency, the inlet velocity of methane should also be considered.

Energy Transport of Photocatalytic Carbon Dioxide Reduction in Optical Fiber Honeycomb Reactor Coupled with Trough Concentrated Solar Power

Thanks to the high photon efficiency and reaction density, the optical fiber monolith reactor (OFMR) for InTaO4-based CO2 photoreduction is regarded as a promising photoreactor. In this work, the OFMR coupling with parabolic trough concentrator (PTC) is proposed to enlarge the daylighting area by several times without increasing the cost of photocatalysts. Based on the Monte Carlo ray-tracing (MCRT) approach and the finite volume method (FVM), a computational model of the reaction module considering the light, heat, and mass transfer is developed to optimize the fiber honeycomb reactor coupled with the PTC. As a result, the volume-averaged concentration of production reaches 1.85 × 10−4 mol·m−3, which is much higher than the traditional OFMR with the production concentration of 9.61 × 10−6 mol·m−3 under the same condition. The optimized structure of the monolith for better photocatalytic performance is obtained. It shows that the diameters of gas channels ranging from 1.5 to 2 mm are beneficial to the reaction efficiency. Finally, the results suggested that the even number of the gas channel should be avoided due to the pseudo-steady zone in the middle of the monolith. The reaction element with the high serial number along the flow direction has the reduced reaction density and endangers the organic optical fibers especially when the serial number exceeds 5.

Characteristics of liquid-liquid two-phase flow in a constructal honeycomb reactor

Inspired by the bionic structure, a honeycomb network was designed according to Bejan’s Constructal theory and manufactured via 3D-printing. The flow characteristics of the liquid–liquid system with an extremely low viscosity ratio (λ ~ 0.001) were investigated. Typical dumbbell-like plugs were observed and the evolution of their forms in the straight channel was presented. The overall flow status in the honeycomb network was classified into three types, namely, asymmetrical flow, symmetrical flow, and sphere flow. The uneven breakup of mother droplet at the Y-junction of part 2, which caused the final uniformity of droplets distribution, was attributed to the feedback from unbalanced flow resistance of downstream channels. The competition behaviors of the droplet pair, including squeezing, splitting and no-collision, were observed in the convergences, while the coalescence did not occur. Furthermore, it was found that the present constructal design with varied channel size was beneficial to the droplet breakup. The size of droplet decreased and the number of them increased along the honeycomb network, leading to the increased the contact area between the two phases.

Experimental study on honeycomb reactor using methane via chemical looping cycle for solar syngas

The chemical looping process on honeycomb reactor for solar syngas is experimentally studied in this work, which is the key reaction of the liquid sunshine production process. The honeycomb reactor realizes the integration of oxygen carrier and reaction chamber. NiO is placed in the reactor as oxygen carrier and methane is introduced as fuel gas. The results show that, with the development of process, the major reaction in the reactor gradually changed from methane complete oxidation to methane partial oxidation. During the process, the methane conversion and outlet syngas concentration is affected by the methane flow and fractional oxidation. Under the optimal operating conditions, the methane conversion can be maintained more than 95% and the concentration of outlet syngas can be around 90%. Compared with non-honeycomb fixed bed reactor, the methane conversion increases by more than 20 percent point and the concentration of outlet syngas increases by about 10 percent point. In addition, oxygen carrier in honeycomb reactor shows excellent cyclic stability in 30 times experiments.

Power‐to‐Gas: CO2 Methanation Concepts for SNG Production at the Engler‐Bunte‐Institut

AbstractPower‐to‐Gas approaches comprise different activities to store electric power in form of gaseous energy carriers like hydrogen or methane. The synthesis of SNG (substitute natural gas) and its injection into the natural gas grid allows the utilization of the well‐established infrastructure for natural gas storage, distribution and utilization without the need for further changes to the energy system. At the Engler‐Bunte‐Institut research focuses on catalytic methanation in catalytically coated metallic honeycomb reactors and in slurry bubble column reactors with the aim of evaluating alternative reactor concepts offering optimized heat transfer characteristics as well as maximizing the possibility of dynamic operation. Both concepts are attractive for small to medium scale power‐to‐gas applications. Hence, a scale‐up was performed for bothreactor concepts with the aim of implementation on commercial scale.

Testing and Correlation of 8mm Pitch Honeycomb & Plate Type Module Performance in a 20 Litres SCR Test Facility

The main aim of this experiment is to reduce the concentration of NOx in the exhaust gas below 100ppm with the most effective technique named selective catalytic reduction (SCR) with ammonia over to evaluate the performance of honeycomb and plate type catalyst in NOx reduction by varying the performance parameters such as flue gas temperature, space velocity, NH3 /NO molar ratio, etc., and to find the optimum values of the above parameters under which we get the maximum efficiency of NOx conversion at which air is not polluted and we have the sustained and eco-friendly environment. The effect of various performance parameters on the SCR process is also evaluated and the optimum values of performance parameters are also found to get the maximum efficiency of NOx conversion. SCR performance is substantially under the effects of reactant (ammonia) concentration and operating temperature, so that the concentration of untreated ammonia emitted from reactor discharge (ammonia slip) increases significantly at NH3 /NO ratios of more than 1.14 and operating temperatures less than 360 ºC and 300 ºC, respectively, in the catalytic filter medium and honeycomb reactor. low level of ammonia slip can be achieved at the NH3 /NO ratio of 1 and temperature range of 300–350 ºC in both reactors.The temperature of SCR is varied between 300OC to 350OC ,with a fixed space velocity of exhaust gas and a fixed value of NH3/NO ratio of 1.

Reduction Kinetics of Fe-based Oxygen Carriers Using Syngas in a Honeycomb Fixed-Bed Reactor for Chemical-Looping Combustion

Chemical-looping combustion (CLC) is considered to be a vital method for utilizing hydrocarbon fuel with low carbon emissions. A honeycomb fixed-bed reactor is a new kind of reactor for CLC. However, the further application of the reactor is limited by the inadequacy of the kinetic equations for CLC. In this paper, the experimental studies on the kinetic of Fe-based oxygen carriers were carried out by the CLC experiments using syngas which was obtained from one typical type of coal gasification products. The experimental results show that there were two individual stages for the kinetic characteristics during the fuel reaction process. Therefore, the CLC fuel reaction process could be described by a two-stage unreacted-core shrinking model and the reaction rate equations for each of the two phases were provided. In both stages, the dominant resistances were analyzed. The activation energy and the reaction order in both stages were calculated respectively as well. Comparing the experimental results of reaction rate with the calculated results of the obtained rate equations, it could be clearly seen that the reaction kinetics model was appropriate for the CLC in the honeycomb reactor. This work is expected to provide a guideline for the future development and industrial design of the honeycomb CLC reactors from the perspective of kinetics.

Engineering approach in stimulating photocatalytic H2 production in a slurry and monolithic photoreactor systems using Ag-bridged Z-scheme pCN/TiO2 nanocomposite

Ag-bridged pCN/TiO2 Z-scheme heterojunction composite with faster charges separation for stimulating H2 evolution under UV and visible light in different photo-catalytic reactor systems has been investigated. The photo-catalytic activity was tested using slurry, fixed bed and monolith photo-reactor systems for continuous H2 production from glycerol-water mixture. Using slurry system, Ag-pCN/TiO2 photo-catalyst produced 470 µmol h−1 of H2 which is 8.41 and 9.66 times higher than pCN/TiO2 and pristine TiO2, respectively. The efficiency was improved due to development of heterojunction with faster charges separation, whereas, Ag provides hot photo-generated electrons by surface plasmon resonance (SPR) and active sites for H2 production. The parameters study reveals that highest H2 was obtained at pH 7, glycerol concentration of 5 wt% and 0.15 g of catalyst loading. Furthermore, by applying engineering approach Ag-pCN/TiO2 showed H2 production rate of 10150 μmol h−1 using monolith reactor, a 13.36 and 21.6 times higher than fixed-bed and slurry photoreactors. The monolith honeycomb reactor exhibited higher AQY and space yield of 49.15% and 67.67 µmol h−1 cm−3 than slurry reactor (15.77%, 3.615 µmol h-1cm−3) and fixed-bed reactor (1.63%, 3.233 µmol h-1cm−3). The superior performance of a monolith reactor was due to higher photon flux utilization, large illuminated surface area and processing volume. The schematic of conversional and Z-scheme mechanism of Ag-pCN/TiO2 were proposed based on the results. Thus, excellent performance of catalyst using monolith reactor compared to slurry and fixed-bed reactor for H2 production would offer a new opportunity of engineering approach for renewable fuels applications.

Numerical Investigation of Auto-Ignition Characteristics in Microstructured Catalytic Honeycomb Reactor for CH4–Air and CH4–H2–Air Mixtures

Stable ranges of auto-ignition for the microcombustion of CH4 and CH4–H2 mixtures are identified numerically in a platinum-coated microcatalytic honeycomb reactor. Steady and transient simulations under pseudo-auto-thermal conditions were performed to investigate the coupling phenomenon between combustion and heat transfer in such microburner using ANSYS 17.2 coupled with a detailed chemkin reaction mechanism. The model was validated utilizing the available data in the literature on a similar microreactor, and the results showed good agreements. A certain amount of heat is furnished from outside at constant temperature from an external electric furnace to investigate the variations of localized self-ignition temperature while changing the flow rate and mixture strength. It was found that the ignition temperature for CH4–air mixtures is not affected by the mass flow rate. However, the ignition temperature of CH4–H2 air mixtures decreases while increasing the flow rate. The effect of equivalence ratio was studied to demonstrate the variations of flammability limits of the present microreactor. The equivalence ratio required for auto-ignition of CH4–air mixtures was found to be in the range from 0.4 up to 0.85 at a flow rate of 9.5 g/s. The reaction front moved from upstream to downstream under transient conditions matching with the reported experimental behavior in the literature.

Scale-Up of Innovative Honeycomb Reactors forPower-to-Gas Applications - The Project Store&Go.

The German “Energiewende” is heavily based on electric power and, therefore, requests solutions to serve non‐electric energy uses and to store electric energy in large scale. Synthetic natural gas (SNG) produced with hydrogen from water electrolysis and with CO2 from mainly renewable sources is one approach. For the catalytic SNG production efficient removal and utilization of the reaction heat is the main issue. A metallic honeycomb‐like carrier‐based reactor proved in laboratory scale to match this challenge. This type of reactor shows good heat conductivity and enables optimized operation. In the EU‐funded project Store&Go the honeycomb methanation is scaled up to MW‐scale. For this, heat transfer and kinetic data were determined experimentally and used in CFD calculations for the reactor design. Finally a SNG plant with 1 MW feed‐in will be built and fully integrated operation will be shown.

Characteristics of a 10 kW honeycomb reactor for natural gas fueled chemical-looping combustion

Chemical-looping combustion (CLC) is already treated as a promising way to capture CO2 in the utilization of fossil fuels. The most used reactors for the CLC are fluidized-beds, in which the fuel conversion and the conversion of fuel to CO2 is determined by the bed height. Here in this study, the CLC in an advanced 10 kW honeycomb reactor is studied by using natural gas as the fuel and Fe2O3 as the oxygen carrier. In the honeycomb reactor, a honeycomb chamber consisted by the oxygen carrier is employed to enhance the contact area and the disturbance between the fuel gas and the oxygen carrier. Both of these two enhancement are benefit for achieving a high CH4 conversion and a high conversion of CH4 to CO2. The experiment results show that three stages of Fe2O3 to Fe3O4, Fe3O4 to FeO and FeO to Fe are occurred in sequence during the reduction reaction of Fe2O3 and CH4 in the honeycomb reactor. The behaviors and the relationships for these complicated reactions, the oxygen transfer rate, the CH4 conversion and the conversion of CH4 to CO2 at different stages are further experimentally studied. Additionally, to increasing the conversion of CH4 to CO2 in the continuous operation, the characteristics for the honeycomb reactor in redox cycles are also experimentally investigated. Our study here would be expected to provide a new method for developing the energy and environment compatible systems.

Multiscale modeling of methane catalytic partial oxidation: From the mesopore to the full‐scale reactor operation

A multiscale methodology combining three different reactor length‐scales is presented to investigate the role of the catalyst internal pore structure and metal loading and dispersion on the catalyst layer and full‐scale reactor performances. At the catalyst level, the methodology involves pore‐scale simulations in the three‐dimensional mesopore and macropore space. The information gathered at the catalyst level is delivered to the full‐scale reactor model. The methodology is applied to a honeycomb reactor performing methane partial oxidation considering reaction kinetics described through a detailed multistep reaction mechanism. Realistic mesopore and macropore structures were reconstructed and combined to form specific bidisperse porous washcoat layers. The study shows that species effective diffusivities vary significantly but not in the same proportion for different structures. For structures featuring poor transport characteristics, the integral methane conversion and hydrogen selectivity are strongly affected while the reactor temperatures increase substantially. © 2017 American Institute of Chemical Engineers AIChE J, 64: 578–594, 2018