Moving Bed Reactor Research Articles

Thermodynamic Evaluation of Hydrogen Production Modes During the Pyrolysis of Ammonia in a Filtration Combustion Moving Bed Reactor

Thermodynamic Evaluation of Hydrogen Production Modes During the Pyrolysis of Ammonia in a Filtration Combustion Moving Bed Reactor

A Coupled CFD-DEM Approach to Model Reactive Granular Beds

Packed and moving bed reactors are widely used in process industry to process granular material. Shaft furnaces are one example of this. Due to their counterflow layout, a high thermal efficiency can be achieved. Shaft furnaces have a wide range of length and time scales that makes them challenging to model. Geometric details, like injection nozzles, are smaller than the particle size, which need a computationally highly expensive resolved Discrete Element Method (DEM) approach. To overcome this problem, a computing technique called Volume Fraction Smoother (VFS) was developed. Since the time scales in those systems reach from milliseconds for the particle collisions to hours of process time, the process time scale must be separated to model a quasi-steady state with reasonable computing time. For this, the Time Scale Splitting Method (TSSM) was introduced. This method was also adapted to model the self-heating behaviour of direct reduced iron (DRI).

Coproduction of metal oxide and CO2 through decomposition of carbonate in a moving bed with a central gas-flow channel

During carbonate calcination process, the block ores are often directly heated by high-temperature flue gas, which inevitably dilutes the potentially high-concentration CO2 from carbonate decomposition. In this study, we well implemented the coproduction of lightly burned magnesia (LBM) and high-concentration CO2 through decomposition of small-size magnesite in a devised novel moving bed reactor. The reactor is installed with a central gas-flow channel as internals to convert the moving bed into a radially flowing reactor, making it can process small-size particles. Verification of this design was implemented in an electrically heated pilot-scale facility processing about 10 kg h−1 magnesite (0–6 mm), and gaseous product contains about 99% CO2. Systematic tests employing laboratory fixed bed reactors with and without internals further showed that the thickness of particle layer between the heating wall and the central internals substantially affects heat transfer from outside to the inside, thus influencing the decomposition. It is particularly for magnesite because the formed LBM is both heat-resistant and flame-retardant. Therefore, an updated reactor for small-size carbonates decomposition and coproduction of CO2 is proposed.

Integrated CO2 Capture and Utilization by Combining Calcium Looping with CH4 Reforming Processes: A Thermodynamic and Exergetic Approach.

This study investigates a novel concept to coproduce high-purity H2 and syngas, which couples steam methane reforming with CaO carbonation to capture the generated CO2 and dry reforming of methane with CaCO3 calcination to directly utilize the captured CO2. The thermodynamic equilibrium of the reactive calcination stage was evaluated using Aspen Plus via a parametric analysis of various operating conditions, including the temperature, pressure, and CH4/CaCO3 molar ratio. Introducing a CH4 feed in the calcination stage promoted the driving force and completion of CaCO3 decomposition at lower temperatures (∼700 °C) compared to applying an inert flow, as a result of in situ CO2 conversion. A conceptual process design was investigated that employs a system of two moving bed reactors to produce nearly equivalent volumetric flows of pure H2 and a syngas stream with a H2/CO molar ratio close to 1. A solar reactor was examined for the reactive calcination step to cover the energy requirements of endothermic CaCO3 decomposition and dry reforming. The overall exergy efficiency of the process was found equal to ∼75.9%, a value ∼4.0 and ∼8.0% higher compared to sorption-enhanced reforming with oxy-fuel and solar calciner, respectively, without direct utilization of the captured CO2.

Enhanced production of hydrogen-rich gas from municipal sewage sludge gasification using a CaO-RM composite catalyst

Hydrogen-rich gas, characterized by high yield and purity, can be effectively generated through the steam gasification of sewage sludge (SS), offering substantial benefits for organic solid waste treatment and resource conservation. This study evaluated the gasification performance in a horizontal moving-bed reactor employing a wet-mixed CaO-red mud (CaO-RM) composite catalyst. The effects of CaO loading rate (CaO/RM), catalyst-to-SS ratio (CaO-RM/SS), and reaction temperature on the syngas yield, lower heating value (LHV), carbon conversion ratio, H2 to CO (H2/CO) ratio, and H2 yield were investigated. Results indicated that red mud loaded with a calcium-based catalyst significantly enhanced syngas production, particularly for hydrogen generation, during SS gasification. A maximum hydrogen molar fraction of 50.84% and a yield of 7.07 mol/kg were achieved with a CaO/RM of 40% and a CaO-RM/SS of 30% at 750 °C. With the reaction temperature increase from 700 to 900 °C, the catalytic performance for secondary tar cracking and steam reforming was further enhanced. The total syngas yield, H2 yield, hydrogen molar fraction, LHV of syngas, and carbon conversion rate peaked at 0.79 m³/kg, 19.30 mol/kg, 54.41%, 10,249.48 kJ/kg, and 65.67%, respectively, at 900 °C.

Demonstration of CO2 capture with CaO and Ca(OH)2 in a countercurrent moving bed carbonator pilot

Decoupling the carbonation and calcination stages of Calcium Looping (CaL) facilitates the capture of CO2 from small point sources, or even the atmosphere, by transporting CO2 as CaCO3 to centralized calcination plants to obtain pure CO2 and regenerate the Ca-sorbent. In this work, we provide the experimental proof of a novel countercurrent moving bed carbonator particularly suited for such applications. We conducted experiments in a 3-meter-long moving bed reactor with an internal diameter of 0.15 m, using Ca-sorbent particles of varying sizes (in the mm and cm scale). Simulated flue gases with varied concentrations of CO2 (up to 8.5 %v), superficial gas velocities (0.5–2 m/s) and inlet gas temperatures (250–630 °C) have been tested. The temperature profiles we observed along the axial direction confirm the formation of a carbonation zone at optimum temperatures (i.e., 550–700 °C), together with a CO2 polishing region towards the gas exit that leads to CO2 capture rates over 99 % in some cases. Using Ca(OH)2 as a CO2 sorbent, we achieved a molar conversion to CaCO3 of approximately 0.7.

Simultaneous nitrification and denitrification pattern in aerated moving-bed sequencing batch reactor: Choosing appropriate SRT for different COD/N ratios

ABSTRACT The effect of chemical oxygen demand (COD)/N ratio and sludge retention time (SRT) on the simultaneous nitrification and denitrification (SND) process in an aerated moving-bed sequencing batch reactor (A-MBSBR), for treating synthetic municipal wastewater, was studied. Three lab-scale reactors with SRTs of 5, 10, and 15 days were operated under COD/N ratios of 10 (phase 1) and 20 (phase 2). The high correlation coefficients between nitrification and denitrification efficiencies in both phases demonstrated that the denitrification efficiency in A-MBSBRs was strongly affected by nitrification efficiency (nitrate concentration). A high COD/N ratio of 20 in phase 2 provided suitable conditions for the increase and dominance of the population of heterotrophic bacteria over autotrophic nitrifiers, which led to weak nitrification (29.6–39.1%) and consequently weak denitrification (15.8–27.9%) in all reactors. In phase 2, increasing SRT from 5 to 15 days was beneficial for both nitrification and denitrification reactions. Therefore, the optimal SND efficiency in phase 2 was expected to be achieved under SRTs higher than 15 days. Under the COD/N ratio of 10 in phase 1, a better balance between the population of heterotrophs and autotrophs resulted in higher nitrification and denitrification efficiencies (44.4–62.7% and 26.3–42.8%, respectively). In phase 1, the highest and the lowest nitrification and denitrification efficiencies were obtained at SRTs of 10 and 5 days, respectively.

Enabling plastic waste gasification by autothermal chemical looping with > 90 % syngas purity for versatile feedstock handling

The chemical looping gasification of plastics (CLGP) is a process that offers an innovative solution for transforming post-consumer waste plastics into high-value products. The process utilizes a co-current moving bed reducer reactor with iron-titanium-based oxygen carriers to gasify plastic feed and generate syngas autothermally. Its distinguishing feature is its ability to operate over a wide range of feed loadings and co-injection of mixed plastic species without any performance losses. Isothermal bench-scale experiments reveal a syngas purity of ∼95 %, aligning with the thermodynamic simulations. The moving bed reactor facilitates a deeper reduction of the oxygen carriers to the Fe+FeTiO3 phase, leading to the high syngas purity, which is then verified with additional TGA, XRD, and SEM analysis. For an autothermal operation of CLGP process, an active material content of 20 % is found to be sufficient to satisfy the kinetic and thermodynamic constraints. Further integration with downstream production of H2 is presented and compared to a steam gasification process. The process integration simulations show that the CLGP process outperforms the steam gasification system in terms of Cold Gas Efficiency (CGE), Effective Thermal Efficiency (ETE), and H2 yield. CO2 emissions are impressively reduced by ∼30 % in the CLGP system over that in the steam gasification system due to its ability to autothermally operate the process, unlike the highly endothermic steam gasification process.

Multi-injection downdraft moving bed reactor for hydrolysis in thermochemical hydrogen production

This paper investigates a downdraft multi-injection moving bed reactor (MBR) for the hydrolysis reaction in the copper-chlorine (Cu–Cl) thermochemical cycle for hydrogen production. The numerical modelling is conducted for a variety of system configurations of the MBR, with a focus on reducing the energy requirement of the reactor while achieving high conversion rates. Several design variables are investigated, including reactor volume, injection point location, and quantity of steam injection. The numerical predictions show an approximate 23% increase in CuCl2 conversion for the multi-injection MBR compared to a single injection design. A maximum conversion of 66.5% is predicted through design parameter variations. Asymptotic behavior for the quantity of injection locations with respect to conversion extent is presented for several different steam to copper ratios. The results and new insights in this paper suggest opportunities for conversion improvement and steam to copper ratio reduction in the hydrolysis reactor through the MBR design.

A multi-scale modeling of Ca-based material for solar-driven calcium-looping energy storage process: From calcination reactor to energy carrier

The calcium looping (CaL) for thermochemical energy storage possesses a great potential to promote solar thermal utilization. However, the performance of CaL, especially for the Ca-based energy carrier, cannot satisfy the expectations of industrial application, requiring enhancement between multiple length scales. Hence, a model for solar-driven CaL energy storage process, coupled by three-dimensional reactor, two-dimensional light field and one-dimensional particle models, is proposed to study the multiprocess behavior on particle flow, photothermal conversion, calcination reaction, heat-mass transfer and stress response. It is found that moving-bed reactor contributes to achieving continuous calcination and reducing particle waste, while the rapid bouncing particles inhibit the performance of single particle, with up to 45.7 % reduction in conversion. Additionally, energy carrier with stable and continuous flow normally yields high energy storage efficiency and cycle stability when the conversion of outlet particle is closed to 1 and thermal stress is less than 50 MPa.

Multiscale modeling of non-catalytic gas-solid reactions applied to the hydrogen direct reduction of iron ore in moving-bed reactor

Direct hydrogen reduction (H-DR) is a promising technology for green ironmaking. Given the absence of commercial H-DR data, computational simulation is a powerful tool for engineering and overcoming the complexity of the system. This study develops a multiscale moving-bed reactor model to simulate non-catalytic gas-solid reactions and evaluate parameters at the pellet scale that hierarchically impact the performance at reactor scale. The reactor and solid particles are treated as coupled physical domains, enabling the computation of the solid transformations along both scales. Predictions for H-DR process highlight the substantial supply of H2 molar flow in enhancing reactor performance. A sensitivity multivariate analysis revealed the significant effect of pellet structural characteristics and gas inlet conditions on the process. Increased pellet porosity offers flexibility for process optimization, enabling the use of lower H2 percentages and temperatures. These findings provide valuable insights into optimizing H-DR process, improving energy efficiency, and better H2 utilization.

Toward the ultimate efficiency of methane to syngas conversion by partial oxidation: A moving bed reactor with parallel preheating of reactants

The conversion of methane to syngas by partial oxidation combined with steam reforming in a counterflow moving bed reactor is theoretically considered. The conversion proceeds in filtration combustion mode with the non-premixed flows of steam–methane and oxidant gas. The flow of solid granular heat carrier is divided in two subflows used to preheat, respectively, steam–methane flow and oxidant gas flow prior to the reaction. The calculations are performed under assumption of thermodynamic equilibrium established in the reaction products. For the main control parameters – the flow rates of oxidant gas, steam, and solid heat carrier, related to the flow rate of methane – the parametric domain has been determined that provides a highly efficient conversion in the absence of soot in the products. Efficient heat recuperation with the solid heat carrier makes attainable conversion with the oxygen-to-methane molar ratio as low as 0.43. The flow arrangement with separate preheating of the reactants prior to reaction promises a highly efficient method of converting hydrocarbons to syngas or hydrogen.

Continuum modeling of high-temperature (>1000 °C) heat extraction from a moving-bed oxidation reactor for thermochemical energy storage

There is a growing need for efficient and reliable energy storage technologies to expand renewable energy adoption and transit to a decarbonized clean energy future. Thermochemical energy storage (TCES) through reversible gas-solid reactions has exhibited considerable potential. Up to now, TCES has primarily been studied at the material level and within lab-scale reactors. As such, accurate numerical models are needed for further reactor design and scale-up. In this work, a transient three-dimensional heat and mass transfer continuum model was developed to simulate the transport phenomena coupled with exothermic oxidation of magnesium‑manganese-oxide particles in a high-temperature moving-bed reactor for TCES. The reactor included direct heat extraction at temperatures >1000 °C. The predicted temperature distributions, oxygen concentration profiles, and steady-state reactor energy extraction efficiency were in good agreement with measured values from a corresponding experimental setup. The performance of the reactor was further investigated through two parametric studies (varied particle flow rates and gas extraction ratios), which demonstrated a strong dependence of reactor efficiency (varied between 15 %–40 %) on both operating parameters. The present heat and mass transfer model will be valuable in further reactor design and scale-up studies, as well as for selection of operating conditions to maximize efficiency.

Carbonation kinetics of calcium-based solids at the centimeter scale for moving bed applications

Countercurrent moving bed reactors were recently proposed to capture CO2 from dispersed sources using calcium materials. Due to disparities with Calcium Looping systems in particle size and solids residence times, additional investigations are required to identify reaction controlling steps and kinetic parameters. This study examines the carbonation reaction of centimeter-scale CaO and Ca(OH)2-derived-CaO pebbles under conditions relevant to moving bed applications. To this end, the impact of carbonation temperature (450–650 °C) and CO2 concentration in the inlet gas (2.5–7.5 %v) was evaluated in TGA, employing particle sizes from 0.26 to 1.65 cm. The obtained results were fitted to a shrinking core model where the rate-determining step is CO2 diffusion through the gas volume that occupies the pores of the solid CaCO3-rich layer formed during carbonation. The experimental findings can be predicted using the effective porosity of the materials as the sole fitting parameter.

Enhanced simulated moving bed reactor performance for the synthesis of solketal by implementing the ModiCon strategy

The need to extend the range of potential uses for the Simulated Moving Bed Reactor (SMBR) leads the development of new operational strategies that enable the equipment to perform increasingly difficult reactions and separations. Solketal is the valorization product from the reaction between glycerol and acetone, a thermodynamic limited process that faces miscibility and selectivity issues. In this work, the ModiCon SMBR is proposed and optimized aiming to overcome the difficulties of solketal synthesis in the Conventional SMBR. The optimization is based on the “Reactive-Separation Volumes” methodology, a well-established procedure followed for optimizing numerous other SMBR processes. The results demonstrate that the new SMBR operating mode can produce solketal with a purity of 97%, reaching a productivity of over 9.69 kgSolkLAds-1day-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{kg}}_{{{\ ext{Solk}}}} {\ ext{ L}}_{{{\ ext{Ads}}}}^{{ - {1}}} {\ ext{ day}}^{{ - {1}}}$$\\end{document}, 38% higher than the Multifeed, another non-conventional strategy proposed in the open literature for the synthesis of solketal. The desorbent consumption is 6.76 LDesorbentkgProd-1,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{L}}_{{{\ ext{Desorbent}}}} \\,{\ ext{kg}}_{{{\ ext{Prod}}}}^{ - 1} ,$$\\end{document} 35% higher than the Multifeed. The most impressive result is the decrease in the reactants consumption of 12%. Such results demonstrate that this strategy intensifies the process even more than other non-conventional operating strategies proposed in the literature, which makes it more appealing to be implemented in the large scale solketal production.

Physicochemical changes and energy properties of torrefied rubberwood biomass produced by different scale moving bed reactors

This study aimed to investigate the physicochemical changes and energy properties of torrefied rubberwood sawdust (RWS) produced in various sizes of moving bed reactors for further pelletization. The results indicate that the torrefaction of RWS with a small-scale reactor at higher temperatures led to a stronger degree of torrefaction (DT) based on various indicators. Torrefaction at 250 °C for 60 min provided appropriately torrefied RWS with solid yield, energy yield, energy content, and energy density of 70.23%, 81.20%, 22.20 MJ/kg, and 5.40 GJ/m3, respectively. The RWS with higher DT was coal-black instead of brown, as indicated by its L*, a* and b* color coordinates. The changes in color and DT were also consistent with the improvements in fuel ratio, atomic ratios, lignin content and functional groups (FTIR). SEM imaging and BET adsorption also confirmed the surface changes from raw RWS to torrefied RWS. At the same nominal conditions, torrefaction of RWS with a larger scale reactor gave a small difference in solid yield and in properties of the torrefied RWS. In addition, the production and energy costs are the key concerns in a large-scale operation. These results support pursuing further applications, like the pelletization of torrefied RWS.

Biomass chemical looping: Advancements and strategies with the moving bed reactor for gasification and hydrogen generation

This work presents advances in OSU's BTS technology, targeted explicitly toward hydrogen production from experimental and process simulation results. Two experimental parameters: residence time and enhancer steam flowrate, are explored. A volume reduction of ∼67 % can be achieved in Reducer while ensuring high char conversion. The steam injection enhances char gasification and H2 content; however, it may lead to increased tar content due to decreased gas residence time. The steam injection of ∼5 % of the inlet carbon flow rate can be adequate for efficient biomass gasification and injecting additional steam downstream into the WGS unit is optimal for H2 generation. Two cases that implement modularization for tighter process integration are compared with the conventional BTS and BDCL processes for H2 generation. The application of modularization eliminates the energy-intensive AGR unit and increases ETE by ∼17 % over the BTS process. Modularization offers product flexibility and increased control with lower operational risks over the BDCL process but at 7 % lower ETE, which can be attributed to the high amounts of oxygen present in the biomass, leading to decreased syngas purity. H2 yield can be further increased by co-injection of low oxygen feedstocks such as plastics, which can increase H2 yield by ∼12 %.

Experimental demonstration of high-temperature (>1000 °C) heat extraction from a moving-bed oxidation reactor for thermochemical energy storage

Previously developed reduction-oxidation (redox) thermochemical energy storage technologies must store their products at high temperatures, complicating handling and transportation. This work describes a countercurrent, tubular, moving bed oxidation reactor at laboratory scale that produces high grade heat and allows solids to enter and exit the system at ambient temperatures. The particles implemented in the system consist of a novel magnesium‑manganese-oxide material well-suited for thermochemical energy storage. Output heat is obtained via a separate extraction gas flow, which exits from the middle portion of the main reactor tube. With this design, reactor temperatures in excess of 1000 °C and extraction temperatures above 950 °C were achieved. Deviation between the two measurements is a result of extraction thermocouple placement and losses in the reactor extraction arm; improvements to these parameters would bring the extraction temperature closer to the bed temperature. The reactor produces enough energy via oxidation to sustain both heat extraction and continued chemical reaction. During one representative steady state experiment at a particle flow rate of 1.5 g/s, an average of 447 W was extracted from the reactor out of an estimated 1083 W of released chemical energy for a duration of 70 min. Among the four experiments, the maximum bench-scale oxidation reactor energy efficiency of 36.2% and corresponding round-trip efficiency of 13.7% considering both redox reactors were demonstrated. Characteristics of an ideal system are considered and future improvements are proposed.

Hydrolysis phase equilibrium in various reactor configurations of the thermochemical Cu–Cl cycle

This study examines the phase equilibrium trends of the hydrolysis process in the thermochemical Cu–Cl cycle of hydrogen production. Various temperatures, pressures, and steam to copper ratios are modelled to predict CuCl2 conversion and progression of side reactions within the hydrolysis reactor. Novel reactor configurations, such as Moving Bed Reactors (MBRs), reactors in series and outlet gas recirculation are introduced within the analysis. Optimal conversion of CuCl2 and minimal by-product generation are obtained at a reactor temperature of 375 °C and pressure of 1 bar with improved conversion at higher temperatures and lower pressures. Improved reaction conversion is identified at higher steam to copper ratios. A 10:1 steam to copper ratio was used for the remaining reactor configuration scenarios. Reactors in series were simulated to mimic MBR behaviour. Three reactors in series with 10 kmol total steam consumption showed better conversion of 1 kmol of CuCl2 by 17% compared to a single reactor with the same steam inlet conditions. Mitigation of CuCl2 and Cu2OCl2 decomposition was also observed. The outlet gas recirculation improved the total desired product yield, however, the maximum conversion of CuCl2 was significantly impacted due to the high level of HCl concentrated steam. A combination of the gas outlet stream and reactors in series provide a method to improve the conversion rate. This reactor configuration is a challenging approach unless there is a separation technique to shift the reaction equilibrium or reduce HCl concentration within the gas stream.

Hydrogen production from biomass via moving bed sorption-enhanced reforming: Kinetic modeling and process simulation

This study explored a process intensification approach for hydrogen production through biomass gasification. Sorption-enhanced reforming (SER) in an autothermal countercurrent moving bed reformer is proposed as an alternative to multiple units traditionally required for syngas conditioning. This process utilizes the selective sorption and catalytic properties of calcium oxide to integrate multiple reforming reactions into a moving bed reactor. A multistage kinetic model was used to analyze and optimize the key operating parameters of the reformer. Results showed that the moving bed reformer completely converts all tars and increases the hydrogen concentration of syngas from 23 mol% to 80 mol% (dry basis). A comparison between equally sized models showed that the moving bed reformer outperforms a fluidized bed reformer under similar conditions. Simulation of the entire process showed that the hydrogen yield of the proposed SER process is 5% higher than the conventional process. In addition, the proposed process produces surplus electricity, while the conventional process has a 26% power deficit. The overall efficiency of the proposed process is 3.5% higher than the conventional process. The improved process efficiency, coupled with the potentially lower costs of a streamlined process, indicates that the proposed process is a promising route for green hydrogen production.