Spouted Bed Reactor Research Articles

Development of a Spouted Bed Reactor for Chemical Looping Combustion

We have investigated a novel gas/solid contacting configuration for chemical looping combustion (CLC) with potential operating benefits. CLC configurations are typically able to achieve high fuel conversion efficiencies at the expense of high operating costs and low system reliability. The spouted fluid bed (SB) was identified as an improved reactor configuration for CLC, since it typically exhibits high heat transfer rates and offers the ability to use lower gas flows for material movement compared to bubbling beds (BB). Multiphase Flow with Interphase eXchanges (MFIX) software was used to establish a spouted fluid bed reactor design. An experimental setup was built to supplement the model. The experimental setup was also modified for testing under high temperature, reacting conditions (1073–1273 K). The setup was operated in either a spouted fluid bed or a bubbling bed regime to compare the performance attributes of each. Results for the reactor configurations are presented for CLC using a mixture of carbon monoxide and hydrogen as fuel. Compared to the bubbling bed, the spouted fluid bed reactor achieved an equivalent or better fuel conversion at a lower pressure drop over the material bed. The spouted fluid bed design represents a viable configuration to improve gas/solid contacting for efficient fuel conversion, lower energy requirements for material movement and increase operational robustness for CLC. The research laid the groundwork for future research into a multi-phase reacting flow CLC system. The system will be developed from computational fluid dynamic modeling and pilot-scale testing to expedite the development of CLC technologies.

Design, simulation and experimental study of a directly-irradiated solar chemical reactor for hydrogen and syngas production from continuous solar-driven wood biomass gasification

The use of concentrated solar energy as the high-temperature heat source for the thermochemical gasification of biomass is a promising prospect for producing CO2-neutral chemical fuels (syngas). The solar process saves biomass resource because partial combustion of the feedstock is avoided, it increases the energy conversion efficiency because the calorific value of the feedstock is upgraded by the solar power input, and it also reduces the need for downstream gas cleaning and separation because the gas products are not contaminated by combustion by-products. A new concept of solar spouted bed reactor with continuous biomass injection was designed in order to enhance heat transfer in the reactor, to improve the gasification rates and gas yields by providing constant stirring of the particles, and to enable continuous operation. Thermal simulations of the prototype were performed to calculate temperature distributions and validate the reactor design at 1.5 kW scale. The reliable operation of the solar reactor based on this new design was also experimentally demonstrated under real solar irradiation using a parabolic dish concentrator. Wood particles were continuously gasified at temperatures ranging from 1100 °C to 1300 °C using either CO2 or steam as oxidizing agent. Carbon conversion rates over 94% and gas productions over 70 mmol/gbiomass were achieved. The energy contained in the biomass was upgraded thanks to the solar energy input by a factor of up to 1.21.

Spouting behaviour of binary mixtures in square-based spouted beds

From experiments, the influence of the physical characteristics of different binary mixtures of solids on the spouting regime of a pyramidal square-based spouted bed reactor is assessed. The applied methodology permits a more precise evaluation of the effects of the tested variables (diameter, density, sphericity) on the response variables (minimum air flows at which spouting begins and at which to maintain spouting conditions). The associated pressure drops along the bed of particles and the height of the formed fountain are analysed in each case. During the initial stages of fluidisation, binary mixtures containing different density ratios show dead zones. Segregation becomes more evident at large-size and high-density ratios. The lack of sphericity was found to be the main reason leading to blocking, channelling, and start-up problems when system failures occur. Nevertheless, the extent of segregation in all cases decreases with increasing the spouting velocity. In addition, a computational fluid dynamic model based on the discrete element method, previously validated for a single solid bed, is proposed as a tool to predict and evaluate potential segregation phenomena in binary mixtures. This model reproduced with high accuracy the encountered segregation phenomena. Its use may help define the technical limits inherent in the pyramidal spouted bed reactor.

Kinetic study of the catalytic reforming of biomass pyrolysis volatiles over a commercial Ni/Al2O3 catalyst

An original kinetic model has been proposed for the reforming of the volatiles derived from biomass fast pyrolysis over a commercial Ni/Al2O3 catalyst. The pyrolysis-reforming strategy consists of two in-line steps. The pyrolysis step is performed in a conical spouted bed reactor (CSBR) at 500 °C, and the catalytic steam reforming of the volatiles has been carried out in-line in a fluidized bed reactor. The reforming conditions are as follows: 600, 650 and 700 °C; catalyst mass, 0, 1.6, 3.1, 6.3, 9.4 and 12.5 g; steam/biomass ratio, 4, and; time on stream, up to 120 min. The integration of the kinetic equations has been carried out using a code developed in Matlab. The reaction scheme takes into account the individual steps of steam reforming of bio-oil oxygenated compounds, CH4 and C2-C4 hydrocarbons, and the WGS reaction. Moreover, a kinetic equation for deactivation has been derived, in which the bio-oil oxygenated compounds have been considered as the main coke precursors. The kinetic model allows quantifying the effect reforming conditions (temperature, catalyst mass and time on stream) have on product distribution.

Kinetic modelling of pine sawdust combustion in a conical spouted bed reactor

A model has been proposed and validated for the prediction of biomass combustion rate in a conical spouted bed. The model couples the intrinsic kinetics for the process and the flow pattern of the gaseous stream in the unit. The kinetics is described based on a reaction scheme consisting in simultaneous devolatilization and combustion involving the three biomass constituents, i.e., hemicellulose, cellulose and lignin. The gas flow pattern in the combustion chamber and subsequent cleaning system has been modelled using a compartimental model based on two continuous perfectly mixed vessels and a plug flow vessel. Tracer tests have been conducted to determine the residence time distribution in the whole unit and the parameters of the compartimental model. Batch combustion tests have been carried out to determine the composition of the outlet gaseous stream and the evolution of conversion with time, whose fitting to the kinetic model allowed calculating the parameters of best fit (frequency factors and activation energies). The model suitably predicts the evolution of combustion rate in a conical spouted bed, and therefore is a useful tool for the design of industrial plants based on this technology.

Advantages of confining the fountain in a conical spouted bed reactor for biomass steam gasification

A study was carried out on the advantages of inserting a fountain confiner in conical spouted beds for biomass steam gasification and the results (gas yield and composition, tar content, carbon conversion efficiency and H2 production) are compared with those obtained under conventional spouting regime. The experiments were carried out in a bench scale unit operating in continuous regime under the same gasification conditions in all the configurations (850 °C, S/B ratio of 2 and olivine as primary catalyst). The gaseous product was analyzed by on-line gas chromatography and micro-gas chromatography, and the tars by gas chromatography-mass spectrometry. The use of a fountain confiner allows enhancing process versatility, increasing gas velocity over the minimum spouting one, increasing the fountain height and reducing olivine particle size (enhanced fountain regime). Thus, as a result of a better gas-solid contact, tar content was reduced from 49.2 g Nm−3 without fountain confiner to 20.6 g Nm−3 under enhanced fountain regime, with the reduction of heavy PAHs being especially remarkable. In the same line, a great improvement in process conversion efficiency was attained under the enhanced fountain regime, with gas production reaching a value of 1.3 m3 kg−1 and that of H2 production 5.0 wt%.

Coking and sintering progress of a Ni supported catalyst in the steam reforming of biomass pyrolysis volatiles

The valorization of biomass (pine wood) for hydrogen production has been studied in a two-step process, comprising pyrolysis and subsequent steam reforming of the volatiles produced in the first step. This work focuses on the deactivation of the Ni commercial catalyst used in the second step. Pyrolysis of biomass has been performed in a conical spouted bed reactor at 500 °C, and the in-line catalytic steam reforming of the pyrolysis volatiles, in a fluidized bed reactor at 600 °C. Deactivated catalyst samples were recovered at different values of time on stream, and analyzed by means of XRD, N2 adsorption-desorption, SEM and TEM microscopies, TPO, Raman and FTIR spectroscopies. The results show that the deactivation is mainly due to the encapsulation of Ni particles by coke, together with Ni sintering, to a lesser extent (from a Ni particle size of 25 nm in the reduced fresh catalyst, to 39 nm at 100 min). The former is ascribed to the condensation of oxygenates (particularly phenols), and the latter is inevitable within the current conditions. As the fraction of uncovered Ni particles decreases with time on stream, the deposition of encapsulating coke is slowed down (from a formation rate of 0.30 mgcoke gcatalyst−1 min−1 to 0.20 mgcoke gcatalyst−1 min−1, at 0–50 min and 50–100 min on stream, respectively), promoting the deposition of coke on the catalyst support (with a formation rate of 1.04 mgcoke gcatalyst−1 min−1 at 50–100 min on stream), with a more carbonized structure and formed through the thermal decomposition of phenols in the reaction medium.

Large-scale DAE-constrained optimization applied to a modified spouted bed reactor for ethylene production from methane

In this paper, a modified spouted bed reactor is proposed to enhance the yield of the oxidative coupling of methane (OCM). Optimization techniques are used to carry out a theoretical analysis of ethylene production via OCM and define some optimal operating conditions of the reacting system. A model-based DAE-constrained optimization strategy is proposed and applied to the OCM process to illustrate the computational capability of the proposed formulation, and the theoretical feasibility of the proposed reactor. The model developed for the reactor is a one-dimensional model composed of material, energy, and momentum balances. This model along with the kinetic model constitute a non-linear and differential-algebraic system, which is discretized using orthogonal collocation on finite elements with continuous profiles approximated by Lagrange polynomials. The resulting algebraic collocation equations are written as equality constraints in the optimization problem, which is solved with the IPOPT solver within the optimization-modeling platform. An initialization routine based on simulations was carried out to guarantee convergence in optimizations. Results from simulations and optimizations showed the potential of combining different reactor concepts to improve the ethylene production from natural gas via oxidative coupling of methane.

Valorization of citrus wastes by fast pyrolysis in a conical spouted bed reactor

The fast pyrolysis of the juice squeezing derived orange waste has been carried out in a continuous pyrolysis bench-scale plant consisting of a conical spouted bed reactor (CSBR). A prior study performed in thermobalance and a kinetic model consisting of a multi-component mechanism allowed determining the contents of pectin (35 wt%), hemicellulose (16.6 wt%) and cellulose (17.1 wt%), but that of lignin could not be satisfactorily determined as its degradation curve overlapped with other compounds such as sugars, proteins and fats. In the bench scale experiments, the bio-oil yields were very high in the 425–500 °C range (close to 55 wt%) due to the suitable features of the CSBR (high heat and mass transfer rates and short residence time of the volatiles), but they are lower for higher temperatures due to the promotion of secondary cracking reactions. Compared to lignocellulosic biomasses, the orange waste produced a bio-oil with more methanol and furfural and less phenolic species, which is an encouraging fact for its stability and valorization by catalytic cracking or steam reforming. The high concentration of CO2 in the gas is a drawback for use for energy production. The char yield (33–27 wt%) was high in the whole range of temperatures studied and its high carbon content (71–73 wt%) and HHV (≈27 MJ kg−1) are suitable for use as fuel.

Influence of the support on Ni catalysts performance in the in-line steam reforming of biomass fast pyrolysis derived volatiles

The influence the support has on the performance of Ni catalysts used in the reforming of biomass fast pyrolysis volatiles has been assessed. Accordingly, five catalysts have been prepared by wet impregnation method, namely Ni/Al2O3, Ni/SiO2, Ni/MgO, Ni/TiO2 and Ni/ZrO2. These catalysts have been characterized by nitrogen adsorption/desorption, X-ray fluorescence spectroscopy, temperature programmed reduction and X-ray diffraction techniques. The pyrolysis-reforming runs have been performed in a bench scale unit operating in continuous regime. The biomass (pine wood sawdust) pyrolysis step has been carried out in a conical spouted bed reactor at 500 °C, with the volatiles produced (a mixture of gases and bio-oil) being reformed in-line on the prepared catalysts in a fluidized bed reactor at 600 °C. Remarkable differences have been observed amongst the catalyst prepared, with Ni/Al2O3, Ni/MgO and Ni/ZrO2 being those leading to the most encouraging results, whereas Ni/TiO2 and, especially Ni/SiO2, having a limited reforming activity. The performance of each catalyst has been related to its properties determined in the characterization.

Analysis of plasma behavior in a plasma enhanced spouted bed reactor

Analysis of plasma behavior in a plasma enhanced spouted bed reactor

Comparison of catalytic performance of an iron-alumina pillared montmorillonite and HZSM-5 zeolite on a spouted bed reactor

Catalytic pyrolysis of high density polyethylene (HDPE) on HZSM-5 catalyst and an iron-alumina pillared montmorillonite, prepared in laboratory (FAMO), was performed by means of a conical spouted bed reactor. This type of reactor is a suitable technology for plastic pyrolysis due to its high heat and mass transfer rates and excellent performance in the handling of sticky solid materials. The pyrolytic process carried out on HZSM-5 catalyst gave significant yield of gaseous products (above 74 wt%), while FAMO catalyst gave high yields of waxes, particularly rich in diesel hydrocarbon range (C11–C21). Waxes obtained by subjecting HDPE to thermal pyrolysis had a higher range of molecular weight. Waxes have been characterised using different techniques, such as gel permeation chromatography (GPC), polidispersity (PD), Fourier transform infrared (FTIR) spectroscopy, Simulated Distillation, and TDP.

Influence of the conditions for reforming HDPE pyrolysis volatiles on the catalyst deactivation by coke

Pyrolysis of high density polyethylene (HDPE) has been carried out in a conical spouted bed reactor (500°C) and the volatiles have been reformed in-line over a Ni commercial catalyst in a fluidized bed reactor. The evolution of reaction indices (conversion, H2 yield and other gaseous product yields) with time on stream has been studied under the following operating conditions: temperature, 600–700°C; space-time, 8.3–20.8gcatmingHDPE−1, and steam/plastic ratio, 3–5. High initial conversion (>94.5%) and H2 yields (>76.7%) are attained under all the operating conditions studied, with HDPE conversion and H2 yield increasing when the three variables are increased, which is explained by the enhancement of the reforming reaction. However, a significant effect of operating conditions on catalyst stability has been observed. Thus, an increase in temperature, space-time and steam/plastic ratio decreases catalyst deactivation as a consequence of a lower rate of coke deposition on the catalyst due to both a lower C5+ coke precursor amount in the reaction medium and a higher gasification rate of the coke deposited.

Valorisation of different waste plastics by pyrolysis and in-line catalytic steam reforming for hydrogen production

The performance of an original two-step reaction system (pyrolysis and in-line reforming) was assessed in the hydrogen production from different plastics (polyethylene, polypropylene, polyethylene terephthalate and polystyrene) and their mixture. The pyrolysis step was performed in a conical spouted bed reactor at 500 °C, whereas the reforming of pyrolysis volatiles was carried out in a fluidized bed reactor at 700 °C. This two in-line reactor configuration was initially developed for the reforming of high density polyethylene pyrolysis volatiles, and this paper describes the influence composition of pyrolysis products derived from different plastics has on the reforming step, conversion, product yields and deactivation behavior. The products formed in both the pyrolysis and the reforming steps were analysed by on-line gas chromatography and micro-gas chromatography. Significant differences in the reforming behaviour of the plastics were observed, with hydrogen productions being higher in the case of polyolefins (from 34.8 to 37.3 wt% ) followed by polystyrene (29.1 wt%) and remarkably lower for polyethylene terephthalate (18.2 wt%). Furthermore, the evolution of conversion and product distribution with time on stream was assessed for the different plastics studied and the catalyst deactivation rate was related to the amount and morphology of the coke deposited on the reforming catalyst. It was proven that the features of the reactors used in the pyrolysis and reforming steps are suitable for minimizing operational problems, and therefore operating in continuous regime.

CPFD Simulation for Fast Pyrolysis Reaction of Biomass in a Conical Spouted Bed Reactor using Multiphase-particle in Cell Approach

CPFD Simulation for Fast Pyrolysis Reaction of Biomass in a Conical Spouted Bed Reactor using Multiphase-particle in Cell Approach

Kinetic Modeling of the Catalytic Steam Reforming of High-Density Polyethylene Pyrolysis Volatiles

The kinetics of the steam reforming of HDPE pyrolysis volatiles is studied on a Ni commercial catalyst in a fluidized bed reactor in-line with the pyrolysis reactor (a conical spouted bed reactor at 500 oC). Steam reforming reactions have been carried out under the following conditions: 600-700 oC and space time 0-16.7 gcat min gHDPE-1. Based on the composition of HDPE pyrolysis volatiles, a kinetic scheme is assumed with four reactions (C5+ hydrocarbon reforming, C2-C4 hydrocarbon reforming, CH4 reforming and WGS reaction). Moreover, the kinetics of the deactivation has been quantified with an expression dependant on C5+ hydrocarbon concentration (coke precursors). Calculation of the kinetic parameters is conducted by nonlinear multiple regression, fitting the experimental data to those calculated by the mass conservation equations for each component in the reaction medium. The overall kinetic model proposed describes accurately the evolution of the main products (H2, CO2, CO) with time on stream in the ...

Deposition of SiC/Si coatings in a microwave plasma-assisted spouted bed reactor

Silicon carbide (SiC) layers were deposited onto alumina particles in a microwave plasma-assisted spouted bed reactor using methyltrichlorosilane (MTS) and hydrogen mixtures, in argon, as precursor gas feed. The operating parameters studied were enthalpy, gas composition, and pressure. Microwaves were guided from a generator, operating at 2.45GHz, along a rectangular waveguide intersecting a quartz tube, acting as the reaction zone. A graphite nozzle at the bottom of the tube facilitated the spouting action. Growth rates varied from 50 to 140μm/h. Overall results indicate that the optimal region for SiC deposition requires relatively high enthalpy (∼5MJ/kg) and pressure (>−60kPa) conditions, with hydrogen-to-MTS ratios ∼5:1. The quality (i.e. crystallinity, particle size, Si/C ratios) of the layers improve at these conditions, at the cost of decreased deposition rates. Characterisation was done by XRD, FTIR, XPS, SEM, TEM and EDX, which assisted in developing colour and morphological charts to indicate the changes as a function of changing operating parameters. A microwave plasma spouted bed reactor is demonstrated to be a viable alternative technique for SiC layer deposition onto microspheres.

Comparison of Hydrodynamics Characteristics of Bubbling Fluidized Bed and Conical Spouted Bed Reactors using Computational Particle Fluid Dynamics

Comparison of Hydrodynamics Characteristics of Bubbling Fluidized Bed and Conical Spouted Bed Reactors using Computational Particle Fluid Dynamics

Biomass Gasification in an Innovative Spouted-Bed Solar Reactor: Experimental Proof of Concept and Parametric Study

Solar thermochemical gasification of lignocellulosic biomass promises a new path for the production of alternative fuels as well as storage and transport of solar energy as a convertible and transportable fuel. The use of concentrated solar energy as the external heat source for the high-temperature reaction allows producing high-value syngas with both higher energy conversion efficiency and reduced cost of gas cleaning and separation, while saving biomass feedstock. A newly designed solar reactor based on the principle of spouted bed reactor was used for continuous solar-driven gasification of biomass particles. The reliable operation of this 1.5 kW reactor was experimentally demonstrated under real solar irradiation using a parabolic dish solar concentrator. Several types of biomass particles were continuously fed in the reactor at temperatures ranging from 1100°C to 1400°C. The injected particles consisted of beech wood or a mix of resinous wood with size ranging from 0.3 mm to 2 mm. The aim of this st...

Activated carbon preparation from pistachio shell pyrolysis and gasification in a spouted bed reactor

Spouted bed technology was applied for the production of activated carbons from pistachio nut shells for the first time. Both of the pyrolysis and the gasification stages were carried out in the same spouted bed reactor. The produced bio-char and activated carbon were analyzed via scanning electron microscopy (SEM), Iodine number, and BET surface area. Temperature of 600 °C, hold time of 60 min, with particle size of 3.36–4.76 mm were the best conditions to produce a char with 430 m2 g-1. While the carbonization tests were carried out in a shorter time, BET surface area of the bio-chars were as large as those obtained in other reactors. BET surface area of the best produced activated carbon was 2596 m2 g−1 with the burn-off 90 % at temperature 850 °C and 20 min activation. A comparison was made between the activated carbon characteristics produced in spouted bed reactor with those obtained previously in fixed bed reactors. According to the results, spouted bed reactors are suitable equipment for performing the both carbonization and gasification stages thanks to excellent mixing and high circulation rates of the materials inside a spouted bed.