Fluidized Bed Reactor Research Articles

Long-Term performance of composite Cu-Fe ore oxygen carrier by Extrusion-Spheronization in chemical looping combustion

High-performance and low-cost oxygen carrier is vital for engineering demonstration and industrial application of chemical looping combustion. In this work, binary-ore (copper ore and iron ore) oxygen carriers are prepared at a large scale (25 kg/h) by the extrusion-spheronization method, using montmorillonite as the inert support. The anti-sintering ability and long-term stability are systematically investigated through well-organized tests in a thermogravimetric analyzer (TGA) and batch fluidized bed reactor (BFB). Four kinds of low-cost composite oxygen carriers are prepared with montmorillonite content of 10 wt%∼40 wt%, and the montmorillonite loading ratio is optimized as 10 wt% through 100-cycle TGA tests, with the fastest reduction rate of 0.155 %/s. The results show that the CO2 yield is always beyond 90 %, suggesting the stable reactivity of FeCu-10 M, and the average attrition rate is 0.108 %/h. No significant sintering or agglomeration is detected in the inner surface or among the particles, as indicated by SEM images. The specific surface area is developed from 0.125 to 0.185 m2/g, and the rich pore structure remains in the 100-cycle test. Additionally, the crushing strength of FeCu-10 M is higher than 2 N throughout the cyclic experiment, and the lifetime is 2 ∼ 7 times longer than that of the original iron ore. The extrusion-spheronization method has the potential in the industrial-scale preparation of oxygen carriers, and the FeCu-10 M is a favorable oxygen carrier to the chemical looping combustion process.

Desulfurization characteristics of slaked lime and regulation optimization of circulating fluidized bed flue gas desulfurization process—A combined experimental and numerical simulation study

Circulating fluidized bed flue gas desulfurization (CFB-FGD) process has been widely applied in recent years. However, high cost caused by the use of high-quality slaked lime and difficult operation due to the complex flow field are two issues which have received great attention. Accordingly, a laboratory-scale fluidized bed reactor was constructed to investigate the effects of physical properties and external conditions on desulfurization performance of slaked lime, and the conclusions were tried out in an industrial-scale CFB-FGD tower. After that, a numerical model of the tower was established based on computational particle fluid dynamics (CPFD) and two-film theory. After comparison and validation with actual operation data, the effects of operating parameters on gas–solid distribution and desulfurization characteristics were investigated. The results of experiments and industrial trials showed that the use of slaked lime with a calcium hydroxide content of approximately 80% and particle size greater than 40 μm could significantly reduce the cost of desulfurizer. Simulation results showed that the flow field in the desulfurization tower was skewed under the influence of circulating ash. We obtained optimal operating conditions of 7.5 kg·s−1 for the atomized water flow, 70 kg·s−1 for circulating ash flow, and 0.56 kg·s−1 for slaked lime flow, with desulfurization efficiency reaching 98.19% and the exit flue gas meeting the ultraclean emission and safety requirements. All parameters selected in the simulation were based on engineering examples and had certain application reference significance.

Recovery of Sb(Ⅲ) from Aqueous Solution as Cubic Sb2O3 by Fluidized-Bed Granulation Process

In order to recover the antimony from wastewater, a custom-designed fluidized-bed reactor (FBR) was employed to treat antimony-containing wastewater. By single-factor experiments, the effects of the solution pH, the molar ratio of [TA]/[Sb3+], the seed size and dosage, the up-flow velocity (U), and the hydraulic retention time (HRT) on antimony recovery were investigated based on the antimony removal and granulation efficiency. The optimum conditions for antimony recovery were obtained at pH 9.0, the molar ratio of [TA]/[Sb3+] of 2, 6 g/L of 13–38 μm Sb2O3 as the fluidized seed, and the U and HRT of 42 m/h and 40 min, respectively; the antimony removal and granulation efficiency reached 95% and 91%, respectively. The granular products were analyzed by an X-ray polycrystalline diffractometer (XRD) and scanning electron microscopy (SEM) as cubic Sb2O3, widely used in various industries. The fluidized-bed reactor was operated continuously for 7 days, during which the antimony removal and granulation efficiency were stable at 96% and 93%, respectively. This study demonstrated the feasibility of the fluidized-bed granulation process for the recovery of antimony from wastewater. It provides a novel approach for retrieving and managing antimony-containing wastewater.

Insights into the effect of operating parameters and hydrodynamics on hydrolysis reaction in Copper–Chlorine thermochemical water splitting cycle for hydrogen production: Modelling and experimental validation

Copper–Chlorine (Cu–Cl) thermochemical cycle is being explored as one of the promising technologies for large scale production of clean hydrogen from water using nuclear or renewable energy. In this method, water splitting is achieved through a series of reactions in a loop producing only hydrogen and oxygen with complete recycle of all the intermediate copper and chlorine compounds. The first step of the cycle is the hydrolysis reaction wherein steam reacts with solid CuCl2 to form solid Cu2OCl2 (copper oxychloride) and HCl gas. The products enter the subsequent steps of the cycle and are recycled back to complete the loop. Multiple side reactions in the hydrolysis step result in reduced yield and loss of chemicals from the cycle. Efficient reactor design and optimal operating conditions of hydrolysis reactor is imperative towards achieving sustained closed loop operation and reducing the energy demand of Cu–Cl cycle. This paper presents a mathematical model for the simulation of hydrolysis reaction in a bubbling fluidized bed reactor. The one-dimensional model is developed based on modified two-phase theory of fluidization and is coupled with kinetics of multiple side reactions to investigate the effect of operating parameters and hydrodynamics on the conversion and yield of Cu2OCl2. The model results are validated with experimental data in 50 mm and 100 mm semi-batch fluidized bed reactors. The developed model clearly brings out the effect of different process parameters for process optimization and scale-up of the hydrolysis reactor for efficient integration in the cycle.

Advanced stability assessment for control systems: Gelfand’s method with iterated Shanks transformation

ABSTRACT In this paper, we present an efficient method for evaluating the stability of both linear time-invariant (LTI) systems and continuous-time nonlinear systems. Our approach centres around the modulus of the spectral radius derived from a specific matrix transformation of the original system state matrix in the case of LTI systems, or the Jacobian of the nonlinear system. We enhance computational speed by employing the iterated Shanks transformation on Gelfand’s formula, eliminating the need to rely on the system’s characteristic equation. Notably, our stability criterion avoids the computation of all eigenvalues of the system matrix. Illustrative examples, including a fluidised bed reactor, a continuous stirred tank reactor and a hypothetical 20th-order dynamical system, are provided. Additionally, we conduct a CPU-time analysis, revealing that our method demonstrates several orders of magnitude faster computational speed compared to the classical Routh-Hurwitz stability test for systems ranging from two to 80 dimensions.

Biomass source influence on hydrogen production through pyrolysis and in line oxidative steam reforming.

This study evaluates the potential of several biomasses differing in nature and composition for their valorization by pyrolysis and in-line oxidative steam reforming. The first task involved the fast pyrolysis of the biomasses in a conical spouted bed reactor at 500ºC, in which product yields were analyzed in detail. Then, the oxidative steam reforming of pyrolysis volatiles (gases and bio-oil) was approached in a fluidized bed reactor. The reforming experiments were performed at 600 ºC, with an steam/biomass (S/B) ratio of 3 and catalyst (Ni/Al2O3) space times of 7.5 and 20 gcat min gvol-1. Concerning equivalence ratio (ER), a value of 0.12 was selected to ensure autothermal operation. Remarkable differences were observed in H2 production depending on the type of biomass. Thus, pine wood led to a H2 production of 9.3 wt%. The lower productions obtained with rice husk (7.7 wt%) and orange peel (5.5 wt%) are associated with their higher ash and fixed carbon content, respectively, which limit the efficiency of biomass conversion to bio-oil. However, in the case of the microalga, the poor performance observed is due to the lower conversion in the reforming step toward gases due to the composition of its pyrolysis volatile stream.

A new method for solids residence time distribution measurement in continuous fluidized beds

Accurate measurement of solids residence time distribution (RTD) is an important and challenging issue in developing fluidized bed reactors with continuous solids feeding and discharging. In this study, we proposed a new method for measuring solids residence time distribution, where coked bulk material was used for solids tracer and high-precision element analyzers were used to determine solids tracer fraction. A calibration procedure was established to achieve high-accuracy measurement of solids tracer fraction. The following validation tests had successfully proved the pseudo-CSTR solids flow pattern under different operating conditions and the staging effect of an inserted horizontal baffle in a small laboratory-scale fluidized bed cold model, which demonstrate the feasibility and advantages of this new solids RTD measurement method.

Co-pyrolysis of phenolic printed circuit boards with CaO and Ca(OH)2 mixture in a fluidized bed reactor: Optimization of the operating conditions and the kinetic analysis

In a previous study (Haghi et al., 2023), we demonstrated that co-pyrolysis of paper-laminated phenolic PCB (FR2-PCB) with a mixture of CaO and Ca(OH)2 in a fluidized bed reactor results in the simultaneous enhancement of the production of the pyrolysis oil and a significant decrease in its halide content. To advance the utilization of a blend of CaO and Ca(OH)2 for scaling up the pyrolysis of FR2-PCB beyond laboratory-scale pyrolyzers, especially in fluidized bed reactors renowned for their effectiveness in large-scale pyrolysis of polymeric materials, the optimal operating conditions, as well as the kinetic parameters in the presence of CaO and Ca(OH)2 should be explored. To this end, this study focuses on optimizing the temperature (T), retention time (t), and PCB-to-additive ratio (FR2/A) as the parameters controlling the co-pyrolysis of paper-laminated phenolic PCB (FR2-PCB) with a 50:50 mixture of CaO and Ca(OH)2 in a fluidized bed reactor. According to the results of the experiments designed based on the response surface methodology, the maximum recovery of pyrolysis oil (40.6 %) was obtained at T = 620 °C, t = 22 min, and FR2/A= 5.4 g/g. Additional tests were carried out to explore the impact of CaO+Ca(OH)2 concentration on the halogen content of the pyrolysis products. Furthermore, the thermogravimetric analysis (TGA) was performed to investigate the influence of the tested additives on the pyrolysis behavior and the kinetic characteristics of FR2-PCB. By employing three iso-conversional model-free approaches, i.e., the Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Starink integral methods, it was found that adding CaO+Ca(OH)2 to FR2-PCB can reduce the activation energy of the pyrolysis reactions by 20 %.

An Insight into the CO2 Adsorption and Temperature Evolution of a Zeolite Bed in a Fluidized Bed Reactor Using a Two-Fluid Modeling Approach

An Insight into the CO₂ Adsorption and Temperature Evolution of a Zeolite Bed in a Fluidized Bed Reactor Using a Two-Fluid Modeling Approach

CFD Simulation of Biomass Pyrolysis in a Fluidized Bed Reactor: Effect of Particle Shrinkage Model

CFD Simulation of Biomass Pyrolysis in a Fluidized Bed Reactor: Effect of Particle Shrinkage Model

Selective H2 production from plastic waste through pyrolysis and in-line oxidative steam reforming

This study deals with the proposal of pyrolysis and in-line oxidative steam reforming (P-OSR) for plastic waste valorization and assesses the potential of this strategy for the selective production of H2. Overall, the study aims at progressing towards the fine-tuning of the pyrolysis-reforming technology by co-feeding O2. Thus, a multi-point O2 injection system has been developed to ensure a suitable O2 distribution in the reforming reactor and avoid the formation of hot spots, as they may cause catalyst deactivation by metal sintering. Moreover, as O2 is directly supplied into the catalytic bed, pre-combustion of the volatile stream before contacting the catalyst is avoided and in-situ coke combustion is promoted. The P-OSR of HDPE was carried out in a two-step reaction system, which combines CSBR (conical spouted bed reactor) and FBR (fluidized bed reactor) technologies. The experiments were conducted in continuous mode and the influence of the main process conditions at zero time on stream was analyzed. Thus, the effect of reforming temperature was studied in the 550–750 °C range, that of the space time from 3.12 to 15.62 gcat min gHDPE−1, steam to plastic (S/P) ratio between 2 and 5 and equivalence ratio (ER) from 0 to 0.3. Under the optimum conditions (700 °C, S/P of 3, 12.5 gcat min gHDPE−1 and ER of 0.2), a H2 production of 25.0 wt% was obtained, which is only 28.6 % lower than that obtained in the conventional pyrolysis-steam reforming (P-SR) process. The results obtained confirm the potential of continuous P-OSR process for the selective production of H2.

A numerical scale-up study of annular fluidized bed reactor with high centrifugal acceleration

A rotating fluidized bed imposes a strong centrifugal force to form the dense annular bed with high interphase slip velocity for significantly enhanced gas-solids contact. The fundamental fluidization behaviors in rotating fluidized beds have been well understood in small-scale systems. The current study focuses on the scale-up of a rotating fluidized bed from lab-scale to commercial-scale through computational fluid dynamics modeling. The computational model was first validated against a lab-scale horizontal rotating fluidized bed for the general flow behavior and pressure drop. The validated computational model with a column diameter of 0.12 m was then scaled up to 0.48 m and 1.92 m to investigate the flow hydrodynamics at larger scales. By comparing the solids distribution and other flow field variables, major limitations in the stable operation of a rotating fluidized bed at large scales were identified. The challenges faced in the scale-up of an annular fluidized bed with centrifugal acceleration are discussed and ways to overcome such challenges are explored.

Updating mechanism of siderite roasting through insights into reactions between inherent oxides of iron and carbon

The roasting of siderite (FeCO3) was investigated to clarify the reaction mechanism in inert atmosphere using micro fluidized bed reaction analyzer coupled with on-line particle sampling (MFBRA-P). Thermodynamic results indicated that the reactions of 6FeO + CO2 → C + 2Fe3O4 and 3FeO + CO → C + Fe3O4 are both possible to occur in the transformation process of siderite to Fe3O4. The presence of C was identified in the final solid product through analysis scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and calcination experiment of product sample in the atmosphere containing O2. Combining thermodynamic and experimental results, an updated reaction mechanism of siderite roasting in inert atmosphere was proposed. The siderite is first decomposed to form FeO and CO2, and in turn FeO rapidly reacts with CO2 to form Fe3O4 and CO. Meantime, the released CO2 or CO during decomposition reacts with FeO to form C and Fe3O4.

Remediation of 3,4,3′,4′-tetrachlorobiphenyl (PCB77) contaminated soil via a fluidized bed dielectric barrier discharge

In this study, 3,4,3′,4′-tetrachlorobiphenyl (PCB77) contaminated soil was remediated by a fluidization bed dielectric barrier discharge (DBD) reactor and a fixed bed DBD reactor. The fluidized bed reactor could attain superior removal efficiency of PCB77 under same experimental parameters. In-situ discharge mode was more conducive to the degradation of PCB77 than ex-situ discharge mode due to short-lived active species existing in in-situ discharge. The influence of experimental parameters in the fluidized bed DBD reactor on the degradation of PCB77 were discussed such as electric features, gas features, soil features and initial PCB77 concentration. PCB77 removal efficiency in air discharge could reach 88.5 % after 8 min under the alkaline condition. Optical emission spectroscopy (OES) and quench tests showed that reactive oxygen species (ROS) and reactive nitrogen species (RNS) were generated in the discharge system and they both played a vital role in the degradation of PCB77. Scanning electron microscopy (SEM) results demonstrated that discharge had little effect on the morphology of soil particles. Energy dispersive spectrometer (EDS), ion chromatography (IC), and total organic carbon (TOC) results showed that the DBD could effectively mineralize and dechlorinate PCB77. The possible degradation pathway of PCB77 was inferred at the end based on the degradation products determined by gas chromatography–mass spectrometry (GC–MS).

Unlocking potential: Exploring the methane production potential in anaerobic co-digestion of cassava wastewater and glycerol

This study aimed at evaluating the feasibility of CH4 production in a mesophilic (30 °C) single-stage anaerobic co-digestion of cassava wastewater (CW) and glycerol in an anaerobic fluidized bed reactor (AFBR) with mixing ratio of 50 % / 50 % CW/Gly on a (chemical oxygen demand)COD basis. Thus, the following strategy was used: increasing the organic loading rate (OLR) (1–20 g COD.L−1.d−1) by increasing the substrate concentration (1–20 g COD.L−1) and applying a hydraulic detention time (HRT) of 24 h. The AFBR presented a maximum methane (CH4) content of 88.38±1.94 % and a CH4 yield (MY) of 293.48±18.37 mL of CH4.mL−1CODrem in the OLR of 1 g COD.L−1.d−1 and the maximum methane production rate (MPR) of 62.09±2.75 mL of CH4.L−1.h−1 in the OLR of 20 g COD.L−1.d−1. The conversion of glycerol and carbohydrates remained above 91±0.54 % and 82±2.79 %, respectively, and the COD conversion was above 80±0.65 %. The main metabolites were HAc, HPr, HBu, EtOH and HVa. The most abundant genera identified in the AFBR were Izemoplasmatales and Enterobacteriaceae for the bacteria domain, and Methanosaeta, Methanobacterium for the archaea domain. The single-stage system is robust and can operate with higher OLR without reducing the efficiency of wastewater treatment and CH4 production.

Boosted regeneration of coked SAPO-34 catalyst in MTO fluidized bed reactor by diluted air at elevated temperatures

SAPO-34 zeolite as an excellent catalyst for methanol-to-olefins (MTO) reaction suffers rapid deactivation by prevalent coking. Herein, regeneration of coked-SAPO-34 in a fluidized-bed reactor was successfully intensified by altering temperature (550–650 °C) and oxygen content (7–21 vol.%). Fresh, used, and regenerated catalysts were characterized by different methods to understand the correlation between regeneration conditions, coke content, and catalyst performance. The minor residual coke over the regenerated catalyst comprised active hydrocarbon pool intermediates (like naphthalene, benzaldehyde, phenol, and derivatives), which increased by decreasing regeneration temperature and promoted the selectivity to light olefins at earlier reaction times. The restored microporosity and lifetime of regenerated catalyst were superior by increasing temperature. However, higher attrition at 650 °C, as confirmed by SEM images, caused a partial weight loss of the catalyst and a slight decline in relative crystallinity, hence 600 °C was preferred with additional advantage of less energy consumption. Meanwhile, introducing lower oxygen not only moderated the coke oxidation rate but also enhanced the recovery of beneficial catalytic features for the MTO conversion. Consequently, considering an excellent regeneration as well as lower emission of CO2 detected in the flue gas, diluted air containing 14 vol.% O2 at 600 °C was suggested as the most promising method.

The Influence of Solid Heat Carrier Load of Char on Pyrolysis Characteristics of Pulverized Coal in a Fluidized Bed Reactor

Pulverized coal pyrolysis based on solid heat carrier has a huge advantage in high tar yield. In this study, pyrolysis experiments on pulverized coal were conducted in a lab-scale fluidized bed reactor at 650 °C, utilizing char as the solid heat carrier. The influence of mass ratio of char to coal (RATIO) was investigated. Results show that the incorporation of solid heat carrier of char significantly enhanced the primary pyrolysis reaction in coal pyrolysis, resulting in increasing yields of tar and gas but reducing one of char. The yield of tar maximally reached 148.80–262.22% of the Gray–King analysis value at the RATIO of 14.52 g/g. As the RATIO increased, the tar contained more light component content, indicating that incorporating solid heat carriers improved the tar quality. These findings offer significant insights for the design of fluidized bed pyrolysis unit utilizing char as solid heat carrier.

Investigation on desulfurization and ground granulated blast furnace slags reutilization for carbon dioxide sorption in a fluidized bed reactor

BackgroundThe atmospheric CO2 concentration is significantly increasing due to the utilization of fossil fuel in various activities. Implementation of steel slag is considered as a promising strategy for carbon capture MethodsIn this study, the slags from desulfurization (De-S) and ground granulated blast furnace (GGBS) processes in the steel company waste were applied as the sorbent in CO2 removal using a fluidized bed system. Various operating conditions were applied to determine the influence of operating parameters on sorbent performance. Moreover, examination on sorbent characteristic change and kinetics calculation were also carried out in this study. Significant findingOptimum operating temperature was reached by the application of 600 and 500 °C for De-S and GGBS slag, respectively. The higher CO2 concentration and 5 % water vapor improved the sorbent utilization. However, excessive water vapor and low fluidized velocity decreased the performance of sorbent. De-S slag performed better on overall CO2 capture process compared to GGBS slag. Therefore, upscaled study with 10 times greater size was further conducted with the 150–300 µm De-S slag for the CO2 capture from oxy-fuel and air combustion. The higher CO2 partial pressure in the flue gas of oxy-fuel combustion increased the capture process efficiency.

Experimental Studies of Fluidized Bed Calcination of Granulated Clay Material.

The work presents a detailed analysis of the possibilities of the thermal processing of clay raw material granulates in a fluidized bed reactor powered by coal fuel. Potential customers of calcined granulates include the following: plants producing refractory materials for the steel industry, producers of refractory concrete, sanitaryware plants, tile plants, large-size tile plants, industry abrasives, chemicals, paints, paper, food and medical industries and others. The advantage of the presented fluid bed calcination technology is the possibility of the continuous operation of the reactor and the short time of the material in the bed, compared to the previously used methods of calcination in a shaft and rotary kiln, which lasts less than twenty minutes in the temperature range of 650-850 °C. During the experimental studies of calcination in the fluidized bed layer, the influence of the type of coal, its particle size and the mass share of coal in the feed mixture on the calcination process and the final product obtained was analysed. As a result of the conducted research, it was proven that solid fuels such as anthracite and steam coal type 31.2 (flaming) can be successfully used in the fluidized bed calcination process of clay materials. The key parameter determining the fluidized bed calcination process is the fuel particle distribution.

A techno-economic assessment of hydrogen and methane production from the anaerobic treatment of vinasse and glycerol: Single- vs. two-stage process

The best-case scenario for anaerobic digestion (AD) could include co-digestion and two-stage systems, a combination that has not yet been extensively studied. This study aimed at evaluating the effect of increasing the organic loading rate from 5 to 20 kg-COD/m3/d in second-stage thermophilic (55 °C, CH4-RThermo) and mesophilic (25 ± 5 °C, CH4-RMeso) anaerobic fluidized bed reactors (AFBR) fed with sugarcane vinasse and glycerol (1:1 on a COD basis) previously fermented in a thermophilic AFBR. AD was stable with high methane production and COD removal up to 20 kg-COD/m3/d for CH4-RThermo (4.53 L-CH4/L/d; 79 %) and CH4-RMeso (3.85 L-CH4/L/d; 66 %), respectively. At 20 kg-COD/m3/d, CH4-RMeso failed due to acid accumulation (1279 mg/L), which probably inhibited methanogenic activity. Results of two-stage thermophilic + thermophilic (H2-RThermo + CH4-RThermo) were compared with a thermophilic single-stage AFBR. In comparison to the two-stage system, for 10, 15, and 20 kg- COD/m3/d, the single-stage energetic yields were higher at 33, 26 and 22 %, respectively. A techno-economic assessment was conducted. The scale-up and economic analyses revealed that the single-stage would be the most compact system (17,820 vs. 20,560 m3) with the lowest initial investment (USD 45 M vs. USD 52 M), highest net present value (NPV) (USD 58 M vs. USD 47 M), and internal rate of return (IRR) (18 vs. 16 %) compared to the best two-stage system (thermophilic + thermophilic). A Monte Carlo simulation indicated a 12 % risk of financial loss at 20 kg-COD/m3/d for the single-stage system. Furthermore, it showed that variation on the capitalization rate, inflation, and the electricity sales price can significantly affect the NPV. Therefore, in addition to better laboratory performance, the single-stage system is simpler to operate, less costly, and would be more suitable for industrial scale implementation.