Conventional Fluidized Bed Reactor Research Articles

Fluidized Bed Membrane Reactor for the Direct Dehydrogenation of Propane: Proof of Concept.

In this work, the fluidized bed membrane reactor (FBMR) technology for the direct dehydrogenation of propane (PDH) was demonstrated at a laboratory scale. Double-skinned PdAg membranes were used to selectively remove H2 during dehydrogenation tests over PtSnK/Al2O3 catalyst under fluidization. The performance of the fluidized bed membrane reactor was experimentally investigated and compared with the conventional fluidized bed reactor (FBR) by varying the superficial gas velocity over the minimum fluidization velocity under fixed operating conditions (i.e., 500 °C, 2 bar and feed composition of 30vol% C3H8-70vol% N2). The results obtained in this work confirmed the potential for improving the PDH performance using the FBMR system. An increase in the initial propane conversion of c.a. 20% was observed, going from 19.5% in the FBR to almost 25% in the FBMR. The hydrogen recovery factor displayed a decrease from 70% to values below 50%, due to the membrane coking under alkene exposure. Despites this, the hydrogen extraction from the reaction environment shifted the thermodynamic equilibrium of the dehydrogenation reaction and achieved an average increase of 43% in propylene yields.

Methanol to gasoline (MTG): Parametric study and validation of the process in a two-zone fluidized bed reactor (TZFBR)

Methanol to Gasoline (MTG) process transforms methanol to hydrocarbons within the boiling point range of gasoline. The result is a wide spectrum of products (olefins, paraffins, aromatics and naphthenics, among others), with the total conversion of methanol to hydrocarbons and water. Catalyst deactivation by coke is a main problem in this process. This work aims to determine the feasibility of carrying out the production of gasoline from methanol in a two-zone fluidized bed reactor (TZFBR). The hypothesis is that the formation of carbonaceous deposits (coke) on the catalyst particles can be counteracted by its combustion in the regeneration zone that this novel reactor presents, thus achieving stable and continuous operation. In this way, both processes (reaction and regeneration) would be being carried out simultaneously in the same reactor (process intensification). The comparison of results between a conventional fluidized bed reactor and a TZFBR shows that the second one actually provides a better stability over time.

Comparison of Conventional and Two-Zone Fluidized Bed Reactors for Methanol to Olefins. Effect of Reaction Conditions and the Presence of Water in the Feed

The effect of water over the performance of the Methanol-to-Olefins process was studied in a conventional fluidized bed reactor (CFBR) and a two-zone fluidized bed reactor (TZFBR). Both of them contained the same SAPO-34-based catalyst, prepared by agglomeration with bentonite and alumina. In the first section of this paper, the performance was studied in the TZFBR for a wide range of temperatures (350–600 °C, ΔT = 50 °C), and two oxygen concentrations fed to the lower zone (7.5 and 10.8% for 500, 550, and 600 °C). In the second section, a comparison between the performance over the two previously mentioned reactors is presented, followed by a comparison between feeding water or not doing so to the TZFBR. Results showed that the TZFBR increased the initial yield to olefins and the production time of them, an effect that was increased by feeding a mixture of methanol–water (1:1 molar ratio) instead of pure methanol.

Biomass fast pyrolysis in an innovative gas-solid vortex reactor: Experimental proof of concept

Biomass fast pyrolysis has been considered one of the best alternatives for the thermal conversion of biomass into bio-oil. This work introduces a new reactor technology for biomass fast pyrolysis, the Gas-Solid Vortex Reactor (GSVR), to obtain high bio-oil yields. The GSVR was designed to decrease the residence time of the pyrolysis vapors; thus, the secondary cracking reactions are reduced, to enhance the segregation of the char and the unreacted biomass and to improve the heat transfer rate. Biomass fast pyrolysis experiments have been carried out for the first time in a Gas-Solid Vortex Reactor (GSVR) at 773 K, using softwood (pine) and hardwood (poplar) as feedstock. Char yields as low as 10 wt. % in the GSVR were comparable to those reported for the same feedstocks processed in conventional fluidized bed reactors. The yields of non-condensable gases in the range of 15–17 wt. % were significantly lower than those reported for other commonly used biomass fast pyrolysis reactors. Two-dimensional gas chromatography (GC × GC) revealed noticeable differences at the molecular level between the bio-oils from the GSVR and bio-oils from other reactors. The aromatics in the pine bio-oil consist almost entirely (85 wt. %) of guaiacols. For poplar bio-oils no predominant group of aromatics was found, but phenolics, syringols, and catechols were the most pronounced. The experimental results highlight the advantages of the GSVR for biomass pyrolysis, reaching stable operation in around 60 s, removing the formed char selectively during operation, and enabling fast entrainment of pyrolysis vapors. Results indicate a great potential for increasing yield and selectivity towards guaiacols in softwood (e.g., pine) bio-oil. Likewise, decreasing pyrolysis temperature could increase the yield of guaiacols and syringols in hardwood (e.g., poplar) bio-oil.

Catalytic pyrolysis of plastic wastes in a continuous microwave assisted pyrolysis system for fuel production

The soaring use of plastics has resulted in alarming issues such as environmental pollution and unsustainable production of plastics. Pyrolysis of plastic wastes has emerged as a promising chemical recycling method, to recover energy and materials from this resource. In this study, the pyrolysis of plastic wastes was conducted in a novel, continuous, microwave-assisted pyrolysis (CMAP) system for fuel production; the effects of temperature, plastic composition, and catalysis on the product yields and composition were investigated. Higher pyrolysis temperatures promoted the cracking of wax and production of lighter and more stable hydrocarbons. Talc as a plastic filler in polypropylene showed a high cracking activity. Incorporating ZSM-5 catalysts at a weight hourly space velocity of 10 h−1 and a pyrolysis temperature of 620 °C resulted in a liquid yield of 48.9%, and this product consisted of 73.5% gasoline-range hydrocarbons rich in aromatic (45.0%) and isomerized aliphatic (24.6%) contents. The catalyst rapidly lost its activity at a feedstock/catalyst ratio of 5. Energy balance analysis showed that 5 MJ of electrical energy was required to process 1 kg of HDPE with the CMAP system, giving an energy efficiency as high as 89.6% 6.1 MJ electrical energy could be generated from the gas products alone, making the process energy self-sufficient. Overall, the CMAP system, featuring a combination of microwave heating with a SiC mixing-ball-bed, is a promising design for industrial application of energy recovery from plastic wastes due to its advantages, including: 1) higher energy efficiency, and 2) lower processing temperature than conventional fluidized-bed reactors.

Redox performance of manganese ore in a fluidized bed thermogravimetric analyzer for chemical looping combustion

A key issue for commercial application of chemical looping combustion (CLC) technology is the selection of oxygen carriers (OCs) with good fluidization and high reactivity during the long-term redox operation. Conventional fluidized bed reactors and thermogravimetric analyzer (TGA) are fail to simultaneously satisfy the fluidization and real-time mass measurement of bed materials. A fluidized bed thermogravimetric analyzer (FB-TGA) combining the advantages of fluidized bed and TGA is believed to be a novel powerful tool for screening OCs for industrial CLC units. In this work, an innovative FB-TGA with a high weight measurement accuracy is designed to reflect the lifetime, redox reactivity, particle sintering and agglomeration characteristics of OCs during the CLC. Manganese ore was selected as a representative OC and redox cyclic tests with hydrogen as the reduction gas were conducted. Results indicate that the Mn3O4-MnO system acts as the main redox pair. The redox chemical reactions may intensify the attrition of manganese ore particles. This may be due to the pore-opening effect of H2 during the reduction of manganese ore, reducing mechanical strength and accelerating attrition of particles. In the reducing atmosphere, it is speculated that the generation of manganese silicates with a low melting point results in particle sintering and agglomeration at the bottom of the bed. The particle agglomeration gradually spreads inward and upward, and eventually leads to total collapse of the fluidized bed. Therefore, a high-grade manganese ore with less silicon element is more suitable for industrial CLC pilots.

Computational fluid dynamics simulation of methanol to olefins in stage circulating fluidized bed riser: Effect of reactor stage parameters on product yields

The risers of a conventional fluidized bed reactor and a stage fluidized bed reactor for the convention of methanol to olefins (MTO) were simulated using computational fluid dynamics. The reaction rates of the MTO reaction were validated to successfully match with the literature experiment. Then, the reactor stage parameters were examined by using the 2k design of the experiment method, including the number of reactor stages, the thickness of the reactor stage, and the wall temperature of the reactor stage. The stage circulating fluidized bed riser decreased the yield of ethene but increased the yield of propene and light olefins. From the obtained solid volume fraction profile, the stage circulating fluidized bed riser could reduce the back-mixing and increase the system turbulence, which promotes the light olefins of the MTO reaction yield. The wall temperature of the reactor stage did not significantly affect the chemical reaction in the circulating fluidized bed riser.

Prediction of dense phase voidage for group C+ fluidized bed reactor

Group C+ fluidized bed reactor exhibited better reactor performance than conventional fluidized bed reactors, due to the larger specific surface area of the catalysts and the more homogeneous fluidization, especially the extraordinary dense phase expansion which contributes to higher gas–solid contact efficiency. As a critical parameter affecting the reactor performance, the dense phase voidage (εd) was thoroughly characterized and general correlations for predicting εd were derived based on both Richardson-Zaki and Kozeny-Carman approaches. In addition, a new method for predicting the minimum fluidization velocity of Group C+ particles with the consideration of the particle cohesion was proposed. The bed voidage at minimum fluidization (εmf) and the maximum dense phase voidage (εd,max) were shown to correlate well with a dimensionless cohesion index (σ*). All these new correlations showed good agreements with the experimental data for various types of Group C+ particles.

Gas phase polymerization of ethylene towards UHMWPE.

For the first time, ultra-high molecular weight polyethylene (UHMWPE) was produced in gas phase process with a new fluidized bed concept where the solids are dispersed phase and the gas is bulk phase as opposed to conventional fluidized bed reactors (FBRs). With this concept, UHMWPE with average molecular weights about 1-6,9 × 106 g mole-1 were produced with a commercial supported Ziegler-Natta catalyst by using a gas phase mini semibatch reactor system. Additionally, optimum conditions of gas phase polymerization for the best results of productivity, catalyst activity, molecular weight and crystallinity were determined by Taguchi experimental design and catalyst stability at the optimum condition was tested by video microscopy polymerization. The characterization of products was carried out experimentally by TGA, DSC, FTIR, and NMR.

Conventional and improved fluidized bed reactors for dry reforming of methane: Mathematical models

Abstract Dry reforming of methane is a potentially useful reaction, but has some drawbacks: catalyst deactivation by coke and yield limited by thermodynamic equilibrium. New improved fluidized bed reactors may compensate these disadvantages. Mathematical models for the dry reforming of methane in three types of fluidized bed reactors have been developed. These reactors include: a) conventional fluidized bed reactor, b) two zone fluidized bed reactor, which provides simultaneous reaction and catalyst regeneration in a single fluidized bed, and c) two-zone fluidized bed reactor with hydrogen selective membranes, which in addition to the previous one provides increased yield to hydrogen, because the selective removal of hydrogen through the membrane. The situations where these reactors counteract the two main drawbacks of dry reforming of methane are shown. Comparison with previous experimental results shows that the models predict well the effect of operating conditions.

Enhanced roasting of lepidolite for high defluorination efficiency in a fluidized bed reactor

Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium. In this paper, a vacuum was introduced to the fluidized bed reactor, which significantly improved the defluorination efficiency of lepidolite particles. This improvement could be attributed to an increase in the H2O/HF ratio. The highest defluorination rate for the lepidolite particles was obtained in the fluidized bed reactor under vacuum. The rate in the vacuum reactor was 1.5–2 times that in a fixed bed reactor or conventional fluidized bed reactor. The defluorination efficiency of the lepidolite particles also improved and the consumption of steam was greatly reduced by addition of coal char. This enhancement was mainly attributed to changes in the structures of the reduced lepidolite particles. This defluorination roasting method for high lithium extraction with low water steam consumption is a promising method for lithium ore treatment.

Simultaneous decarburization, nitrification and denitrification (SDCND) in coking wastewater treatment using an integrated fluidized-bed reactor

There are two problems in biological treatment of coking wastewater (CWW): incapability of pre-anaerobic treatment to eliminate the toxicity in wastewater, and the lack of carbon source for subsequent denitrification in pre-aerobic treatment. To achieve simultaneous decarburization, nitrification and denitrification (SDCND) in CWW treatment, biological carrier materials was used to build an integrated fluidized-bed reactor (Reactor B, RB). A conventional fluidized-bed reactor (Reactor A, RA) was used as a control reactor under the same condition. The results showed that RB was more advantageous since its removal efficiencies of COD and TN were 90% and 87%, respectively, which were significantly higher than these in RA (82% and 45%), at a hydraulic retention time (HRT) of 60 h. Microelectrode measurement indicated that oxygen transfer was limited inside the carrier where the formation of a dissolved oxygen (DO) concentration gradient was observed. Microbial community analysis showed that the aerobic and anoxic microenvironments in RB promoted the co-existence of a wider variety of bacteria, thus achieving SDCND. These results indicated the integrated fluidized-bed reactor exhibited promising feasibility for simultaneous carbon and nitrogen removal in CWW treatment under the same aeration driven conditions. The SDCND process realized by fluidized-bed reactor provided a reference for the treatment of toxic industrial wastewater with high carbon to nitrogen ratio.

Studies on the fluidization performance of a novel fluidized bed reactor for iron ore suspension roasting

A U-type reduction chamber (URC) is developed as the key component of the novel iron ore suspension roaster. It consists of a fluidization chamber (FC) and a supply chamber (SC), and functions dually as sealing valve and reduction chamber. This roaster has been applied successfully to iron ore reduction roasting, while only limited information is available on its working mechanism. The fluid dynamic behavior of solid particles within URC and effects of operating parameters, i.e., the fluidizing air velocity, aeration air velocity and delivery rate, on its performance were investigated in this study. Simulation experiments on the fluid behavior of feed ores were conducted in a cold operating URC apparatus using alumina particles with an average size of 147 μm. It was found that the feeding particles descend in moving-bed mode in the supply chamber, while the particles move upwards in fluidization mode in the FC under suitable operating conditions. The differential pressure fluctuation reaches the maximum at the middle region of the FC, indicating vigorous gas-solid interactions at this area. The solids holdup presents an “S” shape distribution along the height of the FC. The average solids holdup and axial nonuniformity index range from 0.35 to 0.50 and from 0.10 to 0.40, respectively, which are relatively higher than those found in conventional fluidized bed reactors, ensuring better gas-solids contacting and mixing and promotion of reduction performance. In addition, the solids height in the SC could self-adjust to maintain pressure balance in the URC system under various operating conditions, and the pressure difference produced by solids at a certain height in the SC is the main driving force to keep normal flow of solid particles. The information obtained from this study could be helpful, especially for the regulation and control of industrial iron ore suspension roasting.

An experimental investigation of wall-bed heat transfer and flow characteristics in a swirling fluidized bed reactor

The present work investigates the heat transfer between the immersed heater and bed and hydrodynamics of the bed in swirling fluidized bed. The heat transfer process and bed hydrodynamics characteristics for swirling fluidized bed reactor (SFBR) were compared to those of conventional fluidized bed reactor (CFBR). Then the influence of particle diameter on the bed flow characteristics and heat transfer process in SFBR were studied. The heat transfer coefficient was calculated at different superficial air velocities, radial positions, and bed heights. Compared to a CFBR, the bed pressure drop and distributor pressure drop for SFBR were lower, that characterizes swirling bed reactor. The heat transfer coefficient of SFBR was higher than the corresponding of CFBR at lower portion of the bed and it was lower at the upper portion of the bed for all radial positions and for all air superficial velocities. Increasing particle diameter in SFBR resulted in decreasing both the heat transfer coefficient and bed pressure drop.

Pure hydrogen from biogas: Intensified methane dry reforming in a two-zone fluidized bed reactor using permselective membranes

Methane dry reforming of biogas can be a sustainable source of hydrogen but the development of this technology is hindered by limitations such as endothermicity and catalyst deactivation by coke. A two zone fluidized bed reactor coupling permselective Pd/Ag membranes counteracts them and allows to intensify the process obtaining a stable pure hydrogen production. Here we report the effect of operation variables (i.e., temperature, total bed height, nature and partial pressure of regenerative agent, relative height of the regeneration and reaction zones, and use of an activation period) on the yield to hydrogen and stability of the process. Hydrogen over-yields, compared with the conventional fluidized bed reactor, in the range of +200% to +100% were obtained for the entire interval of temperatures 475–575 °C whilst maintaining stable operation by continuous catalyst regeneration. Around 70% of it was pure hydrogen coming from the permeate side of the membranes. The proposed reactor configuration greatly increases both methane conversion and selectivity to hydrogen (expressed as H2/CO ratio), not only in relation to our own conventional reactor findings but also regarding other published results.

Magnetic field acceleration of CO2 reforming of methane over novel hierarchical Co/MgO catalyst in fluidized bed reactor

Magnetic field acceleration of CO2 reforming of methane over a novel hierarchical Co/MgO catalyst in fluidized bed reactor is reported. The hierarchical Co/MgO catalyst shows good fluidization quality and is suitable for efficient CO2-CH4 reforming in fluidized-bed reactor. Compared to the conventional fluidized bed reactor (CFB), the hierarchical Co/MgO catalyst shows better conversions of CO2 and CH4, higher turnover rate, and higher resistance to coke deposition in the magnetic assisted fluidized bed (MFB) reactor. The enhancement of the magnetic field for the CO2 reforming of methane originates from the high breaking and coalescing frequency of clusters in the MFB reactor, thus improved the gas-solid contact efficiency. The approach of improving the catalytic activity by coupling of hierarchical Co/MgO particles and magnetic fluidized-bed is effective for the syngas production from the perspective of matching catalysts with fluidized-bed reactors.

Modeling and simulation of particle size distribution behavior in gas–liquid–solid polyethylene fluidized bed reactors

In this work, population balance model (PBM) that describes particle size distribution (PSD) and liquid vaporization modeling scheme (VMS) (including the heat transfer model and droplet vaporization model), which describes liquid evaporation, were incorporated into a three-fluid computational fluid dynamics (CFD) model to analyze PSD behavior in an industrial–scale gas–liquid–solid three–phase polyethylene fluidized bed reactor (FBR). The validation of this CFD–VMS–PBM coupled model was conducted through comparing results with industrial and calculated data, which then was applied to discuss the characteristics of PSD behavior in terms of the effects of particle kinetics, node number, and condensed liquid content. Unlike gas–solid polyethylene conventional FBRs, although the PSD behavior was dominated by particle agglomeration, particle breakage kinetics exerted a great impact on PSD, especially at the initial polymerization period when it competed with aggregates to decrease the defluidization risk of the reactor. Furthermore, the number of nodes strongly affected PSD simulation results, and using three nodes was the best configuration. In this three–phase system, the increase in the condensed liquid content improved the particle growth rate, which affected the reactor's productivity and product's properties, such as mean particle size and final PSD.

Process design and intensification for the production of solar grade silicon

Solar grade silicon (SiSG) is typically used in photovoltaic applications, and it is commercially manufactured via the Siemens process. Despite the fact that current levels of demand are satisfied, there may be a shortage of SiSG in the near future. To improve the low yield of the Siemens process, two alternative types of SiSG production processes have been developed and analyzed using a stochastic optimization scheme within ASPEN PLUS. The first one is an intensified Fluidized Bed Reactor (FBR) process using a reactive distillation column. The second one is a hybrid process combining both the Siemens and the conventional FBR processes. In addition to supplying future demand, these processes are intended to reduce the use of raw materials. The results show the great value of optimizing the processes, since it achieves savings in the TAC of 53.28%, 67.65% and 62.58% (Siemens, Intensified FBR and Hybrid process), respectively. Siemens process shows the lowest TAC ($0.50 M/y), but this does not mean that it is the process with the highest potential, since it has the lowest silicon production rate, 0.47 kt/y. The Intensified FBR Union Carbide Process turns out to be the most expensive of the three ($2.57 M/y), with a large production of Si(SG), 1.49 kt/y. However, it is the hybrid process which shows the larger yield by far, with a production of 1.89 kt/y of Si(SG) and TAC of $1.95 M/y, showing the highest profit from sales, $40.47 M/y. However, from the environmental point of view, the Siemens process shows the lowest environmental impact based on the eco-indicator 99, while the Hybrid process is the second best.

Honeywell UOP introduces range of new hydrotreating catalysts, expanding offerings to support production of cleaner-burning gasoline and diesel

Methanol to Gasoline (MTG) process transforms methanol to hydrocarbons within the boiling point range of gasoline. The result is a wide spectrum of products (olefins, paraffins, aromatics and naphthenics, among others), with the total conversion of methanol to hydrocarbons and water. Catalyst deactivation by coke is a main problem in this process. This work aims to determine the feasibility of carrying out the production of gasoline from methanol in a two-zone fluidized bed reactor (TZFBR). The hypothesis is that the formation of carbonaceous deposits (coke) on the catalyst particles can be counteracted by its combustion in the regeneration zone that this novel reactor presents, thus achieving stable and continuous operation. In this way, both processes (reaction and regeneration) would be being carried out simultaneously in the same reactor (process intensification). The comparison of results between a conventional fluidized bed reactor and a TZFBR shows that the second one actually provides a better stability over time.

CFD Modeling of Algae Flash Pyrolysis in the Batch Fluidized Bed Reactor Including Heat Carrier Particles

Abstract The algae biomass is one of the potential biomass resources for extracting lipid to produce fuel. The off grade or residuals of dehydrated algae particles can be used in pyrolysis reactions to produce fuel or useful chemicals. Due to higher ash contents of algae biomass, pyrolysis process needs an appropriate design of pyrolysis reactor. The heating rate of algae biomass is a key factor for increasing of bio-oil production rate. Instead of heat transfer from reactor walls to the biomass, heated inert particles are added to the conventional fluidized bed reactor to increase heat transfer rate and yield of the bio-oil as called flash pyrolysis. The introduced pyrolysis reaction in the novel heating method of fluidized bed reactor studied numerically. For this purpose, an Eulerian-Eulerian CFD model utilized for modeling of the dehydrated algae pyrolysis in the fluidized bed reactor. The appropriate reaction rate of the algae pyrolysis is based on the heating rate, temperature sensitive activation energy and the reaction selectivity utilized to the algae pyrolysis. In addition, the segregation and density change of the biomass particles investigated in the CFD modeling to analysis mixing of the particles and corresponding heat transfer between the mixed particles. The validation of the CFD model investigated using results of prepared experimental setup.