Fluidized Bed Membrane Reformer Research Articles

Solar thermal energy application to dry reforming of methane on the open-cell foam to enhance the energy storage efficiency of a thermochemical fluidized bed membrane reformer: modelling and simulation

The hydrodynamic characterization of the solar-driven CO2 reforming of methane through b-SiC open-cell foam in a fluidized bed configuration is performed by reacting Methane (CH4) with carbon dioxide (CO2). The mathematical modelling is important to design and optimize the reforming methods. Usually, the reforming methods's application through b-SiC foam bed improves the heat transfer and mass transfer due to high porosity and surface area of the b-SiC foam. Fluidized Bed Membrane (FBM) Reformers can be substantially studied as a promising equipment to investigate the thermochemical conversion of CH4 using CO2 to produce solar hydrogen. This work has as main objective a theoretical modelling to describe the process variables of the solar-driven CO2 reforming of methane in the FBM reformer. The FBM reformer is filled with b-SiC open-cell foam where the thermochemical conversion is carried out. The model variables describe the specific aims of work and these objectives can be identified from each equation of the developed mathematical model. The present work has been proposed to study two specific aims as (i) The effective thermal conductivity's effect of the solid phase and (ii) molar flows of chemical components. The endothermic reaction temperature's profiles are notably increased as the numeral value of the effective thermal conductivity's effect of the solid phase. is rised. The solar-driven CO2 reforming method is suggested to improve the Production Rate (PR) of H2 regarding the PR of CO.

Advanced m-CHP fuel cell system based on a novel bio-ethanol fluidized bed membrane reformer

Distributed power generation via Micro Combined Heat and Power (m-CHP) systems, has been proven to over-come disadvantages of centralized generation since it can give savings in terms of Primary Energy consumption and energy costs.The FluidCELL FCH JU/FP7 project aims at providing the Proof of Concept of an advanced high performance, cost effective bio-ethanol m-CHP cogeneration Fuel Cell system for decentralized off-grid applications by end of 2017. The main idea of FluidCELL is to develop a new bio-ethanol membrane reformer for pure hydrogen production (3.2 Nm3/h) based on Membrane Reactors in order to intensify the process of hydrogen production through the integration of reforming and purification in one single unit. The novel reactor could be more efficient than the state-of-the-art technology due to an optimal design aimed at circumventing mass and heat transfer resistances. Moreover, the design and optimization of the subcomponents for the BoP could also be improved. Particular attention has to be devoted to the optimized thermal integration that can improve the overall efficiency of the system at >90% and reducing the cost due to low temperature reforming. The main results obtained until now in terms of performance of the catalysts, membranes and the membrane reactors will be presented in this work.

Advanced m-CHP fuel CELL system based on a novel bio-ethanol Fluidized bed membrane reformer

Advanced m-CHP fuel CELL system based on a novel bio-ethanol Fluidized bed membrane reformer

Enhanced ultraclean hydrogen production by multi-stage reformers

The performance of multi-stage circulating fast fluidized bed membrane reformers (CFFBMRs) for production of ultraclean hydrogen is investigated in comparison to a single circulating fast fluidized bed membrane reformer (CFFBMR). The two-stage reformer configuration gives significant increase in the methane conversion of 27.46% and ultraclean hydrogen yield of 29.61% compared to the single CFFBMR. The concept of the multi-stage short reformers policy is introduced. Impressively, substantial increase of ultraclean hydrogen yield of 83.91% is achieved.

Catalytic reforming of natural gas for hydrogen production in a pilot fluidized-bed membrane reactor: Mapping of operating and feed conditions

A fluidized-bed membrane reformer was operated in two independent laboratories to map various operating conditions, to investigate the effects of changing the composition of the natural gas feed stream and to verify earlier experimental trials. Two feed natural gases were tested, containing either 95.5 or 90.1 mol% of methane (3.6 or 9.9 mol% of other gaseous higher hydrocarbons). Experimental tests investigated the influence of total membrane area, reactor pressure, permeate pressure and natural gas feed rates. A permeate-H 2-to reactor natural gas feed molar ratio >2.3 was achieved with six two-sided membrane panels under steam reforming conditions and a pressure differential across the membranes of 785 kPa. The total cumulative reforming time reached 395 h, while hydrogen purity exceeded 99.99% during all tests.

In-situ CO2 capture in a pilot-scale fluidized-bed membrane reformer for ultra-pure hydrogen production

A novel pilot fluidized-bed membrane reformer (FBMR) with permselective palladium membranes was operated with a limestone sorbent to remove CO2in-situ, thereby shifting the thermodynamic equilibrium to enhance pure hydrogen production. The reactor was fed with methane to fluidize a mixture of calcium oxide (CaO)/limestone (CaCO3) and a Ni-alumina catalyst. Experimental tests investigated the influence of limestone loading, total membrane area and natural gas feed rates. Hydrogen-permeate to feed methane molar ratios in excess of 1.9 were measured. This value could increase further if additional membrane area were installed or by purifying the reformer off-gas given its high hydrogen content, especially during the carbonation stages. A maximum of 0.19 mol of CO2 were adsorbed per mole of CaO during carbonation. For the conditions studied, the maximum carbon capture efficiency was 87%. The reformer operated for up to 30 min without releasing CO2 and for up to 240 min with some degree of CO2 capture. It was demonstrated that CO2 adsorption can significantly improve the productivity of the reforming process. In-situ CO2 capture enhanced the production of hydrogen whose purity exceeded 99.99%.

Kinetic simulation of a compact reactor system for hydrogen production by steam reforming of higher hydrocarbons

AbstractA bubbling fluidized bed membrane reactor for steam reforming of higher hydrocarbons is modelled, using n‐heptane as a model component to represent steam reforming of naphtha. The reformer is modelled as a bubbling fluidized bed reactor, consisting of two pseudo phases, a dense phase and a bubble phase, both in plug flow. In situ H2 permselective membranes remove H2 continuously as a pure product, greatly enhancing the H2 yield per mole of heptane fed. A fluidized bed membrane reformer for higher hydrocarbons could give a very compact reactor system combining all the units from the pre‐reformer to the hydrogen purification system in a traditional steam reforming plant into a single unit.

Sorbent-enhanced/membrane-assisted steam-methane reforming

Thermodynamic equilibrium and kinetic reactor models are used to simulate a fluidized bed membrane reactor with in situ or ex situ hydrogen and/or CO 2 removal for production of pure hydrogen by steam methane reforming. In the equilibrium model, the membranes and CO 2 removal are located in separate vessels downstream of the reformer. As the recycle ratio increases, the overall performance approaches that where membranes are located inside the reactor. Whether located in situ or ex situ, hydrogen removal by membranes and CO 2 capture by sorbents both enhance hydrogen production. In the kinetic reactor model, a circulating fluidized bed membrane reformer is coupled with a catalyst/sorbent regenerator. Sorbent enhancement combined with membranes could provide very high hydrogen yields. In addition, since carbonation is exothermic, with its heat of reaction similar in magnitude to the endothermic heat of reaction of the net reforming reactions, sorbent enhancement can provide much of the heat needed in the reformer. The overall heat needed for the process would then be provided in a separate calciner, acting as a sorbent regenerator. While the technology is promising, several practical issues need to be examined.

Sequential Simulation of a Fluidized Bed Membrane Reactor for the Steam Methane Reforming Using ASPEN PLUS

A simulation model is developed using ASPEN PLUS to predict the performance of a fluidized bed membrane reformer. Because there are physical and chemical phenomena interacting in the fluidized bed membrane reformer, two submodels seem necessary in the model. These submodels are the hydrodynamic and reaction submodels. The hydrodynamic submodel is based on the dynamic two-phase model, and the reaction submodel is derived from the literature. The reformer is divided into two regions: a dense bed and freeboard. The dense bed is divided into several sections. At each section, the flow of the gas is considered as the plug flow through the membrane and bubble phases and perfectly mixed through the emulsion phase. The sets of the experimental data were used from the literature to validate the model. Close agreement was observed between the model predictions and experimental data. This model can be used for the simulation of nonideal fluidized bed membrane reactors inside the ASPEN PLUS process simulator.

Bifurcation Behaviour During the Hydrogen Production in Two Compatible Configurations of a Novel Circulating Fluidized Bed Membrane Reformer

Multiplicity of steady states (static bifurcation behaviour) in a novel circulating fluidized bed (CFB) membrane reformer for the efficient hydrogen production by steam reforming of heptane (model component of heavy hydrocarbons and renewable bio-oils) is investigated. The present paper highlights the practical implications of this phenomenon on the behaviour of this novel reformer with special focusing on hydrogen production. Two configurations are considered. One is with the catalyst regeneration before the gas–solid separation and the other one is with the catalyst regeneration after the gas–solid separation. Multiplicity of the steady states prevails over a number of design and operating parameters with important impact on the reformer performance. The basis of process evaluation is focused on the net hydrogen production. The dependence of the behaviour of this autothermal CFB is shown to be quite complex and defy the simple logic of non-autothermal processes. The unit can be a very efficient hydrogen producer provided its bifurcation behaviour is well understood and correctly exploited.

Economics of the Clean Fuel Hydrogen in a Novel Autothermal Reforming Process

The economics of pure clean fuel hydrogen produced by steam reforming of hydrocarbons in an earlier suggested novel autothermal circulating fluidized-bed membrane reformer (ACFBMR; Chen, Z.; Elnashaie, S. S. E. H. Chem. Eng. Sci. 2004, 59 (18), 3965-3979; Chen, Z.; Elnashaie, S. S. E. H. AIChE J. 2005, 51 (5), 1467-1481) is evaluated. A detailed autothermal reforming pilot plant is suggested and used for the determination of the specifications and costs of the main units/equipments. Using statistical correlations and cost factors, the total capital investment is determined. The economical analysis data show that the hydrogen production cost decreases with an increase of the plant size in the region of 100-100 000 kg of H 2 /day. Above this region, the effect of the plant capacity becomes insignificant. For a small pilot plant with a 100 kg of H 2 /day capacity, the hydrogen cost in the industrial steam methane reforming process is $9.10/ kg of H 2 , while using this novel autothermal technology, the costs are $2.05/kg of H 2 for the methane feed and $2.22/kg of H 2 for the heptane feed. The cost reductions are 77.5% and 75.6%, respectively. For a typical large industrial plant with 214 286 kg of H 2 /day (equivalent to 100 000 Nm 3 of H 2 /h; Scholz, W. H. Gas Sep. Purif. 1993, 7 (3), 131-139), the reported industrial hydrogen production cost by steam methane reforming is $0.74-0.97/kg of H 2 , while using this autothermal technology, the hydrogen production costs are $0.66/kg of H 2 from heptane and $0.50/kg of H 2 from methane, respectively. The cost reductions are 10.8-32.0% and 32.4-48.5%, respectively. The comparison of hydrogen production costs over a wide range of plant sizes shows that this novel ACFBMR can be a more efficient and more economical pure hydrogen producer.

Bifurcation and its implications for a novel autothermal circulating fluidized bed membrane reformer for the efficient pure hydrogen production

The present investigation is a prelude to the experimental exploration of Static Bifurcation Behavior (SBB) in a novel Autothermal Circulating Fluidized Bed Membrane Reformer (ACFBMR) for pure hydrogen production by steam reforming of heavy hydrocarbons. Important impacts of a wide range of design and operating parameters on the reformer performance are explored with two reformer configurations. One is with the catalyst regeneration before the gas–solid separation and another is with the catalyst regeneration after the gas–solid separation. For both configurations there are three steady states (multiplicity of the steady states, static bifurcation behavior). The system behavior in the bifurcation region is quite complex and defies the simple logic of non-autothermal processes. For the first configuration, on the branch of upper temperature steady state the carbon formation and deposition on the nickel catalyst is highest, while the net hydrogen yield is highest on the branch of lower temperature steady state. For the second configuration, the conversion of heptane is always 100%. In the multiplicity region, the order of net hydrogen yield from high to low is the middle, upper and lower temperature steady states, while the order of reformer exit carbon flow rate from high to low is the lower, middle and upper temperature steady states. Efficient production of pure hydrogen for fuel cells requires fundamental and practical understanding of their bifurcation behaviors.

Steady-state modeling and bifurcation behavior of circulating fluidized bed membrane reformer–regenerator for the production of hydrogen for fuel cells from heptane

The production of hydrogen for fuel cells by steam reforming of heptane is investigated in a Circulating Fluidized Bed Membrane Reformer-Regenerator ( CFBMRR) system (A.I.Ch.E. Journal 49(5) (2003) 1250). Palladium based hydrogen permselective membranes are used for hydrogen removal and dense perovskite oxygen permselective membranes are used for oxygen introduction. A series of pseudo-steady-state simulations show that when the catalyst is not regenerated, the circulating nickel reforming catalyst deactivates quickly and the “half catalyst activity life” for efficient production of hydrogen is quite short, especially at high temperatures. Efficient continuous catalyst regeneration can keep the catalyst activity high ( ∼ 1.0 ) . With continuous catalyst regeneration, autothermal operation for the entire adiabatic reformer–regenerator system is achievable when the exothermic heat generated from the catalyst regenerator is sufficient to compensate for the endothermic heat consumed in the riser reformer. This type of autothermal operation becomes less likely at high steam to carbon feed ratios. This is due to the fact that carbon deposition rate decreases leading to the decrease of autothermal circulating feed temperature and energy-based hydrogen yield (adiabatic hydrogen yield in autothermal reformer–regenerator system). Multiplicity of the steady states for the reformer is possible for this configuration. With the steam to carbon feed ratio as the bifurcation parameter, multiplicity occurs between the two bifurcation points 1.444 and 2.251 mol/mol. In this multiplicity region, the energy-based hydrogen yield at the upper steady state with high regenerator output temperature is surprisingly the lowest one. While it is the highest one at the lower steady state with low regenerator output temperature. The maximum energy-based hydrogen yield is about 15.58 moles of hydrogen per mole of heptane fed at the lower steady-state when steam to carbon feed ratio is very close to the bifurcation value of 1.444 mol/mol. After removing the sweep gas steam by downstream cooling and de-humidification, the product hydrogen from steam reforming of hydrocarbons can be used for fuel cells with high purity ( ∼ 100 % ) .

Catalyst deactivation and engineering control for steam reforming of higher hydrocarbons in a novel membrane reformer

The catalyst deactivation and reformer performance in a novel circulating fluidized bed membrane reformer (CFBMR) for steam reforming of higher hydrocarbons are investigated using mathematical models. A catalyst deactivation model is developed based on a random carbon deposition mechanism over nickel reforming catalyst. The results show that the reformer has a strong tendency for carbon formation and catalyst deactivation at low steam to carbon feed ratios (<1.4 mol/mol) for high reaction temperatures (>700 K) and high pressures (>506.5 kPa) . The trend is similar for the cases without and with hydrogen selective membranes. Based on this preliminary investigation, an engineering control approach, i.e., in-site control with a concept of critical/minimum steam to carbon feed ratio, is proposed and used to determine the carbon deposition free regions for both cases without and with hydrogen membranes. The comparison between the reported data and model simulation shows that the critical steam to carbon feed ratio predicted by the model agrees well with the reported industrial/experimental operating data.

Hydrogen Production and Carbon Formation during the Steam Reformer of Heptane in a Novel Circulating Fluidized Bed Membrane Reformer

Hydrogen production and carbon formation during the steam reforming of heptane over nickel-based catalyst are investigated in a circulating fluidized bed membrane reformer (CFBMR) at 723−823 K and 101.3−2026 kPa. A random carbon deposition and catalyst deactivation model is developed to account for the effect of carbon deposition on the overall reforming kinetics. The results show that the deposited carbon can be efficiently gasified by steam, hydrogen, carbon dioxide, or oxygen in this novel CFBMR, making carbon-free operation practically possible, especially when steam to carbon feed ratio is higher than 2.5 mol/mol. The use of hydrogen permselective membranes breaks the equilibrium barriers associated with the reversible re-forming reactions and increases the hydrogen yield significantly. The introduction of oxygen into the adiabatic reformer can efficiently supply the heat necessary for the endothermic steam reforming through the exothermic oxidation, making an autothermal condition possible for the e...

Nonmonotonic Behavior in Hydrogen Production from the Steam Reforming of Higher Hydrocarbons in a Circulating Fluidized Bed Membrane Reformer

The nonmonotonic behavior observed in hydrogen production from the steam reforming of higher hydrocarbons over nickel catalyst in an earlier-suggested novel circulating fast fluidized bed membrane reformer (CFFBMR) (Chen et al. AIChE J. 2003, 49 (5), 1250−1265) is extensively investigated. The investigation is carried out using kinetic model simulation at 623−823 K and 1013 kPa. Hydrogen-permselective membranes are used under cocurrent and countercurrent operations. The results show that the yield of hydrogen decreases at 623−723 K and then increases at 723−823 K. At 623 K, heptane is not fully converted, and thermodynamic equilibrium is not established. In contrast at 723−823 K, heptane is fully converted, and thermodynamic equilibrium is established. The strong methanation reaction at 723 K makes the hydrogen yield much lower, whereas at 823 K, the steam reforming of methane becomes increasingly important, enhancing the production of hydrogen. Using hydrogen-permselective membranes, the thermodynamic eq...

Novel circulating fast fluidized-bed membrane reformer for efficient production of hydrogen from steam reforming of methane

The coupling of steam reforming and oxidative reforming of methane for the efficient production of hydrogen is investigated over Ni/Al 2O 3 catalyst in a novel circulating fast fluidized-bed membrane reformer ( CFFBMR) using a rigorous mathematical model. The removal of product hydrogen using palladium hydrogen membranes “breaks” the thermodynamic equilibrium barrier exists among the reversible reactions. Oxygen can be introduced into the adiabatic CFFBMR for oxidative reforming by direct oxygen (or air) feed and through dense perovskite oxygen membranes. The simulations show that high productivity of hydrogen can be obtained in the CFFBMR. The combination of these two different processes does not only enhance the hydrogen productivity but also save the energy due to the exothermicity of the oxidative reforming. Based on the preliminary investigations, four parameters (number of hydrogen membranes, number of oxygen membranes, direct oxygen feed rate and steam-to-carbon feed ratio) are carefully chosen as main variables for the process optimization. The optimized result shows that the hydrogen productivity (moles of hydrogen produced per hour per m 3 of reactor) in the novel CFFBMR is about 8.2 times higher than that in typical industrial fixed-bed steam reformers.

Simulation for steam reforming of natural gas with oxygen input in a novel membrane reformer

The performance of a novel circulating fast fluidized bed membrane reformer (CFFBMR) is investigated using a reliable mathematical model. The removal of product hydrogen using hydrogen-permselective membranes “breaks” the thermodynamic equilibrium in the reversible system and makes it possible to operate the process at lower temperatures. The oxidative reforming of a part of the feed methane by oxygen input into the reformer using direct feed or through oxygen-permeable membranes supplies the heat needed for the highly endothermic steam reforming of methane. The combination of the exothermic oxidative reforming and endothermic steam reforming not only produces high yield hydrogen but also makes it possible to operate the CFFBMR under autothermal conditions. The novel configuration is a highly efficient hydrogen producer with minimum energy consumption. The simulation results show that the hydrogen productivity (moles of hydrogen produced per hour per m 3 of reactor) of the CFFBMR is about 8 times that in an industrial fixed bed and 112 times that in a bubbling fluidized bed membrane reformer.

Modeling and optimization of a novel membrane reformer for higher hydrocarbons

AbstractA novel circulating fast fluidized‐bed membrane reformer efficiently carries out simultaneous steam and oxidative reforming of heptane over nickel catalysts. A plug‐flow reactor model was developed to investigate effects of the operating parameters. The cases with palladium hydrogen membranes and/or dense perovskite oxygen membranes are investigated. The simulations show that high purity hydrogen can be efficiently produced using hydrogen membranes, which “break” the thermodynamic equilibrium barriers. The perovskite oxygen selective membranes supply oxygen along the length (or height) of the reformer for oxidative reforming of hydrocarbons, providing the heat necessary for the highly endothermic steam reforming reaction. The combination of these two membranes with the characteristics of the fast fluidization reformer makes this process not only an efficient hydrogen producer but also an energy efficient process. The fast continuous flow of catalyst makes the effect of carbon deposition on catalyst activity negligible in the novel process. Process optimization for the maximum hydrogen yield is conducted using the flexible tolerance optimization method.

Novel Circulating Fluidized-Bed Membrane Reformer for the Efficient Production of Ultraclean Fuels from Hydrocarbons

An integrated novel fluidized-bed membrane steam reformer for the efficient production of hydrogen is proposed and investigated. It consists of two connected subsystems, viz., a circulating fluidized-bed membrane reformer and a reactor−regenerator for dry reforming. The steam-reforming part is an extension of the previous successful work regarding a bubbling fluidized-bed membrane reformer. The fast fluidization regime is more efficient and productive than the bubbling regime. Hydrogen-permeable membranes to remove hydrogen are used together with a CO2 acceptor to remove carbon dioxide and enhance the performance. An in situ supply of heat through oxidative steam reforming is also suggested. The deactivated catalyst is regenerated and recirculated back to the reformer. The CO2-rich stream from the efficient fast fluidized membrane steam reformer is used in a reactor−regenerator dry reforming subsystem, and additional syngas is produced. A reliable reaction engineering model is utilized to investigate this novel configuration. A comparison between the predicted performance of the fast fluidized-bed reformer and the industrial data for a fixed bed as well as the pilot-plant data of the bubbling fluidized-bed configurations investigated earlier shows that the fast fluidized bed is more efficient and productive.