Batch Fluidized Bed Reactor Research Articles

Characterization of combined Fe-Cu oxides as oxygen carrier in chemical looping gasification of biomass

Chemical looping gasification (CLG) of biomass is an innovative biomass gasification technology, where oxygen carrier (OC) has the effects of oxygen supply, heat transfer and catalyst for syngas production. In order to integrate the synergistic effect between Fe and Cu oxides, a novel combined OC containing Fe2O3 and CuO was produced for biomass gasification and investigated in a batch fluidized bed reactor in this work. At first, an OC with 50 wt.% Fe2O3 and 10 wt.% CuO (Fe50Cu10) was selected as the representative OC to evaluate the superiority of combined OC. The mono-metallic OC of CuO is unsuitable as oxygen carrier in the CLG of biomass due to its too low syngas yield, although CuO can greatly accelerate biomass gasification process. In addition, combined Fe-Cu oxides OC is also superior to mono-metallic OC of Fe2O3 at enhancing carbon conversion efficiency on the premise that syngas yield tended to be close. Then the blending ratio of Fe/Cu was optimized and Fe50Cu10 had been proven to be the optimal combined Fe-Cu oxides OC in CLG. Next, the influences of the factors including gasification temperature, steam mole fraction and O/C ratio on the performance of Fe50Cu10 were investigated. 900 °C is the best temperature for gasification and higher team mole fraction gave rise to higher carbon conversion efficiency and syngas yield, while O/C ratio was somewhat different. The optimal O/C ratio was deemed to be 0.78. Besides, 10 redox cycles were conducted to investigate the stability of combined OC reactivity. The combined OC after 3 cycles performed worst reactivity, while better performance was demonstrated after 7–10 cycles. Based on the analysis of SEM-EDX, it was found that sintering caused by Cu atomic was the main cause of the reactivity decline. In addition, it was inferred that the distribution of Cu atomic in the combined OC was more uniform with the cycle number.

Assessment of low-cost oxygen carrier in South-western Colombia, and its use in the in-situ gasification chemical looping combustion technology

In Chemical Looping Combustion (CLC), the Oxygen Carrier (OC) is key element of the process. Most OCs have been developed synthetically, using an active metal oxide combined with an inert material. When solid fuels are used, a loss of OC is expected as it mixes with the ashes generated during the CLC process making the costs elevated. As a result, there is a growing interest in using low-cost OCs based in Mn and Fe.In this research, a by-product derived from manganese ore purification is studied. This material has a high silicon content and it is composed of rhodonite as the main specie and wustite as the minority specie. The material, a Mn mineral from the Nariño department in the Southwest of Colombia, was selected in a previous work based on its good properties such as appropriate crushing strength, an oxygen transport capacity of 3.4%, and a relatively high reactivity.Here, tests in a batch fluidized bed reactor were carried out with the selected material with CH4, CO, and H2 at 950 °C during 50 cycles. A good behaviour was observed with CO and H2, with a moderate attrition, and lifetime of 2950 h. The material presented a trend towards agglomerating with CH4, and no agglomeration with CO and H2. The possible oxygen uncoupling effect due to the presence of combined oxides of manganese and silicon was also evaluated, but there was no evidence in the 950–1040 °C interval when the material was oxidized with a 10 vol% O2.Due to its good performance with CO and H2, the material was evaluated for the in-situ Gasification Chemical Looping Combustion (iG-CLC) technology, using a Chilean reactive coal as fuel at temperatures from 900 °C to 1000 °C.Its good behaviour with H2 and CO makes it a promising OC for iG-CLC technology.

Processing and characterization of Fe-based oxygen carriers for chemical looping for hydrogen production

Until now various oxygen carrier particles have been proposed for use in chemical looping processes. Their chemical performance is determined not only by their composition and their microstructure/morphology but also by the reaction condition of the processes in which they are utilized. In the present work, iron based oxygen carriers supported on Al2O3 and MgAl2O4 were spray dried and heat treated to have a suitable morphology and sufficient mechanical properties for chemical looping. The MgAl2O4-support was in situ generated from MgO and Al2O3 by reaction sintering. After physical characterization and determining their compressive strength the oxygen carriers were tested in the chemical looping reforming process for producing syngas in a lab-scale batch fluidized-bed reactor. The suitability of utilizing steam regeneration was investigated for both oxygen carriers by relating their chemical performance to their composition. It was shown that the Al2O3-supported oxygen carrier deactivated after 9 cycles of steam regeneration because of the accumulation of an in-situ formed FeAl2O4-phase due to an irreversible reaction between support and the active phase. This deactivation was successfully avoided by replacing the Al2O3-support with MgAl2O4. This Fe2O3/MgAl2O4 oxygen carrier could be subsequently regenerated by steam, making it suitable for chemical looping for hydrogen generation.

Chemical looping gasification of biomass: Part I. screening Cu-Fe metal oxides as oxygen carrier and optimizing experimental conditions

Fe2O3 and CuO are commonly used as oxygen carrier (OC) for chemical looping gasification (CLG) of biomass. However, Fe2O3 shows relatively low reactivity even though it is cheap, whilst CuO presents too high reactivity to react with the produced syngas and suffers from sintering problem at high temperatures. This paper is the first part of a two-part series work, where synthetic OCs of bimetallic Cu-Fe oxides prepared by the sol-gel combustion synthesis (SGCS) method were proposed for the biomass-derived CLG process. The reforming reactivity of Cu-Fe OCs with sawdust was first investigated in a thermogravimetric analyzer (TGA). The result indicated that Cu-Fe OCs with higher Cu loading ratio demonstrated better reactivity towards sawdust. Subsequently, the performances of five kinds of Cu-Fe OCs in biomass-derived CLG process were evaluated in a batch fluidized-bed reactor. By comparing the product gas components, gas yield, tar yield and carbon conversion, Cu5Fe5 OC (50 mol.% CuO + 50 mol.% Fe2O3) was found to demonstrate the best comprehensive CLG performance. The effects of steam to biomass ratio (S/B), temperature and oxygen carrier to biomass ratio (O/B) on the performance of Cu5Fe5 were further investigated. The optimum operation state can be attained when the S/B was 0.75, the temperature was 800 °C and the O/B was 0.2. The results of XRD and ESEM characterization showed that the addition of Fe2O3 into CuO-based OC significantly improved the sintering resistance, and the existence of CuO component in Fe2O3 was conductive to improving the porous structure of OC.

Release and transformation of phosphorus in chemical looping combustion of sewage sludge

Sewage sludge contains high content of phosphorus and represents an important secondary phosphorus source. Meanwhile, chemical looping combustion (CLC) is an innovative sludge treatment technology with low NO emission and potential to effectively recover phosphorus. A full understanding of the phosphorus transformation mechanism is vital for the development of CLC of sewage sludge. In this work, the release and transformation behavior of phosphorus in CLC of sewage sludge was studied in a batch fluidized bed reactor with hematite oxygen carrier. The increase of fuel reactor temperature had a marginal influence on phosphorus transformation. Approximately 66.81–69.30% of phosphorus in sewage sludge was concentrated in fly ash during CLC of sewage sludge. The fraction of phosphorus in flue gas was relatively constant, since nearly all of the organic phosphorus volatized. Moreover, the available phosphorus in sludge CLC fly ash was vastly superior to that in sludge combustion ash. The higher available phosphorus content could fulfill the quality parameters for a P-fertilizer. Considering the effect of phosphorus on the reactivity of hematite, the promotion by phosphorus catalyzing and weaken by deposition appeared to be in competition with each other. The reduction reactivity of hematite increased at lower phosphorus content, but it decreased at higher phosphorus content (>3%). Regarding the effect of sludge ash on hematite, the reactivity of hematite increased by adding proper content of sludge ash. Simultaneously, the reactivity of sludge ash as oxygen carrier in reducing period was tested. Despite the fact that sludge ash contained high fractions of Fe and Ca, the performance of sludge ash was unstable in CLC process. This indicated that it was infeasible of using sludge ash as oxygen carrier.

Using a hierarchically-structured CuO@TiO2-Al2O3 oxygen carrier for chemical looping air separation in a paralleled fluidized bed reactor

Chemical looping air separation (CLAS) provides a novel route for O2 production, which can be coupled with integrated gasification combined cycle (IGCC) or oxy-fuel combustion to address the O2 source issue. The development of regenerable and robust oxygen carrier, which should be able to release gaseous oxygen in O2-deficient atmosphere (usually CO2/H2O) and regenerate itself by oxidizing with O2 in air, is critical for the successful deployment of CLAS systems. In this work, a CuO@TiO2-Al2O3 oxygen carrier with hierarchical structure (i.e., CuO-rich, TiO2-stabilized and Al2O3-supported), which was prepared by the self-assembly template combustion synthesis (SATCS) method, was adopted for continuous oxygen production in a paralleled fluidized bed reactor. Before which, isothermal experiments in a thermogravimetric analyzer (TGA) were first conducted to analyze the effect of temperature on OC decoupling and regeneration characteristics. The influence of inlet gas flow rate on the oxygen decoupling rate of the oxygen carrier was then investigated in a batch fluidized bed reactor. Appropriate reaction temperature as well as inlet gas flow rate for continuous O2 production in the paralleled fluidized bed reactor was ultimately attained. During a consecutive operation of 10 h, continuous stream of O2/CO2 with relatively stable and high O2 concentration (19.7–27.6 vol, steam free basis) was obtained. The superior reactivity and stability of CuO@TiO2-Al2O3 achieved during the continuous operation in the paralleled fluidized bed reactor indicate that it could be a promising oxygen carrier candidate for the CLAS process.

Experimental study and modelling of the kinetic of biomass char gasification in a fluidized bed reactor

This work presents experimental data on the kinetic of steam gasification of biomass char in a fluidized bed reactor at atmospheric pressure. The char was obtained from fast pyrolysis of cylindrical beech stick in an annex batch fluidized bed reactor at 650°C. The experiments were performed for temperatures in the range of 700–850°C and steam partial pressures between 0.1 and 0.7 bars. The results showed that the char steam gasification is done in two steps. First, a thermal degradation of char takes place just after its introduction in the fluidized bed. This step leads to a partial conversion of the reactive solid and a formation of volatile products. Then, the new carbonaceous residue reacts with steam to produce syngas. The effect of hydrogen partial pressure up to 0.25 bars on the kinetic of char gasification was also investigated. The results revealed that the presence of H2 inhibits the reaction of steam gasification. Besides, interactions also occur between char and H2 which lead to the formation of CH4 in the product gas. Moreover, as the hydrogen partial pressure increases, the methane production also increases. Finally, a modelling kinetic study including the inhibiting effect of H2 showed that experimental data can be well-represented by the Shrinking Core Model with an activation energy and a reaction order with respect to steam equal to 123kJ/mol and 0.62, respectively.

Spray granulated Cu-Mn oxygen carrier for chemical looping with oxygen uncoupling (CLOU) process

One form of Chemical Looping Combustion (CLC) with CO2 capture as an alternative to the burning of solid fuels is the Chemical Looping with Oxygen Uncoupling (CLOU) process. The CLOU process requires metal oxides with O2 release capacity at temperatures that are suitable for solid fuel combustion, e.g. copper and manganese oxides. A Cu-Mn mixed oxide comprising 34wt% CuO and 66wt% Mn3O4 and prepared by fluidized bed granulation was analysed for use as an oxygen carrier for the CLOU process. TGA and batch fluidized bed reactors were used to investigate oxygen generation rates, agglomeration behaviour and oxygen carrier attrition. A medium volatile coal from South Africa and its char were used as fuel in a batch fluidized bed reactor in a temperature range of 800–930°C. The Cu-Mn oxygen carrier showed good release O2 rate and a high rate of oxygen transfer by direct gas-solid reaction. The presence of CO as a combustion product appeared only at low oxygen carrier to coal ratios. This material has the capacity to generate O2 at lower temperatures than needed for Cu-based oxygen carriers, which suggests that this material is suitable for work at lower temperatures in a fuel reactor with complete combustion of the fuel. The low attrition rate and attrition index, together with the stable crushing strength of the particles with redox cycles, make this Cu-Mn oxygen carrier suitable for operation in a continuous CLOU unit.

Kinetic study of biomass char combustion in a low temperature fluidized bed reactor

The purpose of this work is the kinetic study of biomass char combustion in a low temperature fluidized bed reactor. This char was obtained from fast pyrolysis of beech stick in an annex batch fluidized bed reactor at 923K and atmospheric pressure. Operating conditions of the combustion were thoroughly characterized so that the reaction takes place in isothermal conditions and a constant oxygen partial pressure. The kinetic study was performed for temperatures up to 643K, oxygen partial pressures ranging from 5065 to 21273Pa and cylindrical char particles (D=4mm and L=9mm). The Volumetric Model was found to be in very good agreement with experimental data. Values of activation energy and reaction order with respect to oxygen are respectively equal to 144kJ/mol and 0.59. The reaction scheme during char combustion showed that char first reacts with oxygen to form CO which is further oxidized either at the particle surface or in the gas phase to produce CO2. Besides, it was found that the char reactivity in combustion is higher in a fluidized bed reactor compared to TGA. This was explained by diffusional effects of oxygen and CO oxidation within the crucible in the TGA.

Evaluation of a hierarchically-structured CuO@TiO2-Al2O3 oxygen carrier for chemical looping with oxygen uncoupling

High redox reactivity as well as sufficient physical durability of the oxygen carrier (OC) is of critical importance for the successful implementation of chemical looping processes. In this work, CuO@TiO2-Al2O3 OC with hierarchical structure, which is a kind of CuO-rich, Al2O3-supported and TiO2-stablized ternary combined metal oxides system, was prepared by the self-assembly template combustion synthesis (SATCS) method. Performance of the rationally designed OC was cyclically tested with H2 in a thermogravimetric analyzer (TGA), as well as with coal in a batch fluidized bed reactor. TGA results showed that both the reduction and oxidation reactivity of the OC exhibited a reinforcing process during the first few cycles and then stabilized within the next dozens of cycles, and no obvious reactivity degradation phenomenon was observed. Reaction characteristics of the OC were further examined by reacting with coal in a fluidized bed reactor. Several critical performance indexes, like carbon conversion rate, oxygen release rate and combustion efficiency at different temperatures were calculated and compared. Mutual promotion relationship between carbon conversion rate of the coal and oxygen release rate of the OC was observed. Moreover, 20 cycles of redox process with anthracite were further conducted at 900°C to evaluate both the physical and chemical stability of the OC. Stable and high combustion efficiency (higher than 97.2%) was achieved during the cyclic fluidized bed test, and the subsequent physicochemical characterization indicated that neither CuAl2O4 phase was formed nor serious sintering problem occurred within the used OC samples. Thermo-mechanical analysis (TMA) results demonstrated relatively high transformation temperature of the OC, which explains well its superior anti-sintering property. All in all, the SATCS-derived CuO@TiO2-Al2O3 OC exhibited distinguished advantages of preventing the side reaction between CuO and Al2O3 to form copper aluminates as well as inhibiting the OC sintering, which could be a suitable OC candidate for commercial application in chemical looping with oxygen uncoupling (CLOU) processes.

Cement bonded fine hematite and copper ore particles as oxygen carrier in chemical looping combustion

In this work, bimetallic oxygen carriers (OCs) were prepared from waste fine particles (<0.1mm) of natural copper ore and hematite for possible application in chemical looping combustion (CLC) processes. The mixtures with different mass ratios of copper ore to hematite were physically bonded by 20wt% of calcium aluminate cement to obtain OC particles with relatively high disperse structure and good mechanical strength. Cyclic isothermal redox tests were first conducted in a thermogravimetric analyzer (TGA) to optimize the copper ore to hematite mixing ratio in the bimetallic OC. Synergistic effect between copper ore and hematite was observed, and the copper ore to hematite mixing ratio was optimized at 20:80 (namely Cu20Fe80@C) based on a comprehensive consideration of OC reactivity, economic cost and auto-thermal balance in fuel reactor. Subsequently, performance of Cu20Fe80@C and Fe100@C (cement bonded pure hematite) were further evaluated in a batch fluidized bed reactor, using coal as fuel. The Cu20Fe80@C was found to be more reactive towards coal gasification products than that of Fe100@C, which is mainly attributed to the synergistic effect attained by the coexistence of copper ore and hematite in the Cu20Fe80@C OC. Moreover, the effects of steam concentration, oxygen to fuel ratio and coal type on the performance of Cu20Fe80@C were investigated. It was found that both the increase of steam concentration and oxygen to fuel ratio can facilitate the coal conversion, but they are not the higher the better and should be balanced between coal conversion and operational cost when turning to industrial application. Lignite was more suitable to be converted by Cu20Fe80@C OC in iG-CLC process due to its better gasification reactivity than anthracite. 30 cyclic redox tests with lignite showed that Cu20Fe80@C exhibited superior redox reactivity, nice fluidization behavior and good anti-sintering property in fluidized bed tests. This work demonstrated that cement bonded fine particles of hematite and copper ore could be a promising and competitive OC candidate for industrial application in iG-CLC processes.

Development of (Mn0.77Fe0.23)2O3 particles as an oxygen carrier for coal combustion with CO2 capture via in-situ gasification chemical looping combustion (iG-CLC) aided by oxygen uncoupling (CLOU)

Chemical looping combustion (CLC) involves the use of a solid oxygen carrier to transport the oxygen from the air to a fuel. Attention has recently been focused on oxygen carriers based on Mn-Fe mixed oxides because they are cheap materials that are able to release oxygen at high temperature, the so-called oxygen uncoupling step. The aim of this work was to assess the use of (Mn0.77Fe0.23)2O3 material as an oxygen carrier with the ability to transport oxygen both by reduction with gaseous fuels and by oxygen uncoupling, i.e. typical mechanisms in CLC and in Chemical Looping with Oxygen Uncoupling (CLOU), respectively. The particles prepared by mechanical mixing were screened to obtain particles of sufficient reactivity and mechanical strength for use in a fluidized bed reactor. The preparation methodology and calcining temperature were varied. The reactivity of one selected material was evaluated by performing redox cycles both in a TGA and a batch fluidized-bed reactor. Thus, its behaviour was assessed during both decomposition-regeneration of bixbyite phase [(Mn0.77Fe0.23)2O3] in CLOU and the reduction-oxidation of spinel phase [(Mn0.77Fe0.23)3O4] with gaseous fuels, i.e. H2, CO and CH4. Its oxygen uncoupling and re-oxidation capability was highly influenced by the reaction temperature and oxygen concentration. On the other hand, CLC redox cycles with gaseous fuels showed high reactivity with H2 and CO and high oxygen transport capacity by reduction to mangano-wüstite phase [(Mn0.77Fe0.23)O]. Good fluid-dynamic behaviour was observed for the oxygen carrier particles along the redox cycles without agglomeration problems, regardless of the operating conditions used in the batch fluidized-bed reactor. Thus, the selected material was considered a promising candidate for use in both in CLC with syngas and CLC with coal.

Intracrystalline Mesoporosity over Y Zeolites: PASCA Evaluation of the Secondary Cracking Inhibition in the Catalytic Cracking of Hydrocarbons

Two FCC catalyst prototypes were prepared using Y zeolite with different intracrystalline mesoporosity, which were used in the cracking of n-hexadecane (batch fluidized bed reactor, reaction time 4 s, temperatures 500 and 550 °C, catalyst/reactant 2.6). The primary and secondary cracking analysis method (PASCA), based on balances of carbon atoms among cracking products, showed that increasing the mesoporosity in Y zeolite decreases the incidence of secondary cracking as compared to primary cracking, thus increasing the selectivity to intermediate products. This positive effect was the consequence of the improvements in the diffusion transport of primary product molecules which, in diffusing faster out of the pores, have fewer chances to suffer further cracking. The experiments at different temperatures, with both the prototypes and the equilibrium commercial FCC catalysts, confirmed that this method is a simple tool that allows characterizing the cracking performance of FCC catalysts under conditions simi...

Investigation of Two Hematites as Oxygen Carrier and Two Low-Rank Coals as Fuel in Chemical Looping Combustion

Chemical looping combustion (CLC) is a novel technique, which exhibits the merit of CO2 inherent separation and has been proposed as one of the most promising routes for CO2 capture and sequestration (CCS). The economically feasible and environmentally benign oxygen carrier (OC) is of critical importance for the successful implementation of CLC processes for industrial application. Natural iron ore, known as a kind of particularly cheap mineral material, has been verified as an appropriate OC candidate. However, there are differences among the iron ores with variable contents of active and inert phases, which may eventually result in diverse performance in CLC processes. In this work, CLC performance of hematite from Australia (AH) and China (CH) were systematically compared in a batch fluidized bed reactor, using two low-rank coals: Victorian brown coal (VC) from Australia and Inner Mongolia coal from China as fuels. The results showed that the maximum CO2 yield was 0.92 at 1000 °C under the match of CH ...

A twin-bed test reactor for characterization of calcium looping sorbents

The loss of sorbent CO2 capture capacity and the extent of particle attrition over iterated cycles are relevant to the design of calcium looping processes. Thermogravimetric analyzers or single batch fluidized bed reactors are typically used at the lab-scale to evaluate the sorbent performance. One drawback of these devices is that they do not reproduce the thermal history that is actually experienced by sorbent particles in real looping cycles. In this study, a novel experimental device is proposed to overcome this limitation. The apparatus consists of two interconnected batch fluidized bed reactors operating as calciner and carbonator, respectively. The two reactors are connected to each other by a duct (whose openings can be located at an adjustable level above the gas distributor) which permits rapid and complete pneumatic transport of the sorbent (limestone) between the reactors.Preliminary tests at ambient temperature were first performed to find the best operating conditions in terms of limestone conveying efficiency. Under the optimal experimental conditions >95% collection efficiency of the limestone was obtained.High-temperature tests were carried out to simulate multiple calcination/carbonation cycles. The results indicate that the device is able to effectively transfer the sorbent between the two reactors while keeping the temperature variations limited.The test reactor has been used to assess the effect of the thermal history of the limestone on its CO2 capture capacity and attrition tendency. The results were compared to those previously obtained with the same limestone under comparable operating conditions in a single bed apparatus. The comparison reveals that the thermal history experienced by the limestone has a non-negligible effect on its performance.

Experimental investigation and model validation of a CaO/Ca(OH)2 fluidized bed reactor for thermochemical energy storage applications

The CaO/Ca(OH)2 hydration/dehydration chemical loop has long been recognized as a potential candidate for application in energy storage systems for concentrated solar plants. However, the technology still remains at a conceptual level because little information has been published on the performance of the key reactors in the system. In this work, we experimentally investigate the hydration and dehydration reactors in a 5.5 kWth batch fluidized bed reactor, in conditions relevant to larger systems (superficial gas velocities of up to 0.53m/s, temperatures of up to 500°C for dehydration, input H2O(v) fractions between 0 and 0.8 etc.). Furthermore, to assist in the interpretation of the experimental results, a standard 1D bubbling reactor model has been formulated and fitted to the experimental results by including kinetic information at particle level independently measured in a thermogravimetric apparatus. The results indicate that the hydration reaction is mainly controlled by the slow kinetics of the CaO material tested while significant emulsion-bubble mass-transfer resistances were identified during dehydration due to the much faster dehydration kinetics.

Pyrolysis of biomass in a batch fluidized bed reactor: Effect of the pyrolysis conditions and the nature of the biomass on the physicochemical properties and the reactivity of char

This work was carried out in order to understand the effect of the pyrolysis operating conditions and the nature of the biomass on the physicochemical properties of the char and its reactivity toward the combustion. The chars were obtained by fast pyrolysis of two types of cylindrical wood particle (beech stick: diameter of 6mm, length of 10mm and beech bark pellet: diameter of 10mm, length of 15mm) under an inert atmosphere of nitrogen in a fluidized bed reactor for three different temperatures (450, 650 and 850°C) and at atmospheric pressure. The ultimate and FTIR analyses revealed that an increase in the pyrolysis temperature led to a raise of the carbon content and a decrease in the oxygen and hydrogen content. At high pyrolysis temperatures, Raman spectroscopy and XRD analyses showed that the char is more and more aromatic with a large size of the aromatic rings. The different chars prepared at a pyrolysis temperature of 850°C exhibited a true density close to the one of graphite. The reactivity of chars was studied by isothermal combustion at 400°C in TGA. The reactivity was found to be highly dependent on the pyrolysis temperature and the nature of the biomass. An increase in the pyrolysis temperature led to a decrease of the reactivity. Besides, char from fast pyrolysis of beech bark pellet is more reactive than char from fast pyrolysis of beech stick.

Use of Hopcalite-Derived Cu–Mn Mixed Oxide as Oxygen Carrier for Chemical Looping with Oxygen Uncoupling Process

An alternative to the chemical looping combustion process using solid fuels with CO2 capture is chemical looping with oxygen uncoupling (CLOU). The CLOU process requires an oxygen carrier with the capability to give gaseous O2 to burn solid fuels at the appropriate temperature, e.g., manganese oxide and copper oxide. In this work, treated commercial Carulite 300 was evaluated as oxygen carrier for CLOU. Carulite 300 is a hopcalite material composed of 29.2 wt % CuO and 67.4 wt % Mn2O3. The oxygen release rate and the fluidization behavior, with careful attention given to attrition rate and the behavior against agglomeration, were analyzed in a thermogravimetric analyzer and in batch fluidized bed reactors. Experiments in batch fluidized bed reactors were carried out at temperatures ranging from 800 to 930 °C with a medium volatile bituminous coal from South Africa and its char as fuels. The hopcalite-derived oxygen carrier showed high O2 release rate, no unburned products at low oxygen carrier–fuel mass r...

Manganese Minerals as Oxygen Carriers for Chemical Looping Combustion of Coal

In this paper, four different manganese minerals were tested in a batch fluidized bed reactor to evaluate their performance in the chemical looping combustion (CLC) of solid fuels. The char gasification rate in the experiments with the manganese minerals tested was higher than the corresponding values for ilmenite and iron ore, which were taken as benchmark materials. This phenomenon was attributed to the deposition of K, Na, and Ca from the manganese minerals on char particles so that they catalyzed char gasification. The char gasification rate observed using manganese minerals decreased with the number of cycles until a stable value was reached. Under these conditions, one of the materials presented higher char gasification rates than those observed for benchmark materials even when most of the K was already released. An estimation of the CO2 capture efficiency in a continuous unit using one of the selected manganese minerals showed that around 99% CO2 capture efficiency could be reached at 1000 °C with...

Investigation of Cu–Fe and Mn–Ni oxides as oxygen carriers for chemical-looping combustion

Combined Cu–Fe and Mn–Ni oxygen carriers were investigated as bed materials for chemical-looping combustion. The aim was to identify material combinations which yield oxygen carriers with a high reactivity towards gaseous fuels, such as CO, H2 and CH4, as well as sufficient mechanical durability. For this purpose, 18 different oxygen carriers were spray-dried and calcined at defined temperatures.Gas conversion as well as release of gaseous oxygen was investigated in a batch fluidized bed reactor setup at temperatures between 850 and 1050°C. For testing the mechanical durability, a jet-cup attrition rig was used. Moreover, properties like specific surface area, oxygen transfer capacity and crystalline phase composition were examined to physically and chemically characterize the oxygen carrier particles.For both the Cu–Fe and Mn–Ni-based materials, oxygen carriers could be produced which showed a high reactivity with gaseous fuels like CO or CH4 while having a sufficiently high mechanical strength. These properties make them interesting candidates for application in chemical-looping combustion.