Suchergebnisse

13 páginas,8 figuras.-Available online 12 August 2013 ; The chemical looping combustion of solid fuels by in situ gasification (i G-CLC) has great potential to reduce the economical and energetic cost of CO2 capture for generating energy from coal. Previous studies have highlighted that a high CO2 capture rate can be reached, but incomplete combustion is predicted by theoretical models or obtained during experimental work. In this paper, a mathematical model for the fuel reactor and carbon stripper, validated through experimental results, is adapted to evaluate the relevance of several technological improvements in order to increase the combustion efficiency of the iG-CLC process. The technological options evaluated include increasing the gas–solid contact in the fuel reactor, incorporating a secondary fuel reactor, re-circulating exhaust gases to the fuel reactor or the carbon stripper, or feeding coal into the carbon stripper instead in the fuel reactor. Model simulations showed that the use of a secondary fuel reactor has the major impact by reducing the unburnt compounds in the CO2 stream. The origin of the unburnt compounds is determined from a thorough analysis of the results obtained during the evaluation of these technological options. Thus, a new arrangement of the iG-CLC reactors is proposed, one which would minimise the presence of unburnt compounds. In this concept, exhaust gases from the fuel reactor are sent to the carbon stripper. The oxygen demand for this concept is predicted to be XT= 0.9%. 2013 Elsevier B.V. All rights reserved. ; This paper was partially supported by the European Commission, under the RFCS program (ACCLAIM Project, Contract RFCP-CT-2012-00006), the Government of Aragon and La Caixa (2012-GA-LC-076 project) and the Spanish Ministry for Science and Innovation via the ENE2010-19550 project. ; Peer reviewed

6 pages, 5 figures, 4 tables.--Published on Web 07/20/2007 ; Waste management generated from a Chemical-Looping Combustion (CLC) plant using copper-based materials is analyzed by two ways: the recovery and recycling of the used material and the disposal of the waste. A copper recovery process coupled to the CLC plant is proposed to avoid the loss of active material generated by elutriation from the system. Solid residues obtained from a 10 kWth CLC prototype operated during 100 h with a CUO-Al2O3 oxygen carrier prepared by impregnation were used as raw material in the recovery process. Recovering efficiencies of ∼80% were obtained in the process, where the final products were an eluate of Cu(NO3) 2 and a solid. The eluate was used for preparation of new oxygen carriers by impregnation, which exhibited high reactivity for reduction and oxidation reactions as well as adequate physical and chemical properties to be used in a CLC plant. The proposed recovery process largely decreases the amount of natural resources (Cu and Al2O3) employed in a CLC power plant as well as the waste generated in the process. To determine the stability of the different solid streams during deposition in a landfill, these were characterized with respect to their leaching behavior according to the European Union normative. The solid residue finally obtained in the CLC plant coupled to the recovery process (composed by Al2O3 and CuAl2O4) can be classified as a stable nonreactive hazardous waste acceptable at landfills for nonhazardous wastes. © 2007 American Chemical Society. ; This research was carried out with financial support from the Spanish Ministry of Education and Science (Projects PPQ-2001-2111, CTQ-2004-04034) and from the Diputación General de Aragón (Project PIP023/2005). C.R.F. thanks UNIZAR-BSCH for the predoctoral fellowship. ; Peer Reviewed

The integrated use of low-value hydrocarbons from the refining of crude oil under Chemical Looping Combustion (CLC) conditions can satisfy the demands of heat and steam of the refining process itself while at the same time reducing CO2 emissions up to 50% in oil refineries. This work evaluated the use of three different fossil liquid fuels, i.e., diesel, mineral lubricant oil and synthetic lubricant oil in a 1 kWth CLC unit working with a Fe-based oxygen carrier prepared by impregnation method. The effect of key parameters of the CLC process was studied with the same batch of oxygen carrier particles for a total of 150 operation hours. With regard to the results obtained, every fuel tested was able to achieve 90% combustion efficiency being synthetic lubricant oil the most reactive fuel studied. Hydrocarbon reactivity seems to depend on the nature of the chemical bonds, being higher for alkenes (synthetic lubricant oil) than for alkanes (diesel and mineral lubricant oil). CH4 was revealed as a relatively stable intermediate combustion product for these liquid fuels. Therefore, oxygen carrier's reactivity towards this gas becomes crucial for the overall conversion. The characterization carried out to the oxygen carrier after operation revealed no evidence of changes derived from the sulphur or impurities present in the fuel. Therefore, the Fe-based material herein used seems to be suitable for conversion of fossil liquid fuels. ; This work is supported by the Spanish Ministry for Science and Innovation (MICINN project ENE2011-26354), by the European Regional Development (ERDF), and by the Government of Aragón (Spain, DGA ref. T06). A Serrano thanks the Spanish Ministry of Economy and Competitiveness for the F.P.I fellowship. ; Peer reviewed

1 figura.-- Resumen de la comunicación oral presentada en la XV Reunión del Grupo Español del Carbón, 24-27 abril 2022, Granada (España).-- O69.-- D.L. GR 695-2022 ; Una de las opciones más relevantes para la reducción de emisiones de gases de efecto invernadero (GEI) en el sector del transporte es la producción de bio-combustibles sintéticos a partir de gas de síntesis. El proceso Biomass Chemical Looping Gasification (BCLG) es una prometedora opción para producir gas de síntesis de alta calidad mediante la gasificación de biomasa sin emisiones de CO2. En el proceso BCLG un transportador sólido de oxígeno (TO) circula entre dos reactores de lecho fluidizado interconectados, reactor de combustible (RC) y reactor de aire (RA), proporcionanado el oxígeno y el calor necesario para llevar a cabo la oxidación parcial de la biomasa obteniendo un gas de síntesis libre de nitrógeno bajo condiciones autotérmicas. En el RC se produce la gasificación de la biomasa y la combustión parcial de los gases producto con los sólidos, mientras que en el RA se regenera el TO en atmósfera de aire. El objetivo de este trabajo es investigar el efecto de las principales variables operacionales sobre el comportamiento y el rendimiento a gas de síntesis del proceso BCLG en una unidad en continuo de 50 kWt, utilizando ilmenita como TO. ; Este trabajo ha sido financiado por el Proyecto CLARA de Horizon 2020 European Union funding for Research & Invitation y por el AEI/FEDER, UE-ENE2017-89473R. ; Peer reviewed

12 figures.-- This article is part of the 2021 Pioneers in Energy Research: Javier Bilbao special issue. ; Biomass chemical looping gasification (BCLG) uses lattice oxygen from an oxygen carrier instead of gaseous oxygen for high-quality syngas production without CO2 emissions. In this work, the effect of the main operating variables, such as oxygen/biomass ratio (λ), gasification temperature, and steam/biomass ratio (S/B), was investigated using two low-cost materials: a Fe ore and a Mn ore. Oxygen fed to the air reactor for oxidation was used as an effective method for controlling the amount of lattice oxygen used for syngas production. The main variable that affected the process performance and the syngas quality was λ, while the fuel reactor temperature and the S/B ratio had a minor effect. Small performance differences found between the ores can be attributed to different degrees of CH4 and light hydrocarbons reforming in the process. The CO2 content in the syngas was high (40 −43%) under autothermal conditions because the gasification reactions required the heat to be generated by combustion. CH4 contents of around 10% were found in syngas, coming from the unburned or unreformed volatiles. Syngas yields around 0.60 Nm3/kg of dry biomass were found for both ores. Additionally, high biomass conversions (Xb > 94%) and carbon conversion efficiencies (ηcc > 95%) were obtained in all cases, showing the capability of the process of avoiding CO2 emissions to the atmosphere. No agglomeration was found in the bed during the BCLG process, although attrition rates were high, leading to lifetimes of 160 and 300 h for the manganese and iron ores, respectively. Migration of Fe or Mn to the external part of the particle, generating a metal concentrated shell, was observed. Its detachment was responsible for the decrease in the oxygen transport capacity (ROC) of the material with the operating time and the reduced lifetime. The results obtained here allowed the iron ore to be considered as an oxygen carrier suitable for the BCLG process. ; This work has been supported by the European Union's Horizon 2020 Research and Innovation Framework Programme under grant Agreement 817841 [Chemical Looping Gasification for Sustainable Production of Biofuels (CLARA)] and the AEI/FEDER, UE (ENE2017-89473R). ; Peer reviewed

12 figures, 3 tables. ; Biomass Chemical Looping Gasification (BCLG) is an autothermic gasification process that provides pure syngas for many applications, including liquid biofuels production. Finding low-cost materials that can be used in the process is a key issue, especially when they come from waste. In this sense, LD Slag is a by-product of the steel industry used as an oxygen carrier in Chemical Looping Combustion with good results. This work investigates the use of LD Slag as oxygen carrier in a continuous 1.5 kW BCLG unit. The effect of the main operational variables (temperature, oxygen-to-fuel and steam-to-biomass ratios) and the use of CO instead of steam as gasification agent were analysed. LD slag allowed the process with high biomass conversions, X > 90%, carbon conversion efficiencies, η > 90%, and syngas yields, Y ≈ 0.66 Nm/kg of dry biomass, at conditions corresponding to autothermal operation. A lifetime of 300 h under reducing conditions was inferred and agglomeration problems were never detected. LD slag can be considered a suitable material for BCLG since it is possible to obtain high-quality syngas at autothermal conditions from different types of biomass with low tar generation and CO emissions. ; This work has been supported by the European Union's Horizon 2020-Research and Innovation Framework Programme under grant agreement No 817841 (Chemical Looping gAsification foR sustainable production of biofuels - CLARA), and by the AEI/FEDER, UE - ENE2017-89473-R.

The integrated use of low-value hydrocarbons from the refining of crude oil under Chemical Looping Combustion (CLC) conditions can satisfy the demands of heat and steam of the refining process itself while at the same time reducing CO2 emissions up to 50% in oil refineries. This work evaluated the use of three different fossil liquid fuels, i.e., diesel, mineral lubricant oil and synthetic lubricant oil in a 1 kWth CLC continuous unit working with a Fe-based oxygen carrier prepared by impregnation method. The effect of key parameters of the CLC process behavior was studied with the same batch of oxygen carrier particles for a total of 150 operation hours. With regard to the results obtained, every fuel tested was able to achieve 90% combustion efficiency being synthetic lubricant oil the most reactive fuel studied. Hydrocarbon reactivity seems to depend on the nature of the chemical bonds, being higher for alkenes (synthetic lubricant oil) than for alkanes (diesel and mineral lubricant oil). CH4 was revealed as a relatively stable intermediate combustion product for these liquid fuels. Therefore, oxygen carrier's reactivity towards this gas becomes crucial for the overall conversion. The characterization carried out to the oxygen carrier after operation revealed no evidence of changes derived from the sulphur or impurities present in the fuel. Therefore, the Fe-based material herein used seems to be suitable for conversion of fossil liquid fuels. ; This work is partially supported by the Spanish Ministry for Science and Innovation (MICINN project ENE2011-26354), by European Regional Development (ERDF), and by the Government of Aragón (Spain, DGA ref. T06). A Serrano thanks the Spanish Ministry of Economy and Competitiveness for the F.P.I fellowship. ; Peer reviewed

The kinetic of reduction of CuO to Cu2O with N2+O2 mixtures and the oxidation of Cu2O to CuO with O2 of a Cu-based oxygen carrier for the CLOU process has been determined in a TGA. For kinetic determination, the O2 concentrations were varied between 0 and 9 vol.% for reduction, and between 21 and 1.5 vol.% for oxidation reactions; temperature was varied between 1148 and 1273 K for the reduction and between 1123 and 1273 K for the oxidation. The oxygen carrier showed high reactivity both in oxidation and reduction reactions. The nucleation and nuclei growth model with chemical reaction control properly described the evolution of solids conversion with time. The Langmuir-Hinshelwood model was able to describe the effect of oxygen concentration on reduction and oxidation rates. The reaction order was 0.5 for reduction and 1.2 for the oxidation. The kinetic constant activation energies were 270 kJ mol-1 for the reduction and 32 kJ mol-1 for the oxidation. The kinetic model was used to calculate the solids inventory needed in the fuel reactor for complete combustion of three different rank coals. It was possible to use a low oxygen carrier inventory in the fuel reactor (160 kg/MWth) to supply the oxygen required to full lignite combustion. However, to reach high CO2 capture efficiencies (³95%), oxygen carrier inventories in fuel reactor higher than 600 kg/MWth were needed with the lignite. ; This work was supported by the European Commission, under the RFCS program (ACCLAIM Project, Contract RFCP-CT-2012-00006), the Spanish Ministry of Science and Innovation (MICINN Project: ENE2011-26354) and the European Union FEDER Funds. I. Adánez-Rubio thanks CSIC for the JAE fellowship co-financed by the European Social Fund. ; Peer reviewed

8 pages, 2 figures, 2 tbles.-Available online 3 July 2013 ; The Chemical Looping with Oxygen Uncoupling (CLOU) process is a type of Chemical Looping Combustion (CLC) technology that allows the combustion of solid fuels with air, as with conventional combustion, through the use of oxygen carriers that release gaseous oxygen inside the fuel reactor. The aim of this work was to study the behaviour of the sulphur present in fuel during CLOU combustion. Experiments using lignite as fuel were carried out in a continuously operated 1.5kWth CLOU unit during more than 15h. Particles containing 60wt.% CuO on MgAl2O4, prepared by spray drying, were used as the oxygen carrier in the CLOU process. The temperature in the fuel reactor varied between 900 and 935°C. CO2 capture, combustion efficiency and the sulphur split between fuel and air reactor streams in the process were analysed. Complete combustion of the fuel to CO2 and H2O was found in all experiments. Most of the sulphur introduced with the fuel exited as SO2 at the fuel reactor outlet, although a small amount of SO2 was measured at the air reactor outlet. The SO2 concentration in the air reactor exit flow decreased as the temperature in the fuel reactor increased. A carbon capture efficiency of 97.6% was achieved at 935°C, with 87.9wt.% of the total sulphur exiting as SO2 in the fuel reactor. Both the reactivity and oxygen transport capacity of the oxygen carrier were unaffected during operation with a high sulphur content fuel, and agglomeration problems did not occur. Predictions were calculated regarding the use of a carbon separation system in the CLOU process in order to reduce sulphur emissions. Coals with high sulphur content, such as lignite and anthracite, would require a carbon separation system in order to comply with legislation governing sulphur-limits. In conclusion, coals with a high sulphur content can be burnt in a CLOU process using Cu-based material to obtain high carbon capture efficiencies. © 2013 Elsevier Ltd. ; This work was carried out with financial support from the European Commission, under the RFCS programme (ECLAIR Project, Contract RFCP-CT-2008-0008), ALSTOM Power Boilers (France), the Spanish Ministry of Science and Innovation (PN, ENE2010- 19550), and Government of Aragón and La Caixa (Project 2012- GA-LC-076). I. Adánez-Rubio thanks CSIC for the JAE fellowship co-financed by the European Social Fund. ; Peer Reviewed

Autothermal Chemical-Looping Reforming (a-CLR) is a process which allows hydrogen production avoiding the environmental penalty of CO2 emission typically produced in other processes. The major advantage of this technology is that the heat needed for syngas production is generated by the process itself. This heat necessary for the endothermic reactions is supplied by a Ni-based oxygen-carrier (OC) circulating between two reactors: the air reactor (AR), where the OC is oxidized by air, and the fuel reactor (FR), where the fuel is converted to syngas. Other important advantage is that this process also allows the production of pure N2 in the AR outlet stream. A renewable fuel such as bioethanol was chosen in this work due to their increasing worldwide production and the current excess of this fuel presented by different countries. In this work, mass and heat balances were done to determine the auto-thermal conditions that maximize H2 production, assuming that the product gas was in thermodynamic equilibrium. Three different types of bioethanol has been considered according to their ethanol purity; Dehydrated ethanol (≈100 vol.%), hydrated ethanol (≈96 vol.%), and diluted ethanol (≈52 vol.%). It has been observed that the higher H2 production (4.62 mol of H2 per mol of EtOH) has been obtained with the use of diluted ethanol and the surplus energy needed could be compensated by the energy save achieved during the purification of ethanol in the production process. ; This work is partially supported by the Spanish Ministry for Science and Innovation (MICINN project ENE2011-26354), by European Regional Development Fund (ERDF), by the Government of Aragón (Spain, DGA ref. T06) and by CTGAS-ER (project OTT20130989). ; Peer reviewed

Oil refining processes demand and use vast quantities of energy and thus are responsible for the emission of a great deal of CO2. In addition, hydrogen is used in oil refineries for hydrodesulfurization and hydrocraking processes. In this sense, the integration of Chemical Looping technology in an oil refinery using vacuum residues as fuel could drive to significant reductions in CO2 emissions. In this work, Chemical Looping Combustion (CLC) and Chemical Looping Reforming (CLR) experiments have been carried out in a continuously operated 1 kWth unit using a Cu- and Ni-based oxygen carrier, respectively. Diesel, synthetic and mineral lubricant oil were used as fuels as a previous step to the use of low grade residues. Regarding Chemical Looping Combustion conditions, almost 100% of combustion efficiency and full carbon capture were obtained at low oxygen carrier-to-fuel molar ratios (ϕ≥1.6). Regarding Chemical Looping Reforming conditions, a syngas containing a H2 concentration over 50 vol.% in dry basis was obtained with the additional advantage of reaching 100% CO2 capture efficiency in the process. In all cases, syngas composition obtained was close to the given by the thermodynamic equilibrium. These results provide a basis for concluding that the integration of Chemical Looping processes for heat/steam and hydrogen production in an oil refinery is feasible and could lead to significant environmental advantages. ; This work was partially supported by the Spanish Ministry for Science and Innovation (MICINN, project ENE2011-26354, ENE2014-56857-R), European Regional Development Fund (ERDF) and by the Government of Aragón (Spain, DGA ref. T06). A. Serrano also thanks the Spanish Ministry of Economy and Competitiveness for the F.P.I. fellowship. ; Peer reviewed

Chemical-Looping with Oxygen Uncoupling (CLOU) is an alternative Chemical Looping process for the combustion of solid fuels with inherent CO2 capture. The CLOU process needs a material as oxygen carrier with the ability to give gaseous O2 at suitable temperatures for solid fuel combustion, e.g. copper oxide and manganese 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. Oxygen release rate and the fluidization behavior, regarding agglomeration and attrition rate, were analyzed in a TGA and in a batch fluidized bed respectively. Experiments in a batch fluidized bed reactor were carried out at temperatures ranging from 800 to 930 ºC 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 unburnt products at low oxygen carrier to fuel mass ratios and very high oxygen transference rate by gas-solid reaction. This material has the capacity to generate gaseous oxygen at lower temperatures than Cu-based oxygen carriers, which suggest this material is suitable to work at lower temperatures in the fuel reactor without the presence of unburnt products; however its low mechanical resistance after redox cycles makes necessary an improvement of its physical properties for being use as an oxygen carrier. ; This work was partially supported by the Spanish Ministry of Economy and Competitiveness (MINECO Project: ENE2013- 45454-R) and the European Union FEDER funds. Special thanks to Carus Corporation (Illinois, EEUU) for suppling the Carulite 300 material. ; Peer reviewed

The use of mineral materials as oxygen carriers for Chemical Looping Combustion (CLC) is an attractive option due to their low cost. This paper reports an experimental study of four manganese minerals as potential oxygen carriers focusing on the behavior in CLC as well as in Chemical Looping with Oxygen Uncoupling (CLOU). Experiments were carried out in a thermogravimetric apparatus (TGA) and a fluidized-bed reactor. Repeated tests with all the minerals showed no sufficient CLOU properties. Then, they can only be used in CLC applications involving the redox pairs Mn3O4/MnO and Fe2O3/Fe3O4. Oxygen transport capacity and reactivity to the main fuel gases (H2, CO, and CH4) were determined in a TGA. Manganese minerals were also tested during 35–54 h in a fluidized-bed reactor to evaluate the evolution of reactivity to H2, CO, and CH4 as well as their attrition rate and mechanical strength. The reactivity of the materials decreased in the first 10 cycles with CH4 and then became quite stable for the rest of the cycles performed with CH4, CO, and H2. In comparison to previously tested Fe-based minerals, lower reactivity with CH4 was found for the manganese minerals. However, in terms of CO and H2 combustion, their reactivity was adequately high. During the tests, agglomeration and defluidization were never found for any material. Mechanical crushing strength of the particles decreased with cycles, which led to the increase of attrition rate of some materials above acceptable levels. Nevertheless, materials with adequate crushing strength and low attrition were identified. Combining the reactivity and attrition resistance, the manganese minerals MnSA and MnGBHNE from South Africa and Gabon, respectively, can be suggested as promising materials for CLC with coal. ; This work was supported by the Spanish Ministry of Economy and Competitiveness (project ENE 2013-45454-R), by the European Regional Development Fund (ERDF), by the CSIC (project 2014-80E101) and by the Government of Aragón (Spain, Ref. T06). T. Mendiara thanks for the ''Ramón y Cajal'' post-doctoral contract awarded by the Spanish Ministry of Economy and Competitiveness. D. Mei is grateful for the support provided by the China Scholarship Council (CSC201306160054). The authors also thank Hidro Nitro Española S.A. for providing MnSA and MnGBHNE materials and Leopoldo Alcázar (CT-GAS) for providing the MnBR material. ; Peer reviewed

In the in situ Gasification Chemical Looping Combustion of coal (iG-CLC), the fuel is gasified in situ in the fuel reactor and gasification products are converted to CO2 and H2O by reaction with the oxygen carrier. This work is the first study on mercury release in Chemical Looping Combustion of coal. The fraction of the mercury in coal vaporized in the fuel reactor depended mainly on the fuel reactor temperature and the coal type. In the fuel reactor, mercury was mainly emitted as Hg0 in the gas phase and the amount increased with the temperature. In the air reactor, mercury was mostly emitted as Hg2+. In a real CLC system, mercury emissions to the atmosphere will decrease compared to conventional combustion as only mercury released in the air reactor will reach the atmosphere. However, measures should be taken to reduce Hg0 in the CO2 stream before the purification and compression steps in order to avoid operational problems. ; The authors thank the Government of Aragón and La Caixa (2012-GA-LC-076 project) and the Spanish Ministry for Science and Innovation (ENE2010-19550 project) for the financial support. P. Gayán thanks CSIC for the financial support of the project 201180E102. The authors also thank to Alcoa Europe-Alúmina Española S.A. for providing the Fe-enriched sand fraction used in this work. G. Galo is acknowledged for his contribution to the experimental results. ; Peer reviewed

The recently developed Chemical Looping Combustion technology (CLC) is nowadays considered an interesting option to capture CO2 at low cost in fossil fuelled power plants. In the past years, significant advances have been achieved in the combustion of both gaseous and solid fuels. Nevertheless, pollutant gas emissions from CLC systems have received little attention. This paper focuses on sulphur, nitrogen and mercury emissions during lignite combustion in a 500Wth CLC unit. Ilmenite was used as oxygen carrier, as it is one of the most common materials used for CLC of solid fuels. The main sulphur species detected in the fuel reactor were H2S and SO2. The amount and proportion depended on the temperature of the fuel reactor. The higher the temperature, the more H2S converted to SO2. In the air reactor, the sulphur in the unconverted char was released as SO2. Regarding the emission of nitrogen in coal, most of the nitrogen was found as N2 at the outlet of the fuel reactor. No NH3 or HCN were registered and only small amounts of NO were detected. The nitrogen contained in the char reaching the air reactor was released as NO. Mercury speciation was also analyzed and the ratio Hg2+/Hg0 determined. In the fuel reactor, the major mercury species was Hg0 and in the air reactor Hg2+. The incorporation of a carbon separation unit between fuel and air reactors would help to reduce the sulphur emissions in the air reactor and comply with the current legislation for power generation systems. © 2014 Elsevier Ltd. ; The authors thank the Government of Aragón and La Caixa (2012-GA-LC-076 project) and the Spanish Ministry for Science and Innovation (ENE2010-19550 project) for the financial support. T. Mendiara thanks for the "Juan de la Cierva" post-doctoral contract awarded by this Ministry. This work was also partially supported by the European Commission, under the RFCS program (ACCLAIM Project, Contract RFCP-CT-2012-40 ; Peer Reviewed