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International audience; Chemical looping combustion (CLC) technology has emerged as one of the most important clean fossil fuel combustion technologies, because it allows for sequestration of CO2 with a minimal increase in energy requirements and fuel demand in comparison to traditional plants. In the framework of the Chinese–European Emission-Reducing Solutions project, the core technology of the CLC process is being developed in a 3 MWth system prototype for demonstration in an operational environment using petcoke as fuel. One of the main objectives is the selection of the oxygen carrier because it will impact the design and sizing of the demonstration unit as well as the nominal power of the unit. Two minerals, ilmenite T1 and LY Mn ore, with high potential for a well-performing oxygen carrier were tested in a 10 kWth continuous pilot unit. The collected fines were analyzed by scanning electron microscopy and X-ray fluorescence analysis to characterize the compositional and morphological evolution of the particles during operation. The performance of both oxygen carriers was compared with respect to solid fuel conversion, capacity for oxygen transfer, and particle lifetime in continuous circulation. A higher methane conversion can be obtained using ilmenite, while LY Mn is better at converting petcoke. Where the reduction potential of oxygen carriers is concerned, it was observed that LY Mn ore has a high initial R0ΔX value (R0ΔX = 0.8), which leads to a shorter activation period in comparison to ilmenite T1, which requires a longer activation period to reach its full potential. LY Mn ore is however more sensitive to attrition than ilmenite, under similar operating conditions, which is a critical characteristic for large-scale deployment. Finally, key operating parameters were identified for large-scale unit operation, including fuel reactor temperature, oxygen carrier flow rate, and fuel flow rate.

16 figures, 2 tables.-- Supporting information available., The iron and titanium oxide ilmenite is a benchmark oxygen carrier for chemical looping combustion (CLC) and oxygen carrier-aided combustion (OCAC). Both of them are combustion technologies for biomass and waste fuels with lower emissions and low costs for carbon capture. Here, the interaction between the ash component zinc and oxygen carrier ilmenite is studied in a two-staged vertical tube reactor. Three types of ilmenites─Norwegian rock ilmenite, synthesized ilmenite, and ilmenite extracted after 200 h of OCAC in a full-scale fluidized bed unit─were exposed to gas-phase Zn and ZnCl2. Following the exposure, samples were analyzed concerning morphology, chemical distribution, composition, and crystalline phases. The observations were complemented with thermodynamic equilibrium calculations. It is observed that the iron-rich layer formed on the external surface of rock ilmenite after activation promotes the reaction with both gaseous zinc compounds, with zinc ferrite formed in the external Fe-rich layer. In contrast, ilmenite with no segregation of Fe and Ti showed to interact less with zinc species. Metallic Zn penetrated the particles, while the interaction depth was shallow with ZnCl2 for all investigated ilmenite oxygen carriers. The gaseous conditions, particle ash layer composition, and iron availability are shown to play an important role in the interaction between zinc compounds and ilmenite particles. Based on these results, interaction mechanisms for Zn and ZnCl2 are proposed. This interaction could have environmental implications for the toxicity of ash streams from waste combustion in addition to possibilities for Zn recycling., This work was financed by the Swedish Research Council (2016-06023 and 2020-03487), Technical University of Denmark, Sino-Danish Center for Education and Research, and by Nordic Energy Research (project: NEST─Nordic Network in Solid Fuels towards Future Energy Systems, 120626). I. Adánez-Rubio acknowledges “Juan de la Cierva” Program (Grant IJC2019-038987-I funded by MCIN/AEI/10.13039/501100011033).

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).

As far as biodiesel economy and hydrogen production are concerned, steam reforming of glycerol, which is the main byproduct of the biodiesel plants, is an appealing policy. Despite hydrogen abundan...

In this study, Cu–Fe bimetallic oxygen carriers (OCs) were prepared by the impregnation method based on SiO2, Al2O3, or hematite supports and the characteristics of manufactured OCs were investigat...

The distribution characteristics of 17 toxic polychlorinated dibenzodioxin/furan (PCDD/F) isomers are closely related to their toxic equivalents, and hence, knowing the transformation and contribut...

In chemical looping combustion (CLC), oxidation of a reduced oxygen carrier with air occurs in the air reactor and some of the oxygen carrier separated by a cyclone is returned to the air reactor f...

Temperature showed obvious effect on the reaction rate and conversion when CuO was used as an oxygen carrier (OC), in which in situ gasification chemical-looping combustion (iG-CLC) occurred at low...

Chemical looping hydrogen (CLH) production, or hydrogen production combined with CO2 capture, is becoming an emerging alternative technology that has attracted much attention. Iron-based oxygen car...

Because of the low cost and easy availability, iron oxides have been widely used in chemical looping combustion. However, pure iron oxides often suffered from a loss of oxygen carrying capacity in ...

The global market size for acetic acid is expected to increase at a high compounded annual growth rate over the next few years due to an increased demand from the end-users such as the automobile, ...

Chemical looping ammonia generation (CLAG) is thought to be another method for clean utilization of fossil fuels, because fossil fuels can be thoroughly converted into chemical material, CO, and no...

A power system with chemical looping combustion (CLC) has been an effective method to realize efficient energy conversion and CO2 capture with zero energy penalty. Over the past 30 years, CLC power...

The numerical studies are carried out for investigating the performance of the 3D methanation reactor with poly-dispersed solids. The catalyst system comprises particles with different diameter. Th...

Product distribution and kinetic analysis of lignin were investigated during the chemical looping with oxygen uncoupling (CLOU) process. Thermodynamic simulation of the CLOU process was performed o...

Chemical looping is a promising combustion technology utilizing the cyclic oxidation and reduction of a metal oxide to transport oxygen for a variety of applications related to carbon capture and s...

Heterogeneous reduction/oxidation reactions in fluidization state play vital roles in chemical looping combustion (CLC) processes. A key task in studying heterogeneous reduction/oxidation reactions...

Oxygen carriers (OCs) are the key factor in chemical looping combustion (CLC), a promising and efficient technology for converting coal and biomass into pure carbon dioxide and high concentrations ...

CeO2 is a typical fluorite oxide with desirable lattice oxygen conductivity and can be applied as an active support for the Fe-based oxygen carrier in chemical looping hydrogen generation (CLHG). H...

Because the CO2 capture is inherent in chemical looping combustion (CLC), thus ideally avoiding costly gas separation, this process has potential for uniquely low costs of CO2 capture. The review reports on operational experiences with different oxygen carriers in CLC pilot operation. Further, the application to solid fuels is discussed in terms of technology challenges, routes for upscaling to commercial size, downstream gas treatment, options for achieving adequate circulation, and the use of biofuels in CLC to reach negative emissions. It is concluded that the necessary elements for a scale-up are at hand. Oxygen carrier materials of low cost have been tested in extended operation and found to have reasonable performance with respect to reactivity and lifetime. Designs for large-scale units have been performed, indicating that the process is technically realistic and should have a low cost of CO2 capture. A scale-up strategy to minimize risk and costs has been suggested.

Biomass chemical looping gasification (BCLG) is a novel and promising technology for syngas production, in which lattice oxygen in oxygen carriers (OCs) reacts with biomass. OCs can continuously su...

Chemical looping dry reforming of methane is an attractive approach to use carbon dioxide and methane, the two most abundant greenhouse gases. For this scheme, the redox material (or oxygen carrier...

Chemical looping combustion (CLC) can achieve the benefits of efficient conversion of hydrocarbon fuels and zero-energy CO2 capture using oxygen carriers (OC) with facilitated oxygen transport prop...

Spray drying has gradually become an effective method for large-scale preparation of oxygen carriers due to its unique advantages (high efficiency, scalable production, etc.). However, expensive ch...

Controlling carbon emissions is an effective way to mitigate the greenhouse effect. According to the primary energy consumption of China, chemical looping combustion (CLC) using coal as the fuel ha...

In this work, Fe6Al4Ca1 composite oxygen carriers were prepared using the impregnation method with Fe2O3 as the active component, Al2O3 as the inert support and CaO as the modifier. The oxygen carr...

ZhunDong (ZD) coal is one of the abundant and promising coal fuel sources. An alternative technology for ZD coal is vital due to the high sodium content. Hematite-based chemical looping combustion ...

Chemical looping ammonia synthesis (CLAS) is proposed as a novel, milder, and environmentally friendly method for NH3 production. In the CLAS process, a looped metal nitride, with the ability to tr...

Chemical looping combustion (CLC) has emerged as an efficient and promising combustion technique for fossil fuels during the past few decades. The main advantages of CLC lie in its inherent CO2 seq...

Resource utilization of the disposed CaSO4 waste as an oxygen carrier (OC) in chemical looping combustion (CLC) is of great meaning as a result of its attractive strengths, such as easy availabilit...

Cu-based materials have been regarded as suitable oxygen carrier (OC) candidates in chemical looping combustion as a result of their high reactivity. Because Cu is a common reduction product in the...

Under high-pressure conditions, coal chemical looping gasification (CLG) is a potential technology for industrial applications based on its ability to provide clean and efficient conversion of coal...

Iron-based oxides are promising oxygen carriers for chemical looping syngas production from methane; however, facile coke formation over reduced metallic Fe0 largely limits the syngas productivity....

NiFe2O4 exhibits a desirable application prospect in chemical looping process because of the high redox activity and oxygen carrying capacity. However, phase segregation resulting from the outward ...

Chemical looping technology enables achievement of the simultaneous feedstock conversion and product separation without additional processes via circulating solid intermediates (so-called oxygen/ni...

Decreasing the reduction temperature of an oxygen carrier is the key to reduce energy consumption further and avoid the operational difficulties of chemical looping air separation (CLAS). The coppe...

Syngas production is highly critical to the manufacturing of many value-added products, and its economic prospects can be increased through the enhancement of fuel conversion and the syngas yield. ...

The aim of this study was to investigate the effect of torrefaction severity and ratio of oxygen carrier to feedstock on syngas production and tar removal during chemical looping gasification of eu...

As CO2 emission is one of the most critical issues that causes global warming, methods have been developed for carbon capture and storage. Chemical looping combustion (CLC) and chemical looping oxy...

To increase the oxygen concentration in the product gas of a chemical looping air separation (CLAS) system, it is important to reduce the oxygen uncoupling temperature of the oxygen carrier (OC). In this paper, it is investigated whether and to what extent the addition of Mn2O3, Co3O4, Pb3O4, and Cr2O3, all of which have oxygen uncoupling propensity according to thermodynamics, to CuO improves the oxygen uncoupling behavior of the mixed-oxide OC at lower temperatures. Using thermogravimetric analyses, it is shown that the oxygen uncoupling temperature of a Cu-Mn composite OC is decreased by approximately 200 °C relative to a Cu OC. In addition, the oxygen transport capacity of this composite OC can reach up to 0.056 g O2/g OC. Density functional theory calculations have been carried out to analyze the changes in reactivity and stability of the mixed-oxide OC. When a Mn3O4(001) surface adsorbs a Cu4O4 cluster, the average bond length of Cu-O in the Cu4O4 cluster increases from 1.983 to 2.047 Å and the charge is transferred from Cu4O4 to Mn3O4(001). Chemical reaction between the cluster and the surface occurs, and Cu-Mn composite oxides are formed after adsorption. Moreover, the adsorption energy is -3.749 eV, which is higher than that of Cu4O4 on a CuO(111) surface (-2.92 eV), and the composite OC has better stability and sintering resistance than the Cu OC. The stability of the composite OC was also investigated at 900 °C under reducing conditions and at 700 °C under oxidizing conditions. The results show that the Cu-Mn/Zr composite OC remains stable over 15 consecutive cycles. Moreover, the Cu-Mn composite does not only reduce the oxygen uncoupling temperature of CuO but it also overcomes thermodynamic limitations of the oxidation of Mn3O4 to Mn2O3, where the redox reaction of the Cu-Mn composite OC can be expressed as follows: CuxMn3-xO4 ⇋ CuxMn2-x + O2(g). From the results, it can be concluded that Mn2O3 is the most suitable composite oxide to improve the oxygen uncoupling properties of a Cu OC for oxygen uncoupling in the CLAS system.

This study presented a possible alternative to producing hydrogen and power on the basis of different chemical looping combustion technologies. To manifest the feasibility of such a design, the thermodynamics, environment, and economy were assessed in this study. Compared with traditional standalone systems (production of hydrogen and power, respectively), the designed systems were capable of saving beyond 16% of energy input, while reducing more than 98% CO₂ emissions. As promoted by thermodynamic benefits, the chemical looping hydrogen generation (CLHG) system could achieve 3.04% efficiency gain as compared with the system that employs chemical looping combustion to generate heat for the steam methane reforming process (CLC-SMR). Moreover, the CO₂ emissions per unit output energy of the presented method were reduced by 0.09 kg. It is noteworthy that the manufacture of oxygen carrier (OC) could not significantly impact life cycle carbon emissions or hydrogen production costs. To reveal the irreversible distributions, component irreversible analysis was conducted. To delve into the feasibility of the design, a sensitivity analysis was also conducted to explore the relationship between the OC performance and the global warming impact. Furthermore, financial assessment was also employed to analyze the systems’ economic benefits.