Improvement of red mud oxygen carriers in biomass chemical looping gasification using battery cathode materials doping

Performance of Fe–Ni bimetallic oxygen carriers for chemical looping gasification of biomass in a 10 kWth interconnected circulating fluidized bed reactor

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

Chemical looping gasification (CLG) of biomass uses the lattice oxygen of oxygen carriers to convert biomass into syngas with a low tar content, high heating value, and low price. It is of key importance to exploit well-dispersed and thermally stable oxygen carriers for the CLG process. In the current work, a series of oxygen carriers with varied Fe and Ni molar ratios were synthesized from hydrotalcite compound precursors (HTlcs), which made the metallic elements mix at the molecular level. Consequently, highly dispersed complex metal oxygen carriers can be achieved after precursor calcinations. CLG of biomass char was carried out in TGA and a fixed bed reactor accompanied by various physical and chemical analyses for the fresh and used oxygen carriers. The result manifested the HTlcs crystalline form, which was formed in the precursors and produced the Fe0.99Ni0.6Al1.1O4 compound after calcination, suggesting that a high degree dispersion of the multimetal oxygen carrier was synthesized. The main H2 upt...

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

Iron-based oxygen carriers (OCs) have received much attention due to their low costs, high mechanical strengths and high-temperature stabilities in the chemical looping gasification (CLG) of biomass, but their chemical reactivity is very ordinary. Converter steel slags (CSSs) are steelmaking wastes and rich in Fe2O3, CaO and MgO, which have good oxidative ability and good stability as well as catalytic effects on biomass gasification. Therefore, the composite OCs prepared by mechanically mixing CSSs with iron-based OCs are expected to be used to increase the hydrogen production in the CLG of biomass. In this study, the catalytic performance of CSS/Fe2O3 composite OCs prepared by mechanically mixing CSSs with iron-based OCs on the gasification of brewers’ spent grains (BSGs) were investigated in a tubular furnace experimental apparatus. The results showed that when the weight ratio of the CSSs in composite OCs was 0.5, the relative volume fraction of hydrogen reached the maximum value of 49.1%, the product gas yield was 0.85 Nm3/kg and the gasification efficiency was 64.05%. It could be found by X-ray diffraction patterns and scanning electron microscope characterizations that the addition of CSSs helped to form MgFe2O4, which are efficient catalysts for H2 production. Owing to the large and widely distributed surface pores of CSSs, mixing them with iron-based OCs was beneficial for catalytic steam reforming to produce hydrogen.

Chemical looping gasification (CLG) of biomass was performed in a thermogravimetric analyzer (TG) reactor together with a fluidized reactor with natural iron ore oxygen carrier under inert atmosphere. TG experiments indicated that iron ore can provide oxygen source for biomass conversion in the form of lattice oxygen. In the fluidized bed experiments, the influences of reduction temperature on CLG of biomass were emphatically investigated in terms of gas distribution and solid characters. The gas yield and carbon conversion increased, but the tar content decreased in the temperature range of 1,013–1,213 K. In this temperature range, the conversion of oxygen carrier increased from 24.11 to 53.59 %. X-ray diffraction analysis shows that more FeO was generated with temperature increasing. Scanning electron microscope analysis indicates that sintering was observed at elevated temperature. An optimum mass ratio of biomass/oxygen carrier (B/O) of 0.67 was obtained with aim of achieving maximum gasification efficiency of 76.93 %.

Chemical looping gasification of lignocellulosic biomass with iron-based oxygen carrier: Products distribution and kinetic analysis on gaseous products from cellulose

Syngas production by chemical looping gasification of biomass with steam and CaO additive

Chemical looping gasification (CLG) of biomass is an emerging technology for producing synthetic gas with high content in H2, CO, and other valuable compounds in alternative to O2-enriched gasification, an oxygen carrier delivering O2 to the fuel. In the present paper, the results of CLG experiments at the bench scale are presented with a particular focus on the conversion of biomass char that is the least reactive but most energetic constituent of biomass. Synthetic Cu oxygen carrier and CO2-enriched atmosphere were used at temperatures of 900 and 945 °C in a fluidized bed. In inert conditions, the char conversion was not complete for the fixed equivalence ratio that was adopted. Conversely, char was fully converted in the presence of CO2, thanks to the inverse Boudouard reaction. The results show that higher temperature is preferable for thermodynamic reasons, although the related energy balance reduces the range of auto-thermal operability. The CO produced upon combined gasification by O2 and CO2 achieved a yield very close to the theoretical value of 78 mmol per gram of char at 100vol% CO2 and 945 °C.

Inhibition effect of H2 on char gasification during chemical looping gasification of biomass

This paper summarizes the results of an experimental investigation into sorbent chemical looping gasification (SCLG) of biomass for the production of high-purity hydrogen and in situ capture of the resulting CO 2. The key innovation was the use of concrete and demolition waste (CDW) as the source of CO 2 sorbent. A comprehensive series of thermogravimetric analysis (TGA) experiments was carried out over a range of temperatures between 650 and 900 °C and pressures up to 20 atm to benchmark the CO 2 capture efficiency of CDW against conventional lime-based sorbents [e.g., calcined limestone (CL) and hydrated Portland cement (HPC)]. Effects of controlling parameters, such as the Ca/C ratio, steam/carbon (S/C) ratio, steam partial pressure, and total pressure, on the gas yield, gas composition, and CO 2 capture efficiency were thoroughly examined. Experimental results confirmed that CO 2 capture efficiencies as high as 56.4% and high-grade hydrogen production can be achieved when CDW is used as a sorbent. These results combined with the high mechanical strength, durability, and low cost make CDW an attractive sorbent for chemical looping gasification of carbonaceous solid fuels, particularly biomass.

Thermodynamic parameters of chemical reactions in the system were carried out through thermodynamic analysis. According to the Gibbs free energy minimization principle of the system, equilibrium composition of the reactions of chemical-looping gasification (CLG) of biomass with natural hematite (Fe2O3) as oxygen carrier were analyzed using commercial software of HSC Chemistry 5.1. The feasibility of the CLG of biomass with hematite was experimental verified in a lab-scale bubbling fluidized bed reactor using argon as fluidizing gas. It was indicated the experimental results were consistent with the theoretical analysis. The presence of oxygen carrier gave a significant effect on the biomass conversion and improved the synthesis gas yield obviously. It was observed that the gas content of CO and H2 was over 70% in CLG of biomass. The reduced hematite particles mainly existed in form of FeO. It was showed that the reduction of natural hematite with biomass proceeds in a stepwise manner from Fe2O3 →Fe3O4→ FeO. Reduction product of natural hematite can be restored the lattice oxygen by oxidation with air.

Biomass chemical looping gasification (BCLG) offers significant advantages over the conventional biomass gasification process in terms of enhanced gasification efficiency, inherent CO2 capture, process circularity, and mitigated emissions of pollutants. This review discusses the prevailing status of research and development of BCLG in terms of production of high-quality syngas and negative carbon emissions based on the latest experimental and modelling studies. In particular, the design of the BCLG process and reactors is compared with conventional gasification. This review suggests that the BCLG process could be 10–25 % more efficient than the conventional combustion and gasification system in terms of economical H2-production cost (3.37 USD/kg H2-produced) and negative life cycle emissions of CO2 (−14.58 kg-CO2e/ kg-H2 produced). This review has extensively considered the effects of process parameters and oxygen carriers (OCs) on gasification chemistry and reaction engineering during BCLG experiments. More specifically, the properties of OCs have been holistically analysed from technological, economic, and environmental perspectives to screen appropriate and affordable OCs for BCLG. In addition, the state-of-the-art modelling studies on BCLG are compared in terms of thermodynamic equilibrium, kinetics, and integrated processes. Technological challenges and research gaps in experiments and modelling have been highlighted in order to advance the BCLG process for industrial applications. In particular, further experimental work is needed to tackle issues related to stability and deactivation of OCs, fluidisation and circulation, the mechanical strength of OCs, the optimisation of feed conversion, and the integration and management of various thermal reactors. It is also desired to enhance the accuracy of models by incorporating optimisation of integrated processes and a more detailed reaction mechanism. Overall, BCLG is a promising negative emissions technology for renewable energy production, yet more innovative efforts in experimental and modelling studies are imperative to move towards more practical applications.

Over the last 100 years, the average temperatures on the Earth’s surface, water, and atmosphere have risen by 0.75 °C. The temperature increase is mainly caused by human activities such as the burning of fossil fuels releasing a large amount of carbon dioxide into the air, which in turn results in an environmental concern over the world. Currently, the mitigation of carbon dioxide emissions is one of the greatest global challenges. Additionally, the energy demand worldwide has increased in the last few decades because of rapid industrialization and the ensuing improved standard of living. Biomass is abundant in the world and represents one of the most auspicious renewable energy resources to replace fossil fuels. Demand for a renewable source of hydrogen in the world leads to growing research activities in the field of biomass conversion processes. Chemical looping gasification is a novel technology to produce efficiently and sustainably valuable products such as heat, power, and hydrogen-enriched gas from biomass combined with carbon capture. This thesis demonstrates the feasibility of chemical looping gasification of biomass in a pilot-scale bubbling fluidized bed reactor. In a first step, torrefied woodchips as biomass fuel were characterized before further investigations. Non-isothermal experiments were carried out in a thermogravimetric analysis instrument to determine the kinetics of gasification of torrefied woodchips char under steam and CO₂ atmospheres. According to the experimental results, two kinetic models combined with four conversion models were implemented to determine the best fitting kinetic model for biomass char gasification. Johnson model combined with Langmuir-Hinshelwood kinetic model is the best agreement to the experimental data with more than 90 % of the coefficient of determination, R², among the combinations. Afterward, an experimental study of biomass gasification was performed in a pilot-scale bubbling fluidized bed reactor to assess the feasibility of biomass gasification under various operating conditions. It was found that hydrogen fraction in the product gas can reach 49 vol.%, while carbon conversion efficiency achieves around 77 % at high gasification temperature and steam-to-biomass ratio. Furthermore, the results showed that the presence of oxygen in the gasifier could cause a significant decrease in hydrogen production due to oxidation reaction, but the carbon conversion efficiency increases significantly, reaching approximately 90 %. Based on the figure obtained from the study of biomass gasification, an experimental investigation of chemical looping gasification of biomass was conducted to analyze the influences of operating parameters on the process performance. It was observed that the maximum fraction of hydrogen and the carbon conversion efficiency obtained from the experimental results are approximately 43 vol.% and 90 % for both oxygen carriers, respectively. The two iron-based oxygen carriers show good performance in the study, their reactivity with different gaseous fuels decreases in the following order: H₂ > CO > CH₄. Iron-based oxygen carriers perform their capability of hydrogen-enriched gas production from chemical looping gasification of biomass along with a reduction of CO₂ emissions. The evaluation of this study can provide good knowledge of the phenomena of the chemical looping gasification process and the behavior of ilmenite and iron ore during the gasification process. Finally, a comprehensive process simulation model was developed in the Aspen Plus flowsheet environment based on the experimental data to simulate biomass gasification in a bubbling fluidized bed reactor. Hydrodynamics and kinetics were implemented simultaneously in external FORTRAN codes. It was found that the model predictions are in good agreement with the experimental investigations with the mean errors ranging between 0.027 and 0.289. The validated model can simulate biomass gasification in a bubbling fluidized bed reactor and provide a good basis for large-scale applications.

Thermomechanical and thermodynamic analysis of the sintering process of Mn-based oxygen carrier in chemical looping gasification of biomass