Biomass Gasification Technology Research Articles

A parametric study on syngas production by adding CO2 and CH4 on steam gasification of biomass system using ASPEN Plus

Abstract Biomass gasification technology is increasingly employed as an environmentally friendly energy source, primarily due to its minimal impact on the environment and its ability to mitigate pollution. This technology excels in producing gas with exceptionally high hydrogen content, making it a valuable source for both fuel and energy carriers. Hydrogen (H2), renowned for its stability and lack of detrimental environmental effects, holds great significance in various applications related to energy utilization and sustainability. In the current work, wood sawdust was utilized as the biomass feedstock for syngas production. The research focused on examining the impact of introducing carbon dioxide (CO2) and methane (CH4) gases into the Gibbs reactors. The steam gasification process was modeled by the ASPEN Plus software, allowing for comprehensive analysis and simulation of the gasification reactions. According to the obtained results, the modeling performed in this study demonstrates good predictive capability when compared to the experimental data. It was shown that when the ratio of CO2 to biomass (C/B) increases, the MFR (mass flow rates) of H2 as well as CH4 decrease, whereas the flow rates of CO2 and carbon monoxide (CO) increase. These findings indicate the influence of the C/B ratio on the distribution of different gases within the gasification process. The reduction in MFR of hydrogen when transitioning from C/B = 0 to C/B = 1 in modes a and b is quantified as 17.51 % and 16.39 %, respectively. These percentages represent the magnitude of the decrease in hydrogen MFR for each specific mode when comparing two carbon dioxide to biomass ratios. When the CH4 to biomass (M/B) ratio increases, the mass flow rates of H2 exhibit a consistent upward trend, while the MFR of CO2 displays a descending form. Specifically, when in the Gibbs reactor, M/B rises from 0 to 1 for modes a and b, the mass flow rates of H2 experience significant increases of 265 % and 243 %, respectively. These findings underscore the direct relationship between the M/B ratio and hydrogen production, highlighting the potential for enhanced hydrogen yields with higher M/B ratios in the studied modes.

A parametric study on syngas production by adding CO2 and CH4 on steam gasification of biomass system using ASPEN Plus

Abstract Biomass gasification technology is increasingly employed as an environmentally friendly energy source, primarily due to its minimal impact on the environment and its ability to mitigate pollution. This technology excels in producing gas with exceptionally high hydrogen content, making it a valuable source for both fuel and energy carriers. Hydrogen (H2), renowned for its stability and lack of detrimental environmental effects, holds great significance in various applications related to energy utilization and sustainability. In the current work, wood sawdust was utilized as the biomass feedstock for syngas production. The research focused on examining the impact of introducing carbon dioxide (CO2) and methane (CH4) gases into the Gibbs reactors. The steam gasification process was modeled by the ASPEN Plus software, allowing for comprehensive analysis and simulation of the gasification reactions. According to the obtained results, the modeling performed in this study demonstrates good predictive capability when compared to the experimental data. It was shown that when the ratio of CO2 to biomass (C/B) increases, the MFR (mass flow rates) of H2 as well as CH4 decrease, whereas the flow rates of CO2 and carbon monoxide (CO) increase. These findings indicate the influence of the C/B ratio on the distribution of different gases within the gasification process. The reduction in MFR of hydrogen when transitioning from C/B = 0 to C/B = 1 in modes a and b is quantified as 17.51 % and 16.39 %, respectively. These percentages represent the magnitude of the decrease in hydrogen MFR for each specific mode when comparing two carbon dioxide to biomass ratios. When the CH4 to biomass (M/B) ratio increases, the mass flow rates of H2 exhibit a consistent upward trend, while the MFR of CO2 displays a descending form. Specifically, when in the Gibbs reactor, M/B rises from 0 to 1 for modes a and b, the mass flow rates of H2 experience significant increases of 265 % and 243 %, respectively. These findings underscore the direct relationship between the M/B ratio and hydrogen production, highlighting the potential for enhanced hydrogen yields with higher M/B ratios in the studied modes.

Optimal sizing of hybrid PV–diesel–biomass gasification plants for electrification of off-grid communities: An efficient approach based on Benders’ decomposition

Nowadays, millions of people in remote areas do not enjoy an uninterrupted power supply due to the lack of connectivity to the main power grid. Under such circumstances, the only feasible way to access electricity is typically local power generation, often relying on diesel engine–generator sets or photovoltaic arrays. However, on many occasions, this configuration does not fully exploit all available local resources, including biomass. Indeed, most isolated areas have access to local biomass production from agricultural activities, which can be used for local electricity generation through gasification. This paper addresses this challenge by developing an innovative optimal sizing tool for hybrid power plants integrating biomass gasifiers, specifically designed for isolated areas with access to local biomass production. The novel approach models the particular features of biomass gasification technologies, including long on/off times or restrictive ramping limits. To this end, an efficient methodology based on representative weeks is proposed, which is combined with a solution strategy based on the multi-cut Benders’ decomposition, thus resulting in a tractable framework that can deal with a huge amount of data efficiently. One of the most salient features of the new proposal is the consideration of local biomass production, which is included in the methodology through an original algorithm. Accordingly, a certain amount of biomass is sourced locally, leading to more accurate and reliable results. The new methodology is applied to a benchmark off-grid community in Ghana. The results demonstrate that the use of gasifiers reduces the project cost notably (by 90%) driven by the reduced biomass cost, which can be supplemented by locally generated biomass from agricultural activities. In addition, this technology constitutes a clean source of energy, reducing the total CO2 emissions by 83% compared to a baseline case in which only diesel generators are used. Moreover, it is demonstrated that biomass gasification can effectively act as base load power generation technology to reliably cover most of the local demand, thereby enabling a clean and inexpensive dispatchable local power generation. Finally, a sensitivity analysis reveals that the economic feasibility of the plant is more sensitive to the biomass cost than the selling price of biochar, resulting in a 33% increment in the total project cost when the price of biomass increases from 0 to 0.4 $/kg. Nevertheless, gasification remains as the predominant power generation technology even under unfavorable prices.

Numerical study on kinetics of tar production and mechanism of benzene formation during corn straw gasification

Tar production is a key factor hindering the industrialization of biomass gasification technology. Understanding the mechanisms of tar formation can help predict and reduce tar yield. A gasification model was proposed to investigate the effects of oxygen ratio (OR) and temperature on products formation. Its accuracy was validated using experimental data. The relative content of PAHs from corn straw gasification decreased from 95 % to 53 % with OR and temperature increasing, indicating PAHs relative content could be decreased by increasing OR and temperature. The concentrations of phenanthrene from cellulose and corn straw gasification at 900 °C were 0.85 and 378 ppm, separately. The concentrations of pyrene were 52 and 558 ppm, respectively. The content of PAHs from cellulose gasification was much less than that from corn straw gasification. However, the contribution of cellulose to PAHs formation increased with temperature increasing. Furthermore, the mechanism of benzene formation was analyzed qualitatively and quantitatively. C2H2, C3H3, and C4H6 were main precursors and exhibited a considerable role in benzene formation. H, OH, CH3, and C6H5 were the key radicals. The analysis results indicated that CH3→C2H2→C3H3→benzene and C2H3/C2H4→C4H6→n-C4H5→benzene were two main paths for benzene formation during corn straw gasification.

A Comprehensive Exploration of Biomass Gasification Technologies Advancing United Nations Sustainable Development Goals

A Comprehensive Exploration of Biomass Gasification Technologies Advancing United Nations Sustainable Development Goals

Performance of Photovoltaic Thermal and Biomass Gasification for Efficient Renewable Energy Generation: A Review

AbstractThis review presents the technical and operational performances of solar and biomass energy technologies viz photovoltaic thermal (PVT) and biomass gasification systems. This work aims to offer a reference and guidelines to the renewable energy‐related players, especially for those at the operational level and investors. This paper highlights the technical advantage of hybrid PVT with phase change material in terms of electrical and thermal efficiencies. While the operational performance of biomass gasification is thoroughly discussed via sensitivity analysis, the potential integration between solar and biomass gasification technologies is explored to complement and bolster the capabilities of both renewable systems within the power energy mix portfolio. Finally, few directions and significant takeaways considering the technical criteria are addressed for identifying efficient renewable energy generation.

Numerical simulation analysis of biomass gasification and rich-H2 production process in a downdraft gasifier

Biomass gasification technology offers a sustainable solution for managing agricultural waste, mitigating environmental pollution, and enhancing living standards. This work deploys Aspen Plus to simulate a downdraft gasifier with an integrated H2 reforming module. The impact of key factors, including air equivalence ratio (ER), gasification system pressure, water vapor input, gasification agent temperature, and oxygen content, are considered. Specifically, optimal ER initially improved the gasification efficiency, with a peak followed by a decline. Water vapor addition elevated H2 content, while increased gasifying agent temperature and oxygen concentration enhanced efficiency. However, the increased gasification pressure will lead to a decrease in gasification efficiency. Subsequently, the effect of reforming temperature, CaO, and water vapor input in the hydrogen production model was examined. An appropriate excess of water vapor and calcium oxide were crucial for maximizing H2 concentration. As the reforming temperature increased from 200 °C to 600 °C, the H2 concentration showed an initial increase and then stabilizes. However, beyond 600 °C, there was a rapid decline. Under optimal conditions (H2O/C > 1.3, CaO/C > 1.1, temperature 550–600 °C), the product gas generated during gasification and reforming processes achieved a high H2 concentration of 98%–99%. These findings affirmed the substantial potential of biomass gasification in high-efficiency H2 production.

Enhancement of reaction rate prediction of biomass: A focus on experimental and numerical simulation approaches

While the biomass gasification and cofiring technology is promising for future energy, including green technologies, such as carbon capture and storage and bioresource feedstock, negative carbon emissions are simultaneously possible using these technologies. However, despite these functions, our previous study established that for simulating a biomass reactor, a new model needed to be designed that could improve the accuracy of both real and lab-scale simulations for carbonaceous fuels, such as coal-based applications. Hence, in this study, a biomass experiment utilizing a thermogravimetric analyzer was conducted to obtain varying reaction rate data over carbon conversion, which may then be used to simulate the biomass conversion model and 3D simulation was also conducted for a 500 MWe coal-biomass cofiring boiler. Gasification was obtained at 1000 °C and 1200 °C using CO2 at constant temperature for different biomasses. Compared to the peak exhibited by the random pore model, biomass gasification reaction rates shifted into the later stage of the reaction, thereby yielding irregular reaction rate developments and poor prediction accuracies. With flexibility-enhanced random pore model(FERPM), we observed that correlation factors increased from the previously reported value of 0.7–0.95. In the coal-biomass cofiring boiler, the difference between the Kinetics/Diffusion-limited model and FERPM in biomass combustion aspect was examined, and it was ultimately determined that characteristics of particle reactions through FERPM are valid in 3D analysis. Therefore, this paper proposed a flexibility-enhanced random pore model proven to enhance the prediction accuracy of a simulation.

Biomass gasification technology for a distinct renewable electricity/heat production scheme; Developed regression models based on machine learning algorithms for power/hot water/efficiency/emission data analysis

Rice straw is a promising feedstock for gasification, and using it in combined heat and power systems allows us to generate renewable electricity and heat while reducing reliance on fossil fuels and combatting climate change. As the demand for clean energy grows, machine learning will become even more crucial for managing our energy systems. A combined heat and power system was integrated based on rice straw gasification and the applications of linear and quadratic regression machine learning algorithms were evaluated using the residual analysis and the analysis of variance. The results show that quadratic models outperform linear models in all cases. Specifically, for efficiency modeling, the quadratic model scores 98.2 %, surpassing the linear model's 89.6 %. In emission modeling, the quadratic model outperforms the linear model with an R-sq score of 97 % versus 88.1 %. The results show that equivalence ratio of gasifier has the greatest impact, accounting for 65 % of the observed variation on emission linear model. In the quadratic emission model, linear factors contribute 58 % and quadratic factors contribute 42 %. Among the linear factors, pressure ratio has a significant influence with a contribution rate of 89 %. In terms of quadratic factors, pressure ratio has the highest influence, with a remarkable contribution rate of 92 %. This research emphasizes the significance of enhancing the precision of regression machine learning algorithms by conducting residual analysis and variance analysis.

Experimental Study on Properties of Syngas, Tar, and Biochar Derived from Different Gasification Methods

Biomass gasification technology is a clean and renewable energy utilization approach. Understanding the evolution of gasification product properties is crucial to achieving carbon neutrality goals. A fixed-bed reactor is employed for the biomass gasification with CO2 in this study. Various methodologies have been conducted to characterize the syngas, tar, and biochar produced from the electric gasification (EG) and microwave gasification (MG) of oak and corn stalk samples at different temperatures. When gasifying the same biomass at the same temperature, the syngas yield of MG is generally 3–7% higher than that of EG, and the difference increases with decreasing temperature. The biochar yield of MG is 3–6% higher than that of EG. EG produces more tar at 600–800 °C. The yield of syngas increases as the gasification temperature rises from 600 to 1000 °C, but that of tar and biochar falls. The syngas mainly comprises H2, CH4, CO, and CO2. MG produces 8–15% higher CO content and 2.5–3.5% higher H2 content than EG. This is due to different heating mechanisms. The net calorific value of syngas increases with temperature, reaching a maximum of 11.61 MJ m−3 at 1000 °C for syngas from corn stalk MG. When the temperature rises from 600 to 1000 °C, more primary tars are converted into polycyclic aromatic hydrocarbons (PAHs). At 900 °C, corn stalk biochar from MG has a maximum specific total pore volume (0.62 cm3 g−1), surface area (525.87 m2 g−1), and average pore diameter (4.18 nm). The intensities of the characteristic peaks of biochar functional groups decrease gradually. The heating method has little effect on the types of functional groups.

Assessing the current state of biomass gasification technology in advancing circular economies: A holistic analysis from techno-economic-policy perspective in Malaysia and beyond

Biomass gasification technology has gained significant attention as a potential solution for circular economies by converting organic waste into valuable energy and products (Waste-to-Power-to-X). This paper comprehensively evaluates biomass gasification technology from a techno-economic-policy perspective, providing valuable insights for circular economies. It examines technical aspects such as processes, feedstocks, and syngas production, assessing advancements that would improve efficiency and environmental performance by addressing key challenges like tar removal and gas cleaning. Economic feasibility is analysed through a techno-economic assessment, considering capital costs, operational expenses, revenue streams, and potential markets. Real-world examples and case studies offer insights into economic viability of these processes. The paper emphasizes the significance of supportive policy frameworks, discussing stimulus measures like feed-in tariffs, tax incentives, and regulatory reforms to promote biomass gasification adoption. By combining technological, economic, and policy perspectives, this paper provides a holistic reality check of biomass gasification technology, identifying opportunities, challenges, and pathways for leveraging as a sustainable and economically viable solution for waste management and energy production. The findings and insights presented in this paper can assist policymakers, investors, and stakeholders in making informed decisions regarding the implementation of biomass gasification projects in the future.

Simulation of the Catalytic Gasification of Banana Biomass in the Production of Hydrogen, Using Glucose as a Model Compound

In the face of the climate change problem caused by fossil fuels, it is essential to seek efficient alternative energies with a lower environmental impact that are derived from renewable resources. Biomass gasification technology continues to generate significant interest in sustainable energy research as an alternative to traditional combustion technology. Gasification involves the thermochemical conversion of raw materials, resulting in a highly valuable gaseous product known as synthesis gas, commonly used as a fuel. Its numerous advantages include the availability of raw materials, the reduction in harmful emission streams, performance, and costs. As this topic gains momentum in the global energy framework, it is imperative to advance the maturity of this technology by addressing its weaknesses, primarily in terms of efficiency. The objective of this project was to investigate the hydrogen production process through the simulation of glucose gasification as a representative compound for biomass. This was achieved by conducting an integrated simulation of glucose gasification, encompassing both the heat transfer in the external system and the conversion of glucose into hydrogen gas, using the results obtained in the external system as initial conditions. Interrelated aspects of this complex process, including heat transfer and the kinetics of the gasification process, were modeled. Glucose was selected as the model compound due to its availability, simplicity, fundamental understanding, reproducibility, comparability, knowledge of reaction pathways, and simplification of mathematical models. The simulation resulted in a H2:CO ratio of 2.2, and molar fluxes were obtained for H2, CO, CO2, CH4, and H2O consistent with those typically observed in the gasification process of organic matter. These models were constructed, laying the foundation for the adaptability of subsequent optimization studies.

Applying the solar solid particles as heat carrier to enhance the solar-driven biomass gasification with dynamic operation power generation performance analysis

Solar-driven biomass gasification is a promising technology to improve the utilization efficiency of solar energy and biomass, which also enhances the thermochemical storage and the subsequent stable utilization. Whereas, the intermittence of solar energy deteriorates the stability and continuity of the thermochemical reaction process, which limits the efficient conversion of the reaction. In this regard, this work proposes a new solar-driven biomass gasification technology based on solid particle heat carrier. Different from the direct solar-driven gasification, solid particles are performed as medium to receive the concentrated solar radiation energy and transfer energy to biomass feedstocks. In addition, the combined power generation scenario is adopted to evaluate the thermodynamics and economics of the technology. The integration of solid particle heat storage, the system dispatch and stable operation will be further enhanced. Results show that under the optimal condition, the system maximum thermal and exergy efficiencies are increased by 12.94% and 12.51%, respectively. Considering the system off-design operation, with the evaluated typical periods of four seasons, the averaged power generation efficiency is increased by 5.16%, with the highest efficiency improvement of 9.41% occurring in the typical winter days. With the change of receiver price and biomass price, the maximum decline of levelized cost of electricity reaches to 17.6%, which presents the favorable economic benefits. As a new solar thermochemical technology, this technology exhibits competitive characteristics, significantly improving the utilization efficiency of solar and biomass energy.

High Dimensional Model Representation Approach for Prediction and Optimization of the Supercritical Water Gasification System Coupled with Photothermal Energy Storage

Supercritical water gasification (SCWG) coupled with solar energy systems is a new biomass gasification technology developed in recent decades. However, conventional solar-powered biomass gasification technology has intermittent operation issues and involves multi-variable characteristics, strong coupling, and nonlinearity. To solve the above problems, firstly, a solar-driven biomass supercritical water gasification technology combined with a molten salt energy storage system is proposed in this paper. This system effectively overcomes the intermittent problem of solar energy and provides a new method for the carbon-neutral process of hydrogen production. Secondly, the high dimensional model representation (HDMR) approach, as a surrogate model, was used to predict the production and lower heating value of syngas developed in Aspen Plus, which were validated using experimental data obtained from the literature. The ultimate analysis of biomass, temperature, pressure, and biomass-to-water ratio (BWR) were selected as input variables for the model. The non-dominated sorted genetic algorithm II (NSGA II) was considered to maximize the gasification yield of H2 and the LHV of syngas in the SCWG process for five different types of biomass. Firstly, the results showed that HDMR models demonstrated high performance in predicting the mole fraction of H2, CH4, CO, CO2, gasification yield of H2, and lower heating value (LHV) with R2 of 0.995, 0.996, 0.997, 0.996, 0.999, and 0.995, respectively. Secondly, temperature and BWR were found to have significant effects on SCWG compared to pressure. Finally, the multi-objective optimization results for five different types of biomass are discussed in this paper. Therefore, these operating parameters can provide an optimal solution for increasing the economics and characteristics of syngas, thus keeping the process energy efficient.

Species transport model and custom field function algorithm for computational fluid dynamics-based design and exergy analysis of downdraft biomass gasifiers

Biomass gasification holds great promise as a technology for generating renewable energy from biomass feedstocks. Ensuring efficient operation necessitates the evaluation of energy efficiency within the gasification process. However, traditional energy-based analysis has limitations as it fails to account for the impact of inherent irreversibilities in the process. In contrast, exergy-based analysis offers a more rigorous technique that considers these irreversibilities, providing a comprehensive assessment of the process. In this study, a laboratory-scale downdraft biomass gasifier was modelled and simulated using computational fluid dynamics (CFD). The model incorporated a species transport model to predict concentrations of different species and reaction rates occurring within the gasifier. To evaluate the gasifier's performance comprehensively, an exergy analysis algorithm was integrated into the model through a custom field function, assessing three types of exergy: physical exergy, chemical exergy, and mixing exergy. The developed model achieved superior results compared to a previously reported model, achieving a syngas composition of 1:1.55 and a gasification temperature of 1100 °C. The application of the exergy analysis algorithm enabled a more comprehensive evaluation of the gasifier's performance, revealing areas for improvement that were not apparent in traditional energy-based analyses. The findings of this study highlight the potential of combining CFD simulations, species transport models, and exergy analysis algorithms to enhance the efficiency and sustainability of biomass gasification processes. This approach provides valuable insights into the intricate physical and chemical processes taking place within the gasifier, thereby facilitating the development of more efficient and sustainable biomass gasification technologies.

BIOMASS GASIFICATION FOR HYDROGEN PRODUCTION

Biomass gasification is emerging as a promising technology for producing hydrogen, addressing the dual challenges of sustainable energy supply and environmental conservation. This process converts biomass into syngas—a mixture primarily composed of hydrogen, carbon monoxide, and carbon dioxide—through thermal decomposition in a controlled environment. The syngas is then processed to extract hydrogen, which can serve as a clean fuel for various applications, including transportation and industrial processes. This paper provides an overview of the biomass gasification process, detailing suitable biomass feedstock types and gasifier types, such as fixed-bed, fluidized-bed, and entrained-flow gasifiers. It explores the conversion of syngas to hydrogen, highlighting essential catalytic reforming and purification techniques for producing high-purity hydrogen. The environmental benefits of this technology includes the utilization of renewable resources and reduction of greenhouse gas emissions compared to fossil fuel-based hydrogen production. Economically, biomass gasification offers a feasible pathway for decentralized hydrogen production, potentially lowering transportation costs and enhancing energy security, especially in biomass-rich regions. However, the deployment of biomass gasification technology is not void of challenges – some common challenges with biomass gasification technology include coping with the variability of biomass feedstock, tar formation, and the need for technological advancements to improve efficiency and scalability. This paper also discusses ongoing research and potential innovations aimed at overcoming these obstacles, ensuring biomass gasification's viability as a key player in the future hydrogen economy. Through case studies and real-world applications, this paper illustrates the practical implementation and successes of biomass gasification projects, offering valuable insights into best practices and lessons learned. In conclusion, biomass gasification stands out as a sustainable and economically viable solution for hydrogen production, with the potential to significantly advance global clean energy goals. Keywords: Biomass, Gasification, Hydrogen, Production.

Hierarchically porous carbon from biomass tar as sustainable electrode material for high-performance supercapacitors

The byproduct tar from biomass gasification process had seriously impeded development and applications of this technology, thus novel path for biomass tar valorization is had been continuously pursued. Given its high carbon content, this work attempted to convert biomass tar into hierarchically porous carbon by thermal activation with acetate potassium. The optimal product produced with mass ratio of biomass tar to acetate potassium of 1:3 and activation temperature at 800 °C was revealed as excellent electrode material for high-performance supercapacitor, which demonstrated electrochemical capacitance up to 310.4 F/g at 0.2 A/g, whilst preserved 91% of initial capacitance after 5000 charge-discharge circles at current density of 5 A/g. These excellent properties had arisen from the open and hierarchical porosity and large surface area. This work disclosed the great potential of biomass tar as sustainable and competent candidate for fabricating high-performance electrode material for electrochemical energy devices, and may bring up new opportunities to development of biomass gasification technologies.

Exploring Simultaneous Upgrading and Purification of Biomass−Gasified Gases Using Plasma Catalysis

Tar and substantial CH4 and CO2 are contained in gasified fuels, which pose an obstacle to direct chemical synthesis, and this is a predominant challenge for biomass gasification technology. Herein, a packed−bed dielectric barrier discharge (DBD) reactor was built for simultaneous CH4 dry reforming and tar removal with a La−Ni/γ−Al2O3 catalyst. The interaction between CH4 dry reforming and tar removal in plasma catalysis was investigated. The results indicated that plasma catalysis can achieve high−efficiency simultaneous tar removal and CH4 dry reforming, as indicated by the reactants’ conversion (14% increase for CCH4 and CCO2 at 450 °C in the presence of tar and a 37% increase for the tar removal rate at 360 °C when CH4 and CO2 were introduced), and the mechanism for mutual promotion of CH4 dry reforming and tar removal was elucidated through catalyst characterization results. In addition, a possible reaction mechanism for tar removal via plasma catalysis was proposed. These findings provide valuable insights for simultaneous upgrading and purification of gases generated by biomass gasification.

Regulation of partial oxidation in biochar-catalyzed tar reforming for hydrogen upgrading in syngas: The effect of oxygen concentration

Effective methods for maintaining catalyst activity in tar reforming have been a major focus during the development of biomass gasification technology. The role of partial oxidation in regulating the catalytic efficiency of biochar in tar reforming was investigated using a fluidized bed/fixed bed reaction system. The physico-chemical structures of biochar were characterized by FTIR, Raman, nitrogen adsorption and thermosgravimetry analysis. The tar characterization was analyzed by GC–MS and the production of gas components was monitored on-line with synthetic gas analyzer. The results reveal that partial oxidation regulation (0.2 % – 0.4 % O2) can potentially maintain the biochar’s catalytic efficiency and facilitates the production of hydrogen in gas. The addition of oxygen effectively inhibits the coke deposition on biochar. As the O2 concentration is increased to 0.4 %, the total conversion of tar increasing to a maximum of 0.056 g/g, an increase of 27 % compared to the absence of oxygen. The H2 yield is also increased to a maximum of 0.523 L/g. When the O2 concentration is further enhanced (∼0.6 %), more H2 is consumed by oxygen, the H2 yield is reduced and the tar conversion capacity of biochar is significantly weakened. Partial oxidation regulation maintains the pore structures of the biochar, but there is a conversion of microporous pores to meso-macroporous pores. Partial oxidation regulation effectively inhibits the loss of O-containing structures on biochar, but also contributes to its increased graphitization.

Syngas production and gas-N evolution over heterogeneously doped La-Fe-O perovskite-type oxygen carriers in chemical looping gasification of microalgae

Chemical looping gasification (CLG) is a promising technology for syngas production with low pollutant emission. In this study, doped La-Fe-O perovskites including LaFeO3 (LF), LaFe0.5Ni0.5O3 (LN5F5) and La0.3Ba0.7FeO3 (L3B7F) were developed for microalgae CLG. The as-prepared perovskites exhibited an outstanding performance in syngas production with accumulative syngas yield > 33 mol/kg. For gas-N evolution, perovskites were beneficial to the formation of NH3 and HCN, while the iron ore may convert precursors to NO. Below 400 °C, NOx can be stored on the perovskite surface in the form of nitrite/nitrate species. When the temperature was above 700 °C, NOx can be selectively reduced by reducing components in tar or syngas under the catalysis of L3B7F, resulting in the final reduction of NOx emission. Thus, CLG over L3B7F may be a promising way for efficient utilization of microalgae to overcome the intractable nitrogen-related obstacles in the commercial application of biomass gasification technologies.