Gasification Agent Research Articles

Thermochemical conversion of agricultural waste to hydrogen, methane, and biofuels: A review

With the depletion of fossil fuels, the energy crisis can now be visualized shortly. At the same time, waste production in various fields is also on the rise. This has led to a global waste management challenge. Agricultural wastes are produced in abundant amounts in various parts of the world, and they offer a potential substitute for fossil fuels. Agricultural wastes can be used to produce Methane, Hydrogen and biofuels along with various useful chemicals. This review provides insight into the composition of agricultural waste, the process of gasification, gasification agents, and challenges in the process. The fuels made from agricultural wastes, the pretreatment of agricultural waste and its challenges and future of energy production from agricultural waste are also discussed. The paper discusses in depth the reactions involved in the gasification process and the various types of gasifiers, their advantages and disadvantages. Energy production from agricultural waste is already being employed in few countries, but further research needs to make the processes more environmentally benign and eco-friendly. The logistics cost to transport the agricultural waste to biofuel plants is a major challenge that needs to be tackled. The feasibility of installing biofuel plants closer to agricultural fields is much better. For a smart usage of agricultural waste and to meet the sustainability criteria, it is necessary to integrate the available waste streams with local technical solutions.

Recent Progress on Hydrogen-Rich Syngas Production from Coal Gasification

Coal gasification is recognized as the core technology of clean coal utilization that exhibits significant advantages in hydrogen-rich syngas production and CO2 emission reduction. This review briefly discusses the recent research progress on various coal gasification techniques, including conventional coal gasification (fixed bed, fluidized bed, and entrained bed gasification) and relatively new coal gasification (supercritical water gasification, plasma gasification, chemical-looping gasification, and decoupling gasification) in terms of their gasifiers, process parameters (such as coal type, temperature, pressure, gasification agents, catalysts, etc.), advantages, and challenges. The capacity and potential of hydrogen production through different coal gasification technologies are also systematically analyzed. In this regard, the decoupling gasification technology based on pyrolysis, coal char–CO2 gasification, and CO shift reaction shows remarkable features in improving comprehensive utilization of coal, low-energy capture and conversion of CO2, as well as efficient hydrogen production. As the key unit of decoupling gasification, this work also reviews recent research advances (2019–2023) in coal char–CO2 gasification, the influence of different factors such as coal type, gasification agent composition, temperature, pressure, particle size, and catalyst on the char–CO2 gasification performance are studied, and its reaction kinetics are also outlined. This review serves as guidance for further excavating the potential of gasification technology in promoting clean fuel production and mitigating greenhouse gas emissions.

Fluidized bed gasification of wood chips using bottom ash derived from coal: optimization of operating conditions

ABSTRACT Although biomass gasification is well recognized as a practical method for producing syngas, the generated gas cannot be used in a variety of applications because of technological issues like tar formation. In this research, coal bottom ash (CBA) was used as an in-bed material for the experimental examination of biomass (wood chips) gasification in a fluidized bed system. All tests were conducted at reaction temperatures between 750 and 900 C, steam to biomass ratios between 0.24 and 0.96, CBA particle sizes between 0.22 and 1.2 mm, and biomass particle sizes between 0.5 and 3.0 mm. The primary objective of this research is to use an experimental set-up to assess the effectiveness of steam gasification of biomass using CBA with various particle sizes. The findings showed that using steam as a gasification agent and raising the temperature improved tar cracking and H2 generation. The findings also demonstrated that the catalyst particle size is efficient for H2 production and that CBA can be used as an in-bed material for the production of H2-rich syngas. Under an 850°C reaction temperature, a S/B of 0.96, a CBA size of 0.2–0.4 mm (Case I), and a biomass particle size of 0.5–1.2 mm, the H2 concentration achieved a maximum of 65.7 vol%. (Case I).

Gasification of Waste Machine Oil by the Ultra-Superheated Mixture of Steam and Carbon Dioxide

Reported in the article is further progress in the development of the novel pulsed detonation gun (PDG) technology for the conversion of organic wastes into syngas in a two-component gasifying agent (GA) containing ultra-superheated steam and carbon dioxide obtained by pulsed detonations of a natural gas–oxygen mixture at a frequency of 1 Hz. Experimental studies were carried out on a waste converter with a 40 dm3 flow reactor and two PDGs with a total volume of 2.4 or 3.2 dm3, which is approximately a factor of 6 and 4.5 less than in previous studies, respectively. The objective of the research was to find the design and operation parameters of the waste converter that provide a minimum amount of CO2 in the gasification products. Waste machine oil was used as a feedstock. It is shown that, compared with the earlier experiments with a higher average temperature of the reactor wall and with a PDG of a much larger volume, the contents of H2, CO, CH4, and CO2 in the syngas remained virtually unchanged, whereas the efficiency of the gasification process increased significantly: the use of 1 g of natural gas made it possible to gasify up to 4 g of the feedstock. It is also shown that the determining role in the gasification process of liquid feedstock is played by the feedstock residence time in the PDG rather than in the reactor. The minimum ratio between the flow rates of the GA and liquid feedstock, the minimum ratio between the flow rates of combustible gas and liquid feedstock, as well as the actual GA consumption in the gasification process are determined experimentally.

Large-Scale Experimental Simulations of In Situ Coal Gasification in Terms of Process Efficiency and Physicochemical Properties of Process By-Products

This paper presents a series of surface experiments simulating underground coal gasification (UCG). The main goal of the experiments was to investigate the influence of the gasification medium and the coal rank on the gasification process. Four multi-day trials were carried out using a laboratory gasification facility designed for the large-scale experimental simulations of UCG and located in the Experimental Mine “Barbara”, located at Mikołów, Poland. Two Polish bituminous coals were investigated: coal sourced from “Piast-Ziemowit” mine and coal sourced from “Wesoła” mine. Each of the two coals was gasified in two separate experiments using oxygen-enriched air (OEA) and pure oxygen as the respective gasifying agents. Gasification with oxygen resulted in significantly higher gas quality and higher process efficiency than gasification with OEA. Higher concentrations of hydrogen (23.2% and 25.5%) and carbon monoxide (31.8% and 33.4%) were obtained when oxygen was used as a gasifying reagent, while lower concentrations were obtained in the case of gasification with OEA (7.1% and 9.5% of hydrogen; 6.4% and 19.7% of carbon monoxide). Average gas calorific values were 7.96 MJ/Nm3 and 9.14 MJ/Nm3 for the oxygen experiments, compared to 2.25 MJ/Nm3 and 3.44 MJ/Nm3 for the OEA experiments (“Piast-Ziemowit” coal and “Wesoła” coal, respectively). The higher coalification degree of “Wesoła” coal (82.01% of carbon) compared to the “Piast-Ziemowit” coal (68.62% of carbon) definitely improves the gas quality and energy efficiency of the process. The rate of water condensate production was higher for the oxygen gasification process (5.01 kg/h and 3.63 kg/h) compared to the OEA gasification process (4.18 kg/h and 2.63 kg/h, respectively), regardless of the type of gasified coal. Additionally, the textural characteristics (porosity development) of the chars remaining after coal gasification experiments were analyzed. A noticeable development of pores larger than 0.7 nm was only observed for the less coalified “Piast-Ziemowit” coal when analyzed under the more reactive atmosphere of oxygen.

Gasification of MSW and Biomass using Aspen Plus®

Municipal Solid Waste (MSW) refers to solid waste generated by towns and cities from different types of household activities1. Over 2 billion tons of MSW are produced annually. Improper disposal can lead to adverse health outcomes through water, soil and air contamination. Hazardous waste or unsafe waste treatment such as open burning can directly harm waste workers or other people involved in waste burning and neighbouring communities. At the same time, in order to keep up with the need in development, the energy demand also increasing. Therefore, utilize MSW to produce energy is gaining more recognition from public interest. Gasification offers some advantages over traditional method of utilize MSW (incineration, compost). Gasification plants produce significantly lower quantities of air pollutants. The process reduces the environmental impact of waste disposal because it allows for the use of waste products as a feedstock. In this paper, Aspen Plus software was deployed to assess and predict the outcome of the gasification process of MSW. The model was calibrated and validated with various observed data. The condition of input MSW and biomass, as well as the gasification agent were considered. The results revealed that primary products of gasification process are similar to other previously conducted experiments.

Biomass pellet fueled chemical looping gasification: Reaction kinetics study with a fluidized bed - thermogravimetric analysis

Biomass pellets show the advantages of higher energy density, lower transportation and storage costs compared to powder biomass, making them attractive for future industrial applications. In this work, a fluidized bed-thermogravimetric analysis (FB-TGA) is developed. The gas-solid process for gram-scale biomass pellets under fluidization state at high temperature is characterized. The effects of gasification agents, bed material components and operating conditions on devolatilization and char gasification are investigated. The devolatilization is revealed to be a rapid phase transition process of volatiles, of which the rate is mainly affected by the intense heat and mass transfer with increasing temperature. While the char gasification is significantly slower, taking more than 600 s for all conditions, therefore be considered as the rate-control step. The hematite oxygen carrier can effectively promote the char gasification by breaking the concentration balance of gas components near the char surface. The char reaction kinetics is fitted based on the isothermal differential method. Results show that the cylindrical geometrical contraction model exhibits an excellent linear correlation. With a mass ratio of oxygen carrier/quartz sand of 1:9, the average activation energies of 130.58 kJ/mol and 104.17 kJ/mol are obtained when CO2 and steam as gasifying agents.

Physical Simulation Test of Underground Coal Gasification Cavity Evolution in the Horizontal Segment of U-Shaped Well

A key point in the underground coal gasification process is the cavity evolution in the horizontal segment. The morphological evolution law of the gasification cavity has not been clarified, which is the bottleneck restricting the analysis of its controllability. In this paper, a physical simulation system for cavity generation was developed, and the cavity evolution in a targeted coal seam with overburden pressure was duplicated in the laboratory. A set of temperature field synchronous monitoring devices was developed to realize temperature sampling within a cavity and the surrounding rock. By analyzing the relationship between the overall temperature distribution pattern and the gasification agent injection condition, the morphological propagation law of the cavity is verified to be water drop-shaped, and influencing factors including the injection flow rate and the gasification agent component ratio are investigated. The axial length and volume of the cavity increase with an increasing injection flow rate. Higher oxygen content results in increased size in all dimensions. The research results provide theoretical support and reference for applying controlled cavity formation in the horizontal segment of U-shaped wells.

Challenges in Syngas Fermentation for Bioethanol Production: Syngas Composition

Energy challenges in developing countries are more significant if they continue to use fossil materials and have an impact on air quality. Lignocellulosic biomass can be an alternative to new renewable sources to replace fossil materials. Indonesia produces various sources of lignocellulosic biomass, which can be used in multiple energy sources such as bioethanol. The hybrid pathway is one of the routes for producing bioethanol. The first stage of the hybrid process is the conversion of biomass into CO, CO2, and H2 (syngas) gas through the gasification process. Then the syngas is converted into bioethanol through fermentation using microorganisms as biocatalysts. The bioethanol production line is the Wood-Ljungdahlii pathway. Factors that affect syngas are the type of biomass (chemical, physical, and morphological properties) and the gasification process (type of gasifier, temperature, gasification agent, and ratio equilibrium (ER)). This paper reviews the challenges in implementing syngas fermentation. In particular, variations in the composition of syngas as a substrate for fermentation.

Gasification performance of olive pomace in updraft and downdraft fixed bed reactors

This study aims to investigate the gasification potential of olive pomace with using different fixed-bed gasifier systems. Olive pomace as a dried form was supplied from a chemical industry plant working on olive oil soap, located in Izmir, Türkiye. After a complete characterization of olive pomace, gasification experiments by using fixed bed reactor systems were done at three different gasifier temperatures as 700, 800 and 900 °C. As a gasification agent, dry air was used with four different flowrates (0.4, 0.2, 0.1, 0.05 L/min) while pure oxygen experiments were carried out with a flow rate of 0.01 L/min. Syngas with H2 content of 48% and 45% (volumetric) were obtained in updraft and downdraft gasifiers, respectively, by using dried air as a gasifying agent. Heating value of syngas was around 12.4 MJ/Nm3. In the pure oxygen atmosphere, H2 contents of the syngas were measured as 53% and 39%vol. In the updraft and downdraft gasifiers. This paper presents the research results on the olive pomace gasification study as a part of a large-scale research project and discuss them in the context of hydrogen production from the fixed bed reactors.

Influence of Oxygen/Steam Addition on the Quality of Producer Gas during Direct (Air) Gasification of Residual Forest Biomass

Biomass gasification is a relevant option to produce a gaseous fuel, it faces, however, several barriers regarding its quality for energetic applications. Therefore, in this study, air-steam and O2-enriched air mixtures were used as gasification agents during the gasification of residual biomass from eucalyptus to improve the producer gas quality. The steam addition promoted an increase in CO2 and H2 concentrations, whilst decreasing the CO and CH4 concentrations. The steam addition had no evident impact on the lower heating value of the dry producer gas and a positive effect on gas yield and the H2:CO molar ratio, attaining the later values up to 1.6 molH2∙mol−1CO. The increase in O2 concentration in the gasification agent (φ) promoted an increase in all combustible species and CO2 concentrations. The lower heating value of the dry producer gas underwent an increase of 57%, reaching a value of 7.5 MJ∙Nm−3dry gas, when the φ increased from 20 to 40 %vol.O2, dry GA. The gas yield had a significant decrease (33%) with φ increase. This work showed that the addition of steam or O2 during air gasification of residual biomass improved producer gas quality, overcoming some of the barriers found in conventional air gasification technology.

Polycyclic aromatic hydrocarbons (PAHs) and soot formations under different gasifying agents: Detailed chemical kinetic analysis of a two-stage entrained flow coal gasifier

The injection of CO2 with coal into coal gasifier is a promising approach to achieve CO2 recirculation. Predicting the formation and evolution of polycyclic aromatic hydrocarbons (PAHs) and soot during coal gasification is particularly important as their presence poses challenges to the gasifier operation and environment. However, the effect of CO2 injection on their formation must be elucidated in more detail to optimize the gasifier design. This work investigates PAHs and soot formations in gas-phase reactions under different gasifying agents (Air, O2/CO2, O2/H2O) in a two-stage entrained flow coal gasifier using a detailed chemical kinetic model (DCKM). Under the O2/CO2– and O2/H2O-blown conditions, aromatics reforming was progressed whereas the yields of tar and soot were effectively suppressed. The benzene was observed as the most abundant PAHs species, followed by naphthalene and acenaphthalene. Regarding the relative oxygen concentration, the conversion behavior of aromatics was significantly influenced in the O2/CO2-blown condition, while the somewhat effect was found in the O2/H2O-blown condition. Tar yield peaked at 50% relative oxygen concentration in the O2/CO2-blown condition. The present finding may have practical significance in the O2/CO2-blown gasifier to facilitate CO2 recirculation for the oxy-fuel IGCC system.

Study on Steam Co-Gasification of Waste Tire Char and Sewage Sludge

The large and growing volume of tire waste and sewage sludge requires disposal, for which thermochemical processes such as gasification can be used. Co-gasification of these two waste products allows the tire char to be used as a charge stabilizer and the sewage sludge to improve reactivity and efficiency. The purpose of this study was to evaluate the effect of the composition of a waste tire char and sewage sludge fuel blend on the gasification process, using steam as the gasification agent. Tests were carried out for tire char, municipal sewage sludge, and blends of the two in ratios of 90:10 and 67:33. An analysis of the materials used was carried out (ultimate and proximate analysis as well as ash composition), and isothermal measurements of steam gasification were taken using the thermal volumetric method for temperatures of 800, 850, and 900 °C at an elevated pressure of 1 MPa. On the basis of the results, the formation curves of the main gasification products (H2, CO, CO2, and CH4) were created, the curves for the degree of carbon conversion were plotted, the reactivity indexes were determined for different degrees of conversion (0.25, 0.5, and 0.75), and the quantity and composition of the resulting gas were analyzed. Using the grain model, the kinetic parameters (activation energy and pre-exponential factor) of the gasification reaction were calculated. The addition of municipal sewage sludge had a positive effect on the reactivity of tire char and increased the efficiency of gasification, because it contained components that act as catalysts in the gasification process. There was a favorable effect from the addition and higher amount of sewage sludge on lowering both the activation energy (49.5 kJ/mol and 89.2 kJ/mol for 90:10 and 67:33 blends, respectively) and the pre-exponential factor. A significant improvement in reactivity, with a high degree of conversion and the best gas composition, was obtained for a 90:10 blend at 900 °C.

The Realization of complete carbon conversion and hydrogen purification in the coal-fueled chemical looping technology using a cost-effective iron-based oxygen carrier

The development of cost-effective and reactive oxygen carriers and the fast and complete conversion of solid fuels are two critical issues in the solid fuel chemical looping technology. Red mud, a solid waste from the alumina industry, was found to be an economic oxygen carrier candidate simultaneously realizing the use of solid wastes and the CO2 abatement after comparing with other two different iron-based materials (pure Fe2O3 and hematite). This study validated red mud as an excellent oxygen carrier to achieve the almost complete conversion of char in solid fuels (SFs) (99.4%) and meanwhile the hydrogen production with high-purity (97% H2 purity) and higher H2 yield (around 500 mL/g), in the optimized pyrolysis procedure of solid fuels with proper gasification agent and rationalized reaction temperatures (1000 °C) and residence time (10mins). Characterizations of red mud using SEM-EDS and XRD revealed that the unique microscopic crystalline structures of both Fe2O3 and Ca2Al2SiO7 particles nested on Na4Al2Si2O9 molten substrate, implying that the existence of Na-containing component of the red mud OC likely accounts for its higher reactivity and stability in multiple redox cycles.

Gasification integrated with steam co-reforming of agricultural waste biomass over its derived CO2/O2/steam-mediated porous biochar for boosting H2-rich syngas production

This study proposed a novel concept of producing H2-rich syngas and eliminating tar formation via biomass gasification integrated with inline steam co-reforming (BGSCR). Initially, direct gasification of wheat straw in diverse gasifying agents was conducted to produce CO2/O2/steam-mediated porous biochar materials (PBMs), which were innovatively used as catalytic reforming agents and co-reactants for BGSCR process. With the aid of gasifying agents, the surface structures of PBMs were apparently fabricated with more micropores. Particularly, C[steam] achieved the highest surface area (502 m2/g) and total pore volume (0.297 cm3/g). Further, catalytic reforming temperature and type of PBMs were examined in relation to gas formation behaviors during BGSCR process. The maximum gas yield (58.53 mmol/g), H2 yield (28.29 mmol/g), and syngas yield (45.96 mmol/g) were achieved in the presence of C[10%O2]. Simply put, this study presents a promising gasification route to directly integrate H2-enriched syngas generation and in-situ tar abatement with biochar reutilization.

Optimal integration design of sustainable ethylene glycol production process considering economic benefit and environmental impact

The requirement for ethylene glycol (EG) continues to surge owing to the booming demand for indispensable platform materials. Unfortunately, there is limited insight into engineering modeling, process enhancement, and process optimization to achieve carbon neutrality in ethylene glycol production. Herein, four biomass-to-ethylene glycol (BtEG) processes that integrate renewable energy for hydrogen production and CO2 utilization are proposed to find the best strategy for the carbon-neutral and cost-effective development of the ethylene glycol industry. Rigorous steady-state modeling and simulation of the proposed BtEG processes with various gasification agents are conducted to investigate the effect of different gasification agents on the performance of the BtEG processes. The technoeconomic and environmental performance of the proposed processes is assessed and compared with the conventional process. Results show that the proposed BtEG processes can significantly boost the system performance of the conventional process. The carbon utilization efficiency, exergy efficiency, and internal rate of return of four proposed BtEG processes are improved by 38.96%–43.2%, 0.98%–7.13%, and 1.94%–11.28%, respectively. The environmental performance of the proposed BtEG processes is greatly superior to that of the conventional process since the life cycle GHG emissions of the proposed processes are negative, which are lower than −1.47 t/t. Therefore, this study provides a sustainable and cost-efficient improvement direction for the carbon-intensive ethylene glycol industries.

Precise in-situ infrared spectra and kinetic analysis of gasification under the H2O or CO2 atmospheres

Studying the mechanisms of bagasse conversion into syngas is essential to sustain the growing use of biomass in energy economy production. In this work, the precise kinetics of bagasse gasification with various gasification agents was firstly investigated employing in-situ infrared spectra with Coats-Redfern integration, combining qualitative infrared spectroscopy allowed for kinetic analysis, so as to explore how the intermediate species vary in each basic reaction. The results demonstrate that the CO2 agent reduces the activation energy of nitryl after amino oxidation, making the lignin involved in gasification more easily as well as causing higher gasification efficiency. On the one hand, steam serving as a gasification agent enhances the concentration of hydroxyl groups and produces H2-rich syngas. On the other hand, the strong oxidizing hydroxyl group reduces the energy barrier of carbonyl and carboxyl groups in cellulose, which facilitates the gasification process. Furthermore, this study compared the effects of gasification agent (H2O or CO2) on syngas composition, reactor temperature distribution, carbon conversion rate, gasification efficiency, as well as low calorific value, providing essential information for understanding the micro-reaction pathways and pathway regulation during bagasse gasification.

Modeling and optimization of fuel cell systems combined with a gasifier for producing heat and electricity

In this research, a proton-conducting membrane fuel cell is used in conjunction with a gasifier for producing electricity with air considered as the gasification agent. The simultaneous electricity, heat, and hot water generation of these two when coupled with an Organic Rankine Cycle (ORC) installed within a Thermoelectric Generator (TEG) was studied. Additionally, to utilize the electricity generated from various parts of the process; i.e. the fuel cell, organic Rankine cycle turbine, and the thermoelectric generator, the reverse osmosis (OR) water desalination unit was coupled to the process. The aforementioned system was studied and analyzed based on thermodynamic and thermos-economic aspects. A parametric study was also carried out to analyze the effect of main factors on power output, energy/exergy yield, and the total cost of each system. Finally, a dual objective optimization was achieved by taking the main factors into consideration and using a genetic algorithm. Results indicated that the work generated by the system was not significant; however, the amount of hot water produced was relatively promising. Based on exergy and exergoeconomic evaluation, the After-Burner is an important non-renewable energy source while the fuel cell has a higher inefficiency cost which could be due to low work generation. Results indicate that the moisture in the biomass and the figure of merit, are important parameters that have to be kept as low as possible. The energy yield of the fuel cell was calculated to be 45.05%. Additionally, considering the optimized operating point, pure power output and system cost rate will be 1.81 KW and 5.15 $/hr respectively.

A proposed configuration of biomass based combined power and cooling plant and its 6E analyses

The paper reports 6E analyses (energy, exergy, economic, environmental, exergo-economic and exergo-environmental) of a biomass based combined power and cooling plant that uses sawdust as its fuel, steam as its sole gasifying agent. The gasification model includes tar in the producer gas and yields maximum hydrogen content when steam-to-biomass ratio (STBM) and reactor temperature are set to 2 and 800 °C respectively. The performance of the cogeneration plant is assessed by varying different input parameters viz. air compressor pressure ratio (pr) and turbine inlet temperature (TIT). Simulation results show that the optimum performance is achieved when TIT is 1100 °C and pr is in the range of 6 to 8. The exergo-economic factor and exergo-environmental factor are evaluated by considering these optimised conditions. Exergy analysis suggests that the gasifier is subjected to maximum exergy destruction. From economic analysis, the computed effective price of electricity (EPOE) is 0.064 USD/kWh with the discounted payback period of the plant being 8.5 years. The exergo-economic and exergo-environmental factors obtained are 51.5 % and 0.0288 % respectively at the favourable operating conditions.

Syngas production from municipal sewage sludge by gasification Process: Effects of fixed bed reactor types and gasification agents on syngas quality

In this experimental study, the results obtained from sewage sludge gasification carried out in two different fixed bed gasifiers, up draft and down draft, are presented. In addition, the effects of using three different heating temperatures (700, 800, 900 °C), two different gasification agents (dry air and pure oxygen), and their different flow rates (0.05, 0.1, 0.2, 0.4 L/min for dry air, 0.01 L/min for pure oxygen) on gasification efficiency are investigated. 75 g of sludge sample was used in each experimental study. The syngas composition produced from sludge gasification studies was measured by using online syngas analyzers. The maximum H2 content in syngas from updraft and downdraft gasifiers was achieved as 42 vol% and 46 vol% by using dry air as gasifying agent. H2 content for updraft and downdraft gasifiers was also obtained as 40 vol% and 45 vol%, respectively in the case of pure oxygen used as a gasifying agent. This paper presents a critical discussion identifying key points and contributing to a deeper understanding of its remarkable potential for sludge gasification by using different fixed bed gasifier configurations.