Gasification Agent Research Articles

Simulation of co-production system based on coal partial gasification under different reactant gas atmospheres

In order to explore the comparison of coal partial gasification hydrogen-electricity cogeneration systems under different gasification agent atmospheres, based coal partial gasification, including steam cycle power generation and syngas processing for hydrogen production, a hydrogen-electric co-production system and its model of partial coal gasification and semi-coke combustion are constructed, respectively using (H2O/O2) and (CO2/O2) as gasification reactant gas. The effects of oxygen-coal ratio and carbon conversion on exergy efficiency and syngas composition under different gasification reaction gas atmospheres were studied by Aspen Plus simulation. The exergy efficiency under different gasification agent atmospheres increases first and then decreases with the increase of oxygen-coal ratio and carbon conversion rate. Using (CO2/O2) as gasification agent has higher exergy efficiency. The composition of syngas changes little under different oxygen-coal ratios, while the overall content of H2, CO and CH4in syngas will increase with the increase of carbon conversion rate, but the growth rate will continue to decline.

Effects of throat sizing and gasification agents in a biomass downdraft gasifier: towards CO2-free syngas production.

The gasification process in a downdraft biomass gasifier is investigated using Computational Fluid Dynamics (CFD). The aim is to develop a novel approach to reduce CO2 emissions from producer syngas while increasing the higher heating value (HHV). To this end, the effects of varying the throat diameter of the gasifier and gasifying media (air and oxygen) on the performance of gasification are investigated. The results reveal that as the throat ratio decreases for oxy-gasification, more CO, H2, and CH4 are produced, thus resulting in a HHV of 12.1 MJ Nm-3. For the same working conditions (ER, MC, and feedstock), the suggested design/optimum throat ratio of 0.14 is found to reduce CO2 by ∼55% compared to any other higher throat ratios, while simultaneously increasing HHV by ∼20% for both air and oxy-gasification cases. Additionally, the suggested throat ratio increases the gasification efficiency, carbon conversion and producer gas yield by 19%, 33%, and 22% respectively. Therefore, it shows a significant potential for CO2-free syngas production in the gasification process, demonstrating a promising technique that does not require any solvents, catalysts, absorbers, or additional CO2 removal. Lower throat ratios further favour the higher yield of syngas, HHV, gasification and conversion efficiencies, with better gasifier performance.

Reaction engineering during biomass gasification and conversion to energy

Bioenergy, as a perspective of the global energy paradigm, makes a significant contribution to the increase in global energy demand and the development of technologies for converting biomass into energy. Biomass gasification is the most preferred option for thermochemical processing. We conducted a comprehensive analysis of biomass gasification and concluded: 1) that the properties of biomass can be both attractive from the point of view of obtaining value-added products and limiters in the final use of biomass products; and 2) most publications are focused on a narrow range of issues dedicated to a specific technology. To eliminate these shortcomings, we consider as common factors affecting the efficiency of thermochemical processes: type of biomass and humidity; gasification agents range of operating temperatures of gasifiers; efficiency of heat transfer; pressure and actually obtaining the necessary characteristics of the final products obtained in combinations of various thermochemical methods of processing biomass, and particular factors: the influence of new techniques (chemical cyclic gasification and catalysis), design features of gasifiers and variability of their use. Based on the conducted research, we believe that the hybrid approach (combining thermochemical, hydrothermal and biological methods) could help in solving the above-mentioned problems and can contribute to the circular economy by reducing waste production and obtaining value-added by-products through the use of machine learning and artificial intelligence methods.

Prospective of Response Surface Methodology as an Optimization Tool for Biomass Gasification Process

The worldwide population growth and the technological advancements reported in the past few years have led to an increase in the production and consumption of energy. This has increased greenhouse gas (GHG) emissions, the primary driver of climate change. As a result, great attention has been paid to sustainable and green energy sources that can replace or reduce reliance on non-sustainable energy sources. Among the different types of renewable energy sources currently available, bioenergy has been reported as an attractive resource mainly due to its low cost and great availability. Bioenergy can be produced from different biomass sources and converted into biofuels or value-added products through thermochemical, biochemical, and chemical processes. Gasification is a thermochemical process commonly used for bioenergy production, and it is particularly attractive mainly due to its high efficiency. However, its performance is influenced by parameters such as type of feedstock, size of biomass particle, feed rate, type of reactor, temperature, pressure, equivalence ratio, steam to biomass ratio, gasification agent, catalyst, and residence time. In this paper, the influence of different performance parameters in the gasification process is analyzed, and optimization and modelling techniques are proposed as a strategy for product yield enhancement.

Thermodynamic analysis of a carbon capture hydrogen production process for end-of-life tires using plasma gasification

In view of the rapid increase in the number of end-of-life tires and their impact on the environment, this study proposes a disposal process for end-of-life tires that uses plasma gasification to convert end-of-life tires into syngas and produce hydrogen. By comparing the effect of oxygen and air with that of steam and air on the hydrogen production performance of end-of-life tires, we found that the carbon conversion rate, energy recovery rate, and exergy efficiency of the gasification process using steam and air as the gasification agent could reach 99.12%, 93.67%, and 80.04%, respectively. In addition, a carbon capture process suitable for this process was explored further. The results show that the CO2 capture rate of the monoethanolamine absorption process was better than that of Rectisol, and the amount of monoethanolamine was only 0.26 times that of methanol. However, the exergy efficiency of the monoethanolamine absorption process was only 40.04%, which was 5.96% lower than that of Rectisol. The best process for hydrogen production from end-of-life tires by plasma gasification used steam and air as the gasification agent and integrated Rectisol to achieve carbon capture. The total exergy efficiency of the process was 36.45%. This study provides theoretical support for end-of-life tire management and pollution minimization.

A Review of Research on Cavity Growth in the Context of Underground Coal Gasification

Underground Coal Gasification (UCG) is a leading-edge technology for clean and effective utilization of coal resources, especially for deep coal seams with a depth of more than 1000 m. Since the core operation place of UCG is the cavity, mastering the cavity growth pattern is a prerequisite to ensure the efficient and economic development of UCG. At present, scholars have conducted numerous research works on cavity growth, but the simulation conditions limit the research results. Hence, it is necessary to summarize and sort out the research results of cavity growth patterns, which contribute to deepening the understanding of UCG and pointing out the direction for subsequent research. First of all, this paper summarizes the development history of UCG technology and describes the cavity growth mechanism from chemical reactions and thermo-mechanical failure. Then, the research methods of cavity growth are summarized from three aspects: a field test, laboratory experiment, and numerical simulation. The results show that the appearance of the cavity is teardrop-shaped, and its growth direction is obviously related to the gas injection method, including the injection direction and rate. Subsequently, the factors affecting the cavity growth process are expounded from the geological factors (permeability, moisture content, and coal rank) and operating factors (temperature, pressure, gasification agent’s composition, and gasification agent’s flow pattern). Finally, the existing problems and development trends in the cavity growth are discussed. The follow-up research direction should focus on clarifying the cavity growth mechanism of the controlled-retractable-injection-point (CRIP) method of UCG in the deep coal seam and ascertain the influence of the moisture content in the coal seam on cavity growth.

Study on gasification characteristics and kinetics of polyformaldehyde plastics in supercritical water

Supercritical water (SCW) treatment technology has been applied in the field of waste plastics recycling due to its advantages of clean, high efficiency and low carbon. Previous research has focused on liquefaction of plastics to produce oil, mainly for some general-purpose plastics. Different plastics have different structures, which will affect their gasification behavior in SCW. As one of the five engineering plastics, polyoxymethylene (POM) plastics will also become one of the main sources of waste plastics recycling industry in the future. In this paper, the supercritical water gasification (SCWG) experiment of POM plastics was carried out. The effects of temperature, residence time, feedstocks concentration, pressure on the gasification reaction were discussed. The carbon balance of the products under different working conditions was investigated. The optimum condition for SCWG of POM plastics was determined. On this basis, the gasification kinetics of POM plastics were studied. It was found that the gasification efficiency of plastics was significantly improved by temperature increase. The total carbon content of gas and liquid phase products increased gradually. At 700 °C, the total conversion rate reached 99.79%. With the prolongation of the reaction time, the organic carbon in the liquid phase was gradually converted into gas and the gasification reaction proceeds more completely. The increase in concentration reduced the contact area between the raw material and the gasification agent. At the same time, the diffusion of organic matter was hindered, resulting in a lower gasification rate. The effect of pressure on the plastics gasification reaction was not significant. Under the optimum gasification reaction conditions, the carbon gasification efficiency reached 97.15%. Finally, a gasification kinetic model was established, and the activation energy of paraformaldehyde was 160.38 kJ/mol.

The pyrolysis and gasification pathways of automotive shredder residue targeting the production of fuels and chemicals

Automotive shredder residue (ASR), also referred to as car fluff, is the 15-25% of end-of-life vehicle’s mass remaining after de-pollution, dismantling, shredding of the hulk and removal of metals from the shredded fraction. ASR typically consists of metals, plastics, rubber, textile, wood and glass, and is commonly landfilled. The use of ASR as a fuel in incineration processes is controversial since toxic pollutants can be generated as by-products if operational conditions and gas cleaning systems are not carefully controlled. Thermochemical treatment of ASR consists of advanced technology processes that convert ASR components liable to decomposition under the application of heat into liquids and/or gases and a solid residue containing metals. Within the thermochemical treatment options for ASR, pyrolysis and gasification are generally considered as the emerging technologies. The pyrolysis process uses medium temperatures (400-600°C) and an oxygen-free environment to decompose ASR chemically, thus producing minimum emissions and allowing metals to be recovered. Gasification is operated at higher temperatures (>700-800°C) and typically uses air as a gasification agent, which raises some issues in terms of emissions. Lab and pilot-scale plants fed with ASR have been built using both technologies, also considering a combination of them. The aim of this paper is the identification of the best conversion pathway for the production of transportation fuels, aviation fuels or chemicals (hydrogen, methanol, etc.) from ASR. The intermediate products from gasification and pyrolysis are used as feedstock in secondary processes for the production of the final products. The heterogeneous and complex composition of ASR raises several challenges upon its thermochemical treatment, so that the second step of the conversion process is typically not even addressed. Instead, this further step is fundamental to obtain some valuable products that can directly replace fossil derived fuels or chemicals. The updated picture presented in this work should help identify the main advantages and drawbacks of the pyrolysis and gasification processes when considered part of an overall ASR to fuels or chemicals plant.

Biomass oxy-CO2 gasification process for bio-methane production: an experimental and numerical activity

Biomass gasification is a thermochemical process in which the biomass is converted into a mixture of gases, called syngas, commonly utilised in thermal machines to produce electricity and heat. In the present research activity, the conventional air-gasification in downdraft gasifier is replaced by oxy-CO2 gasification technology. This strategy allows to obtain a nitrogen-free syngas, mainly composed by CO, H2, CO2 and CH4, which can be used into the synthesis of various bio-fuels like methanol or synthetic natural gas (SNG). Carbon dioxide is utilized as gasifying agent together with oxygen to mitigate the reactivity of the latter, which can lead to excessive reaction temperatures. In particular, the present work shows the preliminary results of an experimental campaign carried on utilizing a small scale downdraft gasifier (max thermal power of roughly 100 kW) fed with wood pellet and using a mixture of oxygen and CO2 as gasification agent. The experimental results have been utilized to calibrate a pseudo-kinetic model of the oxy-CO2 gasification process, implemented in Aspen Plus environment. To analyse the possibility to transform the produced syngas into methane, an additional numerical model of a methanation plant was then utilised. As a whole, the numerical analysis confirms its usefulness in predicting the performance of the gasifier, which can reach a cold gas efficiency of around 70%, while the methanation plant can achieve a production of roughly 20 kg of methane per 100 kg of gasified wood.

Polyurethane Foam Waste Upcycling into an Efficient and Low Pollutant Gasification Syngas.

Waste treatment has attracted much attention and, in this regard, gasification processes offer an efficient thermochemical technique that can produce a syngas rich in hydrogen. This technique has been well developed for solid waste and biomass while investigations on gasification of polymeric foam are rare. Therefore, this study explores the treatment of polyurethane foam waste with different gasifying agents, based on thermodynamic modeling. The polymeric foam gasification was developed using the best model for estimating higher heating value (gross calorific value). As the results indicated, models based on both ultimate and proximate analyses had better performance in predicting higher heating value. As one of the main objectives and novelties, the steam and air gasification performance of flexible and rigid polyurethane foam wastes was investigated and compared from efficiency and CO2 emission viewpoints. Polyurethane foam gasification by steam resulted in higher hydrogen efficiency, led to lower energy efficiency and produced lower CO2 emissions compared to gasification by air. A hydrogen efficiency of 41.4% was obtained for gasification of waste flexible polyurethane foam by steam. An energy efficiency of 76.6% and CO2 emission of 7.43 g per mole of feedstock were attained for waste flexible polyurethane foam gasified by air.

Energy and Economic Assessment of a System Integrated by a Biomass Downdraft Gasifier and a Gas Microturbine

This work focuses on the energy and economic evaluation of a power generation system composed of a downdraft gasifier and gas microturbine. The gasification process was studied using wood pellets as fuel, while the influence of two gasification agents (air and oxygen-enriched air) on parameters, such as low heating value (LHV), composition, and yield of syngas, were analyzed. The syngas produced from oxygen-enriched air gasification in a downdraft gasifier had an LHV higher than 8 MJ/Nm3, being suitable to be supplied in the gas microturbine. Subsequently, syngas use in the gas microturbine was evaluated, and the results demonstrated that microturbine efficiency dropped from 33.00% to 21.35%, while its power decreased from 200 kW to 81.35 kW. The power generation system was modeled using Aspen Plus® v 11.0 software and validated using results obtained from published experimental studies. Accordingly, the integrated generation system presented an overall efficiency of 11.82% for oxygen-enriched air gasification cases. On the other hand, an economic assessment through risk analysis using Monte Carlo simulations was performed using Crystal Ball® v11.1.2.4.850 software. The economic results indicated that the implementation of a generation system was economically unfeasible, however, if the electricity rate price was increased by 63%, the proposed configuration could be feasible.

Techno-Economic Assessment of Producer Gas from Heavy Oil and Biomass Co-Gasification Aiming Electricity Generation in Rankine Cycle

Heavy oil and biomass co-gasification has been analyzed through a model developed in Aspen Plus™ v 11.0 software. The model was used to assess main gasification parameters, such as cold gas efficiency, yield, low heating value (LHV), and producer gas composition, using air and oxygen as gasification agents. Subsequently, producer gas energy use in the Rankine cycle was performed using a model developed in GateCycle™ v11.1.2.4.850 software. Likewise, the economic indicators of the integrated Rankine cycle-gasification system were calculated. The economic evaluation was developed through Monte Carlo simulation using Crystalball™. The results showed a LHV producer gas decreasing trend as the equivalence ratio (ER) increased, oscillating between 6.37 and 3.63 MJ/Nm3 for ER values greater than 0.30 in the air co-gasification case, while the scenario that used oxygen presented better LHV results, ranging from 9.40 to 11.79 MJ/Nm3. For air co-gasification, the Rankine cycle efficiency range was between 13.0% and 9.5%, while for oxygen co-gasification, values between 14.0% and 13.2% were obtained. Regarding the economic assessment, the two scenarios evaluated (with a reliability of 95%) have a probability higher than 92.1% of economic losses due mainly to the lower electrical power and the local electricity rate.

Study on the monitoring method of cavity growth in underground coal gasification under laboratory conditions

The growth state of the combustion cavity during underground coal gasification (UCG) affects the gasification process's efficiency, stability, and accurate monitoring and control. In this study, a simulation experiment of UCG was performed, and a horizontal coaxial gasification channel was drilled based on the constructed artificial coal seam. Oxygen and air are used as gasification agents to provide a sufficient temperature field to sustain the gasification process. Moreover, the derivation of the gasification zone during UCG was developed using stratified temperature monitoring and acoustic emission damage monitoring. After the experiment, the artificial coal seam was cut to obtain the profile shape of the combustion cavity, which was compared with the temperature and acoustic emission monitoring results. The results show that the temperature distribution results in the coal seam and the calibration results of the acoustic emission source during horizontal coaxial UCG are consistent with the two-dimensional and three-dimensional combustion cavities reconstructed by the profile. Thus, the effectiveness of stratified temperature monitoring and acoustic emission monitoring to infer the gasification combustion cavity is proven.

Steam Gasification of Refuse-Derived Fuel with CaO Modification for Hydrogen-Rich Syngas Production

Steam gasification of refuse-derived fuel (RDF) for hydrogen-rich syngas production was investigated in a lab-scale gasification system with CaO modification. A simulation model based on Aspen Plus was built to study the characteristics and the performance of the RDF gasification system. The influences of gasification temperature, steam to RDF ratio (S/R), and CaO adsorption temperature on the gas composition, heating value, and gas yield were evaluated. Under the gasification temperature of 960 °C and S/R of 1, H2 frication in the syngas increased from 47 to 67% after CaO modification at 650 °C. Higher syngas and H2 yield were obtained by increasing both S/R and gasification temperature. However, as the CaO adsorption temperature increased, a lower H2 fraction was obtained due to the limitation of the CaO adsorption capacity at high temperatures. The highest H2 fraction (69%), gas yield (1.372 m3/kg-RDF), and H2 yield (0.935 m3/kg-RDF) were achieved at gasification temperature of 960 °C, S/R of 2, and CaO modification temperature of 650 °C. The variation trends of simulation results can match well with the experiment. The deviation was mainly because of the limitation of contact time between the gasification agent and RDF, uneven temperature distribution of the reactors, and the formation of tar during the experiment.

A Scientometric Review: Biomass Gasification Study from 2006 to 2020.

Biomass gasification represents a significant way to produce energy from biomass. It features renewable properties and offers great potential for utilization. The application of biomass gasification products, design of the gasifier, type of biomass feedstock, gasification agents, and gasification parameters are key for the biomass gasification process. This work applies bibliometric approaches to provide a comprehensive and objective analysis of worldwide biomass gasification study trends over the period from 2006 to 2020 according to the Web Of Science core collection data. A total of 3222 articles associated with biomass gasification was retrieved, and its number grew annually. The subjects of study are diversified, primarily classified into "Energy & Fuels", "Engineering Chemical", and "Green Sustainable Science Technology". Moreover, Energy was a top published journal in the field of biomass gasification. Austrian contributors had the majority of publications, next to China and the USA. Liejin Luo from Xi'an Jiaotong University possessed the greatest H-index. Keyword evaluation showed that biomass gasification is a current hotspot, among which life-cycle assessment, sustainability, and deep processing of gasification products are future research directions. This work is predicted to offer further research interest in biomass gasification.

Steam Gasification of Biomass for Hydrogen Production – A Review and Outlook

This article summarizes various biomass gasification methods and explains their advantages and disadvantages. First, theoretical aspects of gasification and the variety in reactor designs are overviewed. Despite the eminent effect of reactor design on gas product quality, gasification agents remain the dominant factor that determines the gas composition. Steam gasification is a thermochemical process that promotes organic carbonaceous substances into carbon monoxide and hydrogen while reducing the presence of dilutants. However, several obstacles during gasification and downstream processing have to be overcome to achieve adequate maturity. Gasification characteristics of steam were compared to the other gasification agents, including air, oxygen and CO2. The key performance parameters affecting steam gasification include raw material properties, additive and catalytic materials. While the key operating parameters include operating temperature, residence time, superficial velocity, equivalence ratio and steam-to-biomass ratio. Finally, the techno-economic evaluation and challenges facing the commercialization of steam gasification were discussed.

Revealing the Mechanism of Dioxin Formation from Municipal Solid Waste Gasification in a Reducing Atmosphere.

Gasification is an effective technology for the thermal disposal of municipal solid waste (MSW) with lower dioxin emission compared to the prevailing incineration process. Nevertheless, the mechanism of dioxin formation in the reducing atmosphere during the gasification process was seldomly explored. Herein, the effects of the atmosphere, temperature, and chlorine source were systematically investigated in terms of dioxin distribution. With CO2 and H2O as gasification agents, a reducing reaction atmosphere was formed with abundant H2 which effectively suppressed the generation of C-Cl, contributing to a substantial decrease of dioxin concentration by ∼80% compared to the incineration process. The formation of dioxin was favored at temperatures below 700 °C with its peak concentration achieved at 500 °C. It was unveiled that inorganic chlorine played a dominant role in the reducing atmosphere, with a lower proportion of C-O-C/O-C═O on residual slag compared to an oxidizing atmosphere. Additionally, the generated H2 reduced the concentration of dioxins by attacking C-Cl and inhibiting the crucial Deacon reaction for dioxin formation, validated by density functional theory calculation. Eventually, the formation route paradigm and the reaction mechanism of dioxin formation from MSW gasification were revealed, facilitating and rationally guiding the control of dioxin emission.

Upcycling of biomass using gasification process based on various biomass types and different gasifying agents: systematic multi-criteria decision and sensitivity analysis

Upcycling of biomass using gasification process based on various biomass types and different gasifying agents: systematic multi-criteria decision and sensitivity analysis

Gasification Characteristics of High Moisture Content Lignite under CO2 and Auto-Generated Steam Atmosphere in a Moving Bed Tubular Reactor

An external thermal high-temperature continuous feed moving bed tubular reactor was used for the gasification of high moisture content lignite (30.41 wt.%) under CO2 and an auto-generated steam atmosphere. The objectives of this study are to illustrate the synergistic gasification characteristics of high moisture content lignite and CO2 in the tubular reactor; CO2 and auto-generated steam (steam released from the lignite) were used as gasification agents for lignite gasification. The effects of temperature and CO2 flow rate were also investigated. Experimental results showed that when the gasification temperature increased from 800 °C to 1000 °C, the H2 yield also increased from 8.45 mol kg−1 to 17.86 mol kg−1. This may indicate that the H2O-CO2 gasification of semi-coke was enhanced with the rise in temperature. At 900 °C, the gas yield increased with the increase in CO2 flow rate, while the yield of char and liquid product showed an opposite trend. The lower heating value of the H2-rich syngas varied from 11.73 MJ m−3 to 12.77 MJ Nm−3. The experimental results proved that the high moisture content lignite in-situ CO2 gasification process is an effective methodology for the clean and efficient utilization of lignite.

The dimensional design of a laboratory-scale fluidized bed gasifier using machine learning based on a kinetic method

Gasification provides various environmental and technological advantages, and the efficiency of the gasification system is affected by several factors, including the kind of fuel and gasification agent used, the gasifier's length and diameter, the operating pressure and temperature, etc. Experimental optimization approaches are more realistic, but they are time demanding; also, a reactor operating at high temperatures and pressures could be dangerous and expensive. Thus, researchers use a variety of modeling techniques, including the process simulators. Additionally, artificial neural network (ANN) as a machine learning approach, which is one of the process modeling methods, is a remarkable approach, and several papers have been published in which it has been utilized in combination with other modeling techniques. On the other hand, a combined process simulator/ANN model that considers gasifier design/operational parameters for the kinetic modeling of gasification process has not been reported.In this study, after kinetic modeling and validation of seven different circulating fluidized gasifiers using Aspen Plus, parametric studies were performed. Parametric analysis was used to examine the impacts of gasifier diameter, length, gasifier temperature, air/fuel ratio, and fuel type, and a dataset was created for ANN training. The syngas composition and thermal value were predicted using the ANN model. Therefore, a model was developed that takes into consideration both design and operating variables. The investigations revealed that heterogeneous reactions were the most critical factor in defining syngas characteristics. Although design factors have a considerable impact on syngas characteristics, the gasifier temperature is a key factor in the whole process. Furthermore, the ANN model estimates syngas specifications with great accuracy (R2 > 0.99 and MAPE < 3%) based on fuel attributes and gasifier design/operating parameters. Hence, ANN models can be used to analyze the effectiveness of systems including a complex combination of reactions and thermochemical processes.