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Biosolids is a by-product of wastewater treatment that needs to be further processed. Traditional biosolids treatment and disposal technologies are inefficient under the current demanding standards. Thermochemical conversion technologies have been employed for biosolids management, with gasification being the most promising due to the production of syngas, a gaseous product that may be used for the production of energy or high-added-value substances through reforming reactions. Gasification is a complex thermochemical process; its performance and yield are strongly affected by the type of feedstock, but also by the system configuration and process conditions. Gasification usually takes place at temperatures between 700 and 1,200 °C, but it may also occur at lower temperatures (above 375 °C: supercritical water gasification) or at higher temperatures (above 3,000 °C: plasma gasification). The present review briefly presents the biosolids management practices, focusing on the gasification process and syngas treatment, while the state of the art in biosolids gasification is critically presented and discussed. A number of types of gasifiers (more frequently fluidized bed, but also fixed bed, rotary kiln, downdraft, etc.), gasifying agents, and operational conditions have been used for biosolids gasification. The key results of the study regarding biosolids gasification are: (i) the increase of temperature and equivalence ratio enhances the gasification performance, resulting in high syngas yield and quality, high cold gas efficiency, and low tar and char production; (ii) the calorific value of the obtained syngas tends to decrease with the increase of equivalence ratio; and (iii) the use of catalysts has been proven to substantially improve the gasification performance, compared to non-catalytic gasification. The proper selection of technical parameters determines the effectiveness of biosolids gasification, which is considered as a promising technology for the energy recovery from biosolids, so to upgrade wastewater treatment and improve environmental quality., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

This study investigates the potential of using sewage sludge and low-rank coal for the sustainable production of sulfuric acid, which can then be used for the hydrolysis of straw through ASPEN PLUS simulation. Pyrolysis and gasification processes were used to convert sewage sludge and low-rank coal into syngas, which were then purified and oxidized to produce H 2 SO 4 and NH 3 gas. The pyro-gasification enhanced syngas yield. The effects of key process parameters such as temperature, steam-to-biomass ratio, equivalence ratio, and feedstock composition on the yield and composition of syngas and H 2 SO 4 coupled with minor parameters like pressure were investigated. The simulation was conducted over the temperature and pressure range of 400 - 900°°C and 70 - 150 kPa respectively. While the steam-to-biomass ratio and equivalence ratio were respectively varied from 0.66 - 1.65 and 0.14 - 0.35. Part of the 1012.88 kg/h of H 2 SO 4 produced was used to hydrolyze straw, producing glucose as a valuable feedstock for biorefineries. About 3989.10 kg/h of NH 3 was produced. Results showed that the use of sewage sludge and low-rank coal as feedstocks for syngas production can be a sustainable and cost-effective alternative to traditional fossil fuels. The resulting H 2 SO 4 can also be used for various other applications, such as in the production of fertilizers and detergents. Overall, this study agrees with the literature, demonstrates the potential of integrating biomass and waste resources for the sustainable production of high-value chemicals and fuels, and contributes to the field of sustainable chemical and energy production while addressing environmental and economic considerations., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Due to environmental issues, disposing of household garbage is a significant obstacle for life on Earth. Due to this, several sorts of research on biomass conversion into useable fuel technologies are carried out. Among the most popular and effective technologies is the gasification process, which transforms trash into a synthetic gas that can be used in industry. Several mathematical models have been put out to mimic gasification; however, they often fall short of accurately investigating and fixing flaws in the model's waste gasification. The current study used EES software to estimate the equilibrium of Tabriz City's waste gasification using corrective coefficients. The output of this model demonstrates that raising the temperature of the gasifier outlet, waste moisture, and equivalence ratio decreases the calorific value of the synthesis gas generated. Moreover, when using the current model at 800 °C, the synthesis gas has a calorific value of 1.9 MJm3. By comparing these findings to those of previous studies, it was shown that the biomass's chemical composition and moisture content, numerical or experimental methods, gasification temperature, and preheating of the gas input air all had a major influence on process outcomes. The C p of the system and the η II are equivalent to 28.31 $/GJ and 17.98%, respectively, according to the integration and multi-objective findings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Biomass, which is a renewable resource, is regarded as an essential energy source due to its accessibility and abundance. In this study, the gasification of wood-based biomass wastes from the medium density fiberboard (MDF) facility was carried out and investigated utilizing an updraft fixed bed gasifier. The feeding capacity of the upstream gasifier is 2100 kg/h. MDF wastes are loaded into the system with feeding capacities of 1500, 1750 and 2100 kg/h. As a reference, the system has also been tested with oak wood chips at a maximum rate of 2100 kg/h. Produced syngas production rate to biomass waste is approximately 2.5 Nm 3 /kg. The measured gas compositions are CO, CO 2 , CH 4 , H 2 , O 2 and N 2 . Test results with 2100 kg/hMDF wastes have similar gas composition compared to the test results with oak wood chips. The quality of the syngas produced by gasification is directly related to the fuel. It has been observed that the efficiency of the gasification process can be directly or indirectly impacted by the properties of the fuel, such as the moisture content, chemical compositions, and size. The temperature of the produced gas is approximately 430 °C, and it isdirectly combusted with tars and soot it contains to ensure that no chemical energy is lost. The thermal gasification system converts approximately 88% by weight of MDF residue to syngas. The calorific value of produced syngas is obtained between 6.0 and 7.0 MJ/Nm 3 . The hot syngas containing tars produced from the gasifier was directly burned in the thermal oil heater retrofitted to vortex syngas burner to recover thermal energy, which was then utilized in the production of energy via an ORC turbine. The thermal oil heater has a thermal capacity of 7MWh and the power generation capacity of the ORC turbine is 955 kW of electricity., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The use of renewable fuels leads to reduction in the use of fossil fuels and environmental pollutants. In this study, the design and analysis of a CCPP based on the use of syngas produced from biomass is discussed. The studied system includes a gasifier system to produce syngas, an external combustion gas turbine and a steam cycle to recover waste heat from combustion gases. Design variables include syngas temperature, syngas moisture content, CPR, TIT, HRSG operating pressure, and PPTD. The effect of design variables on performance components such as power generation, exergy efficiency and total cost rate of the system is investigated. Also, through multi-objective optimization, the optimal design of the system is done. Finally, it is observed that at the final decisioned optimal point, the produced power is 13.4 MW, the exergy efficiency is 17.2%, and the TCR is 118.8 $/h., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

This work presents a study of synthesis and characterization of catalysts-based cerium and nickel supported on the pumice stone (Ce/Pumice and Ni/Pumice) to be used in the gasification process of an invasive species present in the Canary Islands, such as Pennisetum setaceum to obtain syngas. Specifically, the effect of the metal impregnated on the pumice, and the effect of catalyst on the gasification process was studied. For this purpose, the composition of the gas was determined and the results obtained were compared with those obtained in non-catalytic thermochemical processes. Gasification tests were performed using a simultaneous thermal analyzer coupled with a mass spectrometer, providing a detailed analysis of the gases released during the process. The results showed that during the catalytic gasification process of the Pennisetum setaceum, the gases produced appear at lower temperatures in the catalytic process that in the non-catalytic process. Specifically, H 2 appears at 640.42 °C and 641.84 °C when Ce/pumice and Ni/pumice were used as catalyst, respectively, compared to 697.41 °C for the non-catalytic process. Moreover, the reactivity at 50 % of char conversion for the catalytic process (0.34 and 0.38 min -1 for Ce/pumice and Ni/pumice, respectively) was higher than for the non-catalytic process (0.28 min -1 ), indicating that the incorporation of Ce and Ni on the pumitic material increases the gasification rate of the char compared to the pumitic support. Catalytic biomass gasification is an innovative technology that can provide new opportunities for research and development of renewable energy technologies, as well as for the creation of green jobs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Supercritical water gasification has emerged as a promising technology to sustainably convert waste residues into clean gaseous fuels rich in combustible gases such as hydrogen and methane. The composition and yield of gases from hydrothermal gasification depend on process conditions such as temperature, pressure, reaction time, feedstock concentration, and reactor geometry. However, catalysts also play a vital role in enhancing the gasification reactions and selectively altering the composition of gas products. Catalysts can also enhance hydrothermal reforming and cracking of biomass to achieve desired gas yields at moderate temperatures, thereby reducing the energy input of the hydrothermal gasification process. However, due to the complex hydrodynamics of supercritical water, the literature is limited regarding the synthesis, application, and performance of catalysts used in hydrothermal gasification. Hence, this review provides a detailed discussion of different heterogeneous catalysts (e.g., metal oxides and transition metals), homogeneous catalysts (e.g., hydroxides and carbonates), and novel carbonaceous catalysts deployed in hydrothermal gasification. The article also summarizes the advantages, disadvantages, and performance of these catalysts in accelerating specific reactions during hydrothermal gasification of biomass, such as water-gas shift, methanation, hydrogenation, reforming, hydrolysis, cracking, bond cleavage, and depolymerization. Different reaction mechanisms involving a variety of catalysts during the hydrothermal gasification of biomass are outlined. The article also highlights recent advancements with recommendations for catalytic supercritical water gasification of biomass and its model compounds, and it evaluates process viability and feasibility for commercialization.

This paper presents new results on the gasification of spent pot lining (SPL) waste material generated in the primary aluminium smelting industry. The main objective is to test the performance of the gasification process of treated SPL materials and to develop an optimization method to maximize the quality of syngas fuel. The novelty of this study is the development of statistical models to predict the syngas composition and the gasification performance indicators during the SPL waste materials thermal conversion process. Modelling and simulation analysis are performed to convert the SPL solid materials to syngas fuel. The percentage of hydrogen (H 2 ) and carbon monoxide (CO) in the syngas fuel, the cold gasification efficiency (CGE) and the carbon conversion (CC) are determined. The response surface methodology (RSM) is used for the optimization of the performance of the gasification process. The effects of the input factors such as the temperature, the equivalence ratio and the steam to fuel ratio on the output variables (H 2 and CO in the syngas, the CGE and the CC) are determined. The optimization results show that the optimized operating parameters to maximize the H 2 , CO, CGE and CC were T = 1200 °C, ER = 0.1 and SFR = 1.29, respectively. The optimum values for the H 2 , CO, CGE and CC were 37.2%, 22.2%, 79.75% and 97.7%, respectively. New correlations for the variation of the output variables versus the input factors are also presented., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Fossil fuels are currently the dominant source of electricity and energy production around the world. Biomass is one of the most referred renewable carbonaceous resource(s) that can be employed for the waste-to-energy concept. Syngas obtained from biomass gasification can be utilized for a variety of key industrial purposes, including internal gasification engine operation, power generation, and hydrocarbon compound production using the Fisher-Tropsch technique. However, the existence of impurities such as hydrogen sulfide, tar, and particulate matter along with other undesirable chemicals present in syngas are major disadvantages of biomass gasification. Tar is the most difficult among all the pollutants to be removed from syngas; it also causes serious problems in downstream syngas applications. For decades, studies have been performed with various catalysts to remove the tar. Dolomite has shown positive response for tar elimination and hydrogen-enriched gas production. Several studies have been carried out on dolomite for eliminating the tar from syngas. This review encompasses sources of solid waste, the mechanism of catalysis, and in-situ and ex-situ usage of dolomite in the gasification process. It addresses the key issues such as fragmentation and attrition, elutriation, and coke formation along with dolomite's usefulness in amalgamation with other catalysts, environmental consequences, and economic viability of dolomite applications. It also discusses the challenges and opportunities for tar removal using catalysts, with a specific focus on dolomite along with economic and environmental sustainability considerations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Char-based catalyst has a promising application for biomass thermal conversion technology. In this work, Fe-Ni/Activated Char (AC) catalyst was prepared by impregnation method and used for the catalytic gasification of pine wood to obtain syngas. Further, the catalytic performance of Fe-Ni/AC was established by doing a comparative study of catalytic gasification of different biomass feedstocks. The results showed that under the catalysis of Fe-Ni/AC, the increase of gasification temperature was beneficial to increase gas yield, but not conducive to regulate the H 2 /CO ratio of syngas. The steam flow rate was directly related to the catalytic effect of Fe-Ni. The H 2 /CO ratio of syngas could reach 1.97 under the optimal conditions. Fe-Ni/AC had different catalytic effects on different biomass feedstocks, with the best for pine wood and the worst for cotton stalk, indicating that gasification intermediates of pine wood were difficult to decompose and depended more on catalyst., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Online measurements of the raw gas composition, including tars and water, during biomass gasification provide valuable information in fundamental investigations and for process control. Mainly consisting of hydrocarbons, tars can, in principle, be measured using Fourier transform infrared (FT-IR) spectroscopy. However, an instrument subjected to raw gas runs the risk of condensation of tars on optical components and subsequent malfunction. Therefore, an external cell, heated to at least  400 ℃, has been designed to ensure that tars remain in the gas phase during FT-IR measurements. The cell was used for on-line FT-IR measurements of permanent gases (CO, CO 2 , CH 4 ), water, and tars during the operation of a lab-scale downdraft gasifier using wood pellets, bark pellets, and char chips. Based on calibration, the measurement error of permanent gases was estimated to be 0.2%. Concentrations evaluated from spectral signatures of hydrocarbons in tar are in good agreement with results from solid-phase adsorption measurements and correlated well with operational changes in the gasifier.

Herein, we investigated the influence of gasification and fluidization parameters on the H 2 content of syngas and the retention of heavy metals (Cu and Pb) in a bed material during a two-stage fluidized bed gasification process. The results indicated that a temperature of 900 °C in both stages resulted in the highest H 2 content (32.4 mol%) in syngas. When different equivalence ratios (ERs) were investigated, it was found that the highest H 2 content in syngas (25.4 mol%) was achieved at an ER of 0.3. A particle size of 0.46 mm in the fluidized bed led to an increase in the H 2 content of syngas. Moreover, increasing the operating gas velocity led to an increase in the H 2 content of syngas. The heavy metal concentration in the bed material was the highest at 500 °C. When the influences of different particle sizes and operating gas velocities were compared, it was observed that a particle size of 0.46 mm and gas velocity of 1.5 U/U mf resulted in increased heavy metal concentrations in the bed material, which indicates that the reduction in the particle size and the increase in the operating gas velocity enhanced gasification and improved the retention of heavy metals.

Algae are one of the most viable feedstock options that can be converted into different bioenergies viz., bioethanol, biobutanol, biodiesel, biomethane, biohydrogen, etc. owing to their renewable, sustainable and economic credibility features. Algal biomass to fuel biorefining process is generally classified into three categories as chemical, biochemical and thermochemical methods. The present article aims to provide a state-of-the-art review on the factors affecting the thermochemical conversion process of algal biomass to bioenergy. Further, reaction conditions of each techniques (torrefaction, pyrolysis, gasification and hydrothermal process) influence biochar, bio-oil and syngas yield were discussed. Reaction parameters or factors such as reactor temperature, residence time, pressure, biomass load/feedstock composition, catalyst addition and carrier gas flow affecting process efficiency in terms of product yield and quality were spotlighted and extensively discussed with copious literature. It also presents the novel insights on production of solid (char), liquid (bio-oil) and gaseous (syngas) biofuel through torrefaction, pyrolysis and gasification, respectively. It is found that the energy intensive drying was more efficient mode involved in thermochemical process for wet algal biomass. However other modes of thermochemical process were having unique feature on improving the product yield and quality. Among the various factors, reaction temperature and residence time were relatively more important factors which affected the process efficiency. The other factors signposted in this review will lay a roadmap to researchers to choose an optimal thermochemical conditions for high quality end product. Lastly, the perspectives and challenges in thermochemical conversion algae biomass to biofuels were also discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Thermochemical techniques are being operated for the complete conversion of diverse biomasses to biofuels. Among the feedstocks used for thermochemical processes, algae are the promising biomass sources owing to their advantages over other feedstocks such as biomass productivity, renewability and sustainability. Due to several advantages, algal biomass is considered as a source for third generation biofuel. This review work aims to provide a state-of-the-art on the most commonly used thermochemical methods namely torrefaction, pyrolysis, and gasification processes. Furthermore, the production of biofuels from algal biomass was comprehensively articulated. Different algal strains used in thermochemical techniques and their conditions of operation were compared and discussed. The yield and quality of solid (char), liquid (bio-oil) and gaseous (syngas) products obtained through thermochemical methods were reviewed and analysed to understand the efficacy of each technique. End product percentage, quality and advantages of the torrefaction, pyrolysis, and gasification were summarized. It is found that the biofuel produced from the torrefaction process was easy to store and deliver and had higher utilization efficiency. Among the existing thermochemical methods, the pyrolysis process was widely used for the complete conversion of algal biomass to bio-oil or char. This study also revealed that the gasification (supercritical) method was the most energy efficient process for conversion of wet algal biomass. The reactor used in the thermochemical process and its subprocess was also highlighted. This study revealed that the fixed bed reactor was suitable for small scale production whereas the fluidized bed reactor could be scaled up for industrial production. In addition to that environmental impacts of the products were also spotlighted. Finally, the perspectives and challenges of algal biomass to bioenergy conversion were addressed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Biomass, as a renewable energy source, has high potential for supplying the energy needs of modern societies. Gasification is a thermochemical route for converting biomass into combustible gas at high temperatures. The main purpose of the present study was to develop an Aspen Plus model of air-steam gasification of biomass (sawdust) to predict the gasification characteristics and performances. The prediction capability of the model was evaluated by comparison with experimental data obtained in a fluidized bed biomass gasifier. First, the influence of gasification temperature on gas composition, product yields and gasifier performances was investigated. The biomass feeding rate and air flow rate were set at~0.445 kg/h and 0.5 Nm 3 /h, respectively, while the gasifier temperature was varied between 700 °C to 800 °C. With the increase of temperature, the gas yield (DGY) increased steadily from 1.72 to 2.0 Nm 3 /kg, while the HHV of the produced syngas (HHV gas ) increased initially from 5.38 to 5.73 MJ/Nm 3 and then decreased to 5.69 MJ/Nm 3 . After determining optimal temperature (800 °C), the influence of equivalence ratio (ER) and steam/biomass ratio (S/B) on gasification characteristics, dry gas yield (DGY) and tar yield (TRY) was studied. As ER increased from 0.19 to 0.23, TRY decreased from 9.13 g/Nm 3 to 8.45 g/Nm 3 . In contrast, DGY initially increased from 2.02 Nm 3 /kg to 2.43 Nm 3 /kg as ER increased from 0.19 to 0.21 and then dropped to 2.24 Nm 3 /kg at ER of 0.23. An increase in S/B from 0.61 to 2.7 also resulted in a slight increase in HHV gas ; however, TRY showed a decreasing trend (from 9.65 g/Nm 3 to 8.95 g/Nm 3 ). The results showed that the model developed in this paper is a promising tool for simulating the biomass gasification at various operating conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

The syngas that is produced from waste biomass often has high levels of CH 4 and CO 2 , which are greenhouse gases. This investigation presents an integrated gasification and catalytic reforming process with a closed gas loop that can improve quality of syngas from corn straw and mitigate CH 4 and CO 2 emission. The effects of the support type, reforming temperature, steam-to-biomass (S/B) ratio, and catalyst-to-biomass ratio (C/B) ratio on gas yield and composition were experimentally examined with waste corn straw as the feedstock gasified at 850 °C in the proposed closed-loop apparatus. Reformation of syngas using Ni/γ-Al 2 O 3 at 850 °C, S/B = 1 and C/B = 0.5 yielded 1.16 m 3 /kg of syngas, which contained 48.5% H 2 , 33.9% CO, 12.2% CO 2 and 5.3% CH 4 , corresponding to 71.0% and 81.5% enhancements of the first two and -77.8% and -58.1% reductions of the last two components., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Acetaldehyde removal tests were performed to compare the catalytic activity of the Kraft lignin char (KC), KOH-treated Kraft lignin char (KKC), and activated carbon (AC) along with their impregnation with Mn in a plasma reactor. The gasification characteristics (syngas content, and H 2 /CO ratio) of yellow poplar were investigated using nickel catalysts supported on KC, KKC, AC, and γ-Al 2 O 3 in a U-type quartz reactor. KKC and Mn/KKC improved significantly the surface area and contents of O and N functional groups over the raw char. In particular, Mn/KKC showed the highest acetaldehyde-removal efficiency. The catalytic activity of Ni-impregnated KC, KKC, AC, and γ-Al 2 O 3 decreased in the order of Ni/KKC > Ni/AC > Ni/KC > Ni/γ-Al 2 O 3 for the gas yield and Ni/γ-Al 2 O 3 >Ni/KC > Ni/AC >Ni/KKC for the oil yield, respectively. The Ni/KKC provides a more conducive environment for gasification, resulting in larger amounts of syngas (H 2 and CO) in the product gases. Moreover, Ni impregnated with char may be the most inexpensive and effective solution for achieving maximum tar reduction and syngas generation., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Gasification is one of the most important thermochemical routes to produce both synthesis gas (syngas) and chars. The quality of produced syngas wieldy depends on the operating conditions (temperature, residence time, heating rate, and gasifying agent), hydrodynamic properties of gasifier (particle size, minimum fluidization velocity, and gasifier size), and type of feedstock (coal, biomass, oil, and municipal solid wastes). In the present study, simulation of syngas production via circulating fluidized bed (CFB) gasification of algal biomass (Cladophora glomerata L.) at different gasifying agents and particle sizes was carried out, using Aspen Plus simulator. The model which has been validated by using experimental data of the technical literature was used to evaluate the influence of operating conditions on gas composition and performance parameters. The results show that biomass gasification using pure oxygen as the gasification agent has great potential to improve the caloric value of produced gas and performance indicators. It was also found that the produced gas caloric value, syngas yield, and performance parameters (CCE and CGE) increase with reaction temperature but are inversely proportional to the biomass particle size.

The paper provides a comparison of five distinct models, often used in thermodynamic equilibrium modeling that allows the study of feedstock effect on gasification process. The five models were thus formulated and solved using MATLAB software. The results were compared with published experimental data. The model based on equilibrium constant derived using methane formation reaction and water gas shift reaction showed comparatively better performance. Once the model was selected, the response surface analysis was employed to predict the parameters, such as reactor temperature and feedstock moisture content, for a maximum heating value of the producer gas. Simulations were performed for 50 different biomass feedstocks and simplified correlations were developed from simulated producer gas composition using multiple linear regression. These correlations may be suited for the quick comparison of different feedstocks in gasification process., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

There is a growing market demand for small-scale biomass gasifiers that is driven by the economic incentives and the legislative framework. Small-scale gasifiers produce a gaseous fuel, commonly referred to as producer gas, with relatively low heating value. Thus, the most common energy conversion systems that are coupled with small-scale gasifiers are internal combustion engines. In order to increase the electrical efficiency, the operators choose dual fuel engines and mix the producer gas with diesel. The Wiebe function has been a valuable tool for assessing the efficiency of dual fuel internal combustion engines. This study introduces a thermodynamic model that works in parallel with the Wiebe function and calculates the emissions of the engines. This "vis-à-vis" approach takes into consideration the actual conditions inside the cylinders-as they are returned by the Wiebe function-and calculates the final thermodynamic equilibrium of the flue gases mixture. This approach aims to enhance the operation of the dual fuel internal combustion engines by identifying the optimal operating conditions and-at the same time-advance pollution control and minimize the environmental impact.

The compositions of food wastes and their co-gasification producer gas were compared with the existing data of sewage sludge. Results showed that food wastes are more favorable than sewage sludge for co-gasification based on residue generation and energy output. Two decentralized gasification-based schemes were proposed to dispose of the sewage sludge and food wastes in Singapore. Monte Carlo simulation-based cost-benefit analysis was conducted to compare the proposed schemes with the existing incineration-based scheme. It was found that the gasification-based schemes are financially superior to the incineration-based scheme based on the data of net present value (NPV), benefit-cost ratio (BCR), and internal rate of return (IRR). Sensitivity analysis was conducted to suggest effective measures to improve the economics of the schemes., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Dried leaves are a potential source of energy although these are not commonly used beside to satisfy daily energy demands in rural areas. This paper aims at preparing a leafy biomass feedstock in the form of briquettes which can be directly used for combustion or to extract the combustible gas using a gasifier. Teak (Tectona grandis) and rubber (Hevea brasiliensis) leaves are considered for the present study. A binder-assisted briquetting technique with tapioca starch as binder is adopted. Properties of these leafy biomass briquettes such as moisture content, calorific value, compressive strength, and shatter index are determined. From the study, briquettes with biomass-to-binder ratio of 3:5 are found to be stable. Higher mass percentage of binder is considered for preparation of briquettes due to the fact that leafy biomasses do not adhere well on densification with lower binder content. Ultimate analysis test is conducted to analyze the gasification potential of the briquettes. Results show that the leafy biomass prepared from teak and rubber leaves has calorific values of 17.5 and 17.8 MJ/kg, respectively, which are comparable with those of existing biomass feedstock made of sawdust, rice husk, and rice straw.

A fluidized bed two-stage gasification process, consisting of a fluidized-bed (FB) pyrolyzer and a transport fluidized bed (TFB) gasifier, has been proposed to gasify biomass for fuel gas production with low tar content. On the basis of our previous fundamental study, an autothermal two-stage gasifier has been designed and built for gasify a kind of Chinese herb residue with a treating capacity of 600 kg/h. The testing data in the operational stable stage of the industrial demonstration plant showed that when keeping the reaction temperatures of pyrolyzer and gasifier respectively at about 700 °C and 850 °C, the heating value of fuel gas can reach 1200 kcal/Nm(3), and the tar content in the produced fuel gas was about 0.4 g/Nm(3). The results from this pilot industrial demonstration plant fully verified the feasibility and technical features of the proposed FB two-stage gasification process., (Copyright © 2016. Published by Elsevier Ltd.)

Modeling can be a powerful tool for designing and optimizing gasification systems. Modeling applications for small scale/fixed bed biomass gasifiers have been interesting due to their increased commercial practices. Fixed bed gasifiers are characterized by a wide range of operational conditions and are multi-zoned processes. The reactants are distributed in different phases and the products from each zone influence the following process steps and thus the composition of the final products. The present study aims to improve the conventional 'Black-Box' thermodynamic modeling by means of developing multiple intermediate 'boxes' that calculate two phase (solid-vapor) equilibriums in small scale gasifiers. Therefore the model is named ''Multi-Box''. Experimental data from a small scale gasifier have been used for the validation of the model. The returned results are significantly closer with the actual case study measurements in comparison to single-stage thermodynamic modeling., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

To achieve environmental-friendly and energy-efficiency synthetic natural gas (SNG) production routing from municipal solid waste (MSW), a MSW-to-SNG process is unprecedentedly presented in this work, of which the designed configuration is developed and simulated with the aid of Aspen Plus. In addition, sensitivity analyses on major operation parameters, such as equivalence volume ratio (ER), steam-to-MSW mass ratio (S/M) and methanation pressure, are performed with the discussion of process efficiencies and SNG quality. In parallel, the comparison analysis is considered by adopting various MSW material. In this work, the composition of SNG mainly consists of 87.7% CH4, 2.9% CO2, 2.3% H2 and 7.1% N2. And lower heating value (LHV) together with Wobbe index of SNG are separately 31.66MJ/Nm(3) and 45.90MJ/Nm(3). Moreover, the wood-to-SNG, MSW-to-SNG and coal-to-SNG processes are carried out to demonstrate the superiority of the MSW-to-SNG process. The results reveal that the MSW-to-SNG process is a promising option to dispose MSW environmentally, meanwhile converting MSW to the valuable SNG., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The paper presents a study for food processing industry waste to energy conversion using gasification and internal combustion engine for power generation. The biomass we used consisted in bones and meat residues sampled directly from the industrial line, characterised by high water content, about 42% in mass, and potential health risks. Using the feedstock properties, experimentally determined, two air-gasification process configurations were assessed and numerically modelled to quantify the effects on produced syngas properties. The study also focused on drying stage integration within the conversion chain: either external or integrated into the gasifier. To comply with environmental regulations on feedstock to syngas conversion both solutions were developed in a closed system using a modified down-draft gasifier that integrates the pyrolysis, gasification and partial oxidation stages. Good quality syngas with up to 19.1% - CO; 17% - H2; and 1.6% - CH4 can be produced. The syngas lower heating value may vary from 4.0 MJ/Nm(3) to 6.7 MJ/Nm(3) depending on process configuration. The influence of syngas fuel properties on spark ignition engines performances was studied in comparison to the natural gas (methane) and digestion biogas. In order to keep H2 molar quota below the detonation value of ⩽4% for the engines using syngas, characterised by higher hydrogen fraction, the air excess ratio in the combustion process must be increased to [2.2-2.8]. The results in this paper represent valuable data required by the design of waste to energy conversion chains with intermediate gas fuel production. The data is suitable for Otto engines characterised by power output below 1 MW, designed for natural gas consumption and fuelled with low calorific value gas fuels., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The main characteristics and environmental properties of the bottom ash (BA) generated from thermal treatment of waste may vary significantly depending on the type of waste and thermal technology employed. Thus, to ensure that the strategies selected for the management of these residues do not cause adverse environmental impacts, the specific properties of BA, in particular its leaching behavior, should be taken into account. This study focuses on the evaluation of potential environmental impacts associated with two different management options for BA from thermal treatment of Refuse Derived Fuel (RDF): landfilling and recycling as a filler for road sub bases. Two types of thermal treatment were considered: incineration and gasification. Potential environmental impacts were evaluated by life-cycle assessment (LCA) using the EASETECH model. Both non-toxicity related impact categories (i.e. global warming and mineral abiotic resource depletion) and toxic impact categories (i.e. human toxicity and ecotoxicity) were assessed. The system boundaries included BA transport from the incineration/gasification plants to the landfills and road construction sites, leaching of potentially toxic metals from the BA, the avoided extraction, crushing, transport and leaching of virgin raw materials for the road scenarios, and material and energy consumption for the construction of the landfills. To provide a quantitative assessment of the leaching properties of the two types of BA, experimental leaching data were used to estimate the potential release from each of the two types of residues. Specific attention was placed on the sensitivity of leaching properties and the determination of emissions by leaching, including: leaching data selection, material properties and assumptions related to emission modeling. The LCA results showed that for both types of BA, landfilling was associated with the highest environmental impacts in the non-toxicity related categories. For the toxicity related categories, the two types of residues behaved differently. For incineration BA the contribution of metal leaching to the total impacts had a dominant role, with the highest environmental loads resulting for the road scenario. For the gasification BA, the opposite result was obtained, due to the lower release of contaminants observed for this material compared to incineration BA. Based on the results of this study, it may be concluded that, depending on the type of BA considered, its leaching behavior may significantly affect the results of a LCA regarding its management strategies., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The major technical problems faced by stand-alone fluidized bed gasifiers (FBG) for waste-to gas applications are intrinsically related to the composition and physical properties of waste materials, such as RDF. The high quantity of ash and volatile material in RDF can provide a decrease in thermal output, create high ash clinkering, and increase emission of tars and CO2, thus affecting the operability for clean syngas generation at industrial scale. By contrast, a two-stage process which separates primary gasification and selective tar and ash conversion would be inherently more forgiving and stable. This can be achieved with the use of a separate plasma converter, which has been successfully used in conjunction with conventional thermal treatment units, for the ability to 'polish' the producer gas by organic contaminants and collect the inorganic fraction in a molten (and inert) state. This research focused on the performance analysis of a two-stage fluid bed gasification-plasma process to transform solid waste into clean syngas. Thermodynamic assessment using the two-stage equilibrium method was carried out to determine optimum conditions for the gasification of RDF and to understand the limitations and influence of the second stage on the process performance (gas heating value, cold gas efficiency, carbon conversion efficiency), along with other parameters. Comparison with a different thermal refining stage, i.e. thermal cracking (via partial oxidation) was also performed. The analysis is supported by experimental data from a pilot plant., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Gasification is a thermochemical pathway used to convert carbonaceous feedstock into syngas (CO and H2) in a deprived oxygen environment. The process can accommodate conventional feedstock such as coal, discarded waste including plastics, rubber, and mixed waste owing to the high reactor temperature (1000 °C-1600 °C). Pyrolysis is another conversion pathway, yet it is more selective to the feedstock owing to the low process temperature (350 °C-550 °C). Discarded tyres can be subjected to pyrolysis, however, the yield involves the formation of intermediate radicals additional to unconverted char. Gasification, however, owing to the higher temperature and shorter residence time, is more opted to follow quasi-equilibrium and being predictive. In this work, tyre crumbs are subjected to two levels of gasification modelling, i.e. equilibrium zero dimension and reactive multi-dimensional flow. The objective is to investigate the effect of the amount of oxidising agent on the conversion of tyre granules and syngas composition in a small 20 kW cylindrical gasifier. Initially the chemical compositions of several tyre samples are measured following the ASTM procedures for proximate and ultimate analysis as well as the heating value. The measured data are used to carry out equilibrium-based and reactive flow gasification. The result shows that both models are reasonably predictive averaging 50% gasification efficiency, the devolatilisation is less sensitive than the char conversion to the equivalence ratio as devolatilisation is always complete. In view of the high attained efficiency, it is suggested that the investigated tyre gasification system is economically viable., (© The Author(s) 2015.)

A multi-gene genetic programming technique is proposed as a new method to predict syngas yield production and the lower heating value for municipal solid waste gasification in a fluidized bed gasifier. The study shows that the predicted outputs of the municipal solid waste gasification process are in good agreement with the experimental dataset and also generalise well to validation (untrained) data. Published experimental datasets are used for model training and validation purposes. The results show the effectiveness of the genetic programming technique for solving complex nonlinear regression problems. The multi-gene genetic programming are also compared with a single-gene genetic programming model to show the relative merits and demerits of the technique. This study demonstrates that the genetic programming based data-driven modelling strategy can be a good candidate for developing models for other types of fuels as well., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Interest in biomass to produce heat, power, liquid fuels, hydrogen, and value-added chemicals with reduced greenhouse gas emissions is increasing worldwide. Gasification is becoming a promising technology for biomass utilization with a positive environmental impact. This review focuses specifically on woody biomass gasification and recent advances in the field. The physical properties, chemical structure, and composition of biomass greatly affect gasification performance, pretreatment, and handling. Primary and secondary catalysts are of key importance to improve the conversion and cracking of tars, and lime-enhanced gasification advantageously combines CO2 capture with gasification. These topics are covered here, including the reaction mechanisms and biomass characterization. Experimental research and industrial experience are investigated to elucidate concepts, processes, and characteristics of woody biomass gasification and to identify challenges.

A new concept is proposed for combined fermentation (two-stage high-load fermenter) and gasification (two-stage fluidised bed gasifier with CO2 separation) of sewage sludge and wood, and the subsequent utilisation of the biogenic gases in a hybrid power plant, consisting of a solid oxide fuel cell and a gas turbine. The development and optimisation of the important processes of the new concept (fermentation, gasification, utilisation) are reported in detail. For the gas production, process parameters were experimentally and numerically investigated to achieve high conversion rates of biomass. For the product gas utilisation, important combustion properties (laminar flame speed, ignition delay time) were analysed numerically to evaluate machinery operation (reliability, emissions). Furthermore, the coupling of the processes was numerically analysed and optimised by means of integration of heat and mass flows. The high, simulated electrical efficiency of 42% including the conversion of raw biomass is promising for future power generation by biomass., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Aim of this work is to introduce an alternative to the standard biodiesel production chain, presenting an innovative in situ system. It is based on the chemical conversion of vegetable oil from oleaginous crops in synergy with the gasification of the protein cake disposed by the seed press. The syngas from the gasifier is here used to produce electrical power while part of it is converted into methanol. The methanol is finally used to transform the vegetable oil into biodiesel. Through a coupled use of ASPEN PLUS(TM) and MATLAB(TM) codes, a rapeseed, soy and sunflower rotation, with a duration of three year, was simulated considering 15ha of soil. This surface resulted sufficient to feed a 7kWel power plant. Simulation outputs proven the system to be self-sustainable. In addition, economical NPV of the investment is presented. Finally the environmental, economical and social advantages related to this approach are discussed., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

A technical analysis has been completed for a commercial-scale two-stage gasification-combustion system. The CLEERGAS (Covanta Low Emissions Energy Recovery GASification) process consists of partial combustion and gasification of as-received municipal solid waste (MSW) on a moving grate producing syngas followed by full combustion of the generated syngas in an adjoining chamber and boiler. This process has been in operation since 2009 on a modified 330-tonne day(-1) waste-to-energy (WTE) line in Tulsa, Oklahoma. Material balances determined that the syngas composition is 12.8% H2 and 11.4% CO, the heating value of the gas in the gasifier section is 4098 kJ Nm(-3), and an aggregate molecular formula for the waste is C6H14.5O5. The analysis of gas measurements sampled from the Tulsa unit showed that the gasification-combustion mode fully processed the MSW at an excess air input of only 20% as compared to the 80-100% typically found in conventional WTE moving grate plants. Other important attributes of the CLEERGAS gasification-combustion process are that it has operated on a commercial scale for a period of over two years with 93% availability and utilizes a moving grate technology that is currently used in hundreds of WTE plants around the world., (© The Author(s) 2014.)

The effect of ash composition on the fluidized bed gasification behaviour of poultry wastes was investigated by operating a pre-pilot scale reactor with two batches of manure obtained from an industrial chicken farm. The experimental runs were carried out by keeping the fluidized bed velocity fixed (at 0.4m s(-1)) and by varying the equivalence ratio between 0.27 and 0.40, so obtaining bed temperature values between 700 and 800 °C. The performance of the gasification process was assessed by means of mass balances as well as material and feedstock energy analyses, and reported in terms of cold gas efficiency (CGE), specific energy production, low heating value of obtained syngas and yield of undesired by-products. The experimental results indicate the crucial role of ash amount and composition of the two poultry wastes. In particular, higher ash content (25.1% instead of 17.2%) and higher fractions of calcium, phosphorous and potassium (with an increase of 24, 30 and 28%, respectively) induce a dramatic reduction of all the process performance parameters: CGE reduces from 0.63 to 0.33 and the specific energy from 2.1 to 1.1 kWh kg(fuel)(-1). At the same time, the formation of alkali compounds and their behaviour inside the fluidized bed reactor determine an increase of feedstock energy losses, which is related to occurrence of sintering and bridging between bed particles.

In the present study, a microwave-assisted biomass gasification system was developed for syngas production. Three catalysts including Fe, Co and Ni with Al2O3 support were examined and compared for their effects on syngas production and tar removal. Experimental results showed that microwave is an effective heating method for biomass gasification. Ni/Al2O3 was found to be the most effective catalyst for syngas production and tar removal. The gas yield reached above 80% and the composition of tar was the simplest when Ni/Al2O3 catalyst was used. The optimal ratio of catalyst to biomass was determined to be 1:5-1:3. The addition of steam was found to be able to improve the gas production and syngas quality. Results of XRD analyses demonstrated that Ni/Al2O3 catalyst has good stability during gasification process. Finally, a new concept of microwave-assisted dual fluidized bed gasifier was put forward for the first time in this study., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The gasification kinetic analysis of the three pseudocomponents (hemicellulose, cellulose and lignin) of biomass decomposition in the agent of CO2 were investigated. The Multi-peaks method was used to fit the Gaussian distribution model of DTG curves. The Friedman method was used to estimate the effective Eα, and the master plot method was used for the determination of the kinetic model. The results showed that there were two reaction stages for semi-cellulose and lignin. The DTG curves of semicellulose and lignin cannot be fitted by Gaussian distribution model. The Eα were ranged from 80 to 220kJmol(-1) for the three pseudocomponents. The Fn model could describe the kinetic process of stage I of semi-cellulose decomposition. Both cellulose and stage II of semicellulose decomposition could be described by An model and the two reaction stages of the lignin were fitted the Rn model very well., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Gasification is considered to be an effective process for energy conversion from various sources such as coal, biomass, and waste. Cleanup of the hot syngas produced by such a process may improve the thermal efficiency of the overall gasification system. Therefore, the cleanup of hot syngas from biomass gasification using molten carbonate is investigated in bench-scale tests. Molten carbonate acts as an absorbent during desulfurization and dechlorination and as a thermal catalyst for tar cracking. In this study, the performance of molten carbonate for removing H2S was evaluated. The temperature of the molten carbonate was set within the range from 800 to 1000 °C. It is found that the removal of H2S is significantly affected by the concentration of CO2 in the syngas. When only a small percentage of CO2 is present, desulfurization using molten carbonate is inadequate. However, when carbon elements, such as char and tar, are continuously supplied, H2S removal can be maintained at a high level. To confirm the performance of the molten carbonate gas-cleaning system, purified biogas was used as a fuel in power generation tests with a molten carbonate fuel cell (MCFC). The fuel cell is a high-performance sensor for detecting gaseous impurities. When purified gas from a gas-cleaning reactor was continuously supplied to the fuel cell, the cell voltage remained stable. Thus, the molten carbonate gas-cleaning reactor was found to afford good gas-cleaning performance., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Gasification technologies for waste processing are receiving increased interest. A lot of gasification technologies, including gasification and melting, have been developed in Japan and Europe. However, the flue gas and heavy metal behaviors have not been widely reported, even though those of grate furnaces have been reported. This article reports flue gas components of gasification and melting technology in different flue gas treatment systems. Hydrogen chloride concentrations at the inlet of the bag filter ranged between 171 and 180 mg Nm(-3) owing to de-acidification by limestone injection to the gasifier. More than 97.8% of hydrogen chlorides were removed by a bag filter in both of the flue gas treatment systems investigated. Sulfur dioxide concentrations at the inlet of the baghouse were 4.8 mg Nm(-3) and 12.7 mg Nm(-3), respectively. Nitrogen oxides are highly decomposed by a selective catalytic reduction system. Owing to the low regenerations of polychlorinated dibenzo-p-dioxins and furans, and the selective catalytic reduction system, the concentrations of polychlorinated dibenzo-p-dioxins and furans at the stacks were significantly lower without activated carbon injection. More than 99% of chlorine is distributed in fly ash. Low-boiling-point heavy metals, such as lead and zinc, are distributed in fly ash at rates of 97.6% and 96.5%, respectively. Most high-boiling-point heavy metals, such as iron and copper, are distributed in metal. It is also clarified that the slag is stable and contains few harmful heavy metals, such as lead. The heavy metal distribution behaviors are almost the same regardless of the compositions of the processed waste. These results indicate that the gasification of municipal solid waste constitutes an ideal approach to environmental conservation and resource recycling.

Selective oxygen (O2) removal from wood-derived syngas was investigated over three types of ceria-modified alumina supported metal catalysts (i.e., Pt, Pd, and Cu). Complete O2 removal was observed with the Pt and Pd catalysts at a lower temperature than with the Cu catalyst. Gas hourly space velocity (GHSV) was another critical parameter affecting O2 removal, substantially reducing O2 conversion by all three catalysts at 4000 h(-1) or above. The Cu catalyst appeared to be most sensitive to GHSV. Among three catalysts, the Pd catalyst had the best performance on O2 removal. In addition to reaction conditions, CO2 and water vapor in the syngas also influenced O2 removal, both of which had adverse effects on O2 conversion. Stability tests indicated that both Pt and Pd catalysts were quite stable over a 300 h testing period while the Cu catalyst was deactivated after 50h and regenerated by elevating reaction temperature., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Downdraft stratified gasifiers seem to be the reactors which are most influenced by loading conditions. Moreover, the larger the reactor is, the higher the possibility to stumble across a channeling phenomenon. This high sensitivity is due to the limited thickness and superficial placement of the flaming pyrolysis layer coupled with the necessity to keep all the zones parallel for a correct running of this kind of gasifier. This study was aimed at modeling and investigating the channeling phenomenon generated by loading condition variations on a 250-kWe nominal power gasification power plant. The experimental campaign showed great variations in most of the plant outputs. These phenomena were modeled on two modified mathematical models obtained from literature. The results of the models confirmed the capability of this approach to predict the channeling phenomena and its dependency on the loading method., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The gasification of a two-layer porous solid fuel in a combined charge of a low-temperature gas generator has been studied using a mathematical model and a computational algorithm implemented in the OpenFOAM software. In the computational experiments, the influence of the two-layer nature of a porous solid fuel on its gasification has been investigated for gasifiers containing polymethylmethacrylate and polyethylene as fuels with different relative position of their layers. It has been shown that in two-layer fuels, two gasification waves can propagate simultaneously, due to which the relative mass flow rate of gasification products can have two local maxima. The operating time of a gas generator with a two-layer porous fuel depends ambiguously on the relative position of the layers and can go beyond the range between the operating times of the gasifier with each of the fuels. [ABSTRACT FROM AUTHOR]

A method is proposed for the thermochemical processing of biomass (lignin) meant for the use of one reactor for the production of two synthetic gases dissimilar in composition and calorific value: low-calorie (1800–2000 kcal/nm3) and medium-calorie (~ 4000 kcal/nm3) with a low resin content. Two methods for calculating the composition of pyrolysis gas have been developed. Various variants of the operation of installation in cyclic and quasi-stationary modes are considered, taking into account unique technical solutions for supplying coke–ash residue from the pyrolyzer to the gasifier. [ABSTRACT FROM AUTHOR]

• Dedusting of real hot producer gas from gasification of biomass. • Guidelines for the development of hot gas filters and their bullet-proofing. • Technical and process solutions for stable dedusting hot producer gases. • Methods for determining operational windows for hot gas filters. • Comparison and evaluation of several pulse-jet cleaning designs. The paper aims to summarize the technical and process development of hot gas filtration technology that was tested and optimized under the conditions of producer gases generated through the gasification of wood chips in a fixed-bed 60kWth GazEla reactor. The paper describes the results of testing two generations of hot gas filters, four types of filtration elements, as well as a range of auxiliary subunits (i.a. methods for secure fixing and sealing of the filters). Additionally, an in-depth analysis was performed on the efficiency of pulse-jet cleaning, which through a statistical study indicated change-effect relationships between the main pulse-jet parameters. Based on this learning curve, the paper presents a set of guidelines that can be used for the development of robust hot gas filters, as well as for resolving their unstable operation. [ABSTRACT FROM AUTHOR]

This paper presents an improved mathematical model for gasification of a solid porous fuel when hot gases are filtered through it. Gasification modes were studied at a constant pressure drop between the gasifier inlet and outlet and at a constant gas velocity at the gasifier inlet using polymethyl methacrylate as an example. In the case of a constant pressure drop, fuel gasification takes longer and the gas temperature at the outlet increases more slowly than in the case of a constant gas velocity at the inlet under comparable conditions. [ABSTRACT FROM AUTHOR]

This work evaluated the influence of superheated water steam injection in an autothermal 80 kW th pilot-scale bubbling fluidized bed during biomass direct (air) gasification, focusing on the effect of steam to biomass ratio in the producer gas composition and gasification efficiency parameters. The process was also evaluated in an externally heated 3 kW th bench-scale bubbling fluidized bed and simulated in a thermodynamic equilibrium model. For low-density biomass, the steam injection resulted in a producer gas with higher H 2 concentration and H 2 /CO molar ratio, although with lower energy content, and in a decrease of the process efficiency. Thus, steam injection promoted a trade-off between parameters, that can be associated with a higher occurrence of the water-gas shift reaction. For high-density biomass, along with an increase of H 2 concentration and H 2 /CO molar ratio, steam injection promoted an increase of the producer gas energy content and process efficiency, which can be justified by a higher char accumulation in the reactor bed and consequent higher occurrence of char-steam reforming reactions. Therefore, steam injection shows high potential to improve the producer gas quality from high-density biomass air gasification, however, for low-density biomass, it shows limited potential and should only be used to adjust H 2 /CO molar ratio. • Steam injection was tested to improve producer gas quality from direct (air) biomass gasification. • Steam injection impact was dependent on the biomass and respective reactor bed char inventory. • Under some conditions, steam injection improved producer gas quality and gasification efficiency. • A steam to biomass ratio of 0.5 is recommended for air-steam gasification of high-density biomass. • For low-density biomass, steam addition should only be used to adjust H2/CO molar ratio. [ABSTRACT FROM AUTHOR]