Biomass Air-steam Gasification Research Articles

A combined approach-based techno-economic-environmental multi-optimization of a hydrogen generation system through waste biomass air-steam gasification

In this study, a biomass air-steam gasification system for hydrogen production was simulated in Aspen Plus and validated using experimental studies. Sewage sludge was considered as the biomass feed. A combined approach including the combination of the NSGA-II algorithm, the response surface methodology (RSM) and TOPSIS decision-making method, was used to multi-optimize this hydrogen production system. To optimize the performance of the system, first, mathematical equations between equivalence ratio (ER), steam to biomass ratio (SBR), and gasifier temperature as the decision variables and the mole flow of H2 and CO2 and the levelized cost of hydrogen (LCOH) as the objective functions were obtained by the RSM technique. To maximize the mole flow of H2 and minimize CO2 emission and LCOH, a multi-objective optimization using NSGA-II was conducted. The ER, SBR and gasifier temperature were analyzed in the range of 0.1–0.4, 0.2 to 2 and 600 °C–1000 °C, respectively. By employing the TOPSIS decision-making method, several optimum points were obtained by giving each of the decision variables a specific weight. The lowest LCOH was found to be 1.5 €/kg H2 at the ER of 0.103, SBR of 0.83, and gasification temperature of 956 °C.

Insights into exergy analysis of air-steam biomass gasification for H2 production via kinetic modeling

Insights into exergy analysis of air-steam biomass gasification for H2 production via kinetic modeling

Hydrogen Production Enhancement and Tar Reduction using New Three-Layer Annular Downdraft Air-Steam Biomass Gasifier

This study presents experimental analysis of biomass air-steam gasification for the enhancement of H2 production in producer gas (PG). Wood pellets which are widely available in Malaysia are used in this investigation. A pilot scale downdraft gasifier based on new three-layers annular reactor design was implemented to produce hydrogen enriched PG. The reactor is initially heated using hot flue gas from LPG combustion which is switched to PG when the reactor reaches stable operation. The effect of steam to biomass (S/B) ratio from 1.1 to 1.5 on PG quality in terms of gas composition, HHV and tar contamination is studied. Maximum H2 production of 27.7% was achieved at optimum air flow rate of 75 LPM and S/B ratio of 1.2. At the optimum air flow rate, HHV and tar contamination in PG where in the range of 5.06 - 6.08 MJ/Nm3 and 187 - 30mg/m3, respectively.

H2-rich gas production from wood biomass air-steam gasification over a multifunctional Ni1.5Ca4.0Mn1.0Ox catalyst derived from biomaterial

Solid waste is a vexing and widespread issue, especially in urban and rural areas, where waste wood and eggshells generate significant pollution. Wood-based biomass features high-quality carbon neutral energy source properties, and discarded eggshells can be employed to develop a calcium-based multifunctional catalyst for wood gasification, thereby converting the waste into green hydrogen. In this work, an oxygen-rich vacancy (82.1%) Ni1.5Ca4.0Mn1.0Ox catalyst with a dual pore size nanostructure was derived from waste eggshell and demonstrated anti-coking, CO oxidation, CO2 fixation and high performance in H2-rich gas production during wood air-steam gasification. The mechanism for removing carbon deposition was based on the transfer of carbon species on Ni metal surfaces by using Mn and Ca substances. The behavior of wood non-catalytic gasification and catalytic gasification were quantitatively analyzed and compared on a time scale. Effects of temperature, duration time, and steam/biomass mass ratio were studied to determine the optimal gasification conditions. Catalytic gasification achieved an increase of 32.3% and 5.42 of H2 proportion and H2/CO as well as a decline of 8.51% of CO and 21.05% of CO2 contents when compared to non-catalytic air-steam gasification. This work might provide an innovative perspective on using waste to generate green hydrogen.

Techno-economic and environmental assessment of a novel polygeneration system based on integration of biomass air-steam gasification and solar parabolic trough collector

Renewable energy-based polygeneration energy systems, in addition to providing a variety of products, can effectively improve this planet's environmental conditions and reduce emissions. Therefore, in the present work, a novel polygeneration system has been proposed to produce power, heat, freshwater, and hydrogen-based on biomass and solar energy. In the present system, the Kalina cycle, Gas turbine cycle, double-pressure steam cycle, and organic Rankine cycle are used to produce power, Multi-effect desalination and reverse osmosis are used to produce freshwater, and the PEM electrolyzer is used to produce hydrogen. Also, the exhaust syngas from the gasification process has been used to supply steam to the gasifier reactor. Considering the determination of environmental laws and the need to transform Kish Island into a green island for residents and tourists, a proposed system has been defined for Kish Island in Iran. In the proposed system, the feasibility of three biomass fuels, Municipal Solid Waste (MSW), Mixed Paper Waste (MPW), and Date Palm Waste (DPW), was studied from a technical, economic, and environmental point of view. Air and steam agents have been used for the gasification of mentioned fuels. To evaluate the performance of the system in terms of thermodynamics, economics, and environment during the year, the analysis of the average monthly solar for the studied system has been used. MED has been analyzed using artificial intelligence techniques. Finally, a sensitivity analysis is performed for the main operational parameters. The results of the proposed system modeling show that MSW is the most economical fuel and the use of DPW has the least environmental impact on the system, but in terms of operating conditions, MPW with overall energy and exergy efficiency of 41.68% and 34.19% compared to other fuels perform better. The overall results of the 4E analysis for MSW fuel show that the overall energy and exergy efficiency of the polygeneration system is 39% and 32.01%, respectively. Power generation costs and environmental impacts for MSW biomass are 0.014 $/kWh and 0.002 Pts/kWh, respectively. The monthly analysis of the studied system for all three fuels shows that the net power generation decreases in the summer months. The results of the sensitivity analysis of the studied system show that the optimal design of gasification temperature, air compressor pressure ratio, condenser pressure, and the number of MED effects play a key role in the objective functions of the studied system.

Hydrogen Rich Product Gas from Air–Steam Gasification of Indian Biomasses with Waste Engine Oil as Binder

Production of hydrogen rich product gas through thermochemical energy conversion having the biomass gasification is making significant inroads for green hydrogen fuel generation. In the present work, detailed physical and chemical characterization, air and air–steam biomass gasification of four biomasses i.e., Kasai Saw Dust, Lemon Grass, Wheat Straw and Pigeon Pea Seed Coat from four different group of biomass production system at different steam to biomass ratio, equivalence ratio and with and without binder is analysed. Waste engine oil as an additive/binder is used. Experimental investigation for air and air–steam gasification is applied and compared. Product gas constituents, hydrogen production is examined with different steam to biomass (S/B) ratio and equivalence ratio. The equivalence ratio varies from 0.20 to 0.40 and the S/B ratio between 0 and 4. The waste engine oil (5 and 10 wt%) is mixed with the biomass during palletization. Results show maximum H2 production and HCV of product gas at an air to fuel of 0.26 and 2.4 steam to biomass ratio. This study considers the rarely studied Indian biomasses with waste engine oil as an additive for hydrogen-rich product gas production having small scale biomass gasifier.

Comparative exergoeconomic analysis of indirect and direct bio-dimethyl ether syntheses based on air-steam biomass gasification with CO2 utilization

Dimethyl ether (DME) is a potential energy source because it is a clean fuel and a crucial intermediate in various chemical productions. The main purposes of this work were to assess and compare the indirect and direct bio-DME syntheses from air-steam biomass gasification with CO2 utilization using energetic, exergetic, and exergoeconomic analyses. The effects of hydrogen to carbon monoxide (H2/CO) and carbon dioxide to carbon monoxide (CO2/CO) ratios on DME yield of the indirect and direct processes were firstly investigated. When considering the combined processes, the results were found that the DME yield of the system with direct DME synthesis is higher than that of the indirect system. Moreover, the energy consumption and exergy destruction of biomass gasification and DME synthesis processes in the indirect system are considerably higher when compared to the direct system. For exergoeconomic analysis, the DME unit cost of the direct system (1.66 $/kg DME) also has lower than that of the system with indirect DME synthesis (2.26 $/kg DME). In addition, the CO2 emission of both systems was also considered. The CO2 emission intensity of the system with direct DME synthesis shows 32.35% lower than the system with indirect DME synthesis.

Eulerian-Lagrangian simulation of air-steam biomass gasification in a three-dimensional bubbling fluidized gasifier

A CFD-DEM (computational fluid dynamics – discrete element method) model, with heat transfer, and homogeneous and heterogeneous chemical reactions accounted for, is implemented here to numerically study the biomass gasification in a three-dimensional bubbling fluidized bed. The results show that the biomass inlet on the right sidewall results in laterally asymmetrical profiles of important bed hydrodynamics and gas concentrations. Increasing the temperature, steam-biomass ratio and equivalence ratio all enlarge the gas voidage, fluid force, collision force and dispersion coefficient of the solid phase, but have different effects on the different homogeneous reaction rates. Vigorous horizontal and vertical solid dispersions occur in the lateral central and sidewalls of the bed, respectively. The results of the current work provide valuable insights regarding the hydrodynamics of the bubbling fluidized bed for biomass gasification, and are expected to be useful for the operation, scale-up and optimization of such systems for sustainable energy production.

Numerical Investigation of the Air-Steam Biomass Gasification Process Based on Thermodynamic Equilibrium Model

In the present work, the air-steam biomass gasification model with tar has been developed based on the equilibrium constants. The simulation results based on two different models (with and without tar) have been validated by the experimental data. The model with tar can well predict the tar content in gasification; meanwhile, the predicted gas yield (GY), based on the model with tar, is much closer to the experimental data. The energy exchange between the gasifier and the surrounding has been studied based on the dimensionless heat transfer ratio (DHTR), and the relationship between DHTR and the process parameters is given by a formula. The influence of process parameters on the syngas composition, tar content, GY, lower heating value (LHV), and exergy efficiency have been researched.

Exergoeconomics of hydrogen production from biomass air-steam gasification with methane co-feeding

Biomass is one of the most promising energy sources for hydrogen production. However, biomass gasification has a low hydrogen content in the producer gas. To increase the hydrogen yield, the co-feeding of methane into biomass gasification is proposed in this study. The type of gasifying agent is a key factor in the determination of the content of the hydrogen product. To compare the designs and find the best performance criteria of a process, not only energy and exergy analyses but also a cost analysis of the process should be investigated. In the present study, the effects of various types of gasifying agent, i.e., air and both steam and air, for the biomass gasification with/without methane co-feeding are investigated through an exergoeconomic analysis. It is observed that the air-steam used as an agent achieves high energy and exergy efficiency. Methane co-feeding can improve the energy and exergy efficiency. In exergoeconomic analysis, the specific exergy cost (SPECO) method is applied to investigate the unit cost of hydrogen. The economic reveal that the biomass gasification using air-steam as an agent with methane co-feeding also presented the lowest unit hydrogen cost of 2.69$/kg. The unit exergy cost of hydrogen is 0.068$/kWh.

Design of an integrated biomass gasification and proton exchange membrane fuel cell system under self-sustainable conditions: Process modification and heat-exchanger network synthesis

The design and analysis of an integrated biomass gasification and PEMFC system to generate heat and power demand for residential applications are presented in this study. Two biomass gasification configurations using sawdust as a feedstock are considered: air–steam biomass gasification (AS-BG-PEMFC) and steam-only biomass gasification (SO-BG-PEMFC). The biomass processing consists of a biomass gasification which is used to produce H2-rich gas (syngas), followed by high- and low-temperature shift reactors and a preferential oxidation reactor. Pinch analysis is performed to evaluate and design a heat-exchanger network in the two biomass gasification systems. The remaining useful heat is recovered and employed for a reactant preparation step and for a heating utility system in a household. The simulation results indicate that the SO-BG-PEMFC generates syngas with a greater H2 content than the AS-BG-PEMFC, resulting in higher fuel processor and electric efficiencies. However, the AS-BG-PEMFC provides a higher thermal efficiency because a high-temperature gaseous product is obtained, and more energy is thereby recovered to the system. The total heat and power efficiencies of the AS-BG-PEMFC and the SO-BG-PEMFC are 83% and 70%, respectively. The Sankey diagram of energy flows reveals that the performance improvement depends entirely on the utilization of useful energy in the exhaust gas.

Air–steam biomass gasification: Experiments, modeling and simulation

Biomass is one of the most widely available energy sources and gasification is as an efficient process of converting biomass into combustible gases by partial oxidation at high temperature. In order to increase the hydrogen content of the producer gas, steam is used along with air in a gasifier. In the present study, extensive experimental work is carried out in a downdraft gasifier using air and steam both and termed as air–steam gasification. Upon reaching the steady state conditions with air gasification, saturated steam is injected into the reduction zone of gasifier and its effects on gasifier performance is evaluated. The steam addition boosts the water gas shift reaction and increases the hydrogen content in the producer gas. The dynamic behavior of the gasifier in terms of the variation of composition of producer gas and zone temperatures with time is incorporated in the present study. The performance of gasification has been evaluated by varying the operating parameters like moisture content (0.015–0.042 wet basis), steam to biomass ratio (0.76–1.21) and equivalence ratio (0.1288–0.303). With the variation in the above parameters biomass consumption rate, composition of producer gas and cold gas efficiency is analyzed. Equilibrium model is developed to predict the composition of producer gas and calorific values. Component balances and energy balance are coupled with the equilibrium relations in the model. The developed model is validated using the experimental data. The effects of moisture content, equivalence ratio, and steam to biomass ratio on the composition are predicted.

Parametric analysis of a circulating fluidized bed biomass gasifier for hydrogen production

Biomass is considered a potential energy source which can be efficiently converted to useful gaseous products via a gasification process. Circulating fluidized bed (CFB) gasifiers have attracted significant attention due to their high reaction rates and thermal efficiency. This study aims to investigate the CFB biomass gasification process to generate H2-rich synthesis gas. A process simulator is used to analyze the gasifier performance by assuming that the gasification is fast and reach equilibrium. Parametric analysis of the CFB gasifier shows that steam gasification generates the synthesis gas attained the highest H2 content (50–65 vol.%) and the highest product gas quality (higher heating value, HHV = 10–13 MJ/Nm3) at operating temperatures approximately 650–700 °C. High-temperature steam cannot provide enough energy for the gasifier, reducing the gross cold gas efficiency of this process to only 16%. The biomass air-steam gasification process is investigated while avoiding high energy consumption, but less H2 is produced under these conditions.

Simulation of Enriched Air-Steam Biomass Gasification in a Bubbling Fluidized Bed Gasifier

A model was developed for the enriched air-steam biomass gasification in a bubbling fluidized bed (BFB) gasifier using Aspen Plus. Restricted equilibrium method was used to eliminate the deviation caused by the diffusion effect of gas-particle. The model has been divided into three stages (drying and pyrolysis, partial combustion and gasification) for predicting the gasifier performance. Simulation results for gas composition, carbon conversion and cold gas efficiency versus oxygen percentage and steam to biomass ratio (S/B) were compared with the experimental results. Higher oxygen percentage improves the gasification process, increases the production of H2 and CO and results in better gasification efficiency. With increasing oxygen percentage, the production of CO2 and CH4 show decreasing trends. Steam injection enhances the H2 and CO2 production but decreases CO and CH4 production. Carbon conversion presents a slight decrease trend over the S/B range, while cold gas efficiency is first constant and then decreased.

Quasi-equilibrium thermodynamic model with empirical equations for air–steam biomass gasification in fluidized-beds

Gasification is one of the most promising technologies for converting biomass into a fuel. This study presents a simple and practical biomass gasification model based on thermodynamic equilibrium to find effective operating conditions of the air–steam gasification system in fluidized-beds. The carbon conversion fraction empirically obtained was involved in a global gasification reaction. Two empirical equations as the non-equilibrium factor expressing the deviation from equilibrium were derived as the function of the equivalence ratio (ER) from 43 experimental data sets of various operating conditions and different feedstocks. One energy balance was also solved for determining the gasification temperature (T). After the producer gas composition with respect to ER and steam to biomass ratio (SBR) was obtained from the air–steam biomass gasification (ASBG) model, process performances such as lower heating value, heat efficiency, net heat efficiency, and H2/CO molar ratio were evaluated. An effective operating area was suggested from the contour plot of the process performances with respect to ER and SBR in the auto-thermal gasification temperature from 700 to 830°C.

Modeling the effects of the operational parameters on H 2 composition in a biomass fluidized bed gasifier

In this study, effects of the operational parameters such as gasifier temperature, bed operational velocity, equivalence ratio, biomass particle size and biomass-to-steam ratio on hydrogen production from an atmospheric biomass FB gasifier is simulated by presently developed model. The model is one-dimensional, isothermal and steady state, and the fluid-dynamics are based on the two-phase theory of fluidization. Tar conversion is taken into account in the model. The model simulation results are also compared with and validated against experimental data given in the literature. As a result of this study, it is observed that H 2 composition increased remarkably with the rise of the gasifier temperature. Small biomass particles improves H 2 composition. It is unfeasible to apply too small or too large ER in biomass air–steam gasification. The increases in the mole fractions of H 2 with increases in the steam flow rate indicated that the gas shift reaction has a substantial effect in air–steam gasification.

Air–steam gasification of biomass in a fluidised bed: Process optimisation by enriched air

The effect of oxygen concentration in the gasification agent was studied by enriched–air–steam biomass gasification tests in a bubbling fluidised-bed gasification (FBG) plant. The oxygen content in the enriched air was varied from 21% (v/v, i.e. air) to 40% (v/v), aiming at simulating FBG where enriched air is produced by membranes. The stoichiometric ratio (ratio of actual to stoichiometric oxygen flow rates) and steam-to-biomass ratio (ratio of steam to biomass, dry and ash-free, flow rates) were varied from 0.24 to 0.38 and from 0 to 0.63, respectively. The tests were conducted under simulated adiabatic and autothermal conditions, to reproduce the behaviour of larger industrial FBG. The temperature of the inlet gasification mixture was fixed consistently at 400 °C for all tests, a value that can be achieved by energy recovery from the off-gas in large FBG without tar condensation. It was shown that the enrichment of air from 21 to 40% v/v made it possible to increase the gasification efficiency from 54% to 68% and the lower heating value of the gas from 5 to 9.3 MJ/Nm 3, while reaching a maximum carbon conversion of 97%. The best conditions were found at intermediate values of steam-to-biomass ratio, specifically within the range 0.25–0.35. The enriched-air–steam gasification concept explored in this work seems to be an interesting option for the improvement of standalone direct air–blown FBG because it considerably improves the process efficiency while maintaining the costs relatively low as compared to oxygen-steam gasification.

Modeling and simulation of biomass air-steam gasification in a fluidized bed

By considering the features of fluidized-bed reactors and the kinetic mechanism of biomass gasification, a steady-state, isothermal, one-dimensional and two-phase mathematical model of biomass gasification kinetics in bubbling fluidized beds was developed. The model assumes the existence of two phases — a bubble and an emulsion phase — with chemical reactions occurring in both phases. The axial gas dispersion in the two phases is accounted for and the pyrolysis of biomass is taken to be instantaneous. The char and gas species CO, CO2, H2, H2O, CH4 and 8 chemical reactions are included in the model. The mathematical model belongs to a typical boundary value problem of ordinary differential equations and its solution is obtained by a Matlab program. Utilizing wood powder as the feedstock, the calculated data show satisfactory agreement with experimental results and proves the effectiveness and reliability of the model.

Non-premixed Combustion Model of Fluidized Bed Biomass Gasifier for Hydrogen-Rich Gas

Fluidized bed biomass gasifiers can be employed to produce hydrogen-rich gas. A non-premixed combustion model is used for biomass air-steam gasification in the gasifier, and the simulations were carried out by using the FLUENT 6.0 software. The simulation results are compared with the experimental data. The effects of the steam to biomass ratio (S/B), the equivalence ratio (ER), and the size of biomass particles on the hydrogen yield were studied. Meanwhile, the distributions of hydrogen inside the gasifier at different conditions are also described.

05/02271 An experimental study on biomass air-steam gasification in a fluidized bed

05/02271 An experimental study on biomass air-steam gasification in a fluidized bed