Exergoeconomic analysis of hydrogen production from biomass gasification

In this study, we investigate biomass-based hydrogen production through exergy and exergoeconomic analyses and evaluate all components and associated streams using an exergy, cost, energy and mass (EXCEM) method. Then, we define the hydrogen unit cost and examine how key system parameters affect the unit hydrogen cost. Also, we present a case study of the gasification process with a circulating fluidized bed gasifier (CFBG) for hydrogen production using the actual data taken from the literature. We first calculate energy and exergy values of all streams associated with the system, exergy efficiencies of all equipment, and determine the costs of equipment along with their thermodynamic loss rates and ratio of thermodynamic loss rate to capital cost. Furthermore, we evaluate the main system components, consisting of gasifier and PSA, from the exergoeconomic point of view. Moreover, we investigate the effects of various parameters on unit hydrogen cost, such as unit biomass and unit power costs and hydrogen content of the syngas before PSA equipment and PSA hydrogen recovery. The results show that the CFBG system, which has energy and exergy efficiencies of 55.11% and 35.74%, respectively, generates unit hydrogen costs between 5.37 $/kg and 1.59 $/kg, according to the internal and external parameters considered.     

Syngas production from biomass gasification in China: A clean strategy for sustainable development

Biomass gasification, which can be categorized as a set of relatively clean processes, is a good option for hydrogen production. The main purpose of the present work was to focus on the use of natural olivine as a bed material to minimize the tar content and enhance the hydrogen yield. The catalytic gasification tests were carried out in a fluidized bed gasifier using steam as the fluidizing medium. Hydrogen yield slightly increased from 51.9 to 53.1 g/kg biomass, as biomass particle size (BP) decreased from 5.0 to 2.0 mm. The yield of tar also decreased from 0.15 to 0.07 g/Nm³ with BP decreasing from 5.0 to 2.0 mm. With an increase in the catalyst-to-biomass ratio (C/B) from 0.2 to 0.8, HY increased from 47.8 to 51.9 g/kg biomass and tar content (TC) decreased from 0.8 to 0.15 g/Nm³. Temperature and steam/biomass ratio (S/B) were also affected the syngas composition and HY, significantly.     

A review of oxy‐fuel combustion in fluidized bed reactors

Presently, there is no detailed review that summarizes the current knowledge status on oxy‐fuel combustion in fluidized bed combustors. This paper reviewed the existing literature in heat transfer, char combustion and pollutant emissions oxy‐fuel combustion in fluidized beds, as well as modelling of oxy‐fuel in FB boiler and gaps were identified for further research direction. Copyright © 2016 John Wiley & Sons, Ltd.     

生物质流化床气化技术应用研究现状

按所得产品不同,可将生物质气化技术分为制氢、发电和合成液体燃料3大类。文章介绍了生物质流化床水蒸气气化制氢、催化气化制氢和超临界水气化制氢的工艺特点;分析了生物质流化床气化发电的技术、经济可行性;简述了生物质流化床气化合成液体燃料的研究现状;指出气化产出气化学当量比调变、焦油去除问题和合成气净化是生物质流化床气化技术应用的主要瓶颈,认为定向气化是今后研究的主要方向。     

Investigation of syngas exergy value and hydrogen concentration in syngas from biomass gasification in a bubbling fluidized bed gasifier by using machine learning

In this study, an artificial neural network (ANN) model as a machine learning method has been employed to investigate the exergy value of syngas, where the hydrogen content in syngas reached maximum in bubbling fluidized bed gasifier which is developed in Aspen Plus® and validated from experimental data in literature. Levenberg-Marquardt algorithm has been used to train ANN model, where oxygen, hydrogen and carbon contents of sixteen different biomass, gasification temperature, steam and fuel flow rates were selected as input parameters of the model. Moreover, four different biomass samples, which hadn't been used in training and testing, have been used to create second validation. The hydrogen mole fraction of syngas was also evaluated at the different steam to fuel ratio and gasification temperature and the exergy value of syngas at the point where the hydrogen content in syngas reached maximum were estimated with low relative error value.     

Exergy analysis of hydrogen production from steam gasification of biomass: A review

Exergy analysis of hydrogen production from steam gasification of biomass was reviewed in this study. The effects of the main parameters (biomass characteristics, particle size, gasification temperature, steam/biomass ratio, steam flow rate, reaction catalyst, and residence time) on the exergy efficiency were presented and discussed. The results show that the exergy efficiency of hydrogen production from steam gasification of biomass is mainly determined by the H₂ yield and the chemical exergy of biomass. Increases in gasification temperatures improve the exergy efficiency whereas increases in particle sizes generally decrease the exergy efficiency. Generally, both steam/biomass ratio and steam flow rate initially increases and finally decreases the exergy efficiency. A reaction catalyst may have positive, negative or negligible effect on the exergy efficiency, whereas residence time generally has slight effect on the exergy efficiency.     

Oxy–steam gasification of biomass for hydrogen rich syngas production using downdraft reactor configuration

The paper focuses on the use of oxygen and steam as the gasification agents in the thermochemical conversion of biomass to produce hydrogen rich syngas, using a downdraft reactor configuration. Performance of the reactor is evaluated for different equivalence ratios (ER), steam to biomass ratios (SBR) and moisture content in the fuel. The results are compared and evaluated with chemical equilibrium analysis and reaction kinetics along with the results available in the literature. Parametric study suggests that, with increase in SBR, hydrogen fraction in the syngas increases but necessitates an increase in the ER to maintain reactor temperature toward stable operating conditions. SBR is varied from 0.75 to 2.7 and ER from 0.18 to 0.3. The peak hydrogen yield is found to be 104 g/kg of biomass at SBR of 2.7. Further, significant enhancement in H₂ yield and H₂ to CO ratio is observed at higher SBR (SBR = 1.5–2.7) compared with lower range SBR (SBR = 0.75–1.5). Experiments were conducted using wet wood chips to induce moisture into the reacting system and compare the performance with dry wood with steam. The results clearly indicate the both hydrogen generation and the gasification efficiency (η_g) are better in the latter case. With the increase in SBR, gasification efficiency (η_g) and lower heating value (LHV) tend to reduce. Gasification efficiency of 85.8% is reported with LHV of 8.9 MJ Nm^?3 at SBR of 0.75 compared with 69.5% efficiency at SBR of 2.5 and lower LHV of 7.4 at MJ Nm^?3 at SBR of 2.7. These are argued on the basis of the energy required for steam generation and the extent of steam consumption during the reaction, which translates subsequently in the LHV of syngas. From the analysis of the results, it is evident that reaction kinetics plays a crucial role in the conversion process. The study also presents the importance of reaction kinetics, which controls the overall performance related to efficiency, H₂ yield, H₂ to CO fraction and LHV of syngas, and their dependence on the process parameters SBR and ER. Copyright © 2013 John Wiley & Sons, Ltd.     

A review of hydrogen production via biomass gasification and its prospect in Bangladesh

Hydrogen has been using as one of the green fuel along with conventional fossil fuels which has enormous prospect. A new dimension of hydrogen energy technology can reduce the dependency on non-renewable energy sources due to the rapid depletion of fossil fuels. Hydrogen production via Biomass (Municipal solid waste, Agricultural waste and forest residue) gasification is one of the promising and economic technologies. The study highlights the hydrogen production potential from biomass through gasification technology and review the parameters effect of hydrogen production such as temperature, pressure, biomass and agent ratio, equivalence ratios, bed material, gasifying agents and catalysts effect. The study also covers the all associated steps of hydrogen separation and purification, WGS reaction, cleaning and drying, membrane separation and pressure swing adsorption (PSA). To meet the huge and rising energy demand, many countries made a multidimensional power development plan by adding different renewable, nuclear and fossil fuel sources. A large amount of biomass (total biomass production in Bangladesh is 47.71 million ton coal equivalent where 37.16, 3.49 and 7.04 MTCE are agricultural, MSW and forest residue based biomass respectively by 2016) is produced from daily uses by a big number of populations in a country. It also includes total feature of biomass gasification plant in Bangladesh.     

A study of combined biomass gasification and electrolysis for hydrogen production

An integrated system for the production of hydrogen by gasification of biomass and electrolysis of water has been designed and cost estimated. The electrolyser provides part of the hydrogen product as well as the oxygen required for the oxygen blown gasifier. The production cost was estimated to 39 SEK/kg H₂ at an annual production rate of 15?000 ton, assuming 10% interest rate and an economic lifetime of 15 years. Employing gasification only to produce the same amount of hydrogen, leads to a cost figure of 37 SEK/kg H₂, and for an electrolyser only a production cost of 41 SEK/kg H₂. The distribution of capital and operating cost is quite different for the three options and a sensitivity analyses was performed for all of these. However, the lowest cost hydrogen produced with either method is at least twice as expensive as hydrogen from natural gas steam reforming.     

Supercritical water gasification of biomass for hydrogen production

Hydrogen from waste biomass is considered to be a clean gaseous fuel and efficient for heat and power generation due to its high energy content. Supercritical water gasification is found promising in hydrogen production by avoiding biomass drying and allowing maximum conversion. Waste biomass contains cellulose, hemicellulose and lignin; hence it is essential to understand their degradation mechanisms to engineer hydrogen production in high-pressure systems. Process conditions higher than 374 °C and 22.1 MPa are required for biomass conversion to gases. Reaction temperature, pressure, feed concentration, residence time and catalyst have prominent roles in gasification. This review focuses on the degradation routes of biomass model compounds such as cellulose and lignin at near and supercritical conditions. Some homogenous and heterogeneous catalysts leading to water–gas shift, methanation and other sub-reactions during supercritical water gasification are highlighted. The parametric impacts along with some reactor configurations for maximum hydrogen production and technical challenges encountered during hydrothermal gasification processes are also discussed.     

The effect of biomass feeding location on rice husk gasification for hydrogen production

The objective of this study is to investigate the impact of biomass feeding location on rice husk gasification for hydrogen production. By comparing the results between top-feed and bottom-feed of the feedstock of the fluidized bed biomass gasification at the reaction temperature between 600～1000 °C and ER = 0.2, 0.27, and 0.33 without steam, the optimum low heating value was increase by 2.35 kJ/g-rice husk by the top-feed to gasifier. Although the yield of hydrogen was decreased by 42% for the rice husk gasification by the top-feed operation, the yield of CO, CO2, and CH4 were highly increased, which enhancing the heating value of the effluent gas. The study results suggested the potential route of the biomass gasification at the different feeding location.     

Hydrogen-rich gas production with CO2 capture from steam gasification of pine needle using calcium oxide: Experimental and modeling study

A research-scale bubbling fluidized bed reactor (BFBR) has been assembled and used to study the steam gasification of pine needles with calcium oxide (CaO) as sorbent and catalyst. The output parameters such as syngas composition, higher heating value, lower heating value, and cold gas efficiency, have been analyzed at the operating conditions of a temperature of 650°C to 850°C, steam/biomass (S/B) ratio of 0.4 to 1.6, and CaO/biomass ratio of 0.3 to 1.5. Furthermore, an ASPEN PLUS model of BFBR has been developed using Gibbs free energy minimization technique and model values have been compared with experimental values. From the experimental results, it is analyzed that the concentration of H₂ is increased from 37.02 vol% to 68.36 vol% with an increase in temperature from 650°C to 750°C at the S/B ratio of 1 and CaO/biomass ratio of 0.9 and after that, it decreased slightly. Furthermore, the concentration of CO₂ in syngas captured from 5.49 vol% to 0 vol%, when the CaO/biomass ratio is varied from 0.3 to 1.5. From the result analysis, it is concluded that higher temperature and higher CaO/biomass ratio has a significant impact on H₂ production while excess S/B ratio has a negative impact.     

A techno-economic review of biomass gasification for production of chemicals

Gasification is a thermochemical process which can be used as a low-emission and highly efficient method to produce syngas and chemicals such as biomethanol and dimethyl ether (DME). In this paper, a review of technologies and methods for economic production of chemicals through gasification of biomass and other fuels has been carried out. A variety of techno-economic studies and analysis have been proposed in order to better understand the technical and economic assessments during the biomass gasification. Results showed that the methanol production cost for biomass (wood) is from 195 to 935 €/t, for waste residues is from 200 to 930 €/t, for coal is from 160 to 480 €/t, and for natural gas is from 90 to 290 €/t. It also concluded that fuel (wood) cost has positive linear relationship with ethanol production cost, meaning as the feedstock cost increases from 30 to 50 $/day-ton, the ethanol production cost enhances from 1.66 to 1.95 $/gal.     

Catalytic steam reforming of tar for enhancing hydrogen production from biomass gasification: a review

Presently, the global search for alternative renewable energy sources is rising due to the depletion of fossil fuel and rising greenhouse gas (GHG) emissions. Among alternatives, hydrogen (H₂) produced from biomass gasification is considered a green energy sector, due to its environmentally friendly, sustainable, and renewable characteristics. However, tar formation along with syngas is a severe impediment to biomass conversion efficiency, which results in process-related problems. Typically, tar consists of various hydrocarbons (HCs), which are also sources for syngas. Hence, catalytic steam reforming is an effective technique to address tar formation and improve H₂ production from biomass gasification. Of the various classes in existence, supported metal catalysts are considered the most promising. This paper focuses on the current researching status, prospects, and challenges of steam reforming of gasified biomass tar. Besides, it includes recent developments in tar compositional analysis, supported metal catalysts, along with the reactions and process conditions for catalytic steam reforming. Moreover, it discusses alternatives such as dry and autothermal reforming of tar.     

Techno-economic analysis and life cycle assessment of hydrogen production from different biomass gasification processes

The paper presents techno-economic analyses and life cycle assessments (LCA) of the two major gasification processes for producing hydrogen from biomass: fluidized bed (FB) gasification, and entrained flow (EF) gasification. Results indicate that the thermal efficiency of the EF-based option (56%, LHV) is 11% higher than that of the FB-based option (45%), and the minimum hydrogen selling price of the FB-based option is $0.3 per kg H₂ lower than that of the EF-based option. When a carbon capture and liquefaction system is incorporated, the efficiencies of the EF- and FB-based processes decrease to 50% and 41%, respectively. The techno-economic analysis shows that at a biomass price of $100 per tonne, either a minimum price of $115/tonne CO_2e or a minimum natural gas price of $5/GJ is required to make the minimum hydrogen selling price of biomass-based plants equivalent to that of commercial natural gas-based steam methane reforming plants. Furthermore, the LCA shows that, biomass as a carbon-neutral feedstock, negative life cycle GHG emissions are achievable in all biomass-based options.     

生物质水蒸气气化制氢模拟研究

利用ASPEN PLUS软件建立了生物质水蒸气气化制氢模型,对各种影响因素进行了深入分析。结果表明:随着碳转化率的增加,H2浓度略有降低,H2产量大幅增加,在碳转化率为1时达到最大值142.54 g/kg;随着水蒸气/生物质质量比的增加,H2浓度和产量大幅增加,而后趋于稳定,水蒸气/生物质质量比取2比较适宜。适当的升温和低压对制备H2有利,在加压条件下,H2浓度与产量达到最大值的温度升高。     

Neural network modeling of biomass gasification for hydrogen production

Hydrogen plays a significant role as an alternative feedstock in the production of several industrial chemicals such as methanol and ammonia; it can also be used as a clean fuel for power generation in the Internal Combustion (IC) engines and Proton Exchange Membrane (PEM) fuel cells. The main objective of this work is to develop a computer-based model based on the experimental data to predict the gasification behavior of biomass particles for hydrogen and syngas production. The results showed that an increase in gasification temperature significantly increased the hydrogen yield and CGE. The maximum CGE also found to be increased by about 230% when the reaction temperature increases from 700 to 900 ^?C.     

A review on the development and commercialization of biomass gasification technologies in China

With the fast economic growth, the energy demand in China has increased two-fold in the past three decades. Various energy resources have been exploited and utilized and biomass is one of the energy resources that is abundant and has been widely used in China for a long time. Biomass gasification is an efficient and advanced technology for extracting the energy from biomass and has received increasing attention in the energy market. In this paper the development of biomass gasification for various energy applications in China is reviewed and their prospects are discussed. Among the different biomass gasification technologies, biomass gasification and power generation is found to be the most promising biomass gasification technology that has great potential to be further developed in China.     

一种确定CFBB最优循环倍率的方法

在将床料粒度分布及循环倍率耦合的基础上,提出了一种从能量角度确定最优循环倍率的方法,对循环流化床锅炉的设计与运行具有指导意义。     

流化床生物质气化发电过程动力学建模与验证

为更好地描述生物质气化过程的反应机理,文章从模型采用的反映速率形式出发,对已建立的动力学模型[1]做了进一步修正,并拟和了以松木屑为生物质原料的气化反应动力学参数,建立了包括质量平衡方程、反应动力学方程以及能量平衡方程在内的整体生物质气化动力学模型。最后以MATLB为平台,通过模型仿真,从反应进程以及最终气体组分两个方面验证了模型的可靠性。为进一步应用该模型评价和优化流化床生物质气化过程气化方案和气化参数打下了基础。