Performance of large‐scale biomass gasifiers in a biorefinery,a state‐of‐the‐art reference

The Gothenburg Biomass Gasification plant (2015) is currently the largest plant in the world producing biomethane (20 MW_biomethane) from woody biomass. We present the experimental data from the first measurement campaign and evaluate the mass and energy balances of the gasification sections at the plant. Measures improving the efficiency including the use of additives (potassium and sulfur), high‐temperature pre‐heating of the inlet streams, improved insulation of the reactors, drying of the biomass and introduction of electricity as a heat source (power‐to‐gas) are investigated with simulations. The cold gas efficiency was calculated in 71.7%LHV_daf using dried biomass (8% moist). The gasifier reaches high fuel conversion, with char gasification of 54%, and the fraction of the volatiles is converted to methane of 34%_mass. Because of the design, the heat losses are significant (5.2%LHV_daf), which affect the efficiency. The combination of potential improvements can increase the cold gas efficiency to 83.5%LHV_daf, which is technically feasible in a commercial plant. The experience gained from the Gothenburg Biomass Gasification plant reveals the strong potential biomass gasification at large scale. © 2017 The Authors. International Journal of Energy Research published by John Wiley & Sons Ltd.     

Design of experiments and analysis of dual fluidized bed gasifier for syngas production: Cold flow studies

Biomass gasification is a thermo-chemical process widely accepted as a future technology for syngas production. Numerous types of gasification systems have been proposed and studied in the past. Recent developments have shown that Dual Fluidized Bed (DFB) gasifier are commercially more attractive for production of the hydrogen-rich syngas as compared to others. DFB gasification system is very complex in construction and operation. Hence, a detailed understanding of hydrodynamics in such systems is essential for optimum design and scale-up. Hydrodynamics of DFB gasifier mainly depends on the Solid Circulation Rate (SCR). SCR is governed by riser velocity, gasifier velocity, and loop seal velocities. In present work, Central Composite Rotatable Design (CCRD) based Response Surface Method (RSM) was employed to determine the effect of riser velocity, gasifier velocity, recycle chamber velocity, supply chamber velocity, and vertical supply chamber velocity and their interaction on the SCR. Adequacy of regression model developed from RSM was confirmed using ANOVA analysis. The value of coefficient of determination (R²) of the model was 0.9729, which confirms model represents the experimental results satisfactorily. Riser and recycle chamber velocity were found to be most significant parameters, plays an important role in SCR in DFB gasifier.     

Bubbling fluidized bed biomass gasification—Performance, process findings and energy analysis

Bubbling fluidized bed gasifiers (BFG) has potential for rural electrification projects especially in third world countries where biomass supplies are abundant from agricultural, wood industries and where electricity supply from the grid is not available. In this paper the performance of a BFG was observed in terms of its thermal output. Gas chromatography (GC) was used to check the gas composition. The size of the wood chips was irregular but mostly falls in the range of 30 mm in both length and width, with the thickness at an average of 3.0 mm. It showed that the gas produced had an energy content of 4.74 MJ/m³ at a bed temperature of 733 °C, with the equivalence ratio at 0.23. The resulting thermal efficiency was 61.32% with a thermal output of 355.55 kW_th. For village electrification projects, this thermal output is able to supply 100 kW_e through a diesel generator, enough for electricity consumption in 100 households. An energy balance of the system was done to determine its work potential. It was found that the heat loss was 29.64%. A Shankey diagram of the energy distribution of the BFG system shows that the rest of the thermal output is not utilized and exits the system in the form of char and tarry liquids. Condensates were collected for high-performance liquid chromatograph (HPLC) analysis. It was found that phenol was high when the bed temperature was 450 °C, which makes the outlet condensate very soluble in water and can cause water contamination.     

Performance evaluation of an innovative 100 kWth dual bubbling fluidized bed gasifier through two years of experimental tests: Results of the BLAZE project

In this work, the results of two years of experimental tests on an innovative dual bubbling fluidized bed gasifier are reported. These are related to the activities of the BLAZE project (Horizon 2020) for the integration of steam biomass gasification and solid oxide fuel cell. Several tests were carried out on the pilot-scale reactor at various operating conditions, and in this work the results are reported in terms of dry gas composition and yield, organic and inorganic contaminants (tar, particulate matter, H₂S). The compact design of the gasifier (a single reactor with two concentric chambers and in-situ hot gas cleaning and conditioning) reduces the heat losses and produces close to nitrogen-free syngas. Preliminary tests using a filter candle filled with conventional catalyst, installed in the freeboard of the gasifier, show that the tar content dropped to about 2 g/Nm³, and the H₂ concentration increased up to 41%_vol,dry.     

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。     

Chemical‐looping combustion — an overview and application of the recirculating fluidized bed reactor for improvement

This paper propose recirculating fluidized bed (RCFB) reactor for chemical‐looping combustion (CLC) to overcome some of the issues associated with the existing interconnected reactors arrangements like low residence time of bed material in the air reactor, high attrition of bed material in the cyclone separator, cluster formation in the air reactor, complex operation involving loop seals and high heat losses. RCFB has high solid circulation rate, long residence time, efficient fuel–oxygen carrier contact, low heat losses and low gas leak in between the reactors, as compared to the existing reactor configurations. A cold model study was performed on a Perspex made, semicircular, transparent RCFB reactor. A single RCFB reactor was operated in the alternate oxidation and fuel burning cycles to simulate the interconnected reactors arrangement for CLC. The generated experimental data has been used to predict the optimal RCFB reactor configuration for a RCFB‐based CLC power plant. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

Particle holdup in a liquid–solid circulating fluidized bed

An experiment was conducted to acquire a set of systematic data of particle holdup in risers of a liquid–solid circulating fluidized bed. In the experiment, two kinds of riser were provided, their inner diameter being 24 mm and 36 mm, respectively. Tested particles were of glass and ceramics, having a diameter range from 2.10 to 4.95 mm. Water at ambient conditions was used as the fluidizing liquid. Particle holdup was measured using a shut‐off method. Based on the experimental data, a correlation for predicting the particle holdup was derived, which could reproduce almost all experimental data with an accuracy of ±15%. The effect of the wall was not recognized within the experimental range, i.e., the diameter ratio of particle to riser is less than 0.2. The independent parameters affecting the flow characteristics of liquid–solid circulating fluidized beds were identified. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(3): 184–196, 2008; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/htj.20194     

Eulerian simulations of bubble behaviour in a two‐dimensional gas–solid bubbling fluidized bed

In the present study, the CFD model is based on a two‐fluid model extended with the kinetic theory of granular flow. The simulation results of bubble diameter and bubble rise velocity are compared to the Darton equation and the Davidson model in a free bubbling fluidized bed. The predicted values are in reasonable agreement with the values from the Darton bubble size equation and the Davidson model for isolated bubbles. It is shown that the break‐up and direct wall interaction effects influence the dynamic bubble behavior in the free bubbling fluidized beds. Copyright © 2002 John Wiley & Sons, Ltd.     

Influence of chemical and thermodynamic parameters on the flue gas desulphurization efficiency in a circulating fluidized bed

IneductionEven there are W successful Mods Of flue gasdesulPhuriZation (FGD), people have been searching fOrnew ones, which are more econondcal, with higherefficiency and more reliable. Lap, Thyssen and WullffMasclunen developed the teChnulogy of circulatinfluldized bed flue gas desulPhurization (CFBFGD) inlate 1980s, which is similar with circulating fluidized bedboilers in enhancing chendcal reachvity As flue gas andabsothent are Inixed in theulent bed, SO2 is absothedand changed in…     

生活垃圾流化床锅炉进料问题及装置研制

针对目前生活垃圾流化床焚烧炉一直沿用的给料形式,分析其存在的问题,阐述了流化床锅炉对生活垃圾进料的要求,开发研制了实用型双螺旋垃圾进料机。     

Experimental investigation into cavity‐type inertial separators—a novel technique for development of subcompact circulating fluidized bed boilers

Cavity‐type inertial separators developed by GRI (Patent no. 2, 159, 949, Canada, 2002) were tested in a semi‐industrial size circulating fluidized bed pilot plant operated at room temperature. Three rows of separators were hung from the roof of the pilot plant where one row was kept inside the riser and the others were kept in the primary separation chamber, located between the back‐pass and the riser. Parameters measured were axial pressure drops along the height of the riser, vertical solids flux on the separator walls, lateral outwards solids flux in the riser with and without separator and local temperatures on the separator walls. A net downwards solids flux is on the inner wall of the separators; however, no downwards solids flux is on the outer walls of the separators. Heat transfer coefficients on the outer wall are found higher than those on the inner walls of the separator. It is also found that the presence of inertial separators not only provides additional heat transfer surfaces but also indirectly increases the heat transfer coefficients on the riser wall. Copyright © 2005 John Wiley & Sons, Ltd.     

Optimization of emissions from fluidized bed combustion of coal,biofuel and waste

Several types of fuel can be burned in a fluidized bed. This paper discusses the impact of low‐ or medium‐volatile fuels (coal) and high‐volatile fuels (biomass and waste) on the emissions of NO, N₂O and other pollutants. It is found that high‐ and low‐volatile fuels behave in different ways, and measures to reduce emissions from coal combustion are not necessarily effective for high‐volatile fuels. This forms a basis for various design options. Copyright © 2002 John Wiley & Sons, Ltd.     

Theoretical performance analysis of the multi‐stage gas–solid fluidized bed air preheater

The multi‐stage fluidized bed can be used to preheat the combustion air by recovering the waste heat from the exhaust gas from industrial furnaces. The dilute‐phase fluidized bed may be formed to exclude the excessive pressure drop across the multi‐stage fluidized bed. But, in this case, the solid particles do not reach to the thermal equilibrium due to relatively short residence time in each layer of fluidized bed. In this study, a theoretical analysis on the dilute phase multistage fluidized bed heat exchanger was performed. A parameter related to the degree of thermal equilibrium between gas and solid particles at the dilute‐phase fluidized beds was derived. Using this parameter, a relatively simple expression was obtained for the thermal efficiencies of the multi‐stage fluidized bed heat exchanger and air preheater. Copyright © 2001 John Wiley & Sons, Ltd.     

Anaerobic fluidized bed reactor with expanded clay as support for hydrogen production through dark fermentation of glucose

This study evaluated hydrogen production in an anaerobic fluidized bed reactor (AFBR) fed with glucose-based synthetic wastewater. Particles of expanded clay (2.8–3.35 mm) were used as a support material for biomass immobilization. The reactor was operated with hydraulic retention times (HRT) ranging from 8 to 1 h. The hydrogen yield production increased from 1.41 to 2.49 mol H₂ mol⁻¹ glucose as HRT decreased from 8 to 2 h. However, when HRT was 1 h, there was a slight decrease to 2.41 mol H₂ mol⁻¹ glucose. The biogas produced was composed of H₂ and CO₂, and the H₂ content increased from 8% to 35% as HRT decreased. The major soluble metabolites during H₂ fermentation were acetic acid (HAc) and butyric acid (HBu), accounting for 36.1–53.3% and 37.7–44.9% of total soluble metabolites, respectively. Overall, the results demonstrate the potential of using expanded clay as support material for hydrogen production in AFBRs.     

Experimental study on combustion characteristics and NO<Subscript>X</Subscript> emissions of pulverized anthracite preheated by circulating fluidized bed

A 30 kW bench-scale rig of pulverized anthracite combustion preheated by a circulating fluidized bed(CFB)was developed.The CFB riser has a diameter of 90 mm and a height of 1,500 mm.The down-fired combustion chamber(DFCC)has a diameter of 260 mm and a height of 3,000 mm.Combustion experiments were carried out using pulverized anthracite with 6.74%volatile content.This low volatile coal is difficult to ignite and burn out.Therefore,it requires longer burnout time and higher combustion temperature,which results in larger NOX emis-sions.In the current study,important factors that influence the combustion characteristics and NOX emissions were investigated such as excess air ratio,air ratio in the reducing zone,and fuel residence time in the reducing zone.Pulverized anthracite can be quickly preheated up to 800℃in CFB when the primary air is 24% of theoretical air for combustion,and the temperature profile is uniform in DFCC.The combustion efficiency is 94.2%,which is competitive with other anthracite combustion technologies.When the excess air ratio ranges from 1.26 to 1.67,the coal-N conversion ratio is less than 32%and the NOX emission concentration is less than 371 mg/m 3(@6%O2).When the air ratio in the reducing zone is 0.12,the NOX concentration is 221 mg/m 3(@6%O2),and the coal-N conversion ratio is 21%,which is much lower than that of other boilers.     

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.     

Comparison of biohydrogen production in fluidized bed bioreactors at room temperature and 35 °C

The aim of this work was to compare the H₂ production in a lab scale anaerobic fluidized bed bioreactors (AFBRs) at two levels of operational temperature: ambient temperature (A) and 35 °C (M) and two organic volumetric loading rates B_v: 5 and 8 g sucrose/L.day, with a constant hydraulic residence time of 1 day.     

Direct‐contact heat exchange between fluidizing particles and a heat transfer surface in a fluidized bed: Temperature visualization of fluidizing particles

Heat conduction during contact between a heat transfer surface and fluidizing particles, a phenomenon which is one of the effective heat transfer mechanisms in a gas–solid fluidized bed, has been empirically investigated. The temperature profile of the fluidizing particles during the contact period is visualized with the aid of an infrared imager. The visualization reveals that the particles have been considerably heated in the thermal boundary layer on the heat transfer surface before contact. Based on the visualized temperature profile of the particles, the contact conductance between a fluidizing particle and the heat transfer surface is estimated by an in inverse analysis. Using the evaluated contact conductance, the contributions of the conductive heat transfer to the total heat transfer are also evaluated. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(3): 165–181, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10027     

CFD simulation of jet behaviour and voidage profile in a gas–solid fluidized bed

Based on an Eulerian–Eulerian approach, a computational fluid dynamic (CFD) model for gas–solid system has been developed to investigate the hydrodynamics in fluidized beds. With this model, jet penetration height, jet frequency, time‐averaged axial gas velocity profile, and time‐averaged voidage profile have been simulated in a two‐dimensional bed. The computational results indicate that the jet penetration height increases with increasing the jet gas velocity. The jet frequency decreases with increasing the jet gas velocity and decreasing particle diameter. The time‐averaged axial gas velocity profile becomes ‘lower’ and ‘wider’ and the time‐averaged voidage decreases with increasing distance from the jet nozzle. These conclusions appear in good agreement with the experimental and simulated data in the literature. Copyright © 2004 John Wiley & Sons, Ltd.