| 1. |
- Biollaz, S., et al.
(author)
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Gas analysis in gasification of biomass and waste : Guideline report: Document 1
- 2018
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Reports (peer-reviewed)abstract
- Gasification is generally acknowledged as one of the technologies that will enable the large-scale production of biofuels and chemicals from biomass and waste. One of the main technical challenges associated to the deployment of biomass gasification as a commercial technology is the cleaning and upgrading of the product gas. The contaminants of product gas from biomass/waste gasification include dust, tars, alkali metals, BTX, sulphur-, nitrogen- and chlorine compounds, and heavy metals. Proper measurement of the components and contaminants of the product gas is essential for the monitoring of gasification-based plants (efficiency, product quality, by-products), as well as for the proper design of the downstream gas cleaning train (for example, scrubbers, sorbents, etc.). In practice, a trade-off between reliability, accuracy and cost has to be reached when selecting the proper analysis technique for a specific application. The deployment and implementation of inexpensive yet accurate gas analysis techniques to monitor the fate of gas contaminants might play an important role in the commercialization of biomass and waste gasification processes.This special report commissioned by the IEA Bioenergy Task 33 group compiles a representative part of the extensive work developed in the last years by relevant actors in the field of gas analysis applied to(biomass and waste) gasification. The approach of this report has been based on the creation of a team of contributing partners who have supplied material to the report. This networking approach has been complemented with a literature review. The report is composed of a set of 2 documents. Document 1(the present report) describes the available analysis techniques (both commercial and underdevelopment) for the measurement of different compounds of interest present in gasification gas. The objective is to help the reader to properly select the analysis technique most suitable to the target compounds and the intended application. Document 1 also describes some examples of application of gas analysis at commercial-, pilot- and research gasification plants, as well as examples of recent and current joint research activities in the field. The information contained in Document 1 is complemented with a book of factsheets on gas analysis techniques in Document 2, and a collection of video blogs which illustrate some of the analysis techniques described in Documents 1 and 2.This guideline report would like to become a platform for the reinforcement of the network of partners working on the development and application of gas analysis, thus fostering collaboration and exchange of knowledge. As such, this report should become a living document which incorporates in future coming progress and developments in the field.
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| 2. |
- Biollaz, S., et al.
(author)
-
Gas analysis in gasification of biomass and waste : Guideline report: Document 2 - Factsheets on gas analysis techniques
- 2018
-
Reports (peer-reviewed)abstract
- Gasification is generally acknowledged as one of the technologies that will enable the large-scale production of biofuels and chemicals from biomass and waste. One of the main technical challenges associated to the deployment of biomass gasification as a commercial technology is the cleaning and upgrading of the product gas. The contaminants of product gas from biomass/waste gasification include dust, tars, alkali metals, BTX, sulphur-, nitrogen- and chlorine compounds, and heavy metals. Proper measurement of the components and contaminants of the product gas is essential for the monitoring of gasification-based plants (efficiency, product quality, by-products), as well as for the proper design of the downstream gas cleaning train (for example, scrubbers, sorbents, etc.). The deployment and implementation of inexpensive yet accurate gas analysis techniques to monitor the fate of gas contaminants might play an important role in the commercialization of biomass and waste gasification processes.This special report commissioned by the IEA Bioenergy Task 33 group compiles a representative part of the extensive work developed in the last years by relevant actors in the field of gas analysis applied to (biomass and waste) gasification. The approach of this report has been based on the creation of a team of contributing partners who have supplied material to the report. This networking approach has been complemented with a literature review. This guideline report would like to become a platform for the reinforcement of the network of partners working on the development and application of gas analysis, thus fostering collaboration and exchange of knowledge. As such, this report should become a living document which incorporates in future coming progress and developments in the field.
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| 3. |
- Neves, Daniel Santos Felix, 1982, et al.
(author)
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Characterization and prediction of biomass pyrolysis products
- 2011
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In: Progress in Energy and Combustion Science. - : Elsevier BV. - 0360-1285. ; 37:5, s. 611-630
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Journal article (peer-reviewed)abstract
- In this study some literature data on the pyrolysis characteristics of biomass under inert atmosphere were structured and analyzed, constituting a guide to the conversion behavior of a fuel particle within the temperature range of 200-1000 degrees C. Data is presented for both pyrolytic product distribution (yields of char, total liquids, water, total gas and individual gas species) and properties (elemental composition and heating value) showing clear dependencies on peak temperature. Empirical relationships are derived from the collected data, over a wide range of pyrolysis conditions and considering a variety of fuels, including relations between the yields of gas-phase volatiles and thermochemical properties of char, tar and gas. An empirical model for the stoichiometry of biomass pyrolysis is presented, where empirical parameters are introduced to close the conservation equations describing the process. The composition of pyrolytic volatiles is described by means of a relevant number of species: H(2)O, tar, CO(2), CO, H(2), CH(4) and other light hydrocarbons. The model is here primarily used as a tool in the analysis of the general trends of biomass pyrolysis, enabling also to verify the consistency of the collected data. Comparison of model results with the literature data shows that the information on product properties is well correlated with the one on product distribution. The prediction capability of the model is briefly addressed, with the results showing that the yields of volatiles released from a specific biomass are predicted with a reasonable accuracy. Particle models of the type presented in this study can be useful as a submodel in comprehensive reactor models simulating pyrolysis, gasification or combustion processes.
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| 4. |
- Bu, C. S., et al.
(author)
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Effect of CO2 on oxy-fuel combustion of coal-char particles in a fluidized bed: Modeling and comparison with the conventional mode of combustion
- 2016
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In: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 177, s. 247-259
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Journal article (peer-reviewed)abstract
- A char combustion model is developed to study the effect of CO2 on the combustion of coarse char particles under oxy-fuel conditions in a fluidized bed (FB). It is a transient one-dimensional model, taking into account the heat and mass transfer from the bed to the particle and the heterogeneous combustion and gasification of char. The model shows good ability to predict the char temperature history measured in our previous work for different combinations of O2/CO2 and O2/N2 with various coal types. Simulations are carried out to establish the role of CO2 in oxy-fuel conversion at different O2 levels, particle sizes, and bed temperatures. The model is used to analyze the relative contribution of carbon in the char consumed by CO2 (gasification) and O2 (combustion), as well as the differences of the peak temperatures and the burnout times in O2/CO2 and O2/N2 for char particles in a commercial FB combustor. The results indicate that the conversion of coarse (mm size) char particles in an oxy-FB is controlled by the diffusion of O2 both in the O2/CO2 and O2/N2 case. The burn-out time decreases with the bed temperature also in both cases. The lower O2 diffusion rate in CO2 compared to N2, is the main reason for the longer burnout time and lower peak temperature found using O2/CO2 at bed temperatures of 1073–1173 K. In that temperature window, the contribution of the CO2-char gasification is limited, being notable only at high bed temperature in O2/CO2, e.g. 1223 K. In such high temperature conditions (rarely expected to be found in commercial coal FBC) the predicted burnout time of a lignite char-particle becomes shorter in O2/CO2 than in O2/N2.
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| 5. |
- Bu, C. S., et al.
(author)
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Ignition behavior of single coal particle in a fluidized bed under O-2/CO2 and O-2/N-2 atmospheres: A combination of visual image and particle temperature
- 2014
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In: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 115, s. 301-308
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Journal article (peer-reviewed)abstract
- Single coal particle ignition behavior was studied in a two-dimensional (200 mm x 20 mm x 400 mm) fluidized bed under O-2/N-2 and O-2/CO2 atmosphere with O-2 volume concentration in the range of 0-40%, by a combination of visual observation of the volatile flame and measurement of the particle center temperature. A piece of transparent quartz glass was used as the front wall of the fluidized bed to allow visual observation. The investigated fuel particles were spherical sub-bituminous coal particles with diameter in a range of 6-13 mm, which were artificially carved from selected original coal particles. The volatile combustion flame was recorded by a color video camera to analyze its ignition time delay and extinction behavior. The temperature in the particle center was measured by a very thin thermocouple to follow the particle heating process. Results indicate that under O-2/CO2 atmosphere the ignition delay time is much longer than in O-2/N-2 atmosphere. The devolatilization process is controlled by internal and external heat transfer but it is almost unaffected by atmosphere at the same O-2 concentration. The effect of volatile combustion on heating and extinction delay time can be neglected for larger coal particles.
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| 6. |
- Gómez-Barea, Alberto, et al.
(author)
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Analytical solutions of sharp interface models with nth order kinetics.
- 2012
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 183, s. 408-421
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Journal article (peer-reviewed)abstract
- When a reaction occurs in a narrow layer of a porous particle, it is practical to simplify the calculation ofthe reaction rate by assuming global kinetic parameters based on the surface of the reaction front. Theassumption of such simplified situation allows formulation of a sharp interface model (SIM). Though,there are three difficulties for the application of a SIM in reactor simulations: (1) No analytical solutionis available for general SIM with nth order kinetics with respect to gas reactant. For reactor model simulation,with a variety of particles and operating conditions, a numerical model is still necessary to beapplied, leading to numerical difficulties and time consumption; (2) The global surface kinetic coefficientis not a priori known. The reason is that this coefficient depends not only on the intrinsic reactivity, butalso on physical factors such as the size and density of the solid, as well as operation conditions of thereactor like gas reactant concentration and temperature, varying during conversion of the particle; (3)The SIM is applicable when chemical reaction is rapid compared to intraparticle diffusion because in thissituation the reaction occurs within a narrow region compared to the size of the particle. However, noquantitative criteria has been developed to delimit the conditions for application of SIM. In the presentwork these questions are answered. Char conversion (combustion and gasification) is taken as reference,but most conclusions are applicable to isothermal non-catalytic gas–solid irreversible reactions with asingle gaseous reactant.b
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| 7. |
- Gómez-Barea, Alberto, et al.
(author)
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Improving the performance of fluidized bed biomass/waste gasifiers for distributed electricity: A new three-stage gasification system
- 2013
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In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 50:2, s. 1453-1462
-
Journal article (peer-reviewed)abstract
- Methods to increase the conversion of char and tar in fluidized bed gasifiers (FBG) are discussed, with thefocus on small to medium-size biomass/waste gasifiers for power production (from 0.5 to 10 MWe).Optimization of such systems aims at (i) maximizing energy utilization of the fuel (maximizing charconversion), (ii) minimizing secondary treatment of the gas (by avoiding complex tar cleaning), and(iii) application in small biomass-to-electricity gasification plants. The efficiency of various measures toincrease tar and char conversion within a gasification reactor (primary methods) is discussed. The optimizationof FBG by using in-bed catalysts, by addition of steam and enriched air as gasification agent, andby secondary-air injection, although improving the process, is shown to be insufficient to attain the gaspurity required for burning the gas in an engine to produce electricity. Staged gasification is identified asthe only method capable of reaching the targets mentioned above with reasonable simplicity and cost, so itis ideal for power production. A promising new stage gasification process is presented. It is based on threestages: FB devolatilization, non-catalytic air/steam reforming of the gas coming from the devolatilizer, andchemical filtering of the gas and gasification of the char in a moving bed supplied with the char generatedin the devolatilizer. Design considerations and comparison with one-stage FBG are discussed.
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| 8. |
- Suárez-Almeida, M., et al.
(author)
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Modeling the transient response of a fluidized-bed biomass gasifier
- 2020
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In: Fuel. - : Elsevier BV. - 0016-2361. ; 274
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Journal article (peer-reviewed)abstract
- The dynamic response of a bubbling fluidized-bed biomass gasifier (FBG) is examined. A transient model is developed by extending a previous steady-state model to account for key processes occurring during the ramp-up and/or changes in loading of fuel and gasification agent. The model is validated against measurements from transient tests in a laboratory-scale FBG. The model results are also compared with steady-state measurements and previous FBG models from the literature. A sensitivity analysis is performed to identify the most influencing parameters. The model is then used to study the transient response of industrial FBG under different operating conditions. It is shown that for given operational conditions (biomass flowrate, equivalence ratio, initial temperature, and initial char inventory in the bed), there is always an optimal start-up procedure (rate of change in feeding the gasifying agent and/or the fuel) leading to the shortest start-up time and lowest peak temperature. The transient period can be reduced by up to 75% compared to the reference value, in which the transient response can extend for more than an hour, due to the slow change in the inventory of char in the reactor. The model can be used to optimize the operation of hybridized power plants with biomass gasification and thermal energy storage.
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| 9. |
- Suárez-Almeida, Montserrat, et al.
(author)
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Simulation of the Transient Response of a Fluidized Bed Gasifier for Hybridized Concentrated Solar Thermal Power Plant
- 2018
-
In: 23rd International Conference on Fluidized Bed Conversion - Innovative Fluidized Bed Conversion Technology for a Sustainable Development. - 9788995000571 ; 1
-
Conference paper (peer-reviewed)abstract
- A model to predict the dynamic response of a fluidized bed biomass gasifier (FBG) to changes in air and fuel feed rates is developed. It extends a previous pseudo-equilibrium model originally developed for steady-state operation, by considering the accumulation of char and the dynamics in the release of volatiles during transient periods. The model calculates the gas yields of the main species as well as char conversion, taking into account chemical reaction, attrition and elutriation. The influence of the change in fuel and air flowrate, on the syngas flowrate, heating value, and bed inventory of char is analyzed. Two transient periods in an FBG after a change of feed rate are shown: a devolatilization transient, lasting a few seconds, followed by a longer transient (from minutes to hours) resulting from the char accommodation until a new steady state is reached. The model is being used to assess the dynamic performance of the backup and storage system in biomass-hybridized concentrated solar power (CSP) plants.
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