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Liuyun Li - One of the best experts on this subject based on the ideXlab platform.
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coal combustion under calcium looping process conditions
Fuel, 2014Co-Authors: Takayuki Takahashi, Hiroko Narisawa, Ayato Yoshizawa, Liuyun LiAbstract:Abstract Coal of three kinds was burned in an oxygen-enriched atmosphere using a twin-fluidized bed solid circulation system under conditions of the Calcium Looping Process. This twin-fluidized bed system comprised a fast bed regenerator (calciner), into which fuel and oxygen-enriched gas were fed, and a bubbling bed absorber (carbonator), into which air was fed. Inert quartz sand was used as the bed material to evaluate the coal combustion behavior, including char transportation from regenerator to absorber and formation of CO and CO 2 there. First, the circulation rate and the residence time of solids in the regenerator (calciner) were measured to determine the suitable operation conditions. The effect of gas feed staging to the regenerator on the solid residence time was evaluated. By reducing the ratio of the primary gas feed rate to total gas feed rate to 0.5, average solid residence time of about 40 s was attained. Under this gas-feed condition, coal combustion experiments were conducted. Effects of Volatile Matter content of coal on CO and CO 2 formation in the absorber and NO x emissions from the regenerator were investigated. High-Volatile Matter coal was found to be favorable to reduce CO and CO 2 formation in the absorber, but conversion of the fuel-N to NO x of high-Volatile Matter coal was higher than that from low-Volatile coal.
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role of char in nox formation during coal combustion at a regenerator temperature of calcium looping process
Fuel, 2014Co-Authors: Takanori Higuchi, Ayato Yoshizawa, Liuyun LiAbstract:Abstract Coal of three kinds was burned in an oxygen-enriched atmosphere using two types of reactor both of which had the same fast fluidized bed for coal combustion. One was a dual-fluidized bed system (dual-FB), simulating Calcium Looping process comprised a fast fluidized bed regenerator and a bubbling bed carbonator. The other was a conventional single circulating fluidized bed combustor (single-CFBC). In both systems, coal combustion in oxygen-enriched atmosphere was carried out under regenerator temperature condition of Calcium Looping process. Inert quartz sand was used as the bed material to evaluate carbon consumption in the carbonator of dual-FB. Formation of NOx in the fast fluidized beds was measured for both reactors. For dual-FB, formation of CO and CO2 in the carbonator was also measured. High-Volatile Matter coal was found to be favorable to reduce CO and CO2 formation in the carbonator, but conversion of the fuel-N to NOx of high-Volatile Matter coal was higher than that from low-Volatile coal. The emissions of NOx from single-CFBC were less than those from the regenerator of dual-FB under the same combustion condition. From the emissions of CO and CO2 from the carbonator, the decrease in char combustion in the regenerator of dual-FB was calculated. An empirical relationship between the conversion of fuel-N to NOx in the fast fluidized bed and the ratio of fixed carbon to Volatile Matter of the fuel was obtained.
Piero Salatino - One of the best experts on this subject based on the ideXlab platform.
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modelling fluidized bed combustion of high Volatile solid fuels
Chemical Engineering Science, 2002Co-Authors: Fabrizio Scala, Piero SalatinoAbstract:Abstract A model of an atmospheric bubbling fluidized bed combustor operated with high-Volatile solid fuel feedings is presented. It aims at the assessment of axial burning profiles along the reactor and of the associated temperature profiles, relevant to combustor performance and operability. The combustor is divided into three sections: the dense bed, the splashing region and the freeboard. Three combustible phases are considered: Volatile Matter, relatively large non-elutriable char particles and fine char particles of elutriable size. The model takes into account phenomena that assume particular importance with high-Volatile solid fuels, namely fuel particle fragmentation and attrition in the bed and Volatile Matter segregation and postcombustion above the bed. An energy balance on the splashing zone is set up, taking into account Volatile Matter and elutriated fines postcombustion and radiative and convective heat fluxes to the bed and the freeboard. Results from calculations with a high-Volatile biomass fuel indicate that combustion occurs to comparable extents in the bed and in the splashing region of the combustor. Due to Volatile Matter segregation with respect to the bed, a significant fraction of the heat is released into the splashing region of the combustor and this results in an increase of the temperature in this region. Extensive bed solids recirculation associated to solids ejection/falling back due to bubbles bursting at bed surface promotes thermal feedback from this region to the bed of as much as 80–90% of the heat released by afterburning of Volatile Matter and elutriated fines. Depending on the operating conditions a significant fraction of the Volatile Matter may burn in the freeboard or in the cyclone.
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segregation of fuel particles and Volatile Matter during devolatilization in a fluidized bed reactor ii experimental
Chemical Engineering Science, 1997Co-Authors: M Fiorentino, Antonio Marzocchella, Piero SalatinoAbstract:An experimental study on the segregation of fuel particles and of Volatile Matter during devolatilization in a fluidized-bed reactor is presented. The study was purposely carried out with beds of solids kept at incipient fluidization in order to focus attention on the segregation phenomena associated with the generation of endogenous bubbles. This term is used to denote bubbles of Volatile Matter formed around each fuel particle during devolatilization, as opposed to exogenous bubbles of fluidizing gas always present in aggregative fluidized beds. Experimental evidence of Volatile bubble formation and of fuel particle as well as of Volatile Matter segregation is provided. Qualitative characterization of segregation patterns and quantitative assessment of the effect on segregation of variables like fuel particle size, density and Volatile Matter content, of bed solids size, of bed temperature are presented and discussed. Experimental data are further analyzed in the light of the theory developed in Part I (Fiorentino et al., 1996) in order to validate the model.
David Honore - One of the best experts on this subject based on the ideXlab platform.
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shadowgraphy investigation of the combustion of raw and pre treated single biomass particles influence of particle size and Volatile content
Fuel, 2019Co-Authors: Hassan Mohanna, Jeanmichel Commandre, Bruno Piriou, Gilles Vaitilingom, Benoit Taupin, David HonoreAbstract:An experimental study of single particle combustion is performed in a high temperature particle reactor. The particle degradation is simultaneously monitored by high magnification direct imaging and by shadowgraph imaging techniques giving access to the full behaviour of the particle even when enveloped by a flame. This allows tracing the time-resolved evolution of the particle shadow during its degradation as a function of its burnout. The method provides access to the whole process timeline, especially the onset of the heterogeneous oxidation even during the flame phase. It is observed to occur earlier for larger particles containing lower Volatile Matter. The latter occupies around 40% of the initial particle shadow, which decreases with devolatilisation progress following a power trend. The char burns at the surface until the reaction front penetrates the particle leaving an ash matrix behind. Effects of particle size and Volatile Matter on the different steps of particle combustion are discussed. Moreover, biomass behaviour is compared to that of coal. The whole results give new insights in the combustion of single biomass particle and are available for the development and validation of dedicated solid fuel combustion models.
Jidong Lu - One of the best experts on this subject based on the ideXlab platform.
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feasibility study of gross calorific value carbon content Volatile Matter content and ash content of solid biomass fuel using laser induced breakdown spectroscopy
Fuel, 2019Co-Authors: Zhimin Lu, Ziyu Yu, Xiaoxuan Chen, Lifeng Zhang, Jidong LuAbstract:Abstract Rapid determination of the solid biomass fuel properties is essential for optimizing the combustion process of biomass. In this work, a feasibility study on using laser-induced breakdown spectroscopy (LIBS) in conjunction with partial least squares (PLS) for simultaneous measurement of gross calorific value, carbon content, Volatile Matter content and ash content was carried out for 66 wood pellet samples. The best quantitative analysis results were obtained with the PLS model based on spectra that combined baseline correction with Z-score standardization. The root mean square error of prediction (RMSEP) of the gross calorific value, carbon content, Volatile Matter content and ash content were 0.33 MJ/kg, 0.65%, 1.11% and 0.38% respectively, while the average standard deviation (ASD) were 0.08 MJ/kg, 0.15%, 0.43% and 0.16% respectively.
Ayato Yoshizawa - One of the best experts on this subject based on the ideXlab platform.
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coal combustion under calcium looping process conditions
Fuel, 2014Co-Authors: Takayuki Takahashi, Hiroko Narisawa, Ayato Yoshizawa, Liuyun LiAbstract:Abstract Coal of three kinds was burned in an oxygen-enriched atmosphere using a twin-fluidized bed solid circulation system under conditions of the Calcium Looping Process. This twin-fluidized bed system comprised a fast bed regenerator (calciner), into which fuel and oxygen-enriched gas were fed, and a bubbling bed absorber (carbonator), into which air was fed. Inert quartz sand was used as the bed material to evaluate the coal combustion behavior, including char transportation from regenerator to absorber and formation of CO and CO 2 there. First, the circulation rate and the residence time of solids in the regenerator (calciner) were measured to determine the suitable operation conditions. The effect of gas feed staging to the regenerator on the solid residence time was evaluated. By reducing the ratio of the primary gas feed rate to total gas feed rate to 0.5, average solid residence time of about 40 s was attained. Under this gas-feed condition, coal combustion experiments were conducted. Effects of Volatile Matter content of coal on CO and CO 2 formation in the absorber and NO x emissions from the regenerator were investigated. High-Volatile Matter coal was found to be favorable to reduce CO and CO 2 formation in the absorber, but conversion of the fuel-N to NO x of high-Volatile Matter coal was higher than that from low-Volatile coal.
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role of char in nox formation during coal combustion at a regenerator temperature of calcium looping process
Fuel, 2014Co-Authors: Takanori Higuchi, Ayato Yoshizawa, Liuyun LiAbstract:Abstract Coal of three kinds was burned in an oxygen-enriched atmosphere using two types of reactor both of which had the same fast fluidized bed for coal combustion. One was a dual-fluidized bed system (dual-FB), simulating Calcium Looping process comprised a fast fluidized bed regenerator and a bubbling bed carbonator. The other was a conventional single circulating fluidized bed combustor (single-CFBC). In both systems, coal combustion in oxygen-enriched atmosphere was carried out under regenerator temperature condition of Calcium Looping process. Inert quartz sand was used as the bed material to evaluate carbon consumption in the carbonator of dual-FB. Formation of NOx in the fast fluidized beds was measured for both reactors. For dual-FB, formation of CO and CO2 in the carbonator was also measured. High-Volatile Matter coal was found to be favorable to reduce CO and CO2 formation in the carbonator, but conversion of the fuel-N to NOx of high-Volatile Matter coal was higher than that from low-Volatile coal. The emissions of NOx from single-CFBC were less than those from the regenerator of dual-FB under the same combustion condition. From the emissions of CO and CO2 from the carbonator, the decrease in char combustion in the regenerator of dual-FB was calculated. An empirical relationship between the conversion of fuel-N to NOx in the fast fluidized bed and the ratio of fixed carbon to Volatile Matter of the fuel was obtained.