Energy conversion of biomass char: Oxidation rates in mixtures of O2/CO2/H2O

Kärlstrom, Oskar; Hupa, Leena

doi:10.1016/j.energy.2019.05.192

Cited by 26 publications

(12 citation statements)

References 36 publications

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“…This can be explained by the fact that the char is more reactive toward H 2 O than toward CO 2 . The influence of CO 2 and H 2 O on the mass loss of carbon has been investigated in numerous other publications (e.g., ref ) and will not be discussed further here.…”

Section: Resultsmentioning

confidence: 99%

“…Figure shows a schematic picture of the reactor. A detailed description of the reactor can be found elsewhere. , The single-particle reactor consists of a quartz tube reactor, with an inner diameter of 44 mm, inserted in a ceramic furnace. Gas mixtures of synthetic air, nitrogen, CO 2 , and steam were inserted in the bottom of the reactor system, and the product gases exited the reactor from the top of the reactor system.…”

Section: Methodsmentioning

confidence: 99%

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Role of CO₂ and H₂O on NO Formation during Biomass Char Oxidation

et al. 2020

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We have investigated how CO2 and H2O influence NO release rates during char oxidation of biomass. In addition, the role of catalytic elements in these processes has been studied. NO release rates were determined from single-particle experiments of softwood and straw at 900 °C, in CO2/O2 (34/3%) and H2O/O2 (17/3%), with N2 as the balance gas. The NO release profiles differed in CO2/O2 and H2O/O2. In CO2/O2, the NO release increased as the char conversion proceeded. On the other hand, in H2O/O2, the NO release decreased as the char conversion proceeded. In neither of these cases, the conversion rates of char-N to NO were proportional to the conversion rates of char-C. To investigate how the ash-forming matter influenced the NO release rates, the biomasses were demineralized and the experiments were repeated. For the chars of the demineralized biomasses, the NO release profiles were almost identical in CO2/O2 and H2O/O2. In addition, for the demineralized chars, the conversion rates of char-N to NO were proportional to the conversion rates of char-C. The conversions of char-N to NO were significantly higher for the demineralized chars. For softwood, the total conversion of char-N to NO was as high as 85%. These results show that (i) CO2 and H2O influence the formation of char-N to NO in different ways and (ii) the ash-forming matter contributes to the differences in the NO release rates.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Role of CO₂ and H₂O on NO Formation during Biomass Char Oxidation

et al. 2020

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“…Recently, Li et al have used an isotope tracer technique to clarify steam gasification behavior during coal combustion in the O 2 /CO 2 /steam atmosphere with the presence of CaO, which provides a viable way to investigate the char reaction in the complex atmospheres. Karlström et al . investigated the oxidation rates of energy conversion of biomass char in mixtures of O 2 /CO 2 /H 2 O.…”

Section: Factors Affecting Biomass Char Gasificationmentioning

confidence: 99%

“…Recently, Li et al 125 have used an isotope tracer technique to clarify steam gasification behavior during coal combustion in the O 2 /CO 2 /steam atmosphere with the presence of CaO, which provides a viable way to investigate the char reaction in the complex atmospheres. Karlstrom et al 126 investigated the oxidation rates of energy conversion of biomass char in mixtures of O 2 /CO 2 /H 2 O. The results show that, for large particles and high temperatures, CO 2 and H 2 O gasification reactions play a dominant role, while, for sufficiently small particles and low temperatures, the O 2 oxidation reaction is primarily important in the case of mixtures of O 2 /CO 2 /H 2 O/ N 2 .…”

Section: Factors Affecting Biomass Char Gasificationmentioning

confidence: 99%

A Review on Biomass Gasification: Effect of Main Parameters on Char Generation and Reaction

et al. 2020

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Reactions between char and gasifying agents are usually the controlling step and of a core role for the overall biomass gasification process due to the relatively low reaction rate. Char reactivity will be greatly affected via interacting with volatiles, such as steam, hydrocarbons, tarry compounds, and other light gas species. By taking the updraft/downdraft moving bed and fluidized bed gasifier as examples, this review discussed the effects of char generation and evolution in various reactor environments on its following reaction behaviors. The characteristics of biomass and subsequent char gasification are further examined in terms of feedstock types and their inherent inorganics. Then, the effects of operation conditions and gasifying reagents on biomass gasification are outlined mainly from the point of char production and the subsequent volatiles−char interaction. Finally, some directions and suggestions considering char conversion and utilization are addressed for the design and betterment of the biomass gasification process.

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“…For example, the gasification reactions were in the regime II condition of the three-zone theory at 900 • C, the rate of which is limited by the combined effects of chemical kinetics and diffusion [4]. For large particles or at high temperatures, the gasification caused by CO 2 and H 2 O played a dominant role in char conversion [12]. Therefore, these reactions must be taken into consideration in the numerical modeling of biomass combustion.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Unburned Carbon Release and NOx Emission from a Pulverized Wood Pellet Boiler Retrofitted for Fuel Switching from Coal

Lee

Park

et al. 2020

Energies

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For renewable electricity production, biomass can fully displace coal in an existing power plant with some equipment modifications. Recently, a 125 MWe power plant burning mainly anthracite in Korea was retrofitted for dedicated wood pellet combustion with a change of boiler configuration from arch firing to wall firing. However, this boiler suffers from operational problems caused by high unburned carbon (UBC) contents in the bottom ash. This study comprises an investigation of some methods to reduce the UBC release while achieving lower NOx emissions. The computational fluid dynamics approach was established and validated for typical operating data. Subsequently, it was applied to elucidate the particle combustion and flow characteristics leading to the high UBC content and to evaluate the operating variables for improving the boiler performance. It was found that the high UBC content in the bottom ash was a combined effect of the poor fuel grindability and low gas velocity in the wide burner zone originating from the arch-firing boiler. This prevented the operation with deeper air staging for lower NOx emissions. Reducing the particle size to <1.5 mm by modifying mills or pretreating the fuel using torrefaction was the only effective way of lowering the UBC and NOx emissions with deeper air staging while increasing the boiler efficiency.

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Energy conversion of biomass char: Oxidation rates in mixtures of O2/CO2/H2O

Cited by 26 publications

References 36 publications

Role of CO₂ and H₂O on NO Formation during Biomass Char Oxidation

Role of CO₂ and H₂O on NO Formation during Biomass Char Oxidation

A Review on Biomass Gasification: Effect of Main Parameters on Char Generation and Reaction

Reduction of Unburned Carbon Release and NOx Emission from a Pulverized Wood Pellet Boiler Retrofitted for Fuel Switching from Coal

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Energy conversion of biomass char: Oxidation rates in mixtures of O2/CO2/H2O

Cited by 26 publications

References 36 publications

Role of CO2 and H2O on NO Formation during Biomass Char Oxidation

Role of CO2 and H2O on NO Formation during Biomass Char Oxidation

A Review on Biomass Gasification: Effect of Main Parameters on Char Generation and Reaction

Reduction of Unburned Carbon Release and NOx Emission from a Pulverized Wood Pellet Boiler Retrofitted for Fuel Switching from Coal

Contact Info

Product

Resources

About

Role of CO₂ and H₂O on NO Formation during Biomass Char Oxidation

Role of CO₂ and H₂O on NO Formation during Biomass Char Oxidation