Characteristics of high heating rate biomass chars prepared under N2 and CO2 atmospheres

Borrego, Ángeles G.; Garavaglia, Lorenzo; Kalkreuth, W.

doi:10.1016/j.coal.2008.06.004

Cited by 72 publications

(41 citation statements)

References 26 publications

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“…Previous works in literature [7][8][9] reported higher apparent volatile yield values after devolatilization of coal at temperatures of 1000-1400 ºC under CO 2 than under N 2 and they attributed this effect to the char-CO 2 gasification reaction. However, other authors [8,12] obtained slightly lower values after devolatilization in CO 2 at lower temperatures (800-1000 ºC), since the gasification reaction rate was considered to be not significant at low temperature. Brix et al [14] gasification is an intense endothermic reaction which can only take place when high temperatures are present.…”

Section: Apparent Volatile Yieldmentioning

confidence: 91%

“…This was attributed to the high oxygen content (30%) in the oxy-fuel combustion atmosphere that could have concealed possible differences in the reactivity of both chars. However, Borrego et al [12] focused on the characteristics of the biomass chars prepared under N 2 and CO 2 atmospheres in a DTF at 950 ºC and they also found that similar morphology, optical texture and specific surface were shown by the biomass chars generated under both atmospheres. Therefore, more research is needed on the differences in the chars obtained by devolatilization in N 2 and CO 2 of biomass samples to achieve an effective introduction of biomass in the oxy-fuel combustion technology.…”

Section: Introductionmentioning

confidence: 99%

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Biomass devolatilization at high temperature under N2 and CO2: Char morphology and reactivity

Gil

Riaza

Álvarez

et al. 2015

Energy

114

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Section: Apparent Volatile Yieldmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Biomass devolatilization at high temperature under N2 and CO2: Char morphology and reactivity

Gil

Riaza

Álvarez

et al. 2015

Energy

114

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“…The specific area greatly expanded in the presence of CO 2 . In a study on biomass char pyrolysis in a drop tube furnace respectively un der N 2 and CO 2 [11], Borrego et al performed textural characterisa tion on wood chip chars and found similar specific areas: 277 and 331 m 2 /g respectively under N 2 and CO 2 . The char reactivity to wards air at 550°C in a TG device was also the same.…”

Section: Interpretation and Discussion Of Resultsmentioning

confidence: 99%

“…Borrego et al [11] performed pyrolysis experiments on pulver ised wood (particle size of 36 75 lm) in a drop tube furnace at 950 C under N 2 and CO 2 . They performed textural characterisation of the residual chars and found similar specific areas: 277 and 331 m 2 /g under N 2 and CO 2 .…”

Section: Introductionmentioning

confidence: 99%

Effects of CO2 on biomass fast pyrolysis: Reaction rate, gas yields and char reactive properties

Guizani

Sanz

Salvador

2014

Fuel

141

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. Effects of CO2 on biomass fast pyrolysis : reaction rate, gas yields and char reactive properties. Fuel, Elsevier, 2014, 116, pp.310-320. 10.1016/j.fuel.2013 Effects of CO 2 on biomass fast pyrolysis: Reaction rate, gas yields and char reactive properties t r a c tThe effect of CO 2 introduction in a biomass fast pyrolysis process at 850°C was investigated. It was found that CO 2 impacts the final gas yield and composition, and the char yield and properties. Introducing CO 2 in the pyrolysis medium alongside nitrogen enhanced CO production as a result of homogeneous and het erogeneous reactions of CO 2 with gases, tars and char. The char yield was lower compared to a reference char yield in pure nitrogen. The char obtained in a CO 2 containing atmosphere has its surface area increased nearly sixfold and has a chemical composition different from that of chars obtained in N 2 atmo sphere. However, the reactivity of the two chars towards H 2 O, CO 2 and O 2 was almost the same. Temper ature programmed oxidation experiments on both chars those obtained in pure nitrogen and those obtained in a CO 2 containing atmosphere revealed quite different oxidation profiles and peak temper atures. Taken together, these results tend to confirm that CO 2 is impacting the biomass fast pyrolysis pro cess. In the light of these results and of the literature findings, we propose a mechanism illustrating the role of CO 2 during fast pyrolysis of biomass.

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“…These authors concluded that char reactivity (in 21%O 2 /79% CO 2 ) prepared in CO 2 is almost equivalent to that prepared in N 2 in a study where coal chars were obtained at low temperature (~1073 K) in a tubular furnace. Borrego et al [38] studied the characteristics of the chars from various biomass materials generated at a high heating rate in a drop tube furnace (DTF) under N 2 and CO 2 atmospheres and they found that similar morphology, optical texture and specific surface area were shown by the biomass chars generated under both atmospheres.…”

Section: Kinetic Parametersmentioning

confidence: 99%

Kinetic models for the oxy-fuel combustion of coal and coal/biomass blend chars obtained in N2 and CO2 atmospheres

Gil

Riaza

Álvarez

et al. 2012

Energy

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The thermal reactivity and kinetics of five coal chars, a biomass char, and two coal/biomass char blends in an oxy-fuel combustion atmosphere (30%O 2 -70%CO 2 )were studied using the non-isothermal thermogravimetric method at three heating rates.Fuel chars were obtained by devolatilization in an entrained flow reactor at 1273 K under N 2 and CO 2 atmospheres.Three nth-order representative gas-solid models -the volumetric model (VM), the grain model (GM) and the random pore model (RPM) -were employed to describe the reactive behaviour of the chars. The RPM model was found to be the best for describing the reactivity of the high rank coal chars, while VM was the model that best described the reactivity of the bituminous coal chars, the biomass char and the coal-biomass blend char. The kinetic parameters of the chars obtained in N 2 and CO 2 in an oxy-fuel combustion atmosphere with 30% of oxygen were compared, but no relevant differences were observed. The behaviour of the blend of the bituminous coal (90%wt.) and the biomass (10%wt.) chars resembled that of the individual coal concealing the effect of the biomass. Likewise, no interaction was detected between the high rank coal and the biomass chars during oxy-fuel combustion of the blend.

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Characteristics of high heating rate biomass chars prepared under N2 and CO2 atmospheres

Cited by 72 publications

References 26 publications

Biomass devolatilization at high temperature under N2 and CO2: Char morphology and reactivity

Biomass devolatilization at high temperature under N2 and CO2: Char morphology and reactivity

Effects of CO2 on biomass fast pyrolysis: Reaction rate, gas yields and char reactive properties

Kinetic models for the oxy-fuel combustion of coal and coal/biomass blend chars obtained in N2 and CO2 atmospheres

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