The gasification reactivity of high-heating-rate chars in single and mixed atmospheres of H2O and CO2

Abstract

. The gasification reactivity of high-heating-rate chars in single and mixed atmospheres of H2O and CO2. Fuel, Elsevier, 2013, 108, pp.812-823. 10.1016/j.fuel.2013 The gasification reactivity of high-heating-rate chars in single and mixed atmospheres of H 2 O and CO 2 C. Guizani ⇑ , F.J. Escudero Sanz, S. Salvador t r a c tGasification reactivity of high heating rate chars (HHR chars) in steam, carbon dioxide and their mix tures was investigated in a new macro TG experimental device. The higher reactivity of the HHR chars was highlighted by a comparison with reference chars prepared at a low heating rate (LHR chars). It was found that the char reactivity in a mixed atmosphere of steam and carbon dioxide can be expressed as the sum of the individual reactivities obtained in single atmosphere gasification experiments. This result was not dependent on the pyrolysis heating rate. In addition, gas alternation gasification experi ments for both HHR chars and LHR chars showed that gasifying the char with CO 2 up to 30% of con version does not affect its reactivity to H 2 O. Altogether, the results tend to indicate that the two reactant gases H 2 O and CO 2 react on separate active sites when mixed atmospheres are used, and that CO 2 does not affect the char structure to favor or inhibit the char H 2 O gasification reaction.

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

“…The increase in the reactivity from 40 to 50% of conversion is due to a developed char porosity and a higher catalytic activity of the minerals. Moreover, we found in our previous study on char gasification in mixed atmospheres of H 2 O and CO 2 [14], that gasifying biomass chars with CO 2 up to 30% of conversion does not affect its reactivity towards H 2 O, which corroborates the cur rent findings. In a fluidized bed, a major part of the char will be carried in the riser and combusted with air.…”

“…M TG apparatus. The new M TG device is described in detail in our previous work on char gasification in mixed atmospheres of CO 2 and H 2 O [14]. In general terms, the experimental apparatus consists of a 2 m long, 75 mm i.d.…”

Influence of temperature and particle size on the single and mixed atmosphere gasification of biomass char with H 2 O and CO 2

“…In our previous work on the gasification of HHR chars and LHR chars at 900°C, we found that regardless of the pyrolysis conditions, and for various CO 2 + H 2 O concentrations in the gasification medium, the char reactivity in mixed atmospheres can be fairly described by sum ming the single reactivities obtained respectively under H 2 O and CO 2 [11].…”

“…Pyrolysis conditions Mixed atmosphere mechanism [3] Wood char (4 cm) Same activation energy and dependance on the sum of partial pressure [4] Birch wood char (45-63 μm) Slow pyrolysis Competition 24°C/min [5] Pine wood char (5.5 mm) Medium rate pyrolysis in a screw reactor at 60°C/s Synergy [7] Various biomasses Slow pyrolysis 10°C/min Synergy [9] Dried sewage sludge char (1.2 mm) Fast pyrolysis in FBR Additivity [10] Olive tree pruning char (1.9 mm) Fast pyrolysis in FBR Additivity [11] Beech wood char ( More recently, Chen et al [16] investigated the effect of the pyrolysis conditions on the gasification reactivity of lignite chars in mixtures of H 2 O + CO 2 . Two kinds of char were prepared from a lignite by fast py rolysis using a drop tube furnace and by slow pyrolysis using a fixed bed furnace at a temperature of 1273 K. Char gasification reactions with CO 2 , H 2 O and their mixtures were performed in a thermogravimetric analyser (TGA) system.…”

“…These results are in accordance with those of [24] who evidenced the large char particle homogeneity when prepared in low heating rate conditions. The M TG device is described in detail in our previous work on char gasification in mixed atmospheres of CO 2 and H 2 O [11]. In general terms, the experimental apparatus consists of a 2 m long, 75 mm i.d.…”