Influence of the pyrolysis heating rate on the steam gasification rate of large wood char particles

Abstract

This work was carried out in order to quantify the impact of the pyrolysis heating rate both on the properties of the residual charcoal and on the behaviour during gasification by H 2 O of the charcoal. The experiments were conducted on 10 mm diameter beech wood spheres, pyrolysed at atmospheric pressure under heating rates covering the range from very slow, 2.6 K min K1 , to very rapid, over 900 K min K1 , i.e. the highest value that can be reached. When charcoal is submitted to gasification at 20% H 2 O i nN 2 at 1200 K, the ratio of the times for complete conversion reach 2.6. Such a difference is considerable as far as an industrial application is concerned. The initial properties of the charcoal such as apparent density, porosity, and pore surface area obtained by N 2 or Ar adsorption were measured in order to explain the differences in gasification kinetics within the charcoal. The charcoal particles exhibit densities as different as 219-511 kg m K3 and porosities between 87 and 70% for charcoal prepared at 900 and 2.6 K min K1 respectively. The specific surface area is higher than 600 m 2 g K1 for three charcoals. Influence of ash content of the initial charcoals, at 1.6-2.7%, is also regarded with particular attention to explain the observed differences in gasification kinetics.

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

“…The respective BET specific surfaces are 68.9 ± 14.33 m 2 /g and 408.3 ± 3.1 m 2 /g. Former studies showed the same order of magnitude for the specific area of chars prepared with a high heating rate under nitrogen: S BET < 70 m 2 /g [4]. The specific area greatly expanded in the presence of CO 2 .…”

“…The mass of the residual char is known to depend on the tem perature and on the pyrolysis heating rate [2,4,18]. The final tem perature was the same in the two experiments.…”

“…Higher residence times in the reactor are also required to maximise the tar thermal cracking to gas. The particle heating rate which depends on the particle size and shape, as well as on the operating conditions in the reactor (temperature and gas flow) is a key parameter which influences the pyrolysis product yields and the char properties [1,4].…”

“…The pyrolysis mediums were N 2 , CO 2 , CO, CH 4 and H 2 . The authors found that the liquid yield, composition and higher heating value depend on the compo sition of the pyrolysis bath gas.…”

Hydrogen production from algal biomass via steam gasification

“…Gasification is also alternative to produce bio-gas from algae. There are many studies of biomass gasification using different agents such as CO 2 , steam, air (Hanaoka et al, 2005;Garcia et al, 2001;Gil et al, 1999) Steam gasification has more advantage among the other agents (Mermoud et al, 2006). Furthermore, the good quality of the gas with a high percentage of hydrogen is obtained by steam.…”