TY - JOUR
TI - Biomass gasification with preheated air: Energy and exergy analysis
AU - Karamarković Rade M
AU - Karamarković Vladan M
AU - Jovović Aleksandar M
AU - Marasević Miljan R
AU - Lazarević Anđela D
JN - Thermal Science
PY - 2012
VL - 16
IS - 2
SP - 535
EP - 550
PT - Article
AB - Due to the irreversibilities that occur during biomass gasification,  gasifiers are usually the least efficient units in the systems for production  of heat, electricity, or other biofuels. Internal thermal energy exchange is  responsible for a part of these irreversibilities and can be reduced by the  use of preheated air as a gasifying medium. The focus of the paper is biomass  gasification in the whole range of gasification temperatures by the use of  air preheated with product gas sensible heat. The energetic and exergetic  analyses are carried with a typical ash-free biomass feed represented by  CH1.4O0.59N0.0017 at 1 and 10 bar pressure. The tool for the analyses is  already validated model extended with a heat exchanger model. For every 200 K  of air preheating, the average decrease of the amount of air required for  complete biomass gasification is 1.3% of the amount required for its  stoichiometric combustion. The air preheated to the gasification temperature  on the average increases the lower heating value of the product gas by 13.6%,  as well as energetic and exergetic efficiencies of the process. The optimal  air preheating temperature is the one that causes gasification to take place  at the point where all carbon is consumed. It exists only if the amount of  preheated air is less than the amount of air at ambient temperature required  for complete gasification at a given pressure. Exergy losses in the heat  exchanger, where the product gas preheats air could be reduced by two-stage  preheating.