Thermodynamic methodology to support the selection of feedstocks for decentralised downdraft gasification power plants

ABSTRACT

Thermodynamic criteria as a feedstock selection tool for decentralised downdraft gasifiers coupled to spark-ignition engines are presented in this work. The methodology consists of an energy and exergy analysis of gasification process. The analysis is carried out by computational modelling of the gasification process as a function of biomass type (ultimate analysis, moisture content and heating value) and fuel/air ratio. Considering a system operating with different wood species, analysed parameters are gas heating value, energy and exergy efficiencies and engine fuel quality (EFQ). With a fixed fuel/air ratio (2.6) and moisture content (20%wt), it is highlighted that as the carbon-oxygen molar ratio of wood decreases from 2.0 to 1.78 as model input, reaction temperature increases by 9%, energy and exergy efficiencies diminish by 1.8% and 4.2%, respectively, while EFQ increases by 3.2%. Therefore, for decentralised power plants, biomass should be selected to produce higher EFQ.

KEYWORDS:

• Energy
• exergy
• engine fuel quality
• feedstock selection methodology
• downdraft gasification
• biopower plant

Acknowledgements

The authors would like to thank the Universidad de Antioquia for financial support for this research through the project ‘Integration strategies of wood planted in Colombia under thermochemical bio-refinery concepts: thermodynamic analysis and characterisation of bioproducts - PRG2014-1016’ (in Spanish). One of the authors, Juan F. Pérez, acknowledges the support of the Erasmus Mundus Program for the postdoctoral grant from the Eurica Program at the University of Valladolid (Spain).

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Juan F. Pérez is an Associate Professor from Mechanical Engineering Department at the University of Antioquia (Colombia). He is working on biomass as renewable source for bioenergy and bio-products.

Andrés Melgar is an Associate Professor from Energy Engineering and Fluidmechanics Department at the University of Valladolid (Spain). He is currently working on renewable energies and thermal engines.

Alfonso Horrillo is a Senior Researcher in the CIDAUT Foundation for Research and Development in Transport and Energy (Boecillo, Spain). His work fields are engineering and thermal systems.