Experimental study on biomass air-steam gasification effectiveness in downdraft gasifier

Abstract

Biomass gasification has been regarded as a promising technology to utilize bioenergy sustainably. However, further exploitation of biomass gasification still needs to overcome a significant number of technical and technological challenges. The results of an investigation of straw pellet air-steam gasification process effectiveness in downdraft gasifier are presented. The method is based on definition of CoP of a gasification process through composing material and heat balances. A design of a pilot gasifier plant with a downdraft gasifier is presented. An outcome of dry syngas from 1kg of pellets with HHV 14.18 MJ·kg-1 was 2.25 m3 ·kg-1 . The HHV of dry syngas was 11.836 MJ·kg-1 . The calculation errors of balances are: 1.82 % for material and 0.83 % for heat. It was found that use of an air-steam mixture as blast gases raises CoP of the gasification process to 83.4 %, which is more than classical methods of gasification. The analysis of balance made it possible to define harmful heat loses of the proсess. It was revealed that losses into environment 861 kJ·kg-1 (6.04 %), losses with coke-like remainder 861 kJ·kg-1 (6.0 %) and around 1 % in total of losses are with moisture and tar. Directions of improvement of a downdraft gasifier are the design or operational mode optimization. The presented investigations could become a basis for a modern method of defining the effectiveness of the gasification process for stationary and mobile gasifiers as well. Using the obtained results the new laboratory practice for students of engineering courses was prepared and successfully tested.