Development of novel fixed-bed gasification for biomass residues and agrobiofuels

The project concerned three different approaches to achieve reliable operationin fixed-bed gasification of available biomass residues. The first approach was based on the pretreatment of fuels for use in standard downdraft gasifiers. The second one was based on using a commercially available updraft fixed-bed gasifier for heating applications. The third was based on the developmentg of a new type of gasifier that were independent of the natural descending fuel flow caused by gravity. The downdraft gasification tests were carried out in Italy in a gasifier-engine-generator facility with a range of Italian biofuels, the aim being to create criteria for fuel selection, collect reliable performance data with suitable fuels and to identify technical possibilities for broadening the feedstock basis by using mixture fuels and additives. The test results and experiences clearly demonstrated the limitations of this type of commercial gasification technology. Operation experiences of commercial updraft gasifiers operating in Finland and Sweden were collected and evaluated. These updraft gasifiers operate well with sod peat and wood chips. However, these gasifiers cannot operate reliably with low-bulk density fibours fuels like bark, sawdust and shavings. The third technical approach was realised by designing, constructing and testing a pilot plant of a new type of gasifier, based on forced fuel flow and suitable for low-bulk-density fibrous biomass fuels. The pilot plant was connected to a secondary catalytic gas cleaning device, which made it possible to produce tar-free gas suitable for engine use. This new fixed-bed gasifier makes it possble to utilise such biomass residues and energy crops that cannot be used in the presently available fixed-bed gasifiers, like forest residue chips, sawdust and crushed bark. However, further work is required to demonstrate the whole gasifier, gas cleaning and engine concept and to define the lifetime and availability of the catalytic gas cleaning system.