Gasification Archive for February 2001

The maximum possible mass flow per 24-hours
was for densified wood pellets
Z=(24/18)*(0.5*0.57/0.43)*X = 0.88 X tons/24h
is for non-densified sawdust pellets
> Z=(24/18)*(0.5*0.17/0.83)*X = 0.14 X tons/24h
> 
The adjusted coal flow per 24-hours
was for densified wood pellets
Y= X*(-0.14)/(-0.43) = 0.34 X tons/24h
is for non-densified sawdust pellets
Y= X*(-0.75)/(-0.83) = 0.90 X tons/24h

Total mass flow coal+biomass
was for densified wood pellets
Y+Z = 0.88+0.34 = 1.22 X tons/24h
is for non-densified sawdust pellets
Y+Z = 0.14+0.90 = 1.04 X tons/24h

Subconclusion:
when energy input stays the same
and volume of fuel is allowed to go up to 150%
then in case of non-densified sawdust pellets with CV=18 MJ/kg
total tonnage goes to 104% (was 122%)
and cofiring mixture on a mass/mass basis
can reach up to 0.14X / 1.04X = 13% (was 0.88X / 1.22X = 72%)
and cofiring mixture on energy basis
can reach up to (0.14*18) / (0.14*18 + 0.90*24) =  10.5% (was 66%)


7. CONCLUSION

By comparing the substantial drop in cofiring percentages (both on a
mass/mass and energy basis) between densified wood pellets and non-densified
sawdust pellets, the relevance of densification has been shown.

If not DRY sawdust pellets had been taken as the second example but low
density biomass with a higher moisture content and sebsequent lower Caloric
Value, the drop in maximum reachable cofiring percentages had been even more
drastic.

Hope this provides some insight.

Best regards,
Andries Weststeijn
EPZ