Focus on Biomass Ash

Utilization of biomass with thermal route which is combustion and gasification will be generated ash residue. While the pyrolysis due to work at low temperatures (400-600 C) and without oxygen / air then there is no ash. Minerals contained in the biomass will remain behind in the form of charcoal products in the pyrolysis process. Ash content and ash chemistry greatly affects the utilization of biomass in addition to heating value, particle size and moisture content. In general characterization of ash from biomass is described by Bryers as follows:

1.     High  silica (Si) and potassium (K) ash content  while the calcium (Ca) is low, with low fusion temperature derived from the group of agricultural biomass wastes.

2.     Low silica (Si) and potassium (K) ash content while calcium (Ca) is high, with a high fusion temperature derived from a group of nearly all the woody biomass. Specifications are best for combustion and gasification.

3.     High potassium (K) and phosphorus ash content, with low fusion temperature derived from faecal matter such as poultry and cattle dung.

Biomass Ash Content

The ash content of various types of biomass indicate slagging behavior.  In general, the higher ash content, the greater the tendency of its slagging behavior. But this does not mean that low ash slagging not show the phenomenon.  Operating temperature, ash chemistry and ash content are variables the occurrence of slagging. If conditions favor the slagging will be even greater. Minerals such as SiO2, Na2O and K2O more tendency toward the occurrence of slagging. Usually slagging occurs in biomass with ash content of more than 4% and non-slagging fuel with ash content less than 4%. According to the composition of the melt, fuel-biomass fuels are grouped into severe or moderate slagging.

Biomass Ash Chemistry 

Issues arising from these ashes is clogging the air intake holes or slagging that will reduce the thermal efficiency of the gasification and combustion process related air supply and biomass distribution in the process unit.

Ash Slagging

So before processing the biomass waste, consider and note the ash content and its chemistry so that it can deliver optimum results.