Engineering Properties of Biomass - Engineering and Science of Biomass Feedstock Production and Provision - page 26

Calorific value of each biomass sample can be measured by a Parr calorimeter
model 6300 (Parr Instrument Company, Moline, IL). A sample consisting of 40 g was
ground in a knife mill through a 2-mm screen. Approximately 1 g of the ground par-
ticles was weighed. A pellet was made from the ground particles using the manually
operated Parr Pellet Press. The weight of the pellet was entered as an input data to the
calorimeter. The pellet was placed in a crucible immersed in a bucket filled with 1 L
of distilled water. The bucket was placed in the calorimeter. The calorific value of the
pellet was recorded as the high heat value (HHV) in MJ per kg of dry biomass.

2.2.6 Ash Content

Biomass ash causes lots of operational problems during biomass processing, com-
bustion, and emissions. For example, silicon of biomass ash is the main contributor
to wear out of the blades of the size reduction unit [ 46 ]. Potassium and calcium
cause fouling of heat exchangers and slagging in the bottom of the furnace. These
require shutting down the units regularly, reducing the operating time of the produc-
tion units, and also increasing the maintenance cost. Therefore, the quantitative
analysis of biomass's ash content is critical for process design. Sometimes, a leach-
ing pretreatment process is required to extract the ash from the biomass before the
downstream processing. This helps to facilitate an efficient and economical down-
stream process with a high-quality product yield.
Ash content of the oven-dried biomass was measured using the NREL/
TP-510-42622 procedure [ 47 ]. A sample of softwood chips consisting of 40 g was
ground in a knife mill through a 2-mm screen. Three replicates of 0.5-0.8 g of each
ground sample were placed inside a muffle furnace equipped with a thermostat. The
temperature control for the furnace was set at 575 °C furnace based on the sug-
gested temperature program. At the end of the test, the ash sample was placed in a
desiccator to cool. The final weight of the sample was measured and recorded. Ash
content was expressed on a dry mass basis. The ash compositional analysis can be
done by EDAX or ICP-MS [ 48 ].

2.2.7 Color

Color is an important attribute of the biomass. For the biomass without thermal treat-
ment, a sample with dark color is usually correlated to high ash content. For exam-
ple, the pellets made with bark are darker in color [ 42 ]. For the biomass with thermal
pretreatment, the degree of the darkness of the sample can be highly correlated to
their degree of thermal treatment (e.g., torrefaction and steam explosion [ 49 ]), as
well as to the calorific value of the biomass.
The color of the biomass particle with different degrees of thermal pretreatment
was measured using a color spectrophotometer (Konica Minolta CM-5, Osaka,