2.4. The production process
The continuous feed pellet machine was run until steady state
conditions were obtained. Before every new test, there was a break-in
period of 5 min with the current additive to ensure steady state conditions.
Every test run lasted for 5 min. The feed control for the dried
sawdust of 12.2–12.7% (wb) was set at a fixed rpm (4.0 Hz) corresponding
to approximately 85 kg of sawdust/h. The additive flow was
subsequently increased, going from 1.1% to 4.2% based on the weight
of the pressing mass dry bases.
In order to test the lignin's additive characteristics, pellets were
produced with 1%, 2%, 3% or 4% of kraft lignin added. The kraft lignin
had two different moisture contents: 32.2%, as received directly from
the process, and 9.0% (wb), as dried.
The moisture content (wb) was determined according to SS-EN
14774-1. The moisture content for kraft lignin was measured by taking
5 samples of each assortment — altogether 10 samples were taken.
During the test production of pellets, samples of approximately 300 g
of dried sawdust were taken every 15 min, which resulted in a total of
12 samples. The moisture content of the cooled pellets was examined
by taking one sample fromeach 5-minute test, i.e., a total of 12 samples.