Pellets are growing more common when it comes to generating heat and energy in our society. There are advancements in the actual production of the pellets, where the end-product is of high quality but made with a minimum energy consumption. One of the questions being posed is; do you get a better result if you do the torrefaction before or after palletisation?
Torrefaction improves the biomass properties when pellets are supposed to be used as an energy/chemical commodity.
At present, there are some limitations to torrefied biomass, one of them being that the density is lower and therefore challenging to transport over long distances. The biomass needs to be densified to be able to trade as an energy source, but with one problem being that the biomass is hard to bind during densification.
Why densify torrefied biomass?
You get an increase in bulk density, better flowability characteristics and a predictable quality as well as thermal performance. It is of importance that torrefied biomass particles are densified with a minimum energy consumption, and they must maintain the higher properties of torrefied biomass which means a high-energy value that is less susceptible to moisture and mechanical damage.
How is torrefied pellets produced?
According to research there seems to be two possible options of making torrefied pellets. One would be to densify torrefied biomass but a torrefied biomass is not as easy to bind as raw biomass. The need for a binder or a high use of energy are likely to be required, and seems to be apparent in the densification of torrefied biomass.
The other possible option would be to torrefy densified biomass. The questions that are being posed concerning this way are if the physical compaction can be maintained in the pellets if they are torrefied, and can pellets be torrefied as effectively as wood chips?
The early results of these questions being posed are of a promising nature but only a beginning of answers yet to come.