Pellets torrefaction in the Netherlands
The torrefied wood pellets development interests greatly the Netherlands energy research centre and various companies, which take part in it. In November 2007, a consortium of three Dutch organizations (Econcern, the Energy research Centre of the Netherlands (ECN) and Chemfo), has concluded a memory of understanding the aim of which is to build a new type of biomass plant, that will manufacture ‘second-generation’ pellets. These pellets production technology lies in the following: the feedstock is torrefied, and processed into torrefied pellets. The consortium, currently working on the first commercial torrefaction plant creation, named them the BO2-pellets.
Torrefaction is a thermal pre-processing technology conducted at atmospheric pressure in the absence of oxygen. A solid, uniform product with a very low moisture content and a high calorific value is produced at 200-300oC . About 10% of the energy value of the original biomass is lost, at less than 75% of the original weight is lost during treatment process. The additional investments and losses in energy during the pretreatment process may be refunded due to the higher energy density, and subsequent lower transportation costs for torrefaction pellets, especially if it goes about long distance transportation. For example, one industry expert specifies that typically their pellets have an energy density of 18 - 20 GJ per m3 in comparison with the 10 - 11 GJ per m3 the conventional wood pellets have. In comparison (see below), industry professionals specify that torrefied pellets may have an energy density of 20.4-22.7 GJ per ton, compared to 17-18 GJ per ton for the one of conventional pellets . They consider it to be a key technology to process a large variety of different feedstocks (such as wood chips and agricultural residues) into a high-energy density pellet. Plus they think that second generation pellets may overcome all the difficulties related to the1st generation wood pellets: a limited energy density, indoor storage necessity and extra pulverization step, separation from coal pulverization, as they are hydrophobic, can be stored outside, and chopped together with coal in standard hammer mills. Typically the torrefied pellets will be used in coal fired power plants and as a feedstock for gasification-based transportation fuels9 manufacturing. At the same time the industry professionals doubt that such pellets will be applied for heat generation, as it is related to smaller distances valid within the chain of conventional wood pellets for heating.
