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Torrefied pellets are more energy efficient in comparison with wood pellets. This kind of fuel has a wide range of beneficial properties, which make it possible to reduce emission of harmful chemical compounds. Special technology is applied to produce torrefied pellets and provide them with a big amount of advantages.
What is torrefaction? It is a method to produce fuel, based on the thermochemical handling of biomass. This technology requires high temperature, approximately 300 degrees Celsius, in terms of biomass heating. Torrefaction must be conducted with little or no oxygen.
A coal-like substance is the result of torrefaction process. Torrefied pellets are made of different kind biomass. It can be, for instance sawmills or agro residues. While these basic materials are heated, practically all the moisture evaporates.
After having been heated, the feedstock loses approximately 30 per cent of its mass. This waste material becomes converted into torrefaction gases, which are almost useless in terms of energy production.
However, the remaining 70 per cent of feedstock contain 90 per cent of initial energy density. It means, that torrefied pellets are extremely efficient, since power generation requires respectively small amount of this fuel.
Torrefaction process consists of several manufacturing stages, which are conducted in the following order. First, basic material is loaded in the torrefaction reactor in order to remove all the moisture.
The next step is to heat the feedstock at a high temperature, between 250 and 300 degrees Celsius. At this stage processed material decomposes, several gases are emitted and torrefied pellets are produced.
Still, there is one more stage. Torrefied pellets are cooled and grounded. They also require additional treatment in order to become hydrophobic. After this stage, torrefied pellets are ready to be combusted.
The main beneficial property of torrefied pellets, which makes them easy to handle, is their extremely high grindability. After having been processed, torrefied wood pellets lose their initial structure and become brittle.
In this case, this kind of fuel is quite similar to coal. It means that torrefied pellets can be utilized in co-firing at the coal-fired power stations. They do not require any specially designed equipment to be combusted, by contrast with regular wood pellets. Consequently, the use of this kind of fuel is much cheaper than the use of wood pellets.
The fuel, produced by using torrefaction technology, is also hydrophobic. It means that torrefied pellets are resistant to rotting. This advantage of torrefied pellets makes it possible to store them on the outside, since they will not absorb moisture and become useless as a result.
It may happen that torrefied pellets will become popular in the European Union in the nearest future. This industry is in its infancy at present; however, several European companies have announced their intentions to involve torrefied wood pellets in the production of energy.
For instance, Swedish power generating company Vattenfall that it is going to purchase torrefied pellets, as its demand for a clean fuel will have increased by 2020. This figure is estimated at 20 million tonnes of pellets.
What is more, there are facilities in several European countries, which are enabled to produce torrefied pellets. Such facilities are situated in the Netherlands and Belgium, for example. Michael Wild, director of the Austria-based firm Wild&Partner, assures, that the European Union needs a new kind of environment-friendly fuel, and torrefied pellets can be an appropriate solution.
In summary, torrefied pellets are produced by using special technology. Torrefaction process provide pellets with a number of beneficial properties that are to make this kind of fuel popular in the nearest future. Moreover, some European countries have already announced their intention to include torrefied wood pellets in the production of energy.
