Pelleting "On Location"
The future for mobile pelleting ?
Mobile pelletizing of biomass ONLOCATOR
Status of project "ONLOCATOR" at the beginning of 2009
Through my work on investigating whether there is basis for producing a mobile pelletizing machine for pelletizing biomass, I have experienced - within the field "Sustainable, renewable, and CO2 neutral energy supply" - great interest for how to exploit best the enormous potential, which consists in exploiting the biomass energy. To pelletize the biomass where it grows seems obviously logic but it seems hard to reach really efficient machines with satisfactory capacity and satisfactory operational reliability.
Such a machine shall have a very high capacity in order to produce a large numbers of tonnes of fuel pellets during a relatively short harvest period. The length of the harvest period in the Scandinavian countries is relatively short, but naturally it looks differently in other countries. The optimum method is of course that the biomass is dried by means of solar energy to prevent artificial drying. Moreover, one can imagine that the biomass, which cannot be pelletized directly from the field/wood, is gathered and pressed in big bales and then brought to local decentralised storerooms, which can serve as storages which a group of farmers have established and will run jointly.
The imaginary machine ; according to the plans, ONLOCATOR shall be designed so that it can be used both directly in the field and can work as an easy mobile machine, which relatively easy can be converted to work as a stationary unit, which can pelletize the biomass being stored in these storerooms, outside the harvest season. A minimization of the risk is also obtained by limiting the size of the storages as a possible fire will have local consequences only. Usually, it is a regular disaster, if a fire breaks out as a result of incident or self-ignition in some of the big storages as fire fighting here is very difficult.
This year, Denmark is going to hold a climate summit and in the long run, it is the vision of the Danish government to become independent of fossil fuel and to reduce the CO2 emission considerably; here efficient exploitation of biomass enters the picture. The advantage of using biomass energy is, as everybody knows, that it has the required buffer effect. In this way, you are independent of the fact whether the wind is blowing or the sun is shining. Biomass energy and the two energy sources, mentioned previously, supplement each other well.
However, a lot of technical problems, which shall be solved before mobile pelletizing seriously can enter the picture, exist. In the field, the problem is that the pelletizing machine will be fairly heavy and therefore it shall be pulled by a fairly big tractor and moreover it shall be equipped with strong tyres. These problems can yet be solved.
Another problem is that a very high degree of safety shall be obtained to separate foreign objects such as soil, stones, and any metal parts before they reaches the cutting unit and the pelletizing unit of the machine. A lot of suggested solutions to solve this problem exist. Combined with each other, they might give a high degree of safety against expensive damages to the machine.
The demands on the fuel pellets are that they shall be storage-proof and the amount of dust shall be most limited. In order to reduce the amount of dust, the pellets shall have good compression and in some cases, it is necessary to add a binding agent e.g. in the shape of vapour prior to the pelletizing process itself. Speaking of mobile pelletizing, it is to a great extent necessary to control completely the pelletizing process, which shall be carried out in a ring die press or a disc cutter die press. The hole geometry of the ring die or the disc cutter die is of vital importance to both energy consumption and to the mechanical stability of the pellets. In some cases, it might be necessary to exchange the die from one biomass type to another one.
As the ONLOCATOR, as previously mentioned, must have a high capacity, it is considered that the tractor, which shall pull the machine and operate pick-up, cutter, and crusher/grinder, at least shall have an effect of 200 kW. Nowadays, this is not a problem with the sizes of tractors available. It is estimated that an installed effect of 350-400 kW can give a fairly high capacity, to operate the ring- or disc cutter die unit itself.
Besides being protected against the fact the foreign objects get into the machine, devices to protect against overload or blocking shall also be fitted. Moreover, cooling of the ready-pressed pellets shall be available as rather heavy heat formation is anticipated in the press unit, no matter if it is about the ring die type or the disc cutter die type.
Some of these technical problems, above mentioned, are best solved by doing experiments in order to find the optimum solution. INNOACTIVE still attempts to find financing to produce a prototype in order to test the theories in practice. In Denmark, much research is going on in the biomass energy field and they have access to the latest know-how in this field.
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Pelleting "On Location"
