Most people react in a negative way the first time they hear about firing grain, but the fact is that we within the country (Sweden, and the whole EU) have a surplus of arable acreage. Our surplus on grain does not automatically reach the people that starve but instead costs the society a great amount of money in different support actions. Today, the prices on the fuel are too high to make it profitably to fire it. Maybe, just now, it is only sutably for farmers who can fire surplus and grain that has been too damaged to be sold to the food industry.
If we should be able to reach the climate goals it is necessary to use the surplus acreage within the agriculture for energy production. If we choose to grow salix we might loose our open farm land that we are used to see. If we use grain for energy production we keep the option of producing alcohol motor fuel, firing or eating, as long as possible.
Grain - and especially oats - can be localy produced over the whole country and give valuable occupation also in rural areas. For the farmer it is not about any new and expensive investments, instead he can use the machinery he has already got. As fuel, grain is nature's own pellets. It is easy to transport, contains little fine fractions and, at combustion, does not contribute to the greenhouse effect.
By firing grain you can in the long term decrease the costs of the society on support actions and at the same time keep the open landscape. A developed grain firing would also give the farmer an alternative return for grain of bad quality. |
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| The experiences of firing grain on farming level are still quite limmited. But there is some technology to choose from. But firing grain is still not very common even among the farmers them selves. But the interest to start firing is enormus. |
The heat value in grain varies after kind, dryness, cleanness, manuring etc. But generally we can assume that oats is the most suitable fuel if you can choose. Oats has because a slightly higher fat content, a little better heat value than other types of energy and the soft shell makes the grain more inflammable as the same time as the melting point of the ash from oats permits a higher combustion temperature before the ash sinters.
If you should cultivate for energy purposes it could be favourably to grow oats and a kind that is easy to thresh and gives an early ripeness. Most economic for you own use is otherwise to cultivate as usual and fire the parts that for different reasons have a lower market price.
Combustion technology wise there are no bigger differenses between firing with wood chips, pellets or grain. The available equipment can handle this with similar preformance. But you can not fire grain in a traditional pellet burner or chip stoker since the ash content and hardness of the grain cause combustion technological problems. Though, there are special grain burners that can also operate with pellets. |
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| Technological solutions |
Burners for existing boiler
If there is an already working existing boiler it can normally easilly be complemented with a special grain burner. A normal wood pellet burner noramlly does not work with grain. The reason is that the hard shell of the grain and the slightly higher moisture content make the ignition time longer and the burner looses effect. Though, a burner ment for grain normally works without any problems with pellets as fuel. |
Cermically lined furnace
There are two different kinds of grain burners on the market. One construction is with a stoker fed and ceramically lined furnace. The cermics gives a high combustion temperature which makes it possible to handle fuel with a little higher moisture content. Though, the higher temperature increases the risk of sintering which can be a problem when fireing grain. |
Burners with a cooled burner pipe
During the past few years more compact burner constructions have been developed, burners that look more like the pellet - and oil burners. These do not have ceramic brick lining and have metallic and cooled burner pipes. The biggest advantage with these burners is, except for the handy size, that they are easy to install and have a considerably lower radiation loss to the boiler room. The disadvantage is that they normally only work well with oats as fuel. Some burner brands can handle a mixture of oats and barley.
Integrated boilers
There are prepared installations where the burner is completely connected (integrated) in the boiler. This minimizes the radiation losses. A boiler with built-in burner can normally therefore give 5-10 % fuel saving compared to a new boiler and separate burner. They are most suitable for oats because of sintering problems to other types of grain. The risk of sintering decreases if the boiler has a movable roasting bed or a ceramic lump that rotates in the bed. |
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Burners for all types of grain.
The development moves forward and new technology with burners mounted on the side has shown optimal circumstances. Inside the combustion head a fast ignition takes place and gasification of the fuel. Secondary air is added when the gas is leaving the combustion head and finally combusted in the boiler. The burnt material immediately leaves the hot combustion zone via a movalble roster and falls down in the cold bottom part of the boiler. This kind of burner can manage to combust all types of grain with a good result.
The whole function of the system is important
Mutual for all solutions where an existing boiler is combined with a grain burner, is that there is almost always a compromise. If the boiler and burner are not adjusted to each other, the combustion does not work with maximum efficiency. |
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