Firing with grain

Most people react in a negative way the first time they hear about firing grain, but the fact is that we within Sweden (and indeed other parts of the EU) have a surplus amount of arable acreage. Our surplus of grain does not automatically reach the people that are starving in the world but instead costs the society a large amount of money in different support actions. Today, the price of the fuel is too high to make it profitable to fire it. Maybe, just now, it is only suitable for farmers to fire surplus amounts of grain that has been too damaged to be sold to the food industry.
If we should be able to try to reach the global climate goals it is necessary to use the surplus acreage within the agriculture sector for energy production. If we choose to grow crops we might loose our open farm land that we are used to seeing. 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 locally produced over the whole of the EU and provide a valuable occupation for many also in rural areas. For the farmer it is not about any new and expensive investments, instead he can use the existing machinery he has already got. As a fuel, grain is nature's own pellets. It is easy to transport, contains little fine fractions and, during combustion, does not contribute to the greenhouse effect.
By firing grain you can, in the long term, decrease the costs upon society on agricultural support measures, whilst at the same time retain the open landscape. Developed grain firing would also give the farmer an alternative return for grain of bad quality.
To fire with grain
Experience of firing grain so far on a farming level is still quite limited. However, there are still some different technologies to choose from. However, firing grain is still not very common even amongst farmers themselves. However, the interest to start firing with grain is enormous.
The heat value in grain varies dependent upon its dryness, cleanliness and manuring etc. Still, generally we can assume that oats are the most suitable fuel if you can choose. Oats have typically a slightly higher fat content and a little better heat value than other types of energy, and the soft shell makes the grain more flammable, whilst at the same time the melting point of the ash from oats produces a higher combustion temperature before the ash then sinters.
If you should cultivate for energy purposes it could be then be favourable to grow oats, growing a type that is easy to thresh and gives an early ripeness. The most economic for your own use otherwise is to cultivate as usual and fire the parts of the crop that for different reasons have a lower market price.
When considering the combustion technology side of things there are no bigger differences between firing with wood chips, pellets or grain. The equipment presently available can handle each of these fuels and with a similar performance. However, you can not fire grain in a traditional pellet burner or woodchip stoker due to the increased ash content and the hardness of the grain causes technological problems with the combustion. However, there are special grain burners that can also operate with pellets.
Technological solutions
Burners for existing boiler
If there is an existing working boiler it can normally easily be complemented with a special grain burner. Normally a wood pellet burner does not work with grain. The reason for this is due to the hard shell of the grain and the slightly higher moisture content, making the ignition time longer and the burner then loses effect. However, a burner meant for grain normally works without any problems with pellets as fuel.
Cermically lined furnace
There are two different kinds of grain burners available on the market today. One construction is with an integrated stoker feed and a ceramic lined furnace. The ceramics used give a high combustion temperature which makes it possible to handle fuels with slightly higher moisture contents. However, the higher temperature then increases the risk of sintering which can be a problem when firing with grain.
Burners with a cooled burner pipe
During the past few years more compact burner constructions have been developed, resulting in burners that look more like the typical pellet and oil burners. These do not have ceramic brick lining but do have metallic and cooled burner pipes. The biggest advantage with these burners, except for their handy size, is 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 a built-in burner can normally achieve a 5-10 % fuel saving compared to a new boiler and separate burner. They are most suitable for oats because of sintering problems with other types of grain. The risk of sintering decreases if the boiler has a movable grate or a ceramic lump that rotates within the bed.
Burners for all types of grain.
The development continues to move forward with burn graining and new technology with burners mounted on the side has shown optimal results. Within the combustion head a fast ignition takes place and gasification of the fuel begins. Secondary air is then added when the gas is leaving the combustion head and finally combusted within the boiler. The burnt material immediately leaves the hot combustion zone via a movable grate and then falls down into the cold bottom part of the boiler. This kind of burner can manage to combust all types of grain and 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 others characteristics, the combustion does not work with maximum efficiency.

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