| About wood chip combustion |
| Wood chip combustion has become very popular concurrently with the rising energy prices. Today, not only home-owners who have access to their own forest use wood chips as fuel but private persons by prepared chips. If you have a good intallation for this purpose it works as well as oil or pellet combustion. Keep in mind that wood chip combustion normally requires a little extra space than pellet combustion. |
| Wood chips can be used in many different kinds and sizes of boilers. There are two different ways of wood chip combustion. You use a stoker or a so called furnace. The efficiency is high. The combustion is so efficient that 1 m³ of wood chips does not leave any liters of ash behind. |
GOTFire heating system |
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| In larger installations the chips burn on a roasting bed that moves or in a sand bed that is upheld by a heavy air flow. The fuel can also be gasified in a specific chamber and burnt as wood-gas. In a stoker installation a small amount of wood chips is being fed at a time (or continuously) that then gets to burn under optimal circumstances. Air is being provided when needed, normally divided into primary - and secondary air. The ash is colected in the ash part of the boiler and can then be removed manually or with mechanical aid. Chips with a higher moisture content require hearth temperature. This can be done with a ceramic jacketed furnace. From the furnace the burning gas is transmitted to the hearth of the boiler. The largest heat and mechanical stress then accure in the end part of the furnace and inside the flue pipe between the furnace and the boiler. |
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| If you have dryer chips or processed fuel (pellets) a so called stoker installation is the best alternative. The chips are fed from a container or from a storage with augers to the combustion part that normally only consists of a combustion cup in cast iron or high-temperature resistant steel. Compare with a traditional pellet burner. Chip stoker installation exist both as over or under fed burners. Though, the size is a little bigger than the pellet burner. For the chip combustion you use a chip storage with automatic feed of the fuel via an auger. The whole process can be compared to pellet - or grain combustion. The ignition of the chips can be made via hot air or fumer.
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| Chips used in smaller installations shall have a homogeneous particle size, and should not exceed a lenght of 50 mm. Unknown objects like sand, metal, should not exist. The moisture content decides the choice of equipment. If you choose a stoker, the mouisture content should not be higher than 20-25%. The dryer fuel, the higher heating value. The best chip quality is reached by using branches and tops (GROT) that could have been left in the forest for one year and shed. The grot should be kept covered until the chipping. Cold-air drying of chips is also possible. |
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| The storage should have a tight lid made of sheet with a switch that prevents the feed auger operates with the lid off and that the auger stops if the furnace is filled with chips at a power failure. The sprinkler system should have a thermostat set on approx. 70 °C. The stoker auger should have the lowest point at the chip pocket and work as a water seal. |
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