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Possible Problem Situations


On the left side ash that has solidificated and turned into stones due to the use of low quality chips. It contains impurities such as nails, sand, pebbles and wire.

On the right side a back burn situation. The fire has started to move towards the fuel tank because the incinerator is blocked by solidificated ash and its impurities.

Low-Quality Fuel or Equipment Failure

It is more usual that problems occurring in heating plants have to do with low-quality fuel and the impurities it contains rather than the combustion device itself. To avoid these problems, the equipment must be installed correctly and with expertise, the adjustments must be right and the system must be regularly serviced.

Low-quality and moist fuel brings along many challenges. Most common of these are vaulting of the fuel, interrupted feeding of the fuel, and, in the worst case, backburn. Low-quality fuel may also prohibit the system’s ability to raise temperature on the required level. Read more about the challenges that low-quality fuel can cause here.


Sometimes backburns occur in bio heating plants. Various different factors can cause backburns. One major risk factor is solidification of ash into hard stones, which forces the fire to spread backwards. When low-quality fuel is used, the incinerator should regularly be cleaned from the stones.

Backburn can also be caused by the chimney’s low extraction, insufficient replacement air required by the burning, or a loose fuel tank lid.

It is possible that in the older systems, the feeding pipe between the burner and the incinerator is too short, causing a backburn when heated up too much. This problem is solved by lengthening the feeding pipe and the screw inside it. With older systems it is advisable to check that adequate backburn protection is added.

Always after possible incipient backburn situation, find out the reason. Thus in the future similar situations can be avoided.

Lengthened feeding pipe in an old stoker burner. The lengthening is done in order to avoid backburn situations. Also the former extinction system, beeswax plug, is replaced with an automatic extinction system, which operates without electricity.

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Power & Energy Africa 2015 Kenya
Power & Energy Africa 2015 in Dar-es-Salaam, Tanzania.RENEXPO® BiHtcbiomass2015: Technology for the Bioeconomy