Woodchip boilers are now being used in space heating, replacing fossil-fuel-fired boilers. Despite high thermal efficiency and low emissions of particulates, the fuel-feeding systems of small-scale woodchip boilers account for nearly 90 % of unexpected plant shutdowns. This limits power plant availability and results in increased harmful emissions. Scientists of the EU-funded project BIOCHIPFEEDING (Wood chip feeding technology of the future for small-scale biomass boilers) developed a new low-cost feeding system that will overcome all relevant drawbacks of current systems. The new system is based on a gripper that withdraws fuel material from the storage room and transports it to a storage container. It is equipped with sensors to screen fuel quality in terms of particle size and moisture content. Intelligent software that communicates with the feeding system can map locations of low- or high-grade woodchip. It can thus ensure that the quality of the overall fuel mixture remains the same when discharging the fuel. Unlike previous systems that take fuel from the bottom of the pile, the new lightweight gripper extracts fuel material from above. In addition to minimising maintenance costs, this translates to significant savings in operating costs due to lower power consumption. A new fuel-feeding screw constantly supplies the combustion plant with woodchip from the intermediated storage container. A control system allows fully automatic operation. This means that only suitable material based on the burner operating state will be supplied. The fuel is evenly supplied with a constant quality that is adjusted to the boiler operating state. These changes significantly improved boiler performance. Two prototypes with grippers of varied sizes with flexible solutions for different plants were successfully installed. The grippers are compatible with conventional cranes and can therefore be easily integrated into existing systems. The new system promises to boost boiler efficiency and utilisation ratio. Apart from being particularly attractive for future small-scale woodchip heating, it can also substitute old biomass combustion plants. The number of newly installed woodchip boiler units is expected to increase from about 700 000 today to more than 1.6 million units per year by 2020.
Fuel feeding, biomass, wood chip, heating, low emissions, BIOCHIPFEEDING