Development of an electrostatic precipitator designed for straw and chip boilers.

The objective of this project is to develop a low-cost, efficient and reliable flue gas filter designed for small biomass boilers. Starting point for the development work will be a prototype of a flue gas filter, which was developed in a previous project. The technology and concept used in this prototype gave very promising results. A large amount of very fine-grained dust is emitted from the chimney when the fuel is straw. A cyclone is not suitable for separating this fine dust. For large straw-fired plants fabric filters are used for dust removing. Today in Denmark in rural areas, there is no threshold for dust emission from small straw-fried boilers. However, from January 2018, the common European standard EN 303-5 for smaller straw-fried boilers will be implemented in Denmark. This means that the threshold for automatically fried boilers will be 40 mg of dust per normal m3 flue gas. With traditional techniques, this threshold can only be met by using a fabric filters. A fabric filter is relatively expensive both in procurement and in operation. This filter requires a large fan to overcome the pressure drop across the filters. The bags are vulnerable to high flue gas temperature, which often occurs in small straw boilers. Therefore high operating cost for the replacement of filter will be necessary when using fabric filters. This project will develop a flue gas filter for small straw fired boilers. The filter will be simple and inexpensive and the pressure drop will be low and thus having low energy consumption. The filter has only few moving parts and there by the maintenance costs will be low.
The project divided into three work packages: In work package 1 the existing prototype will be renovated and optimized. All the known weaknesses of the prototype will be rectified if possible. Based on the experience and test results on the optimized prototype, a new prototype adapted to a 200 kW boiler will be made in work package 2. This prototype will be tested over a long period at AU Foulum. The construction parts and components will be developed with a view to future commercial production. In work package 3 a final near commercial market prototype is constructed and tested both at AU Foulum and on full scale biomass boilers in practice.
The development of an effective and low-cost flue gas filter for small biomass-fired boilers is crucial for the use of these boilers in the future both in Denmark and in the rest of Europe. There exists a large surplus of straw throughout Europe. If the straw could be used in these boilers, reduced CO2 emissions will be achieved and the straw, a renewable energy source, could replace fossil fuels. The project will help in full filling the Danish political goal on 100 percent renewable energy by 2050.