Investigation of warm gas clean-up of biofuel flue and producer gas using electrostatic precipitator

Abstract The use of biofuels has been increasing in Europe over recent years. However, NO x and emissions of fine particulates are important and in that respect biofuel is still at a disadvantage when compared with oil and natural gas-fired systems. Electrostatic precipitators are the most widely used of the high-efficiency devices for the catching fine particulates. In this comparative study on biofuel (wood pellets), the ESP collection efficiency was investigated for solid particles from a boiler (50 kW) and from a gasifier (100 kW). Although releases of solid particles from modern boilers are low, a combination of such a boiler with an electrostatic precipitator may reduce the release of particles to a minimum. The collection efficiency of the ESP obtained during the investigation with the flue gas was ∼98–99%. There is a big difference in particle concentrations when comparing the systems with flue gas and producer gas. As the working conditions in the test section with the producer gas were more challenging, this leads to a lower efficiency for the electrostatic precipitator (∼75%). The obtained particle sizes and chemical composition of solid particles give better understanding of the problem under investigation.