HetKond

Due to the political objective to considerably increase the percentage of renewable energies in Germany, biomass is more and more combusted primarily in small and medium-sized combustion plants. Because of their emissions, a complex waste gas cleaning is required to protect health and environment.

Especially dust emissions are critical because the total dust output consists of more than 90% fine particles. The latter are particularly hazardous to health because they are respirable. In biomass combustion and similar cases with high particle concentrations, the currently available separators do no longer work effectively; there is a lack of alternative separation systems.

Air cleaning based on heterogeneous condensation is a low-investment and energy-efficient approach: for potential retrofittings or as alternative for conventional separation mechanisms. Water vapor condenses on the surfaces of the particles dispersed in the gaseous phase; the particles start to grow. Thus, the grown and water-coated aerosols from biomass combustion can be separated by conventional separators in an energy-efficient way; an effective separation of those aerosols is made possible. An innovative approach to achieve a heterogeneous condensation is to use spray towers in combination with trays. Due to an intelligent arrangement of modern full cone nozzles or hollow cone nozzles and a specific interaction of the individual sprays, a secondary atomization renews the surfaces of the droplets and creates smaller secondary droplets. In addition, the effective mass transfer surface can be further increased by using trays: an intensive bubbling zone is formed above the tray with a low pressure loss only. Due to this innovative approach, higher possible oversaturations can be expected, with lower water quantities and lower energy expenditure compared to packed columns. Therefore the heterogeneous condensation shall be achieved by using spray towers.

In this project, the unexplored heterogeneous condensation on the particles from biomass combustion shall be investigated. This includes the activability of the particles and their growth. Non-contact optical measurement technology as well as specific sampling shall enable to gain deep insight into the complex processes. In order to achieve a high oversaturation, the use of spray towers shall be optimized to ensure a successful heterogeneous condensation so that the aerosols can be efficiently separated.