Efficiency enhancement in biomass heating plants by an innovative integration of flue gas condensation and heat pumps

In Germany, around 1,200 biomass heating plants have been built with a thermal power of > 500 kW each, especially in the years 1995 to 2005. Many more were installed all over Europe. Along with the development of biomass heating plants, many district heating networks have been implemented which provide a low-emission heat supply for surrounding facilities in the local area. District heating networks usually operate for many decades with up to 50 years possible. In general, refinancing district heating in urban areas takes about 15-30 years. However, biomass heating plants are designed for around 20 years. Thus, operators of biomass heating plants from 1995 to 2005 will have to make new investments into system components, like firing, installation, boiler, and pumps. With new investments, operators have the chance to undertake additional efficiency-enhancing measures such as an integration of flue gas condensation. Flue gas condensation can increase the efficiency of a biomass heating plant by more than 20 %. However, flue gas condensation needs low and stable back flow temperatures in the district heating network to avoid negative effects such as corrosion. The idea is to implement heat pumps in combination with flue gas condensation. Heat pumps ensure stable conditions for the condensation of flue gas by cooling the flue gas on the cold side. In addition, the temperature of the latent heat is increased by the heat pumps and can be fed back into the district heating network.