By drying lignite in a unique pressurised process, Vattenfall is able to increase efficiency and flexibility while lowering CO2 emissions in lignite-fired power plants.
Lignite is Germany’s primary source of energy. However, more than 50 percent of the fuel’s weight is water. In a conventional lignite power plant, this results in energy losses of about 20 percent.
Steam is used to heat the lignite
Since 2008, Vattenfall has been working in its pilot plant in Schwarze Pumpe, Germany, to develop an efficient process – called pressurised fluidised bed drying (PFBD) – to reduce the moisture content of lignite before combustion and thus increase efficiency. In the process, steam from the powerplant’s turbines is diverted to the bed dryer, where it is used to heat the lignite to between 100 and 160 degrees Celsius. In this way, the water content is reduced to between 5 and 20 percent, depending on its intended use.
“So far, more than 5,000 operation hours have been spent conducting tests on more than 30,000 tons of lignite,” says Benjamin Jentzsch at Vattenfall R&D in Cottbus, Germany, who is responsible for the program. “The process results in a net efficiency increase of up to 5 percent and a 10 percent reduction in CO2emissions."