WASTE TO ENERGY
single truckload of prepared fuel takes place upon delivery. T e fuel shipments are sorted into quality classes and stored in separate fractions based on visual criteria such as grain size distribution and the amount of needles, leaves, and bark. T is incoming control also ensures that no contaminants or old wood have been delivered. In addition, a sample is taken from every load delivered to determine the water content as the basis for the calculation. Several photos are also taken to document the quality classifi cation. T is strict quality management is the result of extensive process optimisations. T ey ensure not only that the requirements are met for upholding remuneration under the Renewable Energies Act, but also that fuel use, plant failure, and ash disposal are minimised.
90,000 TONS OF RENEWABLE FUEL PER YEAR T e power station receives 90,000 tons of wood from rural conservation per year from around 80 regional fuel suppliers – 70 to 100 truckloads per week. TEAtherm uses only fresh, undried wood from rural conservation. To ensure that the system is able to reach full capacity, the water content and fuel quality need to be just right. T e fuel proceeds to the infeed grate via the vibration chute, trough chain conveyor, and hydraulic pusher. T e combined heat and power station with steam turbine has a maximum electrical output of 9.6MW and is fed with 36 tons of steam per hour. T e turbine exhaust steam is condensed at a temperature of 45°C and is used to heat the neighbouring greenhouse. In comparison with conventional district heating networks
TEAtherm produces 64,000MW hours of green energy
with a temperature of 90°C, this use of exhaust steam not only avoids the loss of power caused by steam withdrawal from the turbine, it also increases the electrical effi ciency of the system. With 40,000MWh per year, the greenhouse is already the largest heat consumer by far. By the end of 2021, however, the greenhouse area is set to be expanded by a further fi ve hectares and will then consume another 15,000MWh of heat.
DRYING 20,000 TONS OF WET SLUDGE TEAtherm uses around 13,000MWh of heat to operate the sewage sludge dryer. T e belt dryer made by Andritz has a drying capacity of 22,000 tons of wet sludge per year. T e volume of dry material produced annually is 4,800 tons. At 20m in length with a width of 10m, the dryer has a throughput of 2.7 tons
The TEAtherm site in Bavaria
of wet sludge per hour. For the drying process, the sludges delivered with a water content of 78% are evenly spread onto a slowly moving process belt made from PPC in an 80mm-thick layer. T e air in the dryer is circulated via two circulation fans, heated in heat exchangers, and channelled through the product for drying. T e dryer is fed with hot steam at a temperature of 200°C at a pressure of 8 bar. T e sludge then moves through diff erent temperature zones on the process belt for 30 to 50 minutes - from 140°C at the start of the dryer to 100°C at the end. T is causes the water in the sludge to evaporate and the water content drops from 78 to less than 10% at the dryer outlet. Some of the dry material generated is mixed with the wet sewage sludge in the mixer at the dryer infeed to achieve a granulate with better drying properties. T e exhaust air is channelled via another fan through a washer and biofi lter for cleaning. Cleaning the exhaust air produces an ammonium sulphate solution of fertiliser quality.
SEVEN-YEAR BELT LIFE IN CONTINUOUS OPERATION When the system was put into operation by TEAtherm, there was still a GKD 5099 PPC process belt on the dryer – around 36m long, 3.80m wide, with L-seam and edge coating. Unlike with polyester belts, the material of this belt type means that no hydrolysis occurs, so that the mesh design comprised of robust monofi laments permanently withstands the large surface weights. Woven in 3/2 twilled weave, the belt is particularly
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