Obtaining energy from waste

According to the Federal Statistical Office, every German adult produces 158 kg of residual waste per year. In total, around 130 billion tonnes of waste are generated nationwide, 82% of which is re-used – not only through recycling, but also by means of thermal waste plants. EEW Energy from Waste operates 16 of these plants in Germany, including one in Stapelfeld in Schleswig-Holstein. HANSA‑FLEX supplies industrial hoses for the flue-gas cleaning system of the waste incineration plant (WIP) and handles the plant’s hose management.

"The Stapelfeld waste-to-energy plant recycles up to 1,400 tonnes of waste every day,” says Christian Riepold, Junior Engineer at EEW Energy from Waste Stapelfeld GmbH. What do you do with so much waste? “You burn it in one of our two incinerators,” says Riepold with a smile, “because waste is a resource that can be used very efficiently to generate energy. And that’s exactly what we do here.” By “here” he means an area of four and a half hectares on which a number of different buildings stand close together. “Only one third of the entire plant is assigned to burning the waste,” Riepold explains. “Two-thirds is accounted for by the flue-gas cleaning system.” But how is waste turned into energy?

6:35 a.m. on the site of the Stapelfeld waste incineration plant: the first lorries have already brought their waste to the unloading hall, from where it is transported to the garbage bunker via a huge concrete chute. 140 vehicles arrive here every day. With a capacity of 6,000 tonnes the bunker offers sufficient space. “We need a stockpile in order to be able to guarantee supplies at weekends as well,” explains Riepold. The crane operator, who overlooks the mountains of waste from an odour-proof glass box, mixes the waste thoroughly with a five-ton grab. “The waste will only burn evenly and with little residue if the mixture is balanced,” says Riepold. The crane operator then drops the waste mix into one of the two feed hoppers, from where it enters the incinerator. “Here the temperature is more than 1,000 degrees Celsius all year round,” Riepold says. “At such high temperatures, the waste burns all by itself.” The heat from the waste incinerator generates around 63 tonnes of water vapour at 380 degrees Celsius per hour, which drives a turbine at a pressure of 26.5 bar. In this way 136,000 megawatt hours of electricity are generated annually – enough for 39,000 households.

Once the steam has done its work and driven the turbine, it still has a temperature of 130 degrees Celsius. “We transmit this energy to the district heating network. In this way we make optimum use of the fuels and supply environmentally-friendly heating energy for the residents of our neighbourhood.” This is because the calorific value of waste is comparable to that of lignite, but emits significantly less carbon dioxide. In addition, the Stapelfeld plant is one of the cleanest incineration facilities in Europe. “Our emissions are far below the prescribed limits,” says Riepold. In addition to optimum combustion, this is due to the highly modern flue-gas cleaning system, which consists of flue-gas scrubbers as well as electric and activated carbon filters. Waste also shrinks to ten percent of its original volume and is then recycled as well: The slag is processed and used in road construction, while fly ash and filtered dust are used to fill old mine shafts in order to prevent the ground from subsidence. The dirty water from the flue gas cleaning system is also treated and re-used.

The waste water from the wet flue-gas cleaning process in the flue-gas scrubbers is reprocessed and evaporated in the so-called “water house”, a 37-meter-high building through which pipes and hoses wind. This is where technicians from the HANSA‑FLEX Industrial Service are to be found. “We take care of all the hose lines here,” reports Jacek Boraczynski, Account Manager at HANSA‑FLEX.

The aim is to set up an efficient hose management system. The basis for this is the X-CODE, which uniquely identifies each hose. “This is important for two reasons,” says Riepold. “In the customer portal MY.HANSA‑FLEX we can see how long each individual hose line has been in use, and when the next test is due. In addition, we can now reorder spare parts quickly and easily.”

For this purpose the HANSA‑FLEX industrial hose centre in Geisenfeld and the special hose production facility in Hamburg-Stellingen work hand in hand. “We get the special hoses without fittings and assemble them ourselves,” reports Boraczynski. This also applies to the CHEM UPE SD industrial hose which is installed in the water house. “This chemical-conveying suction hose is very durable. In addition to water and waste water from the flue gas scrubbers it also transports gypsum sludge and saline media arising from the treatment of the waste water,” explains Boraczynski. In addition, HANSA‑FLEX uses corrosion-resistant plastic fittings. “In this way we can ensure a service life of up to ten years,” he adds.

The work is carried out routinely and professionally. “We don’t need to provide a lot of support from our side,” Riepold says happily. “We only get together twice a day, in the morning to set the day’s objectives and in the evening to check they have been completed.” The project, in which 160 hose lines were laid, was completed in just under eight weeks. Since then HANSA‑FLEX has continued to provide support for the waste incineration plant in Stapelfeld. On the inspection dates the Industrial Service examines every hose closely. “The cooperation is just right: efficient maintenance for an efficient waste incineration plant,” sums up Riepold.