Tower will turn garden waste into energy
An enormous tower that will be able to convert biological residues such as garden waste, olive stones and chicken manure into electricity and hydrogen will be built in Germany by the end of the year.
The 42m-high Blue Tower is being built as a demonstration project in Herten, in North Rhine-Westphalia. Its proponent, H2Herten, said it would save 17.8 million m3 of natural gas and 15,000 tonnes of carbon dioxide a year.The tower will use regenerative feedstock for energy production, producing a CO2-neutral gas, called Blue Gas. The conversion takes place in multiple process steps known as staged reforming.First, garden waste, roadside green cuttings, and other organic matter are all fed into the tower. Temperatures of 600°C lead to thermal decomposition of the feedstock (pyrolysis). Around 80% of this feedstock is converted into a gas, with the rest converted into solid material which is subsequently used to generate the process heat required by the tower.Phase two sees the gas purified into Blue Gas in a reforming stage by the addition of steam at 950°C. Blue Gas has 50% hydrogen content and is low in tar. It can be filtered and used in gas motors for electricity generation or processed to pure hydrogen. The Blue Gas also contains carbon monoxide and a small amount of methane.The final stage sees the heat required for thermal decomposition and gas refinement provided by heated ceramic beads. These ceramic beads move through the process steps from top to bottom in the Blue Tower in a closed cycle, and dissipate their heat. The solid material (coke) is burned to heat up the beads. The processes can run continuously. In doing so, Blue Tower can produce large amounts of Blue Gas, approximately 3,000m3 an hour. H2Herten said Blue Tower was a multi-feedstock technology, so it had the potential to be situated at different sites across the world. It said the product gas created in Blue Tower was especially rich in hydrogen, low in tar and practically nitrogen-free, and had many different uses. The process takes place under atmospheric pressure.The tower is being designed and built by engineering firm M+W Zander and it is expected to have thermal power of 13MW, generating up to 5MW of electrical energy. H2Herten said it would provide 12,000 households with environmentally friendly electricity, while the hydrogen will go to a nearby technology centre.
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