Monday, November 18, 2013

No. 144: Building the concept of urban coalfield to help a local government get revenue (November 18, 2013)

Toshiba got an order from a local government in the Tokyo metropolitan area for a plant to produce fuel using sludge coming from the sewerage treatment plant jointly with JEF Engineering. Toshiba’s technology eliminates water from sludge and heats the dewatered sludge for 2-3 hours, and produces fuel that has a half amount of energy as coal. Sludge is heated at 160-170 degrees centigrade for one hour to eliminate water in the first stage, and subsequently heated at 400-600 degrees centigrade for one-two hours in the second stage. As fuel for these two stages, Toshiba’s technology uses flammable gases, such as methane and carbon monoxide, and recycles waste heat. Auxiliary fuel, such as city gas and heavy oil, accounts only for several percentages in the fuel used for burning.  

 The concept of urban coalfield is no longer a dream.

It is possible to produce 80-100 kg of fuel from one ton of sludge. Toshiba’s technology produces fuel that has 60-70% calorie as coal, and the produced fuel can be used for fuel in cement plants and coal-fired thermal power stations. The first plant to be constructed by Toshiba will treat 62,000 tons of dewatered sludge annually. In addition to producing fuel, Toshiba’s technology can reduce carbon dioxide emissions by more than 80% as compared with the existing method that reduces volume of sludge by dewatering and burning.

What is more, Toshiba’s technology will help the local government get revenue by selling the produced fuel. This is the concept of urban coalfield. As of 2010, 78% of sludge is recycled, and 40% of the recycled sludge is used as a raw material of cement and only 1% is recycled as energy. It is expected that fuel equivalent to 1.5 million tons of coals can be produced by utilizing sewage sludge annually in Japan.

 Producing fuel for power plants from sewage sludge

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