Reppie is a unique facility, not just because of its location at an altitude of 2,300m, a level at which few WtE facilities of this size have ever been built, but because of the lower heat value and higher moisture content found in the waste stream. It was therefore critical that the facility was designed by a firm with extensive experience in constructing facilities with similar waste conditions to Addis Ababa. For this reason the Consortium engaged CNEEC’s affiliate, China Urban Construction Design and Research Institute Co, Ltd (CUCD). CUCD is China’s vastly experienced national design institute who has been responsible for designing dozens of such facilities across China, a country with a waste stream composition that is similar to that found in Africa.
The Consortium combined the requisite local and international reach with the design and financial strength required to ensure the facility could be custom-made for SSA and then scaled to neighbouring countries.
Environmentally-friendly Flue Gas Treatment
Incineration plants have been around for more than 100 years, but modern incineration plants are very different from their forebears. The Reppie Facility has adopted modern back-end flue gas treatment technology which ensures that almost all of the nitrogen oxides (NOx), sulphur dioxide (SO2), heavy metals and dioxins produced by the plant are drastically reduced, thus ensuring the plant operates safely within the strict Emission limits of the European Union. Any residues leftover from the flue gas treatment is recycled or safely disposed of whilst the scrubbed and cleaned flue gas is released into the atmosphere through the Plant’s twin 50 high stacks.
There are thousands of waste-to-energy plants around the world, and most of them employ a similar process to that at Reppie. The unsorted Municipal Solid Waste will be delivered to the waste reception hall by the Municipality’s 16t compactor IVECO trucks. Two semi-automatic grab cranes mix the waste before it is loaded onto the Martin’s SITY2000 Grates (2 x separate lines) where the waste is combusted. Martin’s moving grates are world leaders and ensure an optimal burn-off of the diverse waste stream. The Plant is designed to accept a calorific value range of 5.5 – 9.5 MJ/kg of waste. Over 80% of this waste is eliminated and what remains is converted into ash. The bottom ash will be sold as a building material to the local construction industry or safely used as landfill cover in the new Sendafa Landfill site. The Facility uses magnets to recover steel and other ferrous metals for additional recycling. The Facility’s energy-recovery comes from the generation of superheated steam to drive a 25 MWe steam generator and produces an expected 185 GWhr of electricity every year. To meet the demands of the Employer, there are two sets of 25MWe turbines for redundant operation, which will ensure increased plant availability and reliability.