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Rehabilitation of the Maritsa East 3 TPP, Stara Zagora Region
Under our contract with Entergy Bulgaria for implementation of construction supervision for the "Rehabilitation of the Maritsa East 3 TPP, Stara Zagora Region" project, in conjunction with our duties, we performed the following:
The Maritsa East 3 TPP is the latest thermal power plant in Bulgaria. It is one of the three power plants in the Maritsa East Complex which is situated in the south west part of the country. The Plant is located 280 km away from Sofia, and 68 km away from Stara Zagora. It is built on an area of 1000 acres, and in the closest vicinity of the village of Mednikarovo.
The Plant's total installed output capacity is 840 MW, and comprises four Units. The Plant uses local lignite coal which are mined in the Maritsa East's Troyanovo 3 mine, and are transported to the TPP through belt conveyors.
The project for rehabilitating Maritsa East 3 TPP amounted to 600 million euros. The funding was provided by a bank consortium with the participation of the EBRD and comprised a plurality of measures for increasing the plant's life, and bringing the installations in line with the modern environmental and equipment-safety standards. The project was implemented between 2001 and 2010.
The Technical Equipment
The rehabilitation comprised facilities and parts thereof whose resource had expired, and/or had with defects that would limit the Plant's work. The pipes and the fittings for primary and reheated steam, and feedwater pipelines were entirely, or partially replaced. All materials containing asbestos, including boiler and pipework insulation, and the cooling tower’s irrigation system, were replaced; the milling fans, the coal-preparation systems and the burners were reconstructed; the screens of the combustion chambers and the convective heating surfaces, including the air heaters were replaced; the electric filters of the boilers were reconstructed; the ash pipelines were replaced; a new draining system for the ash ponds was built; a zero usage of water for technical needs was ensured; a new Ø 800 + Ø 600 fibreglass technical water pipeline was built between the pump station of the Rozov Kladenec Dam and the TPP (16 km); the steam turbines were repaired; the Low Pressure Cylinders were reconstructed: the Bauman stages were replaced with rotor blades having high-strength stellite attacking edges. As a result, the active output of the turbine generators was increased to 227 MW/block. The Units control were replaced.
The lignite coal that the Maritsa East 3 TPP uses has high sulphur content. A Flue Gas Desulphurisation Installation (FGD) was built in order to decrease the sulphur oxides omitted in the atmosphere. The FGD operates via a wet method, wherein the flue gases from each two boilers are fed to an absorber. The purified flue gases are discharged by chimneys located above the absorbers. The limestone needed for the FGD is delivered by railway to the unloading station, and is stored outdoors. After having passed through a system of crushers and mills, the limestone solution is fed for flue-gas treatment. A by-product of the reduction is a gypsum suspension that is treated in dewatering installation which separates the water from the gypsum suspension through a system of cyclones and belt vacuum filters, resulting in gypsum with about 20% moisture. The gypsum is deposited at a gypsum landfill, or is used by a Knauf factory for producing plasterboards (outside the scope of the project).