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1. Introduction - Firenze University Press

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Fig. 6. Temperature profiles in compressors intercoolers preheating steam cycle condensate<br />

(case 3)<br />

Rise of energy efficiency,<br />

% points<br />

4<br />

3,5<br />

3<br />

2,5<br />

2<br />

1,5<br />

1<br />

0,5<br />

0<br />

0,55<br />

1,91<br />

Case 1 Case 2 Case 3 Case 4 Case 5 Theoretical<br />

Case number<br />

sum of Cases<br />

2-4<br />

Fig. 7. Increase of energy efficiency related to the reference case<br />

The influence of proposed improvements on the energy efficiency of analysed oxy-fuel power<br />

unit is clearly visible. The highest increase, nearly 2 percentage points, brings heat recovery<br />

from the flue gas compression train to steam cycle (case 3). The substantial increase of<br />

efficiency (<strong>1.</strong>3 % point) is caused also by lignite drying (case 4). The parameters of lignite<br />

after dryer have been presented in Table 5. Heat recovery from the flue gas to combustion<br />

oxygen (case 2) provides relatively low (0.5 % point) increase of plant efficiency. Case no 5<br />

which includes all proposed modifications is, as expected the best one, achieving the 3.4%<br />

52<br />

1,32<br />

3,43<br />

3,78

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