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1. Introduction - Firenze University Press

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N<br />

el<br />

el, brutto <br />

(8)<br />

m1c<br />

Wdp<br />

The net efficiency of electricity generation depends on the gross efficiency of electricity generation<br />

( el, brutto),<br />

the auxiliary power rate of air separation unit ( pw, ASU ), the auxiliary power rate of carbon<br />

dioxide capture unit ( pw, CCS ), the auxiliary power rate of steam cycle ( pw, bloku)<br />

and the auxiliary<br />

power rate of the boiler ( pw, koto ). The equation showing the relationship between these quantities is<br />

as follows:<br />

el, nettoel,<br />

brutto (<br />

1<br />

pw, ASU <br />

pw, CCS <br />

pw, bloku <br />

pw, koto )<br />

Auxiliary power rates except the auxiliary power rate of the air separation unit, depends on<br />

auxiliary power of unit ( N pw, i ) and the steam turbine electric power ( N el ).The equation showing the<br />

relationship between these quantities can be written as:<br />

<br />

pw, i<br />

N<br />

pw, i<br />

N<br />

el<br />

(10)<br />

The auxiliary power rate of the air separation unit depends on the mechanical power used to drive<br />

the compressor ( N SN ), the mechanical power generated in expander ( N TR ) and the steam turbine<br />

electrical power ( N el ).The equation showing the relationship between these quantities is as follows:<br />

N N<br />

SN TG<br />

pw, ASU <br />

(11)<br />

Nel<br />

Figure 5 shows a graph of auxiliary power rates of the boiler, steam cycle and carbon dioxide<br />

capture unit as a function of oxygen recovery rate. Figure 6 shows a graph of the auxiliary power<br />

rate of the air separation unit. It should be noted that the auxiliary power rate of the air separation<br />

unit, unlike the other auxiliary power rates, has a negative value in the studied range of oxygen<br />

recovery rate.<br />

Auxiliary power rate, %<br />

12<br />

11<br />

10<br />

9<br />

8<br />

7<br />

6<br />

5<br />

4<br />

Steam cycle<br />

3<br />

40 45 50 55 60 65 70 75 80 85 90 95 100<br />

257<br />

(9)<br />

Oxygen recovery rate, %<br />

Fig.5. The auxiliary power rates of the carbon dioxide capture unit (CCS), boiler and steam cycle<br />

as a function of the oxygen recovery rate

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