1. Introduction - Firenze University Press

Table 4. Assumed lignite parameters (as received, mass shares)
Total moisture % 45,00
Ash % 20,00
Carbon % 23,80
Hydrogen % 2,17
Nitrogen % 0,25
Sulphur % 0,70
Oxygen % 8,08
LHV kJ/kg 8340
4. Results
The energy efficiency calculated for a whole oxy-fuel power unit has been selected as a main
assessment factor of the proposed improvements. Calculated efficiencies have been presented
in Fig. 4. Moreover, the more detailed results of simulation have been collected in Table 6.
Temperature profiles for waste heat utilizing units have been shown in Figs 5 and 6.
Table 5. Lignite parameters after drying (mass shares)
Total moisture % 41,05
Ash % 21,44
Carbon % 25,51
Hydrogen % 2,321
Nitrogen % 0,268
Sulphur % 0,750
Oxygen % 8,661
LHV kJ/kg 9116
Table 6. Results of simulation
Case 1
Case 5
Parameter Unit (reference) Case 2 Case 3 Case 4 (cumulative)
Live steam flow rate kg/s 620 620 620 620 620
Chemical energy flow rate (LHV 1875,9 1856,2 1875,9 1816,5 1798,6
based) MW
Generator terminal power MW 842,5 842,5 879,7 842,5 872,7
Net power output MW 554,3 558,8 590,2 560,7 593,2
Auxiliary power consumption
including:
MW 288,2 283,8 289,5 281,8 279,5
- ASU MW 130,7 129,3 130,7 127,3 125,7
- CO2 compression and
86,1 87,6 88,6 86,3 85,2
purification line MW
- steam cycle MW 6,0 6,0 6,9 6,0 6,8
- others MW 65,6 60,8 63,3 62,2 61,8
Total waste heat recovered MW 0,0 40,2 187,5 30,4 240,3
Net plant efficiency % 29,55 30,10 31,46 30,87 32,98
50