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1. Introduction - Firenze University Press

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conversion to elemental sulphur. The H2S-free gas is supplied to the second stage of AGR where it<br />

is brought in contact with a low-temperature lean Selexol solvent for CO2 absorption. The reverse<br />

CO2 desorption process occurs in flash drums operating on 3 different pressure steps. Desorbed<br />

CO2 is compressed and pumped into the transportation pipeline.<br />

The hydrogen-rich (ca 90%) syngas leaving the AGR is diluted by ASU nitrogen and used as a gas<br />

turbine (GT) fuel. An F-class GT has been selected. As already mentioned, the steam turbine<br />

receives steam from both the HRSG and syngas cooling equipment. All compressors within the<br />

ASU and AGR islands have been assumed as electric motor – driven machines. Table 2 summarizes<br />

the assumptions/specifications concerning the input/output for the system.<br />

Waste heat recovery concept involves final flue gas cooler located in the HRSG, syngas cooler in<br />

syngas treating and conditioning line prior to AGR unit, as well as, intercoolers in compression<br />

trains of ASU air, nitrogen and CO2 product. All waste heat recovery exchangers are marked in red<br />

boxes in Fig.<strong>1.</strong><br />

For further transportation, the CO2 stream is compressed to 13 MPa.<br />

Table 2. Assumed parameters for IGCC CHP Plant<br />

Parameter IGCC CHP plant<br />

<strong>Press</strong>ure in the reactor MPa 4,238<br />

Temperature of syngas at scrubber outlet<br />

119<br />

O C 180<br />

Nitrogen to fuel ratio (for fuel transportation), mass basis - 0,175<br />

Steam to fuel ratio, mass basis - 0,005<br />

Oxygen to fuel ratio, mass basis - 0,66<br />

Specific electricity consumption kWh/Mgfuel 67<br />

Syngas treating and conditioning line<br />

CO conversion ratio at 1 st WGSR % 63,6<br />

CO conversion ratio at 2 nd WGSR % 86,2<br />

H2O to CO ratio at 1 st WGSR - 2,34<br />

H2O to CO ratio at 2 nd WGSR - 4<br />

Syngas temperature prior to AGR<br />

Acid gas removal and CO2 compression<br />

O C 35<br />

Effectiveness of H2S removal % 99<br />

Effectiveness of CO2 removal % 90<br />

Process steam consumption kg/s 1,81<br />

CO2 capture miscellaneous auxiliary load kWh/MgCO2 60<br />

Gas turbine<br />

Combustor exit temperature<br />

O C 1300<br />

Compressor pressure ratio - 15,5<br />

Steam cycle<br />

Live (HP) steam temperature<br />

O C 565<br />

Live (HP) steam pressure MPa 12,8<br />

MP steam pressure MPa 3,95

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