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1. Introduction - Firenze University Press

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Abstract:<br />

PROCEEDINGS OF ECOS 2012 - THE 25 TH INTERNATIONAL CONFERENCE ON<br />

EFFICIENCY, COST, OPTIMIZATION, SIMULATION AND ENVIRONMENTAL IMPACT OF ENERGY SYSTEMS<br />

JUNE 26-29, 2012, PERUGIA, ITALY<br />

Comparison of IGCC and CFB cogeneration<br />

plants equipped with CO2 removal<br />

Marcin Liszka a , Tomasz Malik b , Micha Budnik c , Andrzej Zibik d<br />

a Institute of Thermal Technology, Silesian <strong>University</strong> of Technology, 44-100 Gliwice, Konarskiego 22,<br />

Poland, marcin.liszka@polsl.pl,<br />

b Institute of Thermal Technology, Silesian <strong>University</strong> of Technology, 44-100 Gliwice, Konarskiego 22,<br />

Poland, tomasz.malik@polsl.pl, CA<br />

c Institute of Thermal Technology, Silesian <strong>University</strong> of Technology, 44-100 Gliwice, Konarskiego 22,<br />

Poland, michal.budnik@polsl.pl,<br />

d Institute of Thermal Technology, Silesian <strong>University</strong> of Technology, 44-100 Gliwice, Konarskiego 22,<br />

Poland, andrzej.ziebik@polsl.pl<br />

The introduction of CO2 removal processes into coal-fired power units causes usually generation of waste<br />

heat which is not possible to utilize within steam cycle. Normally, the waste heat is rejected to cooling water<br />

and then to the environment. As the temperature of waste heat carriers is usually moderately high (ca. 80 -<br />

100C), there is a potential possibility for using them in district heating systems. The main goal of the present<br />

paper is thus the energy and CO2 emission analysis of large-scale CHP plants equipped with CO2 removal<br />

and utilizing waste heat generated within the plant. Two case studies have been formulated. First of them is<br />

dealing with the CFB plant equipped with a tap-backpressure steam turbine and post-combustion chemical<br />

CO2 absorption. The steam necessary for CO2 solvent (MEA) regeneration is taken from the steam turbine<br />

exhaust, while district heat is produced mainly in CO2 dehumidifier and CO2 compression train. The second<br />

case is dealing with an IGCC equipped with the pre-combustion CO2 removal by physical absorption. The<br />

district heat is then produced using classical final flue gas cooler located in HRSG, syngas cooler, as well as,<br />

compression trains of ASU air, nitrogen and CO2 product. For both analyzed cases, the peak-load district<br />

heat production using steam turbine extraction is also possible. Both CFB and IGCC plants have been<br />

modelled on the Thermoflex software. The reference, CFB-based CHP plant without CO2 removal has also<br />

been modelled. The district heat production and district water parameters have been fixed for all analyzed<br />

cases to the same values. The energy utilization factor, exergy efficiency and electricity-to-heat ratio have<br />

been calculated for both plants as main assessment factors. The methodology of alternative electricity<br />

production (equivalent power unit) has been involved for calculation of CO2 emissions. The obtained results<br />

indicates, that IGCC plant has better thermodynamic indicators than CFB-based unit. Moreover, the CO2<br />

emission considering system interconnections within the electricity production network is negative for both<br />

the CFB and IGCC plants equipped with CCS. When comparing exergy efficiency, the highest value is<br />

achieved for the reference CFB plant (without CO2 capture). The decrease of exergy efficiency caused by<br />

CO2 capture and compression is ca. 8 percentage points, but in case of IGCC CHP plant the exergy<br />

efficiency plant is only 3 points lower than for the reference system.<br />

Keywords:<br />

IGCC, CFB, CHP, CCS, waste heat<br />

<strong>1.</strong> <strong>Introduction</strong><br />

The CO2 removal processes integrated with coal-fired power units cause significant drop of energy<br />

efficiency and economic profitability of the overall power generation process. The decrease of<br />

power generation efficiency is externalized usually by increased amount of waste heat rejected to<br />

the environment. The waste heat coming from the CO2 removal and compression installations is<br />

often of moderate temperature (ca. 80-100C), and therefore its utilization within the power cycle or<br />

for external purposes could be possible. On the other hand, the decrease of CO2 emission without<br />

its removal is also possible. The combined heat and power production (CHP) is a good example<br />

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