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1. Introduction - Firenze University Press

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In the area of coal technologies all of these solutions can be used. However, the first solution is<br />

predisposed for IGCC systems [3], in which there is the possibility of generating carbon dioxide<br />

before combustion of synthesis gas. The fuel before entering the combustion chamber is subjected<br />

to a carbon sequestration. Due to the lower gas stream from which the carbon dioxide is removed<br />

such a separation process is connected with less energy consumption. The next technology is based<br />

on removing carbon dioxide from flue gases leaving the power system. The post-combustion<br />

technology is predisposed for the conventional coal-fired power plants. In the area of postcombustion<br />

technology, as in the case of pre-combustion, the research on absorption and adsorption<br />

techniques, as well as membrane and cryogenic separation are realized [4÷5]. Among of clean coal<br />

technology large hopes are associated with oxy-combustion technology, of which the principal<br />

purpose is combustion of coal in the oxygen-rich atmosphere in order to eliminate from the exhaust<br />

gases the inert gas (nitrogen). In this case the exhaust gases leaving the steam boiler consists mainly<br />

of carbon dioxide and steam, so the carbon capture process is much less energy intensive. Currently<br />

in the research area of oxy-combustion technology, the solutions aiming for decreasing the energy<br />

consumption connected with oxygen production in the air separation unit are searched for [6÷10].<br />

The results presented in the paper were realized within the framework of the Strategic Project<br />

”Advanced Technologies for Energy Generation: Oxy-combustion technology for PC and FBC<br />

boilers with CO2 capture”. In the paper the results of the analysis of the steam cycles of energy<br />

generation units are shown. These steam cycles will be the basis for creation of the models of the<br />

whole oxy-combustion power plants. In the paper the results of analysis including the influence of<br />

different solutions of steam cycles, and thus their assumed parameters, on the energy effectiveness<br />

evaluation indicators are shown.<br />

2. Model of the air separation unit integrated with the oxy type<br />

pulverized boiler and assumptions for calculations<br />

Air separation unit structure consists of: a counter-current air heater (APH), an air compressor (C),<br />

an expander (EX), a generator (G) and a "four end" type membrane (M). The expander drives the<br />

air compressor. Depending on the assumed quantities the expander and compressor can give or take<br />

electricity from the grid. The structure of the air separation unit is shown in Figure <strong>1.</strong><br />

Fig. <strong>1.</strong> Scheme of the air separation unit (ASU)<br />

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