1. Introduction - Firenze University Press

Table 2. Comparison of the three CO2 purification and compression options
The most important streams of the process are shown in Table 3. The second method of separation
is more efficient as far as rec is concerned, resulting in higher purity CO2-rich stream. What is
more, in this case, the CO2 content in the recovered gas stream is lower.
Table 3. Outlet streams from PCU for the three purification methods
It should be mentioned that high recovery rates do not mean high efficiency of the total plant. The
way that the recovered combustibles are exploited plays significant role on the choice of the most
suitable technique. To this end, the thermodynamic comparison of the purification options under
investigation is completed by the process integration and the investigation of their effects on total
plant operation.
3.2 Effect of purification methods on total plant operation
Unlike other cryogenic CCS applications, due to the fact that the recovered gas stream has a
considerable amount of chemical energy, it can be fed back to the system for increased energy
efficiency. The proposed alternatives for its utilisation are either to reform or to burn it.
Although returning them to the ATR would decrease fuel consumption, the inert compounds that
are contained in the stream (mainly N2 and Ar) would accumulate in the reactor since there is no
way to escape from the system. Given that there is not an available method to remove them, this
option is abandoned. The alternative choice suggests the injection to the GT combustor. In this case,
the carbon capture rate of the system is less than the capture rate at the PCU due to the produced
CO2 from the combusted CH4 in the GT. Given that the system under investigation is aimed to the
maximization of the final H2 rich fuel and not the maximization of electrical power production, a
different approach concerning the recovered fuel should be adopted.
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