CO2 CAPTURE

CO2 Capture By Fuel Cell involving Hydrogen gas

CO2 Capture By Fuel Cell involving Hydrogen gas

Introduction

Reduction of greenhouse gas emissions is one of the most important challenges that the power industry will face in the next decades. Different strategies may be implemented to comply with this requirement. Improving the conversion efficiency or switching to low carbon content primary feedstock (such as natural gas), may lead to moderate CO2 emission reductions, probably useful to achieve the goals imposed by present international agreements (Kyoto Protocol), but absolutely inappropriate in fulfilling long term objectives of sustainable development ( [IEA, 2008a, p. 4], [IPCC, 2007, p. 7] and [EU Council, 2009, p. 26]). On the contrary carbon capture and storage (CCS) is potentially able to cut by at least an order of magnitude the CO2emissions from fossil fuel fired power plants ( [IEA, 2008b, p. 48] and [DOE, 2007, p. 15]). Wide application of CCS could therefore allow to make power generation from fossil fuel sustainable in terms of greenhouse gas emissions compared to competing technologies such as nuclear and renewables.

Why I am doing this project?

As far as the last category is concerned, virtually the whole research effort will focuses on high temperature cells, and it is primarily pushed by the very high efficiency that can be achieved by fuel cell-based power cycles, potentially maintained after integration with CO2 concentration and separation processes. Solid Oxide Fuel Cells (SOFCs) and Molten Carbonate Fuel Cells (MCFCs) will presents interesting characteristics for the arrangement of low CO2 emissions plant configurations and even if the development stage of these devices is considered not so mature to result in commercial applications within the next decade, a vast technical literature has been devoted to the subject. The examination of such literature as well as the findings of previous works of the authors ( [Araki et al., 2007, p. 12], [Haines et al., 2002, p. 10], [Akai et al., 1997], [Campanari and Chiesa, 2000, p. 165] and [Campanari, 2002, p. 105]), leads to conclude that SOFC-based power cycles take advantage from the strong CO2 concentration induced on the anode side by the oxygen ions transport taking place across the cell electrolyte. Therefore CO2 separation poorly affects conversion efficiency, that may approach 70% in large SOFC hybrid cycles with CO2 removal higher than 90% ( [Campanari and Chiesa, 2000, p. 122] and [Campanari, 2002, p. 108]). The main drawbacks of this solution consist in the unfavorable share of power generation between the plant components: the fuel cell, that is by far the most expensive component in term of specific costs (euro per kW of installed power), provides about 80% of the overall system power, requiring very large networks of FC modules which are very far from present experimentations, while only the remaining 20% comes from the gas cycle. On the other hand, the latter tends to operate at low pressure ratio and turbine inlet temperature, conditions significantly different from the typical design specifications of current commercial gas turbines; even if this situation does not represent any substantial technical ...