Carbon capture boundary conditions

For the ZEPP system presented in Fig. 2.7 the allowable installed costs for the capture plant have been estimated to be in between 80 and 120M for a 1.4GWthermai input natural gas combined cycle (NGCC) plant. To meet the cost targets, an ITM based ZEPP power plant should have an electric efficiency of at least 52%. Capture ratios (carbon captured/carbon fed to the process) of 100% result in plant efficiencies lower than 50%. Capture ratios of the order of 85% are accompanied with plant efficiencies of about 52%. The allowable installed costs window is satisfied when the oxygen flux is at least 20 ml/cm min and the costs of the ITM tubes should be less than 1,500 /m. This clearly sets the targets for materials and turbine development in order for the system to be economically viable within the capture cost boundary conditions. 

Similarly to any separation problem, the definition of the system boundary conditions is an essential prerequisite before simulations are performed. In the case of post-combustion carbon capture, the boundary conditions will correspond to the flue gas composition at the inlet, and the target purity specifications for pipeline transport at the outlet (Figure 2.1). 

Figure 2.1 Schematic representation of the different steps included in the carbon capture and storage chain, showing the inlet and outlet boundary conditions of the capture step.

A general sketch of the inlet-outlet boundary conditions which will be defined for the carbon dioxide capture process, according to the previous analysis, is presented on Figure 2.1. The membrane process simulation framework will be presented in the next paragraph, based on a binary feed mixture in a first step, as explained above. 

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