A drastic reduction of greenhouse gas emissions can only be achieved if CO2 capture will be introduced to fossil fueled power plants. Since CO2 capture lowers the efficiency of the overall power cycle tremendously, technologies have to be developed which reduce the loss in efficiency as much as possible. Due to the resources of fossil fuels, coal will still play an important role in future power generation processes. Especially, the emerging and developing countries such as India and China are already using an enormous amount of coal for power production. In this work, an IGCC process with an integrated H2-selective membrane has been investigated to substitute the CO2 capture unit by such a membrane reactor. Hydrogen-selective membranes have been studied intensively in combination with power generation processes [22, 23]. Palladium has been considered as membrane material in the present study. Due to its catalytic surface, high hydrogen permeability, and infinite hydrogen selectivity palladium and Pd-based alloys show a high potential for hydrogen separation [24, 25, 26]. The investigation has shown that the advantage of the H2-selective membrane reactor, it uses nitrogen as sweep gas on the permeate side of the membrane reactor, cannot defeat the existing drawbacks of the process layout: small mass flow rate through the gas turbine (and consequently through the HRSG) and higher energy requirements for oxygen production and CO2 compression, respectively. The net efficiency of the investigated IGCC process with integrated hydrogen-selective membrane reactor and capture of CO2 is compared with other IGCC concepts — with and without CO2 capture. The net efficiency of the overall process is 34.30%, which is about 3%-points lower compared to an IGCC process with chemical absorption and cryogenic ASU. Moreover, in comparison with an IGCC process with integrated OTM reactor and CO2 capture the efficiency is 1.7 percentage points lower than that of the process option with the lowest efficiency. Although no cost evaluation has been carried out, it can be assumed that hydrogen-selective membrane reactor would increase the capital cost of the overall IGCC process. The results indicate that the IGCC process with integrated hydrogen-selective membrane reactor and CO2 capture is less attractive from the thermodynamic point of view but also from a thermo-economic point of view.
The effect of the catalytic layer composition on the hydrogen permeability of assymetric tantalum-based membranes
