Martini, Michela (PhD)
New CO2 capture process for pure hydrogen production combining Ca and Cu chemical loops
M. Martini, F. Gallucci, M. van Sint Annaland
Room: STW 0.35, E-mail: M.Martini@tue.nl
The increase of greenhouse effects as a result of the anthropogenic emissions is the main cause of the climate change, being CO2 the major responsible gas. Carbon Capture and Storage (CCS) is an interesting technology which involves CO2 capture following by storage underground. Moreover, H2 is considered a promising energy carrier in future energy systems. In this project, a novel process is proposed to provide hydrogen production with integrated pure CO2 capture. In this process, the high temperature CO2 capture during the production of hydrogen fuel by means of the steam-methane reforming using Ca-Cu looping cycle is carried out. The heat needed to drive the endothermic steam-methane reforming reaction is matched with in-situ heat production from the calcium carbonate formation reaction. At the same time, the heat required to regenerate a calcium carbonate material is matched with in situ heat production through the reduction of CuO to Cu metal. The process is carried out in a packed bed reactor and, as we can see in the figure, is divided into 3 steps:
a) the production of hydrogen-rich stream by the sorption enhanced reforming (SER) of CH4 with steam and simultaneous carbonation of CaO with the CO2 resulting from the reforming reaction;
b) the oxidation of Cu to CuO with air, in conditions such that no major decomposition of CaCO3 takes place;
c) the calcination of CaO3 and the reduction of CuO with a fuel gas in order to obtain most or all of the heat necessary for calcination.
In this project, experimental work is carried out to identify and quantify the relationship between particle characteristics of the oxygen carriers, CO2 sorbents and reforming catalysts and their reaction rates during the different stages of the process. The results of this experimental campaign will be used to determine apparent reaction rates and also to develop a detailed particle model which will be integrated into a reactor model for dynamically operated packed bed. The behavior of the reactions in the different steps at different pressures and temperatures, the right Ca/Cu ratio and the composition of the feeds have to be studied. The proof of concept will be done and the experimental results will be used to validate the combined reactor/particle model for the Ca-Cu looping process.
First of all literature study on Ca/Cu looping process, oxygen carriers, CO2 sorbents, kinetic models was done. Then energy and mass balance of the Ca/Cu looping process using the sharp front approach was used to obtain preliminary values of the temperatures of the gas streams, the maximum temperature reached in the bed and the heat- and reaction-front velocities. Work on the 1-D model for packed bed reactors was done to adapt it for this process in order to describe more in detail the process. Experimental work was done on the oxygen carrier (CuO) and CO2 sorbent (CaO) in order to find the kinetics of the reactions that occus in the process. From preliminary experiment on the CuO-based solid, it was seen that oxygen uncoupling was occurring. The material was studied in the TGA with different concentration of O2 during the reduction time in order to describe the behaviour. In the figure below some results.
Figure: Conversion of CuO under different concentration of O2 during the reduction time at 870°C.