Resumen de Development of electrocatalytic layers and thermo-fluid dynamic evaluation for high temperature membrane reactors
In this thesis several studies were developed about membranes reactor at high temperature. Two differentiated blocks could be identified: (i) experimental works; (ii) modelling works.
In the experimental block, electrodes based on copper was developed for tubular protonic based cells. The deposition of the copper layer on the tubes was developed by different techniques. Dip-coating method was optimized to a copper-based cermet on the tube. Conditions of the dip-coating procedure has a critical impact in the final performance of the electrochemical cell whose supposes several orders of magnitude in the polarization resistance. It is a sensitive process with the defect of the tube as shows the copper spread over these defects. Additionally, sputtering technique was used to deposit copper layer on the tube. High temperature is required to achieve suitable attachments copper-tube. This high temperature deposited layer present polarization resistances lower than 0.1 ¿·cm2.
In the modelling block, finite element methodology was used to build different models to study different phenomena concerning membrane reactors at high temperature. It was studied: (i) the oxygen permeation across a mixed ionic and electronic conducting membrane; (ii) water electrolysis based on high temperature protonic cells; (iii) hydrogen extraction from a steam methane reforming using a protonic cell; (iv) the intensification of the methane dehydromatization reactor using co-ionic membrane.
Oxygen permeation model was built to evaluate the effect of the dilutive and the sweep contribution over the permeation process. The fitted model allowed the importance of the dilutive and sweep effect over the oxygen permeation. Although the sweep effect present lower influence in the oxygen transport across the membrane, its effect prevents concentration polarization limitations.
Modelling the protonic cell based electrolysis allowed to study the effect of the scale up in this process and to evaluate the efficiency in the energy storing in form of hydrogen.
Modelling protonic membrane reformer allowed checking the thermal microintegration of all the heats which take place in the setup. The electrocompression of hydrogen is an isothermal phenomenon which releases the demanded energy as heat. The model allowed to check the coarsening of the Ni particles does not limit the hydrogen extraction for the studied cell.
A final model was built to study a catalytic membrane reactor for the methane dehydroaromatization using co-ionic conducting cells. The model was validated using experimental data. Additionally, different studies were performed to analyze possible limitation in the process. Results show that there are no hydrogen diffusion limitations in this process. Additionally, the shift of the equilibrium by extracting hydrogen has to be stopped because kinetic limitations.
