Zero Emission Gas Power Technology Qualification for Industrial Scale ZEG Plants

The project focuses on technology development of high efficiency co-production of electricity and hydrogen by the Zero Emission Gas (ZEG) process. ZEG is a promising method for producing hydrogen and electricity from natural gas with CO₂ capture in an efficient and cost-effective way. The process combines sorption enhanced reforming (SE-SMR) and high temperature solid oxide fuel cells (SOFC), two technologies that will be developed in this project.

By utilizing the excess heat from the SOFC for production of hydrogen, the overall efficiency for the process including separation of CO₂ is exceeding 80 %. The main objective for this project is technology qualification of the SOFC stack and CO₂ sorption materials to ensure the technology basis for future industrial scale ZEG plants. This will include testing of new SOFC design and materials at realistic operation condition and long term cycling of state of the art sorption materials.

The SOFC stack was built by using the materials that are best suited for operation at the high temperatures that the SE-SMR requires, membranes with thick electrolytes and ceramic interconnects. The testing of the SOFC stack started beginning of February. The SOFC stack was tested in different operation conditions with variation of temperature, air flow, fuel flow and fuel composition. The overall performance was to some extent limited by some additional contact resistivity between the layers, but it was possible to increase the performance significantly by identifying the best operation conditions. The total operation period in this phase reached 1350 hours. Some degradation was evident, and especially the robustness of the stack materials must be improved before this technology can be used in upscaled processes.

The multiple tests performed during the course of this project have revealed the challenging task that constitutes the integration of two chemical functionalities (CO₂-sorption with CaO and catalyst reforming of methane) in a unique single particle. If the potential of a combined particle is large in term of process efficiency and reduction of operating cost for the development of future SE-SMR technology, the strong chemical interaction between the three chemical phases present in the system: Ni, CaO and mayenite constitute an exciting and difficult challenge for the engineering of this novel material.

Results collected so far have demonstrated the strong influence of the method employed for the impregnation of the solid particles. The interaction between the CaO phase and the aqueous solvent of the metal solution was evidenced. However, control of the pH of the impregnation solution has shown promising results in term of catalyst activity and particle stability. Preliminary test performed in TGA and in fixed bed reactor has shown that it was possible to produce stable “all-in-one” with satisfying performances during cycling in SE-SMR conditions (66 cycles with 85vol% dry H2 during reforming).

So far the goal to produce >95% H2 for 50 cycles has not been achieved yet, but further work will be performed to improve the operating conditions and increase the yield during reforming. New preparation paths are also under investigation to optimize the Nickel dispersion in the particles, to increase the homogeneity of the particles and reduce the deactivation of the metal by sintering.