In view of the climate policy challenges ahead, using regenerative carbon sources to produce renewable energy carriers will play an important role in efforts to reduce greenhouse gas emissions. P2X technology is a key component in this context – it provides the means of converting and, if necessary, storing renewable (surplus) electricity into C-based raw materials for industry, renewable fuels and combustibles. Replacing fossil energy sources with renewables will leave countries less exposed to geopolitical dependencies.
There are several categories of P2X processes distinguished by the physical state of the product:
The technology that links all three conversion paths is electricity-to-hydrogen electrolysis. Hydrogen can be converted into a C-based material or energy carrier by adding a carbon carrier (e.g. carbon dioxide). This takes place in a process downstream from hydrogen production known as synthesis and involves various catalysts, operating conditions and process controls.
ZSW draws on many years’ experience with synthesis in power-to-gas and power-to-liquid technologies. This expertise enables us to serve as a contact, partner and technology supplier. We have thoroughly investigated methanol and methane synthesis, especially, and have developed processes to ensure high product yields.
Methane synthesis, the process by which carbon oxides are converted into methane using hydrogen, has been a research priority at ZSW for close to 20 years. We have amassed a trove of knowledge over the years encompassing everything from the first step of selectively methanating carbon monoxide to produce a fuel gas suitable for fuel cells to synthesizing the P2X technology’s stoichiometrically adjusted gas mixtures to produce a natural gas substitute. This expertise is needed to make the adjustments required by varying applications and gas composition. To this end, we adapt the operating conditions and process control to suit methane synthesis, a highly exothermic process, and select suitable catalysts. Cooled fixed-bed reactors are our preferred choice of medium for methane synthesis processes.
Various test facilities are available to investigate heterogeneous catalysts and develop reactors and even entire process chains. These assets enable us to conduct both fundamental research and engage in application-oriented development.
Extracting renewable energy from regenerative carbon sources is part of a larger process chain that usually involves treating raw gases or conditioning product streams. Impurities can trigger deactivation mechanisms, which is why minor components such as sulfur compounds are removed from raw gases to prevent problems in downstream catalytic processes. ZSW uses mainly sorbents and catalytic processes to eliminate minor components.
Membrane gas separation technology conditions gas flows to modify gas quality to the given specifications. It uses the different mass transfer rates (permeation rates) of individual gas components traveling through a membrane as a filtering mechanism. Membrane-based technology requires a lot less process engineering effort than other gas conditioning processes, and its modular design quickly adapts to changing operating conditions and a wide load range. Equipped with a suitable membrane, this technology can serve other separation purposes and also lends itself to smaller plants.
ZSW has various experimental facilities at its disposal to investigate individual gas generation, conditioning and purification steps, and to characterize materials such as sorbents and catalysts. We use temperature-controlled micro and macro reactors with downstream gas analysis systems as well as thermogravimetric analysis (TGA) to determine the relevant parameters. TGA involves measuring a sample’s change in mass as a function of temperature and time to track conversion in gas-solid reactions. The influence of individual parameters such as temperature, pressure and gas composition can be determined by varying the conditions in which the reaction takes place.
ZSW has two test facilities for characterizing materials via thermogravimetric analysis: