Before natural gas, biomethane or hydrogen can be fed into the grid or used industrially, the water it contains must be reliably removed. Conventional processes are based on absorption with triethylene glycol (TEG) and subsequent energy-intensive distillation at high temperatures. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS have now developed an alternative solution that does not require chemicals or high heat input.
The new method uses nanoporous ceramic membranes through which water molecules are specifically separated from the gas flow. The gas flows through a ceramic tube whose inner wall is covered with an extremely thin, porous membrane layer. Due to their small size, water molecules can pass through the pores while the gas molecules are retained.
Up to 90 percent less energy required
According to the Fraunhofer IKTS, membrane technology can save up to 90 percent energy compared to conventional processes. As no TEG is used and no residues need to be incinerated, there are also no CO₂ emissions from the drying process. In addition to the significantly improved energy efficiency, the technology also reduces plant costs and avoids unwanted by-products.
The membranes have pore sizes of around 0.4 nanometers with a layer thickness in the micrometer range. Water molecules with a size of around 0.28 nanometers can pass through the membrane, while larger molecules are retained. To ensure selective separation, a completely closed membrane layer is crucial.
Different membranes for different gases
The research team developed two variants of membrane technology: carbon-based membranes for biomethane and zeolite membranes for natural gas and hydrogen. While the zeolite layers consist of crystalline structures based on silicon and aluminum, the carbon membranes are produced by pyrolysis of a polymer precursor at temperatures above 700 degrees Celsius. Both approaches build on Fraunhofer IKTS's many years of expertise in the field of high-performance ceramic membranes.
Scaling up for industrial use
The technology is currently being scaled up for industrial applications. The aim is to provide gas network operators, energy suppliers and plant constructors with an economical alternative to conventional gas drying. The process contributes to low operating costs as well as to the reduction of climate-damaging emissions and thus supports the expansion of renewable energies and a future hydrogen economy.
The research work was funded by the German Federal Environmental Foundation, among others. In addition, the technology has already been tested in other research projects on decentralized hydrogen supply.