Advancing Ceramic Membrane Technology for Carbon Capture
This project was funded through Round 1: Open Call in 2011 and aimed to develop a hydrogen-selective ceramic membrane for carbon capture and hydrogen separation. The project wrapped up earlier than anticipated, in 2012, due to challenges in scaling up defect-free membranes and a lack of economic benefit for hydrogen production via natural gas reformation at that time. The investment climate for this technology may have changed since.
In traditional amine-based carbon capture, the gas stream is first cooled to approximately 200 degrees Celsius and then dissolved in a chemical solvent. The solvent is regenerated and reused upon heating. This method of carbon capture is expensive, as the solvent used is toxic, corrosive, and reduces the overall plant efficiency. Membrane technologies could reduce the cost of capture by decreasing both the required capital investment and the energy loads needed to produce sequestration-grade carbon. Because ceramic membranes operate at high temperatures, the hydrogen-carbon separation process is less energy-intensive than the traditional capture process because the system does not need to be cooled and re-heated.
When applied to pre-combustion capture, membranes can be permeable to either hydrogen or carbon, with the details of the system configuration dependent on which gas permeates the membrane. The membrane materials investigated in this project are naturally occurring zeolites which are sedimentary rocks that are formed when volcanic rocks and ash reacts with alkaline ground water and are naturally compressed under extremely high geological pressures. Zeolites have well-defined cage structures (molecular sieve) that are small enough to allow hydrogen to pass, but not carbon making them an option for hydrogen-carbon separation.
Previous efforts to develop hydrogen-selective membranes for pre-combustion capture have been limited by two key technology gaps: performance and scalability. The performance gap stems from existing materials’ inability to simultaneously achieve the required selectivity, permeance, and stability under realistic operating conditions. The scalability gap exists because the methods for fabricating defect-free membranes at large scale were too expensive to be commercially attractive.
Testing Novel Methods to Repair Cracks
While the General Electric Company was initially optimistic about its potential, the project ended up facing similar challenges as previous attempts to develop hydrogen-selective membrane. Zeolite membranes showed promise, but their manufacturability at scale remained a major hurdle. The team struggled to fabricate defect-free membrane tubes, with issues such as microcracks. Several repair techniques were explored including chemical vapor infiltration and chemical and hydrothermal healing. Chemical vapor infiltration involves an organic liquid, called tetraethyl orthosilicate, and water, which flowed from opposite ends of the damaged tube. When heated, these chemicals reacted on the surface of the coating to form silica, which filled in the defects. Chemical and hydrothermal healing involves injecting a chemical gel into the cracked membrane tube and then heating it under high pressure and temperature. This process turned the gel into zeolite, which filled and repaired the cracks. While these methods repaired some of the issues, other defects like long term degradation were not resolved.
What’s next? While this project ended early, it provided valuable insights into the ceramic technology for carbon capture, such as methods to repair some defects that may occur. Since the project’s completion, there have been significant advancements in ceramic membrane technology, although it is not yet commercially deployed. Factors such as a high production cost and design optimization are still being explored and resolved. The climate for carbon capture and hydrogen have both changed and been largely de-risked, partly due to rising price on carbon as well as global demand for low carbon products. A significant example is Air Products autothermal hydrogen production facility with carbon capture and storage also supported by ERA, which may catalyze additional investments in this sector.