Climate change is commonly regarded as one of the biggest problems for humanity to be solved in the 21st century. Every year, the world’s leaders meet at the UN Climate Change Conference to tackle this global problem. Equally, scientists warn that the progress is too slow for stopping the temperature rise above the critical value of 1.5-2.0°C. Even in a fully sustainable energy industry, some processes will require burning fossil fuels. As such, technologies enabling a negative CO2 footprint will become a cornerstone of a circular economy. The question arises: Can we capture the emitted carbon dioxide in some way? Well, the simple answer is yes! But it comes with challenges.
The idea already dates back to the 1970s. CO2 contained in a gas can be adsorbed to different materials and solutions which can be stored underground afterward or further use in different industrial processes. In general, there are two strategies to be distinguished: Carbon Capture and Storage (CCS) as well as Direct Air Capture (DAC). CCS aims at capturing emissions right at the source of emission, i.e., in fossil fuel power plants. A CO2 washer filters about 90% of the CO2 in the exhaust gas, and the current prime solution is to pump it then into geological formations about 1km below the ground to store the CO2. Newer developments are aiming at further processing the CO2 either by making it available to industries that require CO2 in their production processes or further splitting the CO2 in carbon and oxygen, with focus on creating high value carbon products like graphene, carbon black or other carbon products in high demand.
Why don’t we do it right now if it is that simple? Besides the costs and energy losses due to the filtering, opponents of the technology argue, that it will slow down the installation of real renewable energies by keeping fossil-fueled power plants longer alive.
Direct Air Capture takes a different approach. It aims at reducing the carbon dioxide levels of the ambient air, i.e., it captures CO2 emissions that have already been released. The general idea is the same as above. Ambient air is passed through special adsorption filters to capture and remove the CO2. The challenge is that the ambient air contains about 1000 times less carbon dioxide than the exhaust of a fossil fuel power plant. This means that much more air needs to be fed through the filter to be able to capture the same amount of CO2 as in CCS. When fully loaded, the system needs to be closed to allow for the regeneration of the filters and removal of the CO2. This calls for the installation of very large-sized vacuum systems and their supporting periphery.
VAT provides the largest vacuum isolation doors
VAT has a long-standing tradition of supplying unconventional vacuum systems for special applications. The young DAC industry noticed and relied on the valuable know-how of VAT right from the start. “The challenge in large vacuum systems is always the valves”, explains Theresa Thang, business development manager at VAT. “Requirements are comparable to the door of your house. On the one hand, you want it to be big enough to even get your next big couch in, comfortably. On the other hand, you also want to keep out any sneaky burglars. And still, it should not be too heavy that your children can still open it. Our DAC customers face the same challenge.” The isolation doors should be as large as possible to get in high airflows during normal operation. They should be easy to open and close with a minimum energy consumption. During the thermal regeneration of the adsorption filters, the isolation doors are closed to seal the filter system, ensuring that the CO2 is not released back into the atmosphere. To provide an optimal sealing the sealing surface should be as small as possible and the pressure difference relatively high creating a substantial pressure load on the door.
One of VAT’s unique solutions to overcome these challenges is the 06.6 large transfer valve / door series. It was originally designed as a slot valve for the semiconductor industry to allow the transfer of thin large-screen TV displays from one production step to the other. With the new requirements from the DAC industry to get as much air volume as possible through the door, VAT has now extended its diameter from 3m to 8m as well as its opening height. The more wide than high shape of the opening was maintained compared to e.g. a fully round or square opening because closing and opening time, energy consumption as well as total foot print (incl. actuation) are lower with this design. “Our engineers needed to put in all their experience and know-how to make this possible. The change is not only mechanical but comes along with significant challenges regarding the weight and reliable closure along the whole circumference of the valve gate.”, remembers Theresa Thang. “But our engineers have a lot of experience in finding the optimum solution for the specialized use cases.”
VAT acting as a technology enabler
The DAC technology is still in its infancy, and so far, no real alternative to the direct reduction of carbon emissions. But it is an investment into the future. VAT has always worked with technology partners ahead of their time on vacuum isolation and control challenges. This undermines VAT’s claim to maintain its position as technology leader in the field of vacuum valve and systems solutions. “Our current developments aiming at improved energy-efficiency in valve actuation. We want to move technology ahead, and as such, we are proud to be an integral part of this young and dynamic DAC industry paving the ground to reverse CO2 emissions in the future.”, states Theresa Thang.