A team from the Oak Ridge National Laboratory has invented a 3D printed absorption device made from aluminum that is capable of capturing carbon dioxide emissions from fossil fuel plants. The innovative device, which can also be used in other industrial processes, could help to curb global emissions of greenhouses gases like CO2 which trap heat in the atmosphere and contribute to global warming.
The 3D printed device consists of a heat exchanger with a mass-exchanging contactor and integrates internal coolant channels to improve heat exchange. A final prototype of the device measures 20.3 centimeters in diameter and 14.6 centimeters in height and has a total fluid volume capacity of 0.6 liters. The piece was printed from aluminum because of the material’s high thermal conductivity, structural strength and printability, though other materials could also be used.
The CO2 trapping device was tested inside of an absorption column measuring one meter in height and eight inches in width. The 3D printed intensified part was placed in the top half of the column between some of the structure’s seven packing elements. 3D printing was crucial in creating a part that could fit inside the column, conforming to the geometries of the packing elements and optimizing the contact surface area between the gas and liquid streams.
“We call the device intensified because it enables enhanced mass transfer (the amount of CO2 transferred from a gas to a liquid state) through in-situ cooling,” explained Costas Tsouris, one of the project’s lead researchers at ORNL. “Controlling the temperature of absorption is critical to capturing carbon dioxide.”
In the research project, the ORNL team set out to address a specific problem with conventional absorption processes for CO2 which use solvents. Typically, these processes create heat when the gas reacts with the solvent, which can inhibit the entire process’ efficiency. By leveraging 3D printing, the researchers were able to design a custom device that could essentially reduce the temperature increase caused by the solvent reaction in the column by using coolant channels.
“Prior to the design of our 3D printed device, it was difficult to implement a heat exchanger concept into the CO2 absorption column because of the complex geometry of the column’s packing elements,” said Xin Sun, the project’s principal investigator. “With 3D printing, the mass exchanger and heat exchanger can co-exist within a single multifunctional, intensified device.”
Lonnie Love, the lead manufacturing researcher at ORNL who designed the device, added: “The device can also be manufactured using other materials, such as emerging high thermal conductivity polymers and metals. Additive manufacturing methods like 3D printing are often cost-effective over time because it takes less effort and energy to print a part versus traditional manufacturing methods.”
In tests, the 3D printed device performed well inside the column: it enhanced the system’s ability to capture carbon dioxide using an amine solution. The research team actually conducted two types of test to find which operating conditions would have the best results: in one, they varied the CO2 containing gas flow rate and in the other they varied the solvent flow rate. In the end, both approaches demonstrated improvements compared to conventional absorption, however the results were linked to the gas flow rates.
“The success of this 3D printed intensified device represents an unprecedented opportunity in further enhancing carbon dioxide absorption efficiency and demonstrates proof of concept,” Sun concluded. Going forward, the ORNL team will seek to optimize the operating conditions and the device’s geometry for even better carbon absorption. The groundbreaking research was recently published in the AIChE Journal.