Novel 3D-printed device enhances carbon dioxide capture

ORNL scientists have designed and additively manufactured a first-of-its-kind aluminum device that enhances the capture of carbon dioxide emitted from fossil fuel plants and other industrial processes.

ORNL’s device focuses on a key challenge in conventional absorption of carbon using solvents: the process typically produces heat that can limit its overall efficiency. By using additive manufacturing, researchers were able to custom-design a multifunctional device that greatly improves the process efficiency by removing excess heat while keeping costs low.

Absorption, one of the most commonly used and economical methods for capturing CO₂, places a flue-gas stream from smokestacks in contact with a solvent such as monoethanolamine, known as MEA, or other amine solutions that can react with the gas.

The research team tested the novel circular device, which integrates a heat exchanger with a mass-exchanging contactor inside an absorption column consisting of seven commercial stainless-steel packing elements. The 3D-printed intensified device was installed in the top half of the column, between the packing elements.

Additive manufacturing made it possible to have a heat exchanger within the column as part of the packing elements without disturbing the geometry, maximizing 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,” said Costas Tsouris, one of ORNL’s lead researchers on the project. “Controlling the temperature of absorption is critical to capturing carbon dioxide.”

When CO₂ interacts with the solvent, it produces heat that can diminish the capability of the solvent to react. Reducing this localized temperature spike in the column through cooling channels helps increase the efficiency of CO₂ capture.

“Prior to the design of our 3D-printed device, it was difficult to implement a heat exchanger concept into the absorption column because of the complex geometry of the column’s packing elements. With 3D printing, the mass exchanger and heat exchanger can co-exist within a single multifunctional, intensified device,” said ORNL’s Xin Sun, the project’s principal investigator.

Embedded coolant channels were added inside the packing element’s corrugated sheets to allow for heat exchange. The final prototype measured 20.3 centimeters in diameter and 14.6 centimeters in height, with a total fluid volume capacity of 0.6 liters. Aluminum was chosen as the initial material for the intensified device because of its excellent printability, high thermal conductivity and structural strength.

The prototype demonstrated that it was capable of substantially enhancing CO₂ capture with the amine solution, which was chosen because it is highly reactive to CO_2. ORNL researchers conducted two separate experiments: one that varied the CO₂-containing gas flow rate and one that varied the MEA solvent flow rate. The experiments aimed to determine which operating conditions would produce the greatest carbon capture efficiency.

Both experiments produced substantial improvements in the carbon capture rate and demonstrated that the magnitude of the capture consistently depended on the gas flow rates. The study also showed a peak in capture at 20 percent of CO₂ concentration, with the capture rates increasing from 2.2 percent to 15.5 percent depending on the operating conditions.

“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 said.