Acrylic Desublimating Heat Exchanger

A critical component of Cryogenic Carbon Capture

This heat exchanger was part of a project funded by ARPA-E, a new part of the United States Department of Energy. ARPA-E funds higher risk projects with high potential early in development. This heat exchanger satisfied the deliverable to capture over 90% of the CO2 from synthetic flue gas for a minimum of 3 hours without fouling. We are proud to declare that we completed this milestone on the first trial run! This heat exchanger was filled with challenges, most of which arose from the need to make it transparent. In order to capture 90% of the CO2 in the Cryogenic Carbon Capture process, the gas stream must be cooled to below -190 Farenheight (-123 C). All materials contract when cooled this much, but polymers contract much more than metals. For this reason, I chose to spring-load the nylon flanges and double-walled acrylic shell to prevent leaks when the parts shrunk.

Design Drawings

The full assembly drawing with cut-away view.
The full assembly drawing with cut-away view.
Insulation was provided by pulling a vacuum between the two acrylic tubes. This stainless steel plug both sealed the tubes and provided the connection to the vacuum pump.
The full acrylic tube assembly. There are two concentric acrylic tubes which allow for a vacuum to be pulled between them for insulation.

Completed Project

Preparing for carbon capture: The contact liquid is being cooled and recirculated through the system to get down to the operating temperature of -190 F.
The desublimator captured 95% of the CO2 in the gas stream.
The sparger flange compression springs which keep the nylon and PTFE gaskets under compression during the contraction that occurs from the extremely cold operating temperature.
During construction.
Stephanie, Eric, and I monitoring the carbon capture performance during the first test run.
A very basic prototype of a desublimator used to test the dynamics of the gas distribution plates. (blue LED for effect)