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Thursday, December 18, 2014

#200 - Nova Analyzers from the Field - Episode 9 (Studies of CO2 Absorption / Desorption by Amine Solutions)

We were recently sent a published paper containing a brief mention of a Nova analyzer. The paper itself is about the kinetics of CO2 absorption in various aqueous amine solutions. We have periodically addressed this type of application over the years. As carbon dioxide (CO2) becomes more prominently connected with concerns about greenhouse gases, we expect to see more of it in the future also.

From the Introduction of the paper: 
“The separation of acid gas impurities such as carbon dioxide (CO2) and hydrogen sulfide (H2S) from gas mixtures is an important operation in natural gas processing, petroleum refining, coal gasification and ammonia manufacturing industries. Since CO2 is widely regarded as a major greenhouse gas, potentially contributing to global warming, recently, there has also been considerable interest in developing technologies for capturing and sequestering large quantities of CO2 produced from industrial sources such as fossil-fuel electric power generation facilities. Various technologies have been developed for CO2 and H2S removal from gas streams. These include absorption by chemical and physical solvents, cryogenic separation and membrane separation. Among these methods, gas absorption by chemical solvents such as aqueous solutions of alkanolamines is one of the most popular and effective methods.”

Even though this area of study has been active and applied in industry for over 50years, the authors note that complete investigations with mathematical models for absorption and desorption have been lacking. The authors then present a more unified approach in an effort to allow more standardized evaluations of this application across different reactions.

In this study, a novel design of laboratory contactor apparatus was used for interfacial contact between the amine and CO2. This apparatus allows for accurate and easier evaluation of physical mass transfer between the reactants. A diagram of the apparatus as presented in the paper is shown below.

The complete experimental setup from the paper is shown below:

After the dryer and just prior to the fume hood, the CO2 analyzer is shown in the above setup diagram. In this particular study the authors cite the Nova Model 300 infrared analyzer. In our experience, we have supplied a couple of different instruments for this type of application.
-          Model 302A – CO2 analysis by infrared detector
-          Model 336BT – CO2 analysis by thermal-conductivity (not shown in on-line catalog)

In one application in 2013, we supplied multiple units of Model 336BT in two ranges:
-          0-25.0 % CO2 in Air
-          0-100.0 % CO2 in Air

This application was for a large educational training assembly that involved the same absorption reactions between amine & CO2 mentioned above. The different instrument ranges corresponded to different points in the process before & after CO2 absorption. Purchasing separate instruments allowed simultaneous measurement of each point over a specific period of time.

In most cases, these studies are performed using portable instruments that provide accurate analysis on a temporary / intermittent basis. A wall-mounted version of this instrumentation can also be produced. For study apparatuses that are large enough to be permanently installed, a wall-mount analyzer in its own steel cabinet may be desired.

The study mentioned above is actually described in a two part paper as follows:

Part 1
Kinetics of carbon dioxide absorption and desorption in aqueous
alkanolamine solutions using a novel hemispherical contactor—I:
Experimental apparatus and mathematical modeling.

Part 2
Kinetics of carbon dioxide absorption and desorption in aqueous alkanolamine solutions using a novel hemispherical contactor—II: Experimental results and parameter estimation

Aqil Jamal
Axel Meisen
C. Jim Lim
Department of Chemical and Biological Engineering,
The University of British Columbia
Vancouver, BC Canada V6T 1Z3

For information on these and other gas analyzer systems, give Mike or Dave at Nova a call, or send us an e-mail.
sales at nova-gas dot com
websales at nova-gas dot com

Hey, this is Post #200 in our blog. Still haven’t run out of things to say!

Author: Aqil Jamal, Axel Meisen and C. Jim Lim
Publication: Chemical Engineering Science
Publisher: Elsevier
Date: October 2006
Copyright © 2006 Elsevier Ltd.
All rights reserved.
* Experiment diagrams and information property of authors


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