(630s) Adsorption and Diffusion of CO2, N2 and Water Vapour On 13X Zeolite and Silica Gel

K.Shreenath¹, R Haghpanah², Arvind Rajendran² and S. Farooq¹

¹Department of Chemical and Biomolecular engineering,

National University of Singapore, Singapore -117576

²School of Chemical and Biomedical engineering,

Nanyang Technological University, Singapore-637459

Since the industrial revolution, anthropogenic activities like burning of coal and oil have ultimately led to the present alarming rise of carbon dioxide concentration in the atmosphere. Coal fired power plants using post-combustion technology currently dominate the power industry and is projected to continue unabated for some time. Capture of carbon dioxide from this single major stationary source presents an important technological challenge where the desired indicators are high purity and recovery at minimum energy penalty. In this regards, adsorption technology is emerging as a strong contender among the potential alternatives and is being pursued by several groups.

Flue gas from a coal fired power plant after desulphurisation contains around 10-15 % carbon dioxide, 10% moisture, 5% oxygen, and balance nitrogen. Although it is well known that water has a substantial effect on the adsorption of carbon dioxide in most commercial adsorbents that show significant affinity for the latter, this aspect has been neglected in most studies by assuming that gas entering the capture process is dry. While drying of flue gas prior to carbon dioxide capture is a viable proposition, the two processes are coupled and must be studied together including a good understanding of the consequence of water accidentally breaking through the drying unit. 

In preparation for undertaking a comprehensive study of the coupled drying cum carbon dioxide capture, adsorption and diffusion of carbon dioxide, nitrogen and moisture and their mixture on Zeochem 13X and silica gel are currently being investigated. Gravimetrically measured pure component isotherms are used to carry out detailed modelling of the single component and mixture breakthrough experiments conducted in a laboratory-scale rig fitted with a mass spectrometer for gas analysis. Understanding of thermodynamic interaction of the adsorbed gases and their transport mechanisms in the adsorbent pores revealed by the modelling study will be covered in the presentation.

 Key words: Binary adsorption, VSA, Water vapour, 13X, Silica gel