Kinetic Studies of Carbon Dioxide Capture By Potassium Carbonate Supported on Activated Carbon Using a Fluidized Bed Reactor

CO2 is a major anthropogenic gas contributing to global warming. The growing concerns for climate change have encouraged research activities towards developing more-efficient processes for CO2 capture. Some of the excellent adsorbents like zeolites, carbon nanotube-based solid sorbents and carbon molecular sieves have been suggested for adsorption of CO2 in a dry gas stream. However, presence of moisture content creates a deteriorating effect on these sorbents [1].

CO2 can be chemically adsorbed on dry regenerable alkali-metal carbonate-based sorbents (M2CO3, where M = K, Na, Li) by the reaction: . This shows that this class of sorbents have an inherent advantage as moisture is a necessity for this reaction. It is seen that K2CO3 gives the best performance and has a wide range of carbonation temperature where the sorbent efficiency is almost 100% [2].

In the present work, Activated Carbon (AC) is chosen as a support for potassium carbonate, due to its highly porous structure and high surface area. A 30 wt % of K2CO3 is coated on AC by wet impregnation method [3]. This sorbent is then characterized by XRD, EDX, SEM and BET Surface area.

Kinetic studies are done in a fluidized bed column heated in a furnace, using a mixture of air or N2 and CO2, humidified to desired moisture content as the fluidizing medium. The reaction is followed by measuring the concentration of CO2 in the exit gas as a function of time. The effect of various parameters such as flow rate of gas, composition of gas, height of the bed and temperature on the conversion of K2CO3 is studied. The reaction is carried out in the temperature range of 60-90^oC. The composition of both CO2 and water vapor is varied between 5-20% with gas velocities ranging from 1-3 times of minimum fluidization velocity.

References:

1.      Samanta, A., A. Zhao, G.K.H. Shimizu, P. Sarkar and R. Gupta, ?Post-Combustion CO2 Capture Using Solid Sorbents: A Review?, Ind. Eng. Chem. Res., 51, 1438-1463 (2012)

2.      Hayashi, H., J. Taniuchi, N. Furuyashiki, S. Sugiyama, S. Hirano, N. Shigemoto and T. Nonaka, ?Efficient Recovery of Carbon Dioxide from Flue Gases of Coal-Fired Power Plants by Cyclic Fixed-Bed Operations over K2CO3-on-Carbon?, Ind. Eng. Chem. Res., 37, 185-191 (1998)

3.      Lee, S.C., B.Y. Choi, T.J. Lee, C.K. Ryu, Y.S. Ahn, and J.C. Kim, ?CO2 Absorption and Regeneration of Alkali Metal-Based Solid Sorbents?, Catal. Today, 111, 385-390 (2006)