(195c) Kinetic Studies of Carbon Dioxide Capture By Potassium Carbonate Supported on Activated Carbon Using a Fluidized Bed Reactor

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

Aditya
Prajapati, T. Renganathan, K. Krishnaiah

Department of Chemical Engineering, Indian Institute
of Technology Madras, Chennai

Abstract

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)