Development of a method to reduce the rotary kiln flue gas CO2 emission in cement manufacturing process

In this thesis, capturing CO2 from rotary kiln flue gas through adsorption was studied. In mixtures invented as adsorbent, zeolitic natural pozzolana (trass), expanded perlite, bentonite clay and industrial lime were used as raw materials. Besides, in order to synthesize zeolitic phases and to observe the catalysis effect, NaOH was added to one mixture. It was aimed that the adsorbents could be recycled to the process as alternative raw material, mineral additive and/or concrete additive. Adsorbate CO2 gases with the concentration of 20 %, diluted with 80 % N2 were fed into the experimental columns. Being considered efficiencies and adsorption times together, mean efficiencies between 37-46 % were calculated in the adsorbent groups showing the best performances. The isotherm models to which the experimental data fitted best were determined as Freundlich and Redlich-Peterson and rate limiting kinetic steps as Elovich model and Bangham pore diffusion. Raw materials coming into contact with the CO2 gases given into the column at 100°C and with a flow rate of 3,7 lt/min presented the same results, as well. It was understood that the raw materials were suitable materials for multi layer adsorption due to their surface porosities, crystal framework structures and high cation exchange capacities. Among the four mixtures showing the best performances, the adsorbent to which NaOH was mixed up can not be used as a raw material or mineral additive, because of its high alkali content. However, the other three adsorbents, containing bentonite and perlite together can be consumed up as both alternative raw material and mineral additive. As a result, it was concluded that the adsorbent samples could be presumed as alternative materials for capturing the CO2 from cement manufacturing. Keywords: CO2 capture, adsorbent, adsorption, rotary kiln fue gas, zeolite, bentonite, perlite