STATISTICAL MODELING AND OPTIMIZATION OF CARBON SEQUESTRATION BY ABSORPTION USING AQUEOUS AMMONIA

SOURCE:

Faculty: Engineering
Department: Chemical Engineering

CONTRIBUTORS:

Nwokedi, I. C.
Igbokwe, P. K.

ABSTRACT:

Carbon sequestration by absorption into aqueous ammonia was investigated in this research using a designed and fabricated prototype batch absorption column. The fabricated prototype column was used in carrying out the research with consideration of three independent variables, concentration of ammonia solvent (2 to 10 mol/dm3), operating/contact time (2 to 100 seconds) and volume of ammonia solvent (40 to 200 millilitres) with ambient temperature and atmospheric pressure adopted for the absorption process. The optimum yields for captured carbons were obtained at concentration of solvent at 6 mol/dm3, operating/contact time of 60 seconds, volume of solvent at 120 millilitre with optimum removal efficiency results of 90 and 70 percent obtained for CO2 and CO respectively. Overall Mass Transfer Coefficient (KGAV) was found to increase with an increase in concentration of ammonia solvent and also increased with the volume of ammonia solvent with good linearity shown on the graphical representation from the plotted values. The hatta number was calculated as one of the factors for determining the order of the reactions. Absorption of CO2 into ammonia solution followed first order as the values of the calculated Hatta Number was (HA > 100) with its correlation coefficient close to unity and attained good linearity whereas that of CO is pseudo first order. Response surface methodology was used in obtaining the statistical models, as well as analyzing and optimizing the amount of CO2 and CO absorbed with the Analysis of Variance (ANOVA) estimating its significance which showed that quadratic model was suggested because of the closeness of the adjusted R-squared and predicted R-Squared values. Material balance was carried out to determine the amount of materials introduced, withdrawn and consumed while the energy balance was done to determine the energy requirements during the carbon sequestration process.