In this research, kinetics and absorption rate of CO2 were studied using partially carbonated ammonia solutions. A correlation was proposed to calculate CO2 absorption rate based on two dimensionless parameters: conversion film parameter and carbonation ratio. Absorption rate experiments have been performed employing a laboratory absorption packed column. More than 60 items of experimental data were used for obtaining the correlation parameters. In the experiments, total ammonia concentration range was 30 to 750 (mol center dot m-3), carbonation ratio range was 0.22 to 0.785, and CO2 partial pressure in the gas mixture was 10, 14, or 18 (kPa). A comparison of the predictions indicated that the proposed correlation was more accurate than other correlations reported in the literature.