A Novel Correlation for Considering the Effect of Neighbouring Droplets On the Evaporation Rate of Solvent Droplets Used in Carbon Capture Applications

Abstract

Chemical sprays like Monoethanolamine (MEA) and aqueous ammonia are commonly used in spray columns to remove CO2 from combustion flue gases. This process involves interactions between spray droplets and the flue gas, resulting in both CO2 absorption and droplet evaporation due to temperature differences. The presence of neighboring droplets can influence the evaporation and gas absorption of a given droplet. Understanding this interaction is crucial for creating accurate models for CO2 capture from flue gases.This study investigated the impact of neighboring droplets on the evaporation of a specific droplet, comparing it to evaporation in isolation. Various configurations of suspended water, aqueous ammonia, and MEA droplets were examined across a temperature range from 75°C to 125°C. The droplets were placed on a microfiber grid and observed in a heating chamber. The evaporation rate was determined through image analysis and MATLAB algorithms, considering temperature and available surface area for vapor diffusion. Results demonstrated that neighboring droplets significantly influenced droplet evaporation, especially for MEA. A novel parameter, Surface Area Ratio (SAR), combining the number of droplets and their proximity, was introduced to account for this influence. The normalized evaporation rate correlated linearly with SAR, providing a basis for correcting evaporation rates in computational models across different conditions. This correlation between the normalized evaporation rate and SAR was developed from the collective data, offering a valuable tool for refining computational models of evaporation in CO2 capture processes.