Comprehensive spray characterization of air-assisted impinging jet atomizer for carbon capture applications

Abstract

Spray scrubbing for carbon dioxide (CO₂) absorption has attracted research interest because it is a viable retrofitting option for existing power plants. For effective absorption, desired spray characteristics must be attained for a wide range of absorbent liquids with distinct physical properties. In this study, an air‑assisted impinging jet atomizer was evaluated to determine its suitability for CO₂ absorption using monoethanolamine (MEA). The study focused on understanding the influence of various physical parameters on the overall atomization process. Spray experiments were performed under quiescent atmospheric conditions at different liquid flow rates and air-to-liquid mass flow rate ratios (ALR). High-speed imaging and laser diffraction techniques were used for spray visualization and droplet size characterization, respectively. The study revealed that the primary atomization was either a hydrodynamic mode of breakup caused by hydrodynamic instabilities in a liquid sheet or an aerodynamic mode of breakup, where the breakup was dominated by gas-liquid interaction. A transition between these breakup processes occurred at an air-to-liquid momentum ratio of ∼0.6, and a gas Weber number of ∼30. Improved atomization was obtained in the aerodynamic mode of the breakup. A Sauter mean diameter (SMD) of the order of 60 µm, along with a narrow size distribution, was obtained at high liquid flow rates, even at an ALR of 4 %. Furthermore, empirical correlations were proposed for SMD and spray angle as functions of gas Weber number, liquid Weber number, and Ohnesorge number. The detailed spray characterization performed in this study provides valuable insights into the atomization process of an air-assisted impinging jet atomizer and is crucial for testing this atomizer configuration in a spray column for CO₂ capture.