Importance of atomizer choice for CO2 capture in spray columns

journal article in Web of Science

en

CO2 is one of the most severe greenhouse gases released into the atmosphere and is responsible for increasing global temperatures. Post-combustion CO2 capture can reduce the amount of CO2 released. Spray columns, as simple gas cleaning reactors, can utilize different types of atomizers. The CO2 capture process requires well- tailored spray characteristics, such as suitable mean drop size and drop size distribution, droplet density, spray cone angle, and droplet velocity. Small droplets are prone to be carried away by ambient flow causing significant sorbent losses, while large droplets have a small surface area, which limits the rate of CO2 mass transfer. This paper compares pressure-swirl, flat-fan, twin-fluid, and showerhead atomizers operated at a constant solvent flow rate of 140 kg/h. Atomizer rescaling was used to change the liquid pressure. Droplet sizes were probed with a high-resolution shadowgraph sizer. Absorption tests were carried out on a laboratory-scale spray tower with a diameter of 0.2 m and a height of 2.5 m. The absorption liquid was a 30 wt% monoethanolamine (MEA) solution, and the modeled flue gas contained a 10% CO2 mole fraction. The absorption efficiency systematically increased with a reduction in Sauter mean diameter (D32), i.e. with atomizer input energy. Pressure loss in the spray column is directly proportional to absorption efficiency. Effervescent atomizers achieved the worst energy efficiency and the largest fraction of droplets carried away by the ambient flow, resulting in significant sorbent loss. Flat-fan and pressure-swirl types were found to be excellent all-round atomizers.

CO2 is one of the most severe greenhouse gases released into the atmosphere and is responsible for increasing global temperatures. Post-combustion CO2 capture can reduce the amount of CO2 released. Spray columns, as simple gas cleaning reactors, can utilize different types of atomizers. The CO2 capture process requires well- tailored spray characteristics, such as suitable mean drop size and drop size distribution, droplet density, spray cone angle, and droplet velocity. Small droplets are prone to be carried away by ambient flow causing significant sorbent losses, while large droplets have a small surface area, which limits the rate of CO2 mass transfer. This paper compares pressure-swirl, flat-fan, twin-fluid, and showerhead atomizers operated at a constant solvent flow rate of 140 kg/h. Atomizer rescaling was used to change the liquid pressure. Droplet sizes were probed with a high-resolution shadowgraph sizer. Absorption tests were carried out on a laboratory-scale spray tower with a diameter of 0.2 m and a height of 2.5 m. The absorption liquid was a 30 wt% monoethanolamine (MEA) solution, and the modeled flue gas contained a 10% CO2 mole fraction. The absorption efficiency systematically increased with a reduction in Sauter mean diameter (D32), i.e. with atomizer input energy. Pressure loss in the spray column is directly proportional to absorption efficiency. Effervescent atomizers achieved the worst energy efficiency and the largest fraction of droplets carried away by the ambient flow, resulting in significant sorbent loss. Flat-fan and pressure-swirl types were found to be excellent all-round atomizers.

Spray column; CO 2 capture; Pressure-swirl; Effervescent; Flat-fan

01.04.2025

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