Increasing seawater alkalinity using fly ash to restore the pH and the effect of temperature on seawater flue gas desulfurization

Wet type flue gas desulfurization (FGD) using lime or limestone is popular because of its operational simplicity and the availability of lime and limestone. Seawater FGD (SWFGD) utilizes the alkalinity of seawater, and its efficiency varies depending on the seawater alkalinity. This study examined the effects of temperature, gas/water ratio, and total alkalinity of the absorbing solution on the removal efficiency of SO ₂ from flue gas by seawater. In addition, this study showed the possibility of increasing the total alkalinity of seawater using fly ash from coal power plants. The experimental results showed a 8% increase in removal efficiency, while temperature decreased by 10 °C from 25 °C under the conditions of a gas/water ratio of 100 and a resultant pH of 3. The increase in removal efficiency with increasing alkalinity was measured as 0.27%/ppm of bicarbonate alkalinity. This study showed that fly ash has the ability to increase the total alkalinity of seawater. The pH restoration experiment was conducted using fly ash and limestone. The conceptual design processes of SWFGD using NaOH, fly ash, and limestone for a 400 MW coal power plant were developed, and the material balance was calculated using ASPEN Plus software.