Neutralization of the acidified seawater effluent from the flue gas desulfurization process: Experimental investigation, dynamic modeling, and simulation

The neutralization of the seawater effluent in a wet flue gas desulfurization (FGD) process was investigated. Before discharge, the acidified seawater effluent from a absorber is neutralized, using the natural alkalinity in seawater, and aeration is performed to enhance the neutralization due to the stripping of carbon dioxide dissolved in the effluent. Experimental investigation, dynamic modeling, and simulation have been performed to elucidate the neutralization of the seawater effluent in a FGD process. We have measured changes in solution pH and the dissolved carbon dioxide concentration and carbon dioxide concentration in the outlet gas, relative to the time of aeration. Increases in the aeration rate, salinity, dissolved SO2 concentration, and temperature increased the neutralization rate. We have developed a rate-based model to simulate the neutralization process of the acidified seawater effluent. In the modeling, nonideal mixing in the gas phase is described using a tanks-in-series model while the liquid is assumed to be completely mixed. The model, which is based on reaction kinetics and equilibrium in the liquid phase and gas-liquid mass transfer, combined with the nonideal mixing in the gas phase, consists of five ordinary differential equations. In simulating the neutralization of the acidified seawater effluent, the effects of its temperature and salinity on the neutralization rate were taken into account. The proposed model, which included no adjustable parameters, could describe the present experimental results for the dynamic changes of solution pH, dissolved CO2 concentration, and CO2 concentration in the gas phase successfully.