Optimization of Slurry PH Value for Limestone Wet Desulfurization Technology
Based on limestone wet desulfurization spray scrubber technology, this paper explicitly introduces the ionization process of water in slurry, deduces controlled range of slurry PH value and equation of slurry PH value in slurry droplet by analyzing the main origin of H+ and OH-, and other factors that influence ionization balance of water in slurry, provides theories for simulation of slurry PH value and optimization in practical operation. Besides, it concludes the reasonable range of slurry PH value by analyzing various factors such as increasing SO2 removal efficiency, decreasing operation cost, dissolution of CaCO3, oxidation of SO32- andHSO3-, and relationship of slurry PH values between slurry surface and the undersurface, provides reference for optimization of slurry PH value in practice. Finally, an optimization experiment of slurry PH value is designed for#11FGD in Taiyuan co-generation power plant, and the slurry PH value is optimized effectively.
Optimisation of a wet FGD pilot plant using fine limestone and organic acids
Abstract The effects of adding an organic acid or using a limestone with a fine particle size distribution (PSD) have been examined in a wet flue gas desulphurisation (FGD) pilot plant. Optimisation of the plant with respect to the degree of desulphurisation and the residual limestone content of the gypsum has been the aim of the work. In contrast to earlier investigations with organic acids, all essential process parameters (i.e. gas phase concentration profiles of SO 2 , slurry pH profiles, and residual limestone in the gypsum) were considered. Slurry concentrations of adipic acid in the range of 0– 7 mM were employed. The overall degree of desulphurisation in the plant increased from 83% at 0 mM to 90% at 3 mM and the residual limestone level was reduced from 4.6 to 1.4 wt % . Increasing the slurry concentration of adipic acid above 3 mM gave only a slightly higher degree of desulphurisation. The wet FGD model of Kiil et al. (Ind. Eng. Chem. Res., 37 (1998) 2792) was extended to include buffer systems and verified against experimental data. Subsequently, the model was used as a tool to identify the optimal organic acid dissociation constants (as pK a values) and concentration levels at different operating conditions. At a holding tank pH of 5.5 and a temperature of 50°C, simulations with Bryozo limestone and a monoprotic buffer suggested that the optimum pK a value is between 4.5–5.5 and 5.5–6.5 with respect to the degree of desulphurisation and the residual limestone level, respectively. Adipic acid has pK a values close to these ranges ( pK 1 =4.40 and pK 2 =5.41 at 50°C). Changing limestone type (in the absence of organic acids) to one with a lower average particle size (i.e. from 20 to 4 μm ) increased the overall measured degree of desulphurisation from 83 to 87% and reduced the residual limestone level from 4.6 to 1.3 wt % . Increasing the holding tank pH level from 5.5 to 5.8 affected the degree of desulphurisation and the residual limestone level only slightly. At holding tank pH levels between 5.88 and 5.90, a high degree of desulphurisation was observed, but the residual limestone content in the gypsum increased to somewhere between 19 and 30 wt % , making this pH range unsuitable for use in a full-scale plant. The investigations have shown that both the addition of organic acids and the use of a limestone with a fine PSD can be used to optimise wet FGD plants.
Absorption of sulfur dioxide into limestone slurry in a stirred tank
The absorption rate of sulfur dioxide into limestone slurries has been observed under various experimental conditions, using a stirred tank absorber which had a plane surface. The effects of the interfacial concentration of SO2, the slurry concentration, the concentration of SO2−2 ion, and the limestone particle size on the rate have been examined.

Taking the effect of SO2−2 ion on the rate into consideration, a mathematical model for SO2absorption into limestone slurries based on the film concept has been developed. The model can explain the mechanism of SO2 absorption into limestone slurries.