Study on a Novel Semidry Flue Gas Desulfurization with Multifluid Alkaline Spray Generator

Abstract

The advantages and disadvantages of the typical semidry flue gas desulfurization (FGD) processes are analyzed, and a novel semidry FGD process with multifluid alkaline spray generator is first proposed to improve the colliding contact efficiency between sorbent particles and spray water droplets, and to form a large amount of aqueous lime slurry. The experimental results show that the colliding contact efficiency between lime particles and water droplets in the prefix alkaline spray generator may reach about 70%, which is significantly higher than the colliding contact efficiency of 25% in duct sorbent injection. The SO2 removal efficiency can reach 64.5% when the Ca/S molar ratio is 1.5, the approach to the saturation temperature is 10.3 °C, and the flue gas residence time is 2.25 s. It is higher than that of in-duct sorbent injection under similar conditions, and the sorbent utilization is improved to 43%. Therefore, the FGD process with a prefix alkaline spray generator can greatly improve SO2 removal efficiency and sorbent utilization and it will be a new, simple and efficient semidry FGD process for industrial application in the future.

The effect of hydrogen peroxide solution on SO2 removal in the semidry flue gas desulfurization process

“…It can be seen that SO 2 removal efficiency increases significantly when Ca/S molar ratio increases from 1.0 to 2.0 at the same approach to adiabatic saturation temperature, and it increases relatively slow when Ca/S molar ratio exceeds 2.0. Thus, the suitable Ca/S molar ratio in the semidry FGD process is 2.0 or so when operation costs are taken into account, which agrees well with the results in the typical semidry FGD process of sorbent humidification activation [2]. The approach to adiabatic saturation temperature decreases with the increase of spray water mass flow rate.…”

“…The effect of Ca/S molar ratio and approach to adiabatic saturation temperature on SO 2 removal efficiency when spraying hydrogen peroxide solution of 1% to 3% to humidify Ca(OH) 2 in Fig. 4a-c is the same as that when only spraying water to humidify Ca(OH) 2 in Fig. 2.…”

“…Compared with spraying water to humidify Ca(OH) 2 , SO 2 removal efficiency was improved significantly by spraying hydrogen peroxide solution of 1-3 wt.% to humidify Ca(OH) 2 because hydrogen peroxide solution enhanced the dissolution and absorption rate of SO 2 . Moreover, XRD and SEM analyses show that the desulfurization products contain less amount of unreacted Ca(OH) 2 and more amount of stable calcium sulfate with increasing hydrogen peroxide solution concentration. Thus, the process mechanism of the enhanced absorption of SO 2 by spraying hydrogen peroxide solution to humidify Ca(OH) 2 was elucidated on the basis of the experimental results.…”

“…The semidry flue gas desulfurization (FGD) processes are effective in reducing SO 2 emission from medium-and small-scale coal-fired power stations with the advantages of small space requirement, low water consumption and low investment and operation costs [1][2][3]. Thus, these processes are very attractive for the desulfurization retrofits in the old units.…”

“…However, compared with wet FGD processes, SO 2 removal efficiency and sorbent utilization in the semidry FGD processes are relatively low [4,5]. Moreover, a great variety of analytical methods have revealed that the products of the semidry FGD processes primarily contain Ca(OH) 2 and CaSO 3 ·1/2H 2 O [6][7][8]. The unstable calcium sulfite could release SO 2 again at high temperature or acid atmosphere, which restricts the reuse of the desulfurization products.…”