Study On Simultaneous Removal Of SO₂, NO And Hg From Flue Gas With Complex Ca-based Sorbent

The emission of SO2, NOx and mercury resulting from coal combustion is one of the great problems that lead to undesirable severe damage to the environment and to human health. Compared with the separate air pollution control devices for each pollutant, the simultaneous removal of SO2, NOx and Hg in one device is gaining importance for both investigations and applications because of its low energy comsuption, low capital costs and small space requirements, which is the trend of multi-pollutant control technology development. The semidry simultaneous removal of SO2, NOx and Hg from flue gas in one device based on the complex Ca-based sorbent has a wide prospect of development and application.This thesis conducted a research on the modification of Ca-based sorbents, the preparation of the complex Ca-based sorbent and the experimental prameters that affect the removal of SO2, NO and mercury. The effects of the fly ash/CaO mass ratio, the initial hydration water temperature and the hydration time on the Ca(OH)2/fly ash sorbent’s specific surface area and the SO2capturing capacity were investigated. The results indicate that under a certain experimental condition and within a range of experimental parameters, the Ca(OH)2/fly ash sorbent’s specific surface area and the SO2capturing capacity increased quite significantly with increasing the initial hydration water temperature and the hydration time. While the Ca(OH)2/fly ash sorbent’s specific surface area decreased when the fly ash/CaO mass ratio increased and the SO2capturing capacity of the sorbent increased with the increment of the fly ash/CaO mass ratio. The preparation of the complex Ca-based sorbent was studied. The fly ash and CaO with a mass ratio of4:1were hydrated at ambient temperature to make the basic sorbent. NaClO2/KMnO4and water were added to the basic sorbent to make the complex Ca-based sorbent. The effects of influencing factors including the dosage of NaClO2/KMnO4, water content, temperature, O2concentration, SO2concentration, NO concentration and mercury concentration on the SO2, NO and Hg capturing capacity of the complex Ca-based sorbent were investigated at low temperature. The results indicate that high mass percent of additives and water content made SO2, NO and Hg captures increase significantly while temperature rise resulted in SO?, NO and Hg captures decreasing. There was a competition between SO2, NO and Hg when they were reacting with the complex Ca-based sorbent. Under the experimental conditions, the maximum SO2, NO and Hg captures reached17.79mg SO2/g sorbent,7.31mg NO/g sorbent and2391.63ng Hg/g sorbent respectively.The research did in the thesis made a foundation for the development and the industry application of the semidry simultaneous removal of SO2, NOx and Hg from flue gas in one device based on the complex Ca-based sorbent.