Effects of additives on wet flue gas desulfurization with ethylenediamine

Experiments were conducted in a small self-designed bubbling apparatus to investigate the effect of acid additives including hydrochloric acid, sulfuric acid, phosphoric acid, citric acid and boric acid on the wet flue gas desulfurization by ethylenediamine. The results show that the acid additives can observably increase the available absorption capacity of the absorbents. The available absorption capacity of ethylenediamine/boric acid (266mg/L) and ethylenediamine/phosphoric acid (269mg/L) are higher, and have good pH buffering ability. It is found that the desulfurization efficiency of ethylenediamine sharply decreases with time. After adding acid additives, a higher desulfurization efficiency can be maintained for a long time. The recovery of SO₂ in ethylenediamine/boric acid, ethylenediamine/phosphoric acid and ethylenediamine/citric acid was studied. All the mean SO2 removal efficiency of the three absorbents in ten cycles can reach 99%, and the SO₂ desorption efficiency follows the order: ethylenediamine/boric acid＞ethylenediamine/phosphoric acid＞ethylenediamine/citric acid. According to the experimental results, boric acid and phosphoric acid seem to be the most promising additives.