Study On The Flue Gas Desulfurization With Ethylenediamine/Phosphoric Acid

The wet flue gas desulfurization with ethylenediamine/phosphoric acid can recover SO₂. Experiments were conducted in the absorption and desorption apparatus to study the absorption and desorption efficiency of SO₂, using the simulated flue gas. The suitable absorbents were selected. The effects of different operation conditions on SO₂ absorption efficiency and desorption efficiency were also investigated and the optimum conditions were obtained. Moreover, the anti-oxide ability of the absorbents was researched, and the oxidation kinetic of the ethylenediamine/phosphoric acid solution was obtained through the method of the initial series rate.The absorption volume, absorption and desorption efficiency and the oxidation efficiency of the absorbents as evaluation indexes, the absorbents screening experiments were carried out on the bases of batch absorption and desorption experiments. The results showed that ethylenediamine, tetramethylethylenediamine and diethylenetriamine have higher absorption capacity and better efficiency. The absorption efficiency was over 95% in the 70 min after phosphoric acid was added into the three absorbents. Comparing sulphuric acid, the efficiency absorption capacity of the absorbents was two times. So, phosphoric acid was selected as the appropriate additive. In consideration of the material cost, ethylenediamine/phosphoric acid was selected as the optimum absorption solution.Moverover, the effects of the liquid gas ratio (L/G), flue gas flow rate, the pH value of absorption solution and the concentration of the inlet SO₂ on the desulfurization efficiency were studied in the packed tower continuous absorption apparatus with a diameter of 150mm. When L/G was 0.83L-m^-3and the initial pH value of the absorbent was 6.00, the absorption efficiency obtained over 97%.The SO₂ absorbed solutions desorption was also studied. The effects of desorption time, the absorbed pH value of the solution and temperature on SO₂ desorption efficiency were considered. The optimum desorption conditions were desorption time 60min, desorption temperature 105℃, pH value of the rich absorbents at 5.50. Ethylenediamine/phosphoric acid was recycled for 10 times. The average SO₂ absorption efficiency were over 99% and the SO₂ desorption efficiency of latter 9 times were above 90%.The effect of air flow rate [Q], the concentration of ethylenediamine [C], pH value of the absorbent [pH] and temperature T on the anti-oxide ability of ethylenediamine/phosphoric acid absorbent were investigated. The activation energy of oxide reaction was 23.00KJ·mol^-1. In the oxide kinetic equation of ethylenediamine/phosphoric acid absorption, reaction order of [Q], [C] and [pH] was 0.72,0.54 and 0.55 respectively.