Removal Of SO₂ By Aqueous Blends Of Piperazine Organic Amine And Its Absorption Phase Equilibrium

As a new desulfurization technology,piperazine organic amine was widely used in flus gas desulfurization?FGD?because of its high desulfurization rate,low desorption energy consumption,recycling of desulfurization fluid,and low secondary pollution.In this work,the foaming properties and desulfurization properties of piperazine?PZ?and its derivatives 1-?2-hydroxyethy?piperazine?HEP?,N,N?-bis?2-hydroxyethyl?piperazine?BHEP?,1-?2-hydroxyethy?-4-?2-hydroxypropyl?piperazine?HEHPP?,N,N?-bis?hydroxypropyl?piperazine?HPP?were studied.The solubility model of SO₂in the phase equilibrium system of HEHPP-HEP/H₂SO₄-H₂O-SO₂was established.Firstly,the foaming properties and desulfurization properties of five pure aqueous piperazines amine solutions were studied,and the effects of temperature and amine concentration on the foaming height and defoaming time were also discussed.Experimental results showed that the foaming height and defoaming time of PZ were much higher than those of other organic amines.The foaming height of HPP was the lowest,and the defoaming time of HEP was the shortest.As the temperature rose,the foaming height of amine solution increased and the defoaming time decreased.The foaming height and defoaming time of amine solution increased when the concentration of organic amine solution increased.Among the five amines,PZ had the highest saturated absorption capacity and HPP was the lowest,while the desorption rate of HPP was the largest and PZ was the smallest.Then,the foaming properties and desulfurization properties of aqueous HEHPP-HEP solution were studied.The results showed that with the increase of HEP content in aqueous blended amine solution,the surface tension of aqueous blended amine solution increased and the defoaming time decreased.When HEP with high viscosity was added to the solution,on the one hand,the viscosity of the solution will be raised,on the other hand,hydrogen bond may be formed between the two amine molecules to reduce the solution viscosity.So,the viscosity and the foaming height of aqueous blended amine solution will decreased first and then increased with the increased of HEP content.The saturated absorption capacity,absorption rate,oxidation rate and desorption energy consumption of aqueous blended amine solution increased with the proportion of HEP,but the desorption rate will decreased.A method for evaluating the performance of aqueous blended amine solution was proposed.It was found that the comprehensive performance of aqueous blended amine solution was better when the mass fraction ratio of HEHPP to HEP was 8:2.Finally,the solubility of SO₂in aqueous solution of HEHPP and HEP was measured by semi-dynamic absorption method at the ranges of 303.15?353.15K,the amine concentration ranges of 0.3?0.9mol/L and the partial pressure of SO₂ranges of 0?500Pa.The results showed that the solubility of SO₂in aqueous organic amine solution will be decreased with temperature rising,the concentration of amine and the partial pressure of SO₂decreasing.The solubility model of SO₂in the phase equilibrium system was established by using the quasi-equilibrium constant method and the second-order ionization equilibrium constant of aqueous blended amine solution as the fitting parameter.The average relative deviation between the calculated value of this model and the experimental value of 126 groups was 6.22%,which meets the demand of industrial production.The solution enthalpy of SO₂in the system was estimated to be between 50 and 55k J/mol by using the solubility model and the Gibbs-Duhelme equation.