Effects Of Mineral Acid And Fe²⁺/Fe³⁺ On SO₂Absorption And Desorption In Organic Amine Solution Aqueous Solution

Industrial flue gases contained acidic components such as HCl, HF and metal oxidessuch as Fe₂O₃, FeO, which had impact on renewable amine absorption-desorption of SO₂from flue gas process and its stability. Aimed at these problems, the effects of mineral acidand Fe²⁺/Fe³⁺on the absorption and desorption performance of SO₂by1,4-bis（2-hydroxypropyl）piperazine （referred to as HPP） were investigated, andmechanism of the process was analyzed.The effect of initial pH of absorbent and absorption temperature on the absorption anddesorption performance of SO₂by HPP was investigated. And desorption processes,temperature and time are also optmized on desorption rate of SO₂absorbed.The technicsconditions of HPP solution adsorbing SO₂was optimized. The combination of theabsorbent initial pH was5.40, absorption temperature was40℃, desorption temperature is102℃, and desorption processes of direct heating, descorption time was3h. Under theoptimal conditions, the saturated absorption capacity reached0.472mol·mol^-1, thedesorption rate came to86.4%, and the oxidation efficiency was2.29%.The addition of sulphuric acid, hydrochloric acid and hydrofluoric acid simulate SO3,HCl and HF three kinds of acid gases on the absorption and desorption performance of SO₂by HPP was investigated. The results showed that the saturated absorption capacity ofabsorption solution reduced gradually, the desorption rate of absorption solution increasedgradually, with increasing sulphuric acid, hydrochloric acid and hydrofluoric acidconcentration of absorption solution. The effect results of sulphuric acid and hydrochloricon the absorption performance of SO₂by HPP acid showed basically the same, and biggerthan hydrofluoric acid. Added0.50mol H2SO4or1.0mol HCl into1.0mol absorptionsolution，the saturated absorption capacity reduce0.47mol·mol^-1. Added1.0mol HFinto1.0mol absorption solution, the saturated absorption capacity reduce0.44mol·mol^-1,thetheory of saturated absorption capacity error rate experimental values less than±1%.Theimportant effect that acid gases have on absorpting SO₂process is the existence ofhydrogen ions, reacting with HPP amine ions, the anion with the amine root formation heatstable salts, thereby reducing the saturated amount of absorbing SO₂.The addition of Fe2（SO4）3and FeSO4simulated Fe₂O₃and FeO two kinds of metaloxide on the absorption and desorption performance of SO₂by HPP was investigated.The results showed that, in the gas absorbed without oxygen conditions, the existence of Fe³⁺the ability of the absorption and desorption of SO₂by HPP was reduced, while Fe²⁺haven’ta certain effect on the absorption and desorption performance of SO₂by HPP. Under thepresence of oxygen in the gas absorbed, with the absorption solution of Fe³⁺and Fe²⁺concentration increased, the saturated amount of absorbing SO₂and desorption ratedecreased slowly, the oxidation rate increased slowly. And in the presence of oxygen in thegas absorbed, the effect Fe³⁺and Fe²⁺on absorbtion/desorption of SO₂performance wasbigger than non-oxygen conditions. When SO₃^2-concentration greater than or equal to0.112mol·L^-1, the rate of Fe³⁺cyclic catalytic oxidation SO₃^2-no longer increases. Therelationship between C(SO₃^2-)and time was straight line, the roder rate of SO₃^2-was0level,with the gradually Fe³⁺increasing concentration, the reaction rate increased.