Removal And Recovery Of Sulfur Dioxide From Flue Gas Using Organic Amines

The pollution of sulfur dioxide is an unavoidable environmental problem concerning all the countries worldwide.It makes the quality of air dropping into low level and causes the further acid-rain disaster.Now flue gas desulfurization is considered to be the most promising method that could also be applicable to all other fossil fuels.A novel FGD process using organic amine as absorbent to absorb the sulfur dioxide in flue gas gradually won people's attentions.In this paper,a complete desulfurization system including absorption device and desorption device for gas-liquid absorption were set up.A series of analytical methods were selected for detecting the concentration of SO₂ within flue gas and solute in solution.Meanwhile relative criterions to estimate the performance of absorbent were brought in and some representative organic amines as absorbents were chosen.The concept of effective desulfurization capacity of SO₂ to evaluate the performance of the organic amine absorbent was firstly proposed.Absorption performance of organic amines was studied by using a packed isothermal reactor at room pressure.Through comparison among MDEA,EDA,NMP, PZ,and other organic amines upon the absorption ability,a much higher efficiency and bigger capacity of absorption were shown by piperazine aqueous solution.By studying on several factors affecting the desorption as well as absorption ability,such as reaction temperature,concentration of inlet flue gas,concentration of absorbent,the following results are gained:piperazine aqueous solution with the concentration of 0.3～0.8mol/L would exert satisfying result when the flow rate of flue gas is 0.8L/min and the temperature of the solution keeps at 40℃;while feed-in solution could achieve an average desorption rate of 95%and remain in a very low missing rare of solute less than 1.0%when the nitrogen flow rate is 2 L/min and the temperature of desorption is 85℃.Taking the desorption rate and effective desulfurization capacity of SO₂ into consideration,experiments of selective and multiple absorption were carried out.The final results showed that pH value of piperazine aqueous solution could be able to maintain fluctuating within 4～7,in this way,guarantying a high SO₂ selectivity.Data of multiple absorption/desorption experiments repeated for 10 times show that the effective desulfurization capacity of piperazine aqueous solution can reach 8.01 g(SO₂)/g(PZ),which is much higher than that of MDEA and EDA.Above all,this technology of by using piperazine aqueous solution to remove and recover SO₂ from flue gas is characterized by its high desulfurization efficiency, no secondary pollution,recycling sulfur from the flue gas.However,there is still much more work should be done to make this technology be industrialized.