Study On The Preparation And Application Of PH-Buffering Desulfurizer

The combustion of fossil fuels leads to a large amount of sulfur dioxide（SO₂）emission,which causes acid rain,smog and other environmental problems and is harmful to human health.Currently,there are a variety of sulfur dioxide pollution control technologies at home and abroad.The development of high desulfurization efficiency and renewable absorbent is the key research direction.Organic amine absorbents have been widespreadely concerned because of their great absorption performance and high stability.An organic macromolecule,poly（1-vinylimidazole）（PVIM）,was proposed and mixed with water to form a novel aqueous absorbent for SO₂ capture.The absorption/desorption capacity of the absorbent and absorption mechanism has been investigated by experiments and characterization.The corresponding parameters were calculated by the mathematic models and with the use of the thermodynamic parameters;a technical feasibility study was conducted.Poly（1-vinylimidazole）（PVIM）,a kind of organic macromolecules with an appropriate polymerization degree was synthesized and characterized by ¹H NMR and FTIR.Its thermal stability was investigated by TGA/DSC.The water solution of PVIM was prepared as absorbent,and its density and viscosity were measured.The unique pH-responsive characteristic of the absorbent provides it with a suitable physicochemical property,the viscosity reduced drastically in the absorption process.The pH value of the absorbents is 9.1 and the viscosity is 131.6 cP at 25°C before the absorption process;The pH value decreased to 5.0 and the viscosity is2.42 cP during the absorption process.The results of the absorption experiments showed that the absorbent can capture SO₂ efficiently at low partial pressure.For example,the SO₂ absorption capacity at 25°C is 0.431 mol SO₂ per kg absorbents at0.3 kPa and 2.215 mol SO₂ per kg absorbents at 9.4 kPa.The equilibrium solubilities of SO₂ in the absorbent decreased with the increase of temperature.As verified by FTIR,the reversible absorption of SO₂ was attributed to the reversible protonation reaction of PVIM which promotes the ionization of sulphuric acid and dissolution of sulfur dioxide.Almost all of the absorbed SO₂ could be released easily by the method of heating reflux.After absorption and desorption process repeated 5 times,the absorption capacity and chemical structure were still able to maintain unchanged,indicating that the absorbent has good reusability.The pK_a values and reaction enthalpy of protonation reaction of PVIM were determined by acid titration and parameter analysis based on the reaction equilibrium model.Further more,a technical feasibility study was conducted based on the thermodynamic parameters and the reaction equilibrium model,an operating region that both the absorption and desorption rates could maintain high efficiency was get.In summary,this aqueous solution absorbent has the advantages of simple preparation,good physicochemical properties,environment-friendliness,high ability in deep removal of SO₂,and excellent reusability and its technical feasibility in industrial application has been verified.This study provides a new research idea and experimental basis for the development of renewable FGD absorbent.