The Study Of SO₂ Absorption System Based On Ionic Liquid

The burning of fossil fuels can provide energy for production activity and human life,it also brings serious pollution to the encology and environment due to the emittion of SO₂.In the flue gas desulfurization technology used in industry,the widely used lime-stone method is known as its quick absorption speed and high efficiency,but it also has the disadvantages of the generation of a large amount of wasted Ca SO₄ and water.The new emerging green ionic liquids and deep eutectic solvents show good application prospects in the flue gas desulfurization process because of their merits such as low vapor pressure,good thermal stability,extensive tuning properties and satisfactory dissolving ability for gases.It has the theoric significants and economic values to construct green and efficient absorbents for SO₂,investigate their behavior of SO₂ absorption,and provide fundamental data and property parameters for developing new SO₂ desulfuaiton technology.In present work,Emim Cl was selected as Hydrogen bond acceptor?HBA?and compaired with N-formylmorpholine,N-acetylmorpholine,DMI and NMP as Hydrogen bond donor?HBD?to form a series of deep eutectic solvents?DESs?.Their physical properties and performace for absorption of SO₂ were systematically investigated.The corresponding absorption mechanism for SO₂ in the DESs was analysized according to FTIR and NMR spectroscopy.The results show that among all the eutectic solvents prepared,Emim Cl-NFM?1:1?has high efficiency and reversible absorption capacity,and the absorption capacity of at reaches 0.22 and 0.135g SO₂/g DES at 293.15 K for 1 k Pa and 2000 ppm SO₂,respectively;the absorption performance can keep stable after several absorption and desorption cycles,the long-term thermostability of the DES at the desorption temperature is good;the ideal selectivity of of SO₂/CO₂?0.1/1?and SO₂/CO₂?0.01/1?reaches 88 and 46,respectively;the main reason for the efficient absorption of SO₂ with low concentration maybe the relatively strong interaction between chloride ion in Emim Cl and SO₂.Compared with DESs in the literatures,Emim Cl-NFM demonstrated better absorption performance and capacity for SO₂ with low concentration.Subsequently,a hybrid mixture of[TMG][acac]-PEG200 with low viscosity was prepared by the combination of functionalized ionic liquid[TMG][acac]and environmentally friendly PEG200.For the prfered mixture,its physical property change and absorption performance for SO₂ with various pressures were investigated.It was found that the addition of PEG200 can enhance the thermostability of the mixture.20%[TMG][acac]-PEG200 was regarded as the preferred mixture according to the comprehensive results of viscosity and absorption capacity,which could efficiently capture SO₂ with the absorption capacity of 0.331 and 0.838 g SO₂/g IL at 303.15 K and pressures of 10 and 100 k Pa,respectively.The viscosity of 20%[TMG][acac]-PEG200 mixture decreased to be 60%of the initial values?25 m Pa.s?after the saturation of SO₂.The dissolved SO₂ can be easily stripped out and the hybride mixture possesses good recycling and regeneration performance.Finally,the flue gas desulfurization process based on Emim Cl-NFM?1:1?DES was simulated using Aspen plus software.The critical properties of DES were estimated by group contribution method.A process containing absorption-double flash distillation was designed and optimized according to sensitivity analysis.The obtained operation conditions were as follows:the concentration of SO₂ in purified gas was reduced to be32.5 ppm when the flue gas was treated at atmospheric pressure and 20?with the feeding rate of DES and flue gas at 26000 kg/h and 370 kg/h,respectively.DES was regenerated and recycled after the first?1.0 bar?20??and second?0.1 bar?95??flash distillation.The SO₂ in flue gas was recovered with the recovery and purity higher than99%and 0.99?expressed with molar fraction in the gas?,respectively.The simulated results can provide suitable reference for developing new flue gas desulfurization technology.