Phase Change Absorption Of SO₂ In Organic Alcohol Amine System And Its Regeneration Performance

Sulfur dioxide(SO₂),a major air pollutant,can cause severe damage to environment and human health once it goes into the air.Therefore,the emission of SO₂ should be controlled strictly.Traditional flue gas desulfurization technologies suffered from some drawbacks,such as high regeneration energy consumption.However,phase change absorption of carbon dioxide(CO₂)became a research hotspot in recent years.Typically,the homogeneous absorption solution formed two phases,including liquid-solid or liquid-liquid two phases,after absorption of CO₂.The CO₂-rich phase needs to be heated and the CO₂-lean phase can be reused directly in regeneration process.This technology reduces the amount of solution that needed to be regenerated,which shows a promising application prospect in saving desorption energy.Based on the similarity of SO₂ and CO₂in both structure and property,phase change absorption of SO₂ and its regeneration technologies are studied in this work.Three organic alkanolamines and different organic solvents were used for investigation to study the behavior of phase change absorption of SO₂ in this work.The absorption performance of absorption solution at different concentrations,temperatures,and SO₂ partial pressures was investigated.The absorption mechanism and phase-change mechanism were determined by nuclear magnetic resonance spectroscopy,Fourier transform infrared spectroscopy and Ultraviolet absorption spectroscopy.Besides,the viscosity and density data of absorption solution and products were tested.The distribution rules in liquid-liquid two phases,desulfurization efficiency,SO₂/CO₂absorption selectivity,reusability of absorbents,utilization of SO₂ and synthesis of chemicals containing sulfur were investigated in this work.The main conclusions are summarized as follows:(1)N,N-dimethylethanolamine(DMEA)was chose as absorbent because of the low moleweight and strong alkalinity.Hexadecane was used as solvents because of the high boiling point and low viscosity.The binary mixture performed liquid-liquid phase change behavior after absorption of SO₂.The relationship between the viscosity and absorption capacity was found to conform to an Arrhenius-type equation.The relationship between component distributions and absorption capacities could be described by semi-empirical equations.Namely,the decrease rate of DMEA is proportional to its concentration in upper phase and the decrease rate of hexadecane is also proportional to its concentration in lower phase.The absorption product cannot be regenerated by traditional heating method and can be chemically regenerated by adding cyclohexene oxide and forming a high-value product,cyclohexane sulfite.(2)Considering that the absorption product of DMEA cannot be regenerated by heating method,so 2-[2-(Dimethylamino)ethoxy]ethanol(DMEE)was chose as absorbent,which has a similar structure,but longer alkyl chain and higher boiling point than DMEA.Hexadecane and long-chain alcohols were used as solvents.It was found that long-chain alcohols cannot only increase the mutual solubility of DMEE and hexadecane,but also can decrease the viscosity of absorption product efficiently.For example,the viscosity of the absorption product could be decreased from 2338.1 m Pa·s to 362.02 m Pa·s when adding 20%decanol alcohol.(3)Based on the two alkanolamines DMEA and DMEE,triethanolamine(TEA)was used as absorbent because of lower volatility,and triethylene glycol dimethyl ether(TEGDME)was used as organic solvent because of low viscosity.The binary mixture was found to synergistically absorb SO₂ with high absorption capacity.In conclusion,three technologies about phase change absorption of SO₂ were investigated in this work.These technologies showed a promising application prospect in saving desorption energy,which provided valuable experience for industrial application of SO₂ phase change capture.