Study On The Phase Change Absorption Of SO₂ In Organic Amine Non-aqueous System

Acid rain and global warming are the serious environment pollution problems in the word today,which were caused by SO ₂ and CO₂.With the rapid development of society and economy,the massive combustion of carbon-containing,sulfur-contained fossil fuels had released inestimable SO₂ and CO₂ into the atmosphere.However,clean energy couldn't completely replace fossil fuels in the coming decades.One of the main measures to reduce emissi ons is to capture SO₂ and CO₂.Traditional SO₂capture technology is using chemical absorption method-wet flue gas desulfurization technique.The absorbent is usually using alkaline aqueous.This technology is mature and stable in operation,but it also has many disadvantages such as high energy consumption and serious loss of sorbent during the regeneration processes.In addition,the downstream products of sulfuric acid and sulfite are tending to be saturated.These problems will result in high cost of wet desulfurization and cause secondary pollution.Therefore,it is the key that reducing desorption energy consumption and trying to convert sulfur dioxide into higher-value products to reduce the cost of SO ₂ capture.What's more,it can realize efficient use of industrial flue gas SO₂.Non-aqueous system phase-change absorption of SO₂ only requires to heat the SO₂ rich phase to achieve regeneration.The SO₂lean phase does not need to be heated and is directly mixed with the d esorption liquid of rich phase.And then they will be returned to absorption tower for reuse.This method will be possible effectively to reduce the regeneration energy consumption.In this paper,organic solvents with excellent performance were used to dissolve primary amine,secondary amine and tertiary amine to form organic amine absorption solutions.It can achieve liquid-solid phase change absorption of SO₂.At the same time,the paoducts of tertiary amine can provide stable sulfur for sulfa drug.During the experiment,w e explored the SO₂ absorption products in different organic amine aqueous without water.Based on the various characterization results,the mechanism of SO ₂ absorption by tertiary amines was initially proposed.And the regeneration of tertiary amine absorbents was achieved through traditional heating desorption method.The specific research contents are as following aspects:First,a variety of organic solvents were chosen to dissolve primary amine,secondary amine and tertiary amine,which were used as the absorption solutions.Liquid-solid phase-change phenomenon appeared after absorption of SO₂ in these solutions.Powder X-ray diffraction?XRD?and Fourier transform infrared?FTIR?spectrometry indicated that organic solvents had no influence on the natur e of absorption product.FTIR,XRD,single crystal XRD and organic element analysis results showed that the absorption products of the primary amine,secondary amine and mixed amine absorption were easy to absorb water and converted to sulphite or hydration sulfite.The absorption product of the tertiary amine was the electron transfer product,which was stable and hardly to absorb water and oxidization.Then the thermogravimetric analysis and differential scan ning calorimeter calorimetry?TG-DSC?tests demonstrated that the absorption product of tertiary amine could be decomposed by conventional heating method,and the absorption product of primary amine,secondary amine couldn't be.Second,based on the absorption product of tertiary amine was more stable than primary amine and secondary amine and it could realize desorption by conventional heating method,the tertiary aromatic amine N,N,N',N'-tetramethyl para-phenylene diamine?TPD?was chosen as absorbent.Some solvents with the advantages of low vi scosity,high boiling point were selected to dissolve TPD.Orange solid product would be obtained after organic amine non-aqueous solution absorbing SO₂.Powder XRD and Fourier transform infrared?FTIR?spectroscopy characterization results indicated diffe rent organic solvents also had no influence on the properties of the absorption product.The organic elemental analyzer and single crystal X-ray diffraction analysis results showed that the precipitate of tertiary aromatic amine was electron transfer compo unds.The characterization results also suggested one mole absorbent TPD could absorb equimolar or double mole SO ₂.The electron compounds would convert to hydrogen sulfate salt when it was placed in the air for a long time,but the oxidation process was very slowly.TG-DSC analysis results proved that the absorption products could be desorbed by conventional heating method.The multiple cycle absorption-desorption experiments showed the performance of this absorption system was very stable.The effect of solvent,water,time on the absorption products and the effect of solvent and water on the absorption rate were examined in the experiment.The absorption rate would decrease with the increasing of organic solvent Henry's coefficient the moisture content.For the absorption product,a coordination electron transfer would gradually convert into a bicoordination electron transfer products when the reaction time increased.Besides,water could promote this conversion reaction.In order to explore the absorption performance of tertiary amine in the other non-aqueous system,tertiary amines were used as cations for the function ionic liquidfinally.Inthisexperiment,tertiaryaminesTPD,DABCO,tetraethylethylenediamine?TEEDA?wereusedascationsand carboxylate-containing dichloroacetic acid,methanesulfonic acid,formic acid,and lactic acid were used as anions to synthesize basic ionic liquids.Then the ILs was dissolved in the organic acid,which achieved liquid-solid phase change absorption SO₂.This may be result from the polarity of electron transfer product was greater than the organic acid.XRD characterization results indicated that the absorption product also was electron transfer compounds.The effect of anion,cation,concentration,temperature,moisture,etc.on the absorption performance of the absorption solution was examined in the experiment.The absorption capacity and absorption rate of the absorption solution were increased with t he increasing of anionic alkali.The absorption capacity wou ld increase with the increasing of concentration in the strong acid.However,with the formation of the absorption product,the viscosity of the solution would increase in the weak acid,so that the mass transfer effect in the high concentration solution is poor.So there is an optimum concentration value under the weak acid condition.Absorption capacity decreased as the temperature increased.Water and cations had no effect on the absorption performance of this system.Absorption-desorption cycle experiments proved that this system had a stable circulation absorbing performance.