Study On New Wet Desulfurization Process Intensification And Its Modeling Research In Rotating Packed Bed

Sulfur dioxide（SO₂）is known to be one of the atmospheric contaminants which lead to respiratory system illness of human beings.Besides,it also causes several big environmental problems such as acid rain,fog and haze.To control SO₂ emission,various desulfurization technologies have been widely studied and applied.But at present,the waste disposal and secondary pollution problems caused by absorbent volatilization still exist in commonly used SO₂removal methods.In addition,most industrial desulfurization processes can not realize the recovery of sulfur resource.With the improvement of environmental standards,SO₂ emission limit has been reinforced gradually.Developing green and efficient SO₂ removal methods is significant for improving the natural ecosystems and developing the social economy.There are two typical ways to realize the sulfur resource utilization.One approach is regenerating desulfurization rich solvent to produce SO₂ and reuse absorbent.Another way is directly converting rich solvent to useful product.The renewable sodium lactate（Na La）-water deep eutectic solvent（DES）is used in the first kind of method.The kinetic characteristics of reaction between Na La and SO₂ are studied.SO₂ removal performance in the rotating packed bed（RPB）is investigated.The modeling to describe SO₂-DES mass transfer and reaction process in RPB is established.The desorption performance using direct steam stripping technology in RPB is explored.For the second kind of desulfurization method,the feasibility of SO₂ removal using hydrogen peroxide（H₂O₂）in RPB is studied.The mass transfer coefficient（K_Ga）and height of mass transfer（HTU）are calculated.The conclusions obtained from this work are as follows:（1）Sodium bisulfite（Na HSO₃）and lactate acid（HLa）are formed in the reaction process between Na La and SO₂.The reaction is first order with respect to both Na La and SO₂.The pre-exponential factor is 3.93×10¹⁰ L/mol·s^-1.The activation energy is 33.89 k J/mol.The reaction rate is fast.Therefore,the SO₂removal performance is controlled by mass transfer step and expected to be improved through intensifying the gas-liquid mass transfer process.（2）The SO₂ deep removal can be achieved in RPB using Na La-water DES.SO₂ content is able to be reduced to below 35 mg/m³.SO₂ is still high-efficiently removed under conditions of high gas-liquid flow rate ratio（500～600）using low concentration（0.11 mol/L）of Na La-water DES.The absorption system shows a great flexibility to the variation of gas flow rate.SO₂ removal efficiency can keep a high level under wide temperature range of 303.15～333.15 K,which is favorable to the optimization of successive absorption and desorption process.（3）The model to describe the SO₂-DES reaction and mass transfer process in RPB is established.The mass transfer area in RPB is divided into the packing zone and the cavity zone.The liquid flows in film form over the packing surface in packing zone.In the cavity zone,liquid flows in the form of spherical droplets.The mass transfer coefficient is calculated based on two-film theory.The mass transfer coefficient of RPB is the volume-weighted average of K_Ga values of packing zone and cavity zone.The predicted mass transfer coefficients have an average relative error of 7.85%.Most results have deviations of below 15%.It is concluded that the proposed model in this work has great predictability and reliability.（4）The desulfurization rich solvent can be regenerated using direct steam stripping in RPB.The desorption efficiency is 72.16%under optimized conditions and SO₂ loading can be reduced to 0.276.The mass transfer coefficient（K_La）and height of mass transfer（HTU）are theoretically calculated.Under experimental conditions,values of HTU are in the range of 5.74～7.92 cm,which are usually lower than those in conventional packed tower,demonstrating RPB is able to intensify gas-liquid mass transfer of desorption process and equipment volume is expected to be reduced.（5）The SO₂ removal performance using hydrogen peroxide（H₂O₂）in RPB is studied.It is evidence that SO₂ removal efficiency can be above 98.25%using only 0.25～0.38%H₂O₂ aqueous solution.The SO₂ outlet concentration is below35 mg/m³,realizing SO₂ ultra-low emission.The efficiency of atoms utilization reaches 100%.This process is expected to realize high-efficient SO₂ removal and sulfur resource utilization when used in the gas treatment of the factory with H₂SO₄ need,such as refineries and H₂SO₄ plants.The HTU values of RPB are in the low range of 1.60～2.07 cm,which illustrates that the use of RPB can greatly reduce equipment size and investment cost.