Regulating The Maximum Concentration Of Organic Waste Gas By Absorption/Adsorption-Desorption Technology

Many processes in the chemical industry use batch operation,and volatile organic compounds（VOCs）generally have the characteristic of large concentration fluctuations.VOCs with the characteristic of large concentration fluctuation cause a heavy load on the terminal organic waste gas treatment facilities.It not only affects the treatment efficiency,but more importantly,brings great safety hazards.Therefore,it is important to effectively regulate the concentration of organic waste gas emitted from chemical industry production equipment.Firstly,the porous inorganic silica gel was used as the skeleton of the adsorbent material.After silanization modification,the adsorption-desorption toluene characteristics of silanized silica gel and ZSM-5 molecular sieve were investigated.Through the analysis of the microscopic morphology of the two adsorbents,it is found that the silica gel has a specific surface area of 467.62 m²·g^-1 higher than the molecular sieve.And the silica gel has a richer mesoporous structure than the molecular sieve.The mesoporous structure is beneficial for adsorption and desorption.Therefore,silica gel has better adsorption performance for toluene than ZSM-5 and has good concentration adjustment ability.When the concentration of toluene is 12000 mg·m^-3,T=30°C,GHSV=6000 ml·（g·h）^-1,1 g silica gel can adsorb 135 mg toluene.The adsorbed toluene can be substantially desorbed completely below 90°C,indicating excellent regenerability of the silanized silica gel.The adsorption of VOCs by solid adsorbents has certain disadvantages.Therefore,the paper compares the characteristics of H₂O,Tween-80,[Emim]BF₄,[Emim]PF₆ and[Hnmp]HSO₄ to absorb and desorb VOCs.The highly halogenated anions enhance the solubility of toluene in ionic liquids.Since the anion[BF₄]^–is more halogenated than[PF₆]^–,the ionic liquid[Emim]BF₄ exhibits the better absorption performance.As the ionic liquid acts as a buffer,and the toluene with a concentration fluctuation of2000²0000 mg·m^-3 can be stabilized at 6000¹2000 mg·m^-3.Heating distillation（90℃）was highly efficient to recover[Emim]BF₄ from toluene.The regenerated[Emim]BF₄ retains its initial absorption capacity even after multiple cycles.Moreover,[Emim]BF₄ has the same buffer fuction on various aromatic hydrocarbons.Through the test of biodiesel’s own volatility,it shows that biodiesel has low vapor pressure and it is suitable for VOCs absorption.The characteristics of biodiesel absorption of toluene were researched.It is found that when the concentration of toluene is 12000 mg·m^-3,T=30°C,1 g BDO can absorb 60.5 mg toluene.By using BDO to absorb and desorb the toluene concentration,the toluene outlet concentration can be stabilized at 9000 mg·m^-3.