Study On The Effects Of Molecular Sieve And Its Modification For SO₂ Adsorption Performance

With the rapid development of world economy,science and technology,as the burning of fossil fuels such as coal,oil to provide energy,at the same time also brings a variety of environmental pollution problems.The SO2 from the coal-fired power plant coal has become one of the main air pollution all over the world.A large number of SO2 emissions have caused serious harm for humans,animals and plants and ecological environment.Therefore,developing a method to reduce the emissions of SO2 have a research hot topic.At present,various measure have used to control SO2 emissions,such as desulfurizer,desulfurization technology and other method.In these methods,the calcium limestone method is more widely used for flue gas desulfurization.Although these measures displayed excellent efficiency for reducing SO2 emissions,these desulfurization technology exists some disadvantage.Solid adsorption material were the most promising for flue gas desulfurization,due to its own features,such as low cost,low energy consumption,simple operation,thermal stability,generation,and no secondary pollution.The microporous or mesoporous material are the best choice for flue gas desulfurization because of its advantage,such as activated carbon,diatomite and molecular sieve.Therefore,this topic preliminary explored the effect of the activated carbon,diatomite and four kinds of molecular sieve(4A,10X,13X,ZSM-5)for the performance of adsorption and desorption of SO2.In this study,the adsorption and desorption of SO2 on adsorbent,thermal stability,residual amount of salt and recycling times used as evaluation indexes.Ultimately,we choose active carbon,diatomite,and four kinds of molecular sieve(4A,10X,13X,ZSM-5)as research materials by means of preliminary laboratory experiments.Then we modified these materials and researched the effect of these materials for the adsorption and desorption of SO2.Finally,we choose the best and the worst sample to for testing actual flue gas.and we also researched the adsorbent efficiency for SO2 adsorption under the condition of a variety of mixed gas.In order to improve the adsorption of SO2 on adsorbent material,in this study,four methods used as modification adsorption material:the first is different activation temperature modification method;the second is different NaOH concentration of alkali modified method;the third is different KH-550 modification method of load;the fourth is optimization experiments of modified method.The results show that:(1)the best activation of molecular sieve method and parameters follow as:water molecular sieve;put in drying oven drying;take some molecular sieves in muffle furnace,preheat 1h under 150?.the temperature to 350?(activation temperature)roasting 3h.then the temperature to 550? calcination 3h,stop heating and natural cooling to 100-200? from the muffle furnace,put in dryer spare;(2)comprehensive the point of adsorption and desorption of SO2,when NaOH concentration was 0.1 ‰,processing of SO2 adsorption and desorption performance of ZSM-5 zeolite was the best effect.Large concentration of alkali can make the most of the molecular sieve of SiO2 eroded,thus seriously changed the structure characteristics of molecular sieve has been also reduces the SiO2/Al2O3,which changes its adsorption performance;(3)when the load of 8%KH-550,10X.13X and ZSM-5 molecular sieve adsorption and desorption of SO2 effect are best,but not equal to 10X ZSM-5 adsorption quantity,13X molecular sieve adsorption capacity,reduce the amount of residual the 10X,13X molecular sieve,but not as good as ZSM-5 molecular sieve as a result,improve the ZSM-5 zeolite adsorption capacity and reduce the amount of residual 10X,13X molecular sieve is the research emphasis in the future;(4)the four kinds of molecular sieves were modification treatment by optimizing the experiment and the SO2 adsorption and desorption properties were analyzed,and finally the best alkali concentration of NaOH was 0.1 ‰,KH-550 load is 8%;(5)testing the actual flue gas analysis showed that the existence of the flue gas CO2 does not affect the removal of SO2 adsorption material,but the existence of the flue gas NOx will affect the removal of SO2 adsorption material.Therefore,the process of denitration should be carried before desulfurization.