Comprehensive Evaluation For Flue Gas Denitration Technologies And The Selectively Catalytic Reduction Of NO_x Over MoO₃-WO₃/TiO₂ Catalysts

Haze weather originating from PM2.5 has caused a serious threat to people's health.As the main composition of PM2.5,NO_x has unshirkable responsibility for the formation of haze.Refinery as the biggest supplier of natural gas and clean oil production in our country,is an important contributor to the regional air pollution.The emission of NO_x from refinery is as high as thousands of tons per year,and NO_x from FCC regeneration flue gas has the biggest amounts,which is more than half of the total refinery NO_x emissions.As more and more strict national standards coming out,NO_x emission limit to refining enterprise is stricter.At present,de-NO_x technologies applied at domestic and overseas mainly include selective catalytic reduction?SCR?technology,ozone oxidation at low temperature?LoTOx TM?technology,de-NO_x additives,low nitrogen burner technology,etc.Different technologies have their own characteristics.Flue gas denitration involves many factors such as environment,economy,technology and so on,and the choice of denitration technology is a complicated multi-index problem.How to effectively deal with the relationship between various factors and indexes is the urgently problem to be solved for refineries.It needs to establish a set of practical evaluation system,and then to select the suitable for different pollution situation of flue gas denitration technology.In this thesis,an evaluation was designed about six major denitration technologies?LoTOx TM,SCR,SNCR,de-NO_x additives,low nitrogen burner technology and SNCR-SCR?using fuzzy mathematic theory in three aspects of environment,economy and technology.And the evaluation value is?0.5417,0.6287,0.3715,0.5628,0.7654,0.4272?.This means that the applicability order of six technologies in turn is LoTOx TM,low nitrogen burner technology,SCR,de-NO_x additives,SNCR,SNCR-SCR.For SCR technology,MoO₃-WO₃/TiO2 catalysts with different contents of Mo supported on carrier of industrial titanium tungsten are prepared,and they are characterized by means of XRD?BET?TEM?UV-Vis DRS etc..And the catalytic activitives of the catalysts for deNO_x were evaluated by NH3-SCR reaction.NH3-SCR catalytic activity test results show that,the addition of Mo widens the active window of catalyst.When the Mo content is 6%,the catalyst gives the best catalytic activity.The highest denitration rate can reach 100%,and the conversion rate in the temperature from 300 oC to 530 oC can keep more than 80%.In order to improve the water resistance of the catalyst,beta molecular sieve doped titanium tungsten powder is prepared by mechanical mixing method,and the catalysts with 10% Mo content and different contents of beta molecular sieve are synthesized by stir-ultrasonic immersion method.NH3-SCR catalytic activity test results show that,the catalytic activity increases after doping beta molecular sieve within the temperature range of 325 oC to 525 oC.The activity of catalyst doping 10% beta molecular sieve increases by 5% 10%.Meanwhile,the NO conversion remains above 90% in the temperature window from 300 to 450 oC after the catalysts dope beta molecular sieve.