670t-h多燃料切圓鍋爐NOx生成與排放控制數值模擬.pdf

1、Air Quality Standardsare requiring increasingly stringent ozoneemissions from numerous furnaces in the chemical process industry.NOxemissions have been identifiedasamajor contributor to ground-level ozone.Available techn

2、ical solutions range from Co-firing pulverized coal combustiontechnologyandaddition of Separated OverfireAir or(overfireair)systems topost-combustion control methods suchas selective non-catalytic ReductionSNCR.This diss

3、ertation describes(Chinese Power Station),approach to NOxcontroland its use of CFD modelingasan integral tool in the designandimplementation of NOx reduction technologies ina200MW Tangentiallycoal-fired utility boilerapp

4、lications.Several technologies were presented onhow(Chinese Power Station),has used CFD modelingand measuring datatodevelop the combustion performance upgradesand modifications for reducingNOx emissions on real size tang

5、entially fired utility boiler.They involve thestaging of furnace combustion with co-firing of coal combustion(two fuelsystemsand three fuel systems),separated overfireair(SOFA)and selectivenon-catalytic Reduction(SNCR)to

6、 reduce NOx emissions from the tangential-fired utility furnace.Furnace simulations were used to optimize theamount offlow rate of co-firing fuels,also to optimize the OFAport placementas wellas to identify locations of

7、highest emission concentration.The co-combustionconsequence of coaland blast furnace gas BFG(two fuel system),on furnacecombustion'performance,and NOx destruction,was investigated.The overallfurnace temperature distribut

8、ion was decreased with the maximum range1601-1722k,that cause to reduce the NOx formed in the main combustionzone by37.5％.Inaddition,the concentration of02decreasedalong thefurnace with maximum exit percentage of2.O％.Fin

9、ally for the two-fuelsystem.The two methods probability density function method,and eddydissipation method were investigated.The results showaqualitativelyagreeswell with each other,with negligible variation onall measur

10、ed parameters.
　　Foradvance co-combustion technique of coal,BFG,and coke oven gas(COG),the eddy dissipation model was used to perform the numericalsimulation of three-fuel combustion inautility boiler,and to simulate

11、theturbulent gas-phase reaction The validated CFD model is thenapplied toinvestigate the effects of different BFGand COG flow rates on the boilerperformance.It is found that increasing the BFG flow rate brings negativeef

12、fects on the ignition of primaryairand pulverized-coal mixture,pulverized-coal burnout,and heat transfer in the furnaceand,consequently,decreases thethermal efficiency.However,increasing the COG flow rate can increase th

13、ethermal efficiency viaimproving the pulverized-coal burnoutand heat transfer.Increasing both the BFGand COG flow rates is favorable to reducing NOemissions.The resultsalso indicate that co-firing pulverized coal with BF

14、G ofabout20％heat inputand COG ofabout10％heat input isan optimaloperating condition for improving the boiler performanceat180MW load.The validated CFD model is thenapplied to investigate the effects on thetemperatureand v

15、elocity deviationsalong the upper furnace width.It is foundthat the maximum temperature deviation isabout200Kalong the furnacewidth of the boiler load of180MW.The temperature in the right side ishigher than that in the l

16、eft side.With the increase of BFG flow rate,both thetemperatureand velocity deviations decrease.It indicates increasing the BFGflow rate have little effect on the temperatureand velocity deviationalong thefurnace width.T

17、he COG was conductedas reburning fuel,because of itscontent hydrocarbons.When the COG flow rate increased100％,the in-furnace temperature decreased,and has more effect on NOx reduction.For theflue gas's treatment(flue gas

18、es washing out),the separated overfireair(SOFA)and selective non-catalytic reduction techniques were used to evaluate theNOx destruction through boiler.Firstly,the boiler was simulated under fullload180MWand20％overfireai

19、r.The result shows for the exitingtangentially fired boiler with SOFAgroup location(2and4meter)upper thereburningzone,the NOx destructionabout63％.
　　Finally,the ureawas usedas SNCR reagent.Numerical simulation wascond

20、ucted using CFD code to investigate the SNCR technology on NOxreduction,for three types of coal under three different loads.The resultsobtained theaverage NOx emissionsat full,medium,and lower load rangefrom290-491,226-4

21、80,and166-350ppm respectively.The NOx reductionsfor these three loads ranged from39.69％,and61.59％percent.While theresults varied from coal type-to-coal type for the same boiler load.Inaddition,the urea(NH3)slip for these