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Study On The Adsorption Removal Of SO2 And NOx From Flue Gas With Industrial Semi-Cokes

Posted on:2008-03-03Degree:DoctorType:Dissertation
Country:ChinaCandidate:D S XingFull Text:PDF
GTID:1101360242486942Subject:Thermal Engineering
Abstract/Summary:PDF Full Text Request
Activated industrial semi-coke can be used to remove SO2 and NOx from flue gas without any wastes produced. It is compliant with resources-conservation-oriented society and recycling economy. It can be utilized for pollution control of small and medium-scale boilers, industrial furnaces and other industrial equipments, and has broad applicational prospects.Twelve coal cokes or coal gasification specimens are gathered, and component analysis and pore structure analysis are conducted. The experimental testrigs of water vapor activation are designed and built. Optimal water vapor activation parameters are obtained for bituminous coal semi-cokes and activation semi-coke samples with excellent performances are produced. Based on fractal theory perspective,the fractal characteristic of the semi-cokes are calculated before and after activation. A significant pore characteristic of activated samples is found. A experimental testrig for semi-cokes adsorbing SO2 and/or NOx are designed and built. The breakthrough curves are obtained through experiments,and the adsorption performances of the samples are evaluated. The adsorption competition is approved when SO2 and NOx coexist. The diffusion control mechanism of the mass transfer process in SO2 adsorption is clarified. Time-averaged mass transfer coefficient is proposed and is correlated with experimental data. Density functional theory is applied to calculate the adsorption potential and density distribution of SO2 and NO,so the essence of adsorption competition of SO2 and NO are revealed from microscale.After activation, the intruded volume and the specific surface area of micropore increase more remarkablely than those of larger radius pores. The BET specific surface areas of the activated samples are all over 600m2/g. The pores with radius of less then 10nm increase more remarkablely. There is dense pore distribution around radius of 3nm in activated samples. Samples have fractal characteristic whether activated or not, but activated samples have more remarkable fractal characteristic and larger calculated fractal dimensions. The adsorption capacity for unit mass activated adsorbent is 210 mg/g,which is 13.5 times of original semi-cokes. SO2 and NOx can be absorbed by semi-cokes, but adsorption capacity to absorb SO2 is larger than that to NOx. There is adsorption competition when SO2 and NOx coexist.Time-averaged mass transfer coefficient is proposed, which can evaluate mass transfer rate in a adsorption process quantitatively. Regression expression indicates that to increase adsorption bed temperature or gas flow rate can induce the increment of the time-averaged mass transfer coefficient.DFT theoretical calculations show that the absolute values of adsorption potentials that the carbon atoms in semi-cokes impose on the molecules of SO2 are larger than those of NO. Hence, semi-cokes absorb SO2 more easily when SO2 and NO coexist. The maximum of density distribution of SO2 is larger than that of NO,which predicts the adsorption quantity of SO2 is larger than that of NO under similar operating conditions.
Keywords/Search Tags:semi-coke, activation, pore structure, fractal dimension, adsorption, mass transfer coefficient, density functional theory
PDF Full Text Request
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