Understanding the Enhanced Catalytic Desulfurization Mechanism: Gas-Phase and Surface Reactions with a CuCeOx Catalyst under Nonthermal Plasma Conditions
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To understand the mechanisms of enhanced catalytic technologies under nonthermal plasma (NTP) conditions, complex surface processes must be assessed. However, the predictive capability of the Langmuir–Hinshelwood (L-H) and Eley–Rideal (E-R) processes is limited by various factors. The present study aimed to clarify the interaction mechanisms between NTP and catalysts in the enhancement process, explore the specific pathways of the enhancement process based on E-R and L-H model validations, and obtain data to support the rational design of NTP-enhanced catalytic processes. We investigated CuCeOx catalysts and SO2 removal reaction as a probing reaction using two enhancement scheme configurations, combined with gas-phase reaction process simulations. During the gas-phase reaction stage of the enhancement process, no significant differences were observed among the different configurations caused by the generation of radicals that were induced by N2 (A3Σu+)-excited species. However, introducing CuCeOx catalysts altered the enhancement process, and the placement of the catalyst influenced the corresponding desulfurization mechanism.Keywords:
Nonthermal plasma
A novel mechanism for the gas-phase Fe(CO)(5) and base catalyzed water gas shift reaction has been examined. The reaction pathway described here is predicted at the B3LYP/6-31++G(d,p) level to be energetically competitive with the classic mechanism. The reaction path explored here involves the energetically barrierless formation of (CO)(4)FeCOOH(-) (the catalyst of the system) decarboxylation induced by the addition of CO to give (CO)(4)FeCHO, and evolution of H(2) upon addition of H(2)O to the (CO)(4)FeCHO intermediate. The energetic barriers predicted for the last two steps are 21.2 and 42.0 kcal/mol, respectively, using the B3LYP method.
Water-gas shift reaction
Decarboxylation
Water gas
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A series of imitating tannin extract desulfurization solution that contained by-products of different concentration was prepared according to the accumulation process of by-products in desulfurization solution. The effect of by-products in desulfurization solution of tannin extract on desulfurization solution density was investigated. The conclusion was that the accumulation of by-products in tannin extract desulfurization solution made desulfurization solution density increase and the main factors which influenced tannin extract desulfurization solution density were Na2S2O3and NaSCN. Relation between desulfurization solution density and main by-products concentration was discussed. A good linear relationship was obtained through the regression analysis of experimental data by excel. Theory reference was offered to estimate density of tannin extract desulfurization solution in actual production.
Tannin
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The effect factors on carbide wet flue gas desulfurization were studied by orthogonal test and single-factor experiment,the mass transfer reaction model was established,too.The results show that the order of important factors is the ratio of liquid-gas(L/G) gas SO2 concentrationslurry pHcarbide concentrationAbsorption temperature.The ratio of liquid-gas,flue gas SO2 concentration,and slurry pH can improve the desulfurization rate significantly.The ratio of liquid-gas increases from 10 to 30,the desulfurization rate increases by 54.91% while dropped by 6.94% when L/G greater than 60.High flue gas SO2 concentration can improve the desulfurization efficiency increase,but when greater than 1 000×10-6,the desulfurization rate gradually declines.Increasing the slurry pH improved the desulfurization rates,the system desulfurization rate remaines above 90% at pH=9.The principle of carbide desulfurization is hydration and stabilization of SO2 by forming H+ and HSO-3.A stable compound CaSO3·2H2O is formed in this process to achieve flue gas desulfurization.The mass transfer-reaction process of flue gas desulfurization by carbide slug was established on film model,the reaction film of SO2 and HSO-3 was divided into 3 sections.
Reaction rate
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Based on sulfur dioxide absorbing dual film theory,the main factors that influenced desulfurization efficiency in wet limestone flue gas desulfurization process were analyzed.It would provide reference for other flue gas desulfurization system design.
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Reaction rate
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The power plants not only need to ensure stable operation of the desulfurization system,but also maintain high desulfurization efficiency,for meeting the requirement of the SO2 emission concentration.The wet desulfurization is a complex process,which includes SO2 absorption and chemical reaction;any factors that influence on the process will eventually have an impact on the desulfurization efficiency.Some measures are pointed out to improve the desulfurization efficiency by analyzing the main influence factors.
Absorption efficiency
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This paper studies the application of desulfurization additives in the desulfurization system for 600MW units, Results show that desulfurization additives have a positive effect on the desulphurization efficiency, and it can gain notable economic benefits when it guarantees the effective concentration of the desulfurization additives and the quantity of limestone
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Sulfur dioxide is a kind of poisonous and harmful gas, and will pollute atmosphere environment if exhaust it directly. There are a lot of desulfurization methods so far. The desulfurization efficiency of dry-desulfurization agent that is made under the same proportion, hydration temperature and hydration time is studied in this paper. The results indicate that the desulfurization efficiency of the pocket-fly ash increase while the desulfurization time and hydration time increase, and the desulfurization efficiency of the pocket-fly ash decrease while the desulfurization time and hydration temperature increase, and The desulfurization efficiency of pocket-fly ash is little lower than activity carbon, at the same time introduce the desulfurization mechanism.
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Slag (welding)
Ladle
Refining (metallurgy)
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According to test results and almost one year's application experiences of desulfurization additives in limestone-gypsum wet flue gas desulphurization system for a 600 MW thermal power generation unit,the effect of desulfurization additives on safe economic operation of desulfurization system and the attentions in the application process are analyzed in this paper.Results show that desulfurization additives can improve the efficiency of sulfur removal,reduce the operational cost,expand the scope of using fuel and enhance the flexibility of operation.Moreover,the effective concentration of the desulfurization additives and the quality of limestone should be guaranteed when the desulfurization additives are used.
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