Kinetics and Mechanism of Sulfite Oxidation in the Magnesium-Based Wet Flue Gas Desulfurization Process

Shen, Zhongjin; Guo, S.Y.; Kang, Wanzhong; Zeng, Kun; Yin, Ming; Tian, Jun; Lu, Jun

doi:10.1021/ie300163v

Cited by 61 publications

(39 citation statements)

References 30 publications

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“…Figure 7 showed that when the pH was increased from 5.0 to 7.0, the constant increase in the oxidation capability of dissolved oxygen engendered an increase in the oxidation rate. This phenomenon is consistent with the results reported by Shen [3]. When the pH was increased from 7.0 to 9.0, the constantly increasing OH 2 could easily combine with the transition metal Co on the surface of the catalyst, covering active sites and inducing catalyst deactivation; this led to a continuous drop in the oxidation rate of magnesium sulfite.…”

Section: Kinetics Of Catalytic Oxidation Of Magnesium Sulfitesupporting

confidence: 92%

Kinetics of magnesium sulfite oxidation catalyzed by cobalt using a straw/sludge substrate as support

Wang

Zhang

et al. 2018

Env Prog and Sustain Energy

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Oxidation of magnesium sulfite is a key step in the wet magnesia desulfurization. Using the mixture of waste corn stalk (CS) and activated sludge (AS) as a support, the cobalt‐based catalyst was prepared by the impregnation method to promote the oxidation rate. The results indicated that the catalysis performance is highly dependent on the ratio of CS/AS in which 8:2 is the optimal, and that with the cobalt loading of 0.6% dominates the catalytic activity. The physicochemical properties of catalyst were identified by FTIR, XRD, TEM and XPS to reveal the catalytic mechanism. The catalyzed oxidation kinetics of magnesium sulfite was investigated in a bubbling tank. The reaction orders with respect to catalyst, magnesium sulfite and oxygen were achieved to be 0.75, 0 and 0.67, respectively. The apparent activation energy were derived as 34.9 kJ·mol−1. Integrating with a three‐phase reaction model, it was inferred that the overall oxidation is controlled by the inner diffusion of oxygen. The research results can serve as a reference for the development of low‐cost catalytic techniques for the magnesia desulfurization. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 201–207, 2019

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Section: Kinetics Of Catalytic Oxidation Of Magnesium Sulfitesupporting

confidence: 92%

Kinetics of magnesium sulfite oxidation catalyzed by cobalt using a straw/sludge substrate as support

Wang

Zhang

et al. 2018

Env Prog and Sustain Energy

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“…AISI 1010) contains a significant amount of Mn, which can be corroded into Mn 2+ ion. This ion has a catalytic oxidation effect on sulfite [38]. The catalytic oxidation rate of sulfite is generally expressed as [39],…”

Section: Water Film Region Equationsmentioning

confidence: 99%

A comprehensive predictive corrosion model incorporating varying environmental gas pollutants applied to wider steel applications

Nazir

Saeed²,

Khan

2017

Materials Chemistry and Physics

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A comprehensive model has been developed to predict uniform corrosion rate of structural steel under the effect of low pH conditions for example acid rain. Acid rain is mainly caused by emissions of sulfur dioxide (SO 2 ) which reacts with the water droplets in atmosphere to produce acidic solution which is the primary cause of corrosion of steel structures such as bridges, and weathering of stone buildings and statues. A five-stage division was applied to mathematically describe the model as: (i) the growth rate of air-suspended water droplets (i.e. moisture) depending on the condensation/evaporation rate, (ii) the absorption of gas phase SO 2 in the droplets forming bisulfite HSO 3 − ions, (iii) the coalescence of these SO 2 absorbed water droplets under the effects of wind speed and gravity, (iv) the deposition rate of SO 2 absorbed droplets on steel substrate depending on the inclination and azimuth angles of steel surfaces and, (v) the corrosion rate of steel due to the deposition of these SO 2 absorbed droplets. The incorporation of all the above stages develops a comprehensive corrosion prediction model which not only includes the electrochemical parameters but also large number of physical, environmental and material parameters. Experiment was performed to analyse the corrosion rate of steel samples by exposing them to moist SO 2 corrosion test. A comparative analysis between the model predictions and experimental results was performed to verify the reliability of model. The predictive trends of corrosion rate of steel were also generated for different values of temperature, relative humidity, and SO 2 mole percentage.

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“…However, MgO flue gas desulfurization features high desulfurization efficiency, low energy consumption, less investment requirement, and reliable operation; thus, it satisfies the ultra-low emission requirements of industrial boilers under fluctuating flue gas conditions. Moreover, magnesium sulfate, which is obtained as the desulfurization product, can be used as an industrial raw material or agricultural fertilizer and has a high economic value [5][6][7]. To prevent the crystallization of magnesium sulfate in the absorption tower in a traditional magnesia desulfurization process, the concentration of magnesium sulfate in the desulfurization solution should be controlled below 10%.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Catalysis of Sulfite Oxidation and Uptake of Heavy Metals by Bifunctional Activated Carbon Fiber in Magnesia Desulfurization

Wang

et al. 2020

Catalysts

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Sulfite and heavy metals are crucial pollutants in the slurry produced by flue gas desulfurization. In this study, a novel cobalt-based activated carbon fiber (Co-ACFs) catalyst-adsorbent was synthesized using an impregnation method; this bifunctional catalyst-adsorbent was used in wet magnesia desulfurization for the simultaneous catalytic oxidation of magnesium sulfite and uptake of heavy metal (Hg 2+ , Cd 2+ , and Ni 2+ ) ions. The morphology and surface chemistry of ACFs before and after cobalt loading were investigated using various characterization methods. The kinetics on catalytic oxidation of magnesium sulfite was investigated, and the effects of operation conditions on the simultaneous adsorption capacity of heavy metals were examined. Relative to a non-catalysis material, the 40% Co-ACFs material increased the oxidation rate of magnesium sulfite by more than five times. The Langmuir model can describe the adsorption behavior of Co-ACFs on Hg 2+ , Cd 2+ , and Ni 2+ , indicating that the simultaneous uptake of heavy metals is a single-layer adsorption process. The maximum adsorption capacities for Hg 2+ , Cd 2+ , and Ni 2+ are 333.3, 500, and 52.6 mg/g, respectively. A pseudo-second-order model confirmed that the removal of heavy metals is controlled by the chemisorption process.Catalysts 2020, 10, 244 2 of 18 oxidation rate of magnesium sulfite, the oxidation is difficult to accomplish in a real desulfurization process. This problem has become the paramount bottleneck of the oxidation enrichment technology. The excessive sulfite might exhaust the dissolved oxygen in the effluent and decomposed into SO 2 , resulting in further environmental risks. Meanwhile, a large number of heavy metal particles are collected in the desulfurization slurry, which can migrate and transform during the desulfurization process. For example, Hg 2+ present in the desulfurized slurry is easily released into the atmospheric environment because the ion is reduced to Hg 0 by sulfite [9][10][11]. Some co-existing Cd 2+ ions may co-crystallize with the saturated magnesium sulfate in the recovered products to cause secondary pollution. Therefore, the simultaneous removal of heavy metals from desulfurized slurries becomes another technical problem for magnesium sulfate recovery.Studies have shown that transition metal ions such as Co 2+ , Mn 2+ , Fe 2+ , and Cu 2+ can be used for improving the oxidation rate of sulfite. Among these ions, Co 2+ exhibits the highest performance in terms of sulfite oxidation [12]. However, separating the homogeneous catalyst from the desulfurization slurry is difficult and the material must be supplemented continuously, thus resulting in a high operation cost and secondary pollution due to the use of magnesium sulfate products. To address this problem, our research group developed a series of cobalt-based heterogeneous catalysts [13-18] by using impregnation, coprecipitation, and hydrothermal synthesis. These catalysts effectively solved the catalyst separation problem. However, a magnesium desulfurizat...

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Kinetics and Mechanism of Sulfite Oxidation in the Magnesium-Based Wet Flue Gas Desulfurization Process

Cited by 61 publications

References 30 publications

Kinetics of magnesium sulfite oxidation catalyzed by cobalt using a straw/sludge substrate as support

Kinetics of magnesium sulfite oxidation catalyzed by cobalt using a straw/sludge substrate as support

A comprehensive predictive corrosion model incorporating varying environmental gas pollutants applied to wider steel applications

Simultaneous Catalysis of Sulfite Oxidation and Uptake of Heavy Metals by Bifunctional Activated Carbon Fiber in Magnesia Desulfurization

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