Simultaneous calcination and sulfation of limestone in CFBB

Wang, Chunbo; Chen, Liang; Jia, Lei; Tan, Yewen

doi:10.1016/j.apenergy.2015.05.070

Cited by 29 publications

(24 citation statements)

References 33 publications

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“…One more phenomenon to be noted in Figure b is that the samples under all four conditions were calcined completely at 300 s. This is different from the findings on Massicci limestone in the work of Wang et al, where they found that the samples which experienced 90 min of reaction still contained 3%–5% mass fraction of undecomposed CaCO 3 . The reason may be that the sulfation reactivity of the limestone used in the present work is lower than for Massicci limestone, as has been pointed out elsewhere …”

Section: Resultscontrasting

confidence: 75%

“…But it should be noted that in the simultaneous calcination/sulfation reaction, the minimum mass point occurs when the mass loss rate caused by the calcination reaction equals the mass gain rate caused by the sulfation reaction, not the end of the calcination reaction or the beginning of the sulfation reaction like that in the calcination‐then‐sulfation reaction. This means that both calcination and sulfation reactions occur in both stages in the simultaneous calcination/sulfation reaction . The mass‐growth stage can also be divided into two stages according to the sulfation rate, namely the fast‐sulfation stage (from the minimum mass point to 40 min) and the slow‐sulfation stage (beyond 40 min).…”

Section: Resultsmentioning

confidence: 99%

“…The actual process proceeds as follows: after limestone reaches hot flue gases containing SO 2 , the calcination and sulfation reactions occur simultaneously, and the two reactions affect each other. We call this process the “simultaneous calcination/sulfation of limestone” and have carried out preliminary investigations on it . Some important phenomena were demonstrated in our earlier work, in particular, the decomposition rate of limestone particles was impeded by SO 2 , and some of the CaCO 3 did not decompose completely even after 90‐min reaction in the presence of 0.38% SO 2 .…”

Section: Introductionmentioning

confidence: 98%

“…It is worth noting that the issue of reaction product interfering with limestone calcination is not only limited to SO 2 capture in CFBs, but is also important for other processes like CO 2 capture by calcium looping . Therefore, in our previous work, the characteristics of the simultaneous calcination/sulfation reaction were investigated by thermogravimetric analysis (TGA).…”

Section: Introductionmentioning

confidence: 99%

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The combined effect of H₂O and SO₂ on the simultaneous calcination/sulfation reaction in CFBs

et al. 2019

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The combined effect of H2O and SO2 on the reaction kinetics and pore structure of limestone during simultaneous calcination/sulfation reactions under circulating fluidized bed (CFB) conditions was first studied in a constant‐temperature reactor. H2O can accelerate the sulfation reaction rate in the slow‐sulfation stage significantly but has a smaller effect in the fast‐sulfation stage. H2O can also accelerate the calcination of CaCO3, and should be considered as a catalyst, as the activation energy for the calcination reaction was lower in the presence of H2O. When the limestone particles are calcining, SO2 in the flue gas can react with CaO on the outer particle layer and the resulting CaSO4 blocks the CaO pores, increases the diffusion resistance of CO2, and, in consequence, decreases the calcination rate of CaCO3. Here, gases containing 15% H2O and 0.3% SO2 are shown to increase the calcination rate. This means that the accelerating effect of 15% H2O on CaCO3 decomposition is stronger than the impeding effect caused by 0.3% SO2. The calcination rate of limestone particles was controlled by both the intrinsic reaction and the CO2 diffusion rate in the pores, but the intrinsic reaction rate played a major role as indicated by the effectiveness factors determined in this work. This may explain the synergic effect of H2O and SO2 on CaCO3 decomposition observed here. Finally, the effect of H2O and SO2 on sulfur capture in a 600 MWe CFB boiler burning petroleum coke is also analyzed. The sulfation performance of limestone evaluated by simultaneous calcination/sulfation is shown to be much higher than that by sulfation of CaO. Based on our calculations, a novel use of the wet flue gas recycle method was put forward to improve the sulfur capture performance for high‐sulfur low‐moisture fuels such as petroleum coke. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1256–1268, 2019

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Section: Resultscontrasting

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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The combined effect of H₂O and SO₂ on the simultaneous calcination/sulfation reaction in CFBs

et al. 2019

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“…In our preliminary previous work [30,31], the simultaneous calcination and sulfation of limestone in CFBs was investigated and from this work some important observations were made. First, the weight loss rate was slower for limestone calcined with SO2; and second, some CaCO3 was still undecomposed after 90 min of reaction [31]. However, two questions still remained: how the SO2 influenced the calcination rate of limestone; and by what mechanism this influence occurs.…”

Section: Introductionmentioning

confidence: 99%

The kinetics and pore structure of sorbents during the simultaneous calcination/sulfation of limestone in CFB

Chen

Wang

et al. 2017

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The interaction of calcination and sulfation in the simultaneous calcination/sulfation of limestone sorbent under circulating fluidized bed boiler conditions was studied. A specially designed constant-temperature reactor which can stop the reaction at a given time was employed. When limestone entered the furnace of mixed gases of CO2, O2, SO2, etc., its weight went down first, then up, so there was a minimum weight point. The whole reaction period could be divided into two stages by this minimum weight point, named the weight-loss stage and the weight-growth stage, which were dominated by the calcination reaction and by the sulfation reaction, respectively. In the weight-loss stage, the sulfation reaction took place and CaSO4 formed simultaneously together with limestone calcination as long as SO2 was present. In the weight-growth stage, the sulfation ratio at 60 min in simultaneous calcination/sulfation is 30.7% higher than that in the sequential calcination then sulfation process. The weight loss rate of limestone calcined in the presence of SO2 was lower than that without SO2 present but the final weight was higher. The calcination of limestone was slowed by the presence of SO2; a probable mechanism was proposed, namely that the CaSO4 formed may fill or plug the pores in the CaO layer, and impede the transfer of CO2 and, therefore, retard the calcination reaction. This mechanism was supported by the observation that the effective diffusion coefficient of CO2 in CaO produced in the presence of SO2 was reduced. The impeding effect increased with increasing SO2 concentration (0-3000 ppm), while, when the particle size decreased from 0.4-0.45 mm to 0.2-0.25 mm, the calcination rate of limestone was higher, no matter whether there was SO2 present or not. The impeding effect was less pronounced at 880°C than at 850°C. The reason for this appears to be the fact that there was less CaSO4 formed at 880°C and, therefore, fewer pores of the particle were filled or plugged.

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Experimental study and parametric analysis of SO₂ capture in limestone fixed bed reactor

Bontzolis

Petraki

Spartinos

2019

J of Chemical Tech & Biotech

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BACKGROUND The use of absorbents, based on calcium, for the reduction of sulfur dioxide (SO2) emissions from power plants has been studied for the last 90 years. The present work is part of a research project, which aims at the development of a fixed and a moving bed limestone filter. A filter is placed after the burning, in order to capture SO2 from the flue gases of pulverized lignite combustors. An experimental study and a parametric analysis in a limestone and lignite fixed bed reactor for SO2 capture were conducted in previous works. RESULTS This work studies experimentally the SO2 capture by analyzing the following parameters: inlet mole fraction of SO2, inlet mole fraction of O2, volumetric flow rate, average temperature in bed, type of calcium carbonate (CaCO3) and length of the solid bed. Under specific circumstances, conversion of SO2 values were found to be greater than 0.99 in the gas outlet for more than 110 min. CONCLUSION Useful conclusions are drawn regarding the behavior of a fixed bed reactor in different conditions. The results highlight the importance of technological interest in the dry process for SO2 capture. © 2019 Society of Chemical Industry

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Simultaneous calcination and sulfation of limestone in CFBB

Cited by 29 publications

References 33 publications

The combined effect of H₂O and SO₂ on the simultaneous calcination/sulfation reaction in CFBs

The combined effect of H₂O and SO₂ on the simultaneous calcination/sulfation reaction in CFBs

The kinetics and pore structure of sorbents during the simultaneous calcination/sulfation of limestone in CFB

Experimental study and parametric analysis of SO₂ capture in limestone fixed bed reactor

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Simultaneous calcination and sulfation of limestone in CFBB

Cited by 29 publications

References 33 publications

The combined effect of H2O and SO2 on the simultaneous calcination/sulfation reaction in CFBs

The combined effect of H2O and SO2 on the simultaneous calcination/sulfation reaction in CFBs

The kinetics and pore structure of sorbents during the simultaneous calcination/sulfation of limestone in CFB

Experimental study and parametric analysis of SO2 capture in limestone fixed bed reactor

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The combined effect of H₂O and SO₂ on the simultaneous calcination/sulfation reaction in CFBs

The combined effect of H₂O and SO₂ on the simultaneous calcination/sulfation reaction in CFBs

Experimental study and parametric analysis of SO₂ capture in limestone fixed bed reactor