Bench-Scale and Modeling Study of Sulfur Capture by Limestone in Typical CO<sub>2</sub> Concentrations and Temperatures of Fluidized-Bed Air and Oxy-fuel Combustion

Rahiala, Sirpa; Hyppänen, Timo; Pikkarainen, Toni

doi:10.1021/ef401971m

Cited by 10 publications

(5 citation statements)

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“…The dense CaSO 4 is the main reason for relatively low calcium utilisation for sulphur capture in fluidised bed combustion applications. It has been observed also in earlier experimental work [5][6] that the sulphur capture is worse in direct sulphation region but capture is enhanced by higher CO 2 partial pressure in indirect sulphation region. Only conditions in test 5 were clearly on CaCO 3 side of CaCO 3 -CaO equilibrium curve, when sulphur is directly captured by CaCO 3 without calcination.…”

Section: Pilot Scale Cfbsupporting

confidence: 72%

Development of 2nd Generation Oxyfuel CFB Technology – Small Scale Combustion Experiments and Model Development Under High Oxygen Concentrations

Pikkarainen

Saastamoinen

et al. 2014

Energy Procedia

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The 1 st generation oxyfuel CFB (Circulating Fluidised Bed) technology has been demonstrated up to 30MW th scale and the commercial concept for 300 MW e air/oxy flexible CFB power plant is available. Currently, the development of 2 nd generation oxyfuel CFB technology is ongoing aiming to reduce significantly -around 50% -the overall efficiency penalty of CO 2 capture in power plants compared to 1 st generation concepts. The 2 nd generation oxyfuel CFB plants are designed only to oxyfuel operation with CCS.The experimental results of the test campaigns with 0.1 MW th pilot scale CFB unit and laboratory scale BFB (Bubbling Fluidised Bed) unit under high oxygen concentrations of feed gas are presented. The pilot scale tests were carried out with Spanish anthracite and petroleum coke mixture and with Polish bituminous coal. Two Spanish limestone types were used for infurnace sulphur capture. Test matrix of pilot scale CFB unit contained 11 test balances with varying feed gas O 2 concentrations (between 21…42 vol-%) and O 2 staging to primary and secondary gas feeds (primary gas O 2 share 50…80 vol-%) at different bed temperature levels (820…920ºC). Combustion performance and emission formation was studied at air combustion and varying oxyfuel combustion conditions.The fuel impulse tests with laboratory scale BFB included 16 tests with Spanish anthracite and Polish bituminous coal in varying feed gas O 2 concentrations (5…50 vol-%) with two fuel size fractions (0.5-2.0 mm and 4.0-8.0 mm) at constant bed temperature level (850ºC). The main objective was study how high O 2 concentration effects on char reactivity and formation of nitrogen oxide emissions.Toni Pikkarainen et al. / Energy Procedia 63 ( 2014 ) 372 -385 373 A one dimensional model for laboratory scale BFB was used to further develop existing sub-models' descriptions and parameters in the one dimensional model (1D-model) for pilot scale CFB in order to improve modelling capabilities in oxygen combustion conditions. Firstly the sub-models' equations for different phenomenon -e.g. pyrolysis, char combustion and reactions of nitrogen species -were implemented and validated with bench scale experimental data. Secondly, the sub-model parameters found in bench scale modelling for char reactivity and NO x formation were implemented to the 1D-model of pilot scale CFB combustor. According to the results of the validation modelling against pilot scale experimental results, the combustion was successfully scaled up as the modelled temperature profiles and flue gas oxygen contents were well in line with measurements. Anyhow, further validation of the combustion model is needed by modelling of dynamic responses of pilot scale experiments. The pilot scale 1D-model was not able to predict NO x formation with the sub-model adapted from the bench scale model. Further model development and experimental work are needed with different particle size fractions at different operating conditions. The improved modelling capabilities under high oxygen concentrations can be utiliz...

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Section: Pilot Scale Cfbsupporting

confidence: 72%

Development of 2nd Generation Oxyfuel CFB Technology – Small Scale Combustion Experiments and Model Development Under High Oxygen Concentrations

Pikkarainen

Saastamoinen

et al. 2014

Energy Procedia

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“…A calcination and sulfation model established by Keener et al [32] showed that calcination had an influence on sulfation of limestone in typical air-fired CFBB conditions, but how calcination was influenced by sulfation was not described. Several experiments were conducted by Rahiala and Takkinen [33,34] with a bench-scale bubbling fluidized-bed reactor to study the influence of temperature and CO 2 concentration on sulfur capture of limestone, but bubbling fluidized-bed reactor cannot give precise chemical kinetics curves to analyze every stage of the reaction, and more importantly, their tests did not focus on the condition in real air fired CFBBs. An investigation by Olas et al [35] on mechanical activation of limestone under high concentrations of CO 2 in CFBB found that both the diffusion of SO 2 and CO 2 could be limited by the formation of CaSO 4 layer on the surface of the limestone particles, and mechanical treatment may increase both the sorbent calcination and sulfation rates.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous calcination and sulfation of limestone in CFBB

Wang

Chen

Jia³

et al. 2015

Applied Energy

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“…That is why it is widely acknowledged and applied. There have been various studies about the technology of desulfurization at high temperatures in the boiler where coal is fired with biomass, , the effect of CO 2 in oxy-fuel combustion, , and modification of sorbents. , However, the problem on utilization of sorbents is still unsolved.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Impacts of Impurities and Water Vapor on Limestone Calcination in a Laboratory-Scale Fluidized Bed

et al. 2015

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In-furnace desulfurization has been widely used in circulating fluidized bed boilers. SO 2 is removed by reacting with limestone during the process of sulfation after calcination in air combustion. Although CaCO 3 is the main component of limestone, there are also other impurities such as CaMg(CO 3 ) 2 and SiO 2 which can influence the desulfurization. The porous CaO produced by calcination plays an important role in sulfation, and water vapor in the furnace influences the calcination. This work aims to understand the impacts of impurities and water vapor on limestone calcination. Two kinds of China limestone were used to investigate the issues in a rotatable fluidized bed reactor. Mercury injection apparatus (MIP), scanning electron microscope−energy dispersive spectrometer (SEM-EDS), and X-ray diffraction (XRD) techniques were employed to analyze the pore structure, micromorphology, and crystal structure of the CaO calcined, respectively. The results show that the water vapor improves the calcination rate and shortens the reaction time, and those influences are stronger for higher impurity limestone possibly because of more defects in the crystal structure. Water vapor can directly influence the chemical reaction of calcination without affecting the diffusion property of CO 2 . Higher water vapor content results in slightly lower ultimate degree of conversion of limestone, but for different kinds of limestone the difference is not obvious. The results of SEM and MIP also mean that the existence of water vapor improves sintering and growth of grains. The results of XRD give further evidence to the previous conclusion. These tests and analysis give rise to the mechanisms behind the impacts of water vapor on limestone calcination: the binding ability of H 2 O to active site O* in Ca−O is stronger than that of CO 2 . H 2 O tends to replace CO 2 on the active site to increase the release of CO 2 in calcination. Water vapor also accelerates sintering, most possibly in the initial stage when the sintering neck is formed. There exist two possibilities: H 2 O molecules are absorbed on the active site of Ca−O* to promote the formation of the sintering neck of CaO by interaction between H 2 O molecules (such as hydrogen bond). Water vapor can also act as a solvent to improve the solid state diffusion from surface to sintering neck which also benefits the fusion and growth of minicrystals.

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Bench-Scale and Modeling Study of Sulfur Capture by Limestone in Typical CO₂ Concentrations and Temperatures of Fluidized-Bed Air and Oxy-fuel Combustion

Cited by 10 publications

References 29 publications

Development of 2nd Generation Oxyfuel CFB Technology – Small Scale Combustion Experiments and Model Development Under High Oxygen Concentrations

Development of 2nd Generation Oxyfuel CFB Technology – Small Scale Combustion Experiments and Model Development Under High Oxygen Concentrations

Simultaneous calcination and sulfation of limestone in CFBB

Understanding the Impacts of Impurities and Water Vapor on Limestone Calcination in a Laboratory-Scale Fluidized Bed

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Bench-Scale and Modeling Study of Sulfur Capture by Limestone in Typical CO2 Concentrations and Temperatures of Fluidized-Bed Air and Oxy-fuel Combustion

Cited by 10 publications

References 29 publications

Development of 2nd Generation Oxyfuel CFB Technology – Small Scale Combustion Experiments and Model Development Under High Oxygen Concentrations

Development of 2nd Generation Oxyfuel CFB Technology – Small Scale Combustion Experiments and Model Development Under High Oxygen Concentrations

Simultaneous calcination and sulfation of limestone in CFBB

Understanding the Impacts of Impurities and Water Vapor on Limestone Calcination in a Laboratory-Scale Fluidized Bed

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Bench-Scale and Modeling Study of Sulfur Capture by Limestone in Typical CO₂ Concentrations and Temperatures of Fluidized-Bed Air and Oxy-fuel Combustion