Modeling the behavior of limestone particles in oxy-fuel CFB processes

Rahiala, Sirpa; Myöhänen, Kari; Hyppänen, Timo

doi:10.1016/j.fuel.2013.08.019

Cited by 24 publications

(13 citation statements)

References 43 publications

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“…In oxy-fuel CFB combustors, sulfation can occur directly without the calcination step (Equation (3)). Theoretical calculations [20][21][22] and a previous study in a lab-scale fluidized bed batch reactor [23] revealed that carbonate minerals do not fully decompose under oxy-fuel combustion environment and the sulfur binding rate decreases, similar to the experiments of Li et al [24]. On the contrary, some other experiments [18,25,26] showed a decrease in sulfur emissions or increased sulfur capture efficiency when applying oxy-combustion.…”

Section: Introductionsupporting

confidence: 78%

Ash and Flue Gas from Oil Shale Oxy-Fuel Circulating Fluidized Bed Combustion

et al. 2018

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Carbon dioxide emissions are considered a major environmental threat. To enable power production from carbon-containing fuels, carbon capture is required. Oxy-fuel combustion technology facilitates carbon capture by increasing the carbon dioxide concentration in flue gas. This study reports the results of calcium rich oil shale combustion in a 60 kW th circulating fluidized bed (CFB) combustor. The focus was on the composition of the formed flue gas and ash during air and oxy-fuel combustion. The fuel was typical Estonian oil shale characterized by high volatile and ash contents. No additional bed material was used in the CFB; the formed ash was enough for the purpose. Two modes of oxy-fuel combustion were investigated and compared with combustion in air. When N 2 in the oxidizer was replaced with CO 2 , the CFB temperatures decreased by up to 100 • C. When oil shale was fired in the CFB with increased O 2 content in CO 2 , the temperatures in the furnace were similar to combustion in air. In air mode, the emissions of SO 2 and NO x were low (<14 and 141 mg/Nm 3 @ 6% O 2 , respectively). Pollutant concentrations in the flue gas during oxy-fuel operations remained low (for OXY30 SO 2 < 14 and NO x 130 mg/Nm 3 @ 6% O 2 and for OXY21 SO 2 23 and NO x 156 mg/Nm 3 @ 6% O 2 ). Analyses of the collected ash samples showed a decreased extent of carbonate minerals decomposition during both oxy-fuel experiments. This results in decreased carbon dioxide emissions. The outcomes show that oxy-fuel CFB combustion of the oil shale ensures sulfur binding and decreases CO 2 production.

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Section: Introductionsupporting

confidence: 78%

Ash and Flue Gas from Oil Shale Oxy-Fuel Circulating Fluidized Bed Combustion

et al. 2018

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“…Oxy-fuel combustion in a CFB for CO 2 capture has been rarely studied so far [20][21][22][23][24][25][26][27][28]. Most of those studies considered bituminous coals and lignites, and some of the studies considered biomass fuels.…”

Section: Introductionmentioning

confidence: 99%

Calculation of the Amount of Estonian Oil Shale Products From Combustion in Regular and Oxy-Fuel Mode in a CFB Boiler

Konist¹,

Loo²,

Valtsev³

et al. 2014

Oil Shale

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Oxy-fuel combustion is considered as one of the promising carbon capture and storage (CCS) technologies for coal-fired boilers. In oxy-fuel combustion, the combustion gases are oxygen and the recirculating flue gas, and the main components of the combustion gas are O 2 , CO 2 and H 2 O [1]. The paper presents the results of the calculation of the flue gas amount during combustion of oil shale using oxy-fuel technology in a circulated fluidized bed (CFB) mode. The calculations were performed for different oil shale heating values and different recycled flue gas (RFG) ratios. Oxy-fuel combustion with flue gas recycling was found to enable the decrease of the extent of carbonate minerals decomposition (ECD), thereby increasing the amount of heat released per 1 kg of fuel. To minimize ECD, the recycled flue gas ratio should be maintained at a level higher than 0.7. This condition allows an increase of the partial pressure of CO 2 over the equilibrium state line of calcite decomposition reaction at the bed temperature. The decrease of ECD was observed up to CO2-min 0.28. k = The decrease of CO2 k leads to an additional increase in the amount of heat released during oil shale combustion per 1 kg and, depending on the mean lower heating value (LHV), the heat can be increased up to 0.34 MJ/kg. A comparison with the bituminous and anthracite coals revealed that the specific emission of CO 2 per input fuel energy for oil shale is expected to be even smaller compared with those of the considered coals.

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“…When the oxyfuel combustion process is investigated the composition of the oxidizer mixture injected to combustion chamber plays crucial role on the behaviour of the combustion process and heat exchange within the combustion chamber [21]. Based on the works [19] and [22] it can be observed that when the volume fraction of oxygen in oxidizer composition is kept close to 30% the combustion process under oxy-fuel mode has comparable trends with air-fuel combustion process. The idea behind selecting the oxygen fraction from range 27%e32% was to check the numerical model flexibility and its possibility to follow the changing of oxidizer composition, and its influence on overall combustion process within the boiler.…”

Section: (Left)mentioning

confidence: 99%

Numerical simulations of the industrial circulating fluidized bed boiler under air- and oxy-fuel combustion

Adamczyk

Kozołub

Klimanek

et al. 2015

Applied Thermal Engineering

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h i g h l i g h t s g r a p h i c a l a b s t r a c tHybrid Euler-Lagrange approach was used for modelling particle transport, air-and oxy-fuel combustion process. Numerical results were validated against measured data. The influence of different boiler operating conditions on calculated temperature profile was investigated. New strategy for resolving particle transport in circulating fluidized bed was shown. a b s t r a c tMeasured and numerical results of air-fuel combustion process within large scale industrial circulating fluidized bed (CFB) boiler is presented in this paper. For numerical simulations the industrial compact CFB boiler was selected. Numerical simulations were carried out using three-dimensional model where the dense particulate transport phenomenon was simultaneously modelled with combustion process. The fluidization process was modelled using the hybrid Euler-Lagrange approach. The impact of the geometrical model simplification on predicted mass distribution and temperature profiles over CFB boiler combustion chamber two kinds of geometrical models were used, namely the complete model which consist of combustion chamber, solid separators, external solid super-heaters and simplified boiler geometry which was reduced to the combustion chamber. The evaluated temperature and pressure profiles during numerical simulations were compared against measured data collected during boiler airfuel operation. Collected data was also used for validating numerical model of the oxy-fuel combustion model. Stability of the model and its sensitivity on changes of several input parameters were studied. The comparison of the pressure and temperature profiles for all considered cases gave comparable trends in contrary to measured data. Moreover, some additional test was carried out the check the influence of radiative heat transfer on predicted temperature profile within the CFB boiler.

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Modeling the behavior of limestone particles in oxy-fuel CFB processes

Cited by 24 publications

References 43 publications

Ash and Flue Gas from Oil Shale Oxy-Fuel Circulating Fluidized Bed Combustion

Ash and Flue Gas from Oil Shale Oxy-Fuel Circulating Fluidized Bed Combustion

Calculation of the Amount of Estonian Oil Shale Products From Combustion in Regular and Oxy-Fuel Mode in a CFB Boiler

Numerical simulations of the industrial circulating fluidized bed boiler under air- and oxy-fuel combustion

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