Numerical Study of Pulverized Coal MILD Combustion in a Self-Recuperative Furnace

Saha, M.; Chinnici, Alfonso; Dally, Bassam B.; Medwell, Paul R.

doi:10.1021/acs.energyfuels.5b01644

Cited by 48 publications

(23 citation statements)

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“…On the other hand, the Reynolds Averaged Navier Stokes (RANS) approach with an adequate turbulence model provides a consistent solution of the mean flow field without the excessive computational effort of an LES approach [38]: the realizable k-model achieves good results in predicting swirling combustion flows [39,40]. The recent work of Saha et al [41] confirms the reliability of the RANS approach in the case of pulverized coal MILD combustion. In order to reach consistent quantitative results, accurate experimental data represent a benchmark to validate the numerical codes and to be confident of the reliability of the numerical results (e.g., [42]).…”

Section: Introductionmentioning

confidence: 94%

Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner

et al. 2017

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Abstract:In the next few years, even though there will be a continuous growth of renewables and a loss of the share of fossil fuel, energy production will still be strongly dependent on fossil fuels. It is expected that coal will continue to play an important role as a primary energy source in the next few decades due to its lower cost and higher availability with respect to other fossil fuels. However, in order to improve the sustainability of energy production from fossil fuels, in terms of pollutant emissions and energy efficiency, the development of advanced investigation tools is crucial. In particular, computational fluid dynamics (CFD) simulations are needed in order to support the design process of low emission burners. Even if in the literature several combustion models can be found, the assessment of their performance against detailed experimental measurements on full-scale pulverized coal burners is lacking. In this paper, the numerical simulation of a full-scale low-NO x , aerodynamically-staged, pulverized coal burner for electric utilities tested in the 48 MW th plant at the Combustion Environment Research Centre (CCA -Centro Combustione e Ambiente) of Ansaldo Caldaie S.p.A. in Gioia del Colle (Italy) is presented. In particular, this paper is focused on both devolatilization and char burnout models. The parameters of each model have been set according to the coal characteristics without any tuning based on the experimental data. Thanks to a detailed description of the complex geometry of the actual industrial burner and, in particular, of the pulverized coal inlet distribution (considering the entire primary air duct, in order to avoid any unrealistic assumption), a correct selection of both devolatilization and char burnout models and a selection of suited parameters for the NO x modeling, accurate results have been obtained in terms of NO x formation. Since the model parameters have been evaluated a priori, the numerical approach proposed here could be suitable to be applied as a performance prediction tool in the design of pulverized coal burners.

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Section: Introductionmentioning

confidence: 94%

Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner

et al. 2017

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“…The wood devolatilization is modeled by the two competing rate (Kobayashi) mechanism . This model is widely used in the literature and can define the rate of devolatilization at high and low temperatures in an acceptable computational time. The rate of devolatilization using the two competing rates empirical formulation is as follows:

\frac{m_{v} ((), t)}{((), 1 - f_{normalw, 0}) m_{normalp, 0} - m_{a}} = \int_{0}^{t} ((), α_{1} k_{1} + α_{2} k_{2}) exp ((), - \int_{0}^{t} ((), k_{1} + k_{2}) italicdt) italicdt,

…”

Section: Model Description and Assumptionsmentioning

confidence: 99%

Development of a high‐temperature two‐stage entrained flow gasifier model for the process of biomass gasification and syngas formation

2019

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Summary This paper presents development of the Mitsubishi Heavy Industries (MHI) gasifier utilizing an analogy between a model with coal feedstock and the model with torrefied woody biomass. A computational fluid dynamics (CFD) model was primarily developed for coal gasification, and the simulation results were validated with similar published work and experimental measurements. The model was extended for the woody biomass to predict the gasifier performance under the gasification process. The results were used to compare the effect of fuel type on the gasifier performance and gaseous product compositions. The second‐level injection nozzles were modified tangentially, and the flow characteristics, species yields, and temperature were evaluated. The possibility of reducing the gasifier length from 13 to 8 m is also evaluated for different total length. The results revealed that using woody biomass leads to a decrease in the mole fraction of CO and H2 at the gasifier outlet compared with coal. An opposite trend was observed for CO2 and CH4 compositions. The contributions of modified second‐level nozzles to the total gas composition and exit temperature only account for less than 3%. Reducing the gasifier length from 13 to 8 m increased the exit temperature from 1289 to 1340 K, but the changes in the exit gas composition were less than 2%. The new design of the MHI gasifier can reduce the investment costs by reducing the gasifier length as well as using biomass instead of coal.

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“…El material seleccionado fue un carbón Colombiano tipo bituminoso alto en volátiles proveniente de la región de Amagá-Antioquia, cuyo poder calorífico superior es de 24,33 MJ/Kg (medido en bomba calorimétrica), este tipo de carbón se selecciona debido a que existen estudios que demuestran que para carbones de alto rango la cantidad de inquemados sólidos es mayor comparativamente con carbones de menor rango, en un estudio realizado por investigadores del Centre for Energy Technology de la universidad de Adelaida en Australia, se obtuvo un porcentaje de inquemados cercano al 10% para un carbón de rango bajo, mientras que el porcentaje de inquemados para un carbón de alto rango tipo antracita fue de alrededor del 60% (Saha, Chinnici, Dally, & Medwell, 2015). El carbón fue pulverizado en un molino de bolas y tamizado con mallas 200-100 que según la norma ASTM (United & Of, n.d.) corresponden a un tamaño de partícula entre 75-150 µm.…”

Section: Metodologíaunclassified

Efecto del contenido de oxígeno y metano en la cinética de oxidación de un carbonizado de carbón

Laverde

Alvarado

Machado

2017

Rev. Acad. Colomb. Cienc. Ex. Fis. Nat.

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ResumenSe evaluó el efecto de la adición de metano en un carbonizado de carbón sometido a reacción con concentraciones de oxígeno bajas. Desde un punto de vista cinético, dicho efecto es determinando por la energía de activación (Ea) y por el factor preexponencial para diferentes concentraciones de oxígeno y mezclas de oxígeno y metano. Se preparó un carbonizado con un tamaño de partícula de 75 a 150 µm a partir de un carbón bituminoso altamente volátil, y se determinaron los parámetros cinéticos de la oxidación empleando el método termogravimétrico de velocidad máxima. Las variables evaluadas en la cinética de oxidación fueron la concentración de oxígeno (5, 8 y 21 %), y el efecto de la adición de metano en el medio de reacción (5, 10 y 14 % de metano mezclado con 5 % de oxígeno). Los resultados mostraron que la Ea disminuía al aumentar la concentración de oxígeno, en tanto que al agregar metano se observó un efecto promotor cuando este correspondía al 5 % de la mezcla total; sin embargo, cuando el porcentaje de metano aumentaba, la Ea también lo hacía debido a la rápida reacción del oxígeno con el metano en fase homogénea comparada con la reacción heterogénea del oxígeno con el carbonizado. La Ea obtenida con 5 % de oxígeno fue de 122,9 kJ/mol y con 21 %, de 90,69 kJ/mol; en presencia de metano al 5 % y 5 % de oxígeno, la Ea fue de 110,7 kJ/mol, y aumentó hasta 170,8 kJ/mol cuando el metano representaba el 14 % de la mezcla. © 2017. Acad. Colomb. Cienc. Ex. Fis. Nat. Palabras clave: Parámetros cinéticos; Carbonizado de carbón pulverizado; Contenido de metano; Contenido de oxígeno. Effect of oxygen and methane on the oxidation kinetics of coal char AbstractIn this work we evaluated the effect of adding methane during the oxidation process of a coal char with low oxygen concentration. We analyzed the effect from a kinetic point of view and we determined the activation energy (Ea) and the pre-exponential factor (A) with different oxygen concentrations and oxygen and methane mixtures. We used a coal char from a highly volatile bituminous coal with particle size of 75 to 150 µm; the kinetic parameters were determined by thermogravimetric method (TGA) with the high-velocity model; oxygen concentration variations were studied with 5, 8 and 21% of oxygen, as well as the effect of adding methane (5,10 and 14%) when oxidation occurred with 5% of oxygen. The results showed that the Ea decreased when oxygen concentration increased, and that adding 5% of methane to the total mixture enhanced the effect. Instead, when we increased the methane percentage, the Ea increased due to the rapid reaction of oxygen and methane in the homogeneous phase as compared with the heterogenous reaction of oxygen and coal char. With 5% oxygen the Ea value was 122.9 kJ/mol and with 21%, it was 90.69 kJ/mol; when methane was added at 5%, the Ea value was 110.7 kJ/mol, and it increased to 170.8 kJ/mol when there was 14% of methane in the mixture.

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Numerical Study of Pulverized Coal MILD Combustion in a Self-Recuperative Furnace

Cited by 48 publications

References 50 publications

Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner

Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner

Development of a high‐temperature two‐stage entrained flow gasifier model for the process of biomass gasification and syngas formation

Efecto del contenido de oxígeno y metano en la cinética de oxidación de un carbonizado de carbón

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