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Special Issue "Coal Combustion and Gasification"

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A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (30 June 2013)

Special Issue Editor

Guest Editor
Prof. Dr. Mehrdad Massoudi (Website)

Department of Biomedical Engineering and Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA
Interests: multi-component flows; non-Newtonian fluids; granular materials; heat transfer; mathematical modelling

Special Issue Information

Dear Colleagues,

Coal is an abundant energy resource in the United States, China and many other countries. However, burning coal also carries environmental concerns, such as sulfur compounds, and future concerns regarding carbon dioxide. Clean coal technologies are needed to provide better environmental performance at low cost, enabling power plants to continue using coal for electricity generation. As fossil fuel use increases, the amount of waste materials and the environmental issues dealing with their disposal also increase. One of the promising approaches is the development of coal/waste co-firing technology with fuels such as biomass. To improve efficiency and reduce the cost of electricity, it is important to understand factors such as the operating conditions and the impact of fuel properties and additives on carbon conversion, ash, slag, fouling, etc. In the gasification process, fouling and plugging in the syngas cooler system is the major cause of unplanned downtime. To develop an accurate heat transfer model in any type of coal combustion or gasification process, the heat transfer and the rheological properties of materials such as ash, biomass, and slag, especially in high-temperature environments need to be understood and properly modeled.

Dr. Mehrdad Massoudi
Guest Editor

Submission

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Keywords

• gasifiers
• fluidized beds
• biomass cofiring
• integrated gasification combined cycle (IGCC)
• CFD analysis
• mathematical modelling
• slag
• oxy- fuel combustion
• refractory improvement
• ash management

Published Papers (9 papers)

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Research

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Open AccessArticle Conditional Methods in Modeling CO2 Capture from Coal Syngas
Energies 2014, 7(4), 1899-1916; doi:10.3390/en7041899
Received: 29 October 2013 / Revised: 10 February 2014 / Accepted: 5 March 2014 / Published: 27 March 2014
Cited by 1 | PDF Full-text (871 KB) | HTML Full-text | XML Full-text
Abstract
Gasification of coal or biomass with in-situ CO2 capture is an emerging technology aiming to address the problem of climate change. Development of a CO2 sorbent with desirable properties and understanding the behavior of such a material in carbonation/calcination reactions [...] Read more.
Gasification of coal or biomass with in-situ CO2 capture is an emerging technology aiming to address the problem of climate change. Development of a CO2 sorbent with desirable properties and understanding the behavior of such a material in carbonation/calcination reactions is an important part of developing the technology. In this paper, we report experimental results describing the carbonation behavior of three synthetic CaO-based sorbents. We also present a physically-based model of the reactive transport processes in sorbent particles, which have complicated pore structures. This modeling is based on the conditional approach (i.e., conditional moment closure (CMC)), which has proven to be successful in modeling reactive transport phenomena in porous media. The model predictions are in good agreement with the experimental data. Full article
(This article belongs to the Special Issue Coal Combustion and Gasification)
Open AccessArticle Accidental Continuous Releases from Coal Processing in Semi-Confined Environment
Energies 2013, 6(10), 5003-5022; doi:10.3390/en6105003
Received: 31 July 2013 / Revised: 19 September 2013 / Accepted: 24 September 2013 / Published: 27 September 2013
Cited by 12 | PDF Full-text (1311 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
Notwithstanding the enforcement of ATEX EU Directives (94/9/EC of 23 March 1994) and safety management system application, explosions in the coal sector still claim lives and cause huge economic losses. Even a consolidated activity like coke dry distillation allows the opportunity of [...] Read more.
Notwithstanding the enforcement of ATEX EU Directives (94/9/EC of 23 March 1994) and safety management system application, explosions in the coal sector still claim lives and cause huge economic losses. Even a consolidated activity like coke dry distillation allows the opportunity of preventing explosion risk connected to fugitive emissions of coke oven gas. Considering accidental releases under semi-confined conditions, a simplified mathematical approach to the maximum allowed gaseous build-up is developed on the basis of the intrinsic hazards of the released compound. The results will help identifying and assessing low rate release consequences therefore to set-up appropriate prevention and control measures. The developed methodology was tested at the real-scale and validated by numerical computational fluid dynamics (CFD) simulations showing the effectiveness of the methodology to evaluate and mitigate the risk connected to confined hazardous releases. Full article
(This article belongs to the Special Issue Coal Combustion and Gasification)
Open AccessArticle A New Agro/Forestry Residues Co-Firing Model in a Large Pulverized Coal Furnace: Technical and Economic Assessments
Energies 2013, 6(9), 4377-4393; doi:10.3390/en6094377
Received: 9 April 2013 / Revised: 1 August 2013 / Accepted: 5 August 2013 / Published: 23 August 2013
Cited by 3 | PDF Full-text (381 KB) | HTML Full-text | XML Full-text
Abstract
Based on the existing biomass co-firing technologies and the known innate drawbacks of dedicated biomass firing, including slagging, corrosion and the dependence on fuel, a new model of agro/forestry residue pellets/shreds and coal co-fired in a large Pulverized Coal (PC) furnace was [...] Read more.
Based on the existing biomass co-firing technologies and the known innate drawbacks of dedicated biomass firing, including slagging, corrosion and the dependence on fuel, a new model of agro/forestry residue pellets/shreds and coal co-fired in a large Pulverized Coal (PC) furnace was proposed, and the corresponding technical and economic assessments were performed by co-firing testing in a 300 MW PC furnace and discounted cash flow technique. The developed model is more dependent on injection co-firing and combined with co-milling co-firing. Co-firing not only reduces CO2 emission, but also does not significantly affect the fly ash use in cement industry, construction industry and agriculture. Moreover, economic assessments show that in comparison with dedicated firing in grate furnace, agro/forestry residues and coal co-firing in a large PC furnace is highly economic. Otherwise, when the co-firing ratio was below 5 wt%, the boiler co-firing efficiency was 0.05%–0.31% higher than that of dedicated PC combustion, and boiler efficiencies were about 0.2% higher with agro/forestry residues co-firing in the bottom and top burner systems than that in a middle burner system. Full article
(This article belongs to the Special Issue Coal Combustion and Gasification)
Open AccessArticle A Dynamic Model for the Normal Impact of Fly Ash Particle with a Planar Surface
Energies 2013, 6(8), 4288-4307; doi:10.3390/en6084288
Received: 16 May 2013 / Revised: 3 July 2013 / Accepted: 31 July 2013 / Published: 20 August 2013
Cited by 1 | PDF Full-text (666 KB) | HTML Full-text | XML Full-text
Abstract
The rebound behavior of fly ash particles normally impacting a planar surface is investigated by using a dynamic model. The three forms of soft sphere physical model are obtained using static/quasi-static contact mechanics and energy dissipation theory. The influences of the particle [...] Read more.
The rebound behavior of fly ash particles normally impacting a planar surface is investigated by using a dynamic model. The three forms of soft sphere physical model are obtained using static/quasi-static contact mechanics and energy dissipation theory. The influences of the particle size, the incident velocity of the particle on the damping coefficient and the impact contact time are all examined. We also predict the critical velocity for three particle sizes. It is found that the variation of the damping coefficient (η) with the normal incident velocity (vin) can be roughly divided into the three parts. In the first part, η decreases with increasing vin. In the second part, η is little changed with increasing vin. In the third part, η rapidly increases with increasing vin. For smaller impact velocities, the viscoelastic effect plays a dominant role in the impact process, while for higher incident velocities; the energy dissipation depends mainly on plastic deformation. In addition, the critical velocity shows a distinct dependence on the particle size. Finally, the contact displacement-contact time curves are examined. The work provides a solid basis for the development of a discrete-element-method approach to study ash deposition. Full article
(This article belongs to the Special Issue Coal Combustion and Gasification)
Open AccessArticle Experimental Studies on the Normal Impact of Fly Ash Particles with Planar Surfaces
Energies 2013, 6(7), 3245-3262; doi:10.3390/en6073245
Received: 23 April 2013 / Revised: 25 June 2013 / Accepted: 27 June 2013 / Published: 3 July 2013
Cited by 6 | PDF Full-text (1527 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the results of a comprehensive program of experiments in which fly ash particles were impacted under controlled conditions against a flat steel surface. The overall aim of these experiments was to gain an understanding of the ash deposition process [...] Read more.
This paper presents the results of a comprehensive program of experiments in which fly ash particles were impacted under controlled conditions against a flat steel surface. The overall aim of these experiments was to gain an understanding of the ash deposition process in a pulverized coal boiler system. A continuous nitrogen flow carrying fly ash particles was used to examine the effect of particle incident velocity and particle diameter (dp) on the normal restitution coefficient, and of the particle diameter on the critical velocity. The effect of the incident normal velocity and particle diameter on the normal restitution coefficient was also examined. The results show that the normal restitution coefficient increases rapidly with increasing incident velocity when this incident velocity is less than the yield velocity, and rapidly decreases with increasing incident velocity when the incident velocity is greater than the yield velocity. The critical velocity, determined solely by the first-contact energy loss, is proportional to dp−5/6 and therefore becomes larger for smaller particles. For instance, in the present work, the velocity vc of a particle with diameter of 85 μm is 0.19 m/s, which increases to 0.42 m/s for particles with a diameter of 65 μm. Full article
(This article belongs to the Special Issue Coal Combustion and Gasification)
Open AccessArticle Evaluation of Structural Changes in the Coal Specimen Heating Process and UCG Model Experiments for Developing Efficient UCG Systems
Energies 2013, 6(5), 2386-2406; doi:10.3390/en6052386
Received: 6 February 2013 / Revised: 2 April 2013 / Accepted: 23 April 2013 / Published: 3 May 2013
Cited by 8 | PDF Full-text (2129 KB) | HTML Full-text | XML Full-text
Abstract
In the underground coal gasification (UCG) process, cavity growth with crack extension inside the coal seam is an important phenomenon that directly influences gasification efficiency. An efficient and environmentally friendly UCG system also relies upon the precise control and evaluation of the [...] Read more.
In the underground coal gasification (UCG) process, cavity growth with crack extension inside the coal seam is an important phenomenon that directly influences gasification efficiency. An efficient and environmentally friendly UCG system also relies upon the precise control and evaluation of the gasification zone. This paper presents details of laboratory studies undertaken to evaluate structural changes that occur inside the coal under thermal stress and to evaluate underground coal-oxygen gasification simulated in an ex-situ reactor. The effects of feed temperature, the direction of the stratified plane, and the inherent microcracks on the coal fracture and crack extension were investigated using some heating experiments performed using plate-shaped and cylindrical coal specimens. To monitor the failure process and to measure the microcrack distribution inside the coal specimen before and after heating, acoustic emission (AE) analysis and X-ray CT were applied. We also introduce a laboratory-scale UCG model experiment conducted with set design and operating parameters. The temperature profiles, AE activities, product gas concentration as well as the gasifier weight lossess were measured successively during gasification. The product gas mainly comprised combustible components such as CO, CH4, and H2 (27.5, 5.5, and 17.2 vol% respectively), which produced a high average calorific value (9.1 MJ/m3). Full article
(This article belongs to the Special Issue Coal Combustion and Gasification)

Review

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Open AccessReview Slag Behavior in Gasifiers. Part I: Influence of Coal Properties and Gasification Conditions
Energies 2013, 6(2), 784-806; doi:10.3390/en6020784
Received: 30 October 2012 / Revised: 15 January 2013 / Accepted: 17 January 2013 / Published: 7 February 2013
Cited by 27 | PDF Full-text (1209 KB) | HTML Full-text | XML Full-text
Abstract
In the entrained-flow gasifiers used in integrated gasification combined cycle (IGCC) plants, the majority of mineral matter transforms to liquid slag on the wall of the gasifier and flows out the bottom. However, a small fraction of the mineral matter is entrained [...] Read more.
In the entrained-flow gasifiers used in integrated gasification combined cycle (IGCC) plants, the majority of mineral matter transforms to liquid slag on the wall of the gasifier and flows out the bottom. However, a small fraction of the mineral matter is entrained (as fly ash) with the raw syngas out of the gasifier to downstream processing. This molten/sticky fly ash could cause fouling of the syngas cooler. To improve gasification availability through better design and operation of the gasification process, a better understanding of slag behavior and the characteristics of the slagging process is needed. Char/ash properties, gas compositions in the gasifier, the gasifier wall structure, fluid dynamics, and plant operating conditions (mainly temperature and oxygen/carbon ratio) all affect slagging behavior. Because coal has varying ash content and composition, different operating conditions are required to maintain the slag flow and limit problems downstream. In Part I, we review the main types and the operating conditions of entrained-flow gasifiers and coal properties used in IGCC plants; we identify and discuss the key coal ash properties and the operating conditions impacting slag behavior; finally, we summarize the coal quality criteria and the operating conditions in entrained-flow gasifiers. In Part II, we discuss the constitutive modeling related to the rheological studies of slag flow. Full article
(This article belongs to the Special Issue Coal Combustion and Gasification)
Figures

Open AccessReview Slag Behavior in Gasifiers. Part II: Constitutive Modeling of Slag
Energies 2013, 6(2), 807-838; doi:10.3390/en6020807
Received: 30 October 2012 / Revised: 8 January 2013 / Accepted: 22 January 2013 / Published: 7 February 2013
Cited by 13 | PDF Full-text (385 KB) | HTML Full-text | XML Full-text
Abstract
The viscosity of slag and the thermal conductivity of ash deposits are among two of the most important constitutive parameters that need to be studied. The accurate formulation or representations of the (transport) properties of coal present a special challenge of modeling [...] Read more.
The viscosity of slag and the thermal conductivity of ash deposits are among two of the most important constitutive parameters that need to be studied. The accurate formulation or representations of the (transport) properties of coal present a special challenge of modeling efforts in computational fluid dynamics applications. Studies have indicated that slag viscosity must be within a certain range of temperatures for tapping and the membrane wall to be accessible, for example, between 1,300 °C and 1,500 °C, the viscosity is approximately 25 Pa·s. As the operating temperature decreases, the slag cools and solid crystals begin to form. Since slag behaves as a non-linear fluid, we discuss the constitutive modeling of slag and the important parameters that must be studied. We propose a new constitutive model, where the stress tensor not only has a yield stress part, but it also has a viscous part with a shear rate dependency of the viscosity, along with temperature and concentration dependency, while allowing for the possibility of the normal stress effects. In Part I, we reviewed, identify and discuss the key coal ash properties and the operating conditions impacting slag behavior. Full article
(This article belongs to the Special Issue Coal Combustion and Gasification)

Other

Jump to: Research, Review

Open AccessCorrection Palazzi, E.; Currò, F.; Fabiano, B. Accidental Continuous Releases from Coal Processing in Semi-Confined Environment. Energies 2013, 6, 5003–5022
Energies 2014, 7(2), 735; doi:10.3390/en7020735
Received: 21 January 2014 / Accepted: 22 January 2014 / Published: 12 February 2014
PDF Full-text (113 KB) | HTML Full-text | XML Full-text
Abstract The authors wish to make the following corrections, due to typographical errors, to this paper [1]. [...] Full article
(This article belongs to the Special Issue Coal Combustion and Gasification)

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