The Effect of Pressure on Ash Formation during Pulverized Coal Combustion

Wu, Hongwei; Bryant, Glenn; Wall, Terry

doi:10.1021/ef990080w

Cited by 69 publications

(42 citation statements)

References 30 publications

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“…41 The stages can be broadly categorized as evaporation of moisture, devolatilization (decomposition), and char burnout and fragmentation. 13,15,42 During decomposition, volatile species present in the fuel (alkali metals, SO 2 /SO 3 , and chlorides) are released into the vapor phase. When these vapors cool, they condense to form the fine fraction of the ash, 15 whereas char burnout and fragmentation generally give rise to the coarse fraction of the ash due to coalescence of the nonvolatile components contained within the fuel matrix (included minerals).…”

Section: ■ Introductionmentioning

confidence: 99%

Ash Agglomeration and Deposition during Combustion of Poultry Litter in a Bubbling Fluidized-Bed Combustor

et al. 2013

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In this study, we have characterized the ash resulting from fluidized bed combustion of poultry litter as being dominated by a coarse fraction of crystalline ash composed of alkali-Ca-phosphates and a fine fraction of particulate K 2 SO 4 and KCl. Bed agglomeration was found to be coating-induced with two distinct layers present. The inner layer (0.05−0.09 mm thick) was formed due to the reaction of gaseous potassium with the sand (SiO 2 ) surface forming K-silicates with low melting points. Further chemical reaction on the surface of the bed material strengthened the coating forming a molten glassy phase. The outer layer was composed of loosely bound, fine particulate ash originating from the char. Thermodynamic equilibrium calculations showed slag formation in the combustion zone is highly temperature-dependent, with slag formation predicted to increase from 1.8 kg at 600°C to 7.35 kg at 1000°C per hour of operation (5.21 kg of ash). Of this slag phase, SiO 2 and K 2 O were the dominant phases, accounting for almost 95%, highlighting the role of K-silicates in initiating bed agglomeration. The remaining 5% was predicted to consist mainly of Al 2 O 3 , K 2 SO 4 , and Na 2 O. Deposition downstream in the low-temperature regions was found to occur mostly through the vaporization−condensation mechanism, with equilibrium decreasing significantly with decreasing temperatures. The dominant alkali chloride-containing gas predicted to form in the combustion zone was KCl, which corresponds with the high KCl content in the fine baghouse ash.

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Section: ■ Introductionmentioning

confidence: 99%

Ash Agglomeration and Deposition during Combustion of Poultry Litter in a Bubbling Fluidized-Bed Combustor

et al. 2013

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“…Consequently, the transition from porous char to molten slag at 1400 and 1500 °C is responsible for the sharp decrease in the surface area at around 90% conversion observed in Figure 26. Wu et al (1999Wu et al ( , 2000 concluded that fragmentation plays a key role in the formation of large amounts of fine ash particles in the early and middle stage of pulverized coal combustion, while coalescence of included minerals results in the formation of coarse ash in the later stage of combustion, depending on the structure of the char. Baxter (1992) found that the fragmentation of bituminous coal char is strongly dependent on the size of the particle.…”

Section: Sem Imagesmentioning

confidence: 99%

Clean Coal Program Research Activities

Baxter¹,

Eddings²,

Fletcher³

et al. 2009

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Although remarkable progress has been made in developing technologies for the clean and efficient utilization of coal, the biggest challenge in the utilization of coal is still the protection of the environment. Specifically, electric utilities face increasingly stringent restriction on the emissions of NO x and SO x , new mercury emission standards, and mounting pressure for the mitigation of CO 2 emissions, an environmental challenge that is greater than any they have previously faced. The Utah Clean Coal Program addressed issues related to innovations for existing power plants including retrofit technologies for carbon capture and sequestration (CCS) or green field plants with CCS.The Program focused on the following areas: simulation, mercury control, oxycoal combustion, gasification, sequestration, chemical looping combustion, materials investigations and student research experiences. The goal of this program was to begin to integrate the experimental and simulation activities and to partner with NETL researchers to integrate the Program's results with those at NETL, using simulation as the vehicle for integration and innovation. The investigators also committed to training students in coal utilization technology tuned to the environmental constraints that we face in the future; to this end the Program supported approximately 12 graduate students toward the completion of their graduate degree in addition to numerous undergraduate students. With the increased importance of coal for energy independence, training of graduate and undergraduate students in the development of new technologies is critical.ii

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“…For a lower vitrinite content of 50 percent, again at 25 atmospheres, 75 percent of the particles are predicted to be present as cenospheres. The increase in cenosphere content with increasing pressure increases the char fragmentation during gasification with an attendant increase on char reaction rates 22 and a decrease in the particle size of ash produced (Wu et al, 2000). 18 The microporosity and therefore total surface area of the char is also impacted by the increase in total pressure.…”

Section: Char Morphologymentioning

confidence: 99%

“…The increase in cenosphere content with increasing pressure increases the char fragmentation during gasification with an attendant increase on char reaction rates 22 and a decrease in the particle size of ash produced (Wu et al, 2000). 18 The microporosity and therefore total surface area of the char is also impacted by the increase in total pressure. These changes in surface area and porosity will also influence the high pressure reactivity of the chars.…”

Section: Char Morphologymentioning

confidence: 99%

A Computational Workbench Environment for Virtual Power Plant Simulation

Bockelie¹,

Swensen²,

Denison³

et al. 2004

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This is the thirteenth Quarterly Technical Report for DOE Cooperative Agreement No: DE-FC26-00NT41047. The goal of the project is to develop and demonstrate a Virtual Engineeringbased framework for simulating the performance of Advanced Power Systems. Within the last quarter, good progress has been made on all aspects of the project. Software development efforts have focused on a preliminary detailed software design for the enhanced framework. Given the complexity of the individual software tools from each team (i.e., Reaction Engineering International, Carnegie Mellon University, Iowa State University), a robust, extensible design is required for the success of the project. In addition to achieving a preliminary software design, significant progress has been made on several development tasks for the program. These include: 1) the enhancement of the controller user interface to support detachment from the Computational Engine and support for multiple computer platforms, 2) modification of the Iowa State University interface-to-kernel communication mechanisms to meet the requirements of the new software design, 3) decoupling of the Carnegie Mellon University computational models from their parent IECM (Integrated Environmental Control Model) user interface for integration with the new framework and 4) development of a new CORBA-based model interfacing specification. A benchmarking exercise to compare process and CFD based models for entrained flow gasifiers was completed. A summary of our work on intrinsic kinetics for modeling coal gasification has been completed. Plans for implementing soot and tar models into our entrained flow gasifier models are outlined. Plans for implementing a model for mercury capture based on conventional capture technology, but applied to an IGCC system, are outlined.

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The Effect of Pressure on Ash Formation during Pulverized Coal Combustion

Cited by 69 publications

References 30 publications

Ash Agglomeration and Deposition during Combustion of Poultry Litter in a Bubbling Fluidized-Bed Combustor

Ash Agglomeration and Deposition during Combustion of Poultry Litter in a Bubbling Fluidized-Bed Combustor

Clean Coal Program Research Activities

A Computational Workbench Environment for Virtual Power Plant Simulation

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