Waterwall corrosion mechanisms in coal combustion environments

Nava-Paz, J.C.; Plumley, A.L.; Chow, O.K.; Chen, W.

doi:10.3184/096034002783640431

“…The aluminum data (see Figure 2. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] show a similarly expected decrease in concentration at low particle diameters due to the high volatilization temperature of aluminum. The outlier point for the bottom impactor plate for Case 4 is suspected to be the result of contamination as it occurred in only one of the sample runs in the Case 4 results.…”

Section: Resultsmentioning

confidence: 99%

“…In the CFD simulations conducted with the Glacier code for this project, each "panel" (row of tubes) is modeled as a plate, so that a tube bank is modeled as a series of plates parallel to the flow direction (see Figure 2. [6][7][8][9][10][11][12][13][14][15][16]. At the leading edge of a tube bank, the velocity and ash loading in the computational cell just before the "plate" or row of tubes can be used to calculate the impaction rate at the leading edge of the "plate".…”

Section: Ash Particle Size Distribution and Impactionmentioning

confidence: 99%

“…Figure 2.7-6 shows the effect of local stoichiometry on corrosion rate under an FeS layer; as noted above, corrosion rates are highest under oxidizing gas phase conditions. Nava-Paz et al [16] report that the microclimate under an unburned carbon layer in the presence of a sulfidizing gas atmosphere is as corrosive as that under an FeS layer. Corrosion rates increase with temperature, so supercritical boilers with higher tube temperatures frequently suffer greater wastage than do subcritical boilers.…”

Section: Deposit Based Corrosion (Fes)mentioning

confidence: 99%

See 1 more Smart Citation

Characterization of Oxy-combustion Impacts in Existing Coal-fired Boilers

Adams

¹

,

Fry

²

,

Senior

³

et al. 2010

1

0

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This report summarizes Year 1 results of a research program designed to use multi-scale experimental studies and fundamental theoretical models to characterize and predict the impacts of retrofit of existing coal-fired utility boilers for oxy-combustion. Through the course of Year 1 activities, great progress was made toward understanding the issues associated with oxy-combustion retrofit of coal-fired boilers. All four Year 1 milestones and objectives have been, or will be, completed on schedule and within budget. Progress in the four milestone areas may be summarized as follows:• University of Utah has performed size segregated ash composition measurements in the Oxy-Fuel Combustor (OFC). These experiments indicate that oxy-combustion retrofit may impact ash aerosol mineral matter composition. Both flame temperature and flue gas composition have been observed to influence the concentration of calcium, magnesium and iron in the fine particulate. This could in turn impact boiler fouling and slagging.• Sandia National Labs has shown that char oxidation rate is dependent on particle size (for sizes between 60 and 100 microns) by performing fundamental simulations of reacting char particles. These predictions will be verified by making time-resolved optical measurements of char particle temperature, velocity and size in bench-scale experiments before the end of Year 1.• REI and Siemens have completed the design of an oxy-research burner that will be mounted on University of Utah's pilot-scale furnace, the L1500. This burner will accommodate a wide range of O 2 , FGR and mixing strategies under conditions relevant for utility boiler operation. Through CFD modeling of the different burner designs, it was determined that the key factor influencing flame stabilization location is particle heat-up rate. The new oxy-research burner and associated equipment is scheduled for delivery before the end of Year 1.• REI has completed a literature survey of slagging and fouling mechanisms in coal-fired power plants to understand key issues influencing these deposition regimes and infer their behavior under oxy-fired conditions. Based on the results of this survey, an algorithm for integrating slagging predictions into CFD models was outlined. This method accounts for ash formation, particle impaction and sticking, deposit growth and physical properties and impact of the deposit on system flow and heat transfer. A model for fouling in the back pass has also been identified which includes vaporization of sodium, deposition of sodium sulfate on fly ash particles and tube surfaces, and deposit growth rate on tubes.In Year 1, REI has also performed a review of the literature describing corrosion in order to understand the behavior of oxidation, sulfidation, chloridation, and carburization mechanisms in air-fired and oxycombustion systems. REI and Vattenfall have met and exchanged information concerning oxy-coal combustion mechanisms for CFD simulations currently used by Vattenfall. In preparation for Year 2 of this program, tw...

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“…Figure 4.9-6 shows the effect of local stoichiometry on corrosion rate under an FeS layer; as noted above, corrosion rates are highest under oxidizing gas phase conditions. (Nava-Paz, et al 2002) report that the microclimate under an unburned carbon layer in the presence of a sulfidizing gas atmosphere is as corrosive as that under an FeS layer. Figure 4.9-7 shows predicted corrosion rates under an FeS layer and in a 1% O 2 gas environment as a function of temperature.…”

Section: Deposit Based Corrosion (Fes)mentioning

confidence: 99%

Characterization of Oxy-combustion Impacts in Existing Coal-fired Boilers

Adams

¹

,

Davis

²

,

Senior

³

et al. 2013

View full text Add to dashboard Cite

This report summarizes Year 1 results of a research program designed to use multi-scale experimental studies and fundamental theoretical models to characterize and predict the impacts of retrofit of existing coal-fired utility boilers for oxy-combustion. Through the course of Year 1 activities, great progress was made toward understanding the issues associated with oxy-combustion retrofit of coal-fired boilers. All four Year 1 milestones and objectives have been, or will be, completed on schedule and within budget. Progress in the four milestone areas may be summarized as follows:• University of Utah has performed size segregated ash composition measurements in the Oxy-Fuel Combustor (OFC). These experiments indicate that oxy-combustion retrofit may impact ash aerosol mineral matter composition. Both flame temperature and flue gas composition have been observed to influence the concentration of calcium, magnesium and iron in the fine particulate. This could in turn impact boiler fouling and slagging.• Sandia National Labs has shown that char oxidation rate is dependent on particle size (for sizes between 60 and 100 microns) by performing fundamental simulations of reacting char particles. These predictions will be verified by making time-resolved optical measurements of char particle temperature, velocity and size in bench-scale experiments before the end of Year 1.• REI and Siemens have completed the design of an oxy-research burner that will be mounted on University of Utah's pilot-scale furnace, the L1500. This burner will accommodate a wide range of O 2 , FGR and mixing strategies under conditions relevant for utility boiler operation. Through CFD modeling of the different burner designs, it was determined that the key factor influencing flame stabilization location is particle heat-up rate. The new oxy-research burner and associated equipment is scheduled for delivery before the end of Year 1.• REI has completed a literature survey of slagging and fouling mechanisms in coal-fired power plants to understand key issues influencing these deposition regimes and infer their behavior under oxy-fired conditions. Based on the results of this survey, an algorithm for integrating slagging predictions into CFD models was outlined. This method accounts for ash formation, particle impaction and sticking, deposit growth and physical properties and impact of the deposit on system flow and heat transfer. A model for fouling in the back pass has also been identified which includes vaporization of sodium, deposition of sodium sulfate on fly ash particles and tube surfaces, and deposit growth rate on tubes.In Year 1, REI has also performed a review of the literature describing corrosion in order to understand the behavior of oxidation, sulfidation, chloridation, and carburization mechanisms in air-fired and oxycombustion systems. REI and Vattenfall have met and exchanged information concerning oxy-coal combustion mechanisms for CFD simulations currently used by Vattenfall. In preparation for Year 2 of this program, tw...

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“…In the operation of a pulverized coal combustion facility, incombustible ash can deposit on the surface through slagging or fouling. Ash deposition can lead to the overall heat exchange efficiency decrease, 1 erosion acceleration, 2 and even emergency shutdown. 3 Extensive works have been conducted to investigate depositions in pulverized coal combustion.…”

Section: Introductionmentioning

confidence: 99%

Development of an Online Ash-Deposition Thermogravimetric Analyzer for Pulverized Coal Combustion

Chen

¹

,

Fang

²

,

Zhou

³

et al. 2018

Energy Fuels

3

0

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A novel system consisting of an online ash-deposition thermogravimetric analyzer coupled with an electrically heated down-fired furnace was developed for pulverized coal combustion. A steady high-temperature pulverized coal combustion was achieved in the down-fired furnace. Ash deposition weights were online measured without interference of the deposition process. The developed setup was calibrated to quantify the system error and subsequently used to investigate the ash deposition behavior. First, the gas species, coal conversions, and particle size distributions were quantitatively measured under excess air of 1.2 (oxidizing atmosphere) and 0.7 (reducing atmosphere) under furnace temperatures of 1100–1400 °C. Next, the ash deposition rates were online measured under different surface temperatures (1000–1400 °C), oxidizing and reducing atmospheres (corresponding to excess air of 1.2 and 0.7, respectively), and gas velocities (0.89 to 2.37 m/s,). The deposition samples were collected through the N2 protection method. The morphology and structural property of the sample were characterized by scanning electron microscope. From a low to a high temperature, it was found that the deposition transformed from a porous layer composed of loosely bond particles to a slag layer. The transition was found to be tightly related to the ash fusion temperature and the unburnt carbon fraction of the deposited particle. Finally, the reaction rate of unburnt carbon in the deposition was measured using a specially designed experiment. A deposition model was proposed to model the deposition process and derive the reaction rate. It was found that both the oxidation and the gasification reaction rates were a few orders of magnitude slower than those in pulverized coal combustion.

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Waterwall corrosion mechanisms in coal combustion environments

Cited by 3 publications

References 0 publications

Characterization of Oxy-combustion Impacts in Existing Coal-fired Boilers

Characterization of Oxy-combustion Impacts in Existing Coal-fired Boilers

Characterization of Oxy-combustion Impacts in Existing Coal-fired Boilers

Development of an Online Ash-Deposition Thermogravimetric Analyzer for Pulverized Coal Combustion

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