A Numerical Study on the Effects of SOFA on NOx Emission Reduction in 500MW Class Sub-bituminous Coal-Fired Boiler

Kang, Ki-Tae; Song, Juhun; Yoon, M.K.; Lee, Byoung-Hwa; Kim, Seung-mo; Chang, Young-June; Jeon, Chung-Hwan

doi:10.3795/ksme-b.2009.33.11.858

Cited by 5 publications

(2 citation statements)

References 12 publications

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“…Feher [4] suggested a thermodynamic explanation of a supercritical CO 2 Brayton cycle in power generation applications for high thermal efficiency. Kang et al [5] conducted a numerical analysis to study the effects of separated overfire air (SOFA) of coal-fired boilers for the reduction of NOx emission. They found the optimum position of SOFA for low NOx emission.…”

Section: Introductionmentioning

confidence: 99%

Thermal Characteristics of Tube Bundles in Ultra-Supercritical Boilers

et al. 2016

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Abstract:In this study, flow and thermal characteristics of tube bundles in ultra-supercritical boilers were analyzed. The local heat transfer around the tube bundles was measured to predict the local temperature distribution and vulnerable positions of the superheated tube bundles. The maximally superheated tube bundles were simulated in the laboratory and local heat transfer was measured by using the naphthalene sublimation method. The experiment was conducted on three lines of tube bundles, all with in-line arrangements. Each line consist of six tubes. The distance in the streamwise direction (S x /∅) was 1.99 and that in the spanwise direction (S z /∅) was 5.45. The Reynolds number varied from 5000 to 30,000, which covers a range of different operating conditions. Thermal and stress analyses were conducted numerically, based on the experimental data. The results showed that the flow characteristic changes the local heat transfer of the tube bundles. The flow impinged on the stagnation point of Tube 1 and reattached at 60 • of Tube 2. The high heat transfer occurred at those positions of the tube bundles. The temperature and stress distributions on the surface of each tube bundle also varied. The reattachment point on Tube 2 had the highest heat transfer and temperature distribution. That position on Tube 2 was subjected to the highest stress due to the large temperature gradient. This result indicates that Tube 2 of the ultra-supercritical (USC) boiler is the weakest of the tube bundles, changing the pitch of the streamwise direction of Tube 2 is one method to reduce the highest stress in superheater tube bundles in the USC boiler.

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Section: Introductionmentioning

confidence: 99%

Thermal Characteristics of Tube Bundles in Ultra-Supercritical Boilers

et al. 2016

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“…Low-grade coal is abundant and cheap in price, so it has become a major energy source as energy consumption increases. Thus using of sub-bituminous of high moisture and volatility is inevitable to reduce fuel costs and diversification of energy [15]. These upward trends of the consumption and price of coal have led to the usage of low-grade coals, such as sub-bituminous coal or lignite, becoming increasingly important to reduce fuel costs and ensure energy security [16,17].…”

Section: Introductionmentioning

confidence: 99%

Microscopic Investigation of Geopolymers Made of Fused Slag from Gasification Processes Using Low-Grade Coal and Spent Catalyst Slag

Kim

Choi

Kim

2014

AMM

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Geopolymers are prospective cement substitutes because their production generates smaller amounts of carbon dioxide and they have sufficient mechanical strength. Geopolymers have attracted increasing interest from construction industries because of their recyclability and eco-friendliness. The compressive strength of geopolymers is known to be associated with their Si/Al ratio. Fused slag from gasification processes using low-grade coal (FSLC) and spent catalyst slag (SCS) were used as raw materials for making geopolymers; the Si/Al ratio was controlled by mixing different ratios of FSLC and SCS. The compressive strength of a geopolymer with a Si/Al ratio of 1.04 had the highest strength (125.6 MPa). Scanning electron microscopy (SEM) analysis was also in good agreement with the compressive strength measurements of compressive strength. There were many small crystallites in the geopolymer matrix. Using transmission electron microscopy (TEM), these crystallites were found to be single crystals, which have a perfect crystal structure. It is speculated that the formation of small crystallites 10-30 nm in size, as well as large single crystals with diameters greater than 80 nm, in the matrix of a geopolymer during the geopolymerization process might increase its compressive strength.

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