• Journal of the Korean Society of Safety
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• v.14 no.3
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• pp.84-92
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• 1999

The effects of air velocity and excess air on combustion characteristics were studied in a fluidized bed combustor. The domestic low-grade anthracite coal with heating value of 2010 kcal/kg and the imported bituminous coal from Australia with heating value of 6520 kcal/kg were used as coal samples. The combustion characteristics of mixed fuels in a fluidized bed combustor could be interpreted by pressure fluctuation properties, ash distribution and gas emission. The properties of the pressure fluctuations, such as the standard deviation, cross-correlation function, dominant frequency and the power spectral density function, were obtained from the statistical analysis. From this study, the combustion region increased with increasing air velocity but decreased with excess air due to combustion characteristics of anthracite and bituminous coal.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.155-163
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• 1999

A numerical study for simulating a swirling pulverized coal combustion in axisymmetric geometry is done here by applying the weighted sum of gray gases model (WSGGM) approach with the discrete ordinate method (DOM) to model the radiative heat transfer equation. In the radiative transfer equation, the same polynomial equation and coefficients for weighting factors as those for gas are adopted for the coal/char particles as a function of partial pressure and particle temperature. The Eulerian balance equations for mass, momentum, energy, and species mass fractions are adopted with the standard ${\kappa}-{\varepsilon}$ turbulence model, whereas the Lagrangian approach is used for the particulate phase for soot. The eddydissipation model is employed for the reaction rate for gaseous mixture, and the single-step first-order reaction model for the devolatilization process for coal. By comparing the numerical results with experimental ones, the models used here are confirmed and found to be one of good alternatives for simulating the combustion as well as radiative characteristics.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.609-612
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• 2007

The co-combustion of coal and RPF(Refuse Plastic Fuel) mixture has been experimented in a commercially operating CFB coal boiler and the emissions such as SOx, NOx, TSP and dioxine were measured at the stack. The experimented RPF was supplied by domestic RPF company that is commercially producing RPF pellet from the wasted plastics. Up to 15% of total coal was substituted to RPF and no trouble was happened during normal boiler operation. SOx and NOx concentration was reduced about $15{\sim}20$% and TSP(Total Suspended Particle) was drastically reduced about 30% during co-combustion. Dioxine concentration at mixing ratio of 7.5% was $0.0487ng{\sim}TEQ/Sm^3$ ($O_2$, 12%) that satisfied governmental emission regulation.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.5-7
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• 2014

A skeletal mechanism of coal combustion was derived from a detailed coal combustion kinetic mechanism through an importance analysis of chemical pathways. The reduction process consists of roughly two parts. The first process is performed based on a connectivity analysis between species. In this process, DRGEPSA is chosen for reduction process. Strongly connected species and related reactions from the important species set as start species by the operator are sorted into the reduced mechanism. About 70% of species and reactions can be removed with a limited accuracy loss. Subsequently the second reduction process, CSP, is performed. This method focuses on an importance of each reaction and can reduce a volume of mechanism appropriately. Through these analyses, a skeletal mechanism is generated that is including 65 species and 150 reactions. The generated skeletal mechanism is verified through a comparison with the detailed mechanism in the homogeneous reactor model of CHEMKIN-PRO under wide range of conditions. The generated mechanism can give an advantage in the analysis of coal combustion characteristics in detail in large scale simulations such as LES and DNS.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.3
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• pp.318-322
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• 1997

A prototype of combustion zone monitoring system as been developed and installed into tuyeres of the blast furnace. The system consists of CCD(charge coupled device) cameras, sonic flow meters, an image processor and a personal computer. The personal computer collects raceway luminance data and operational data from the image processor that is connected to the color CCD camera from the blast furnace process computer, respectively. In addition, the sonic flow meters supply coal injection rate data to the personal computer. Then, the personal computer evaluates the combustion conditions with the raceway inspection algorithm. This integrated monitoring system allows us to detect abnormal raceway conditions and the clogging status of coal injection pipe. The image processing techniques of the system enable us to effectively monitor unburnt coal sticking to tuyere tip and injection lance wear conditions. Such a developed system ensures rapid and precise raceway inspection. The image processing capability of the system has helped operator to early detect both the unburnt coal sticking problem and the errosion problem of injection lance. Furthermore, the system could control the abnormal raceway condition based the the analysis results obtained from combustion monitoring.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.677-686
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• 2000

The characteristics of combustion and of emissions in pressurized fluidized bed combustor are investigated. The pressure of the combustor is fixed at 6 atm, and the combustion temperatures are set to 850, 900, and $950^{\circ}C$. The gas velocities are 0.9, 1.1, and 1.3 m/s. The excess air ratio is varied from 5 to 35%. The coal used in the experiment is Shenhwa coal in China. All experiments are executed at 2m bed height. Consequently, NOx & $N_2O$ concentration in the flue gas is increased with incresing excess air ratio but $SO_2$ concentration is decreased with incresing excess air ratio. CO concentration is maintained below 100ppm at over 15% of excess air ratio.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.93-97
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• 2015

The combustion tests for Korean anthracite-bituminous coal blend were carried out in the 200 MW utility boiler. The burning characteristics of the blend were studied with a thermogravimetric analyzer (TGA). From the observation of TGA burning profiles, it was found that the presence of bituminous coal in the blend appeared to enhance the reactivity of anthracite in the higher temperature region, indicating certain interactions between the two coals. The plant test showed the boiler operation was reasonably stable with somewhat poor combustion efficiency, and some modification of the combustion environment in the furnace is necessitate for the further stable plant operation.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.71-73
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• 2012

With numerical simulations, this study investigated the combustion and heat transfer of three different coals under air- and oxy-fuel combustion in a 100 MWe boiler. The boiler is retrofitted to an opposed-firing type while maintain the original furnace shape of downshot firing. The boiler achieved good combustion in both combustion modes for three coals tested. However, the contribution of gasification reactions by $CO_2$ and $H_2O$ significantly increased due to the lack of gaseous mixing. This was different from a typical front-wall firing boiler, which showed larger contribution of char oxidation during air-coal combustion. The wall heat flux was lower in oxy-coal mode at a $O_2$ level of 27%, which has to be considered in further development of the process.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.675-680
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• 2009

This article describes NO emission characteristics in SM coal combustion. Combustion experiments was performed in the method of increasing temperature after feeding coal and feeding coal after increasing temperature. NOx emission is in inverse proportion to combustion temperature at the fuel rich condition and it was caused by conversion fuel N to $N_{2}$ at the strong reduction condition. In addition, feeding gas flow rate increased as total fuel NOx increase by conversion of fuel N to NO at the oxidation condition. It could be separated in total fuel-N, volatile-N, char-N to NO according to analysis of total fuel NO emission from char combustion at each temperature. In the result, almost total NOx emission was caused by volatile-N in SM-coal.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.12
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• pp.1691-1701
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• 1998

Fly ash produced in coal combustion is a fine-grained material consisting mostly of spherical, glassy, and porous particles. A study on the formation mechanism of the fly ash from coal particles in the pulverized coal power plant is investigated with a physical, morphological, and chemical characteristic analysis of fly ash collected from the Samchonpo power plant. This study may contribute to the data base of domestic fly ash, the improvement of combustion efficiency, fouling phenomena and ash collection in the electrostatic precipitator. The physical property of fly ash is determined using a particle counter for the measurement of ash size distribution. Morphological characteristic of fly ash is performed using a scanning electron micrograph. The chemical components of fly ash are determined using an inductively coupled plasma emission spectrometry(ICP). The distribution of fly ash size was bi-modal and ranged from 12 to $19{\mu}m$ in mass median diameter. Exposure conditions of flue gas temperature and duration within the combustion zone of the boiler played an important role on the morphological properties of the fly ash such as shape, particle size and chemical components. The evolution of ash formation during pulverized coal combustion has revealed three major mechanisms by large particle formation due to break-up process, gas to particle conversion and growth by coagulation and agglomeration.