• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.107-109
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• 2012

In Korean coal power plants, rising coal prices have recently led to the rapid utilization of low lank coals such as sub-bituminous coal with low calorific values and low ash fusion temperatures. Using these coals beyond the design range has resulted in important issues including slagging and fouling, which cause negative effects in boiler performances and unstable operations. The purpose of this study is to observe slagging and fouling characteristics resulted from burning various ranks of pulverized coals. We have tested 3 different coals: FLAME(bituminous), KCH(sub-bituminous) and MOOLARBEN(bituminous)coals in the pilot system $50kW_{th}$ scale. A stainless steel tube with preheated air inside was installed in the downstream in order to simulate water wall. Collected ash on the probe and the slag inside the furnace near burner were analyzed by SEM (scanning electron microscopy) to verify the formation degree, surface features and color changes of the pasty ash particles. Induced coupled plasma and energy dispersive X-ray spectroscopy were also performed to figure out the chemical characteristics of collected samples. As a result, KCH was observed that more slag was developed inside the walls of the furnace and on the probe than the other two kinds of coals, as shown in the calculate slagging and fouling indices as well.

• Analytical Science and Technology
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• v.5 no.4
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• pp.433-441
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• 1992

Chemical composition and fusibility of coal ash were measured for 23 Korean anthracite coals. The relationship between chemical properties and fusion temperature of coal ash was investigated. The slagging and fouling in firing the pulverized coal for boiler was assessed for the coal samples. It was found that most ashes contained more than 80% of $SiO_2$ and $Al_2O_3$ whereas less than 1% of $Na_2O$. And also fusion temperature of ashes occured relatively higher for Korean coals. Therefore it can be predictable that the slagging and fouling formation has a little problem in a pulverized coal firing system. A base/acid ratio did show a good correlation with fusion temperature for these coal ashes.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.27-46
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• 1999

Combustion test on two kinds of Indonesian sub-bituminous coals of single and blended with bituminous coal imported for power generation was carried out by using the test furnace at KEPRI. The main items of combustion test were temperature profiles of the inside furnace, the yield of unburned carbon, environmental pollution emissions, slagging/fouling tendency, and the comparison of heat loss of furnace. The test results showed that low sulfur and ash content characterized by the Indonesian coals were advantageous to environmental aspect, but high tendency of heat loss and slagging/fouling were disadvantageous to boiler operation. From the results, the necessity of proper coal blending to compensate these weak points was recommended.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.87-90
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• 2013

In pulverized coal fired boilers, slagging and fouling may cause significant effect on the operational life of boiler. As increasing a consumption of low rank coal, slagging and fouling are main issues in pulverized coal combustion. This study predicts ash deposition propensity in a 0.7 MW pilot-scale furnace. Slagging model is employed as a User-Defined Function (UDF) of FLUENT and validated against measurement and prediction. The results show good agreement compared with experiment. There is need to development of a pulverized coal combustion and slagging analysis at low coal.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1772-1780
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• 2003

An optimal soot blowing system has been developed for an optimal operation of power utility boilers by both minimization of the use of steam and the number of soot blowers worked during soot blowing. Traditionally, the soot blowing system has been operated manually by operators. However, it causes the reduction of power and thermal performance degradation because all soot blowers installed in the plant should be worked simultaneously even there are lots of tubes those are not contaminated by slagging or fouling. Heat transfer area is divided into four groups, furnace, convection area including superheater, reheater and economizer, and air preheater in the present study. The condition of cleanness of the tubes is calculated by several parameters obtained by sensors. Then, a part of soot blowers works automatically where boiler tubes are contaminated. This system has been applied in a practical power plant. Therefore, comparison has been done between this system and manual operation and the results are discussed.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.89-96
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• 2015

Recently, much research has been put into finding the causes and solutions of slagging/fouling problems that occur at the end of the boiler. This slagging/fouling, caused by low-rank coal's ash, disturbs the thermal power and greatly reduces efficiency. In environmental aspects, such as NOx pollution, governments have been implementing restrictions on the quantity of emission gases that can be released into the atmosphere. To solve these problems, research on Ash Free Coal (AFC), which eliminates ash from low-rank coal, is in progress. AFC has advantages over similar high-rank coals because it increases the heating value of the low grade coal, reduces the contaminants that are emitted, and decreases slagging/fouling problems. In this study, using a DTF, the changes of NOx emissions, unburned carbon, and the characteristics of ash deposition were identified. KCH raw coal, AFC extracted from KCH, residue coal, Glencore, and Mixed Coal (Glencore 85wt% and residue coal 15wt%) were studied. Results showed that AFC had a significantly lower emission of NOx compared to that of the raw coal and residue coal. Also, the residue coal showed a higher reactivity compared to raw coal. And finally, In the case of the residue coal and mixed coal, they showed a lower ash deposition than that of low-rank coal.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.293-298
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• 2006

There are many researches in progress on co-firing of coal and biomass to reduce carbon dioxide produced from the coal consumption. This study carried out 200 Kg/h combustion test furnace by mixing coal with timber. Coal was mixed with domestic and imported-wood around 10% to 20% based on input energy. For the mixed fuel, combustion temperature, unburned carbon and the composition of flue gas were analyzed. In addition, the tendency of slagging and fouling was examined using a probe. According to the result of the experiment, combustion temperature was depended on the kind of wood and mixing ratio. The unburned carbon loss was higher with increase of wood biomass mixing ratio, as a result, the total heat loss of furnace was slightly increased. The emission of NOx and SOx were decreased by $3{\sim}20%$ and $21{\sim}60%$ respectively. There are no difference of slagging and fouling tendency between biomass co-firing and coal burning only.

• 한국연소학회:학술대회논문집
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• 1995.06a
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• pp.91-103
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• 1995

In recent years, significant advances have been made in the development of methods to predict ash behavior in utility boilers. This paper provides an overview of methods used to assess and predict ash formation and deposition. It has discussed some of the key problems associated with the formation and deposition of ash during the combustion of pulverized coal. Although considerable progress has been made in understanding of the fundamental mechanisms of ash formation, transport, growth, and strength development, there is still much work to be done. There is a need to develop quantitative relationships between the characteristics of the entrained ash and the physical properties of ash deposits that influence deposit growth, strength development, and cleanability. Also data from bench-scale, pilot-scale, and full-scale units are needed in order to determine operating conditions which will minimize deposition problems, maximize efficiency, and reduce emissions.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.541-543
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• 2004

An optimal soot blowing system has been developed for an optimal operation of power utility boilers by both minimization of the use of steam and the number of soot blowers worked during soot blowing. Traditionally, the soot blowing system has been operated manually by operators. However, it causes the reduction of power and thermal performance degradation because all soot blowers installed in the plant should be worked simultaneously even there are lots of tubes those are not contaminated by slagging or fouling. Heat transfer area is divided into four groups, furnace, convection area including superheater, reheater and economizer, and air preheater in the present study. The condition of cleanness of the tubes is calculated by several parameters obtained by sensors. Then, a part of soot blowers works automatically where boiler tubes are contaminated. This system has been applied in a practical power plant. Therefore, comparison has been done between this system and manual operation and the results are discussed.

• Journal of the Korean Society of Combustion
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• v.22 no.4
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• pp.27-34
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• 2017

Various approaches have been proposed to predict the ash deposition (slagging and fouling) propensity of coal, which is essential in maintaining high efficiency and preventing corrosion/damage of a coal-fired boiler. The common method is to establish an index of the ash deposition propensity based on elementary coal composition and advanced characterization of ash properties, which is readily applicable to design, operation and maintenance of coal-fired boilers. Although many indexes have been developed for this purpose, their validity is still not satisfactory in actual applications to particular coal types or operating conditions. This paper reviews the status of predictive approaches for the ash deposition propensity, and assesses the performance of existing indexes by comparing the results for selected coals. This work will contribute to the development of a comprehensive and practical method for prediction of the ash deposition propensity.