• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.443-450
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• 2008

Efficient use of low rank coals (LRC) have been investigated as a method to cope with recent high oil price. Among the coals used in industry, lignite and sub-bituminous coals are belong to the LRC, and have abundant deposit and are distributed worldwide, but high moisture contents and self ignition properties inhibits their utilization. In this paper, chemical coal cleaning to produce ash-free coal from LRC has been investigated. Two technologies, that is, UCC(Ultra Clean Coal) process removing ash from coal and Hyper Coal process extracting combustibles from coal were compared with. UCC process has merits of simple and reliable when it compared with Hyper Coal process, but the remaining ash contents werehigher than Hyper Coal. Hyper Coal has ash contents under the 200ppm when raw coal is treated with appropriate solvent and ion exchange materials to remove alkali materials in extracted solution. The ash-free coal which is similar grade with oil can be used as alternate oil in the industry, and also used as a high grade fuel for IGCC, IGFC and other advanced combustion technology.

• Journal of the Korean Society of Combustion
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• v.18 no.3
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• pp.44-53
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• 2013

In this study, the economic evaluation for imported coals was conducted for power plant based on thermo-dynamical performance analysis. The number of coal types considered was 1,755 imported by five power generation companies in Korea during the 2010-2012. The higher heating value (HHV) of the coals ranged 4,000-6,500 kcal/kg, mostly sub-bituminous. The 1D thermo-dynamical performance modeling was performed for a 500 MWe standard power plant using PROATES code. It was founded that the low rank coals had negative effects on the plant efficiency mainly due to the increased heat loss by moisture, hydrogen and flue gas. Based on the performance analysis, the economic performance of the coals was evaluated. The apparent price of low-rank coals tended to be significantly lower than design coal; for example, the unit price of coal with a HHV of 4,000 kcal/kg was 57% of the reference coal having 6,080 kcal/kg. Considering the negative effects leading to a decrease in the thermal performance, heating value compensation, and increased parasite load, the corrected unit cost for the coal with 4,000 kcal/kg was 90.7% of the reference coal. Overall, the cost saving by imported coals was not high as expected.

• Economic and Environmental Geology
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• v.22 no.2
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• pp.141-150
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• 1989

In order to make economic and geological evaluation of coal in Korea, proximate and ultimate analyses were carried out as well as coal petrological studies such as maceral analyses, vitrinite reflectance and sporinite fluorescence measurement. The coeffcient of correlation between each factor of both conventional utilization and coal petrological parameters were studied as in Table 5 and 6. Their conclusions were as follow: (1) for anthracite, the good parameters of coal rank are mean vitrinite reflectance, carbon content, hydrogen content and H/C atomic ratio: (2) for brown coal and sub-bituminous coal, the good parameters of coal rank are carbon content, calorific value, moisture content, hydrogen content, oxygen content and O/C atomic ratio as well as vitrinite reflectance and sporinite fluorescence. An attempt is made to infer the coalforming environment by utilization of coal petrological analyses and to make comparison of coal analyses with proximate and ultimate analyses throughout the island arc region including Japan, Philippine and Indonesia and continental region including USA, Canada and Australia. As a result, meceral composition of Paleozoic and Mesozoic anthracite are similar to that of the Paleozoic continental coals, which were formed under dry conditions or low water table, but the coalification degree suddenly increased during Daebo orogeny (middle Jurassic to lower Cretaceous). The Tertiary coal resembles those of Tertiary island arc region coal characterized by higher calorific value, volatile matter content and H/C atomic ratio and by the formation of coal under wet conditions or higher water table.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.312-318
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• 2011

We have investigated the kinetics and catalytic activity of $CO_2$-lignite gasification with various metal precursors as catalysts. $K_2CO_3$, $Mn(NO_3)_2$, and $Ce(NO_3)_3$ were used and impregnated on a coal using an evaporator. The gasification experiments were carried out with the low rank coal loaded with 5 wt% catalyst at the temperature range from $700{\sim}900^{\circ}C$ and atmospheric pressure with the $N_2-CO_2$ reactant gas mixture. The catalytic effect on the gasification rate of the low rank coal with $CO_2$ was determined by the thermogravimetric analyzer. It was observed that the low rank coal reached the complete carbon conversion regardless of the kinds of catalysts at $900^{\circ}C$ from the results of TGA. The catalytic activity was ranked as 5 wt% $K_2CO_3$ > 5 wt% $Mn(NO_3)_2$ > 5 wt% $Ce(NO_3)_3$ > Non-catalyst at $900^{\circ}C$. The gasification rate increased with increasing the temperature. The activation energy of the catalytic gasification with 5 wt% $K_2CO_3$ was 119.0 kJ/mol, which was the lowest among all catalysts.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.231-235
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• 2015

The characteristics of binderless briquettes for dried low-rank coal was studied in this work. Two kinds of Indonesian coals were used to briquette after drying them in electric oven. The characteristics of briquettes have been examined by moisture contents, particle size, hydraulic force, and storing period. The optimum moisture contents of briquettes were observed at between 10 wt% and 15 wt%. The strength of coal briquette was stronger as particle size became smaller. The strength of coal briquette was proportional to the hydraulic force under 300 kN, whereas there was little difference among the briquettes made at more than 300 kN of hydraulic force. The strength of briquettes sharply decreased for a week after produced, and then showed the tendency of converging. The results from this work can be a useful guideline of manufacturing and managing upgraded coal briquettes.

• Journal of Energy Engineering
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• v.18 no.4
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• pp.213-220
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• 2009

The experimental characteristics for fry drying method was investigated using low-rank coal with a high moisture content. Final temperature, mixing ratio between coal and kerosene, content of coal or kerosene, total weight of the mixture and mixing methods were varied to find out the optimum conditions by measuring moisture of coal. Evaporation of the coal moisture was not completed below $120^{\circ}C$ of final temperature. The amount of moisture was not significantly different over $130^{\circ}C$. Coal moisture was easily evaporated by increasing coal content, which showed that the moisture evaporation could be significantly enhanced by the remove of evaporated moisture from kerosene rather than by heat transfer to the coal. High total weight of the mixture resulted in lowering moisture content of coal with long evaporation time. On the other hand, low total weight was difficult to reduce the moisture below a certain level, but could reduce evaporation time. Thus, it can concluded that kerosene content should be lowered to the extent maintaining the mobility of the mixture in order to enhance evaporation. It was also observed that evacuation and mixing by using nitrogen could improve drying of coal.

• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.199-209
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• 2010

Coal gasification technology in the sector of domestic clean coal technologies is being into the limelight since recent dramatic rise of international oil price. In this study, we used a low rank coal from Inner Mongolia, China as a starting material for gasification. Various properties including optical, mineralogical, X-ray spectroscopic, X-ray diffraction, and drying property were measured and tested in order to estimate the suitability of the coal to gasification. The coal was identified as a brown coal of lignite group from the measurement of vitrinite reflectance. The coal has very low slagging and fouling potentials, and the ignition temperature is about $250^{\circ}C$. The major impurities consist of quartz, siderite, and clay minerals. Additionally, the coal had moisture content above 28%. Tests for finding effective drying method showed that the microwave drying is more effective than thermal drying.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1086-1092
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• 2012

In this study, kinetic studies and analysis of the produced syngas were conducted for low rank coal gasification under $CO_2$ atmosphere. 6 coals were analyzed to measure amount of sulfur and ash by proximate and ultimate analyses. And then they were analyzed to select suitable sample by using Thermogravimetric analyzer (TGA). Selected coal sample Samhwa was mixed with catalysts. Mixed samples with catalysts were used to get activation energy under $CO_2$ atmosphere by using Kissinger's method and shrinking core model (SCM). Also, analysis of produced syngas was performed by Gas Chromatography (GC). In this experiment, activation of the $K_2CO_3$ was the best performance, and result of the analysis of the syngas showed similar trend with result of the activation energy.

• 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.

• Environmental Engineering Research
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• v.25 no.4
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• pp.522-528
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• 2020

To achieve the clean and efficient utilization of low-rank coal, the combustion and pollutant emission characteristics of chars from low-temperature and fast pyrolysis in a horizontal tube furnace were investigated in a TG-MS analyzer. According to the results, the combustion characteristic of chars was poorer than its parent coals. The temperature range of gaseous product release had a good agreement with that of TGA weight loss. Gaseous products of samples with high content of volatile were released earlier. The NO and NO₂ emissions of chars were lower than their parent coals. Coals of high rank (anthracite and sub-bituminous) released more NO and NO₂ than low rank coals of lignite, so were chars from coals of different ranks. SO₂ emissions of char samples were lower than parent coals and did not show obvious relationship with coal ranks.