• Transactions of the Korean hydrogen and new energy society
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• v.22 no.2
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• pp.213-222
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• 2011

To check adaptability of low ash coal(hyper coal) to chemical looping combustion, reaction characteristics of two coals (Roto and Hyper coal) with two oxygen carriers (NiO/bentonite, OCN703-1100) have been investigated in a thermogravimetric analyzer. Hyper coal represented low combustion rate and high ignition temperature, high volatile content and high devolatilization rate, and therefore, showed worse oxygen transfer during successive 10 cycle reduction-oxidation test than Roto coal. Finally we selected Roto coal as the candidate coal for chemical looping combustion. For Roto coal, OCN703-1100 particle showed better oxygen transfer than NiO/bentonite particle. During 10 cycle reduction oxidation test, change of the extent of oxidation (Wo) was negligible and we could conclude that both oxygen carriers have sufficient regeneration ability.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.884-894
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• 2011

Effects of temperature, volatile content, particle diameter and solid input weight were investigated in the batch fluidized bed reactor using OCN703-1100 particle as oxygen carrier and Roto coal and char as fuels. Two solid fuels represented the best reactivity at different temperature, $900^{\circ}C$ for Roto coal and $950^{\circ}C$ for char, respectively. However, we selected $900^{\circ}C$ as the best operating temperature because the improvement of reactivity of char at $950^{\circ}C$ was negligible. Char represented better reactivity than Roto coal because char contains low volatile than Roto coal. For both solid fuels, reactivities were improved with increasing of the particle diameter. These results were explained by solid mixing tests in a transparent fluidized bed using two char particles having different particle size ranges and OCN703-1100 particle. The bigger particle showed better solid mixing with OCN703-1100 particle, and therefore, represented better reactivity. For both solid fuels, reactivities were improved with increasing of the solid input weight within the experimental conditions of this study because the weight of coarse particles increased with the solid input weight increased, and therefore, these coarse particles can mix well with the oxygen carrier.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.183-193
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• 2000

A series of studies such as geological logging data analysis, detailed geological survey, rock mass evaluation, in-situ and laboratory tests, rock strength and mechanical properties of the rock were concerned. The stability of the slope were carried out inorder to design the pit slope and individual benches using the stereographic projection analysis and numerical methods in Roto Pit of Pasir coal fetid. The bedding plane was one of the major discontinuities in the Roto Pit and the dip of which is about $60^{\circ}$in the northern part and $83^{\circ}$in the southern part. The dip of bedding becomes steeper from north to south. The plane and toppling failures are presented in many slopes. In laboratory test the average uniaxial compressive strength of mudstone was 9 MPa and that of weak sandstone was 10 MPa. In-situ test showed that the rocks of Roto north mining area are mostly weak enough to be classified in grade from R2(weak) to R3(medium strong weak) and the coal is classified in grades from R1(Very weak) to R2(Weak). The detailed stability analysis were carried out on 4 areas of Roto north(east, west, south and north), and 2 areas of Roto south(east and west). In this paper, the minimum factor of safety was set to 1.2 which is a general criterion for open pit mines. Using the stereographic projection analysis and the limit equilibrium method, slope angles were calculated as 30~$36^{\circ}$for a factor of safety greater than 1.2. Then these results were re-evaluated by numerical analysis using FLAC. The final slope angles were determined by rational described abode. A final slope of 34 degrees can guarantee the stability for the eastern part of the Roto north area, 33 degrees for the western part, 35 degrees for the northern part and 35 degrees for the southern part. For the Roto south area, 36 degrees was suggested for both sides of the pit. Once the pit slope is designed based on the stability analysis and the safety measures. the stability of 니ope should be checked periodically during the mining operations. Because the slope face will be exposed long time to the rain fall, a study such aspreventive measures against weathering and erosion is highly recommended to be implemented.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.430-440
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• 2000

A series of studies such as geological logging data analysis, detailed geological survey, rock mass evaluation, in-situ and laboratory tests, rock strength and mechanical properties of the rock were concerned. The stability of the slope were carried out inorder to design the pit slope and individual benches using the stereographic projection analysis and numerical methods in Roto Pit of Pasir coal field. The bedding plane was one of the major discontinuities in the Roto Pit and the dip of which is about 60$^{\circ}$ in the northern part and 83$^{\circ}$ in the southern part. The dip of bedding becomes steeper from north to south. The plane and toppling failures are presented in many slopes. In laboratory test the average uniaxial compressive strength of mudstone was 9MPa and that of weak sandstone was 10MPa. In-situ test showed that the rocks of Roto north mining area are mostly weak enough to be classified in grade from R2(weak) to R3(medium strong weak) and the coal is classified in grades from R1(Very weak) to R2(Weak). The detailed stability analysis were carried out on 4 areas of Roto north (east, west, south and north), and 2 areas of Roto south(east and west). In this paper, the minimum factor of safety was set to 1.2 which is a general criterion for open pit mines. Using the stereographic projection analysis and the limit equilibrium method, slope angles were calculated as 30∼36$^{\circ}$ for a factor of safety greater than 1.2. Then these results were re-evaluated by numerical analysis using FLAC. The final slope angles were determined by rational described above. A final slope of 34 degrees can guarantee the stability for the eastern part of the Roto north area, 33 degrees for the western part, 35 degrees for the northern part and 35 degrees for the southern part. For the Roto south area, 36 degrees was suggested for both sides of the pit. Once the pit slope is designed based on the stability analysis and the safety measures, the stability of slope should be checked periodically during the mining operations. Because the slope face will be exposed long time to the rain fall, a study such aspreventive measures against weathering and erosion is highly recommended to be implemented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.8
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• pp.613-621
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• 2009

Coal is the energy resource which is important with the new remarking energy resource. Coal combustion produces more NOx per unit of energy than any other major combustion technology. Pollutant emission associated with coal combustion will have a huge impact on the environment. Coal conversion has three processes which are drying, coal devolatilization and char oxidation. Coal devolatilization process is important because it has been shown that HCN which is converted from volatile N contributes 60 to 80% of the total NOx produced. This paper addresses mass release behavior of char, tar, gas and HCN in an experiment of Laminar Flow Reactor with two coals such as Roto middle coal (Sub-bituminous) and Anglo coal (Bituminous). The experiment is compared with the data predicted by CPD model for mass release of HCN about Roto south, Indominco, Weris creek and China orch coals. The results show that HCN increases as a function of decreasing the ratio of fixed carbon(FC)/ volatile matter(VM of the coals contain.)

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.1
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• pp.87-96
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• 2014

Direct combustion characteristics of coal and oxygen carrier were measured in the thermogravimetric analyzer using four coals and two different oxygen carriers. The direct combustion efficiency decreased in order of Roto, Kideco, Sunhwa and Hyper coal for both oxygen carriers. Moreover, OCN703-1100 oxygen carrier showed better combustion efficiency than OCN706-1100 oxygen carrier for all four coals. The reduction characteristics of two oxygen carriers for $CH_4$, CO and $H_2$ gases were measured in the thermogravimetric analyzer to investigate why OCN703-1100 oxygen carrier showed better combustion efficiency than OCN706-1100 for all coals. The OCN703-1100 oxygen carrier represented higher reduction rate than OCN706-1100 for all reducing gases. Moreover, the total pore area and the porosity of OCN703-1100 were higher than those of OCN706-1100 oxygen carrier. The total volatile gas and volatile components of four coals were measured in a batch type fluidized bed reactor to investigate why the direct combustion efficiency decreased in order of Roto, Kideco, Sunhwa and Hyper coal for both oxygen carriers. The direct combustion efficiency was proportional to the total amount of ($CH_4+CO+H_2$) produced during devolatilization of coals.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.544-552
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• 2014

In this study, We have investigated the kinetics on the char-$CO_2$ gasification reaction. Thermogravimetric analysis (TGA) experiments were carried out for char-$CO_2$ catalytic gasification of an Indonesian Roto lignite. $Na_2CO_3$, $K_2CO_3$, $CaCO_3$ and dolomite were selected as catalyst which was physical mixed with coal. The char-$CO_2$ gasification reaction showed rapid an increase of carbon conversion rate at 60 vol% $CO_2$ and 7 wt% $Na_2CO_3$ mixed with coal. At the isothermal conditions range from $750^{\circ}C$ to $900^{\circ}C$, the carbon conversion rates increased as the temperature increased. Three kinetic models for gas-solid reaction including the shrinking core model (SCM), volumetric reaction model (VRM) and modified volumetric reaction model (MVRM) were applied to the experimental data against the measured kinetic data. The gasification kinetics were suitably described by the MVRM model for the Roto lignite. The activation energies for each char mixed with $Na_2CO_3$ and $K_2CO_3$ were found a 67.03~77.09 kJ/mol and 53.14~67.99 kJ/mol.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.83-86
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• 2006

In this study, the syngas producing facility that consists of pulverized coal feeding/gasification and hot gas clean-up system was tested for Indonesian subbituminous coal. And the DME conversion facilities have been developed and tested for converting syngas to DME by reactions with catalysts. So, the entrained-bed slagging type pi lot scale coal gasifier was operated normally in the temperature range of $1,400{\sim}1,450^{\circ}C,\;7{\sim}8kg/cm^2$ pressure. And Roto middle coal produced syngas that has a composition of $36{\sim}38%$ CO, $14{\sim}16%\;H_2,\;and\;5{\sim}8%\;CO_2$. Particulates in syngas were 99.8% removed by metal filters. $H_2S$ composition in syngas was also desulfurized by the Fe chelate system to yield less than 0.1 ppm level. When the clean syngas $70{\sim}100 Nm^3/h$ was provided to DME conversion rector, normally operated in the temperature range of $230{\sim}250^{\circ}C$ and $60kg/cm^2$ pressure, 4.5% DME was yielded.

• Journal of Energy Engineering
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• v.8 no.4
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• pp.560-566
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• 1999

PDTF (Pressurized drop tube furnace) experiments using variations of temperature, oxygen/coal ratio, steam/coal and pressure with Roto coal (Sub A) were performed in order to investigate the effects of these experimental parameters on global gasification characteristics at elevated pressure. The results shows that the gasification at elevated pressure is more profitable than that at atmospheric pressure considering the carbon conversion and cold gas efficiency. The oxygen/coal ratio at which maximum cold gas efficiency was appeared ranged from 0.5 to 0.7 g/g. only when the temperature is sufficiently high enough, the raise of steam/coal ratio brings improvement of cold gas efficiency. As the pressure increased, the volume of carbon conversion by heterogeneous reaction increased but the volume of carbon conversion by pyrolysis decreased relatively.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.23-31
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• 1999

PDTF(Pressurized drop tube furnace) experiments using varied temperature, oxygen/coal ratio, steam/coal ratio and pressure with Roto coal(Sub A) were performed in order to investigate the effects of these experimental parameters on global gasification characteristics at elevated pressure. The results shows that the gasification at elevated pressure is more profitable than that at atmospheric pressure considering the carbon conversion and cold gas efficiency. The oxygen/coal ratio at which maximum cold gas efficiency was appeared ranged from 0.5 to 0.7g/g. Only when the temperature is sufficiently high enough, the raise of steam/coal ratio brings improvement of cold gas efficiency. As the pressure increased, the volume of carbon conversion by heterogeneous reaction increased but the volume of carbon conversion by pyrolysis decreased relatively.