• Journal of the Korean Society of Combustion
• /
• v.15 no.4
• /
• pp.58-64
• /
• 2010

Spontaneous ignition tests of five different coals with non-iso-thermal and iso-thermal test method based on the standard test procedure of NF T20-036 were carried. These five coals included the 2 low rank coals and 3 bituminous coals. Test results showed that the ignition temperatures of all coals at the iso-thermal conditions were higher than that of non-isothermal condition, and those of low rank SM and BR coal in both nonisothermal and isothermal conditions were lower than bituminous AN and CN coals. The chemical species of coals such as oxygen and hematite also plays an important role in enhancing the ignition rate that the ignition temperature of SM coal was lowered. The heat accumulation tendency of five coals inside outdoor stack pile was monitored with emphasis on the change in the temperature of the coal depth in stack pile. In case of low rank BR coal, its temperature inside coal stack pile due to the rate of high heat accumulation and oxidation was $59^{\circ}C$ compared to $51^{\circ}C$ for other SW bituminous coal. And the heat accumulation rate inside coal stack piles was increased with increased the Cp value which it was defined as the specific heat of coal at constant pressure, whereas other factors such as thermal diffusivity and conductivity of coal relatively had less effect on heat accumulation.

• Applied Chemistry for Engineering
• /
• v.31 no.3
• /
• pp.328-333
• /
• 2020

In this study, blended feedstock derived pyrolyzed fuel oil (PFO) and coal-tar was prepared to produce a pitch by thermal polymerization reaction for manufacturing artificial graphite materials. The aromaticity value of 0.355 and 0.818 was obtained for PFO and coal-tar, respectively. In addition, PFO and coal-tar exhibited the difference tendency of weight loss curve for thermogravimetric analysis, which is related to the structural stability depending on the aromaticity and functional groups. The production characteristics confirmed that the pitch derived PFO showed lower production yield and higher softening point than that using blended feedstock. In particular, when comparing P360 (138.5 ℃) and B420 (141.4 ℃) having similar softening points, the production yields of both pitches exhibited 29.89 and 49.03 wt%, respectively. This is mainly due to the blending of PFO and coal-tar having high pitch polymerization reactivity including a large amount of alkyl groups and coal-tar having high thermal stability. This phenomenon indicated that the increased production yield is because of a synergic effect of both the high reactivity of PFO and thermal stability of coal-tar.

• The Journal of Asian Finance, Economics and Business
• /
• v.9 no.5
• /
• pp.475-486
• /
• 2022

The purpose of this paper is to examine the use of material flow cost accounting (MFCA) in Vietnam's coal-fired thermal power plants. This study is based on the contingency and system theories to explain the application of management tools and analyze steps of input, output, and process in manufacturing. Costs in producing process-based MFCA include material cost, energy cost, system cost, and waste management cost. The exploratory case study methodology is used to describe and answer two questions, namely "How coal flow cost is recognized?" and "Why waste in material consumption can be harmful to the environment?". By analyzing the Quang Ninh and Pha Lai coal-fired thermal power plants that are the typical plants, this paper identifies the flow of primary material in these plants as a basis for determining losses for the business. The material flow of coal-fired thermal power plants provides the basis for the use of the MFCA. The manufacturing of electrical items in these plants is divided into four stages, each with its own set of losses. As a result, some phases in the application of MFCA are suggested, as well as some other elements required for MFCA application in coal-fired thermal power plants.

• Asia-Pacific Journal of Business
• /
• v.9 no.4
• /
• pp.67-84
• /
• 2018

This study is about comparing coal thermal plant to LNG combined power plant in respect of environmental and economic cost analysis. In addition sensitive analysis of power cost and discount rate is conducted to compare the result of change in endogenous and exogenous variable. For environmental assessment, when they generate 10,669GWh yearly, coal thermal power plant emits sulfur oxides 959ton, nitrogen oxide 690ton, particulate matter 168ton and LNG combined power plant emits only nitrogen oxide 886ton respectively every year. Regarding economic cost analysis on both power plants during persisting period 30 years, coal thermal power plant is more cost effective 4,751 billion won than LNG combined taking in account the initial, operational, energy and environmental cost at 10,669GWh yearly in spite of only LNG combined power plant's energy cost higher than coal thermal. In case of sensitive analysis of power cost and discount rate, as 1% rise or drop in power cost, the total cost of coal thermal power plant increases or decreases 81 billion won and LNG combined 157 billion won up or down respectively. When discount rate 1% higher, the cost of coal thermal and LNG combined power plant decrease 498 billion won and 539 billion won for each. When discount rate 1% lower, the cost of both power plant increase 539 billion won and 837 billion won. With comparing each result of change in power cost and discount rate, as discount rate is weigher than power cost, which means most influential variable of power plan is discount rate one of exogenous variables not endogenous.

• Journal of Hydrogen and New Energy
• /
• v.27 no.5
• /
• pp.612-619
• /
• 2016

Pitch synthesis reaction was studied based on the effect for chemical composition of feedstock. Feedstock was selected as pyrolyzed fuel oil (PFO) and coal-tar (CT), which are by-products in petroleum and steel industry. Pitch was prepared at $420^{\circ}C$ for 180 minutes on atmospheric pressure by thermal treatment. Thermal stability and softening point (SP) of the prepared pitches were investigated and their molecular weight distribution was analyzed by MALDI-TOF. PFO has various aliphatic compounds and coal-tar has high aromaticity with 3 wt% of primary quinoline insolubles. The thermal property of PFO was enhanced with polymerization reaction during the thermal treatment with increased molecular weight range. But CT was inferior to PFO because of side reaction by hetero elements. CTP was appeared molecular weight by 0~200 m/z.

• Journal of Service Research and Studies
• /
• v.6 no.4
• /
• pp.75-85
• /
• 2016

Coal can be divided into thermal coal and coking coal. The price of thermal coal is basically affected by demand and supply. However, many other factors with regard to economic condition such as exchange rate, economy growth rate also make an influence on the price. This study is targeted to develop a forecast model for thermal coal price by using System Dynamics Method. System dynamics provides results that better reflect the real world by employing an inter-dependent system of variables. This study found out that 8 factors have important influence on the thermal coal price. Most of the data of the variables were acquired from the Bloomberg Database. The period extends to 2 years and 4 months, from May of 2011 to August of 2013. The causal relations among the variables were acquired by regression analysis

• Journal of Environmental Impact Assessment
• /
• v.24 no.5
• /
• pp.472-486
• /
• 2015

More than 8M tons of coal ashes are generated from coal-fired thermal power plants every year in Korea. Excluding the recycled portion (Current recycling rate: approximately 70%), all of the generated coal ashes end up in coastal landfills. Currently, the difficulties faced in establishing new ash treatment fields are attributed to the concerns raised over the environmental impacts caused by the landfills at individual plant facilities. Given the number of coal-fired thermal power plants to be built in the future (reflected in the 7th Basic Plan for Long-term Electricity Supply and Demand), building new ash treatment fields or seeking a new treatment plan seems unavoidable. Based upon a review of coal ash and its management, this study concluded that the most effective and fundamental strategy to minimize the environmental impacts resulting from coal ash landfills is to avoid constructing new coal-fired powerplants and furthermore, suggests that the practice of beneficial use and recycling the produced coal wastes should be encouraged.

• Geomechanics and Engineering
• /
• v.32 no.2
• /
• pp.233-244
• /
• 2023

With the increasing amount of resources required by the society development, mining operations go deeper, which raises the requirements of studying the effects of temperature on the physical and mechanical properties of coal and adjacent rock. For now, these effects are yet to be fully revealed. In this paper, a mechanical-electromagnetic radiation (EMR) test system was established to understand the mechanical deterioration characteristics of coal by the effect of thermal treatment and its deformation and fracture characteristics under thermo-mechanical coupling conditions. The mechanical properties of high-temperature-treated coal were analyzed and recorded, based on which, reasons of coal mechanical deterioration as well as the damage parameters were obtained. Changes of the EMR time series under unconstrained conditions were further analyzed before characteristics of EMR signals under different damage conditions were obtained. The evolution process of thermal damage and deformation of coal was then analyzed through the frequency spectrum of EMR. In the end, based on the time-frequency variation characteristics of EMR, a method of determining combustion zones within the underground gasification area and combustion zones' stability level was proposed.

• Carbon letters
• /
• v.28
• /
• pp.38-46
• /
• 2018

Modified pitch A (MPA) and modified pitch B (MPB) were prepared by oxidative polymerization and thermal polycondensation reaction with refined pitch as the raw material, respectively. The toluene soluble components (TS-1 and TS-2) were obtained by solvent extraction from MPA and MPB, separately. The Flynn-Wall-Ozawa method and Kissinger-Akahira-Sunose method were used to calculate the pyrolysis activation energy of TS. The Satava-Sestak method was used to investigate the pyrolysis kinetic parameters of TS. Moreover, the optical microstructure of the thermal conversion products (TS-1-P and TS-2-P) by calcination shows that TS-1-P has more contents of mosaic structure and lower contents of fine fiber structure than TS-2-P. The research result obtained by a combination of X-ray diffraction and the curve-fitting method revealed that the ratios of ordered carbon crystallite (Ig) in TS-1-P and TS-2-P were 0.3793 and 0.4417, respectively. The distributions of carbon crystallite on TS-1-P and TS-2-P were calculated by Raman spectrum and curve-fitting analysis. They show that the thermal conversion product of TS-2 has a better graphite crystallite structure than TS-1.

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