• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.359-366
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• 2022

In this paper, the effect of compression levels on the strengths of porous concrete using bottom ash aggregates was analyzed. Coal bottom ash (CBA) was used as aggregate in porous concrete in this study. The aggregate size types used in the CBA concrete mixtures were catagorized into two different ones. One included only a single aggregate particle size and the other included hybrid aggregate particles mixed at a ratio of 8:2 volume proportion. The water-binder ratio was fixed at 0.30, and the compression levels were applied at 0.5, 1.5, and 3.0 MPa valu es to fabricate a porou s concrete specimen. The total porosity, compressive, splitting tensile, and flexural tensile strengths were tested and analyzed. When the compression level increased, the total porosity decreased, meanwhile the compressive, split tensile, and flexural tensile strengths increased. The total porosity of concrete using hybrid aggregate was lower and the strength was larger than those of concrete using single-type aggregate. Finally, the correlation between the total porosity, compressive, split tensile, and flexural tensile strengths of porous concrete were presented. The total porosity and strength characteristics showed an inversely proportional correlation.

• Journal of Environmental Science International
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• v.25 no.12
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• pp.1613-1622
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• 2016

Zeolite (FZ), prepared from fly ash, was immobilized with polyacrylonitrile (PAN) to fabricate PAN/FZ beads. The prepared PAN/FZ beads were characterized by scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The optimum ratio to prepare PAN/FZ beads was 0.3 g of PAN to 0.3 g of FZ. The diameter of the prepared PAN/FZ beads was about 3 mm. Sr and Cu ion adsorption experiments were conducted with PAN/FZ beads. A pseudo-second-order model fit the kinetic data for Sr and Cu ion adsorption by PAN/FZ beads well. The equilibrium data fitted well with the Langmuir isotherm model, and the maximum adsorption capacities were 96.5 mg/g and 74.6 mg/g for the Sr and Cu ions, respectively. Additionally, the values of thermodynamic parameters such as Gibbs free energy (${\Delta}G^o$), enthalpy (${\Delta}H^o$) and entropy (${\Delta}S^o$) were determined. The positive values of ${\Delta}H^o$ revealed the endothermic nature of the adsorption process and the negative values of ${\Delta}G^o$ were indicative of the spontaneity of the adsorption process.

• Resources Recycling
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• v.25 no.3
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• pp.20-28
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• 2016

Assessment on adequate dosage of superplasticizer in eco-friendly ultra-high performance concrete (UHPC) containing industrial by-products was carried out from the standpoint of workability. Various types of industrial by-products, including blast-furnace slag, coal bottom ash and rapid-cooled electric arc furnace oxidizing slag, were utilized, and the effects of dosage of superplasticizer on the workability and strength of UHPC containing the by-products were evaluated. By utilizing the by-products, the workability of UHPC was improved and required dosage of superplasticizer was reduced. In addition, the material cost for UHPC with by-products was decreased due to reduced dosage of superplasticizer.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.1
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• pp.24-34
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• 2015

Domestic companies supplying electricity must increase obligatory duty to use renewable energy annually. If not met with obligatory allotment, the electricity-supply companies must pay RPS (Renewable Portfolio Standards) penalty. Although the power plants using a pulverizing coal firing boiler could co-fire up to around 3 per cent with wood pellets mixed in with coal feedstock without any major equipment revamps, they recorded only about 60 per cent fulfillment of RPS. Consequently, USD 46 million of RPS penalty was imposed on the six power supplying subsidiaries of GENCOs in 2014. One of the solutions to reduce the RPS penalty is that the power supply companies adopt the co-firing of torrefied lignocellulosic biomass in coal plants, which may contribute to the use of over 30 per cent of torrefied biomass mixed with bituminous coals. Extra binder was required to form pellets using torrefied biomass such as wood chips, PKS (Palm Kernel Shell) and EFB (Empty Fruit Bunch). Instead of corn starch, 30, 50 and 70 per cent of Larix saw dusts were respectively added to the torrefied feedstocks such as Pinus densiflora chips, PKS and EFB. The addition of saw dusts led to the decrease of the calorific values of the pellets but the forming ability of the pelletizer was exceedingly improved. Another advantage from the addition of saw dusts stemmed from the reduction of ash contents of the pellets. Finally, it was confirmed that torrefied oil palm biomass such as PKS and EFB could be valuable feedstocks in making pellets through improved binding ability.

• Clean Technology
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• v.24 no.4
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• pp.323-331
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• 2018

The results of an experimental investigation on the co-firing characteristics and slagging behavior of dried and hydrothermal carbonization sewage sludge, sub-bituminous coal, and wood pellet in a fluidized bed were presented. Combustion tests were conducted in a lab-scale bubbling fluidized bed system at the uniform fuel-air equivalence ratio, air flow rate, and initial bed temperature to measure bed temperature distribution and combustion gas composition. 4 different fuel blending cases were prepared by mixing sewage sludge fuels with coal and wood pellet with the ratio of 50 : 50 by the heating value. $NO_x$ was mostly NO than $NO_2$ and measured in the range of 400 to 600 ppm in all cases. $SO_2$ was considered to be affected mostly by the sulfur content of the sewage sludge fuels. The cases of hydrothermal carbonization sewage sludge mixture showed slightly less $SO_2$ emission but higher fuel-N conversion than the dried sewage sludge mixing cases. The result of fly ash composition analysis implied that the sewage sludge fuels would increase the possibility of slagging/fouling considering the contents of alkali species, such as Na, K, P. Between the two different sewage sludge fuels, dried sewage sludge fuel was expected to have the more severe impact on slagging/fouling behavior than hydrothermal carbonization sewage sludge fuel.

• Clean Technology
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• v.29 no.1
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• pp.22-30
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• 2023

Mongolia is experiencing some of the world's most serious air pollution problems. The air pollution is especially severe during the winter when raw coal and low-grade fuels are used to heat homes in Ger villages. The impact of this pollution has created significant health and socioeconomic challenges for the country. In order to mitigate this air pollution, this study analyzed the fuel quality of the low-grade fuels and Mongolian waste cooking oils used in Ulaanbaatar, Mongolia. Then the environmental characteristics of traditional stove combustion and a prototype combustion heating device were compared and analyzed. In addition, the effect of replacing the heating devices was evaluated by analyzing their risks to humans. Analysis of the fuel characteristics showed that briquettes had relatively low environmental properties as a result of their high ash, N and S content. Also, after analyzing the combustion characteristics, it was found that the air quality improvement effect was higher when waste cooking oil was burned compared to the three types of coal that were analyzed. Finally, this study evaluated the impact of replacing the Mongolia traditional stove with a prototype stove that uses waste cooking oil. The results of this study are expected to help to mitigate the air quality problems currently observed in Ulaanbaatar, Mongolia.

• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.94-101
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• 2009

The physical properties of artificial aggregates made from clay and inorganic wastes with poor plasticity depends largely on forming method. The artificial aggregates composing of coal fly ash, stone sludge and clay were fabricated using 4 different forming methods and those physical properties were comparatively analyzed. The surface of aggregates made through the extrusion forming process was dense and smooth but was rough for the aggregates obtained by crushing a tile-shaped green body. The aggregates made by pelletizing process had a weak green strength and bumpy surface. The shell generated at surface during a high temperature sintering process induced the most aggregates to be bloated due to a dense shell. But the aggregates made through pelletizing process with dense surface layer showed no significant change in bulk density with sintering temperatures. The water absorption of aggregates decreased with sintering temperature, and that of pelletized specimen was standing $1.8{\sim}2.2$ times higher than that of made by other forming methods. It is concluded that the aggregates having various properties could be fabricated from one batch by using different forming methods.

• Journal of Environmental Science International
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• v.11 no.1
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• pp.75-83
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• 2002

The removal performance of copper ion was studied using Na-P1 zeolites synthesized from Jeju scoria. The scoria which is found in large amounts in Jeju Island, was sampled at four regions, Jeju-shi Bonggae-dong(A). Pukcheju-gun Hanlim-eup Sangmyong-ri Mangoreum(B), Pukcheju-gun Hanlim-eup Keumag-ri(C) and Namcheju-gun Andeok-myun Dongkwang-ri(D). Synthetic Na-P1 zeolites used in this study were more effective than natural zeolite and scoria for the removal of copper ion. The removal performances of copper ion decreased in the order of Na-P1(D) > Na-P1(C) > Na-P1(B) > Na-P1(A) among Na-P1 synthesized from the scoria according to region. These results showed the same trend with cation exchange capacity(CEC) for each synthetic zeolite, i.e., the synthetic Na-P1 zeolite with a higher CEC showed a higher removal performance. The effective diffusion coefficients of copper ion by synthetic Na-P1 zeolites were one hundred and ten times higher than those by a pure zeolite 4A and the zeolite A synthesized from coal fly ash, respectively.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.10a
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• pp.5-21
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• 2005

Urbanization rates of population range from about 1% in the developed countries to about 4% in developing countries. For a global population that may reach 10 billion within the next 40 years, pressure has arisen for an increase in the large-scale use of wastes and byproducts in construction. Ironically, most of the wastes that need to be recycled are generated in large cities where the need for constructed facilities to serve large population is high. Waste and recycled materials (WRM) that are used in construction are required to satisfy material strength, durability and contaminant teachability requirements. These materials exhibit a wide variety of characteristics owing to the diversity of industrial processes through which they are produced. Several laboratory-based investigations have been conducted to assess the pollution potential and load bearing capacity of materials such as petroleum-contaminated soils, coal combustion ash, flue-gas desulphurization gypsum and foundry sand. For full-scale systems, although environmental pollution potential and structural integrity of constructed facilities that incorporate WRM are interrelated, comprehensive schemes have not been developed for integrated assessment of the relevant field-scale performance factors. In this presentation, a framework for such an assessment is proposed and presented in the form of a flowchart. The proposed scheme enables economic, environmental, worker safety and engineering factors to be addressed in a number of sequential steps. Quantitative methods and test protocols that have been developed can be incorporated into the proposed scheme for assessing the feasibility of using WRM as partial or full substitutes for earthen highway materials in the field.

• Journal of the Korean Applied Science and Technology
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• v.28 no.4
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• pp.455-463
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• 2011

The average sulfur content of crude oil is 2.2%. Coal is about 0.3 to 4.0 percent of the sulfur gases or particles being discharged into the atmosphere through the chimney as 1 to 2% $SO_3$(Sulfur trioxide) and about 95% of the $SO_2$ is reported. $SO_3$ gas, which has many different causes of, as the combustion of sulfur containing fuel during the air due to the excess $SO_2$ gas is oxidized to $SO_3$ gas. Sulfur trioxide emitted from high sulfur heavy oil fired boiler caused white plume in stack and high temperature and cold end corrosion of facilities. So, in order to control sulfur trioxide concentration of Fuel gas in boiler, various of additives are used in other foreign. They are injected to Fuel Oil and consumed in boiler and reduce ash and the conversion rate of sulfur trioxide. In domestic, MgO compounds are used as additives but the total volume of them are made from other foreign company. In this study, MgO compounds were developed with liquid MgO compounds and field application was accomplished. The effect of newly developed chemicals and process were nearly equal to foreign products. In Consequent, the chemicals and process produced by newly developed technology can be substituted for foreign products and reduce the cost of plant operation.