• Journal of Korean Society of Environmental Engineers
• /
• 제29권7호
• /
• pp.801-809
• /
• 2007

Fly ash and blast furnace slag are an industrial by-product that can be alkali-activated to yield adhesive and cementitious materials, whose production is less energy-intensive and emits less $CO_2$ than ordinary Portland cement manufacture. A laboratory investigation was carried out to evaluate the effect of alkali-activating conditions on compressive strength of fly ash/slag cement and the acid corrosion resistance of this cement. Two alkali activator solution, NaOH and waterglass + NaOH solutions, were used. Waterglass concentration was the factor that gave the highest compressive strength in all tests. The next significant factor was the NaOH concentration, followed by curing temperature. Acid corrosion resistance of FC(fly ash cement) and FSC(fly ash/slag cement), such as sulfuric$(H_2SO_4)$ and hydrochloric acid(HCl), was for better than Portland cement(PC).

• Resources Recycling
• /
• 제30권5호
• /
• pp.49-56
• /
• 2021

In this study, using strontium sulfate (SrSO₄) recovered from magnetite ore in Hongcheon, the Black Ash process was used to produce strontium carbonate (SrCO₃). In the carbothermic reaction step, SrSO₄ was reacted with carbon (C) at 1273 K under Ar gas atmosphere using a gas-tight quartz reactor to produce strontium sulfide (SrS). Afterward, water leaching of the residues produced from the carbothermic reaction at 353 K and carbonation of the leaching solution using sodium carbonate (Na₂CO₃) at 298 K were conducted to produce SrCO₃. The results of this study demonstrate the feasibility of the production of SrCO₃ via the Black Ash process using domestic magnetite ore containing strontium (Sr).

• Resources Recycling
• /
• 제32권3호
• /
• pp.38-44
• /
• 2023

Leaching tests were conducted using sulfuric acid and sodium hydroxide solutions to remove impurities from domestic graphite concentrate. As a result of the leaching experiment using sulfuric acid solution and sodium hydroxide solution, respectively, the difference of removal efficiency was insignificant when the concentration of sodium hydroxide or sulfuric acid was 2 mol/L or more. The fixed carbon content increased with increasing the temperature in the sulfuric acid solution leaching, while it remains constant above 150℃ in sodium hydroxide solution. For the repeated sequential leaching tests, the leaching conditions were 2 mol/L NaOH, 200℃, 1 hour in the sodium hydroxide solution leaching and 2 mol/L H₂SO₄, 100℃, 1 hour in the sulfuric acid solution leaching, respectively. When sulfuric acid leaching followed by sodium hydroxide solution leaching was repeated 5 times, the fixed carbon increased to 99.95% and ash content decreased to 0.048%, while the fixed carbon increased to 99.98% and ash content was reduced to 0.018 when sodium hydroxide solution leaching followed by sulfuric acid solution leaching was repeated 5 times.

• KEPCO Journal on Electric Power and Energy
• /
• 제5권4호
• /
• pp.287-293
• /
• 2019

Domestic thermal power plant fly ash is at a situation which emissions are increasing every year. Comparing to Fly Ash, Bottom Ash is only 15 %, but it's recycling rate is low, so most of them is being buried in the ground. However, landfill site of every power plant is full, and the construction of a new landfill is difficult. To solve this problem, the best solution is to use Bottom Ash as a landfill of large-scale civil engineering projects. The purpose of this study was to investigate the compression strength behavior characteristics of weak clay and uniaxial compression test to examine the applicability of surface soil solidification method of mixed soils mixed with industrial waste coal ash and weak clay which is buried in bulk. As a result of the test, the fluidity of the Mixed soil with clay + bottom ash + cement was improved to 200 mm at the water content of 91-92 %. The uniaxial compressive strength was also good for the mixed soils (clay + bottom ash + cement) meeting the required strength of 159 kN/㎡ at 28 days. However, the other samples did not meet the required strength. In this study, the prediction equations for the compression strength behavior by cement and curing period were presented.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• 제42권2호
• /
• pp.163-170
• /
• 2022

The present study investigates NO_x-removal and sound-absorption performances of photocatalytic porous concrete prepared by various TiO₂ application methods. Photocatalytic porous concrete samples were prepared by one of the following: 1) mechanically mixing TiO₂ during casting; 2) mixing bottom ash aggregate pretreated with TiO₂ during casting; and 3) spraying TiO₂ solution to the normally fabricated porous concrete. The test results indicated that the mechanical mixing of TiO₂ decreased the compressive strength as the added TiO₂ content increased. The use of pretreated bottom ash aggregate reduced the porosity, yet the compressive strength of the concrete was similar to that measured from the former method. Porous concrete samples sprayed with the TiO₂ solution exhibited enhanced compressive strength, while the porosity was analogous to those measured from other methods. The NO_x-removal performance was the highest in the samples sprayed with the TiO₂ solution, followed by the samples using pretreated bottom ash aggregate and mechanically mixed TiO₂. The samples with mechanically mixed TiO₂ identified a relationship between soundabsorption performance and porosity. However, no particular tendency was observable in the samples with other TiO₂ application methods.

• The Korean Journal of Food And Nutrition
• /
• 제22권1호
• /
• pp.8-13
• /
• 2009

Effects of microwave and ultrasonication on chitin extraction time were investigated in this study. Chitin was extracted from ground crab shell by demineralization in 1.0 N HCl solution at 25$^{\circ}C$ with or without ultrasonication and deproteinization in 1.0 NaOH solution at 100$^{\circ}C$ without ultrasonication and at 70$^{\circ}C$ with ultrasonication. Microwave treatment was also used for deproteinization with 5 min heating and 5 min standing without microwave. The changes in color difference, the contents of ash, calcium and nitrogen were measured during demineralization and deproteinization. Ultrasonication of 4 hr in 1.0 N HCl solution for removal of calcium and 1.5 hr of microwave heating in 1.0 N NaOH for deproteinization corresponded to 6 hr in 0.1 N HCl and 2 hr in 1.0 N NaOH of heating at 100$^{\circ}C$ without those treatments, respectively. The data obtained showed that these treatments were effective reduction of chitin extraction time by 25${\sim}$33% for chitin preparation. The chitin obtained from these ultrasonication and microwave treatments resulted 0.55% of ash, 0.25% of calcium, 2.47% of nitrogen and 20.64% of yield ratio. Those treatments selected were also reduced the darkness development time of the chitin solution during demineralization and deproteinization.

• Clean Technology
• /
• 제26권3호
• /
• pp.177-185
• /
• 2020

All coal ash, generated from coal-fired power plants, is entirely dumped onto a landfill site. As coal ash contains 80% fly ash, a clean floating process was developed in this study to recover useful components from coal ash and to use them as high value-added industrial materials. When the unburned carbon (UC) was recovered from the fly ash, soybean oil, an eco-friendly vegetable oil, was used as collector instead of a non-ionic kerosene collector to prevent the occurrence of odor from the kerosene. After the UC was separated by flotation, particulate ceramic microsphere (CM) was recovered, without generating acidic wastewater, through hydro-cyclone instead of sulfuric acid solution in order to separate ceramic microsphere (CM) and cleaned ash (CA) from the residue. By utilizing soybean oil as a collector, the recovery rate of UC turned high at 85.8% due to the increased adsorption of UC, the high viscosity of soybean oil, and the increase in floating properties caused by the linoleic acid contained in soybean oil. All of the combustible components contained in the recovered UC were carbon components, with the carbon content registering high when soybean oil was used. The recovered UC had many pores with a rough surface; thus, it could be easily ground and then used as an industrial material for its fine particles. The CM and CA recovered by the clean separation process using hydro-cyclone had a spherical shape, and the particles were clearly separated without clumping together. The average diameter (D₅₀) of the particles was 5 ㎛, so it was possible to realize the atomization of CM through a process change.

• Journal of the Korean Recycled Construction Resources Institute
• /
• 제3권3호
• /
• pp.252-260
• /
• 2015

The aim of this research is providing the fundamental data for treating and recycling the byproducts by using the wet processed bottom ash as a fine aggregate replacement for cement-based extruded panel. Although the cement-based extruded panel was used mainly as a cladding component with its high strength and outstanding durability, it was hardly spread because of low economic feasibility due to the high cost of additives or fibers which were used to achieve 14 MPa of flexural strength as a cladding material. As a solution of this drawback, by the previous research, it was possible to replace cement by fly ash up to 80 % by decreasing quality criteria with restricting the application to indoor purpose. In this research, based on the previous research, by using the bottom ash as a replacement of fly ash, improvement of shape retention performance is tried. As a result of the experiment on evaluating the optimum content and PSD of bottom ash, as the fineness modulus and content of bottom ash was increased, the extruding performance was decreased and penetration resistance was increased. Additionally, the optimum content and the maximum particle size was found as 20 %, and 0.3 mm, respectively.

• Journal of the Korean Ceramic Society
• /
• 제48권1호
• /
• pp.80-85
• /
• 2011

The crystallization behavior and microstructural change of the glass-ceramics were analyzed as a function of concentration and etching time of the HF solution in order to enhance the degree of crystallinity induced by heterogeneous nucleation of glass of bottom ash containing 15 wt% $Li_2O$. The nucleation site seemed to be generated where the Si ion was eluted. The main crystal phases in the glass-ceramics fabricated in this study were $\beta$-spodumene and $Li_2SiO_3$. The specimens etched with HF of 0.5 vol% within 0~60 seconds showed increased crystalline peak intensities in XRD pattern with etching time compared to no-etched one. Also the crystal size and crystal occupancy in the glass matrix observed by SEM were increased with etching time. For the glass-ceramics etched with 1.0 and 2.0 vol% HF solution, the etching time over 10 s was not effective to increase the crystallinity. From this study, it was found that the glass-ceramics with the higher crystallinity could be obtained by HF-etching followed by heat treatment process, even though the nucleating agent or 2-stages thermal treatment process were not used.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 한국건축시공학회 2020년도 가을 학술논문 발표대회
• /
• pp.77-78
• /
• 2020

An alkaline activator was synthesized by dissolving waste glass powder (WGP) in NaOH-4M solution to explore its effects on the Class-C fly ash (FA) and ground granulated blast furnace slag (GGBS) based alkali-activated material (AAM). The compressive strength and porosity were measured, and (SEM-EDX) were used to study the hydration mechanism and microstructure. Results indicated that the composition of alkali solutions was significant in enhancing the properties of the obtained AAM. As the amount of dissolved WGP increased in alkaline solution, the silicon concentration increased, causing the accelerated reactivity of FA/GGBS to develop Ca-based hydrate gel as the main reaction product in the system, thereby increasing the strength. Further increase in WGP dissolution led to strength loss, which were believed to be due to the excessive water demand of FA/GGBS composites to achieve optimum mixing consistency. Increasing the GGBS proportion in a composite also appeared to improve the strength which contributed to develop C-S-H-type hydration.