• Journal of Korean Society of Environmental Engineers
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• v.31 no.1
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• pp.21-28
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• 2009

Physico-chemical characteristics of the Ca-based and Na-based dry sorbents were compared using thermo-gravimetric analysis (TGA) and temperature programmed desorption (TPD) methods. The studied characteristics were thermal stability, sulfur dioxide ($SO_2$) absorption capacity and absorption rate at $250^{\circ}C$ which is a typical temperature before a fabric filter, and $SO_2$ absorption capacity at an ambient temperature. Calcium hydroxide ($Ca(OH)_2$) started to decompose into calcium oxide (CaO) at $390^{\circ}C$ and completed at 480~$500^{\circ}C$, showing 76% of an original $Ca(OH)_2$ weight. Sodium bicarbonate ($NaHCO_3$) also converted to sodium carbonate ($Na_2CO_3$) between $95^{\circ}C$ and $190^{\circ}C$, decreasing the weight to 63% of its initial weight. Among four sorbents tested at $250^{\circ}C$, sodium carbonate had the highest capacity, absorbing 0.35 g $SO_2$/g sorbent. Calcium oxide and calcium hydroxide followed that showing 0.156 g and 0.065 g $SO_2$ absorption per absorbent respectively. Ca-based absorbents showed slower rate than sodium carbonate because of initial stagnant step. However, calcium hydroxide caught more $SO_2$ than sodium carbonate at ambient temperature. From this work, it can be concluded that Ca-based absorbent is a proper sorbent for $SO_2$ treatment at low temperature and sodium carbonate, at high temperature.

• Resources Recycling
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• v.14 no.2
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• pp.10-18
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• 2005

The manufacture property of anhydrous calcium sulfate (anhydrite Ⅱ) from flue gas desulfurization (FGD) gypsum discharged from domestic thermoelectric power plants to apply as an auxiliary material of cement and concrete by high temperature treatment were investigated. The FGD gypsum was completely converted to anhydrite Ⅱ at the temperature of 700$^{\circ}C$ and the retention time of 1 hr. In the phase transformation process, particle size was also changed. The chemical composition, particle size and heat property of anhydrite Ⅱ made from the FGD gypsum were similar to them of natural gypsum. In the leaching test of sulfate ion (SO$_4^{2-}$) at the temperature of 90$^{\circ}C$ and the retention time of 1 hr, the amount of leached SO$_4^{2-}$ for the anhydrite Ⅱ that was sintered at 700$^{\circ}C$ for 1 hr was about 50 wt.% based on that of natural gypsum. In addition, the amount of leached SO$_4^{2-}$ for the anhydrite Ⅱ by adding the slaked lime of 3 wt.% decreased about 70 wt.% comparing with that of natural gypsum. In the application test, the compressive strength of cement and concrete manufactured by using the anhydrite Ⅱ as an auxiliary material were similar or superior compared with them of cement and concrete done by natural gypsum as an auxiliary material.

• Clean Technology
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• v.25 no.1
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• pp.19-32
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• 2019

As regional air pollution gets worse by the sulfur oxides emitted from various types of vessels passing through the many countries, the International Maritime Organization establishes the emission control areas and regulates sulfur dioxide in those areas. In order to satisfy these regional regulations, the fuel selection method and the exhaust gas post-treatment device are applied to the ships. Due to the economic reasons, the post-treatment method of exhaust gas for reducing the amount of sulfur oxides discharged is mainly preferred. The scrubber which is dominantly used in the ships are the spray type system where the sprayed liquid drops used for capturing the soluble sulfur dioxides in the exhaust gas. The performance of the spray type system depends on the size distribution of the sprayed droplets. In order to evaluate this performance, we designed counterflow type scrubber and cyclone scrubber and evaluated the desulfurization efficiency and the amount of droplet evaporation according to the size of each droplet by using computational fluid dynamics. The Eulerian-Eulerian analysis method was used because the scrubber had a gas-liquid two-phase flow inside the scrubber. When the diameter of the droplet was $100{\mu}m$, $300{\mu}m$, $500{\mu}m$ and $700{\mu}m$. As a result, both of scrubbers showed high desulfurization efficiency and low evaporation amount at $500{\mu}m$ and $700{\mu}m$.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.687-694
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• 2019

In order to investigate the behavior of limestones which have been usually used for in-situ desulfurization reaction in circulating fluidized bed combustors, the attrition characteristics and calcination reactions of domestic limestones were analyzed in this study by using a thermogravimetric analyzer and an ASTM D5757-95 attrition tester. The average size distribution of limestones in circulating fluidized bed boilers have to be changed due to the attrition of particle-particle and particle-reactor wall and the calcination reaction. Domestic limestones might be used in commercial circulating fluidized bed boilers, but the attrition behaviors and particle size changes of limestones were varied. In calcination experiments at $850^{\circ}C$, the calcination reaction were varied with limestone samples. The calcination reaction time increased with an increase of particle size. Also, fine particles generated the attrition test of calcined limestone was 20% higher than those generated the attrition test of original limestone.

• Resources Recycling
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• v.33 no.1
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• pp.69-76
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• 2024

In an effort to achieve the goal of carbon neutrality, countries around the world are aiming to phase out coal-fired power plants. Due to various reasons, electricity production through coal-fired power generation and sulfur oxide (SOx) emissions are expected to continue in the future. In the South Korea, sodium bicarbonate (NaHCO₃) and lime materials are used to treat SOx, and most of the sodium bicarbonate is imported. Therefore, this research was conducted to replace sodium bicarbonate by improving the physical properties of lime materials using domestic limestone. Limestone was heat-treated through a box-type electric furnace and a vertical electric furnace. Due to the structural characteristics of the vertical electric furnace, a lime material(quicklime) was possible to improve the physical properties like a specific surface area and a pore volume. Then, they were reached to 22.33 m²/g specific area and 0.14 cc/g pore volume.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.2
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• pp.66-72
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• 2024

In this study, the applicability of CCMs (Carbondioxide conversion capture materials) manufactured by reacting carbon dioxide gas with DG (Desulfurization gypsum) as a cement substitute for secondary concrete products were evaluated and the basic physical properties of CCMs-mixed mortar and concrete specimens were measured to derive the optimal mixing ratio. The main chemical oxides of CCMs were CaO and SO₃, and the main crystalline phases were CaSO₄·2H₂O, Ca(OH)₂, CaCO₃, and CaSO₄. In addition, by the results of particle size analysis and heavy metal measurement, the applicability of CCMs as a cement substitute for secondary concrete products was confirmed. As a result of measuring the strength behavior using mortar and concrete specimens with CCMs, the compressive and flexural strength decreased as the mix ratio of CCMs increased, but requirements by the standards for interlocking blocks and retaining wall blocks, which are target products in this study, were satisfied up to the optimal mixing ratio of 10 wt.% substitution. Therefore, its applicability as a cement substitute for secondary concrete products was confirmed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.3
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• pp.86-91
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• 2024

In this study, the characteristics of mortar using carbondioxide conversion capture materials (CCMs), fabricated by reacting CO₂ with desulfurization gypsum (DG) by-produced from a oil refinery, as a cement mixture. Based on the chemical component and particle size analysis results, it estimated that desulfurized gypsum reacted with carbon dioxide to produce carbonate crystals such as CaCO₃. Using CCMs as a cement mixture, physical property and durability analysis were conducted by measuring such as workability, compressive strength, compressive strength ratio after freezing-thawing and accelerated carbonation depth. The experimental results showed that as the content of the admixture increased, workability and compressive strength characteristics decreased. Compressive strength after freezing-thawing and accelerated carbonation depth also showed similar characteristics to the physical property measurement results. In addition, compared to desulfurized gypsum, using CCMs showed better physical properties and durability. This was assumed to be due to differences in the crystal phases of the mixed materials such as free-CaO and CaCO₃.

• Corrosion Science and Technology
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• v.4 no.6
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• pp.242-249
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• 2005

A lot of parts in FGD (Flue Gas Desulfurization) systems of fossil-fuel power plants show the environments in which are highly changeable and extremely acidic corrosive medium according to time and locations, e.g. in duct works, coolers and re-heaters etc. These conditions are formed when system materials are immersed in fluid that flows on them or when exhausted gas is condensed into thin layered acidic medium to contact materials of the system walls and roofs. These environments make troublesome corrosion and air pollution problems that are occurred from the leakage of the condensed solution. To cathodically protect the metallic structures in extremely acidic fluid, the properties of the protective coatings on the metal surface were very important, and epoxy Novolac coating was applied in this work. On the base of acid immersion tests, hot sulfuric acid decreased the hardness of the coatings and reduced greatly the content of $Na_2O$, $Al_2O_3$, and $SiO_2$ among the main components of the coating. A special kind of CP(Cathodic Protection) system has been developed and tested in a real scale of the FGD facility. Applied coating for this CP system was peeled off and cracked in some parts of the facility. However, the exposed metal surface to extremely acidic fluid by the failure of the coatings was successfully protected by the new CP system.

• Journal of Korea Foundry Society
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• v.15 no.2
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• pp.175-183
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• 1995

It is difficult to remove such interstitial impurities as sulfur, oxygen, hydrogen and carbon in Fe-Ni alloys. Thermodynamic and kinetic studies were carried out on the behavior of hydrogen gas, oxygen gas, Si, Al and slag, and the reaction time by the $Ar/Ar-H_2$ plasma and electron beam melting. After the addition of Al, Si, they were melted by Ar plasma with reaction time changed. 80%Ni-Fe alloys showed a better deoxidation than 36%Ni-Fe alloys. At $Ar-H_2$ plasma melting, the deoxidation was significant. In the case of the electron beam melting, the residual oxygen was higher than in Ar plasma melting because electron beam melting temperature was lower than that of Ar plasma. For the decaburization, it was melted by $Ar-O_2$ plasma melting, which could remove effectively carbon by activated oxygen in plasma. We added slag to Fe-Ni alloys for the desulfurization. As the result of this experiments, the amount of residual sulfur was not changed according to the slag ratio and reaction time.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.2
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• pp.84-96
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• 1995

The dewatering characteristics of the sewage sludge was investigated through the experimental observations and model simulations. The activated sludge and the anaerobically digested sludge were examined for the dewaterability evaluation within the pressure range of $0{\sim}10^6N/m^2$. Modified Buchner funnel test and compression test by the consolidometer were conducted to evaluate average specific resistance, porosity, and moisture percentage of filter cake. Shirato's technique of compression-permeability test was followed for the pressure range lower than about $10^2N/m^2$. The flocculation effects on sludge dewatering was also examined for ferric chloride and polymeric flocculant. The application of hydrated lime which can be used for flue-gas desulfurization showed improved moisture percentage, and was thought to have positive feasibility in combined system of sludge dewatering and incineration. Determined characteristic constants were applied to Tiller's cake filtration model to simulate liquid pressure distribution and porosity distribution in cake. Model simulations showed a sharp drop of the porosity close to the cake-medium interface for the highly compressible material such as the activated sludge and the anaerobically digested sludge.