Hee-Chan Cho

Neutralizing capacity of bottom ash from municipal solid waste incineration of different particle size

This study measures the neutralizing capacity of bottom ash from municipal solid waste incineration of different particle sizes. We examine the effect of particle size on the weathering process, a method popularly used for stabilization of heavy metals in incineration of bottom ash. The distribution of particle sizes in municipal solid waste incineration bottom ash is rather broad, ranging from fine powder to as large as 40 mm in diameter. Although considered a by-product highly suitable as a road construction material, the high level of heavy metal leaching is an obstacle to its reuse. Weathering, a method used to reduce heavy metal leaching, is a lengthy process taking over thee months to complete. The chief reaction involved in weathering is carbonation occurring between Ca(OH)2 in bottom ash and CO2(g) in the atmosphere. During this process, CaCO3 is produced, causing the pH level to drop from over 12 to about 8.2 and reducing heavy metal leaching. In this paper, we attempt to determine the particle size best suited for reducing the period required for weathering bottom ash by identifying characteristics of different particle sizes that affect heavy metal leaching and neutralization.

Effect of Carbonation in Removal of Chloride from Municipal Solid Waste Incineration Bottom Ash

ABSTRACT Most of chloride in municipal solid waste incineration bottom ash are easily soluble in water. As a reason of that, bottom ash limited its use as a road materials and cement contrete as well as landfill. Thus, the characteristic of chloride in bottom ash was investigated, though the distribution of chloride from based on particle size, characteristic of friedels salt(3CaO•Al2O3• CaCl2•10H2O) in bottom ash and the removal of friedels salt via caibonation process. As a result, the content of chloride was increased with the smaller particle size, especially friedels salt too. The soluble chloride like KCl, NaCl in bottom ash was possible to be removed by washing process, reversely friedels salt (insoluble) was difficult. But friedels salt could be removed via carbonation process because that has difficulties of preventing progressive carbonation and in controlling the activity of CO2.

Beneficiation of coal pond ash by physical separation techniques

In this study, investigations to develop a beneficiation process for separating coal pond ash into various products were undertaken. To this end, coal pond ash samples with different particle size ranges were tested in terms of their washability characteristics in a float-and-sink analysis. It was found that coal pond ash was heterogeneous in nature consisting of particles that varied in terms of their size and composition. However, it can be made more homogenous using a gravity separation method. Therefore, the possibility of separating coal pond ash was tested on standard equipment typically used for gravity concentration. To increase the separation efficiency, coal ash was separated according to the size of the particles and each size fraction was tested using equipment appropriate for the corresponding sizes. A hindered-settling column and a shaking table were tested for their ability to treat the 1.19 × 0.074 mm size fraction, and a Falcon concentrator was evaluated for its ability to treat the -0.074 mm size fraction. The results showed that various marketable products, such as lightweight aggregate, sand and high-carbon fuel, can be recovered from coal pond ash using simple physical separation techniques.

Change of Mineral Phases in Carbonation Reaction of MSWI Bottom Ash

ABSTRACT Municipal solid waste incineration(MSWI) bottom ash consists of glassy materials, ceramics, ferrous materials mainly. Therefore, in some European countries, it is used as construction material. But, the bottom ash is more considered as a chemically reactive material that releases hazardous heavy metals. In order to manage the bottom ash, understanding of the carbonation process is necessary. Because their influence on carbonation reaction in bottom ash may has a significant effect on the leaching characteristics of contaminants such as heavy metals. To gain a proper appreciation of the carbonation role of mineral constituent in bottom ash, it is essential to understand the relationships between their morphology, composition and their influence on carbonation reaction. Therefore, we carried out the study on mineral constituent of bottom ash and their influence on carbonation reaction.

Recovery of ferromagnetic material by wet magnetic separation in coal bottom ash

ABSTRACT A coal ash generated from a coal-fired power plant largely divided into fly ash and bottom ash. All of the coal fly ash has been recycled and the coal bottom ash (CBA) in only a part restricted within narrow field. But, many researchers have investigated the study about recycling of CBA by physical separation because it has various materials such as silicate, aluminate, unburned carbon and magnetic-substance. For example, it is easy to be removed by magnetic separation in the case of magnetic-substance contained in CBA. Thus, we investigated the recovery of ferromagnetic material by wet magnetic separation in CBA. For this study, we researched the recovery rate of ferromagnetic material, such as iron and magnetite through wet magnetic separator at various magnetic forces and confirmed the distribution of ferromagnetic material as a various particle size.

Effects of Leaching of Heavy Metals in Cement-based Recycling via Carbonation of Municipal Solid Waste Incineration Bottom Ash

ABSTRACT The paper describes the effect of replacing part of Portland cement with municipal solid waste incineration (MSWI) bottom ash with various treatments such as washing and carbonation. MSWI bottom ash was subjected to washing or carbonation treatment to reduce the chloride content and expansion property. And mortars using each bottom ash were manufactured. Results showed that MSWI bottom ash is potentially attractive as mineral addition if chloride is removed and aluminium particles are stabilized.

Characteristic of Cu and Pb Leaching Behavior of Municipal Solid Waste Incineration Bottom Ash

ABSTRACT The leaching test with municipal solid waste incinerator (MSWI) bottom ash was studied in order to investigate leaching property of Cu and Pb and stabilization. Also carbonation reaction was processed in MSWI bottom ash and conform their effect on the leaching of Cu and Pb for maximization of weathering process. It was sampled one size of bottom ash lower than 0.15mm. In the leaching test of bottom ash (2 types) was resulted that leaching volume of Cu and Pb was high, although. Also dissolved Cu and Pb was investigated as a change of pH. Through interaction of CO2 with bottom ash (carbonation), maximize stabilization of Cu and Pb leaching. As a result, leaching volume of Cu and Pb was decrease.

Synthesis of Amorphous Calcium Carbonation in Ethanol and its Crystallization in the Aqeous Solution

ABSTRACT Amorphous calcium carbonate (ACC) was synthesized by reaction to the Ca(OH)2-C2H5OH-CH2OHCH2OH-CO2 systems. The ACC was then crystallized in aqueous solutions while observing the changes in crystal phases. Using lL/min of CO2 flow rate, 600rpm of stirring rate and various concentrations of Ca(OH)2 as the conditions, the reaction was divided into three stages according to changes of electrical conductivity that depends on Ca2+ concentration. ACC synthesized by these reactions was stabilized to calcite through vaterite according to time. When crystallizing the ACC in an aqueous solution, it was transferred to calcite by means of a low stirring speed regardless of temperature. However, a small amount of aragonite was obtained with higher stirring rate at high temperatures. Furthermore, the addition of NH4 + ions resulted in an irregular shape and size of the produced calcite, while Mg2+ ions enhanced aragonite production.

Removal of Heavy Metals from Aqueous Solution by Fly Ash

ABSTRACT The present work investigated the possible use of fly ash for the removal of heavy metal ions from aqueous solutions. Batch experiments were conducted and the influences of metal concentration, pH, and fly ash concentration were investigated. Heavy metals used in this study were zinc, lead and cadmium. Adsorption studies were done over a range of pH values (3–10) at 25°C and heavy metal concentrations of 10–400 mg/L using fly ash concentrations of 10, 20 and 40 g/L respectively. Experiments were also conducted without fly ash to determine the extent of heavy metal removal by precipitation. Kinetic and equilibrium experiments were performed and adsorption data were correlated with both Langmuir and Freundlich adsorption models. The results indicate that fly ash can be used as an adsorbent for heavy metals in the aqueous solutions, yet the degree of removal depends on the pH.

Characterization of Coal Pond Ash for Reutilization

ABSTRACT In Korea, most of coal bottom ash produced by coal power plants is being disposed to the ash pond as slurry, and more than 80% of the coal power plant sites are occupied for the storage of the huge quantity of ash, which leads to environmental problems and managerial burden for plant operators. In this study, investigations were taken to develop a beneficiation process for separating the coal pond ash into valuable products for various applications. To determine the characteristics of the bottom ash stored in an ash pond, core samples were taken through the pond. These samples were then evaluated for the particle size distribution and the carbon content. The core samples with similar characteristics were fractionated into several size fractions. And they will be then subjected for float-sink separations to determine the cleanability. The results will be used for developing a multi-stage process to separate the coal pond ash in various products such as lightweight aggregate, sand, high-carbon fuel, and very fine inorganic fillers.