이철희 Chul Hee Lee , 현재혁 Jae Hyuk Hyun , 이광연 Kwang Yun Lee , 박기정 Ki Jung Park , 이우성 Woo Seong Lee , 한규성 Kyu Sung Han

DOI:

Abstract

Over the past few decades, many scientists and environmental activists emphasized the importance of sustainable society and warned the global warming. As one of efforts to achieve the sustainable society and maintain no more of global warming, the RDF (Refuse Derived Fuel) production from domestic solid is taken into account seriously in Daejeon, Korea. Currently, the pay per throw system is active from 1995 and is quite stabilized. Recyclable wastes such as metal scraps, glass, papers, and fibers like clothes should be discarded separately and not be mixed with other types of waste being disposed of eventually. To assess the potential for the conversion of domestic solid waste into a heat source, i.e., RDF, the proximate analysis, the classification into 10 components, and the calculation of heat value based on the result of the elemental analysis were performed. Based on the preceding analysis, the domestic solid waste produced daily in Daejeon, Korea has a potential for conversion into an alternative energy source, RDF in technical aspect. Proper blending of combustibles, however, is necessary to enhance the heating value of RDF being produced and to be more viable in economic aspect.

Key Words

RDF, Domestic solid waste, Recycling, Pre-treatment system, Caloric value

강종우 Jong Woo Kang , 전용우 Yong Woo Jeon , 유해민 Hae Min Yoo , 이동훈 Dong Hoon Lee , 이홍규 Hong Gyu Lee

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Abstract

A food waste disposer is an electrically powered device installed under a kitchen sink. It is located between the sink`s drain and the trap which shreds food waste into tiny pieces so that they can go through plumbing. Use of this unit is convenient and hygienic for discharging food waste in kitchen. Nevertheless, this unit has been illegal until now in Korea because of both conflict with the government`s policy-resource recovery from food waste-and perceived threat to the city`s sewer system. An attempt was made recently to meet growing need to introduce this unit for advantage of using disposer and maintenance of sewer system, etc. So an attempt was made to introduce the food waste disposer system of ``treatment type before discharging to sewer``, but it was inappropriate for conditions in Korean. In this study, we developed a suitable disposer system for Korea based on an innovative solid recovery technology. And continuous operating experiments were carried out to evaluate the performance of the system for 18 days. The amount of food waste fed into the system was equivalent to the daily amount of food waste made from 30 households living in apartment units, which was calculated to be 14.44kg/day. After grinding, SS/TS of food waste was 60 percent and it was the maximum amount of solid that could be recovered using this system. In the system of solid collection type using screw press, more than 70 percent of suspended solids were recovered. And less than 20 percent of total soilds were discharged through wastewater and it satisfied the legal standard of Korea. This novel food waste disposer system will satisfy with both the government`s environmental policy and higher quality resource recovery from food waste in the facilities.

Key Words

Disposer, Food waste, Solid recovery, Solid-liquid separation

정다위 Da Vid Chung , 유혜영 Hye Young Yoo , 박호연 Ho Yeun Park , 윤철우 Cheol Woo Yoon , 김용준 Young Jun Kim , 이지영 Ji Young Lee , 신선경 Sun Kyoung Shin , 오길종 Gil Jong Oh

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Abstract

In this study, asbestos in air during dismantlement and removal of slate roof tiles and asbestos that could linger in mask filter and safety wear were investigated. In addition, a wetting agent and its physical properties for water were studied, while the possibility of prevention of drift was assessed based on the properties. According to the analysis of 100 air samples, asbestos concentrations ranged from 0.001 to 0.007f/cc and the average was 0.002f/cc. The concentrations of asbestos in all the samples were below 0.01f/cc, emission limit for asbestos-removal facilities. The use of a wetting agent and the use of water were compared to analyze asbestos concentration in air during asbestos removal. According to the analysis, asbestos concentration was 0.002f/cc on average with wetting agents and the concentration was 0.003f/cc when water was used. The surface tension of wetting agents showed 28.9 to 42.1mN/m range and the average was 34.9mN/ m. The surface tension of tap water showed 72.2mN/m. Water-absorption time was from 16 seconds to 300 seconds for wetting agents and the agents showed a significant difference with one another. Surface area on the roof tiles was measured by instillation of its spread. For wetting agents, the range was from 31.2 to 64.7cm^2, with the average of 40.6 cm^2 and all wetting agents showed larger areas than tap water. Drying rate was measured for the assessment of wetting. According to the measurement, the rate ranged from 0.094 to 0.144min^-1 and 0.110min^-1 was the average. It was found that the drying rate of tap water was bigger than those of all the wetting agents, but some wetting agents did not show a big difference.

Key Words

Asbestos, Slate, Roof tiles, Dismantling, Air sampling, Wetting agent, Surface tension, Absorption time, Surface area, Drying rate

심성훈 Sung Hoon Shim , 정상현 Sang Hyun Jeong , 하지수 Ji Soo Ha

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Abstract

MILD (Moderate and Intense Low oxygen Dilution) combustion using high temperature exhaust gas recirculation is applied to solid fuels of dried sewage sludge and pulverized coal combustion to investigate the effect of reduction of NOx emission in a pilot scale combustor. High temperature exhaust gas recirculation is accomplished by entraining high temperature exhaust gas to air jets at just exit of the combustion chamber without a heat exchanger. High temperature exhaust gas recirculation makes the solid fuel flame stable and extremely uniform color and uniform temperature distribution. NOx concentration at the combustor exit was 62% and 40% less in the high temperature exhaust recirculation MILD combustion compared with the conventional combustion using air jet only for sewage sludge and pulverized coal respectively.

Key Words

Nitric oxide, High temperature exhaust recirculation, Low NOx MILD combustion, Solid fuel

정대운 Dae Woon Jeong , 장원준 Won Jun Jang , 심재오 Jae Oh Shim , 노현석 Hyun Seog Roh

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Abstract

Simulated waste-derived synthesis gas has been tested for hydrogen production through water gas shift (WGS) reaction in the temperature range of 240℃∼400℃ over supported Pt catalysts prepared by an incipient wetness impregnation method. MG30, MgO, ZrO_2, Al_2O_3 and CeO_2 were employed as supports for WGS reaction in this study. 1 wt.% Pt/CeO_2 catalyst exhibited the highest CO conversion as well as 100% CO_2 selectivity. This is due to easier reducibility of Pt/CeO_2 and high oxygen mobility and oxygen storage capacitiy of CeO_2. Pt/CeO_2 catalyst can be a promising catalyst for WGS reaction from waste-derived synthesis gas.

Key Words

Waste-derived synthesis gas, Hydrogen, Water gas shift, Pt, Reducibility

권영주 Young Joo Kwon , 이병하 Byung Ha Lee

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Abstract

Recycling of bottom ash which is the part of the non-combustible residues of waste combustion is very important for saving energy and resource recycling. In this research, we tried to develop recycling method for the bottom ash as the roadbase, the layer of aggregates under the paved layer of a road. We first removed ferrous and non-ferrous metals from the bottom ash with a 20 mm mesh strainer. After grinding ceramics and glass using jaw crusher, we mixed them with the bottom ash, and then they were further finely grounded up to the particle size less than 150 mm with ball mill. XRD analysis of the final ground material showed that the main ingredients were CaO, SiO_2, Al_2O_3, P_2O_5, Fe_2O_3 and MgO. Also there were some heavy metals such as Cu^2+, Pb^2+ and Cr^6+ in it. To make roadbase out of the processed bottom ash, we mixed it with purified sludge, pink kaolin (from Hadong, Gyeongnam, Korea), and silica sludge, and fired in an electric kiln at 1150∼1200℃. Finally, the usefulness of the roadbase made of bottom ash was analyzed by testing absorption rate, crystallizing and strength as well as indoor California Bearing Ration (CBR) test, abrasion test, sand reduction test. The developed material from recycling the wasted bottom ash satisfied the requirement of roadbase properties.

Key Words

Bottom ash, Roadbse, Recycling

윤정아 Jung A Yoon , 이윤희 Yun Hee Lee , 황선진 Sun Jin Hwang

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Abstract

The most effective chemical pretreatment method for Scenedesmus dimorphus was evaluated based on solubilization rate and saccharification yield. When 1% of S. dimorphus with 0.5 N of chemicals such as HCl, H_2SO_4, HNO_3, NaOH and KOH was autoclaved at 120℃ and 1.1 atm for 60 min, the solubilization rate was high with alkali chemicals while the saccharification yield was low compared to that with acid chemicals. The pretreatment efficiency was significant in order in HNO_3, HCl and H_2SO_4, however, HCl would be effective for field application considering the cost. The proper concentration and time to treat with HCl were concluded in 1 N and 10 min. In the conditions with 1 : 1 mixed acid chemicals such as H_2SO_4+HNO_3, HCl+HNO_3 and HCl+H_2SO_4, the solubilization rate was similar to that with single acid treatment, while the saccharification yield was enhanced about 34% in the mixed condition with H_2SO_4 and HNO_3 compared to that treated with H_2SO_4.

Key Words

Acid pretreatment, Alkali pretreatment, Saccharification yield, Scenedesmus dimorphus, Solubilization rate

장산 Shan Zhang , 이윤희 Yun Hee Lee , 김태형 Tae Hyeong Kim , 황선진 Sun Jin Hwang

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Abstract

The effects of NaCl concentration on bio-hydrogen production and microbial community by dark-fermentation were evaluated. The examined NaCl concentration was varied from 0 to 5%. When NaCl concentration ranged from 0 to 3%, the hydrogen production was insignificantly affected. 4% or more NaCl concentration decreased accumulated hydrogen production and the lag time was longer. In addition, the metabolite pathway of the bacteria were shifted from butyrate to acetate by microbial community changes with high concentration of NaCl. FISH analysis was achieved to analyze the microbial community after the dark-fermentation performance. Hydrogen producing bacteria, Clostridium sp. Cluster I and Cluster XI, was dominated with 0∼3% of NaCl, while Eubacteria, general bacteria, was dominated with 4∼5% of NaCl. Therefore, the growth and hydrogen production of the hydrogen producing bacteria were inhibited with over 4% of NaCl.

Key Words

Bio-H_2, Dark-fermentation, NaCl, Fluorescent in situ Hybridization, Clostridium sp

박진규 Jin Kyu Park , 강정희 Jeong Hee Kang , 김은철 Eun Cheol Kim , 김경 Kyung Kim , 윤석표 Seok Pyo Yoon , 이남훈 Nam Hoon Lee

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Abstract

In this study, anaerobic digestion tests for municipal solid wastes were performed in order to estimate their methane production rates. To simulate methane production rate, the first derivatives of the sigmoidal equations were calculated. The sigmoidal equations used were Gompertz and Logistic equations. Also, diauxic growth was employed to simulate methane production rate from municipal solid wastes. The equations were fitted to simulate methane production rate by nonlinear regression with a Marquardt-Levenberg algorithm. This is a statistical analysing methodology to minimize the sum of the squares of the differences between the predicted and measured values. Data fittings obtained by using the equations were compared statistically by using the RMSE (Root mean square error) and AIC (Akaike`s information criterion). The equations derived from sigmoidal equations successfully described methane production rate for municipal solid wastes. RMSE and AIC were decreased significantly for the equations considering diauxic growth, compared to the equations without diauxic growth. These results showed that the equations derived from sigmoidal equations with diauxic growth can be a useful tool to simulate methane production rate for municipal solid wastes.

Key Words

Municipal solid waste, Landfill, Anaerobic digestion test, Methane production rate, Diauxic growth

원유라 Yu Ra Won , 김동수 Dong Su Kim

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Abstract

The variation of the stable region of lead ion in aqueous environment has been studied according to the temperature change based on its stable region at standard state by constructing Pourbaix diagrams at different temperatures. The temperature range considered was between 278∼338 K and the stable region of Pb^2+_(aq) was observed to decrease as temperature rises, which was due to the decrease of the stable region of water and the increase of the stable region of solid lead hydroxide. The solid lead compounds considered were PbO_(s), Pb_3O_4(s), and PbO_2(s), and the pH at the boundary between the stable regions of PbO_(s) and Pb^2+_(aq) was observed to be lowered with temperature. For Pb_3O_4(s) and PbO_2(s), their stable regions were estimated to be enlarged as temperature is raised. Considering the change of the stable region of lead ion with temperature, in the application of the precipitating method for the treatment of lead ion in water it was considered to be more desirable to treat lead ion as its hydroxide form rather than its elemental form at higher temperature.

Key Words

Pourbaix diagram, Lead ion, Precipitation, Lead hydroxide, Temperature condition

김정대 Joung Dae Kim , 박준석 Joon Seok Park

DOI:

Abstract

This research was performed to evaluate the recycling characteristics by physico-chemical analysis of wasted and regenerated activated carbons. Three types of waste carbons for gas treatment, drinking water purification, and wastewater treatment were sampled and analyzed. Heavy metals concentrations of As, Zn, Pb and Cd for all regenerated carbons satisfied the standard criteria of the granular activated carbon for drinking water purification. The sieve residues of the regenerated activated carbons for drinking water purification and wastewater treatment were in the range of 85.3∼97.7% and 97.7∼99.7%, respectively. Some samples of the regenerated activated carbons were not able to satisfy the standard criteria for methylene blue adsorption (150mL/g) and iodine adsorption (950mg/g). All activated carbons for gas treatment and drinking water purification satisfied the standard criteria for hardness and bulk density. One of three activated carbon samples for drinking water purification did not satisfied the standard criteria for phenol number and ABS (alkyl benzene sulfonate) number. The observed results concluded that there was no problem of heavy metals accumulation in the regenerated activated carbon, but partially against standard criteria such as sieve residue, moisture content, methylene blue adsorption, and iodine adsorption.

Key Words

Waste activated carbon, Regenerated activated carbon, Recycling, Heavy metal, Methylene blue adsorption, Iodine adsorption

유흥민 Heung Min Yoo , 이장수 Jang Su Lee , 양원석 Won Seok Yang , 박준경 Jun Kyung Park , 박세원 Se Won Park , 한병현 Byung Hyun Han , 조성진 Sung Jin Cho , 김미호 Mi Ho Kim , 서용칠 Yong Chil Seo

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Abstract

Expanding economic growth, the increased and shortened of electronic products rapidly last a couple of decades in Korea. Furthermore, as converting to digital broadcasting system, the amount of discarded analog type TV containing cathode ray tube(CRT) glasses are increasing significantly. Accordingly, since there is no demand for CRT glass anymore, it is very important to find out how to recycle a waste CRT glass. The research was carried out to investigate the best available technologies for recycling waste CRT glass. Primary feasibility studies to find the appropriate technologies were performed in advance and then the use as aggregates of cement bricks was found as a simple and economic way of recycling CRT panel glass cullet. Based on the selection of proper technology, which is the aggregate of cement bricks fabrication using CRT glass crushed, the evaluation of recyclability were made by replacing CRT glass particles to aggregates in the mixture of cement bricks. Up to 50% of sand or stone powder was replaced and the bricks with CRT glasses were manufactured and tested in their qualities as concrete bricks. The bricks including 20 to 30% of CRT particles instead sand or stone powder were good enough to meet the standard in bending strength and absorption rate.

Key Words

Cathode Ray Tube, Concrete brick, E-waste, Recycle

이장수 Jang Su Lee , 유흥민 Heung Min Yoo , 양원석 Won Seok Yang , 박준경 Jun Kyung Park , 조성진 Sung Jin Cho , 김보생 Bo Saeng Kim , 서용칠 Yong Chil Seo

DOI:

Abstract

Consumers increasingly prefer HDTV (high definition television), including LCD (liquid crystal display), LED (light emitting diode), and plasma TVs (television), and existing analog TV broadcasting system will be switched to digital broadcasting at the end of 2012 in Korea. Even for computer monitors, CRT (cathode-ray tube) monitors are no longer preferred because of customers` increasing desire for thinner and lighter monitors and mobile computers. It is anticipated that these shifts will lead to a dramatic increase in disposal of analog TV sets. In 2012, it is estimated that about 117 thousand tons of CRT glass waste will be generated in Korea. CRT glass waste is not only Korea`s problem but also global issue, which needs worldwide attentions and policies for conserving useful resources and preventing groundwater pollution from heavy metals contained in CRT glass waste in case of landfill. It is important to develop BATs (best available technologies) to recycle CRT glass waste properly in short times. Therefore, in this study recycling possibility of CRT class was evaluated for the clay brick including powder of CRT glass of after crushing. Compressible strength and absorption factor of fabricated sample clay bricks were measured and observed whether they could satisfy the Korean Industrial Standard to use as normal bricks or not. The clay bricks containing under 5% of CRT panel glass powders were found to show enough quality as bricks, therefore the recycling of CRT cullet as materials of clay bricks could beutilized as one of the options.

Key Words

Cathode-Ray Tube, waste glass, Clay brick, Panel

이종근 Jong Keun Lee , 김재영 Jae Young Kim

DOI:

Abstract

The recovery potential of rare earth elements (REE) in coal ash was evaluated in this study. The previous researches were reviewed, and the physicochemical analysis of coal ash collected from a thermal power plant in Korea was conducted. According to the results of particle-size distribution, fly ash could be classificed as a fine-grained soil by unified soil classification system, and showed a uniform particle size distribution. The particle size of bottom ash was a coarse grained soil and the particle-size distribution was well graded compared to that of fly ash. However, there was no significant difference in the physicochemical composition between both the ashs and particle-size. Although REE was not found in the coal ash specimens used in this study, various valuable metallic compounds were observed. The silicate compounds showed the highest contents being 50% (by wt.), followed by 20 and 10% in aluminum oxide and iron hydroxide. There were also the trace elements in oxide forms (e. g., Ca, Mg, K). Unlike previous researches there are no REE detected in the coal ash specimens used in this study. The composition of ash depends on the coal used in the power plant and the detection limits of analytic instruments may be critical.

Key Words

Coal ash, Rare earth metals, Recovery