A NUMERICAL ANALYSIS FOR ADVECTION-DISPERSION IN HETEROGENEOUS SUBSURFACE FORMATIONS

이승희,주현종 경기대학교 1995 論文集 Vol.37 No.-

Monte Carlo 방법으로 형성된 불균일성 지하토양의 모형을 통하여 유해폐기물에 대한 차수층(Confining Layers)에서의 이류-분산(Advection-Dispersion)을 조사하였다. 차수층에 대한 지하토양은 순수한 사암(Sandstone)관 순수한 혈암(shale)으로 구성된 임의의 이항 구조로 가정하여 모델을 형성하였다. 차수층은 주로 혈암으로 구성되어 있기 때문에 불균일성 차수층에서의 혈암분률을 0.66. 0.7, 0.8, 0.88로 하여 수치모사를 하였다. 미국 EPA에 의해 심정분산 시스템에서 규정된 10,000년 동안 유해폐기물 소멸과 이동의 조사를 위해 형성된 차수층에서의 유해폐기물의 농도분포는 정상상태의 흐름과 이류-분산 식을 통한 유한요소모델에 의해 결과를 얻었다. 이류-분산(Advection-Dispersion)모델과 확산(Diffusion)모델과의 차이는 시간이 경과하면서 증가되었다. 혈암의 비율이 증가함에 따라 이류(Advection)가 감소되기 때문에 혈암분율이 증가할수록 이 차이는 감소하였다. 불균일성 차수층에서의 수착(Sorption)은 혈암에서만 일어난다고 가정하였음에도 불구하고 오염물질일 acrylonitrile을 지연시켰다. 그러므로 사암과 혈암으로 구성된 지하토양에서의 이류-분산은 높은 혈암분율에서 혈암의 지질, 물리학적 특성값에 의해 지배받는다는 것을 입증하였다. 평균 유효확산계수를 사용한 일차원 확산의 해는 수치모사의 평균농도결과와 아주 잘 일치하였다. 이류-분산에 대하여 평균 유효투수계와 평균 유효확산계수를 분리하여 평가한 결과는 이러한 특성값들의 복합효과를 고려하지 않았다(즉, 혈암에서는 낮은 투수계와 낮은 유효확산 계수를 나타낸다). 이류-분산에서의 실제 특성값은 직접적으로 농도결과로부터 최화적 방법에 의해 얻어졌다. 이러한 실제 특성값은 평균 특성값 보다 작고, 실제 특성값과 평균 특성값의 차이는 혈암분율이 증가함에 따라 감소하였다. 그러므로 평균 유효계수들을 독립적으로 사용하여 2차원의 불균일성 지하토양에서 얻은 오염물질의 농도 분포는 불균일성 지하토양에서 실제 유효계수를 사용한 농도분포보다 과대하게 평가되었다. The advection-dispersion of hazardous waste was investigated through a hypothetical heterogeneous subsurface formation for confining layers which was generated by using a Monte Carlo technique. The subsurface formation was modeled as a combination of binomial random structures composed of either pure sand or pure shale. Since there are usually high shale fractions in confining layers, shale fractions in the heterogeneous formation of 0.66, 0.7, 0.8 and 0.88 are used in numerical simulation. The requirement of 10,000 year in EPA proposed regulation demands models to project the fate and transport of the wastes over this time period. The concentration profile of each hypothetical confining layers is obtained by solving the steady-state subaurface flow and advection-dispersion equation via a finite element method. Comparison between an advection-dispersion model and a diffusion model showed differences that increased with time. This difference decreased as shale fraction increased because advection decreased with increasing shale fraction. Sorption in the heterogeneous confining layers retarded a model compound, acrylonitrile, despite the assumption that sorption only occurred in shale zones. Hence, it proved that advection-dispersion through sand-shale formation was dominated by the geophysical properties of shale regions in higher shale fractions. The one-dimensional analytical solution for diffusion only using the expected effective diffusivity quite well with the mean concentration of the results from numerical simulations. For advection-dispersion, the separated estimations of the expected effective permeability and the expected effective diffusivity do not take into account the combined effect of in these paramerters (i.e. sllale zones exhibit both low hydraulic conductivity and low effective diffusivity). The estimated parameters for advection-dispersion problem were directly estimated from the concentration results using an optimization method. These estimated parameters were less then the expected parameters, and the differences between the expected and the estimated parameters were decreased with increasing shale fraction. Hence, the contaminant concentration profile using independently the expected effective parameters that were obtained from the heterogeneous subsurface system overestimated the results of numerical simulations for two-dimensional heterogeneous systems.

Tertiary Treatment with Stored Substrate Induced SBR System

이승희,주현종 경기대학교 1995 論文集 Vol.37 No.-

A bench scale SBR system was operated to treat septic wastewater for both organics and nitrogen removal. Due to the inherent characteristics of collected septic wastes from urban household, transient response strong SBR application showed many advantages such as in handling extraordinarily high ammonia wastes. With proper cyclic control strategy organic removal over 80% with the rate 7.2 mg COD/mg MLVSS/d, nitrification over 95% with the rate 0.018 mg NH_(3)-N/mg MLVSS/d, and during anoxic cycle denitrification over 42% with the rate 0.035 mg NO_(3)-N/mg MLVSS/d were attained. Among many unique features to the conventional completely mixed system SBR under study could achieve denitrification without exogenous substrate sources. By applying relatively short period of fill time bacterial substrate storage could be induced and this stored substrate was utilized as endogenous substrate sources by microorganisms under anoxic condition provided.

Separation Performance for Aluminium Recovery from Base-cap of Spent Fluorescent Lamp

Seung-Whee Rhee,Hun-Su Park,Min-Seok Lee,Jae-Kyung Kim,Hoe-Kyong Jung 한국폐기물자원순환학회 2013 한국폐기물자원순환학회 학술대회 Vol.2013 No.2

The estimated that 114 million units of fluorescent lamp are sold every year, and that 70% or more spent fluorescent lamps (SFLs) are generated at business sites. According to Korea Lighting Recycling Corporation, recycled amount of SFLs selected as EPR (Extended Producer Responsibility) items from 2004 has been improved from 35,250,000 units in 2010 to 37,950,000 units in 2011, which recorded the greatest amount. Based on the year 2011, SFLs have been recycled by 31.5%, but their recycled rate is insufficient yet, compared to the recycling rate of metal cans or glass bottles, which are about 80%. The base cap of SFLs as a raw material was used in this experiment. Base cap contains an insulation sieve plate, aluminum cap, copper terminal, tempered glass, filament, and copper/iron mixed wire that goes through this glass. In order to protect a filament that is made up of tungsten for the electricity to flow, circular plate consisted of iron encloses the filament. Separating apparatus of SFL base cap used in this experiment is a device which has used impact crushing technique using hammer, screen separation and magnetic separation for the purpose of recovering aluminum, copper and iron contained in SFL. Impact hammer crusher, a device that separates aluminum from other materials by hammer impaction on the base cap that is separated by end-cutting, causes a significant reduction for other materials to be included in the collectible materials by separating aluminum, copper and iron from the base cap by using hammer crusher at 3 stages. Iron was collected by using a magnetic separation unit and the collectible materials were separated into aluminum with larger particles, and glass and other materials with smaller particles by screen separation. The separation performance was estimated for the 3 stages of hammer crusher unit to recover aluminum from the base-cap of SFLs and the separation performances are 94% at the 1st stage, 97% at the 2nd stage, and 98% at the 3rd stage, respectively.

An Evaluation for Property of Pavement Mixture Using Spent Foundry Sand

( Seung Whee Rhee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2008 WASTE RECYCLING AND MANAGEMENT RESEARCH Vol.13 No.2

A Study on Optimal Conditions of Ceramic Support Process for Recycling of Spent Foundry Sand

Seung-Whee Rhee 한국자원공학회 2006 Geosystem engineering Vol.9 No.4

Characteristics of ceramic support made by spent foundry sand-loess mixtures are investigated by bulk density, porosity, durability, and compressive strength. And the basic properties of SFS and loess are estimated. The effect of drying time after cutting process, elevated temperature time, sintering temperature, and sintering time is also estimated to obtain the optimal condition in the process of manufacture ceramic supports. From the basic properties of SFS and loess, the content of SiO2 in furan sand is much higher than that in loess but the content of Al2O3 and Fe2O3 in furan sand is much lower than that in loess. In order to make ceramic supports, cylinder shape is the most desirable to sustain the properties of ceramic support. If annulus shape has an enough compressive strength, however, annulus shape may be decided. For the optimal condition to manufacture ceramic supports, drying time after cutting process is decided to 24 hrs and elevated temperature time is decided by 9hrs. And sintering temperature and sintering time are decided to 900oC and 9hrs, respectively in order to prevent solidification of sand materials.

New Recycling Processes of E-wastes using AI and IoT Technologies

( Seung-whee Rhee ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-

Since E-wastes contain various valuable metals as well as heavy metals and hazardous substances, it can pose a serious environmental risk if they were not managed in an environmentally sound manner. E-wastes are collected and recycled by the system of Extended Producer Responsibility (EPR) in many countries. In Republic of Korea (Korea), recycling of E-wastes is an inevitable means to conserve renewable resources because Korea imports more than 90% of resources and energy from foreign countries. Currently, the dismantling of certain parts in the recycling processes of E-waste, containing hazardous substances or valuable resources, is done manually. A partial manual dismantling can be recognized as an important bottleneck because it is labor intensive and has a potential exposure by hazardous substances in E-wastes. Automated dismantling in the recycling of E-wastes is extremely challenging due to diverse types of E-waste and the uncertainty of status. Recently, new recycling processes using Artificial Intelligence (AI) and Internet of Things (IoT) technologies are being studied as efficient measures to solve these barriers. This study aims to provide systematic and future-oriented perspectives on the recycling process of E-waste using AI and IoT technologies. In this presentation, it can be explained recycling of e-waste using AI and IoT technologies with five processes such as E-wastes target identification, screening and sorting of E-wastes, decision-making and planning for recycling, component (target) identification for recycling and dismantling and automated separation of components.

Current Status and Perspectives on Recycling of Electric Car Battery in Korea

( Seung-whee Rhee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-

A study on Mercury of Component from Compact Fluorescent Lamp

Seung-Whee Rhee,Hun-Su Park,Min-Suk Lee,Jae-Kyung Kim,Hoe-Kyung Jung 한국폐기물자원순환학회 2013 한국폐기물자원순환학회 학술대회 Vol.2013 No.2

Compact fluorescent lamps are strongly encouraged to manage separately in Korea because Compact fluorescent lamps contain mercury. Compact fluorescent lamps have managed as household waste in Korea, however, even though Compact fluorescent lamps contains hazardous material such as mercury. The aim of management of Compact fluorescent lamps separately is to reduce the release of mercury from Compact fluorescent lamp lamps into the environment and to reuse of the glass, metals and other components of Compact fluorescent lamps. The amount of mercury in a fluorescent lamps varies, depending on the type of lamp and manufacturer, but typically ranges between 5 milligrams and 30 milligrams. The mercury content of fluorescent lamps has been reported to be between 0.72 and 115 mg/lamp with an average mercury content of about 30 mg/lamp in 1994. Although manufacturers have greatly reduced the amount of mercury used in fluorescent lamps over the past 20years, mercury is an essential component to fluorescent lamps and can’t be eliminated completely in lamps. In the crushing process, CFL(compact fluorescent lamp) is separated into glass, plastic, ballast, phosphor powder and vapor. Using the crushing technique, concentration of mercury vapor emission from CFL is evaluated. Through the experiments, the efficiency of the crushing and separation for the unit is estimated by measuring the volume of CFL. In this study, the concentration of mercury is analyzed by MVI(Mercury Vapor Indicator) method for vapor in CFL. From the results of mercury distribution for 3 companies, the concentration of mercury in compact fluorescent lamp is less than that in the other type lamps. And phosphor powder has greater than 99% of total mercury amount in CFL and the mercury concentration in phosphor powder is measured between 1,008ppm and 1,349ppm. The mercury concentration in phosphor powder can be changed by the type of company and period of usage. KET and TCLP are carried out for phosphor powder, glass, plastic, ballast and base cap to estimate the hazardous characteristic. From the results of KET and TCLP test for CFL, phosphor powder from CFL should be controlled separately by stabilization or other methods to reuse as a renewable material because the phosphor powder is determined as a hazardous waste. From the results of characteristics of CFL, the carbonization system of CFL should be carried out in the temperature of less than 350℃. The amount of mercury in a fluorescent lamps varies, depending on the type of lamp and manufacturer, but typically ranges between 5 milligrams and 30 milligrams. The mercury content of Compact fluorescent lamps has been reported to be between 0.72 and 115 mg/lamp with an average mercury content of about 30 mg/lamp in 1994. Although manufacturers have greatly reduced the amount of mercury used in fluorescent lamps over the past 20years, mercury is an essential component to fluorescent lamps and can’t be eliminated completely in lamps. In Korea, demonstration for recycling of U type lamps had once begun in the area of Seoul Metropolitan, 2000. In 2004, U type lamps was included as an item in EPR(Extended Producer Responsibility) system. According to Korea Lighting Recycling Association, approximately 38 million Compact fluorescent lamps were recycled in Korea, 2011 because 3 recycling facilities for Compact fluorescent lamps are operated in Korea. Recycling rate of Compact fluorescent lamps in Korea is about 31.0% but about 70% of Compact fluorescent lamps may not manage properly. Hence, discarded lamps release approximately 2 to 3 tons of mercury per year into the environment[6]. In USA, Compact fluorescent lamps has controlled by Universal Waste Rule and merchandises containing mercury prohibited to produce. Also, MEBA(Mercury Export Ban Act) is activated in USA from 2013. According to Association of Lighting and Mercury Recycler, member companies accomplish about 85% of the lamp recycling done each year. In Germany, best available technology (BAT) system for recycling of Compact fluorescent lamps is established and about 20 companies are involved in recycling of Compact fluorescent lamps. In 1994, approximately 70-80% of total Compact fluorescent lamps are recycled in 1994 and Compact fluorescent lamps was included as an item in EPR(Extended Producer Responsibility) system in 1996. In Sweden, MRT System, which was developed by Lumalampan, separated mercury from Compact fluorescent lamps by distillation operation, 1979. Reverse route collection system is active to improve the collection of Compact fluorescent lamps. Compact fluorescent lamps was included as an item in EPR(Extended Producer Responsibility) system in 2001. In Austria, about 40 companies are involved in recycling of Compact fluorescent lamps to recycle glass and ferrous metals. And wastes containing mercury are treated in landfill site by using special container [7,8]. In this study, Compact fluorescent lamps is cut by a end-cutting unit with a cam crusher and base-cap is separated from glass part. In the end-cutting unit, a vacuum system is operating to collect mercury vapor to prevent leaking from the end-cutting unit. First of all, characteristics and major composition of Compact fluorescent lamps are estimated. Through the experiments, it is measured mercury concentration in the parts of Compact fluorescent lamps such as glass tube, phosphor powder, and base cap after separation in the end-cutting unit. Also, it is evaluated mercury emission from Compact fluorescent lamps by measuring the concentration of effluent gas in the end-cutting unit with changing flow rate. Finally, Korea Extraction Method (KET) and TCLP(Toxicity Characteristic Leaching Procedure) test are applied to phosphor powder to verify that phosphor powder is a hazardous waste [9].

A Study on Decomposition Characteristics of Sewage Sludge by Pre-Treatment of Ozonization

( Seung Whee Rhee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2005 WASTE RECYCLING AND MANAGEMENT RESEARCH Vol.10 No.1

An Evaluation of Moisture Content in LFG at SUDOKWON Landfill Site

( Seung-whee Rhee ),( Hyo-hyun Choi ),( Hun-su Park ),( Young-min Lee ),( Nack-joo Kim ) 한국폐기물자원순환학회 2010 APLAS Vol.2010 No.0