조윤아 Yoon A Cho , 신선경 Sun Kyoung Shin , 오정근 Jung Keun Oh , 김기헌 Ki Heon Kim

DOI:10.9786/kswm.2017.34.7.649

Abstract

Waste telecommunication equipment generated by the domestic mobile telecommunication industry is classified and distributed, not as waste electrical and electronic equipment, but as scrap iron, which can cause international problems such as violations of the agreements of the Basel Convention on the control of transboundary movement of hazardous waste and its disposal. The purpose of the study is to establish the infrastructure for the correct implementation of an export-and-import declaration by determining both the identification of hazardous materials and the composition ratio for recycling waste mobile communication equipment. In total, 16 pieces of waste equipment from three companies was collected for leaching and contest analysis: repeaters, base stations, antennae, cables, batteries, and wires. In the resultant composition ratio, 99% of a coupler and more than 80% of a repeater sample were composed of scrap metal, whereas 30 ~ 50% of a base station sample was made of printed circuit board (PCB). The lead leaching concentrations in two PCBs exceeded the standard value (13.9 mg/L and 5.5 mg/L), which means that it is necessary to control them in the transboundary movement of waste. The type and concentration of hazardous chemicals are different for each component and product, suggesting that waste mobile communication equipment has to be separated and sent out in parts.

Key Words

Telecommunication equipment, Mobile communication equipment, Appropriate management, Electronic product recycle

박선오 Seon-oh Park , 오길종 Gil-jong Oh , 김기헌 Ki-heon Kim

DOI:10.9786/kswm.2017.34.7.657

Abstract

With the increase in food consumption, the amount of animal and plant residues in food manufacturing has continued to increase. In particular, the residues generated from food manufacturing industries have a high recycling value because they are generated in large quantities, are homogeneous, and their recycling costs are less than that of households or small restaurants. In this study, we selected industries that produce large amounts of homogeneous animal and plant residues, including manufacturers of animal oils and fats, vegetable oils and fats, starches and glucose or maltose, and conducted material flow analysis using statistical data, field surveys, and questionnaires. In the results of material flow analysis, the amount of raw materials used in the surveyed industries was 3,029,830 tons per year, and 8,487 tons of animal and plant residues were generated through manufacturing and processing. In addition, the import substitution effect of recycling byproducts from industries into animal feed or similar was estimated to be \847,007 million KRW per year.

Key Words

Animal-plant residues, Material flow analysis, Food waste, Recycling

김상국 Sang-guk Kim , 이승재 Seung-jae Lee , 이정배 Jung-bae Lee , 손병권 Byung-kwon Son , 이광헌 Kwang-heon Lee

DOI:10.9786/kswm.2017.34.7.668

Abstract

This study was carried out to investigate the economic and environmentally friendly process of drying sludge by combining a mechanical dewatering filter press and thermal dryer. The dryer for 40 kg/hr of dewatered sludge consisted of a main dryer, a heat exchanger, a pre-dryer, and supplementary equipment. During the dewatering process, 100 kg of sludge with 80.11% water content was diluted and mixed with 400 kg of water and ferric chloride solution was added as a sludge conditioner. The average water content of dewatered sludge cake was 60.9% and the energy consumption rate (ECR) for removing water was 226.9 kcal/kg-H₂O. Hot flue gas generated from the main dryer was utilized as heating air for the pre-dryer in the heat exchanger. When 36 kg/hr of dewatered sludge cake was dried, the ECR was 1,009 kcal/kg-H₂O with 3.96% water content. The combined operation of the dewatering and the thermal drying processes showed that the ECR was reduced sharply to 521 kcal/kg-H₂O. The high humidity gas generated from each drying unit in the main dryer was recirculated to the odor decomposition chamber in the main dryer to destroy odor components at a high temperature. The odor concentration of humid gas generated by the pre-dryer was very low due to the relatively low operating temperature.

Key Words

Sludge, Dewatering, Water content, ECR (Energy Consumption Rate), Main dryer, Pre-dryer

장성호 Seong-ho Jang , 김고은 Go-eun Kim , 배종명 Jong-myeong Bae , 홍성철 Sung-chul Hong , 서정민 Jeong-min Suh , 이재용 Jae-yong Lee , 박진식 Jin-sick Park , 문추연 Choo-yeun Moon

DOI:10.9786/kswm.2017.34.7.678

Abstract

The use of Soluble Cutting Fluids (SCF) is essential in the development of industrial technology. However, it is difficult to decompose biologically due to its high concentrations of organic substances and nitrogen compounds, which interfere with microbial growth. Recently, Advanced Oxidation Processes are being studied both domestically and internationally. Electrolysis is highly adaptable industrial wastewater treatment because it has high removal efficiency and short processing time, regardless of the contaminant’s biodegradable nature. Accordingly, this study shows the characteristics of total nitrogen removal in SCF on the operating time, current density, and electrolytes when using aluminum in a batch-type reactor. The results are as follows: ① Under the condition of without the electrolyte when the current density was adjusted to 40 A/㎡, 60 A/㎡, or 80 A/㎡, the respective T-N removal efficiencies were 71.7%, 80.6%, and 87.2% at 60 min. ② In the comparison for the condition of whether NaCl was added, the removal efficiency of adding NaCl (5 ~ 10 mM) was higher than non-addition at 60 min for all current densities. ③ In the comparison for the condition of whether Na₂SO₄ (5 ~ 10 mM) was added, the removal efficiency when adding Na₂SO₄ showed no significant difference compared to non-addition at 60 min for all current densities.

Key Words

T-N, Electrolysis, Electro coagulation, Soluble Cutting Fluids (SCF)

박훈채 Hoon Chae Park , 최항석 Hang Seok Choi

DOI:10.9786/kswm.2017.34.7.685

Abstract

This study focuses on computational particle fluid dynamics (CPFD) modeling for the fast pyrolysis of biomass in a conical spouted bed reactor. The CPFD simulation was conducted to understand the hydrodynamics, heat transfer, and biomass fast pyrolysis reaction of the conical spouted bed reactor and the multiphase-particle in cell (MP-PIC) model was used to investigate the fast pyrolysis of biomass in a conical spouted bed reactor. A two-stage semi-global kinetics model was applied to model the fast pyrolysis reaction of biomass and the commercial code (Barracuda) was used in simulations. The temperature of solid particles in a conical spouted bed reactor showed a uniform temperature distribution along the reactor height. The yield of fast pyrolysis products from the simulation was compared with the experimental data; the yield of fast pyrolysis products was 74.1wt.% tar, 17.4wt.% gas, and 8.5wt.% char. The comparison of experimental measurements and model predictions shows the model’s accuracy. The CPFD simulation results had great potential to aid the future design and optimization of the fast pyrolysis process for biomass.

Key Words

Biomass, Conical spouted bed, Fast pyrolysis, Multiphase flow, MP-PIC

안해영 Hae Young Ahn , 송지현 Ji Hyeon Song

DOI:10.9786/kswm.2017.34.7.697

Abstract

In this study, alkali-activated slag (AAS) concrete made with blast furnace slag (BFS) was investigated as a replacement for ordinary Portland cement (OPC) concrete for changes in the compressive strength before and after CO₂ exposure and chemical reactions with CO₂. Before CO₂ exposure, the compressive strength of AAS concrete was found to be up to 21 MPa, which was higher than that of OPC concrete. Exposing AAS concrete to CO₂ at 5,000 ppm for 28 days did not significantly change the compressive strength. In contrast, the compressive strength of OPC concrete decreased by 13% in the same conditions. In addition, AAS concrete had the highest CO₂ capture capacity of greater than 50 g CO₂/kg, while the CO₂ capture capacity of OPC concrete was only 2.5 g CO₂/kg. Rietveld analyses using XRD results showed that fractions of main calcium-silicate-hydration (C-S-H) gels on the surface of AAS concrete did not significantly drop after CO₂ exposure; the C-S-H gel on the AAS concrete was continuously produced by reacting with the SiO₂ produced after the reaction with CO₂ and Ca(OH)₂ inside the concrete, with the result that the compressive strength of AAS concrete did not change after CO₂ exposure. Thus, AAS concrete can be applied to CO₂-rich environments as both a stable construction material and a CO₂ sequestrate agent.

Key Words

Blast-furnace slag, Alkali-activated slag concrete, Carbon dioxide exposure, Compressive strength, Chemical characteristics, Calcium-silicate hydration gels

이소라 Sora Yi , 이희선 Hi Sun Lee , 이정민 Jeongmin Lee

DOI:10.9786/kswm.2017.34.7.705

Abstract

In order to promote the resource circulation and upcycling of waste refrigerators, it is necessary to analyze the material flow of recovered valuable resources and low-value residues after they are discharged. This study divided the flow of waste refrigerators into the five steps of discharge, collection, pretreatment, resource recovery, and sale/export/disposal and conducted material flow analysis (MFA) in each step. Waste refrigerators are treated via official (formal sectors, 65.6% of total amount) and unofficial (informal sectors, 34.4% of total amount) channels. Officially, waste refrigerators are collected through free collection by national and local governments, recovery by product producers and distributors, and waste collection·transportation·recycling companies and are recycled at public and private recycling centers. Unofficially, waste refrigerators are collected through junk shops and individual collectors. Waste refrigerators recycled in the formal sectors undergo pretreatment processes such as the disassembly, shredding, and separation and recovery of resources such as scrap irons, plastics, PCB (printed circuit board), cables, glasses, waste refrigerants, urethane, etc. Waste refrigerators recycled in informal sector treated through disassembly of the exterior, the shredding process by the excavators in illegal facilities and recovered waste refrigerants, plastics, glasses, scrap irons, copper, nickel silver, PCB, urethane, etc. MFA results show that in 2015, the amount of waste refrigerators collected from formal sectors reached 121,642 ton/year, the amount of recycling was 107,684 ton/year, and the amount of residues was 13,955 ton/year respectively. Thus, actual recycling rate per a waste refrigerator was estimated 88.15% in 2015. To promote the resource circulation and upcycling of waste refrigerators, it is necessary to find a way to improve the recycling of urethane, which accounts for 10.8% of the total weight of a refrigerator.

Key Words

Waste resource circulation flow, MFA, Upcycling, Actual recycling rate

장미정 Mi-jeong Jang , 전태완 Tae-wan Jeon , 김용준 Young-jun Kim , 손지환 Ji-hwan Son , 강준구 Jun-gu Kang , 신선경 Sun-kyoung Shin

DOI:10.9786/kswm.2017.34.7.713

Abstract

Hazardous waste is also becoming more important as opportunities for industrial waste recycling are extended. Some hazardous industrial wastes that contain many inorganic materials and heavy metals can be reused as resources: Heavy metal recovery, heat energy, etc. To facilitate the waste-to-energy system, waste generation characteristics should be defined and managed by analyzing hazardous material content. This study examines the inorganic materials (Pb, Cu, As, Hg, Cd, Cr⁶⁺, CN, Ni, Zn, F, and Ba) of industrial wastes and the generation process (case of the Korean Standard Industrial Classification) using Absolutely Hazardous (AH) Waste Lists (LoW and EU). In particular, manufacture classification was a main waste generation process (82% for “AH”). Moreover, these 10 components (Pb, Cu, As, Hg, Cd, Cr⁶⁺, CN, Ni, Zn, and F, but not Ba) are compared with the regulatory limits on heavy metals in soil: Hg and As must be under the limit of the 3 Level (0.3 ~ 7.3 mg/kg).

Key Words

Hazardous waste, Recycling, Inorganic materials, LoW, KSIC

신명섭 Myung-seop Shin , 전용우 Yong-woo Jeon

DOI:10.9786/kswm.2017.34.7.721

Abstract

The technology for sludge drying using a microwave is a primary process in producing solid refuse fuel in the waste-toresource process. In this paper, the drying efficiency is improved by investigating chamber types such as square and circle with various mechanical conditions such as the magnetron power, the height of microwave irradiation, and the sludge thickness. In identical conditions, the moisture content was generally uniform in the circle chamber due to the uniform distribution of microwave irradiation, and the drying efficiency was higher in the circle chamber compared to the square chamber. In the case of the circle chamber, the drying rate was increased by more than 30% and the energy for sludge drying 507.9 kcal/kg of water was reduced. Hence, the application of a circle chamber should save energy consumption in sludge drying.

Key Words

Microwave, Drying, Chamber, Sludge, Drying efficiency

정지현 Jihyun Jeong , 강호 Ho Kang , 허남효 Namhyo Heo , 이승헌 Seungheon Lee , 현재혁 Jaehyuk Hyun

DOI:10.9786/kswm.2017.34.7.728

Abstract

Anaerobic mesophilic batch tests of energy crops (forage barley, rye, Italian ryegrass, and oats) were carried out to evaluate their ultimate biodegradability and two distinctive decay rates (k₁ and k₂) with their corresponding degradable substrate fractions (S₁ and S₂). Graphical statistical analysis and biochemical methane potential (BMP) tests showed that the ultimate biodegradability was 82 ~ 88% for forage barley, 70 ~ 77% for rye, 66 ~ 79% for Italian ryegrass, and 59 ~ 67% for oats. The readily biodegradable fraction (S₁) of 73% of forage barley biodegradable volatile solid (BVS, S₀) degraded within the initial 40 days at k₁ of 0.055 day^-1, whereas the slowly biodegradable fraction (S₂) of BVS degraded over more than 80 days with long term batch reaction rates of 0.002 day^-1. For oats, this readily biodegradable portion (S₁) was 57%, which degraded with a k₁ of 0.023 day^-1 for the initial 60 days. The minimum hydraulic retention time (HRT) for the anaerobic digestion of forage barley, rye, and Italian ryegrass were estimated in the range 45 ~ 55 days and 65 days for oats.

Key Words

Energy crops, Batch test, Anaerobic digestion, Ultimate biodegradability, Decay rate, Biodegradable fraction

윤영욱 Young Wook Yoon , 손지환 Ji-hwan Son , 권영현 Young-hyun Kwon , 강준구 Jun-gu Kang , 신선경 Sun-kyoung Shin , 전태완 Tae-wan Jeon

DOI:10.9786/kswm.2017.34.7.737

Abstract

Emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurnas (PCDFs) in stack gas were analyzed from 21 municipal solid waste incinerators (MSWs) using high resolution gas chromatography equipment with a high resolution mass spectrometer (HRGC/HRMS) in 2015. The concentration of PCDDs/DFs was in the range 0.09 ~ 354.54 pg-TEQ/S㎥ based on the International Toxicity Equivalency Factor (I-TEF) and all MSWs complied with emission standards. The congener distribution of PCDDs/DFs was categorized into one group and two outliers via principal component analysis (PCA). Among the 17 PCDDs/DFs, 1,2,3,4,6,7,8-HpCDD showed the highest mass fraction (20.8%) and 2,3,4,7,8-PeCDF showed the largest TEQ contribution (42.9%).

Key Words

PCDD, PCDF, Municipal solid waste incinerator, Congener distribution

양승빈 Seung-bin Yang , 장성호 Seong-ho Jang , 홍성철 Sung-chul Hong , 서정민 Jeong-min Suh , 송영채 Young-chae Song , 정병길 Byung-gil Jung , 이원기 Won-ki Lee

DOI:10.9786/kswm.2017.34.7.744

Abstract

Soluble Cutting Fluids (SCFs) have been used in metal machining processes to improve the quality of metal processing equipment and products. Although SCFs are useful and essential material, wasted soluble cutting fluids are harmful in hydroecological systems because of the high concentration of COD and nitrogen material. If discharged to hydroecological systems without specific treatment, they may cause eutrophication in rivers and lakes. Therefore, the removal efficiency of the COD contained in the SCFs is investigated in this study using electrochemical treatment with an insoluble electrode. The electrode was made of titanium with iridium plating, made from a perforated metal sheet to agitate the sample in the reactor. Cathode and anode electrodes were inserted into acrylic reactor alternately and the reaction time was one hour. The experimental results were as follows: First, for 60 A/㎡, 80 A/㎡, and 100 A/㎡ current densities, the COD removal efficiencies were 42.0%, 63.9%, and 78.4%, respectively.

Key Words

Insoluble electrode, Soluble cutting fluids, COD, Ti-IrO₂

성진호 Jin-ho Sung , 김정훈 Jeong-hun Kim , 백승기 Seung-ki Back , 이은송 Eun-song Lee , 이주찬 Joo-chan Lee , 문경림 Kyung-lim Moon , 박용준 Yong-joon Park , 서용칠 Yong-chil Seo

DOI:10.9786/kswm.2017.34.7.751

Abstract

A metal halide lamp was developed to improve the performance of high pressure mercury lamps. In South Korea, these are used in street lamps, fishing lamps, and automobile headlights; however, these are not specified in Annex A part 1 of the MINAMATA convention. In this study, valuable materials were investigated in automobile headlights and street lights and were minimized to contaminate mercury via staged crushing. The staged crushing prevents mercury emissions in the crushing process. Thus, the mercury concentration in glass-type byproducts from waste HID lamps was increased from 260.29 mg-Hg/kg to 2,907.16 mg-Hg/kg. In addition, glass from waste street lamps was increased from 1,083.71 mg-Hg/kg to 14,101.95 mg-Hg/kg. In the case of street light crushing, mercury-containing glass waste decreased by 67%. The specific wastes from staged crushing were mainly glass type. In this material, mercury species vaporize at over 800℃. The elemental mercury was estimated to oxidize during its use and crushing. Therefore, to ensure the harmless treatment of specific wastes from staged crushing, treatment at over 800℃ is recommended.

Key Words

Mercury, Metal halide lamp, Staged crushing, Leaching test, DTG curve