윤주형 Joohyeong Yoon , 김상범 Sangbum Kim , 김종수 Jongsu Kim , 구본진 Bonjin Koo , 김범종 Beomjong Kim , 류태우 Taeu Yu

DOI:10.9786/kswm.2022.39.2.87

Abstract

Combustible solid waste usually contains inorganic elements and compounds such as solid oxides (e.g., SiO₂, Al₂O₃, TiO₂, and Fe2O₃), alkali metals (e.g., Na, K, Mg, Ca, and Cs), and non-metals (e.g., S, P, and Se). When this waste is treated using thermal conversion processes such as combustion, gasification, or pyrolysis, the removal of inorganic substances depends on the process operating conditions. In this study, inorganic elements with a low melting temperature (S, Se, and Cs) were studied experimentally to analyze their evaporation process during thermal conversion and their cooling while passing through a gas-cleaning facility followed by collection in a filter. In the experiments, S, Se, or Cs (as a compound of CaNO₃) was mixed with combustible solid waste and fed into an electric heater with N₂. The proportion of these elements that were evaporated, condensed, or collected by filters installed in a post-cleaning system was then measured. It was found that the evaporation rate for S, Se, and Cs depends on the interaction between the vapor pressure and molecular weight. The amount of inorganic particles decreased linearly with the ratio of the wire temperature to the boiling temperature. In addition, the amount of Cs particles was higher than that of S and Se. This is because Cs has a much lower vapor pressure and thus condenses earlier on the reactor wall than S and Se at the same temperatures.

Key Words

Captured mass, Behavior, Cesium, Molecular Weight, Temperature

임진홍 Jin Hong Im , 장용철 Yong-chul Jang

DOI:10.9786/kswm.2022.39.2.96

Abstract

Many synthetic resins manufactured using foaming polystyrene (PS) have been reported, including expanded PS (EPS), a thermoplastic polymer widely used in insulation, packaging, aquaculture floats, and buoys. There has been increasing demand for packaging EPS in recent years due to the growth of online shopping and food delivery markets. However, if not adequately managed, EPS decomposes into microplastics, adversely affecting human health and the ecosystem. In this study, the material flow of EPS packaging in Korea was analyzed quantitatively according to its life cycle. In addition, greenhouse gas emissions reduction from recycling EPS was estimated using the US EPA waste reduction model WARM. In 2019, approximately 47,000 tons of EPS were sold and ultimately discharged into plastic waste streams. About 42,000 tons were recycled, of which 40,000 tons (96%) were recycled as ingots, 287 tons as pellets, and 1,521 tons as a fireresistant coating for steel frames. As a result of this recycling, 62,700 tons of CO₂eq was reduced in 2019, while the cumulative greenhouse gas reduction from 2003 to 2019 was estimated to be about 592,000 tons of CO₂eq. This study demonstrated the potential benefits of minimizing environmental emissions and reducing greenhouse gases through recycling. However, more detailed research is needed to ensure more effective EPS packaging management and thus further minimize potential environmental impacts and microplastic pollution, including investigations into the impacts of restrictions and bans and the consequences for marine littering.

Key Words

EPS recycling, MFA, GHG reduction, Microplastic, Circular economy

김승환 Seunghwan Kim , 이창민 Changmin Lee , 김준현 Junhyeon Kim , 조흠 Xin Zhao , 이상명 Sang Myung Lee , 이승철 Seung Chul Lee , 김재영 Jae Young Kim

DOI:10.9786/kswm.2022.39.2.110

Abstract

The livestock industry produces large volumes of cattle manure, which can be used as an organic fertilizer after composting and renewable energy after anaerobic digestion. In the anaerobic digestion process, cattle manure is usually stored in a cowshed until it is transferred to treatment facilities, and its physicochemical characteristics vary depending on this storage environment. Any change in these characteristics acts as a source of instability in the operation of an anaerobic digester. This study investigated the physicochemical characteristics and biochemical methane potential of cattle manure between seasons. The total solid content of Hanwoo (Korean beef) cattle manure and dairy cattle manure was 29.1 ~ 33.8 and 21.1 ~ 29.5% (by wet wt.), respectively, while the biochemical methane potential was 113.3 ~ 180.8 mLCH₄/g-VS for Hanwoo cattle manure and 94.0 ~ 166.2 mL-CH₄/g-VS for dairy cattle manure. The amount of methane generated per wet weight of cattle manure, taking into account the change in volatile solid content and biochemical methane potential, differed by 42.8% for Hanwoo cattle manure and 129% for dairy cattle manure. No distinct seasonal patterns in the physicochemical characteristics of the manure were observed due to the influence of other factors (e.g., the storage period). Overall, these results indicate that it is important to design treatment facilities that consider variations in the physicochemical properties and methane generation of cattle manure.

Key Words

Anaerobic digestion, Hanwoo cattle manure, Dairy cattle manure, Methane potential, Seasonal variation

박종근 Jongkeun Park , 유승한 Seunghan Yu , 김희윤 Heeyoon Kim , 류창국 Changkook Ryu , 김종현 Jonghyun Kim , 이재하 Jaeha Lee , 허준 Joon Heo

DOI:10.9786/kswm.2022.39.2.117

Abstract

Marine waste plastic is a source of a variety of health and safety concerns in marine ecosystems. One disposal option for marine waste plastic is pelletization and subsequent combustion for energy recovery. However, with plastic pellets in a fixed bed, which is widely employed in waste combustion processes, it is difficult to achieve stable and continuous propagation of the ignition front from the surface to the bottom of the bed because of the melting of the plastic and subsequent blockage of air passages. This study investigated the fixed bed combustion of plastic pellets with the cofiring of wood pellets at different cofiring ratios and airflow rates. It was found that the steady propagation of the ignition front can be achieved via cofiring with at least 20 wt.% wood pellets. The burning rate was approximately 123 kg/m²h, and this figure can be used to determine the minimum area required for the design of the moving grate.

Key Words

Plastic pellets, Wood pellet, Fixed bed combustion, Flame propagation, Burning rate

박찬 Chan Park , 김혁진 Hyeok Jin Kim , 송민정 Min Jeong Song , 오세천 Sea Cheon Oh

DOI:10.9786/kswm.2022.39.2.127

Abstract

The carbon emitted by the use of fossil fuels pollutes the environment, necessitating the development of alternative energy sources. However, renewable energy derived from nature such as solar energy and wind power is insufficient in practical applications. As a result, studies on the combustion efficiency of various forms of biomass, including empty fruit bunches (EFB) generated as a by-product of palm oil production, have been conducted. However, the generation of clinkers in the combustor during high-temperature combustion reduces the combustion efficiency and increases the treatment costs. Therefore, the effect of additives on clinker formation in the EFB combustion process was studied in this study. Kaolin and dolomite were tested as additives to inhibit clinker formation at additive-to-EFB-ash mass ratios of both 1 : 2 and 1 : 4, and the experimental reaction temperature was increased from 800℃ to 1000℃ at intervals of 50℃. The characteristics of the clinkers, including their sintering shape, were analyzed using X-ray diffraction and Xray fluorescence spectrometry for each experimental condition.

Key Words

Biomass, Clinker, Combustion, Kaolin, Dolomite

권은혜 Eun-hye Kwon , 박세인 Sein Park , 강준구 Jungu Kang , 이승재 Seungjae Lee , 이원석 Wonseok Lee , 김기헌 Kiheon Kim

DOI:10.9786/kswm.2022.39.2.139

Abstract

Dioxin is unintentionally generated during waste incineration and heat treatment processes. The Stockholm Convention conducts research, development, and monitoring to eradicate persistent organic pollutants (POPs), so some countries are currently calculating dioxin emissions. Emissions are also being calculated in Korea, and we would like to improve the dioxin calculation method currently in use. In this study, two different calculation methods were used and compared. Calculation method A is now in use, and data measured on the same day was used as the calculation factor. Calculation method B was developed, where the average of the annual data was used as the calculation factor. The emission factors were calculated using methods A and B for municipal waste incineration facilities with a 2 t/h or higher processing rate. The method A results were 81 ~ 204 ng I-TEQ/ton, and the method B results were 79 ~ 284 ng I-TEQ/t. Also, the emission factors were calculated using both methods for medical waste incineration facilities with a processing rate of 1 t/h or higher. The method A results were 834 ~ 2,737 ng I-TEQ/t, and the method B results were 737 ~ 2,049 ng I-TEQ/ton. The range of fluctuations was small. In the future, if the facility operation data of small incineration facilities are confirmed, it is judged that comparative analysis is also helpful.

Key Words

Dioxin, Emission factor, Waste incineration, Municipal waste, Medical waste

박미숙 Mi Sook Park , 황용우 Young Woo Hwang , 김다연 Da Yeon Kim , 양수진 Soo Jin Yang , 문진영 Jin Young Moon

DOI:10.9786/kswm.2022.39.2.152

Abstract

As carbon neutrality emerges as a global challenge, the government announced the “Data Dam” as one of the ten major projects of the Korean New Deal. Accordingly, the number of data centers and the amount of power usage for equipment operation are expected to increase due to the acceleration of the data economy. In this study, the costs of existing heating systems and district heating systems using data center waste heat are compared according to the life cycle cost analysis using the payback period method. However, the payback period method has difficulty reflecting future value, so the value was complemented using the present value method. When the data center waste heat is used as district heating, assuming that the energy cost is frozen (scenario 1), the benefit is about KRW 4 billion for 1,000 households, and the investment cost recovery takes 18 years. On the other hand, if the energy cost goes up by 5% every five years from the start of the project (scenario 2), the resulting energy savings is about KRW 30 billion, and the time to recoup the initial investment is shortened by eight years. The study calculated greenhouse gas (GHG) emissions according to energy consumption for each scenario in accordance with the 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines. The results are 14.9 tCO₂-eq for scenario 1 and 0.006 tCO₂-eq for scenario 2 (a reduction of more than 99% in GHG emissions compared to scenario 1).

Key Words

Data center, Waste heat, energy, District heating, Greenhouse gas emissions

전수민 Soomin Jeon

DOI:10.9786/kswm.2022.39.2.160

Abstract

Recycled coarse aggregates are tested twice for certification. If an aggregate passes both tests, the aggregate is certified; if it fails both, the aggregate is not certified. If the aggregate only passes one, then a third test is conducted to certify it for conformance or to terminate it if it does not conform. In other national certifications, such as fire-resistance structures, if one of two quality tests fails, the case is closed, so it can be considered that the quality test for aggregate certification that can be used for the third test is relatively easy. Follow-up audits for the certified products for the past three years were analyzed to see if there is a difference in the post-quality of aggregates certified by the secondary and tertiary tests. The results show no statistically significant difference between the two, and therefore, the tertiary test procedure of the certification process did not negatively affect the quality assurance of recycled aggregate.

Key Words

Recycled aggregate, Coarse aggregate, Certified aggregate, Follow-up Audit

유재호 Jae-ho Yoo , 김하나 Hana Kim

DOI:10.9786/kswm.2022.39.2.166

Abstract

Since the Wastes Control Act of 1987, Korea has laid the groundwork for proper waste management. The Framework Act on Resource Circulation was enacted in 2016 to manage and use waste throughout the entire lifecycle efficiently. Furthermore, “resource circulation” has recently become mainstream in domestic policies, such as establishing a digital-based resource circulation industrial complex as a part of the Korean New Deal 2.0. This study collected domestic studies on resource circulation, which has recently emerged as a major environmental issue, and analyzed research trends using topic modeling analysis. Relevant articles were collected from the Korea Citation Index using the keywords “resource circulation” and “circular economy,” and topic modeling analysis was performed on 207 papers and 712 keywords. Seven topics were drawn from the analysis: (1) energy-climate change policy, (2) eco-friendly design and systems, (3) waste electronics and plastic management, (4) revitalization of circular economy and local community, (5) environmental laws related to resource circulation, (6) concrete using recycled resources, and (7) matter flow analysis and management systems. In sum, it was found that many resource circulation studies have been conducted to address energy and climate change issues. In addition, resource circulation studies are not limited to policies and laws. Various studies are carried out across disciplines, such as engineering research on the management and utilization of specific resources and analytical research using tools, such as life cycle analysis (LCA). The findings of this study contributed to organizing major issues in recent resource circulation-related research and guiding future resource circulation-related studies.

Key Words

Research trend, Resource circulation, Topic modeling, Text network analysis

이재희 Jae-hee Lee , 최장욱 Jang-wook Choi , 상병찬 Byung-chan Sang , 엄태인 Tae-in Ohm

DOI:10.9786/kswm.2022.39.2.174

Abstract

The water content of the coffee grounds discharged from coffee beverage production facilities and coffee stores is about 75 wt.%. When the coffee grounds is used as solid energy source, drying technology is important because the high water content of the coffee grounds causes lower heating values reduction and combustion deterioration. In particular, it is necessary to maintain a constant water content of the dried coffee grounds with low energy consumption. In this study, two types of coffee ground batch dryer were tested: an electric heating and a gas burning system. After coffee grounds were injected into each dryer, vapor evaporation, drying rate, specific moisture evaporation rate, and drying efficiency were measured. The drying systems applied the moisture intensity (pulse, P) sensor and an automatic control program to maintain the moisture content of the dried coffee grounds. The drying performance and efficiency of the electric heating dryer were 21% and 33% higher than the gas burning dryer, respectively. The water content of dried coffee grounds is about 2.1 wt.%, and the ash content is 1.5 wt.%. The lower calorific value of dried coffee grounds is 5,710 kcal/kg, satisfying Bio-SRF (solid refuse fuel, Korea) quality standard. Therefore, when the dried coffee grounds is used as a solid energy source, it is advantageous to reduce the amount of greenhouse gas and save fossil fuels compared to the case of landfilling the dried coffee grounds.

Key Words

Coffee grounds, Gas combustor, Specific moisture evaporation rate, Drying efficiency