안정윤 Jeong-yoon Ahn , 정석주 Seok-joo Chung , 김지태 Ji-tae Kim

DOI:10.9786/kswm.2020.37.1.1

Abstract

The purpose of this study is to manufacture an effective CO₂ methanation catalyst to convert CO₂ into CH₄ in order to produce a renewable energy source and to reduce greenhouse gas emissions. Numerous studies on CO₂ methanation technologies are in progress, but the industrial application of such catalysts has not yet been developed. In this study, high-performance catalysts that can be operated at low temperatures were manufactured. For the industrial application, the catalysts were prepared in disk, pellet, and honeycomb structures. The catalytic performance for each type of catalyst structure was evaluated at atmospheric pressure at 350℃. Results of the tests showed that the pellet-type catalyst had a CO₂ conversion efficiency of 89%, which is much higher than that of the other two catalyst structures investigated. Therefore, the pellet-type catalyst is an attractive option for the CO₂ methanation industry in view of its high performance and simple manufacturing process.

Key Words

CO₂ methanation, Nickel catalysts, Various shapes of catalyst, Carbon dioxide

Md Akhte Khirul , Beom-geun Kim , Daechul Cho , Sung-hyun Kwon

DOI:10.9786/kswm.2020.37.1.9

Abstract

Blocking the influx of nutrients from contaminated sediment and reducing terrigenous loads are essential to control eutrophication in coastal water areas. In this study, the use of an oyster-shell-based ORC (oxygen-releasing compound) was investigated with respect to nutrients such as nitrogen, phosphorous, and sulfur compounds in the sediment environment. The ORC, which was produced by pyrolyzing oyster shell powder, was found to be overoxidized and consisted of calcium peroxide. A series of experiments simulating a typical overlying water-sediment system were carried out in open-lid cylindrical columns over the fifteen-day experimental period. The elution and distribution of crucial contaminating species within that system are discussed. T-N, NH₄ ⁺-N, T-P, and Pi propagated with time toward the overlying water from the sediment through diffusive migration, showing a constrained increase over distance at the sediment-water interface. The nitrate levels decreased with time, possibly due to local denitrification. Partial oxidation in a homogenized mixture of sediment and oxidized oyster shell powder resulted in an increased DO level within the experimental time frame, which in turn caused T-N, NH₄ ⁺-N, T-P, and Pi to propagate at a lower rate than sediment without any ORC. Analyses for sulfates and sulfides in the sediment mixed with ORC confirmed that the chemical environment changed into a more oxidized state in fifteen days. Diffusive migration, along with chemical reactions and/or adsorption, successfully explained the propagation and distribution of the concerned nutrient species resulting from the use of oyster shell powders.

Key Words

Eutrophication, Oxygen releasing compound, Bacterial community, Nutrients release, Diffusive migration

김용준 Yong-jun Kim , 김교근 Kyeo-keun Kim

DOI:10.9786/kswm.2020.37.1.19

Abstract

In order to evaluate the possibility of recycling waste in contact with environmental media, leaching tests and ecotoxicity tests were performed using samples of coal ash and slag wastes. The hazardous characteristics of the waste materials and leachates from those materials were assessed based on their concentrations of chemical components, including heavy metals. The acute toxicity tests were performed with Daphnia magna. In the ecotoxicity tests, the pH ranged from 10.87 ~ 11.11, which is too high for good Daphnia growth. Results of the acute toxicity tests showed that the coal ash as TU is 1.66 and the slag was 0.3, which was lower than the regulatory limit of 2 in both samples. Despite these encouraging results, it may be necessary to consider using the chronic toxicity leaching test because the wastes are exposed to the environment for an extended time period relative to the fifteen days used in this study.

Key Words

Environmental hazardous impact, Ecotoxicity, TU, Recycling possibility, Heat treatment facility

김용준 Yong-jun Kim , 김교근 Kyeo-keun Kim

DOI:10.9786/kswm.2020.37.1.28

Abstract

The seven wastes generated from the nonferrous metals industry were analyzed in order to propose an efficient landfilltype recycling procedure. In the leaching tests, As and Pb levels in the leachate from the sludge (WTS2) exceeded regulation. Analysis of the dust (DST3) indicated that concentrations of Cd, Pb and Hg also exceeded regulation. In addition, when results of the chemical analyses were compared to the soil pollution zone regulation, all seven waste samples exceeded the regulatory limits. Therefore, the seven wastes generated from the nonferrous metals industry were judged to be unsuitable for recycling using a landfill-type recycling procedure. In addition, one of the sludge samples contained 55.3% SO3, and the leachate from the sludge had a pH of 2.69. Despite the low pH, the corrosion rate of that sample was only 0.0012 mm/yr., which is within the corrosion standard of 6.35 mm/yr. Three samples (SLG1, SLG2, and DUT2) with a high ratio of alkali metal and alkaline earth metal were measured the metal and water reactivity, and no hazardous characteristics were observed. Based on the results of this study, a new environmental impact assessment procedure for recycling wastes from the nonferrous metals industry is proposed.

Key Words

Landfill type recycling procedure, Corrosion rate, Metal and water reactivity

최성원 Sung-won Choi , 김한준 Han-jun Kim

DOI:10.9786/kswm.2020.37.1.37

Abstract

In order to establish an efficient waste management plan, it is essential to forecast waste generation accurately, and such estimates become the basis for optimizing and developing the existing waste management infrastructure. The unit generation rate method used to estimate waste generation is widely used because it is convenient to apply. However, because it has various problems, methods for forecasting waste generation must be improved. Machine learning techniques are being used to forecast prices and demand in various areas, such as economy and industrial engineering. This study applies those techniques for predicting waste generation and compares the results with those obtained using existing methodologies. In this study, 80% (January 2013 to December 2016) of the data were used for training purposes, and 20% (January 2017 to December 2017) were used for testing. The results of five hundred iterations show that the minimum value of 515.4 ton/day, the one-quartile value of 573.6 ton/day, and the median value of 590.4 ton/day in 2020, are significantly different from the results obtained using the unit generation rate method (547.7 ton/day). It was also shown that future waste generation will continue to increase despite a decrease in population, and then it converges on 614.9 ton/day in 2030. In other words, the model that was applied in this study is more suitable for short-term forecasts than for long-term forecasts. In addition, results of this study suggest that future increases in waste generation would be due to changes in the population structure and the developing delivery service.

Key Words

Forecasting model, Multiple layer perceptron, The unit generation rate method, Waste generation

김남균 Nam-kyun Kim , 오재성 Jea-sung Oh , 김경문 Kyoung-mun Kim

DOI:10.9786/kswm.2020.37.1.44

Abstract

Since January 2018, China’s ban on imports of waste plastics has reduced the profitability of recycling styrofoam through recycling. Accordingly, the recycling industry is avoiding the collection and processing of waste styrofoam, and the resulting waste problems are becoming a social problem. Therefore, this study aims to develop semi-incombustible building insulation through the upcycling of waste EPS, and perform the efficiency analysis through flame retardant performance test and fire simulation (FDS). The results of cone calorimeter test and FDS analysis showed the improved performance in terms of fire safety by confirming the reduction of heat release rate and the decrease of temperature, CO and CO₂ generation, and the increase of visible distance and oxygen concentration. The upcycling technology development of waste EPS is expected to greatly contribute to the utilization of waste resources, reduction of building material cost, and improvement of profitability of recycling business.

Key Words

Waste EPS, Upcycling, Flame retardant performance

박민주 Min-ju Park , 장원준 Won-jun Jang , 정대운 Dae-woon Jeong

DOI:10.9786/kswm.2020.37.1.51

Abstract

The production and reforming of biogas from food waste (FW) to produce hydrogen was investigated. First, two-phase anaerobic digestion was used to produce the biogas. The anaerobic digestion process was stable over a 60-day period and did not accumulate VFAs. Biogas production rates varied from 38.1 L/kg FW to 84.1 ± 1.7 L/kg FW, while CH₄ and CO₂ concentrations fluctuated between 43 ~ 64% and 36 ~ 56%, respectively. Second, the carbon dioxide reforming (CDR) reaction was performed to reform the biogas, which consisted of a 50/50 mixture of CH₄ and CO₂. A Ni-Ce_0.8Zr_0.2O₂ catalyst was prepared by the co-precipitation method, and CDR was performed at T=600-800℃, CH₄: CO₂: N₂=1 : 1 : 3, and GHSV 480,000 h-1 in a fixed-bed catalytic reactor. The CDR reaction is activated with increasing temperature of reaction. Especially concentration of H₂ was highest as 24.6% at 800℃. The catalyst deactivated with time, which correlated with sintering and carbon deposition on the catalyst.

Key Words

Anaerobic digestion, Biogas, Carbon dioxide reforming, Hydrogen, Ni catalyst

이승훈 Seung-hoon Lee , 김재경 Jae-kyung Kim

DOI:10.9786/kswm.2020.37.1.62

Abstract

The amount of greenhouse gas emissions from sewage treatment plants depends largely on the methane emission factor for BOD loading, and the methane emission factor of anaerobic treatment is higher than that of aerobic treatment. In the K-ETS (Korea Emissions Trading Scheme), the methane emission factor for anaerobic treatment of sewage is 0.48 kg CH₄/kg BOD, but the emission factor is overcalculated compared to the actual amount of methane generated in the sewage treatment systems. To solve this problem, a specific country-wide emission factor was developed by using data from five domestic sewage treatment plants from 2018 to 2019. Details on developing the plant-specific emission factor are also provided. The country-specific emission factor was applied immediately using the emission calculation from the 2019 data. Developing a plant-specific emission factor is recommended because adopting the country-specific emission factor, which is developed using an average of data from five plants, can be overcalculated in many plants. However, an economic analysis must be performed prior to developing plant-specific emission factors because developing plant-specific emission factor costs annual development expenses continually. Therefore, a preliminary evaluation method is provided in this study to determine the emission factor by comparing the cost and benefit of developing a plant-specific emission factor relative to that of adopting a country-specific emission factor.

Key Words

Sewage disposal plant, Plant-specific emission factor, Preliminary Evaluation

정석주 Seok-joo Chung , 라빈드란 Ravindran Balasubramani , 김지태 Ji-tae Kim

DOI:10.9786/kswm.2020.37.1.69

Abstract

Composting livestock manure emits various air pollutants, including greenhouse gases. Because of the sorption properties of activated carbon, the effects of palm shell activated carbon on CO₂ and NH₃ reduction during composting of chicken manure were investigated. Tests were performed using chicken manure containing four different activated carbon contents: Treatment A, 0wt. %; Treatment B, 5wt. %; Treatment C, 10wt. %; and Treatment D, 15wt. %). For these tests, the moisture content was set to 65% in order to minimize the effects of moisture on gaseous emissions. During fifty days of composting, the temperature reached a maximum of 55℃ for tests B, C, and D at the thermophilic stage. The total amount of CO₂ produced in treatments A, B, C, and D was 4.08 m³, 3.44 m³, 2.54 m³, and 2.08 m³, respectively. Similarly, the total amount of NH³ produced in tests A, B, C, and D was 0.03 m³, 0.025 m³, 0.020 m³, and 0.018 m³, respectively. For treatments A, B, and C, emissions of CO² and NH³ decreased as the activated carbon content increased, but treatment D had a relatively limited effect. In addition, the highest microbial activity was observed in treatment C, and the palm shell activated carbon significantly decreased the pathogens in the compost. When factoring in the price of palm shell activated carbon, using chicken manure containing 10% palm shell activated carbon (treatment C) during composting is recommended in order to reduce CO₂ and NH₃ emissions.

Key Words

Chicken manure, Palm shell activated carbon, Carbon dioxide, Ammonia

양승재 Seung-jae Yang , 노희지 Hee-ji Rho , 채종성 Jong-seong Chae , 엄태인 Tae-in Ohm

DOI:10.9786/kswm.2020.37.1.76

Abstract

Incineration is a stable, high-temperature thermal treatment method for flammable waste that has the advantage of recovering energy through incineration heat use. With the growing interest in combustible waste treatment, research has focused on combustion technologies that use solid refuse fuel (SRF) to improve fuel quality. This study investigated the effect of the cross-sectional area of the upper part of the secondary air inlet of an SRF combustion furnace under constant fuel properties and air ratio to optimize the SRF incinerator design. We calculated the temperature, velocity, and concentration distributions of the combustion furnace for two cases: cases A (larger cross-sectional area of the secondary air inlet) and B (smaller cross-sectional area of the secondary air inlet). The primary and secondary air injections for both cases were fixed at 50%. The fluctuations in the combustion gas temperature and velocity in the combustion furnace were calculated. In addition, the emission characteristics were compared according to the combustion furnace height. In Case A, the outlet temperature was 1321 K, and the SRF and CO concentrations were 130 and 2,140 ppm at the outlet, respectively. In Case B, the outlet temperature was 1362 K, and the SRF and CO concentrations were 230 and 30 ppm at the outlet, respectively. In conclusion, the cross-sectional area of the secondary air injector can influence the combustion characteristics of SRF combustion furnaces. We expect these findings to help optimize SRF incinerator designs in terms of maximizing energy efficiency and minimizing environmental impacts.

Key Words

SRF, Combustor, CFD, Optimal Design