김용진 Yong-jin Kim , 이혜성 Hye-sung Lee

DOI:10.9786/kswm.2021.38.5.377

Abstract

Although the effects of marine microplastics on living organisms and their roles as carriers of organic pollutants to living organisms and the marine environment have already been studied, this paper focuses on the effects of marine microplastics on climate that haven’t been studied yet. Microplastics in the oceans absorb more solar radiation and alter the biophysical properties of the surface microlayer, resulting in an increase in the sea surface temperature (SST). An increase in the SST and the concentration of microplastics that cover the surface layer, interrupts the physical interaction between seawater and carbon dioxide (CO₂) in the atmosphere. Consequently, the solubility of carbon dioxide in seawater is lowered, and thereby increases the retention time of CO₂ in the atmosphere. Furthermore, plastics that are in the ocean can be decomposed by solar radiation, such as UV-B rays and directly release greenhouse gases such as methane, ethylene, ethane, and propylene, and thereby accelerates the greenhouse effect. Therefore, considering the marine microplastics as a new factor in the ocean- atmosphere coupled model, the extent of the impact of microplastics on weather should be quantitatively reviewed.

Key Words

Marine microplastics, SML, SST, Heat build-up, Climate change

이상철 Sang-chul Lee , 김관용 Gwan-yong Kim , 정득준 Deuk-jun Jung

DOI:10.9786/kswm.2021.38.5.387

Abstract

This study investigated the use of leather shaving scraps, which is inevitably produced during leather processing, in an upcycling technology. Particularly, this study investigated the development of eco-friendly ceiling panels material as alternatives to currently used built-in gypsum ceiling panels for building construction. Existing gypsum ceiling panels exhibit very poor moisture absorption characteristics, which increase the cost of raw materials during the manufacturing process. In addition, exposure to radon, which is present in the raw materials used for the manufacturing of phosphoric acid gypsum, poses hazardous risks to the human body, such as lung cancer and stomach cancer. Moreover, the release these raw materials into the environment results in secondary pollution in high-moisture environment, as these materials facilitate the growth of fungi. Furthermore, gypsum ceiling panels exhibit a poor durability owing to their weak impact strength. In addition, the high production cost of gypsum has restricted its continuous mass production for building construction materials. To address these problems, this study employed a pulverization process to mix, cross-link, and vulcanize leather waste and rubber to fabricate ceiling panels materials for building construction using a dry method. The fabricated panel materials exhibited good strength, flame retardancy, waterproofness, and radon-free properties. The upcycling technology proposed in this study is an eco-friendly, halogen-free method that utilizes leather waste as the main raw material and aluminum hydroxide as a flame retardant. The cross-linking characteristics of the material with a change in the filler and cross-linking system were analyzed. In addition, the manufacturing characteristics and physical properties of the ceiling panels with a change in the flame retardants were investigated. The results revealed that the manufactured ceiling panels with the optimal formulation satisfied the UL-94 standard, and exhibited a hardness of 55 D and density of 1.339.

Key Words

Shaving scrap, Construction materials, Ceiling panels, Leather waste recycling

이년호 Yeon-Ho Lee , 김지은 Jee-eun Kim , 공지현 Ji-hyeon Gong , 전경원 Kyung-won Jeon , 윤조희 Cho-hee Yoon , 장원준 Won-jun Jang

DOI:10.9786/kswm.2021.38.5.395

Abstract

This study investigated the optimal reaction condition for the production of hydrogen from the steam reforming of mixed alkane hydrocarbons using thermodynamic analysis. C₁-C₄ alkane hydrocarbons (CH₄, C₂H₆, C₃H₈, and C₄H₁₀) were utilized as the reactants in the thermodynamic equilibrium analysis using Gibbs free energy minimization. The equilibrium composition, CH₄ moles, CH₄ conversion, selectivity (CO, CO₂, C, and CH₄), and H₂ moles were estimated at various temperatures (200-1,000℃) and H₂O/C ratios (0.5-3.0). The steam reforming of mixed alkane hydrocarbons is a complex reaction that proceeds simultaneously with the cracking of C₂-C₄, carbon formation, steam reforming, and water gas shift reactions. In addition, the results revealed that the reaction temperature and H₂O/C ratio are important factors for these reactions. Furthermore, the reaction temperature and H₂O/C ratio had no significant effect on the decomposition of C₂-C₄ alkanes (i.e., C₂H₆, C₃H₈, and C₄H₁₀), as they were totally converted into CH₄ at temperatures below 650℃. In contrast, the H₂O/C ratio had a significant effect on the carbon formation, as carbon formation did not proceed at H₂O ratios of 2.0 and above. In addition, carbon was primarily produced in the temperature range from 350-550℃. Furthermore, the steam reforming reaction of CH₄ dominantly occurred at a high temperature (>650℃) and H₂O/C ratio (>1.5). In addition, high H₂O/C ratios favored the water gas shift reaction, which could be attributed to the presence of excess H₂O. The inhibition of cracking and coke formation and the maximization of the steam reforming and water gas shift reactions were considered for the stable operation of the process and production of hydrogen. The results revealed that the optimum temperature and H₂O/C ratio for achieving a high CH₄ conversion (>80%) and H₂ moles (>25 mol) were ≥700℃ and >2.0, respectively.

Key Words

Hydrogen, Steam reforming, Alkane, Thermodynamic equilibrium analysis, Carbon formation

장은석 Eun-suk Jang , 김대기 Daegi Kim

DOI:10.9786/kswm.2021.38.5.405

Abstract

In this study, livestock manure was converted into fuel using hydrothermal carbonization, and the chemical composition of the resulting fuel was investigated. The results revealed that the hydrogen and oxygen content of the resulting fuel decreased, whereas the carbon content increased. In addition, there was a reduction in nitrogen content, which could be attributed to the gradual reduction in potential NOx emission, and the decomposition of organic nitrogen under thermal reaction conditions to liquid and gas. Furthermore, the hydrothermal carbonization removed some of the volatile matter in the manure and increased the proportion of fixed carbon content; thus, resulting in an increase in fuel ratio from 0.32 to 0.68 with an increase in the reaction temperature. These results indicated that the calorific value increased after hydrothermal carbonization. However, at hydrothermal carbonization temperatures above 250℃, the formed products exhibited a high ash content of 36.07- 41.54%, which had no effect on the increase in the calorific value. The storage and stability of the biomass fuel was investigated using a moisture reabsorption experiment. There was a sharp decrease in the moisture reabsorption value of the fuel, and only 75% of the raw reabsorption value was retained. This could be attributed to the removal of hydrophilic groups, such as OH (hydroxyl group) and C=O (carboxyl group), from the manure by the hydrothermal carbonization process.

Key Words

Iivestock manure, Hydrothermal carbonization, Fuel properties, Hydrophobicity

한건호 Gun Ho Han , 기동원 Dongwon Ki , 강신영 Shin Young Kang , 오대성 Dae Sung Oh , 김명기 Myoung Kee Kim , 박세원 Se Won Park

DOI:10.9786/kswm.2021.38.5.412

Abstract

Since the 1970s, waste tires have been used as auxiliary fuel in Korea, and the Korean cement industry has employed various wastes as auxiliary fuels and alternative materials. The main fuels used in cement kiln are bituminous coal and coke, and as of 2018, the rate of waste tires used as auxiliary fuel in Korea was only 23% (based on the heating value by the fossil fuel). This value was almost half of that of Europe (46%) and one-third of that of Germany (68%). Owing to the high temperature conditions of the gas and solid (materials) in cement kilns (2,000 and 1,450°C, respectively), most harmful pollutants, such as heavy metals, are volatilized; thus, eliminating the environmental impact of waste fuel. However, the use of waste fuel and materials in cement production process has garnered the negative perceptions of people. To address this problem, the Korean government and cement industry established the “Waste Use and Management Standard for Cement Kilns” in 2009; however, this had no significant effect on the negative perceptions of the people. The effective disposal of waste in Korea has remained a challenge owing to lack of additional landfill areas and incinerators; particularly, China’s ban on waste imports in April 2018 has compounded this problem. To actively utilize combustible waste as alternative fuels for cement production process, this study proposed thermal/environmental and quality/environmental analysis candidates and standards, and suggested a standard operating procedure for cement kilns. The standard operating procedure of waste proposed in this study included heating value, elementary, and heavy metals content analyses, and that of cement included physical and chemical composition, heavy metals content and leaching, and radioactivity analyses. We believe that the proposed standard operating procedure can be employed in the future to ensure the reliability and enhancement of the utilization of waste as alternative fuels for cement production. Additionally, the standard proposed in this study may solve problems related to domestic waste disposal.

Key Words

Waste, Cement, Analysis, Standard operating procedure, Alternative fuel

안준 June An , 김하진 Ha Jin Kim , 전영남 Young Nam Chun

DOI:10.9786/kswm.2021.38.5.426

Abstract

The effects of conventional fossil fuels on the environment, such as air and carbon pollutions, have limited their use as an energy resource. To address this problem, biogas has emerged as an alternative energy source owing to its sustainable and renewable characteristics. In this study, we proposed a new type of cavity matrix combustor that can directly burn the products of small and medium-sized biogas facilities without the use of complicated facilities, such as CO₂ separation or purification facilities. To identify the combustion characteristics of the cavity matrix combustor, parametric screening studies were conducted based on changes in air ratio, total gas supply, biogas composition, and exhaust recirculation, and the optimal operating conditions were suggested based on the results. The performance test of the cavity matrix combustor revealed that the combustor exhibited excellent biogas combustion characteristics. In addition, the optimal operating air ratio and total gas supply conditions at which the combustor exhibited a combustion efficiency of 79.2% for a biogas composed of 60% CH₄ and 40% CO₂ were 1.1 and 30 L/min, respectively. Furthermore, the content of CO and UHCs, which were unburned gases, in the combustor were 0.03 and 0.01%, respectively, and that of NOx was 1 ppm. In addition, the combustion efficiency of the combustor slightly increased to 86.59% when combustion gas recirculation was performed.

Key Words

Biogas, Super adiabatic combustion, Microwave heating, Matrix burner, Climate technology

조수진 Soo-jin Cho , 서용칠 Yong-chil Seo , 이은송 Eun-song Lee , 고주인 Ju-In Ko

DOI:10.9786/kswm.2021.38.5.434

Abstract

This study conducted thermal desorption experiments for the remediation of mercury-contaminated soils with a mercury concentration of 26.39 mg-Hg/kg from gold-silver mine tailings. The thermal desorption experiments were performed in a muffle furnace at a pressure of 1 atm in the temperature range from 300 to 700℃. In addition, indirect thermal treatment experiments were conducted by adding 20 g of homogeneous samples into the crucible for 1 to 30 min. The mercury concentrations of the residual samples were analyzed using EPA method 7471a. Based on the results of the analysis of mercury concentration in the thermal treatment, the thermal desorption characteristics of mercury contaminated tailings were analyzed using reaction rate theory. The reaction rate constants (k) were calculated from 1.3 × 10^-3 to 1.9 × 10^-2 sec^-1 with a change in the temperature conditions. The results revealed that k increased with increasing temperature. In addition, the calculated pre-exponential factor and activation energy were 0.118 sec^-1 and 2.76 kcal/gmol, respectively. Furthermore, the thermal treatment conditions required to achieve the 4 mg-Hg/kg criteria for Hg content were approximately 1,451 s at 300℃ and 992 s at 400℃.

Key Words

Mercury, Mercury Contaminated Tailing, Thermal Treatment, Kinetics, Gold-Silver Mine

이두길 Doo Gil Lee , 박성용 Seong Yong Park , 이상조 Sang Jo Lee , 정재우 Jae Woo Chung

DOI:10.9786/kswm.2021.38.5.442

Abstract

This study employed the analytic hierarchy process (AHP) to investigate the main decision-making factors involved in the selection of materials forrecycled aggregates for constructing public buildings. The factors, which consisted of five main items and 15 detailed items in the AHP model, were devised through consultations with construction experts. Based on the weights of the main and detailed items, the “Subject to mandatory use” element exhibited the highest level of importance, followed by the “supplier” and “price” elements in the procurement sector, and the “specification content” in the construction sector. Furthermore, the results revealed that it is essential to reflect the use of recycled aggregates at the initial design stage and to introduce a mandatory use of recycled aggregates. In addition, the criteria for suppliers to meet upgrading the production technology of recycled aggregates are required.

Key Words

Construction waste, Recycled aggregates, Public building, Recycling activation, AHP

정회석 Hoesuk Jung , 이수정 Sujeong Lee , 선제호 Jeaho Seon , 요스케카츠라 Yousuke Katsura , 한인섭 Ihnsup Han

DOI:10.9786/kswm.2021.38.5.452

Abstract

This study compared H₂S removal efficiency of two types of deodorants (NOx deodorant ACE and Fe³⁺ deodorant S) at high temperature versus low temperature (summer/winter). For both temperature conditions, NOx deodorant ACE removed H₂S by 99% or more within 2 hours at the least dose of 2.5% (w/w), and this lasted for about 8 hours maximum. Fe³⁺ deodorant S removed H₂S by 99% or more at the dose of 5.0% (w/w), and this lasted for about 6 hours maximum. For the sludge where H₂S exists at high concentration, NOx deodorant ACE was the most appropriate. For Fe³⁺ deodorant S, additional alkaline chemicals are expected to be necessary.

Key Words

Sludge, H_{2S, Deodorant}

박영규 Young Gyu Park , 선영근 Young Geun Sun

DOI:10.9786/kswm.2021.38.5.458

Abstract

The palm oil mill industry in Malaysian generates 100 million ton of palm oil mill effluent (POME) and EFB (empty fruit bunch) as byproducts annually. This study identified the location, capacity and technology of biogas refinery plants for the production of biogas from the byproducts of the Malaysian palm oil mill plant. This study investigated the production of biogas via the anaerobic co-digestion of EFB under mesophilic anaerobic condition. The results revealed that subjecting EFB to an alkaline pretreatment method enabled a high-concentration methane yield. The raw biogas obtained from the anaerobic co-digestion of POME and EFB at 1.013 bar contained 61% CH₄, 33.5% CO₂ and 180 ppm H₂S and was produced at rate of 51 - 68㎥/h. The utilization of biomethane as a bio-CNG gas has been unexplored: hence, this study investigated the purification of POME biogas into bio-CNG gas. The pretreatment of raw biogas using chelate-iron (EDTA-iron solution) process, which is the most promising technique for the removal of 99% H₂S, was employed in this study. A pilot-scale separation plant with a capacity of 20㎥/hr that utilize cellulosic spiral wound membrane (MTR, USA) for upgrading biogas to CNG fuel quality was constructed and operated at the biogas plant. The result contained 99.1% CH₄, 1.8% CO₂, 0.004% H₂O and 0.9 ppm H₂S. These results indicate that the energy contents of biogas can be significantly enhanced by upgrading it to CNG fuel.

Key Words

Malaysia, bioCNG, membrane technology, biogas, POME