김한별 Hanbyeol Kim , 제정호 Jungho Jae

DOI:10.9786/kswm.2022.39.4.297

Abstract

Growing interest has been shown in the production of petrochemical feedstocks and bio-plastic from lignocellulosic biomass. This study reports a novel method in which ZSM-5 catalysts with a hierarchical micro-mesoporous structure were applied to produce green p-xylene via the tandem reaction of Diels-Alder cycloaddition of biomass-derived 2,5- dimethylfuran and ethanol and subsequent dehydration. Specifically, this study investigated the effects of the catalyst synthesis method and Si/Al ratio on the catalytic performance for p-xylene production. Commercial ZSM-5 catalysts with various SiO₂/Al₂O₃ ratios (e.g., 23, 30, 80) were used as parent materials and were subjected to NaOH treatment for forming mesopores by desilication. XRD, BET, and ammonia-TPD analyses were performed to observe the change in the degree of mesopore formation and the distribution of acid sites. A soft-templating method using an amphiphilic surfactant was also applied to synthesize an ordered mesoporous ZSM-5 for comparison with the desilicated ones. The ZSM-5 catalyst with the highest SiO₂/Al₂O₃ ratio (80) and a number of hierarchical mesopores formed through alkali treatment exhibited the highest 2,5-dimethylfuran conversion (> 90%) and p-xylene selectivity (~55%) along with the production of useful alkyl aromatics (~20%). This high activity can be attributed to high hydrophobicity and high mesopore volume combined.

Key Words

Biomass, 2, 5-Dimethylfuran, Bioethanol, Diels-Alder cycloaddition, p-Xylene

박가연 Gayeon Park , 나춘기 Choonki Na

DOI:10.9786/kswm.2022.39.4.308

Abstract

Sulfonated polystyrene (PS-SO₃H) fibers were prepared using plastic waste. The sulfonation of the PS-SO₃H fibers was evaluated based on the adsorption of Cu²⁺ ions. The maximum adsorption capacity was 142.9 mg/g, based on the Langmuir adsorption model. The adsorption equilibrium was achieved within 20 min. The adsorption system followed the secondorder kinetic model, indicating that the system was dominated by chemical adsorption. The adsorption elution cyclic results demonstrated that the adsorbent PS-SO₃H fibers were effectively regenerated using a 0.2 M HCl solution. Therefore, adsorbent PS-SO₃H fibers may be used repeatedly without a significant reduction in adsorption performance.

Key Words

Recycling of polystyrene waste, Polystyrene fiber, Sulfonation, Copper adsorption

김연수 Younsu Kim , 이채영 Chaeyoung Lee

DOI:10.9786/kswm.2022.39.4.315

Abstract

The purpose of this study was to analyze the effect on the operation of the continuous anaerobic digester according to the organic loading rate (OLR) increase method at the beginning of the operation in the anaerobic digestion process. To evaluate the effect of the OLR on the anaerobic digestion process, the method (R1) of reducing the dilution factor of the substrate and the method (R2) of reducing the hydraulic retention time (HRT) were applied on a continuous stirred tank reactor (CSTR). Methane production in the R2 reactor was the highest at 0.45 m³ CH₄/kg VS at OLR 2.10 kg VS/m³·d, and the methane generation rate in the R1 reactor was the highest at 0.41 m³ CH₄/kg VS at OLR 3.10 kg VS/m³·d. Additionally, at OLR of 1.7 kg VS/m³·d, VS and COD removal efficiencies were 88% and 69% for R1, respectively, and 95% and 96% for R2, respectively. This can be seen as the effect of an increase in the residence time of the anaerobic microorganisms in the R2 reactor, maintaining a relatively long HRT, and as the experiment progressed, it was confirmed that it showed a more stable behavior even with an increase in the organic matter load and fluctuations in the injection substrate. Therefore, an HRT reduction method can be suggested to increase the stability and efficiency of the initial operation during the anaerobic digestion of food waste. Since the inhibitory effect of methanogenic microorganisms occurs, it can be concluded that it is essential to maintain the ammonia nitrogen concentration below 3,000 mg/L for stable long-term operations.

Key Words

Anaerobic digestion, Food waste, Organic loading rate increase method, Continuous stirred tank reactor (CSTR)

서덕만 Deockman Seo , 박현 Hyeon Park , 서승범 Seung Beom Seo , 이상경 Sangkyung Lee

DOI:10.9786/kswm.2022.39.4.324

Abstract

This study aims to analyze the effects of water temperature reduction at SUDOKWON Landfill Site via the Integrated Water Temperature Management System (“the System” hereafter) on biological leachate treatment. The effect of reduced water temperature of the leachate treatment with the System is compared with the effect of the unaltered temperature without the System. The analysis shows that the System lowered the temperature by 3.4℃ on average, ranging from 1.6 ~ 5.7℃, resulting in the leachate treatment plant operating at the optimum temperature for biological process, which ranges from 33 ~ 38℃. By lowering the water temperature, the System was able to retain the performance of the biological process to treat the increased COD and T-N loads and maintain the same leachate treatment efficiency ratio. In addition, the System prevented foam overflow in the operation of the biological process basin, which contributed to the increase in the quantity of leachate treatment, as it allowed the biological process to be stably operated from April to September. The results of this research show that the System can be a good alternative solution to other treatment plants suffering from reduced efficiency due to high temperatures in the biological process of leachate treatment.

Key Words

Integrated water temperature management system, SUDOKWON Landfill Site, Water temperature reduction, Leachate, Biological processes

조문환 Mun-hwan Cho , 장용철 Yong-chul Jang

DOI:10.9786/kswm.2022.39.4.333

Abstract

This study examines the energy utilization methods of waste heat from medical waste incineration facilities. The economic feasibility of converting energy from incineration surplus heat and its effect on reducing greenhouse gases (GHGs) are also analyzed. The medical waste in 2019 was approximately 235,754 tons with an increase of 56% compared with 2013 (151,438 tons), while the treatment capacity of incineration facilities only slightly increased by 9.5% (equivalent to 20,000 tons/year). This study found that the ultimate analysis of the waste from five medical waste incinerators indicated ash 5.00%, moisture 20.07%, and combustibles 72.58%. The elemental composition was C 56.58%, H 8.46%, O 13.61%, N 0.81%, S 0.16%, and Cl 1.86%, in addition to a lower heating value of 6,353 kcal/kg (dry weight basis). The amount of combustible air required for incineration was 65,421.9 Sm3/kg·hr, resulting in the combustion gas of 71,271.2 Sm³/kg·hr. The calorific value of mixed gas was found to be 6,458.7 kcal/kg, and the recoverable calorie was 19.55 Gcal/hr or 157,182 Gcal/yr. Based on the heat recovery of the incineration facilities, the electricity sales, and heat sales are estimated to be 32,800 MW/year and 126,000 Gcal/year, respectively, equivalent to a total of KRW 6,876 million in revenue. The annual steam production is estimated to be 260,000 tons, equivalent to 17.55 million liters of heavy oil and 13.02 million LNG. GHGs by steam utilization can be approximately 48,000 tCO₂-eq on a heavy-oil basis or 30,000 tCO₂-eq on an LNG basis. When expanded to 190,000 tons of medical waste incineration in 2020, approximately 1.5 million tons of steam can be produced annually, replacing the energy of approximately 100 million liters based on heavy oil.

Key Words

Medical waste, Incineration heat recovery, Heat balance, Greenhouse gas reduction

전수민 Soomin Jeon

DOI:10.9786/kswm.2022.39.4.342

Abstract

The quality test pass rate for fine aggregate used for concrete among quality-certified recycled aggregates is relatively low. This paper examines the failure rate and items of follow-up inspection tests conducted over the past three years for recycled fine aggregate for concrete. In addition, if two out of three tests are suitable for the certification of recycled aggregates, certification is performed. Considering that other certification systems fail one out of every two tests, it is possible to assume that tertiary test opportunities have a negative effect on quality securing recycled aggregates. Therefore, this study analyzed whether there is a statistically significant difference between the follow-up inspection test results for the twice- and thrice-tested certifications. In conclusion, this study found that the tertiary test did not negatively affect the quality of the recycled fine aggregate for concrete.

Key Words

Recycled aggregate, Fine aggregate, Certified aggregate, Follow-up inspection test

김수향 Su Hyang Kim , 오민아 Mina Oh , 조우리 Woori Cho , 임호진 Ho Jin Lim , 이정한 Jung Han Lee , 이재영 Jai-young Lee

DOI:10.9786/kswm.2022.39.4.349

Abstract

In this study, an environmentally friendly solution was devised by replacing the tetraethyl orthosilicate (TEOS) used in the manufacture of mesoporous silica (SBA-15) with SiO₂ from clay defective molding sand waste to produce a novel adsorbent (W-SBA-15). The prepared W-SBA-15 was used to remove antimony (Sb) from groundwater. The content of SiO₂ in W-SBA-15 and its recyclability were evaluated. The surface properties of W-SBA-15 and SBA-15 were compared. The performance of the novel adsorbent (W-SBA-15) was compared with that of traditional SBA-15 made with TEOS and an adsorbent made of pure Jumunjin sand (J-SBA-15). The content of SiO₂ in W-SBA-15 was 89%, and the concentration of harmful substances did not exceed the legal standard. Thus, the molding sand waste was considered to be suitable for synthesizing mesoporous silica. The surface properties of the W-SBA-15 prepared here were similar to those of the traditional mesoporous material according to SEM, TEM, BET, and FT-IR measurements. To evaluate the adsorption performance, a batch test evaluating Sb adsorption was performed under various concentration, time, pH, temperature, and isothermal adsorption equilibrium conditions. As a result, the Sb removal efficiency was in the order of SBA-15 > W-SBA-15 > J-SBA-15. The Sb removal efficiency of SBA-15 and W-SBA-15 was over 90%. Therefore, the W-SBA-15 prepared in this study can be used as an adsorbent.

Key Words

Clay defective molded sand waste, Antimony, SiO₂, Mesoporous silica(SBA-15), Adsorption

최성은 Seongeun Choi , 황진환 Jin Hwan Hwang , 김재영 Jae Young Kim , 김승환 Seunghwan Kim , 이상명 Sang Myung Lee , 이승철 Seung Chul Lee

DOI:10.9786/kswm.2022.39.4.357

Abstract

Mechanical stirring is one of the representative methods to mix and agitate the sludge inside a digester. It significantly affects the amount of biogas production by changing the number of propellers, the distance between the bottom and the propellers, and the distance between propellers and the operating cycle. Since the various factors affect the digester's efficiency, the optimal configuration of the mechanical agitators needs to be investigated in terms of the internal flow and turbulence structures inside the digester. We conducted a laboratory-scale digester experiment and Computational Fluid Dynamics (CFD) simulations, which both have the 40:1 scale, to find the optimal configuration of the digester located in Jeongeup, South Korea. The validity of the CFD model was verified by the comparison between the observation data taken from the laboratory experiment and the CFD results. Then, the flow velocity and the amount of sludge over time inside the digester, which has the actual scale, were numerically quantified by the verified CFD model. In addition, the position of the dead zone inside the digester depending on the different positions of the propellers was estimated. We confirmed that the array of the propellers significantly affects the flow structure and sludge sedimentation inside the digester.

Key Words

Anaerobic digestion, Computational fluid dynamics (CFD), Dead zone, Mechanical mixing system, Sediment

이웅걸 Woong-geol Lee , 김석규 Suk-kyu Kim , 김태형 Tae-hyeong Kim , 이병철 Byeongcheol Lee , 송현진 Hyeon-jin Song , 송명신 Myong-shin Song

DOI:10.9786/kswm.2022.39.4.368

Abstract

In this study, coal ash buried in a landfill was recycled to manufacture an artificial daily covering material, and a field experiment was conducted to evaluate its usability. The coal ash used was fluidized-bed boiler coal ash and pulverized boiler coal ash. The artificial daily covering material produced was able to immobilize heavy metal ions. The unconfined compression strength was improved by the formation of C-S-H hydrate through the reaction of SiO₂ in soil with calcium hydroxide. The permeability coefficient of each type of coal based covering was similar to that of the standard. Re-slurring was not performed, and the odor emission standard was satisfied. the wind tunnel tes showed a weight reduction of 2.9% to 8.7% at a wind speed of 25 m/s depending on the type of covering. This study found that artificial daily covering materials made using fluidizedbed boiler coal ash are not harmful to the environment, so they can be used to replace traditional daily covering materials.

Key Words

Landfill, CLSM, Daily cover materials, Fly ash, C-S-H

전인서 In-seo Jeon , 황수정 Su-jeong Hwang , 박정현 Jeong-hyeon Park , 장용철 Yong-chul Jang , 권영선 Youngsun Kwon , 김병환 Byeonghwan Kim

DOI:10.9786/kswm.2022.39.4.376

Abstract

The consumption and disposal of single-use plastics (SUP) has become a critical issue of environmental concern in international solid waste communities. Many countries have begun adopting regulatory measures to reduce consumption and disposal of SUPs, including banning their production, restricting their uses, imposing plastic taxes, implementing ecofriendly designs, and encouraging proper recycling methods. In this study, we analyzed policy measures and recent efforts in SUP management between Korea and Japan by life-cycle stage. In Korea, the regulatory measures have focused on single-use plastic bags and cups, over-packaging, strengthened extended producer responsibility, and the introduction of bioplastics. However, there is still a lack of definition, scope, and detailed strategy for banning SUPs, restricting their use, and resource circulation. Japan recently legislated the Plastic Resource Circulation Promotion Act and bioplastic roadmap to properly manage SUPs. Based on comparative analysis, more policy countermeasures and efforts to reduce SUPs are still needed for mitigating environmental burdens. Such countermeasures may include legally defining SUPs and highlighting their scope of use, banning the production of extended SUP items with industry cooperation and consultation, reducing consumption of SUPs by implementing multi-use cups and containers supported by civil society and local governments, using recycled content in products, and introducing bioplastics. The results of this study will be beneficial for policy-makers, the plastic industry, and the scientific community by providing a comparative analysis and showing recent trends of SUP policy measures in Korea and Japan toward a circular economy society.

Key Words

Single-use plastic, Plastic bag, Bioplastic, Circular economy, EPR