연소 전 및 연소 후 이산화탄소 포집공정의 모델링 및 비교분석에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부, 2016. 2. 한종훈.Climate change and its consequences have raised global awareness to reduce the anthropogenic emission of greenhouse gases, especially Carbon Dioxide (CO2). Among the various sources of the CO2 emission, power plants combusting fossil fuel such as coal, oil and gas occupy the most amount of CO2 emission. Several methods of removing CO2 from power plant flue gas have been proposed, and post-combustion and pre-combustion capture processes are most widely used candidates. Although post-combustion capture process is known as the most mature and economically feasible technology, its high energy consumption and efficiency penalty associated with process retrofit still remain as an obstacle towards commercialization. Pre-combustion capture process, on the other hand, has higher efficiency than the conventional coal power plant and has no penalty associated with capturing CO2. Although pre-combustion capture is more energy efficient and environmental-friendly, its high economic barrier still makes it difficult to be widely implemented. In this study, both options of CO2 capture process are modeled with reliable data source and analyzed technically and economically. For the post-combustion capture process, mechanical vapor recompression process is suggested as a solution to reduce the energy consumption to regenerate the absorbent. For the pre-combustion capture process, lean vapor compression, which is a widely used configuration for post-combustion capture, is also applied to reduce the steam consumption in the acid gas removal unit. As another application derived from the IGCC plant, substitute natural gas production process is also proposed which can produce a methane-rich product from coal.CHAPTER 1. Introduction 1 1.1. Research motivation 1 1.2. Research objective 4 1.3. Outline of the thesis 5 CHAPTER 2. Modeling of the Post-combustion CO2 Capture Process 6 2.1. Process overview 6 2.2. Process modeling and simulation 7 2.2.1. Thermodynamic model 9 2.2.2. Flowsheet description 12 2.3. Process validation 15 2.4. Results and discussion 18 CHAPTER 3. Analysis of the Post-combustion CO2 Capture Process 20 3.1. Overview 20 3.2. Mechanical Vapor Recompression (MVR) process 22 3.2.1. Process description 22 3.2.2. Simulation results 25 3.2.3. Technical analysis 27 3.2.4. Economic analysis 31 3.3. Results and discussion 37 CHAPTER 4. Modeling of the Pre-combustion CO2 Capture Process 39 4.1. Process overview 39 4.2. Process modeling and simulation 42 4.2.1. Air separation unit (ASU) 43 4.2.2. Water-gas shift reactor (WGS) 45 4.2.3. Acid gas removal unit (AGR) 50 4.2.4. Combined Cycle system (CC) 54 4.3. Results and discussion 58 CHAPTER 5. Analysis of the Pre-combustion CO2 Capture Process 60 5.1. Overview 60 5.2. Lean vapor compression (LVC) for AGR unit 61 5.2.1. Process description 63 5.2.2. Simulation results and analysis 65 5.3. Substitute Natural Gas (SNG) Production 67 5.3.1. Process description 68 5.3.2. Simulation and model validation 70 5.3.3. Technical analysis 76 5.3.4. Economic analysis 84 5.4. Results and discussion 87 CHAPTER 6. Concluding Remarks 89 6.1. Conclusion 89 6.2. Future works 91 Literature Cited 92 Abstract in Korean (요약) 101Docto

Advanced CO2 Capture Process Using MEA Scrubbing: Configuration of a Split Flow and Phase Separation Heat Exchanger

AbstractCO2 capture process using aqueous Monoethanolamine (MEA) scrubbing is a well-proven and commercially-ready technology for reducing CO2 emission to the atmosphere. Although the MEA scrubbing is the one of the most suitable technologies for post-combustion CO2 capture, the MEA process has a critical problem which is high consumption of reboiler heat energy for solvent regeneration. In order to reduce the reboiler heat requirement, this paper suggests an advanced configuration of MEA process which consists of split flow and a phase separation heat exchanger. The split flow permits to reduce the reflux ratio in the stripper and the phase separation heat exchanger permits to alleviate preheating duty loss. As a result, the regeneration energy of the advanced process is reduced by 2.84GJ/ton CO2, which is lower than one of the reference process by 27%.CO2 capture; post combustion CO2 capture; advanced stripper configuration; cold solvent split; rich vapor compressio

Development of a thorium coating on an aluminium substrate by using electrodeposition method and alpha spectroscopy

A thin coating of thorium on aluminium substrates with the areal density of 110 to 130 $\mu g/cm^2$ is developed over a circular area of 22 mm diameter by using the electrodeposition method. An electrodeposition system is fabricated to consist of three components; an anode made of a platinum mesh, a cylindrical-shape vessel to contain the thorium solution, and a cathode in the form of a circular aluminium plate. The aluminium plate is mounted horizontally, and the platinum mesh is connected to an axial rod of an electric motor, mounted vertically and normal to the plane of the aluminium. The electrolyte solution is prepared by dissolving a known-weight thorium nitrate powder in 0.8 M HNO3 and isopropanol. The system is operated either in constant voltage (CV) or constant current (CC) mode. Under the electric field between the anode and cathode, thorium ions were deposited on the aluminium substrate mounted on the cathode. In the CV mode at 320, 360, and 400 V and in the CC mode at 15 mA, thorium films were formed over a circular area of the aluminium substrate. The areal density of thorium coating was measured by detecting emitted alpha particles. The areal density of thorium varied from 80 to 130 $\mu g/cm^2$ by changing the deposition time from 10 to 60 min. The results from the CV mode and CC mode are compared, and the radial dependence in the measured areal density is discussed for different modes of the electric field. The developed thorium coatings are to be used in the in-house development of particle detectors, fast neutron converters, targets for thorium fission experiments, and other purposes.Comment: 11 pages, 5 figures, 1 tabl

Empirical Validation of Heat Transfer Performance Simulation of Graphite/PCM Concrete Materials for Thermally Activated Building System

To increase the heat capacity in lightweight construction materials, a phase change material (PCM) can be introduced to building elements. A thermally activated building system (TABS) with graphite/PCM concrete hollow core slab is suggested as an energy-efficient technology to shift and reduce the peak thermal load in buildings. An evaluation of heat storage and dissipation characteristics of TABS in graphite/PCM concrete has been conducted using dynamic simulations, but empirical validation is necessary to acceptably predict the thermal behavior of graphite/PCM concrete. This study aimed to validate the thermal behavior of graphite/PCM concrete through a three-dimensional transient heat transfer simulation. The simulation results were compared to experimental results from previous studies of concrete and graphite/PCM concrete. The overall thermal behavior for both materials was found to be similar to experiment results. Limitations in the simulation modeling, which included determination of the indoor heat transfer coefficient, assumption of constant thermal conductivity with temperature, and assumption of specimen homogeneity, led to slight differences between the measured and simulated results

High triglyceride/HDL cholesterol ratio is associated with silent brain infarcts in a healthy population

Background Triglycerides (TG)/high-density lipoprotein (HDL) cholesterol ratio is a marker of small/dense low-density lipoprotein particles, which are closely associated with various metabolic and vascular diseases. However, the role of TG/HDL cholesterol ratio in cerebrovascular diseases has not been well studied. In this study, we evaluated the relationship between TG/HDL cholesterol ratio and the presence of silent brain infarct (SBI) in a neurologically healthy population. Methods We retrospectively evaluated consecutive participants in health check-ups between January 2006 and December 2013. SBI was defined as an asymptomatic, well-defined lesion with a diameter of ≥3 mm on T1- or T2-weighted images. TG/HDL cholesterol ratio was calculated after dividing absolute TG levels by absolute HDL cholesterol levels. Results Of 3172 healthy participants, 263 (8.3%) had SBI lesions. In multivariate analysis, TG/HDL cholesterol ratio was independently associated with SBI (adjusted odds ratio [aOR] = 1.16, 95% confidence interval [CI] = 1.00 to 1.34, P = 0.047). This association was prominent in males (aOR = 1.23, 95% CI = 1.03 to 1.48, P = 0.021), but not in females. In the analyses of the relationships between lipid parameters and SBI lesion burden, TG/HDL cholesterol ratio was positively correlated, and total cholesterol/TG ratio was negatively correlated with SBI lesion burden, in dose-response manners (P for trend = 0.015 and 0.002, respectively). Conclusions The TG/HDL cholesterol ratio was positively associated with the prevalence of SBI in a neurologically healthy population

High triglyceride-glucose index is associated with subclinical cerebral small vessel disease in a healthy population: a cross-sectional study

The triglyceride-glucose (TyG) index is a marker of insulin resistance (IR) and has been associated with various metabolic syndromes, cardiovascular diseases, and cerebrovascular diseases. However, limited information is available regarding its association with subclinical cerebral small vessel disease (cSVD). In this study, we evaluated the relationship between the TyG index and cSVD, including silent brain infarcts (SBIs) and white matter hyperintensity (WMH). We assessed health check-up participants aged 40–79years from 2006 to 2013. The TyG index was calculated using the log scale of fasting triglyceride (mg/dL) × fasting glucose (mg/dL)/2. The Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) was also calculated. This was compared with two insulin surrogates and cSVD as another IR indicator and compared the association between two insulin surrogates and cSVD. SBI was measured for both prevalence and burden. The WMH volume was quantitatively rated using a computer-assisted semi-automated technique. Results A total of 2615 participants were evaluated (median age: 56years, male sex: 53%). In the multivariable logistic regression analysis, the TyG index was seen to be associated with SBI prevalence (adjusted odds ratio: 1.39; 95% confidence interval [CI] = 1.06–1.81). Further quantitative analyses showed a positive dose–response relationship between the TyG index and SBI burden (P for trend = 0.006). In multivariable linear regression analysis, the TyG index was also found to be related to the volume of WMH (β = 0.084; 95% CI = 0.013 to 0.154). Additionally, the TyG index showed a similar or slightly stronger association with the prevalence of SBI and the volume of WMH than did HOMA-IR. A high TyG index was associated with a higher prevalence and burden of cSVD in a neurologically healthy population. This marker of IR could be a convenient and useful predictor of cSVD

Identification of gut dysbiosis in axial spondyloarthritis patients and improvement of experimental ankylosing spondyloarthritis by microbiome-derived butyrate with immune-modulating function

IntroductionDysbiosis is an environmental factor that affects the induction of axial spondyloarthritis (axSpA) pathogenesis. In the present study, we investigated differences in the gut microbiota of patients with axSpA and revealed an association between specific gut microbiota and their metabolites, and SpA pathogenesis.MethodUsing 16S rRNA sequencing data derived from feces samples of 33 axSpA patients and 20 healthy controls (HCs), we examined the compositions of their gut microbiomes.ResultsAs a result, axSpA patients were found to have decreased α-diversity compared to HCs, indicating that axSpA patients have less diverse microbiomes. In particular, at the species level, Bacteroides and Streptococcus were more abundant in axSpA patients than in HCs, whereas Faecalibacterium (F). prausnitzii, a butyrate-producing bacteria, was more abundant in HCs. Thus, we decided to investigate whether F. prausnitzii was associated with health conditions by inoculating F. prausnitzii (0.1, 1, and 10 μg/mL) or by administrating butyrate (0.5 mM) into CD4+ T cells derived from axSpA patients. The levels of IL-17A and IL-10 in the CD4+ T cell culture media were then measured. We also assessed osteoclast formation by administrating butyrate to the axSpA-derived peripheral blood mononuclear cells. The CD4+ IL-17A+ T cell differentiation, IL-17A levels were decreased, whereas IL-10 was increased by F. prausnitzii inoculation. Butyrate reduced CD4+ IL-17A+ T cell differentiation and osteoclastogenesis.DiscussionWe found that CD4+ IL-17A+ T cell polarization was reduced, when F. prausnitzii or butyrate were introduced into curdlan-induced SpA mice or CD4+ T cells of axSpA patient. Consistently, butyrate treatment was associated with the reduction of arthritis scores and inflammation levels in SpA mice. Taken together, we concluded that the reduced abundance of butyrate-producing microbes, particularly F. prausnitzii, may be associated with axSpA pathogenesis

Quality of life in patients with diabetic nephropathy: findings from the KNOW-CKD (Korean Cohort Study for Outcomes in Patients with Chronic Kidney Disease) cohort

Background Diabetic nephropathy (DN) can affect quality of life (QoL) because it requires arduous lifelong management. This study analyzed QoL differences between DN patients and patients with other chronic kidney diseases (CKDs). Methods The analysis included subjects (n = 1,766) from the KNOW-CKD (Korean Cohort Study for Outcomes in Patients with Chronic Kidney Disease) cohort who completed the Kidney Disease Quality of Life Short Form questionnaire. After implementing propensity score matching (PSM) using factors that affect the QoL of DN patients, QoL differences between DN and non-DN participants were examined. Results Among all DN patients (n = 390), higher QoL scores were found for taller subjects, and lower scores were found for those who were unemployed or unmarried, received Medical Aid, had lower economic status, had higher platelet counts or alkaline phosphatase levels, or used clopidogrel or insulin. After PSM, the 239 matched DN subjects reported significantly lower patient satisfaction (59.9 vs. 64.5, p = 0.02) and general health (35.3 vs. 39.1, p = 0.04) than the 239 non-DN subjects. Scores decreased in both groups during the 5-year follow-up, and the scores in the work status, sexual function, and role-physical domains were lower among DN patients than non-DN patients, though those differences were not statistically significant. Conclusion Socioeconomic factors of DN were strong risk factors for impaired QoL, as were high platelet, alkaline phosphatase, and clopidogrel and insulin use. Clinicians should keep in mind that the QoL of DN patients might decrease in some domains compared with non-DN CKDs

Antitumor Activity of TRAIL Recombinant Adenovirus in Human Malignant Glioma Cells

Tumor necrosis factor-Related Apoptosis-Inducing Ligand (TRAIL) has been reported to specifically kill malignant cells but to be relatively nontoxic to normal cells. One of disadvantages to previous in vivo protocols was the need for large quantities of TRAIL recombinant protein to suppress tumor growth. To evaluate the antitumor activity and therapeutic value of the TRAIL gene, we constructed adenoviral vectors expressing the human TRAIL gene (Ad.hTRAIL) and transferred them into malignant glioma cells in vitro and tumors in vivo, as an alternative to recombinant soluble TRAIL protein. The results show that TRAIL-sensitive glioma cells infected Ad.hTRAIL undergo apoptosis through the production and expression of TRAIL protein. The in vitro transfer elicited apoptosis, as demonstrated by the quantification of viable or apoptotic cells and by the analysis of cleavage of poly (ADP-ribose) polymerase. Furthermore, in vivo administration of Ad.hTRAIL at the site of tumor implantation suppressed the outgrowth of human glioma xenografts in SCID mice. These results further define Ad.hTRAIL as an anti-tumor therapeutic and demonstrate its potential use as an alternative approach to treatment for malignant glioma