Hyundong Lee

Hydrogen trapping by TiC particles in iron

Abstract The interaction of hydrogen with the interface of TiC inclusion in iron was studied by thermal analysis technique using gas chromatrograph as hydrogen detector. The amount of hydrogen evolved from trap site was measured and its relations with activation energy and trap binding energy were studied. The evolution rate peak appeared at 996 K when heated with 3 K/min heating rate. It is due to the hydrogen release from the interface of TiC inclusions. The trap activation energy needed to escape from the interface of TiC inclusion is obtained from the relation between peak temperature and heating rate as 86.9 kj/mol and the trap binding energy obtained from the relation between peak area and the hydrogen charging temperature is 28.1 kJ/mol. The energy level of the hydrogen around the trap site is estimated from the above values.

Characteristics of Corrosion and Water Quality in Simulated Reclaimed Water Distribution Pipelines

Water reuse has been highlighted as a representative alternative to solve the lacking water resource. This study carried out a study on the pipe corrosion and water quality change which can occur through the supply of reclaimed water, using a simulated reclaimed water distribution pipeline. Galvanized steel pipe (GSP), cast iron pipe (CIP), stainless steel pipe (STSP) and PVC pipe (PVCP) were used for the pipe materials. Reclaimed water(RW) and tap water(TW) were respectively supplied into simulated reclaimed water distribution pipelines. As a result of performing a loop test to supply reclaimed water to simulated reclaimed water distribution pipelines, the weight reduction of pipe coupons showed the sequence of CIP > GSP > STSP ≈ PVCP. In addition, reclaimed water showed a high corrosion rate comparing to that of tap water. In case of CIP, the initial corrosion rate showed 3.511 mdd(milligrams per square decimeter per day) for reclaimed water and 2.064 mdd for tap water and the corrosion rate for 90 days showed 0.833 mdd for reclaimed water and 0.294 mdd for tap water. Also in case of GSP, the initial corrosion rate showed 2.703 mdd for reclaimed water and 2.499 mdd for tap water and the corrosion rate for 90 days showed 0.349 mdd for reclaimed water and 0.248 mdd for tap water, which was a tendency similar to that appeared in CIP with a tendency to reduce the corrosion rate. As a result of water quality changes of reclaimed water at pipe materials to carry out the loop test, there was higher conversion ratio of ammonia into nitrate in CIP and GSP with higher corrosion rate than that in STSP and PVCP where no corrosion has occurred. The highest denitrification rate of nitrate could be observed from CIP with the most particles generated from corrosion. In CIP, it could be confirmed that there was MIC (Microbiologically Induced Corrosion) as a result of EDS (Energy Dispersive X-ray spectrometer System) analysis results.

HYDROGEN TRAPPING BY TiC PARTICLES IN IRON

The interaction of hydrogen with the interface of TiC inclusion in iron was studied by thermal analysis technique using gas chromatrograph as hydrogen detector. The amount of hydrogen evolved from trap site was measured and its relations with activation energy and trap binding energy were studied. The evolution rate peak appeared at 996 K when heated with 3 K/min heating rate. It is due to the hydrogen release from the interface of TiC inclusions. The trap activation energy needed to escape from the interface of TiC inclusion is obtained from the relation between peak temperature and heating rate as 86.9 kJ/mol and the trap binding energy obtained from the relation between peak area and the hydrogen charging temperature is 28.1 kJ/mol. The energy level of the hydrogen around the trap site is estimated from the above values.

Concentration Characteristics of Runoff Pollutants using Statistical Techniques during a Storm: the Case Research of Driveway Site in Korea

This research was conducted to investigate the magnitude and nature of the emission of runoff pollutants with the goal of quantifying stormwater pollutant concentrations from driveways site. A statistical summary for concentration characteristics of driveway runoff is provided based on the various analysis techniques. Runoff water qualities in temporal variation were generally higher in wet season than in dry season with a high degree of variability. The 95 % confidence intervals of washed-off pollutant concentration are ranged to 82.4-141.4 mgL -1 for TSS, 53.3-87.6 mgL -1 for Turbidity, 19.0-38.7 mgL -1 for BOD, 34.0-59.2 mgL -1 for COD, 16.4-27.4 mgL -1 for DOC, 4.3-5.6 mgL -1 for TN and 0.25-0.34 mgL -1 for TP, showing the high values based on the surface or lake quality standards in Korea. The first flush effect is mostly occurred within initial 30 min of storm duration. Concentrations of water quality constituents in urban stormwater are often expressed in probabilistic terms using statistics such as the mean and standard deviation and selected quintiles. Three probability distributions, weibull in TSS and Turbidity, lognormal in BOD and COD and gamma in DOC, TN and TP were fitted and the goodness-of-fit was assessed using the Anderson-Darling test. The correlation matrix of all water quality variables shows significant relationships between all parameters (P<0.001) and the correlation of between TSS and Turbidity showed relatively strong positive relationship (r=0.825). This research presents the concentration changes and characteristics during storm occurrence. The new concept explaining the relationship among the emission effects of runoff pollutants are suggested using statistical techniques.

Safety Monitoring Sensor for Underground Subsidence Risk Assessment Surrounding Water Pipeline

IoT(Internet of Things) based underground risk assessment system surrounding water pipeline enables an advanced monitoring and prediction for unexpected underground hazards such as abrupt road-side subsidence and urban sinkholes due to a leak in water pipeline. For the development of successful assessment technology, the PSU(Water Pipeline Safety Unit) which detects the leakage and movement of water pipes. Then, the IoT-based underground risk assessment system surrounding water pipeline will be proposed. The system consists of early detection tools for underground events and correspondence services, by analyzing leakage and movement data collected from PSU. These methods must be continuous and reliable, and cover certain block area ranging a few kilometers, for properly applying to regional water supply changes.

A Study on the Availability Modelling and Assessment with Failure Density Function of Major Equipment for a Sewage Treatment Plant

The simulation investigation on the availability with failure density function of major equipment for a sewage treatment plant has been carried out. This study focuses on the availability of the plant and criticality with equipment module induced by component layout and its failure function. The equipment classification of sewage treatment plant and its failure function are established. Also solution methodologies are introduced as Monte-Carlo simulation method and event algorithm for uncertainty problem. The availability in the case of serial connection of equipment with all exponential function is calculated as around 50.4%. In other case of parallel combination with back up equipment, the availability showed over 80.1%. The criticality that a ffects availability showed high value over 77% in the dehydration and concentration process of sludge.

Characteristics of Residual Free Chlorine Decay in Reclaimed Water

The reclaimed water has been highlighted as a representative alternative to solve the lacking water resources. This study examined the reduction of residual free chlorine by temperature (5, 15, 25°C) and initial injection concentration (1, 2, 4, 6 mg/L) in the reclaimed water and carried out propose on the calculating method of the optimal chlorine dosage. As the reclaimed water showed a very fast reaction with chlorine at the intial time comparing to that of drinking water, the existing general first-order decay model (Ct = Co(e b)) was not suitable for use. Accordingly, the reduction of residual free chlorine could be estimated in a more accurate way as a result of applying the exponential first-order decay model (Ct = a + b (e b)). (r = 0.872~0.988). As a result of calculating the bulk decay constant, it showed the highest result at 653 day under the condition of 1 mg/L, 25°C for the initial injection whereas it showed the lowest result at 3.42 day under the condition of 6 mg/L, 5°C for the initial injection. The bulk decay constant tends to increase as temperature increases, whereas the bulk decay constant tends to decrease as the initial injection concentration increases. More accurate calculation for optimal chlorine dosage could be done by using the experimental results for 30~5,040 min, after the entire response time is classified into 0~30 min and 30~5,040 min to calculate the optimal chlorine dosage. In addition, as a result of calculating the optimal chlorine dosage by temperature, the relationships of initial chlorine demand (y) by temperature (x) could be obtained such as y = 1.409 + 0.450x to maintain 0.2 mg/L of residual free chlorine at the time after 4 hours from the chlorine injection.