• Computers and Concrete
• /
• v.17 no.6
• /
• pp.787-799
• /
• 2016

Climate anomalies in recent years, numerous natural disasters caused by landslides and a large amount of entrained sands and stones in Taiwan have created significant disasters and greater difficulties in subsequent reconstruction. How to respond to these problems efficaciously is an important issue. In this study, the sands and stones were doped with recycled materials (waste LCD glass sand, slag powder), and material was mixed for recycled ready-mixed soil. The study is based on security and economic principles, using flowability test to determine the water-binder ratio (W/B=2.4, 2.6, and 2.8), a fixed soil: sand ratio of 6:4 and a soil: sand: glass ratio of 6:2:2 as fine aggregate. Slag (at concentrations of 0%, 20%, and 40%) replaced the cement. The following tests were conducted: flowability, initial setting time, unit weight, drop-weight and compressive strength. The results show that the slump values are 220 -290 mm, the slump flow values are 460 -1030 mm, and the tube flow values are 240-590 mm, all conforming to the objectives of the design. The initial setting times are 945-1695 min. The unit weight deviations are 0.1-0.6%. The three groups of mixtures conform to the specification, being below 7.6 cm in the drop-weight test. In the compressive strength test, the water-binder ratios for 2.4 are optimal ($13.78-17.84kgf/cm^2$). The results show that Recycled ready-mixed soil materials (RRMSM) possesses excellent flowability. The other properties, applied to backfill engineering, can effectively save costs and are conducive to environmental protection.

• Journal of Energy Engineering
• /
• v.6 no.1
• /
• pp.96-103
• /
• 1997

Coal gasification experiments were performed to characterize the bench scaled unit of 0.5∼1.0 T/D entrained coal gasifier developed by KIER. Datong coal from China was selected for this study. The system was operated at the temperature range of 1300∼1550$^{\circ}C$, with 62.5% of coal water mixture on the basis of dry coal. Oxygen and slurry mixture were preheated prior to feeding into burner and the ratio of oxygen/coal was in the range of 0.8∼1.2. In the preparation of coal water mixture, 0.3 wt% of CWM1002 and 0.05 wt% of NaOH wire added to reduce viscosity as well as to enhance theological properties of slurry. The resultant gaseous products consist primarily of hydrogen, carbon monoxide, carbon dioxide, and minor amounts of methane. Formation of H$_2$and CO was increased, while CO$_2$was decreased as the reacting temperature being increased due to the char-CO$_2$reaction. Maximum production of H$_2$and CO occurred in the O$_2$/coal ratio of 0.9 at 1530$^{\circ}C$. Heating values of product gases were in the range of 1700∼2400 kcal/N㎥.

• Journal of Energy Engineering
• /
• v.8 no.4
• /
• pp.553-559
• /
• 1999

This study has been implemented to investigate various characteristics of coals which are imported from abroad. KIER has developed 1 T/D bench-scale unit, entrained-flow coal-slurry gasification technology to investigate the followings: 1) to assess the appropriate foreign coals for gasification. 2) to establish the data base for gasification phenomena, 3) to minimize the technical risks prior to introduction of commercial scaled IGCC power plant, 4) to develop essential key technologies and to establish operational experiences for coal gasification. The foreign coals used in the gasification are Cyprus and Alaska coals from U. S. A. Cyprus coal(bituminous) and Alaska coal (lignite) were shown about 1.29$0^{\circ}C$. The concentrations of coal-slurry for Cyprus were maintained up to 58%, 62% and 65% in order to enable to feed satisfactorily it into the gasifier without any other problems at feeding systems. However, the Alaska coal was unable to maintain slurry concentration over the 60% due to its high viscosity. During the experiments, $O_2/coal$ ratios in both coals ere maintained from 0.6~1.2, but especially Alaska coal was required excessive oxygen feed due to its high ingerent moisture contents. During the experiments with two different coals, the concentrations of syngas $(H_2+CO)$ were shown as 40~62%, and the heating value of syngas were detected as 1,400~2,050 kcal/N㎥

• Journal of the Korean Society of Hazard Mitigation
• /
• v.10 no.4
• /
• pp.25-32
• /
• 2010

High performance shotcrete has been recently researched partly as a result of high consensus on high strength and durability. However, they are very initial step compared from the advanced countries. For instance, they has been mainly on high strength or durability without any consideration on pumpability and shootability which are very crucial on workability. The purpose of this dissertation was to make a high performance wet-mix shotcrete (high workability) which would solve the general problems of wet-mix process in Korea. For this, the main experimental variables were selected to be silica fume(0.0, 4.5, 9%), air entrained agent(0.0, 0.005%). Rheology with IBB rheometer was measured for evaluating pumpability and shootability as well as pump pressure, rebound rate and build-up thickness. The conclusions from a series of experiments were as follow: The results of analyzing the effects of AE agent and silica fume on rheology indicated that AE agent reduced both of flow resistance(G) and torque viscosity(H) and silica fume increased flow resistance (G) and reduced torque viscosity(H). An increase in the value of torque viscosity(H) produces an increase in the requried pumping pressure. These result indicated that the reduction of torque would work better at improving pumpability. And an increase flow resistance(G) improved shootability(increase build-up thickness and reduce rebound).

• Journal of the Korean Society of Propulsion Engineers
• /
• v.6 no.2
• /
• pp.45-52
• /
• 2002

An experimental investigation on the structure and dynamic behavior of two dimensional over-expanded air jets exiting into water was carried out. The hish speed digital video imaging and static pressure distribution measurement were made to characterize the structure and time-dependant behavior of the jets. Mach number at the jet exit was 2.0 and was slightly less than the value predicted by the ideal nozzle calculation. Variance of jet spreading angle at different stagnation condition was measured as a function of mass flow rate. Periodic nature of the air jet distortion in water was observed and the frequency of the repetition was approximately 5-6 Hz for all cases tested. Three characteristic length scales were defined to characterize jet structure. $L_1$, maximum width of the plume when the periodic instability occurs, $L_2$, width of the jet where secondary reverse flow entrained jet flow and $L_3$, distance from the jet exit to the location where entrainment of the secondary reverse flow occurs. The ratio of $L_1$ and $L_2$ decreased with increasing stagnation pressure, i.e. mass flow rate. $L_3$ increased with increasing stagnation pressure. The temporal behavior of static pressure measurements also showed peak around frequency of 5, which corresponds the frequency obtained by visual measurements

• Korean Chemical Engineering Research
• /
• v.54 no.5
• /
• pp.659-664
• /
• 2016

In order to resolve the AAEM species migration routes and the interaction relationship between biochar structure and AAEM species during biomass pyrolysis, experiments were performed in an entrained flow reactor with $N_2$ at $500{\sim}900^{\circ}C$. ICP-AES, XPS and SEM-EDX were used to examine content and distribution of AAEM species and the physicochemical structures of biochar. The results show that at $500{\sim}700^{\circ}C$, the precipitation rate of AAEM species is relatively high. At high temperature (>$700^{\circ}C$), the AAEM species continue to migrate from interior to exterior, but little precipitation from biochar surface. And the migration of AAEM species is mainly realized by the C-O bond as the carrier medium. The AAEM species on biochar surface are mainly Na, Mg and Ca (<$700^{\circ}C$), while changing to K, Mg and Ca (${\geq}700^{\circ}C$). From $500^{\circ}C$ to $900^{\circ}C$, the biochar particle morphology gradually changes from fibers to porous structures, finally to molten particles. At $700{\sim}900^{\circ}C$, Ca element is obviously enriched on the molten edge of the biochar porous structures.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.451-454
• /
• 2009

Production and application of biodiesel are expected to grow steadily in the coming years and thus output of its by-product, crude glycerin, will accordingly increase as well. In the present study, gasification of biodiesel by-product as a renewable energy was performed in an entrained flow gasifier to investigate the gasification performance with the operating conditions. Crude glycerin shows a high heating value of 6,000 kcal/kg and low ash and sulphur content. Gasification was conducted in a temperature range of $950\;{\sim}\;1500\;^{\circ}C$. The variation of syngas composition with excess air ratio of 0.17 ~ 0.7 for air or oxygen as a gasification agent was investigated. From the results, syngas heating value, carbon conversion and cold gas efficiency of more than $2500\;kcal/Nm^3$, 95% and 65% were achieved, respectively. The temperature dependency of syngas composition, carbon conversion, and cold gas efficiency shows a similar tendency to excess air ratio at the temperature corresponding to the excess air ratio. The $H_2/CO$ ratio of the product gas was varied from 1.25 to 0.7 with the excess air ratio and this gas composition was favorable for DME synthesis. The optimum excess air ratio for gasification of biodiesel by-product was evaluated to be an approximately 0.35 to 0.4. The present results indicate that crude glycerin can be utilized as a feedstock for gasification to make syngas.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.20 no.5
• /
• pp.472-481
• /
• 2008

In this study hydraulic experiment was carried out to investigate the flow characteristics in the submerged outlet structure of Boryeong power plant and the efficiency of bubble reduction by installing horizontal porous plate in the outlet structure. The cross-sectional mean velocity in the submerged outlet structure was smaller than 1 m/s, the target value at the design stage to prevent bubble outflow to the open sea area. In addition, it was found that the maximum depth of bubble penetration is reduced 30 to 50% by installing the horizontal porous plate at the second falling location in the submerged outlet structure. It is expected that the total bubble amount entrained in the water will be most efficiently reduced by installing square-hole-shape porous plate of 20 cm hole size and making its central section as non-porous structure to dissipate the energy of falling water.

• Korean Chemical Engineering Research
• /
• v.46 no.3
• /
• pp.561-566
• /
• 2008

Gasification plant using petroleum coke for refinery and power generation process is increased from considering petroleum coke as a valuable fuel. In this study, gasification of petroleum coke was performed to utilize petroleum coke and to develop essential technology using 1T/D coal gasification system. In case of petroleum coke gasification, because of lower reactivity, consumption of oxygen is higher than coal gasification. The calorific value of syngas from petroleum coke mixed with coal at a mass ratio of 1:1 shows about $6.7{\sim}7.2MJ/Nm^3$. Although carbon conversion could reach more than 92% according to oxygen amount, cold gas efficiency shows lower value than the case of coal. Therefore, it was shown that complemental study in burner design to atomize slurry droplet is required to elevate gasification performance of petroleum coke which has lower reactivity than coal.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.29 no.1
• /
• pp.46-61
• /
• 2017

In the present work, the interaction analysis between tsunami bore and onshore bridge is approached by a numerical method, where the tsunami bore is generated by difference of upstream side and downstream side water levels. Numerical simulation in this paper was carried out by TWOPM-3D(three-dimensional one-field model for immiscible two-phase flows), which is based on Navier-Stokes solver. In order to verify the applicability of force acting on an onshore bridge, numerical results and experimental results were compared and analyzed. From this, we discussed the characteristics of horizontal force and vertical force(uplift force and downward force) changes including water level and velocity change due to the tsunami bore strength, water depth, onshore bridge form and number of girder. Furthermore, It was revealed that the entrained air in the fluid flow highly affected the vertical force.