• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.10
• /
• pp.1881-1891
• /
• 2000

Cenosphere particles of different fly ash formed at the pulverized coal power plant were hollow sphere or filled with small particles inside solid particles. And size was relatively larger than other fly ash particles as well as specific gravity was small to suspend in the water. In this paper, it was demonstrated to contain a variety of morphological particle type, and the physical and chemical properties related to the cenosphere and fly ash particles. Furthermore it was estimated the possibility to reuse the cenosphere particles on the base of cenosphere properties. Cenosphere formation resulted from melting of mineral inclusion in coal, and then gas generation inside the molten droplet. As the aluminosilicate particle was progressively heated, a molten surface layer developed around the solid core. Further heating leaded to cause the formation of fine particles at the core. The mass median diameter(MMD) of cenosphere particles was $123.11{\mu}m$ and the range of size distribution was $100{\sim}200{\mu}m$ with single modal. It was represented that specific density was $0.67g/cm^3$ fineness was $1135g/cm^3$. The chemical components of cenosphere were similar to other fly ash including $SiO_2$, $Al_2O_3$, but the amount of the chemical component was different respectively. In the case of fly ash, $SiO_2$ concentration was 54.75%, and $Al_2O_3$ concentration was 21.96%, so this two components was found in 76.71% of the total concentration. But in the case of cenosphere, it was represented that $SiO_2$ concentration was 59.17% and $Al_2O_3$ concentration was 30.16%, so this two components was found in 89.33% of the total concentration. Glassy component formed by the aluminosilicate was high in the cenosphere, so that it was suitable to use insulating heat material.

• Korean Chemical Engineering Research
• /
• v.52 no.2
• /
• pp.233-239
• /
• 2014

The slagging which generated from ash deposition on furnace wall and tube in boiler reduces the heat transfer efficiency and damages to safety of boiler. The slag flow behavior in boiler is affected by melting temperature which is related to ash compositions. In this study, the behavior of slag is researched by using ash fusibility test, called TMA (Thermo-Mechanical Analysis). The technique measures the percentage shrinkage as the function of temperature, T25%, T50%, T75%, T90%. These temperatures indicate different stages of melting. Then, the effect of ash chemical compositions measured from XRF (X-ray Fluorescence Spectrometer) to ash fusion temperatures is discussed. Among the chemical compositions, refractory and fluxing influence on ash fusibility is described. High levels of refractory component and limited amount of fluxing components ($Fe_2O_3$, $K_2O$, CaO) increase overall melting temperatures. High $SiO_2/Al_2O_3$ ratio decrease high melting temperatures (T75%, T90%). Meanwhile, the presence of reasonable levels of fluxing components reduces overall melting temperature. A presence of fluxing component such as $K_2O$ and CaO is found to decrease the T25% values significantly. From this research, it is possible to make a reasonable explanation and prediction of ash fusion characteristic from analysis of TMA results and ash chemical compositions.

• International Journal of Highway Engineering
• /
• v.3 no.4 s.10
• /
• pp.127-136
• /
• 2001

To increase the structural integrity of concrete box culvert good compaction by the dynamic compaction roller with bi9 capacity is as effective as good backfill materials. It is needed for effective compaction that a compaction roller closes to concrete structure with high frequency. However structural distress of the culvert could be occur due to the excessive earth pressure by great dynamic compaction load. To investigate the characteristics of Induced stress by compaction, a box culvert was constructed with changing cushion materials and compaction methods. Two types of cushion material such as tire rubber chip and EPS(Expanded Polystyrene) were used as cushion panels and they are set on the culverts before backfill construction. Laboratory test result of cushion material says that the value of dynamic elastic modulus of rubber is lesser than that of EPS. On the other hand, material damping of rubber material is greater than that of EPS. In most case, dynamic compaction rollers with 10.5 ton weights were used and vibration frequency was applied 30Hz for the great compaction energy. This paper presents the main results on the characteristics of dynamic earth pressures during compaction. The amounts of induced dynamic pressures$(\Delta\sigma\;h)$ by compaction are affected with construction condition such as compaction frequency, depth of pressure cell, distance between roller and the wall of culvert and roller direction. Based on the measured values dynamic lateral pressure on the culverts, it could be said that orthogonal direction of roller to the length of culvert is more effective to compaction efficiency than parallel direction.

• Applied Chemistry for Engineering
• /
• v.5 no.2
• /
• pp.199-208
• /
• 1994

In this study, the ultrasound which provides the properties of mixing, and surface cleaning effect, the increase of the effective reaction surface area and the enhancement of the effective collision frequency, was used to enhance the recovering efficiency of Cu from the Cu-ion containning waste water. The ultrasonic reactor used in this study was designed and constructed for improving the disadvantage of the existing ultrasonic reactor. From the experimental result and its analysis, we obtained following conclusions. 1. The ultrasound increased the rate of electrochemical deposition to 582.2% in maximum at the condition of $0.1M-CuSO_4$, and 2.1 V-overpotential. 2. The enhancement effect of ultrasound induced by the reduction of diffusion layer thickness was 277.8% in maximum and induced by the other effect except for the reduction effect of the diffusion layer thickness was 253.6% in maximum at $0.1M-CuSO_4$ and 2.1V overpotential. 3. This study gave the possibility of the scale-up of ultrasonic reactor and in particular, ultrasonic reactor would be effective in the treatment of waste water containning a low concentration of Cu ion.

• Journal of the Korean Institute of Gas
• /
• v.26 no.6
• /
• pp.9-15
• /
• 2022

In order to verify the durability of the high-pressure hydrogen tank in the operating pressure range, a hydraulic rupture test should be performed. However, if the bubbles generated by the initial injection process of water are attached to the inner wall of the tank and remain, a sudden pressure change of the bubbles during the rupture of the pressurized tank may cause shock and noise. Therefore, in this study, the flow velocity required to remove the bubbles remaining on the inner wall of the tank was predicted through simplified formulas, and the shape of the injection nozzle to maintain the flow velocity was determined based on the shape of the hydrogen tank for the hydrogen bus. In addition, a numerical model was developed to predict the change in flow velocity according to the inlet pressure, and an experiment was performed through a model tank to prove the validity of the prediction result. As a result of the experiment, the flow velocity near the tank wall was similar to the predicted value of the analysis model, and when the inlet pressure was 1.5 to 5.5 bar, the minimum size of the removable bubble was predicted to be about 2.2 to 4.6 mm.

• Journal of Korean Society of Forest Science
• /
• v.37 no.1
• /
• pp.1-16
• /
• 1978

The study describes on the identification and morphological characteristics of each species, ecological characteristics and propagation techniques, and developing utilization measures of the Parthenocissus plants for environment conservation and revegetation of the babe rock-slopes. The following species and varieties are disscussed in this study; Parthenocissus tricuspidata (S. et Z.) Planch. var. veitchii Rehd. var. lowii Rehd. var. pupurea Hort. Parthenocissus quiquefolia (L.) Planch. var. engelmanni Rehd. var. saint-pauli Rehd. var. hirsuta Planch. Parthenocissus henryana Diels et Gilg. Parthenocissus thomsoni Planch. Parthenocissus heptaphylla Small. Parthenocissus inserta (Kern.) K. Fritsch. Parthenocissus laetevirens Rehd. Parthenocissus himalayana Planch. These are, in general, all vigorous self-clinging climbers that will quickly cover a wall and bare rock surfaces with a dense network of branch growths and beautiful green leaves which change to shades of scarlet and crimson before they fall in Autumn. Parthenocissus tricuspidata out of 8 species in the genus Parthenocissus is the most useful plant for the environment conservation including the bare rock-slope revegetation and for the production of food and shelter for wildlifes. This native of Korea clings by means of small rootlike holdfasts (adhesive discs) and holds (tendrils) to stone work or any other solid support, tenaciously.

• Journal of Mushroom
• /
• v.19 no.3
• /
• pp.210-215
• /
• 2021

For sterilization of microorganisms of the Listeria genus contaminating enoki mushroom, pilot mushroom grower equipped with air sterilization devices were developed. Sterilization experiments were performed using physical and chemical treatments. Internal temperature and humidity were controlled, maintaining 6.62℃±0.30 in the upper shelves, 6.46℃±0.24 in the middle shelves, and 6.48℃±0.25 in the lower shelves. Humidities were 79.97%±4.42, 79.43%±4.06, and 79.94±4.30%, respectively, with a temperature setting of 6.5℃, and a relative humidity of 75%. A suitable enoki mushroom cultivation stage for air sterilizer application was during the growth stage, with temperature in the 6.5~8.5℃ range, and humidity of 70~80%. At these same internal conditions, the ozone concentration in the mushroom cultivator was found to be 160 ppb during ion-cluster generator operation. After physical sterilization, the Listeria innocua survival rate was 0.1 to 0.9% using ion cluster sterilization, and 9.3 to 10.6% using UV air sterilization. The Listeria innocua survival rates on different materials were 9.3~10.6% on the metal specimen, and 9.9~16.2% on the plastic wrapper. The survival rate was particularly high on the rough side of the plastic wrapper. Ion cluster air sterilization is a labor-saving and effective method for suppressing the occurrence of Listeria bacteria on mushroom growers walls and shelves. For the plastic wrapper, chemical sterilization is more effective than physical sterilization.