• Proceedings of the IEEK Conference
• /
• 2001.10a
• /
• pp.357-361
• /
• 2001

The possibility of producing Cr$_2$O$_3$powder from waste magnesia-chromium refractory was investigated by sulfuric acid reaction, alkali fusion, water leaching & purification and heat treatment. The effects of temperature, the amount of NaOH added and the flow rate of air on chromium extraction efficiency in an alkali fusion step were investigated. The fusion product was leached with methanol to solve free-NaOH, and then leached with water to produce a Na$_2$CrO$_4$solution. The purity of chrome(Ⅵ) oxides, prepared both from monochromate with an impurity content and monochromate purified with $CO_2$were also examined. The purified monochromate solution was reduced from Cr(Ⅵ) to Cr(III) with NaHSO$_3$solution. The reduced solution was neutralized with NaOH to produce Cr(OH)$_3$. Water washing was treated to eliminate Na$_2$SO$_4$from neutralized Cr(OH)$_3$slurry. The washed Cr(OH)$_3$was dried and thermally treated to produce Cr$_2$O$_3$powder. The properties like lightness and hue of Cr$_2$O$_3$fabricated in this study were L=47.47, a=-14.40 and b=17.21.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.05a
• /
• pp.47-48
• /
• 2023

In the domestic industrial sector, greenhouse gases emitted from the cement industry account for about 10%, with most of them generated during the cement clinker calcination process. During the calcination process, 57% of carbon dioxide is emitted from the decarbonation reaction of limestone, 30% from fuel consumption, and 13% from electricity usage. In response to these issues, the cement industry is making efforts to reduce carbon dioxide emissions by developing technologies for raw material substitution and conversion, improving process efficiency by utilizing low-carbon alternative heat sources, developing CO₂ capture and utilization technologies, and recycling waste materials. In addition, due to the limitations in purchasing and storing industrial byproducts generated from industrial facilities, many studies are underway regarding the recycling of construction waste. Therefore, this study analyzes the manufacture of calcium silicate cement (CSC), which can store carbon dioxide as carbonate minerals in industrial facilities, and aims to contribute to the development of environmentally friendly regenerated cement using construction waste.

• Journal of Fisheries and Marine Sciences Education
• /
• v.20 no.3
• /
• pp.508-519
• /
• 2008

Hot air drying is a method that let moistures evaporate by heat exchange between heating air and dry target. This way is dominating more than about 70% of dryers that the use extent is wide fairly, and is established in domestic than dryer that use conduction or radiation etc. Most of research about drying had been emphasized in size of device through analysis for these dry phenomenon plain, heating topology, and aspect of form and so on by dry target's special quality, and research about device development or waste heat withdrawal technology in energy utilization efficiency side is slight real condition. Therefore, in this study, Investigated numerically about thermal efficiency elevation that is leaned against as that change the temperature of inlet and outlet in heat exchanger of the hot air drying tower.

• Journal of Energy Engineering
• /
• v.11 no.2
• /
• pp.106-113
• /
• 2002

While the demand for energy has shown a sharp increase recently, the supply seems to be limited by the fact that the conventional fossil fuel energy or nuclear energy has its own environmental problems such as, for example, global warming or nuclear waste disposal. To overcome such limited supply of energy, the utilization of natural thermal energy such as river water and sea water as well as treated sewage can be a substantial supplement. The potential use of the unused energy has become more and more feasible these days as the heat pump technology has been advanced. In the present study, the unused energy reserves are estimated on regional and monthly basis for each resource based on the method developed here in order to establish the base data for its utilization. The potential use of the unused energy is also discussed.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.697-700
• /
• 2005

Aquifer Thermal Energy Storage (ATES) system can be very cost-effective and renewable energy sources, depending on site-specific parameters and load characteristics. In order to develop an ATES system which has certain hydrogeological characteristics, understanding of the thermo hydraulic processes of an aquifer is necessary for a proper design of an aquifer heat storage system under given conditions. The thermo hydraulic transfer for heat storage is simulated using FEFLOW according to two sets of pumping and waste water reinjection scenarios of heat pump operation in a two layered confined aquifer. In the first set of model, the movement of the thermal front and groundwater level are simulated by changing the locations of injection and pumping well in seasonal cycle. However, in the second set of model the simulation is performed in the state of fixing the locations of pumping and injection well. After 365 days simulation period, the temperature distribution is dominated by injected water temperature and the distance from injection well. The small temperature change is appears on the surface compared to other slices of depth because the first layer has very low porosity and the transfer of thermal energy are sensitive at the porosity of each layer. The groundwater levels and temperature changes in injection and pumping wells are monitored to validate the effectiveness of the used heat pump operation method and the thermal interference between wells is analyzed.

• Journal of Energy Engineering
• /
• v.6 no.1
• /
• pp.87-95
• /
• 1997

A chemical heat pump based on the reversible reactions between metal chlorides and ammonia gas is attractive alternative to compression system and liquid absorption systems in cooling and refrigerating fields. The advantages of chemical heat pump are no regulatory constants due to CFC refrigerants, utilization of gas, industrial waste heat, electricity, fuel oil etc. as heat sources and wide applications to energy storage system, large-scale energy managements for industrial process. The scale-up of chemical heat pump from laboratory prototype to pilot plants necessitates the interpretation of system performance and evaluation of dynamic behavior in the chemical reactor. This study contains the prediction of performance of chemical refrigerator according to operating condition, the dynamic simulations through reactor modelling, which is used for the calculation of reactive medium temperature and the conversion variation with reactor cooling temperature, and the effect survey of block parameters on the power of refrigerator.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.782-787
• /
• 2008

The Kalina cycle simulation study was carried out for a preliminary design of a geothermal power generation system. The Kalina cycle system can be used for the utilization of a low-temperature heat sources such as geothermal and industrial waste heat that are not hot enough to produce steam. The sea/river water can be considered as a cooling media. A steady-state simulation model was developed to analyze and optimize its performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump were modelled by an isentropic efficiency, while a condenser, an evaporator and a regenerative heat exchanger were modeled by UA-LMTD method with a counter-flow assumption. The simulation results show that the power generation efficiency over 10% is expected when a heat source and sink inlet temperatures are $100^{\circ}C$ and $10^{\circ}C$ respectively.

• Nuclear Engineering and Technology
• /
• v.56 no.3
• /
• pp.832-845
• /
• 2024

Reactor cavity cooling systems (RCCSs) comprising passive safety features use the atmosphere as a coolant, which cannot be lost. However, their drawback is that they are easily affected by atmospheric disturbances. To realize the commercial application of the two types of passive RCCSs, namely RCCSs based on atmospheric radiation and atmospheric natural circulation, their safety must be evaluated, that is, they must be able to remove heat from the reactor pressure vessel (RPV) surface at all times and under any condition other than under normal operating conditions. These include both expected and unexpected natural phenomena and accidents. Moreover, they must be able to eliminate the heat leakage emitted from the RPV surface during normal operation. However, utilizing all of the heat emitted from the RPV surface increases the degree of waste heat utilization. This study aims to understand the characteristics and degree of passive safety features for heat removal by comparing RCCSs based on atmospheric radiation and atmospheric natural circulation under the same conditions. It was concluded that the proposed RCCS based on atmospheric radiation has an advantage in that the temperature of the RPV could be stably maintained against disturbances in the ambient air.

• Journal of the Korea Furniture Society
• /
• v.11 no.2
• /
• pp.67-72
• /
• 2000

Some physical characteristics as thickness swelling, heat conduction, and bending properties of composite hoards made of waste wood chip and charcoal were measured. Wood-charcoal composite boards of three types and cement board were prepared for this study as shown in Table 1, Keeping duration of strawberries in the boxes($25cm{\times}25cm{\times}25cm$) manufactured with the boards was also examined. Thickness swelling and bending properties(MOR and MOE) of board B and C were lower than those of board A. Among the wood-charcoal composite boards except cement board, there were no differences in heat conduction(mm/sec.). Strawberries in the box with board C were kept longer duration in fresh condition than that with cement board. From the results, it is suggested that wood-charcoal composite boards can be used for eco-material.

• Journal of the Korean Wood Science and Technology
• /
• v.37 no.1
• /
• pp.94-104
• /
• 2009

It is urgently required to develop the production of fermentation-heat energy from the waste agricultural and forest biomass and its effective heat exchanging system for the supply of warm water to rural households and greenhouses. In this study 3 helical-type and 1 plate-type heat exchangers using 3 different waste biomasses [e.g. hardwood (HW) sawdust (100%), softwood (SW) sawdust : HW sawdust (50 : 50) and HW sawdust : grass (90 : 10)] were applied in order to find out the best heat recovery system. The heat exchanger was basically considered to improve the overall heat recovery efficiency, to minimize heat loss and to simplify manufacturing, assembling and breaking up the fermenting beds. The helical-type heat exchanger (HX-H3) installed in fermenting bed of HW sawdust : grass (90 : 10) showed relatively higher temperature profiles, in particular mid- and upper-parts than lower and surface parts during 45-day fermentation process. The maximum temperature was ranged from $40^{\circ}C$ to $65^{\circ}C$ with average $60^{\circ}C$. The water temperature of tank outlet was ranged to $33{\sim}48^{\circ}C$ during whole measuring periods. By the way plate-type one (HX-P) installed in same biomass compositional fermenting bed showed $64.5{\sim}76.5^{\circ}C$ at center part, and $43{\sim}56^{\circ}C$ and $42{\sim}58^{\circ}C$, water tank and tank outlet temperatures, respectively, during 100 day measurement. It could be concluded that the plate-type heat exchanger (HX-P) provides not only the effective heating for the rural households and greenhouses, but also having the best heat recovery performance, easy manufacturing, assembling and breaking up the systems.