• Resources Recycling
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• v.27 no.1
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• pp.55-63
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• 2018

Physical property changes of printed circuit board (PCB) according to heat treatment conditions were investigated. The heat treatment was carried out in air and nitrogen atmosphere at temperature range from $200^{\circ}C$ to $325^{\circ}C$. Thermogravimetric analysis showed that the PCB was pyrolyzed in two steps. The thickness of PCB expanded by 11~28% at about $300^{\circ}C$ in both air and nitrogen atmosphere as layer disintegration occurred. Mechanical strength of PCB decreased from 338.4 MPa to 20.3~40.2 MPa due to the delamination caused by the heat treatment. The heated printed circuit boards were crushed and sieved for analysis of density distribution and liberation degree of copper according to particle size. As a result of the density distribution measurement, non metallic particles and copper particles were concentrated into different size range, respectively. The liberation degree of copper was improved from 9.3% to 100% at size range of $1,400{\sim}2,000{\mu}m$ by heat treatment.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.58.2-58.2
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• 2012

Heavy hydrocarbon reforming is a core technology for "Dirty energy smart". Heavy hydrocarbons are components of fossil fuels, biomass, coke oven gas and etc. Heavy hydrocarbon reforming converts the fuels into $H_2$-rich syngas. And then $H_2$-rich syngas is used for the production of electricity, synthetic fuels and petrochemicals. Energy can be used efficiently and obtained from various sources by using $H_2$-rich syngas from heavy hydrocarbon reforming. Especially, the key point of "Dirty energy smart" is using "dirty fuel" which is wasted in an inefficient way. New energy conversion laboratory of KAIST has been researched diesel reforming for solid oxide fuel cell (SOFC) as a part of "Dirty energy smart". Diesel is heavy hydrocarbon fuels which has higher carbon number than natural gas, kerosene and gasoline. Diesel reforming has difficulties due to the evaporation of fuels and coke formation. Nevertheless, diesel reforming technology is directly applied to "Dirty fuel" because diesel has the similar chemical properties with "Dirty fuel". On the other hand, SOFC has advantages on high efficiency and wasted heat recovery. Nippon oil Co. of Japan recently commercializes 700We class SOFC system using city gas. Considering the market situation, the development of diesel reformer has a great ripple effect. SOFC system can be applied to auxiliary power unit and distributed power generation. In addition, "Dirty energy smart" can be realized by applying diesel reforming technology to "Dirty fuel". As well as material developments, multidirectional approaches are required to reform heavy hydrocarbon fuels and use $H_2$-rich gas in SOFC. Gd doped ceria (CGO, $Ce_{1-x}Gd_xO_{2-y}$) has been researched for not only electrolyte materials but also catalysts supports. In addition, catalysts infiltrated electrode over porous $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.2}O_3-{\delta}$ and catalyst deposition at three phase boundary are being investigated to improve the performance of SOFC. On the other hand, nozzle for diesel atomization and post-reforming for light-hydrocarbons removal are examples of solving material problems in multidirectional approaches. Likewise, multidirectional approaches are necessary to realize "Dirty energy smart" like reforming "Dirty fuel" for SOFC.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.660-667
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• 2020

This study focused on the epoxy resin production process, which uses the steam of 155 ℃ or higher as a heat source, and discards all condensate generated. A part of the process is operated at low temperatures of 70 ℃ or below, thus there are opportunities to reduce the steam consumption by recycling wasted condensate as a heat source for the low temperature section of process. In this study, we developed process models that can reduce steam by recovering waste heat through recycling condensate and conducted a case study to find an optimal condensate recycling system. Three different process designs were proposed and economic evaluations were performed by comparing annual capital costs and steam savings in each case. Finally, an annual steam consumption of the low-temperature section could be reduced by up to 67.6%, which could also bring an additional economic benefit of 522.1 million won/yr.

• 연구논문집
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• s.27
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• pp.75-86
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• 1997

Combined cycle power plant is a system where a gas turbine or steam turbine is used to produce shaft power to drive a generator for producing electrical power and the steam from the HRSG is expanded in a steam turbine for additional shaft power. Combined cycle plant is a one from of cogeneration. The temperature of the exhaust gases from a gas turbine ranges from $400^\circC$ to $600^\circC$, and can be used effectively in a heat recovery steam generator to produce steam. Combined cycle can be classed as a "topping(gas turbine)" and a "bottoming(steam turbine)" cycle. The first cycle, to which most of the heat is supplied, is called the topping cycle. The wasted heat it produces is then utilized in a second process which operates at a lower temperature level and is therefore referred to as a "bottoming cycle". The combination of gas/steam turbine power plant managed to be accepted widely because, first, each individual system has already proven themselves in power plants with a single cycle, therefore, the development costs are low. Secondly, the air as a working medium is relatively non-problematic and inexpensive and can be used in gas turbines at an elevated temperature level over $1000^\circC$. The steam process uses water, which is likewise inexpensive and widely available, but better suited for the medium and low temperature ranges. It, therefore, is quite reasonable to use the steam process for the bottoming cycle. Only recently gas turbines attained inlet temperature that make it possible to design a highly efficient combined cycle. In the present study, performance analysis of a dual pressure combined-cycle power plant is carried out to investigate the influence of topping cycle to combined cycle performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.593-600
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• 2012

The exergy characteristics for R245fa and water working fluids have been analyzed for an electric generation system utilizing the Rankine cycle to recover heat from the wasted exhaust gas from a diesel engine used for the propulsion of a large ship. The theoretical calculation results showed that the efficiencies of exergy and system exergy improved as the turbine inlet pressure increased for R245fa at a fixed mass flow rate. Furthermore, the exergy destruction rates of the condenser and evaporator were relatively larger than those in other components. The exergy efficiency of the system increased with increasing mass flow rate. For a water working fluid, although the exergy destruction rate of the evaporator was similar to that for R245fa, the exergy loss rate varied significantly in response to variations in the pressure and mass flow rates at the turbine inlet.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.74-82
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• 1998

Combined cycle power plant is a system where a gas turbine or a steam turbine is used to produce shaft power to drive a generator for producing electrical power and the steam from the HRSG is expanded in a steam turbine for additional shaft power. The temperature of the exhaust gases from a gas turbine ranges from $400{\sim}650^{\circ}C$, and can be used effectively in a heat recovery steam generator to produce steam. Combined cycle can be classed as a topping and bottoming cycle. The first cycle, to which most of the heat is supplied, is a Brayton gas turbine cycle. The wasted heat it produces is then utilized in a second process which operates at a lower temperature level is a steam turbine cycle. The combined gas and steam turbine power plant have been widely accepted because, first, each separate system has already proven themselves in power plants as an independent cycle, therefore, the development costs are low. Secondly, using the air as a working medium, the operation is relatively non- problematic and inexpensive and can be used in gas turbines at an elevated temperature level over $1000^{\circ}C$. The steam process uses water, which is likewise inexpensive and widely available, but better suited for the medium and low temperature ranges. It therefore, is quite reasonable to use the steam process for the bottoming cycle. Recently gas turbine attained inlet temperature that make it possible to design a highly efficient combined cycle. In the present study, performance analysis of a 3 pressured combined cycle power plant is carried out to investigate the influence of topping cycle to combined cycle performance. Present calculation is compared with acceptance performance test data from SeoInchon combined cycle power plant. Present results is expected to shed some light to design and manufacture 150~200MW class heavy duty gas turbine whose conceptual design is already being undertaken.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.345-358
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• 2021

This study focuses on the development of the liquid air production process that uses LNG (liquefied natural gas) cold energy which usually wasted during the regasification stage. The liquid air can be transported to the LNG exporter, and it can be utilized as the cold source to replace certain amount of refrigerant for the natural gas liquefaction. Therefore, the condition of the liquid air has to satisfy the available pressure of LNG storage tank. To satisfy pressure constraint of the membrane type LNG tank, proposed process is designed to produce liquid air at 1.3bar. In proposed process, the air is precooled by heat exchange with LNG and subcooled by nitrogen refrigeration cycle. When the amount of transported liquid air is as large as the capacity of the LNG carrier, it could be economical in terms of the transportation cost. In addition, larger liquid air can give more cold energy that can be used in natural gas liquefaction plant. To analyze the effect of the liquid air production amount, under the same LNG supply condition, the proposed process is simulated under 3 different air flow rate: 0.50 kg/s, 0.75 kg/s, 1.00 kg/s, correspond to Case1, Case2, and Case3, respectively. Each case was analyzed thermodynamically and economically. It shows a tendency that the more liquid air production, the more energy demanded per same mass of product as Case3 is 0.18kWh higher than Base case. In consequence the production cost per 1 kg liquid air in Case3 was $0.0172 higher. However, as liquid air production increases, the transportation cost per 1 kg liquid air has reduced by $0.0395. In terms of overall cost, Case 3 confirmed that liquid air can be produced and transported with $0.0223 less per kilogram than Base case.