• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.51-57
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• 2019

A plant layout problem has a large impact on the overall construction cost of a plant. When determining a plant layout, various constraints associating with safety, environment, sufficient maintenance area, passages for workers, etc have to be considered together. In general plant layout problems, the main goal is to minimize the length of piping connecting equipments as satisfying various constraints. Since the process may suffer from the heat and friction loss, the piping length between equipments should be shorter. This problem can be represented by the mathematical formulation and the optimal solutions can be investigated by an optimization solver. General researches have overlooked many constraints such as maintenance spaces and safety distances between equipments. And, previous researches have tested benchmark processes. What the lack of general researches is that there is no realistic comparison. In this study, the plant layout of a real industrial C3MR (Propane precooling Mixed Refrigerant) process is studied. A MILP (Mixed Integer Linear Programming) including various constraints is developed. To avoid the violation of constraints, penalty functions are introduced. However, conventional optimization solvers handling the derivatives of an objective functions can not solve this problem due to the complexities of equations. Therefore, the PSO (Particle Swarm Optimization), which investigate an optimal solutions without differential equations, is selected to solve this problem. The results show that a proposed method contributes to saving the capital expenditures.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.233-234
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• 2006

LNG is extremely cold, $-160^{\circ}C$ in its liquid state. When it vaporizes, returning to its natural state (re-vaporization), it cools its surroundings. This is cold energy. The manufacturing of liquid air is the first processes developed as the most effective utilization of LNG cold. In this paper, adopting the LNG cold process for manufacturing liquid air was developed and analysed. The result showed that as the higher air pressure and adapting nitrogen precooling, liquefaction rate and cumulative mass was increased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.457-463
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• 1999

The Joule-Thomson cryocooler with $H_2$gas has been developed. Cool-down characteristics and the cooling performance of a JT cryocooler have been investigated in detail. The JT cryocooler consists of JT expansion valve, heat exchanger, expansion chamber, compressed $H_2$gas storage tank, $LN_2$precooler, heater and a cryostat. The precooling process using both $GN_2$and $LN_2$was peformed to cool down the inside components of cryocooler under the maximum inversion temperature of $H_2$. The $H_2$expansion experiments have been peformed for 2-5MPa of H$_2$pressure to evaluate steady state temperatures of the cryocooler. It is found that the steady state temperatures are decreased as the H$_2$pressures are increased. The effects of cooling temperatures on the performance have been evaluated for various $H_2$and $N_2$pressures. It is seen that the cooling loads are increased, as the cooling temperature and operating pressure are increased.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.6
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• pp.571-577
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• 2020

Thermal analysis was performed for a cold box of a hydrogen liquefaction pilot plant with 0.5 ton/day capacity. The pilot plant has adopted a hydrogen liquefaction process using two-stage helium Brayton cycle with precooling of liquid nitrogen. The cold box for hydrogen liquefaction has generally vacuum insulation but inevitable heat invasion by conduction and radiation exists. The heat loads were calculated for cold box internals according to multilayer insulation emissivity. Total heat load of 181.7 W is estimated for emissivity of 0.03 considered in field condition.

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.200-208
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• 2021

Compare to the gaseous hydrogen, liquid hydrogen has various advantages: easy to transport, high energy density, and low risk of explosion. However, the hydrogen liquefaction process is highly energy intensive because it requires lots of energy for refrigeration. On the other hand, the cold energy of the liquefied natural gas (LNG) is wasted during the regasification. It means there are opportunities to improve the energy efficiency of the hydrogen liquefaction process by recovering wasted LNG cold energy. In addition, hydrogen production by natural gas reforming is one of the most economical ways, thus LNG can be used as a raw material for hydrogen production. In this study, a novel hydrogen production and liquefaction process is proposed by using LNG as a raw material as well as a cold source. To develop this process, the hydrogen liquefaction process using hydrocarbon mixed refrigerant and the helium-neon refrigerant is selected as a base case design. The proposed design is developed by applying LNG as a cold source for the hydrogen precooling. The performance of the proposed process is analyzed in terms of energy consumption and exergy efficiency, and it is compared with the base case design. As the result, the proposed design shows 17.9% of energy reduction and 11.2% of exergy efficiency improvement compare to the base case design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.438-444
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• 2015

The aim of this research was to apply a HACCP system (Hazard Analysis Critical Control Point) to fermented milk. The main ingredients of fermented milk, work facilities and workers were obtained from a company named YD, which is located in Seobuk-gu, Cheonan-si between November 5 2013 to April 13, 2014. A manufacturing process chart was prepared by referring to the manufacturing process of fermented milk manufacturers in common. The manufacturing process chart was made with raw materials; Raw milk, High Fructose Corn Syrup, Oligosaccharides, Lactic Acid bacteria and Subsidiary ingredients, Warehousing of packaging materials, Storage, Input, Preheating, Mixing, Homogeneity, Sterilization, Precooling, Culture, Filtration, In packaging, Out packaging, Storage, and Consignment, as listed Table 1. The results of the microbiological hazard analysis on the raw materials was safe after sterilization($90^{\circ}C{\pm}5^{\circ}C$, $35{\pm}3min.$) On the other hand,a microorganism test of an environment and workers suggested that the microbiological hazard should be reduced through systematic cleaning and disinfection accompanied by improved personal hygiene based on hygienic education on workers and the management of microorganisms in air.

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.574-580
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• 2014

Storage tanks of Carbon dioxide ($CO_2$) carriers utilized for the purpose of carbon capture and storage (CCS) into subsea strata have to undergo a pre-cooling session before beginning to load cryogenic liquid cargos in order to prevent physical and thermal deterioration of tanks which may result from cryogenic $CO_2$ contacting tank walls directly. In this study we propose dynamic model to calculate the tank inflow of $CO_2$ gas injected for precooling process and its dynamic simulation results under proportional-integral control algorithm. We selected two cases in which each of them had one controlled variable (CV) as either the tank pressure or the tank temperature and discussed the results of that decision-making on the pre-cooling process. As a result we demonstrated that the controlling instability arising from nonlinearity and singularity of the mathematical model could be avoided by choosing tank pressure as CV instead of tank temperature.

• Applied Biological Chemistry
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• v.27 no.2
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• pp.55-63
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• 1984

Lethal effect on Chinese radish Kimchi was investigated by using a pilot scale Kimchi pasteurizer. A simulation model was presented so as to predict the change in viable cell concentration of the Kimchi during pasteurization. D values of microorganisms in the Kimchi were found to be 2.21, 1.62, 0.73, 0.39 and 0.21min at 60, 64, 70, 75 and $80^{\circ}C$, correspondingly, and thereby z value was $19^{\circ}C$. One cycle time required was 0.99min at flow rate of 4 l/min. The ratio of lethality in preheating section to total lethality was 0.3 and the ratio of lethality in holding, precooling and cooling sections to total lethality was 0.7. The experimental data were in good agreement with the values simulated by two model equations to which linear and exponential temperature profiles were applied at $65^{\circ}C\;and\;70^{\circ}C$ in holding section.

• Horticultural Science & Technology
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• v.28 no.5
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• pp.902-911
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• 2010

Oriental melon ($Cucumis$ $melo$ var. $makuwa$) is a popular and high-value market fruit cultivated in Korea. Consumers are becoming increasingly interested in oriental melon as a healthy diet over the past few years. However, the melons have relatively high quality loss because the fruit are mainly produced for a limited period of time in the summer season. Lack of the proper postharvest treatments and high temperature exposure at harvest or during distribution are the most critical environmental factors limiting postharvest life of fruit. This review focuses on the overview of current research studies for postharvest treatment and functional packaging technology of oriental melon in Korea. Major physiological problems of the harvest fruit include the ripening process in quality changes of the produce such as loss of weight, firmness, flavor, and decay during the storage periods. Low temperature at 7 to $10^{\circ}C$ with high relative humidity of 90 to 95% is the suitable environmental condition used to maintain the quality of fresh oriental melon. Controlled atmosphere (CA) storage or modified atmosphere (MA) packaging can be used as supplemental treatments to extend postharvest-life. For oriental melon, an optimum CA is currently recommended to be 2-3% oxygen and 5-10% carbon dioxide atmosphere. Precooling, pretreatments of ethylene action and functional packaging system can be applied to oriental melon after harvest in order to extend storage life. Major active packaging technologies are concerned with a selectively gas permeable film related to respiration of produce and the packaging applications of ethylene removal, antimicrobial, and antifogging substances to keep the effective freshness of fruit.