Inkyu Lee

Measurement and correlation of excess molar volumes for mixtures of 1-propanol and aromatic hydrocarbons

Excess molar volumes (VmE) have been measured at 303.15 K for 1-propanol+benzene or toluene or o- or m- or p-xylene mixtures using V-shape dilatometer. The VmE values, for an equimolar composition, vary in the order: benzene>toluene∼m-xylene>o-xylene>p-xylene. The VmE data have been used to calculate partial molar volumes, excess partial molar volumes, and apparent molar volumes of 1-propanol and aromatic hydrocarbons over the entire range of composition. The excess volume data have also been interpreted in terms of graph-theoretical approach and Prigogine-Flory-Patterson theory (PFP). While PFP theory fails to predict the VmE values for systems with s-shaped VmE versus x1 graph, the VmE values calculated by graph theory compare reasonably well with the corresponding experimental values. This graph theory analysis has further yielded information about the state of aggregation of pure components as well as of the mixtures.

Design and analysis of multi-stage expander processes for liquefying natural gas

Multi-stage expander refrigeration cycles were proposed and analyzed in order to develop an efficient natural gas liquefaction process. The proposed dual and cascade expander processes have high efficiency and the potential for larger liquefaction capacity and are suitable for small-scale and offshore natural gas liquefaction systems. While refrigeration cycles of conventional expander processes use pure nitrogen or methane as a refrigerant, the proposed refrigeration cycles use one or more mixtures as refrigerants. Since mixed refrigerants are used, the efficiency of the proposed multi-stage expander processes becomes higher than that of conventional expander processes. However, the proposed liquefaction processes are different from the single mixed refrigerant (SMR) and dual mixed refrigerant (DMR) processes. The proposed processes use mixed refrigerants as a form of gas, while the SMR and DMR processes use mixed refrigerants as a form of gas, liquid- or two-phase flow. Thus, expanders can be employed instead of Joule-Thomson (J-T) valves for refrigerant expansion. Expanders generate useful work, which is supplied to the compressor, while the high-pressure refrigerant is expanded in expanders to reduce its temperature. Various expander refrigeration cycles are presented to confirm their feasibility and estimate the performance of the proposed process. The specific work, composite curves and exergy analysis data are investigated to evaluate the performance of the proposed processes. A lower specific work was achieved to 1,590 kJ/kg in the dual expander process, and 1,460 kJ/kg in the cascade expander process. In addition, the results of exergy analysis revealed that cycle compressors with associated after-coolers and companders are main contributors to total exergy losses in proposed expander processes.

Optimization of Pure-Refrigerant Cycle Compressing Ratio on C3-MR Process

Abstract The natural gas liquefaction process is an energy intensive process due to its low temperature. Compressor units are one of primary factors in minimizing energy consumption of natural gas liquefaction process. Among various natural gas liquefaction processes, C3-MR (Propane Pre-cooled Mixed-Refrigerant) process is the most commonly used in LNG market. C3-MR process uses two types of refrigerants such as mixed-refrigerant and pure-refrigerant. In this study, pure-refrigerant cycle is simulated, along with different compressing ratios and different pressure levels. The simulation of case studies shows that energy consumptions mainly depend on both compressing ratios and pressure levels.. This study has achieved the energy consumption savings by 27.7% through different case studies with an emphasis on compressing ratios and pressure levels.

Data on conceptual design of cryogenic energy storage system combined with liquefied natural gas regasification process

This paper describes data of an integrated process, cryogenic energy storage system combined with liquefied natural gas (LNG) regasification process. The data in this paper is associated with the article entitled “Conceptual Design and Exergy Analysis of Combined Cryogenic Energy Storage and LNG Regasification Processes: Cold and Power Integration” (Lee et al., 2017) [1]. The data includes the sensitivity case study dataset of the air flow rate and the heat exchanging feasibility data by composite curves. The data is expected to be helpful to the cryogenic energy process development.

Flow diagram of waste double base propellant treatment including fluidized bed reactor

Abstract Dealing with explosive wastes appropriately is a difficult problem recently. Many of them are just being buried and some of them are being treated. The main method to treat explosive wastes is to burn it with Rotary-kiln reactor. However this has a risk of explosion during the process because it is based on explosion mechanism. In addition, Rotary-kiln method can not deal with enough amount of explosive waste because Rotary-kiln method use batch reactor. Lastly, because of the limit of non-successive process, the efficiency of the purification process is low which results in an incomplete combustion. This incomplete combustion makes the exhaust gas more dirty which contains more harmful substances. To overcome the limits of Rotary-kiln method which are introduced above, development of combustion-based process is necessary. Therefore, a flow diagram which includes fluidized bed reactor was developed with Aspen Plus. A mixture of explosive waste slurry and water with the same ratio was fed in the fluidized bed reactor. Also, additional units were chosen and designed which clean exhaust gas to make the reactor more adaptable. The proposed process was thermodynamically analyzed and the efficiency evaluation was held. Also, the improvement possibility of the process was derived. The final exhaust gas from this process satisfied the environment regulation of Korea. This process can deal with 3000 ton/yr which is the total amount of waste propellant in Korea, while the exhaust gas fits the regulation of CO 25ppm/hr, NO 2 0.10ppm/hr. This study is expected to contribute to the improvement of the efficiency of the explosive waste treatment process and the possession of domestic technology in Korea.

Application of Cryogenic Energy Storage to Liquefied Natural Gas Regasification Power Plant

Abstract A liquefied natural gas (LNG) must be regasified prior to use, and seawater is generally used as heat source. To meet natural gas demand, LNG is continually gasified and its cold energy is highly wasted. This research focuses on the applying LNG cold energy to cryogenic energy storage (CES) system. Moreover, an alternative use of LNG cold energy is proposed with an integration of CES system and LNG regasification power plant; called LNG regasification power plant integrated with cryogenic energy storage (LPCES) system. In the CES unit of proposed LPCES system, entire power consumption and generation are optimized to enhance its storage efficiency. Optimization model is developed mainly focused on compressors and turbines of CES unit. Additionally, a thermodynamic analysis is carried out to explain its cryogenic behavior. Furthermore, an hourly electricity demand and generation in Ontario are applied to evaluate the effect of LPCES system. As a result, a case of applied LPCES system indicated 21.4% minimum reserve margin, which represents electricity reserve over the capacity, compare to 17.7% of the base case. In addition, the result shows a round trip efficiency corresponding to 95.2% for the proposed LPCES system, which is a significantly improved value than efficiencies of developed bulk power management systems. In conclusion, we proposed a novel concept of energy storage system which has a substantial efficiency by LNG cold energy utilization.

Web-based multi-dimensional education system for the simulated moving bed process

This paper describes the development of an operator-education program for a simulated moving bed (SMB) pilot plant that separates para-xylene isomer from mixed xylenes. The education program was motivated from reliable and safe operations for a newly developed SMB technology, in particular, a priori education on preventing accidents such as explosion, fire and toxic material release, most of which result from the lack of understanding of the processes being operated. This SMB process education program has overall SMB process description, sixteen operating screen and response procedure for accident of leak and explosion. The proposed system was implemented based on client/server architecture in company-wise LAN environment and applied previously operator heuristics. In addition, it features multi-dimensional animation for virtual reality of process flow, using multi-media techniques. Operators are expected to benefit from education that is free of time and space constraints. The education system for the pilot plant will contribute to keeping the full scale SMB operation workforce performing at a high level of proficiency as well as refreshing the operational skills of senior operators.

Current status of optimal design of natural gas liquefaction process

Abstract Natural gas liquefaction process is an energy intensive process due to its cryogenic condition. Therefore, one of the major objectives for the design and the optimization is the minimizing total energy consumption. Another important objective is the minimizing cost of the energy supply system. This research focused on the cost based optimization. First, the energy minimization for the mixed and the pure refrigerant systems was performed by deterministic optimization model. Then, the cost minimization for energy supply to the process was performed by the driver selection model. The driver selection model was built as mixed integer linear programming (MILP). As the result, 15 to 17% of energy saving was checked for the refrigerant system. At that time, optimal driver set which is the minimum cost for the energy supply system was found.