• New & Renewable Energy
• /
• v.20 no.1
• /
• pp.135-144
• /
• 2024

The present study investigated waste medium from a domestic shiitake mushroom farm, which was pyrolyzed to produce biochar. The yield rate of the biochar was compared after exposure to various pyrolysis temperature conditions, and the characteristics of the produced biochar were analyzed. The present study focused on the carbon dioxide (CO₂) adsorption capacity of the resulting biochar. The CO₂ adsorption capacity exhibited a correlation with the pyrolysis temperature of the biochar, with increasing temperatures resulting in higher CO₂ adsorption capacities. Brunauer-Emmett-Teller (BET) analysis showed that the CO₂ adsorption capacity was related to the surface area and pore volume of the biochar. Calcium is added to the process of producing mushroom medium. Experiments were performed to investigate the CO₂ adsorption capacity of the biochar from the waste medium with the addition of calcium. In addition, CO₂ adsorption experiments were conducted after the pyrolysis of kenaf biochar with the addition of calcium. The results of these experiments show that calcium affected the CO₂ adsorption capacity.

• Korean Chemical Engineering Research
• /
• v.50 no.3
• /
• pp.505-510
• /
• 2012

The gas hold-up has a strong relationship with the size distribution and rising velocities of bubbles in a bubble column. Therefore, many previous researchers have studied on the hydrodynamics focusing on the bubble size variation in bubble column. In this study, the bubble behavior was influenced by partitioning porous plates installed at a certain height in a trayed bubble column. The gas hold-up was increased in non-sparging region (H/D > 5) as well as sparging region. We identified the effect of the partitioning porous plate using three trayed bubble columns with different reactor geometries. Furthermore, the bubble break-up frequency and size distribution were observed before and after individual bubbles penetrated through the plate. The arrangement of the plates was also investigated using a 0.15-m-in-diameter bubble column. Based on the result, we applied this design concept to a 0.36-m-in-diameter, 22 m tall trayed bubble column and identified the effect of the partitioning porous plate on the gas hold-up increase.

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.4
• /
• pp.395-403
• /
• 2020

In this paper, the performance characteristics of the impeller and volute in the 2 vane pump were investigated using response surface method (RSM) with commercial computation fluid dynamics (CFD) code. Design variables were defined with the impeller blade angle and volute area distribution. The objective functions were defined as the total head, total efficiency and solid material size of the 2 vane pump. The design optimization of the design variables was determined using the RSM. The numerical results for the reference and optimum models were compared and discussed in this work.

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.3
• /
• pp.293-301
• /
• 2020

This paper describes a numerical study on the improvement of performance of the 2 vane pump impellers. The design of these impellers was optimized using a commercial computation fluid dynamics code and design of experiments. Geometric design variables were defined by the impeller blade angle distribution. The objective functions were defined as the total head, total efficiency and solid material size of the impellers. The importance of the geometric design variables was analyzed using 2^k factorial designs. The interaction between the total head, total efficiency and solid material size, according to the impeller blade angle distribution, is discussed by analyzing the 2^k factorial design results.

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.5
• /
• pp.480-488
• /
• 2020

This study was conducted to improve the flow uniformity inside the chip tester through changing the flow path formation according to the inlet and outlet position of chamber. The internal flow and velocity distributions of the modified chamber models (Cases 1-3) were compared with the reference chamber model through three-dimensional Reynolds-averaged Navier-Stokes equations with k-ε turbulence model. The modified chamber models showed the superior flow uniformity characteristics compared to the reference chamber model. To investigate the flow uniformity in the chip tester, the standard deviation of the velocity was defined and compared. Through the internal flow analysis and assesment of the standard deviation, Case 2 among the test cases including the reference model showed the best flow uniformity generally.

• Carbon letters
• /
• v.3 no.4
• /
• pp.187-191
• /
• 2002

In the present research, we prepared the activated carbon (AC) sorbents to remove gas-phase mercury. The mercury adsorption of virgin AC, chemically treated AC and fly ash was performed. Sulfur impregnated and sulfuric acid impregnated ACs were used as the chemically treated ACs. A simulated flue gas was made of SOx, NOx and mercury vapor in nitrogen balance. A reduced mercury adsorption capacity was obtained with the simulated gas as compared with that containing only mercury vapor in nitrogen. With the simulated gas, the sulfuric acid treated AC showed the highest performance, but it might have the problem of corrosion due to the emission of sulfuric acid. It was also found that the high sulfur impregnated AC also released a portion of sulfur at $140^{\circ}C$. Thus, it was concluded that the low sulfur impregnated AC was suitable for the treatment of flue gas in terms of stability and efficiency.

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.5
• /
• pp.436-443
• /
• 2020

The performance prediction model of a solid oxide fuel cell stack has been developed using deep neural network technique, one of the machine learning methods. The machine learning has been received much interest in various fields, including energy system mo- deling. Using machine learning technique can save time and cost requried in developing an energy system model being compared to the conventional method, that is a combination of a mathematical modeling and an experimental validation. Results reveal that the mean average percent error, root mean square error, and coefficient of determination (R2) range 1.7515, 0.1342, 0.8597, repectively, in maximum. To improve the predictability of the model, the pre-processing is effective and interpolative machine learning and application is more accurate than the extrapolative cases.

• Journal of environmental and Sanitary engineering
• /
• v.10 no.3
• /
• pp.131-138
• /
• 1995

As the energy consumption increases continuously, the emission amount of air pollutants is growing, and after all it can influence the global environment as welt as the regional atmosphere. So, the clean energy which emits less air pollutants should be developed and widely used to reduce emission of pollutants. Electricity, known for clean energy in the side of consumption, is not actually clean in the process of generation. Electric power is generated using fossil fuels which produce acidic gases like $SO_{2}$, $NO_{x}$, etc. The emission rates of $SO_{2}$, $NO_{x}$, $CO_{2}$ are 2g,0.78g and 1 l0g per electric power generating Ikwh. If one light(60 watt bulb) be turned off at each house for a month electricity will be saved about 1.Skillion kwh a year. This is almost the same as 4,170 tons of $SO_{2}$ and $NO_{x}$. As a result the economization of electricity will be one of the effective strategy to reduce the air pollution and to keep our life clean and comfortable.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.5
• /
• pp.273-281
• /
• 2009

In recent semiconductor manufacturing clean rooms, the energy consumption of outdoor air conditioning systems represents about 45% of the total air conditioning load required to maintain a clean room environment. Meanwhile, there is a large amount of exhaust air from a clean room. From an energy conservation point of view, heat recovery from the exhaust air is therefore useful for reducing the outdoor air conditioning load for a clean room. In the present work, an energy-efficient outdoor air conditioning system was proposed to reduce the outdoor air conditioning load by utilizing an air washer to recover heat from the exhaust air. The proposed outdoor air conditioning system consisted mainly of a preheating coil, an air washer, two stage cooling coils, a reheating coil, a humidifier and two heat recovery cooling coils inserted into the air washer and connected to a wet scrubber. It was shown from the lab-scale experiment with outdoor air flow of $1,000\;m^3/h$ that the proposed system was more energy-efficient for the summer and winter operations than an outdoor air conditioning system with a simple air washer.

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.4
• /
• pp.387-394
• /
• 2020

A parametric study of a 2.5 kW class propeller type micro hydraulic turbine was performed. In order to analyze the internal flow characteristics in the hydraulic turbine, three dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used and the hexahedral grid system was used to construct computational domain. To secure the reliability of the numerical analysis, the grid dependency test was performed using the grid convergence index method based on the Richardson extrapolation, and the grid dependency was removed when about 1.7 million nodes were used. For the parametric study, the axial distance at shroud span (L) between the inlet guide vane and the runner, and the inlet and outlet blade angles (β₁, β₂) of the runner were selected as the geometric parameters. The inlet and outlet angles of the runner were defined in the 3 spans from the hub to tip, and a total of 7 geometric parameters were investigated. It was confirmed that the outlet angles of the runner had the most sensitive effect on the power and efficiency of the micro hydraulic turbine.