• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.6_2
• /
• pp.1007-1014
• /
• 2020

IMO(International Maritime Organization) continues to strengthen environmental regulations on exhaust gases such as CO2, NOx, SOx. As for sulfur oxides, from 1 January 2020, all ships on international voyages must use fuel with a sulfur content of 0.5% or less. Or, it is obligatory to use an exhaust gas treatment device that has the same effect. Shipping companies are using low-sulfur oil, replacing them with LNG fuel, or installing scrubbers that suppress sulfur oxide emissions. In the case of ships using bunker C oil, the load on the engine is lower when entering and departing, so the exhaust gas pressure is lowered and the scrubber cannot be properly utilized. Therefore, diesel oil with low sulfur content is used when entering and leaving the coast. When diesel oil is used, exhaust gas is directly discharged through the control system and piping system, and when bunker C oil is used, sulfur oxides are reduced by scrubbers through other control systems and piping systems to discharge exhaust gas. Accordingly, a company has developed a system called a three-way damper valve that can control exhaust gas emissions while integrating these two control systems and piping systems into one. In this study, the control characteristics of the integrated exhaust gas control system and structural safety against external loads in a high-temperature exhaust gas environment were reviewed.

• Nuclear Engineering and Technology
• /
• v.52 no.10
• /
• pp.2230-2237
• /
• 2020

Self-priming venturi scrubber is one of the most effective devices used to collect aerosols and soluble gas pollutants from gaseous stream during severe accident in a nuclear power plant. The present study focuses on investigation of dust particle removal efficiency of the venturi scrubber both experimentally and theoretically. Venturi scrubber captures the dust particles in tiny water droplets flowing into it. Inertial impaction is the main mechanism of particles collection in venturi scrubber. The water injected into venturi throat is in the form of jets through multiple holes present at venturi throat. In this study, aerosols removal efficiency of self-priming venturi scrubber was experimentally measured for different operating conditions. Alumina (Al₂O₃) particles with 0.4-㎛ diameter and 3950 kg/㎥ density were treated as aerosols. Removal efficiency was calculated for different gas flow rates i.e. 3-6 ㎥/h and liquid flow rates i.e. 0.009-0.025 ㎥/h. Experimental results depict that aerosols removal efficiency increases with the increase in throat velocity and liquid head. While at lower air flow rate of 3 ㎥/h, removal efficiency decreases with the increase in liquid head. A theoretical model of venturi scrubber was also employed and experimental results were compared with mathematical model. Experimental results are found to be in good agreement with theoretical results.

• Journal of Korean Society for Atmospheric Environment
• /
• v.26 no.3
• /
• pp.339-345
• /
• 2010

There have been a number of efforts to satisfy national emission regulations and reduce the amount of emitted air pollutants. There are several air pollution control devices, however, only wet scrubber is efficiently used to remove particulate matters and gaseous pollutants, even if it has minimum collection efficiency in the particle size range of $0.1{\sim}1{\mu}m$. This study aimed to improve the collection efficiency of a spray tower type scrubber by introducing an electrospray system with two-flow nozzle. We found that the collection efficiency of a spray tower type scrubber was similar to that of a conventional wet scrubber. However, installation of an electrospray system in the scrubber resulted in drastic further improvement of collection efficiency comparing to that of a conventional scrubber, which is 26%, 35.2%, and 45.1% at the liquid to gas ratio of 0.26 $L/m^3$ and 19.9%, 35.1%, and 42.5% at 0.34 $L/m^3$ for the applied voltage of -30 kV, -35 kV, and -40 kV, respectively. Therefore, we found that the introduction of an electrospray system is very effective to improve the collection efficiency of a spray tower type scrubber.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.1
• /
• pp.159-166
• /
• 2014

In recent years, researchers have put a considerable effort to decrease the emission of harmful gaseous pollutants to the atmosphere. In order to remove simultaneously $SO_2$ and $NO_X$ from the flue gas of small and medium-sized ship, we designed minimal wet scrubber inside a compact multistage modular system. In this study we proceed experiment of elemental technology at each stage of the scrubber. The each stage is oxidation of NO which is the main component of $NO_X$, and removal of $SO_2$, respectively. $NaClO_2$ was used to oxidize NO gas, and NaOH was used to remove $SO_2$ gas. The maximum NO conversion efficiency and the $SO_2$ removal efficiency are both indicate 100%.

• Journal of ILASS-Korea
• /
• v.24 no.1
• /
• pp.8-14
• /
• 2019

The purpose of this study is to develop a packing-free wet scrubber to prolong the maintenance interval compared with the conventional packed bed wet scrubbers with which frequent operation stops are unavoidable to clean the packing materials. The main- and interaction-effects were quantitatively analyzed by regression analysis for the measured ammonia scrubbing data from the experiments prepared by experimental design. The scrubbing efficiency of the newly developed wet scrubber was found to be over 95% under the condition of flue gas flow rate of 90CMM and liquid-to-gas ratio $2l/m^3$ for all considered trials of experimental design. The interaction effect between the inlet duct spray and the filter was found to be important, which controls the droplet growth due to the droplet collisions between the duct- and scrubbing tower-spray. The presented methodology to analyze the impacts of operational and design factors on the scrubber efficiency showed potential for applications to optimize the future flue gas abatement process in semiconductor plants.

• Journal of the Korean Society of Safety
• /
• v.35 no.6
• /
• pp.85-92
• /
• 2020

Wet Scrubber reacts the incoming pollutant gas with cleaning water (water + absorbent) to absorb pollutants and release the clean air to the atmosphere. Wet scrubbers and packed tower scrubbers using this principle are widely used in businesses that emit acid gases. In particular, in the etching process using hydrochloric acid (HCl), alkaline washing water (NaOH) having a pH of about 8 to 11 is used to absorb a large amount of acid gas. However, These salts are attached to the injection nozzle (nozzle), filling material (packing), and the demister (Demister), causing air pollution, human damage, and inoperability due to clogging and acid gas discharge. Therefore, In this study, an improvement plan was proposed to manage the washing water with pH 3~4 acidic washing water. The test method takes samples from the Wet Scrubber flue measurement laboratory twice a month for 1 year. Hydrogen chloride (HCl) concentration (ppm) was measured, and nozzle clogging and scale conditions were measured, compared, and analyzed through a differential pressure gauge and a pressure gauge. As a result of the check, it was visually confirmed that the scale was reduced to 50% or less in the spray nozzle, filler, and demister. In addition, the emission limit of hydrogen chloride in accordance with the Enforcement Regulation of the Air Quality Conservation Act [Annex 8] met 3 ppm or less. Therefore, even if the washing water is operated in an acidic pH range of 3 to 4, it is expected to reduce air pollution and human damage due to clogging of internal parts, and it is expected to reduce maintenance costs such as regular cleaning or replacement of parts.

• Asian Journal of Atmospheric Environment
• /
• v.8 no.2
• /
• pp.89-95
• /
• 2014

There have been a lot of efforts to keep permissible emission standards and to reduce the amount of emitted air pollutants. There are several air pollution control equipments, however, wet scrubber is used to remove particulate matters and gaseous pollutants simultaneously, even if it has low collection efficiency in the particle size less than $5.0{\mu}m$. To overcome this problem, we introduced a spray tower scrubber with an electrospray system which a high voltage was indirectly applied. We found that collection efficiency of fine particles in the electrospray system was improved by increasing electrical field strength and the ratio of liquid-gas flow rate (from 41% to 84% for $0.3{\mu}m$ particles). In addition, a number of small droplets generated from an electrospray system led high collection efficiency, resulting from electrostatic attraction between droplets and particles and higher collision frequency. Therefore, we can conclude that the introduction of an electrospray system is quite effective to increase the particle removal efficiency of a spray tower scrubber.

• Nuclear Engineering and Technology
• /
• v.55 no.1
• /
• pp.169-179
• /
• 2023

Filtered containment system is a passive safety system that controls the over-pressurization of containment in case of a design-based accidents by venting high pressure gaseous mixture, consisting of air, steam and radioactive particulate and gases like iodine, via a scrubbing system. An indigenous lab scale facility was developed for research on iodine removal by venturi scrubber by simulating the accidental scenario. A mixture of 0.2 % sodium thiosulphate and 0.5 % sodium hydroxide, was used in scrubbing column. A modified mathematical model was presented for iodine removal in venturi scrubber. Improvement in model was made by addition of important parameters like jet penetration length, bubble rise velocity and gas holdup which were not considered previously. Experiments were performed by varying hydrodynamic parameters like liquid level height and gas flow rates to see their effect on removal efficiency of iodine. Gas holdup was also measured for various liquid level heights and gas flowrates. Removal efficiency increased with increase in liquid level height and gas flowrate up to an optimum point beyond that efficiency was decreased. Experimental results of removal efficiency were compared with the predicted results, and they were found to be in good agreement. Maximum removal efficiency of 99.8% was obtained.

• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.2
• /
• pp.57-62
• /
• 2000

The effect of exhaust gas recirculation(EGR) on the characteristics of exhaust gas emissions, and SFC are experimentally investigated by four-cylinder, four-cycle and direct injection marine diesel engine. In order to reduce the soot contents in the recirculated exhaust gas to intake system of the engines, a soot removal system of a cylinderical-type scrubber is specially designed and manufactured for the experimental system. (1) SFC is increased in downward convex curve style with increasing excess air ratio, it is increased with increasing EGR rate at the same excess air ratio. (2) NOx emission is reduced in downward convex curve style with increasing excess air ratio, it is reduced with increasing EGR rate at the same excess air ratio. (3) Soot emission is decreased in downward convex curve style with increasing excess air ratio, it is reduced with increasing EGR rate at the same excess air ratio. (4) CO emission is increased in nearly straight line style with increasing excess air ratio, it is increased with increasing EGR rate at the same excess air ratio. (5) HC emission is not constant tendency with increasing excess air ratio, it is increased with increasing EGR rate at the same excess air ratio.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.3
• /
• pp.262-268
• /
• 2020

The IMO (International Maritime Organization) has mandated the restriction of SOx emissions to 0.5 % for all international sailing vessels since January 2020. And, a number of countries have designated emission control areas for stricter environmental regulations. Three representative methods have been suggested to cope with these regulations; using low-sulphur oil, installing a scrubber, or using LNG (Liquefied Natural Gas) as fuel. In this paper, economic analysis was performed by comparing the method of installing a scrubber with the method of using low-sulphur oil without installing additional equipment. We suggested plausible layouts and compared the pros and cons of dif erent scrubber types for retrofitting. We selected an international sailing ship as the target vessel and estimated payback time and benefits based on navigation route, fuel consumption, and installation and operation costs. Two case of oil prices were analyzed considering the uncertainty of fuel oil price fluctuation. We found that the expected payback time of investment varies from 1 year to 3.5 years depending on the operation ratio of emission control areas and the fuel oil price change.