• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.981-987
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• 2011

Biologically treated water contains a large quantity of organic matters and microorganisms which can cause various problems to membrane. The membrane fouling occurred by these reasons is hard to control by single physical cleaning. This study analyzes the efficiency of aeration with chemical backwashing and foulants removal during chemical backwashing. The cleaning efficiency improves when the chemical concentration is high and the contact time of chemical is long. Chemical backwashing with aeration shows exceptional cleaning efficiency which leads the physical cleaning is required during chemical backwashing since it forms flow inside the membrane submerged tank. From the foulants removal analysis, the particles such as turbidity and TOC removal rate increase when the aeration is applied. Dissolved matter of DOC and UV254 removal is dependent on higher chemical concentration. According to FTIR analysis, one of major foulants, the polysaccharide is controlled by the chemical backwashing with aeration condition.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.10
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• pp.710-715
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• 1999

The purpose of this work is to develop a high-efficiency air cleaning system for air pollutants such as particulate and gaseous state in indoor environments. In order to enhance a removal efficiency of gaseous state pollutants, we suggested that pulsed discharge plasma be combined with $TiO_2$ photocatalyst (photocatalytic plasma air cleaning unit). We investigated experimentally the basic characteristics of photocatalytic plasma air cleaning unit and measured air pollutants removal efficiency. The wavelength of light radiated from pulsed discharge plasma under the atmospheric condition was 310~380nm. Its energy is enough to excite the $TiO_2$ photocatalyst and it makes a photochemical reaction in the surface of $TiO_2$ photocatalyst. The removal quantity of trimethylamine$((CH_3)_3N)\; was\; 130mg/m^34 which is twice quantity of pulsed discharge plasma without $TiO_2$ phtocatalyst unit. From the result of gas analysis using FT-IR, nitric oxide was not detected and trimethylamine was decomposed to $H_2O\; and \;CO_2$. And trimethylamine removal efficiency was 95%. These experimental results indicate that photocatalytic plasma air cleaning unit is a potential method in removing the pollutants.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1016-1022
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• 2010

An Experimental study of cleaning solution has been performed on a high capacity steam boiler burning heavy fuel oil to on-line cleaning of deposit. The deposit is mixture of soot, slag, ash, metal oxide and clinker. The traditional technology of deposit cleaning was carried hand-crafted. The conventional technology of boiler cleaning method is mechanical removal by the worker while the boiler shut down operation. In this experiment, the deposit of mixture of soot, slag, ash, metal oxide and clinker has been removed by the cleaning agents without shut down of boiler burning. This study found out the optimum cleaning solution composition. The best results have been obtained when the mixture of ammonium nitrate and $MgNO_3$ were used in cleaning solution. The various transition metal effect was investigated for optimum mixing condition. In this research, the metal compound additive of the clean solution compoition was obtained. The combustion efficiency was improved by on-line cleaning with derived clean solution compoition. On-line cleaning method prevents the fouling and corrosion in the boiler and heat exchanger.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.2
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• pp.169-175
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• 2017

This study applied microbubbles to reduce membrane fouling in wastewater reuse membrane processes, evaluated and compared the transmembrane pressure with or without the application of microbubbles and the cleaning efficiency with the application of aeration and microbubbles. In addition, this study analyzed foulants removed from the membrane surface. Changes in the transmembrane pressure of membranes with the presence or absence of microbubbles were observed. As a result, transmembrane pressure (TMP) increasing rate decreased twofold when applying microbubbles to realize stable operations. This study compared and evaluated cleaning efficiency applying aeration and microbubbles. As a result, the cleaning efficiency was 5% higher on average when applying microbubbles. In turbidity and total organic carbon (TOC), foulants were discharged when applying microbubbles twice as much as applying aeration. It is thought that particulate foulants precipitated on the membrane surface were more likely to desorb because the adhesion between the membrane surface and particle was weakened by microbubbles. Therefore, it is considered possible to effectively control membrane fouling because of the increase in cleaning efficiency when applying microbubbles to wastewater reuse membrane processes.

• Journal of ILASS-Korea
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• v.12 no.4
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• pp.185-190
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• 2007

There is a growing interest to develop a new cleaning technology to overcome the disadvantages of wet cleaning technologies such as environmental pollution and the cleaning difficulty of contaminants on integrated circuits. Laser cleaning is a potential technology to remove various pollutants on a wafer surface. However, there is no fundamental data about cleaning efficiencies and cleaning mechanisms of contaminants on a wafer surface using a laser cleaning technology. Therefore, the cleaning characteristics of a wafer surface using an excimer laser were investigated in this study. Fingerprint consisting of inorganic and organic materials was chosen as a representative of pollutants and the effectiveness of a laser irradiation on a wafer cleaning has been investigated qualitatively and quantitatively. The results have shown that cleaning degree is proportional to the laser irradiation time and repetition rate, and quantitative analysis conducted by an image processing method also have shown the same trend. Furthermore, the cleaning efficiency of a wafer contaminated by fingerprint strongly depended on a photothermal cleaning mechanism and the species were removed in order of hydrophilic and hydrophobic contaminants by laser irradiation.

• Membrane and Water Treatment
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• v.8 no.2
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• pp.149-160
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• 2017

This study investigated effects of NaOH cleaning on the intrinsic permeability of polyvinylidene fluoride (PVDF) membranes and flux recoveries and membrane resistances under various conditions encountered during ultrafiltration in water treatment plants. The NaOH cleaning using 10,000 mg/L NaOH led to discoloration of PVDF membranes and had little effect on water flux. The NaOH cleaning was efficient in removing the fouling layer caused by humic water. However, long filtration induced a fouling layer that was not removed easily by NaOH cleaning. The lower temperature during filtration yielded rapid increases in transmembrane pressure and decreases in NaOH cleaning efficiency. The alkaline cleaning of PVDF changed the membrane properties such as the hydrophobicity and morphology. Foulant properties, operational conditions such as temperature, and chemical agents should be considered for cleaning strategies for PVDF applied in water treatment.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.401-404
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• 2010

A spray-type cleaning agent in utilizing dust-remover on PCB was chosen to study. In cleaning of electronic and semiconductor equipment, a substrate(IPC-A-36) was used to test the jet forces of the agent. And according to the jet forces time of the cleaning agent, the corresponding moving distances were compared with the spray times, and for the pollutants of iron powder and dust, the cleaning efficiency was tested with the IPC-A-36 by a weight method. The moving distance increased with the spray cleaning time longer. For a spray cleaning time of 3sec, the cleaning efficiency decreased with the amount of dust and the iron powder. It was also observed that the dust was remarkably removed, compared to the iron powder.

• Journal of Biosystems Engineering
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• v.33 no.4
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• pp.230-238
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• 2008

Mechanization such as machine harvesting, precleaning, drying and cleaning for rapeseed harvested with high moisture content should be accomplished for biodiesel production. In addition, machine drying and cleaning is inevitable in the mechanization of work, just because rice should be transplanted right after harvesting rapeseed in Korea. Particularly, early harvested rapeseed with the combine have high moisture content and undesirable materials such as stalks and stones which make drying-process difficult and lower the efficiency of drying. Therefore, this study was conducted to develop precleaner and cleaner which could remove foreign substances from harvested rapeseeds. The precleaner consists of throw-in hopper, conveyor, feeding hopper, two precleaning sieves and discharging sections. Precleaning capacity was 1,505 kg/hr in shaking frequency of 370 cpm (cycles per minute) and tilt angles of between $5^{\circ}$ and $7^{\circ}$. The efficiency of precleaning was between 90.9% and 91.5%. The cleaner consists of feeding, shaking, blowing, cleaning and discharging sections. Cleaning performance was 435.4kg/hr in the number of rocking motions of 475 cpm and tilt angle of $10^{\circ}$. The ratios of cleaning, foreign substances and loss were 96.5%, 3.5% and 0.2%, respectively.

• Clean Technology
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• v.16 no.3
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• pp.162-171
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• 2010

The objective of this study is to develop cleaning agents for the indoor water supply pipe which is environmentally friendly and suitable for removing scale by using various organic acids, inorganic acids, and some additives. Among various organic acids, oxalic acid, citric acid, and malic acid showed good cleaning efficiency of iron oxides which were main components of the indoor water supply pipe scale. Several cleaning agents were formulated by adding chemical additives into these organic acids and evaluated for removal of iron oxides. In this study, it was found that nonionic surfactants were excellent for the removal of iron oxide scale among various additives. Two types of cleaning agents($F_1$, $F_2$) with comparatively high solvent power for iron oxides were formulated in this study. The cleaning agents $F_1$ made by organic acids and some additives were formulated to be safe and environmentally friendly, but seemed to have disadvantage due to their comparatively low cleaning efficiency of iron oxide than $F_2$. But, the cleaning agents $F_2$ prepared by adding inorganic acid a little to $F_1$ showed comparatively good cleaning efficiency of iron oxide and could be recommended for removing hard scale of iron oxides in the indoor water supply pipe. Thus, it is considered that the formulated cleaning agents should be selected based on the extent of scale in the indoor water supply pipe.

• Journal of the Korean institute of surface engineering
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• v.28 no.1
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• pp.23-33
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• 1995

AISI 304 stainless steel has high resistance to corrosion due to the presence of a self-healing chromium oxide film on the surface, which also accounts for the difficulty in plating. Surface cleaning of this alloy is of fundamental importance in gold plating since its effectiveness puts an upper limit on the quality of the final coating. The cleaning of AISI 304 stainless steel was investigated with elimination of artificial passive oxide film and degreasing of remaining buffing wax as stearic acid. The familiar cleaning methods i.e. ultrasonic cleaning, electro-cleaning and activation treatment were fabricated in this study. Activation treatment showed best cleaning efficiency for elimination of passive oxide film among these methods, which was also confirmed by AES (Auger electron spectrometer) analysis. However, the best condition of cleaning was obtained by combining these methods. Electrocleaning time, for degreasing the stearic acid layer, was decreased with increasing amount of added KCN.