• Clean Technology
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• v.21 no.1
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• pp.45-52
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• 2015

We have introduced switching poles in the conventional electrolysis for the removal of ammonia in aquaculture wastewater to prevent the fouling on the electrode surface by the deposition of insoluble metallic compounds. We have also tried to locate the optimal period of switching poles considering the effect of the current loss during switching poles on the free chlorine generation. First, we have observed the decrease of free chlorine generation with the decrease of the period of switching poles due to the expected current loss, and this would lead to the decrease of ammonia removal efficiency. Meanwhile, the measurement of calcium and magnesium concentration in wastewater vs. the period of switching poles have demonstrated that a properly low level of fouling on the electrode surface could be retained with a period of switching poles of less than 60 sec by the decomposition of metallic compounds during switching poles. In a summary, we have optimized the period of switching poles to gain a high level of free chlorine generation and a high level of fouling prevention on the electrode at the same time.

• Journal of the Korean Chemical Society
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• v.26 no.2
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• pp.88-94
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• 1982

The concentrations of gaseous ammonia and particulate ammonium emitted from a urea plan were measured, and the conversion rate of ammonia to ammonium was estimated. The conversion of ammonia to ammonium has two stages with transport time in the atmosphere. In the initial 15min the conversion rate was 3.2% min$^{-1}$, and thereafter 0.26% min$^{-1}$. The high conversion rate of ammonia to ammonium at the initial period of it's transport might be due to the dissolution of ammonia into water droplets formed by the decrease in temperature of the stack effluent. The concentration of ammonium is further increased by the decomposition of urea in alkaline droplet formed. Half-lives of ammonia gas at initial and latter slag were 16 min and 192 min respectively. No correlation of particulate ammonium concentration to temperature, relative humidity, and concentrations of sulfur dioxide, nitrogen oxides and airborne particulate matter were found in this field measurement.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.177-182
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• 2015

The NOx emissions from diesel engines and industrial boilers are a major cause of environmental pollution. The selective catalytic reduction of urea is an aftertreatment technology that is widely used for the reduction of NOx emissions. The objective of this study was to investigate the characteristics of the thermal decomposition of a urea aqueous solution using laboratory-scale experimental equipment under conditions similar to those of marine diesel engines. A 40 wt. urea aqueous solution was used in this study. It was found that the total conversion rate varied with the inflow gas conditions and flow rates of the urea aqueous solution. In addition, there were conversion rate differences between NH3 and HNCO. At inflow gas temperature conditions of $210^{\circ}C$ and $250^{\circ}C$, the $NH_3$ conversion rate was found to be higher than that of the HNCO, depending on the residence time.

• Journal of the Korean Applied Science and Technology
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• v.35 no.1
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• pp.163-172
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• 2018

In this study, selective catalytic reductions (SCR) of NO commercial catalysts were used to investigate the effect of ammonia gasification from urea solution. The effects of catalytic chemical composition on the reaction temperature and space velocity were studied. $V_2O_5/TiO_2$ catalysts, which are widely used as SCR catalysts for removal of nitrogen oxides, have better ammonia formation compare to $TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalysts. The $TiO_2$ catalyst not supporting the active metal was not affected by the space velocity as compared with the catalyst supporting $V_2O_5$ or $WO_3-V_2O_5$. The active metal supported catalysts decreased in the ammonia formation as the space velocity increased.

• Korean Journal of Plant Tissue Culture
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• v.28 no.3
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• pp.165-171
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• 2001

New visible and fast assay system have been developed for tobacco transformant introduced with adenosine deaminase (ADA) marker gene, which converts cytotoxic adenosine analogues to non-toxic inosine analogues and ammonia. Ammonia was changed to blue color in the solution of phenol-nitoprusside and alkaline-hypochlorite. It was possible to detect activity of ADA visibly on the holes of 96 well plate using tiny explant of transgenic tobacco leaves within 1 hour incubation time. As substrates of ADA enzyme from transgenic plant on the plate, a number of adenosine analogues such as 9-D-arabinofuranosyl adenine, cordycepin, 2'-deoxyadenosine, adenosine and xylofuranosyl adenine were possible for detection of ADA activity. Optimal condition of substrate for ADA enzyme was each 10 mM and pH 7.5 in adenosine solution. Especially, transgenic plant did not convert adenosine to inosine and ammonia in the presence of ADA inhibitor deoxycoformycin, which means that ammonia produced from transgenic plant is due to expression of ADA gene. Now, we show that this detection system can be easily, sensitively, fast and cheaply as well as visibly assayed in vitro as GUS gene system with very small size of transformant explant.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.806-812
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• 2008

The ammonia decomposition reaction has been of increasing interest as a means of treating ammonia in flue gas in the presence of precious metal catalyst. Various catalysts, $Pt-Rh/Al_2O_3$, $Pt-Rh/TiO_2$, $Pt-Rh/ZrO_2$, $Pt-Pd/Al_2O_3$, $Pd-Rh/Al_2O_3$, $Pd-Rh/TiO_2$, $Pd-Rh/ZrO_2$, $Pt-Pd-Rh/Al_2O_3$, $Pd/Ga-Al_2O_3$, $Rh/Ga-Al_2O_3$, and Ru/Ga-$Al_2O_3$, were synthesized by using excess wet impregnation method. Using a homemade 1/4" reactor at $10,000{\sim}50,000hr^{-1}$ of space velocity in the presence of precious metal catalyst ammonia decomposition reactions were carried out to investigate the catalyst activity. The inlet ammonia concentration was maintained at 2,000 ppm, with an air balance. Both $T_{50}$ and $T_{90}$, defined as the temperatures where 50% and 90% of ammonia, respectively, are converted, decreased significantly when alumina-supported catalysts were applied. In terms of catalytic performance on the ammonia conversion in the presence of hydrogen sulfide, $Pt-Rh/Al_2O_3$ catalyst showed no effect on the poisoning caused by hydrogen sulfide. These results indicate that platinum-rhodium bimetallic catalyst is a useful catalyst for ammonia decomposition.

• Elastomers and Composites
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• v.34 no.4
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• pp.350-359
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• 1999

Conversion and oil-yield of a used automotive tire sample in supercritical decomposition and extraction for three solvents such as water, 28% ammoina solution and ammonia, were compared. Supercritical extraction with ammonia gave the highest conversion and oil-yield at the same temperature and pressure. In this paper, supercritical ammonia was used as major solvent and tetralin acting as hydrogen-donor, was used as cosolvent. As the amount of tetralin increased, oil-yield was Increased. When a tire sample was extracted by supercritical ammonia, oil-yield was 48.8% at $280^{\circ}C$, 22.3MPa. But when the weight ratio of tetralin to tire sample (weight of tetralin/weight of tire sample) was 5, oil-yield was 61.2% at $280^{\circ}C$ and 22.3 MPa. These phenomena indicate that as radicals produced in supercritical decomposition become stable, the polymerization and the second decomposition of products may be inhibited. Supercritical extraction of a tire sample swollen by tetralin gave high oil-yield although the amount of tetralin was a little.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.339-342
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• 2000

A three phase fluidized bed bioreactor including Thiobacillus sp.IW was used to remove hydrogen sulfide and ammonia simultaneously. In this study, hydrogen sulfide was oxidized to sulfate by the microorganism and ammonia was reacted with the sulfate to form ammonium sulfate. Removal efficiency of hydrogen sulfide was almost perfect up to 45 mg/l h of inlet loading rate, whereas that of ammonia was reduced as inlet loading rate increased from 10 mg/1 h.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.1013-1016
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• 2008

Nitrogen in the form of nitrate was electrochemically reduced with different cathode materials including Fe, Ni, Cu, and Zn. Zn cathode shows the greatest electrocatalytic activity on the transformation of nitrate ions into ammonia and the $NO_3^-$ removal efficiency has highest value at pH 8.5. Nitrogen in the form of nitrate was initially reduced into nitrite and sequentially, converted into nitrogen inside $NH_3$. Nitrogen in the form of ammonia was completely removed by the reaction with HOCl.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.10a
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• pp.201-202
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• 2000

순환여과식 양식은 어류를 효과적으로 대량 생산할 수 있는 반면 어류의 배설물과 미섭취 사료 등에 의해서 암모니아, 아질산 및 유기질 고형 성분 등이 발생하여 사육중인 어류에 나쁜 영향을 야기하게 된다. 배설물과 미섭취 사료는 대부분 유기성 고형물로 어류의 아가미에 끼여 질병을 유발시키며 미생물에 의해 분해되면서 어류에 유해한 암모니아나 아질산으로 전환되어 어류에 유해하다. 그러므로 미생물에 의해 분해되기 전에 신속하고 효과적으로 제거하여야 한다. (중략)