• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.68-78
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• 2006

In the past few years, considerable efforts have been directed towards the further development of Urea-SCR(selective catalytic reduction) technique for diesel-driven vehicle. Although urea possesses considerable advantages over Ammonia$(NH_3)$ in terms of toxicity and handling, its necessary decomposition into Ammonia and carbon dioxide complicates the DeNOx process. Moreover, a mobile SCR system has only a short distance between engine exhaust and the catalyst entrance. Hence, this leads to not enough residence times of urea, and therefore evaporation and thermolysis cannot be completed at the catalyst entrance. This may cause high secondary emissions of Ammonia and isocyanic acid from the reducing agent and also leads to the fact that a considerable section of the catalyst may be misused for the purely thermal steps of water evaporation and thermolysis of urea. Hence the key factor to implementation of SCR technology on automobile is fast thermolysis, good mixing of Ammonia and gas, and reducing Ammonia slip. In this context, this study performs three-dimensional numerical simulation of urea injection of heavy-duty diesel engine under various injection pressure, injector locations and number of injector hole. This study employs Eulerian-Lagrangian approach to consider break-up, evaporation and heat and mass-transfer between droplet and exhaust gas with considering thermolysis and the turbulence dispersion effect of droplet. The SCR-monolith brick has been treated as porous medium. The effect of location and number of hole of urea injector on the uniformity of Ammonia concentration distribution and the amount of water at the entrance of SCR-monolith has been examined in detail under various injection pressures. The present results show useful guidelines for the optimum design of urea injector for reducing Ammonia slip and improving DeNOx performance.

• Journal of Aquaculture
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• v.13 no.2
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• pp.137-145
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• 2000

Capacity of water treatment of the three phase fluidized bed reactor as a biofilter in the seawater recirculating system was evaluated. The water treatment system consists of fluidized bed reactor for ammonia removal, cartridge filter for solid removal and ozone contactor for disinfection. Mean concentration of water quality parameters: COD, TAN, $NO_2$-N, $NO_3$-N, SS and alkalinity were 9.0, 0.22, 0.05, 20.0, 9.5 and 70.0 mg/l, respectively; the relevant values were 7.6 for pH and 3.64 NTU for turbidity. These indicate the maintenance of good water quality by the treatment system. The influent TAN loading rate in to the fluidized bed reactor ranged from 4.3 to 32.9 g/$m^3$/day, and averaged to 20 g/$m^3$/day. TAN removal efficiency of each phase of the fluidized bed reactor was 47-60%, indicating the effective ammonia removal. During operation the effluent of fluidized bed reactors also maintained the unionized ammonia nitrogen level below 0.002 mg/l.

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.2032-2038
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• 2009

The amount of phenol and NaOH for the colorimetric determination of ammonia in Korean standard methods (KSM) is found to be highly excessive compared to the standard methods of several other countries. The absorbance of indophenol formed by the Berthelot reaction for ammonia analysis was measured under the various reaction conditions classified in experiment groups 1, 2, 3, 4 and KSM and American standards methods (ASM), and the relationships between the absorbance of indophenol and concentration of ammonia were compared. The amount of phenol can be reduced to 10 g (current 25 g in KSM) and NaOH can be reduced to 1.76 g (current 11 g in KSM) for the preparation of 200 mL phenate solution, and the absorbance sensitivity increased. The concentration of the phenol and NaOH correlatively affect the pH of the solution, which is a critical variable in achieving the maximum sensitivity and rapid and stable color development.

• Journal of environmental and Sanitary engineering
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• v.19 no.1
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• pp.1-7
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• 2004

This study was conducted to supply basic informations on development of water treatment process for the ozonation of ammonia depend on pH variation with or without bromide catalysis. The results were as follows: The oxidation rate of ammonia increased depend on pH increase at ozone/bromide process. It was found that overall kinetics was zero order with respect to reaction time and reaction velocity constant of zero order increased depend on pH increase from 4.9 to 9.5 and the equation of linearization was $k_{o}$ = 0.00565 ${\times}$ [pH] + 0.0069 at ozone/bromide process. The denitrification reaction of ammonia was superior as the pH increase in the presence of bromide.

• Journal of Marine Bioscience and Biotechnology
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• v.4 no.1
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• pp.1-5
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• 2010

With the world's population increase, demands of fish production increased rapidly. Because of the demand increase, methods of aquaculture also become more intense. With the increasing intensity of aquaculture, more metabolites in the system are accumulated. The metabolites accumulated in the system turn to the causatives of water quality deterioration and become limiting factors for fish growth. Due to the toxicity of ammonia, ammonia removal is needed in aquaculture system. Biofilters, often referred as biological filter or nitrification filter are commonly used in recirculating aquaculture system to remove ammonia and convert it to nitrite, and then to nitrate.

• YAKHAK HOEJI
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• v.19 no.2
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• pp.96-100
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• 1975

2-Ethoxy-4-acetamidobenzoate (III) was synthesized by ethylation of N-formyl compound obtained with formylation of methyl 4-aminosalicylate and 2-ethoxy-4-acetamidobenzamide (VIII) was synthesized by ethylation of 4-acetamidosalicylamide (VII) formed by reacting methyl 4-acetamido-2-acetoxy benzoate with concentrated ammonia water under pressure. 2-Ethoxy-4-acetamido benzamide (VIII) was also synthesized by acetylation of 2-ethoxy-4-aminobenzamide (VI) obtained by pressure eraction of methyl 2-ethoxy-4-formylamido-benzoate (I) with concentrated ammonia water.

• Resources Recycling
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• v.12 no.3
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• pp.31-37
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• 2003

A study on the characteristics of ammonia desorption from aqueous solutions has been performed by air stripping as the first stage of ammonia recycling for the preparation of ammonium sulfate from it. For air stripping experiments, a stripping column made with acrylic tube of 40 mm diameter was employed and compressed air was injected into solutions through air sparger equipped at the bottom of stripping column. As a result of experiments, the stripping efficiency was increased with the aqueous pH and it was found that the appropriate pH for air stripping of ammonia was between pH 10 and 12. As far as the effect of air flow rate on ammonia stripping was concerned, ammonia stripping was not proportional to the air flow rate although it was affected by the air flow rate to some extent. Moreover, when more than 20 cm of water height was maintained, total ammonia desorbed from solution was not varied with the water height. Stripping temperature was also found to play an important role in ammonia desorption and about 90fo of initial ammonia was desorbed in 14 hours at pH 12.8 and at $60^{\circ}C$ Finally, it was believed that stripping temperature as well as the aqueous pH was one of the most important factors in air stripping of ammonia.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.6
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• pp.483-491
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• 2014

In this study, a thermodynamic analysis was carried out for a combined power generation system using a low-temperature heat source in the form of sensitive energy and liquefied natural gas cold energy. An ammonia-water mixture, which is a zeotropic mixture, was used as the working fluid, and systems with and without a regenerator were comparatively analyzed. The effects of the mass fraction of ammonia and the condensation temperature of the working fluid on the system variables, including the net work production, exergy destruction, and thermal and exergy efficiencies, are analyzed and discussed. The results show that the performance characteristics of the system varied sensitively with the ammonia concentration or condensation temperature of the working fluid. The system without regeneration was found to be better in relation to the net work per unit mass of the source fluid, whereas the system with regeneration was better in relation to the thermal or exergy efficiency.

• Journal of Microbiology and Biotechnology
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• v.22 no.9
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• pp.1193-1201
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• 2012

The analysis and quantification of ammonia-oxidizing bacteria (AOB) is crucial, as they initiate the biological removal of ammonia-nitrogen from sewage. Previous methods for analyzing the microbial community structure, which involve the plating of samples or culture media over agar plates, have been inadequate because many microorganisms found in a sewage plant are unculturable. In this study, to exclusively detect AOB, the analysis was carried out via denaturing gradient gel electrophoresis using a primer specific to the amoA gene, which is one of the functional genes known as ammonia monooxygenase. An AOB consortium (S1 sample) that could oxidize an unprecedented 100% of ammonia in 24 h was obtained from sewage sludge. In addition, real-time PCR was used to quantify the AOB. Results of the microbial community analysis in terms of carbon utilization ability of samples showed that the aeration tank water sample (S2), influent water sample (S3), and effluent water sample (S4) used all the 31 substrates considered, whereas the AOB consortium (S1) used only Tween 80, D-galacturonic acid, itaconic acid, D-malic acid, and $_L$-serine after 192 h. The largest concentration of AOB was detected in S1 ($7.6{\times}10^6copies/{\mu}l$), followed by S2 ($3.2{\times}10^6copies/{\mu}l$), S4 ($2.8{\times}10^6copies/{\mu}l$), and S3 ($2.4{\times}10^6copies/{\mu}l$).

• Journal of environmental and Sanitary engineering
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• v.18 no.1
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• pp.15-22
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• 2003

Treatability tests were conducted using EMC process to study the feasibility of applying this process as recycling-water treatment system in high density seawater aquaculture farm. To study the effect of organic and ammonia nitrogen loading on system performance, hydraulic retention time of reactor was reduced gradually from 12hr to 10min. The conclusions are can be summarized as follows. When the system HRT was reduced from 12hr to 10 min gradually, there was little noticeable change(reduction) in ammonia nitrogen removal efficiencies until 2hr of HRT, however, removal efficiencies were decreased dramatically when the system was operated under the HRT of less than 2hr. In case of organics(COD), there was no dramatic deterioration in removal efficiencies depending on HRT reduction. More than 90% of removal efficiencies were maintained successfully when the system was operated at the HRT of 10 min. In case of system performance depending on media packing ratio in reactor, there was little difference in each reactor performance depending on media packing ratio in reactor when the reactors were operated under the HRT of longer than 1hr, however, differences in reactor performances were considerably evident when the reactors were operated under the HRT of shorter than 1hr. That is, the more reactor was packed, the better reactor performed. When comparing reactor performance among 25%, 50%, 75% packed reactor, it can be judged that media packing ratio more than 50% plays no significant role in increasing reactor performance. For this reason, packing the media less than 50% is more reasonable way in view of economic. Such a tendency well agreed with the variation of ammonia-nitrogen removal efficiencies according to the media packing ratio in reactors at each HRT. Difference in effluent ammonia-nitrogen concentration between 50% media packing reactor and 75% media packing reactor was negligible. When comparing with the results of 25% packing reactor, difference was not so great.