• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.352-359
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• 2005

This work has studied the changes of pH in both of anodic and cathodic chambers of a divided cell due to the electrolytic split of water during the ammonia decomposition to nitrogen, and has studied the continuous decomposition characteristics of ammonia in a multi-cell stacked electrolyzer. The electrolytic decomposition of ammonia was much affected by the change of pH of ammonia solution which was caused by the water split reactions. The water split reaction occurred at pH of less than 8 in the anodic chamber with producing proton ions, and occurred at pH of more than 11 in the cathodic chamber with producing hydroxyl ions. The pH of the anodic chamber using an anion exchange membrane was sustained to be higher than that using a cation exchange membrane, which resulted in the higher decomposition of ammonia in the anodic chamber. By using the electrolytic characteristics of the divided cell, a continuous electrolyzer with a self-pH adjustment function was newly devised, where a portion of the ammonia solution from a pHadjustment tank was circulated through the cathodic chambers of the electrolyzer. It enhanced the pH of the ammonia solution fed from the pH-adjustment tank into the anodic chambers of the electrolyzer, which caused a higher decomposition yield of ammonia. And then, based on the electrolyzer, a salt-free ammonia decomposition process was suggested. In that process, ammonia solution could be continuously decomposed into the environmentally-harmless nitrogen gas up to 83％, when chloride ion was added into the ammonia solution.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.287-291
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• 2009

The heterogeneous decomposition of ammonia on a quartz surface in an inverted, stagnation-point flow reactor was investigated using a measurement reactor and a numerical model of the reactor. In the experiments, 8 mole% of ammonia in nitrogen was used and the temperature of an electric heater was set in the range $300{\sim}900^{\circ}C$ to heat the quartz surface where the decomposition took place. Gas temperatures and ammonia concentrations in the reactor obtained using in situ Raman spectroscopy were analyzed with the numerical model and it was revealed that, depending on the heater temperature, the temperature of the quartz surface was estimated to be in the range $235{\sim}619^{\circ}C$ and the activation energy of the decomposition on the surface was in the range 10.9~15.8 kcal/mol.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2001.11a
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• pp.77-79
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• 2001

본 연구에서는 전기분해에 의한 양식장 배출수중의 유기물질 및 암모니아를 전류밀도, 전극간격에 따른 제거 특성을 살펴보았다. 전극간격 및 전류밀도에 따른 제거효율은 전극간격이 가까울수록, 전류밀도가 클수록 제거효율은 증가하였다 유기물질은 107.5A/$m^2$의 전류밀도에서 반응기 체류시간 8분동안 98.5%, 암모니아는 전류밀도를 107.15A/$m^2$로 유지하고, 간격을 변화시키면서 반응기 체류시간 120sec동안 암모니아의 제거율을 보면 92.6%의 제거효율을 나타내었다.

• Journal of Hydrogen and New Energy
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• v.34 no.6
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• pp.594-600
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• 2023

In this study, a process model and optimization design direction for a hydrogen production plant through ammonia decomposition are presented. If the reactor decomposition rate is designed to approach 100%, the amount of catalyst increases and the devices that make up the entire system also have a large design capacity. However, if the characteristics of the hydrogen regeneration process are reflected in the design of the reactor, it becomes possible to satisfy the total flow rate of fuel gas with the discharged tail gas flow rate. Analyzing the plant process simulation results, it was confirmed that when an appropriate decomposition rate is maintained in the reactor, the phenomenon of excess or shortage of fuel gas disappears. In addition, it became possible to reduce the amount of catalyst required and design the optimized capacity of the relevant processes.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.487-495
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• 2023

Ammonia is either a crucial resource of fertilizer production for solving the food problem of mankind or an important energy source as both an eco-friendly hydrogen carrier and a carbon-free fuel. Therefore, nowadays ammonia synthesis and decomposition become promising. Then, a catalyst is required to effectively perform the ammonia synthesis and decomposition. In order to design high-performing as well as cheap novel catalysts for ammonia synthesis and decomposition, it is necessary to test huge amount of catalyst candidates, but it is inevitably time-consuming and expensive to search and analyze using only traditional approaches. Recently, new methods using machine learning which is one of the core technologies of the 4th industrial revolution that can quickly and accurately search high-performance catalysts has been emerging. In this paper, we investigate reaction mechanisms of ammonia synthesis and decomposition, and we described recent research and prospects of machine learning-driven methods that can efficiently find high-performing and economical catalysts for ammonia synthesis and decomposition.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.9-15
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• 2005

In order to know the electrochemical decomposition characteristics of ammonia to nitrogen, this work has studied several experimental variables on the electrolytic ammonia decomposition. The effects of pH and chloride ion at $IrO_2$, $RuO_2$, and Pt anodes on the electrolytic decomposition of ammonia were compared, and the existence of membrane equipped in the cell and the changes of the current density, the initial ammonia concentration and so on were investigated on the decomposition. The performances of the electrode were totally in order of $RuO_2{\approx}IrO_2>Pt$ in the both of acid and alkali conditions, and the ammonia decomposition was the highest at a current density of $80mA/cm^2$, over which it decreased, because the adsorption of ammonia on the electrode surface was hindered due to the evolution of oxygen. The ammonia decomposition increased with the concentration of chloride ion in the solution. However, the increase became much dull over 10 g/l of chloride ion. The $RuO_2$ electrode among the tested electrodes generated the most OH radicals which could oxidized the ammonium ion at pH 7.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.5
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• pp.622-630
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• 1998

Rotating Biological Contactor (RBC) was tested for the removal of total ammonia nitrogen (TAN) by using simulated aquaculture system. RBC performance was evaluated by controlling revolution rate of disk and hydraulic residence tile (HRT). The optimum revolution rate of disk was 4 rpm, As HRT of RBC was increased, TAN removal efficiency of RBC and TAN concentration of rearing water were increased. HRT for maintaining lowest TAN concentration of rearing water was 9.5 minutes and at that condition TAN concentration of rearing tank was $1.03 g/m^3$

• KSBB Journal
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• v.19 no.3
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• pp.231-235
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• 2004

This paper was investigated to clarify the possibility of ammonia gas removal by essential oil. First of all, the chemical analysis was peformed to analyze the composition of an essential oil by GC-MS. The monoterpenes in an essential oil react with ammonia by neutralization and their reaction mechanism was elucidated. Based on their chemical neutralized reaction, the removal efficiencies of ammonia gas were studied to derive the optimal conditions in the scrubber tower such as optimal temperature and pH. The experimental result shows that the removal efficiency of ammonia gas was achieved over 98 % by the misty aerosol dispersion of scrubber tower.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.1-8
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• 2023

Research, such as developing alternative energy in the transportation field, including aviation, is being actively conducted to solve the issue of current climate change. Interest in ammonia fuel as a carbon free energy (CFE) source is increasing due to the ease of liquefaction and transportation and similarity in energy density to that of methanol. However, explosiveness and toxicity of ammonia make it difficult to handle. Therefore, in this study, stable ammonia production was attempted using relatively easy-to-handle urea water solution (UWS). High temperature steam was used to promote the hydrolysis of ammonia. In order to determine the causes for ammonia production below the theoretical equivalent ratio, it was suggested that there were not enough collisions to promote the hydrolysis based on the kinetic theory of gases. The hydrolysis of unreacted isocyanic acid (HNCO) was tested according to the change in water supply. As a result, an increased amount of ammonia produced was confirmed. The increased amount of ammonia produced in a certain section was dependent on the steam temperature and the flow rate of water supplied.

• 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.