• Journal of the Korean Society of Industry Convergence
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• v.25 no.5
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• pp.835-842
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• 2022

In this study, the membrane degassing process of the sweep gas - vacuum combination type was proposed for ammonia wastewater treatment. The effect of pH, initial ammonia concentration and scale-up on ammonia degassing performance was investigated. As a result, as the pH and the initial ammonia concentration increased, the degassing permeate flux was improved. On the other hand, the ammonia mass transfer coefficient increased as the initial ammonia reduced, which seems to be due to the driving force of the sweep gas-vacuum combination type membrane degassing system proposed in this study. In addition, 80 mg NH₃/min of the ammonia degassing rate was achieved using a 6×28 inch size module. Better degassing performance is expected if consideration for maintaining vacuum pressure is involved in the scale-up design.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.760-763
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• 2007

The properties of carbon nanotube obtained by thermal chemical vapor deposition (CVD) process were investigated as a function of ammonia $(NH_3)$ gas in hydrocarbon gas, Fe catalyst thickness, and growth temperature. Fe catalyst was prepared by DC magnetron sputter and pre-treated with ammonia gas. CNTs were then grown with ammonia-acetylene gas mixture by thermal CVD. The diameter of these CNTs shows a strong correlation with the gas rate, the catalyst film thickness and temperature. From our results, it was found that the factors of grown CNTs positively acted to improve CNT quality.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.253-258
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• 2010

In the field of the $CO_2$ absorption process using aqueous ammonia, the effects of regeneration pressure and temperature on $CO_2$ absorption performances of the aqueous ammonia were investigated. The absorbents were prepared by dissolving ammonium carbonate solid in water to grant the resulted solution 0.5 $CO_2$ loading ($mol\;CO_2/mol\;NH_3$) and various ammonia concentration (14, 20, 26 and 32 wt%). As-prepared absorbents were regenerated at high pressure and temperature (over $120^{\circ}C$ and 6 bar) before the absorption test. The absorption test was carried out by injecting the simulated gas that contains 12 vol% of $CO_2$ into a bubbling reactor. The introduction of 26 wt% of the ammonia concentration for $CO_2$ absorption test resulted in the higher absorption capacities than other experimental conditions. In particular, when the absorbents with 26 wt% of the ammonia were regenerated at $150^{\circ}C$ and 14 bar, the highest absorption capacity, $45ml\;CO_2/g$, was obtained. According to the analysis of absorbents using acid-base titration, the ammonia loss during the regeneration of the absorbents with a fixed ammonia concentration decreased as the regeneration pressure increased, while it increased as the regeneration temperature increased. In the condition of fixed regeneration pressure and temperature, as expected, the ammonia loss increased as the ammonia concentration increased. The measured $CO_2$ loadings and ammonia concentrations of absorbents were compared to the values calculated by Electrolyte NRTL model in Aspen Plus.

• Polymer(Korea)
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• v.31 no.6
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• pp.479-484
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• 2007

In this study, the hybrid ion exchange fibers (HIEF) were prepared by using web spraying muthod with hot melt adhesive. Characteristics of HIEF and their adsorption properties for ammonia gas were investigated. The ion exchange capacity (IEC) of HIEF was increased with increasing the resin contents and their values were higher than those of pure resin and ion exchange fabrics. The removal efficiency for ammonia gas increased with an increase in packing density of hybrid ion exchange fabrics in the column. The adsorption breakthrough time was 270 min, which was slower than those of the resin and fibers. The maximum value of adsorption for ammonia gas was 94%. The breakthrough time was also increased with increasing the concentration and flow rate of ammonia gas. The reaction constant(k) for ammonia gas was increased with increasing the concentration and flow rate of the gas, while it was decreased an the mass was increased.

• Korean Journal of Organic Agriculture
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• v.8 no.2
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• pp.89-96
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• 2000

To reduce loss of nitrogen and generation of ammonia gas during composting, poultry manure and sawdust were mixed at the equivalent ratio and calcium chloride, fused superphosphate and vermiculite were added. Ammonia and sulfurous gas during composting, and NH4-N and NO3-N contents of composts were periodically measured. With the treatments of 0.5∼3% calcium chloride and 3% fused superphosphate, ammonia and sulfurous gas during composting significantly decreased, and especially generation of gases sharply reduced and a increase of calcium chlorde. Extractable NH4-N content in composts treasted with calcium chloride and fused superphosphate were high but extractable NO3-N markedly decreased. In conclusion, the results suggest that it is necessary the additon of 1∼3% calcium chloride or 3% fused superphosphate to reduce loss of nirogen and generation of offensive odor during composting of poultry manure mixed with sawdust.

• Microbiology and Biotechnology Letters
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• v.37 no.4
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• pp.408-412
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• 2009

A study on the screening and isolation of microorganism was performed for the removal of main malodor, such as ammonia, produced from the livestock farm. The main malodor components in livestock farm are ammonia, volatile fatty acids, sulfur compounds and trimethylamine. Damages to man and livestock were originated from malodors mainly due to ammonia, and thus ammonia reduction experiments were performed. Sludge of sewage treatment plant was inoculated in the sesame dregs culture, from which ammonia gas was produced. An aerobically grown, pure cultured isolated from the 10th enrichment culture was analyzed by 16S rRNA sequencing and identified as Alcaligenes sp. NS-1. This strain NS-1 precultured in the sesame dregs was found to remove ammonia gas with an efficiency of approximately 99-100% at an average concentration of 40 ppmv of ammonia gas. When the strain NS-1 sprayed to pig excrements, the removal efficiency at an average concentration of 100 ppmv of ammonia was approximately 60% after 16 hr.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.5
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• pp.201-211
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• 2019

Low carbon steel (S20C steel) and SPCC steel sheet have been austenitic nitrided at $700^{\circ}C$ in a closed pit type furnace by changing the flow rate of ammonia gas and heat treating time. When the flow rate of ammonia gas was low, the concentration of residual ammonia appeared low and the hardness value of transformed surface layer was high. The depth of the surface layer, however, was shallow. With increasing the concentration of residual ammonia by raising up the ammonia gas flow, both the depth of the surface layer and the pore depth increased, while the maximum hardness of the surface layer decreased. By introducing a large amount of ammonia gas in a short time, a deep surface layer with minimal pores on the outermost surface was obtained. In this experiment, while maintaining 10~12% of residual ammonia, the flow rate of inlet ammonia gas, 7 liter/min, was introduced at $700^{\circ}C$ for 1 hour. In this condition, the thickness of the surface layer without pores appeared about $60{\mu}m$ in S20C steel and $30{\mu}m$ in SPCC steel plate. Injecting additional methane gas (carburizing gas) to this condition played a deteriorating effect due to promoting the formation of vertical pores in the surface layer. For $1^{st}$ transformed surface layer for S20C steel, maintaining 10~12% residual ammonia condition via austenitic nitriding process resulted in ${\varepsilon}$ phase with relatively high nitrogen concentration (just below 4.23 wt.%N) among the mixed phases of ${\varepsilon}+{\gamma}$. The ${\varepsilon}$ phase was formed a specific orientation perpendicular to the surface. For $2^{nd}$ transformed layer for S20C steel, ${\gamma}$ phase was rather dominant (just above 2.63 wt.%N). For SPCC steel sheet, there appeared three phases, ${\gamma}$, ${\alpha}(M)$ and weak ${\varepsilon}$ phase. The nitrogen concentration would be approximately 2.6 wt.% in these phases condition.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.63-70
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• 2022

Compared with hydrogen, ammonia has the advantages of high gravimetric hydrogen densities (17.8 wt.%), ease of storage and transportation as a chemical hydrogen storage medium, while its application in small-scale on-site hydrogen production scenarios is limited by the need for complex separation equipment during high purity hydrogen production. Therefore, the study of PEMFC, which can directly utilize ammonia decomposition gas, can greatly expand the application of fuel cells. In this paper, the output characteristics, fuel efficiency and the variation trend of hydrogen concentration and local current density in the anode channel of fuel cell with the output voltage of PEMFC fueled by ammonia decomposition gas were studied by experiment and simulation. The results indicate that the maximum output power of the hybrid fuel decreases by 9.6% compared with that of the pure hydrogen fuel at the same inlet hydrogen equivalent. When the molar concentration of hydrogen in the anode channel is less than 0.12, the output characteristics of PEMFC will be seriously affected. Employing ammonia decomposition gas as fuel, the efficiency corresponding to the maximum output power of PEMFC is approximately 47%, which is 10% lower than the maximum efficiency of pure hydrogen.

• Journal of Sensor Science and Technology
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• v.25 no.6
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• pp.423-430
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• 2016

This study used a single metal oxide semiconductor (MOS) sensor to classify the major odorous gases hydrogen sulfide ($H_2S$), ammonia ($NH_3$) and toluene ($C_6H_5CH_3$). In order to classify these odorous substances, the voltage on the MOS sensor heater was gradually reduced in 0.5 V steps 5.0 V to examine the changes to the response by the cooling effect on the sensor as the voltage decreased. The hydrogen sulfide gas showed the highest sensitivity compared to odorless air under approximately 2.5 V and the ammonia and toluene gases showed the highest sensitivity under approximately 5.0 V. In other words, the hydrogen sulfide gas reacted better in the low temperature range of the MOS sensor, and the ammonia and toluene gases reacted better in the high-temperature range. In order to analyze the response characteristics of the MOS sensor by temperature in a pattern, a two-dimensional (2D) x-y pattern analysis was introduced to clearly classify the hydrogen sulfide, ammonia, and toluene gases. The hydrogen sulfide gas was identified by a straight line with a slope of 1.73, whereas the ammonia gas had a slope of 0.05 and the toluene gas had a slope of 0.52. Therefore, the 2D x-y pattern analysis is suggested as a new way to classify these odorous substances.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.35-40
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• 2023

In order to prevent an ammonia container from bursting under conditions such as overcharging and abnormal temperature rise, it is necessary to prepare accident prevention measures through analysis of the operating mechanism of the Thermally Activated Pressure Relief Devices (TPRD) attached to the container. In this study, stress analysis acting on the ammonia container under pressurized conditions, density change analysis according to temperature change, and correlation between container filling amount and temperature and pressure change were presented. In addition, the maximum filling amount of the ammonia container was calculated, and the temperature and pressure at the filling amount were calculated through the phase equilibrium diagram. Based on this, the appropriate melting point of the Thermally Activated Pressure Relief Devices was derived and verified through a melting temperature experiment. Based on the results of this study, conditions for preventing ammonia container rupture accidents were suggested.