Papers by Keyword: Ammonia

Abstract: Silicon carbide (SiC) is one of the ideal electronic materials for producing high-temperature, high-frequency, and high-power electronic devices. In the past 20 years, with the continuous improvement of silicon carbide material processing technology, its application have been expanding. Unlike Si devices, SiC devices cannot be directly fabricated on crude wafers. Instead, epitaxial films need to be deposited and grown on SiC wafers, then the epitaxial films will be used to produce devices. The doping concentration performance of the epitaxial layer can determine the device performance, making it the most important indicator of the epitaxial layer quality. For a long time, nitrogen has been used as the dopant in the production of SiC epi-wafers. Due to the difficulty of nitrogen cracking and its adsorption in graphite, the concentration is prone to significant drift, resulting in a decrease in yield and low production efficiency. In this research a vertical epitaxial equipment was used to consecutively grow 10 8-inch SiC substrate with nitrogen and ammonia as dopant separately. The concentration and thickness of the grown epitaxial films were measured and studied. The results indicate that compared to nitrogen as a dopant, the results of ammonia doping are significantly better in terms of intra-wafer concentration uniformity and inter-wafer consistency. Using nitrogen as the dopant, the doping concentrations uniformity of epi-layer ranges from 1.31% to 2.18%, and the deviation is between ± 8.0%. As a comparison, using ammonia as the dopant, the doping concentration uniformity of epi-layer ranges from 0.65% to 0.89%, and the deviation is between ± 1.0%. Meanwhile, the thickness performance is at the same level. Therefore, ammonia as a dopant can solve the concentration drift problem that has long been a headache in large-scale production of SiC epitaxy, greatly improving production efficiency. Its advantages are obvious. This study analyzed the possible reasons for the superior performance of ammonia gas as a dopant for 4H SiC epitaxy compared to nitrogen.

Abstract: This study aimed to analyze the atmospheric dispersion of dense gases, such as ammonia (NH₃), resulting from hypothetical leaks in a truck's cistern during road transport. By employing mathematical models, it was possible to estimate the distance that the gas cloud, formed after an accidental leak, would travel in the atmosphere until it was sufficiently diluted to no longer pose a toxicity risk. The analysis was conducted using the ALOHA software in conjunction with Google Earth to visualize the different scenarios. The results showed that during the nighttime period, scenario 6 exhibited the longest plume reach, with a distance of 484 meters in the red zone. During the daytime period, scenario 4 had the longest reach, with a plume extending 139 meters in the red zone.

Abstract: Natural gas has diverse content such as Methane, Ethane, Carbon dioxide, Hydrogen Sulfide, and other gases. In addition, natural gas is formed over a very long time, where it comes from fossil fuels. Natural gas that has been treated and produced products are called synthesis gas which can be used to make ammonia (NH₃). To produce ammonia, steam compounds (H₂O) are used which are reacted with natural gas to produce hydrogen (H₂) and Nitrogen (N₂) obtained from the air. Ammonia manufacturing can be done by several processes, namely desulfurization (natural gas purification), Steam Reforming, Shift Converter, CO₂ removal, methanation, and refrigeration units. The data used in this simulation is data on the ammonia plant at PT. Petrokimia Gresik. What is seen from this simulation is the influence of the composition of natural gas with variations in composition, namely 75% – 99% methane. The largest yield was obtained in the composition of 75% methane with an ammonia product yield of 82.34 tons/hour, this is because the division of the composition is divided propositionally into other compounds such as ethane, and propane, i-butane, etc. which have more H₂ content. Then there is the ratio of methane flow rate to steam using a variation of 1:3.5 - 1:7.5 where the largest ammonia product is obtained from a ratio of 1:7.5 with ammonia product yields of 84.79 tons/hour because more and more steam causes the formation of more hydrogen. Furthermore, there is a ratio of methane flow rate to air with a variation of 1:5.5 - 1:7.5 where the largest ammonia product is obtained from a ratio of 1:5.5 with an ammonia product yield of 84.87 tons/hour because the air content consists of N₂ and O₂, where if the O₂ content is a lot it will react with Methane so that the H₂ produced will be less if methane reacts also with O₂ not only with H₂O.

Abstract: Ammonia is a poisonous compound that can harm fish. Fish feed and manure are the primary sources of ammonia in catfish farming ponds. High concentrations of ammonia can cause death. Therefore, it is necessary to control the presence of ammonia to minimize the potential for fish mortality. Microbial Fuel Cell (MFC) is a technology that can help with ammonia bioremediation. This study aims to analyze the effectiveness of Microbial Fuel Cell (MFC) in reducing ammonia. The research method used is an experimental research method with qualitative descriptive analysis. The research was conducted on a laboratory scale using a dual-chamber Microbial Fuel Cell (MFC) reactor connected using a salt bridge. This research was conducted with variations in the use of sticky media, including without media, with bioball, and with bioring media. The results showed that the percentage of ammonia reduction in each treatment was 94.52%, 98.09%, and 99.28%. From this research, it can be concluded that Microbial Fuel Cells (MFC) are effective in reducing ammonia.

Abstract: Ammonia is a harmful substance on wastewater if discharged to the river, then it must be treated well. This research was aimed to examine the potential for the type of bacteria Brevundimonas diminuta in the ammonia degradation process of wastewater. Earlier step was done to examine bacteria growth in synthetical medium of ammonia concentration ranged 5 – 25 ppm. It shows that the bacteria could grow well within that ranges. Then, the bacteria performances were examined to grow in wastewater sampled from Musi River containing ammonia ranged 1.9 – 2.94 mg/L in the airlift bioreactor. The wastewater used in bioreactor was 1 L. Air was injected into the bioreactor with variations in the air flow rate of 1.5 to 4.5 L/m and with varying observation times from 1.5 to 6 hours. The optimal decrease in ammonia levels has occurred when the air flow rate was 3 L/min for 6 hours and the ammonia level was reduced from 2.94 mg/L to 1.76 mg/L.

Abstract: The availability of oxygen and the minimum amount of ammonia in the water media are crucial in catfish larvae hatchery performance. The condition with a balanced amount of required oxygen and the presence of ammonia resulting from the feces of striped catfish larvae is essential to maintain the health of the aquaculture media. This study aims to remove ammonia by introducing fine bubbles (FBs) into recirculating aquaculture media and investigating reserved dissolved oxygen inside the bubbles in the media. The water media for the striped catfish larvae hatchery was designed and set up with three containers in a recirculating system. Also, a separate container was utilized as bubble storage connected to FBs generator. The water treatment was conducted in three different scenarios using air and pure oxygen as the FBs generator sources. The generated FBs were investigated in terms of their size and zeta potential concerning the dissolved oxygen (DO). The media’s DO was measured using the titration method and digital DO meter. The difference in DO concentration received from titration and DO meter define as potential reserved oxygen. Furthermore, the removal of synthetic effluent (ammonia, NH₄Cl) and effluent in the media with FBs resources were investigated and tested at a different duration of FBs applications. The results showed that bubbles size was 518.5 – 607.6 nm independent of gas resource, either pure oxygen or air. However, the gas resources affected the zeta potential value of suspended bubbles, air (-11.5 to -16.7 mV), and pure oxygen (-21.4 to -25.2 mV). When pure oxygen was used as a gas resource, the media reach the oxygen supersaturation DO condition (25.39 ppm) within 45 minutes with reserve oxygen potential (ROP) of 2.95 ppm. Thus, this condition allowed the synthetic effluent removal of 83.33% and effluent removal of 39.93%. It is emphasized that the ammonia removal due to the presence of reactive oxygen species when the FBs collapsed and the information of ROP due to FBs application is important to preserve the fitness of aquaculture media for catfish larvae hatchery.

Abstract: Activated carbon is one of the most widely used adsorbents, but it shows low removal efficiency for polar molecules such as ammonia or ions due to the low content of oxygen containing groups. To increase the amount of oxygen containg groups, activated carbon was modified by the oxidation of activated carbon using the HNO₃/H₃PO₄-NaNO₂. The results showed that the carboxyl content of the modified activated carbon (MAC) increased with an increase in reaction time and temperature. The condition at 50°C for 60 hours yielded the MAC with a carboxyl content 1.07 mmol/g. The oxygen content of MAC also increased, suggesting the formation of carboxyl or carbonyl groups in the products after the oxidation. Brunauer-Emmett-Teller (BET) analysis and scanning electron microscopy (SEM) images demonstrated an increase in porosity of the MAC. The maximum capacity of ammonia adsorption was 5.81 mg/g for MAC.

Abstract: In a quest for a cleaner planet and to have alternative forms of energy generation apart from the fossil-based power supply, fuel cell technology has emerged as an alternative energy source for usage across all economic sectors. The application of this age-old technology is found in alkaline (AFC), molten carbonate (MCFC), phosphoric acid (PAFC), polymer electrolyte membrane (PEMFC) and solid oxide (SOFC) fuel cells. These fuel cells are named based on the type of electrolyte employed in their applications and the fuel of choice for energy generation is hydrogen. This fuel can be used in its pure form or extracted from other sources such as methanol, water and syngas. Ammonia in its liquefied and gaseous forms may be used as a non-carbonaceous fuel for the hydrogen source in some of these fuel cell technologies due to its safety, lower price, ease of storage and transportation. In this review, all the fuel cells will be investigated in their capability of using ammonia as a direct fuel. The role of earth abundant metal catalysts in comparison to TiO₂ was evaluated in terms of molecular orbital theory and in the decomposition of organic compounds and other material into nitrogen and hydrogen products under the visible light radiation. The p-orbital participation in earth abundant metals or metal oxides doping, emerged as a strong contribution to bandgap attenuation.

Abstract: Using a CO₂ laser photoacoustic spectroscopy with intracavity setup and multicomponent method we have done measurement on the ammonia, ehtylene and acetone gas concentrations in the breath of liver disease patients and in the healthy volunteers. The results of multicomponent analysis show that the average concentration of ammonia gas obtained from the breath of liver disease patients and healthy volunteers are (3.27 ± 0.75) and (1.34 ± 0.24) ppm, respectively. The highest and the lowest ammonia gas concentration of liver disease patients are 4.77 and 1.99 ppm. While, the highest and the lowest ammonia gas concentration of healthy volunteers are 1.89 and 1.08 ppm. For the ethylene and acetone concentrations, we found no significant difference between the average concentrations in the liver disease patients and in the healthy volunteers.

Abstract: Modified charcoal was prepared from the oxidation of charcoal using the HNO₃/H₃PO₄-NaNO₂ system in a range of temperatures from 30 to 50 °C for 24 to 72 hours of reaction time. The reaction was the oxidation by cleavage of a double bond and converting it into a carboxyl group (-COOH) or carbonyl group (-C=O). The results showed that the carboxyl content of the modified charcoal (MC) increased with an increase in reaction time and temperature. The condition at 50°C for 60 hours yielded the MC with a carboxyl content of 1.81 mmol/g. Fourier transform infrared spectrometry (FT-IR) revealed that MC had a new adsorption peak at 1712 cm^-1. The oxygen content of modified charcoal also increased, suggesting the formation of carboxyl or carbonyl groups in the products after the oxidation. Brunauer-Emmett-Teller (BET) analysis and scanning electron microscopy (SEM) images demonstrated an increase in porosity of the MC. The maximum capacity of ammonia adsorption of MC was 6.14 mg/g.