Mixture Of Ammonia Research Articles

Tetra-ammonium μ-ethyl-enedi-amine-tetra-acetato-1κ3 O,N,O':2κ3 O'',N',O'''-bis-[trioxidotungstate(VI)] tetra-hydrate.

The title compound, (NH4)4[W2(C10H12N2O8)O6]·4H2O, was obtained from a mixture of tungstic acid, ammonia and ethyl-enedi-amine-tetra-acetic acid (H4edta) in a 2:4:1 ratio. The anion of the complex contains two WO3 units and one bridging edta4- ligand. Each central metal atom is tridentately coordinated by nitro-gen and two carboxyl-ate groups of the edta4- ligand, together with the three oxido ligands, producing a distorted octa-hedral coordination environment around each tungsten atom. The center of the carbon-carbon bond of the ethyl-ene bridge represents a crystallographic inversion center. The crystal structure consists of a three-dimensional supra-molecular framework built up by the dinuclear cations, the ammonium counter-ions and the solvent water mol-ecules via hydrogen bonds of the N-H⋯O and O-H⋯O type.

Chemical speciation and soot measurements in laminar counterflow diffusion flames of ethylene and ammonia mixtures

Ammonia is considered as one of the most promising alternative fuels due to its carbon neutrality and the existing infrastructure for its mass production and delivery. However, burning neat ammonia has the issue of poor flame stability and high NOx emissions, making co-firing ammonia with conventional fuel a more feasible approach. The present work investigated the sooting characteristics of counterflow diffusion flames of ethylene/ammonia mixtures. Experimentally, soot volume fraction (SVF) and average soot particle diameter in the neat ethylene, ammonia- and nitrogen- doped flames were non-intrusively measured. Both SVF and average soot particles diameter were found to decrease with the addition of ammonia. Flame temperature were measured with tunable diode laser absorption spectroscopy and the results suggested that the inhibiting effect of ammonia on soot formation was chemical instead of thermal. For further kinetic insights, numerical simulation with newly-constructed reaction mechanisms were performed and the results were compared against chemical speciation data from gas chromatography (GC) measurements; the results showed that ammonia doping would lead to more significant reduction of benzene concentration than nitrogen doping. Kinetic pathways of the chemical suppressing effect of ammonia addition on soot and its precursor formation were then explained based on numerical results. The major contribution of the present work can be summarized in the following aspects: 1) New comprehensive experimental data on sooting characteristics, important intermediate species concentrations of diffusion counterflow flames of ethylene/ammonia mixtures were provided for model validation; 2) One coupled mechanism with detailed hydrocarbon-nitrogen interactions was established to predict PAHs formation and soot formation; 3) Detailed chemical kinetics insight of ammonia effect on soot formation was presented in the counterflow flame.

Use of Taguchi Methods for Hierarchy of Influence Factors in the Application of Carbonitration in a Fluidized Bed Steel for 41Cr4 Steel

The work is based on carbonitriding in a fluidized layer with methane and ammonia gas applied to 41Cr4 steel samples. To achieve the best possible results, other factors must be taken into account, than those specific to carbonitring. It was necessary to use a partially factorial working procedure due to the increase in the number of factors. An A18 matrix has been used, with 18 lines of experiments in which three levels have been modified for 6 factors. The objective function was fixed at the final hardness after carbonitriding, hardening and tempering. The carbonitriding was performed in fluidized bed with granular solid ground and sorted to 0.1- to 0.16mm, and brought to fluidization with a mixture of methane and ammonia. The hardening has been done directly after carbonitriding in the fluidized bed. The experiments have been performed according to Taguchi Methods and the results indicate an optimal regime and the influence of the factors considered on the hardness after the thermo-chemical treatment and the thermal treatment. Metallographic analysis has been performed on the carbonitrided layer.

A flow-circulation reactor for simultaneous photocatalytic degradation of ammonia and phenol using N-doped ZnO beads

In this study, a novel continuous flow-circulation photocatalytic reactor was acquired for treatment of synthetic wastewater containing a binary mixture of ammonia and phenol. Performance of the photo-reactor was examined using synthesized N-Doped ZnO Beads (N-ZnB) within the existence of Hydrogen peroxide (H2O2) and UV irradiation. The Beads of catalyst were synthesized using modified sol–gel method. A protocol was followed for the characterization of N-ZnB catalyst by performing some common analytical methods such as SEM, EDS, Raman and DRS. N-Doping narrows in band gap energy as calculated from DRS the band gab energy reduced from 3.2 eV to 3.16 eV and reduces electron – hole pair recombination and accordingly improves the efficiency of ammonia and phenol photo-degradation. The optimum photo-degradation conditions were detected by examining the effect of operational parameters as the flow rate, pH, catalyst dosage, H2O2 concentration and initial concentration for both ammonia and phenol. At optimum conditions, N-ZnB catalyst achieved 98.3% and 95.8% degradation for both ammonia and phenol, respectively, after 2 hr of UV irradiation. Also, the reusing ability and strength of N-ZnB was investigated. The developed beads could be used as an effective catalyst for the degradation of binary mixture of ammonia and phenol from wastewater.

Experimental and numerical study on premixed partially dissociated ammonia mixtures. Part II: Numerical study of premixed combustion characteristics

Adding dissociated ammonia (NH3) is an effective way to improve the combustion properties of NH3. Research on the laminar burning velocity of partially dissociated NH3 mixtures was shown in part I. In order to further explore the feasibility of enhancing ammonia combustion by adding dissociated ammonia, several essential combustion properties were numerically studied in part Ⅱ of this study. The burned gas Markstein length was obtained by the experiment and theoretical calculation, and the relevant combustion parameters such as adiabatic flame temperature, heat release rate and NO formation were calculated by planar flame simulation. Results show that the Markstein length increases with the increasing dissociating degree on the lean side, but decreases under rich conditions, which is mainly due to the determination of flame thickness, effective Lewis number and Zel’dovich number. The addition of dissociated NH3 increases the mixture heating value, but the combustion efficiency decreases slightly. The primary exothermic elementary reactions in the combustion are gradually replaced by the reactions in the H2 system, and the exothermic process shifts to a lower temperature with the increase of dissociating degree. NO is the main NOx emission, the formation of NO is determined by the concentration of the O/H radicals and NH3, its mole fraction first increases and then decreases with the increase of dissociating degree. Moreover, the NO emission on the rich side only decreases slightly under high dissociating degree conditions, which is different from the significant plummet under the low and medium dissociating degree conditions.

Laminar burning characteristics of ammonia/hydrogen/air mixtures with laser ignition

Ammonia, as a zero-carbon fuel, is drawing more and more attention. The major challenge of using ammonia as a fuel for the combustion engines lies in its low chemical reactivity, and therefore more fundamental researches on the combustion characteristics of ammonia are required to explore effective ways to burn ammonia in engines. In this study, the laminar burning characteristics of the premixed ammonia/hydrogen/air mixtures are investigated. In the experiment, the laser ignition was used to achieve stable ignition of the ammonia/air mixtures with an equivalence ratio range from 0.7 to 1.4. The propagating flame was recorded with the high-speed shadowgraphy. Three different processing methods were introduced to calculate the laminar burning velocity with a consideration of the flame structure characteristics induced by the laser ignition. The effects of initial pressure (0.1 MPa–0.5 MPa), equivalence ratio (0.7–1.4), hydrogen fraction (0–20%) on the laminar burning velocity were investigated under the initial ambient temperature of 360 K. The state-of-the-art kinetic models were used to calculate the laminar burning velocities in the CHEMKIN-pro software. Both the simulation and experimental results show that the laminar burning velocity of the ammonia mixtures increases at first, reaches the peak around ϕ of 1.1, and then decreases with the equivalence ratio increasing from 0.7 to 1.4. The peak laminar burning velocities of the ammonia mixture are lower than 9 cm/s and are remarkably lower than those of hydrocarbon fuels. The laminar burning velocity of the ammonia mixture decreases with the increase of the initial ambient pressure, and it can be drastically speeded up with the addition of hydrogen. While the models except for those by Miller and Bian can give reasonable predictions compared to the experimental results for the equivalence ratio from 0.7 to 1.1 in the ammonia (80%)/hydrogen (20%)/air mixtures, all the kinetic models overpredict the experiments for the richer mixtures, indicating further work necessary in this respect.

Transcriptomic and metabolomic profiles of Zea mays fed with urea and ammonium.

The simultaneous presence of different N‐forms in the rhizosphere leads to beneficial effects on nitrogen (N) nutrition in plants. Although widely used as fertilizers, the occurrence of cross connection between urea and ammonium nutrition has been scarcely studied in plants. Maize fed with a mixture of urea and ammonium displayed a better N‐uptake efficiency than ammonium‐ or urea‐fed plants (Buoso et al., Plant Physiol Biochem, 2021a; 162: 613–623). Through multiomic approaches, we provide the molecular characterization of maize response to urea and ammonium nutrition. Several transporters and enzymes involved in N‐nutrition were upregulated by all three N‐treatments (urea, ammonium, or urea and ammonium). Already after 1 day of treatment, the availability of different N‐forms induced specific transcriptomic and metabolomic responses. The combination of urea and ammonium induced a prompt assimilation of N, characterized by high levels of some amino acids in shoots. Moreover, ZmAMT1.1a, ZmGLN1;2, ZmGLN1;5, ZmGOT1, and ZmGOT3, as well transcripts involved in glycolysis‐TCA cycle were induced in roots by urea and ammonium mixture. Depending on N‐form, even changes in the composition of phytohormones were observed in maize. This study paves the way to formulate guidelines for the optimization of N fertilization to improve N‐use efficiency in maize and therefore limit N‐losses in the environment.

Numerical study of a swirl gas turbine combustor for turbulent air and oxy-combustion of ammonia/kerosene fuels

Since ammonia has a carbon-free substance and involves hydrogen atoms per volume unit, many scientists think it could be used as an alternative fuel instead of natural gas or kerosene-based fuels in gas turbine combustors. The main goal of this study is to investigate turbulent swirl combustion ammonia-assisted kerosene fuels with air and pure oxygen combustion conditions in a model gas turbine combustor. For this purpose, numerical modelings have been performed by using a commercial computational fluid dynamics (CFD) code. Ammonia was introduced into the combustor from the different inlets. The ammonia composition was determined until 70% kerosene-30% ammonia mixture in an interval of 10% by heat fraction. During this addition, the total heat load provided was kept constant. The results showed that there was no considerable change over the combustion performance of kerosene. However, the maximum temperature levels and its locations changed somewhat in the combustor with ammonia addition. In addition to temperature distributions of kerosene and ammonia-assisted kerosene fuels, NOX emission levels have been addressed by performing post-processing of the CFD code used in this study. According to the predicted NOX levels, it was seen that the predicted NOX emissions levels increased significantly in the high temperature flame zone due to bound-nitrogen in ammonia (fuel-NOX mechanism). But, the predicted NOx emission levels were not too high at the exit of the combustion chamber. Therefore, it can be concluded that ammonia-assisted kerosene fuels have considerable potential in terms of combustion performance as a new and renewable fuel.

Identification of Existing Challenges and Future Trends for the Utilization of Ammonia-Water Absorption–Compression Heat Pumps at High Temperature Operation

Decarbonization of the industrial sector is one of the most important keys to reducing global warming. Energy demands and associated emissions in the industrial sector are continuously increasing. The utilization of high temperature heat pumps (HTHPs) operating with natural fluids presents an environmentally friendly solution with great potential to increase energy efficiency and reduce emissions in industrial processes. Ammonia-water absorption–compression heat pumps (ACHPs) combine the technologies of an absorption and vapor compression heat pump using a zeotropic mixture of ammonia and water as working fluid. The given characteristics, such as the ability to achieve high sink temperatures with comparably large temperature lifts and high coefficient of performance (COP) make the ACHP interesting for utilization in various industrial high temperature applications. This work reviews the state of technology and identifies existing challenges based on conducted experimental investigations. In this context, 23 references with capacities ranging from 1.4 kW to 4500 kW are evaluated, achieving sink outlet temperatures from 45 °C to 115 °C and COPs from 1.4 to 11.3. Existing challenges are identified for the compressor concerning discharge temperature and lubrication, for the absorber and desorber design for operation and liquid–vapor mixing and distribution and the choice of solution pump. Recent developments and promising solutions are then highlighted and presented in a comprehensive overview. Finally, future trends for further studies are discussed. The purpose of this study is to serve as a starting point for further research by connecting theoretical approaches, possible solutions and experimental results as a resource for further developments of ammonia-water ACHP systems at high temperature operation.

Appropriate NH4 +/NO3 - Ratio Triggers Plant Growth and Nutrient Uptake of Flowering Chinese Cabbage by Optimizing the pH Value of Nutrient Solution.

Compared with sole nitrogen (N), the nutrition mixture of ammonium (NH4+) and nitrate (NO3–) is known to better improve crop yield and quality. However, the mechanism underlying this improvement remains unclear. In the present study, we analyzed the changes in nutrient solution composition, content of different N forms in plant tissues and exudates, and expression of plasma membrane (PM) H+-ATPase genes (HAs) under different NH4+/NO3– ratios (0/100, 10/90, 25/75, 50/50 as control, T1, T2, and T3) in flowering Chinese cabbage. We observed that compared with the control, T1 and T2 increased the economical yield of flowering Chinese cabbage by 1.26- and 1.54-fold, respectively, whereas T3 significantly reduced plant yield. Compared with the control, T1–T3 significantly reduced the NO3– content and increased the NH4+, amino acid, and soluble protein contents of flowering Chinese cabbage to varying extents. T2 significantly increased the N use efficiency (NUE), whereas T3 significantly decreased it to only being 70.25% of that of the control. Owing to the difference in N absorption and utilization among seedlings, the pH value of the nutrient solution differed under different NH4+/NO3– ratios. At harvest, the pH value of T2 was 5.8; in the control and T1, it was approximately 8.0, and in T3 it was only 3.6. We speculated that appropriate NH4+/NO3– ratios may improve N absorption and assimilation and thus promote the growth of flowering Chinese cabbage, owing to the suitable pH value. On the contrary, addition of excessive NH4+ may induce rhizosphere acidification and ammonia toxicity, causing plant growth inhibition. We further analyzed the transcription of PM H+-ATPase genes (HAs). HA1 and HA7 transcription in roots was significantly down-regulated by the addition of the mixture of NH4+ and NO3–, whereas the transcription of HA2, HA9 in roots and HA7, HA8, and HA10 in leaves was sharply up-regulated by the addition of the mixture; the transcription of HA3 was mainly enhanced by the highest ratio of NH4+/NO3–. Our results provide valuable information about the effects of treatments with different NH4+/NO3– ratios on plant growth and N uptake and utilization.

Recovery of Copper from Ammoniacal Leachates by Ion Flotation

Sulfidic copper–lead–zinc tailings can pose a significant environmental threat, ranging from generation of acid mine drainage (AMD) to dam failures. On the other hand, they can also be considered as low-grade ore resources for zinc and copper provided that novel economically feasible metal extraction and metal recovery techniques are developed. Due to the low metal concentrations in these resources, the leaching will generate dilute leachates from which metal recovery is a challenge. Ion flotation is a foam separation technique capable of recovering metal ions from dilute aqueous leachates. In this paper, ion flotation was applied to separate copper from ammoniacal leachates of microwave-roasted sulfidic tailings samples. The sulfidic tailings were first roasted at 550 °C for 60 min, for the oxidation of sulfide minerals to more easily soluble sulfates using microwave-assisted irradiation as heating source. The microwave-roasted material was then leached with a mixture of ammonia and ammonium carbonate solutions. The optimum leaching efficiencies of zinc (86%) and copper (75%) were obtained under the following conditions: liquid-to-solid ratio = 10 mL g−1, T = 90 °C, [NH3 + NH4+] = 4 mol L−1, NH3:NH4+ = 2:1, t = 5 h. From the generated pregnant leach solution, it was possible to selectively separate 85% of copper to the foam phase by ion flotation, with sodium dodecyl sulfate (SDS) surfactant, as colloidal copper(II) tetraamine dodecyl sulfate under the optimized conditions: [SDS]total = 5.85 mmol L−1, [EtOH] = 0.5 % (v/v), ttotal = 5 h, flotation stages = 3. The zinc that remained in the solution after ion flotation was recovered by precipitation (95%) as basic zinc carbonate.Graphical AbstractCopper and zinc extraction by ammoniacal leaching from microwave-roasted Cu-Zn-Pb sulfidic tailings followed by recovery of copper and zinc by ion flotation and precipitation.

Theoretical investigation of the combustion performance of ammonia/hydrogen mixtures on a marine diesel engine

Ammonia is a good hydrogen carrier and can be well combined with hydrogen for combustion. The combustion performance of the mixtures of ammonia and hydrogen in a medium-speed marine diesel engine was investigated theoretically. The HCCI combustion mode was selected for reducing thermal-NOx production. The start fire characteristic of the NH3–H2 mixtures was studied under different equivalence ratio, hydrogen-doped ratio, and intake air temperature and pressure. Then, the combustion performance of the NH3–H2 mixtures (doping 30% hydrogen) was analyzed at a typical operation condition of engine. The addition hydrogen improved the laminar flame velocity of ammonia, and affected the NOx emission. For the medium-speed marine engine fueled with NH3–H2, reducing combustion temperature, introducing EGR and combining with post-treatment technology would be a feasible scheme to reduce NOx emission.

New nitriding process of high-alloyed maraging steel for cryogenic operation

The paper considers the gas nitriding process with cyclic alternation of atmospheres: ammonia and an ammonia mixture with air for strengthening the corrosion-resistant high-alloyed steel 03Cr11Ni10Mo2Ti, designed to operate at cryogenic temperatures. The formation in steel of a nitrided layer of 130—150μm thickness with increased microhardness (more than 12GPa) is shown experimentally. During the final stage in the ammonia and air environment, iron oxides remain in the compound zone, and a sharp drop in hardness is observed at the border of the core. At the completion of the cyclic process with the stage of saturation in ammonia, a nitrides zone is formed based on the γ′-phase, the layer thickness increases (up to 180(…200μm) and the microhardness profile is smoothed, which reduces the risk of embrittlement.

Self-aligned-TiSi2 bottom contact with APM cleaning and post-annealing for sputtered-MoS2 film

Electrical contact characteristics between self-aligned titanium silicide (TiSi2) and sputtered-molybdenum disulfide (MoS2) films were newly demonstrated. In contrast with metal contacts, the surface of the TiSi2 bottom-contact was cleaned by using an ammonia and hydrogen peroxide mixture (APM) before MoS2 deposition, because the TiSi2 film has high oxidation resistance. In order to extract the contact resistance, a transmission line model device was fabricated. A two-order reduction in the contact resistance was achieved by a post-annealing at 650 °C in forming gas ambient (3% H2 in N2). This reduction was attributed to selective titanium diffusion from bottom contact into the MoS2 film. The TiSi2 contact is thus speculated as a candidate for a practical contact material in MoS2 devices.

Ionic Phases of Ammonia-Rich Hydrate at High Densities

Mixtures of ammonia and water are major components of the "hot ice" mantle regions of icy planets. The ammonia-rich ammonia hemihydrate (AHH) plays a pivotal role as it precipitates from water-rich mixtures under pressure. It has been predicted to form ionic high-pressure structures, with fully disintegrated water molecules. Utilizing Raman spectroscopy measurements up to 123GPa and first-principles calculations, we report the spontaneous ionization of AHH under compression. Spectroscopic measurements reveal that molecular AHH begins to transform into an ionic state at 26GPa and then above ∼69 GPa transforms into the fully ionic P3[over ¯]m1 phase, AHH-III, characterized as ammonium oxide (NH_{4}^{+})_{2}O^{2-}.

Nanostructured iron-nitrogen martensite synthesized from Fe79Mo10B10Cu1 magnetic nanocomposite alloy

A Fe79Mo10B10Cu1 nanocomposite alloy was prepared by rapid solidification processing and subsequent isothermal annealing of ribbons with 6 nm, α-Fe grains embedded in an amorphous matrix. The nanocrystalline alloy was then nitrided in a gas mixture of ammonia and hydrogen at 650 and 700 °C for varied time between 300 and 7200 s followed by quenching. A majority (~55 vol%) of nitrogen austenite γ-(Fe,N) with a grain size of ~20 nm was produced when nitriding conditions were at a temperature of 700 °C in 12% NH3–88% H2 for 3600 s. The nitrided alloy has a magnetization of 50 ± 20 A·m2/kg at an applied field of 1.19 MA/m. Retained α-Fe, the only ferromagnetic phase in the sample, is responsible for the magnetization. And paramagnetic phases of γ-(Fe,N) and η-Fe3Mo3N account for ~80% of the material by volume. After the high-temperature nitridation, the alloy was soaked in liquid nitrogen and then tempered at 117 °C. Nanostructured iron-nitrogen martensite (α′) was transformed from the nitrogen austenite phase in the nitrided Fe79Mo10B10Cu1 alloy, and was characterized to have an amount of ~20 vol% and a grain size of ~12 nm. This iron-nitrogen martensite nanocomposite has a magnetization of 65 ± 8 A m2/kg at an applied field of 1.19 MA/m and coercivity of 14 ± 6 kA/m.

Minimum ignition energies and laminar burning velocities of ammonia, HFO-1234yf, HFC-32 and their mixtures with carbon dioxide, HFC-125 and HFC-134a

Given the safety issues associated with flammability characteristics of alternative environmentally-friendly refrigerants, it is vital to establish measurement systems to accurately analyse the flammability of these mildly flammable refrigerants. In this study, we used a customised Hartmann bomb analogue to measure the minimum ignition energy (MIE) and laminar burning velocity (BV) for refrigerant/air mixtures of pure ammonia (R717), R32, R1234yf and mixtures of R32 and R1234yf with non-flammable refrigerants of R134a, R125 and carbon dioxide (R744). The MIEs of R717, R32, and R1234yf were measured at an ambient temperature of 24 °C to be (18.0 ± 1.4), (8.0 ± 1.5) and (510 ± 130) mJ at equivalence ratios of 0.9, 1.27 and 1.33, respectively. Adding the non-flammable refrigerants R134a, R125 and R744 along with R32 at volumetric concentrations of 5% each to R1234yf reduced the latter compound’s flammability and increased its MIE by one order of magnitude. The laminar burning velocities of pure R717 and R32 were measured at an equivalence ratio of 1.1 using the flat flame method and found to be 8.4 and 7.4 cm/s, respectively. Adding 5% R1234yf to R32 decreased the laminar burning velocity by 11%, while a further 5% addition of R1234yf resulted in a decrease of over 30% in the laminar burning velocity.

Permeation of water, ammonia and dichloromethane through graphene oxide/polymeric matrix composite membranes

The permeation of polar molecules (water and ammonia), non-polar dichloromethane and a mixture of ammonia and dichloromethane through graphene oxide (GO)/polymer matrix composite membranes was investigated. Results indicated that a hydrophilic poly(2-acrylamido -2 -methyl propane sulfonic acid) (PAMPS) based membrane had the highest permeability for water and ammonia due to the high hydrophilicity of the polymer matrix while a hydrophobic polyurethane (PU)-based membrane had the best permeation performance for dichloromethane and the worst performance for water and ammonia. Adding the GO to PU or PAMPS polymers increases the negative charge due to the negatively charged nature of GO caused by its oxygen-containing functional groups, which increases the amounts of absorbed water and ammonia due to the positive charge of the hydrogen atoms in these two molecules.

Irradiation dose affects the composition of organic refractory materials in space

Context. Near- and mid-infrared observations have revealed the presence of organic refractory materials in the Solar System, in cometary nuclei and on the surface of centaurs, Kuiper-belt and trans-neptunian objects. In these astrophysical environments, organic materials can be formed because of the interaction of frozen volatile compounds with cosmic rays and solar particles, and favoured by thermal processing. The analysis of laboratory analogues of such materials gives information on their properties, complementary to observations. Aims. We present new experiments to contribute to the understanding of the chemical composition of organic refractory materials in space. Methods. We bombard frozen water, methanol and ammonia mixtures with 40 keV H+ and we warmed the by-products up to 300 K. The experiments enabled the production of organic residues that we analysed by means of infrared spectroscopy and by very high resolution mass spectrometry to study their chemical composition and their high molecular diversity, including the presence of hexamethylenetetramine and its derivatives. Results. We find that the accumulated irradiation dose plays a role in determining the composition of the residue. Conclusions. Based on the laboratory doses, we estimate the astrophysical timescales to be short enough to induce an efficient formation of organic refractory materials at the surface of icy bodies in the outer Solar System.

A perspective on the use of ammonia as a clean fuel: Challenges and solutions

A perspective on the use of ammonia as a clean fuel: Challenges and solutions