Influence Of Ammonia Concentration Research Articles

Studies of the diluent, temperature and pressure effect on the lower and upper flammability limits of ammonia in air

Ammonia safety and environmental protection research forms the basis for its role as a clean energy carrier. In this work, an experimental study was conducted in this work to analyze the effect of different inhibitors (nitrogen, argon and water vapor) on the flammability limits (FLs) of ammonia at elevated temperatures and pressures. In addition, the influence of diluents on the compositions and flame temperature changes was evaluated, and the temperature sensitivity coefficients of the elementary reactions and the ROP of free radicals and partial products at the FL concentrations were analyzed. The findings indicated that water vapor provided the strongest flame retardant effect on ammonia in three inhibitors. Within a certain temperature and pressure range, the FLs of ammonia in ammonia/diluent/air can be predicted using the extended Le Chatelier equation. The flame temperature decreased at the lower flammability limit (LFL) concentrations and increased at the upper flammability limit (UFL) concentrations of ammonia with increasing initial pressure. As the initial temperature increases, the flame temperature decreases during ammonia combustion. The influence of ammonia concentration on flame temperature is greater than that of diluents dilution. The elementary reactions H+O2<=>O+OH (R1) and NH2+NO<=>NNH+OH (R82) were the primary reactions that increased the flame temperature at the FL ammonia concentrations in ammonia/diluent/air. Conversely, NH2+NO<=>N2+H2O (R80) and H+O2(+M)<=>HO2(+M)(R15) were the main reactions that decreased the flame temperature. H, OH and NH2 radicals played a crucial role in the combustion reaction process at ammonia FL concentrations. At the LFL concentrations of ammonia, the molar fraction of the OH radical showed the greatest variation, while at the UFL concentrations of ammonia it was NH2 radical. The elementary reaction NH3+OH<=>NH2+H2O (R158) was the primary reaction that consumed OH radical and promoted the formation of NH2 radical. Free radical concentrations decreased with increasing pressure and temperature, while the change rate of free radical ROP accelerated with increasing pressure. In addition to nitrogen and water, the partial products were mainly nitric oxide at the LFL concentrations, while at the UFL concentrations were mainly hydrogen.

Influence of Ammonia Concentration on Solvay Soda Process Parameters and Associated Environmental and Energetic Effects

Modifying the absorption process in soda production by the Solvay method requires performing many calculations and determining a new equilibrium process. An increase in ammonia concentration in the reaction solution causes kinetic changes in equilibrium. Changes to the Solvay soda production technology were determined using chemical and instrumental analysis methods. A modification of the process in the form of SAB was introduced. Information allowing the design of an additional absorber and its location in the network of technological devices was presented in the form of parameters using typical chemical engineering assumptions. Spectroscopic and electrochemical techniques were used for this purpose. The increase in total alkalinity due to the addition of ammonia to 135 mmol·20 cm−3 resulted in cooling savings of about 152.4 MJ·Mg−1 of soda. The ammonia desorption rate and process energy parameters were determined for the new system. The temperature requirements for the carbonation column were defined, and in particular, a technique was developed to minimize the cooling of the lower part of the reactor, which reduces the consumption of process energy. Emissions of CO2 were reduced from 11.70 to 7.85% and NH3 from 5.52 to 4.89% in exhaust gases from the carbonation column.

Influence of ammonia concentration on the structural, composition and optical properties of CdZnS thin films

This paper is a systematic study on the effects of ammonia concentration on the morphology, structure, atomic percentage of major elements and optical properties of chemical bath deposition(CBD) Sulfur-zinc-cadmium (CdZnS) semiconductor thin films.By using Ultrahigh-Resolution Scanning Microscope (SEM) and when the ammonia concentration is 0.4 M, 0.5 M and 0.6 M, The CdZnS nanoparticles on the surface of the thin film, it is observed, exhibit better compactness and uniformity and the pores on it are less. With the increase of ammonia concentration, as it is shown in EDS, the content ratio of Zn to Cd in the thin films increased slightly at first and then decrease gradually. X-ray diffraction (XRD) studies show that the crystal structure of the thin film is always hexagonal phase with increasing ammonia concentration, and the crystallinity of the film is better with higher concentration of ammonia. A research is carried out with spectrophotometer on the optical properties of the thin film, and the results show that the highest transmittance of the sample is above 85%. With the increase of ammonia concentration, it is also found, the trend of the optical band gap of the thin film is consistent with the trend of the zinc content in the EDS measurement.

The consequences of niche and physiological differentiation of archaeal and bacterial ammonia oxidisers for nitrous oxide emissions

High and low rates of ammonium supply are believed to favour ammonia-oxidising bacteria (AOB) and archaea (AOA), respectively. Although their contrasting affinities for ammonium are suggested to account for these differences, the influence of ammonia concentration on AOA and AOB has not been tested under environmental conditions. In addition, while both AOB and AOA contribute to nitrous oxide (N2O) emissions from soil, N2O yields (N2O–N produced per NO2−–N generated from ammonia oxidation) of AOA are lower, suggesting lower emissions when AOA dominate ammonia oxidation. This study tested the hypothesis that ammonium supplied continuously at low rates is preferentially oxidised by AOA, with lower N2O yield than expected for AOB-dominated processes. Soil microcosms were supplied with water, urea or a slow release, urea-based fertiliser and 1-octyne (inhibiting only AOB) was applied to distinguish AOA and AOB activity and associated N2O production. Low ammonium supply, from mineralisation of organic matter, or of the fertiliser, led to growth, ammonia oxidation and N2O production by AOA only, with low N2O yield. High ammonium supply, from free urea within the fertiliser or after urea addition, led to growth of both groups, but AOB-dominated ammonia oxidation was associated with twofold greater N2O yield than that dominated by AOA. This study therefore demonstrates growth of both AOA and AOB at high ammonium concentration, confirms AOA dominance during low ammonium supply and suggests that slow release or organic fertilisers potentially mitigate N2O emissions through differences in niche specialisation and N2O production mechanisms in AOA and AOB.

Influence of ammonia concentration on the microstructure, electrical and raman properties of low temperature chemical bath deposited ZnO nanorods

Nanostructured zinc oxide synthesized using an easy and low temperature chemical bath deposition method are among the most promising low cost semiconducting nanostructures investigated for a variety of applications. We successfully report the effects of ammonia solution in the growth of ZnO nanorods at a temperature of 60°C. Successive addition of ammonia altered the degree of supersaturation of the growth solution, causing a significant deviation in the morphology and crystal orientation of ZnO nanorods. Field emission scanning Electron Microscopy images revealed changes in surface morphology of ZnO nanorods with respect to addition of specific amounts of ammonia. X-ray diffraction analysis revealed wurtzite crystal structure of ZnO which was further supported by X-ray photoelectron studies, optical absorbance and Raman spectra that also revealed the existence of wurtzite ZnO. The current-voltage measurement showed the electrical properties of the synthesized ZnO nanorods. The vertically grown nanorods with flat tops, effect more rectifying Schottky contacts to be realized on comparison to needle like structures.

Sol-Gel Derived Sensitive Films for Ammonia Sensors

Sol–Gel Derived Sensitive Films for Ammonia Sensors C. Tyszkiewicz∗, P. Karasinski and R. Rogozinski Department of Optoelectronics, Silesian University of Technology, Krzywoustego 2, 44-100 Gliwice, Poland The sol–gel technology allows the preparation of silica thin films ranging in porosity from dense to highly porous films (50%). Porous silica films can function as a matrix that is able to bind the molecules of pH-sensitive indicators and therefore can be utilized as a sensitive film in construction of intensity based fibre or planar optical sensors for ammonia detection. We report the fabrication and characterization of ammonia sensitive, highly porous silica films deposited on soda-lime glass plates and doped with the bromocresole purple, and bromothymol blue molecules. In this paper we present the influence of the substrate withdrawal speed from sol on a thickness and a refractive index of the undoped silica films, as well as spectral absorbance characteristics of the doped films. An influence of ammonia concentration in air and relative humidity on a transmission of produced sensitive films is also presented.

Morphological and stoichiometric study of chemical bath deposited CdS films by varying ammonia concentration

The influence of ammonia concentration on stoichiometric, surface morphological, and optical properties of chemical bath deposited cadmium sulphide thin films has been studied systemically. Chemical bath deposition (CBD) of CdS thin films was carried out via using cadmium acetate as the cadmium ion source, thiourea as the sulphur source and ammonia as the complexing agent. Ammonia concentration was changed from 0 to 2.5 M. At ammonia concentration greater than or equal to 0.1 M and lower than 0.6 M, nanowires or flake-like structures were obtained. At ammonia concentration ranging from 0.8 to 2.0 M, uniform, dense, and continuously coated films were obtained. The energy dispersive X-ray spectroscopy (EDXS) analysis revealed that as the ammonia concentration changed from 0.1 to 2.0 M, the Cd/S ratio in the obtained film increased from 0.24 to 2.61. Not only typical cadmium-poor but also unusual sulphur deficiency phenomena were observed for CBD CdS thin films. The films deposited with ammonia concentration of 1.0 M show the highest degree of crystallinity and closest stoichiometry Cd/S≅1, and have a preferred orientation. The direct band energy gaps of as-grown films were found to be 2.23–2.77 eV. The formation mechanism of the films with various morphologies and cadmium and sulphur deficiencies are discussed.

Shape-Controlled Synthesis of Single-Crystalline CdCO3 and Corresponding Porous CdO Nanostructures

Low-dimensional single-crystalline CdCO3 nanostructures such as nanowires, nanobelts, nanorolls, and one-dimensional (1D) hierarchical structures have been synthesized through a convenient, low-temperature hydrothermal method, and the products have been characterized by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, and selected area electronic diffraction. The influences of ammonia concentration, reaction time, and temperature on the morphologies of CdCO3 have been investigated. In addition, these low-dimensional nanostructures can be transformed into oriented CdO nanoporous structures through heat treatment processing, and the corresponding shapes can be preserved completely.

Influence of ammonia concentration on anodic deposition of nickel oxide

Nickel oxide was prepared by anodic deposition in a basic solution comprising nickel chloride, ammonium chloride and ammonia. The influence of ammonia was investigated using galvanostatic reduction techniques and cyclic voltammetry (CV). It was found that the oxidization peak potentials shift positively with decreasing ammonia concentration, while the oxidization peak currents firstly increase with decreasing ammonia concentration and then decrease when the ammonia concentration is lower than 1.67 mol L−1. This is mainly attributed to the fact that the equilibrium concentration of Ni(OH)2(aq) varies with the ammonia concentration. A potential plateau at about 0.75 V was observed in galvanostatic reduction curves for nickel oxide, and the length of the potential plateau in solution with 1.67 mol L−1 ammonia concentration was longer than that in the other solutions, which agreed well with the CV results.

Chemistry of copper trimercaptotriazine (TMT) compounds and removal of copper from copper‐ammine species by TMT

AbstractThe acid dissociation constants of 2,4,6‐trimercaptotriazine (H3TMT) were determined by acid‐base titration and now can be employed in the preparation of complexes having specific Cu–TMT ratios. IR, EA and TGA characterized the compounds. We analyzed the relevant IR spectra and attribute 2910–2925, 3030–3250 and 3430 cm−1 to triazine ring overtone, NH stretching vibrations and water in the TMT complexes, respectively. The solubility of Cu–TMT complexes was determined with ICP‐AES. The results indicate that Cu3 (TMT)2 · 2H2O (3) is much more insoluble and more stable than Cu (H2TMT)2 (1), Cu (HTMT)·0.5H2O (2) and CuS. The extremely small value of KSP for compound 3 (2.11 × 10−46) indicates that Na3TMT is a very advantageous chelating agent in precipitating complex copper (e.g. copper‐ammine species) from industrial wastewaters. The influences of ammonia concentration, pH and settling time on the effectiveness of copper precipitation were investigated. Also, a ‘real world’ printed circuit board factory effluent initially containing 350.9 ppm of Cu was treated and it was found that more than 99.9% of the copper was removed from the solution as an insoluble compound 3. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Influence of Ammonia Concentration on Particle Size Distributions in Seeded Reaction of Hydrolysis and Condensation of Tetraethyl Orthosilicate

シリコンアルコキシドの加水分解反応を利用したシード成長において生成する粒径分布に及ぼすアンモニア濃度の影響を調べるために，アンモニア濃度0.25–1.0kmol/m3の範囲でシード成長実験を行った．高濃度の1.0kmol/m3ではシード粒子同士がわずかに凝集し，一方，低濃度の0.25kmol/m3では多数の新粒子が発生した．これに対し中間の0.5kmol/m3では，凝集や新粒子発生がほとんどないことから，シード成長には最適なアンモニア濃度が存在することがわかった．新粒子の発生原因を検討するため，シード成長中の実測pHに基づき反応中のイオン強度を算定し，高アンモニア濃度におけるイオン強度の増大が新粒子発生を抑制することを指摘した．この考察の妥当性を確認するため，電解質であるLiClまたはKClをシード成長溶液に添加する実験も行った．いずれの電解質でもサブmol/m3の添加で新粒子発生数が大幅に減少した．

Influence of ammonia concentration on thermophilic anaerobic digestion of cattle manure in upflow anaerobic sludge blanket (UASB) reactors

Ammonia concentrations of 5 g N/litre or more inhibited thermophilic anaerobic digestion of cattle manure in upflow anaerobic sludge blanket (UASB) reactors. A stable digestion of cattle manure could be maintained with ammonia concentrations up to 7 g N/litre after 6 months of operation. However, the methane yield was reduced and the concentration of volatile fatty acids increased from 1 to 3 g/litre as acetic acid, compared to controls with an ammonia concentration of 3 g N/litre. The temporary strong inhibition following a one-step increase in ammonia concentration was reduced by applying a gradual increase. The specific methanogenic activity of ammonia-inhibited reactors (7 g N/litre) with acetate or hydrogen as substrate was reduced by 72 and 56%, respectively. Tests of ammonia toxicity on the acetate- and hydrogen-utilizing populations showed a higher sensitivity of the aceticlastic compared to the hydrogenotrophic methanogens; the specific growth rate for the aceticlastic methanogens was halved at ammonia concentrations of 4 g N/litre, compared to 7·5 g N/litre for the hydrogenotrophic methanogens.

The corrosion of copper in copper (II)-Ammonium sulphate solutions: the influences of ammonia concentration, of temperature and of the substitution of sulphates by carbonates

The influence of the concentration of ammonia (4·0–6·5 mol 1 −1) and of temperature (15–45°C) on the velocity of the corrosion of copper in copper (II)-ammonium sulphate solutions containing Cu 0·5 and SO 4 1·2 mol 1 −1 was investigated by means of the rotating disc method. The following equation describes the stoichiometry of the process: Cu+Cu 2+( am) → 2 Cu +( am) Within the limits of the experimental parameters a curvilinear dependence of the corrosion rate on the square root of the disc rotation frequency was observed. Linearity was obtained in the coordinate system of the reciprocal values of those two variables, indicating an example of mixed control kinetics. The corrosion rate decreases with increase of ammonia concentration. An analysis of the experimental results leads to the conclusion that it is connected with the decrease of the velocity of the reactant. It may be connected with an increase in the size of transported copper(II)-ammine complexes, i.e. the increase in the number of ligands. The diffusion activation energy is surprisingly high and is twice the value of the activation energy for viscous flow. The analysis of the experimental results concludes that it is practically impossible to move from mixed control to either activation or diffusion control of the kinetics. An attempt was made to relate the dependence of corrosion velocities and potentials on experimental parameters to the hypothetical polarization curves of the partial cathodic and anodic reactions. Substitution of sulphates by carbonates increases the corrosion rate. It is associated with an increase in the rate coefficient of the surface reaction.