Amount Of Inert Gas Research Articles

Novel one-stage process for manufacturing 1,3-butadiene from ethanol

This paper proposes a novel process for manufacturing 1,3-butadiene from renewable bioethanol, and re-evaluates two alternative processes: one-stage (Lebedev) and two-stages (Ostromislensky). The work presents an innovative design of the one-stage process employing Hf(IV)/Zn(II) catalyst and a consistent comparison of the above processes. The analysis is based on detailed reaction kinetics and systematic process synthesis. This work is distinct from previous studies by its use of inert gas in the reactor design in order to reproduce laboratory conditions, namely low ethanol partial pressure. Methane is proposed instead of the less-efficient nitrogen. The innovative reaction system involves adiabatic radial-flow reactors hosting catalyst particles of 2 mm that ensure high efficiency and reduced pressure drop. Cryogenic distillation and DMF absorption are assessed as alternatives for butadiene separation. Original methods are developed for removing by-products and impurities. Hence, the proposed flowsheet is generic for one-stage processes. Economic analysis reveals that the compression of inert-gas rich mixtures contributes substantially to the increase in capital and operation costs. Therefore, with today’s available catalysts, the two-stage process appears more efficient than the one-stage process. To reduce this gap, a performant one-stage catalyst should show high butadiene selectivity by employing a small or no amount of inert gas.

Experience of Estimating Amount of Inert Gases in Compressed Gas Mixtures

For production planning and for mutual settlements with suppliers and customers it is important to accurately determine the amount of inert gases at all stages of the technological sequence of their extraction. Gravimetric and manometric methods are proposed for estimating the volumes of compressed gases as applied to pure gases and their mixtures. A comparative evaluation has been made of the methods proposed by various authors for estimating amounts of valuable components in compressed gas mixtures based on manometric method. A universal manometric method that allows determination of the amount of neon and helium in compressed gas mixtures with an adequate degree of accuracy has been developed. The reliability of the calculation method has been verified by comparing the calculated volumes of the inert gases with the results obtained by gravimetric method. Based on the developed method and the data on the compressibility of the mixture components, a program has been developed. Application of the developed program simplifies calculations for helium- and neon-containing mixtures.

A new type of experimentally proposed in situ heat/gas clean foam fracturing fluid system

When cold fluid is injected into low-temperature, low-pressure, low-permeability reservoirs containing wax-bearing heavy oil, cryogenic paraffin deposition and heavy oil condensation will occur, thus damaging the formation. Moreover, the formation pressure coefficient is low and the working fluid flowback efficiency is low, which affects the fracturing stimulation effect. Therefore, an in situ heat/gas clean foam fracturing fluid system is proposed. This system can ensure that conventional fracturing fluid can create fractures and carry proppant in the reservoir, generate heat in situ to avoid cold damage, reduce the viscosity, and improve the fluidity of crude oil. The in situ heat fracturing fluid generates a large amount of inert gas while generating heat, thus forming foam-like fracturing fluid, reducing fluid loss, improving proppant-carrying performance, improving gel-breaking performance, effectively improving crack conductivity, and is clean and environmentally friendly. Based on the improved existing fracturing fluid system, in this paper, a new type of in situ heat fracturing fluid system is proposed, and a system optimization evaluation is conducted through laboratory experiments according to the performance evaluation standard of water-based fracturing fluid. Compared with the traditional in situ heat fracturing fluid system, the fracturing fluid system proposed in this study generates a large amount of inert gas and form foam-like fracturing fluid, reduces fluid loss, enhances the proppant-carrying capacity and gel-breaking performance, improves crack conductivity, the gel without residue and that the gel-breaking liquid is clean and harmless.

A versatile and compact reference gas generator for calibration of ion mobility spectrometers

We developed a versatile and compact reference gas generator for the calibration of ion mobility spectrometers or other gas detection technologies. The principle is based on the use of permeation tubes or diffusion vessels. This approach allows the reference gas to be generated with very low concentrations of analytes. In contrast to most of the commercially available instruments, which dilute the complete permeation gas stream, we only used an aliquot for further dilution and the necessary quantity of inert gas can be considerably reduced. The permeation cell can be operated at elevated or reduced temperatures relative to ambient temperature. This temperature control allows the permeation rate to be adjusted depending on the volatility of the investigated substance and the membrane material used in the permeation tubes. As all connection lines and the mixing chamber after the permeation chamber are held at 70 °C, memory effects can be minimized. As a result, stable permeation rates can be rapidly achieved and the regeneration period after removing the substances from the permeation vessel significantly reduced. In this study, the analytical performance of the reference gas generator was validated using DMMP due to its importance for ion mobility measurements.

Possible origin of inert gases in hydrocarbon reservoir pools of the Zindapir Anticlinorium and its surroundings in the Middle Indus Basin, Pakistan

The natural gas in several gas fields in Pakistan is associated with varying percentages of inert gases (e.g., CO2, N2, and H2S). The heating capacity of such natural gas is measured in British thermal units (BTU) in Pakistan and is based on the combustion of the natural gases. The study area of this work belongs to the Middle Indus Basin, which also covers some parts of the Sulaiman Foldbelt and the Punjab Platform. Petroleum wells drilled in the study area contain inert gases (mostly CO2 and N2) in varying percentages, which decreases the BTU value of sweet gases and the economic value of the gas reserves.Attempts were made to analyze the varying compositions of inert gases (mostly CO2 and N2) along the deep-seated basement faults in the Zindapir Anticlinorium, eastern Sulaiman Foldbelt, but no specific relation could be established. Similarly, geothermal gradient zones were identified and the distribution of inert gases in these zones was studied, but even so, no well-established relation could be tracked. However, variations in the amounts of inert gases in the Chiltan Limestone of the Rodho Structure and the Afiband Structure point to the generation of in situ inert gases because both wells were drilled on the same anticlinorium and share the same geology, and possibly, the same source rock. Post-accumulation changes probably play an important role in the generation of in situ inert gases in varying concentrations. H2S is also present in some parts of the Indus Basin. Therefore, a brief discussion about the possible origin of the H2S is also included in this paper.

Experiment to Recover Tritium from Li-Pb Blanket and Understanding Chemistry of the Li17Pb83–H System

Various properties of Li-Pb eutectic alloys have been reported aiming at adopting the tritium breeder for the next-step fusion reactor, DEMO. Relations among several physical or chemical properties are reinvestigated here based on not only macroscopic views of the H isotope solubility in Li-Pb and the chemical activity of Li and Pb atoms in the alloy but also a microscopic view on the state of being of H and Li atoms in alloy based on the 1st principle molecular dynamic (MD) numerical calculation. The Sieverts’ constant of H dissolved in Li-Pb is closely related with the chemical activity of Li in Li-Pb. It is found that H dissolved in Li-Pb eutectic alloy has an ionic Li+-H− bond with a single Li atom independent of other Li or Pb atoms and the Li+-H− ionic bond is isolated from another Li atom surrounded by Pb ones. The isotope effect for the Sieverts’ constant is also understood in terms of the state of being of the Li+-H− bond in the alloy. The amounts of inert gases dissolved in the Li-Pb eutectic alloy are evaluated, and it is found that their solubilities are in proportion to the square of the molecular diameter which is estimated from exclusive volume of dissolved gas and consequently with the open space volume among Li-Pb atoms. Two experimental results of hydrogen isotopes recovery are introduced using a permeation window and a Li-Pb and inert gas direct contact method, and mass-transfer coefficients to correlate the overall hydrogen transfer process are determined as a function of diffusivity and flow velocity.

DEPHOSPHORIZATION OF FERROMANGANESE

Phosphorus in steelmaking processes is a harmful admixture and at every stage of the production of steel must be removed from the melt . One of the sources are ferroalloys , which are used to introduce alloying element for steel. The paper presents method of de phosphorization of high and medium carbon ferromanganese using mixture based on CaO - CaF 2 , containing in its composition CaSi and CaC 2 . The experimental heats were conducted in an induction furnace with the capacity of 20 kg, in temperature about 1450 °C. While the dephosphorizing mixture was being added, a stream of argon was being injected into the metal bath. Dephosphorization efficiency raged from 21 to 42%. Th is work has been shown the relationship between dephosphorization, and the amount of inert gas and initial concentration of phosphorus in ferromanganese.

Mechanistic Modeling of Cobalt Based Catalyst Sintering in a Fixed Bed Reactor under Different Conditions of Fischer–Tropsch Synthesis

A three-step sintering mechanism is proposed for Co-based catalysts under Fischer–Tropsch reaction conditions. This mechanism includes an intermediate formation of oxide layer on cobalt metal nanoparticles in the presence of water. The partially reversibly oxidized surface accelerates sintering by both reducing the surface energy and enhancing the diffusion rates of cobalt particles. The proposed mechanism is then employed for a fixed-bed unsteady state reactor. The effect of particle growth on the catalytic activity was analyzed within a diverse range of operating conditions (syngas ratio = 1.5–4, water co-feed ratio = 0–6, inert co-feed ratio = 0–6). It is found that, at the same gas space velocity, sintering proceeds faster at higher H2/CO ratios. At the same initial conversion, a low H2/CO syngas ratio increases sintering severity, i.e., catalyst deactivation due to the crystallite growth, as it brings about higher relative water partial pressure. Dilution of syngas with different amounts of inert gas does not affect the cobalt sintering rate. Cobalt sintering proceeds more rapidly if water is co-fed during the reaction.

Influence of Gravity and Ambient Pressure on Combustion and Flammability of n-Heptane and 1-Propanol Droplets in Air-Diluent Environments

Reduced gravity and normal gravity combustion experiments were performed with individual fiber-supported n-heptane and 1-propanol droplets with initial diameters in the 1-mm size range. Experiments were performed with air-inert mixtures at 0.1 MPa or 0.3 MPa and about 298 K, where helium, carbon dioxide, or xenon were separately used as inerts. The amount of inert gas required to suppress combustion was generally higher in reduced gravity than normal gravity, and higher mole fractions of xenon were required for suppression of combustion relative to helium or carbon dioxide. Helium was found to perform the best as a flame suppressant on a mass basis, i.e., mass fractions of helium required to suppress combustion were significantly smaller than for the other inert gases. Increasing the amount of inert gas generally decreased burning rates. Results indicate that ambient gas transport properties and the fuel type play an important role in determining flammability and combustion behaviors of the droplets. Comparison with cup burner results also show that gas transport properties influence flammabilities much more strongly for droplets than for cup burners.

Peculiarities of the subchloride metallurgy of titanium

Conditions of the gas-phase reactions of reducing titanium tetrachloride to metal with aluminum subchloride are investigated in the approximation of equilibrium thermodynamics. It is established that the reduction process has a threshold character by three parameters: temperature, the amount of subchloride, and the radius of the metallic surface. Above the threshold values that were found, these parameters, along with the amount of inert gas in the gas mixture, unambiguously determine the yield of titanium and its aluminide. The conditions for obtaining aluminum-free titanium are determined. A comparative analysis of the advantages and disadvantages of subchloride and vapor-phase metallothermic methods of reducing titanium is carried out.

PROPANOL DROPLET FLAMMABILITY AND COMBUSTION IN AIR-DILUENT ENVIRONMENTS UNDER NORMAL AND REDUCED GRAVITY

Reduced gravity and normal gravity combustion experiments were performed with individual fiber-supported propanol droplets with initial diameters that were typically in the 1.2 to 1.3 mm range. The environment was composed of an air-inert mixture at 0.1 MPa and about 298 K, where helium, carbon dioxide and xenon were separately used as inerts. In the experiments, the amount of inert gas in the environment was progressively increased until droplets could no longer be ignited. Droplet ignitability depended on the gravitational level as well as the inert gas in the environment. In general, the amount of inert gas required to suppress combustion was higher in reduced gravity than normal gravity. Use of xenon required significantly higher mole fractions for suppression of combustion relative to helium or carbon dioxide. Increasing the amount of inert gas generally decreased burning rates and increased flame standoff ratios. The data indicate that ambient gas transport properties play an important role in determining flammability and combustion behaviors of droplets.

Mold-Filling Characteristics of AZ91 Magnesium Alloy in the Low-Pressure Expendable Pattern Casting Process

The magnesium (Mg) alloy low-pressure expendable pattern casting (EPC) process is a newly developed casting technique combining the advantages of both EPC and low-pressure casting. In this article, metal filling and the effect of the flow quantity of inert gas on the filling rate in the low-pressure EPC process are investigated. The results showed that the molten Mg alloy filled the mold cavity with a convex front laminar flow and the metal-filling rate increased significantly with increasing flow quantity when flow quantity was below a critical value. However, once the flow quantity exceeded a critical value, the filling rate increased slightly. The influence of the flow quantity of inert gas on melt-filling rate reveals that the mold fill is controlled by flow quantity for a lower filling rate, and, subsequently, controlled by the evaporation of polystyrene and the evaporation products for higher metal velocity. Meanwhile, the experimental results showed that the melt-filling rate significantly affected the flow profile, and the filling procedure for the Mg alloy in the low-pressure EPC process. A slower melt-filling rate could lead to misrun defects, whereas a higher filling rate results in folds, blisters, and porosity. The optimized filling rate with Mg alloy casting is 140 to 170 mm/s in low-pressure EPC.

Maximum conversion in presence of inert gas

In the case of equilibrium reactions in gaseous phase or solid-gas phases, that takes place in the presence of inert gas and under isothermal-isobaric or isothermal-isochoric conditions, the conversion is maximum, if reactants are stoichiometrically mixed and the amount of inert gas is constant. A particular case is represented by the oxidation reactions with air, in which nitrogen is the inert gas, 2 NO + O 2 + 4 N 2 ↔ 2 NO 2 + 4 N 2 , and certain reactions in which it is both inert gas and product, 4 NH 3 + 3 O 2 + 12 N 2 ↔ 2 N 2 + 6 H 2 O + 12 N 2 We took into consideration a number of 20 oxidation reactions with air, many of them having practical importance. Calculations made by using Lagrange's method of undetermined multipliers, when reactions take place under isothermal-isobaric or isothermal-isochoric conditions, point out that, for high values of equilibrium constants (K x → ∞, K c → ∞), the conversion is maximum in case of stoichiometric mixture. On the other hand, for medium and low values of the equlibrium constants, conversion is maximum if the added amount of air is less than the amount corresponding to a stoichiometric mixture.

A new combustion concept for clean diesel system with DPNR

This article presents a new combustion concept that enables effective after-treatment. A sufficient quantity of inert gas lowers the combustion temperature and therefore suppresses soot formation. Smokeless and yet stable rich combustion can be achieved in the advanced injection timing and high EGR rate region. In the European transient test mode, this combustion concept enables a diesel engine to maintain a high catalyst bed temperature with a minor fuel penalty and to drastically reduce NOx and PM emissions.

Physical modelling of a sidewall‐blowing converter

The flow patterns of the chromium converter (CRC) during top and side‐wall blowing have been studied using a physical model (1:7). The dynamic similarity between model and real system has been determined by the Froude number and specific mixing energy. This ensures reliability of model studies, although some simplifications have had to made. The model tests demonstrated clearly that mixing was not sufficient to form slag‐steel emulsion by the old blowing practice. Furthermore, the mixing time was 27% shorter in the model by the new practice according to conductivity measurements. Calculations and process tests indicated that back‐attack diminished and penetration of gas jets to the steel bath increased. The blowing practice of the CRC has been changed, based on the model tests and semi‐empirical calculations. The portion and amount of inert gas from the sidewall tuyeres have been increased and oxygen is brought mainly with a lance to liquid steel. In the previous practice, minor penetration of gas jets and hot reactive oxide mass effected an uneven wearing profile of tuyere area. The addition of an inert gas volume rate prevented forming of ‘hot spot’ areas near uyeres. As a result of practice change, the lining life in the tuyere area has increased by 12%. The processing time has decreased by 13% because of a more effective mixing and increased oxygen flowrate.

Revised emergency vacuum relief device sizing for atmospheric distillation systems

Abstract Conventional vacuum relief methodologies are usually protective responses; that is, they accomplish their purpose by substitution of an inert gas (usually nitrogen) for the process gases removed by an external vacuum source, or for condensable vapour collapsed by an internal process mechanism (e.g. condensation). While this approach is theoretically possible for all potential vacuum scenarios, it becomes practically impossible to implement for installations where a rapid phase change can impart near-instantaneous system pressure reductions. The procedure outlined in this paper takes a preventive approach: eliminate the source of vacuum generation before the safe lower system pressure limit is reached. For distillation and other refluxing systems, this vacuum source is usually the main overhead condenser, which is designed to collapse large volumes of condensable vapour. To eliminate the vacuum source requires elimination of the system's ability to rapidly condense vapour. This goal is accomplished by introduction of inert gas directly into the condensing system to ‘blanket’ the heat transfer surface and stop condensation. The procedure determines the rate, amount and location for introduction of inert gas. The required design data include: (i) system starting pressure, (ii) maximum allowable system vacuum, (iii) volume of the condensing system, and (iv) normal system condensing rate. By determining the rate at which the condenser removes vapour volume from the system, and designing an inert gas delivery system to meet or exceed this rate, the vacuum generation potential of the system is effectively eliminated using a much smaller quantity of inert gas than with the more traditional volume substitution methods.

Kinetic theory based nonlinear treatment for motions of a binary gas mixture involving slightly strong evaporation and condensation processes ? A system of macroscopic equations, the boundary conditions and the Knudsen-layer corrections

An analysis for the steady behaviour of a binary mixture of a vapour and an inert gas in a general domain has been carried out based on the Boltzmann equation of BGK type subject to the diffusive boundary condition under the following situations: i) the amount of inert gas is dense enough so that the mean free path of the inert gas molecules is small compared with the characteristic length of the system. However, the collision between the molecules of the vapour and those of the inert gas is so frequent that the mean free path of the vapour molecules is comparable to that of the inert gas molecules; hence, the mean free path of the vapour molecules is adopted for the definition of the Knudsen number of the system, which is small compared with unity; and ii) the deviation of the system from a reference stationary equilibrium state is small, but its magnitude is of the order of the Knudsen number. In this case, the problem becomes nonlinear, and the kinetic equation and its boundary condition cannot be linearized. Since the Mach number of the system is a measure of the degree of the deviation of the system and is proportional to the Knudsen number times the Reynolds number, the Reynolds number in the present case is finite. By the singular perturbation method, we have derived, as an asymptotic solution to the Boltzmann equation of BGK type for small Knudsen numbers, the macroscopic equations governing the fluid dynamic quantities and the appropriate boundary conditions for them at the interface together with the Knudsen-layer corrections near the interface up to the second order of approximation in the analysis. The equations obtained are essentially of Navier-Stokes type at each order; the macroscopic boundary conditions are those of no slip and no jump at the first order of approximation but, at the second order, they are slip and jump conditions and comprise several terms, each of which is expressed by one of the set of solutions of the macroscopic equations at the previous approximation times aconstant; the Knudsen-layer corrections are of the same type as the boundary conditions with theconstant replaced by a rapidly decreasingfunction of the distance from the interface. Theseconstants andfunctions are universal in the sense that they are totally independent of the geometry of the problems. The derived system of the macroscopic equations and boundary conditions makes possible at the level of ordinary fluid dynamics the treatment of various flow problems of a binary gas mixture, giving an adequate description of the behaviour of the mixture and its component gases for moderate values of the concentration of inert gas. The vapour-mass transfer for these values of the concentration is quite small because it is governed by the diffusional ability of the vapour through the inert gas.

Analytical method for inert gases in alloy powders

A vacuum fusion technique has been developed for quantifying the argon and helium contents of metal powders. Samples are melted in a high vacuum system of known volume and the released gas is passed through a fixed pinhole leak and quantitatively measured with a previously calibrated quadrupole mass spectrometer. The amounts of inert gases are then calculated from the ideal gas law. The detection limit for both argon and helium in samples of about 0.15 g is 0.05 at.ppm. Measurements for powders with concentrations between 0.5 and 10 at.ppm are repeatable within ±5%. The mass spectrometer is equipped with an electron multiplier, thus providing greater sensitivity and enabling analyses to be performed upon samples as small as 0.015 g. This economical analytical method is suitable for both research and process-quality control applications.

A Nonlinear Analysis on the Behavior of a Small Amount of Inert Gas during Evaporation and Condensation of a Vapor between the Parallel Surfaces

The behavior of an inert gas contained slightly in a vapor is studied analytically together with the behavior of the vapor itself, when the evaporation and condensation process is taking place between the two parallel plane condensed phases. The analysis is based on a general asymptotic theory for small Knudsen numbers which has been derived systematically from the kinetic equation of B-G-K type under the diffusive boundary condition. The results obtained here are valid for finite values of the Reynolds number based on the flow due to evaporation and condensation. The inert gas, in this case, does not affect the behavior of the vapor because of its smallness in its amount, it is greatly affected by the vapor motion and exhibits strong nonlinearity in its pressure and density variations. Nonlinear effects due to the presence of the flow also manifest themselves distinctly on the temperature of the vapor. The well-known negative temperature gradient and negative mass flow phenomena are also observed.

Combustion of Stratified Methane/Air Layers

Abstract Combustion of horizontally layered methane/air mixtures have been studied. Methane-diluted with Ar, or N2, or CO2—and air, initially separated by a thin plate, form a flat combustible layer only by interdiffusional mixing upon withdrawal of the plate. Simultaneous line ignition was made at one side of the layer for the whole range of the combustible mixture ratio. The ignition took place at only a stoichiometric position and failed elsewhere. Addition of the inert gases caused serious ignition delay. The induction distance depends primarily on the amount of inert gases in the fuel. The flame speed first accelerated and, as the flame traveled way off the igniter wall it drastically decreased down to 1.5 times the burning velocity of the corresponding stoichiometric premixed flame. It has been found that a travel distance more than 5 cm is required for the flame to establish steady propagation.