Stability Of Condensate Research Articles

Simulation analysis of stripping fractionation process of gas condensate treatment and practical application

Stripping fractionation is posed an advancing and promising process for gas condensate stabilization and desulfurization. Most of H2S, light mercaptan and part of organic sulfur are removed while the condensate is stabilized in same column, reducing the capital investment for conventional condensate treatment process. In terms of this newly designed process, two approaches for raw liquid inlet to a stabilizer were considered, i.e. split-flow and straight-through for comparison purpose between them and their respective scope of application. The whole process was simulated by ASPEN HYSYS software. According to the simulation results in conjunction with the running experience in a natural gas processing plant in Mary, Turkmenistan, the priority of this new process in the field of condensate treatment has been demonstrated, meeting the requirement of Reid Vapour Pressure (RVP) and sulfur concentration restriction. Finally, the spilt-flow approach with the optimal split ratio range from 10% to 30%, was inherently beneficial related to economic aspects in large processing scale case. Also, the economical analysis of split-flow method was involved in detail.

Temperature effects in excitonic condensation driven by the lattice distortion

AbstractThe stability of the excitonic condensation at low temperature driven by a coupling of electrons to vibrational degrees of freedom in a semimetal two‐dimensional electronic system is discussed. In the framework of the unrestricted Hartree–Fock approximation, we derive a set of equations to determine both the excitonic condensate order parameter and lattice displacement self‐consistently. By lowering the temperature, we find a semimetal–insulator transition in the system if the coupling is large enough. The insulating state typifies an excitonic condensation accompanied by a finite lattice distortion. On increasing temperature, both excitonic condensate order parameter and the lattice distortion decrease and then disappear in the same manner. Microscopic analysis in momentum space strongly specifies that the excitonic condensate driven by the lattice distortion favors the BCS type.

Stability of a Bose-Einstein condensate in a driven optical lattice: Crossover between weak and tight transverse confinement

We explore the effect of transverse confinement on the stability of a Bose-Einstein condensate (BEC) loaded in a shaken one-dimensional or two-dimensional square lattice. We calculate the decay rate from two-particle collisions. We predict that if the transverse confinement exceeds a critical value, then, for appropriate shaking frequencies, the condensate is stable against scattering into transverse directions.

Toward an intelligent approach for H2S content and vapor pressure of sour condensate of south pars natural gas processing plant

In this study, artificial neural network is employed to develop a model to predict process output variables of an industrial condensate stabilization plant. The developed model is evaluated by process operating data of south pars natural gas processing plant located Asaluyeh/Iran. A large dataset of 4 variables consisting of temperature and pressure of the stabilization column in addition to Ried Vapor Pressure (RVP) and H2S content of the processed condensate is utilized to train the network. In order to determine the optimized topology and decision parameters of the network, the values of Mean Square Error (MSE), Mean Absolute Error (MAE) and the coefficient of determination (R2) are minimized by the method of trial and error. Since precision of ANN model is dependent on the amount of training data used, the extensive set of samples applied in this work can offer accurate reliable predictions. Model output is compared to actual data of the plant and the values of Average Absolute Deviation percent (ADD%) are reported as 1.6 for RVP and 3.8 for H2S concentration.

Stability of self-gravitating Bose-Einstein condensates

We study the ground state and the first three radially excited states of a self-gravitating Bose-Einstein- Condensate with respect to the influence of two external parameters, the total mass and the strength of interactions between particles. For this we use the so-called Gross-Pitaevskii-Newton system. In this context we especially determine the case of very high total masses where the ground state solutions of the Gross-Pitaevskii- Newton system can be approximated with the Thomas-Fermi limit. Furthermore, stability properties of the computed radially excited states are examined by applying arguments of the catastrophe theory.

Prethermal Floquet Steady States and Instabilities in the Periodically Driven, Weakly Interacting Bose-Hubbard Model

We explore prethermal Floquet steady states and instabilities of the weakly interacting two-dimensional Bose-Hubbard model subject to periodic driving. We develop a description of the nonequilibrium dynamics, at arbitrary drive strength and frequency, using a weak-coupling conserving approximation. We establish the regimes in which conventional (zero-momentum) and unconventional [(π,π)-momentum] condensates are stable on intermediate time scales. We find that condensate stability is enhanced by increasing the drive strength, because this decreases the bandwidth of quasiparticle excitations and thus impedes resonant absorption and heating. Our results are directly relevant to a number of current experiments with ultracold bosons.

Stability and stabilization of unstable condensates

It is possible to condense a macroscopic number of bosons into a single mode. Adding interactions the question arises whether the condensate is stable. For repulsive interaction the answer is positive with regard to the ground-state, but what about a condensation in an excited mode? We discuss some results that have been obtained for a 2-mode bosonic Josephson junction, and for a 3-mode minimal-model of a superfluid circuit. Additionally, we mention the possibility to stabilize an unstable condensate by introducing periodic or noisy driving into the system: this is due to the Kapitza and the Zeno effects.

Dynamical stability of dipolar Bose-Einstein condensates with temporal modulation of the s-wave scattering length.

We study the stabilization properties of dipolar Bose-Einstein condensate by temporal modulation of short-range two-body interaction. Through both analytical and numerical methods, we analyze the mean-field Gross-Pitaevskii equation with short-range two-body and long-range, nonlocal, dipolar interaction terms. We derive the equation of motion and effective potential of the dipolar condensate by variational method. We show that there is an enhancement of the condensate stability due to the inclusion of dipolar interaction in addition to the two-body contact interaction. We also show that the stability of the dipolar condensate increases in the presence of time varying two-body contact interaction; the temporal modification of the contact interaction prevents the collapse of dipolar Bose-Einstein condensate. Finally we confirm the semi-analytical prediction through the direct numerical simulations of the governing equation.

English

English

Process simulation and assessment of a back-up condensate stabilization unit

A simulation was conducted using Aspen HYSYS® software for an industrial scale condensate stabilization unit and the results of the product composition from the simulation were compared with the plant data. The results were also compared to the results obtained using PRO/II software. The results show that the simulation is in good agreement with the plant data, especially for medium range hydrocarbons. For hydrocarbons lighter than C5, the simulation results over predict the plant data while for hydrocarbons heavier than C9 this trend is reversed. The influences of steam temperature and pressure, as well as feed conditions (flow rate, temperature and pressure) for the product specification (RVP and sulphur content) were also investigated. It was reported that the operating conditions gave rise to the production of off-specification condensate and it was also found that the unit could be utilized within 40–110% of its normal throughput without altering equipment sizing and by the operating parameters.

Modifying effect of tungsten on vacuum condensates of iron

Laws of the structure formation, as well as the strength properties and thermal stability of vacuum condensates of the Fe-W system have been studied. It has been found that the alloying of iron foils with tungsten to 1 at % makes it possible to disperse the grained structure of the condensates to nanometric dimensionality and to markedly enhance their strength properties and recrystallization temperature. Thus, the foils containing ∼0.8% tungsten and grains of about 50 nm in size exhibit the hardness 5.5 GPa and recrystallization temperature 800°C. These results can be used to devise compositions of the steels designed for subsequently obtaining high-strength and thermostable nanostructural states.

Transverse collisional instabilities of a Bose-Einstein condensate in a driven one-dimensional lattice

Motivated by recent experiments, we analyse the stability of a three-dimensional Bose-Einstein condensate (BEC) loaded in a periodically driven one-dimensional optical lattice. Such periodically driven systems do not have a thermodynamic ground state, but may have a long-lived steady state which is an eigenstate of a "Floquet Hamiltonian". We explore collisional instabilities of the Floquet ground state which transfer energy into the transverse modes. We calculate decay rates, finding that the lifetime scales as the inverse square of the scattering length and inverse of the peak three- dimensional density. These rates can be controlled by adding additional transverse potentials.

Stability of binary condensates with spatial modulations of quintic nonlinearities in optical lattices

The stability and collective excitations of binary Bose–Einstein condensates with cubic and quintic nonlinearities in variable anharmonic optical lattices are investigated. By using the variational approach, the influences of the quintic nonlinearities and the shape of the external potential on the stability are discussed in details. It is found that the quintic intraspecies and interspecies interatomic interactions profoundly affect the stability criterion and collective excitations of the system. The shape dependent potential form that characterizes the optical lattice deeply alters the stability regions. Direct numerical simulations of the mean-field coupled Gross–Pitaevskii equation describing the system agree well with the analytical predictions.

Stability and spatial coherence of nonresonantly pumped exciton-polariton condensates

We investigate the stability and coherence properties of one-dimensional exciton-polariton condensates under nonresonant pumping. We model the condensate dynamics using the open-dissipative Gross-Pitaevskii equation. In the case of spatially homogeneous pumping, we find that the instability of the steady state leads to significant eduction of the coherence length. We consider two effects that can lead to the stabilization of the steady state, i.e. the polariton energy relaxation and the influence of an inhomogeneous pumping profile. We find that, while the former has little effect on the stability, the latter is very effective in stabilizing the condensate which results in a large coherence length.

Debottlenecking of condensate stabilization unit in a gas refinery

The increase in throughput or reduction in the operational costs is the common example of change in production criteria in retrofit projects. In this study, the condensate stabilization unit of a gas refinery, which is one of the most energy consuming units in natural gas refineries, is considered for analysis and retrofitting study. This unit comprises of a two-stage compressor and a side-reboiler associated with the stabilization column that uses HP steam as hot utility. It is shown that by applying the optimum pressure drops method for debottlenecking of this unit, after 20% increase in throughput, utility consumption can be maintained at existing level, if 1554 m2 of additional heat transfer area is installed.

Predicting structural change of lignin macromolecules before and after heat treatment using the pyrolysis-GC/MS technique

Milled wood lignin extracted from poplar wood was subjected to a heat treatment in the temperature range of 150–300°C at 50°C intervals. The results of several chemical characterizations (proton nuclear magnetic resonance (1H NMR), derivatization followed by reductive cleavage (DFRC), elemental composition) and thermogravimetric analysis revealed that cleavage of the β-O-4 linkage accompanied by condensation and a charring reaction occurred during the heat treatment, leading to the formation of a thermally stabilized lignin at 300°C (300-L) with enrichment of the condensed carbon–carbon bond. Pyrolysis-GC/MS data showed that 41 kinds of pyrolysis products, mainly composed of monomeric phenols, were released from the heat-treated lignin, and the yield of such products was significantly dependent on the lignin sample and the pyrolysis temperature. The maximum yield of total pyrolysis products from 300-L was obtained at a pyrolysis temperature of 600°C, whereas the maximum yield from the other samples was observed at 500°C due to the high thermal stability and degree of condensation of 300-L. Moreover, the pyrolysis-GC/MS results suggested that the side chain in the phenol skeleton (C3C6) was considerably degraded at 300°C, resulting in the accumulation of a C6/C1C6/C2C6-type lignin structure in the 300-L sample. With an increase in the pyrolysis temperature, the syringyl/guaiacyl (S/G) ratio of all lignin samples, as determined from the pyrolysis products, constantly decreased due to an increase in G-type compounds released in the high temperature region.

Stability of a Floquet Bose-Einstein condensate in a one-dimensional optical lattice

Motivated by recent experimental observations (C.V. Parker {\it et al.}, Nature Physics, {\bf 9}, 769 (2013)), we analyze the stability of a Bose-Einstein condensate (BEC) in a one-dimensional lattice subjected to periodic shaking. In such a system there is no thermodynamic ground state, but there may be a long-lived steady-state, described as an eigenstate of a "Floquet Hamiltonian". We calculate how scattering processes lead to a decay of the Floquet state. We map out the phase diagram of the system and find regions where the BEC is stable and regions where the BEC is unstable against atomic collisions. We show that Parker et al. perform their experiment in the stable region, which accounts for the long life-time of the condensate ($\sim$ 1 second). We also estimate the scattering rate of the bosons in the region where the BEC is unstable.

Stability of chromomagnetic condensation and mass generation for confinement in SU(2) Yang-Mills theory

We show that the Nielsen-Olesen instability of the Savvidy vacuum with a homogeneous chromomagnetic condensation disappears in the framework of the functional renormalization group. This result follows from our observations: (i) the vanishing imaginary part of the effective average action is realized for arbitrary infrared cutoff as a novel fixed point solution of the flow equation for the complex-valued effective average action and (ii) an approximate analytical solution for the effective average action is obtained without the pure imaginary part for large infrared cutoff. This result suggests that there exists a physical mechanism for maintaining the stability or staying on the fixed point even for sufficiently small infrared cutoff. We argue that dynamical gluon mass generation (related to two-gluon bound states identified with glueballs) occurs due to the Becchi-Rouet-Stora-Tyutin-invariant vacuum condensate of mass dimension two without causing instability.

Selective generation of ultracold high-density 1s orthoexcitons in Cu_2O with phase-modulated pulse using acousto-optic programmable filter

Ultracold and high-density 1s orthoexcitons in semiconductor cuprous oxide are prepared via resonant two-photon absorption of a phase-tailored femtosecond pulse, by utilizing an acousto-optic programmable dispersive filter. The stability of the quantum degenerate exciton gas is studied using excitonic Lyman spectroscopy. A density of 10(16) cm(-3) is realized without creating hot carriers, and the Lyman spectrum remains unchanged at this density. This result assures the stability of a spontaneous Bose-Einstein condensate of excitons at sub-Kelvin temperatures.

Theoretical and experimental determination of initial reservoir fluid in a lean gas condensate reservoir

Abstract In this work, a new theoretical and experimental method has been proposed to obtain initial reservoir fluid from well head separator samples in a depleted lean gas condensate reservoir. Condensate stabilization technique (CST) is a new recombination method based on simultaneous matching of dew point pressure and gas condensate ratio of initial reservoir fluid. The proposed method is applied to a real lean gas condensate reservoir in Iran, namely Jahroom. The modified Esmaeilzadeh–Roshanfekr equation of state and the Genetic Algorithm in MATLAB environment are used to simulate the CST method. The reservoir depletion process has been simulated by the constant volume depletion test. For nine pressure steps in the CVD test the proposed method was applied on separator samples. The average absolute deviation for composition of the recombined samples was found to be less than 3.5%. The proposed method was also experimentally checked by applying on the Jahroom separator samples. The experimental results show that the absolute deviation of 3.5% for the gas–condensate ratio (GCR) and 1.72% for the dew point pressure are achieved. Additionally, the average absolute deviation for composition of the recombined sample was found to be 4%. The results of calculation and experiment show that the proposed recombination method can produce a fluid with a similar phase behavior of initial reservoir fluid with an acceptable accuracy.