Zeolite-based separation and production of branched hydrocarbons

Separation and selective production of branched paraffins are among the most important and still challenging processes in the oil and gas industry. Addition of branched hydrocarbons can increase the octane number of a fuel without causing additional environmental concerns. Conversion of linear hydrocarbons into branched ones also improves the performance of lubricants at low temperatures. Zeolites are commonly used for separation of branched hydrocarbons and selective conversion of linear long chain hydrocarbons into shorter branched ones...Engineering Thermodynamic

Investigation of the effects of drag reducing polymers on stratified flows

According to the increasing distance between the processing facilities and the oil and gas production sites, especially at subsea production sites (where multiphase flows commonly occur), innovative methods are demanded to help reducing the cost of multiphase flow transportation through the pipelines. In the past decades, Drag Reducing Polymers (DRPs) have been drawing attention in industry and academia. However, in these works it was predominately focused on single phase flows while limited attention was paid to multiphase flows. In order to improve the understanding of the influences of the DRPs on horizontal stratified gas-liquid flows, a conventional air-water flow loop is used in this study. The “Conductance probes method” and flow visualization with high speed camera are used to examine the morphology of the gas-liquid interface. The conductance probe sensors and required electrical circuits are built as a part of this project. The stratified flow of gas and liquid provides the most suitable flow configuration to validate the equipment which was built to measure the time variations of the liquid film height. The effects of drag reducing polymers on stratified gas-liquid flows and particularly the effects of DRPs on the interfacial phenomena as the crucial characteristics of the stratified flows are discussed in this study. Polyacrylamide with the molecular weight of 15000 kg/mol is used in this study. To get more insight on the rheological properties of polymeric solutions, the characteristics of solutions including static and dynamic surface tensions, dynamic and complex viscosities are measured. In order to find a link between these properties and the results obtained from the flow loop tests, the effects of polymer concentration on these properties are also investigated. In this research the relevance of the gas and liquid flow rates to the drag reduction phenomenon is studied. The highest drag reduction observed in this study (about 55 percent) is obtained at the greatest liquid and gas superficial velocities. The maximum drag reduction of a stratified flow is compared with the one obtained from single phase flow of water. Additionally, in this study it is tried to focus on the behavior of the interface between the gas and the liquid by adding polymers. Roll waves’ frequency, velocity and shape as well as the influences of the drag reducing polymers on the roll wave’s properties are discussed as well. Finally a model is proposed to assess the drag reduction of stratified flows as a function of the changes in liquid holdup and the interfacial properties such as disturbances and the shape of the interface.Process and EnergyMechanical, Maritime and Materials Engineerin

Computation of the heat and entropy of adsorption in proximity of inflection points

The adsorption of different heptane isomers in MFI- and MEL-type Zeolites is studied to investigate the performance of molecular simulation for computing the heat and entropy of adsorption as a function of loading. It is :shown that none of the conventional methods are capable of computing the heat or entropy of adsorption of bulky molecules such as 2,4-dimethylpentane around the inflection point of the adsorption isotherm. The "Energy Slope" method, is introduced which outperforms the present techniques at loadings near and above the inflection point. There is a quantitative agreement between the heats of adsorption computed with the energy slope method for a butane/isobutarie mixture and the ones computed by the method based on energy/particle fluctuations in the grand-canonical ensemble. This verifies that the energy slope method is a valuable and robust tool for computing the heat and entropy of adsorption for a wide range of hydrocarbon lengths and loadings

Computation of thermodynamic properties in the continuous fractional component Monte Carlo Gibbs ensemble

It is shown that ensemble averages computed in the Gibbs Ensemble with Continuous Fractional Component Monte Carlo (CFCMC GE) are different from those computed in the conventional Gibbs Ensemble (GE). However, it is possible to compute averages corresponding to the conventional GE while performing simulations in the CFCMC GE. In this way, one can benefit from the nice features of CFCMC GE (e.g. more efficient particle exchange) and at the same time compute the ensemble averages that correspond to the conventional GE. As a case study, the equilibrium pressure and densities of the systems of 256 and 512 LJ particles at different reduced temperatures ((Formula presented.)) are computed in the conventional GE and CFCMC GE. The validity of the expressions derived for computation of the thermodynamic pressure and densities corresponding to the conventional GE and computed in the CFCMC GE is examined numerically. The thermodynamic pressure in the conventional GE and CFCMC GE typically differs by at most 4%. It is shown that a very good estimate of the average pressure and densities corresponding to the conventional GE can be obtained by performing simulation in CFCMC GE and ignoring the contributions of the fractional molecule. It is also shown that the fractional molecule does not have an influence on the structure of the liquid, even for very small system sizes (e.g. 40 particles). The approach used here to compute the equilibrium pressure and densities of the conventional GE using the CFCMC GE can be easily extended to other thermodynamic properties and other ensembles.Accepted Author ManuscriptEngineering Thermodynamic

Enhancing the water capacity in Zr-based metal-organic framework for heat pump and atmospheric water generator applications

\u3cp\u3eAccording to the European Commission, in 2016 the residential sector represented 25.4% of the final energy consumption. Heating and cooling in EU households account for 69.1% of the total energy consumption. The fraction of 84% for heating and cooling is still generated from fossil fuels, and only 16% is generated from renewable energy. To decrease carbon dioxide emissions of fossil fuel consumption, it is crucial to find alternatives to supply the heating and cooling demand. Alternatives such as adsorption-based heat pumps and desiccant cooling systems are receiving much attention because of their moderate energy consumption. These systems are based on the energetic exchange during the adsorption/desorption of working fluids. In this work, we combined experiments and simulations to evaluate the viability of several zeolites and MOFs with water for cooling systems applications. We combined the study of adsorption mechanisms and the dynamics of water inside the pores of the structures, thereby obtaining an overall understanding of the working pair. We found that the Al content in FAU-topology zeolites is a key factor for an efficient process. We also identify ZJNU-30 metal-organic framework as a suitable candidate for cooling applications because of its outstanding water capacity, cooling capacity, and coefficient of performance.\u3c/p\u3

Chemical potentials of water, methanol, carbon dioxide and hydrogen sulphide at low temperatures using continuous fractional component Gibbs ensemble Monte Carlo

Chemical potentials of coexisting gas and liquid phases for water, methanol, hydrogen sulphide and carbon dioxide for the temperature range (Formula presented.) K to (Formula presented.) K are computed using two different methodologies: (1) Widom’s test particle insertion (WTPI) method in the conventional Gibbs Ensemble (GE), and (2) the Continuous Fractional Component Gibbs Ensemble Monte Carlo (CFCGE MC) method. It is shown that the WTPI method fails to accurately compute the chemical potentials of water and methanol in the liquid phase at low temperatures, while accurate chemical potentials in the liquid phase are computed using CFCGE MC method. For the CFCGE MC method, the statistical uncertainty for computed chemical potentials of water and methanol in the liquid phase are considerably smaller compared to the WTPI method. For the water models considered in this study (SPC, TIP3P-EW, TIP4P-EW, TIP5P-EW), computed excess chemical potentials based on three-site models are in better agreement with the chemical potentials computed from an empirical equation of state from the NIST database. For water, orientational biasing is applied during test particle insertion to check whether certain orientations of test particle are energetically unfavourable. A two-dimensional Overlapping Distribution Method (ODM) in the NVT ensemble is derived for this purpose. It is shown that failure of the WTPI method for systems with a strong hydrogen bonding network does not depend on orientation of the test molecule in that system. For all systems in this study, the WTPI method breaks down when the void fraction of the system drops below approximately 0.50.Engineering Thermodynamic