Polymeric membranes for the oxygen enrichment of air in sulfur recovery units: Prevention of catalyst deactivation through BTX reduction

Shooshtari Seyed Heydar Rajaee,Bastani Kiarash,Eslampanah Hamidreza 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.12

The modified Claus process is one of the most commonly used methods for hydrogen sulfide conversion into sulfur. However, one of the problems of this unit is the presence of benzene, toluene, and xylene (BTX) compounds at the inlet of the catalytic reactors that can deactivate the catalyst and decrease the efficiency of the sulfur recovery unit. One of the methods of BTX destruction in a furnace is to increase its temperature by increasing the oxygen concentration in the inlet air. In the present work, the application of polymeric membranes for the destruction of BTX was investigated by modeling and simulating a sulfur recovery unit and a membrane unit. The numerical results obtained from the simulations were validated successfully with industrial and experimental data for both sulfur recovery and membrane units. The simulation results for an industrial case study indicate that using five PI carbon membrane units with a total area of 26.82 m2 can increase the concentration of oxygen in the inlet air to a level of 60%. In this condition, the reduction in BTX compounds can also be increased up to 59%. Furthermore, for two-stage membrane configuration, by employing five two-stage membrane units with a total area of 58.3m2, the oxygen concentration increases to 82%, and the reduction in BTX compounds will be 75%.

A multiple scales method solution for the free and forced nonlinear transverse vibrations of rectangular plates

Shooshtari, A.,Khadem, S.E. Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.24 No.5

In this paper, first, the equations of motion for a rectangular isotropic plate have been derived. This derivation is based on the Von Karmann theory and the effects of shear deformation have been considered. Introducing an Airy stress function, the equations of motion have been transformed to a nonlinear coupled equation. Using Galerkin method, this equation has been separated into position and time functions. By means of the dimensional analysis, it is shown that the orders of magnitude for nonlinear terms are small with respect to linear terms. The Multiple Scales Method has been applied to the equation of motion in the forced vibration and free vibration cases and closed-form relations for the nonlinear natural frequencies, displacement and frequency response of the plate have been derived. The obtained results in comparison with numerical methods are in good agreements. Using the obtained relation, the effects of initial displacement, thickness and dimensions of the plate on the nonlinear natural frequencies and displacements have been investigated. These results are valid for a special range of the ratio of thickness to dimensions of the plate, which is a characteristic of the Multiple Scales Method. In the forced vibration case, the frequency response equation for the primary resonance condition is calculated and the effects of various parameters on the frequency response of system have been studied.

Pushover analysis of gabled frames with semi-rigid connections

Ahmad Shooshtari,Sina Heyrani Moghaddam,Amir R. Masoodi 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.6

The nonlinear static analysis of structure, which is under the effect of lateral loads and provides the capacity curve of the structure, is defined as a push-over analysis. Ordinarily, by using base shear and the lateral displacement of target point, the capacity curve is obtained. The speed and ease of results interpretation in this method is more than that of the NRHA responses. In this study, the nonlinear static analysis is applied on the semi-rigid steel gabled frames. It should be noted that the members of this structure are analyzed as a prismatic beam-column element in two states of semi-rigid connections and supports. The gabled frame is modeled in the OpenSees software and analyzed based on the displacement control at the target point. The lateral displacement results, calculated in the top level of columns, are reported. Furthermore, responses of the structure are obtained for various support conditions and the rigidity of nodal connections. Ultimately, the effect of semi-rigid connections and supports on the capacity and the performance point of the structure are presented in separated graphs.

Predictions of wet natural gases condensation rates via multi-component and multi-phase simulation of supersonic separators

Seyed Heydar Rajaee Shooshtari,Akbar Shahsavand 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.10

Proper correction of water and heavy hydrocarbon dew points of sweet natural gases is essential from vari-ous technical and economical standpoints. Supersonic separators (3S) are proved to be capable of achieving these taskswith maximum reliability and minimal expenses. The majority of the previous articles have focused on the flow behaviorof pure fluids across a 3S unit. Multicomponent fluid flow inside 3S accompanied with condensation phenomenonwill drastically increase the complexity of the simulation process. We tackle this issue by considering a proper com-bination of fundamental governing equations and phase equilibrium calculations to predict various operating conditionsand composition profiles across two multi-component and multi-phase 3S units. Various Iranian sweet gases are usedas real case studies to demonstrate the importance of 3S unit practical applications. Simulation results clearly illustratethe effectiveness of 3S units for faithful dehydration of various natural gases, while successfully controlling its dewpoint, suitable for any practical applications. Conventional HYSYS simulation software is used to validate the simulationresults.

Forced vibration analysis of a dam-reservoir interaction problem in frequency domain

Keivani, Amirhossein,Shooshtari, Ahmad,Sani, Ahmad Aftabi Techno-Press 2014 Coupled systems mechanics Vol.3 No.4

In this paper, the forced vibration problem of an Euler-Bernoulli beam that is joined with a semi-infinite field of a compressible fluid is considered as a boundary value problem (BVP). This BVP includes two partial differential equations (PDE) and some boundary conditions (BC), which are introduced comprehensively. After that, the closed-form solution of this fluid-structure interaction problem is obtained in the frequency domain. Some mathematical techniques are utilized, and two unknown functions of the BVP, including the beam displacement at each section and the fluid dynamic pressure at all points, are attained. These functions are expressed as an infinite series and evaluated quantitatively for a real example in the results section. In addition, finite element analysis is carried out for comparison.

Forced vibration analysis of a dam-reservoir interaction problem in frequency domain

Keivani, Amirhossein,Shooshtari, Ahmad,Sani, Ahmad Aftabi Techno-Press 2013 Interaction and multiscale mechanics Vol.6 No.4

In this paper, the forced vibration problem of an Euler-Bernoulli beam that is joined with a semi-infinite field of a compressible fluid is considered as a boundary value problem (BVP). This BVP includes two partial differential equations (PDE) and some boundary conditions (BC), which are introduced comprehensively. After that, the closed-form solution of this fluid-structure interaction problem is obtained in the frequency domain. Some mathematical techniques are utilized, and two unknown functions of the BVP, including the beam displacement at each section and the fluid dynamic pressure at all points, are attained. These functions are expressed as an infinite series and evaluated quantitatively for a real example in the results section. In addition, finite element analysis is carried out for comparison.

A closed-form solution for a fluid-structure system: shear beam-compressible fluid

Keivani, Amirhossein,Shooshtari, Ahmad,Sani, Ahmad Aftabi Techno-Press 2013 Coupled systems mechanics Vol.2 No.2

A closed-form solution for a fluid-structure system is presented in this article. The closed-form is used to evaluate the finite element method results through a numeric example with consideration of high frequencies of excitation. In the example, the structure is modeled as a cantilever beam with rectangular cross-section including only shear deformation and the reservoir is assumed semi-infinite rectangular filled with compressible fluid. It is observed that finite element results deviate from the closed-form in relatively higher frequencies which is the case for the near field earthquakes.

Output-only modal identification by in-operation modal appropriation for use with enhanced frequency domain decomposition method

Morteza Ghalishooyan,Ahmad Shooshtari,Maher Abdelghani 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7

Output-only modal identification or operational modal analysis (OMA) has gained increasing popularity in many fields of engineering. In the context of OMA there is no need to measure the input. Modal parameters of dynamic systems are estimated just based on the output responses. One of the most robust and popular frequency domain methods of OMA is enhanced frequency domain decomposition (EFDD) method. EFDD is widely used as an interesting solution for OMA in a large number of researches, projects, and commercial software. We first assessed the EFDD features considering the design parameters selection and then introduced our recently proposed algorithm named in-operation modal appropriation (INOPMA) for use with EFDD method to improve the identification of modal frequencies and damping ratios and overcome some of the existing drawbacks. Modal identification process starts with EFDD and then INOPMA is applied on derived normalized auto-correlation functions (NACF) to estimate modal damping ratios and natural frequencies. Typical EFDD takes advantage of logarithmic decrement (LD) algorithm and zero crossing (ZC) method at this stage. A simulated fourstory shear frame has been employed to perform the evaluation of the proposed method on output-only prediction of ideal natural frequencies and modal damping ratios. The outcomes show that the modal parameters are estimated with much less bias error and variance compared to the typical EFDD procedure. The real data of the heritage court tower ambient vibration test is also used to perform sensitivity analysis of EFDD-INOPMA modal parameter estimation in the presence of measurement noise, and favorable results have been obtained.

Exact mathematical solution for free vibration of thick laminated plates

Mohammad Asadi Dalir,Alireza Shooshtari 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.56 No.5

In this paper, the modified form of shear deformation plate theories is proposed. First, the displacement field geometry of classical and the first order shear deformation theories are compared with each other. Using this comparison shows that there is a kinematic relation among independent variables of the first order shear deformation theory. So, the modified forms of rotation functions in shear deformation theories are proposed. Governing equations for rectangular and circular thick laminated plates, having been analyzed numerically so far, are solved by method of separation of variables. Natural frequencies and mode shapes of the plate are determined. The results of the present method are compared with those of previously published papers with good agreement obtained. Efficiency, simplicity and excellent results of this method are extensible to a wide range of similar problems. Accurate solution for governing equations of thick composite plates has been made possible for the first time.

Investigating the effect of bond slip on the seismic response of RC structures

Fallah, Mohammad Mehdi,Shooshtari, Ahmad,Ronagh, Hamid Reza Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.5

It is reasonable to assume that reinforced concrete (RC) structures enter the nonlinear range of response during a severe ground motion. Numerical analysis to predict the behaviour therefore must allow for the presence of nonlinear deformations if an accurate estimate of seismic response is aimed. Among the factors contributing to inelastic deformations, the influence of the degradation of the bond slip phenomenon is important. Any rebar slip generates an additional rotation at the end regions of structural members which are not accounted for in a conventional analysis. Although these deformations could affect the seismic response of RC structures considerably, they are often neglected due to the unavailability of suitable models. In this paper, the seismic response of two types of RC structures, designed according to the Iranian concrete code (ABA) and the Iranian seismic code (2800), are evaluated using nonlinear dynamic and static analyses. The investigation is performed using nonlinear dynamic and static pushover analysis considering the deformations due to anchorage slip. The nonlinear analysis results confirm that bond slip significantly influences the seismic behavior of RC structure leading to an increase of lateral deformations by up to 30% depending on the height of building. The outcomes also identify important parameters affecting the extent of this influence.