TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''

From ccitonlinewiki
Revision as of 12:41, 4 January 2021 by Alesdaniel (talk | contribs) (Results and Discussions)
Jump to: navigation, search

Introduction

Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy the process of a petroleum refinery, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.

Figure 1. Horizontal Separator Inner Geometry and Flow Direction

Objectives

In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:

1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.

2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.

3. To investigate the suitable separator with and without a perforated separator.

Numerical Geometry

The geometry would be the same as the previous study by Efendioglu, A., et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition.

Figure 2. Horizontal Separator 3D Geometry

Methodology

Software

The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.

Mathematical Model (Verification)

The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:

GovEq.jpg

These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as:

TurbulenceUAS.jpg

Cij represents the rate of convection, Pij is the rate of production, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions, and Ωij is the transport due to rotation.

In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation.

Grid independent study

Boundary Conditions and Solver Control

The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. The height uses the bottom outlet as the datum and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:

Fluid Properties
Fluid Type Density (kg/m3) Dynamic Viscosity (Pa.s) Mass Flow Rate (kg/s)
Oil 824.95 0.00237 0.5
Gas 1.225 1.79E-5 0.5
Figure 3. Boundary Conditions of the Horizontal Separator System

Results and Discussions

Validation

The simulation at first was investigated undertwo-dimensional numerical simulation, using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation.

Conclusions

References

[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.

[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.

[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.

[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.

[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.

[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.

[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.