Gas Sweetening System Hydrodynamic Analysis - ANSYS Fluent CFD Simulation

Project Overview

This computational fluid dynamics study focuses on the hydrodynamic behavior within a gas sweetening facility using ANSYS Fluent software. Gas sweetening represents a critical industrial process for eliminating hydrogen sulfide, carbon dioxide, mercaptans, and additional contaminants from natural gas and synthetic gas streams, ensuring safe transportation and end-use applications. The treatment of sour gas is essential due to the severe corrosive properties of hydrogen sulfide and carbon dioxide on pipeline infrastructure, along with their toxic effects on human health.

Simulation Scope and Methodology

Process Modeling Approach

The computational domain incorporates two distinct materials: a specific sour gas composition and an amine solution stream. This investigation concentrates exclusively on hydrodynamic modeling aspects, excluding actual gas removal mechanisms that typically involve complex physical or chemical interactions. Water serves as the amine material substitute for this hydrodynamic analysis.

Multiphase Flow Configuration

A Volume of Fluid (VOF) multiphase model defines the two-phase computational environment. The system features dual inlet configurations for amine and gas streams, with the amine flow entering at 0.3 m/s velocity before encountering the gas stream within the processing equipment.

Geometric Design and Computational Grid

Three-Dimensional Geometry Development

The gas sweetening equipment model was constructed using Design Modeler software, incorporating realistic inlet configurations for both gas and amine stream introduction into the processing vessel.

Mesh Generation Specifications

Computational grid development utilized ANSYS Meshing software, generating an unstructured mesh containing 2,168,649 elements. This mesh density provides adequate resolution for capturing the complex multiphase flow interactions within the sweetening equipment.

CFD Simulation Configuration

Fundamental Assumptions

• Pressure-based solver implementation for incompressible flow analysis

• Steady-state simulation approach

• Gravitational acceleration of -9.81 m/s² applied along the vertical direction

Turbulence and Multiphase Modeling

Boundary Condition Specifications

Numerical Methods and Solution Algorithms

Initial Conditions

Standard initialization with zero gauge pressure, zero velocity components, and zero water volume fraction throughout the computational domain.

Results and Flow Analysis

Flow Interaction Characteristics

The simulation results present comprehensive two-dimensional and three-dimensional contour visualizations for pressure distribution, velocity fields, and phase volume fractions for both gas and water phases. The analysis reveals that gas and amine streams undergo collision after navigating through internal flow barriers within the processing equipment.

Hydrodynamic Performance

The collision interaction between the two streams demonstrates the amine current’s capability to redirect portions of the gas flow toward the equipment outlet. This hydrodynamic behavior forms the foundation for understanding the mixing and contact efficiency in actual gas sweetening operations, where chemical absorption would occur between the amine solution and acid gas components.

Engineering Insights

The velocity and pressure contours provide valuable insights into flow distribution patterns, mixing zones, and potential areas for equipment optimization. These hydrodynamic characteristics are essential for designing efficient gas-liquid contact systems in industrial sweetening applications.