Design and simulation of high pressure cyclones for a gas city gate station using semi-empirical models, genetic algorithm and computational fluid dynamics

• A high efficiency Stairmand cyclone was designed to separate black powder from natural gas for CGS #1 of Kerman city.
• The vortex length of cyclone was optimized by using Genetic algorithm.
• The Lieth and Licht theory was used to obtain the cyclone diameter.
• CFD simulation was used to evaluate the performance of designed cyclone.
• The inlet of cyclone was placed to a shell for working the cyclone at high pressure.

Solid particles suspended in natural gas pipelines cause many fundamental problems in transmission and distribution network of natural gas. Conducted measurements in the natural gas network of Kerman city, Iran showed a high concentration of black powder in the pipeline. It was found that the current filtration system not to be efficient to remove the solids. Thus, with regarding to the size of black powder, to improve the filtration a cyclone separator before the filtration process was proposed. In this study, the required cyclones for separating black powder from natural gas at high pressure for CGS #1 of Kerman city, Iran were designed. Then, using computational fluid dynamics, simulations were done and their performance evaluated at different conditions. The Reynolds Stress model was used to model the turbulent flow due to existence of swirling flow inside the cyclone. Particle trajectories were calculated by discrete phase model. A high efficiency Stairmand cyclone was selected. To increase the efficiency and prevent direct escapement of particles entering into the cyclone from the internal vortex finder, the vortex length was optimized using Genetic Algorithm (GA). In order to design the cyclone, a number of algorithms were written to calculate the required number of cyclones. The cyclone was designed at pressure and temperature of 1000 psi and 20 °C respectively for maximum capacity of CGS #1 of Kerman city. It is attempted to satisfy the standards of American Society of Mechanical Engineers for pressure vessels in cyclone design. Diameter and thickness of the designed cyclone are 55 cm and 1.125 inches respectively. Simulation validation was done using the Grid Convergence method. The cyclone is able to separate particles with efficiency of more than 96% in summer (the lowest consumption time) and winter (the highest consumption time) well.

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