Natural gas is one of the important sources of energy and, due to the huge reserves of natural gas, it is transferred using a network of pipelines and through the urban network, it is available to industrial, commercial and domestic consumers. In natural gas tanks, a significant amount of it is available, but along with that, there are also amounts of condensate, moisture, and solid particles, which can cause pressure drops and damage the transmission lines and facilities [1]. Using a suitable filtration system with optimal performance while preventing gas flow pressure drop in the gas supply network, prevents damage to the equipment of gas stations. The best economical solution to deal with problems and save operating and maintenance costs is to use a high-efficiency filtration system that separates solid particles and moisture from natural gas [2]. The results show that changes in key parameters such as particle diameter, fibre diameter and fluid velocity have a significant impact on filtration performance. Also, the filtration efficiency for particles with an average diameter of 2.5 and 5 to 8 microns is only about 83% and 89% to 92% [3]. From examining the performance of 4 different types of filter cartridges that were used to purify high pressure natural gas, it was observed that the decrease in the performance of the filters is related to the increase in the pore size of the cartridge layer [4].

The objective of this project is to simulate the flow of natural gas, considering a mixture of gas and sand, passing through a filter separator, inlet a gas reduction station, in order to calculate the efficiency and pressure drop of the filter under operating conditions. The results obtained from the software will be compared with the pressure drop data obtained from DP which is installed on the inlet of the filters of the gas reduction station, and the results were consistent. In previous research the material and dimensions of the dry filter medium were obtained based on the information provided in the gas standards. The fluid flow simulation is using ANSYS FELUENT 2021 software. This project dealt with a three-phase gas-liquid-solid flow due to the presence of solid particles (sand) and moisture in the natural gas pipelines. The Eulerian-Lagrangian method and Discrete Phase Model (DPM) and k-ε turbulent model have been used to investigate gas-solid three-phase flow. The operating pressure of the filter separator ranged from 150 to 250 pounds per square inch (psi), the permissible flow rate was between 400 to 2500 cubic meters per hour. Compressible flow is assumed. The results show that