Session: 09-07-02 GHG emissions reductions, hydraulics for H2, other

Paper Number: 134090

134090 - Applying Computational Fluid Dynamics to Reduce Greenhouse Gases Emissions in Natural Gas Compressor Stations 

Abstract: 

Concerns about greenhouse gas (GHG) emissions are rapidly increasing and becoming a priority in operations involving hydrocarbons.
In natural gas transportation systems, compressor stations are commonly found to be the primary sources of emission of these gases.
Some compression stations with emergency depressurization systems are designed with a continuous purge of natural gas into the environment to prevent the entry of atmospheric air into the depressurization system, therefore avoiding any formation of an explosive atmosphere within the line.
Many of these projects were conceived when the ESG topic was not yet as widely discussed, resulting in less concern about the amount of natural gas purged.
To adapt such stations to the emission reduction targets established by oil and gas-related companies, the industry applies solutions to eliminate natural gas purging. Among these solutions are the replacement of the purge fluid with less aggressive gases, such as nitrogen, and the use of seals that prevent atmospheric air from entering the piping.
However, such methods require changes in the plant's safety characteristics and call for specific risk analyses, in addition to more costly and complex actions for their implementation.
Intending to allow the immediate reduction of unwanted emissions in compressor stations until the most appropriate elimination method for each specific installation is defined, this work proposes a quick and low-cost method to obtain the minimum value of natural gas flow still capable of preventing the formation of an explosive atmosphere inside the depressurization piping.
The proposed method consists of carrying out a series of simulations in Computational Fluid Dynamics (CFD) in which the boundary conditions at the vent tip of the depressurization line are varied to obtain the minimum value of natural gas flow that yet prevents atmospheric air from occurring inside the line.
The iterations are conducted by varying temperature and wind velocity values according to historical data obtained from the record of the meteorological station closest to the installation and considering the atmospheric pressure value fixed.
From these simulations, the combination of conditions that results in the highest pressure at the tip of the vent is determined.
With this pressure value, the corresponding flow rate, which can be considered the minimum required for the system, is calculated.
The method was applied to a test case in a compressor station that operated with flow rates of nearly 1,700 m³/day (20°C, 1 atm). The simulations indicated a minimum flow of 858 m³/day, allowing adaptations to be proposed at the station to lead to a reduction of approximately 50% in natural gas emissions from the system.

Presenting Author: Fernando Silva NTS

Presenting Author Biography: Metallurgical and materials engineer (Instituto Militar de Engenharia, 2008). Coordinator of projects at the transportation pipeline industry.

Authors:

Fernando Silva NTS
Carlos Junior NTS
Carlo Saggio NTS
Fabio Fundo Safe Solutions
Matheus Silva Safe Solutions