Technical Article
Stainless Steels in Carbon Capture , Utilization , and Storage
As governments worldwide strive to reduce carbon emissions and mitigate the effects of climate change , industries have taken on the challenge of meeting strict carbon reduction targets . Carbon capture has emerged as a crucial player in its ability to achieve these goals . The United States has set itself an ambitious target of capturing and storing 2.0 metric gigatons of CO 2 per year by 2050 , which could require up to 32 metric megatons of steel for the creation of pipelines , capture units , drilling wells , and other essential infrastructure , according to estimates from the Department of Energy .
By Mark McLeod , Mechanical Engineer , OGC Energy
How Does Carbon Capture , Utilization and Storage ( CCUS ) Reduce Emissions ?
Carbon Capture , Utilization , and Storage ( CCUS ) is an umbrella term that encompasses a range of technologies designed to remove CO 2 from fluids , including air ( Direct Air Capture ) and flue gas ( Industrial Capture ), as well as utilizing or storing the captured CO 2 underground . Usually , saline aquifers or abandoned oil and gas wells are used to store these emissions . This article will focus on Industrial Capture .
Industrial capture CCUS technology , which is based on gas sweetening and the removal of CO 2 from natural gas , employs amines such as MEA , MDEA , and PIP to separate CO 2 from flue gases . The process begins by directing the flue gas to an absorber tower , where aqueous amines bond with CO 2 molecules .
The resulting gas mixture is then sent to a stripper tower , where captured CO 2 is separated and prepared for further processing and transport . Typically , after capture and separation , the CO 2 is dehydrated before being directed to a compressor station and ultimately either to a trunkline or a storage site .
For industries that cannot decarbonize using traditional methods , such as reducing energy consumption or changing processes , carbon capture provides a viable solution to reduce emissions . It is expected that industries such as power generation , steel , cement , and fertilizer production will significantly benefit from the implementation of carbon capture technology .
The Importance of Stainless Steel in CCUS
Stainless steel is playing a crucial role in the proliferation of CCUS technology .
Two significant differences set CCUS projects apart from other oil and gas operations : the highly corrosive environment that can be present when there is free water in CO 2
, which is exacerbated by the presence of impurities from the industrial source .
The other main factor is the potential for low-temperature service due to severe cooling caused by the Joule-Thomson effect . Currently , corrosion-resistant alloys such as duplex stainless steel and high-nickel alloy stainless steel have already been used in large capture plants worldwide , with several large orders of Duplex OCTG already in place for CCUS projects .
Stainless steel plays a crucial role in numerous CCUS projects . For instance , the Carbfix project in Iceland , which stores CO 2 as mineral deposits underground , requires large volumes of water to fuel the process . Since access to fresh water is limited , saltwater is used , demanding the need for stainless steel . The Carbfix project made extensive use of 316 ( L ) stainless steel to protect its asset against saltwater corrosion . Similarly , in Norway , the Sleipner project has been injecting CO 2 into a saline aquifer for over 20 years . The condition of the wellhead requires the use of duplex tubing and casing for injection . The selection of the 25Cr Duplex ensures the longest-running CCUS project continues to operate smoothly .
Corrosion and Material Selection
Impurities in industrial CCUS have been shown to facilitate several damage mechanisms . The presence of O 2
, Chlorides , and CO can lead to stress corrosion of stainless steel , and the formation of H 2
SO 4 due to sulfurous impurities , such as H 2
S and SO 2
. This can lead to localized attacks when a separate water-dominated phase forms .
It is important not to rely solely on injection and storage well material standards already present for environments containing H 2
S or CO 2
, as there are significant differences when injecting a CO 2 stream containing impurities such as
O 2
, NO 2 , SO 2
, CO , and H 2
.
Standards and Design Codes
Currently , there is no unified design code for the development of CCUS infrastructure . However , AMPP is set to release a guidance document that will serve as a starting point for the approach to materials selection and design . A good understanding of API , IOGP , and ISO standards will be essential for selecting appropriate materials . ISO 13680 , API 5 CRA , and API 617 are excellent starting points for this purpose .
8 Stainless Steel World Americas - August 2023 | www . ssw-americas . com