As the focus on reducing carbon dioxide emissions increases in various industries around the world, efforts to prevent carbon dioxide from escaping into the atmosphere by sequestering it have become the subject of much interest. These techniques are known as carbon capture and storage (CCS). For example, the Quest Carbon Capture and Storage (CCS) facility near Edmonton, Alberta, Canada, has captured and sealed more than 6.8 million tonnes of carbon dioxide since it opened at the end of 2015, and has safely stored it 2 kilometres underground. Corrosion-generated materials and proper equipment material selection are key to the safe, reliable and economic operation of CCS infrastructure. The low temperature environment and free water produced during many CCS processes can create acidic conditions that can lead to corrosion of the treatment equipment. For this reason, nickel-containing stainless steels and nickel alloys with higher levels of corrosion resistance are preferred for the manufacture of such equipment.
Carbon captured from gases usually comes from combustion processes and contains high levels of moisture. Capture and sequestration processes are either carried out under humid and acidic conditions, or require prior drying to capture the carbon dioxide, or may be carried out at high temperatures and under harsh conditions. In addition, the transport of carbon dioxide from capture to underground storage is mainly by pipeline, shipping, trucks and rail, and the carbon dioxide needs to be liquefied before it is transported to the storage site. The equipment used to transport carbon from capture to underground storage is usually made of low alloy steel containing nickel, stainless steel or nickel alloys.
The carbon dioxide injected into underground storage is usually dry and non-corrosive. The design of the well must take into account the risk of corrosion in a sour environment during the life of the well. Well design data from the U.S. and the EU show that nickel-containing stainless steels and nickel alloys are commonly used to fabricate critical well infrastructure where there is a risk of corrosion. Pada masa ini, the United States has developed clear guidelines for the design and construction of CO2 injection wells that emphasise the importance of nickel as an equipment material for underground CO2 storage.
In addition, the International Association for Materials Performance and Protection (AMPP) is developing guidelines for material selection and corrosion control for CO2 transport and injection, identifying nickel-containing materials as the preferred choice for equipment fabrication. This suggests that nickel will play an important role in net-zero greenhouse gas emissions for some time to come.
What steps specifically in the CCS process does nickel play a vital role? Recovery of carbon dioxide from the flue gas of coal-fired power plants, which is contaminated with sulphur dioxide and water and produces acidic condensates that can corrode carbon steel; the absorption of carbon dioxide from gas streams by liquid solvents (e.g., amines), which can lead to acidic corrosive conditions in the carbon dioxide absorber, liquid amine handling systems, and in the vessels of vapour strippers where the clean carbon dioxide is released; and the recovery systems for solid absorbents, such as temperature-variable adsorption (TSA), which also remove carbon dioxide from the gas stream through interaction with the absorbent, a process that involves humid conditions with temperatures fluctuating between 40 degree and 100 degree , where carbonic acid may be formed, so the key step at risk is drying. For all these processes, the use of austenitic nickel-containing stainless steel is recommended, while nickel-containing duplex stainless steel is more recommended for pre-capture blowers. In addition, innovative processes for the utilisation and capture of CO2, such as the Allam-Fetvedt power generation cycle, require CO2 turbines and burners made of nickel-containing alloys, heat exchangers and high-temperature piping connecting the two components.
