Decarbonisation Technology August 2022 issue

Aluminosilicate adsorbents provide a reliable, low-energy solution for CO 2 dehydration prior to transport, storage or usage Choosing the ideal CO 2 drying solution for CCS applications

Kirstie Thompson, Margaret (Peg) Greene and Manish Mehta BASF

C arbon capture and storage (CCS) is a rapidly growing market and will continue to grow as stakeholders emphasise the implementation of sustainable practices. In the CCS realm, much focus has been on the CO₂ capture itself, but dehydration of CO₂ for transportation and storage is also a key step. Many CO 2 capture technologies utilise aqueous amine solutions, saturating the CO₂ during the capture process. This wet CO₂ is extremely corrosive, causing concern for pipelines and other surfaces it may contact. Thus, before the captured CO₂ can be transported, stored, or utilised, a dehydration step is necessary. A robust and efficient method for the dehydration of CO₂ will be necessary for the emerging CCS market. BASF has been providing materials for the dehydration of CO₂ in the beverage industry and enhanced oil recovery (EOR) applications for decades. Based on this experience and an extensive study comparing available technologies, BASF has concluded Sorbead, a specialty aluminosilicate, is best suited for the dehydration of CO₂. This article will discuss the CO₂ dehydration technologies currently available and the criteria that should be considered when making technology selection decisions. It will also detail the benefits of choosing aluminosilicates such as Sorbead for CO₂ dehydration, including longer material lifetimes, lower energy duties, smaller bed sizes, and lower Capex/Opex costs compared to glycol and other adsorbent solutions. Glycol – the old guard of dehydration The archetypical dehydration solution for natural gas, and most industrial plant-based operations,

is a triethylene glycol (TEG) solvent-based system. In these operations, ensuring efficiency and employee/environmental safety is of utmost concern. The solvent-based nature of TEG systems necessitates the use of circulating equipment, frequent chemical quality checks, and chemical make-up adjustments. In these complex plants, additional maintenance and chemical storage requirements can be very burdensome and limiting in some cases, i.e. off-shore operations. Also, the addition of any liquid-based chemical increases safety concerns by introducing the possibility of chemical spills and emissions. Along with water, TEG will co-adsorb heavy hydrocarbon components such as benzene, toluene, and xylenes. After adsorption, these components would then be released into the atmosphere along with desorbed water in the regenerator off-gas stream. Additionally, recoveries greatly depend on the system used, and without enhancements such as a vapour recovery system, additional contaminants such as CO₂ and H₂S can also be present in the off-gas vapour stream. These emissions cause serious concern for the plant and the surrounding environment. Standard TEG systems can achieve outlet H₂O contents o f <100 ppmv. Though these systems are considered standard practice, they struggle to keep up with ever-changing pipeline specifications (<<50 ppmv H₂O), often requiring additional modifications or add-ons such as enhanced stripping and vapour recovery systems. It is also increasingly common for pipelines to dictate very strict glycol specifications, often <15 ppbv. With TEG