PTQ Q4 2026 Issue

Enhancing amine unit reliability in undergoing refinery transformation

Summary of evolving refinery amine unit demands, focusing on solvent limits, circuit optimisation, and the role of advanced formulations in maintaining treating efficiency

Lorenzo Spagnuolo Dow

T he refining industry is undergoing a profound transformation driven by the pursuit of higher energy efficiency, compliance with increasingly stringent environmental and emissions regulations, tran - sition towards more sustainable operations, adoption of advanced digital technologies, and the growing imperative to reduce operating costs to remain competitive. These developments are reshaping traditional refining operations while addressing both environmental challenges and oper - ational performance. A relevant example is a European refinery that is con - tinuing a comprehensive modernisation process aimed at increasing its market presence through fuels produced from non-fossil feedstocks, supporting the overall decarbonisa - tion of its activities. This transition includes the gradual shift from fossil-based raw materials to alternative inputs, including renewable feedstocks and selected processed urban waste streams. In many cases, especially in Europe, this change has been so radical that many traditional min - eral oil refineries have been completely converted into biorefineries. This evolution also requires the modernisa - tion and revision of all amine units to ensure alignment with new feedstocks, evolving operational requirements, and the goal of maximising overall performance. Amine units in refining The main purpose of a refinery amine unit is to remove H₂S. However, today’s refinery context is more complex. Many plants now hydrotreat renewable feedstocks such as vege - table oils, which generate significant CO₂ during deoxygen - ation. As a result, the CO₂ load entering the amine system is often much higher than that in conventional fossil feed operations. Another key driver is the processing of less expensive crudes. While these crudes can increase margin, they often bring challenges such as higher acid content, solids, metal, or other contaminants. As an example, mercaptans require tailored mitigation strategies to protect equipment integrity, maintain product quality, and meet environmental and emission regulations, such as those related to sulphur oxides (SOx). Furthermore, a growing number of refineries are under - taking initiatives to reduce Opex and energy costs across all

refinery processes, including amine units. As a result of these evolving process conditions, solvent selection and circuit-spe - cific optimisation have become more critical than ever. Amine units play a fundamental role in refinery opera - tions. Their design can vary significantly from site to site. However, many refineries operate complex treating net - works that include multiple absorber circuits, sometimes with dozens of absorbers connected within the same loop. These units often treat gas streams with a wide range of H₂S concentrations, hydrocarbon compositions, and temperature/pressure conditions. In several refinery con - figurations, liquefied petroleum gas (LPG) absorbers are integrated into the same amine circuit. In many cases, even tail gas absorbers are not separated but are included in the primary loop. Solvents currently used in amine units Methyldiethanolamine (MDEA) is the most widely used amine solvent in refinery treating units. Its dominance over the last two decades is due to several advantages: lower regeneration energy, higher H₂S selectivity, and the abil - ity to boost capacity without capital investment simply by switching from less effective solvents. Despite these benefits, MDEA has two key weaknesses: u High solubility in cracked LPG: This leads to significant solvent losses in circuits handling LPG streams. v Limited organic sulphur removal: If the refinery requires organic sulphur control for environmental or downstream unit reasons, MDEA alone is likely insufficient. The solvent’s selectivity, its preferential absorption of H₂S over CO₂, can represent either an advantage or a limitation. When stringent specifications for both H₂S and CO₂ must be met simultaneously, this selectivity may prevent the sol - vent from achieving the required targets. Diethanolamine (DEA) is often used in circuits with LPG absorbers because it has lower solubility than MDEA. Selecting DEA for these circuits reduces solvent losses. The trade-off is higher regeneration energy, so DEA is not always the best option for complex or energy-constrained systems. The proprietary Ucarsol-fomulated solvents are widely applied where traditional amines underperform. They are used either to resolve specific operational challenges or to

PTQ Q4 2026