PTQ Q4 2026 Issue

solvent. Dow employs its pro- prietary simulation software for precise prediction of sol- vent performance under the refinery’s specific operating conditions. Case 1: Opex reduction A Central European refinery operating an amine treat- ment system for gas and LPG streams from its delayed coker unit (DCU) achieved a

LPG – Copper strip corrosion test

DEA

UCARSOL

DAY

1a-2b

2a-2e

3a-3b

4 a- 4 c

Figure 5 Conversion from DEA to the Ucarsol system resolved persistent non-compliance

variable that determines whether the unit can operate effi - ciently, reliably, and with long-term stability. An amine that is not suited to the specific gas/LPG com - position, operating conditions, and performance targets will inevitably lead to avoidable costs and persistent opera- tional challenges. For this reason, Dow consistently encour- ages refineries, through detailed audits, performance assessments, and rigorous process simulations, to evaluate whether their current amine and operating strategy are appropriate. There is often significant room for optimisa - tion, and selecting the right solvent becomes a key lever for improving both unit and refinery-wide performance. Hence, a refinery achieves these targets by evaluating the ‘best fit solvent’ for each loop, rather than relying solely on traditional MDEA/DEA choices. Improving reliability and performance Formulated solvents are designed to address the oper- ational gaps seen in traditional amines, including lower LPG phase solubility, higher energy, improved mercaptan removal, and better handling of CO 2 from renewable feed- stocks. Formulated solvents can significantly reduce losses to LPG. In many circuits where DEA was historically chosen to limit losses, a formulated solvent can deliver the same or better performance while reducing energy consumption. Switching from MDEA/DEA configurations to formulated solvents often decreases regeneration duty while main- taining or even improving absorber performance. Specific Ucarsol blends are tailored to effectively target mercaptan absorption, a key benefit for refineries facing SOx compli - ance issues or producing gas streams destined for sensitive petrochemical downstream units. Formulated solvents can help maintain stable absorber operation when CO₂ levels increase due to renewable feed co-processing. This avoids performance deterioration that might occur when relying solely on MDEA. Overall, formu- lated solvents offer refineries a more flexible and reliable way to optimise performance without capital investment. Performance case studies Several case studies demonstrate how the implementa- tion of a specifically formulated solvent can resolve oper - ational issues within amine treating systems. Notably, these improvements were achieved without the need for mechanical modifications or significant process redesign, relying solely on the optimisation and replacement of the

significant performance improvement after replacing its MDEA solvent with a Ucarsol formulated amine system. Following the solvent replacement, the refinery recorded an approximate 13% reduction in energy. Additionally, annual solvent losses decreased from 30 m³/year to 22 m³/year. Encouraged by these outcomes, the refinery is currently evaluating the conversion of the remaining units to these bespoke proprietary-formulated solvent systems. Case 2: Stringent regulations A refinery in Southern Europe was experiencing diffi - culties meeting its SOx emissions. The treatment system comprises several gas absorbers, all of which consistently achieved the required gas specification except for the unit processing visbreaking off-gas. This particular absorber exhibited elevated COS concentrations and light mercap - tans that were not adequately removed using the existing MDEA solvent system. The refinery’s objective was to achieve less than 35 ppm total sulphur compounds in the treated gas in order to reduce overall SO₂ emissions. Transitioning to one of the formulated solvents, as shown in Figure 3, improved the removal efficiency of these sulphur species, thereby enabling the plant to meet total sulphur specifications and return to compliance with its SOx emission limits. Case 3: Renewable feedstocks Another Southern European refinery is undergoing a major transformation with the addition of advanced biofuel pro- duction units. These new units will produce aviation fuel, biodiesel of biological origin, and green hydrogen. The bio- fuels unit will convert treated vegetable oils and animal fats into biodiesel. Historically, the refinery has used MDEA in a large amine circuit dedicated to removing H₂S from gas and LPG streams originating from various plants. As part of the transforma- tion, a new absorber is being introduced to remove CO₂ from the recycle gas generated during the deoxygenation process. A formulated solvent was evaluated and imple- mented across all absorbers to treat both H₂S and CO₂, as MDEA was no longer able to deliver adequate performance. Case 4: Capital cost savings The copper strip corrosion test is routinely employed to evaluate the corrosive behaviour of green LPG in a Southern European refinery. Corrosion is primarily attributed to the

PTQ Q4 2026