ERTC Newspaper 2022

ERTC 2022

Environmental and economical benefits of improving amine unit operations

Donato Vinciguerra veolia water technologies & solutions

Amine unit in refineries The alkanolamine system in a refinery, bet- ter known as the ‘amine unit’, is used to remove hydrogen sulphide (H₂S), carbon dioxide (CO₂), and mercaptans (collectively referred to as acid gases) from process gas and liquid hydrocarbon streams. Amine units are an essential part of the refin- ery operation to maintain product qual- ity and environmental compliance. Their importance is increasing as refinery feeds become more sour and refinery product sulphur limits are lowered. A poorly oper- ated amine unit can result in high amine losses, poor unit reliability, amine solution contamination, off-specification products, operating headaches, and increased oper- ating costs to the refinery. Also, for post-combustion CO₂ capture from flue gas, the amine-based CO₂ cap- ture system is commercially the best avail- able technology today. There is currently a worldwide R&D effort taking place to improve this technology mainly to reduce the high energy penalty of this technology and focus on reduction in the degradation products. Challenges Despite their importance, amine unit oper- ations are often not well understood or operated optimally. This is due to several factors, including: • Amine units enable a refinery to make a profit but do not directly produce a profit- able product • The various parts of an amine unit are typically spread out across different oper- ating units: lean amine solvent is typically pumped to absorber towers in the process units containing the production fluids, then rich amine is pumped back to the stripper tower for acid gas removal, so control of the entire circuit is not straightforward. • Many refinery amine units are operated well beyond their original design capacities. • Amine systems are often robust enough to maintain refinery product quality, even when operating far from either original design or best operating practices. Conversely, there are many benefits that can be realised by improving amine unit operations, such as: • More consistent product quality, result- ing in reduced frequency of ‘event-driven’ activities to blend off or retreat episodic off-spec products • Lower energy costs • Reduced costs for filters, activated car- bon, and replacement amine • Improved reliability that lowers equip- ment replacement/repair costs • Improved operation of the sulphur plant by providing a more consistent feed quality to this unit. Amine units tend to accumulate ther- mally stable amine salts (HSAS), which cause issues like corrosion, fouling, loss of efficiency, foaming, operational insta- bility, and excessive loss of amine solvent.

Concentrated brine

Demineralised process uid

Concentrated brine

X–

M+

Anode (+)

Cathode (–)

M+

X–

M+

X–

Cation exchange membrane

Anion exchange membrane

Cation exchange membrane

Anion exchange membrane

Makeup water

Process uid containing salt (MX)

Makeup water

Figure 1 Veolia’s electrodialysis process

Veolia dedicated amine reclaiming unit

Best practices indicate that the maximum allowable concentration of HSAS is 2.0% wt in the amine solution. A key aspect of successfully operating an amine unit for optimal performance is a good amine man- agement programme. This involves moni- toring the condition of the amine solution and managing the feed quality, operating conditions, and the amine solvent itself to avoid issues associated with highly con- taminated or degraded amine. Case study A refinery in Europe had a high HSAS con- centration (>5.0% wt as methydiethan- olamine, MDEA) and a formate content greater than 15,000 ppm, which caused corrosion problems, fouling, and an exces- sive loss of amine solvent. Veolia Water Technologies & Solutions performed the reclaiming of amine solvent using a cus- tom-built mobile electrodialysis (ED) unit. Veolia’s ED technology provides several advantages: when in stable operation and if there is no necessity to perform a clean- ing procedure, a mobile ED unit can stay in operation for several days or weeks, and the waste stream generated is a neu- tral salt solution. Additionally, during this period, no water is introduced into the

amine stream, except for a ‘flush’ sequence required before a clean in place (CIP). A lean amine stream was passed through the reclaiming unit, sending back the reclaimed stream to the amine unit. The effluent generated in the reclaiming process (brine formed by neutralised sta- ble salts) was sent directly to the refin- did you know veolia’s total amine solutions customers ery wastewater plant without causing any negative impact. The double ED mobile unit is fully automated by a programma- bale logic controller (PLC) System + human machine interface (HMI). Flow rates, tem- peratures, conductivities, and pressures are controlled and measured automati- can achieve up to A 90% reduction in formate content to a level of 1,500 ppm?

cally during operation. The system will be monitored and controlled by a single oper- ator per shift without exclusive dedication, given the degree of automation. At the end of operation, 850 m³ of amine solution was reclaimed. A 90% reduction in formate content was achieved, down to 1,500 ppm – below our control guide- line of 2,000 ppm. The HSAS was reduced to 0.5% wt. Amine losses throughout the regeneration process were less than 1% wt, based on total system volume. The cost of the reclaiming for the refinery was less than 30% of the amine solution replacement cost, without considering dis- posal costs of the contaminated amine. The total saving for the refinery was more than $400K (US). The reclaiming mobile unit has wide applicability and can be successfully used for different types of amine solvent, including MDEA, monoethanolamine (MEA), diethanolamine (DEA), diisopropanolamine (DIPA), formulated solvents, and others. Veolia can also offer a dedicated amine reclaiming unit to customers. This ED unit can be put into continuous feed & bleed operation (at lower capacity) to keep HSAS at a continuous low level operated by Veolia. Conclusion While amine units do not directly contrib- ute to producing the products from a refin- ery, they are an essential unit operation to maintain product specification and to safely handle the acid gases in the refin- ery operation and carbon capture plants. Attention to operating parameters, amine system condition, and performance can minimise operating costs and improve refinery unit reliability and operations. Veolia’s total amine solutions will provide a full scope of technology to increase the reliability of amine units, reduce the energy footprint, and lower operational costs and the environmental footprint. Contact: donato-gabriele.vinciguerra@ suez.com

30000

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Formic acid ppm CHO HSAS %

25000

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Figure 2 HSAS and formic acid trends