Optimizing heat exchanger performance in sour water stripping units
Sour Water Stripping( SWS) units are critical in refinery wastewater treatment, removing ammonia( NH3) and hydrogen sulfide( H2S) before the water is reused or discharged. However, maintaining optimal performance between shutdowns is a challenge, particularly due to fouling, corrosion, and hydrocarbon contamination.
By Jaya Kulshreshth, Heat Exchanger Design Specialist
One of the most overlooked yet crucial components in SWS units is the heat exchanger network. Proper design modifications, operational improvements, and cleaning strategies can significantly enhance the efficiency and longevity of these exchangers. In this article we will be looking at the most common heat exchanger challenges in SWS units.
Fouling in feed / effluent exchangers Fouling in feed / effluent heat exchangers reduces heat transfer efficiency, increasing steam demand and leading to off-spec treated water. The most common types of fouling include: 1. Hydrocarbon fouling – Naphtha and heavy hydrocarbons agglomerate with particulates, forming sticky sludge that accumulates in exchangers.
2. Particulate fouling – Coke fines, corrosion byproducts, and catalyst fines create deposits that reduce flow and heat transfer.
3. Salt precipitation – Calcium and magnesium compounds form scales on heat exchanger surfaces.
Solutions & modifications:
• Install bypasses around exchangers to enable on-stream cleaning without requiring a full unit shutdown.
• Enhance upstream separation by installing coalescer filters or feed stabilization tanks to reduce hydrocarbons and particulates entering the heat exchangers.
• Periodic chemical washing using weak acids / bases or vapor-phase hydrocarbon washes can break down fouling deposits without dismantling equipment.
Corrosion risks and mitigation in heat exchangers Corrosion is a major concern in SWS heat exchangers, particularly in overhead condensers and reflux exchangers, due to the presence of ammonium bisulfide( NH4HS), hydrogen cyanide( HCN), and free cyanide ions. Key corrosion mechanisms include:
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