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SPE-188706-MS Corrosion Control in Sulphur Recovery Units – Claus Process A. Alkasem, A. Slavens, H. Dhinda, UniverSUL Consulting; A.S. Berrouk, The Petroleum Institute
Agenda 1. Introduction 2. Corrosion Mechanisms in SRUs and Their Control Methods 3. Guidelines for Corrosion Control through Construction and Fabrication A. Individual Equipment Items B. General Design Guidelines 4. Guidelines for Corrosion Control through Process Operation A. Normal Operation B. Startup C. Shutdown 5. Conclusions SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Typical Three Stage Claus Sulphur Recovery Unit 2 nd Reheater 3 rd Reheater 1 st Reheater Steam Drum RF Incinera Fuel Gas tor WHB Air 2 nd 3 rd 1 st Reactor Reactor K.O drum Reactor Air Acid Gas 1 st 2 nd 3 rd Final Sour Condenser Condenser Condenser Condenser Water Sulfur Pit SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Corrosion & damage Mechanisms in SRUs (API 571) Steam Drum 2 nd Reheater 1 st Reheater 3 rd Reheater RF Incinerator Fuel Gas WHB Air 2 nd Reactor 3 rd Reactor 1 st Reactor K.O drum Air Acid Gas 1 st Condenser 2 nd Condenser 3 rd Condenser Final Condenser Sour Water Sulfidation Wet H2S Damage Sulfur Pit Oxidation Refractory Degradation Steam Blanketing Sulfuric Acid Flue Gas Dew Point Corrosion Boiled Water / Condensate Corrosion SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Effective Corrosion Control Process & equipment design, material selection, and operating & maintenance practices. Process & Equipment Design Ignoring any part of the “triangle” can lead to: Cost effective corrosion Early failure of process control Operating Material equipment Conditions Selection Poor unit reliability. SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Guidelines for Corrosion Control through Construction and Fabrication Individual Equipment Items Carbon steel can Refractory lined Stainless steel , for Proper materials be used in all other carbon steel very hot service selection is areas up to a should be used in (e.g. burner tips, important to reduce temperature of services above catalyst screens, corrosion problems. 600 ° F. 600 ° F mesh elements in condensers) SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Individual Equipment Items Steam Drum CS ; sometimes CS ; sometimes CS ; sometimes Refractory- SS for tubes SS for tubes SS for tubes lined CS with 2 nd Reheater 1 st Reheater 3 rd Reheater air shroud Refractory - RF lined CS with air shroud Incinerator Fuel Gas WHB Refractory- 1 st Reactor lined CS Air 2 nd Reactor 3 rd Reactor K.O tubesheet CS with CS with CS with drum and ceramic partial Air Acid partial partial ferrules refractory Gas refractory refractory lining lining lining Refractory - lined CS with 1 st Condenser 2 nd Condenser 3 rd Condenser air shroud Final Condenser Sour Water CS with partial CS with partial CS with partial CS with partial refractory refractory CS with HIC refractory refractory lining lining lining resistance lining CS and SS for internals Sulfur Pit Note: Burner tips in the reaction furnace, burner tips of acid gas reheaters, catalyst screens, sulfur pit piping, refractory anchors and mesh elements in sulfur condensers / coalescers should all be Type 316 stainless steel, or 309 stainless steel SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
General Design Guidelines 2 1 3 4 5 Refractory Plant design Metallurgy Keep hot Accumulation of lining liquids Plant should be - steam jacketing, carbon steel Probability of steel designed so the electric heat Gas piping design metallurgy with a Sulfidation due to operating conditions tracing, or steam should avoid that 1/8” corrosion high temperature are always above tracing allowance exposure to H2S water dew point 6 Thermal shroud designed to maintain metal temperature between 150-315° C (300-600°F) SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Thermal shroud maintain metal temperature between 150 -315 ° C (300 - 600 ° F). provide an insulating air gap that allows free air flow between the shell and shroud protecting the carbon steel shell and internal refractory from thermal shock. Ref. Duiker Combustion Engineering Book SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
General Design Guidelines 2 1 3 4 5 Refractory Plant design Metallurgy Keep hot Accumulation of lining liquids Plant should be - steam jacketing, carbon steel Probability of steel designed so the electric heat Gas piping design metallurgy with a Sulfidation due to operating conditions tracing, or steam should avoid that 1/8” corrosion high temperature are always above tracing allowance exposure to H2S water dew point 6 7 Thermal shroud Ferrules design very important to designed to maintain protect WHB tubes. metal temperature crack develops between 150-315° C hot gases will reach (300-600°F) the tubesheet and tubes SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Tubesheet Failure Crack develops hot gases will reach the tubesheet and tubes SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
General Design Guidelines 2 1 3 4 5 Refractory Plant design Metallurgy Keep hot Accumulation of lining liquids Plant should be - steam jacketing, carbon steel Probability of steel designed so the electric heat Gas piping design metallurgy with a Sulfidation due to operating conditions tracing, or steam should avoid that 1/8” corrosion high temperature are always above tracing allowance exposure to H2S water dew point 6 7 8 9 Thermal shroud Ferrules design External Insulation liquid sulfur lines - to maintain a metal very important to designed to maintain wall temperature protect WHB tubes. metal temperature above 120° C (250°F) Slope to promote crack develops between 150-315° C draining hot gases will reach - tail gas piping (300-600°F) the tubesheet and should be kept as tubes short as possible SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Guidelines for Corrosion Control through Process Operation Normal Operation 2 1 3 4 5 Operating burner Shutdowns Capacity sub-stoichiometric Temperatures performance combustion Poor burner Do not permit any Do not purposely operate the burner in operate the units as performance, equipment surfaces shut down unless it a sub-stoichiometric close to design resulting in unstable to be colder than is for a scheduled combustion condition capacity as possible firing conditions and 120ºC (250ºF) turnaround to avoid sulphur fire then refractory in reactors damage SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Hot Spots SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Guidelines for Corrosion Control through Process Operation Normal Operation 2 1 3 4 5 Operating burner Shutdowns Capacity sub-stoichiometric Temperatures performance combustion Poor burner Do not permit any Do not purposely operate the burner in operate the units as performance, equipment surfaces shut down unless it a sub-stoichiometric close to design resulting in unstable to be colder than is for a scheduled combustion condition capacity as possible firing conditions and 120ºC (250ºF) turnaround to avoid sulphur fire then refractory in reactors damage 6 7 8 9 Shroud louvers blowdown BFW Quality steam flow and intermittent blowdown pressure connections on a Continuous designed to maintain Maintain adequate routine basis to monitoring of the metal temperature steam flow and control solids BFW in condensers between 150-315° C pressure on steam accumulation in all and proper chemical (300-600°F) jacket and steam boilers and injection. tracing systems condensers SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Flue gas dew point corrosion SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Guidelines for Corrosion Control through Process Operation Startup 2 1 refractory excess oxygen curing - Not allowed if Particular care after there is any sulphur the main burner is lit on the catalyst to avoid sudden variations of - Allowed during the Reaction Furnace initial startup and temperature refractory dry out SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
Refractory Failure SPE-188706-MS • Corrosion Control in Sulphur Recovery Units – Claus Process • A. Alkasem
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