Hydrogen formation in sulfuric acid plants:
- Hydrogen can be produced as result of sulfuric acid corrosion with metals (Iron). H2SO4 + Fe = FeSO4 + H2.
- Hydrogen is extremely flammable and easy to ignite. It can create local explosions and damage facilities. 2H2 + O2 = 2 H2O + ?H
- The accumulation of hydrogen occurs mainly while the plant is shut down and since the main blower is stopped.
- Therefore, the hydrogen is generated in presence of weak acid mainly in the below equipment which are in contact with weak acid : Economizers, acid towers (final and intermediate), acid coolers (tubes & shell), storage tanks.
How to prevent H2 formation and incidents?
- Higher acid temperature or less concentration lead to increase corrosion reaction with metal. So, keep acid storage in the within the range (more than 98% concentration and less than 40°C).
- Main equipment that may contain weak acid (acid towers, acid coolers, economizers) must have drains and vents with relevant sizes.
- For Economizers:
- In case of moisture in the gas side (due to drying tower low efficiency, or internal water tubes leak), SO3 will generate weak acid that can corrode tubes and create hydrogen.
- Consider having large size drains in the bottom side to avoid plugging with sulfates and scales. Drains must be cleaned during shutdowns and inspected periodically.
- Develop and implement procedures for monitoring and limiting weak acid creation to avoid contact with metallic surfaces.
- No Welding or cutting job authorized without implementing safety procedures related to ATEX area and measuring H2 concentration inside vessels.
- Improve operation team’s awareness of hydrogen risk through periodic drills.
Note: This publication for technical sharing and exchanges only.
Engineering,Commissioning & Start-up Expert
11 个月Merci Ssi Oussama pour ces articles et partages instructifs.
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1 年Never ever drain Sulphuric acid without taking any additional precautions from a storage tank which had been carrying acid from a long time, same we Experienced at workplace where trapped hydrogen caused a major acid splash when vessel had to be drained as Pressurized Hydrogen came out along with liquid Acid, So before draining acid ensure there's no such trapped gas already present in the storage vessel.
Sr. Operations Executive for the (petro)chemical industry - Sulphuric acid, ammonia and turnaround specialist.
1 年A good way to protected your plant is to install an XPV on top of your (HRS)-Tower/diluter that will open when you have a plant trip due to a scenario with possible H2 formation. At www.h2so4.pm you can find all our sulphuric acid services and also our details to contact us.
Business & Sales Representative
1 年Hi Mr.Ousama Thank you so much for sharing. below are the statistics of hydrogen accidents in SAP since 2015. Incident location : ? Australia (2) ? Brazil (3) ? Holland (1) ? India (2) ? Italy (1) ? UK (1) ? US (6) ? Chile (2) Cause of incident: ? Acid Cooler leak (7) ? Boiler leak (2) ? Economizer leak (6) ? Tower/pump tank acid strength out of control (2) ? Chemical cleaning of the coolers (1) There's a lot to be said about this problem. Cordially
DG Société INDUSTRIAL SERVICES NORTH AFRICA ENGINEERING EXPERTISE
1 年Bravo Oussama pour ces publications. C’est très instructif. Ce transfert de savoir pertinent et ciblé est d’une importance capitale pour le développement des métiers du process. Avez vous pensé à la création d’une communauté métier pour échanger et rassembler les bonnes pratiques : H2SO4 Book… beaucoup d’ami des anciens seront ravis d’en faire partie…