1 / 20

Metal Dusting Corrosion in Steam Reforming Plants J. Bohle, Dr. C. Beyer, U. Wolf, Dr. D Ulber Steam Reforming Technolo

Metal Dusting Corrosion in Steam Reforming Plants J. Bohle, Dr. C. Beyer, U. Wolf, Dr. D Ulber Steam Reforming Technology User Conference Labuan, Malaysia March 5-7, 2007. Metal Dusting Corrosion (MDC).

jovan
Download Presentation

Metal Dusting Corrosion in Steam Reforming Plants J. Bohle, Dr. C. Beyer, U. Wolf, Dr. D Ulber Steam Reforming Technolo

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Metal Dusting Corrosion in Steam Reforming Plants J. Bohle, Dr. C. Beyer, U. Wolf, Dr. D Ulber Steam Reforming Technology User Conference Labuan, Malaysia March 5-7, 2007

  2. Metal Dusting Corrosion (MDC) Disintegration of metals and alloys into a dust of graphite and metal particles after carbon ingress and over-saturation.

  3. Overview • Phenomena of Metal Dusting Corrosion (MDC) • Mechanism involved / Reactions • Material considerations • Examples of MDC in Steam Reforming Plants • Prevention of MDC • Influence of MDC on process design • Literature

  4. Steps in Metal Dusting Corrosion • Diffusion of reducing / carburizing gas through oxide protection layers to metal surface • Formation & supersaturation of carbides • Dissociation into metal particles and graphite • Diffusion of catalytically active metal particles • Loss of carbon, metal, metal carbide, metal oxide

  5. Phenomena involved in MDC • Gas-phase and gas-metal reactions (T, p, composition fi) • Diffusion of reducing gas, carbon and metals (T, fi) • Flow and temperature distribution (vel, T) – equipment design • Catalytically active components in gas and metal • Thermodynamic & mechanical stability of protective layers • Stresses / fractures imposed on surfaces by gradients • Metal crystallographic structure • Sulfidic components in gas

  6. Reactions Carburization reactions • CO + H2<-> C + H2O aC=K1*pCO*(pH2/pH2O) • 2 CO <-> C + CO2 aC =K2*(p2CO/pCO2) • CH4 <-> C + 2 H2 aC =K3*(pCH4/p2H2) Gas-phase reactions • H2O + CO <-> CO2 + H2 • H2O + CH4 <-> CO + 3 H2 aC carbon activity Ki equilibrium constant Pi partial pressure

  7. Potential for Metal Dusting Corrosion

  8. Temperature rangePromoting components • 450°C < MDC temp. range < 800°C / Boudouard temp. • At [Fe/Ni] > ~ 2/3 mass-frac, metal dusting is retarded at the lower regimes of the metal dusting temp. range • MDC promoting gas components (negative impact on metal oxide protection layer)

  9. Material Considerations • Surface oxide stability is enhanced by alloying elements such as Cr, Al, Si, Ti, Mo providing a barrier to carbon diffusion • Carbon and alloying elements diffusion is influenced by crystallographic structure and surface condition (e.g. grain size) • Surface coatings or surface finish (grinding) can provide added stability by influencing the carbon diffusion and/or physical resistance to mechanical and thermal effects

  10. Material Considerations • Fe-based and Ni-based metals show different behaviour • Empirical equation of alloying material resistance to MDC (Parks & Schillmoller) Crequiv. = Cr % + 3 x (Si % + Al %) • Inclusion of the effects of other alloying elements such as Ti, Mo, Ni outstanding • Preferred material Nicrofer® 6025 HT – alloy 602 CA • No alloy is MDC resistant under all conditions

  11. Where can Metal Dusting Corrosion occur? • Reducer Sockets • Transfer Line at Reformer Outlet • Process Gas Boiler (PGB) Inlet chamber • PGB tube inlet section (ferrules) and tube sheet • PGB bypass tube, bypass flow control device • PGB outlet chamber • Heat Exchanger d/s of PGB, e.g. Feed Preheater

  12. SMR Outlet System – Reducer Sockets

  13. Manifold, Transfer LineGas Barriers

  14. Process Gas Boiler„Cold“ Bypass Design

  15. Process Gas BoilerFlow and temperature distribution

  16. Process Gas Boiler Flow and temperature distribution Temperature distribution in outlet chamber mixing zone of a process gas boiler Gastemperatures: below 450°C 450 – 1000°C Bypass open Bypass closed

  17. Inserts in PGB tubes for temp. control

  18. Measures against MDC Pro & Cons • Avoid metal wall temperatures in MDC temperature range • Use of non-metallic materials in critical areas • Change gas atmosphere • Introduction of process gas (for purge) in critical areas • Catalytically activated refractory (Lurgi Patent) • Material science, Protection layers • Sulfidic compounds in gas • Design for easy maintenance / replacement

  19. Influence of MDC on process design Process efficiency / consumption figures • Steam to Carbon Ratio • Steam Superheater for Process Gas Cooling • Export Steam Value • Gas-heated Steam Reformer design

  20. Literature References • R.T. Jones, K.L. Baumert; Metal Dusting – An Overview of Current Literature; Corrosion 2001; No. 01372 • H.J. Grabke, E.M. Müller-Lorenz; Occurrence and Prevention of Metal Dusting on Stainless Steel; Corrosion 2001; No. 01373 • F. Hohmann; Improve Steam Reformer Performance; Hydrocarbon Processing; 03/1996; p. 71-74

More Related