Advancements in Catalytic Coatings for Coke Gasification: Year-11 Update of Three Full Life Cycle Field Trials of CAMOL Products in Medium Severity Cracking

Hydrocarbon steam pyrolysis is a mature commercial process producing over 180 and 120 million tonnes of ethylene and propylene, respectively, per year. As economics have continued to favour higher severities in steam cracking, the materials supply industry has striven to provide tube alloys / coatings / surfaces / internal profiles to contain and manage the process’ severity demands. In the last 20 years alone, medium severity ethane cracking (primarily defined as ~64-67% ethane conversion, with 0.25-0.35 Steam-to-Hydrocarbon ratio, maximum End-of-Run (EOR) Tube-metal-Temperature (TMT) <1090 °C, and well controlled decoking) has advanced from an average of 20-40 day runlengths to 60-100 days being now common. Some operators routinely achieve 500+ day runlengths with proper furnace coil alloy and surface technologies, along with proper furnace and feedstock controls. Extreme bookends of ethane medium severity runlength range from as low as 1 day and up to as much as 1,000 days. To a great degree, much of this variability is due to the engineering, control, and sustainability of the topmost few atomic layers (~1 nanometre) of the furnace coils’ internal surface, and the ability to sustain and repair such surfaces in the field.

Inert Furnace Coil Coatings: Development efforts on internal coatings for furnace tubes (coils) during the 25-year period from ca. 1980 to 2005, focused mainly on coatings engineered to render the internal tube surface chemically inert to filamentous coke via alumina-formers, silica-formers, chromia-formers, and [Cr,Mn]-spinel-formers. Some commercial-scale advancements were realized but achieving field longevity exceeding 1 year of functional anti-coking benefit proved challenging. Inert coating suppliers were driven primarily by securing compatibility with maximum EOR TMT, and working to advance their product offerings from early maximums of ~1040°C through to ~1060 °C, and reaching best-of-class technology of ~1080 °C. Three decades of learnings suggest that TMT as the critical engineering temperature stability target is likely not the best key process variable affecting internal tube surface/coating robustness, degradation and longevity. Results indicate that the critical limiting temperature affecting internal coating lifetime and benefits is the internal tube surface temperature experienced during air-based decoking and from other exothermic phenomena acting on the internal surface. This may explain why inert coating technologies of the last 30 years engineered to a TMT maximum have been limited to <1 year of anti-coking benefits in service.

Catalytic Furnace Coil Coatings: Development of catalytic (gasifying) furnace coil coatings has been advancing since ~2000, driven by the preference to manage both filamentous and amorphous coke-make. To date, some products have achieved laboratory/pilot-scale success. Quantiam has been at the forefront of catalytic coating developments with its CAMOL™-Gen1 and Gen2 (“Catalytically-assisted Manufacture of Olefins”) product lines commercialized in 2012. Extensive field demonstration trials, now exceeding 10 furnace installations at various cracking severities, have demonstrated CAMOL^TM benefits across full coil life cycles when remaining reasonably within the operating envelopes of the base steel and the coating. Runlength improvements of >10X in ethane cracking and >2X in naphtha cracking have been shown for furnace-specific coil life cycles ranging from 4.5 to 7.5 years, depending on operating conditions. These runlength improvements have also been accompanied by energy reductions of up to 6% per unit of production. The first two installations in ethane cracking furnaces (2006-2011 and 2008-2016), and a third installation in naphtha cracking (2010-2016), have now completed one full life cycle and have been well autopsied. This paper follows up the 1-year and 4-year updates previously presented at the AIChE Ethylene Producers’ Conferences in 2008 and 2010, and provides a Year-11 update on the three CAMOL^TM full life cycles noted in medium severity cracking of ethane and naphtha. The focus will be on autopsy results from start-of-life to end-of-life coating microstructure and properties, and specifically on those coating and surface properties responsible for delivering the anti-coking benefit and their correlation with furnace operating benefits realized or realizable.

New Tube (Coil) Coating Advancements: Finally, based on all field learnings to date across a range of cracking severities, an update will be provided on advancements in process of coating technologies beyond CAMOL^TM Gen1/Gen2 (at TRL8/7, respectively) for medium severity cracking, and which target higher severities with: (1) SGX (super gasification) catalytic coatings not utilizing oxygen (steam) for carbon gasification; (2) Inert-1300 coatings targeting internal surface thermal stability of >1200^°C and up to 1300^°C for short duration thermal and thermal-mechanical upsets, and for temperature-problematic parts of furnaces; and (3) high heat transfer tube technologies through internal and/or external tube surface profiles.