Centralloy® HT E
Aluminum Oxide Forming AlloyWith their innovative, patented chemical composition, Centralloy® materials provide maximum mechanical strength at highest temperatures and develop a stable, protective and self healing oxide layer against corrosive process conditions - without any preconditioning or coating.
Centralloy® HT E takes this concept to the maximum: Due to the addition of aluminum, this material develops a dense and protective aluminum oxide layer which, contrary to the conventional chromium oxide formers, is resistant to cyclic operating conditions and stable at very high temperatures. Furthermore, the stability and morphology of this aluminum oxide layer massively reduces undesirable coke deposition on the inner tube surface and thus considerably increases the efficiency of the steam cracker.
Exceptional performance and long service life
Properties and Benefits
Over the years, new technologies developed for latest radiant coils in steam cracking furnaces including new coil materials. It´s generally well known that high temperatures and short residence times are required to maximize the yields in the steam cracking process. However, coke formation within the radiant tubes is an undesirable side effect of the pyrolysis process, leading to pressure drop and therefore reduction of the product yield. In order to extend the run length between two decoking processes and maximize the yields, it is therefore essential to use the coil material Centralloy® HT E, which forms in service conditions an inert and stable oxide layer, thus drastically reducing coke formation.
Furthermore, the lifetime of components in the radiation zone is crucial for the economic operation of a steam cracker. With currently available standard alloy metallurgies, the typical service life of a coil is five years. However, in almost every steam cracker furnace where our Centralloy® HT E is installed, operators benefit from a significantly longer service life. Those tubes remain in operation for well over eight years. Due to this extended service life, many reports from industrial applications indicate, that the degree of carburization (if present) is no longer the criterion for plant operators to replace the tubes.
To date, S+C has already installed its superior Centralloy® HT E material in over 650 steam crackers worldwide, including all relevant coil designs and components.
Operators are keen to use the most advanced materials for their steam cracker tubes, not only for reasons of cost-effectiveness, but also to ensure a high level of reliability, structural integrity, and safety for their plants. The Centralloy® HT E is designed to meet these requirements.
This material has the following characteristics:
- Formation and regeneration of a protective and strongly adhesive oxide layer during operation
- Excellent carburization resistance
- Excellent ability to prevent or retard coke formation
- Thermal stability of the oxide scale up temperatures well above the current maximum design temperatures (T > 1130 °C)
- Excellent creep properties
Chromium Oxide vs. Aluminum Oxide Forming Alloys
Maximizing service life through advanced oxide layer technologyStandard chromia forming alloys form a dense and complex oxide layer during operation in a steam cracker. If operated at high temperatures, investigations carried out on aged materials removed from steam cracking coils often show that the original protective oxide layers are damaged as these cannot be regenerated during operation. Standard materials therefore do not fulfill their function of protecting the material from corrosion attack after some longer exposure in the steam cracking furnace.
The following comparison reflects the condition of oxide layers in different operating conditions – from initial furnace start-up to several coking and decoking cycles – and demonstrates why aluminum oxide-based protection is beneficial for the long-term reliability of the plant.
Conclusions
Chromium Oxide vs. Aluminum Oxide Forming AlloysChromium oxides have a limited resistance to high temperature degradation – limitation set by thermodynamics.
Due to their far better thermodynamic stability, aluminium oxides are favourable as protection under severe cracking conditions at high tube metal temperatures.
- Oxygen and carbon ingress into the alloy is effectively blocked
- Less influence to mechanical properties during ageing (carburisation, nitriding)
S+C manufactures the outstanding SCOPE® Fusion HT E tubes by centrifugally casting. Stringently controlled melting and casting practice are in place. The careful blend of elements in our Centralloy® HT E material ensures optimum high temperature properties. Thus provides extended operational intervals (well beyond 100 days of continuous operation), significantly improved yield pattern as well as excellent energy efficiency, for the plant operator.
S+C has supplied tubes in SCOPE® Fusion HT E for many projects around the world and life of radiant coils with “the perfect match” expected to last much longer and perform more reliable even under adverse conditions. Frequently, clients enjoy performance well beyond expectation.
Point of contact
S+C Petrochemical Industry
Contact Department
Phone: +49 2266 92-929
Email: salespetro(at)schmidt-clemens.com
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