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Mitigation Of CRU Heater Tube Carburization By Modified High Heat Transfer Ceramic Cladding Materials

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Common materials employed in catalytic reforming unit tubes are typically resistant to carburization due to protective chromium oxide films, but under low excess oxygen conditions can become compromised and allow carbon penetration and carbide formation at the exposed surface. Embrittlement and material wastage as a result of these mechanisms causes premature failures, with production loss, in addition to shutdown maintenance and replacement costs. Carburization in this environment is simulated in this paper through a pack carburizing method designed to create an environment optimal for diffusing carbon in an ASTM 335 9Cr-1Mo tube material.

Product Number: 51322-17831-SG
Author: Natalie Hana Frank, Iain Stuart Hall, Paolo Brunello
Publication Date: 2022
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Carburization is a failure mechanism common to the petrochemical industry in Catalytic Reforming Units (CRU’s) where atmospheres containing hydrocarbons and/or carbon monoxide are prominent. Elevated fuel prices cause refineries to run with low excess oxygen to generate cost savings. The resulting atmosphere at elevated temperatures creates an environment where carbon is favorably transferred to iron and low alloy steels, forming a hardened layer of carbides that reduce the life of the steel tubing and vessels.

Ceramic coatings have previously been applied in CRUs to increase radiant efficiency. A dual functionality was hypothesized for select materials to aid in the prevention of carburization. To evaluate this potential, ceramic coatings were applied to a commonly used low-alloy steel tube material and exposed to a low-oxygen, high-temperature, carbon-rich environment. Chemical etching, optical microscopy, and microhardness evaluations were completed to determine the degree of carburization on the ceramic-coated and uncoated control tube surfaces. Results indicate that some ceramic coating materials are highly effective at the prevention of carburization of the treated tube surface when compared to the uncoated control. The implementation of cladding with this class of materials would be optimal for not just improving heat transfer but additionally extending the serviceable life of CRU units in low excess oxygen environments.

Carburization is a failure mechanism common to the petrochemical industry in Catalytic Reforming Units (CRU’s) where atmospheres containing hydrocarbons and/or carbon monoxide are prominent. Elevated fuel prices cause refineries to run with low excess oxygen to generate cost savings. The resulting atmosphere at elevated temperatures creates an environment where carbon is favorably transferred to iron and low alloy steels, forming a hardened layer of carbides that reduce the life of the steel tubing and vessels.

Ceramic coatings have previously been applied in CRUs to increase radiant efficiency. A dual functionality was hypothesized for select materials to aid in the prevention of carburization. To evaluate this potential, ceramic coatings were applied to a commonly used low-alloy steel tube material and exposed to a low-oxygen, high-temperature, carbon-rich environment. Chemical etching, optical microscopy, and microhardness evaluations were completed to determine the degree of carburization on the ceramic-coated and uncoated control tube surfaces. Results indicate that some ceramic coating materials are highly effective at the prevention of carburization of the treated tube surface when compared to the uncoated control. The implementation of cladding with this class of materials would be optimal for not just improving heat transfer but additionally extending the serviceable life of CRU units in low excess oxygen environments.

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Application of HVAS Cladding to Mitigate Sulfide Stress Cracking and Hydrogen Induced Cracking in a De-ethanizer Column

Product Number: 51315-5952-SG
ISBN: 5952 2015 CP
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Modelling Electrolytic Hydrofluoric Acid In The Fractionation Phase Change Corrosion Zone Of HF Alkylation Units

Product Number: 51322-17520-SG
Author: Andy C. Gysbers, J. Tim Korstanje, Michael S. Cayard, Peiming Wang, Ezequiel Vincent
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Hydrofluoric acid (HF) is used as a catalyst in the alkylation process to react isobutane with olefin feeds to manufacture a high octane alkylate product used in gasoline blending. The HF catalyst is added in its anhydrous liquid form (< 400 ppmw H2O) but as it circulates in the reaction system, residual water in the Paper No. 17520 liquid hydrocarbon feed is absorbed by the acid such that the circulating reaction acid builds up a small percentage (0.5 to 2.0 mass%) of water. This water/HF mixture is also referred to as rich HF (RHF). In addition, the alkylation reactions also will generate fluorocarbons and acid soluble oils (ASOs).
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Naphthenic Acid Corrosion And Sulfidic Corrosion In Crude Oil Fractions

Product Number: 51322-17533-SG
Author: Yuhchae Yoon, Hui Li, Kwei Meng Yap
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In the petroleum industry, much greater attention has been focused on more highly sour and acidic oil resources due to the gradual depletion of conventional sweet oil resources. In addition, reducing crude oil costs have forced to look for opportunity (alternate) crudes, usually low-quality corrosive crude oils with high concentrations of naphthenic acids and sulfur compounds.1 The main constituents in the crude that cause corrosion are sulfur compounds, organic and inorganic chlorides, salt water, organic and inorganic acids. Processing of these highly acidic and sulfur-containing crudes at high temperatures in refineries has promoted significant corrosion problem in hot oil distillation units and associated piping systems.
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