Applications and Technological Advantages of Stainless Steel Pipes in the Petrochemical Refining Field

I. Introduction

The petrochemical refining industry, as a core industry for energy and chemical raw material production, handles complex media such as crude oil, heavy oil, and various chemical intermediates. It faces extreme conditions including high sulfur content (H₂S content ≤15000ppm), high chlorine content (Cl⁻ content ≤5000ppm), high temperature (≤550℃), high pressure (≤15MPa), and mixed acid corrosion. This places top-level industry requirements on the corrosion resistance, mechanical stability, and sealing safety of pipeline materials. Stainless steel pipes (based on 316L, 2205 duplex steel, 310S heat-resistant steel, and 904L super austenitic steel, containing Cr ≥16%, Ni ≥8%, and partially added Mo, N, and Si elements) have become key materials in the core processes of reaction, separation, and transportation in refining and chemical plants due to their broad-spectrum corrosion resistance, high-temperature and high-pressure adaptability, and long-term reliability.

As the refining industry transforms towards "deep processing, high added value, and green low carbon," stainless steel pipes, through material upgrades and process innovation, are continuously ensuring the safe and efficient operation of refining and chemical plants. II. Core Characteristics of Stainless Steel Pipes Adapt to the Needs of the Refining and Chemical Industry Extreme Media Corrosion Resistance: The dense passivation film formed by the chromium-nickel alloy can resist sulfides and chlorides in crude oil, mixed acids such as sulfuric acid and hydrofluoric acid in the refining process, as well as high-temperature water vapor corrosion. 316L's resistance to sulfur-containing media corrosion is 3 times better than 304; 2205 duplex steel can withstand chloride ion corrosion above 3000ppm; 904L super stainless steel is suitable for extreme corrosion conditions with high sulfur and high chloride content; and 310S heat-resistant steel can withstand high-temperature oxidation at 550℃.

 

High Temperature and High Pressure Load Capacity: Yield strength range 205-550MPa, tensile strength 480-800MPa. It can operate continuously within a temperature range of -20℃ to 550℃ and a pressure condition of 0.1-15MPa without deformation or performance degradation. Suitable for high temperature and high pressure units such as catalytic cracking and hydrorefining.

Sealing and Fatigue Resistance Reliability: The inner wall of the pipeline is smooth (roughness Ra ≤ 0.4 μm), with low fluid resistance and less prone to coking and carbon buildup. The welded joints undergo special treatment, achieving a strength of over 95% of the base material, with excellent fatigue resistance (cycle life ≥ 10⁶ cycles), avoiding the risk of weld leakage under high pressure conditions.

 

Anti-scaling and easy-to-clean properties: The non-porous surface does not absorb asphaltenes or colloids from the medium, reducing scaling and clogging, and lowering the frequency of equipment cleaning; the smooth inner wall ensures stable medium transmission efficiency, meeting the continuous operation requirements of refining and chemical plants.

Long-lasting environmental protection and economy: Service life of 15-25 years, far exceeding carbon steel pipes (3-5 years), and 100% recyclable; reducing the frequency of pipe replacement and maintenance, reducing downtime losses, conforming to the green and low-carbon transformation trend of the refining and chemical industry, and complying with GB/T 14976 "Seamless Stainless Steel Pipes for Fluid Transportation" standard.

 

III. Typical Application Scenarios in the Petrochemical Refining Field

(I) Reaction Unit System: The "Safe Passage" for Core Reactions

Hydrorefining/Hydrocracking Unit:

Reaction Feed Piping: 316L/2205 duplex stainless steel seamless pipe (diameter DN25-DN200), resistant to corrosion from high-sulfur crude oil (H₂S content 8000-15000ppm), suitable for 300-400℃, 8-12MPa operating conditions, avoiding stress corrosion cracking caused by sulfides;

Reactor Inlet/Outlet Manifold: 2205 duplex stainless steel pipe, yield strength ≥ 450MPa, resistant to high pressure and hydrogen embrittlement corrosion, ensuring uniform distribution of the reaction medium.

 

Catalytic Cracking Unit:

Regenerator Flue Gas Piping: Constructed of 310S heat-resistant stainless steel pipe (diameter DN300-DN800), resistant to 550℃ high-temperature flue gas oxidation and catalyst particle abrasion, with a high-temperature strength retention rate of ≥90%;

Fracturing Tower Feed Piping: Constructed of 316L stainless steel pipe, resistant to high-temperature oil vapor (350-400℃) and acidic media corrosion, preventing pipe coking and blockage.

Reforming Unit:

Reforming Reactor Feed Piping: Constructed of 316L/904L stainless steel pipe, resistant to hydrogen chloride (Cl⁻ content 2000-5000ppm) and high-temperature (450-500℃) corrosion generated during the reforming process, ensuring reforming reaction efficiency.

(II) Separation and Heat Exchange System: The “Key Carrier” for Efficient Mass and Heat Transfer Heat Exchanger Tube Bundles and Shell-Side Piping: Shell-and-tube Heat Exchanger Tube Bundles: Utilizing seamless 316L/2205 stainless steel tubes (wall thickness 1.5-4mm), resistant to corrosion from heat transfer oil, steam, and acidic cooling media, with a 30% increase in heat transfer efficiency compared to carbon steel, suitable for crude oil cooling and process medium heating applications; Plate Heat Exchanger Flow Channels: Selecting 316L stainless steel thin-walled tubes (wall thickness 0.8-1.2mm), with a precision-formed corrugated surface design to increase heat transfer area, resistant to acid and alkali media corrosion, suitable for light hydrocarbon separation and solvent recovery processes.

 

Fracturing and Rectifying Column Internals:

Downcomer and Receiving Pan: Made of 316L stainless steel tubing, resistant to high temperatures (300-400℃) and corrosion from acidic and alkaline media, preventing impurities from falling off and contaminating the product;

Reflux Piping of Rectifying Column: Utilizes 316L stainless steel tubing, resistant to corrosion from organic acids and sulfides in the reflux medium, ensuring the purity of the distilled product.

(III) Media Conveying and Storage System: The "Safety Link" for Refined Materials Sulphur-Containing Crude Oil/Intermediate Product Conveying Pipelines: Crude Oil Main Conveying Pipeline: Utilizing 2205 duplex stainless steel pipe (diameter DN500-DN1000), resistant to high-sulfur crude oil corrosion and soil stress, suitable for long-distance transportation, with a leakage rate approaching zero; Liquefied Gas and Propylene Conveying Pipelines: Selecting 316L stainless steel seamless pipe, resistant to high pressure (≤10MPa) and low temperature (-20℃~50℃) conditions, with no risk of brittle fracture, ensuring safe transportation of flammable and explosive media.

 

Chemical Raw Material Storage and Distribution Piping:

Solvent (Benzene, Toluene, Ethanol) Transport Piping: Constructed with 304/316L stainless steel pipes, resistant to organic solvent corrosion, with no heavy metal migration, ensuring raw material purity;

Acid and Alkali Storage Tank Connections: Utilize 904L super stainless steel pipes, resistant to concentrated acids (sulfuric acid, nitric acid) and strong alkalis (sodium hydroxide) corrosion, with an IP68 sealing rating to prevent tank leakage.

(iv) Environmental Protection System: A “Purification Barrier” for Green Refining Desulfurization and Denitrification Equipment: Desulfurization Tower Spray Pipeline: Made of 316L/2205 stainless steel, resistant to corrosion from ammonia and ammonium sulfate solutions, suitable for wet desulfurization processes, with a service life 5 times longer than carbon steel; Denitrification Reaction Pipeline: Made of 310S heat-resistant stainless steel, resistant to corrosion from 350-400℃ high-temperature flue gas and denitrification agent (urea solution), ensuring denitrification efficiency. Oily Wastewater Treatment Pipelines: Wastewater Transport Pipelines: Constructed of 304/316L stainless steel, resistant to corrosion from high-salt, high-COD oily wastewater, preventing secondary pollution, and suitable for biochemical treatment and membrane separation processes; Sludge Transport Pipelines: Constructed of 2205 duplex stainless steel, resistant to abrasion from solid particles in sludge and chloride ion corrosion, preventing pipe blockage and leakage.

 

IV. Key Processing Technologies and Adaptation

Forming and Welding Processes:

Seamless Forming: Seamless stainless steel pipes are manufactured through hot extrusion and cold drawing processes, eliminating weld defects and making them suitable for high-pressure and high-corrosion conditions (such as feed pipes for hydrogenation units);

Welding Forming: Welded stainless steel pipes are manufactured using TIG welding and submerged arc welding. The weld seams are pickled and passivated, resulting in corrosion resistance close to that of the base material, making them suitable for medium and low-pressure pipelines;

Thick-Walled Pipe Forming: For high-pressure conditions (≥10MPa), forging and rolling processes are used, with a wall thickness uniformity error of ±5%, ensuring pressure-bearing stability.

 

Anti-corrosion and surface treatment processes:

Passivation treatment: All stainless steel pipes are immersed in nitric acid-hydrofluoric acid passivation solution before leaving the factory to form a dense passivation film with a thickness of ≥0.006mm. Salt spray test corrosion resistance is ≥3000 hours.

Acid pickling treatment: Welded pipe welds are acid-pickled to remove oxide scale, restore the integrity of the passivation film, and improve corrosion resistance.

Inner surface polishing: For applications prone to coking (such as catalytic cracking pipelines), electrolytic polishing is used, achieving an inner wall roughness Ra ≤0.2μm, reducing coking and carbon buildup.

 

Testing and Quality Control Processes:

Material Testing: Spectroscopic analysis verifies the content of Cr, Ni, Mo, N, and Si elements to ensure material compliance and avoid risks associated with substandard corrosion resistance and heat resistance;

Pressure Testing: Hydrostatic testing (test pressure 1.5 times the working pressure), holding pressure for 30 minutes without leakage; pneumatic testing (test pressure 1.15 times the working pressure), suitable for pipelines transporting flammable and explosive media;

Non-destructive Testing: Ultrasonic testing, X-ray inspection, and penetrant testing (PT) ensure welds are free of defects such as porosity and cracks; corrosion testing (eddy current testing) verifies the uniformity of pipe wall thickness;

High-Temperature Performance Testing: For heat-resistant stainless steel pipes, a 550℃ high-temperature tensile test is conducted to ensure high-temperature strength meets standards.

V. Application Cases and Development Trends Typical Cases A large-scale refining and chemical enterprise's hydrocracking unit: 2205 duplex stainless steel seamless pipes are used as the reaction feed pipeline. The pipe diameter is DN150, the wall thickness is 8mm, suitable for 400℃ and 12MPa operating conditions, resistant to H₂S corrosion at 12000ppm, and has been in operation for 6 years without leakage or rust. Maintenance costs are reduced by 80% compared to carbon steel pipes. A petrochemical enterprise's desulfurization unit: The spray pipeline uses 316L stainless steel pipes, with a total length of 5km. It is resistant to corrosion from ammonia and ammonium sulfate solutions, and its salt spray corrosion resistance reaches 4000 hours. The equipment has been in operation for 5 years without blockage or corrosion perforation. A fine chemical enterprise's distillation tower reflux pipeline: 904L stainless steel is used. Super stainless steel pipes are resistant to hydrogen chloride and high-temperature (450℃) corrosion. After 3 years of operation, no scale buildup occurs on the inner wall, and the purity of distilled products remains above 99.9%. Future Trends Upgraded Corrosion and Heat Resistance: Developing super duplex steels (such as 2507) and nickel-based alloy stainless steel pipes (such as Inconel 625) with higher Mo, Cu, and N content, suitable for extreme refining conditions with high sulfur content and ultra-high temperatures (above 600℃), extending equipment maintenance cycles; High Strength and Lightweighting: Promoting high-strength stainless steel pipes of 500MPa and above, achieving a 15%-20% reduction in pipe wall thickness, reducing material usage and transportation and installation costs, while improving the pipe's vibration and deformation resistance; Functional Integration: Developing "corrosion resistance + wear resistance + heat insulation" composite pipes. Composite coated stainless steel pipes, with a ceramic coating formed on the surface through plasma spraying technology, are suitable for conveying media containing solid particles (such as catalysts and sludge), reducing wear. Intelligent monitoring integration: Corrosion sensors, temperature and pressure sensors are embedded in the inner wall of the stainless steel pipes, combined with IoT technology to achieve real-time monitoring of pipeline corrosion levels and media parameters, improving the safety management level of refining and chemical plants. Green manufacturing and recycling: Stainless steel pipes are produced using short-process smelting technology, reducing carbon emissions and establishing a recycling and reuse system for waste stainless steel pipes (with a recycling rate of over 99%), aligning with the refining and chemical industry's "dual carbon" goals. VI. Conclusion With its core advantages of "extreme corrosion resistance, adaptability to high temperature and high pressure, reliable sealing, and long-term durability," stainless steel pipes have constructed a complete application system in petrochemical refining, from reaction, separation, and transportation to environmental treatment, becoming a core material support for ensuring the continuous, safe, and efficient operation of refining and chemical plants. As the refining and chemical industry transforms towards deep processing, high added value, and green low-carbon practices, and with the continuous commissioning of units operating under extreme conditions, highly corrosion-resistant, high-temperature-resistant, high-strength, and intelligent stainless steel pipes will continue to break through application boundaries, providing crucial support for the innovative development of key units such as hydrocracking, catalytic reforming, and desulfurization and denitrification, and helping the refining and chemical industry move towards a safer, more efficient, and environmentally friendly direction.