China Heavy Oil Reactor Manufacturer

China Heavy Oil Reactor Manufacturer

Answering the core question: What does a heavy oil reactor from Shijiazhuang Zhengzhong Technology Co., Ltd provide to refiners? Shijiazhuang Zhengzhong Technology Co., Ltd (Center Enamel) fabricates heavy oil upgrading reactors that convert vacuum resid and heavy crude into lighter, saleable products, including fixed-bed hydrocracking and hydrotreating reactors, resid hydrotreaters and coking drums. Hydrocracking runs at 10 to 20 MPa with hydrogen partial pressure up to 18 MPa at 350 to 450°C, and the reactors are built as hot-wall vessels with 347SS or 316L cladding over SA-387 chrome-moly steel, with wall thickness up to 200 mm and design against high-temperature hydrogen attack and creep.

1. Heavy Oil Conversion Routes

Four routes turn the bottom of the barrel into value, and each defines a different reactor:

• Hydrocracking: Heavy gas oil and resid are reacted with hydrogen over a bifunctional catalyst at 10 to 20 MPa and 350 to 450°C, breaking large molecules into naphtha, jet and diesel with near-complete conversion. The reactor is a multi-bed fixed bed with quench between beds to control the strongly exothermic reaction, built as a hot-wall vessel with internal cladding because the whole shell sits in hydrogen at high temperature. Hydrocracking gives the highest-value product slate but demands the most severe pressure and materials.
• Resid Hydrotreating: Vacuum resid is desulfurized, demetallized and decarbonized at 5 to 15 MPa and 350 to 420°C to feed a fluid catalytic cracker or fuel oil blender. Because resid carries metals and conradson carbon, the catalyst deactivates from the top down, so the reactor uses graded catalyst loading and guard material, and the shell must resist the same hydrogen attack as hydrocracking though at lower pressure. Throughput and run length are set by metals removal, not by kinetics alone.
• Visbreaking and Mild Upgrading: Resid is heated to 420 to 450°C at near atmospheric pressure and held briefly to crack the heaviest fraction without coke formation, improving fluidity and reducing fuel oil yield. The reactor is a simple soaking drum or a coil plus flash, far milder than hydrocracking, with carbon steel or low-alloy construction and no hydrogen requirement. It is the lowest-capital route but also the lowest conversion, used where only a modest upgrade is needed.
• Delayed and Fluid Coking: Resid is heated to 480 to 510°C in the absence of hydrogen so the heavy fraction cracks to vapor and coke, leaving a coke bed in the drum that is decoked on a cycle. The coking drum is a carbon-steel pressure vessel with a refractory lining and thermal cycling every 12 to 24 hours, designed for repeated stress from heating and water quenching. It is the route of last resort for the heaviest feeds but recovers the most light product from them.

2. Engineering Heavy Oil Reactors for Hydrogen Service

Hydrogen at high temperature is the hardest service in refining. Four design responses apply:

• High-Temperature Hydrogen Attack Resistance: Above about 200°C and a few MPa, hydrogen diffuses into carbon steel and reacts with carbides to form methane, causing blisters and fissures. Resistance is provided by chrome-moly steel (SA-387) and by 347SS or 316L weld overlay cladding on the wetted surface, with the cladding thickness and the base metal chrome content chosen from the Nelson curve for the operating temperature and hydrogen partial pressure. A vessel specified below the curve will fail in service regardless of pressure rating.
• Creep and Long-Term Strength: At 350 to 450°C the base metal creeps, so wall thickness up to 200 mm is calculated not just for pressure but for the allowable stress at temperature over a 20-year life, with the nozzles and heads reinforced against local creep. The design uses Div 2 analysis where weight and thickness matter, and the material certificate reports the long-term elevated-temperature properties, not just ambient tensile strength.
• Cladding Integrity and Overlay: The internal stainless overlay must survive thermal cycles, hydrogen exposure and catalyst abrasion without cracking or dilution. It is applied by automatic weld overlay, examined by ultrasonic testing for bond and dilution, and the dilution is kept low enough that the surface chemistry meets the corrosion requirement. Any through-thickness defect in the overlay exposes the chrome-moly base to wet hydrogen sulfide, the most damaging combination in the unit.
• Thermal Cycling and Refractory: Coking drums and some hydrotreaters see temperature swings that fatigue nozzles and lining anchors. The design provides for thermal growth, supports the refractory through hundreds of cycles, and keeps the shell below the creep range at the hot end. Seam-to-seam cycle life, not just the first fill, is the measure of a coking drum, and the lining attachment system is qualified for the actual heating and water-quench profile.

Heavy Oil Upgrading Reactor Comparison Matrix

Frequently Asked Questions (FAQ)

Q: What is high-temperature hydrogen attack and how is it prevented?

A: Above roughly 200°C and a few MPa, atomic hydrogen diffuses into carbon steel and reacts with iron carbides to form methane inside the metal, causing internal blisters and fissures that eventually rupture the wall. It is prevented by using chrome-molybdenum steel such as SA-387 and by applying a 347SS or 316L stainless weld overlay on the wetted surface, with both the base chrome content and the overlay chosen from the Nelson curve for the actual temperature and hydrogen partial pressure. A vessel specified below that curve will fail in service no matter how high its pressure rating, so hydrogen attack resistance is designed in, not inspected for afterward.

Q: Why are heavy oil reactors built as hot-wall clad vessels?

A: In hydrocracking and resid hydrotreating the entire shell sits in hydrogen at 350 to 450°C, so the pressure boundary itself must resist hydrogen attack and the process corrosion. A hot-wall vessel uses a chrome-moly base for strength and a thin internal stainless overlay for corrosion resistance, keeping the cost far below a solid-alloy forging while meeting the service. The alternative, a cold-wall vessel with a thick refractory and a cooler shell, is used where the duty allows it, but once the shell is in the hydrogen envelope the hot-wall clad approach is required.

Q: How does a coking drum differ from a hydrocracking reactor?

A: A coking drum operates at near atmospheric pressure and 480 to 510°C with no hydrogen, converting the heaviest resid into vapor and solid coke that builds up inside and is removed on a 12 to 24 hour cycle. The drum is a carbon-steel vessel with a refractory lining that is heated, steamed and water-quenched repeatedly, so its design measure is seam-to-seam thermal cycle life rather than steady hydrogen service. A hydrocracking reactor, by contrast, runs continuously at 10 to 20 MPa in hydrogen, built as a thick hot-wall clad vessel. The two share almost nothing but the word reactor.

Q: What should a buyer verify for a heavy oil hydrogen-service reactor?

A: Four checks. Code and curve: confirm ASME VIII Div 2 or the project spec and that the material sits inside the Nelson curve for the operating temperature and hydrogen partial pressure. Cladding: require ultrasonic examination of the overlay for bond and dilution, with a documented threshold. Creep basis: require the elevated-temperature allowable stress over the 20-year design life, not just ambient tensile data. Testing: the hydrostatic test at 1.3 times design pressure plus the post-weld heat treatment records, the welding procedure qualifications for the chrome-moly and overlay, and the NDE of all seams, must be in the delivered file before acceptance.