Materials of the Main Reactor for Batch-Type Pyrolysis Equipment

Materials of the Main Reactor for Batch-Type Pyrolysis Equipment

The main reactor (pyrolysis reactor) of a batch-type pyrolysis oil refining equipment is a core vessel for high-temperature oxygen-free reactions. Its materials are required to meet the stringent criteria of high temperature resistance, corrosion resistance, creep resistance and good airtightness. The mainstream configuration adopts a three-layer composite structure, and there are special material selection schemes for key components. The detailed extended supplements are as follows:

I. Inner Layer (Medium-Contact Layer): Extended Material Selection and Application Scenarios

The inner layer is in direct contact with high-temperature pyrolysis raw materials and corrosive oil-gas, serving as the core load-bearing and corrosion-resistant barrier of the reactor. In addition to the conventional Q345R boiler steel and 310S heat-resistant stainless steel, there are two advanced materials suitable for special working conditions:

Q345R Special Boiler Steel

Extended Characteristics: It not only has high temperature resistance of 400-650℃, but also can withstand the micro-positive pressure of 0.02-0.05MPa inside the reactor. With excellent weldability, weld defects can be eliminated through flaw detection, making it suitable for the pyrolysis of waste tires and waste plastics in most small and medium-sized production lines.

Limitations: When exposed to high-sulfur raw material pyrolysis gas for a long time, slight corrosion may occur. It is recommended to inspect the steel plate thickness every 6-12 months to prevent failure due to thinning.

310S Heat-Resistant Stainless Steel (06Cr25Ni20)

Extended Characteristics: With chromium and nickel content as high as 25% and 20% respectively, its oxidation resistance temperature can reach 1000℃. Its corrosion resistance in acidic pyrolysis gas environments (e.g., containing hydrogen chloride and hydrogen sulfide) is far superior to Q345R, and the service life of the equipment can be 2-3 times that of Q345R. It is suitable for the pyrolysis of high-value-added raw materials such as waste engine oil and waste rubber products.

Cost Note: The price is about 3-4 times that of Q345R, which is mostly used in large-scale batch-type production lines with high requirements for equipment stability and service life.

Advanced Material: Hastelloy (Optional)

For highly corrosive raw materials (e.g., halogen-containing waste plastics), Hastelloy C-276 can be selected as the inner layer material. It has excellent resistance to strong acids and oxidants, but the cost is extremely high, and it is only applicable to the niche scenario of pyrolysis of special chemical waste.

II. Middle Layer (Insulation and Heat Preservation Layer): Extended Material Performance and Construction Technology

The core function of the middle layer is to block heat conduction and reduce heat loss. There are significant differences in thermal insulation effect and construction methods among different materials:

Aluminum Silicate Refractory Fiber Cotton

Extended Characteristics: With a thermal conductivity as low as 0.03-0.04W/(m·K) and high temperature resistance up to 1260℃, it is light in weight. During construction, it can be directly pasted on the inner steel plate, which has both thermal insulation and shock absorption effects, and can buffer the stress caused by thermal expansion and contraction of the reactor.

Precautions: Fiber cotton is prone to moisture absorption. After construction, a layer of refractory mortar should be applied on the surface for sealing to prevent water vapor from penetrating and reducing thermal insulation performance.

Lightweight Refractory Castable

Extended Characteristics: Mixed with refractory aggregates, powder and binders, it has strong integrity and is not easy to fall off after casting and forming. The thermal insulation performance is durable and stable, and the high temperature resistance can reach 1400℃, which is suitable for working conditions with large temperature fluctuations of the reactor.

Construction Requirements: On-site formwork and pouring are required, with a curing period of 7-14 days. Drying treatment is needed after forming to avoid cracking caused by water evaporation during operation.

Energy-Saving Optimization Scheme: Some high-end models adopt a composite insulation structure of aluminum silicate fiber cotton + nano insulation board. The nano insulation board can control the outer wall temperature of the reactor below 50℃, saving 15%-20% energy compared with a single insulation layer.

III. Outer Layer (Protective Layer): Extended Structural Reinforcement and Anti-Corrosion Treatment

As the "protective shell" of the reactor, the outer layer needs to balance structural strength and corrosion resistance:

Ordinary Carbon Steel Plate (Q235B)

Extended Function: In addition to fixing the insulation layer, it can enhance the overall rigidity of the reactor by welding reinforcing ribs to prevent deformation when the horizontal reactor rotates. The thickness of the plate is usually 6-10mm, which can resist slight collision and external impact.

Anti-Corrosion Process Upgrade

Conventional models are coated with high-temperature resistant anti-rust paint, with a high temperature resistance of about 200℃. For coastal or humid areas, a double-layer protection of hot-dip galvanizing + high-temperature resistant anti-corrosion coating can be adopted. The thickness of the hot-dip galvanized layer is ≥80μm, which can effectively prevent the steel plate from rusting and extend the outdoor service life of the equipment.

IV. Extended Materials for Key Auxiliary Components

Reactor Door Sealing Components

High-temperature resistant graphite packing: With a temperature resistance up to 600℃, it has good elasticity, can compensate for the gap between the reactor door and the reactor body, and has stable sealing performance, but it needs to be replaced every 3-5 batches.

Metal spiral wound gasket: Wound with stainless steel strip and graphite strip, it has a temperature resistance above 800℃ and strong pressure resistance. Its service life is 5-8 times that of graphite packing, which is suitable for working conditions where the reactor door is frequently opened and closed.

Rolling Rings and Supporting Rollers of Rotary Main Reactor

After quenching and tempering treatment of 45# steel, the hardness can reach HB220-250, with excellent wear resistance. To further extend the service life, the surface of the rolling ring can be subjected to surface quenching treatment, with a quenching layer depth of 2-3mm and hardness increased to above HRC55. It can bear the weight of the reactor when fully loaded (usually 10-50 tons) to avoid wear deformation during operation.

Internal Stirring Components (Equipped in Some Models)

If the main reactor is equipped with built-in stirring paddles, the material should be 310S stainless steel to prevent deformation or corrosion at high temperatures. The connecting shaft between the stirring paddle and the reactor body is made of 2Cr13 stainless steel, which has strong creep resistance.

V. Summary of Material Selection Principles

Cost Priority Principle: For small and medium-sized production lines, the cost-effective configuration of "Q345R inner layer + aluminum silicate fiber cotton middle layer + Q235B outer layer" is recommended.

Service Life Priority Principle: For large-scale or high-corrosion raw material production lines, the high-end configuration of "310S stainless steel inner layer + lightweight refractory castable middle layer + hot-dip galvanized outer layer" is recommended.

Working Condition Adaptation Principle: Select materials with corresponding corrosion resistance according to the sulfur and chlorine content of raw materials to avoid premature reactor failure due to improper material selection.