Application of Refractories in Cracking Furnaces

Application of Refractories in Cracking Furnaces

Cracking furnaces serve as core production equipment for ethylene manufacturing, functioning to process cracked gas and feed the downstream ethylene production units. The throughput and process efficiency of cracking furnaces directly govern the output and product quality of the entire ethylene plant, making them a pivotal component of petrochemical production; accordingly, proper selection of refractory materials is critically essential.
As the heart of ethylene production, cracking furnaces’ service life hinges heavily on the performance of their refractory lining. Among mainstream furnace types, Lummus SRT cracking furnaces see the widest field deployment, whose lining configuration and material grade are engineered around furnace chamber temperature, which in turn varies with furnace coil alloy composition.
Two primary lining classifications exist based on coil material: furnaces fitted entirely with HK40 coils operate at a lower hearth temperature (~1150°C), while units partially lined with HP40 coils sustain elevated temperatures exceeding 1300°C.
1. Low-temperature Lining for Lummus SRT‑I & SRT‑II Furnaces
These conventional ethylene production furnaces adopt full HK40 furnace coils with maximum design hearth temperature capped at 1200°C (typical operating temperature: 1150°C) under negative pressure conditions. Furnace walls are lined with calcium silicate insulation boards and lightweight refractory bricks in anchored brickwork construction. Castable refractory concrete is applied for the radiant section base, convection section base and corner structures, with refractory fiber or asbestos rope packed into expansion joints.
Typical refractory consumption per furnace:
55,000 lightweight refractory bricks, 373 burner blocks, 2,300 stainless steel anchor rods for brick fixing, 4,637 pieces of calcium silicate insulation board, 31 tons of castable refractory concrete, 1.6 tons of refractory mortar and 0.31 tons of refractory coating.
2. High-temperature Lining for SRT‑III, SRT‑IV & Staged-type Cracking Furnaces
Partial replacement of original coils with HP40 alloy raises hearth working temperature from 1150°C up to 1320°C, rendering conventional refractory bricks inadequate. They are substituted with plastic refractory (rated for continuous service at 1320°C) and advanced refractory fiber products.
Radiant chamber sidewalls and lower convection section walls feature a three-layer composite lining:
Outer layer: 75 mm-thick calcium silicate insulation slab
Intermediate layer: laid lightweight refractory brick
Working face: 165 mm-thick plastic refractory
Total lining load transfers via anchor bricks and support plates onto the outer steel shell structure.
The junction between radiant roof and lower convection chamber is built with seven layered refractory fiber felts to replace the previous suspended brick lining, cutting dead weight, simplifying site installation and boosting thermal insulation performance. An additional 30 mm mineral wool mat plus lightweight brick lining is fitted on convection chamber walls to enhance gas tightness and heat retention. Total lining weight per unit: approx. 200 tons (147 m³).
3. Key Refractory Grades for Furnace Lining
(1) Plastic Refractory
A malleable refractory batch with outstanding high-temperature mechanical strength and thermal stability, widely deployed as lining material for diverse industrial furnaces with aluminosilicate formulation.
Domestic product specifications comply with GB4758.1‑84; imported furnace-grade air-set plastic refractory is supplied in standard dimension: 50 mm × 165 mm × 300 mm.
(2) Refractory Fiber
Flexible advanced refractory material. Fiber felt lining is installed on radiant roof and adjacent lower convection section walls, with operational temperature 1060 °C, design temperature 1140 °C, flue gas velocity 5 m/s and working pressure −2.5 mmH₂O.
The composite lining consists of seven layers across three fiber grades: two layers of 50 mm Grade 306, four layers of 25 mm Grade 308 and one 25 mm Grade 318 working layer, total lining thickness 225 mm.