During the production process, coke oven doors need to be opened and closed frequently, with high surface temperature and rapid drop in coke outlet temperature. Traditional linings are built with cordierite bricks or clay bricks, with short cycles and frequent maintenance. The root cause is:
1. The composition of coking products is complex, acidic gases penetrate into the brick body along the apparent pores, continuously erode the lattice, and the performance deteriorates rapidly;
2. Rapid heating and cooling cause surface cracks and cause corner peeling;
3. Tar carbon deposits are severely adhered, and mechanical force further damages lining bricks during removal.
The ideal refractory castable for this duty must therefore combine four performance pillars: thermal-shock tolerance, high-temperature volume stability, resistance to carbon deposition and ease of on-site installation.
Thermal-shock performance
A magnesia-alumina spinel matrix withstands >50 rapid quench cycles without cracking because the spinel crystals absorb thermal stress by micro-cracking and re-healing . Independent tests on doors retrofitted with this refractory castable showed no spalling after 18 months, whereas conventional high-alumina mixes required patching every six months.
Volume stability and creep resistance
The spinel phase locks the microstructure above 1 500 °C, preventing the 1–2 % expansion that typically leads to door warping and gas leakage . This stability is further enhanced by 5–8 % fused-quartz aggregate, which introduces controlled micro-porosity, reducing thermal conductivity and cutting heat loss by 12 % compared with dense castables.
Resistance to carbon build-up
Coke-oven atmospheres are rich in CO and tar vapours that deposit carbon on refractory hot faces. The low Fe₂O₃ content (<0.5 %) in the spinel castable prevents catalytic carbon growth, allowing doors to be cleaned by simple air-lancing rather than mechanical chipping .
Installation and maintenance advantages
Because the castable sets at room temperature and gains full strength after a 24-hour cure at 200 °C, a complete door reline can be carried out during a routine 36-hour outage. Plant managers report that downtime is cut by 40 % compared with brick relines .
In recent years, large-volume coke ovens have turned to "clay + fused quartz" composite refractory castable prefabricated blocks, which solve the three major contradictions of weight, thermal shock and erosion at one stroke:
1. Matrix: Clay raw materials are cheap, high in strength, and have mature molding processes;
2. Functional phase: Fused quartz has an extremely low thermal expansion coefficient (≈0.5×10⁻⁶/℃). After introduction, it can: reduce the thermal expansion of the system and reduce temperature difference stress; induce microcrack toughening and improve thermal shock stability; It is acid-resistant and carbon-resistant, preventing tar penetration; The bulk density and thermal conductivity are both low, and the furnace door is light and has excellent thermal insulation.
Clay + fused quartz composite refractory castable prefabricated blocks take into account both economy and functionality, and fully match the working conditions of coke oven doors "high temperature, frequent opening and closing, strong erosion, and light weight". It is the preferred solution for the lining of large-volume coke oven doors in the current and future.
