Sulfur-rich fuels and waste streams generate aggressive SO₂, SO₃, and H₂S in combustion flue gases. These acidic gases attack silica- and alumina-rich refractories, forming low-melting sulfates that erode brick surfaces. For US and Canadian incinerators and sulfur recovery units, selecting a firebrick grade resistant to high-temperature sulfur corrosion is essential to maintain lining integrity and avoid unplanned outages.
Magnesia-Chrome Bricks (MgO–Cr₂O₃):
With Cr₂O₃ contents of 40–60%, these basic refractories form protective chromate layers that repel sulfate flux. They withstand service to 1,500 °C and boast hot crushing strengths > 100 MPa. Use in primary combustion zones where SO₃ and chlorides peak—burner blocks, throat areas, and roof tiles.
Calcium Aluminate-Bonded Magnesia Bricks:
Combining 85–95% MgO with calcium aluminate binders improves slag resistance and thermal shock (ΔT ≥ 900 °C). Their lower porosity (< 12 %) minimizes gas penetration. Ideal for sidewalls and arches in sulfuric acid regenerators and Claus process reactors.
Spinel-Forming Grades:
High-alumina bricks engineered to develop in situ MgAl₂O₄ spinel at operating temperatures exhibit enhanced chemical resistance. With service ratings to 1,400 °C and spalling resistance ΔT ≥ 1,000 °C, they suit mid-zone applications in sulfur recovery furnaces.
Silicon Carbide (SiC) Refractories:
While expensive, SiC bricks (≥ 90% SiC) resist both abrasion and sulfur corrosion up to 1,400 °C. Use in high-velocity ductwork and transition elbows where particle flux and acid attack co-exist.
Recommendation: For sulfur-heavy combustion, prioritize MgO–Cr₂O₃ and calcium aluminate–bonded magnesia bricks in high-attack zones, employ spinel-forming high-alumina bricks mid-process, and reserve SiC for the most erosive, high-velocity sections. Proper zone mapping and mortar compatibility complete a robust anti-sulfation lining strategy.
