Low Porosity Fire Clay Brick

Low porosity fire clay bricks are densified clay-based refractories with an Al₂O₃ content of at least 45% and apparent porosity of only 12% or 15%. Reducing open porosity is the whole point: a fireclay brick with fewer connected pores takes up alkali vapour and sulphate condensate far more slowly, so it lasts longer in the chemically hostile parts of a regenerator.

XZK Group presses the low porosity clay series in two grades, XZK-DN12 and XZK-DN15, and supplies them as the exterior wall, bottom support and structural brick of the regenerator and the tank bottom.

Why Porosity Decides Fireclay Life

Ordinary fireclay brick is a porous material, with apparent porosity of 20–26% being normal. That open porosity is the path by which a glass furnace destroys it. Alkali vapour from the batch migrates into the brick and reacts with sulphur oxides in the flue gas, and in the 800–1100°C condensation zone those reactions form sulphate salt that crystallises inside the pores. The salt occupies more volume than the gas it came from, so it wedges the structure apart and eventually blocks flues.

Densifying the body closes much of that pore path. XZK-DN12 holds apparent porosity to 12% or below, and XZK-DN15 to 15% or below, roughly halving the accessible porosity of a standard fireclay brick. Less pore volume means less room for condensate, a slower reaction front, and a longer interval before the brick spalls or the checkerwork blocks.

Low porosity clay bricks are produced from selected fireclay and bauxite with a controlled particle size distribution, pressed at high force and fired to a dense body. They cost more than ordinary fireclay brick, so their use is normally confined to the walls and courses where the chemical load is real, with standard fireclay reserved for the coolest and least aggressive positions.

Key Properties

• Low apparent porosity of 12% (XZK-DN12) and 15% (XZK-DN15), against the 20–26% typical of ordinary fireclay brick.
• Reduced uptake of alkali vapour and sulphate condensate, the main degradation route in the regenerator condensation zone.
• Cold crushing strength of at least 60 MPa (DN12) and 50 MPa (DN15) for a dense structural body.
• Refractoriness under load of 1470°C (DN12) and 1450°C (DN15) at 0.2 MPa.
• Alumina content of at least 45% with iron held to 1.2–1.5% Fe₂O₃.
• Dimensional tolerance and flatness suited to the tight joints that low porosity work demands.