5.1 Blast furnace ironmaking

Valve requirements: hot air valve, cold air valve, reverse air valve, gas shut-off valve.

Technical challenges: Resistance to high temperatures of 1200℃ (water-cooled structure), resistance to dusty flue gas erosion, and large diameter (DN2000+).

Typical applications: inlet of hot blast stove dome, main blast furnace gas pipe cutoff, and pre-adjustment of dust collector.

5.2 High-pressure water descaling for steel rolling

Valve requirements: high-pressure water descaling valve (ball valve or angle valve), check valve, accumulator quick-action shut-off valve.

Technical challenges: Withstand water hammer impact exceeding 30MPa, high-frequency opening and closing (several times per minute), and wear resistance (iron oxide scale particles).

Typical applications: control before the descaling box nozzle, outlet of high-pressure pump, and isolation of accumulator.

5.3 Alumina production (Bayer process)

Valve requirements: slurry valve (knife gate valve or eccentric hemispherical valve), alkali-resistant ball valve, three-way reversing valve.

Technical challenges: resistance to high-temperature alkali solution (NaOH concentration 250-300g/L), prevention of scarring (with smooth interior and no dead spaces), and resistance to erosion (alumina particles).

Typical applications: feeding of leaching units, discharge of underflow from settling tanks, and circulation regulation of decomposition tanks.