Danieli zero-liquid discharge: up to 100% blow-down water reuse
A large volume of water from the cooling circuits of steelmaking plants –meltshops, casting, rolling and strip processing lines–can be recovered for reuse as blow-down water.
The Danieli Zero Liquid Discharge -ZLD system is a compendium of technologies that allow the recovery and reuse of 80% of blow-down water as good make-up water in cooling systems.
The remaining 20% of the blow-down water is commonly exploited for slag cooling or fume cooling within quenching towers, bringing the reuse of blow-down water to 100%, achieving no water discharge and of course make-up water savings of 32%. To achieve this, ultrafiltration and reverse-osmosis membrane technologies are applied. Alternatively, the amount of rejected blown-down water (20%) can be recovered by using evaporation and crystallization processes.
80%
blow-down water reused as good make-up water
20%
blow-down water exploited for slag or fume cooling
32%
make-up water saved
Danieli minimills are generally supplied with the Zero-Liquid Discharge system, which is also available for plant upgrades. Since 2007, fourteen ZLD units have been supplied with capacities rated for 20 up to 180 m3/h; the latest installation is serving a cold-mill complex in Uzbekistan, where all the mentioned technologies were implemented.
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