Scrap Pre-Heating — AFC

AFC — "Always Furnace Closed": the STEB scrap pre-heating system that charges hot scrap laterally into the furnace, without ever opening it.

How it works

The furnace never opens

With the AFC system the scrap is loaded laterally into a heating tank, where the furnace fumes pre-heat it before charging. During melting the fumes pass through the charging tank; during charging they are diverted into a dedicated by-pass, avoiding any exit of fumes. The by-pass also helps to mix the fumes and maintain a high temperature.

The process is fully monitored by software, phase by phase:

Scrap preparation and transport
Scrap bucket charging
Scrap pushing into the furnace (closed in normal operation)
Melting
De-slagging
Tapping
Software monitoring of the whole cycle

Performance

Measured results

Data from the reference installation (75-ton tapping furnace, Aceros DM, Mexico) and from process calculations.

~300kWh/ton — energy consumption with pre-heated scrap

−100kWh/ton vs. charging cold scrap

~678 °Cscrap temperature after 35 minutes in the tank

120 m³heating tank: 60–85 tons of scrap per charge

~8 M€estimated yearly saving on energy, gas and electrodes

Energy saving vs. scrap temperature — chart

The new AFC solution

More production, no compromises

Double charging system — scrap charging no longer stops the furnace: no extra power-off, more performance.
By-pass for the fume circuit — no fume exit during charging, better fume mixing and temperature.
Flexible charging mode — lifting electrodes or complete charging stroke of the carriage.
Full back-up mode — in case of pre-heating problems the customer can always charge a standard bucket into the furnace.

One full heating-tank charge (about 78 tons at average scrap density) covers a complete heat of 65 tons plus around 15% of scrap losses.

Gallery

The AFC system

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Write to sales@stetechnology.com