Steelmaking facility comprising a direct reduction plant and an electric-arc furnace

A method of making steel in a mini-mill plant comprising

• a direct reduction reactor for producing hot direct reduced iron, DRI;
• a DRI melting furnace;
• a DRI cooler;
• a pressurized disengagement buffer bin located above said melting furnace;
• a dosing depressurizing bin located in series between said disengagement buffer bin and said melting furnace,
• said disengagement buffer bin having an upper portion, with space sufficient to disengage DRI from the carrier gas, and also having as its lower portion a buffering capacity to receive a continuing influx of DRI in sufficient excess of one heat size for said furnace to accommodate delays in the melting furnace until the buffering capacity is full;
• a diverter valve;
• and
• suitable conduits for transferring said hot DRI from said reduction reactor to said disengagement buffer bin and successively from said disengagement buffer bin to said dosing depressurizing bin and then to said melting furnace and/or for selectively conveying a portion of said hot DRI from said reduction reactor to said DRI cooler;
• which method comprises the steps of:
• 1. producing hot DRI in said reduction reactor;
• 2. selectively and continuously pneumatically conveying by means of a carrier gas said hot DRI to the disengagement buffer bin;
• 3. determining the amount of hot DRI which will be charged to said melting furnace according to the heat size;
• 4. determining at what level the DRI is in said dosing depressurizing bin;
• 5. conveying hot DRI from said disengagement buffer bin to said dosing depressurizing bin to at least match said amount to be charged to the melting furnace;
• 6. thereafter isolating said dosing depressurizing bin from said disengagement buffer bin:
• 7. depressurizing said dosing depressurizing bin and dosing the DRI now isolated in the dosing depressurizing bin into the furnace by said amount to be charged;
• 8. thereafter re-pressurizing and reconnecting said dosing depressurizing bin to said disengagement buffer bin;
• continuing the cycle of foregoing steps 1-8;
• except that upon determining that the level of DRI in said disengagement buffer bin has reached its buffering capacity then the pneumatic conveying by means of a carrier gas of said hot DRI is diverted to the cooler.