Pre-treatment process for feed material for direct reduction process
A pretreatment process for solid lump feed material for a gas and pellet/lump-based direct reduction process, comprising preheating feed material to a temperature of from about 200 C to about 500 C, without reduction, in a non-reducing atmosphere prior to charging the feed material to gas-based direct reduction furnace, thereby minimizing the formation of fines within the furnace.
1. A pre-treatment process for solid lump feed material for a gas and pellet/lump-based shaft furnace direct reduction process, comprising:
preheating and predrying hematite lump feed material to a temperature of from about 200° C. to less than or equal to 500° C., without reduction, in a non-reducing atmosphere prior to charging the feed material to gas-based direct reduction furnace;
transporting the lump feed material through an insulated charging system having either an inert or oxidizing atmosphere;
charging the feed material from the insulated charging system to the furnace; and
increasing the temperature of the pre-heated feed material within the furnace from the material introduction temperature to about 750° C. within the first 20 minutes of charging the feed material into the furnace;
whereby the formation of fines within the furnace is minimized.
2. A process according to claim 1 , wherein the feed material is pre-heated to a temperature of about 200° C. to 425° C.
3. A process according to claim 1 , wherein said preheating is accomplished in a feed storage bin by introduction of waste off-gases at a sufficient temperature to heat the feed material in the storage bin.
4. A process according to claim 3 wherein the waste off-gas temperature is in excess of 500° C. upon introduction into the feed storage bin.
5. A process according to claim 3 , wherein said waste off-gases are removed from a reformer associated with the direct reduction process.
6. A pre-treatment process for solid lump feed material for a gas and pellet/lump-based shaft furnace direct reduction process, comprising:
preheating and predrying hematite lump feed material to a temperature of from about 200° C. to less than or equal to 500° C., without reduction, in a non-reducing atmosphere prior to charging the feed material to gas-based direct reduction furnace;
transporting the lump feed material through an insulated charging system having either an inert or oxidizing atmosphere;
charging the feed material from the insulated charging system to the furnace; and
increasing the temperature of the preheated feed material within the furnace from the material introduction temperature of less than or equal to 500° C. to about 750° C. in less than 20 minutes while the feed material descends the first half meter in the furnace after introduction of the feed material into the moving bed of the furnace;
whereby the formation of fines within the furnace is minimized.