The cold-bonded pelletizing method is currently the primary approach used by metallurgical enterprises for treating steelmaking sludge. The process flow is as follows: First, the converter dust and sludge, which have been filter-pressed and contain about 30%-40% moisture, are mixed with 20-30% of steel rolling iron oxide scale and fed into a rotary dryer for drying. Iron powder pellet binder, iron powder binder, the moisture content of the dried material is generally below 5%. Second, the dried material is sieved to remove large impurities, especially iron blocks, and then fed into a mixer where 2%-10% binder is added and thoroughly mixed. Third, the material mixed with the binder is directly fed into a high-pressure briquetting machine for cold-bonded pelletizing. Fourth, the formed cold-bonded pellets first pass through a fixed screen; the undersized material is returned to the high-pressure briquetting machine, while the oversized material enters a flap dryer for dehydration and drying. The dried finished pellets, with a moisture content generally below 3%, are transported to the finished product yard for storage.
Production process flow:
1) Various materials are first blended on the ground using a forklift and then shoveled and transported to the raw material bin; 2) The materials are conveyed via belt to the rotary dryer for drying, and the dried materials are transferred to a belt; 3) Quicklime, after manual slaking, is quantitatively conveyed by a dry powder feeder to the belt as well, and finally sent to the buffer bin by the belt; 4) The materials are quantitatively fed from the metering belt under the bin to the feeding belt, which then enters the mixing section; 5) The binder can be purchased directly or prepared on-site in a reaction kettle. Starch glue is recommended here, as it is an organic formula and does not damage the converter lining. 6) The binder is quantitatively added to the mixer, and the materials and binder are thoroughly mixed and moistened in the mixing section before entering the buffer bin. They are then uniformly and quantitatively fed from the buffer bin to the briquetting machine; 7) A fixed screen is installed at the discharge of the briquetting machine. The oversized material enters the flap dryer for drying, and the dried material goes to the finished product yard. The undersized material is returned by belt to the feeding belt of the briquetting machine, iron powder forming binder, iron powder binder, and is re-pelletized by the briquetting machine. 8) The hydrated lime in the process flow diagram is mainly used to reduce the amount of binder used, which can lower the cost of binder. However, excessive hydrated lime tends to pulverize due to moisture absorption if stored for too long, while too short a storage time may result in pellets with high moisture content, affecting steel quality. Excessive calcium ions can also put pressure on the plant's wastewater treatment. Therefore, unless production cost control is extremely strict, hydrated lime may be omitted.