Process of Cold-solid Briquetting

 Cold-solidified briquetting is the main method for steelmaking sludge treatment in metallurgical enterprises at present.

The process flow is as follows: 
First, the filter-pressed converter dust and mud with water content of about 30%-40% is added with 20-30% rolled iron scale, and then dried in a rotary drum dryer, and the moisture content of dried materials is generally below 5%. The second step is to filter out large impurities, especially iron blocks, from the dried materials with a screen, then enter a mixer, add 8% ~ 10% binder, and fully mix evenly. The third step is to directly enter the materials mixed with binder into a high-pressure briquette machine for cold solidification into balls. Fourthly, the molded cold-solid briquettes pass through a fixed screen, the materials under the screen return to a high-pressure briquette machine, the materials on the screen enter a flap dryer for dehydration and drying, and the dried finished briquettes, whose moisture content is generally below 3%, are transported to the finished product stockyard for later use. 

                                                                                                   
 
Production process flow: 
 
1) All kinds of materials are mixed on the ground with forklifts, and then shoveled and transported to the raw material warehouse. 
 
2) The materials are transported to the rotary drum dryer through the belt for drying, and the dried materials are conveyed to the belt. 
 
3) Quicklime is also quantitatively transported to a belt by a dry powder feeder after artificial digestion, and finally sent to a buffer silo by the belt. 
 
4) The material is quantitatively sent to the feeding belt through the metering belt at the lower part of the silo, and the feeding belt enters the mixing section. 
 
5) The binder can be purchased directly or prepared from the reactor site. Starch glue is used here, and this organic formula has no damage to the converter lining. 
 
6) The binder is quantitatively added into the mixer, the material and the binder are fully mixed in the mixing section and then enter the buffer silo, and then the buffer silo is uniformly quantitatively added into the briquette machine. 
 
7) A fixed sieve is arranged at the discharging place of the briquette machine, the materials on the sieve enter the flap dryer for drying, the dried materials enter the finished product stockyard, the materials under the sieve are returned to the loading belt of the ball press by the belt, and are re-formed by the briquetting machine. 
 
8) The slaked lime in the technological process is mainly used to reduce the amount of binder, which can reduce the use cost of the binder. However, more slaked lime is easy to be pulverized due to damp when piled up for too long, and the quality of steel will be affected because of too much water content in pellets when piled up for too short. Excessive calcium ions will also cause pressure on sewage treatment in the plant. Therefore, slaked lime can not be added if the production cost is not strictly controlled. Generally speaking, steel mills require that the strength of finished balls should not be less than 800N to meet the needs of steelmaking. However, it should be considered that the pellets will be damaged during transportation, resulting in more small particles and ash in pellets, which is not conducive to steelmaking environment. Therefore, the strength of finished balls should be ensured to be above 1000N as much as possible. Therefore, the finished pellets just out of the flap dryer can be stacked for 48-72 hours, which can not only reduce the moisture, but also naturally increase the strength of the finished pellets. 
 
If the flap dryer is not used in the steelmaking sludge treatment process, and the moisture content of the finished briquette is above 10%, it is better to stack it for 7 days or even longer before using it. Cold-solidified pellets have good water resistance and weathering resistance when treated with steelmaking sludge, and do not weathering when placed in air for a long time.