Key Points on Iron Ore Pellet Production Process

The production of pellets is a critical process in the mining and metallurgical industries, particularly for iron ore. This process involves several key stages, each contributing to the quality and efficiency of the final product. Understanding these stages—ore blending, pelletizing, drying, preheating, roasting, and cooling—is essential for optimizing production.

1. Ore Blending

Ore Blending?is the initial step, where different grades of iron ore are mixed to achieve a consistent chemical composition. This blending is crucial as it ensures uniformity in the pellets, which directly affects their performance in subsequent processes. The right blend can enhance the efficiency of the pelletizing stage.

Characteristics of iron fines:

Since different iron fines (e.g. SiO? content, Bryan coefficient, etc.) will have an effect on the performance of the pellets, the ratios need to be adjusted according to the characteristics of the different iron fines;

Moisture control:

Too high or too low moisture will affect the moulding and roasting process of the pellet; too much moisture will lead to the deformation of the surface of the pellet, affecting the quality of roasting; it is better to control the moisture at about 8.5% to ensure the denseness and strength of the pellet.

2. Pelletizing

Pelletizing directly affects the compactness, uniformity and size of the pellets.

By adjusting the ratio of binder and moisture, the size and compactness of the pellets can be controlled to avoid oversized pellets;

Pelletising compactness: oversized or not compact pellets will lead to insufficient roasting, thus affecting the final strength.

Pellet surface smoothness: smooth surface, no powder, no deformation is the key to improve the roasting quality.?The surface of the pellet is not smooth will cause more powder, affecting the permeability and strength during roasting, resulting in lower CCS.

Pelletizing equipment?adjustment: the inclination angle of disc is 45°-50°, and the rotation?speed is about 25r/min.

Too fast rotation speed?will lead to short residence time of green?balls in the disc, resulting in incomplete and deformed pellets.

Appropriate rotation speed can ensure uniform and dense pellets.

3.Drying

Drying stage is the key process to remove the moisture of the pellet, too high or too low temperature may affect the quality of the pellet.

Temperature control: divided into air blast and exhaust stages to reduce cracks and damage to the pellets.

Too high a temperature in the drying section will easily lead to drying and cracking on the surface of the pellet, while too low a temperature will affect the efficiency of moisture removal.

According to the test data, one section of drying is blasting air, and the temperature of the air box can be controlled between 300-350°C, and the second section of drying is extracting air, and the temperature of the air box can be controlled at 250-300 °C to ensure that the surface of the pellet will not be dried too fast and cracks will be produced.

This step is essential to prevent issues during roasting, such as uneven heating or structural integrity problems. Proper drying ensures that the pellets are ready for the next phase.

4.Preheating

Preheating is the next critical stage, where the dried pellets are heated to a temperature that prepares them for roasting. This step helps to enhance the physical properties of the pellets, making them more robust and less prone to breakage.

Preheating temperature: Reasonable control of the preheating section temperature to about 350-450°C can reduce the cracks and breakage of the pellets.

Too high or too low temperature in preheating section will adversely affect the pellets; too high temperature of air box in preheating section (e.g. 550°C) will lead to cracking of green?pellets, which will be improved after cooling down to 450°C.

Hot airflow distribution: when the temperature in the preheating section is not uniform, the uneven distribution of airflow will lead to uneven heating of the pellet, resulting in ball bursting or cracking and thus affecting the strength of the pellet; maintaining the uniformity of the airflow and the stability of the temperature will help to improve the quality of the pellet.

5.Roasting

The roasting?process involves heating the pellets to high temperatures, typically in a furnace. This step is crucial for the transformation of iron ore into iron oxide, which is essential for further processing,it is the most critical link in the production of iron ore pellets, and the adequacy of roasting directly affects the strength of iron ore pellets (CCS).

Roasting temperature control: It is ideal to control the roasting temperature at about 1300°C. The roasting temperature directly affects the liquidity of the pellets.

Roasting temperature directly affects the liquid phase formation and strength of the pellet; too low a temperature (e.g. 1180°C) may lead to insufficient roasting of the pellet and lower strength; too high a temperature (e.g. 1350°C or more) may lead to rapid sintering of the outer part of the pellet, while the inner part of the pellet is not burnt through;

6.Cooling

The cooling stage is to bring the pellets down from the roasting temperature to the ambient temperature in order to avoid rupture of the pellets by excessive thermal shock.?This step is important for handling and storage, ensuring that the pellets maintain their integrity and quality.

Temperature gradient:

The cooling process should maintain an appropriate temperature gradient; sudden temperature drop will lead to excessive temperature difference between the surface and internal temperature of the pellet, resulting in cracks; reasonable cooling rate and temperature distribution can help reduce the generation of thermal cracks.

Cooling rate: The cooling rate should be adjusted according to the actual situation of the pellet. If the cooling is too fast, the stress inside the pellet may lead to crack formation; if the cooling is too slow, the production efficiency may be affected. The cooling temperature should be controlled within a reasonable range to ensure the strength and stability of the pellet.

The improvement effect of Jianjie organic binder:

1. Improvement of CCS strength of pellets after roasting with the same feeding quantity;

2. Reduced the amount of bentonite, increased the feeding amount, the qualification rate of green pellets improved by 10%.

3. Improve the porosity of the pellet, increase the amount of divalent iron oxidised to trivalent iron during roasting, increase the oxidising atmosphere during roasting, and the high content of trivalent iron improves the pellet reduction index in the blast furnace;

In summary, the pellet production process is a complex interplay of various stages, each playing a vital role in producing high-quality pellets. By focusing on ore blending, pelletizing, drying, preheating, roasting, and cooling, manufacturers can optimize their operations and enhance the overall efficiency of their production systems.

If you have other suggestions or comments,feel free to contact me if you have any questions regarding binder :

Vicky Wen

Mobile/Whats:+86 18828077176

E-mail:?[email protected]