Pellet

Earlier in the article on iron ore and its uses, we examined iron ore and its importance in various industries. During the extraction of iron ore, a part of it is obtained as a dark silver-brown powder, which was considered useless and waste in the past; But with the advancement of technology, a technique called pelletizing was invented to use the iron in this powder. In this way, many steel products can be found in the market today, which use pellets as raw materials to make them.

What is a pellet? (pellets iron ore)

Pellet is one of the raw materials used in the production of steel sections, which is made using the powder obtained during the extraction process or crushed iron ore. After crushing, iron ore is used as a concentrate to make pellets. To obtain iron ore concentrate, it removes impurities and increases its iron grade compared to mined iron ore. The size of these particles should be at most 45 microns.

Concentrated iron ore is combined with other materials such as lime, cement, milk of lime, organic materials, bentonite and water and is made into small balls. Therefore, in addition to iron price, many other factors will also affect the production cost and the final price of the product in the market. The use of these compounds has affected the physical and chemical properties of the pellet and given it special characteristics compared to limestone.

In this picture you can see the bullet.

Specifications and physical and chemical characteristics of pellets

What we know as pellet is actually the result of compounding concentrate iron ore It is with additives that have adhesive properties and cause the following physical and chemical characteristics in the pellet:

• Increasing pellet porosity

Pellet is one of the most widely used raw materials in the blast furnace and is used in the production of steel products by the direct regeneration method. Because the components used in pellet production increase the degree of porosity, contact surface and solid contact and increase the regenerability of iron. Porosity of all types of pellets is usually between 25 and 30%.

• Reducing the density of iron pellets

One of the effects of pellet components on its physical properties is the reduction of density. There is always an inverse relationship between porosity and density. Therefore, as the porosity increases, the pellet density decreases.

• Create slag

One of the products of the pelletizing process is slag. Slag is actually a combination of silicate and complex metal oxides, which after cooling, is used in solid form in various applications such as road infrastructure materials, refractory materials, railway ballast, asphalt and concrete stone materials, etc.

• Facilitating the pelleting process

Additives used in making pellets adjust the metallurgical properties of the balls and act like a strong glue to create pellet pieces.

• Increasing pellet strength

In fact, these are compounds like bentonite that bind the compounds and components used in making balls together and make the balls strong. These pellets show high strength even against heat stress in regenerating environments.

Types of pellets

According to the most common methods of classifying iron pellets, they are divided into the following 4 categories:

• Large pellet: One of the most widely used types of pellets in the cement and steel industry is the large pellet, which is produced in various diameters between 20 and 30 mm.
• Normal pellet: In the classification of pellets based on size, types with a diameter of 10 to 15 mm are introduced as normal pellets. Normal pellets are most commonly used in direct regeneration units of blast furnaces.
• Small pellets: the smallest types of pellets with diameters of 3 to 8 mm are used in making cloche. This type of iron ball is known as small ball in the market.
• Sponge ball: Sponge ball has a spherical structure and Iranian steel factories produce it in different sizes. The most application of this type of pellet can be seen in industries based on scrap metals and casting.

The pellet is the result of combining iron ore concentrate with additives.

What is soft pellet?

Granule softener is one of the most useful products in various industries, which is sold in the form of grains of up to 6 cm and usually circular. The pulp of the pellet is brown in normal state; But there are also black and cream-colored samples in the market, whose quality is not as good as the brown ones. Pellets are widely used in making all kinds of steel sections. However, the slurries can be milled and subjected to the pelletization process after being converted into iron concentrate.

Application of pellets

All types of pellets are widely used in various industries based on their favorable chemical properties and some physical properties such as porosity and high strength. The most common use of pellets can be seen in the bridge building industry, automobile manufacturing, airplane manufacturing, home appliance manufacturing, bicycle manufacturing, etc. Among the advantages of using pellets in the production of steel sections, we can mention a 14% reduction in the emission of carbon dioxide and greenhouse gases; which is very important for environmentally friendly customers and users.

The difference between a lump and a pellet

The most important difference between pellets and lumps is their production process, which is the beginning of other differences. Soft iron, smelting aids and recycled materials from steel factories are used in the production of iron lumps. In the slag production process, this composition is burned to provide the energy needed to connect iron particles and increase the strength of steel sections by burning coke. This is despite the fact that recycled materials from factories are not used in the production of pellets, and iron concentrate, bentonite, etc. are among the raw materials of its production.

Lumps are small pellets with an irregular appearance and smaller dimensions than pellets. They have a high ability to reduce waste and increase the production efficiency of steel products. The maximum size of the pellets is 16 mm. When producing pellets, their size is very important. If the pellets are produced with a different size than the desired size, they are recycled and returned to the production cycle.

The difference between pellets and sponge iron

Sponge iron is one of the steel products in which pellets are used in its production. However, there are many differences between them. The first and most important difference is the grade of iron. The grade of iron in the pellet is 67% and for sponge iron is 84%. It is very easy to maintain and move the pellets; While Sponge iron Due to its self-igniting ability, it must be stored and transported under special conditions.

Pellet production process and types of methods

To produce pellets, it is necessary to make the necessary preparations first, such as preparation of raw materials, iron concentrate, etc., and after the formation of raw pellets, it reaches the baking stage. Two methods, Alice Charlesmers and Lorgi, are used for pellet production, the only difference being in the cooking stage. In Iran, the Lorgi method is mainly used. In this method, the third stage includes blowing, suction, preheating and baking, which is done to harden the pellet and by passing air through it. Finally, the pelletizing process is completed by cooling the pellets.

تأثیرگذارترین عوامل بر قیمت گندله آهن

مهم‌ترین عوامل تعیین‌کننده قیمت گندله آهن، مشخصاتی مانند قطر، استحکام و خواص فیزیکی مانند مقاومت در برابر فشار، ضربه و فرسایش است.  هرچه قطر گندله بیشتر باشد، وزن آن نیز بالاتر رفته و به مواد اولیه بیشتری برای تولید نیاز دارد. به همین دلیل، گران‌تر از گندله‌های سبک‌تر خواهد بود. خواص مکانیکی گندله موجب کیفیت و دوام بالاتر آن می‌شوند. ازاین‌رو، بر روی قیمت آن نیز مؤثرند. علاوه بر مشخصات توپ‌های آهنی، می‌توان عوامل دیگری را نیز در قیمت روز گندله دخیل دانست. ازجمله مهم‌ترین این عوامل می‌توان به قیمت دلار و مواد اولیه اشاره کرد که همواره نوسان داشته‌اند.