Pelletizing bentonite is a commercial grade of bentonite that holds specific properties, making it a perfect component in producing iron ore pellets as a binding agent. This grade, usually derived from Na bentonite, is capable of swelling up to many times, which is directly related to the Enslin value for pellets. After mixing this substance into iron ore concentrate, the clay layers expand and disperse due to the hydration of exchangeable interlayer cations, forming a matrix that binds the ore particles together. Pelletizing bentonite also improves the strength and bursting temperature resistance of pellets. As a result, this substance is widely used as a crucial binder in pelletizing.
Iran Bentonite Co. is a leading producer of pelletizing bentonite with a high purity that holds various properties. The outcomes of this Iran Bentonite manufacturer are unique in the marketplace by the modern techniques and the advanced tools this company employs in the process. Iran Bentonite Co’s products are perfect choices for applying in the pelleting process due to the unique characteristics that make them a specific option for this application. It is also helpful to know that customers worldwide can rely on this Iran Bentonite Supplier to enjoy smooth shipping to their intended destinations.
What is Bentonite?
Bentonite is a type of clay created by the transformation of tiny glass particles found in volcanic ash. It was given the name Fort Benton, Montana, after the area in which it was found. Bentonite is created when volcanic glass is converted into clay minerals, which requires hydration (the taking up or mixing with water). Hydration involves the loss of alkalies, bases, and possibly silica while maintaining the textures of the original volcanic glass. Bentonite is mainly composed of hydrous aluminum silicates with iron, magnesium, sodium, or calcium, crystalline clay minerals from the smectite group. There are two recognized varieties of bentonite, each with unique uses based on its physical characteristics, sodium and calcium bentonite.
When exposed to significant amounts of water, sodium bentonites expand to many times their initial size and produce persistent suspensions of gel-like masses. This type has been used to seal dams, bond foundry sands, asbestos, and mineral wool. On the other hand, calcium bentonites are nonswelling and decompose into a finely granular aggregate, frequently employed as an absorbent clay and occasionally referred to as fuller’s earth.
Early applications of bentonite in the 1800s included soap, sealant for log cabin roofs, and lubricant for wagon wheels. The uses of today vary greatly. Bentonite and sand are combined to create the molds used in metal casting or foundries. The sand grains and bentonite combine to form a flexible connection that helps the mixture maintain its shape. The casting is then created by pouring molten metal into the impression. The casting can be removed when finished, allowing the bentonite and sand mold to be reused. Animal and poultry feeding pellets are bound with bentonite, also employed as a delivery system for nutritional supplements. Additionally, bentonite absorbs excess moisture and oils, reducing pellet odor, lumping, and caking. Recent studies have demonstrated that the base-exchange capabilities of bentonite enable it to assist in the removal of specific pollutants, including ammonia.
What is Pelletizing Bentonite?
Bentonite offers various physiochemical properties, making it a reliable substance applicable to diverse industries. Each producer counts on specific characteristic bentonite to meet their intentions. For instance, pelletizing bentonite serves as a binding agent to produce iron ore pellets. Below, we will go into the detail of this grade and the pelletizing process.
Pelletizing is a method of compressing or shaping a substance into a pellet shape. Pellets are made from various resources, including waste, chemicals, iron ore, animal compound feed, plastics, etc. The procedure is an excellent choice for transporting and storing relevant goods. In the fields of powder metallurgy, engineering, and medicine, the technology is frequently used. The outstanding physical and metallurgical qualities of iron ore pellets are the reason that this substance is pelletized. Iron ore pellets are spheres ranging from 6 to 16 mm (0.2 to 0.63 in) and are the primary fuel for blast furnaces. They typically have a Fe content of 64–72% and several other materials that modify the pellets’ chemical make-up and metallurgical characteristics. Commonly, bentonite acts as a binder along with limestone, dolomite, and olivine.
Bentonite clay was used as binding bentonite when the current method of pelletizing iron ore concentrates was established in the 1950s. Because of its efficiency and comparatively low cost, it has continued to be the most used binder ever since. Nowadays, pelletizing bentonite is the primary grade of this substance, which is a binding agent in making iron ore pellets. This method transforms iron ore fines into spherical pellets that may be used as feedstock in blast furnaces to produce pig iron or direct reduction iron (DRI). This material is mainly used for iron concentrate pellets’ dry compressive strength so they can undergo procedures like smelting with minor damage. Pure Pelletizing bentonites have a maximum of 12% moisture, superior colloidal properties, great capacity to absorb water, and low suspension fluid loss. It also holds the following effects that make it a reliable substance for such applications:
- It takes up moisture, making it possible to pelletize foods with higher moisture concentrations. Changes in bentonite dosage can be made to compensate for differences in moisture;
- When the clay is wet and introduced to the iron ore concentrate, the exchangeable interlayer cations hydrate and cause the clay to expand and spread, creating a matrix that binds the ore particles together;
- The particles that adhere to one another in layers during tumbling are what create the pellets, which are then compressed into a spherical shape by the weight of the other pellets. Bentonite is evenly distributed throughout the wet pellet and maintains this moisture distribution as it expands;
- By creating a moisture-removal route, bentonite speeds up the drying process.
Different Grades of Pelletizing Bentonite
Geologically, “bentonite” refers to a form of claystone (a clay rock, not a clay mineral) made primarily of montmorillonite. It is often formed in a maritime environment by devitrification volcanic ash or tuff. As a result, a very soft, porous rock is created that may still include crystals of harder minerals and feels greasy or soapy to the touch. However, in commercial and industrial uses, the name “bentonite” is more broadly used to refer to any swelling clay made up primarily of smectite clay particles, which includes montmorillonite. The functions of this multipurpose substance in various industries make different grades from it. As an example, Strengthening bentonite and Binding bentonite are two vital grades of bentonite, widely employed as binding agents in the production of direct reduction iron (DRI) or pig iron.
The employment of Na bentonite mainly produces pelletizing bentonite. Sodium bentonite (or Na bentonite) holds unique properties, making it a beneficial additive to many industries. It is helpful to know that the montmorillonite that goes into manufacturing bentonite is an aluminum phyllosilicate mineral with a low-charge TOT crystal structure. It indicates that the layers of a montmorillonite crystal are composed of two T sheets joined to either side of an O sheet. The T sheets are so named because they contain four oxygen ions grouped in a tetrahedron around each aluminum or silicon ion. The name “O sheets” comes from the fact that each aluminum ion is surrounded by six oxygen or hydroxyl ions that are grouped in an octahedron shape. Since there is just a little electrical charge on the entire TOT layer, calcium or sodium cations that link the adjacent layers together at a distance of around 1 nm balance out the weak negative charge. The weak negative charge means that only a tiny portion of the potential cation sites on the surface of a TOT layer contain calcium or sodium. Water molecules can readily penetrate between sheets and fill empty spaces. This explains why smectite clay minerals like montmorillonite and other smectite clay minerals swell.
As a result, sodium bentonite and calcium bentonite are two significant grades of this substance with particular properties. Moreover, bentonite is classified into different grades in the market for its detailed properties. For instance, as a binder, pelletizing bentonite holds specific characteristics that make it a reliable choice for its function. Still, pelletizing bentonite can be divided into various grades. Below, you can discover the properties of this substance, which can vary depending on the manufacturer, making other grades.
Physical Features
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- Sieve analysis: maximum of 20% plus 325 mesh plus 45 microns;
- Top 10% moisture;
- 7.5% attrition at most;
- Value of Enslin: 650 min (24 hours basis);
- 450 min. for the plastic index;
- 900 min Water Absorption Capacity (PWA);
- Particular Weight: 2.4.
Chemical Properties
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- Si O2: 55 to 63%;
- Al2 O3: 16 to 23%;
- Fe2 O3: 3% maximum;
- Na2 O: 2% minimum;
- Ca O: 2% maximum;
- Mg O: 2% maximum;
- K2O: 1,25% maximum.
Pelletizing Bentonite Production Process
The production process of pelletizing bentonite plays a vital role in determining its physiochemical properties. For instance, because of changes in iron content, bentonite can have a range of 85–90%, a hardness of 1, and a density of 2-3 g/m3. This substance can also be divided into sodium, hydrogen, and calcium depending on various characteristics, such as adsorption, expansibility, and palpability, that result as variables of the process. It is also essential to produce this material in a specific color. Different colors of bentonite include white, light yellow, light grey, light green, pink, brown red, brick red, grey, and black, among others.
Considering these facts, the method and tools bentonite manufacturing companies (so-called الشركة المصنعة إيران البنتونيت in the Arabic language) utilize greatly influence the outcome they provide. Briefly speaking, the bentonite production process includes mining the ore, activating the sodium (in specific cases), drying, and milling.
The Mining Process
Although there is a lot of bentonite on earth, a consistent supply must be ensured by carefully choosing the best bentonites for each use. Manufacturers typically hire geologists, mineralogists, and mining engineers to discover acceptable deposits for their client’s demands. These professionals travel to various locations across the world. Through the back-casting technique, bentonite is surface mined, and while the mine is operating, reclamation is carried out by filling the mining pits with soil from successive holes. Heavy machinery is usually used to remove the topsoil layer, typically around 30 inches thick.
The Sodium Activation Process
The sodium activation process, an illustration of chemical modification, was created in the 1930s. Bentonite producers employ various equipment and methods for Na-Activation of Bentonite; in this subsection, you can get familiar with one of these ways. It entails rehydrating a montmorillonite component of the bentonite with an aqueous solution of Na2CO3, which serves as both the rehydrating medium for the montmorillonite and the carrier of Na+ cations for the exchange process. The process calls for thermally treating raw, calcium-rich bentonite to dry it out in advance at a temperature that removes interlayer water from montmorillonite. The expansion of the clay layers caused by the rehydration and the replacement of Na+ for Ca2+ are the two goals of the subsequent impregnation with the aqueous Na2CO3 solution. The activated clay is kept macroscopically dry during the impregnation process, ready for future applications.
The Drying Process
When mined, bentonite typically has a moisture content of 25–35% and needs to be dried to a minimum of 5% to 12%. Utilizing a rotary drum drier is a common way to achieve this. While drying is a relatively simple activity in processing minerals, special care must be taken with bentonite because overdrying could result in the clay losing some functionality. To determine how a particular source of bentonite would react to drying, Iran bentonite producers use a variety of instruments, including rotary dryers on a pilot scale. It allows them to obtain the information required to develop bentonite dryers on a larger scale. Critical process parameters, including Temperature profiles, retention times, feed and product rates, rotational speeds, and gas sampling and analysis, are frequently identified during dryer testing.
The Agglomerating Process
For its final use, like pelletizing bentonite as a binding agent or making it more manageable and flowable in a production context, producers usually seek to agglomerate the material. Bentonite is no different from other materials in its reaction to agglomeration, especially in light of the variations between and within sources.
These testing programs, whether for drying or agglomeration, allow companies to evaluate the viability of their intended process while resolving any production issues and acquiring the information required for scale-up. It also fine-tunes important product parameters like moisture content, bulk density, attrition, green/wet strength, and dry crush strength.
Pelletizing Bentonite Applications
Sodium bentonites can swell up to 25–30 times their original volume, whereas activated calcium bentonites only swell about 5–6 times. The Enslin value needed for the pellet has a direct impact on swelling. As a result, because of the faster and more fluid rate of water swelling, sodium bentonites are better suited for use in pelletizing than calcium bentonites. So, pelletizing bentonite is usually produced by the use of Na bentonite.
The filter cake’s moisture content, the kind of ore’s specific surface area, the distribution of bentonite particles inside the filter cake, and the bentonite’s quality are the essential variables for the successful usage of bentonite in pelletizing as a binding agent. To avoid affecting the quality of the iron ore, it is advised to utilize the pelletizing or binding bentonite grades with a high plastic index and liquid limit values. These grades are produced specifically to be used as a binder; they hold various advantages, including:
- Due to their structure, they can absorb the necessary moisture and produce pellets with a higher moisture content;
- When the clay layers adhere to the iron ore concentrate, they expand and scatter through a matrix-transforming concentrate, which hydrates the interstitials that can act to bind the ore particles to one another;
- These grades have an even moisture distribution in wet pellets and can spread well;
- These compounds facilitate the removal of humidity during drying, speeding up the process;
- Using these grades during manufacture could produce a “slag bond” that boosts the cooked pellet’s resilience;
- The pressure resistance of the pellets produced by adding activated calcium bentonite is significantly lower than that of the pellets produced by pelletizing bentonite.
Bentonite as a Pellet Binder
Pellets should have high grades, vigorous intensity, and uniform granularity characteristics to be an efficient furnace load throughout the ironmaking process. The acidic pellet can be coupled with highly basic pellets to generate the proper burden structure, boosting yield, decreasing coke use, and improving economic benefits. As the appropriate burden design of “high basicity sinter + acidic pellet” has spread worldwide, pellet production has significantly advanced.
Traditionally used as a metallurgical pellet binder, bentonite guarantees that the dry, roasted pellets have specific strength characteristics that match transportation standards. Several studies examined the effects on green pellets’ breaking strength, compression strength, and shock temperature by adding different types and quantities of pelletizing bentonite to iron concentrates. Results indicate that:
- The swelling, water absorption, and methylene blue absorption of bentonite are all directly connected with the amount of montmorillonite present. As montmorillonite content rises, so do swelling, water absorption, and blue ethylene absorption. These qualities demonstrate the high caliber of bentonite;
- The strength of the green pellet increases by adding bentonite. As the bentonite concentration rises, the green pellet’s falling strength and compression strength also grow;
- The green pellet’s resistance to bursting at high temperatures is improved by incorporating more premium bentonite into the iron concentrates.
About Iran Bentonite Co’s Product
Iran Bentonite Co. is among the world’s top producers of Bentonite due to its superior products. At the factories of this prominent producer, Cutting-edge tools and experienced chemists are in the service to ensure a pure outcome that passes universal quality tests. This Iran bentonite manufacturer (so-called Иран производитель бентонита in the Russian language) provides in-demand companies from every corner of the world with different types of this substance, such as binding and strengthening Bentonite suitable for pelletizing. Customers can also count on this company as a powerful Bentonite Supplier and exporter that presents their intended material under international packing with a reliable shipping plan. It is also worth mentioning that you can go for your desired way of packing and shipping; in this case, please navigate to the About Us section.
Conclusion
Pelletizing bentonite exhibits significant expansibility and hygroscopicity. It may absorb up to 8 to 15 times its dry mass in water. It can even swell up to 30 times its dry mass when wet. Bentonite solutions exhibit lubricating, viscous, and changeable characteristics. The interactions between heterogeneous or homogeneous bentonites and iron concentrate and the pellet characteristics are affected by the various forms of this substance. Pelletizing bentonite may be produced by different methods, utilizing various equipment. Still, these methods share main stages, such as mining, sodium activating, and drying. The production process can influence the outcome’s properties, so finding a perfect way to produce pelletizing bentonite is vital. This substance mainly functions as a binder in making pellets from iron ore concentrate (wet, crushed iron ore beneficiated).
