Sponge Iron rotary kiln Introduction

Sponge Iron rotary kiln is the calcination equipment used for processing the sponge Iron. Sponge iron is mainly used in electric furnace steelmaking, as scrap steel or used in combination with scrap steel to improve the furnace charge. Compared with the use of scrap steel smelting in electric furnaces, the advantage of using sponge iron is that its chemical composition is stable, which is beneficial to control the quality of steel; sponge iron contains less impurity elements (especially P, S, N), and it can be used in conjunction with poor-quality scrap steel. It can smelt steel types that can only be smelted using scrap steel, which is conducive to improving the quality of steel and expanding the variety of steel products; During the operation of the sponge iron rotary kiln, the slurry that has been homogenized to meet the is fed requirements into the kiln by the feeder at the kiln head to calcine the sponge iron, and the fuel is injected from the kiln head and burned in the kiln, and the heat emitted is heated to the raw material. The raw material is calcined and finish product is discharged from the bottom of the kiln shell, enters the cooling machine, and is collected after cooling.

Sponge Iron rotary kiln structure

Rotary kiln thrust roller：The thrust roller is a critical part of the rotary kiln system. It serves the purpose of supporting the kiln's weight and maintaining its axial position, ensuring that the kiln remains properly aligned along its axis. The thrust roller is typically positioned on the downhill side of the kiln and is attached to the kiln shell, it consists of a central shaft or journal and a roller assembly.

Rotary kiln pinion: The pinion is an essential part of the rotary kiln drive system, responsible for transmitting rotational motion and torque from the driving mechanism to the rotary kiln itself. It consists of a gear wheel with teeth that mesh with the teeth of a larger gear, often referred to as the "girth gear" or "ring gear." The girth gear is attached to the outer shell of the rotary kiln. When the pinion is rotated by the drive system, it drives the girth gear, causing the rotary kiln to rotate.

Rotary kiln bearing housing: The bearing housing serves as the support structure for the kiln's rotating motion and is responsible for holding and guiding the kiln's trunnion bearings. Trunnion bearings are large, heavy-duty bearings that support the weight of the kiln and allow it to rotate smoothly. These bearings are subject to high loads, extreme temperatures, and potentially harsh environments due to the nature of the processes occurring inside the rotary kiln. The bearing housing provides a stable mounting point for the trunnion bearings and ensures proper alignment of the kiln's rotation. It is typically designed to accommodate the axial and radial forces generated during the rotation of the kiln.

Kiln Shell: The rotary kiln shell is a thick, steel cylindrical structure that provides the necessary strength and rigidity to withstand the high-temperature environment inside the kiln. It also serves as a containment vessel for the materials and gases during the manufacturing process. Inside the kiln shell is the refractory lining usually refractory bricks or sometimes refractory castable. Tongli kiln shell has good sealing performance, the edge of each shell is machined smoothly, enhance the sealing and service life of the rotary drum.

Kiln Hood Cover: The rotary kiln hood is located at the discharge end of the kiln and provides sealing to retain heat and gases. The rotary kiln operates under the negative pressure, therefore Tongli implied SS304 lining plate and ceramic felt both in the front and back end to prevent heat leakage.

Rotary Kiln Transmission device: The transmission device of the rotary kiln is mainly composed of main transmission, auxiliary transmission, mechanical thrust roller/hydraulic thrust roller, motor, gearbox and other components. The unique design of tongli transmission can greatly improve the service life and safety performance of the equipment.

PLC control system: A PLC is a digital computer-based system that is designed to control various industrial processes automatically. In the context of a rotary kiln, a PLC is used to monitor and control parameters such as temperature, rotation speed, air flow, fuel flow, and other critical variables that affect the performance of the kiln and the quality of the products being processed. Usually, the rotary kiln control system is integrated in the whole factory’s plc system, therefore we will provide the on-site cabin and a signal cable to the central plc.

Design principles of Sponge Iron rotary kiln

Temperature Control: Maintaining precise and controlled temperature profiles within the rotary kiln is essential for the success of the reduction process. The kiln should be designed to provide uniform heating and minimize temperature variations along its length.

Refractory Lining: The selection of appropriate refractory materials for lining the kiln is vital to withstand the high temperatures and chemically aggressive environment inside the kiln. Different zones within the kiln may require different types of refractories to withstand varying conditions.

Material Flow: The design should facilitate the smooth flow of material inside the kiln. Proper mixing and agitation of the iron ore feed, as well as any additives or fluxes, are important to ensure consistent and efficient reduction.

Gas Flow and Circulation: The flow of gases within the kiln is essential for carrying heat and reducing agents to the iron ore. Adequate gas circulation and flow patterns should be designed to maximize heat transfer efficiency and optimize reduction reactions.

Retention Time: The residence time of the material inside the kiln is crucial for achieving the desired reduction reactions. The kiln's dimensions and rotational speed should be chosen to ensure the required retention time for the reduction process.

Waste Gas Management: The waste gases generated during the reduction process contain various components, including carbon dioxide and volatile byproducts. Proper design of the waste gas management system, including off-gas treatment and heat recovery, is important for environmental compliance and energy efficiency.

Instrumentation and Control: The design should incorporate instrumentation and control systems to monitor and regulate various process parameters, such as temperature, gas composition, and material flow. This helps ensure consistent product quality and operational safety.

Mechanical Integrity: The rotary kiln's mechanical design should account for factors such as thermal expansion, mechanical stress, and potential wear due to the abrasive nature of the process. The kiln's support structure and components must be robust and durable.

Specifications of Sponge Iron rotary kiln

Note: *The diameter is the inner diameter, Weight excludes refractory material.

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Industry Knowledge extension

What is the application of calcined Sponge Iron?

Calcined sponge iron, also known as direct reduced iron (DRI), is a highly porous and metallic material that is produced by the reduction of iron ore in the form of pellets or lumps. It is used as a feedstock in various industries for its iron content and specific characteristics.

Electric Arc Furnaces (EAFs): Calcined sponge iron is used as a substitute for scrap iron in electric arc furnaces for steelmaking. It provides a source of metallic iron that helps control the chemical composition of the steel produced.

Induction Furnaces: In some cases, calcined sponge iron can be used as a source of iron in induction furnaces, which are also used for steelmaking.

Iron Casting: Calcined sponge iron can be used as a partial replacement for pig iron in foundry applications, such as iron casting. It can help reduce costs and improve the properties of cast iron products.

Sinter Plant: In the sintering process of iron ore, calcined sponge iron can be used as a part of the raw materials mix. It contributes to the formation of sintered agglomerates used in the blast furnace.

Cement Production: In some cement manufacturing processes, calcined sponge iron can be used as an iron source to provide the necessary iron oxide for the production of clinker.

Chemical Industry: Calcined sponge iron can be used as a reducing agent in various chemical processes, where reduction reactions are required. It can help convert certain metal ores or compounds into their reduced forms.

Hydrogen Reduction: Calcined sponge iron can be used as a catalyst or reducing agent in hydrogen production processes.

Wastewater Treatment: In some wastewater treatment processes, calcined sponge iron can be used as a media for removing contaminants through adsorption and chemical reactions.

What is the difference between rotary kiln and vertical roller mill?

The rotary kiln and vertical roller mill are both essential pieces of equipment in the cement manufacturing process, but they serve different purposes and are used at different stages of the process.

The rotary kiln is a large cylindrical vessel used for calcining raw materials at high temperatures. It's a core component of the cement manufacturing process and is responsible for transforming raw materials, particularly limestone and clay, into clinker. In the rotary kiln, the raw materials are heated to temperatures exceeding 1400°C (2552°F), where chemical reactions occur that result in the formation of clinker nodules. And they need to be ground into a fine powder to produce cement. This final grinding process is often performed using a vertical roller mill. The clinker is mixed with gypsum and possibly other additives to create the final cement product.

Vertical Roller Mill (VRM): The vertical roller mill is a grinding machine that grinds materials into fine powders, after the raw material is crushed by the crusher, it enters the vertical roller mill. It is typically used for grinding raw materials, clinker, and additives in the cement manufacturing process. The VRM operates by applying hydraulic pressure and vertical force to the grinding rollers, which then grind the materials between the rollers and the grinding table. This grinding process results in a fine powder that is later used as a key ingredient in the production of cement which is important for the subsequent chemical reactions in the rotary kiln.