Slag rotary dryer Introduction

Slag rotary dryer structure

Dryer Shell: The rotary dryer shell is the main body of the dryer, where the material is loaded and rotated. It has a cylindrical shape and is equipped with lifting plates or flights to lift and disperse the material. The drum is heated by hot air or gas that flows through it, either in parallel or countercurrent direction. The drum transfers heat to the material and evaporates the moisture.

Dryer Flights: Rotary dryer flights, also known as "flights" or "lifters," are the inclined, curved structures that are attached to the internal shell of a rotary dryer. A rotary dryer is a device used to remove moisture from materials like powders, granules, and bulk solids through the process of drying. It consists of a large cylindrical drum that rotates while the material is fed into one end and is discharged from the other end after being dried.

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

Dryer pinion: The pinion is an essential part of the rotary dryer drive system, responsible for transmitting rotational motion and torque from the driving mechanism to the rotary dryer 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 dryer. When the pinion is rotated by the drive system, it drives the girth gear, causing the rotary dryer to rotate.

Dryer bearing housing: The bearing housing serves as the support structure for the dryer's rotating motion and is responsible for holding and guiding the dryer's trunnion bearings. Trunnion bearings are large, heavy-duty bearings that support the weight of the dryer 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 dryer. The bearing housing provides a stable mounting point for the trunnion bearings and ensures proper alignment of the dryer's rotation. It is typically designed to accommodate the axial and radial forces generated during the rotation of the dryer.

Dryer Hood Cover: The rotary dryer hood is located at the discharge end of the kiln and provides sealing to retain heat and gases. The rotary dryer 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 dryer Transmission device: The transmission device of the rotary dryer 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 dryer, 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 dryer and the quality of the products being processed. Usually, the rotary dryer 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 slag rotary dryer

Drying Rate: The drying rate is influenced by factors like the temperature and velocity of the drying medium (usually hot air or gases). Proper design ensures that these factors are optimized for the specific characteristics of the slag being dried.

Retention Time: The time the slag spends in the rotary dryer affects the drying efficiency. The design should provide sufficient retention time to ensure that the moisture content reaches the desired level without overheating or damaging the material.

Material Movement: The rotary motion of the dryer ensures that the material is continuously exposed to the drying medium from different angles. This movement enhances drying uniformity and prevents the formation of agglomerates.

Inlet and Outlet Design: The design of the inlet and outlet points for the slag and the drying medium is critical. They should be arranged in a way that promotes uniform distribution of heat and airflow across the material bed.

Airflow Patterns: The airflow pattern within the rotary dryer should be carefully designed to avoid dead zones where moisture-laden air can stagnate. A well-designed airflow pattern ensures even drying and prevents material accumulation.

Heat Source: Depending on the heat source available (e.g., natural gas, electricity, biomass), the design should accommodate the necessary equipment and infrastructure for generating and delivering the required heat.

Insulation and Heat Loss: To maximize energy efficiency, the rotary dryer should be properly insulated to minimize heat losses to the surroundings. This helps maintain a high temperature within the dryer, reducing the energy required for drying.

Safety Measures: The design should incorporate safety features such as temperature and pressure sensors, emergency shutdown systems, and proper ventilation to ensure the safety of personnel and equipment.

Specifications of slag rotary dryer

Note: *The initial moisture is assumed to be 2~6% and final moisture is 1~4%; Inlet temperature of hot air is 150~250 Celsius and outlet temperature is 70~90 Celsius; Production Capacity will vary according to the composition and moisture of the material.

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Industry Knowledge extension

What is the application of dried slag? 

Dried slag, a byproduct of industrial processes such as metal smelting and refining, can find various applications in different industries due to its unique properties. Here are some common applications of dried slag:

Construction and Building Materials:Dried slag can be used as an aggregate in the production of construction materials like concrete and asphalt. When crushed and mixed with cement, it can enhance the properties of these materials by improving their durability, strength, and resistance to chemicals and environmental factors.

Road Construction:Dried slag can be used as a substitute for natural aggregates in road construction. It improves the load-bearing capacity of roads, reduces rutting, and enhances skid resistance. Additionally, using slag in road construction can help in recycling waste materials and reducing the demand for virgin aggregates.

Cement Production:Dried slag can be used as a supplementary cementitious material in the production of Portland cement. When finely ground and mixed with cement, it reacts with calcium hydroxide to form additional cementitious compounds, improving the overall strength and durability of concrete.

Agriculture:Some types of slag, particularly those rich in calcium, can be used as soil amendments in agriculture. They can help improve soil structure, increase pH levels in acidic soils, and provide essential nutrients to plants. This application can enhance crop growth and productivity.

Abrasive Material:Dried slag can be processed and used as an abrasive material for cleaning, polishing, and surface preparation. It's commonly used for removing rust, paint, and other coatings from metal surfaces.

Manufacturing:Some types of slag can be used in the manufacturing of glass and ceramics. The silica content in the slag can act as a raw material in glass production, while other mineral components can contribute to ceramic formulations.

Fertilizer Production:Certain types of slag, such as phosphorous slag, can be used as a source of phosphorus in the production of fertilizers. Phosphorus is an essential nutrient for plant growth.

Landfill Cover:Dried slag can be used as a cover material in landfills. It helps reduce the infiltration of rainwater and minimize the generation of leachate, which can help mitigate environmental impacts.

What is the difference between rotary dryer and rotary kiln?

Rotary dryer: A rotary dryer is used to remove moisture from materials, such as minerals, ores, chemicals, food products, and biomass. The primary purpose of a rotary dryer is to reduce the moisture content of the material through the application of heat and the movement of the material within the drum. In a rotary dryer, materials are fed into the rotating drum, and hot gases or air are introduced to evaporate the moisture. The material is tumbled and agitated as it moves through the drum, allowing for efficient drying. Rotary dryers operate at elevated temperatures to facilitate drying, the temperatures used are generally lower compared to those in rotary kilns. Rotary dryers are used in industries such as agriculture, mining, chemicals, and food processing to remove moisture from bulk solids, powders, and other materials.

Rotary Kiln: A rotary kiln is designed for high-temperature processes, such as calcination, sintering, pyrolysis, and other thermal treatments. It's used to process raw materials or products at elevated temperatures, often in a controlled atmosphere, to bring about physical or chemical changes in the material. In a rotary kiln, materials are typically fed into one end of the kiln and gradually move towards the other end. The kiln is heated to very high temperatures, and the material undergoes chemical reactions, phase changes, or thermal treatments as it progresses through the kiln. Rotary kilns operate at much higher temperatures, often reaching well over 1000 degrees Celsius (1800 degrees Fahrenheit), depending on the specific process. These high temperatures are necessary to achieve the desired chemical or physical transformations in the material. Rotary kilns are used in industries such as cement production, lime calcination, metallurgy, and waste incineration. They are designed for processes that require high-temperature reactions, phase changes, or material transformation.