Fly ash rotary dryer Introduction

Fly ash rotary dryer is a kind of drying equipment that can handle a large number of wet Fly ash powders. Fly ash is a kind of volcanic ash-like mixture that is formed after coal powder is burned at high temperatures. It is produced by power plants that grind coal into coal powder below 100 micrometers and spray it into the furnace with preheated air to form a suspended state. The combustion generates high-temperature flue gas mixed with a large amount of unburned substances, which are captured by dust collectors to obtain fly ash. Fly ash rotary dryer has reliable operation, large operation flexibility, strong adaptability, large processing capacity, and strong adaptability of materials. It can dry various materials, and the equipment operation is simple and reliable. It is widely used in building materials, metallurgy, chemical industry, cement industry and so on.

Fly ash 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 fly ash rotary dryer

Drum Design and Angle: The design of the drum or shell of the rotary dryer plays a significant role in achieving proper mixing and tumbling of the material. The drum's inclination angle affects the material's movement and residence time, impacting the overall drying efficiency.

Heat and Mass Transfer: The primary purpose of a rotary dryer is to remove moisture from the material through heat transfer. Heat is applied to the material, causing the moisture within it to evaporate. As the material rotates inside the dryer, it is exposed to hot gases or air, ensuring efficient heat transfer. The design focuses on optimizing the contact between the heated air and the fly ash particles.

Drying Kinetics: Drying kinetics refers to the study of how moisture content decreases over time during the drying process. Different materials, including fly ash, have distinct drying characteristics. The design of the rotary dryer should consider the drying rate, equilibrium moisture content, and other factors that influence the drying kinetics of fly ash.

Airflow and Gas Flow: Efficient airflow and gas flow management within the rotary dryer are crucial for uniform drying. The design ensures that the hot gases or air are evenly distributed throughout the drum, preventing uneven drying or overheating of certain areas. Adequate ventilation is necessary to carry away the evaporated moisture.

Retention Time: The time the material spends inside the rotary dryer, also known as the retention time, is carefully determined based on the drying kinetics of fly ash. Insufficient retention time can result in incomplete drying, while excessive retention time can lead to unnecessary energy consumption.

Temperature Control: The design should incorporate temperature control mechanisms to maintain the optimal drying temperature. Controlling the temperature ensures that the fly ash is dried effectively without causing thermal degradation or unwanted chemical reactions.

Heat Source: The heat source for the rotary dryer can vary, including direct or indirect heating methods. The design should account for the type of heat source being used and its compatibility with the material's properties.

Specifications of fly ash 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 fly ash? 

Dried fly ash, a byproduct of coal combustion in power plants, has several applications across various industries due to its beneficial properties. 

Construction Industry: Fly ash is widely used as a partial replacement for cement in concrete and mortar production. It enhances the workability, durability, and strength of concrete while reducing the amount of cement required. This not only makes the concrete more sustainable but also reduces the overall cost of construction.

Road Construction: Fly ash can be used as a stabilizing agent in road construction. It improves the mechanical properties of soil, reducing swelling and increasing load-bearing capacity. This makes it useful in creating strong and stable subgrades for roads.

Brick and Block Manufacturing: Fly ash can be incorporated into the production of bricks, blocks, and other construction materials. It improves their strength, reduces efflorescence, and enhances their insulating properties.

Soil Improvement: In agriculture, fly ash can be added to soil to improve its structure, drainage, and fertility. It can also be used to remediate soils contaminated with heavy metals due to its ability to bind with these pollutants.

Waste Stabilization: Fly ash can be used to stabilize and solidify certain types of hazardous waste, making them less prone to leaching and thus reducing environmental risks.

Manufacturing of Ceramics and Tiles: Fly ash can be incorporated into the production of ceramics, tiles, and glass-ceramic materials. It can enhance their mechanical properties and reduce energy consumption during the firing process.

Mine Reclamation: Fly ash can be used for mine land reclamation, helping to stabilize the soil and promote plant growth in areas affected by mining activities.

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.