Kaolin rotary kiln Introduction

The Kaolin rotary kiln is a non-metallic mineral calcination equipment. Kaolin rotary kiln is the main equipment for calcining kaolin. Kaolin is a common mineral, its main component is kaolinite, calcined kaolin can be used in many fields. Calcined kaolin can improve the strength of ceramics, and because of its high compressive strength and fire resistance, it can be used to make high-performance building materials. Calcined kaolin has high whiteness, can be used as paint, pigment, and has high added value. During the operation of the kaolin 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 kaolin, 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.

Kaolin 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 Kaolin rotary kiln

Thermal Efficiency: Kaolin rotary kilns require precise control of temperature profiles to achieve the desired calcination or processing results. The kiln's design should focus on maximizing thermal efficiency by minimizing heat losses through proper insulation and well-designed refractory lining.

Material Flow and Residence Time: The kiln's internal design should promote the proper flow of kaolin material from the inlet to the outlet. Adequate residence time ensures that the kaolin is exposed to the required temperature for the necessary reactions without over- or under-processing.

Refractory Selection: Choosing the right refractory materials for the kiln's lining is crucial. Refractories must withstand the high temperatures inside the kiln and resist chemical reactions with the processed kaolin. Proper refractory selection helps maintain the kiln's integrity and prolong its service life.

Kiln Length and Diameter: The dimensions of the kiln, including its length and diameter, influence the processing capacity and residence time of the material. The design should strike a balance between these parameters to achieve optimal processing efficiency.

Burner Configuration: The burner system plays a vital role in achieving uniform temperature distribution within the kiln. The design should ensure even heat distribution to prevent hotspots and promote uniform calcination.

Air Flow and Flue Gas Management: Proper control of air and flue gas flows helps regulate the temperature and atmosphere inside the kiln. This is important for achieving the desired calcination reactions and minimizing emissions.

Automation and Control Systems: Implementing advanced automation and control systems allows for precise monitoring and adjustment of the kiln's operating parameters. This enhances operational efficiency, product quality, and safety.

Waste Heat Recovery: Consider incorporating waste heat recovery systems to capture and utilize the heat generated during the kaolin calcination process. This can help improve overall energy efficiency and reduce operating costs.

Specifications of Kaolin 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 kaolin?

Calcined kaolin, also known as metakaolin, is a processed form of kaolin clay that is heated to high temperatures to remove water and other volatile compounds, resulting in a highly reactive and pozzolanic material. Calcined kaolin finds various applications in different industries due to its unique properties. Here are some common applications of calcined kaolin:

Pozzolanic Additive: Calcined kaolin is used as a supplementary cementitious material (SCM) in concrete to improve its performance. It reacts with calcium hydroxide produced during cement hydration to form additional cementitious compounds, enhancing strength, durability, and reducing permeability. It can be used to produce high-performance concrete and self-consolidating concrete.

Mortar and Plaster: Calcined kaolin is used in mortar and plaster formulations to improve workability, adhesion, and durability.

Ceramic Production: Calcined kaolin is used in the production of ceramics and refractory materials to improve properties like mechanical strength, thermal stability, and resistance to thermal shock.

Titanium Dioxide Extension: Calcined kaolin is used as a partial replacement for titanium dioxide (TiO2) in paints and coatings to extend titanium dioxide and improve opacity and whiteness. This helps reduce formulation costs.

Reinforcing Filler: Calcined kaolin is used as a reinforcing filler in rubber and plastics to improve mechanical properties like tensile strength, tear resistance, and elongation.

Paper Coating: Calcined kaolin is used in paper coatings to improve opacity, brightness, smoothness, and printability. It reduces the consumption of more expensive raw materials like titanium dioxide.

Catalyst Support: Calcined kaolin can be used as a catalyst support in various chemical reactions due to its high surface area and porosity.

Water Treatment: Calcined kaolin can be used in water treatment as a coagulant aid to enhance the removal of impurities and particulates.

Geopolymer Binders: Calcined kaolin can be used in the production of geopolymer binders, which are alternative cementitious materials that have lower environmental impact compared to traditional cement.

High-Temperature Insulation:

Insulating Refractories: Calcined kaolin is used in the production of insulating refractories due to its low thermal conductivity and high-temperature stability.

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.