Clinker rotary kiln Introduction

Clinker rotary kiln structure

A clinker rotary kiln is a large, refractory-lined cylindrical furnace used for the production of clinker, which is a crucial ingredient in the manufacturing of cement. The kiln is inclined slightly from the horizontal and rotates on its longitudinal axis. The clinker rotary kiln is composed of rotary kiln hood cover, rotary kiln shell, rotary kiln riding ring, rotary kiln girth gear, rotary kiln transmission unit and so on.

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 clinker 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 clinker 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 clinker rotary kiln

Counter-Current Flow: Tongli clinker rotary kilns are designed with a counter-current flow arrangement. In this design, the raw materials and combustion gases move in opposite directions. The raw material enters from the upper end, while the hot gases and combustion products exit from the lower end. This counter-current flow enhances heat transfer efficiency and reduces energy consumption.

Gradual Heating: The raw materials are gradually heated as they move through the clinker rotary kiln. This gradual heating is crucial to avoid thermal shocks and to facilitate the complex chemical reactions that convert raw materials into cement clinker.

Finite element analysis: Finite element analysis is adopted during the design of the clinker rotary kiln, make sure all the rotary kiln components girth gear, riding ring(tyre), supporting roller, pinion, shell is well suited for its specific job.

Sealing: Both the inlet and the outlet has a hood cover which improves the sealing effect, integrates labyrinth sealing, ceramic felt sealing, double leaf sealing, ss304 fish scale sealing to remain heat escape inside the kiln.

Filler padding: floating padding are used under the riding ring to strengthen the shell and reduce the heat induction to the riding ring.

Girth gear spring plate: Due to the high temperature of the rotary kiln, Tongli clinker rotary kiln is equipped with spring plate that is attached in between the girth gear and the shell to ensure smooth rotation and reduce heat transfer.

Girth gear/riding ring: All the metal casting are quality assured, Tongli has its own foundry and from the raw material to the finished product, the quality is reliable.

Quality inspection: Tongli offers magnetic testing and ultrasonic testing, which ensures the quality of all the metal castings and the welding seam.

Lubrication system: Tongli clinker rotary kiln is equipped with an oil station which lubricates the essential part of the rotary kiln to prolong the service lifetime as well as the smooth operation.

Specifications of clinker rotary kiln

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

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Industry Knowledge extension

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.

What is the difference between ball mill and vertical roller mill?

Both ball mills and vertical roller mills plays a vital role in the cement grinding plant. Ball mills are versatile and cost-effective, suitable for various materials and simple to maintain.

Ball mill advantages: Suitable for fine and coarse grinding; versatile and can handle a wide range of materials; simple structure and easy maintenance; high grinding efficiency, especially for hard materials.

Ball mill limitations: Energy-intensive process; may produce high heat during grinding; material retention time can be longer, affecting fineness control.

On the other hand, vertical roller mills offer superior energy efficiency and particle size control, making them ideal for cement and ore grinding applications.

Vertical roller mill advantages: Energy-efficient due to the combination of grinding, drying, and separation processes in one unit; Compact layout, requiring less space than a ball mill; Consistent and controlled product quality; Low maintenance requirements; Low vibration and noise levels.

Vertical roller mill limitations: May have higher initial costs; Limited ability to handle very hard materials; Some setups require external heat sources for drying.

Both ball mills and vertical roller mills are used for grinding raw materials, they have distinct working principles, applications, and advantages. Ball mills offer versatility and simplicity but can be energy-intensive, while vertical roller mills offer energy efficiency and a compact layout, but with limitations in handling very hard materials. The choice between the two depends on factors such as the material characteristics, desired product fineness, and specific operational requirements.