Cement rotary kiln Introduction

Cement rotary kiln structure

A cement 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 cement 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 cement 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 cement 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 cement 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 cement 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 cement rotary kiln

Counter-Current Flow: Tongli 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 rotary kiln. This gradual heating is crucial to avoid thermal shocks and to facilitate the complex chemical reactions that convert raw materials into cement.

Finite element analysis: Finite element analysis is adopted during the design of the Alumina 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 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 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 cement rotary kiln

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

HIGH-TECH ENTERPRISES

Modern intelligent processing base integrating R&D, production and sales.

Zhejiang Tongli Heavy Machinery Manufacturing Co., Ltd (Formerly known as Tongxiang Coal&Mining Machinery Factory) established in year 1958 is a member of the Chinese National Building Material Machinery Association. Tongli is on the vendor list of designated production enterprise of the Ministry of Coal Industry. ISO9001、ISO14001、ISO45001 certified, accredited as High-tech & new technology enterprise of Zhejiang Province. With 65+ years of experience, Tongli has earned first class R&D and manufacturing capabilities, dedicated to provide satisfactory manufacturing equipments for global customers.   

Industry Knowledge extension

What is the step Prior to the rotary kiln calcination?

The first step of making cement is the raw material crushing, conveying and storage. The limestone raw material from the mine needs to be crushed, ground and mixed, and the crushing process is carried out by cement crusher. When the maximum size of the input ore is ≤1600mm and the output particle size is ≤80mm, the limestone discharged from the crusher is then sent to the Φ80m circular pre-homogenization yard by the belt conveyor for pre-homogenization and storage.

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

The rotary kiln is usually used as an intermediate process. The large raw materials are crushed by the crusher and then enter the grinding equipment for grinding. After being mixed with other raw materials, they are added to the rotary kiln for redox reactions. The calcined finished products need to enter the vertical roller mill or ball mill for secondary grinding to get the finished product.