Zinc oxide rotary kiln Introduction

Zinc oxide rotary kiln is a kind of metallurgical kiln. Its function is to extract zinc oxide from the slag of steelmaking plant and recycle it. Zinc oxide is an inorganic compound with a chemical formula of ZnO. It is an oxide of zinc and is insoluble in water. It is a commonly used chemical additive and is widely used in plastics, silicate products, synthetic rubber, lubricating oil, In the production of paint coatings, ointments, adhesives, food, batteries, flame retardants and other products. The raw material enters the Metallurgical rotary kiln from the inlet and heated to high temperatures to undergo a complex series of physical and chemical reactions, the official terms for this process are called Metallurgical calcination. Due to the special extraction process of zinc oxide, the finished product is already in powder form after collection, so it does not need to be ground by a ball mill or a vertical mill.Tongli Offers one stop solution to zinc oxide recycling plant solution to retrieve the zinc oxide from the steel slag, our most recent project is commissioned successfully, site visit is available.

Zinc oxide rotary kiln structure

A zinc oxide rotary kiln is a large, refractory-lined cylindrical furnace used for the production of clinker, which is a crucial ingredient in the manufacturing of zinc oxide. The kiln is inclined slightly from the horizontal and rotates on its longitudinal axis. The zinc oxide 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 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 zinc oxide 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 Incineration rotary kiln. This gradual heating is crucial to avoid thermal shocks and to facilitate the complex chemical reactions that convert raw materials into final product.

Finite element analysis: Finite element analysis is adopted during the design of the 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 Incineration 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 Incineration 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 Incinerator 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 incineration kiln and rotary kiln?

A rotary kiln is primarily used for high-temperature processing of materials. It is widely used in industries such as cement, lime, minerals, and more. Its primary purpose is to carry out processes like calcination, sintering, roasting, and other thermal treatments. In a rotary kiln, the material to be processed is placed on a rotating refractory-lined drum. The material moves through the kiln due to the rotation of the drum, and it is exposed to high temperatures for the desired thermal transformation.

An incineration kiln is specifically designed for the thermal treatment of waste materials, typically with a focus on waste disposal and environmental considerations. It is used to combust waste materials at high temperatures to reduce their volume and convert them into inert residues. In an incineration kiln, waste materials are introduced into a controlled combustion environment, where they are subjected to high temperatures and combustion gases. The process is designed to break down organic materials and reduce waste to ash and gas.

The fundamental difference lies in the purpose of the equipment. Rotary kilns are used for various high-temperature material processing operations, while incineration kilns are specifically designed for waste combustion and disposal.

Rotary kilns process raw materials, minerals, and other materials for various industrial applications. Incineration kilns process waste materials, aiming to reduce waste volume and ensure proper disposal.

Both types of kilns involve high temperatures, but incineration kilns are operated at even higher temperatures to achieve complete combustion of waste materials.

Incineration kilns are subject to strict environmental regulations due to the potential emission of pollutants. Special measures are taken to control emissions, ensure clean combustion, and minimize environmental impact. Rotary kilns also have environmental considerations, but the focus is primarily on optimizing the thermal processes.

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.