Gypsum rotary kiln Introduction

Gypsum rotary kiln is a special equipment for calcining gypsum. During the operation of the gypsum 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 gypsum, 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 discharge hood cover. Gypsum stone or industrial by-product gypsum exists in the form of calcium sulfate dihydrate. There are two crystal waters in its molecular formula. Has gelling properties. The process of removing crystal water is gypsum calcination. 

Gypsum 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 gypsum rotary kiln

Material Flow and Heat Transfer:The design should facilitate a smooth and controlled flow of gypsum material through the kiln. Adequate heat transfer mechanisms, such as radiation and convection, should be considered to ensure uniform heating of the gypsum.

Kiln Shell and Lining: The kiln shell should be designed to withstand high temperatures and mechanical stresses. It may be composed of refractory materials and protective coatings. The lining should be resistant to thermal, chemical, and mechanical wear caused by the movement of materials and gases within the kiln.

Kiln Length and Diameter: The kiln's length and diameter influence the retention time of materials inside the kiln, which affects the calcination process. These dimensions should be optimized for efficient gypsum calcination.

Temperature Control and Monitoring: A robust temperature control system should be implemented to maintain consistent calcination temperatures within the kiln. This ensures the desired chemical reactions occur without over- or under-calcination. Temperature sensors and feedback mechanisms can help monitor and adjust the kiln's operation.

Specifications of gypsum 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 gypsum?

Calcined gypsum, also known as "Plaster of Paris," is a widely used material with various applications across different industries due to its unique properties. It is produced by heating gypsum (calcium sulfate dihydrate) to a high temperature, causing it to lose water molecules and transform into a dry, powdery form.

Cement Additive: Calcined gypsum, when ground into a fine powder, is used as a cement additive to control the setting time and improve the workability of concrete mixtures.

Industrial Applications: Calcined gypsum is used in various industrial applications, including manufacturing plaster casts for industrial components and products.

Plaster and Wallboard: Calcined gypsum is the primary component of plaster used for interior wall and ceiling finishes. It is mixed with water to form a paste that can be applied to surfaces and then hardens as it dries.

Drywall and Gypsum Board: Calcined gypsum is used to manufacture drywall panels and gypsum board, which are widely used for interior wall and ceiling construction.

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.