Equipment Introduction

A cage crusher, also known as a cage mill, squirrel cage crusher, or medium-sized horizontal cage bar crusher, is an industrial crushing equipment designed based on the principle of impact crushing. This equipment belongs to the category of mechanical impact crushers. Its core feature is the repeated impact, collision, and shearing of materials by two sets of high-speed, counter-rotating cage rotors, thereby achieving fine crushing of the materials.

Cage crushers are widely used in various industries such as fertilizer, mining, building materials, chemicals, feed, food, pharmaceuticals, and plastics due to their simple and compact structure, high crushing efficiency, stable operation, good sealing performance, and ease of cleaning and maintenance. They are especially considered a powerful tool for crushing compound fertilizers.

Equipment Structure

The cage crusher mainly consists of the following components:

1. Foundation Support

Base and Frame: The overall supporting foundation of the equipment, bearing all working parts.

Bearing Seats and Bearing Support Frames: Used to support the main shaft and rotor system, ensuring operational accuracy.

2. Power Transmission

Electric Motors: Usually two independent motors, driving the inner and outer cages respectively.

Transmission Components: Including V-belt pulleys, belts, etc., transmitting the motor’s power to the main shaft.

Main Shaft: The core transmission shaft connecting the motor and the rotating cage.

3. Core Working Component – ​​Rotating Cage System

The rotating cage is the core working component of the cage crusher, with the following structural features:

Disc: Each cage has a steel disc fixed to the hub.

Steel Bars (Cage Bars): Two or three rings of steel bars are fixed on each disc, arranged concentrically and perpendicular to the disc.

Steel Rings: The other end of each ring of steel bars is fixed by a steel ring to increase overall strength.

Staggered Arrangement: The steel bar rings of the two rotating cages are staggered to form a crushing chamber.

4. Casing and Feed/Discharge Sections

Casing (Upper and Lower Housings): Metal outer shell enclosing the two cages.

Feed Inlet: Located at the top of the casing, used for material input.

Discharge Inlet: Located at the bottom of the casing, used for finished product discharge.

5. Auxiliary Devices

Screw Feeder: Equipped on some models, used to push materials axially for initial crushing.

Cage Loading/Unloading Device: For easy maintenance and replacement of steel bars, a device is provided to facilitate cage loading and unloading. A screw and handwheel allow the bearing bracket to move the bearings, shaft, and cages horizontally on the base.

6. Structural Types

Cage crushers are mainly divided into two types:

Double-Rotor Cage Crusher: Both cages rotate independently, each driven by a motor, rotating at high speed in opposite directions. High crushing efficiency and large output.

Single-Rotor Cage Crusher: Only one cage rotates, while the other remains stationary. Compared to the double-rotor type, it has one less shaft and related transmission components, resulting in a smaller overall size, but lower productivity.

Working Principle of the Equipment

The cage crusher employs the “reverse high-speed impact” principle: Material enters the center of the inner cage through the side feed inlet. Under the action of centrifugal force, the material is thrown towards the high-speed rotating cage ribs. The inner and outer cages rotate in opposite directions driven by two motors. As the material shuttles between the inner and outer cage ribs, it undergoes extremely violent repeated impacts, friction, and collisions.

1. Multi-stage crushing: The material first contacts the inner cage ribs, is crushed, and then flies towards the counter-rotating outer cage ribs.
2. Self-collision crushing: The material also undergoes violent collisions with each other during high-speed motion, further refining the particle size.

Finally, the material that meets the particle size requirements is discharged from the bottom under the combined action of gravity and centrifugal force.

Suitable Raw Materials for the Equipment

Cage crushers have certain requirements for raw materials and are mainly suitable for materials with the following characteristics:

Applications of the Equipment

The cage crusher has a wide range of applications, mainly covering the following industries and scenarios:

1. Fertilizer Industry (Main Application Area)

Compound Fertilizer Production: Crushing hard granular raw materials such as monoammonium phosphate, diammonium phosphate, urea, ammonium chloride, ammonium sulfate, superphosphate, and heavy calcium carbonate.

Organic Fertilizer Production: Processing fermented livestock and poultry manure, straw, biogas residue, sludge, and other organic materials.

Blended Fertilizer Production: Raw material pretreatment and return material crushing.

BB Fertilizer Production: Raw material refinement.

2. Chemical Industry

Fine crushing of various chemical raw materials.

Material crushing in salt production.

3. Building Materials and Mining Industry

Crushing of low-hardness materials such as limestone, shale, gypsum, slag, and coal.

Crushing of ceramic raw materials such as clay and earthenware.

Fine crushing in iron ore processing.

4. Feed and Food Industry

Crushing of feed raw materials such as grains and soybean meal.

Fruit and vegetable crushing (dedicated cage crusher).

Crushing of traditional Chinese medicine and food additives.

5. Other Industries

Plastics, pharmaceuticals, environmental protection (sludge treatment), etc.

Equipment operation and maintenance methods

Equipment Applications in Production Lines

(I) Applications in Compound Fertilizer Production Lines

In the compound fertilizer production process, the cage crusher mainly undertakes the two core processes of raw material crushing and screening/return material crushing. It is a key piece of equipment to ensure granulation quality and stabilize the particle size of the finished product.

Complete Process Flow: Raw Material Batching → Raw Material Mixing → Cage Crushing → Raw Material Granulation → Granule Drying → Granule Cooling → Granule Grading → Finished Product Coating → Finished Product Packaging

Raw Material Crushing Before Batching

Urea, ammonium phosphate, potassium salt, and other easily agglomerated, large-particle fertilizer raw materials are finely crushed to the fineness required for the granulation process, ensuring uniform batching and stable granulation in subsequent batching.

Return Material Crushing After Screening

Oversized and unqualified particles screened out in the granulation grading process are returned to the cage crusher for further crushing. After being refined, they are re-involved in batching and granulation, reducing waste loss and improving the finished product qualification rate.

(II) Application in Organic Fertilizer Production Lines

In the organic fertilizer production process, cage crushers are mainly used for the fine crushing of fermented and decomposed materials. They are suitable for medium- to high-moisture organic materials, are not prone to clogging, and are a core piece of equipment in organic fertilizer pretreatment.

Complete Process Flow: Organic raw material collection → High-temperature fermentation and decomposition → Cage crusher fine crushing → Ingredient mixing → Granulation → Drying and dehydration → Finished product screening → Finished product packaging

The moisture content of the fermented organic materials is generally 30%–35%. After screening and iron removal, they enter the cage crusher for fine crushing. The crushed powder is uniform in particle size, loose, and free of lumps. It can be fully mixed and homogenized with nitrogen, phosphorus, and potassium inorganic raw materials, significantly improving the subsequent granulation rate and particle uniformity, ensuring stable quality of the finished organic fertilizer.

(III) Production Line Equipment Combinations

The cage crusher can be flexibly combined with various fertilizer equipment to form a complete automated production line. The supporting equipment is divided into front-end, back-end, and auxiliary systems:

1. Front-end Supporting Equipment

Belt conveyor, bucket elevator, automatic batching system, screening and impurity removal equipment, iron remover

2. Back-end Supporting Equipment

Twin-shaft mixer, rotary drum granulator, extrusion granulator, drum dryer, cooler, grading and screening machine, automatic packaging machine

3. Auxiliary Supporting Equipment

Cyclone dust collector, induced draft fan, complete electrical control system, safety protection and sealing dust removal device

Common Equipment Problems and Solutions

Key Features of the Equipment:

1. Simultaneous crushing and mixing: Multiple materials can be fed simultaneously, achieving both crushing and mixing.
2. Concentrated and uniform particle size range in the finished product, with minimal over-crushing.
3. Compact structure, small footprint, simple foundation construction, and some models can be made mobile.
4. Sealed casing facilitates the integration with dust collection systems, ensuring controllable dust levels.
5. Wear parts are concentrated in the cage bars, allowing for convenient disassembly and replacement, and intuitive maintenance.

Cage crushers, as a classic impact crushing equipment, occupy an irreplaceable position in industries such as fertilizer, chemical, and building materials due to their advantages of simple structure, high crushing efficiency, and uniform particle size. Although traditional limitations such as rapid steel bar wear and high noise levels exist, the development of technologies such as dust-free operation, intelligent systems, and wear-resistant materials has significantly improved modern cage crushers in terms of environmental friendliness, reliability, and automation. When selecting a model, users should fully consider material characteristics, production capacity requirements, environmental requirements, and maintenance costs to choose the most suitable model for their production scenario. Through standardized operation and scientific maintenance, long-term stable and efficient operation of the equipment can be ensured.

We have been deeply involved in the fertilizer equipment field for many years, and our products cover process design, equipment manufacturing, installation, commissioning, and after-sales maintenance for multiple categories of production lines, including organic fertilizer, compound fertilizer, BB fertilizer (blended fertilizer), and bio-fertilizer, providing you with full-process services.