Vibrating screening machine for limestone

Vibrating screening machine for limestone is a special screening equipment designed for limestone material characteristics. Limestone, as a sedimentary rock with calcium carbonate as the main component, has the typical characteristics of density 2.7-2.9g/cm³ and Mohs hardness 3-4. It has a wide range of natural particle size distribution and is often accompanied by impurities such as clay minerals. The vibrating screening machine uses the controllable exciting force generated by the vibrating motor to achieve the stratification and screening of materials on the screen surface. The screen surface inclination, vibration frequency and amplitude parameters are all designed according to the limestone particle size distribution and moisture content characteristics.

Working principle

The vibrating screening machine for limestone achieves material stratification and screening based on the exciting force generated by the vibrating motor. The equipment adopts a dual vibration motor synchronous counter-rotation structure. By adjusting the angle of the motor eccentric block, three motion modes can be achieved: when the angle of the upper and lower eccentric blocks is 0°, the material is radially dispersed, which is suitable for coarse particle screening; when the angle is adjusted to 15°, eddy current motion is formed, which meets the needs of conventional screening; when the angle is 45°, a high-frequency vortex effect is generated to meet the requirements of fine powder separation.

In terms of kinematic parameters, the vibration frequency of the equipment is usually controlled in the range of 15-30Hz, and the amplitude range is 3-6mm. For the screening of block stones with a particle size of >25mm, low-frequency and large-amplitude parameters (15Hz/6mm) are used to enhance the material turning by throwing motion; for fine-grained materials with a particle size of <5mm, high-frequency and small-amplitude parameters (30Hz/3mm) are used to destroy the bonding force between particles through high-frequency vibration. The inclination angle of the screen surface of the equipment is designed to be 5°-15°, and it is dynamically adjusted according to the material characteristics to ensure the balance between the material conveying speed on the screen and the screening efficiency.

The selection of the screen surface material fully considers the physical properties of limestone. For high-hardness limestone, wear-resistant manganese steel screen is used, and the service life can reach more than 8,000 hours; for materials with high mud content, polyurethane screen is used, and its self-cleaning performance can effectively prevent the sieve hole from being blocked. The shape of the sieve hole is customized according to the processing requirements. The square hole screen is suitable for block stone classification, and the round hole screen is more suitable for powder separation.

Equipment structure

The main structure of the screening machine adopts a modular design concept and consists of a screen box, a vibrator, a spring shock absorber and a support base. The screen box frame is made of Q345B steel with a wall thickness of 8-12mm. A three-layer composite screen surface is set inside: the upper layer uses a 30mm square hole screen to control the maximum particle size, the middle layer is equipped with a 10mm round hole screen to achieve classification, and the bottom layer uses a 0.5mm woven screen to separate fine powder. The screen is fixed with a quick tensioning device, and the replacement time of a single-layer screen is controlled within 20 minutes.

The vibrator adapts to the high dust environment of the limestone processing site. The spring damping device adopts rubber-metal composite spring, and the vertical stiffness coefficient is controlled in the range of 800-1200N/mm, which effectively isolates vibration transmission and ensures that the basic dynamic load of the equipment is <0.5MPa. In view of the common negative pressure dust collection needs in limestone processing, a dust removal interface is set on the top of the equipment, which can be directly connected to the pulse bag dust collector.

The design of the feeding device reflects the adaptation to the flow characteristics of limestone. The variable frequency speed feeder is used to control the material flow by adjusting the excitation frequency (20-50Hz) to avoid the blockage of the screen surface caused by instantaneous overload. For wet materials with a moisture content of >8%, a forced distributor is configured to evenly spread the material on the screen surface through a rotating scraper to improve the utilization rate of the effective screening area.

Typical application scenarios

In the field of limestone mining, the vibrating screen plays a key role in raw material pretreatment. For a limestone aggregate production line with an annual output of 3 million tons, two vibrating screens are usually configured, using a combination of a 15° screen surface inclination and a 25Hz vibration frequency to achieve a screening efficiency of >95%. In cement production in the building materials industry, a double-layer vibrating screen is used in the raw material preparation section. The upper layer separates uncrushed raw materials >50mm, and the lower layer controls the inlet particle size <5mm, ensuring that the raw material mill has a stable output of 180-200 tons per hour.

The chemical industry has strict requirements on the purity of limestone. It uses a wet screening process to spray process water (flow rate 5-8m³/h) on the screen surface to increase the screening efficiency of limestone powder with a moisture content of 12% to 88%. In the field of metallurgical auxiliary material preparation, in response to the production needs of active lime, the vibrating screen is linked with the rotary kiln system, and the screen surface inclination is adjusted through feedback from the online particle size detector to ensure that the content of fine powder <3mm is stable in the range of 15%-20%.

In view of the easy clogging characteristics of dolomite limestone, the equipment is equipped with an ultrasonic anti-clogging device. By installing an ultrasonic transducer under the screen, a high-frequency vibration of 20-40kHz is generated, so that the particles adhering to the screen holes are continuously peeled off, and the screening efficiency is increased by 25% compared with the traditional mechanical cleaning method. For high-magnesium limestone, a variable amplitude vibration mode is adopted. In the early stage of screening, a large amplitude (6mm) is used to crush soft inclusions, and then a small amplitude (3mm) is switched to protect hard particles in the later stage.

The Vibrating screening machine for limestone realizes flexible adjustment of the screen surface inclination, vibration frequency and amplitude through modular design, which can cover the full particle size range from pre-screening of coarse crushed raw materials to separation of fine powder. In view of the common bonding and clogging problems in limestone processing, by adjusting the vibration parameters and the screen surface structure, it can adapt to the needs of multiple scenarios from mining to building materials production. In the fields of limestone aggregate preparation, cement raw material processing and chemical raw material grading.