Horizontal Scraper Discharge Centrifuge: Centrifuge Special Introduction-Hezhong Environment (Beijing) Co., Ltd. was established in 2003

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Horizontal Scraper Discharge Centrifuge: Centrifuge Special Introduction

Published Time:

2023-06-28

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A horizontal scraper discharge centrifuge is a continuous operation, intermittent discharge solid-liquid separation equipment with a fixed filter bed. Under the action of centrifugal force, it periodically performs feeding, separation (dewatering), washing, and scraping, and is automatically controlled by a combination of hydraulic and electrical systems.

Horizontal scraper discharge centrifuges are suitable for materials where the solid-phase particle size is greater than 10μm, the mass fraction of solid particles is 25%~60%, and the liquid phase viscosity is less than 0.01Pa·S.

0 1 Working Principle

After the rotating drum of the horizontal scraper discharge centrifuge reaches full speed, the feed valve automatically opens, and the slurry enters the rotating drum through the feed pipe. With the help of the rake teeth, the solid matter in the slurry is evenly distributed in the filter drum. Under the action of centrifugal force, the liquid phase is thrown out through the filter screen and the filter holes on the drum wall. As the filter cake layer thickness increases, the rake teeth rotate relatively. When the rake teeth rotate to a certain angle (the material layer thickness reaches the maximum allowable thickness), they touch the limit switch and cut off the relay, causing the feed valve to close and the feeding to stop. At the same time, the washing valve automatically opens, and the washing liquid is sprayed onto the filter cake. When the filter cake is sufficiently washed, the washing valve closes. The centrifuge performs dewatering and drying, then the scraper rises and rotates to scrape the material. The scraped material is discharged from the discharge chute by gravity. After the material in the drum is discharged, the filter screen is regenerated, and one work cycle is completed, automatically proceeding to the second work cycle. For most materials, it is not necessary to wash the residual filter cake layer after each scraping; generally, the residual filter cake layer is washed every 4-8 hours.

0 2 Structural Type and Operating Method

Horizontal scraper discharge centrifuges are divided into two types: ordinary filtration and siphon filtration. Siphon scraper discharge centrifuges have strong separation capabilities and easily adjustable filtration speeds. They are suitable for occasions where filter cake dewatering is difficult, filter cake washing requirements are high, and higher requirements are placed on the final moisture content of the filter cake.

The control system of a horizontal scraper centrifuge usually adopts a combined hydraulic and electrical control method, which can achieve a high degree of automation.

03 Discharge Mechanism and Vibration Damping Device

The discharge mechanism of a horizontal scraper discharge centrifuge is related to the properties of the filter cake. For firm filter cakes, narrow scrapers can be used; while most loose filter cakes can use wide scrapers. The feeding method of the scraper can be divided into lifting scraping and rotating scraping. The discharge method can be divided into inclined chute discharge and screw conveyor discharge. The blade material is often lead-iron bronze, 1Cr18Ni9Ti, 2Cr13, or spring steel.

The rotating drum of a horizontal scraper discharge centrifuge has a residual unbalance. The interference force caused by feeding and scraper discharge, the uneven distribution of materials, and the deformation of the cantilever support structure of the centrifuge can make the vibration of the centrifuge very prominent. Therefore, a vibration damping device is needed for the scraper discharge centrifuge. The vibration damping device mostly uses rubber vibration isolators or metal spring vibration isolators. When the natural frequency of the vibration system is 1/4~1/3 of the machine's rotational frequency, and the natural frequency is higher than 300r/min, a rubber vibration isolator should be used. When the natural frequency is lower than 300r/min, a metal spring vibration isolator should be used.

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04 Model Selection

1. Horizontal scraper discharge centrifuges are suitable for materials with a solid phase mass fraction of 25%~60%, or with an average solid particle size greater than 15μm and a viscosity less than 10Pa·S. For flammable, explosive, or toxic materials, a closed explosion-proof scraper centrifuge should be selected.

2. To improve equipment production capacity, or when the filtration speed of the separated material is low and high requirements are placed on filter cake washing and moisture content, a siphon scraper discharge centrifuge can be selected.

3. When selecting a horizontal scraper centrifuge, it is necessary to ensure that the feed rate and solid concentration in the feed of the process system are stable. Otherwise, the centrifuge will produce large vibrations and noise, affecting the use effect of the centrifuge or creating safety hazards.

4. The discharge of a horizontal scraper discharge centrifuge has a certain crushing effect on the dewatered solid particles. Therefore, horizontal scraper discharge centrifuges are not suitable for materials whose solid particles cannot be crushed.

5. Horizontal scraper discharge centrifuges are also not suitable for occasions where the filter residue after dewatering is easily caked, or where the solid phase precipitation easily blocks the filter medium.