[nickel, Cobalt and Lithium Summit] interpretation and Analysis of the Application of centrifuges in New Energy Industry

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SMM May 21: at the 2021 China International Nickel-Cobalt-Lithium Summit Forum sponsored by SMM Information & Technology Co., Ltd., Yan Guoliang, technical director of Xiangtan Huibo centrifuge Co., Ltd., made a detailed interpretation and analysis on the application of centrifuges in the new energy industry.

The development of separation equipment:

From the beginning of pure manual operation, harsh environment and high labor intensity, to the later semi-automatic operation, manual intervention, effective improvement of environment and labor intensity, and then to fully automatic operation, intermittent unloading, to meet the requirements of large-scale production, finally to today's fully automatic operation, continuous operation, so that the process layout is more reasonable, the development of separation equipment is changing with each passing day, gradually moving towards the direction of full automation.

Application status of centrifuges in Lithium Industry

Separation characteristics of lithium carbonate and lithium hydroxide Filter:

The crystal particles are small and the slurry is viscous. In the separation process, the particles need to be washed to obtain a lower water content filter cake.

Scraper discharge centrifuge

Advantages: continuous operation, intermittent discharge, using filter cloth or metal filter mesh as Filter medium; if different Filter medium is replaced, the centrifuge can separate a variety of materials; the machine has strong adaptability, even when the process conditions are ripe, unattended can be achieved.

However, the shortcomings of the equipment are also very obvious, one is the low degree of automation of the process, and the other is the limited production capacity, which is difficult to meet the requirements of large-scale production.

Workflow:

The work flow of the scraper discharge centrifuge is divided into five steps, first feeding and primary dehydration, then secondary dehydration after washing, scraping and solid shooting after secondary dehydration, and finally the removal of residual filter cake.

Sodium sulfate: sodium sulfate is precipitated after freezing crystallization, and lithium hydroxide is obtained by clear liquid phase evaporation crystallization.

Iron phosphate: the filter residue is washed by multi-stage pure water and finally the filter cake is dried.

Horizontal snail centrifuge: horizontal snail settling centrifuge, horizontal snail Filter centrifuge

Horizontal snail settling centrifuge: clear mother liquor can be obtained and high solid water content can be obtained.

Horizontal snail Filter centrifuge: the solid phase with very low moisture content can be obtained, and the solid content of mother liquor is high.

Centrifuge working principle:

LW series horizontal screw settling centrifuge is mainly composed of Rapid Spin drum, screw conveyor which rotates in the same direction as drum and speed slightly higher or lower than drum, differential that ensures stable speed difference between drum and screw conveyor, casing, bearing chamber, machine base, drive motor and other parts.

When the suspension that needs to be separated enters the inner cavity of the screw conveyor through the centrifuge feed pipe, after acceleration by the acceleration cone, it flows out from the outlet of the screw conveyor and evenly distributes to the inner wall of the drum, and after entering the drum of the centrifuge, the rotating drum is adjusted to produce a strong centrifugal force, and the suspension forms an annular liquid flow in the drum, and the strong centrifugal force causes the solid particles with high density in the suspension to quickly settle to the inner wall of the drum. The sediment ring layer is formed, and due to the different rotational speed of the screw and the drum, there is a relative motion between the two. The solid phase deposited on the inner wall of the drum is further dehydrated by the relative motion of the screw and the drum, and then discharged through the slag outlet at the small end, and the continuously added liquid phase is discharged from the overflow hole at the big end of the centrifuge, thus completing the solid-liquid separation process.

Section view of the rotary part of the centrifuge:

Application characteristics of horizontal screw centrifuge:

The utility model has the advantages of compact structure, small footprint and no ancillary devices.

Continuous operation is beneficial to process layout.

Due to continuous operation, the unit consumption of space, time and energy consumption is very low.

The solid recovery rate is more than 99%, and the separation effect fully meets the requirements of ash-water recycling;

The dewatering rate of filter cake is high, which reduces the transportation difficulty and cost of gasification residue.

Fully enclosed automatic operation, friendly on-site environment, unattended operation;

There are few vulnerable parts, so the operation and maintenance become very simple.

In addition to the horizontal screw centrifuge mentioned above, now, considering that most of the industrial solid waste-industrial by-product gypsum, which is discharged in the process of industrial production, is not used, it occupies a lot of land and is piled in the open air. It has become an industrial waste residue that seriously pollutes the environment, so the special gypsum centrifuge arises at the historic moment.

Features:

Fully automatic unattended;

Low energy consumption and low energy cost;

Occupies a small area (relative to the belt filter);

The fully closed dehydration system makes the environment cleaner and less noisy.

The solid-liquid separation efficiency is high, and the residual water content of gypsum is low (compared with the plate and frame filter press).

The centrifuge can deal with thiogypsum, titanium gypsum and phosphogypsum which are common at present.

Work flow of gypsum centrifuge:

In the first step of feeding, before feeding, the classifier installed in the solid discharge nozzle is transferred to the liquid discharge position, which can prevent the liquid from flowing to the next solid process step, and the suspended gypsum can be uniformly input into the drum of the dehydrator through two feed pipes, and the excessive filling in the drum of the dehydrator can be prevented with liquid level control.

During a centrifugal dehydration, the drum of the dehydrator should be accelerated to facilitate the dehydration of part of the filter cake; in the flushing stage, a flushing tube should be used to evenly use the washing liquid in the filter cake and flush out the impurities.

After secondary dehydration, it should be noted that this step must require that the residual moisture in the filter cake meets the fixed requirements; then there is the scraping and solid discharge step, before scraping, the product classifier is transferred to the solid discharge position, and in the case of a decrease in speed, the product is scraped out by placing the scraper to the filter cake position.

The last is the removal of the residual filter cake. in order to protect the filter cloth during the scraping period, some residual filter cakes will be distributed on the filter cloth. Before removing the residual filter cake, the product classifier needs to be transferred to the solid discharge position, and then a separate flushing tube is used to remove the residual filter cake regularly according to the characteristics of the product.

Application of centrifuge in new energy industry

At a time of more fierce competition in the industry, fine equipment selection will reduce investment costs; and the popularity of continuous operation separation equipment is also conducive to chemical process design; in addition, due to continuous operation, its unit consumption of space, time and energy consumption is very low. On the other hand, the new energy industry centrifuge also provides users with a variety of separation equipment combination of separation technology solutions, and fully enclosed automatic operation, on-site environment-friendly, but also gives it the advantage that other equipment can not match.