Published at 2022-06-11, published by cyanbat | Keywords: magnesium production process

Development of magnesium production process:

The production process and equipment of metal magnesium are relatively simple, the construction investment is less, and the production scale is flexible; the purity of the finished magnesium is high;
The furnace body is small, the construction is easy, and the technical difficulty is small;

And can directly use the resource-rich dolomite as raw material. The main disadvantage is that the heat utilization rate is low, the life of the reduction tank is short, the cost of the reduction furnace is large, it is labor-intensive, and the production process is discontinuous.

In view of the above shortcomings, a series of technical transformations have been carried out. Improve the structure of the reduction tank, use new insulation materials, cut off thermal short circuits, and improve the comprehensive thermal conductivity of the internal medium; improve the furnace type, such as using coal-water slurry to heat the bottom of the reduction tank to make it heated evenly. The use of new burners such as regenerative burners to recycle the exhaust gas; the use of modern control technology, the use of mechanized loading and unloading equipment and so on.

Compared with the Pidgeon method, the electrolytic magnesium smelting has the advantages of energy saving, good product uniformity, easy large-scale industrial production, continuous production process of metallic magnesium, and lower production cost than the Pidgeon method. It is an energy-intensive industry. However, the electrolysis method also has the following shortcomings: the production process for the preparation of anhydrous magnesium chloride is difficult to control; the dehydration of bischite requires high temperature and an acidic atmosphere, which makes the energy consumption large and the equipment corrodes seriously; the waste water discharged from the electrolysis production process , waste gas and waste residue, causing pollution to the environment and high treatment costs.

The production process of metal magnesium adopts the new Pidgeon process of magnesium smelting with mature technology, reliable, advanced and reasonable technology. The qualified dolomite is sent to the rotary kiln for calcination; the calcined dolomite, fluorite and ferrosilicon are then batched in a certain proportion, ball milled and pressed into pellets; High temperature thermal reduction is carried out to obtain crystalline magnesium; the crystalline magnesium can be obtained after remelting and refining. Including raw material reserve, dolomite calcination, grinding and briquetting, reduction and refining, etc.

1. Raw material system of magnesium metal production process: Dolomite is crushed to the required particle size in the mine, and stored in the dolomite yard in the factory. Ferrosilicon and fluorite are directly stored in the factory warehouse. Reserves are considered based on the amount required for half-month production.

2. Dolomite calcination system for the production of magnesium metal: The energy-saving and environmentally friendly rotary kiln is selected, with vertical preheater and vertical cooler. The foreign dolomite with the required particle size and quality is unloaded to the material yard, and the loader is used for stacking and reclaiming operations. After being screened by the vibrating screen, the dolomite with a particle size of 10-40mm is transported to the vertical preheater of the rotary kiln by belt. The top silo enters the preheater through the material pipe and exchanges heat with the high temperature flue gas flowing from the rotary kiln, preheats the material to above 800 °C, falls into the transfer chute, and then enters the rotary kiln to be calcined at a high temperature of 1250 °C into active calcined white. It is then unloaded into the cooler, where the high-temperature calcined white is exchanged with the cold air blown by the fan, and the active calcined white is cooled to below 100 °C, and the air is preheated to above 600 °C. The cooled activated calcined white is discharged from the cooler and then transported to the ball making workshop by the scale conveyor. The high-temperature flue gas produced by the combustion of the rotary kiln, after the heat exchange with the dolomite in the preheater, the temperature drops below 220 °C, and then enters the bag filter. The concentration is less than the specified standard. The whole line adopts PLC control system with advanced technology and reliable performance, and centralized operation and management in the main control room.

3. Ball making system for the production process of metal magnesium: the calcined dolomite is fed into the 1# silo by the elevator for standby; the ferrosilicon is crushed to less than 20mm by the jaw crusher, and is lifted into the 2# ferrosilicon block storage material by the elevator Warehouse for spare; fluorite powder is lifted from a single bucket into the 3# silo. The three raw materials stored in the storage bin are continuously batched and mixed by the ball mill under the control of the microcomputer, and the particle size is required to be less than 100 mesh. Made into pellets. The batching system adopts an intelligent control system, and the whole process is fully automated by computer monitoring. T

he ball mill is driven by a 10kV high-voltage motor, which reduces power loss compared with the original 380V low-voltage power distribution operation. There are 3 sets of dust removal systems in the ball making workshop, C1# dust removal system is set up at the ferrosilicon crushing place, C2# dust removal system is set up in batching grinding, and C3# dust removal system is set up at the briquetting place.

After comprehensive dust removal treatment, the operating environment of the ball making workshop is greatly improved compared with the traditional workshop, and the working environment of the workers is improved.

4. Reduction and refining system of magnesium metal production process: The reduction furnace adopts high-temperature air rapid reversal regenerative combustion technology, and the regenerative reduction furnace uses coal gas as fuel for continuous heating. The pellets are fed into the reduction tank in the reduction furnace by the feeder, and the magnesium vapor generated by the reduction tank is condensed into crystalline magnesium (crude magnesium) in the end condenser, and the crude magnesium is taken out and sent to the refining and alloying production line.

Production process of magnesium metal - process flow of calcined dolomite in rotary kiln: the grab crane sends the dolomite to the belt conveyor, and the qualified magnesium metal is screened out by vibration, and sent to the top silo of the preheater by the belt with a large inclination. The dolomite in the silo enters the preheater through six slide pipes respectively, and the hot flue gas at about 900°C produced during the calcination process exchanges heat with the dolomite. When the dolomite is preheated to 800 ℃, the stone is pushed into the end of the rotary kiln by the hydraulic push rod for calcination.

The rotation of the magnesium metal rotary kiln makes the dolomite evenly heated, and at the same time it moves gradually towards the kiln head. A burner is installed at the kiln head cover, and the combustion temperature reaches 1250 °C to meet the temperature requirements of active calcined white. The hot calcined white falls into the cooler from the kiln head, and exchanges heat with the secondary air blown by the blower.

The air is preheated to about 600 ℃ and enters the kiln head to support combustion, the calcined white is cooled to below 100 ℃, and evenly falls to the scale conveyor through the vibrating feeder to be transported to the next process. The tail gas leaving the preheater at about 260°C enters the bag filter through the pipeline to purify the tail gas, realize the discharge up to the standard, and complete the whole process of calcining magnesium metal.


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Source: @cyanbat   Author: cyanbat

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