New Advanced Ferronickel Smelting Technology-Direct Reduction Technology

Use Laterite nickel ore to smelt ferronickel, existing technologies include pyrometallurgy process and hydrometallurgy process. The RKEF technology is a main stream of pyrometallurgy process presently, its process is, firstly the laterite nickel ore is dried by rotary dryer, then is sintered into pellet by chain grate machine, the third step the pellet is fed into rotary kiln with 800℃ for pre-reduction, finally the pellet is fed into submerged arc furnace with 1500℃—1600℃ for reduction and melting, to get ferronickel with Ni 8%-20%.

The disadvantage of RKEF technology is, high investment, high energy consumption, high cost for facilities maintenance and low operating ratio.

New and most advanced pyrometallurgy process for ferronickel smelting is rotary hearth furnace technology, its brief introduction is as follows:

1.      Process Flow Diagram:

2. Description Of Technology Processes

2.1 Preparation Of Coal

a. Raw coal is divided into 4 classifications by screening, the first is 0-5mm, the second is 5-25mm, the third is 25-50mm, the fourth is above 50mm.

b. 0-5mm granular coal is ground into -200 mesh and screening again, granular coal with above 200 mesh is returned to grind again, powdery coal with below 200 mesh as internal blending coal is for standby application.

c. 5-25mm granular coal as reducer is for standby application.

d. 25-50mm lump coal is for coal gas generator to produce coal gas as heat source.

e. >50mm granular coal is crushed and conveyed to screening machine for classifying.

2.2 Preparation Of Nickel Ore Powder

a.       Use slide sieve to separate into +100mm lump ore and 0-100mm granular ore. The +100mm lump ore is firstly coarse crushed and then fine crushed into -30mm granular ore.

b.      The 0-100mm granular ore is dried by a rotary dryer, the moisture declines to below 3%, and uses afterheat from RHF as drying heat source. Subsequently the granular ore is separated into 0-30mm granular and 30-100mm granular ore by vibrating screen, the 0-30mm granular ore is fed into air-blowing ball mill for grinding and the 30-100mm granular ore is fed into hammer crusher for fine crushing together with the granular ore come from coarse crushing process, After fine crushing, the granularity is below 30mm.

c.       The 0-30mm granular ore is ground into powdery ore with granularity of above 75% with 0.075mm by air-blowing ball mill. The heat source for air-blowing ball mill is from RHF.

2.3 Coal Gas Generator（Or Natural Gas, LPG）

Coal gas produced as heat source is supplied to rotary hearth furnace.

2.4 Batching and Mixing

a. Totally set up 5 batched weigher with hoppers, they are for nickel ore powder, coal powder, lime powder, accessory ingredient and coal as reducer respectively, therein one batched weigher is for feeding the coal into RHF in a fixed quantity.

b. After batching, the materials is uniformly mixed by cylindrical mixer, then the mixture is conveyed to pelletizer by belt conveyor.

c. To prepare binder according to a certain proportion with raw binder and water, attenuated binder is fed into charging bucket for standby application.

2.5 Pelletizing

After mixing, the mixture is made into pellet with below Ø16 by disc pelletizer.

2.6 Screening

Green pellets are via roll screen, the crushed pellet and powder is separated out, and is returned to cylindrical mixer for recycling. The qualified pellets go into next process.

2.7 Drying

To dry pellets for increasing their strength by mesh belt furnace, after drying, the moisture of pellet is below 0.5%. The Heat source for drying is from RHF.

2.8 Reduction

      In the condition of high temperature, the pellets are reduced and molten, realize the separation of ferronickel and slag. In the process, the coal gas generated as heat source is recycled. 

2.9 Rapid Cooling ( Water Quenching )

   After reduction, the material is fed into water cooling cylinder hermetically for rapid cooling to 160℃-200℃.

2.10 Magnetic Separation And Polishing

   The mix materials from cooling cylinder is separated into magnetic material and non-magnetic material by dry-type magnetic separator, the non-magnetic material is mixture of slag and residual coal, via simply sorting by manpower, residual coal as internal blended coal is recycled. The magnetic material is granular ferronickel with a little slag, via polishing and magnetic separation, granular ferronickel and slag are separated.

3.      Environmental Protection

This project has no discharge beyond national standards, waste gas is discharged out after being treated, waste slag is made into bricks as building material, no waste water is discharged out and noise pollution is controlled within national standards.

4.      Electrical Control

  High automation control, supervisory control by computer, centralized control and site decentralized control work together.

5. Its Advantage Of Rotary Hearth Technology:

a.                Less investment, small covering area

b.     Low production cost, high economic benefit

c.                   Automatic operation, high operating ratio

To know the rotary hearth technology in detail, please visit the website: http://www.electricity-machinery.com