Silicon Metal Project Description

1. Electric Arc Furnace Capacity and Production

33,000 kVA semi-enclosed electric arc furnace, industrial silicon rotating furnace;
Daily production of approximately 55 tons of silicon metal products.

2. Product proposal

Category	Chemical composition, %
	Si≥	Impurities ≤
	Nominal silicon content	Fe	Al	Ca
Si4110	99.40	0.40	0.10	0.10
Si4210	99.30	0.40	0.20	0.10
Si4410	99.10	0.40	0.40	0.10
Si5210	99.20	0.50	0.20	0.10
Si5530	98.70	0.50	0.50	0.30

3. Raw material conditions and technical requirements for public and auxiliary media

The production of metallurgical silicon primarily uses quartz as the main raw material, combined with low-ash coal, charcoal, or petroleum coke for charging into the furnace, with wood blocks used as auxiliary material. Charging refined materials into the furnace is an important measure to ensure smooth furnace operation, improve product quality, and reduce production costs. In accordance with the principles of charging refined materials, the technical requirements for the main raw materials are as follows:

3.1 Quartz

The chemical composition requirements of quartz are shown in Table 1.

Table 1-1 Chemical composition of quartz

SiO₂	Fe₂O₃	Al₂O₃	CaO	LOI (Loss on Ignition)	H₂O	UD
99.5%	0.04%	0.15%	0.05%	0.21	1%	0.05

The size of quartz is 20~ 120 mm.

If there is soil in the quartz before batching, it must be washed with water to prevent soil and other attachments from entering the furnace and polluting the product. In addition, the properties of quartz should have strong thermal stability and antiknock rating is greater than 80%, to ensure the thermal strength after being fed into the furnace.

3.2 Reductant

The chemical composition requirements of reductants are shown in Table 1.

Name	LAM Coal	Green Pet coke	Charcoal	Prebaked Carbon Electrode
FC	54~60	88.00	75	95.00
Volatiles	≥35	≥13	21	2.00
Ash	≤3	≤0.5	4	3.00
S	0.500	4	0.02	-
P	0.004	0.02	0. 045
H2O	7.00	12.00	15	-
Particle size, mm	5~25	5~25	25~120	-

3.3 Electrode

For this project, the electrodes of 33 MVA silicon metal electric arc furnace are selected as φ1272 mm electrodes, with a maximum allowable electrode diameter margin of 1320 mm reserved. The technical requirements for the electrodes are shown in the table below:

Resistivity	Tensile strength	Rupture strength	Ash	Volume density
＜25μΩ/m	＞2.5Mpa	＞5Mpa	＜1.5%	1.56-1.61g/cm3

3.4 Oxygen and compressed air

Oxygen is mainly used in liquid silicon metal refining. The purity is more than 92% and the pressure is 0.6Mpa.

Compressed air is used for dust collector cleaning, furnace workshop purging, silicon ladle cleaning, pneumatic control, etc., at a pressure of 0.6 MPa.

3.5 Power source condition

Smelting power supply voltage for the submerged arc furnace: 30 / 35 / 66 / 110 kV

Voltage: 11/10kV
Frequency: 50Hz
Low voltage AC400/230V

4. Project production capacity (33MVA)

No.	Item	Unit	Single Furnace Index	Remarks
1	Capacity		18000	Production at full load after compensation
2	Compensated power factor of submerged arc furnace		≥0.83
3	Smelting power consumption	kWh/t	≤12000
4	Annual working days	Days	330
5	Product output	t/a	~16500	Product yield: 92%
6	Furnace capacity	kVA	33000
7	Capacity of single phase transformer	kVA	Each furnace 3×11000	3 single phase transformer
8	Si recovery		＞82%
9	Water circulation utilization rate		＞98%
10	The emission concentration of main dust collector is equal to or less than	mg/m³	≤10

Smelting process equipment

Introduction to process flow

Preparation of Raw Materials

The workshop is equipped with a complete raw material charging and distribution system. Screening, crushing, washing, and other raw material processing equipment are reasonably configured according to the condition of incoming raw materials.

All qualified raw materials are transported by truck or train to the raw material storage yard. After processing, they are conveyed to the batching station by grab cranes, belt conveyors, or loaders. At the batching station, the qualified raw materials are weighed and mixed according to specified proportions using a metering system. The blended materials are then delivered to the electric furnace for smelting.

industrial silicon Introduction To Process Flow

Electric Furnace Smelting

01/

The blended qualified materials pass through a surge bin, furnace-top belt conveyor, circular distribution car, and storage bin, and are then fed into the electric furnace through charging pipes for smelting and reduction. An auxiliary charging pipe outside the furnace is provided for manual burden surface maintenance under special operating conditions.

02/

The mixed charge undergoes continuous electrothermal reduction inside the furnace. Molten silicon is continuously produced and accumulates at the furnace bottom. Silicon tapping operations are carried out at regular intervals. During tapping, the tap hole is opened using a burn-through machine, allowing the molten silicon to flow into a silicon ladle mounted on a ladle car. When the molten silicon in the ladle reaches a certain level, oxygen is injected for silicon refining.

03/

Refining is performed by blowing oxygen-enriched gas into the ladle to reduce the aluminum and calcium contents. After refining, the molten silicon is transported to the casting area, where it is poured into ingot molds by an overhead crane or a tilting machine. The silicon metal ingot molds are mounted on movable carts, enabling fixed-point casting operations.

04/

After cooling and demolding, the industrial silicon is transported to the finished-products bay for crushing, packaging, sampling, and laboratory analysis. The silicon ladles used for casting are cleaned, repaired, and baked after pouring, preparing them for the next tapping operation.

05/

The furnace off-gas is purified by a dry baghouse dedusting system. The collected dust is densified, packaged, and stored, and can be sold to manufacturers as a raw material for the building materials, refractory materials, ceramics, and other industries.

06/

The dust concentration in the purified exhaust gas is less than or equal to 10 mg/Nm³, meeting the local environmental regulations and atmospheric pollutant emission standards.