3.2　Process

3.2.1　The workshop composition of SAF and refining furnace shall be in accordance with the following requirements:

1　The production system of SAF workshop shall consists of proportioning station，smelting workshop（including transformer room and control room），casting workshop，finishing workshop and slag treatment system.

2　The production system of refining furnace workshop shall consists of proportioning workshop，smelting workshop（including transformer room and control room），casting workshop and finishing and crushing workshop.

3.2.2　The daily production capacity of SAF shall be calculated based on the following formula:

Where:Q—SAF production capacity（t/d）.

P—Rated capacity of transformer（kV·A）.

K1—Utilization factor of transformer power，taking 0.95-1.00，and taking 0.95 for SAF with capacity over 25000 kV·A，and annual working days taking 330 d-335 d.

K2—Fluctuation factor of power grid voltage，taking 0.95-1.00，and taking 0.95 for SAF with capacity over 25000 kV·A，and annual working days taking 330 d-335 d.

cosφ—Power factor，taking 0.85-0.93 after compensation at secondary side.

T—Daily production time of SAF，taking 24h.

W—Specific power consumption（kW·h/t）.

3.2.3　Capacity of SAF transformer is calculated based on the following formula:

Where:ρ—Required rated capacity of transformer（kV·A）.

Q—Required annual production（t/a）.

K1—Utilization factor of transformer power，taking 0.95-1.00.

K2—Fluctuation factor of power grid voltage，taking 0.95-1.00.

cosφ—Power factor，taking 0.85-0.93 after compensation at secondary side.

W—Specific product power consumption（kW·h/t）.

T—Annual working days of SAF，taking 330d-335d.

3.2.4　Annual production capacity of refining furnace shall be calculated based on the following formula:

Where:Q—Annual production capacity（t）.

G—Output per tapping（t）.

N—Annual working days（d）.

T—Furnace smelting time（min）.

3.2.5　The transformer of SAF should adopt high grid voltage，low impedance and on load voltage regulation.

3.2.6　The annual working days of SAF shall not be less than 330d，and the annual working days of refining furnace shall not be less than 300d.

3.2.7　The proportioning，electrode control and dedusting system shall adopt program control or distributed control.

3.2.8　In case computer proportioning is adopted，different raw materials shall be laid on belt conveyor by layers.The weight error shall be controlled within 1% and the error between preceding and following batches shall be compensated.

3.2.9　Inside diameter of feeding tube of lumpy material shall not be smaller than 3 times of max.material diameter，and shall not be smaller than 350mm.The angle between tube and horizon shall not be smaller than 50°.

3.2.10　The electrode cross section current density for smelting different products shall be determined in accordance with the following stipulations:

1　For ferrosilicon（Fe-Si）:5.50 A/cm2-6.00A/cm2.

2　For Ca-Si alloy:7.00A/cm2-8.00A/cm2.

3　For high carbon ferromanganese（Fe-Mn）or Si-Mn alloy with semi-closed or closed SAF:5.80A/cm2-7.00A/cm2.

4　For high carbon ferrochromium（Fe-Cr）or Cr-Si alloy:6.00A/cm2-6.50A/cm2.

3.2.11　Current density of conducting copper tube should be 3A/mm2.

3.2.12　The electrode slipping shall adopt programmed control and frequent and less slipping shall be adopted.The slipping length for each time shall not be over 25mm.The electrode slipping time and slipping length shall be recorded.In case of re-start after shutdown，slipping is not allowed before the electrode power is restored to the full load.

3.2.13　For electrode hoisting，copper contact shoes must be released first，and operation with power on is strictly forbidden.

3.2.14　The roof of closed SAF shall be equipped with thermometer，pressure gauge and anti-explosion hole，and fume duct shall be equipped with hydrogen measuring instrument and alarm device.Each operation platform shall be equipped with CO detector and alarm device.

3.2.15　The pressure inside closed SAF shall be controlled at±20Pa，and the hydrogen content in furnace shall be lower than 2%.

3.2.16　The oxygen content in closed SAF shall be lower than 2%.

3.2.17　The bottom shall be equipped with temperature measuring points with number not less than 3，and the measuring range shall be controlled within range of 0-900℃.

3.2.18　For production of medium and low carbon ferromanganese（Fe-Mn），EAF metal manganese and medium，low and extra low carbon ferrochromium（Fe-Cr），hot charging and hot pouring process shall be adopted.

3.2.19　The hot metal granulating shall be provided with buffer mould.

3.2.20　When SAF with rotary body is selected，it shall be in accordance with the following requirements:

1　When variable frequency motor is adopted，it shall be capable of rotating by 360° around vertical axis or reciprocating by 120°.

2　It should adopt drive with high speed reduction ratio adopting gear drive plus pin gear drive.

3　The rotary drive device should be arranged below 0.00m.

3.2.21　Different lining of SAF and refining furnace shall be selected according to requirements of different smelting products and slag alkalinity.In case slag alkalinity is higher than 1.0，magnesium or carbon lining should be adopted；in case slag alkalinity is lower than 1.0，carbon lining should be adopted.

3.2.22　Hot metal produced from large ferroalloy SAF should be cast with casting machine.

3.2.23　The power consumption and raw material consumption for main products of SAF shall be in accordance with requirements specified in Table 3.2.23.

3.2.24　The element recovery rate for smelting different products shall be in accordance with requirements specified in Table 3.2.24.