Electrode Paste Grade Selection for High-Grade Nickel Matte / Nickel Matte Smelting Furnaces (and Differences from RKEF Furnaces)-FAQ-Graphite Electrode and Electrode Paste Supplier | Rongxing Group-Graphite Electrode and Electrode Paste Supplier

Abstract

Nickel smelting is the field most easily confused in electrode paste applications. Both are called "nickel furnaces", yet the operating conditions of RKEF ferronickel furnaces and high-grade nickel matte (nickel matte) furnaces differ greatly, and their grades are not interchangeable. For ferronickel (RKEF) furnaces, a conventional sealed-furnace paste is sufficient; for high-grade nickel matte / nickel matte furnaces, a low-sulfur, low-ash, high-strength sealed-furnace paste is recommended.

Keywords

Electrode paste；high-grade nickel matte (nickel matte) furnace；RKEF ferronickel furnace；sealed-furnace paste grade selection；Rongxing Group

Last updated

2026-11-05

Owner

Rongxing Group Technical Team

1. First, clarify the two process routes

The key difference lies in whether sulfurization takes place: the ferronickel route performs reduction only, whereas the nickel matte route performs sulfurization simultaneously with reduction, producing a nickel-iron-sulfur alloy. This brings a threefold change in furnace atmosphere, slag type and temperature.

Route	Flowsheet	Product	Smelting temperature	Electrode paste unit consumption
RKEF (ferronickel)	Laterite ore → drying kiln → rotary kiln pre-reduction (700–900 °C) → submerged arc furnace reduction smelting (1400–1500 °C) → crude ferronickel	Ferronickel NPI (Ni + Co 20%–30%)	1400–1500 °C	About 10 kg/t (the lowest)
Nickel matte (high-grade nickel matte)	Based on RKEF, sulfurizing agents (sulfur, pyrite, gypsum) are added in the rotary kiln → electric furnace reduction-sulfurization smelting (1500–1600 °C) → low-grade nickel matte → converter blowing → high-grade nickel matte	High-grade nickel matte	1500–1600 °C	Slightly higher than ferronickel

2. Special requirements of high-grade nickel matte furnaces for electrode paste

Difference in operating conditions	Impact on electrode paste	Grade selection direction
Higher furnace temperature (1500–1600 °C)	Tip erosion intensifies, so oxidation resistance must be improved	Increase the proportion of graphite fines to enhance oxidation resistance
Sulfur-bearing atmosphere	Sulfides may attack the electrode and the electrode shell; sulfur evolution easily causes cracks	Strictly control the sulfur content of the paste and choose low-sulfur grades
Change in slag type (FeO–SiO₂ system)	Slag erosion on the electrode side is intensified	Increase bulk density and compressive strength
Impurities introduced by sulfurizing agents	Ash control must be stricter to avoid contaminating the nickel matte	Ash ≤ 4%; prefer low-ash aggregate
Intermittent converter blowing operation	Furnace load fluctuates, causing frequent thermal cycling of the electrode	Give priority to thermal shock resistance and control the thermal expansion coefficient

3. Grade selection recommendations (engineering basis)

Ferronickel (RKEF) furnace: a conventional sealed-furnace paste is sufficient — ash ≤ 4%, volatile matter 11%–13%, resistivity ≤ 70 μΩ·m, compressive strength ≥ 18 MPa. Unit consumption is about 10 kg/t, the lowest among all types of submerged arc furnaces.
High-grade nickel matte / nickel matte furnace: a low-sulfur, low-ash, high-strength sealed-furnace paste is recommended — ash ≤ 4%, sulfur content as low as possible, compressive strength ≥ 20 MPa, bulk density ≥ 1.45 g/cm³, and the proportion of graphitic raw material appropriately increased to enhance oxidation resistance and thermal conductivity.
Common requirement: both belong to sealed furnaces and must follow the sealed-paste design principle of "low volatile matter + low softening point + easy sintering".

4. Summary of five differences from RKEF furnaces

Comparison item	RKEF ferronickel furnace	High-grade nickel matte / nickel matte furnace
Sulfurizing agent added	No	Yes (sulfur / pyrite / gypsum)
Smelting temperature	1400–1500 °C	1500–1600 °C
Product	Ferronickel (NPI)	Low-grade nickel matte → high-grade nickel matte
Post-treatment	Directly supplied to stainless steel production, or converter refining	Must be enriched by converter blowing
Electrode paste focus	Conventional sealed paste, cost first	Low sulfur, low ash, high strength, stability first

Electrode Paste Grade Selection for High-Grade Nickel Matte / Nickel Matte Smelting Furnaces (and Differences from RKEF Furnaces)

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