Technical Requirements and Selection Recommendations for Electrode Paste in Calcium Carbide Furnaces-FAQ-Graphite Electrode and Electrode Paste Supplier | Rongxing Group-Graphite Electrode and Electrode Paste Supplier

Abstract

Calcium carbide (CaC₂) furnaces are the second-largest market for electrode paste. The biggest difference from ferroalloy furnaces is this: here the electrode paste is both a conductor and a reaction raw material. In the reaction CaO + 3C → CaC₂ + CO↑, part of the carbon comes directly from electrode consumption.

Keywords

Electrode paste；calcium carbide (CaC₂) furnace；submerged arc furnace smelting；electrode paste unit consumption；current density red line (7 A/cm²)；electrode paste grade selection by furnace capacity；resistivity; ash content；volatile matter；softening point；compressive strength；self-baking electrode soft-break prevention；Rongxing Group customer case (19 kg/t)；

Last updated: 2026-11-04Owner: Rongxing Group Technical Team

1. Technical requirements

Parameter	Typical requirement	Explanation
Resistivity	≤ 65–75 μΩ·m	Calcium carbide furnaces draw large currents, and resistivity directly determines power consumption
Ash content	≤ 4%	High ash not only increases paste consumption but also affects the gas yield of calcium carbide
Volatile matter	12%–15.5%	Matched to the sintering speed to avoid soft break
Compressive strength	≥ 18–22 MPa	Withstands burden-layer pressure and the impact of burden collapse
Bulk density	≥ 1.40 g/cm³	Density determines electrical conductivity and oxidation resistance
Softening point	70–110 °C	Must match the electrode descent rate to prevent segregation

2. Selection by furnace capacity

The selection logic for calcium carbide furnaces is strongly correlated with transformer capacity, which is the common industry practice.

Transformer capacity	Furnace positioning	Recommended paste type	Key indicator target
< 25 MVA	Small and medium-sized calcium carbide furnace	Standard electrode paste	Ash < 4%, resistivity 70–75 μΩ·m
25–40 MVA	Large calcium carbide furnace	High-power type	Ash < 4%, resistivity 65–70 μΩ·m
40 MVA	Extra-large modern furnace	Ultra-high-power type	Ash < 4%, resistivity 60–65 μΩ·m

Current density red line: when the operating current density exceeds 7 A/cm², a high-end paste with higher thermal stability must be selected. Otherwise the electrode side and tip overheat at the same time, and the rates of oxidation and erosion multiply.

3. Unit consumption and cleaner-production benchmark

The Cleaner Production Standard — Calcium Carbide Industry lists electrode paste unit consumption as a resource and energy utilization indicator, assessed in three grades.

Grade	Electrode paste unit consumption (t/t calcium carbide)	Converted to kg/t
Grade 1 (international advanced)	≤ 0.020	≤ 20
Grade 2 (domestic advanced)	≤ 0.025	≤ 25
Grade 3 (domestic average)	≤ 0.030	≤ 30

The common industry estimate is about 30 kg of paste per tonne of calcium carbide; after adopting new technologies such as functionally graded paste, some enterprises have already reduced this to 23–28 kg/t. According to feedback on the results achieved by Rongxin Group customers, a calcium carbide furnace at a customer in Henan can reach a consumption as low as 19 kg.

4. Selection economics: do not look only at the unit price

Indicator (33 MVA calcium carbide furnace case)	Standard type	High-power type	Difference
Unit price (CNY/t)	4,500	5,200	+15.6%
Daily consumption (t)	3.2	2.7	-15.6%
Power consumption (kWh/t)	3,250	3,100	-4.6%
Monthly comprehensive cost (10,000 CNY)	58.3	52.1	-10.6%

Conclusion: the unit price of high-end paste is 15% higher, yet the overall cost is instead 10% lower. Selection should be based on a total cost of ownership (TCO) calculation rather than a comparison of unit prices.