Feasibility analysis of graphite electrode Φ600〜800 mm for submerged arc furnace

The feasibility analysis for a high quality graphite electrode with the diameter of 600~800 mm obtained by extruding method for submerged arc furnace was achieved from the view of the technology level, market demand, energy conservation and environmental protection. A new smelting technique that six or nine or twelve electrodes for three phase in the high capacity submerged arc furnace will be matched and applied. The potential effects will be obtained through improving the smelting technology and making the use of GHP graphite electrode advantage in the energy conservation and environmental protection, which could provide a new way for carbon enterprises technology innovation.

In recent years, calcium carbide, ferroalloy, industrial silicon, yellow phosphorus, abrasive and other submerged arc furnace industry, due to environmental protection, energy conservation and emission reduction, safety, cost and other aspects of the impact, most of the business is not smooth. At present, the level of smelting technology in the domestic submerged arc furnace industry is highly homogenized. Companies with better management do not rely on technological innovation to lead their progress, but rely on preferential policies and resource advantages to maintain their survival and development. Domestic large-scale calcium carbide and ferroalloy submerged arc furnaces are still using self-baking electrode technology, which is a primary carbon product introduced from abroad in the 1980s, for production; industrial silicon smelting is still is also developing towards vibration-shaped carbon electrodes and common graphite electrodes with diameters greater than 1 200 mm; although the Yellow phosphorus smelting industry in spite of a breakthrough, but still in the low quality and low price of common graphite electrode around; Abrasive smelting industry is also the use of low quality and low price graphite electrode, most of the smelting is small capacity. This situation and development trend obviously does not meet the requirements of the "Made in China 2025" national strategy for basic industrial technology upgrade planning. This requires the submerged arc furnace industry to innovate and develop and achieve overall breakthroughs, thereby promoting the technological upgrading, innovation and transformation of enterprises. After years of exploration and research, Henan Kefeng Carbon Materials Co., Ltd. has comprehensively analyzed the production technology characteristics of various industries of submerged arc furnaces, and developed suitable extrusion large-size Φ600~800 mm high-quality graphite electrodes (hereinafter referred to as GHP electrodes), and match a new developed smelting technology, that is, arranging and applying three-phase 6 or 9 or 12 GHP electrodes for power supply on large-scale submerged arc furnaces, while optimizing the smelting operation technical conditions, and giving full play to the advantages of good structure, high strength, low-ash content, and high electrical conductivity of GHP graphite electrodes, etc., to achieve high-power, large-capacity, energy-saving and emission reduction, safe, efficient, and low-cost smelting production in the submerged arc furnace industry, completely change the backward status of submerged arc furnace smelting technology, and explore a new way for enterprise technology innovation upgrading and transformation to help the virtuous circle of green economy development.

1 The suitability analysis of extruded large scale and high quality Φ600~800 mm graphite electrode

Extruded large-size and high-quality Φ600~800 mm graphite electrodes were rarely used in large-scale submerged arc furnaces above 20 000 kVA due to factors such as extrusion molding, graphitization, machining equipment, process technology, and price, etc. At present, there are more than 10 large-scale carbon extruders above 35 MN in our country. The large-scale LWG graphitization system and machining system make the production of high-quality Φ600~800mm graphite electrode technology no longer limited. Manufacturers capable of producing Φ600~800mm UHP graphite electrodes have the ability to develop and produce high-quality GHP graphite electrodes. If the three-phase 6 or 9 or 12 GHP electrodes can be used for power supply on large-scale submerged arc furnaces, it can meet the production of submerged arc furnaces with a large capacity of more than 40,000 kVA. Developing the extruded Φ600~800mm GHP graphite electrode with suitable indicators according to different operating requirements of submerged arc furnaces such as calcium carbide, ferroalloys, industrial silicon, yellow phosphorus, abrasives, etc. Compared with other smelting conductive electrode, its physical and chemical indexes are better, the diameter is suitable, the manufacturing is easy and the cost performance is suitable.

1) Excellent performance indicators

Table 1 shows the comparison of the developed extruded GHP graphite electrode with domestic G-grade carbon electrode, foreign UCAR carbon electrode, and vibration formed graphite electrode for submerged arc furnace.

It can be seen from Table 1 that the physical and chemical technical indicators of the extruded GHP graphite electrode are better than other electrodes. Because the large press can continuously and automatically squeeze multiple electrodes up to 7-9 t products, the products will be more homogeneous and the performance indicators will be better. If high-quality needle coke is used as the raw material for extruded GHP graphite electrodes, the anisotropy, high conductivity, homogeneity, high density, high strength, and low ash content of graphite electrodes can meet the needs of different smelting customers.

2) Meet the design requirements of different smelting customers

One is that the GHP electrode with the flexural strength of the electrode body reaching 10-16 MPa and the flexural strength of the nipple reaching 22 MPa or more can be specifically developed. Compared with the Vibration forming electrode, the anti-breaking ability is doubled under the extremely high temperature, which can effectively reduce the probability of furnace shutdown and safety accidents caused by product quality problems.

Second, high-quality needle coke and binder with low ash content can be selected, and graphite electrodes with ash content less than 0.1% can be developed to make it possible to smelt high-grade industrial silicon above Si-2202.

The third is to use more advanced manufacturing processes to develop homogeneous, high-density, high-strength, and oxidation-resistant graphite electrodes with a bulk density greater than 1.73 g/cm³ and a flexural strength greater than 12 MPa.

Fourth, high-quality raw materials can be selected to develop products with good anisotropy, high electrical conductivity and high thermal conductivity, with a resistivity of less than 5.5 μΩ•m, which can achieve enhanced and rapid smelting.

3) High-quality extruded Φ600~800mm graphite electrode is more suitable for submerged arc furnace smelting

At present, most submerged arc furnaces use three-phase alternating current for smelting production. When smelting uses high-power and high-current production, the diameter of the electrode has a great impact on the unit consumption. This is mainly due to the skin effect, which is also the reason why the design current density of vibration forming large-diameter conductive electrodes is generally less than 10 A/cm². When the diameter is larger, the impregnation process cannot be better penetrated, the graphitization and roasting cycle is longer, which leads to higher costs and cannot guarantee the technical performance of the product. Therefore, the maximum specifications of extruded products of graphite electrode manufacturers at home and abroad are Φ800 mm.

GHP graphite electrode has the advantages of low resistivity, high bulk density, high flexural strength and low CTE, which provides a wide space for the design of large-capacity submerged arc furnaces, which can realize the enhanced rapid smelting mode, and can make the current of each column electrode ＞ 20 A/cm².

The application of three-phase 6 or 9 or 12 Φ600~800mm GHP electrode layout submerged arc furnace power smelting can solve the problem that large-capacity submerged arc furnaces must be smelted with electrodes with a diameter of more than 1 200 mm, especially for large-capacity smelting in industries such as calcium carbide and ferroalloys. After adopting this model to replace the self-baking electrode, it becomes possible to reduce the overall cost by 30%, the effect of energy saving and emission reduction will be more obvious, and environmental protection management is easier to achieve talk with us for more related news.