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5 effective measures to slow down the erosion rate of converter lining, increase productivity and reduce production costs

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Physical impact, temperature changes, and chemical reactions aggravate converter lining damage. To ensure the safety and stability of the refractory material throughout the furnace’s service life, we must avoid rapid damage to parts of the lining. Strengthening daily monitoring and repair of the refractory material, especially in severely damaged areas, is essential. This approach balances the damage degree and prolongs the converter’s service life.

Traditional maintenance methods include brick tiling, gunning, slag splashing, material replenishment, and slag replenishment. However, these require shutting down the converter and ensuring sufficient sintering time, impacting cost and production efficiency. Using comprehensive lining maintenance technology effectively reduces erosion rates, improves productivity, and lowers production costs.

Related Product: Magensia carbon bricks

1. Balanced design of molten pool structure

During the blowing process, extremely complex redox reactions are carried out in the converter, and there is a high-speed flow field movement. During the whole furnace operation, various parts of the furnace lining are subjected to different physical and chemical effects and mechanical impacts, and the degree of erosion and damage is different, resulting in large differences in the life of the furnace lining in different parts. In view of this, on the basis of the original comprehensive furnace building technology, combined with the specific situation of the erosion of various parts of the converter lining, a forward-looking design and adoption of a special converter lining structure for steelmaking was adopted.

The working layer of the converter is made of multi-layer magnesia-carbon bricks, and the design and masonry method of gradual transition thickening are adopted in the lower molten pool: the length of the multi-layer annular magnesia-carbon bricks is gradually changed from the upper layer to the lower layer in the height direction. Long, that is, the thickness of the molten pool bricks of the working layer gradually becomes thicker from the upper layer to the lower layer, and the diameter of the inner cavity of the converter gradually decreases from the upper layer to the lower layer. The overall structure of the molten pool for each layer (see Figure 1).

During converter operation, especially during oxygen blowing smelting, we observe serious erosion at the molten pool and bottom slag line. This area remains a weak point in later furnace stages and is a key safety concern.

The special furnace lining design, shown in the figure, addresses this issue. We use multi-layer annular magnesia-carbon bricks to form a large upper and small lower conical molten pool. This design solves fast erosion in the converter’s weak parts. It ensures economic maintenance throughout the furnace life cycle, improves safety and stability, and balances the life of each furnace lining part. This design enhances furnace longevity and economic benefits.

2. Innovative slag splashing furnace protection technology

Optimize and innovate the slag splashing protection process, and innovatively adopt a maintenance method for the converter lining: during the slag splashing protection operation, the oxygen lance changes from the traditional continuous opening of nitrogen to intermittently depositing liquid slag in the converter. Blowing compressed nitrogen, the liquid slag will generate waves and spread outward under the action of high-pressure nitrogen, “surge” to the lining of the converter, and repeatedly contact, slag, bond and solidify with the surface of the lining. The converter final slag with high viscosity and refractoriness is repeatedly sprayed onto the furnace lining under the action of nitrogen gas with high pressure, large flow rate and large impact on the slag at the moment of valve opening, which significantly improves the effect of slag splashing to protect the furnace.

Under the premise of not adding special equipment, prolonging auxiliary time, increasing labor intensity and gunning material cost, and not affecting the rhythm of steelmaking production, this process optimizes the slag splashing furnace protection process, improves the slag splashing furnace protection effect, and effectively Slow down the erosion rate of the molten pool.

3. Explore iron slag filling technology

Commonly used repair methods for large converters include “slag repair” and “material repair.” Material replenishment increases filling material consumption. Falling filling materials increase inclusions in molten steel, complicating slag removal and affecting steel quality. Slag replenishment leaves final slag in the furnace, requiring time to cool and solidify, directly affecting molten steel quality and converter production efficiency.

Iron block slag repair technology uses rapid heat exchange and temperature gradients between iron blocks and high-temperature liquid slag. This achieves efficient cold solidification and bonding. It locally repairs and maintains weak furnace lining parts, saving charging materials and prolonging furnace lining life. Iron block slag filling is suitable for slag filling and pouring the slag surface. We control slag basicity and composition in the previous furnace. We evenly pour pre-prepared iron blocks (2-3t) into predetermined positions with a scrap hopper, shaking them repeatedly. In the second furnace, iron blocks immerse completely in the slag. Rapid heat exchange between pig iron blocks and high-temperature liquid slag lowers the temperature. The iron block cools, solidifies, and adheres to the furnace lining, achieving fast maintenance.

4. Improve the slag retention operation of the converter

In the converter’s slag retention operation, we do not pour out all the slag after slag splashing. Instead, we retain some slag with high temperature, high basicity, and certain (FeO) content for the next furnace. This practice promotes rapid slag formation in the next furnace, enhancing the effect and efficiency of the slag. It also improves thermal efficiency, reduces slag-forming material consumption, minimizes metal loss, and slows down furnace lining erosion.

With the optimization of slag splashing protection technology and improvements in top and bottom double blowing converter equipment, we have analyzed the root causes of slag splashing. By continuously exploring and improving preventive measures, we have gradually optimized and enhanced the slag retention operation process.

The final slag of the converter contains a certain ∑(FeO). When we add slag to the molten iron in the next furnace, it reacts with [C] in the molten iron, as shown in equations (1) and (2). If the slag has high oxidizing properties and the FeO content exceeds 20%, both reactions may occur simultaneously. This increases the gas generation instantaneously, making operation control difficult and potentially causing an explosive splash accident.

(FeO)+[C]=[Fe]+CO

2(FeO)+[C]=2[Fe]+CO2

From the above analysis, we see that controlling gas accumulation and slowing reaction speed is crucial. We must reduce (FeO) and [C] contents in the formula. However, [C] in molten iron changes little. We only control (FeO) in the slag when adding molten iron.

To prevent issues, we take two measures. First, we reduce final slag (FeO) content. We control the blowing end point, carbon pulling timing, increase bottom blowing flow, and reduce slag oxidation. Second, we add 1000 to 1500 kg of lime before adding molten iron. This dilutes and cools the final slag. We also ensure the total slag amount in slag-retaining furnaces is not too large. This avoids high and fluctuating terminal temperatures, reduces final slag (FeO) content, and slows down reactions to prevent splashing.

LMM YOTAI established in 2007. Our production technology comes from Japanese Yotai. As an experienced and international player in the refractories industry. We have succeeded in expanding both the breadth of its product range and the depth of its services. From raw material selection, refractory portofio & optimization, installation & services & recycle of used refractories on site to further reduce client’s Opex & Capex in refractory consumption per ton steel output, meanwhile improve product quality of client.

Our Product have been supplied to world’s top steel manufacturer Arcelormittal, TATA Steel, EZZ steel etc. We do OEM for Concast and Danieli for a long time

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