CN106702043B - Converter final slag treatment method - Google Patents

Abstract

The invention provides a method for treating final slag of a converter. The bottom blowing flow rate of the converter is set to the bottom blowing flow rate of ≥30Nm ³ /min at the end of tapping; 300-500mm thick slag is laid on the bottom of the slag tank for preparing slag dumping; After reaching the zero position, add 95-105 kg of recarburizer per ton of slag, add 58-62 kg of lime particles or lime sieve material and 8-11 kg of aluminum particles after 3 minutes; add aluminum particles for 2 minutes and then carry out the slag dumping operation; the slag is processed in the slag The slag is turned over in the field, and magnetic separation is carried out after the slag solidifies. The slag can be fully reused after reduction treatment, realizing the green treatment of slag; 120-150 kg of high-phosphorus iron containing 15% to 20% of phosphorus can be recovered per ton of slag to replace ferrophosphorus; high-phosphorus iron also contains 20 %‑40% Mn element can be used as medium-carbon ferromanganese; the slag after reduction treatment can replace 0.5 tons of white ash and directly enter the furnace for use.

Description

A method for treating final slag of converter

technical field

The invention belongs to the field of energy-saving and emission-reducing smelting technology, and in particular relates to a green treatment method for final slag of a converter.

Background technique

Converter slag is a by-product produced in the steelmaking process, accounting for 8% to 15% of steel output. The converter slag produced in my country exceeds 70 million tons every year. Due to the limited recycling methods and capacity of converter slag in my country, the comprehensive utilization rate is only 20%. The accumulated steel slag not only occupies land, pollutes the environment, but also wastes resources.

The main methods of domestic steel slag treatment are as follows:

1) Hot splash treatment. The hot pouring method uses the waste heat of steel slag, and after cooling by spraying water, under the thermal expansion and contraction and the hydrolytic expansion of free calcium oxide, the steel slag is broken and self-decomposed into powder.

2) Hot braised method. The thermal braising method is to pour the converter steel slag into the slag pit, cover it when it cools to about 600°C, and spray water intermittently on the hot slag to generate a large amount of steam in the tank. Since the steel slag contains free calcium oxide, it will decompose into calcium hydroxide when it meets water, and the volume will expand, causing the steel slag to disintegrate and pulverize, and then carry out subsequent processing.

3) Roller method. After the slag is discharged from the converter, the liquid slag is poured into the drum device at a certain speed. There are steel balls in the drum. By controlling the amount of water, the liquid steel slag is cooled, solidified and crushed in the drum at the same time, and transported to the granular iron separation workshop for granular iron separation. ,recycle and re-use.

At present, the comprehensive utilization of converter steel slag mainly includes the following types:

1) Recover the iron in the slag. There are a considerable amount of scrap steel particles and iron oxides in the converter slag, and the recycling of scrap iron and steel from steel slag was carried out earlier in foreign countries. In the United States, nearly 3.5 million tons of scrap steel were recovered from steel slag from 1970 to 1972, and Japan’s magnetic mineral processing company processed 2 million tons of steel slag every year. , from which 180,000 tons of granular iron containing more than 95% iron were recovered. Anshan Iron and Steel uses media-free self-grinding and magnetic separation methods to recover 8.0% of scrap steel in steel slag, and Wuhan Iron and Steel recycles 8.5% of metallic iron in scrap steel.

2) Steel slag is used as sintering flux. Converter slag contains useful components such as CaO, MgO and FeO, which are suitable as fluxes. The application of Baosteel steel slag returning to sintering began in 1996, and the current consumption of sintering ore is stable at the level of 150,000 tons per year.

3) The steel slag is returned to the steelmaking process. In the steelmaking process, the high-alkalinity and low-phosphorus steel slag is returned to the converter, and dolomite is used in conjunction with it, which can make steelmaking slag early and reduce the erosion of the furnace lining by the initial slag, which is beneficial to increase the service life of the furnace and reduce the consumption of refractory materials. At the same time, it can replace Part of fluorite. At present, Baosteel has successfully carried out the test of returning the decarburized converter slag, cast slag and steel slag from the decarburization furnace to the converter for utilization. The slag is reduced to reduce the consumption of auxiliary raw materials and achieve the purpose of reducing costs and increasing efficiency. Moreover, the return and utilization of steel slag will not have a negative impact on the quality of molten steel.

4) Steel slag is used in construction field. The hardness and particle shape of steel slag crushed stone are in line with the requirements of road materials. It has good performance, high strength, and good natural gradation. It is a good road backfill material.

Problems in the utilization of converter steel slag:

Converter slag is rich in CaO, MgO, FeO and MnO, and has a large amount of latent heat, so it has high value. Although a variety of steel slag comprehensive utilization technologies have been developed, no effective way to rationally utilize steel slag resources on a large scale has been found so far. The main limiting factor is the high phosphorus content in converter steel slag. In order to avoid the cyclic enrichment of phosphorus, the amount of steel slag added in the sintering and steelmaking process should be limited. According to Baosteel's statistical data, if the amount of steel slag in sinter is increased by 10kg/t, the phosphorus content of sinter will increase by about 0.0038%, and the corresponding phosphorus content in molten iron will increase by 0.0076%. Therefore, it is necessary to control the proportion of steel slag in sinter. The phosphorus content in converter steel slag is about 3%, which is not enough to be used as phosphate fertilizer. In addition, steel slag contains some free calcium oxide, which reduces its volume stability and reduces its application proportion in paving and backfilling projects.

Contents of the invention

The invention provides a method for treating the final slag of a converter, the purpose of which is to use the high temperature of the slag to reduce Fe, Mn, P, etc. in the slag, and to add the dephosphorized slag back into the converter or for sintering in large quantities , so as to realize the efficient reuse of slag.

For this reason, the technical solution that the present invention takes is:

A method for treating the final slag of a converter, the specific method and steps are:

(1) The bottom blowing flow rate of the converter is set to be no less than 30Nm ³ /min at the end of tapping; 300-500mm thick slag is laid on the bottom of the slag tank for slag dumping;

(2) After the converter tapping reaches the zero position, immediately add a carburant of 95-105kg/ton of slag;

(3) After adding the recarburizer for 3 minutes, add 58-62kg/ton of slag lime particles or lime sieve material, and 8-11kg/ton slag of aluminum particles with a particle size not greater than 5mm;

(4) After adding aluminum particles for 2 minutes, carry out slag dumping operation;

(5) The slag is turned over in the slag treatment field. After the slag is solidified, magnetic separation is performed. The iron that is magnetically separated is the iron that is recovered and recovered. The slag is returned to the furnace to be used as a slagging flux.

The positive effect of the present invention is:

1. After the reduction treatment, the slag can be completely reused, realizing the green treatment of the slag.

2. Each ton of slag can recover 120-150kg of high-phosphorus iron containing 15%-20% phosphorus, which can be used instead of iron-phosphorus and used in the production of weathering steel and other phosphorus-containing steels. High phosphorus iron also contains 20%-40% Mn element, which can be used as medium carbon ferromanganese.

3. After reduction treatment, the slag can be used directly in the furnace due to its low phosphorus content. The CaO content of the treated slag is about 45%, which can replace 0.5 tons of lime.

Detailed ways

Taking the production of SPHC steel by a 260-ton top-bottom combined blowing converter as an example, the present invention is further described.

Example 1:

1. After tapping is completed, the bottom blowing flow rate is set to 39Nm ³ /min.

2. After the converter tapping reaches the zero position, add 2 tons of recarburizer immediately, and stand the converter at the zero position to make it fully react.

3. After adding the carburant for 3 minutes, add 1.2 tons of lime pellets and 200kg of aluminum pellets.

4. After adding aluminum particles for 2 minutes, carry out the slag dumping operation, leaving 4.5 tons of slag bottom in the slag tank.

5. When the slag tank arrives at the slag treatment site, it is normal to turn the slag separately. When the slag solidifies, magnetic separation is carried out. The steel scrap and slag after magnetic separation are recovered separately.

6. Recycled scrap steel is used as an alloy in phosphorus-containing weathering steel according to the content of 18% phosphorus and 25% manganese, and the recovered slag is converted into white ash and directly put into the furnace for use.

Example 2:

1. After tapping is completed, the bottom blowing flow rate is set to 43Nm ³ /min.

2. After the converter tap reaches the zero position, add 1.9 tons of recarburizer immediately, and stand the converter at the zero position to make it fully react.

3. After adding the carburant for 3 minutes, add 1.25 tons of lime sieve and 210kg of aluminum pellets.

4. After adding aluminum pellets for 2 minutes, carry out the slag dumping operation, leaving 3.8 tons of slag bottom in the slag tank.

5. When the slag tank arrives at the slag treatment site, it is normal to turn the slag separately. When the slag solidifies, magnetic separation is carried out. The steel scrap and slag after magnetic separation are recovered separately.

6. Recycled scrap steel is used as an alloy in phosphorus-containing weathering steel according to the content of 18% phosphorus and 25% manganese, and the recovered slag is converted into white ash and directly put into the furnace for use.

Claims (1)

1. A converter final slag treatment method, characterized in that: (1) The bottom blowing flow rate of the converter is set to be no less than 30Nm ³ /min at the end of tapping; 300-500mm thick slag is laid on the bottom of the slag tank for slag dumping; (2) After the converter tapping reaches the zero position, immediately add a carburant of 95-105kg/ton of slag; (3) After adding the recarburizer for 3 minutes, add 58-62kg/ton of slag lime particles or lime sieve material, and 8-11kg/ton slag of aluminum particles with a particle size not greater than 5mm; (4) After adding aluminum particles for 2 minutes, carry out slag dumping operation; (5) The slag is turned over in the slag treatment field. After the slag is solidified, magnetic separation is performed. The iron that is magnetically separated is the iron that is recovered and recovered. The slag is returned to the furnace to be used as a slagging flux.