JPH0437129B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a desulfurization method by injecting soda ash into hot metal that has been previously desiliconized or dephosphorized. <Prior art> Conventionally, when hot metal that has been desiliconized or dephosphorized is further desulfurized, soda ash injection has been used from the viewpoint of high desulfurization reaction efficiency (for example, Japanese Patent Application Laid-open No. 166315/1983). reference). However, in such a soda blow desulfurization method, the following problems arise because soda ash has a large decomposition heat absorption amount and is extremely corrosive to refractories. Blockage of the lance due to the formation of solidified iron (referred to as nurdle) at the tip of the blowing lance. Reduced lance life due to the tip of the blowing lance. The lance blockage described above almost always occurs during the desulfurization process, making it impossible to blow soda ash into the desulfurization process, so it is necessary to stop the process, replace the lance with a new one, and then start the process again. It was hot. When a large amount of soda ash is injected or when the hot metal temperature is low, such blockage may occur several times during one heat treatment, and the total treatment time is extended, resulting in a delay in the next process (converter ), leading to problems such as the smooth supply of hot metal, a drop in hot metal temperature, and an increase in the workload of lance replacement. In addition, unstable and intermittent blowing and a large drop in hot metal temperature led to a decrease in desulfurization efficiency. The decrease in lance life as described above has been a cause of a decrease in desulfurization efficiency and an increase in desulfurization treatment costs. <Problems to be Solved by the Invention> The present invention provides a method for desulfurizing hot metal that has been desiliconized or dephosphorized by a soda ash blowing method. To provide a desulfurization method by injecting soda ash into hot metal that has been desiliconized or dephosphorized, which can solve problems such as blockage, decreased desulfurization efficiency, and increased processing costs due to decreased lance life. It has been done. <Means for Solving the Problems> As a result of intensive research into prevention of clogging of immersion lances in hot metal desulfurization treatment, the present inventors have found that, before injecting soda ash as a desulfurizing agent, quicklime etc. are blown into the tip of the immersion lance. The present inventors have found that the objective can be achieved by forming a coating layer on the material, and based on this knowledge, the present invention has been completed. In the present invention, when performing a desulfurization treatment by blowing soda ash into hot metal that has been subjected to a desiliconization or dephosphorization treatment using an immersion lance, the invention provides that, when performing a desulfurization treatment by blowing soda ash into hot metal that has been subjected to a desiliconization or dephosphorization treatment, 6 parts by weight of soda ash is injected in advance by the lance to 100 parts by weight of soda ash. 1 or 2 of powdered quicklime, dolomite clinker, and magnesia clinker
A desulfurization method for hot metal after desiliconization or dephosphorization treatment, which is characterized by blowing in a mixture of more than one species, or brick scrap powder made from one or a mixture of these, and then blowing in a predetermined amount of soda ash. be. <Process and operation leading to the invention> A soda ash injection lance has a structure as shown in FIG. 3, for example. That is, a castable refractory is pasted onto the surface of a steel pipe. The lance tip blockage mechanism due to the generation of nurdles during soda ash injection using the blowing lance having such a structure is thought to be as follows. (a) Erosion of the castable refractory at the tip of the lance due to chemical attack by soda ash, exposing the tip of the steel pipe; (b) Softening and partial melting of the exposed portion of the steel pipe at the tip of the lance due to heat; (c) Softening due to heat. , the adhesion of soda ash inside the partially melted steel pipe and the generation of nurdles due to heat absorption from the decomposition of perilla, and (d) the lance tip blockage due to the growth of nurdles. These are shown in Figure 4 a, b, c, and d. It becomes like this. Therefore, in order to prevent clogging of the lance tip due to knurling, it is important to prevent the castable refractory material at the tip from melting and to prevent the steel pipe from being exposed and coming into direct contact with hot metal. In the present invention, when carrying out desulfurization treatment by blowing soda ash into hot metal that has been subjected to desiliconization or dephosphorization treatment using an immersion lance, a base such as quicklime, dolomite clinker, magnesia clinker, etc. High melting point, high refractory material powder,
Alternatively, by pre-injecting basic brick waste powder consisting of one or a mixture of two or more of these, a high melting point, high refractory coating layer is formed on the surface of the castable refractory at the tip of the lance as described above. This coating layer prevents the chemical erosion of soda ash and prevents the castable refractory from being eroded, thereby preventing the lance tip from clogging due to the mechanism described above, and at the same time extending the life of the lance. Effects occur. As is clear from Figure 2, the amount of pre-blowing agent that can be expected to have such effects is 6 parts by weight per 100 parts by weight of the total amount of soda ash blown into Torpedo, regardless of the type of pre-blowing agent. Below this value, the coating effect of the pre-blowing agent will be small, and the lance tip will no longer be clogged 0 times per torpedo (250t) of hot metal desulfurization, and as the pre-blowing agent ratio decreases, the lance tip will become clogged. The number of blockages (times/1 torpedo) increases, and when the pre-blowing agent ratio is 0,
On average, about 3 times/1 topedo resulted in occlusion. Note that the upper limit of the ratio of the pre-blowing agent is 6 parts by weight or more and there is almost no change from the viewpoint of the lance tip clogging prevention effect, and these pre-blowing agents do not contribute much to the desulfurization of desiliconization or dephosphorization of hot metal. Considering the temperature drop, economy, and blowing time, it is desirable to use 30 parts by weight or less.

【table】

【table】

[Table] The material properties of the castable refractory of the blowing lance used for blowing the pre-blowing agent and soda ash in Figure 2 are shown in Table 1, and the blowing speed of the pre-blowing agent and soda ash was 70 ~100Kg/min. <Example><Example1> Hot metal subjected to dephosphorization treatment in a 350t torpedo
Desulfurization treatment was performed on 280 tons by blowing soda ash. The components before desulfurization treatment are shown in Table 2.

[Table] Treatment was started with plans to blow 1500 kg of soda ash into the above hot metal at a carrier gas (dry air) flow rate of 2.0 Nm ³ /nim. At a blowing speed of 70 kg/min, the lance tip became clogged when 350 kg was blown into it, making it impossible to continue blowing. Therefore, the blowing lance was replaced and reprocessing was carried out, but the lance tip was blocked again when a total of 800 kg had been blown into the lance, and the tip was blocked three times before the entire 1500 kg had been blown. The components after the soda pressure treatment were as shown in Table 3. On the other hand, 1,500 kg of soda ash and 150 kg of quicklime were placed in a dispenser and blown into the hot metal so that the quicklime formed the bottom layer as shown in FIG. In this case, stable treatment was achieved with no occurrence of lance tip blockage. The components after treatment are shown in Table 4. By pre-injecting lime-based flux to prevent clogging of the lance tip, we were able to increase the post-treatment temperature and improve the desulfurization reaction efficiency.

【table】

[Table] <Example 2> Hot metal after desiliconization and dephosphorization treatment as shown in Table 5 was
Put 260 tons/time into a 350t torpedo car, 1
The average amount of soda ash per injection is 1040Kg (4.0
Kg/ton of hot metal) before blowing, apply quicklime powder or dolomite brick waste powder to 6.4%.
(67Kg/time = 0.26Kg/ton of hot metal) 70~100Kg/
After preliminarily blowing soda ash at a flow rate of 70 to 100 min, using a blowing lance lined with castable refractory having the characteristics as shown in Table 1,
The desulfurization treatment was carried out for a total of 20 heats, approximately 10 heats each, by blowing at a flow rate of Kg/min. As a comparative example, soda ash blowing desulfurization was carried out for 10 heats under the same conditions as above without blowing quicklime or other preliminary blowing agent. The lance life of the embodiment of the present invention in which quicklime was blown in advance was 3.5 to 4.0 t/lance (average 3.75 t/lance), expressed as the weight of blown soda ash per lance.
The average lifespan was three times longer than that of the comparative example, which was 1.0 to 1.5 t/piece (1.25 t/piece). In addition, the soda ash desulfurization reaction efficiency was 17 to 25% in the example and 10% in the comparative example.
This was a huge improvement compared to ~15%.

[Table] <Effects of the Invention> The present invention has the following effects in the soda ash blowing desulfurization of hot metal that has been subjected to desiliconization or dephosphorization treatment. Blockage at the tip of the blowing lance is eliminated, preventing extension of the total processing time due to lance replacement during processing, reducing drop in hot metal temperature, and preventing decrease in desulfurization reaction efficiency due to unstable and intermittent blowing, resulting in stable desulfurization in a short time. can be done. The life of the blowing lance is extended by about three times, and the desulfurization cost can be reduced as well as the desulfurization reaction efficiency is significantly improved. Unsafe and high-temperature work such as lance replacement during processing can be omitted.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the apparatus used to carry out the present invention, FIG. 2 is a graph showing the relationship between the preliminary blowing agent and the number of times the lance tip is blocked, and FIG. 3 is a cross-sectional view of the soda ash blowing lance. FIG. 4 is an explanatory diagram of the solidified iron generation mechanism at the tip of the lance. 1... Steel pipe, 2... Castable refractory, 3...
...Exposed part of steel pipe, 3'...Softened part of steel pipe, 4...
Soda ash, 5... Solidified iron (nurdle), 6... Dispenser, 7... Soda ash, 8... Quicklime,
9... Dry air, 10... Blowing lance,
11... Torpedo car, 12... Hot metal, 13...
Piping.

Claims (1)

[Claims] 1. When carrying out desulfurization treatment by blowing soda ash into hot metal that has undergone desiliconization or dephosphorization treatment using an immersion lance, at least 6 parts by weight per 100 parts by weight of the planned amount of soda ash injected using the lance in advance. After blowing in one or a mixture of two or more of powdered quicklime, dolomite clinker, and magnesia clinker, or brick waste made from one or a mixture of these, a predetermined amount of soda ash is injected. A method for desulfurizing hot metal after desiliconization or dephosphorization treatment, characterized by: