JPS6250404A - Melting method for scrap iron - Google Patents

Abstract

PURPOSE:To melt scrap iron at a low cost in a short period by specifying the injection angle and injection rate of gaseous oxygen in the stage of injecting a powder carbon-contg. material by a carrier gas from the center of a burner and injecting the gaseous oxygen from the periphery thereof. CONSTITUTION:A lance 5 having a burner function is used for the scrap iron 7 in a reaction vessel 6 and the scrap iron 7 is heated and melted by the combustion flame 8 thereof to form molten iron 10. A flow passage 1 for injecting and supplying the powder carbon-contg. material (coal) together with the carrier gas is provided to the center of the burner to be used in this stage. A flow passage 2 for injecting the gaseous oxygen from the periphery of the burner is further provided to enclose the carbon-contg. material to be injected. The flow rate of the gaseous oxygen is specified to >=2 times the flow rate of the carrier gas and the angle theta between the injection direction of the gaseous oxygen and the injection direction of the carbon-contg. material is specified to at least >=20 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of heating and melting scrap iron (hereinafter referred to as scrap) using an oxidation exothermic reaction of a carbon-containing substance as a heat source.

(Prior Technology) Conventionally, as a method of heating and melting scrap using the heat generated by burning carbon-containing materials with oxygen gas without using electrical energy, pulverized coal was installed at the bottom of a converter. The method of melting scrap by blowing oxygen gas into one part and another part was disclosed in JP-A-58-5.
It is described in Japanese Patent Application Laid-open No. 8916 and Japanese Patent Application Laid-Open No. 56-33415.

In addition, a method of heating scrap piled above the iron bath with high-temperature gas obtained by simultaneously supplying a carbon-containing substance and oxygen gas into an iron bath and burning the generated Co gas with oxygen gas was disclosed in JP-A-59. It is described in the publication No.-150005.

(Problems to be Solved by the Invention) However, the former method requires molten iron such as "seed hot water" or "remaining hot water" to prevent pulverized coal from flying out of the furnace system during scrap melting. Alternatively, before injecting pulverized coal, it is necessary to supply natural gas, propane gas, etc. together with oxygen gas from the tuyeres at the bottom of the furnace, and use the resulting high-temperature gas to dissolve a portion of the scrubber. There was a problem that required

Furthermore, even with the latter method, molten iron such as ``seed hot water'' and ``remaining hot water'' was required at the start of operation. In either method, a certain amount of molten iron such as "seed water" is required at the start of operation, so if a blast furnace or electric furnace is not available, the above-mentioned methods may not be practical in some cases. Furthermore, even if a blast furnace or electric furnace were available, it was not an economical method because it had to be operated while securing seed water, which lowered production efficiency and caused excess heat loss. Furthermore, the remaining hot water will solidify if it is not used within a short period of time, requiring excessive management of the operating schedule and complicating the process.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing molten iron from only scrap in a short time in order to solve the above-mentioned problems.

(Means for Solving the Problems) In the present invention, when melting scrap, a burner as shown in FIGS. 1a and 1b is used, and powder such as pulverized coal or pulverized coke is At the same time, a granular carbon-containing material (hereinafter referred to as carbon material) is injected into a container containing scrap together with a carrier gas, and at the same time a flow rate of more than twice that of the carrier gas is supplied from around the burner to surround the injected carbon material. Scrap iron characterized in that oxygen gas is injected, and at this time, the angle between the injection direction of the oxygen gas and the injection direction of the carbon material is at least 20 degrees or more, so that the oxygen gas and the carbon material collide and are combusted. This is a method of dissolving.

Examples of burners necessary to carry out the method of the invention are shown in FIGS. 1a and 1b. The burner in FIG. There is no problem even if some or all of the air is used), and an oxygen gas flow path 2 is provided concentrically with the flow path 1 for transporting the carbonaceous material, and a slit-shaped jet port is provided at the tip of the burner. It consists of a nozzle 3, with the oxygen gas ejection port oriented in the direction of colliding with the jet stream of carbonaceous material.

In addition, although the effect is slightly inferior to the case of the slit nozzle described above, as shown in Fig. 1b, the oxygen gas ejection hole can be replaced with a Laval nozzle (wide-spread nozzle) like a normal converter lance.
It can also be done.

(Function) 1) At the collision angle of oxygen gas with respect to the jetting direction of carbonaceous material, a 5-ton converter was used and a barge with the structure shown in Fig. 1 was used to transfer the gas for conveying carbonaceous material and oxygen gas. Fig. 2 shows the results of blowing and investigating the combustion situation by taking specimens at a distance from a normal lance to reach the molten steel. As can be seen from this figure, the ratio of unburned carbonaceous material to the blown carbonaceous material increases rapidly as the collision angle θ decreases.

In addition, Figure 3 shows the relationship between the time required to melt all of the scrap and the collision angle θ when 5 tons of scrap was charged into a 5-ton top-bottom blowing converter and the burner was used. Shown below. As can be seen from this figure, when the collision angle θ becomes 20 degrees or less, the time required for melting increases rapidly, and when the collision angle is 0 degrees, the proportion of unburned carbonaceous material increases, making it impossible to melt the scrap. In addition, the optimal value of the collision angle θ varies depending on the proportion of volatile matter in the pulverized coal and the ejection speed, but if the combustion flame of the carbonaceous material spreads too much, the addition efficiency of the carbonaceous material may decrease and the furnace wall refractories may be damaged. It is desirable that the angle be less than 70 degrees.

Next, as a result of investigating the influence of the meteor ratio of carbon material carrier gas and oxygen gas on the combustion of carbon material, it was found that when the oxygen gas flow rate is less than twice the carrier gas flow rate, there is a large amount of unburned coal. I understand.The reason is that since the carbonaceous material is included in the carrier gas, its kinetic energy is greater than that of oxygen gas at the same flow rate.Therefore, the lower the flow rate of the carrier gas, the more However, the flow rate is determined by the supply rate of the carbonaceous material and the pressure of the carrier gas.However, the oxygen gas flow rate needs to be at least twice the carrier gas flow rate.

The fourth embodiment of the present invention under the conditions described above is described below.
This will be explained based on the diagram.

The lance 5, which has the function of a burner, is lowered to a position where the flame 8 hits only the scrap 7 in the reaction vessel 6, thereby melting the scrap 7.

Once the iron bath 10 is formed at the bottom of the container, gas is supplied from the bottom blowing tuyere 9 to agitate the iron bath 10 and melt away undissolved scraps around it, while at the same time keeping the temperature and composition of the iron bath uniform. Alternatively, blow gas mixed with a refining agent such as quicklime. The type and amount of bottom-blown gas at this time are determined as follows. First, if oxygen gas is used, the hydrocarbon gas or kerosene used to cool the tuyere is burned and high-temperature gas is generated, and melting starts from below the scrap, which shortens the melting time. The disadvantage is that the material and tuyere are subject to relatively large erosion. Furthermore, since the purpose of using oxygen gas is high productivity, the supply rate is desirably 0.2 Nm3/min or more, particularly I Nm'/min or more per ton of molten iron finally produced.

On the other hand, if a small amount of inert gas is used, although the dissolution time becomes somewhat longer, the life of the refractories and lining at the bottom of the reaction vessel is extended, and it is overall economical.

In this case, the inert gas supply rate is I Nn+'/min or less per ton of molten iron finally produced, especially 0
．． 2 Nm'/min or less is desirable. At this time, increase the flow rate range of the inert gas (provide a removable tuyere, and adjust the gas flow rate to about 0.2 Nm from the lowest amount to match the increase in the amount of melt that falls).
It is desirable to gradually increase the speed up to '/min.

In addition, by using the above-mentioned burner, it is possible to simultaneously heat the carbonaceous material by infiltrating the molten iron and carburize it. It is desirable to blow more than the amount. Under carburizing conditions, the melting point of scrap is lowered, which is advantageous for melting.

In the embodiment described above, scrap is efficiently melted using a well-known top-bottom blowing converter as the reaction vessel, but a top-blowing converter can also be used as the reaction vessel. However, top-bottom blowing converters are advantageous in terms of energy consumption for scrap melting and composition adjustment of the iron bath.

(Example) A 5-ton scale top-bottom blowing converter 11 consisting of a top-blowing lance 11 having the function of a carbonaceous combustion burner and a bottom-blowing tuyere 9 as shown in FIGS. 1a and ib, and a carbonaceous material (fine powder) A device with a dispenser 12 for storing and dispensing charcoal is shown in FIG. Using this apparatus, the method of the present invention was carried out with the collision angle θ of 45 degrees between the carbon material carrier flow and the oxygen gas jet flow.

First, the inside of the furnace was preheated to bring the temperature of the furnace inner wall to about 900°C, and about 4 tons of scrap such as trimmings of steel plates and cut pieces of slabs generated in the steel mill were charged and the furnace was made vertical.

At the same time, the lance 5 having the burner function described above is lowered from above the furnace, and the pulverized coal is fed at 35 kg/min and the carrier gas flow rate is 4 Nm. '/m
in, supplying an oxygen gas flow rate of 17Nm37min,
It was burned at the nozzle outlet and fixed at the position where the flame hit the scrap. After holding this state for 30 hours, add 1.5 tons of scrap from above the furnace and hold for another 15 minutes.
The furnace was tilted to confirm that all the scrap inside the furnace had been melted. Table 1 shows the weight of raw materials used in this run as an average of 12 heats.

Table 1 (*Intensity of raw materials used to melt 1 piece of scrap) In addition, since the converter used was small and heat was not stored in the entire furnace refractory due to batch operation, scrap melting In order to obtain the necessary amount of heat, more pulverized coal and oxygen were required. In addition, quicklime has an ash content of A in pulverized coal.
Since the main component is 1□Oz and SiO□, and the silicon in the scrap becomes SiO□, it was added for the purpose of protecting the basic refractory.

Table 2 shows the molten iron components and temperatures after operation.

Table 2 In this table, Si, Mn, and P mainly enter from scrap, and S enters molten iron in large quantities from scrap and pulverized coal, but the amount of quicklime added was adjusted to make the slag basicity 2 or more. In some cases, molten iron with low s concentration was obtained. However, when the mass balance was taken, the unknown amount of S was quite large, and it is thought that it had escaped into the gas phase.

<Comparative example> In the same top-bottom blowing converter as in the example, a lance with a collision angle of 0 degrees as shown in Fig. 6 was used, and 35 kg of pulverized coal was poured from flow path 1.
/min and the carrier gas flow rate was 4 Nm'/min, and oxygen gas was supplied at 17 Nm'/min from the surrounding oxygen gas flow path 2. The lance was fixed in the position where the flame hit the scrap, and it was held in this state for 2 hours, and the furnace was tilted every 30 minutes to observe the state of the scrap inside the furnace. 8 I couldn't figure it out. At this time, when an optical fiberscope was inserted into the furnace and observed, it was confirmed that sufficient combustion did not take place, and as the scrap was not melted, unburned carbonaceous materials were eventually scattered outside the system.

<Comparative Example 2> As in Comparative Example 1, in a top-bottom blowing converter, the angle between the conveying flow of carbon material and the jetting flow of oxygen gas was set to 45 degrees, and pulverized coal was
5kg/min and carrier gas flow rate 9. ONm37min
and oxygen gas from its surroundings at a rate of 17Nm3/min.
supplied. Again, the lance was fixed at the position where the flame hit the scrap, held in this state for 30 minutes, and the furnace was tilted to observe the scrap, but the scrap was not melted. Therefore, the flow rate of the carrier gas was set to 8, ONm3/min.
When the temperature was lowered, the amount of unburned carbonaceous material at the furnace mouth decreased, and it was observed that the scrap inside the furnace was completely dissolved after 30 minutes.

(Effects of the Invention) As explained above, molten iron can be economically obtained from scrap iron that is inevitably generated in industry by using coal, which is an inexpensive and abundant energy source. Furthermore, while conventionally a certain amount of molten iron is required when melting scrap, this is not necessary in the present invention.

[Brief explanation of the drawing]

Figures 1a and 1b are diagrams showing the structure of a burner used in the method of the present invention, and Figure 2 shows the relationship between the collision angle of the carbonaceous material carrier gas flow and the oxygen gas flow and the unburned carbonaceous material. Figure 3 is a diagram showing the relationship between the collision angle of the carbon carrier gas flow and oxygen gas flow and the scrap melting time, and Figure 4 is a diagram showing the positional relationship between the top and bottom blowing lance and the scrap. FIG. 5 is a diagram showing the state in which the method of the present invention is implemented in a top-bottom blowing converter, and FIG. 6 is a diagram showing the collision between the carbon carrier gas and the oxygen gas flow used in a comparative example. FIG. 3 is a diagram representing a lance with an angle of 0 degrees. ■...Charcoal material flow path 2...Oxygen gas flow path 3.
... Nozzle 4 ... Cooling water channel 5 ... Lance with burner function 6 ... Reaction vessel 7 ... Scrap 8 ...
Combustion flame 9...bottom blowing 10...molten iron
11... Top and bottom blowing converter 12... Dispenser

Claims (1)

[Claims] 1. In a scrap iron melting method in which scrap iron charged in a container is heated and melted to obtain high carbon-containing iron, powder or granular carbon-containing material is injected into the container together with a carrier gas from the center of the burner. Oxygen gas is injected from the periphery of the burner at a flow rate more than twice that of the carrier gas so as to surround the carbon-containing material that is injected at the same time, and at this time, the angle between the injection direction of the oxygen gas and the injection direction of the carbon-containing material is at least 2
A method for melting scrap iron characterized by colliding and burning oxygen gas and carbon-containing material at temperatures above 0 degrees Celsius.