JPS61195909A - Method for melting iron scrap in converter - Google Patents

Abstract

PURPOSE:To obtain molten C-contg. iron by blowing simultaneously C-contg. material and gaseous O2 under combustion to the charged iron scrap from above and starting melting of the entire amt. from the iron scrap without a molten seed metal or remaining molten metal thereby heating and melting easily the iron scrap in a short period. CONSTITUTION:A flame 8 formed of gaseous O2 flow and the jet flow of a carboneous material is ejected by a lance 5 from above toward the iron scrap 7 in a reaction vessel 6. Gas or fluid mixture composed of the gas and refining agent such as quicklime is blown through a bottom blowing tuyere 9 when the scrap iron 7 is melted to form an iron bath 10 in the furnace bottom. The bath 10 is thereby stirred and the unmolten iron scrap around the same is melted down; at the same time, the temp. and components of the bath 10 are uniformly maintained. As a result, the melting from the scrap of the entire amt. down to the molten iron is possible, while a specified amt. of the molten iron is heretofore required in the stage of melting the scrap. The molten iron is thus economically and easily obtd. from coal which is the inexpensive and ample primary energy and the iron scrap.

Description

Detailed Description of the Invention (Industrial Field of Application) Regarding the production of molten pig iron for steelmaking by melting scrap iron, this specification describes the use of simply a carbon-containing material as a heat source and the use of its oxidative exothermic reaction to generate electricity. The results of research and development on how to advantageously obtain molten pig iron from scrap iron without using it are described below.

Generally, the mainstream method of steelmaking is to reduce iron ore with coke in a blast furnace to produce molten pig iron (molten iron containing 4% or more carbon), which is then decarburized in a converter after removing impurities as necessary. It is a process that removes silicon and phosphorus at the same time, and refines it to molten steel that contains carbon according to the application.

On the other hand, other iron manufacturing methods suitable for mass production include electric furnaces.
This is a method of heating and melting scrap iron using electrical energy to obtain molten steel.

Both of these methods are well known techniques and are widely practiced industrially.

In melting such scrap, it is necessary to eliminate the use of expensive electrical energy.

(Prior art) Japanese Patent Laid-Open Nos. 56-58916 and 56-33415 disclose a method in which pulverized coal is injected from a part of the bottom tuyere of a converter, and oxygen gas is injected from the other tuyeres. A method of dispensing and melting scrap is disclosed. This method is an excellent technology in that it can replace electricity with cheap coal energy, but
In order to inject pulverized coal through the bottom tuyere, a certain amount of molten iron must be present. Therefore, the first bath is commonly known as “Taneyu”.
The company has no choice but to adopt an irregular method of using the molten iron needed at the start of the next operation, or the molten iron from the previous melting called ``remaining hot water'', in combination with scrap. In this case, it was also necessary to supply natural gas, propane gas, etc. from the bottom tuyere at the same time as oxygen before injecting the pulverized coal, and to preheat the scrap with the resulting high-temperature gas to partially melt it.

As another example, a carbon-containing substance and oxygen are simultaneously supplied into an iron bath, the generated CO gas is further combusted to C island gas on the iron bath, and the resulting high-temperature gas is sent above the iron bath. A method has also been published in which scrap is melted by passing it through a pile of scrap to preheat it and adding the preheated scrap to the above-mentioned iron bath (Tetsu to Hagane, 70).
(1984), 5885° This method also requires the above-mentioned seed water to start operation, and is still not practical.

(Problems to be solved by the invention) As described above, in the conventional technology, a certain amount of molten iron is initially required to burn carbon-containing materials and heat and melt scrap in a converter-like container. there were.

Therefore, in the absence of an electric furnace or blast furnace, the above-described method cannot be practically implemented. Furthermore, even with electric furnaces and blast furnaces, operations must be carried out to produce molten iron while securing seed water, which is an economical process because it reduces production efficiency, causes excessive heat loss, and excessive iron loss. isn't it. Furthermore, the remaining hot water will solidify if not used within a relatively short period of time, requiring excessive management of operational schedules. Moreover, the process becomes complicated, which is disadvantageous for stable operation.

It is an object of the present invention to solve the above problems and provide a method for easily obtaining molten iron in a short time by starting from the entire amount of scrap without using seed hot water or left over hot metal.

(Means for Solving the Problems) The present invention heats and melts the scrap iron by charging scrap iron and simultaneously spraying a carbon-containing substance and oxygen gas from above the scrap metal while burning it. A method for melting scrap iron characterized by obtaining molten iron, charging scrap iron into a reaction vessel, heating and melting the scrap iron by simultaneously spraying a carbon-containing substance and oxygen gas from above the scrap iron under combustion, ``This is a scrap iron melting method characterized by obtaining carbon-containing molten iron substantially without using molten pig iron.In addition, in an embodiment, the reaction vessel has a wall on at least one of the bottom wall and the side wall. It is preferable that the reaction vessel be a top-bottom blowing converter.

As a result of investigating various methods of supplying heat to scrap charged into a reaction vessel, the inventors discovered that carbon-containing materials, particularly pulverized coal or pulverized coke (hereinafter referred to as carbon material), were ) at the same time as oxygen gas and
We have found that it is optimal to feed scrap from above while burning it, and heat and melt it.

According to this method, there is no need for seed water or leftover water;
Any factory can produce molten iron from scrap without time constraints.

Moreover, by controlling the supply rate of the carbonaceous material to be added and the supply ratio with oxygen gas, the carbonaceous material can be allowed to infiltrate into the fallen molten pig iron, thereby increasing the carbon concentration in the molten iron. As the carbon concentration in the molten iron increases, the melting point of the molten iron decreases, promoting the melting of surrounding scrap. With such an operating method, carbon-containing molten iron can be obtained more quickly than by melting scrap by heating with electrical energy in an electric furnace.

As a reaction vessel for carrying out this invention, it is advantageous to have a tuyere on at least one of the bottom wall or the side wall below the surface of the molten iron bath.

When implemented industrially, the best existing reaction vessel for the present invention is a top-bottom blowing converter, and the present invention can be implemented without any modification to the converter body.

An example of a burner-like lance necessary to carry out the invention is shown in FIG. In the figure, reference numeral 1 indicates a flow path for carbonaceous materials, and the carbonaceous materials are normally conveyed using non-oxidizing gas to avoid combustion or explosion within the piping. However, there is no problem even if some or all of the air is used.

Reference numeral 2 denotes an oxygen gas flow path, and a nozzle 3 at the tip directs the blowing direction so as to collide with the jet stream of the carbonaceous material to improve the combustibility of the carbonaceous material.

Intersection angle between the center lines of the oxygen air flow and the carbonaceous jet flow (θ in the figure)
Although the optimum value differs depending on the volatile content ratio in the pulverized coal and the ejection speed, it is suitable within the range of 30° to 75°.

In addition, the arrangement of the oxygen flow path and the carbon material flow path is not limited to that shown in Figure (a).
For example, a structure may be adopted in which oxygen gas is arranged inside and collides with the carbonaceous jet stream on the outside, as shown in FIG. Moreover, as shown in FIG. 3(c), the oxygen gas ejection hole may not be formed into a slit shape, but may be formed into a Laval nozzle (wide-spread nozzle) like a lance for a normal converter.

(Function) Figure 2 shows the positional relationship when the above-mentioned lance 5 is installed with respect to the scrap 7 in the reaction vessel 6, and the flame 8 is ejected downward from above the scrap as shown in the figure. is necessary.

Note that if the direction of the lance 5 is tilted, the flame will hit the furnace wall refractories, causing melting and perforation of the refractories. The lance therefore needs to be lowered substantially vertically, and even if tilted, it needs to be positioned so that the flame only hits the scrap.

9 in the figure is a bottom blowing tuyere. When the scrap is melted and an iron bath 10 is formed at the bottom of the furnace, this iron bath is stirred and unmelted scraps around it are melted off. Blow in a mixed fluid of gas and a refining agent such as quicklime.

The type and amount of bottom-blown gas are determined as follows. First, if oxygen gas is used, hydrocarbon gas or kerosene for cooling the tuyere is burned to generate high-temperature gas, and melting starts from below the scrap, so the melting time can be shortened. On the other hand, there is a disadvantage that the bottom refractory and tuyere are subject to relatively large melting loss.

If a small amount of inert gas is used, the melting time will be somewhat longer, but the life of the furnace bottom and tuyeres will be longer, and it will be more economical overall.

The purpose of supplying oxygen gas from the bottom tuyere is to achieve high productivity, so the supply rate is 1't for the final molten iron produced.
0.2 Nm'/sin per on, especially I N+s3/
A win or higher is desirable.

On the other hand, in the case of inert gas, the minimum necessary amount is sufficient to obtain stirring power, and I Nm'/a+ per 1 ton.
in or less, particularly preferably 0.2 Nm″/win or less.

The above tuyeres do not necessarily have to be at the bottom of the hearth, for example A
It may be installed at the bottom of the side wall like an OD furnace. The selection of such bottom-blown gas and its amount depends on the existing equipment of the reaction vessel and the desired productivity.

Generally speaking, by installing a tuyere that can widen the flow rate range of inert gas, the amount of bottom blowing can be increased from the minimum amount to approximately 0.2 Nm as the amount of molten iron that falls increases! It is desirable to gradually increase the thickness up to /5 in-t.

As described above, the top-bottom blowing converter, which is a well-known technique, is an advantageous reaction vessel for carrying out the present invention, and as shown in the following examples, scrap can be melted with high efficiency.

Furthermore, when using the above-mentioned top blowing lance with the burner function, it is possible to heat the carbonaceous material by burning it, and at the same time, it is also possible to infiltrate the fallen molten iron and carburize the carbonaceous material. It will be done.

As mentioned above, it has been shown that it is possible to obtain carbon-containing molten iron with this invention substantially without using molten pig iron. However, as a matter of course, when molten iron is used in combination to heat and melt scrap iron, It is obvious that this also applies.

(Example) Implementation 1 The following is an example of the present invention using, as a reaction vessel, a 5-ton scale facility that combines a converter capable of bottom-blowing oxygen gas and a lance having the function of a carbonaceous combustion burner.

Figure 3 shows the framework of the equipment, in which 5 is the above-mentioned top blowing lance, 11 is a top and bottom blowing converter, 9 is a bottom blowing tuyere, 7 is charged scrap, and 12 is carbon material (pulverized coal). ) is a dispenser for storing and transporting gas. Oxygen and propane for cooling can be supplied from the bottom blowhole at No. 9.

The operating procedure is shown below. First, the inside of the furnace was sufficiently preheated to bring the temperature inside the furnace to about 900° C., and then about 4 tons of scrap was charged.

The scrap used was trimming scraps of hot-rolled steel sheets, cut pieces of slabs, etc. generated in the steelworks, but the brand and type of scrap are not particularly limited.

Next, set the furnace vertically and introduce oxygen from the bottom tuyeres at 5N/wi.
n and 0.2 Nm of propane gas for tuyere cooling! /
sin was supplied. At the same time, the lance with the burner function described above is lowered from above the furnace, and the pulverized coal is delivered at 35 kg/s.
Oxygen was supplied at 17 Nm'/win and burned at the nozzle outlet of the lance, and the flame was fixed at a position hitting the scrap.

After holding this state for 30 minutes, remove the scrap from the top of the furnace.
After adding 5 tons and holding the furnace for another 15 minutes, the furnace was tilted and it was confirmed that all the scrap in the furnace had been melted. Table 1 shows the weight of the main and auxiliary raw materials used in the above operation as an average value of 12 heats.

Table 1 The quicklime in the table has an ash content of Al2O2, S10 in the pulverized coal.
Since the silicon in the scrap whose main component is □ is oxidized to Sing, Sing was added for the purpose of protecting the basic refractory. Table 2 shows the molten iron components and temperatures after operation.

Si, Mn and P are mainly produced as scrap.

On the other hand, a large amount of S enters the molten iron from scrap and pulverized coal. Adjust the amount of quicklime to add to reduce the basicity of the slag to 2.
A low degree of Ss was obtained when the above was used. However, when calculating the mass balance, the unaccounted for 3 minutes was quite large, and it is thought that it was dissipated into the gas phase.

Because the converter used was small and because it was a batch operation, heat was not stored in the entire refractory of the furnace body, so pulverized coal and oxygen were required in excess of the amount of heat required for scrap melting.

叉■■1 Scrap melting was carried out in exactly the same manner as in the previous example, but the difference was that the bottom blowing tuyere was changed. In other words, in Example 1, the double-pipe structure was used to blow oxygen and tuyere cooling gas, but this was replaced with a single-pipe tuyere, and N2 or Ar gas was injected into the molten iron.
0.008 to 0.15 Nn+”/si per ton
n supply.

For this purpose, the number of tuyeres is 3. The inner diameter of the single tube of the tuyere is 3IIIwφ.
The gas source pressure can be changed from 8 to 50 kg/cm''-G.

The operating procedure is described below. Approximately 4 scraps in the preheated furnace
0.05 N+s at all tuyeres with bottom blowing gas.
! The furnace was stood upright while flowing /win, and a top blowing lance functioning as a pulverized coal combustion burner was lowered to generate a combustion flame, and heating and melting was started from above the scrap. The bottom blowing gas amount is 0.10 N+++, 3/lll1 after 20 minutes.
The amount was increased to n. After 35 minutes, the amount was increased to 0.25 Nm''/sin, and at the same time, approximately 1.5 tons of scrap was added from above the furnace.

Melting was continued for another 20 minutes, during which time the bottom blowing gas was gradually increased from 0.25 to 0.75 N+s'/min. After turning the furnace over and confirming that all the scrap had melted, temperature measurements and sampling were performed. During the melting, a predetermined amount of quicklime was added from above the furnace as in the previous example. Table 3 shows the average amount of main and auxiliary raw materials used in the six heats of this operation.

Table 3] - In this example, where oxygen is not used for the bottom blowing gas, there are advantages such as less erosion of the bottom blowing slats and the bottom of the furnace, and no need for hydrocarbons for cooling the siding. Although the melting time is longer, this method is the most suitable method for implementing the present invention because it can be implemented with a small modification of an ordinary converter.

(Effects of the Invention) With this invention, whereas conventionally a fixed amount of molten iron was required when melting scrap, it has become possible to melt the entire amount of scrap to molten iron. This became possible for the first time with the technology of the present invention, in which the heat source is supplied from above the scrap using a top blowing lance that has the function of a pulverized coal combustion burner.

This invention has made it possible to economically and easily obtain molten iron from coal, which is a cheap and abundant primary energy source, and scrap iron, which is inevitably generated due to industrial structures. The fact that it has become possible industrially to reduce electrical energy, which relies heavily on petroleum, and to reuse waste materials, shows that this invention has great social significance.

[Brief explanation of the drawing]

Fig. 1 is an end view and a sectional view of a top blowing lance having the function of a pulverized coal combustion burner that is suitable for carrying out the present invention. Fig. 2 is a sectional view of a converter showing the positional relationship between the top blowing lance and scrap. , FIG. 3 is an explanatory diagram of an example of operation in which the present invention was implemented in a top-bottom blowing converter. 1...Charcoal material flow path 2...Oxygen flow path 3...
・Blowout nozzle at the tip of the lance 4... Cooling water flow path 5... Lance with pulverized coal combustion function 6... Reaction vessel 7... Scrap (scrap iron) 8... Combustion flame 9... Bottom blowing Tuyere 10... Molten iron that has fallen 11 Top and bottom blowing converter 12... Dispenser for storing and supplying pulverized coal 13... Propane gas flow path for tuyere cooling

Claims (1)

[Claims] 1. Scrap iron is charged into a reaction vessel, and a carbon-containing substance and oxygen gas are simultaneously sprayed from above the scrap iron while it is being combusted, thereby heating and melting the scrap iron to obtain carbon-containing molten iron. A method for melting scrap iron. 2. The method according to 1, wherein the reaction vessel has a tuyere on at least one of the bottom wall and the side wall. 3. The method according to 1, wherein the reaction vessel is a top-bottom blowing converter. 4. Scrap iron is charged into a reaction vessel, and the scrap iron is heated and melted by simultaneously blowing a carbon-containing substance and oxygen gas from above the scrap iron while burning, thereby producing carbon-containing material without using molten pig iron. A method for melting scrap iron characterized by obtaining molten iron.