JPS63166908A - Blast furnace operation method - Google Patents

Abstract

PURPOSE:To save crushing cost of coal and to simplify the treatment, transportation, etc., by increasing using quantity of coarse powdery coal as much as possible under ordinary operating conditions of an oxygen blast furnace. CONSTITUTION:Charging material is charged into the blast furnace 1 from furnace top and furnace gas is fed to a gas holder 3 through furnace top cleaning mechanism 2 and branched on the way and passed through a booster 4, to generate high temp. gas by a preheating gas generator 5 and blow in the furnace from a blowing holes 6 arranged in a shaft part. A part of the furnace gas blown in the furnace from tuyeres 9 through a booster 4' as temp. adjusting gas in front of tuyeres 9. On the other hand, oxygen is fed to the above generator 5 and tuyeres 9 from an oxygen source 7, but ordinarily blown into the furnace from the tuyeres 9 together with fine powdered coal from a fine powdered storing vessel 8 as a part of the substitute for the coke. At this time, the above fine powdered coal containing 5-30% of the coarse powdery coal having +2mm grain size and 5mm max. grain size is used.

Description

[Detailed Description of the Invention] "Objective of the Invention" (Industrial Application Field) This invention relates to a method of operating a blast furnace for iron-making, particularly an oxygen blast furnace, in which the particle size of pulverized coal injected from the tuyere is characterized. It is.

(Conventional technology) Although the conventional blast furnace operation method slightly enriches oxygen,
In high-productivity practical blast furnaces, high-temperature blast (air) from the tuyeres is the main component. Therefore, in a normal blast furnace, the amount of pulverized coal injected into the furnace from the tuyere or the vicinity of the tuyere is usually about 50 to 60 kg/7.
70 to 80% of the particle size composition is 200 mesh or less, and a maximum particle size of 0.5 mm is generally used. However, the cost required to crush coal to such a particle size is considerable. Therefore, in recent years, an example of using relatively coarse grains of pulverized coal is Iron and St.
In the January 1986 issue of eelEngineer, an example of a material containing about 3% of particles having an average particle size of 0.3 to 0, 5 ++n, or less than '2 vm and used in a blast furnace is reported.

Since the temperature at the tuyere tip is over 2,000°C, it was hoped that it would rupture on its own during high-speed thermal decomposition.

A in Figure 1 shows the particle size range of conventional pulverized coal. B indicates the granularity range of the aforementioned report.

In addition, in recent years, an operating method has been proposed in which oxygen at room temperature is blown into the blast furnace through the tuyeres, for example in JP-A-60-159104, for the purpose of further increasing the productivity of the blast furnace. Special Publication No. 37-3356, Special Publication No. 52-32323 using oxygen and furnace top gas, or oxygen as the main ingredient when producing hot metal as a secondary purpose with the main purpose of obtaining gas for coal gasification or chemical industry. As an example of blowing air and using pulverized coal,
9, Japanese Patent Publication No. 31-10755, etc., but none mentions the improvement of the particle size structure of pulverized coal.

(Problems to be Solved by the Invention) The present invention was devised in view of the current situation, and it is possible to use coarse pulverized coal, which cannot be used in conventional blast furnace operations, under normal operating conditions of oxygen blast furnaces. The object is to provide an operating method that increases the amount as much as possible, reduces the cost required for pulverization, and at the same time solves the difficulty of handling in furnace equipment and the like.

"Structure of the Invention" (Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventors have devised a method for injecting gas with an oxygen concentration of 40% or more from the tuyeres at room temperature. Among the pulverized coal injected into the furnace from the vicinity of the tuyeres, we propose a blast furnace operating method characterized by using coarse pulverized coal with a particle size of +211 as 5 to 30%, with a maximum particle size of 5.

By adopting this property, it becomes possible to use a considerable amount of coarse powder coal under normal operating conditions of an oxygen blast furnace, which reduces the cost required for pulverizing the coal and makes handling and transportation convenient.

(Function) According to the present invention, the blast furnace used has an oxygen concentration of 40% from the tuyere.
This is an oxygen blast furnace that operates by blowing the above gases at room temperature and blowing preheated gas from the shaft.

In FIG. 2, the vertical axis represents the height position from the top of the furnace to the tuyere level, and the horizontal axis represents temperature, showing the temperature gradient at each position for each oxygen enrichment rate.

As can be understood from this figure, as the oxygen enrichment rate is increased, the temperature at the tuyere tip increases and the temperature at the upper part of the furnace decreases. Therefore, when blowing with an oxygen concentration of 40% or more, there is insufficient heat in the upper part, and preheating gas from the shaft is required.

An abnormal rise in the tuyere tip temperature during blast furnace operation is caused by reduction and volatilization of Sing, Alz (h, etc.) in the ore and coke and condensation at the top, causing shelving. is used as a temperature regulator, but in the present invention, pulverized coal can be used as a substitute for some of these.In a normal blast furnace, the temperature at the tuyere tip is 2500°C depending on the blast temperature and oxygen enrichment (several percent). However, in the case of an oxygen blast furnace, by reducing the amount of temperature regulator, the temperature can be reduced to 260
It is possible to raise the temperature to about 0 to 2700°C.

Therefore, even if pulverized coal with coarse grains of 2 to 31 cm is injected, the volatile matter is instantaneously evaporated and cranked and gasified, and the remaining char is also instantaneously gasified because the 0□ concentration at the tip of the tuyere is high. Additionally, the atmosphere at the tuyere tip of an oxygen blast furnace is usually higher than that of the blast furnace tuyere tip, so even coarse-grained coal will explode and most of it will explode due to the rapid expansion of the contained gas components, resulting in complete combustion. .

However, even if it is possible to use coarse pulverized coal, blowing an excessive amount within a unit time will result in incomplete combustion, which is undesirable. The addition ratio during normal operation is 5% of the total amount of carbon material injected.
~30% is preferred; blowing in excess of the upper limit causes incomplete combustion. If it is less than the lower limit of 5%, the economic effect aimed at by this invention will not be achieved, and if the maximum particle size is too large, it will cause trouble to the transportation system, so it is necessary to make it less than 5In.

(Example) A blast furnace with a content of 2828nf produces 7500T of iron per day.
Oxygen 330Nrrf/T Tuyere tip temperature adjustment gas 9ON
n? /T Under the condition of pulverized coal 300 kg/T, blowing was performed from the tuyere with a pulverized coal particle size of 70% or less of 200 mesh. When the furnace was switched to the same condition and the air was blown under the same conditions, the wind pressure increased by about 10% and the amount of dust at the top of the furnace increased by about 15%, but the furnace conditions were not affected and continuous operation was possible.

FIG. 1C is an example of a particle size configuration used in the present invention.

Figure 2 shows a typical flow of oxygen blast furnace operation in which the present invention is implemented.
FIG. A charge is charged into the blast furnace 1 from the top of the furnace. The gas inside the furnace passes through the furnace top cleaning mechanism 2 and then to the gas holder 3.
However, the gas is branched on the way, passes through a booster 4, generates high-temperature gas in a preheated gas generator 5, and is blown into the furnace from a gas inlet 6 provided on the shaft. In addition, a part passes through the booster 4' and is used as a tuyere tip temperature adjusting gas to be supplied to the tuyere 9.
It is blown into the furnace. On the other hand, oxygen is sent from the oxygen source 7 to the preheating gas generator 5 and the tuyere 9, but normally pulverized coal from the pulverized coal storage tank 8 is also sent from the tuyere 9 into the furnace as part of coke replacement. is blown into.

"Effects of the Invention" As detailed above, according to the method of the present invention, a large amount of coarse pulverized coal, which cannot be used in a normal blast furnace, can be injected into the furnace from the tuyere or the vicinity of the tuyere. This makes it possible to significantly reduce the running costs required for coal pulverization.

[Brief explanation of the drawing]

FIG. 1 shows the particle size structure of pulverized coal used in the prior art and the present invention. FIG. 2 is a diagram showing the relationship between oxygen concentration and temperature at the tip of the tuyere, and FIG. 3 is a schematic diagram of the flow of blast furnace operation in which the present invention is implemented.

Claims (1)

[Claims] In operations where gas with an oxygen concentration of 40% or more is blown into the furnace from the tuyere at room temperature, 5 to 30% of the pulverized coal injected into the furnace from the tuyere or near the tuyere should have a maximum particle size of 5 mm. A blast furnace operating method characterized by: