JPH06100911A - Operation of blast furnace when blowing large quantity of pulverized coal - Google Patents

Abstract

PURPOSE:To enable stable operation a blast furnace at the time of blowing a large quantity of fine coal by specifying charged hydrogen rate and oxygen enriching according to a specified pulverized coal blowing rate. CONSTITUTION:In the blast furnace operation blowing the fine coal, the fine coal blowing rate is made to be >=150kg/t-p and the charged hydrogen is made to 15-20kg/t-p, and further, the oxygen is enriched to 3-5%. The charged hydrogen is supplied from moisture in the air in blasting, the hydrogen in a coke and hydrocarbon in the fine coal, etc., and the shortage quantity is charged as the steam from a tuyere. By this hydrogen charge, the raceway is deepened and the ventilation in the furnace is improved and the lowering of thermal efficiency is prevented. Further, the oxygen is supplied by enriching the oxygen rate in the blasting to about 24-26%. By enriching the oxygen, the lowering in the heat flowing ratio is restrained and the lowering in the thermal efficiency can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace pulverized coal blowing operation, and more particularly to a method for operating a blast furnace when a large amount of pulverized coal is blown in by blowing pulverized coal at 150 kg / tp or more.

[0002]

2. Description of the Related Art In response to a sharp rise in oil prices, the blast furnace has shifted to an all coke operation in which heavy oil that had been blown as auxiliary fuel is completely stopped. Since then, pulverized coal injection, which has a high economic effect as a stabilization of blast furnace operation and an alternative to coke, has attracted attention, and it has now been adopted by the majority of Japanese blast furnaces.

As described above, many blast furnaces carry out pulverized coal blowing operation in order to reduce energy costs, but the amount of pulverized coal blowing is at most about 150 kg / tp. In Europe, there are more reports (150-200 kg / tp), but almost all of them are data for a very short period of time, and during that time, the furnace heat, ventilation, and descent are extremely unstable,
There is no technology to achieve stable operation of pulverized coal injection of 150kg / tp or more in the long term.

[0004]

In the pulverized coal blowing operation, in order to increase the pulverized coal blowing amount, the following technical problems must be solved. The amount of coke decreases as the pulverized coal ratio increases, and
Poor air permeability due to high coke. As the amount of pulverized coal burned at the tuyere increases, the gas flow becomes a peripheral flow and heat dissipation from the furnace increases, resulting in a decrease in thermal efficiency. A decrease in the heat flow ratio (solid heat capacity / gas heat capacity) raises the temperature of the gas in the furnace, and the sensible heat from the furnace top increases, resulting in a decrease in thermal efficiency.

That is, 150 kg / tp due to instability of operation due to deterioration of air permeability in the furnace, reduction of thermal efficiency, and reduction of substitution rate (amount of coke that can be replaced with pulverized coal).
The above pulverized coal blowing operation has not been achieved.

The present invention has been made in order to solve the above-mentioned problems, and the amount of pulverized coal injected can be increased to 150 kg / tp or more by supplying hydrogen and enriching oxygen. The purpose of the present invention is to provide a blast furnace operating method.

[0007]

[Means for solving the problems] Pulverized coal blowing blast furnace operation, the pulverized coal blowing amount is 150 kg / tp or more, the input hydrogen amount is 15 to 20 kg / tp, and further oxygen is enriched by 3 to 5%. This is a blast furnace operation method when a large amount of air is blown.

[0008]

[Operation] The input hydrogen is the humidity of the air contained in the blast.
~25g / Nm ^3, 0.3~0.5% hydrogen in coke, but is turned from a hydrocarbon 3-6%, etc. in pulverized coal, the amount of hydrogen shortage fed through a tuyere as water vapor. All of these hydrogen amounts are limited to 15 to 20 kg / tp as the input hydrogen amount.

FIG. 6 shows the relationship between the amount of hydrogen input and the raceway depth. As shown in FIG. 6, as the amount of input hydrogen increases, the gas density decreases and the gas viscosity decreases, so that the air permeability near the raceway is improved and the raceway depth tends to increase. Therefore, by setting the input hydrogen amount to 15 to 20 kg / tp, it is possible to deepen the raceway, and by suppressing the increase in the direct reduction rate due to hydrogen reduction, the ore / coke increases in the air permeability in the furnace. It is possible to prevent the deterioration of the thermal efficiency due to the deterioration of the gas flow and the increase of the heat dissipated from the furnace body due to the peripheral flow.

FIG. 7 shows a change in the shape of the cohesive zone in the furnace with a change in the amount of input hydrogen based on the simulation result in the pulverized coal 170 kg / tp blowing operation. The raceway 1 becomes deeper as the amount of input hydrogen increases, the amount of gas to the core increases, and the shape of the cohesive zone 2 changes from a W-shape to an inverted V-shape, improving the air permeability in the furnace.

Normally, the amount of oxygen in the blown air is 21% (volume),
In the present invention, the amount of oxygen is enriched by 3 to 5% and the amount of oxygen in the blast is adjusted to 24 to 26%, and a pulverized coal large amount blowing operation is performed.

FIG. 8 shows the relationship between the oxygen enrichment ratio and the pulverized coal ratio when the furnace top temperature is 160 to 200 ° C. As is clear from Fig. 8, even if the pulverized coal ratio was increased to 150 kg / tp or higher, oxygen was added to maintain the furnace top temperature below 200 ° C.
Need to enrich 3-5%. That is, 3 to 5 oxygen
% Enrichment makes it possible to suppress a decrease in heat flow ratio, prevent a decrease in thermal efficiency due to an increase in furnace top temperature, and secure a pre-tuyere temperature.

[0013]

EXAMPLE An example of the method of the present invention will be described in detail below based on blast furnace operation data in which the amount of pulverized coal injected is increased. Fig. 1 shows changes (total circles) in the total pressure loss in the furnace and the loss of heat dissipation from the furnace body of the prior art in which the pulverized coal ratio was increased, with the input hydrogen amount being constant (12 kg / tp). In the prior art, when the pulverized coal ratio increases, the air permeability deteriorates and the total pressure loss in the furnace increases as the ore / coke rises.
The tendency becomes stronger at g / tp or higher. In addition, the amount of heat radiated from the furnace body increases due to the peripheral gasification of the gas in the furnace. On the other hand, in the method of the present invention (marked with X) in which the input hydrogen amount is 15 kg / tp or more,
Even if the pulverized coal ratio increases, the total pressure loss in the furnace is so large that
Also, the amount of heat dissipated in the furnace body does not increase.

FIG. 2 shows the relationship between the pulverized coal ratio, the hydrogen gas utilization rate and the direct reduction rate. In the conventional technology (circle) in which the amount of input hydrogen is constant, the hydrogen gas utilization rate is constant regardless of the pulverized coal ratio. Therefore, at a high pulverized coal ratio, the ore / coke increases, and the direct reduction rate ( Endothermic reaction) increases, and heat compensation for that amount is required. On the other hand, change the hydrogen input (15 ~
In the method of the present invention (marked with x) increased by 20 kg / tp), the utilization rate of hydrogen gas increases, whereby the direct reduction rate is almost constant. Therefore, by increasing the hydrogen input amount, separate thermal compensation becomes unnecessary.

FIG. 3 shows the relationship between the pulverized coal ratio and the heat flow ratio (solid heat capacity / gas heat capacity), and FIG. 4 shows the relationship between the heat flow ratio and the furnace top temperature. In the conventional technology (circle) that does not perform oxygen enrichment,
As the pulverized coal ratio increases, the heat flow ratio decreases, and the furnace top temperature increases accordingly, but the oxygen-enriched method of the present invention (marked x)
With, it is possible to suppress a decrease in heat flow ratio and an increase in furnace top temperature, and it is possible to prevent a decrease in thermal efficiency due to a rise in furnace top temperature.

As described above, stable operation of the blast furnace can be performed by the method of the present invention even when the amount of pulverized coal blown is increased. That is, it is shown in FIG. 1 that the stability of the blast furnace is maintained (the increase in pressure loss in the furnace is suppressed). Further, it is possible to increase the pulverized coal ratio without lowering the thermal efficiency, as shown in FIGS. 1, 2, 3, and 4,
The relationship between the pulverized coal and the substitution rate of coke is shown in FIG. In the conventional technology (marked with ○), the pulverized coal ratio is 150k
While the substitution rate decreases at g / tp or more, the method of the present invention (marked with x) is almost constant, and the high pulverized coal ratio operation is achieved without reducing the efficiency of the pulverized coal. I understand.

[0017]

INDUSTRIAL APPLICABILITY The present invention provides a pulverized coal blowing blast furnace operation with a pulverized coal blowing amount of 150 kg / tp or more, an input hydrogen amount of 15 to 20 kg / tp, and an oxygen enrichment of 3 to 5%. A method for operating a blast furnace at the time of blowing in a large amount, and according to the method of the present invention, operation instability due to deterioration of air permeability in the furnace due to an increase in the amount of pulverized coal, deterioration of thermal efficiency, and further prevention of a decrease in the replacement rate are prevented, and a weight of Pulverized coal injection operation of / tp or more is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a pulverized coal ratio, a furnace pressure loss, and a furnace body heat loss.

FIG. 2 is a diagram showing a relationship between a pulverized coal ratio, a hydrogen gas utilization rate, and a direct reduction rate.

[Fig. 3] Pulverized coal ratio and heat flow ratio (solid heat capacity / gas heat capacity)
It is a figure which shows the relationship with.

FIG. 4 is a diagram showing a relationship between a heat flow ratio and a furnace top temperature.

FIG. 5 is a diagram showing a relationship between a pulverized coal and a substitution rate of coke.

FIG. 6 is a diagram showing a relationship between an input hydrogen amount and a raceway depth.

FIG. 7 is a diagram showing a change in shape of a cohesive zone in a furnace according to a change in the amount of input hydrogen based on a simulation result.

FIG. 8 is a diagram showing the relationship between the oxygen enrichment rate and the pulverized coal ratio when the furnace top temperature is kept constant.

[Explanation of symbols]

 1 ... Raceway, 2 ... Cohesive zone.

Claims (1)

[Claims] 1. A pulverized coal blowing blast furnace operation, in which the pulverized coal blowing amount is 150 kg / tp or more, and the input hydrogen amount is 15 to
A blast furnace operating method when a large amount of pulverized coal is blown, characterized by 20 kg / tp and further enriching oxygen by 3 to 5%.