JPS62238307A - Method for blowing noncombustible fuel into blast furnace - Google Patents

Abstract

PURPOSE:To improve the combustion efficiency of noncombustible fuel in a blast furnace operation by blowing gaseous fuel at a specific ratio to the outside peripheral part of a blow pipe at the time of blowing the noncombustible fuel into the blow pipe. CONSTITUTION:The fuel blowing nozzle is made into multiple pipe construction at the time of blowing the noncombustible fuel from a fuel blowing burner 7 into the tuyere of the blast furnace. The noncombustible fuel A such as powder fuel, tar or heavy gravity oil is supplied from the inside pipe 7a into the furnace and the gaseous fuel C such as coke oven gas is supplied from an outside pipe 7b thereto. The rate of the gaseous fuel to be blown is adjusted to >=2% in terms of heat quantity relative to the rate of the noncombustible fuel to be blown. The gaseous fuel C on the outside periphery is immediately ignited and burned by hot air and the noncombustible fuel A is simultaneously heated from the outside peripheral side. The time for igniting the noncombustible fuel and starting the combustion thereof is shortened by the above-mentioned blowing method.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for injecting flame-retardant fuel into a blast furnace. The present invention also relates to a method for increasing the combustion rate of kneaded flame-retardant fuel when injecting tar, heavy oil, etc. from a fuel injection burner into a blast furnace.

[Prior Art] The fuel used in blast furnace operation has shifted from injection of heavy oil to all-coke operation, and has also progressed to injection of tar and pulverized coal. However, pulverized fuel such as pulverized coal (hereinafter collectively referred to as pulverized fuel), tar, and heavy oil have poor combustibility compared to ordinary C heavy oil, and pulverized coal contains non-combustible components such as ash. Because of this drawback, it is necessary to take various measures when blowing.

Under these circumstances, the present applicant has been conducting research for some time in order to establish an effective injection method for powdered fuel, and has proposed, for example, a technique disclosed in Japanese Patent Publication No. 60-53081. This method (1) improves the combustion rate of powdered fuel and (2) improves the combustion rate of powdered fuel.
) The injection position of the powdered fuel was moved to the upstream side of the blow vibrator as a means of satisfying both of the two demands of preventing ash from adhering to the inside of the blow vibrator. Since adhesion of ash to the wall surface of the blow vibrator is prevented even if the temperature of the hot air supplied to the blow vibrator is increased, it has become possible to simultaneously satisfy the above two demands.

[Problems to be solved by the invention] That is, in the proposed invention, as shown in Figure 5 on page 4 of the official gazette, the use of hot air at a high temperature of 1050°C or higher is a necessary condition for improving the combustion rate. I think it is 1, and 10
The combustion rate when using hot air below 50°C is very low.

Therefore, the operating temperature of the hot air stove must be increased, which is disadvantageous from the viewpoint of energy conservation, and also shortens the life of the furnace wall refractories and ducts, which deteriorates the maintainability of the equipment.

The present invention was developed in view of these circumstances, and its purpose is to prevent pulverized fuel and tar even when using hot air at a low temperature below 1050°C.

The present invention aims to provide a method for injecting flame-retardant fuel into a blast furnace that can sufficiently increase the combustion rate of flame-retardant fuel such as heavy oil.

[Means for Solving the Problems] The structure of the method of the present invention that has achieved the above-mentioned object is that when injecting flame-retardant fuel into the blow vibrator for blowing hot air connected to the blast furnace siding, Gaseous fuel is blown into the outer circumference of the combustible fuel independently, and the amount of blown gas fuel is set to 1.
The gist of this is that the flame retardant fuel should be 2% or more in terms of calorific value per °C for the fleas injected with the flame retardant fuel.

[Operations and Examples] The configuration and operation effects of the present invention will be explained in detail below along with the progress of experiments. Figure 1 is a schematic diagram of the apparatus used in the combustion experiment, which is designed to resemble an actual blast furnace lining. Flame-retardant fuel A (hereinafter also typically referred to as powdered fuel A) is conveyed from the hopper 1 to the coal bin 3 by the screw conveyor 2. A pulverized fuel quantitative feeder 4 is provided at the bottom of the coal bin 3, and the pulverized fuel A cut out in fixed amounts at this portion is sent to the burner 7 through a transport pipe 6 together with transport air 5. Although the supply of liquid fuel such as tar or heavy oil is not shown, an appropriate method may be used, such as increasing the pressure of tar or heavy oil stored in a heating tank with a pump and supplying it to the burner 7. I can do it. On the other hand, the hot air obtained in the high-temperature hot air stove 8 is sent from the blast pipe 9 to the combustion test furnace 12 via the blow vibe 10 and the water-cooled tuyeres 11. 13 in the figure is a chimney.

Since the fuel injection section of a blast furnace is completely different from a general combustion device and consists of a blow vibe 10 and a water-cooled tuyere 11, this experimental device approximates an actual blast furnace injection section.

In addition, this test furnace is equipped with numerous observation windows for observing the combustion and ignition conditions, as well as inspection holes for measuring the temperature inside the furnace, the gas composition inside the furnace, the dust inside the furnace, the amount of flame radiation, etc. , and at the upstream bend of the blow vibe 10,
A peephole 14 is provided for observing the adhesion of ash to the wall surface of the blow vibrator 10.

The conditions for the series of experiments described later using this apparatus are as follows.

Experimental conditions Flame retardant fuel, 1. Pulverized coal (volatile content 35% by weight) 2, tar fuel injection M: 75 x 10' kcal/hour (constant) Hot air temperature +1000°C Flame-retardant fuel injection position: 9 points, 200 mm upstream from the boundary position of the tuyere and blow vibe First, we tried the method disclosed in the above-mentioned published invention and investigated the reason why the combustion rate could not be improved to 1 minute when the hot air temperature was less than 1050°C, and the following facts became clear. That is, the powdered fuel blown into the blow vibe 10 from the powder fuel injection burner 7 receives heat from the hot air flowing inside the blow vibe 10, and first loses volatile components (hydrogen, carbon monoxide, etc.).
evaporate, these reach the ignition temperature and combustion begins. However, in the conventional method as described above, if the hot air temperature is too low, the powder fuel itself may be damaged! The carrier gas, which is injected in a mixed phase state with A-temperature, takes away a fraction of the amount of heat, and the essential powdered fuel is not heated sufficiently, which not only delays the start of volatilization of volatile components, but also slows down the rate of volatilization. Furthermore, the time required for the volatile gas to reach the ignition temperature also becomes delayed, and it takes a considerable amount of time from injection to ignition combustion. As a result, ignition of the powdered fuel occurs at the tip of the tuyere or within the raceway, and the combustion time from ignition to exit from the raceway is relatively significantly shortened. Therefore, when the hot air temperature is lower than 1050°C, the powder fuel injection position should be adjusted to 100 to 350 mm as shown in the above-mentioned published invention.
Even if the combustion time was moved upstream by eight degrees, the combustion time within the raceway could not be substantially extended, and in the end, the combustion condition of the powdered fuel at the end of the first sway was hardly improved. .

In particular, the time required for powdered fuel to pass through the raceway during blast furnace operation is extremely short compared to the time required for fuel to pass through boilers, kilns, sintering ignition furnaces, etc.
300 to 11,500), under these conditions, nearly half of the total residence time is consumed in so-called preheating, including evaporation of volatile matter and ignition, and the actual combustion time becomes insufficient, resulting in a decrease in the combustion rate. It is considered that this was not possible to improve the results.

Therefore, the inventor of the present invention discovered that in order to increase the combustion rate of powdered fuel or flame-retardant fuel such as tar or heavy oil to a satisfactory level even when relatively low-temperature hot air is used, it is necessary to blow into the blow vibrator. We thought that it would be effective to shorten the time required for the flame-retardant fuel to ignite as much as possible, and conducted further research based on this idea. As a result, when injecting flame-retardant fuel into the blast furnace, the gaseous fuel is injected in parallel, and the combustion heat of the gas promotes rapid volatilization of volatile matter from the powdered fuel and ignition of the volatile matter. I came up with the idea that it would be effective to do so. As a result of further research to realize this idea, we came to the conclusion that the above idea could be realized as a practical technology by injecting gas fuel close to and independently of the flame-retardant fuel. It's arrived. In this case, the gas fuel may be any easily combustible gas, including natural gas, city gas, converter gas, petroleum gas, blast furnace gas, and other types, but coke oven gas has a low combustion rate. It is particularly preferable because it is quick and easy to obtain at steel manufacturing sites.

In other words, the main component of coke oven gas is hydrogen (50% of the total
~60%), and its combustion speed is 7 to 8 times that of LPG or natural gas, and when it is blown into the blow vibe, even relatively low-temperature hot air is quickly ignited and burned. The combustion heat exceeding a certain amount promotes the rapid volatilization of the volatile matter in the flame-retardant fuel and its ignition, resulting in a marked reduction in the time required for the ignition of the flame-retardant fuel. The burning time of sexual fuel will be extended,
The combustion rate can be significantly increased.

When the flame-retardant fuel is a powder fuel, it is possible to simultaneously supply gaseous fuel such as coke oven gas as a carrier gas for supplying the powder fuel, but the inventor has confirmed this through experiments. The reason why it was found that the gaseous fuel should be supplied independently of the powdered fuel is as follows.

In other words, when gas fuel is mixed with powder fuel and supplied into the blow vibe, the temperature of the coke oven gas increases due to the hot air.
Ignition is suppressed by the mixture of powdered fuel, and the expected combustion promotion effect cannot be obtained. To explain this point in more detail, when injecting powdered fuel into a blast furnace, it is said that the amount of low-temperature carrier gas should be as small as possible, and the weight ratio of powdered fuel/carrier gas is generally It is selected from the range of 10 to 30 (g/Kg). Under such injection conditions with high powder fuel concentration,
The radiant heat transfer efficiency and optical transparency in the solid-gas mixed phase flow that is blown in must be extremely low. Moreover, if a method of supplying gas fuel mixed with powdered fuel is adopted, the gaseous fuel will be diluted with a large amount of powdered fuel. The ignition combustion of the multiphase flow proceeds by receiving heat from the hot air on the outermost side, but at the same time, in order for the gas fuel to rise to the ignition temperature, the powder fuel (which has a lower heat capacity than the gas) Since it is necessary to raise the temperature even to a large temperature, the ignition and combustion of the gas fuel itself is delayed due to the ignition delay due to dilution with the powdered fuel, and the combustion promotion effect cannot be increased satisfactorily. In addition, it goes without saying that it is preferable to inject both fuels independently from the standpoint of individually controlling the flow rates of the powdered fuel and the gaseous fuel, as well as ensuring safety.

In contrast, a predetermined amount or more of gas fuel is placed near the flame-retardant fuel (
When supplied independently (preferably to the outer periphery), the gaseous fuel comes in contact with the hot air and instantaneously rises in temperature to the ignition temperature, ignites and burns, and the combustion heat causes the volatile matter in the flame-retardant fuel to volatilize and ignite. As a result, the time it takes for flame-retardant fuel to start burning is significantly shortened. As understood from the above explanation, the amount of gaseous fuel blown needs to be such that a sufficient amount of heat can be generated to promote the volatilization and ignition of the flame-retardant fuel.

The next most preferable burner is, for example, Fig. 2 (longitudinal sectional view).
As shown in the figure, the fuel injection nozzle has a multi-tube structure (in the example, 2
It is also advantageous to supply powder fuel or liquid fuel (flame-retardant fuel A) such as tar or heavy oil from the inner pipe 7a, and supply gaseous fuel C from the outer pipe 7b. However, if such an injection method is adopted, the gaseous fuel C will be injected so as to surround the flame-retardant fuel A, and the gaseous fuel on the outermost side will be immediately ignited and ignited by the hot air.
As it burns, the flame-retardant fuel A is heated all at once from the outer circumferential side, and the time required to ignite and start combustion of the flame-retardant fuel A can be significantly shortened.

Figure 3 shows the combustion experiment using the combustion experiment apparatus shown in Figure 1 above.
This is an example of the results of an experiment using pulverized coal and tar as representative examples of flame-retardant fuel, but similar results can be obtained when coke or heavy oil is used.

(1) and (2) in the figure indicate what was done in the next experiment.

(1) A pulverized coal injection burner with a double tube structure shown in FIG. 2 was used, and pulverized coal was blown into the inner tube 7a, and coke oven gas (COG) was blown into the outer tube 7b independently.

(2) Using a burner with a double g (tube narrower than the above burner) structure as shown in Fig. 2, tar is supplied from the inner tube 7a, and coke oven gas (COG) is supplied independently from the outer tube 7b. Infused.

The horizontal axis is the amount of coke oven gas (COG) blown, and shows the ratio of the amount of heat blown into coke oven gas to the total amount of heat blown into pulverized coal or tar. Therefore, the point where coke oven gas injection is 1/0 corresponds to the case where only pulverized coal or tar is injected. The vertical axis shows the total combustion rate at 0.4 m from the tuyere tip. The amount of pulverized coal or tar injected is 75X 10
' When the coke oven gas injection rate is increased while keeping the keal/hour (constant), the combustion rate gradually increases, from about 75% with pulverized coal injection to 100% with tar injection (
approaching complete combustion).

The effect of increasing the combustion rate can be increased by about 15% by co-combusting coke oven gas with only 2% (calorific value) of a flame-retardant fuel such as pulverized coal or tar. That is, since the combustion rate within the raceway can be improved, the outflow force of unburned components to the outside of the raceway is reduced, and a large amount of fuel can be blown into the raceway. The combustion rate of pulverized coal injection is saturated at about 75% because the remaining 75% depends on the combustion of char, which has a low combustion rate. As is clear from Fig. 3, in order to promote the volatilization and ignition of the flame-retardant fuel and to exhibit the combustion promotion effect, it is necessary to increase the amount of injected flame-retardant fuel by at least 2% in terms of heat i. Gas fuel injection is required. In order to achieve a combustion promoting effect by reducing the amount of coke oven gas blown as much as possible, the amount of coke oven gas blown is preferably in the range of 2 to 10%.

The above combustion promotion effects are applicable to natural gas, city gas, petroleum gas,
This was also confirmed with converter gas and blast furnace gas, but coke oven gas had the best increase in combustion rate at a constant gas injection amount.

[Effects of the Invention] The present invention is configured as described above, and its effects can be summarized as follows.

(1) Even when the hot air temperature is low, the combustion rate of flame-retardant fuel can be increased to a satisfactory level, and even when it is difficult to obtain a high-temperature hot air temperature, it is possible to inject a large amount of flame-retardant fuel. It is possible to achieve significant cost reductions.

(2) It is also possible to operate the blast furnace by actively lowering the hot air temperature, increasing energy saving efficiency. It is also possible to suppress deterioration of refractories including ducts and the like. In addition, the gas fuel in the outer periphery also serves as a cooling gas for the burner, and the temperature of the hot air can also be lowered, so even non-water-cooled burners have a long life.

(3) Since the combustion rate can be sufficiently increased, it is possible to increase the usage ratio of inexpensive flame-retardant fuel such as pulverized coal, and it is possible to reduce fuel costs.

(4) Since the combustion rate is stabilized at a high level, the stability of the blast furnace conditions can also be improved, and the blast furnace operating efficiency can also be improved.

(5) In carrying out the present invention, only the burner of multiple structure or other gas fuel injection device is required separately, so the increase in burden is small.

(6) Coke oven gas and blast furnace gas are produced in the coke manufacturing process, which is essential as a raw material for blast furnace charging, and are usually installed adjacent to blast furnace equipment, so they can be obtained at low cost. .

[Brief explanation of drawings]

Fig. 1 is an explanatory view showing the combustion device used in the experiment, Fig. 2 is a partially cutaway side view illustrating a burner with a multiple structure used in carrying out the present invention, and Fig. 3 shows the effects of the present invention. This is a graph showing.

Claims (1)

[Claims] When injecting flame-retardant fuel such as powdered fuel, tar, and heavy oil into the blast furnace, gas fuel is injected into the vicinity of the flame-retardant fuel independently of the flame-retardant fuel, and the amount of gas fuel injected is adjusted to A method for injecting flame retardant fuel into a blast furnace, characterized in that the amount of flammable fuel injected is 2% or more in terms of calorific value.