JPS5833284B2 - Blast furnace injection method and device for coal/water slurry - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for blowing coal/water slurry into a blast furnace, and particularly to a method and apparatus for blowing coal/water slurry into a blast furnace, which can increase the coke saving rate by using highly concentrated coal/water slurry. Regarding equipment.

In order to save coke used in metallurgical furnaces such as blast furnaces, a so-called method of injecting combustion aids into blast furnaces has been used, in which various combustion aids such as heavy oil and coal are injected into the furnace through the lining of the furnace.

The various combustion aids are listed below.

(a) Heavy oil (b) Heavy oil and coal mixed colloidal fuel, abbreviated as CO
It is called M.

(c) Dry pulverized coal (d) Reducing gas mainly composed of Co, H2, etc., or natural gas or other gas fuel The selection of these combustion aids depends on the method of injecting the combustion aid into the blast furnace that is economically viable in the region. Since this is a condition, each combustion aid has a good track record in each region.

However, due to the abnormal rise in oil prices in recent years, it has become economically difficult to adopt both (a) heavy oil and (b) heavy oil and coal-mixed colloidal fuel in Japan.

In other words, heavy oil-based combustion aids increase the cost of hot metal, and therefore it is necessary to convert them to other combustion aids.

On the other hand, (C) dry pulverized coal is not directly affected by the unusual rise in oil prices, but there are many problems with the handling of dry pulverized coal as follows.

That is, (a) as a measure to avoid the risk of explosion in coal drying and crushing equipment, it is necessary to lower the oxygen partial pressure in the system.

In other words, a closed loop gas circulation system, complete with instrumentation and safety controls, must be constructed.

Therefore, the form of the equipment is limited and special, requiring high equipment and operating costs.

(0) The energy cost for drying coal has reached an amount that cannot be ignored due to the abnormal rise in oil prices in recent years, creating a new problem for this method.

(c) All ancillary equipment, such as the pulverized coal conveyor and storage tank, must have an airtight structure.

2) In the method of injecting dry pulverized coal into a blast furnace, the pulverized coal must be mixed with a carrier gas to form a fluid and pressurized to a level higher than the internal pressure of the blast furnace.

For this purpose, a lock hopper including a pressure equalization valve, a fluidization tank, a compressor, etc. are required.

In this respect, even though the coal/water slurry of the present invention is the same fluid, it can be treated as a liquid rather than a gas like a dry pulverized coal mixed fluid, and is incompressible, so it can be easily pressurized.

(e) When transporting dry pulverized coal through pipes, there are many equipment failures such as wear or blockage of pipes, pulp, etc.

(f) It is technically difficult to charge dry pulverized coal evenly between each tuyere of a blast furnace.

As listed above, there are many problems in handling dry pulverized coal.

Finally, gas fuel (d) has many regional restrictions.

As mentioned above, the conventional methods of injecting combustion improvers into blast furnaces have many problems, and urgent solutions are required.

In particular, oil prices are becoming more unstable and the prospects for stabilization are extremely dark, so a switch to coal is basically required, and in particular, it is necessary to solve the problems of the conventional method of injecting dry pulverized coal into blast furnaces. is strongly required.

The purpose of the present invention is to reduce the amount of coke used in metallurgical furnaces such as blast furnaces by injecting heavy oil, coal, etc. into the furnace from the tuyeres of the furnace. It is an object of the present invention to provide a method and apparatus for injecting a combustion aid into a blast furnace, which solves the problem, is economical, easy to handle, and has a high coke saving rate.

This object of the present invention is distantly related to the method and apparatus for blowing coal/water slurry into a blast furnace of the present invention, which is summarized below.

The gist of the present invention is as follows.

That is, in a method for injecting a combustion improver into a blast furnace, in which heavy oil or the like is injected into the furnace through the siding of the blast furnace, a step of wet pulverizing coal to form a coal/water slurry with a coal concentration of 60 to 70% by weight, and a step of A step of concentrating the water slurry using a separator provided near the lining of the furnace to obtain a highly concentrated slurry of 60 to 80% by weight; A method for injecting coal/water slurry into a blast furnace, which is characterized by comprising the step of injecting coal/water slurry into a furnace at high pressure.

In addition, in order to carry out this method, in a blast furnace injection device for combustion aid material that injects heavy oil etc. into the furnace from the tuyere of the blast furnace,
A call center that wet-pulverizes coal to produce a coal/water slurry with a coal concentration of 60 to 70% by weight, and a coal center that is connected to a slurry transfer pipe for transferring the coal/water slurry by a pump and installed near the tuyere. A coal/water slurry comprising a separator for concentrating the coal/water slurry, and a carrier gas blowing pipe connected to the underflow side of the separator and to the blowing port of the siding to blow the highly concentrated slurry into the furnace. A water slurry blast furnace injection device was constructed.

One important point in this method of injecting coal/water slurry into a blast furnace is how to effectively blow the coal/water slurry, which is not necessarily desirable from the perspective of the heat balance in the blast furnace, into the blast furnace while reducing the negative impact on the heat balance. There is a point where it is said that it will be crowded.

Therefore, in addition to the configuration of the first method invention in which the coal/water slurry produced by the wet pulverization is condensed just before the tuyere of the furnace and made into a highly concentrated slurry and blown into the furnace, the humidity of the air blown into the furnace,
A second method invention for improving the heat balance in the furnace was constructed by adding a step of compensating for the amount of heat absorbed by moisture in the high concentration slurry by adjusting the in-furnace ripening modifying factors such as temperature and oxygen concentration.

This is because the water in the coal/water slurry that is injected into the blast furnace undergoes a thermal decomposition reaction inside the blast furnace, and this reaction is an endothermic reaction, causing a temperature drop in the blast furnace hearth and siding. This will impair the operational performance of the blast furnace.

Therefore, it is desirable that the concentration of the coal/water slurry be as high as possible, and it is necessary to dehumidify, heat, or enrich the blast furnace air with enough oxygen to offset the endothermic effect of moisture in the injected coal/water slurry. It is.

Alternatively, in addition to dehumidification, heating, etc., improvements can also be made by adjusting known heat balance modifying factors such as changing the coke ratio.

The concentration of coal/water slurry is generally 100% between the wet grinding equipment that makes this slurry and the blast furnace tuyere where it is used.
Since it has to be transferred within the transfer pipe back and forth,
It is limited by the diameter of the transfer pipe, the flow rate of the slurry, the diameter of the coal particles, etc., and generally must be 70% or less.

Increasing the concentration of this coal/water slurry to 70% or more is possible for a short period of time, but over a long period of time it will cause problems with pipe blockage and increase pipe wear, leading to many equipment failures. .

Therefore, for long-term operation, it is necessary to use coal made by wet pulverization.
Water slurry concentration must remain below 70%.

Therefore, in the present invention, the coal/water slurry with a concentration of 70% or less made by the wet grinding is concentrated using a separator installed near the furnace wall, and is then pumped into the furnace as a highly concentrated slurry through an injection port installed in the tuyere of the furnace. Infuse.

In addition, the amount that can be blown is determined by the coal concentration in the slurry, air dehumidification, oxygen enrichment, and amount of increase in air temperature.

In other words, when dehumidifying the blast furnace air during injection, it is possible to inject an amount of coal/water slurry that has the same amount of moisture as the amount of water removed by dehumidification, and the amount of coal/water slurry that has the same amount of moisture as the amount of water removed by dehumidification can be injected. If added, it is possible to increase the coal/water slurry injection amount set by the above-mentioned dehumidification and water removal.

Examples of the present invention will be described below.

Table 1 shows Australian uranium (Ula) used in the examples of the present invention.
n) Indicates the properties of charcoal.

Table 1 Properties of Australian Tsuran Coal Rice Calorific Value of Dry Coal Next, to determine the amount of coal/water slurry that can be injected, the blast furnace air was dehumidified using dehumidifying equipment and the following results were obtained.

(a) The amount of moisture removed per 1Nm8 blast furnace air flow is...
Air flow rate per 1 ton of 15gr (b) pig iron is 1,00ON7
Since it is male, the amount of moisture removed per ton of pig iron is...1
5-2 From these results, calculate the theoretical amount of coal/water slurry that can be injected, taking into account that the heat balance at the blast furnace tuyere section will not change compared to before the coal/water slurry injection.

Table 2 is a summary of the possible amounts of coal/water slurry that can be injected under various conditions for the coal/water slurry.

As shown in Table 2, made of coal by separator If you raise the degree, This increases the theoretical amount that can be injected. can be increased.

Next, under these conditions, the coal-water slurry of the present invention was injected into a blast furnace, and as a result, there was a clear difference in the coke replacement ratio to the weight of injected coal in cases A and B, with cases that did not pass through a separator and those that did. The effect of the separator was recognized because the coke replacement ratio to the amount of blown coal was high in the case that passed through the separator.

Table 3 shows the coke replacement ratio to the weight of blown coal in the case of coal/water slurry injection.

Table 3 Coke Replacement for Injected Coal Weight An example of equipment for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an arrangement diagram showing an embodiment of an apparatus for performing the coal/water slurry injection method of the present invention.

In the call center 2, a wet mill is used to pulverize the coal into a coal-water slurry having a concentration of 60-70% by weight.

This coal/water slurry is sent by the slurry transfer pump 4 through the slurry transfer pipe 6 to the slurry pipe 12 near the wall section 10 of the blast furnace 8, where it is distributed to each wall and pressurized 1 to 2 atmospheres higher than the furnace internal pressure. It is then blown into the siding part 10 of the blast furnace 8.

On the other hand, the hot air sent to the blast furnace is sent from the blower 14 to the dehumidifier 16.
, hot blast furnace 18 , hot blast tubular ring 20 and then blast furnace siding 10
From there, it is blown into the blast furnace 8.

FIG. 2 is an arrangement diagram of the equipment used to carry out the coal/water slurry injection method of the present invention.

The coal/water slurry enters the separator 22 from the coal/water slurry transfer pipe 6, is concentrated there, and is blown into the blast furnace 8 from the blowing port 24 in the siding part 10.

The separator 22 and the auxiliary equipment described below are provided below the hot air annular pipe 20 of the blast furnace 8 near the siding part 10.

This separator 22 is specially designed to increase the coal concentration in the slurry and its details are shown in FIG.

The separator 22 processes the coal/water slurry sent from the coal/water slurry transfer pipe 6, discharges the concentrated slurry to the underflow side, and overflows the diluted portion.

The concentrated slurry discharged to the underflow side of the separator 22 is mechanically forced into the blast furnace 8 through the blowing port 24 using a carrier gas.

The installation position of this blowing port 24 is set at the siding part 10 in order to secure the combustion time of the coal/water slurry and improve the combustibility.
Inside, the blowpipe is positioned slightly backwards so that the blown coal/water slurry comes to the center of the hot air flow.

Blast furnace gas, air, nitrogen, etc. are used as the carrier gas, and these gases are sent from a carrier gas blowing pipe 26 communicating with the underflow side of the separator 22 and play the role of transporting the concentrated slurry into the blast furnace 8.

The amount of coal/water slurry blown into each tuyere section 10 is set in advance to be equal by operating the valve 28, and the carrier gas blowing pipe 26 communicates with the separator underflow side so that the operating conditions of the separator 22 can also be kept constant. A pressure gauge 30 is provided at , and a flow valve 32 is controlled by this.

Further, the flow rate valve 32 and the control valve 34 provided in the slurry transfer pipe 6 are controlled in a cascade manner.

A magnetic flowmeter 36 is installed on the overflow side of the separator 22.
and a concentration meter 38.

This overflow is sent to the Shirafuna via piping 40 to the Shirafuna.

The coal/water slurry that is actually injected into the furnace from the siding is based on the preset coal/water slurry concentration and flow rate of the coal/water slurry transfer vibro and the values indicated by the flow meter 36 and concentration meter 38 on the overflow side. Concentration and flow rate can be calculated.

As explained above, the important point of the present invention is to increase the concentration of the coal/water slurry immediately before the tuyere 10 of the blast furnace 8 to minimize heat absorption in the furnace and maximize the coke replacement effect. A method can be added in which the coal in the coal/water slurry is pre-agglomerated before the separator 22, which is the mechanical separation/concentrator, to enhance the concentrating effect of the separator 22.

The equipment for this purpose is to add 0.2% (0.2%) of mineral oil, light oil, jet oil, or other flocculant from the flocculant addition tank
The performance of the mechanical separator 22 can be significantly improved by adding it to the line mixer 44 at a weight of less than .

In addition to the above, a coal/water slurry bypass 46 is provided.

In addition to the separator using the mechanical method described above as a means of increasing the concentration of coal/water slurry, a chemical method is used in which a solvent is mixed with the coal/water slurry, and the hydrophobicity of the solvent is utilized to transfer coal powder to the solvent. A method of concentrating by filtration is also possible.

This chemical separator is not shown.

FIGS. 3 and 4 show cross-sectional views of various separators tested in order to carry out the present invention.

3A and 3B show that coal particles are concentrated and separated by a rapid change in slurry flow velocity and a change in direction of the velocity vector.

FIG. 4 utilizes the centrifugal force of fluid, and A is a front cross-sectional view, and B is a cross-sectional view of A taken along the line B--B.

The separators shown in FIGS. 3A and 3B and FIG. 4 all have a concentration effect and can increase the coal concentration to 70% by weight or more.

This fact seems to be due to the synergistic effect of the separation ability of the separator itself and the water return property of the coal, which further enhances the effect.

Although the effects of the present invention have already been described individually, they can be summarized as follows.

In the present invention, since the coal/water slurry made by wet pulverization can be effectively used as a combustion aid in a blast furnace, (a) a large amount of expensive coke can be replaced and costs can be reduced.

(b) It is possible to switch from heavy oil, whose price has skyrocketed, to coal.

(c) Since various problems in handling pulverized coal have been solved, it is possible to use a large amount of coal.

2) As a future problem, projects are being proposed to create a coal/water slurry in order to reduce transportation costs when seeking steam coal resources overseas.

In this case, marine transportation of coal by slurry ship makes it possible to avoid the danger of heat generation due to oxidation of steam coal, and further reduces transportation costs.

[Brief explanation of the drawing]

FIG. 1 is an arrangement diagram showing an embodiment of the apparatus for carrying out the method of the present invention, FIG. 2 is a detailed arrangement diagram of the apparatus used for carrying out the invention,
3A and 3B are schematic cross-sectional views showing examples of separators used in carrying out the method of the present invention, and FIGS. 4A and 4B show other examples of separators similar to those shown in FIG. A is a front cross-sectional view, and B is a cross-sectional view taken along the line BB of Figure A. 2...Call center, 4...Slurry transfer pump, 6...Slurry transfer pipe, 8...
... Blast furnace, 10 ... Tuyere section, 12 ...
・Slurry piping, 22...Separator.

Claims (1)

[Scope of Claims] 1. In a blast furnace injection method for combustion improver in which heavy oil, etc. is injected into the furnace from the tuyere of the blast furnace, coal is wet-pulverized to reduce the coal concentration to 6.
a step of making a coal/water slurry of 0 to 70% by weight; a step of concentrating the coal/water slurry using a separator provided near the tuyere of the furnace to obtain a highly concentrated slurry of 60 to 80% by weight; A method for injecting coal/water slurry into a blast furnace, comprising the step of injecting a highly concentrated slurry into the furnace from an injection port provided in the tuyere of the furnace at a pressure higher than the furnace internal pressure. . 2. In the blast furnace injection method of combustion improver, in which heavy oil, etc. is injected into the furnace from the tuyeres of the blast furnace, coal is wet-pulverized to a coal concentration of 6.
a step of making a coal/water slurry of 0 to 70% by weight; a step of concentrating the coal/water slurry using a separator provided near a separate port of the furnace to obtain a highly concentrated slurry of 60 to 80% by weight; A process in which high-concentration slurry is injected into the furnace at a pressure higher than the furnace internal pressure from an injection port provided in the tuyere of the furnace, and changes in the heat balance in the furnace such as humidity, temperature, and oxygen concentration of air blown into the furnace. A method for blowing coal/water slurry into a blast furnace, comprising the step of compensating for the amount of heat absorbed by moisture in the high concentration slurry by adjusting a factor. 3. In the blast furnace injection device for combustion aid, which injects heavy oil etc. into the furnace from the tuyeres of the blast furnace, the coal is wet-pulverized to a coal concentration of 60%.
A call center that makes ~70% by weight coal/water slurry, and a separator that is connected to the slurry transfer pipe that transfers the coal/water slurry by this call center or lahompu and is installed near the clapboard to concentrate the coal/water slurry. A blast furnace for coal/water slurry, comprising: a carrier gas blowing pipe that communicates with the underflow side of the separator and connects to the blowing port of the tuyere to blow high concentration slurry into the furnace. Blowing device.