JPS5910969B2 - Coal slurry blast furnace injection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for injecting coal slurry into a blast furnace, and in particular, to reduce coke soot in a blast furnace, stabilize operation,
The present invention relates to a method and apparatus for injecting coal slurry into a blast furnace for the purpose of improving productivity.

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 tuyeres 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 whose main components are CO, H2, etc. or natural gas or other gas fuel The selection of these combustion aids is determined by 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 unusual 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 our country.

That is, heavy oil-based combustion aids increase the cost of hot metal, and for this reason, 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, it is necessary to construct a closed circuit, so-called closed-loop gas circulation system, complete with instrumentation and safety control.

Therefore, the form of the equipment becomes limited and special,
Requires high equipment and operating costs.

(Note) The energy for drying coal is 25 per ton of coal.
It requires ~300,000 Kcal, and the cost has reached a non-negligible amount due to the unusual 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.

(d) 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 and valves.

(f) It is technically difficult to charge dry pulverized coal evenly between each wall of the 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 sought after.

Direct injection of coal slurry into a blast furnace may be considered as a means to solve this problem, but this has never been implemented in a production blast furnace for the following reasons.

(a) The general concentration of coal slurry is limited to 60% by weight, and the coal particle size must be considerably pulverized since it is burned in a limited space such as the blast furnace tuyere combustion zone.

However, on the other hand, the pulverization of coal increases the viscosity of the coal slurry, which essentially causes flow stagnation.

(Example) When the water content in the coal slurry is 40% by weight or more, it is difficult to maintain the average combustion temperature due to the endothermic effect caused by the thermal decomposition reaction.

In other words, thermal decomposition of water in the coal slurry causes an endotherm of 3200 Kcal per kg of water, and this cooling effect absorbs 540 Kcal per kg of heat of vaporization of water.
The value is 6 times that of

In addition, there is a drawback that metallurgical coke in the blast furnace is consumed due to the reaction of HO+C-+H2+CO2, which was considered technically and economically impossible in the past.

One of the inventors of the present invention previously disclosed a method for injecting coal/water slurry into a blast furnace in Japanese Patent Application No. 55-83174.

The gist is as follows. That is, in the blast furnace injection method of combustion improver in which heavy oil etc. is injected into the furnace from the siding part of the blast furnace, a step of wet pulverizing the coal to form a coal/water slurry with a coal concentration of 40 to 70, and a step of wet-pulverizing the coal into a coal/water slurry having a coal concentration of 40 to 70, a step of concentrating the slurry into a highly concentrated slurry using a separator installed near the walls of the furnace, and blowing the highly concentrated slurry into the furnace at a pressure higher than the furnace internal pressure from a blowing boat installed in the tuyere of the furnace. and a step of improving the heat balance in the furnace by dehumidifying, heating, or enriching the air blown into the furnace at the time of injecting the high concentration slurry. This is a method of injecting water slurry into a blast furnace.

The object of the present invention is to provide a method for injecting coal slurry into a blast furnace, which was previously disclosed in Japanese Patent Application No. 55-83174
An object of the present invention is to provide a method and apparatus for injecting coal slurry into a blast furnace, which improves the invention of No. 9807) and improves operational stability and economic efficiency.

The gist of the method for injecting coal slurry into a blast furnace according to the present invention is as follows.

That is, a step of wet pulverizing coal having a C/H molar ratio of 1.5 or more based on ashless dry coal to -200 mesh 50 to 80% by weight, and pulverizing the pulverized coal to a concentration of 6
After making coal slurry of 0 to 70% by weight, there are steps of adding a fluidity improver to this coal slurry, heating the coal slurry with steam, and dehydrating the steam-heated coal slurry to form a highly concentrated slurry. This is a method for injecting coal slurry into a blast furnace, which comprises a step of injecting the high concentration slurry into the furnace at a pressure higher than the furnace internal pressure.

Further, the gist of the apparatus according to the present invention for carrying out this method is as follows.

That is, a device for wet pulverizing coal, a tank for storing the pulverized coal as coal slurry, a service tank for steam heating the coal slurry transported from the tank, and the steam heated coal slurry. and a high-concentration slurry injection device that blows the high-concentration slurry into the furnace at a pressure higher than the furnace internal pressure from a blowing boat installed in the tuyere of the blast furnace. A coal slurry blast furnace injection device comprising: a coal slurry conveying pipe system forming a circulation loop with respect to the service tank; a steam heater and a flow rate and pressure control device provided on the discharge side of a circulation pump of the circulation loop; The high-concentration slurry blowing device has a plurality of sets of high-concentration slurry blowing branch pipes branched from the circulation loop, the separator, an air accumulator, and a pulsation valve, and the circulation loop acts as a ＼tuber. This is a coal slurry blast furnace injection device characterized by being configured as follows.

Details and embodiments of the invention will now be described with reference to the accompanying drawings.

First, the coal used in the present invention must have a q molar ratio of 1.5 or more based on ashless dry coal.

This is because the present inventors tested coal types with a wide range of carbonization degrees ranging from subbituminous coal to anthracite. We found that there is a relationship as shown in the figure.

As is clear from FIG. 1, when the % molar ratio becomes less than 1.5, the coke substitution ratio decreases rapidly.

At the same time, the desulfurization effect represented by the distribution of S between the hot metal and slag in the lower part of the blast furnace deteriorated, and a phenomenon appeared in which the slag formation reaction of S was delayed.

The reason for this is considered to be closely related to the C4 molar ratio of coal and the luminous flame effect (radiation effect) of combustion gas.

Next, the pulverized particle size of the coal needs to be -200 mesh 50-80% by weight.

In other words, coal slurry can be treated as a fluid,
In order to be able to inject into the blast furnace through the piping system, the maximum concentration with good fluidity is desirable, but the inventors have found that there is a
We found that there is a relationship as shown in the figure.

In other words, there is a limit to the fluidity with which coal slurry can be injected into the blast furnace through the piping system.
This limit is governed by the coal-water mixing ratio and coal particle size.

In order to maintain the coal particle size under the operating conditions of a typical modern blast furnace in the siding combustion zone, it is necessary to maintain the combustion condition at -200 mesh 50 mm or higher, and in this case, the viscosity of the coal slurry increases as shown in FIG.

In Figure 2, the coal particle size distribution is in the state of a0〉a2〉a3, and if the coal particle size distribution of the coal slurry becomes a dog, the slurry viscosity decreases. It was found that these contradictory conditions were satisfied within the narrow range of conditions applied.

On the other hand, when the coal concentration exceeds 60% by weight, the fluid resistance of the piping system increases rapidly, leading to substantial flow stagnation due to the relationship with the boost pressure of the pump.

Therefore, as the concentration of coal slurry increases and the coal particle size becomes finer, measures to improve fluidity are required.

As a countermeasure against this problem, one of the present inventors previously disclosed the following countermeasure.

(a) Heating the coal slurry with steam.

(Note) Add fluidity improver.

It is necessary to select the fluidity improver appropriately in relation to the particle size distribution of the coal, and according to the research of the present inventors, -2
For items with a weight coefficient of 0.00 mesh or more than 60, it is preferable to use a flocculant rather than a dispersant.Mineral oil, diesel oil, etc. with a weight coefficient of 0.2 or less are mixed with water in an emulsifying machine in advance, and then added. do.

On the other hand, for a slurry having a relatively coarse coal particle size distribution of -200 mesh less than 60 weight ratio, it is preferable to add a dispersant of about 0.2 weight ratio.

By adding these flowability improvers, the coal forms a cohesive particle size, which, together with heating by steam, lowers the viscosity of the slurry, and significantly improves the dewatering effect of the separator installed in front of the blast furnace tuyere. A highly concentrated coal slurry of 60-80% by weight could be blown into the blast furnace.

The reason why the coal slurry maintained good combustibility even though the particle size became large due to the addition of a fluidity improver and steam heating was because the additives were heated first during combustion. This is believed to be because the coal particles decompose and are substantially freely separated and can be burned in their original pulverized state.

Next, the apparatus for blowing coal slurry into a blast furnace according to the present invention will be described.

FIG. 3 is a schematic diagram showing the arrangement and piping system of the apparatus of the present invention.

The coal is pulverized to -200 mesh 50-80% by a wet pulverizer (not shown) to form a coal/water slurry with a concentration of 60-70% by weight and stored in a storage tank 4 via pipeline 2.

The coal slurry stored in the storage tank 4 is transferred to the service tank 6 as needed.

In the service tank 6, heating with steam and addition of a fluidity improver are performed to stabilize the coal slurry and improve fluidity.

The coal slurry with a concentration of 60 to 70% by weight with improved fluidity is dehydrated by a separator 14 for each tuyere provided near the tuyere 12 of the blast furnace 10, and is made into a highly concentrated slurry with a coal concentration of 70% by weight or more. A carrier gas is blown into the blast furnace 10 at a pressure higher than the internal pressure of the blast furnace 10 by a carrier gas introduced from a carrier gas blowing pipe 16 communicating with the a/der flow side of the separator 14.

The amount of coal slurry that can be injected into a blast furnace is determined by the amount of water removed by dehumidifying blast furnace air that is carried out at the same time when a large amount is injected.

In other words, it is possible to inject a coal slurry with an amount of water equal to the amount of water removed by dehumidification, and in addition, heat generation effect that can compensate for the endothermic effect due to the water content in the coal slurry is achieved by heating blast furnace air or oxygen enrichment. In order to balance the heat balance of the blast furnace wall area.

Specifically, when blowing 10 kg of coal slurry per ton of pig iron, the following operations should be performed: Increase the air temperature by 40 to 45 degrees Celsius, Increase the amount of air dehumidification by 6 to 79/Nm, or increase the oxygen enrichment by 0.7%. It becomes a thermally balanced value.

Blast furnace gas, air, nitrogen, etc. are used as the conveying gas for blowing the coal slurry into the blast furnace, and the amount of coal slurry blown into each tuyere is set equal in advance, and the operating conditions of the separator 14 are kept as constant as possible. It should be set to .

The apparatus for blowing coal slurry into a blast furnace is as disclosed by one of the inventors in Japanese Patent Application No. 83174/1983.

In the present invention, a circulation loop 18 of a coal slurry conveying pipe is formed for the service tank 6, and the circulation loop 18
plays the role of ＼＼dah for each blowing branch pipe 20, and suppresses pressure changes in each blowing branch pipe 20 to a minimum.

In addition, an electromagnetic flow meter 24 is installed on the discharge side of the circulation pump 22 of the circulation loop 18, and the heat balance of the siding part is balanced based on the detected flow rate value, the amount of blown water obtained from the concentration of the coal slurry, and the C4 molar ratio of the coal. The air temperature, air dehumidification amount, and air oxygen enrichment amount are controlled.

In addition, a steam heater 2 is installed on the discharge side of the pipe in the circulation loop 18.
6, steam was blown into the coal slurry in the service tank 6, and the used steam, whose temperature had decreased, was heated and recycled for reuse.

Furthermore, in the present invention, in order to facilitate the injection of the high concentration coal slurry of 70% by weight or more separated by the separator 14 into the blast furnace tuyere, the pressure of the conveying loop is at least 1 atm or more higher than the pressure of the circulation loop system 18. In order to produce gas, a carrier gas accumulator 28 and a pulsation valve 30 are provided on the a/der flow side of the separator 14, and the high-pressure carrier gas is used to intermittently blow coal slurry into the furnace through the tuyere 12 of the blast furnace 10. .

The coal used in the examples was Australian uranium coal having the properties and analytical values shown in Table 1.

The above coal was finely pulverized to -200 mesh 50-80% using a wet mill to obtain a coal slurry having a concentration of 60-70% by weight.

This coal slurry is stored in a storage tank 4, discharged and transported as needed, heated by blowing steam into a service tank 6, and then further added with 0.1% mineral oil as a flocculant.
Via the circulation loop 18, it is dehydrated in the separator 14 to form a high-concentration coal slurry with a concentration of 73, and then transferred to the blast furnace 100 and the tuyere 12 by the high-pressure carrier gas intermittently ejected from the air accumulator 28 through the pulsating valve 30. Infused.

At this time, the amount of dehumidification of the blast furnace air was 15 g/Nm'', and the replacement ratio of coke to the amount of blown coal was 0.85.

According to the coal slurry injection method using the blast furnace injection apparatus according to the present invention, the following effects can be expected.

(a) A portion of expensive blast furnace coke can be replaced with inexpensive steam coal, resulting in a reduction in pig iron costs.

(Note) Compared to pulverized coal, which is blown in using a carrier gas, coal slurry is easier to pressurize and is safer.

(c) A general-purpose mill can be used for pulverizing coal without the need for special pulverizing equipment.

(d) Coal slurry is easy to store and transport.

(e) It can be used to produce clean fuel gas as a method of turning steam coal into scum using a blast furnace.

(f) The equipment is relatively inexpensive.

[Brief explanation of the drawing]

Figure 1 shows the C.I. /I
{A diagram showing the relationship between the molar ratio and the corrected coke replacement ratio, Figure 2 is a diagram showing the relationship between the slurry concentration of coal slurry and slurry viscosity, and Figure 3 is a diagram showing the blast furnace injection apparatus for coal slurry according to the present invention. FIG. 2 is a schematic diagram showing a piping system. 2... Pipeline, 4... Storage tank, 6... Service tank, 8... Steam heater, 10... Blast furnace, 12 ...tuyere,
14...Separator, 16...Carrier gas blowing pipe, 18...Circulation loop, 20...
...Blowing branch pipe, 22...Circulation pump, 28.
...Carrier gas accumulator, 30...
Pulsating valve.

Claims (1)

[Claims] 1 C/}1 molar ratio of coal based on ashless dry coal 1.
5 or more coal to -200 mesh 50 to 80 weight ratio wet pulverization, and the finely pulverized coal to a concentration of 60 to 80.
70% by weight coal slurry, a step of adding a fluidity improver to this coal slurry, a step of heating the coal slurry with steam, and a step of dehydrating the steam-heated coal slurry to obtain a highly concentrated slurry. A method for injecting coal slurry into a blast furnace, comprising: a step of injecting the highly concentrated slurry into the furnace at a pressure higher than the furnace internal pressure. 2. The fluidity improver added to the coal slurry is a coagulant when the coal particle size is -200 mesh 60 weight ratio or more, and is a dispersant when it is less than -200 mesh 60 weight ratio. A method for blowing coal slurry into a blast furnace according to claim 1. 3. A tank for wet-pulverizing coal, a tank for storing the finely-pulverized coal as coal slurry, a service tank for steam-heating the coal slurry transported from the evening/ku, and the steam-heated coal slurry. and a high-concentration slurry injection device that blows the high-concentration slurry into the furnace at a pressure higher than the furnace internal pressure from a blowing boat installed in the tuyere of the blast furnace. A coal slurry blast furnace injection device consisting of a coal slurry conveying pipe system forming a circulation loop with respect to the service tank, a steam heater provided on the discharge side of a circulation pipe of the circulation loop, and a flow rate and pressure. The high-concentration slurry blowing device includes a plurality of sets of high-concentration slurry blowing branch pipes branched from the circulation loop, the separator, an air accumulator, and a pulsation valve, and the circulation loop acts as a pipe. A blast furnace injection device for coal slurry, characterized in that it is configured to: