JPH06299213A - Method and device for charging coal into blast furnace - Google Patents

Abstract

PURPOSE:To produce molten iron in a low cost by using a method and a device for charging low cost coal into a blast furnace from the lower part of a shaft in the blast furnace. CONSTITUTION:The coal having <=30mm grain size is prepared and this coal is charged into the blast furnace through the furnace wall at the lower part of the shaft in the blast furnace. The coal is desirable to charge in the range of 900-1200 deg.C temp. of the furnace gas at the lower part 28 of the shaft in the blast furnace. The device for charging the is provided with a receiving hopper 2 for receiving the coal, a discharging hopper 4 connected with this hopper 2 and provided with a weighing instrument 12 and having a feeder 5 at the lower part and a coal supplying pipe 7 connected with the feeder 5 of the discharging hopper 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for charging coal into a blast furnace from the bottom of a blast furnace shaft.

[0002]

2. Description of the Related Art In a conventional blast furnace, iron ore raw material such as sintered ore and coke are charged from the top of the furnace, and iron ore raw material such as sintered ore is reduced by coke to produce hot metal. However, the cost of coke is extremely high due to the fact that strong coking coal is required in the production of coke, and a coke oven is required in order to produce coke. Therefore, instead of coke, heavy oil is injected from the tuyere of the blast furnace, or recently, inexpensive pulverized coal is blown to replace a part of the coke with these carbon raw materials.

In Japanese Unexamined Patent Publication No. 56-119709, fine blast furnace charging raw material is inserted into a furnace through a plurality of injection nozzles arranged along the periphery of the furnace wall at the upper part of the massive zone below the stock level. However, it is disclosed that the gas flow velocity distribution in the furnace is controlled. In this method, coke and sinter are mainly used as blast furnace raw materials, and the main purpose is to control the gas flow velocity distribution in the blast furnace.

[0004]

As described above, due to the soaring price of heavy oil, instead of blowing heavy oil, pulverized coal (P
The blowing of C) is mainly performed. Since steam coal, which is cheaper than coke, is used as a fuel, it contributes significantly to the reduction of hot metal production cost. On the other hand, as shown in FIG. Since the replacement rate with coke (the amount of reduction in the amount of coke when blowing 1 kg of PC) decreases, the amount of blowing from the tuyere of PC is currently limited to 200 kg / ton.

The reason for this is that the time for which PC blown from the tuyere can exist in the tuyere tip raceway is as short as several μsec. Therefore, when PC is added in a large amount, oxygen is sufficiently supplied to the PC particles. This is because the combustion efficiency decreases because it is not lost. In addition, when coal is easily charged from the top of the blast furnace, tar in the coal is generated, adheres to the gas dedusting equipment, and the equipment fails. Further, when caking coal is charged from the top of the blast furnace, the problem arises that the caking coal is liquefied in the blast furnace and thus impairs air permeability of the shaft.

[0006]

According to the present invention, by charging coal from the lower part of the blast furnace shaft into the furnace, the conventional limit of 200 kg / ton of coal can be greatly increased. The present invention relates to, and has developed a device therefor. This device is equipped with a coal receiving hopper installed in parallel around the shaft part of the blast furnace, a discharging hopper, and a supply pipe connecting the lower part of the hopper to the lower part of the blast furnace shaft.

(1) The invention of claim 1 is a method for charging coal into a blast furnace, which comprises the following steps. (A) a step of preparing coal having a particle size of 30 mm or less,
(B) A step of inserting the coal into the blast furnace through the furnace wall below the shaft of the blast furnace. (2) The invention of claim 2 is characterized in that the coal is non-caking coal, and the temperature of the blast furnace gas inside the furnace wall under the blast furnace shaft is in the range of 900 to 1200 ° C. Is the method of charging coal.

(3) The invention of claim 3 is a coal charging apparatus for a blast furnace, comprising the following members. (A) a receiving hopper for containing the transported coal,
(B) a dispensing hopper which is connected to the lower part of the receiving hopper through a seal valve 1 and which is provided with weighing means and which is connected to a feeder at the lower part; and (c) is connected to the feeder through a seal valve 2. Coal supply that is equipped with pressure equalizing means and that has a supply port in the furnace wall below the blast furnace shaft in each part.

[0009]

[Operation] Although it was conventionally conceived to directly load coal into the blast furnace, as described above, tar is generated from the coal and the dust removing device malfunctions due to the deposition of gas on the dust remover. Further, when caking coal was charged, there was a problem of impairing air permeability of the shaft portion due to liquefaction of coal.

Place of Coal Charging In view of the above, the present invention is based on the idea that the above problems can be solved by mainly charging non-caking coal to the lower part of the blast furnace shaft. First, FIG. 2 shows a gas temperature distribution in the blast furnace. As is well known in the blast furnace from Fig. 2, there is a so-called melting zone region, and this distribution is high in the central part shown in Fig. 2, and decreases downward toward the furnace wall, and reaches the lower part of the blast furnace shaft. Has spread to. If coal is supplied from the furnace wall in the furnace wall gas temperature range of 900 to 1200 ° C in the lower part of the blast furnace shaft, the tar content is decomposed by the gas temperature and therefore does not adhere to the gas dust remover or the like.

Kind of Coal Further, although non-caking coal is mainly used in the present invention, even if it is a strong coking coal, even if a part of coal is liquefied due to high gas temperature, most of it is Turns into coke. Further, when the coal is charged, for example, if the coking coal is charged together with the gas from the blast furnace gas or the gas from the lime firing furnace, a part of the coal liquefied by the CO ₂ gas in the gas is gasified. Is possible.

Grain size of coal The grain size of the coal to be charged next is 30 mm or less in diameter in order to smoothly charge it into the blast furnace from the supply pipe.
Further, it is desirable that the grain size of the coal to be charged finally burns completely in the raceway in front of the tuyere when the coal has fallen to the tuyere level. Therefore, it is desirable that the charged coal has a particle size such that it is completely gasified in the raceway in front of the tuyere. This upper limit is 30 mm, but 25 mm is desirable for convenience in handling. On the other hand, from the viewpoint of not impairing air permeability, the diameter is preferably 4 mm or more and 25 mm or less.

Pressure of Charge Gas Since a normal blast furnace has a pressure of about 4 kgf / cm ² , it is necessary to charge coal at a gas pressure higher than the pressure in the furnace. Therefore, the pressure in the supply pipe 7 must be at least higher than the blast furnace pressure.

Component Composition of Gas Next, regarding the composition of the gas at that time, nitrogen gas which does not react with coal, blast furnace gas, and exhaust gas generated from a lime baking furnace can be used as described above. Both the blast furnace gas and the gas from the lime calcination furnace contain nitrogen at 50 to 7
These gases are effective for containing 0% and reacting with a part of the coal because they contain about 20% of CO ₂ etc. and gasify the coal to change it into CO gas.

Charging Device Next, the charging device, which will be described in detail in the embodiment, is a coal receiving hopper, a discharging hopper for discharging coal, and a coal supply connected to the discharging hopper. Composed of tubes. One or more sets, preferably 4 to 8 sets of such devices are arranged around the shaft of the blast furnace.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A coal charging method and apparatus will be described with reference to FIG. 1, the lower part 2 of the shaft of the blast furnace
8 shows an example of an apparatus having a supply port 8. 1 is a belt conveyor that receives coal and conveys it to a hopper, and 2 is a hopper that receives coal conveyed from the belt conveyor. When coal is loaded into the receiving hopper 2, the exhaust pipe 9
Thus, the pressure of the dispensing hopper 4 is set to the atmospheric pressure, the seal valve 3 is opened, and the coal is moved from the receiving hopper 2 to the dispensing hopper 4.

Next, the amount of coal in the dispensing hopper 4 is weighed by the weighing means 12, the exhaust pressure pipe 9 is closed, and the pressure equalizing pipe 10 is closed.
Open and the pressure in the discharge hopper 4 is set to be almost equal to or slightly higher than the internal pressure of the blast furnace, then the seal valve 6 is opened and coal is supplied from the feeder 5 arranged below the discharge hopper 4. Supply to the pipe 7. As the feeder 5, for example, an L valve or the like can be used.

After the discharged coal has been charged into the supply pipe 7, the seal valve 6 is closed and the gas pipe 11 for injection is opened to make the pressure equal to or higher than the internal pressure of the blast furnace.
Charge coal into the bottom of the blast furnace shaft while applying pressure.
In the blast furnace, there is a unloading of 50 to 100 mm per minute, so that the coal is loaded into the blast furnace as the unloading occurs, and the pressure in the supply pipe 7 causes the gas in the blast furnace to enter the supply pipe 7. And prevent the coal from being charged into the blast furnace.

After all of the coal in the supply pipe 7 is supplied, the above-mentioned operation is repeated again to supply the coal into the supply pipe, and preferably to continuously and continuously load the coal into the blast furnace. In the lower portion of the supply pipe 7, for example, the ultrasonic sensor 1
It is desirable to arrange No. 3 and the like, determine whether all the coal charged in the supply pipe has been charged in the blast furnace, and perform the next coal charging cycle.

As a concrete example, an example of carrying out in a so-called 10,000 ton blast furnace capable of producing about 10,000 ton of hot metal per day will be described. Size of dispensing hopper; inner diameter 3 m, height 5 m, effective internal volume 20 m ³ . Number of dispensing hoppers: 4 (Approximately 90 in the shaft cross section)
Arranged in the ° direction). Coal supply rate: 12.5 ton / hr per hopper
(The total is about 1000 tons per day.) Type of coal; Optimum coal from South Africa, grain size 8
~ 25 mm. Industrial analysis composition; volatile content 22%, fixed carbon content 68%, ash content 8.2%. Operation period: The operation for 1 week to 1 month was performed multiple times.

As a result of the above operation, the hot metal components were the same as in the conventional case, 4.8 wt% for C, 0.23 wt% for Si, and the hot metal temperature was 1511 ° C., which did not change at all. In the above operation, 200 kg / ton of PC was blown from the tuyere as before, and 100 kg / to was further added by the coal charging method of the present invention.
n, that is, 300 kg / ton in total could be charged. Therefore, the manufacturing cost of the hot metal can be significantly reduced. The fuel ratio was 520 kg / ton, which was almost the same as the fuel ratio before the present invention was implemented.

[0022]

According to the present invention, the direct use amount of coal in the blast furnace is conventionally limited to about 200 kg / ton,
Coal usage increased by about 50% as described above. In addition, unlike charging from the blast furnace throat, all the tar content that was generated has been decomposed, and there is no obstacle to the gas cleaning system. Furthermore, when the coal used was non-caking coal or weak coking coal, it was possible to achieve a stable blast furnace state without any ventilation problems in the blast furnace. Further, when strong coking coal was used, the air permeability was slightly impaired, but the operating results were not significantly changed.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an apparatus for charging coal into a lower portion of a blast furnace shaft according to the present invention.

FIG. 2 is a diagram showing an example of gas temperature distribution in a radial direction in a blast furnace.

FIG. 3 is a diagram showing a relationship between a blowing amount of pulverized coal (PC) and a substitution rate of coke.

[Explanation of symbols]

 2 Receiving hopper 3 Seal valve 1 4 Dispensing hopper 5 Feeder (L valve etc.) 6 Seal valve 2 7 Supply pipe 8 Supply port 9 Exhaust pipe 10 Pressure equalizing pipe 11 Press-fitting gas pipe 12 Weigher 13 Ultrasonic sensor 28 Lower part of blast furnace shaft

Claims (3)

[Claims] 1. A method for charging coal into a blast furnace, which comprises the following steps. (A) a step of preparing coal having a particle size of 30 mm or less,
(B) A step of inserting the coal into the blast furnace through the furnace wall below the shaft of the blast furnace. 2. The coal is non-caking coal, and the temperature of the blast furnace gas inside the furnace wall under the blast furnace shaft is 90 degrees.
The method for charging coal into a blast furnace according to claim 1, wherein the temperature is in the range of 0 to 1200 ° C. 3. An apparatus for charging coal into a blast furnace, comprising: (A) a receiving hopper for containing the transported coal,
(B) a dispensing hopper which is connected to the lower part of the receiving hopper through a seal valve 1 and which is provided with weighing means and which is connected to a feeder at the lower part; and (c) is connected to the feeder through a seal valve 2. A coal supply pipe provided with pressure equalizing means and having a supply port in the furnace wall below the blast furnace shaft at the lower part.