JP4608908B2 - Plastic blast furnace injection method - Google Patents

Description

  The present invention relates to a plastic blast furnace blowing method in which used plastic or pulverized coal, which is plastic waste as general waste or industrial waste, is used as a raw material for blowing blast furnace.

  In order to reduce the amount of expensive coke used and reduce the production cost of pig iron, auxiliary reducing material is injected in a blast furnace. Regarding the injection of pulverized coal as an auxiliary reducing material, for example, there is a blast furnace that performs a large amount of pulverized coal injection operation exceeding 200 kg per pig iron ton (see Non-Patent Document 1, for example).

  On the other hand, in addition to pulverized coal, combustible solids such as plastic can be used as the blast furnace blowing material. In particular, it is advantageous from the viewpoint of energy saving and recycling to use used plastic mixed in municipal waste or industrial waste that has been incinerated or landfilled as a reducing material.

However, if the amount of raw material blown into the furnace increases, the deterioration of air permeability in the lower part of the furnace becomes remarkable, and it may be difficult to maintain stable blast furnace operation. Such deterioration of the furnace bottom air permeability is attributed to the “shell” formed at the end of the raceway described below. The principle of shell formation will be described with reference to FIG. FIG. 2 is a schematic view of the cross section near the tuyere at the bottom of the blast furnace, and is a diagram illustrating in detail the vicinity of the hot air and the reducing material blowing part 2 of the blast furnace 1. That is, when a reducing material such as plastic or pulverized coal is blown into the blast furnace 1 through a blow lance 10 installed through the blow pipe 9 connected to the tuyere 8, it is formed in front of the tuyere 8. The acid (mainly SiO ₂ and Al ₂ O ₃ contained in the ash content in plastics and pulverized coal produced at the end (in the back) of the raceway 11 burned at high speed in the raceway 11 This is because the component slag increases and the viscosity and melting point of the slag generated at the end of the raceway 11 increases. The hard-to-flow slag layer generated at the end of the raceway 11 is called a raceway shell 12 here. The presence of the raceway shell 12 blocks the blowing of air to the core, making it difficult for gas to flow, raising the blowing pressure and reducing productivity. Moreover, since the ventilation to a core part is interrupted | blocked, the gas flow which passes an upper part through a furnace wall part increases, heat loss increases, and, thereby, a reducing material ratio rises.

As the origin of the ash of the blown reducing material, it is used on the inner surface of several tens to tens of percent of ash contained in coal and inorganic substances other than organic substances contained in waste plastic, for example, food bags. Examples thereof include aluminum foil and fillers in plastics (SiO ₂ , TiO ₂ , CaO, etc.). These ashes vary greatly in melting point and viscosity depending on the ratio of CaO component to SiO ₂ component (CaO / SiO ₂ ) and the ratio of CaO component to Al ₂ O ₃ component (CaO / Al ₂ O ₃ ). Generally, it has a high melting point and a high viscosity, and accumulates at the end of the raceway 11 as described above to form the raceway shell 12.

As a method for improving the deterioration of the air permeability in the lower part of the furnace as described above, there is known a method in which a CaO-based, MgO-based or SiO ₂ -based flux is blown from the tuyere as a slagging agent (see, for example, Patent Document 1). ). In addition, as a high basicity slagging agent, a basic medium solvent such as pulverized dolomite, serpentine, olivine, limestone, etc. is blown simultaneously with the pulverized coal, and the amount of blowing is mixed with the basic medium solvent and ash in the pulverized coal. The basicity (basic component amount / acidic component amount) is within the range of 0.5 to 1.3 so that the ash content of pulverized coal and dolomite are assimilated in the raceway. A method of forming a viscous slag to thin a high melting point shell is known (for example, see Patent Document 2).
JP-A-3-291313 Japanese Patent Publication No. 6-89382 Mori Shigetosu et al. “Materials and Processes” edited by Japan Iron and Steel Institute 1995, 8, vol. 1, p. 319

  However, in Patent Document 1 and Patent Document 2, since the behavior of the powder-forming agent having a powder form inside the raceway has not been sufficiently elucidated, a method of thinning the shell using a powder-shaped agent Is not realistic. For example, Patent Document 1 and Patent Document 2 describe that it is desirable that the particle size of the blown powder forming agent to be blown is 200 mesh or less. However, with such a particle size, since the inertial force of the powder blown from the tuyere is small, most of the powder does not reach the shell at the end of the raceway and follows the gas flow to the outside of the raceway. It is scattered and difficult to assimilate with the shell effectively. In addition, if a large amount of pulverized powdery agent is blown in order to obtain a shell removal effect, the flammability of the pulverized coal is significantly hindered, and further, the amount of slag increases throughout the lower part of the furnace. We are anxious about liquid permeability being inhibited.

  Therefore, the object of the present invention is to solve such problems of the prior art, and in the operation of blowing a reducing material such as plastic or pulverized coal into the blast furnace, a plastic blast furnace blowing method without deteriorating the breathability of the furnace. Is to provide.

The features of the present invention for solving such problems are as follows.
(1) In operation of a blast furnace using plastic as a furnace blowing raw material, a used plastic in which the composition ratio (CaO / Al ₂ O ₃ ) of the ash generated by combustion in the furnace is 0.5 or more , blast blowing method of the plastic, characterized in that blowing plastic is granules were granulated by mixing the substance for lowering the melting point of the ash produced by the combustion of the spent plastic, a.
(2) In the operation of a blast furnace using plastic and pulverized coal as furnace blowing raw materials, the composition ratio of ash (CaO / Al ₂ O ₃ ) generated by combustion of the plastic and the pulverized coal in the furnace is 0. as will be 5 or more, plastic, characterized in that blowing the used plastic, a material lowering the melting point of the ash produced by the combustion of the spent plastic, the plastic is a granular product was granulated by mixing Blast furnace injection method.
(3) The plastic blast furnace blowing method according to (1) or (2), wherein the plastic is a crushed material of used plastic.
(4) The plastic blast furnace blowing method according to any one of (1) to (3), wherein at least a part of the substance that lowers the melting point of ash is a CaO source.
(5) The plastic blast furnace injecting method according to any one of (1) to (4), wherein the total amount of plastic and / or pulverized coal injected into the blast furnace is 100 kg / t or more.

  According to the present invention, since a poorly ventilated layer in a blast furnace called a raceway shell can be melted and removed, a large amount of reducing material such as pulverized coal or used plastic is blown into the furnace without deteriorating the breathability of the furnace. It can be used as a raw material. Therefore, a large amount of used plastic can be blown into the furnace as a substitute for coke, and the replacement rate of used plastic for coke is increased, thereby reducing the cost of iron making. In addition, the improvement of the air permeability reduces the strengthening of the flow around the furnace, so that heat loss is also reduced.

The inventors of the present invention have studied the behavior of the powder-forming agent having a powder form inside the raceway, and the powdery powder-forming agent is blown because the inertial force of the powder blown from the tuyere is small. Many of the bodies did not reach the shell at the end of the raceway, but followed the gas flow and scattered outside the raceway, making it difficult to assimilate with the shell. Therefore, it is thought that the slagging agent to be blown needs to have a particle size with an inertial force that reaches the shell at the end of the raceway after being blown from the tuyere. In order to give inertial force, reach the shell at the end of the raceway, and effectively assimilate it with the slag derived from the blown raw material, granulate that has been granulated by adding a fossilizing agent into the plastic from the tuyere The present invention has been completed by finding that the method of blowing or injecting granular plastic particles having a high basicity of ash from the tuyere in advance is effective. That is, in the operation of a blast furnace that uses plastic as a furnace blowing material, the blowing of plastic particles such that the composition ratio of ash generated by combustion in the furnace (CaO / Al ₂ O ₃ ) is 0.5 or more. This is a method for injecting plastic into a blast furnace. As a result, the slagging agent is integrated with the plastic, which is a granular material, and blown into the furnace, so it will not be scattered outside the raceway following the injected gas flow, effectively It can be assimilated with the shell.

It is desirable that the melting point of the ash produced by the combustion of the plastic in the furnace is less than 1700 ° C. Preferably it is 1650 degrees C or less. For this purpose, it is desirable to adjust the amount of plastic blown into the blast furnace and the components so that the average composition ratio (CaO / Al ₂ O ₃ ) of ash is 0.5 or more.

The reason why the average composition ratio (CaO / Al ₂ O ₃ ) of the ash content of the blown raw material is 0.5 or more is that the melting point due to the lower basicity of the slag of the raceway shell is reduced when the lower limit is 0.5 or less. This is because the reduction effect may not be fully exhibited, and the air permeability improvement effect due to the removal of the raceway shell cannot be expected. This phenomenon will be described with reference to the ternary phase diagram of SiO ₂ —Al ₂ O ₃ —CaO in FIG. A straight line A in FIG. 3 indicates a position where (CaO / Al ₂ O ₃ ) = 0.5, and a region where (CaO / Al ₂ O ₃ ) is 0.5 or more corresponds to the left portion of the straight line A. In this region, the melting point is approximately 1600 ° C. or lower, which is significantly lower than the initial melting point of 1700-1800 ° C. of the ash content of pulverized coal (B) or the ash content of plastic (usually used plastic) (C). I understand that.

  The particle size of the granular material is preferably 1 mm or more in terms of a spherical equivalent particle size (diameter of a sphere having the same volume). If the particle size is less than 1 mm, it may follow the gas flow and scatter outside the raceway, making it difficult to assimilate with the shell. Particularly preferably, the particle diameter is 4 mm or more. If the particle diameter is 4 mm or more, it has sufficient inertial force to reach the shell at the end of the raceway. However, since this value changes depending on the density or shape factor of the granulated product (degree of deviation from the sphere), it is desirable to determine the lower limit of the particle size each time according to the situation. As for the upper limit particle size, if the particle size becomes too large, it will cause clogging and blockage in the blowing line, so it is desirable that the particle size be about 20 mm or less. The upper limit of the particle size may be determined experimentally as appropriate in consideration of the transport capability of the blowing line.

Further, in the operation of a blast furnace using plastic and pulverized coal as a furnace blowing raw material, the composition ratio of ash content (CaO / Al ₂ O ₃ ) generated by combustion of the plastic and pulverized coal in the furnace is 0.5 or more. It is desirable to blow in plastic so that The shell is made of ash (combustion residue) derived from inorganic substances contained in plastics and mainly burned in a high-temperature furnace, but the shell is not contained in other furnace materials, especially in the furnace. Ingredients derived from the blown pulverized coal are also included, and in the operation of a blast furnace using plastic and pulverized coal as furnace blowing raw materials, the composition ratio of ash (CaO generated by combustion in the furnace at the same time) / Al ₂ O ₃ ) is desirable.

  The plastic is not particularly limited as long as it does not affect the operation of the blast furnace, as long as it does not affect the operation of the blast furnace, as long as it is a plastic mainly composed of C, H, O such as polypropylene, polyethylene, polystyrene, polyethylene terephthalate, vinyl chloride, polyvinyl alcohol, celluloid, etc. Although it may be a product plastic or a waste plastic, it is preferable to use a used plastic (waste plastic) from the viewpoint of cost and effective utilization of industrial waste.

  In addition, used plastics here are plastics which are wastes as so-called trash including scraps and defective products generated at the time of manufacture and processing in factories, etc., and foreign substances (metal, paper, It includes plastics with other inorganic and organic substances) attached or mixed. Specific examples of such waste plastic include plastic bottles, plastic bags, plastic wraps, plastic films, plastic trays, plastic cups, magnetic cards, magnetic tapes, IC cards, flexible containers, printed boards, printed sheets, and wire covering materials. , Bodies and frames for office equipment or home appliances, decorative plywood, pipes, hoses, synthetic fibers and clothing, plastic molded pellets, urethane materials, packing sheets, packing bands, packing cushions, electrical components, toys, stationery , Toner, automotive parts (for example, interior parts, bumpers), shredder dust for automobiles or home appliances, ion exchange resin, synthetic paper, synthetic resin adhesive, synthetic resin paint, solidified fuel (reduced plastic volume reduction) ) Etc. La remains as waste or must be able to use those subjected to predetermined processing in accordance with. Further, a mixture of these waste plastics and product plastics may be used.

The plastic used as the furnace blowing material as described above is preferably a used plastic crushed material having a high composition ratio of ash (CaO / Al ₂ O ₃ ) generated when the plastic is burned. By crushing and using such a plastic with a high basicity of ash, it is possible to obtain a granular material of used plastic without passing through a process such as granulation.

  On the other hand, the basicity of ash produced when used plastic as general waste is burned in a furnace is often not so high, so used plastic and used plastic as plastic It is desirable to use a granular material that is granulated by mixing with a substance that lowers the melting point of the ash produced by the combustion of. It is possible to control the melting point of the ash generated in the furnace by adding a substance that lowers the melting point of the ash generated by burning the used plastic to the used plastic and granulating it as a whole. The above method is also applicable when using plastics other than used plastic, and using granulated material that is a mixture of plastic and a substance that lowers the melting point of ash generated by the combustion of plastic. Is desirable.

It is desirable that at least a part of the substance that lowers the melting point of ash is a CaO source. Since the main component of ash (Ash) contained in waste plastic and pulverized coal is mainly SiO ₂ and Al ₂ O ₃ , the furnace is manufactured by mixing the CaO source with waste plastic to produce a granular material. It is possible to lower the melting point of the ash generated in the inside. The CaO source is a substance that contains CaO or a CaO generation source that generates CaO in a furnace such as CaCO.

  As a substance that lowers the melting point of ash generated by plastic combustion, use a basic substance (medium solvent, sintered ore, etc.) mainly composed of CaO such as dolomite, serpentine, olivine, limestone, and quicklime. Is preferred. Any material can be used as long as it does not hinder the operation of the furnace as long as it lowers the viscosity by reducing the melting point of the ash produced by plastic combustion, but conventional plastic granulation equipment In view of the ease of uniform mixing when mixing with the plastic during granulation and the reactivity when blown into the furnace, it is preferably a powder, and a particle size of about 1 mm or less is the main. It is desirable to use what is. From the viewpoint of the storage stability of the produced plastic granules, it is particularly preferable to use limestone. More preferred is calcium carbonate.

When the amount of plastic and / or pulverized coal injected into the blast furnace is 100 kg / t or more when the total of the plastic and pulverized coal is 100 kg / t or more, the deterioration of the air permeability in the lower part of the furnace becomes remarkable. It is desirable to use when the total amount of plastic and / or pulverized coal blowing is 100 kg / t or more.
It is desirable.

  FIG. 1 is a schematic view showing an embodiment of the present invention. In the operation of blowing hot air and reducing material into the blast furnace 1 from the blowing portion 2 with hot air and reducing material, the pulverized coal is supplied from the pulverized coal supply line 3, and the granular plastic containing the slagging agent is supplied from the supply line 4. The mixing machine 5 is for making a plastic material contain a fouling material and molding it into a granular form. The plastic raw material is introduced into the mixing machine 5 by a supply line 6, and the flocking material is supplied by a supply line 7. To be introduced. In the mixer 5, the necessary amount of the fauxifying agent is mixed from the composition and amount of the ash of the plastic and pulverized coal, which are measured in advance, and processed into a granular form.

  In addition, when not injecting pulverized coal, the pulverized coal supply line 3 may be omitted. Further, in the case of using a plastic corresponding to a state containing a sufficient amount of a faux forming agent, the supply line 7 can be omitted, and a crushing process is performed in the mixer 5 for granulation. Furthermore, the mixer 5 can be omitted when the plastic originally contains the slagging material and is supplied in a granular form.

  When the plastic is granulated into the granular material in the mixer 5, a known method used for granulating a normally used plastic may be used. For example, granulation as in the following (a) to (c) The method can be used. The methods (a) to (c) are particularly suitable for granulation of a film-like used plastic. Whichever method is used, it is desirable that the used plastic is crushed in advance to a size suitable for granulation treatment, washed, and removable foreign matters are removed.

  (A) Compression molding granulation method: A used plastic is granulated by compressing and extruding from a hole of a ring die having a plurality of die holes penetrating the entire circumference. For example, a compression molding apparatus including a ring die having a plurality of die holes penetrating the entire periphery thereof, and a rolling roller that is rotatably disposed in contact with the inner peripheral surface of the ring die inside the ring die The used plastic put into the ring die is pressed into the die hole of the ring die while being compressed and crushed by the rolling roller with the inner peripheral surface of the ring die, and passes through the die hole. Then, the molded plastic product extruded to the outer surface of the ring die is cut or scraped off from the outer surface of the ring die to obtain a granular plastic molded product as a furnace blowing material. At least a part of the used plastic is semi-molten or melted by frictional heat mainly in the die hole, and then solidified to obtain a plastic molding (granular material).

  As a granulating apparatus used in the compression molding granulation method, for example, a ring die having a plurality of die holes penetrating the entire circumference and rotatably supported by the apparatus main body and rotated by a driving apparatus, and an apparatus main body It is known to have one or two or more rolling rollers that are rotatably supported and arranged in contact with the inner peripheral surface of the ring die inside the ring die. Then, the roller is pressed and granulated into the die hole of the ring die while being compressed and crushed by the rolling roller.

  As a method of mixing the substance that lowers the melting point of ash, a separate mixer may be installed to mix the used plastic and the substance that lowers the melting point of ash in advance. In addition, the particle size of the substance that lowers the melting point of ash may be any material as long as it passes through the gap between the ring body and the rolling roller, and there is no problem as long as it is pulverized in the ring die. In order not to come, the average particle size is preferably about 1 mm or less.

  The granular plastic molding obtained by the compression molding granulation method has a large friction between the substance that lowers the melting point of ash and the die hole, and the gap between used plastics is filled with a substance that lowers the melting point of ash. Because it has higher strength compared to conventional granulated plastics only, the combustibility is improved, and the rate of disintegration during handling and pneumatic transportation after granulation is extremely low. Clogging in transportation piping can be prevented appropriately. And when blown into the vertical furnace, the substance that lowers the melting point of the ash mixed with the granular plastic is assimilated with the shell at the end of the raceway, reducing its viscosity and improving the air permeability in the furnace. .

  (B) Semi-melt granulation method: crushing used plastic with a rotating crushing blade, etc., and simultaneously stirring the plastic, semi-melting or melting the plastic by frictional heat or external heating, and then cooling by spraying water This is a method of granulating into granular plastic. Since this granulation method is a batch process, the processing efficiency (productivity) is low, and since water is used for cooling, a post-drying process is necessary. The granularity of the granular plastic obtained by the processing conditions and plastic input varies. There are drawbacks such as Put the used plastic and the substance that lowers the melting point of ash into an apparatus equipped with a rotating crushing blade, or mix the used plastic and the substance that lowers the melting point of ash in advance and put them into the apparatus. A granular material can be produced as in the conventional case. The particle size of the substance that lowers the melting point of ash can be suitably used even if it is coarser than that used in (a).

  (C) Melt extrusion granulation method: After melt-kneading a used plastic using an extrusion molding machine etc., it is extruded and cooled linearly from a die hole or the like, and cut to an appropriate length in the length direction. Granulate. The used plastic and the substance that lowers the melting point of ash are put into the extrusion device, or the used plastic and the substance that lowers the melting point of ash are mixed and put into the extrusion device in advance, and then used plastic And a granular material in which a melting point lowering substance of used plastic ash is mixed. The particle size of the substance that lowers the melting point of ash can be suitably used even if it is coarser than that used in (a).

  For example, plastic granules granulated together with a substance that lowers the melting point of ash using the granulation methods (a) to (c) above are supplied to the tuyere of the blast furnace by air transportation and blown into the furnace. The granular material blown into the furnace burns in the furnace in the same manner as ordinary plastic granular material, and slag is generated from the inorganic material contained in the plastic and the substance that lowers the melting point of ash. However, since the slag has a relatively low melting point and low viscosity, it is difficult to form a shell in the furnace, and the air permeability of the furnace is not deteriorated. For this reason, even if a larger amount of plastic is blown into the furnace than before, the operation remains stable and the coke ratio can be lowered. Moreover, the air permeability of the furnace is improved by changing the component composition of the shell already generated in the furnace to lower the viscosity. By ensuring the air permeability in the center of the furnace, the tendency for the gas flow to flow through the furnace wall side and the peripheral flow becoming stronger is alleviated and the heat loss is reduced, so that the productivity is improved.

  Also, when operating a vertical furnace that performs pulverized coal blowing, the air permeability deteriorates due to the formation of the shell, but the shell is removed by blowing used plastic particulates using the method of the present invention. Improves furnace breathability. Therefore, when operating a furnace in which both pulverized coal and plastic are blown, the method of the present invention is very effective and can improve the air permeability of the furnace as compared with the conventional method, so that the coke ratio can be lowered. , Productivity is greatly improved. When pulverized coal injection is performed, the component composition of the shell formed in the furnace is slightly different from the case where pulverized coal injection is not performed, so by adjusting the plastic injection amount and composition according to the composition , Can remove the shell more effectively.

Using a blast furnace with a furnace volume of 3223 m ³ , using a combination of the components shown in Table 1 as the reducing material blown from the tuyere, operating the blast furnace under the conditions shown in Table 2 over the period 1 to period 11 The grade was evaluated.

  In Table 1, pulverized coals A and B are two typical types of coal. In normal blast furnace operation, these types of coal are used alone or in combination of two or more, and three or more. . In this example, pulverized coals A and B were used alone or in combination.

  As the plastic A, used plastic which is waste from general households and in which a plurality of types of plastics and foreign substances are mixed is used. What is shown in Table 1 is the average composition. Plastic B is a cylindrical granule having a diameter of about 6 mm and a length of about 10 to 20 mm using a ring die by a compression molding granulation method by adding limestone powder having a particle size of 1 mm or less as CaO content of about 3 mass% to plastic A. It is a granulated product.

In Comparative Example 1, the value of the composition ratio (CaO / Al ₂ O ₃ ) is as small as 0.17, but since the amount of reducing material blown is a small amount that is less than 95 kg / t and 100 kg / t, it can be operated smoothly. Met.

In Comparative Example 2, when the reducing material blowing amount was increased to 150 kg / t, the lower furnace ventilation resistance index increased and the furnace condition deteriorated. The reducing material ratio increased, and the amount of brewing was reduced. The furnace lower breathability index (Kl) was calculated by the following equation (A).
Kl = (P _blast ² −P ₄ ² ) × 10 ⁶ / V _bosh (A)
Here, P _blast and P ₄ are the _blowing pressure, shaft four-stage pressure (Kg / cm ² ), and V _bosh is the Bosch gas amount (Nm ³ / min).

  The comparative example 3 is a case where the pulverized coal type is changed from the pulverized coal A alone to the pulverized coals A and B by half with respect to the comparative example 2. In this case, no recovery of the furnace condition was observed.

Comparative Example 4 shows a case where the amount of pulverized coal A injected is reduced and the amount of plastic A used is increased. Also in this case, the composition ratio (CaO / Al ₂ O ₃ ) was as small as 0.28, and the furnace condition was not recovered.

Comparative Example 5 shows a case where 5 kg / t of a fine powder (200 mesh under 100%) of a fossilizing agent (CaO) was blown under the conditions of Comparative Example 2. The value of the composition ratio (CaO / Al ₂ O ₃ ) corresponds to 1.84, but the effect of dissolving the raceway shell was small when fine powder was blown, and no effect was seen.

  In Comparative Example 6, the pulverized coal blowing ratio was lowered to 50 kg / t, and the fine powder (200 mesh under 100%) of the fossilizing agent (CaO) was blown under the condition that the plastic A was blown in 100 kg / t. The same effect as in Comparative Example 5 was not seen.

Example 1 shows the case where plastic B was blown at 50 kg / t and pulverized coal A was blown at 100 kg / t. The composition ratio (CaO / Al ₂ O ₃ ) is 0.69, which is larger than 0.5, and when the blow-in of the plastic B granule is started from the tuyere of the blast furnace, the raceway shell is dissolved and removed. The air permeability was gradually improved, the furnace condition was improved, and the blast pressure was reduced. Therefore, the coke charging amount was reduced and the coke ratio was lowered.

Example 2 shows the case where plastic B was blown at 50 kg / t and pulverized coal B was blown at 100 kg / t. The value of the composition ratio (CaO / Al ₂ O ₃ ) was 0.60, which was larger than 0.5, and the furnace condition was improved as in Example 1.

Example 3 shows a case where plastic B was blown at 50 kg / t, pulverized coal A was blown at 50 kg / t, and pulverized coal B was blown at 50 kg / t. The value of the composition ratio (CaO / Al ₂ O ₃ ) was 0.64, which was larger than 0.5, and the furnace conditions were improved as in Examples 1 and 2.

Example 4 shows a case where plastic B is blown at 150 kg / t and pulverized coal is stopped. The composition ratio (CaO / Al ₂ O ₃ ) was 2.80, which was larger than 0.5, and stable blast furnace operation was possible.

Example 5 shows a case where plastic B was blown in 75 kg / t, plastic A was blown in 75 kg / t, and the blowing of pulverized coal was stopped. The value of the composition ratio (CaO / Al ₂ O ₃ ) was 1.60, which was larger than 0.5, and stable blast furnace operation was possible.

As described above, in Example 1 to Example 5, by using plastic B, the average composition ratio (CaO / Al ₂ O ₃ ) of the total ash content of the plastic and pulverized coal becomes 0.5 or more. The raceway shell was dissolved and removed to maintain the furnace air permeability well, the blast furnace operation was stabilized, the reducing material ratio was reduced, and the productivity was improved.

Schematic which shows one Embodiment of this invention. Schematic of a cross section near the tuyere at the bottom of the blast furnace. Ternary phase diagram of the SiO ₂ -Al ₂ O ₃ -CaO.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Hot air and reducing material injection | pouring part 3 Pulverized coal supply line 4 Supply line 5 Mixer 6 Plastic supply line 7 Ironmaking material supply line 8 Tail 9 Blow pipe 10 Injection lance 11 Raceway 12 Raceway shell A Composition Ratio (CaO / Al ₂ O ₃ ) = straight line showing position of 0.5 B Ash of pulverized coal C Ash of plastic

Claims (5)

In the operation of a blast furnace using plastic as a furnace blowing material, the used plastic in which the composition ratio (CaO / Al ₂ O ₃ ) of the ash generated by combustion in the furnace is 0.5 or more, and the use blast blowing method of the plastic, characterized in that the blowing requires a material lowering the melting point of the ash produced by the combustion of the plastic, the plastic is a mixture of granules granulated. In the operation of a blast furnace using plastic and pulverized coal as a furnace blowing raw material, the composition ratio of ash (CaO / Al ₂ O ₃ ) generated by combustion of the plastic and the pulverized coal in the furnace is 0.5 or more. become such, the used plastic, blast blowing plastic, characterized in that blowing plastic is a substance which decreases the melting point of the ash produced by the combustion of the spent plastic, a mixture of granules was granulated Method.   The plastic blast furnace blowing method according to claim 1 or 2, wherein the plastic is a crushed material of used plastic.   The plastic blast furnace blowing method according to any one of claims 1 to 3, wherein at least a part of the substance that lowers the melting point of ash is a CaO source.   The plastic blast furnace injecting method according to any one of claims 1 to 4, wherein the total amount of plastic and / or pulverized coal injecting into the blast furnace is 100 kg / t or more.

Images