JP2001208317A - Operation method for dust reduction treatment furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the operation method for a dust reduction treatment furnace that can perform control so that a coke bed upper end level does not change, maintains safety operation, and also can efficiently burn waste plastic for treatment by setting concrete conditions for blowing the waste plastic into the dust reduction treatment furnace. SOLUTION: When iron scrap, lumped dust mineral, and coke are loaded into a dust reduction treatment furnace 1 having multi ports 9a and 9b for dissolution/reduction treatment, blast that does not form any raceways is made from the primary port 9a to a coke bed 13, at the same time granular waste plastic is blown, control is carried out so that the upper level of a coke bed does not change, blast that does not form any raceways is made form the secondary port 9b to a filling layer at the upper portion of the coke bed, and granular waste plastic is blown for treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coke by blowing waste plastic from a primary tuyere when melting and reducing iron scrap and dust agglomerate in a dust reduction treatment furnace having a multi-stage tuyere. The present invention relates to an operation method of a dust reduction treatment furnace for controlling a top end level of a bed and blowing waste plastic from a secondary tuyere for treatment.

[0002]

2. Description of the Related Art Generally, wastes are separated into combustibles and incombustibles and collected. However, incombustibles actually include combustible plastic products. Therefore, waste plastics are collected at the final disposal site after being recovered as incombustibles. Though it is the aftermath of the booming era, disposable thinking is still established, but with the increase in the amount of waste in recent years, the method of treating waste plastic has become a problem.

[0003] Waste home appliances such as used washing machines, refrigerators and air conditioners are complex wastes containing metals, plastics, rubber and the like. Conventionally, such a composite waste, despite containing valuable metal materials such as iron, aluminum, and copper, has been disintegrated and crushed into small pieces as a whole and landfilled at a final disposal site.

[0004] However, due to the shortage of final disposal sites and the establishment of a new recycling law, recycling demonstration plants and the like have been constructed, and attempts have been made to separate and treat complex waste to recover valuable metal materials. . That is, the composite waste is classified according to the product type such as a washing machine and a refrigerator,
After extracting dangerous substances such as a cooling medium and a lubricating oil, the components are disassembled for each component and member, and the disassembled pieces are separated for each raw material such as metal or plastic, and a process according to the raw material is performed. For example, separated metal waste is charged into a melting furnace together with coke and the like to be melted, and waste plastic after separation is crushed and landfilled.

[0005] Such a separation method is an effective means in that valuable metal materials can be collected and the amount of crushed pieces to be landfilled can be reduced. But,
Waste plastic is still being landfilled.
Attempts have been made to charge and incinerate waste plastic into shaft furnaces such as blast furnaces and cupolas.

[0006]

In such a shaft furnace, waste plastics can be safely treated without generating harmful substances. However, the tuyere of a blast furnace or cupola is usually configured as a single stage, and waste plastic is blown into a melting furnace with two or more stages of tuyeres, such as a dust reduction furnace, for use in controlling furnace reactions. The specific conditions for doing so have not been elucidated at all.

In view of the above problems, it is an object of the present invention to set specific conditions for injecting waste plastic into a dust reduction treatment furnace having a multi-stage tuyere, and to set an upper end of a coke bed located in a lower part of the furnace. An object of the present invention is to provide a method for operating a dust reduction treatment furnace that can control the level so as not to change and efficiently incinerate waste plastic while maintaining stable operation of the dust reduction treatment furnace.

[0008]

In order to achieve the above object,
The method for operating the dust reduction treatment furnace of the present invention is characterized in that iron dust, dust agglomerate and coke are charged into a dust reduction treatment furnace having a multistage tuyere and melted and reduced.
Ventilation without forming a raceway is performed from the next tuyere to the coke bed, and granular waste plastic is blown to control the upper end level of the coke bed so that it does not change. From the secondary tuyere to the packed bed above the coke bed The air is blown without forming a raceway, and granular waste plastic is blown in for treatment.

In the above method for operating a dust reduction treatment furnace, it is preferable to blow granular waste plastic from the primary tuyere under an oxygen-enriched blast at normal temperature. It is preferable that the amount of oxygen enriched in the normal-temperature air blowing is 2% or more.

[0010] It is preferable that granular waste plastic is blown in from the secondary tuyere under hot air blowing at a temperature of 700 ° C or less.

Furthermore, it is preferable to adjust the amount of waste plastic blown from the primary tuyere so that the raw fuel descending speed is constant.

[0012] It is preferable that the position where the waste plastic is blown from the secondary tuyere is set in a region above the coke bed.

Further, the amount of waste plastic blown is set at 0.1.
It is preferably set to 2 kg / Nm ³ or less.

Further, it is preferable that iron scrap is mixed and charged with large-diameter coke in the center of the furnace and dust agglomerate is mixed and charged with small-diameter coke in the periphery of the furnace.

According to the present invention, in a dust reduction treatment furnace having a multi-stage tuyere, granular waste plastic is blown from a primary tuyere to a coke bed under an oxygen-enriched blast at normal temperature. On the other hand, granular waste plastics are blown from the secondary tuyere to the packed bed above the coke bed under hot air blowing for treatment. At this time, the reason why the raceway is not formed is that when the raceway space is formed, the combustion of the coke and the solution reaction proceed, and the efficiency of the dust reduction furnace decreases.

By blowing the waste plastic from the primary tuyere into the coke bed, it is possible to control so that the upper end level of the coke bed does not change. The reason is to maintain a constant amount of reaction (solution loss reaction) between CO ₂ and coke in the coke bed, and for that purpose, inject waste plastic that reacts with CO ₂ preferentially over coke, In addition, the amount of the solution loss reaction that causes the fluctuation of the descending speed of the raw fuel is adjusted by blowing the waste plastic. On the other hand, by blowing the waste plastic from the secondary tuyere into the packed bed above the coke bed, the waste plastic is efficiently incinerated. However, since there is a large amount of combustion product gas, the gas temperature decreases, and in a process of melting metal such as melting iron dust / reducing dust, the heat tends to be insufficient. In order to compensate for this heat shortage, oxygen-enriched air is blown from the primary tuyere at room temperature, and hot air at 700 ° C or lower is blown from the secondary tuyere.

The amount of oxygen enrichment of the normal temperature blast from the primary tuyere is 2
The reason why the content is set to not less than 2% is that if the content is not more than 2%, the amount of gas in the furnace increases due to the injection of waste plastic, and as a result, the gas temperature decreases, which hinders the dissolution of slag and metal.

On the other hand, the temperature of hot air blown from the
The reason why the temperature is set to 00 ° C. or lower is that if the air blowing temperature exceeds 700 ° C., the combustion reaction of coke and the solution loss reaction are promoted, and the coke ratio is not necessarily reduced.

Further, the amount of waste plastic blown from the primary tuyere is adjusted so that the descending speed of the raw fuel becomes constant. The reason why the injection amount of the waste plastic is adjusted based on the descending speed of the raw fuel is to maintain a constant amount of a reaction (solution loss reaction) between CO ₂ and coke in the coke bed. For this purpose, waste plastics reacting with CO ₂ are injected with priority over coke, and the amount of solution loss reaction that causes fluctuations in the descent speed of raw fuel is adjusted by blowing waste plastics.

Further, the position of blowing the waste plastic from the secondary tuyere in the region above the coke bed is as follows.
This is because the reaction rate is higher than that of coke, so that C in the waste plastic preferentially reacts with combustion and CO ₂ to suppress coke consumption.

The reason why the amount of waste plastic blown is set to 0.2 kg / Nm ³ or less is that if the upper limit of the amount of waste plastic blown exceeds 0.2 kg / Nm ³ , the amount of waste plastic exceeding the upper limit is not exceeded. Because it does not burn
This is because it cannot be used as a fuel substitute for coke and cannot be used effectively.

In addition, iron dust and large-diameter coke are separately charged at the center of the furnace and dust agglomerate and small-diameter coke are separately charged at the periphery of the furnace. At the same time, the dust agglomerate is reduced in the peripheral part of the furnace, and a gas flow is formed in the central part of the furnace to stably operate the dust reduction processing furnace.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the method for operating a dust reduction treatment furnace according to the present invention will be described below in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

FIG. 1A is a schematic view showing a dust reduction treatment furnace used in the method for operating the dust reduction treatment furnace of the present invention. As shown in the drawing, a charging device 2 is provided at the furnace top of the dust reduction processing furnace 1. The charging device 2 includes a bucket 3, a bell 4, a movable armor 5, and a charging guide 6.
And is configured as a device capable of charging the raw material and the fuel separately in the radial direction.

On the upper part of the furnace body 7 of the dust reduction furnace 1,
An exhaust gas pipe 8 for exhausting the countercurrent gas in the furnace is provided. As an exhaust gas system connected to the exhaust gas pipe 8, for example, a waste gas melting furnace is used. On the other hand, at the lower part of the furnace body 7, a tuyere 9 for blowing air to the lower part in the furnace is provided. The tuyeres 9 are provided in multiple stages in the height direction of the side wall of the furnace body 7, and in FIG. 1 (a), the lower tuyeres (primary tuyeres) 9a and the upper tuyeres (secondary tuyeres) 9b are provided. It is formed as a two-stage tuyere. These tuyeres 9a, 9b
A plurality of furnaces 7 are arranged at appropriate intervals in the circumferential direction.

With respect to the blowing conditions, the primary tuyere 9a is used as the main tuyere, the main tuyere 9a performs room temperature oxygen-enriched blowing, the secondary tuyere 9b performs hot air blowing, and observes the top level of the coke bed. Use for When the oxygen-enriched air is blown from the main tuyere 9a at room temperature, the oxygen-enriched amount is set to 2% or more and air is blown. On the other hand, when hot air is blown from the secondary tuyere 9b, it is blown at a temperature of 700 ° C. or less. The tuyeres 9a and 9b are set so as not to form a raceway even when a powdery iron source or waste plastic is blown, and are configured so that the tuyere diameter and the protruding position in the furnace can be changed.

In this embodiment, the multi-stage tuyere 9 provided in the height direction of the side wall of the furnace body 7 is a lower tuyere (primary tuyere).
Although it is formed as a two-stage tuyere of 9a and an upper tuyere (secondary tuyere) 9b, three or more tuyeres may be provided. For example, in the case of three stages, the tuyere located on the side of the coke bed is used as the main tuyere, and waste plastic is blown in while blowing air from the main tuyere to maintain the top level of the coke bed and the combustion efficiency. At the same time, the waste plastic is blown from the tuyere located above the coke bed for treatment.

Further, the raw material and the fuel can be separately charged into the furnace central portion 11 and the furnace peripheral portion 12, and as described above, the furnace top can be separately charged in the radial direction. (Fig. 1 (b),
(C)).

As shown in FIG. 2, the coke bed 13 in the lower part of the furnace is blown with waste plastic from the primary tuyere 9a so that the upper end level is located at substantially the same level as the secondary tuyere 9b. It is formed by adjusting the height. That is, while the primary tuyere 9a is used as a main tuyere, waste plastic is blown from the main tuyere 9a into the coke bed 13 under an oxygen-enriched blast at normal temperature, and the secondary tuyere 9b is used to blow the upper part of the coke bed. Waste plastic is blown into the packed bed under hot air blowing.

As described above, unlike the shaft furnaces such as blast furnaces and cupolas, the dust reduction treatment furnace 1 has multi-stage tuyere and is capable of dissolving iron scrap and reducing dust agglomerate. This is a melting furnace for processing.

Next, a method of operating the dust reduction treatment furnace of the present invention, which is performed using the above-described dust reduction treatment furnace 1, will be described. The raw material charged from the furnace top is mainly iron scrap and dust agglomerate, and the fuel is mainly coke, and granular waste plastic is blown from the primary tuyere (main tuyere) 9a and the secondary tuyere 9b. To process.

The charging method includes charging the coke to form a coke bed and then charging the raw fuel completely or in a layered manner, or charging the raw fuel by dividing the raw fuel in the radial direction. And how to adopt.

As shown in FIG. 3, in the sorting charging method, iron chips and large-diameter coke are mixed and charged into the center of the furnace.
By mixing dust agglomerate and small-diameter coke and charging them around the furnace, it aims at operation with high reaction efficiency. In order to charge iron chips at the center of the furnace and charge dust agglomerates around the furnace, dissolve the iron chips at the center of the furnace and reduce the dust agglomerates around the furnace. This is because the gas flow in the center of the furnace is promoted and the high ηCO condition is maintained.

The operation of the dust reduction treatment furnace is performed in accordance with the sorting charging method according to the size of the raw fuel and the blowing conditions of the main tuyere (blowing temperature, blowing temperature, etc.) in order to maintain the upper end level of the coke bed constant.
(Enrichment amount of oxygen, tuyere diameter, projecting position, blowing ratio), the amount of waste plastic blown based on the descending speed of raw fuel, etc. are controlled. In the coke bed, the combustion reaction of coke and waste plastic and the solution loss reaction after combustion progress.The reaction speed of both reactions is determined by the fuel particle size,
It is adjusted according to the gas flow rate, the blast temperature, etc.

In the present invention, in the dust reduction treatment furnace 1 having a multistage tuyere, a raceway is not formed from the primary tuyere (main tuyere) 9a to the coke bed 13 under normal temperature oxygen-enriched blowing. In addition, granular waste plastic is blown. On the other hand, granular waste plastic is blown into the packed bed above the coke bed from the secondary tuyere without blowing a raceway under hot blast to process. The reason why the raceway is not formed is that when the raceway space is formed, the combustion of coke and the solution reaction proceed,
This is because the efficiency of the dust reduction furnace decreases.

By injecting the waste plastic directly into the coke bed, it is possible to maintain the upper end level of the coke bed 13 unchanged, because the waste plastic injected from the main tuyere is less than the coke. from preferentially react with oxygen and CO _2, can suppress coke consumption in the coke bed, also by adjusting the particle size and the amount of waste plastics blown, to control the coke consumption in the coke bed Because it is possible.

On the other hand, by blowing the waste plastic from the secondary tuyere into the packed bed above the coke bed, the waste plastic is efficiently incinerated.

However, since there is a large amount of combustion product gas, the gas temperature decreases, and in a process of melting metal such as melting iron dust / reducing dust, the heat tends to be insufficient. In order to make up for this heat deficiency, in the present invention, a 2% or more oxygen-enriched normal temperature air blow is performed from the primary tuyere and 700 ° C.
Perform the following hot air blowing.

When the oxygen-enriched air is blown from the primary tuyere 9a at room temperature, the oxygen enrichment is set to 2% or more when the oxygen enrichment is set to 2% or less. As a result, the gas temperature decreases, which hinders the dissolution of slag and metal.

On the other hand, the reason why the temperature of the hot air blown from the secondary tuyere 9b is set to 700 ° C. or less is that when the blown air temperature exceeds 700 ° C., the fuel reaction of coke and the solution loss reaction are promoted, and the coke ratio is not necessarily increased. This is because it does not decrease.

In the present embodiment, the properties of the waste plastic are not limited. However, when the waste plastic is blown from the primary tuyere 9a under an oxygen-enriched blast at normal temperature, for example, 1
Use small waste plastics with a particle size of less than mm. On the other hand, when blowing waste plastic under hot air blowing from the secondary tuyere 9b, for example, waste plastic having a large particle size of about several mm can be used.

The amount of waste plastic blown from the primary tuyere 9a is adjusted so that the raw fuel descending speed is constant. The reason why the injection amount of the waste plastic is adjusted based on the descending speed of the raw fuel is to maintain a constant amount of a reaction (solution loss reaction) between CO ₂ and coke in the coke bed. For this purpose, waste plastics reacting with CO ₂ are preferentially blown over coke, and the amount of solution loss reaction that causes fluctuation in the descending speed of the raw fuel is adjusted by blowing waste plastics.

Further, the position where the waste plastic is blown from the secondary tuyere 9b is set in the area above the coke bed because the reaction speed is higher than that of coke, so that C in the waste plastic preferentially reacts with combustion and CO _2. This is because coke consumption can be suppressed.

The amount of the waste plastic to be blown is set to 0.2 kg / Nm ³ or less. The upper limit of the blowing amount is set to 0.2 kg / Nm ^{3 because} when the blowing amount of the waste plastic exceeds 0.2 kg / Nm ³ , the waste plastic exceeding the upper limit is not burned, so that the fuel is replaced with coke. It is not used effectively.

Next, the processing method employing the radial charging method is effective for stable operation and low fuel ratio operation.
A description will be given of an efficient operation that can be performed regardless of the type and particle size of the raw material, and an operation method for achieving an efficient operation depending on the properties of the raw material and the fuel. Regarding the radial charging method, there is an appropriate charging method depending on the type of raw material. One is an example of increasing the ηCO in the furnace and aiming for efficient operation. This is a separation method based on the metallization ratio (M.Fe / T.Fe) of the raw material. It is a classification method.

First, the metallization ratio of the raw material (M.Fe
/ T. The fact that the fractionation method based on Fe) contributes to the stabilization of operations and enables efficient operations to be directed. There are several kinds of raw materials, Fe / T. In the case where Fe can be separated according to the size of Fe, preferably, a raw material having a high metallization rate, for example, iron scrap, is charged into the center of the furnace, and a raw material having a low metallization rate, for example, dust agglomerate, is mounted around the furnace. Enter. The reason for loading the raw material with a low metallization rate around the furnace and the raw material with a high metallization rate at the center of the furnace is to make it easier to control the height of the coke bed at the center of the furnace, and to use the central gas. The aim is to secure flow and to aim for low fuel ratio operation.

In the case of directing this operation, the main tuyere has a structure in which the tip of the tuyere protrudes into the furnace from the furnace wall. Ideally, it is provided at the boundary of the part. In addition, when importance is placed on making the gas flow the central flow, the fuel in the peripheral portion preferably has a small diameter,
The center fuel preferably has a large diameter.

The reason that the main tuyere is set at the boundary between the central part and the peripheral part of the furnace is that the air from the main tuyere is not used for combustion of the fuel existing in the peripheral part. CO
This is to make it work for gas combustion. In order to promote the melting function in the furnace center, it is most efficient if the operation of ηCO> 90% in the furnace center is directed, and the fuel in the furnace center can be about the carburized content which is the lowest fuel ratio. . Therefore, not only can the sudden change in coke bed height be suppressed,
Because the coke that maintains the particle size becomes a coke bed,
Low fuel ratio operation that ensures ventilation and liquid permeability becomes possible.

In this operation, an appropriate amount of air blown from the main tuyere is determined by the height of the coke bed. When the ηCO at the upper end level of the coke bed is 60% or more, it is possible to set ηCO> 90% by blowing air from the main tuyere, and ideal operation can be performed with respect to the furnace center.

Next, it will be explained that the charging method of mixing the fuel with the fuel when the raw material having a low metallization rate is charged into the periphery of the furnace is efficient. If an operation with a high ηCO can be directed, an operation with a low fuel ratio becomes possible,
When an experiment was conducted in which the reduction was carried out under the condition of CO> 30%, the reduction reaction did not proceed under the condition where it was not mixed with coke, causing smelting reduction which had an adverse effect on the operation in the high temperature part. On the other hand, the results of an offline simulator study clearly show that even a raw material with a low metallization rate has an effect of improving the reduction rate by at least 20% or more when mixed with coke and charged, compared to when not mixed with coke. became.

This means that in the operation of charging the raw material having a low metallization rate, the charging method of mixing with the fuel (small-diameter coke) is less expensive than the operation of mixing with the fuel (small-diameter coke). It is effective in improving reducibility, and as a result,
This shows that the amount of slag melt during melting can be reduced, which also contributes to avoiding hanging on a shelf.

Next, in addition to the injection of waste plastic from the main tuyere into the coke bed, the point that the method of charging in the radial direction of the furnace contributes to maintaining the coke bed height will be described. It is difficult to control the height of the coke bed because it is located in the lower center of the furnace, and if the coke ratio is not appropriate, the unreduced FeO melts and reduces at the lower part of the furnace and consumes the coke bed. This is because abnormal wear of the device is caused. In particular, if such abnormal consumption of coke occurs in the lower center of the furnace,
In addition to hindering the dissolution of iron, there is a possibility that the operation may become impossible due to solidification of the slag, which is a problem.

Therefore, as described above, at the center of the furnace,
Mainly by charging a raw material having a high metallization rate, for example, iron scraps, it is possible to make the operation less likely to cause smelting reduction in the central part of the furnace and suppress abnormal consumption of the coke bed in the central part of the furnace. Also,
In order to suppress the solution loss reaction of coke as much as possible, the fuel to be charged into the center of the furnace is distinguished from the fuel to be charged around the furnace, and large-diameter coke is used. by this,
Abnormal wear of the coke bed at the center of the furnace can be suppressed, and operation with higher combustion efficiency ηCO at the bottom of the furnace can be performed. On the other hand, a raw material having a low metallization ratio, for example, dust agglomerate ore is charged into the furnace peripheral portion, so that the smelting reduction is likely to occur in the furnace peripheral portion.

The installation position of the upper tuyere has an appropriate position depending on the operating specifications such as the coke particle size and the amount of air to be blown. However, basically, the ηCO level at the main tuyere is ηCO> 60%
The degree is a guide.

As a simple method for controlling or monitoring the height of the coke bed, there are visual observation at the upper tuyere, judgment by the furnace pressure loss value, and the like. Observation at the upper tuyere can determine that at least the molten portion of the raw material exists at either the upper part or the lower part of the upper tuyere. Further, by detecting the pressure loss difference between the lower tuyere and the upper tuyere, it is possible to confirm the upper end position of the coke bed. According to the operation example, when the upper end level of the coke bed is below the upper tuyere, a large pressure drop difference between the lower tuyere and the upper tuyere is detected. This is because the presence of the melting portion increases the pressure loss value.

As a method for measuring the height of the coke bed with high accuracy, the height can be determined by measuring the descending behavior of a vertical sonde or iron wire charged from the upper part of the furnace. In the case of a vertical sonde, the temperature in the furnace rises sharply to 1200 ° C. or higher, and when iron wires are used, the point at which the descent speed stops corresponds to the upper end of the coke bed.

The boundary position between the furnace center and the furnace periphery referred to in the present invention moves somewhat in the furnace radial direction depending on the metallization ratio of raw materials and coke particle size. The boundary position ri between the furnace center part and the furnace peripheral part can be obtained by the following equation (1) when the amounts of the raw material and the fuel to be charged into each part are determined. ri ² = (Wm (c) / ρm (c) + Wc (c) / ρc (c)) / ｛(Wm (c) / ρm (c) + Wc (c) / ρc (c)) + (Wm ( p) / ρm (p) + Wc (p) / ρc (p))｝ (1) where ri: dimensionless boundary radius between the center and the periphery (−) Wm (c): at the center Weight of raw material to be charged (kg / charge) Wc (c): Weight of fuel to be charged to the center (kg / charge) Wm (p): Weight of raw material to be charged to the periphery (kg / charge) Wc (p) : Weight of fuel charged in the peripheral part (kg / charge) ρm (c): Bulk density of raw material charged in the central part (kg / m ³ ) ρc (c): Bulk density of fuel charged in the central part (Kg / m ³ ) ρm (p): Bulk density of raw material charged in peripheral area (kg / m ³ ) ρc (p): Bulk density of fuel charged in peripheral area (kg / m ³ )

Note that this ri is represented by a dimensionless radius, and indicates a boundary position when the lowering speed of the charge in the furnace central part and the furnace peripheral part is constant. Various charging methods for adjusting the boundary position indicated by ri can be considered, but even when a bell-type charging device is used, the armor is used, and the central charging and the peripheral charging are performed for each charging charge. By alternately repeating the charging, a partial mixed layer is generated, but a predetermined boundary can be set.

FIG. 4 shows CO2 in a coke bed when waste plastic is blown into a normal coke bed.
₂ , CO and O ₂ FIG. There are two types of consumption of C in coke or waste plastic. C + O ₂ → CO ₂ ・ ・ ・ (2) C + CO ₂ → 2CO ・ ・ ・ (3)

Referring to FIG._Two Shown in the concentration curve
To the upper part of the coke bed from the tuyere
Therefore, CO 2 is obtained by the reaction of the formula (2)._Two The concentration increases,
O_Two Is consumed and decreases. And O_Two Disappeared
Above the position, the reaction of equation (3) causes CO 2_Two Concentration
It decreases and the CO concentration starts to rise.

In the reaction of the formula (2), C in coke is effectively used in the exothermic reaction, but in the reaction of the formula (3), C is not effectively used in the endothermic reaction. Thus, although the coke has to be as much as possible (2) reaction of formula, O ₂
When there is no CO2, contact with high temperature CO ₂ causes solution loss of coke by the reaction of equation (3), and coke is wasted.

[0062] Because of the fast combustion rate compared to the waste plastic coke, and blown into the waste plastics into the coke bed, as compared with the case of not blown, O ₂ Will disappear. Therefore, even if waste plastic is blown into the coke bed unnecessarily under the condition that waste plastic is not blown, O ₂ Is present above the vanishing position of, and even though the coke consumption in equation (2) can be reduced, the coke consumption increases in equation (3),
As a result, the injection of waste plastic cannot contribute to the reduction of coke consumption.

The following two methods are effective for avoiding such a situation and performing coke replacement by blowing waste plastic. That is, the reaction of the formula (3) is not performed in the coke bed, or the C in the coke reacting in the formula (3) is replaced with the C in the waste plastic so that the solution loss of the coke does not occur. It is to be.

The first method is a method in which O is injected from the main tuyere.
_Two There set the upper end level of the coke bed height to disappear by adding also waste plastics, O ₂ This is a method in which waste plastic is blown between the main tuyere level and the upper end level of the coke bed in such a manner that coke does not exist in the area where no waste plastic exists. Corresponding to In this case, the blowing position of the waste plastic may be any position including the main tuyere as long as it is between the main tuyere level and the upper end level of the coke bed, and may be one stage or multiple stages.

The second method is a method in which O is injected from the main tuyere.
_Two In this case, the upper level of the coke bed is set to be higher than the height at which the waste plastic is taken into account, and at this time, the waste plastic is blown between the main tuyere level and the upper level of the coke bed, and O ₂ This is a method in which waste plastic is blown into the upper area of the coke bed where no plastic exists to cause solution loss instead of coke. In this case, the lower part of the waste plastic injection position is the main tuyere level and O ₂ Any position between the vanishing point level and the main tuyere may be used, and one stage or a plurality of stages may be used. In addition, the upper part of the waste plastic injection position is also O ₂ Any position between the vanishing point level and the upper end level of the coke bed may be used, and one or more stages may be used. According to this method, it is possible to increase the amount of waste plastic blown by the amount blown upward.

[0066]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the method for operating a dust reduction treatment furnace according to the present invention will be described below, but the present invention is not limited to the following embodiments. Aiming at the effect of maintaining the top level of the coke bed of the dust reduction furnace, the effect of reducing the coke ratio, and the effect of treating waste plastic, air is blown at room temperature without forming a raceway from the primary tuyere, and a raceway is formed from the secondary tuyere. Under a blowing condition that hot air was blown without being formed, an experiment of blowing waste plastic into a coke bed and a packed bed above the coke bed (hot model experiment) was performed. In addition, the combustibility of waste plastic was investigated from the properties of dust collected at each part of the coke bed and the packed bed above the coke bed, and the combustion behavior and reaction behavior of waste plastic were investigated from the coke consumption rate (falling behavior).

As waste plastic, polyethylene particles (up to 1.0 mm, representative particle size 680 μm, bulk density 0.4
08 t / m ³ ). The composition of the polyethylene particles was as follows: C: 85.2%, H: 14.3%, O: <0.2.
1% and the calorific value is 10,000 cal. The air from the primary tuyere was an oxygen-enriched air at room temperature, and the oxygen-enriched amount was 4%. Hot air was blown from the secondary tuyere at a temperature of 500 ° C. The amount of waste plastic blown was 0.15 kg / Nm ³ .

As a result, FIG. 5 shows an example at the time of the test operation. The test furnace has 7 main tuyeres (primary tuyeres).
Peepholes are provided at 0 cm, 80 cm (secondary tuyere), and 90 cm, and the upper end position of the coke bed (the part where the raw material melts) can be directly observed from these peepholes. In FIG. 5, the waste plastic was constantly injected at 0.15 kg / Nm ³ from the main tuyere.
After 5 hours, the upper end position of the coke bed began to decrease, so that the amount of waste plastic blown was 0.16 kg / N.
This is an experimental example showing a situation where the position of the upper end of the coke bed is returned to the original level by increasing it to m ³ . From the furnace top, no waste plastic granules were found, and no CH ₄ gas was present in the gas, confirming that the waste plastic blown from the tuyere was consumed in the furnace. Also, by injecting waste plastic, the coke ratio has been reduced, and it has been effectively used as a substitute fuel for coke.

Secondly, when polyethylene is blown from the secondary tuyere, ηCO (= CO ₂ / (C
O + CO ₂ ) Was low. This suggests that under hot air blowing conditions, the flammability is better and the solution loss reaction is faster than that of coke. That is, the preferential consumption of polyethylene by the blast oxygen was confirmed.

Third, according to the CH ₄ analysis, as shown in FIG.
_Since the disappearance of ₂ H ₄ and the decrease of CH ₄ and the progress of whitening of the dust are progressing, it is judged that the polyethylene is almost completely burned and decomposed at this site.

Fourthly, as shown in FIG. 7, when polyethylene was blown from the secondary tuyere, it was confirmed that the descent of coke was stagnant (there was no change for at least 30 minutes) in the area above the coke bed. In other words, up to the area above the coke bed, the combustion reaction of coke is extremely small,
It was confirmed that polyethylene was burning and reacting.

From the above experimental results, it was confirmed that the injection of waste plastic into the coke bed under the normal temperature oxygen-enriched blast from the primary tuyere is effective for stable operation without changing the top level of the coke bed. Was done. Also,
Injecting waste plastic into the packed bed above the coke bed under hot air blowing from the secondary tuyere is effective for treating waste plastic, and stable operation is possible by blowing waste plastic into the area above the coke bed. It was confirmed that.

[0073]

As described above, according to the present invention,
By setting specific conditions when blowing waste plastic into a dust reduction treatment furnace with multi-stage tuyeres,
By injecting waste plastic from the primary tuyere, it is possible to maintain the stable operation of the dust reduction treatment furnace and control the upper end level of the coke bed located in the lower part of the furnace so as not to change. Injection of waste plastic has an excellent effect that waste plastic can be efficiently incinerated.

[Brief description of the drawings]

FIG. 1 is a dust reduction treatment furnace used in the method for operating a dust reduction treatment furnace according to the present invention, wherein (a) is a schematic diagram showing the entire configuration, and (b) is a schematic diagram showing the charging device to the furnace center. FIG. 3C is a schematic view showing a charging state, and FIG. 4C is a schematic view showing a charging state of the charging apparatus into a furnace peripheral portion.

FIG. 2 is a schematic diagram showing an upper end level of a coke bed and a waste plastic blowing position in a two-stage tuyere dust reduction treatment furnace.

FIG. 3 is a schematic view showing a state of sorting and charging in a furnace radial direction.

FIG. 4 is an explanatory diagram showing a CO ₂ concentration curve in a furnace.

FIG. 5 is an explanatory diagram showing an operation example in which the amount of waste plastic blown is adjusted so as not to change the upper end level of the coke bed in the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a change in ηCO when polyethylene is blown into a coke bed in the example of the present invention.

FIG. 7 is an explanatory diagram showing a coke descending speed at the time of blowing polyethylene in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dust reduction treatment furnace 2 Charging device 3 Bucket 4 Bell 5 Movable armor 6 Charging guide 7 Furnace body 8 Exhaust gas pipe 9 Tuyere 9a Primary tuyere (lower tuyere) 9b Secondary tuyere (upper tuyere) 11 Furnace central part 12 Furnace peripheral part 13 Coke bed

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K061 AA16 AB02 AC01 AC13 AC20 BA03 BA08 CA08 DB01 DB16 DB20 3K062 AA16 AB02 AC01 AC13 AC20 BA01 BB02 BB05 CB01 DA38 DB01 DB12 4K001 AA10 BA14 BA22 DA05 EA03 GA01 GB03 GB11 HA01 HA10 CB00 CB02 CB05

Claims (8)

[Claims] Claims 1. When charging iron scrap, dust agglomerate and coke into a dust reduction treatment furnace having a multi-stage tuyere and melting and reducing the same, a race from the primary tuyere to a coke bed is performed. Blowing without forming a way is performed, and granular waste plastic is blown to control so that the upper end level of the coke bed does not change.Blowing is performed from the secondary tuyere to the packed layer above the coke bed without forming a raceway. And a method for operating a dust reduction treatment furnace, wherein the treatment is performed by blowing granular waste plastic. 2. The method for operating a dust reduction treatment furnace according to claim 1, wherein granular waste plastic is blown from the primary tuyere under an oxygen-enriched blast at normal temperature. 3. The method for operating a dust reduction treatment furnace according to claim 2, wherein the amount of oxygen enrichment in the normal-temperature blast is 2% or more. 4. The method for operating a dust reduction treatment furnace according to claim 1, wherein granular waste plastic is blown from the secondary tuyere under hot air blowing at a temperature of 700 ° C. or less. . 5. The method of claim 1, wherein the lowering speed of the raw fuel is constant.
The method of operating a dust reduction treatment furnace according to any one of claims 1 to 4, wherein an amount of waste plastic blown from the primary tuyere is adjusted. 6. The method for operating a dust reduction treatment furnace according to claim 1, wherein a position of blowing the waste plastic from the secondary tuyere is set in a region above the coke bed. 7. The blowing amount of waste plastic is 0.2 k.
The method for operating a dust reduction treatment furnace according to any one of claims 1 to 6, wherein the setting is set to g / Nm ³ or less. 8. The method according to claim 1, wherein iron dust is mixed with large-diameter coke and charged into the furnace center, and dust agglomerate is mixed with small-diameter coke and charged around the furnace. 8. The method for operating a dust reduction treatment furnace according to any one of 1 to 7.