JPH11239773A - Method for burning plastic flake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel combustion method using plastic flakes as at least a part of fuel in a high temperature combustion furnace. SOLUTION: As at least a part of fuel, plastic flakes with 5-1,000 μm thickness and 2,500 mm<3> or smaller surface area are supplied to a high temperature combustion furnace such as a cement manufacturing rotary kiln, a calcining furnace, etc., by an air flow at 20 m/s or high flow velocity. Consequently, without causing clogging of a supply inlet due to melting deposition of the plastic flakes, the plastic flakes are stably supplied. As a result, a large quantity of plastic flakes are made usable instead of a main fuel and the treatment amount of plastics is significantly increased as compared with that by a conventional treatment for combustible wastes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel combustion method using plastic flakes as at least a part of fuel in a high temperature furnace, and more particularly to a high temperature furnace,
For example, in a calciner or rotary kiln for cement production, when plastic flakes are used as fuel, there is no clogging due to fusion at the supply port, and a large amount of plastic flakes is obtained while maintaining the quality of the obtained cement stably. Is a method for burning plastic flakes.

[0002]

2. Description of the Related Art Conventionally, most of waste materials discharged from industrial activities and from households have been disposed of by dumping in landfills or incineration by incinerators. However, in recent years, the capacity of landfills has been lacking,
In addition, new construction is difficult due to social restrictions, so it is impossible to expect landfill disposal. In general, incineration treatment by incinerators includes, among waste materials, combustible waste materials such as plastic waste materials and waste paper.In particular, for plastic waste materials, damage to the furnace due to the high combustion temperature or There are problems such as a large amount of dioxin generated due to a decrease in temperature during addition, and it is difficult to stably treat a large amount of waste materials.

Against this background, the recycling of plastic waste has become an important social issue from the viewpoint of environmental protection. Among them, a calciner and a rotary kiln for producing cement with a high combustion temperature are important. Combustion treatment of plastic waste materials in a high-temperature sintering furnace as described above is effective as a method for stably treating the waste plastics, and is about to be promoted.

[0004] In general, plastic waste materials are roughly classified into plastic structures such as cases and parts made of plastic, and thin plastic bodies such as bags, films and sheets. By crushing the plastic structure, it is possible to obtain a granular material that is easy to handle and can be charged into a cement kiln without any problem. Actually, there is also known an example in which the granulated plastic is supplied to a cement kiln together with the main fuel.

[0005]

It is conceivable that the above-mentioned plastic thin body may be used after being crushed as in the case of the plastic structure. However, such crushed flakes are bulky and difficult to handle, so that high-temperature combustion is difficult. It has been pointed out that the supply port to the furnace is melted and adhered and clogged, and that the behavior after supply is unstable and stable combustion cannot be performed.

For this reason, a method has been adopted in which the crushed flakes are compression-molded by adding a binder or melting by heating to form a molded body having a specific bulk specific gravity, and then further pulverized into chips to be supplied to a rotary kiln. ing.

However, the above-mentioned method requires a great deal of labor and equipment and is not economical. Therefore, there has been a demand for the development of a method capable of easily and mass-treating a thin plastic body.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies on the technique of burning thin plastic bodies, and as a result,
It has been found that such an object can be achieved by crushing a plastic thin body into plastic flakes of a specific size and supplying it to a high-temperature combustion furnace at a specific flow rate or higher, thereby completing the present invention.

That is, according to the present invention, at least a part of the fuel has a thickness of 5 to 1000 μm and an area of 2500 mm ^2.
A plastic flake combustion method characterized in that the following plastic flakes are supplied to a high-temperature combustion furnace by an air current having a flow velocity of 20 m / sec or more.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a plastic thin body as a raw material of a plastic flake generally includes:
All objects that can be burned and have a thickness of 5 to 1000 μm are applicable. Among them, it is particularly effective for a plastic flake obtained from a raw material having a thickness of 10 to 600 μm. The thin plastic body has a calorific value of 3000.
Those having a mass of 〜１０10,000 kcal / kg are preferably used because a large amount can be supplied without lowering the temperature of the high-temperature combustion furnace.

Examples of the plastic material include plastics such as polypropylene, polyethylene, polystyrene, polyamide, and polyvinyl chloride. In addition, the form may be a thin body having the above thickness, and a film, a sheet or a processed product thereof, a molded body having a thickness equivalent to that of the film or the sheet, for example, a thermoformed tray, a bag, a flexible container, or the like may be used. No.

Further, the crushing of the plastic thin-walled body is as follows.
A known method is employed without any particular limitation. In particular, a method using a crusher such as a shredder crusher, a hammer crusher, a single-shaft crusher, and a multi-shaft crusher is suitably used. Among them, a uniaxial press-type crusher in which the particle size of the crushed material can be arbitrarily changed by a screen and has a mechanism for cutting the input material by a rotary blade and a fixed blade is preferable.

In the present invention, plastic flakes, which are crushed products obtained by crushing plastic thin bodies,
Its area is 2500 mm ² or less, preferably 650 mm ²
Hereinafter, in particular, those having 100 to 600 mm ² are used.

It is most preferable that all of the plastic flakes satisfy the above requirements.
Preferably, within 5% by weight, it is permissible to include crushed materials outside the above range. However, even in this case, 100
Desirably, there is substantially no plastic flakes greater than 00 mm ² .

The above-mentioned plastic flakes are preferably as close as possible to the maximum length and the minimum length from the viewpoint of handleability, but generally the ratio of the maximum length to the minimum length is preferably 1 to 25. Those having a maximum length of 60 mm or less, preferably 50 mm or less are particularly suitable.

In the present invention, the area of the plastic flake is not particularly limited as long as it is within the above range, and various sizes may be mixed. That is, according to the confirmation by the present inventors, the burning time of the plastic flakes is substantially constant within the above-mentioned area, regardless of the size of the area, and the same burning can be performed. Of course, it is most preferable to use one having the same size as possible.

The flow rate of supplying the plastic flakes to the high-temperature combustion furnace is 20 m / sec or more, preferably 20 m / sec to 6 m / sec.
0 m / sec, particularly preferably 30 m / sec to 50 m / sec. That is, in order to prevent the plastic flakes from being fused to the supply pipe by the cooling action of the supply pipe by the air flow,
It is necessary to maintain the speed of the air flow for the supply at 20 m / sec or more. Further, since the burning time of the plastic flakes is almost the same as that of pulverized coal, the above-mentioned feeding speed is required to prevent flashback.

If the flow velocity of the air flow is too high, the amount of air becomes excessive with respect to the plastic flakes and the temperature in the combustion furnace tends to decrease.
It is preferable to adjust the upper limit to seconds, preferably 50 m / second.

In the present invention, the means for supplying the plastic flakes by air flow is not particularly limited, but a method using a known device such as an air pump or a suction pump is employed without any particular limitation.

The air flow for supplying the plastic flakes to the high-temperature combustion furnace is preferably air (atmosphere), but contains the oxygen necessary for burning the plastic flakes and has no adverse effect in the combustion furnace. Any gas can be used without any particular limitation.

The high-temperature combustion furnace used in the present invention has a temperature of 700 ° C.
Above, preferably a furnace burning at 1000 ° C. or higher is generally used. That is, plastic flakes are generally 700
By setting the temperature to not less than ° C., it is possible to surely ignite and to supply a large amount of plastic flakes.
Particularly, by using a combustion furnace at a higher temperature of 800 ° C. or higher, it is possible to prevent generation of dioxin due to combustion of chlorine-containing plastic, which is preferable.

Examples of suitable high-temperature combustion furnaces include calcining furnaces, rotary kilns, and blast furnaces for cement production.

When the present invention is applied to a high-temperature combustion furnace in which the amount of combustion affects quality, such as a calciner or a rotary kiln for cement production, the total amount of heat of the supplied fuel is accurately controlled. Therefore, it is necessary to grasp the calorific value of the supplied plastic flakes and to accurately control the supplied amount. In order to cope with such a problem, it is extremely effective to control the supply amount of the plastic flakes by using a quantitative feeder based on weight. That is, since the control of the supply amount by the volume of the airflow including the plastic flakes, which is easily affected by the bulk density of the plastic flakes, the concentration of the plastic flakes in the airflow, and the like, lacks accuracy, the amount is controlled before the supply into the airflow. A controlling method is preferred because it can eliminate these variables and can accurately feed the plastic flakes to the high temperature incinerator. In carrying out the above-mentioned supply method, the most effective supply means is a mode in which a screw conveyor is used and the supply amount is controlled by the number of rotations. According to such an embodiment, the plastic flakes can be supplied very accurately by the rotation of the screw.

Also in this case, if the plastic flakes have the above-mentioned size, the occurrence of clogging such as hanging on a shelf in the hopper can be effectively reduced, which is effective for stable supply.

In the supply of the above-mentioned plastic flakes, the calorific value is measured in advance, and the calorific value is appropriately classified, for example, classified into three to five calorific value categories and managed. It is preferable to use a mixture and control the calorific value.

In the present invention, the temperature of the air flow for supplying the plastic flakes to the high-temperature combustion furnace is 100 ° C. or less,
Preferably, a temperature of 10 ° C to 60 ° C is suitable. That is,
If the temperature of the air flow exceeds 100 ° C., the plastic flakes may fuse together in the pipe for supplying the plastic flakes and at the outlet, which may cause trouble.

When a calciner or a rotary kiln for cement production is used as the high temperature combustion furnace of the present invention,
As the cement raw material, a known raw material is used without any particular limitation.

FIG. 1 is a conceptual diagram showing a typical embodiment in which the present invention is applied to a calciner and / or a rotary kiln for cement production.

In FIG. 1, the kiln 31 is a combustion furnace in which a cylindrical steel shell is lined with a refractory, and the kiln is rotating at a constant speed. A kiln main fuel supply nozzle (burner) 30 is provided on the outlet side of the kiln (on the left side of the kiln in the figure), and pulverized coal is supplied from a pulverized coal supply device 32 as fuel for the burner.

Further, the cement raw material fed from the inlet side of the kiln (right side of the kiln in the figure) is calcined while moving in the rotating kiln in the direction of the outlet, and becomes a clinker having a constant mineral composition to form a clinker having a constant mineral composition. Is discharged from
Since a region of several tens of meters from the exit to the entrance of the kiln is a region where the mineral composition of the clinker is finally determined (hereinafter, referred to as a calcination region), strict control of reaction conditions is required, In particular, maintaining a good combustion state of fuel such as pulverized coal in a burner is a critical factor in stably producing a clinker of normal quality. For this reason, it is necessary to control the combustion state of the fuel such as pulverized coal so that the amount of heat required to produce a clinker of normal quality is supplied without excess or deficiency, and the operability of the kiln is not impaired.

In the calcining furnace 34 for calcining the cement raw material to be supplied to the kiln, it is necessary to maintain the calcined state by the burner in order to stabilize the quality of the clinker.

Under such severe combustion conditions, the application of the method for burning plastic flakes of the present invention makes it possible to feed plastic flakes into a furnace without adversely affecting the combustion state, and to obtain normal quality flakes. Clinker can be manufactured stably.

Incidentally, by burning the plastic flakes of the present invention, even if 50% or more, more preferably 60% or more, and in some cases, 100% of the fuel is converted to the above-mentioned plastic flakes, the stability of combustion can be ensured. As a result, it is possible to produce cement stably without variation in clinker quality and without damaging the kiln.

In the above embodiment, the plastic flake is
It is supplied as at least a part of the fuel of the calciner and / or the rotary kiln. The supply point is preferably a supply point of pulverized coal or the like as a main fuel, or a position adjacent thereto. That is, as shown in FIG. 1, in a rotary kiln, it is preferable to install a plastic thin piece supply pipe 40 near the burner 30 on the outlet side. In particular, it is more preferable that the supply pipe is provided so that the plastic flakes can be supplied into the flame of the burner 30.

In the calciner 34, it is preferable to provide a plastic flake supply pipe 33 near the burner 48 of the calciner.

Further, a thin plastic body such as a plastic film is supplied from a hopper 41 to a crusher 42, crushed to a specific size, and then supplied to a screw conveyor 43, which is a quantitative feeder. , The supply amount is controlled accurately. Then, the plastic flakes are, in the figure, kiln 3
The fuel is supplied into the kiln from a supply pipe 40 provided in parallel with the kiln main fuel injection nozzle 30 and burned. In FIG. 1, a supply pipe 48 provided in the calciner 34 is provided.
Also, the mode of supplying plastic flakes is also shown.

It is needless to say that the supply point may be either a rotary kiln or a calciner.

[0038]

As will be understood from the above description, according to the present invention, plastic flakes crushed to a specific size are supplied to a high-temperature combustion furnace, such as a kiln or a calciner, under specific conditions. This makes it possible to stably supply plastic flakes without clogging due to fusion at the supply port. Therefore, it is possible to use a large amount of plastic flakes instead of the main fuel, and it is possible to drastically improve the processing amount in comparison with the conventional processing of combustible waste materials.

[0039]

EXAMPLE 1 Using the apparatus shown in FIG. 1, cement was produced by the following method. First, a 500-μm-thick film-shaped plastic thin body (average calorific value about 8000 kcal / kg)
Was crushed by a crusher 42 to obtain a plastic flake by crushing so that 98% by weight or more had an area of about 2000 mm ² and the ratio of the maximum length to the minimum length was in the range of 1 to 1.5.
This crushed material is supplied to a fixed-quantity feeder 4 comprising a screw conveyor.
3 and weighed.

Next, the plastic flakes were supplied through a suction blower 44 at a flow rate of 40 m / sec from a supply pipe 40 attached to a kiln main fuel injection nozzle (burner) of the kiln and burned to produce cement.

As a result, even when up to about 50% of the amount of pulverized coal used in cement production was switched to the plastic flakes, production could be performed while maintaining the quality of the obtained clinker stably.

As described above, it was confirmed that a thin film-shaped plastic body, which had been difficult to treat up to now, can be sufficiently used for the production of cement according to the present invention.

Example 2 A sheet-shaped plastic thin body having a thickness of 300 μm (average calorific value of about 6000 kcal / kg) was crushed by a crusher 42, 98% or more was about 500 mm ² , and the ratio of the maximum length to the minimum length was 1 Plastic flakes in the range of ~ 1.2 were obtained. The crushed material was supplied to a quantitative feeder 43 composed of a screw conveyor and weighed. Next, the plastic flakes were passed through a suction blower 44 to flow at a flow rate of 20 m.
The fuel was supplied from a supply pipe 40 attached to a kiln main fuel injection nozzle (burner part) of the kiln and burned at a rate per second to produce cement.

As a result, even when up to about 80% of the amount of pulverized coal used in the production of cement was switched to the plastic flakes, production could be performed while maintaining the quality of the obtained clinker stably.

As described above, even when a plastic thin body having a different thickness and shape is used, it can be burned from the kiln sub-fuel injection nozzle and the calciner sub-fuel injection nozzle by crushing to 2500 mm ² or less. It became. In addition, it became possible to supply the water to the kiln stably, and the temperature inside the kiln could be kept stable.

COMPARATIVE EXAMPLE 1 A sheet-like plastic thin body similar to that in Example 1 was crushed by a crusher 42, and 98% by weight or more of the area was about 400 in area.
A plastic piece having a length of 0 mm ² and a ratio of the maximum length to the minimum length of about 1 was obtained. The crushed material was supplied to the quantitative feeder 43 and weighed. Next, the plastic piece is passed through a suction blower 44 at a flow rate of 40 m / sec at a supply pipe 40 attached to a kiln main fuel injection nozzle (burner portion) of the kiln.
It was supplied and burned to produce cement. But,
Frequent clogging occurs in fixed-rate feeders and suction blowers,
Further, it was difficult to keep the temperature inside the kiln stable, and it was difficult to continuously operate the kiln.

Comparative Example 2 The plastic flake obtained in Example 2 was supplied to the quantitative feeder 43.
And weighed. Next, the plastic flakes were supplied through a suction type blower 44 at a flow rate of 10 m / sec from a kiln auxiliary fuel injection nozzle 40 (burner portion) provided in the kiln main fuel injection nozzle (burner section) and burned to produce cement.

However, clogging frequently occurs at the end of the supply pipe 40 and in the pipe, and it is difficult to keep the temperature inside the kiln stable, and it is difficult to continuously operate the kiln.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an embodiment of a typical combustion device for performing the method of the present invention.

[Explanation of symbols]

 Reference Signs List 30 Kiln main fuel injection nozzle 31 Rotary kiln 32 Pulverized coal supply device 33 Calcination furnace main fuel injection nozzle 34 Calcination furnace 40 Supply pipe 41 Plastic waste hopper 42 Crusher 43 Quantitative feeder (screw conveyor) 44 Suction blower 48 Supply pipe

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[Procedure amendment]

[Submission date] March 3, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

In FIG. 1, the kiln 31 is a combustion furnace in which a cylindrical steel shell is lined with a refractory, and the kiln is rotating at a constant speed. Such outlet side of the kiln (kiln right side in the drawing) is installed kiln main fuel supply nozzle (burner) 30, as the fuel of the burner, and pulverized coal is supplied from the pulverized coal supply device 32.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

The kiln inlet side (in the figure, the kiln
Cement material inserted from the left side) is fired while moving within the kiln to rotate the outlet direction, and is discharged from the right-side outlet becomes clinker consisting constant mineral composition.
Since a region of several tens of meters from the exit to the entrance of the kiln is a region where the mineral composition of the clinker is finally determined (hereinafter, referred to as a calcination region), strict control of reaction conditions is required, In particular, maintaining a good combustion state of fuel such as pulverized coal in a burner is a critical factor in stably producing a clinker of normal quality. For this reason, it is necessary to control the combustion state of the fuel such as pulverized coal so that the amount of heat required to produce a clinker of normal quality is supplied without excess or deficiency, and the operability of the kiln is not impaired.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

In the calciner 34, the calciner main fuel is used.
It is preferable to provide a plastic flake supply pipe 48 near the material blowing nozzle (burner) 33 .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0045

[Correction method] Change

[Correction contents]

[0045] As described above, even when the thickness and shape with different plastic thin body, Ri by the crushing to 2500 mm ² or less, it becomes possible to combustion.
In addition, it became possible to supply the water to the kiln stably, and the temperature inside the kiln could be kept stable.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction contents]

Comparative Example 2 The plastic flake obtained in Example 2 was supplied to the quantitative feeder 43.
And weighed. Next, the plastic flakes were supplied through a suction type blower 44 at a flow rate of 10 m / sec from a supply pipe 40 attached to a kiln main fuel injection nozzle (burner portion) of the kiln and burned to produce cement.

Claims (4)

[Claims] 1. A fuel having a thickness of 5 to 5 at least as a part of fuel.
A method for burning plastic flakes, comprising feeding plastic flakes having a size of 1000 μm and an area of 2500 mm ² or less to a high-temperature combustion furnace by an airflow having a flow velocity of 20 m / sec or more. 2. The method for burning plastic flakes according to claim 1, wherein the feed rate of the plastic flakes is adjusted before mixing with the air stream. 3. The method for burning plastic flakes according to claim 1, wherein the temperature of the airflow is 100 ° C. or lower. 4. The high-temperature combustion furnace is a calciner or a rotary kiln for calcining or calcining a cement raw material.
A method for burning plastic flakes as described.