JP2022042573A - Method of producing solid fuel with reduced chlorine - Google Patents

Abstract

To provide a method of efficiently producing solid fuel with reduced chlorine.SOLUTION: The method of producing solid fuel with reduced chlorine, comprises a heating process of heating waste plastic, a crushing process of crushing the waste plastic after being heated, a washing process of washing crushed waste plastic with water, and a water addition process of adding water to the crushed waste plastic after the crushing process and before the washing process.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a chlorine-reduced solid fuel.

Conventionally, a large amount of organic waste such as food waste and paper is discharged as municipal waste from homes, restaurants, convenience stores, etc., and the incineration ash generated when the urban waste is incinerated is disposed of by landfill. Since a substance contains a large amount of carbon, in recent years, attempts have been made to effectively use it as a fuel. However, since municipal waste contains chlorine-containing resin such as vinyl chloride, incinerator ash may contain dioxin.

Therefore, after incinerating fly ash and incinerated ash of municipal waste, chlorine content is removed by washing with water, and a predetermined substance other than chlorine content is removed, then solid-liquid separation is performed and the solid content is used for cement kneading. It has been proposed to use it as a material (Patent Documents 1 to 3).

Japanese Unexamined Patent Publication No. 2006-15190 Japanese Unexamined Patent Publication No. 2014-193456 Japanese Unexamined Patent Publication No. 2005-279370

The present inventors have attempted to create a method for producing a solid fuel in which chlorine is reduced by washing with water according to the above-mentioned prior art from a heat-treated product of waste plastic, and the following problems have arisen. That is, the heat-treated waste plastic has a wider particle size distribution than the incinerated ash (main ash, flying ash) of municipal waste, and contains chlorine that cannot be dissolved by washing with water or acid such as vinyl chloride. In addition to the heat residue of the resin, it contains a wide variety of impurities such as resin that has not been embrittled and metals, glass, fibers, etc. Due to the different characteristics, it was difficult to remove chlorine from the heat-treated waste plastic by washing with water.
Therefore, it is conceivable to miniaturize the heat-treated waste plastic, but since the heat-treated waste plastic contains metal, the work is likely to be interrupted due to blade wear and metal biting. It was difficult to remove chlorine from the heat-treated waste plastic by washing with water because resins having different degrees of embrittlement due to heating were mixed. In addition, it is conceivable that the heat-treated waste plastic is roughly crushed to about several mm, but it may not sufficiently mix with water during washing with water, and depending on the particle size and density, the fluidity and floating / sinking property during washing with water may be affected. Due to the different properties, the efficiency of washing with water is reduced, it is easy to be blocked by pumps and pipes during transportation, and the machine is damaged, worn or damaged during dehydration. It was difficult to remove chlorine from the object.
An object of the present invention is to provide an efficient method for producing a solid fuel with reduced chlorine.

As a result of studying in view of the above problems, the present inventors heated the waste plastic to make it brittle, crushed it, and then added water to the crushed waste plastic before washing with water to chlorine from the crushed waste plastic at the time of washing with water. It has been found that not only is it easier to elute, but also the floating of crushed waste plastic is suppressed and the handleability is improved, so that a solid fuel with reduced chlorine can be efficiently produced.

That is, the present invention provides the following [1] to [4].
[1] A heating process for heating waste plastic,
A crushing process that crushes waste plastic after heating,
Includes a cleaning process to wash crushed waste plastic with water
It has a watering step of adding water to the crushed waste plastic after the crushing step and before the washing step.
Manufacturing method of chlorine-reduced solid fuel.
[2] The method for producing a chlorine-reduced solid fuel according to claim 1, wherein the water content of the crushed waste plastic is adjusted to 5 to 70% by mass in the water addition step.
[3] The method for producing a chlorine-reduced solid fuel according to claim 1 or 2, wherein the cleaning step is performed after a predetermined time has elapsed from the end of the water addition step.
[4] The chlorine-reduced solid fuel according to any one of claims 1 to 3, further comprising a sorting step of collecting crushed waste plastic having a major axis of a predetermined value or less by physical sorting after the crushing step and before the water addition step. Manufacturing method.

According to the present invention, a solid fuel with reduced chlorine can be efficiently produced by a simple operation.

The method for producing a chlorine-reduced solid fuel of the present invention includes a heating step, a crushing step, a water addition step, and a washing step. Hereinafter, each step will be described.

[Heating process]
The first step is a step of heating the waste plastic. As a result, the decomposition of the waste plastic progresses, voids are generated on the surface and inside of the waste plastic, and the waste plastic becomes brittle and its strength decreases, so that crushing in the next step can be efficiently performed. Two or more waste plastics may be mixed.
The waste plastic used in the present invention is a used plastic product, scraps or defective products generated during the manufacture and processing of plastic in factories, etc., and foreign substances other than plastic (for example, metal, paper, wood, etc.) Inorganic substances and organic substances) may be attached or mixed.
Examples of the waste plastic include shredder dust, construction waste plastic, agricultural waste plastic, fishery waste plastic, and marine waste plastic. These waste plastics usually contain chlorine-containing resins such as polyvinyl chloride and polyvinylidene chloride. Here, the term "shredder dust" as used herein refers to a mixture of debris that is discarded after crushing industrial waste or general waste with an industrial shredder and recovering the metal. Specific examples of industrial waste include scrapped automobiles, scrapped home appliances, vending machines, and OA equipment.

The heating temperature is not particularly limited as long as it can embrittle the waste plastic, but from the viewpoint of preventing the generation of dioxins, a temperature higher than the melting temperature and lower than the combustion temperature is preferable. Specifically, 250 to 500 ° C. is preferable, 275 to 475 ° C. is more preferable, and 300 to 450 ° C. is further preferable.
The heating time is not particularly limited as long as the waste plastic can be embrittled, but is usually 0.5 to 5 hours, preferably 0.5 to 4 hours, and more preferably 1 to 3 hours.
The heating device is not particularly limited as long as it can accommodate waste plastic and can be set to the above temperature, and examples thereof include a fixed furnace, a stoker furnace, a rotary kiln furnace, a fluidized bed furnace, a rigid furnace, and a multi-stage furnace.

[Crushing process]
The crushing step is a step of crushing the waste plastic after the heating step. This turns the waste plastic into particles, making it easier to remove chlorine.
The waste plastic after the heating step becomes brittle due to heating and its strength is lowered, so that it can be easily made into particles by crushing, but usually a crusher is used.
The crusher is not particularly limited as long as it can crush waste plastic, but an impact type crusher is preferable. For example, an impact crusher, a hammer crusher, a roll crusher, and a rotary crusher can be mentioned.

In the present invention, it is preferable to control the major axis of the waste plastic after crushing from the viewpoint of reducing chlorine and improving production efficiency. In order to collect waste plastic crushed material having a controlled major axis, for example, a crusher may be equipped with a screen having a desired sieve. The screen may be a two-stage screen. By controlling the major axis of crushed waste plastic in this way, incombustibles such as metal and glass, plate-shaped and rod-shaped resins, etc. can be removed, preventing operational troubles such as machine damage, wear, and damage. Not only that, it becomes easier to remove chlorine from the crushed material in the cleaning process.
The major axis of the crushed waste plastic is preferably less than 30 mm, more preferably less than 20 mm, still more preferably less than 15 mm. Here, the “major diameter” in the present specification is a value obtained by collecting the largest crushed material among the crushed waste plastics and measuring the portion where the diameter of the crushed material is maximum.

[Sorting process]
In the present invention, it is possible to have a sorting step of physically sorting the crushed waste plastic in order to collect the waste plastic crushed material highly controlled to a desired major axis.
The physical sorting is not particularly limited, and examples thereof include wind sorting, specific gravity sorting, magnetic force sorting, eddy current sorting, sieving, and sorter sorting (optical, electromagnetic induction, transmitted X-rays, fluorescent X-rays, etc.). The sorting conditions may be appropriately set according to the sorting method so that the above-mentioned crushed waste plastic having a long diameter can be collected.

The wind power sorter can use a known wind power sorter, and is not particularly limited, and examples thereof include a zigzag type and an internal circulation type.
In wind power sorting, for example, when an internal circulation system is used, when an air flow is created from bottom to top by a fan, heavy objects of waste plastic crushed material move downward against the air flow, while being lightweight. Objects move upward on the flow of air. In this way, the crushed waste plastic is sorted into heavy and lightweight materials, and the lightweight materials are collected. In this case, it is preferable to set the wind speed for wind sorting so that the heavy products are mainly incombustibles such as metal and glass. For example, the wind speed is preferably 5 m / s or more, more preferably 7.5 m / s or more, and even more preferably 10 m / s or more. The upper limit of the wind power can be appropriately set depending on the type of waste plastic, but is usually 30 m / s or less, preferably 25 m / s or less.

As the specific gravity sorter, a known specific gravity sorter can be used, and either a dry type or a wet type may be used, but a dry type table type specific gravity sorter is preferable, and an air table is more preferable.
In the specific gravity sorting, for example, when an air table is used, the waste plastic crushed material supplied to the upper surface of the vibrating table is in a state of floating from the upper surface of the vibrating table by the air flow passing through the vibrating table. Due to the vibration applied in the tilting direction of the table, the high specific gravity object with a large specific gravity moves to the lower layer, the low specific gravity object with a small specific gravity moves to the upper layer, and the high specific gravity object in the lower layer has frictional force and vibration force from the upper surface of the vibrating table. In response to this, it moves diagonally upward, and the low-weight object in the upper layer is swept diagonally downward from the upper surface of the vibrating table without receiving frictional force and vibrating force. Then, the high-density substance and the low-density substance are separately discharged from the vibration table, and the low-density substance is recovered.

The magnetic force sorting can be performed by using a known magnetic force sorting machine, and may be, for example, any of a drum type, a pulley type and a hanging type, and is not particularly limited.
In the magnetic force sorting, for example, a magnetic force sorting having a magnet drum in which a magnetic field of high magnetic force exists, a belt conveyor (mobile belt) wound around the magnet drum, and a feeder for supplying a sample on the belt surface of the belt conveyor. Using the device, the non-magnetic material is sorted into a magnetic material and a non-magnetic material, and the non-magnetic material is collected.
The surface magnetic flux density of the magnetic force sorter is preferably 700 to 10000 gauss, more preferably 1000 to 7500 gauss, still more preferably 1500 to 5000 gauss, from the viewpoint of removing magnetic deposits.

As the eddy current sorter, a known eddy current sorter can be used, and the eddy current sorter is not particularly limited, and examples thereof include a rotating magnet type, a orthogonal belt conveyor type, and a rotating cylindrical type.
In eddy current sorting, for example, the interaction between the induced current generated inside by receiving the electromagnetic induction action of the moving magnetic field of the rotating magnet body provided on the tip side of the conveyor belt and the moving magnetic field causes the tip side of the conveyor belt. A thrust is applied to the transported waste plastic crushed material in the direction of rotation of the rotating magnet body, and the conductive material is ejected from the surface of the conveyor belt in the direction of the combined force of this thrust and the gravity acting on the conductive material to be removed. , Recover non-conductive material.
From the viewpoint of removing the conductive substance, the rotation speed of the rotating magnet body is preferably 1500 rpm or more, more preferably 3000 rpm or more, still more preferably 4500 rpm or more.

Examples of the sieving type include, but are not limited to, a vibration type, an in-plane motion type, a rotary type, and a fixed type. For sieving, the sieving product is sorted into a sieving product and a sieving product, and the sieving product whose particle size is adjusted is collected.

Further, the physical selection can be performed by combining two or more. For example, when a lightweight object selected by wind power contains a wire or a piece of metal, the wind power sorting and sieving can be performed in combination. Specifically, the light-weight items sorted by wind power are screened and sorted into a sieve upper item and a sieve lower item, and the sieve lower item is collected. In this case, the sieve mesh is preferably 5 to 30 mm, more preferably 5 to 20 mm, and even more preferably 5 to 10 mm. Further, the heavy material selected by wind power may be selected by specific gravity to be classified into a high specific density material and a low specific weight material, and the low specific weight material may be recovered. In this case, the heavy objects selected by wind power may be screened and sorted into a sieve upper item and a sieve lower item, the sieved lower item may be subjected to specific gravity sorting, and the low specific density item may be recovered.

As the physical sorting, 1 or 2 or more selected from wind power sorting, specific gravity sorting, magnetic force sorting and sieving is preferable, and 1 or 2 or more selected from wind power sorting, specific gravity sorting and sieving is more preferable.

[Water addition process]
The water addition step is a step of adding water to the crushed waste plastic. When the crushed waste plastic is physically sorted, water is added to the above-mentioned recovered material. As a result, water permeates into the center of the crushed waste plastic, and chlorine contained in the crushed material is eluted, so that chlorine can be easily removed from the crushed material in the cleaning step.
If the amount of water added to the crushed waste plastic is too large, the fluidity will decrease and handling will be impaired, while if it is too small, it will be difficult for water to penetrate into the center of the crushed material, thus removing chlorine. Will be inadequate. Therefore, the water content of the crushed waste plastic is preferably adjusted to 5 to 70% by mass, more preferably 15 to 65% by mass, further preferably 20 to 60% by mass, still more preferably 20 to 55% by mass. preferable. Here, the "moisture content" in the present specification shall be analyzed in accordance with JISZ7302-3: 1999 Waste Solidified Fuel-Part 3: Moisture Test Method.

Examples of the water include tap water specified in Annex C of JIS A 5303 and water other than the tap water (for example, river water, lake water, well water, groundwater, industrial water).
Further, the water may be any of cooling water, normal temperature water and hot water, and is not particularly limited.
The watering method may be either during transportation of the crushed material or before or after transportation as long as it is after crushing the waste plastic. For example, a method of adding or spraying water to waste plastic crushed material at the entrance of a screw conveyor, on a belt conveyor, or at a transfer point of transportation, the waste plastic crushed material is stored in a continuous or batch type agitator, and the waste plastic crushed material is stored. Examples thereof include a method of adding or spraying water to the crushed material and stirring the mixture, but the method is not particularly limited as long as the water content can be adjusted as described above.

[Standing]
In the present invention, it is preferable to allow the crushed waste plastic after the water addition step to stand for a predetermined time. As a result, the water permeates the central part of the crushed waste plastic, and the chlorine contained in the crushed material is more easily eluted, so that the removal rate of chlorine can be further increased.
For standing still, the crushed waste plastic that has been hydrated may be left as it is, and may be heated if necessary. Further, the standing time may be set so that the crushed waste plastic after hydration is transported to the cleaning device used in the next step by a transport conveyor and the elapsed time until cleaning is a predetermined time.
From the viewpoint of reducing chlorine, the standing time is preferably 10 to 1500 minutes, more preferably 20 to 900 minutes, still more preferably 30 to 600 minutes, and 45. ~ 300 minutes is even more preferable.

[Washing process]
The washing step is a step of washing the crushed waste plastic after the water addition step with water. When the crushed waste plastic after hydration is allowed to stand, the crushed waste plastic after the completion of the standing step is washed with water. As a result, chlorine can be sufficiently removed from the crushed waste plastic in which water permeates to the central part and chlorine is eluted. Further, by targeting the crushed waste plastic having a controlled major axis for cleaning, it is possible to prevent operation troubles during washing with water and improve the manufacturing efficiency.

The cleaning step is not particularly limited as long as the crushed waste plastic can be brought into contact with water, and for example, a method of accommodating the crushed waste plastic in a cleaning device and stirring it, a method of immersing the crushed waste plastic in water, and a waste plastic. A method of spraying water on the crushed material can be mentioned.
The stirring method of the cleaning device may be, for example, either a rigid type or a horizontal type, but the horizontal type is preferable from the viewpoint of chlorine removal. Further, the cleaning may be performed in two stages, or one or two or more cleaning devices may be combined.

From the viewpoint of chlorine removal and production efficiency, the amount of water used is the total amount of the solid content of the crushed waste plastic after hydration, the water content of the crushed waste plastic after hydration, and the amount of water used for cleaning. The mass ratio (solid content of crushed material / total amount of water) is preferably 1 to 30, more preferably 1.5 to 20, further preferably 2 to 10, and even more preferably 2.5 to 5. Here, in the present specification, the "solid content of the crushed waste plastic after water addition" means the residue obtained by removing the water content from the crushed waste plastic after water addition.
The cleaning time can be appropriately set depending on the amount of crushed waste plastic and the amount of water used, but is usually 2 to 30 minutes.
The water may be cooling water, normal temperature water or hot water, but hot water is preferable from the viewpoint of chlorine removal. The temperature of the water is preferably 25 to 80 ° C, more preferably 30 to 70 ° C, still more preferably 35 to 60 ° C.

[Solid-liquid separation process]
The solid-liquid separation step is a step of solid-liquid separating the crushed waste plastic after washing and recovering the solid. As a result, it is possible to recover the solid fuel having reduced chlorine as a solid substance.
The solid-liquid separation is not particularly limited as long as the solid substance and water can be separated, and examples thereof include centrifugal separation. The operation method for centrifugation may be a continuous method or a batch method.
Centrifugation includes, for example, centrifugal filtration and centrifugal sedimentation. Centrifugation may be performed a plurality of times, or a combination of centrifugal sedimentation and centrifugal filtration may be performed.

Centrifugal filtration can be performed using a centrifugal filter. There are various types of centrifugal filters, but the present process is not particularly limited. Above all, the continuous screw discharge type is preferable from the viewpoint of manufacturing efficiency.
Examples of the filter medium of the centrifugal filter include a filter cloth and a screen, but it is preferable to use a screen having a pore size of 0.05 mm or more in that solid-liquid separation can be performed efficiently.
The centrifugal force in centrifugal filtration is usually 200 to 2000 G, but from the viewpoint of production efficiency, 300 to 1500 G is preferable.

Centrifugal sedimentation can be performed using a centrifugal sedimentation machine. There are various types of centrifugal settler, but the present process is not particularly limited. Above all, the continuous decanter type is preferable from the viewpoint of manufacturing efficiency.
The centrifugal force in centrifugal sedimentation is usually 300 to 4000 G, but from the viewpoint of production efficiency, 500 to 2000 G is preferable.

The wastewater in the solid-liquid separation step may contain a large amount of fine particles. Therefore, it is possible to have a step of recovering the solid matter from the wastewater after the solid-liquid separation. For wastewater treatment, for example, a dehydrator can be used. Examples of the dehydrator include a centrifugal settler. The dehydration treatment may be performed a plurality of times.

In this way, the chlorine-reduced solid fuel of the present invention can be produced, but the obtained solid fuel is reduced not only in chlorine but also in metal. In addition, the water content is reduced to 20% by mass or less, the handling property is good, and the combustibility is excellent, so that it can be used as it is as a fuel before the kiln.
Further, it may be mixed with waste plastic, waste tatami mat, pulverized coal, waste oil and the like and used as a fuel before the kiln, and may be further put into a coal mill together with coal to be dried and crushed.

Although the present invention has been described in detail based on the embodiment thereof, the present invention is not limited to the above embodiment. The present invention can be modified in various ways without departing from the gist thereof. For example, a high specific density substance recovered by specific gravity sorting, a magnetic substance recovered by magnetic force sorting, and a conductive substance recovered by eddy current sorting may be further subjected to physical sorting. As a result, valuable metals such as gold, silver, palladium, platinum, and copper are recovered, so that a high-grade chlorine-reduced solid fuel can be produced.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

Chlorine content analysis Chlorine content was analyzed according to ISO 587 Solid minoral fuels-Determination of chlorine using Eschka mixture.

Analysis of Moisture Content Moisture content was analyzed according to JISZ7302-3: 1999 Waste Solidified Fuel-Part 3: Moisture Test Method.

The devices used in this embodiment are as follows.
(1) Crusher: Made by Oike Iron Works, Model: MHM-50R
(2) Wind power sorter: manufactured by Oike Iron Works, model: zigzag type (3) Vertical washing machine: manufactured by Satake Kagaku Kikai Kogyo, model: A720 mounted on 1m ³ tank (4) Horizontal washing machine: Ki Kosha Made, Model: KDW610 mounted in a 1m ³ tank (5) Centrifugal filter: Kotobuki Giken Kogyo, Model: N452K

The waste plastics used in this example are as follows.
・ Raw material A: Automobile shredder dust (source A company)
・ Raw material B: Automobile shredder dust (source B company)
-Raw material C: Shredder dust including waste home appliances, vending machines and OA equipment (discharge source C company)

Examples 1-5
(Heating process, crushing process)
The raw materials A to C were heated under the conditions shown in Table 1 and then crushed by a hammer crusher equipped with a 30 mm screen. Next, using a zigzag type wind power sorter, the crushed waste plastic was sorted into heavy and lightweight materials under the condition of a wind speed of 10 m / s, and the lightweight materials were collected. Then, the chlorine content of the lightweight material was analyzed. The results are shown in Table 1.

(Water addition process, cleaning process)
After adding water to a lightweight substance so that the water content was 25% by mass, the mixture was allowed to stand for 1 hour. Next, the lightweight material after water addition was washed with warm water at 50 ° C. using the washing equipment of the method shown in Table 2. Then, it was dehydrated by a filter cloth type centrifugal filter, separated into a solid and a filtrate, and the solid was recovered as a solid fuel. Then, the chlorine content of the solid fuel was analyzed. As for the amount of water added, the water content of the lightweight material after water addition was analyzed. The amount of water used in the washing step is the mass ratio of the solid content of the crushed waste plastic after water addition to the water content of the crushed waste plastic after water addition and the total amount of water used for washing. (Solid content of crushed material / total amount of water) was set to 3. Furthermore, the presence or absence of floating substances on the water surface during washing was observed. These results are shown in Table 2.

Comparative Example 1
The solid fuel was produced by the same operation as in Example 1 except that the water addition step was not performed. Table 2 shows the observation results of the presence or absence of floating substances on the water surface during washing, the analysis results of the water content of the lightweight substances after water addition, and the chlorine content of the solid fuel.

Examples 6-10
In the water addition step, a solid fuel was produced by the same operation as in Example 3 except that water was added to the lightweight material so as to have the water content shown in Table 3. Table 3 shows the observation results of the presence or absence of suspended matter on the water surface during washing, the analysis results of the water content of the lightweight material after water addition, and the chlorine content of the solid fuel, together with the results of Example 3.

Examples 11 to 15
A solid fuel was produced by the same operation as in Example 3 except that the lightweight product after water addition was allowed to stand for the time shown in Table 4. Table 4 shows the observation results of the presence or absence of suspended matter on the water surface during washing, the analysis results of the water content of the lightweight material after water addition, and the chlorine content of the solid fuel, together with the results of Example 3.

From Table 2, it can be seen that by heating and crushing the waste plastic, adding water to the crushed waste plastic, and washing the crushed waste plastic after hydration with water, a solid fuel with reduced chlorine can be efficiently produced. Further, from Table 3, it can be seen that chlorine in the solid fuel can be further reduced by setting the amount of water added to the crushed waste plastic to a certain amount or more. Further, from Table 4, it can be seen that chlorine in the solid fuel can be further reduced by washing the crushed waste plastic hydrated with water after allowing it to stand for a certain period of time.

Claims (4)

A heating process that heats waste plastic,
A crushing process that crushes waste plastic after heating,
Includes a cleaning process to wash crushed waste plastic with water
It has a watering step of adding water to the crushed waste plastic after the crushing step and before the washing step.
Manufacturing method of chlorine-reduced solid fuel. The method for producing a chlorine-reduced solid fuel according to claim 1, wherein the water content of the crushed waste plastic is adjusted to 5 to 70% by mass in the water addition step. The method for producing a chlorine-reduced solid fuel according to claim 1 or 2, wherein the cleaning step is performed after a predetermined time has elapsed from the end of the water addition step. The method for producing a chlorine-reduced solid fuel according to any one of claims 1 to 3, further comprising a sorting step of collecting crushed waste plastic having a major axis of a predetermined value or less by physical sorting after the crushing step and before the water addition step. ..