JP7413991B2 - Waste plastic pretreatment method and pretreatment device - Google Patents

Description

The present invention relates to a waste plastic pretreatment method and pretreatment device.

BACKGROUND ART Conventionally, fluidized bed incinerators have been widely used as incinerators that completely burn materials to be incinerated, such as sludge, efficiently, reliably, and in a short time. The dehydrated sludge that is incinerated in this fluidized bed incinerator has a high water content even after dehydration, so it often does not self-combust. In addition, fossil fuels such as kerosene, city gas, and A heavy oil are used as combustion aids and burned within the sand layer, but there is a problem in that the operating costs are high.

On the other hand, it is a well-known fact that the treatment of waste plastic has become an issue in recent years, and there is a need for a place where it can be used effectively. Therefore, Patent Document 1 proposes incinerating waste plastics and sludge in a mixed state in a fluidized bed sludge incinerator. According to this patent document 1, when incinerating sludge, waste plastic can be effectively used as a combustion aid and disposed of.

Japanese Patent Application Publication No. 11-182834

In addition, in the case of solid combustion auxiliary materials such as the waste plastic disclosed in Patent Document 1, it is physically difficult to blow directly into the sand layer of the fluidized bed like fluid fossil fuels, so it is difficult to directly blow into the sand layer of the fluidized bed. It is necessary to supply the fluidized bed from the upper part of the sludge incinerator (at least above the fluidized bed formation area).

However, since the specific gravity of waste plastic itself is smaller than that of sand particles in the fluidized bed, it quickly burns near the surface of the fluidized bed (top of the bed) while it descends into the fluidized bed. Although the temperature of the freeboard area, which is the space above the sand layer, increased, heat transfer to the entire sand layer was not good. Therefore, there was a problem in that the temperature of the fluidized bed decreased, causing problems in the combustion of sludge. Furthermore, since waste plastics contain a certain amount of chlorine unevenly, depending on the waste plastic used, the concentration of hydrogen chloride generated during incineration may increase in the short term, and the after-combustion equipment after the furnace exit may increase. The problem was that corrosion progressed.

The present invention was made in view of the above circumstances, and it minimizes the impact on after-combustion equipment, and also allows waste plastic as a combustion aid to quickly reach the inside of the fluidized bed in the furnace. An object of the present invention is to provide a waste plastic pretreatment method and a pretreatment device that can improve the efficiency of heat transfer to a fluidized bed.

According to the present invention, the above-mentioned problems are solved by the following waste plastic pretreatment method and waste plastic pretreatment apparatus.

<Pretreatment method for waste plastic>
A method for pre-treatment of waste plastics to be supplied as a combustion aid to a fluidized bed incinerator includes a crushing step of crushing the waste plastics with a crusher to obtain crushed waste plastics, and extracting polyvinyl chloride from the crushed waste plastics. a first separation step in which a waste plastic molded object is obtained by separating and removing it with a first specific gravity separator; and a compression molding step in which the waste plastic molded object is compressed and molded in a compression molding machine to produce a waste plastic molded object. , the waste plastic moldings are separated into high specific gravity waste plastic moldings with an apparent specific gravity of 0.7 g/cm ³ or more and low specific gravity waste plastic moldings with an apparent specific gravity of less than 0.7 g/cm ³ by a second specific gravity separator. a second separation step of separating the high-density waste plastic moldings into the waste plastics and selecting the high-density waste plastic moldings as a combustion aid to be supplied to the fluidized bed incinerator.

In the present invention, the low specific gravity waste plastic molded product separated in the second separation step may be returned to the compression molding machine and compression molded again in the compression molding step to produce the high specific gravity waste plastic molded product. preferable.

<Waste plastic pre-treatment equipment>
A device for pre-processing waste plastics to be supplied as a combustion aid to a fluidized bed incinerator, which includes a crusher for crushing the waste plastics into crushed waste plastics, and a crusher for separating polyvinyl chloride from the crushed waste plastics. a first specific gravity separator that removes the waste plastic molded material to obtain a waste plastic molded product; a compression molding machine that compression molds the waste plastic molded material to produce a waste plastic molded product; is separated into high specific gravity waste plastic moldings with an apparent specific gravity of 0.7 g/cm ³ or more and low specific gravity waste plastic moldings with an apparent specific gravity of less than 0.7 g/cm ³ , and the high specific gravity waste plastic moldings are placed in the fluidized bed. A pre-treatment device for waste plastics, comprising a second gravity separator selected as a combustion aid supplied to a type incinerator.

According to the present invention, the influence on after-combustion equipment is minimized, and the waste plastic as a combustion aid quickly reaches the inside of the fluidized bed in the furnace, improving the efficiency of heat transfer to the fluidized bed in the furnace. It is possible to provide a pretreatment method and a pretreatment device for waste plastics.

1 is a configuration diagram showing a sludge incinerator and exhaust gas treatment equipment according to an embodiment of the present invention. FIG. 1 is a configuration diagram of a waste plastic pretreatment device.

Embodiments of the present invention will be described below based on the accompanying drawings.

FIG. 1 shows the configuration of a sludge incinerator (hereinafter referred to as "incinerator") 1 and exhaust gas treatment equipment that use waste plastic combustion improver material that has undergone a pretreatment process in this embodiment. In this embodiment, the incinerator 1 is a fluidized bed type incinerator that forms a fluidized bed with a sand layer.

In FIG. 1, on the downstream side of the incinerator 1, there is a heat exchanger 3 for recovering heat from the exhaust gas exhausted from the incinerator 1, a dust removal device 4 for removing dust from the exhaust gas, and a smoke scrubber 5 for cleaning the exhaust gas after dust removal. are arranged in sequence. As shown in FIG. 1, the heat exchanger 3 is connected to the exhaust section 1A of the incinerator 1 through a flue A, and the dust removal device 4 is connected to the heat exchanger 3 through a flue B. The smoke washing tower 5 is connected to the dust removal device 4 through a flue C. Further, a flue D extends from the smoke washing tower 5, and the smoke washing tower 5 is connected to a chimney (not shown) located on the downstream side.

The side wall of the furnace body 1-0 of the incinerator 1 includes a sludge supply section 1B that receives sludge as a material to be incinerated from the outside and supplies it into the furnace body 1-0, and a sludge supply section 1B that receives combustion aid from the outside and supplies the sludge to the furnace body 1-0. A combustion auxiliary material supply section 1C is provided for supplying the fuel into the combustion chamber -0. The combustion aid supply section 1C includes a fossil fuel supply section 1C-1 that supplies a fossil fuel combustion aid and a waste plastic supply section 1C-2 that supplies a waste plastic combustion aid. As seen in FIG. 1, the sludge supply section 1B is provided at the top of the furnace body 1-0. The fossil fuel supply section 1C-1 is located in the middle of the furnace body 1-0 in the vertical direction, and is located slightly below the surface (upper surface) of the sand layer (fluidized bed) in the furnace body 1-0. . The waste plastic supply section 1C-2 is located in the middle of the furnace body 1-0 in the vertical direction, and is located slightly above the surface of the sand layer within the furnace body 1-0. The combustion auxiliary material supply section 1C is provided with a regulator 1J such as a valve that adjusts the supply amount of the combustion auxiliary material. The regulator 1J includes a fossil fuel supply regulator 1J-1 connected to a fossil fuel supply unit 1C-1 and a waste plastic supply amount regulator 1J-2 connected to a waste plastic supply unit 1C-2. ing.

The waste plastic supply unit 1C-2 is connected to a pre-treatment device 2, which will be described later, which pre-processes waste plastic as a raw material to give it properties suitable as a combustion aid before supplying it to the furnace main body 1-0. It is designed to receive waste plastic combustion aid after pretreatment.

Inside the furnace body 1-0 of the incinerator 1, a plate-shaped air-permeable member 1E is provided at a position directly above the bottom wall 1D of the furnace body 1-0, and the sand stored on the air-permeable member 1E A sand layer is formed. The sand forming the sand layer is, for example, silica sand. Combustion air is introduced from the outside into the lower space 1F located below the air permeable member 1E via the air inlet part 1G, and the introduced air passes through the air permeable holes of the air permeable member 1E. and flowing into the sand layer. The sand layer on the air-permeable member 1E is fluidized by the air passing through the air-permeable member 1E to form a fluidized bed 1H.

FIG. 2 is a configuration diagram of the waste plastic pretreatment device 2. As shown in FIG. The pretreatment device 2 includes a crusher 2A that appropriately crushes waste plastic PO as a raw material to produce crushed waste plastic P1, and a crusher 2A that separates and removes polyvinyl chloride (PVC) with a high specific gravity from the crushed waste plastic P1. A first specific gravity separator 2B that obtains a waste plastic molded product P2, a compression molding machine 2C that receives and compression molds the waste plastic molded product P2 to obtain a waste plastic molded product P3, and a compression molding machine 2C that obtains a waste plastic molded product P3. It has a second specific gravity separator 2D that separates high specific gravity waste plastic moldings P4 having a predetermined apparent specific gravity or more and low specific gravity waste plastic moldings P5 having less than a predetermined apparent specific gravity. The second specific gravity separator 2D selects and discharges the high specific gravity waste plastic molded product P4 as a combustion aid supplied to the incinerator 1, while returning the low specific gravity waste plastic molded product P5 to the compression molding machine 2C.

In this pre-processing device 2, waste plastic PO as a raw material to be pre-processed is first fed into the crusher 2A and crushed to produce crushed waste plastic P1 of an appropriate size for molding (crushed process ). Here, the waste plastic PO is a mixture of various types of plastics, such as polyethylene (PE), polypropylene (PP), and PET. Moreover, PVC containing a large amount of chlorine is also mixed in this waste plastic PO.

PVC is mixed in the waste plastic crushed material P1 obtained by the crusher 2A. This PVC contains a large amount of chlorine, and when burned in an incinerator, increases the concentration of hydrogen chloride in the exhaust gas, so it is not suitable as a combustion auxiliary material. Since this PVC has a higher specific gravity than other plastics, it is separated and removed by the first specific gravity separator 2B (first separation step). Regarding the first specific gravity separator 2B, there is no limitation on the specific gravity separation method, but for example, an air table (not shown) can be used as the specific gravity separator. In this air table, a waste plastic crushed material P1 is placed on a porous inclined plate, and while the inclined plate is vibrated in a direction parallel to the plate surface, air is caused to flow from below the inclined plate. A buoyant force is applied to the crushed waste plastic material P1 to separate heavy objects in the crushed waste plastic material P1 upward and light objects downward. In this embodiment, by separating and removing PVC as a heavy object, other lightweight waste plastics are obtained as the waste plastic molded object P2. This waste plastic molded object P2 is sent to a compression molding machine 2C.

In this manner, in this embodiment, since PVC is removed by the first specific gravity separator 2B, the amount of PVC contained in the combustion auxiliary material supplied into the incinerator 1 is significantly reduced. As a result, the concentration of hydrogen chloride generated in the furnace is reduced, and the progress of corrosion of the after-combustion equipment after the furnace exit can be suppressed.

The compression molding machine 2C is a device that compresses the waste plastic molded material P2 to increase the specific gravity and makes it into granules of an appropriate size in the compression molding process, and the format is not limited, but for example, a ring die is used. A type molding machine (not shown) can be used.

The ring die type molding machine serving as the compression molding machine 2C has a cylindrical rotary die, a roller that rolls at a fixed position in contact with or close to the inner surface of the rotary die, and a cutter located on the outer surface of the rotary die. The rotary die is formed with forming holes penetrating in the radial direction at a plurality of positions in the circumferential direction. In this molding machine, when the granular waste plastic to be molded P2 is put into the inside of the rotary die, the waste plastic to be molded P2 is pressed by the roller on the inner surface of the rotary die, and as the rotary die rotates, It is extruded from the forming hole to the outer surface of the rotary die. The compression molded product extruded from the molding hole of the rotary die is cut by a cutter that moves relative to the rotary die as the rotary die rotates, resulting in a waste plastic molded product P3 of a predetermined size. The size of the waste plastic molded product P3 can be set to a predetermined value by changing the position of the cutter with respect to the outer surface of the rotary die.

The waste plastic molded product P3 of a predetermined size falling from the outer surface of the rotary die is sent to the second specific gravity separator 2D. As the second specific gravity separator 2D, a device based on the same principle as the first specific gravity separator 2B can be used. The second specific gravity separator 2D separates the waste plastic molded product P3 into a high specific gravity waste plastic molded product P4 having a predetermined apparent specific gravity or more and a low specific gravity waste plastic molded product P5 having less than a predetermined apparent specific gravity (second separation step ). The second specific gravity separator 2D selects and discharges the high specific gravity waste plastic molded product P4 as a combustion auxiliary material to be supplied to the incinerator 1.

In this embodiment, the above-mentioned predetermined apparent specific gravity is set to 0.7 g/cm ³ . The reason is that if the apparent specific gravity of the waste plastic molding is 0.7 g/ ^cm3 or more, after being supplied to the incinerator 1 as a combustion aid, it will reach the inside of the fluidized bed in the furnace sufficiently and quickly, and the This is because the heat transfer efficiency to the layer can be improved. The upper limit of the apparent specific gravity of the high specific gravity waste plastic molded product P4 is approximately equal to the true specific gravity of the main plastic contained in the high specific gravity waste plastic molded product P4. For example, when the main plastic component of the high specific gravity waste plastic molding P4 is PE or PP, the upper limit of the apparent specific gravity is about 0.98 g/cm ³ .

The high specific gravity waste plastic molded product P4 discharged from the second specific gravity separator 2D has its supply amount adjusted by the waste plastic supply amount regulator 1J-2, and is supplied into the incinerator 1 by the waste plastic supply section 1C-2. Ru. On the other hand, the low specific gravity waste plastic molded product P5 is returned to the compression molding machine 2C and is again used to generate the waste plastic molded product P3.

Next, a procedure for incinerating sludge using the incinerator 1 in this embodiment having such a configuration will be explained.

A furnace body 1-0 of the incinerator 1 contains sand for forming a fluidized bed 1H on an air-permeable member 1E. Combustion air sent into the lower space 1F from the outside via the air inlet part 1G passes through the air permeable member 1E and rises, causing sand to flow on the air permeable member 1E and form a fluidized bed 1H. It is formed.

Fossil fuel combustion aid material is supplied from the fossil fuel supply section 1C-1, and waste plastic combustion aid material, that is, high specific gravity waste plastic molded product P4, is supplied from the waste plastic supply section 1C-2 into the furnace main body 1-0. Since the fluidized bed 1H is in a predetermined high temperature state. In this embodiment, the fossil fuel combustion aid is used as an auxiliary to the waste plastic combustion aid, and the waste plastic combustion aid is mainly used as much as possible.

Sludge is supplied falling from the sludge supply section 1B toward the fluidized bed 1H. The sludge is burned while flowing together with the sand in the high-temperature fluidized bed 1H. Exhaust gas generated by combustion of sludge passes through the flue A from the exhaust section 1A, recovers heat in the heat exchanger 3, passes through the flue B, is removed by a dust remover 4, and further passes through the flue C. After being washed in the smoke washing tower 5, the smoke passes through the flue D and is released into the atmosphere from the chimney in a harmless state.

2 Pretreatment device 2A Crusher 2B First gravity separator 2C Compression molding machine 2D Second gravity separator PO Waste plastic (raw material)
P1 Crushed waste plastic P2 Waste plastic molded product P3 Waste plastic molded product P4 High specific gravity waste plastic molded product P5 Low specific gravity waste plastic molded product

Claims (3)

In a pretreatment method for waste plastics that are supplied as combustion aids to fluidized bed incinerators,
a crushing step of crushing the waste plastic with a crusher to produce crushed waste plastic;
a first separation step of separating and removing polyvinyl chloride from the crushed waste plastic material using a first specific gravity separator to obtain a waste plastic molded product;
a compression molding step of producing a waste plastic molded product by compression molding the waste plastic molded product using a compression molding machine;
The waste plastic moldings are separated into high specific gravity waste plastic moldings with an apparent specific gravity of 0.7 g/cm ³ or more and low specific gravity waste plastic moldings with an apparent specific gravity of less than 0.7 g/cm ³ by a second specific gravity separator. a second separation step of separating the high-density waste plastic moldings into two parts, and selecting the high-density waste plastic moldings as a combustion aid to be supplied to the fluidized bed incinerator;
A method for pre-processing waste plastic. A claim characterized in that the low specific gravity waste plastic molded product separated in the second separation step is returned to the compression molding machine and compression molded again in the compression molding step to produce the high specific gravity waste plastic molded product. The method for pre-processing waste plastic according to item 1. In equipment that pre-processes waste plastics that are supplied as combustion aids to fluidized bed incinerators,
a crusher that crushes the waste plastic to produce crushed waste plastic;
a first specific gravity separator that separates and removes polyvinyl chloride from the crushed waste plastic material to obtain a waste plastic molded product;
a compression molding machine that compresses the waste plastic molded material to produce a waste plastic molded product;
The waste plastic moldings are separated into high specific gravity waste plastic moldings with an apparent specific gravity of 0.7 g/cm ³ or more and low specific gravity waste plastic moldings with an apparent specific gravity of less than 0.7 g/cm ³ . a second gravity separator that selects the gravity waste plastic molded material as a combustion auxiliary material to be supplied to the fluidized bed incinerator;
A waste plastic pre-treatment device with

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