JP4594607B2 - Separating and collecting plastic waste - Google Patents

Description

  The present invention makes the separation more efficient by passing the garbage collected in plastic bags from the waste generated from citizens' life and the container and packaging materials for food that are collected separately to the fermentation processing equipment. The present invention relates to a separation and recovery method.

Currently, mixed waste made of garbage, paper, fiber, wood, metal, plastic, etc., discharged from ordinary households is collected under the responsibility of each local government, and many of them are incinerated.
Mixed waste discharged from ordinary households once contained plastics such as vinyl chloride, but because it is a causative substance that generates dioxins harmful to the human body during the incineration process,
The need to suppress the use of vinyl chloride products and separate discharge has come to be desired.
Also, many plastic bags have been switched to those made of polyethylene or polypropylene that do not contain chlorine.

In this way, due to an increasing concern for environmental issues and increased recycling momentum, the form of garbage collection is changing from mixed garbage collection based on incineration to separate collection based on recycling. The current general waste collection includes (1) garbage, paper, plastic, fiber, wood and bamboo, etc., which are combustible materials suitable for incineration, and (2) glass, metal, which is non-burnable waste, (3) There are about 4 types of wastes, such as dry batteries, fluorescent lamps, and (4) furniture, electrical products and other oversized garbage.
The degree of separation varies depending on the local government, but in recent years, there are some local governments that have started sorting plastics for so-called used containers and packaging such as food trays, packaging bags, and lunch boxes.
By the way, plastic bags are hygienic and low in cost because sewage and odors generated from garbage are not leaked, so they are used as garbage collection bags in each household and for collection when the local government collects them. As a bag, it is still widely used today.

Garbage discharged from ordinary households has a high moisture content and is not very valuable as a fuel. On the other hand, plastic garbage for bags, containers and packaging has a high calorific value and high value as a fuel. Therefore, if biodegradable garbage such as garbage is separated from plastic garbage, plastic garbage can be effectively reused as fuel, and such needs are high.
In addition to waste discharged from ordinary households, used containers and packaging plastic contained in garbage discharged from convenience stores and the food service industry are calling for thorough washing with water. Separation collection after completely removing oils is difficult as a real problem, and there is a problem that decay occurs during storage, leading to generation of odors and pests, creating an unsanitary environment .

An example of a method for treating garbage in which a plastic for containers and packaging or a plastic bag and a biodegradable material such as garbage is mixed as described above is disclosed in Patent Document 1, for example. In Patent Document 1, a bag containing garbage and the like is mechanically crushed and sorted according to size, and organic matter is subjected to fermentation processing, combustible material is converted into solid fuel, and the like, and the efficiency of processing mixed waste We are trying to make it.
JP 9-24360 A

  Originally, it would be desirable to separate raw garbage from plastic waste at the discharge stage, and to select a treatment method according to each. However, as a matter of fact, further separation is difficult. However, mixed discharge of garbage and plastic waste is expected to continue.

  The present invention has been made in view of the above-mentioned problems of the prior art, and is mixed garbage (used for container packaging of foods) made of garbage, paper, fiber, wood, plastic, etc., discharged from ordinary households. It is an object of the present invention to provide a means for separating and collecting plastics more hygienically and economically (including waste plastics) and more effectively reusing mixed waste in which plastics and biodegradable materials are mixed.

  The present inventors separated the mixed waste, which is a mixture of plastic and biodegradable material, into a part mainly composed of plastic and a part mainly composed of non-plastic after fermentation treatment, not before fermentation treatment, It was found that the separation between the two becomes more efficient.

That is, the invention described in claim 1 is a fermentation apparatus in which mixed waste containing at least a plastic and a biodegradable material is adjusted so that the ratio of carbon to nitrogen (C / N) is 30 to 40. From the end opposite to the supply end of the mixed waste in the above, after being fermented and decomposed with air flowing in such a flow rate that the oxygen concentration in the exhaust gas is 15 to 20% by volume , the plastic is A plastic recovery method characterized by separating a main part and a non-plastic main part.

  The means for separating the portion mainly made of plastic and the portion mainly made of non-plastic may be at least one selected from sieve sorting, wind sorting, and submergence sorting (Claim 2).

  The biodegradable material may be at least one of food residue, animal manure, vegetation, woody material, paper, fiber, and sewage sludge.

In the present invention, the mixed waste containing at least the plastic and the biodegradable material is adjusted so that the carbon to nitrogen ratio (C / N) is 30 to 40, and then the mixed waste supply end in the fermentation apparatus. From the end opposite to the part, after being fermented and decomposed while circulating air at a flow rate such that the oxygen concentration in the exhaust gas is 15 to 20% by volume , the part mainly composed of plastic and the non-part It may be divided into parts mainly made of plastic, and each may be burned using a burner. By this method, the mixed waste in which the plastic and the biodegradable material are mixed can be used more effectively as fuel.

Moreover, after adjusting the mixed waste containing at least a plastic and a biodegradable substance so that the ratio of carbon to nitrogen (C / N) is 30 to 40, what is the supply end of the mixed waste in the fermentation apparatus? From the opposite end , after being fermented and decomposed while circulating air at a flow rate such that the oxygen concentration in the exhaust gas is 15 to 20% by volume , mainly plastic and non-plastic mainly And may be used as raw materials for gasification (claim 5).

Conventionally, there has been no technical idea for actively separating and recovering plastic from mixed waste made of garbage, paper, fiber, wood, plastic, etc. discharged from ordinary households. Further, in the case of waste plastics used for food containers and packaging, even if separated, it has been a cause of unsanitary environment due to the decay of food waste adhering.
According to the present invention, instead of fermenting after separating the mixed waste in which the plastic and the biodegradable material are mixed, by performing fermentation first, even when food waste or the like is attached, it is sanitary due to spoilage. Without causing the above problems, mechanical crushing of plastics and biodegradation of biodegradable materials can be performed at the same time. As a result, it is possible to economically and easily separate and collect plastic waste with high value as fuel. it can.

Next, an example of the present invention will be described with reference to the flowchart of the steps in FIG.
In the present invention, at least a mixed waste in which a plastic and a biodegradable material are mixed (hereinafter, simply referred to as “mixed waste”) is an object to be treated. Examples of such mixed waste include garbage that is discharged from ordinary households, such as garbage, paper, fiber, wood, metal and plastic, which are stored in plastic bags, Collected by a collection and transportation vehicle from a contractor commissioned by the local government. In the present invention, waste plastics used for food containers and packaging are also included in the object to be treated as mixed waste. Waste plastics used for food containers and packaging include those that are separated and discharged from ordinary households and collected by collection vehicles from local governments or contractors entrusted by local governments, those that are discharged from convenience stores, the restaurant industry, etc. is there. Waste plastics are attached to waste plastic used for food containers and packaging. If this food waste is fermented together with the containers and packaging plastics, the subsequent separation and recovery of the containers and packaging plastics becomes easy.

  The collected mixed waste is first put into a fermentation treatment apparatus. At this time, the biodegradable material contained, particularly food waste adhering to the plastic surface, should be immediately put into the fermentation treatment apparatus so as not to proceed. At the time of charging, other biodegradable materials may be added to the mixed waste and fermented. When the target mixed waste is mainly waste plastic used for food containers and packaging, and the amount of adhering food waste is insufficient, the entire waste can be mixed by adding other biodegradable materials. Fermentation is surely made. The mixed waste and other biodegradable organisms may be charged into the fermentation treatment apparatus separately, or both may be mixed prior to charging. Depending on the size of the garbage, it is also preferable to perform cutting or grinding.

  Examples of biodegradable waste that is fermented with mixed waste include food residues, animal manure, vegetation, wood, paper, fiber, and sewage sludge.

  Fermentation equipment is not limited to paddle type fermenters, scoop type with mechanical turning function, auger type horizontal fermenter, or rotary kiln type rotary fermenter, vertical paddle type, trapdoor type, silo type Any of a vertical fermenter such as a batch fermenter or a batch type box fermenter can be used. In these fermenters, in consideration of continuous operation of the process, it is preferable to use a rotary kiln type rotary fermenter.

In order to perform efficient fermentation, the mixed waste supplied to the fermentation treatment apparatus is adjusted to have a moisture content of 40 to 70% by weight, preferably 50 to 60% by weight. Moreover, it is preferable to adjust by adding animal excrement, urea, etc. so that the ratio (C / N) of carbon and nitrogen may be 30-40.
Alternatively, the ratio of the plastic and the biodegradable material may be adjusted appropriately, and the entire mixed waste may be mixed well beforehand so that the biodegradable material is uniformly attached to the outer surface of the plastic. Thereby, fermentation can be performed more efficiently.

  A rotary kiln-type fermentation treatment device is equipped with a rake mechanism, and out of the supplied mixed waste, household waste, including raw garbage collected in plastic bags, is immediately broken into plastic bags / Containers and garbage and other biodegradable garbage are separated. Plastics are also gradually reduced in size due to the effects of physical contact and partial biodegradation. At this time, even if biodegradable materials such as food waste adhere to the outer surface of the plastic, it is efficiently removed from the outer surface of the plastic due to its own fermentation and scraping effect by other biodegradable waste. Removed. A part of the biodegradable material including plastic waste and plastic in the mixed waste is subjected to a fermentation process after a residence time of about 3 days by the action of a fermentation microorganism added in advance.

  In order to promote the fermentation treatment, air is circulated from the end opposite to the supply end of the mixed waste in the fermentation treatment apparatus. The amount of circulation is such that the oxygen concentration in the exhaust gas is 15 to 20% by volume. It is preferable to circulate. Since exhaust gas contains odor components, ammonia gas, etc., it can be incinerated or used as combustion air for other combustors.

  The fermented mixed waste is discharged from the discharge end of the fermenter, and the fermented waste is wrapped in wrap sheets, plastic packaging containers, food trays, beverage containers and caps, and those It becomes a mixture of the crushed material and the powdery material that has undergone the fermentation treatment. Depending on the initial state of the mixed waste, it may contain metals such as empty cans and stainless steel spoons.

The fermented waste is passed through a crusher, a magnetic separator, a stainless steel separator, and an aluminum separator as necessary to remove the metal. In particular, magnetic separators remove dry batteries, crowns, metal scrubbers, razor blades, stainless steel separators remove spoons, knives, forks, etc., and aluminum separators remove aluminum cans and sheets.
If the garbage is thoroughly collected and collected at home and there is almost no contamination of iron products such as empty cans, the magnetic sorting process, stainless steel sorting process, and aluminum sorting process can be omitted.

  The fermented waste from which the metal has been removed is composed of cut plastic waste and powdered waste after the biodegradable material has been fermented. This is supplied to a trommel (screen), and is divided into a part mainly composed of plastic dust that does not pass through the sieve and a part mainly composed of non-plastic that passed through the sieve. In the fermentation process, the plastic-based part is smaller than the original size due to cutting and partial biodegradation, but the non-plastic-based part (after the biodegradable product has been fermented) It is still large compared to powdered waste). Therefore, both can be easily separated by the trommel. Here, the “parts mainly made of plastic” and the “parts mainly made of non-plastic” are not strict, and may be considered simply as a part that does not pass through the sieve and a part that does not pass through the sieve. As described above, since plastic waste and the others produce a significant difference in size during the fermentation process, most of the plastic remains on the sieve, and most of the plastic other than the plastic passes through the sieve.

The opening of the sieve may be 40 mm or less, more preferably 20 mm or less, and even more preferably 10 mm or less, and the plastic recovery rate is further improved. The lower limit of the sieve opening is preferably about 5 mm because clogging is likely to occur if it is too fine. In order to perform the separation by the trommel, it is preferable to sample the fermented waste from which the metal has been removed, and select the sieve opening after confirming the particle size ranges of plastic and non-plastic. As the sorting means, instead of the trommel, a vibrating screen, a wind sorter, a repulsive sorter, an electrostatic sorter, a submerged sorter, etc. can be employed. Even when using a separation means other than Trommel, as described above, after sampling the fermented waste from which the metal has been removed, and confirming the particle size ranges of plastic and non-plastic, separation by each separation means It is good to set conditions. In the case of submerged sorting, it is based on the principle that plastic floats in water and powdery waste mainly composed of non-plastic sinks in water.
The fermented waste from which the metal has been removed should be crushed before being supplied to Trommel, and adjusted so that the powdered waste after fermenting the biodegradable material has an appropriate size for the sieve used. It does not matter. A sufficient time can be allocated to the fermentation treatment step, and the crushing step can be omitted in the case where the powdered waste after the biodegradable material is fermented in the fermentation treatment apparatus can be achieved.
In this way, waste mainly composed of plastic is collected from mixed waste made of garbage, paper, fiber, wood, metal, plastic, and the like discharged from ordinary households.

The fermented waste from which the metal has been removed can be used as a fuel for recovering thermal energy by supplying it to a burner by air transportation means and burning it by blowing it toward a high-temperature combustion field. If the mixed waste discharged from ordinary households does not contain coarse metals, the fermented waste discharged from the fermenter can be used as fuel, but the main part is plastic and non-plastic. After separating the parts to be processed, it is better to use them separately as fuel. In particular, the plastic-based part is bulky and contains a chlorine component, so it should be dechlorinated while being reduced in volume by compression or heating, pulverized again, and finely divided into fuel for the burner. .
On the other hand, since the portion mainly composed of non-plastic discharged from the fermentation treatment apparatus has a relatively high water content, it is preferable to carry out a drying treatment prior to fuel conversion.

Further, the fermented garbage can be used as a raw material for gasification. It is preferable that after separating the part mainly made of plastic and the part mainly made of non-plastic, they are separated into gasified fuels. In particular, the portion mainly made of plastic has a large calorific value, and when it is intended to generate fuel gas with a large amount of heat, it is preferable to separate only the portion of garbage mainly made of plastic and use it as gasified fuel.
In addition, if it is used as a raw material for gasification, the mixing of some metals will not be a problem, so the fermentation process waste discharged from the fermentation processing equipment is mainly made of plastic without going through the metal removal process. And a portion mainly composed of non-plastic, and each can be used as gasified fuel as it is. At this time, it is also possible to solidify a portion mainly composed of plastic to obtain a gasified fuel. Solidification is more preferable because the quantitative supply to the gasifier is improved and the generation of dust inside the gasifier is suppressed.

In Example 1, mixed waste discharged from ordinary households of a municipality with a population of about 54,000 who are performing separate collection was used. The mixed garbage was received in a bucket-shaped receiving facility called a skip conveyor from a municipal collection and transport vehicle while being stored in a plastic bag.
The composition of the mixed waste discharged from ordinary households is shown in Table 1. Raw garbage and paper / cloth accounted for about 50% and 32%, respectively. The main plastics were wrap sheets, packaging containers, food trays and beverage containers. Non-combustible components included metals such as beverage container caps, empty cans, and stainless steel spoons.
The water content was 50%, and the higher heating value was 9500 KJ / kg.

The mixed waste collected by the plastic bag was fed from the skip conveyor directly to the fermentation treatment apparatus at a rate of 60 tons per day. The fermentation treatment apparatus used was a rotary kiln type having an inner diameter of 4.6 m, a length of 60 m, and an inclination of 1 °. The interior of the fermentation treatment apparatus was divided into four chambers by openable partition plates, and each room was equipped with a raked blade.
The rotation speed of the rotary kiln was set to 0.5 rotations per minute, and the fermentation treatment was performed for about 3 days.

  During the fermentation treatment, air was circulated from the end opposite to the supply end of the mixed waste so that the oxygen concentration in the exhaust gas was 15% by volume. The exhaust gas from the rotary kiln-type fermentation treatment equipment is used as combustion air for the main fuel of the adjacent rotary kiln for manufacturing Portland cement, and incinerated so that odors and ammonia gas in the exhaust gas do not leak to the surrounding environment. Processed.

  The fermented mixed waste discharged from the discharge end of the fermentation treatment apparatus passed through a magnetic sorter, a stainless steel sorter, and an aluminum sorter in this order to remove metals contained in the mixed waste. Subsequently, it was passed through a crusher and cut into sheet-like and string-like plastic waste, paper / cloth waste.

The fermented mixed waste that has been subjected to metal removal and pulverization is supplied to a trommel (screen) having a screen diameter of 10 mm, and the portion that does not pass through the screen (mainly plastic waste), and the screen It was separated into the parts that pass through (mainly non-plastic). The portion mainly composed of non-plastic was powdered by the fermentation process and easily passed through the sieve.
As a result, about 100 parts by weight of the mixed waste discharged from a general household, about 23 parts by weight mainly of plastic waste that does not pass through the sieve and about 61 parts of mainly non-plastic that passes through the sieve. The weight part could be separated. The high calorific values of the part mainly composed of plastic dust not passing through the sieve and the part mainly composed of non-plastic passing through the sieve were 21900 KJ / kg (wet base) and 6600 KJ / kg (wet base), respectively. .

  In this way, mechanical waste bags and biodegradation of plastics can be achieved at the same time by mixing mixed waste that is stored in plastic bags and discharged from ordinary households through fermentation treatment equipment, and mixing after fermentation treatment is achieved. The plastic waste could be easily separated and collected from the waste.

Example 2: The non-plastic-based part (powder product) that passed through the sieve by the trommel separation in Example 1 was stored in a hopper container after drying.
The equipment of Example 2 is a powder installed in parallel with a storage hopper, a quantitative cutting device, an air supply equipment for pneumatically transporting the powdered product, a pipe connected to the burner, and a main burner of a kiln for cement firing. A special burner was used to blow the product into the kiln.
The powdery product was cut out from the storage hopper at a rate of 0.5 tons per hour and blown into the kiln front of the cement fired kiln by pneumatic transportation. The powdery product could be burned by forming a stable flame in the rotary kiln space. As a result, about 2% of the amount of heat required at the front of the kiln for cement firing could be replaced with the powdered product.

Example 3 A part mainly composed of plastic that did not pass through the sieve obtained by the separation by the trommel in Example 1 was solidified through a pressure extrusion molding machine and temporarily stored in a storage hopper.
The equipment of Example 3 was composed of a storage hopper, a quantitative cut-out device, a rotary kiln-type dry distillation gasifier, a gas attractor for sucking the generated gas, and a gas incinerator.
From the storage hopper, a portion mainly composed of plastic solidified at a rate of 70 kg per hour was supplied to a dry distillation gasifier and gasified at a temperature of 800 ° C.
As a result, a combustible gas having a calorific value of 17000 KJ / Nm ³ mainly composed of hydrogen, carbon monoxide and hydrocarbons could be generated at 0.48 Nm ³ per 1 kg of the portion mainly composed of solidified plastic. Although the produced | generated gas was incinerated disposal in Example 3, it can be used for many uses as fuel gas.

It is a flowchart which shows the process of this invention.

Claims (5)

The mixed waste containing at least plastic and biodegradable material is adjusted so that the ratio of carbon to nitrogen (C / N) is 30 to 40, and the side opposite to the supply end of the mixed waste in the fermentation apparatus From the end, after having been fermented and decomposed while circulating air at a flow rate such that the oxygen concentration in the exhaust gas is 15 to 20% by volume, a portion mainly made of plastic and a non-plastic mainly A method for recovering plastic, characterized by being separated into parts .   2. The plastic recovery method according to claim 1, wherein the sorting means is at least one selected from sieve sorting, wind sorting, and submersion sorting.   The method for recovering plastic according to claim 1, wherein the biodegradable material contains at least one of food residues, animal manure, vegetation, wood, paper, fiber, and sewage sludge. The mixed waste containing at least plastic and biodegradable material is adjusted so that the ratio of carbon to nitrogen (C / N) is 30 to 40, and the side opposite to the supply end of the mixed waste in the fermentation apparatus From the end , after having been fermented and decomposed while circulating air at a flow rate such that the oxygen concentration in the exhaust gas is 15 to 20% by volume , a portion mainly made of plastic and a non-plastic mainly A method for fuelizing mixed waste containing plastic and biodegradable organisms, characterized in that the waste is separated into parts and burned using a burner. The mixed waste containing at least plastic and biodegradable material is adjusted so that the ratio of carbon to nitrogen (C / N) is 30 to 40, and the side opposite to the supply end of the mixed waste in the fermentation apparatus From the end , after having been fermented and decomposed while circulating air at a flow rate such that the oxygen concentration in the exhaust gas is 15 to 20% by volume , a portion mainly made of plastic and a non-plastic mainly A method for recycling mixed waste containing plastics and biodegradable materials, which are separated into parts and used as raw materials for gasification.

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