JP2001335783A - Method for treatment of waste plastics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a method for the treatment of waste plastics that coke as the product may not decrease in the strength and to provide a method for the use of a returned coal. SOLUTION: The above methods comprise the steps (1) feeding a mixture of coal, a caking filler and waste plastics into a coke furnace and dry-distilling it: and the following simultaneous steps, (2) the above caking filler and the above waste plastics have been previously mixed; (3) the above caking filler and the waste plastics have been previously mixed and then molded; (4) the above waste plastics have a particle diameter in the maximal length of 5 mm or longer; (5) the above waste plastics have a particle diameter in the maximal length of 100 mm or shorter; and (6) above coal is added with the returned coal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating plastics or waste containing plastics in a coke oven (hereinafter, plastics or waste containing plastics is also referred to as waste plastics).

Here, plastics refers to plastics such as polyethylene terephthalate (PET), polyethylene, polypropylene, polystyrene and vinyl chloride.

[0003]

2. Description of the Related Art One of recent social and environmental problems is that it has become difficult to secure landfill sites for waste. The amount of waste plastic waste is 1,0 per year
It is increasing at a rate of as much as one million tons, the amount used effectively is small, and most of it is landfilled or incinerated.

[0004] In addition, since the problem of dioxin during incineration has become apparent, the development of a waste plastics treatment method or an effective utilization method capable of avoiding adverse effects on the environment is urgently required. Against this background, many tests have been conducted in which waste plastics is charged into a coke oven and pyrolyzed.

For example, Japanese Patent Application Laid-Open No. 6-228565 discloses a method of producing coke using the following granular plastics. (1) A method in which granular plastics crushed to an appropriate particle size is mixed with charged coal and carbonized in a coke oven.

(2) A method in which granular plastics crushed to an appropriate particle size is mixed with shaped coal and carbonized in a coke oven. According to the publication, it is possible to produce coke of good quality by mixing granular plastics crushed to an appropriate particle size and carbonizing in a coke oven.

[0007]

However, if granular plastics are simply mixed with the above-mentioned charged coal or molded coal (hereinafter also referred to as raw coal), there is a problem that the coke strength of the product is reduced.

It is widely known that the coke strength is reduced by the addition and mixing of plastics, and the cause can be estimated as follows. That is, in the coal carbonization process, since the inside of the furnace is at a high temperature, the plastics added to the coke is easily volatilized, and pores as traces of volatilization are easily generated in the coke, and the generated pores lower the coke strength. It is estimated from.

The invention disclosed in the above-mentioned publication is to mix granular plastics crushed to an appropriate particle size and to dry distill in a coke oven in order to prevent a decrease in coke strength of the product. And

[0010] However, there is no description about specific particle size, and the content cannot be evaluated as well as embodying the invention. On the other hand, after charging waste plastics together with coking coal into the coke oven, waste plastics-containing coking coal (hereinafter also referred to as return coal) discharged out of the coke oven during the leveling operation of the coking coal charged by the extruder. ) Occurs.

[0011] The returned coal temporarily stops in the coke oven and receives the heat history, so its quality deteriorates, and it is difficult to return it to the coke oven at present, and it is used as a heat source for sintering in steel works. The method used as a raw material for coke was being studied.

An object of the present invention is to provide a method for treating waste plastics and a method for using returned coal in which the coke strength of a product is not reduced.

[0013]

Means for Solving the Problems The present inventors conducted various carbonization tests in which waste plastics were added to coal, examined the method of treating waste plastics, and obtained the following findings.

(A) At the same amount of waste plastics, the larger the particle size of the waste plastics, the more the decrease in coke strength can be suppressed. As a result of observing the generated coke, the more coke to which waste plastics with a small particle size is added, the more pores are present in the coke. I have.

That is, with the same addition amount, the larger the particle size of the waste plastics, the smaller the number of particles of the waste plastics, so that the number of pores in the coke can be reduced. That is,
The addition of waste plastics having a relatively large particle size can suppress a decrease in coke strength as compared with the addition of the same amount of waste plastics having a small particle size.

(B) However, even if the number of particles of waste plastics decreases, only the number of pores decreases,
It is difficult to completely suppress the decrease in coke strength. Especially when processing large quantities of waste plastics,
It becomes difficult to increase the coke strength.

(C) Therefore, as a result of further study on a method for increasing the coke strength, it is effective to increase the coke strength by mixing coal and waste plastics and further adding a caking filler. Turned out to be.

(D) In addition, if the waste plastics and the caking filler are mixed in advance and then coal is mixed and carbonized, the coke strength can be increased as compared with the above (C). There was found.

(E) Furthermore, it was found that when waste plastics and a caking filler were mixed and the mixture was molded, the coke strength could be increased as compared with the above (D).

(F) On the other hand, the same findings as in the above (A) to (E) were obtained even when the return coal was blended with the raw coal. The present invention has been made based on the above findings, and the gist is as follows. (1) A method for treating waste plastics, comprising charging a mixture of coal, caking filler, and waste plastics into a coke oven and carbonizing the mixture. (2) The method for treating waste plastics according to (1), wherein the caking filler and the waste plastics are mixed in advance. (3) The method for treating waste plastics according to (1), wherein the caking filler and the waste plastics are preliminarily mixed and molded. (4) The method for treating waste plastics according to any one of (1) to (3), wherein the particle size of the waste plastics is 5 mm or more in maximum length. (5) The particle size of the waste plastics is 100 at the maximum length.
mm or less, the method for treating waste plastics according to the above (4). (6) The method for treating waste plastics according to any one of (1) to (5), wherein return coal is added to the coal.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Coal charged in a coke oven is pulverized so that, for example, a particle size of 3 mm or less is about 80% by mass, a predetermined amount of waste plastics is added to the raw coal and mixed.

The shape of the waste plastics is not particularly limited. However, when the waste plastics is simply cut, the bulk density is extremely small, for example, about 0.1 g / cm ^3, so that the transfer efficiency is low. Could be.

If the bulk density is extremely small, the powder is liable to be scattered when charged into a coke oven, and the yield may be reduced. Therefore, it is preferable to compress and mold the waste plastics into, for example, a column shape.

Further, it is preferable that the maximum length (hereinafter, also simply referred to as the maximum length) of the crushed waste plastics or the molded waste plastics is large. Here, the maximum length refers to the length of the longest part in each of the crushed waste plastics or the molded waste plastics. Desirable maximum length is 5 mm or more.

[0025] The reason is that if it is less than 5 mm, there is a possibility that crushing or molding efficiency is reduced, or that the particles are easily scattered during transportation. However, if it exceeds 100 mm, there is a risk of a blockage trouble during the transfer or charging process, and it is preferable that the length be 100 mm or less.

However, if such crushed waste plastics or molded waste plastics are mixed in coal and carbonized, the strength of coke decreases as the amount of added waste plastics increases. . As described above, the cause of the decrease in coke strength can be presumed to be that pores were formed in the portion of the coal where the waste plastics existed when coke was generated, because the waste plastics were volatile.

Therefore, it is effective to fill the pores formed during the production of coke with a caking filler. This caking filler is not particularly limited as long as it has an effect of filling pores in coke generated by the volatilization of waste plastics, but, for example, petroleum asphalt,
Asphalt pitch or coal tar pitch can be used.

The addition amount of the caking filler may be appropriately determined based on the addition amount of waste plastics. A desirable addition amount is a ratio (N) of the waste plastics amount P (kg / tonne of coal) and the addition amount N of the caking filler (kg / tonne of coal).
/ P) is preferably 0.5 to 5.

The reason is that if it is less than 0.5, the effect of filling the pores may be small, and if it is more than 5, the effect of filling the pores may be saturated and not economical. Thus, by adding the caking filler together with the waste plastics, it is possible to prevent a decrease in coke strength as compared with a case where it is not added.

The addition of the caking filler may be carried out by, for example, a method of attaching to the waste plastics by brush coating or a method of adding the caking filler at the time of molding the waste plastics. . For the molding of the waste plastics, an ordinary method such as extrusion molding can be used.

The difference between the molded product and the mere mixture is that the waste plastics and the caking filler can be brought closer to each other as compared to a state where the waste plastics and the caking filler are simply mixed. Therefore, the pores formed in the coke can be efficiently filled with the caking filler by the close proximity of the waste plastics and the caking filler.

It is desirable that the amount of the returned charcoal is not more than 10% by mass. If the content exceeds 10% by mass, the coke strength may be significantly reduced.

[0033]

EXAMPLES Table 1 shows the properties of the raw coal used in the test.
Table 2 shows the properties of the returned coal used in the test.

Table 3 shows the results of analyzing the components of the waste plastics used in the test. Table 4 shows the properties of petroleum pitch as a caking filler used in the test.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4] (Example 1) The water content of coking coal was adjusted to 6.5% by mass (hereinafter simply expressed as%), and a predetermined amount of waste plastics having a particle size of 6 mm or 20 mm and a petroleum pitch were added and mixed. And a test coke oven with a mass of 250 kg (furnace temperature: 1150
(° C.) to dryness until the temperature in the coal reaches 950 ° C.

The coke after carbonization is immediately discharged and cooled, and the cooled coke has a cold drum strength DI
(15 mm sieve ratio after 150 rotations of the drum) was measured.
Table 5 shows the test results.

[0040]

[Table 5] Test No. 1 as a reference example in the same table shows an example in which the amount of waste plastics added was zero and a good coke having a DI value of 82% could be produced.

As shown in Test Nos. 2 and 3 in the same table, when petroleum pitch was not added, the DI value decreased extremely due to the increase in the amount of waste plastics added (2 → 5%).
0% or less.

However, as shown in Test Nos. 4 and 5 in the same table, when 2% of petroleum pitch was added, the DI value was slightly lowered due to an increase in the amount of waste plastics added, but 80%.
That's all.

As shown in Test Nos. 6 and 7 in the same table, when the petroleum pitch was increased (2 → 4%) and added, the DI value was higher than in Test Nos. 4 and 5. on the other hand,
As shown in Test Nos. 8 and 3 in the same table, even if the addition of petroleum pitch was zero, the particle size of waste plastics was 6 mm to 2 mm.
By increasing it to 0 mm, the DI value is 80%
The DI value was relatively high although the value was as low as the following.

As shown in Test Nos. 9 and 7 in the same table, when the particle size of waste plastics was increased from 6 mm to 20 mm under the same conditions with the addition amount of petroleum pitch being 4%, DI
The value could be increased from 82.2% to 83%.

(Example 2) 2% of petroleum pitch was added to waste plastics, mixed and molded into a particle size of 6 mm in advance, and then the molded product was charged into a coke oven and subjected to a carbonization test.

A dry distillation test was performed under the same conditions as in Test No. 5 of Example 1 except that the particle size was previously formed to 6 mm. Table 6 shows the test results.

[0047]

[Table 6] As shown in Table 6, two oil pitches were added to waste plastics.
%, And the DI value charged in a coke oven after forming into a particle diameter of 6 mm in advance was 82.1%, which was higher than the DI value of Test No. 5 shown in Table 5 of 80.6%. .

(Example 3) The water content of the raw coal was adjusted to 6.5%, and then the returned coal was blended with 8% to form a 6 mm or 20 mm coal.
A predetermined amount of waste plastics having a particle size of and a petroleum pitch are added and mixed, and a 250 kg-scale test coke oven (oven temperature: 11
(50 ° C.) and carbonized until the temperature in the coal reached 950 ° C.

The coke after the carbonization is immediately discharged and cooled, and the cooled coke has a cold drum strength DI
(15 mm sieve ratio after 150 rotations of the drum) was measured.
Table 7 shows the test results.

[0050]

[Table 7] Test Nos. 3 and 8 as reference examples in the same table were obtained when the particle size of the waste plastics was 6 mm and 20 mm, the amount of waste plastics added was 5%, and the amount of returned coal was zero. It is a test result.

As shown in test numbers 11 and 12 in the table,
When the amount of the returned charcoal was 8%, the DI value was extremely lower than that of Test Nos. 3 and 8 of Reference Example. However, as shown in Test Nos. 12 and 14 in the same table, when 4% of petroleum pitch was added, the DI value became 80% or more.

[0052]

According to the present invention, waste plastics can be added to a coke oven without reducing the coke strength of the product, and return coal can also be used.

Claims (6)

[Claims] 1. A method for treating waste plastics, comprising charging a mixture of coal, caking filler and waste plastics into a coke oven and carbonizing the mixture. 2. The method for treating waste plastics according to claim 1, wherein the caking filler and the waste plastics are mixed in advance. 3. The method according to claim 1, wherein the caking filler and the waste plastics are mixed and molded in advance.
4. The method for treating waste plastics according to item 1. 4. The method for treating waste plastics according to claim 1, wherein the particle size of the waste plastics is 5 mm or more in maximum length. 5. The method for treating waste plastics according to claim 4, wherein the particle size of the waste plastics is 100 mm or less in maximum length. 6. The method for treating waste plastics according to claim 1, wherein return coal is added to said coal.