JP5845124B2 - Waste disposal method - Google Patents

Description

  The present invention relates to a waste treatment method. More particularly, the present invention relates to a method for treating waste containing chlorine.

  In recent years, wastes such as medical waste, waste plastic, building waste, waste car shredder dust, city waste, etc. (including RPF processed from these) have come to contain a large amount of chlorine-containing plastics such as polyvinyl chloride. It was. Most of these wastes were simply incinerated or landfilled.

  However, because of the shortage of landfill sites and numerous laws and regulations, instead of simply incineration and landfill treatment, the active ingredients contained in the waste are recovered and reused as solid fuel. It is being considered. Specifically, a method of obtaining a low chlorine fuel by thermally decomposing waste containing chlorine-containing plastic and washing the resulting carbide with water has been proposed (for example, see Patent Document 1).

  However, in this method, chlorine is removed from the waste together with other volatile components as hydrogen chloride (HCl) gas to thermally decompose the waste. Since other volatile components are removed, the fuel quality is deteriorated, and various components are contained in the gas, so that there is a problem that a gas processing step is required.

  In addition, an alkali metal compound and a calcium compound are introduced into the combustion device, and the waste contained in the combustion device is fixed in the solid phase, while the waste is burned, and chlorine is separated from the resulting residue. A waste disposal method has been proposed (see, for example, Patent Document 2).

  However, in this method, the generation of hydrogen chloride gas is hindered depending on the alkali metal compound or the like to be introduced, chlorine remains in the waste, and corrosion of the furnace supplied when used as a solid fuel, etc. There was a problem or a problem of deterioration in cement quality when used as a solid fuel for cement production.

  Furthermore, in order to sufficiently reduce the content of chlorine remaining in the obtained solid, a water washing treatment using a large amount of water was necessary.

JP 2000-96066 A JP 2003-39038 A

  Accordingly, an object of the present invention is to provide a method for treating a waste containing chlorine by a simple method to obtain a product having a low chlorine content and reusable as a solid fuel or the like.

  As a result of various investigations in view of such circumstances, the present inventors have prevented the volatilization of fuel components by suppressing the volatilization of chlorine in waste by addition of alkali, and further supplied superheated steam to the reaction vessel, Hydrogen chloride generated by the decomposition of chlorine in the waste in the reaction vessel is fixed to the solid phase with alkali, and the solid content remaining in the reaction vessel is led out of the reaction vessel as a recycled solid fuel, and out of the reaction vessel The present invention was completed by finding that a solid fuel of superior quality can be obtained with less energy than in the past by crushing the solid content and washing only the fine solid content classified with a predetermined particle size with water. .

  That is, the present invention relates to a waste treatment method for decomposing and desalinating chlorine-containing waste at a high temperature, wherein chlorine containing waste and alkali having a particle size smaller than the particle size of the waste Introducing into the reaction vessel, supplying and discharging superheated steam to the reaction vessel, fixing the hydrogen chloride generated by the decomposition of chlorine in the waste to the solid phase with alkali, and remaining in the reaction vessel The obtained solid content is led out as a regenerated solid fuel to the outside of the reaction vessel, and after pulverizing the solid content led out of the reaction vessel, it is preferably classified with a sieve having a sieve pore diameter of 1 to 5 mm and passed through the sieve mesh. Therefore, the present invention provides a waste processing method in which only the solid content is washed with water.

  According to the present invention, waste containing chlorine can be decomposed with less energy, waste containing chlorine can be decomposed, chlorine can be efficiently removed, and continuous treatment at normal pressure can be performed. In particular, since the amount of drainage during washing can be reduced, the cost for wastewater treatment can be reduced.

  In addition, the addition of alkali promotes the fixation of hydrogen chloride and other volatile components to the solid phase, so it is possible to reduce the cost of exhaust gas treatment and to obtain a solid fuel with excellent quality. Has an effect.

It is a schematic diagram which shows the apparatus used by one Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

In Figure 1, waste 1 containing chlorine to be processed of the present invention, which comprises plastic containing chlorine, for example, medical waste, waste-flop la, building waste, waste automotive shredder residue, municipal waste (Including RPF (Refuse Paper & Plastic Fuel) processed from these wastes).

  The particle size range of the waste containing chlorine is preferably 0.5 to 50 mm, and the waste preferably contains 80% by mass or more of particles having a particle size of 0.5 to 50 mm. Moreover, it is more preferable that the range of the particle size of the waste containing chlorine is 2 to 50 mm from the viewpoint of reducing the desalination rate and the amount of washing water, and in the waste, particles having a particle size of 2 to 50 mm are 80% by mass or more. More preferably it is included. Furthermore, the range of the particle size of the waste containing chlorine is more preferably 2 to 30 mm, and more preferably 80% by mass or more of particles having a particle size of 2 to 30 mm.

  The shape of the reaction vessel 5 into which such waste is introduced is not particularly limited, and various commercially available shapes can be used. For example, a batch type reaction vessel or a reaction vessel having a conveying function such as a conveyor type, a rotary kiln type, a fluidized bed furnace, a vertical furnace, a multistage type, a paddle type stirring is preferable in the case of continuous processing.

  The reaction vessel 5 is preferably an externally heated reaction vessel in order to efficiently decompose the waste in the reaction vessel. As a heat source for external heat, heating using electricity, heavy oil, gas as a heat source, factory waste heat, or the like can be used. It is preferable to adjust the external heat temperature of the reaction vessel 5 to be 250 to 450 ° C.

  After the saturated steam is generated, the superheated steam is secondarily heated by the superheater to obtain superheated steam, which is supplied to and discharged from the reaction vessel 5. The apparatus for generating saturated water vapor is not particularly limited, and for example, a commercially available water tube boiler, round boiler, or the like can be used.

  In addition, a waste heat boiler that generates saturated steam using factory waste heat generated in a cement manufacturing process or the like can also be used. The heat source of the superheater is not particularly limited, and it is also preferable to use a fuel burner, a high frequency heating device or the like, or to use waste heat generated in a cement manufacturing process or the like.

  From the viewpoint of carbonizing the surface of the mixture of waste and alkali, the temperature of the superheated steam is preferably in the range of 210 ° C to 350 ° C.

  In the conventional pyrolysis, a treatment at a temperature of 350 ° C. or higher was necessary, so a great deal of energy was required. However, in the present invention, the waste containing chlorine is treated by a treatment at a temperature lower than this. It is possible to decompose and remove chlorine.

  The temperature of saturated steam for obtaining superheated steam is preferably in the range of 100 ° C. to 130 ° C., which is the temperature range of a general low-pressure boiler, and the degree of superheat by secondary heating is in the range of 80K to 250K. It is preferable to do this. In the treatment of the present invention, when a waste containing moisture is treated, a drying effect is also obtained. Therefore, in order to transfer more moisture from waste to superheated steam, it is preferable that the degree of superheat is high.

  Note that the degree of superheat refers to the amount of temperature rise that is caused by secondary heating of saturated steam to raise the temperature to a predetermined superheated steam.

  Such superheated steam can be supplied using a commercially available superheated steam generator 7. In the reaction vessel, the time for treating the waste with superheated steam is preferably in the range of 10 minutes to 60 minutes, more preferably in the range of 20 minutes to 60 minutes. Treatment with superheated steam is possible even at normal pressure.

  The amount of superheated steam to be used varies depending on the shape and filling rate of the reaction vessel, the chlorine content, water content, properties, etc. of the waste to be treated, and is not particularly limited, but is 0.5 L / hr or more per 1 kg of waste. Is preferred.

  By treatment with superheated steam, chlorine in the waste is thermally decomposed in the reaction vessel. The hydrogen chloride generated by the decomposition of chlorine is promoted to be fixed to the solid phase by the alkali added in advance, and the hydrogen chloride that cannot be fixed is led out of the reaction vessel together with the superheated steam. Superheated steam containing discharged hydrogen chloride is rendered harmless by processes such as condensation and wastewater treatment (neutralization treatment) of condensed water.

In the present invention, solid, slurry, or liquid alkali 2 is introduced into the reaction vessel. As the alkali, for example, an alkali metal compound, an alkaline earth metal compound, or the like can be used. Examples of the alkali metal compound and alkaline earth metal compound include alkali metal hydroxide, alkaline earth metal hydroxide, alkali carbonate metal, alkaline earth carbonate carbonate, etc., for example, Ca (OH) ₂ , CaCO ₃ , NaOH, Na ₂ CO ₃ or the like is preferably used.

  In the present invention, when solid and slurry alkalis are used, the alkali particle size is preferably smaller than the particle size of the waste containing chlorine. Furthermore, it is preferable that the alkali particle size be less than 0.5 mm from the viewpoint of improving the mixing ratio with chlorine-containing waste and the contact rate with hydrogen chloride volatilized from the waste, and the range of 10 μm to 500 μm is preferable. Is more preferable. When a liquid alkali is used, the particle size is not particularly limited because the alkali is dissolved.

  And from the point which suppresses volatilization of the component useful as a fuel accompanying volatilization of hydrogen chloride, it is preferable that the alkali amount to introduce | transduce shall be 3 mol equivalent or more with respect to the chlorine amount in waste, especially 6 mol. It is more preferable that the range be equal to or greater than the equivalent. The upper limit of the amount of alkali to be introduced is not particularly limited, but is preferably 10 molar equivalents or less with respect to the amount of chlorine in the waste.

  On the other hand, the solid content remaining in the reaction vessel is led out of the vessel and used as the regenerated solid fuel 14.

The solids, is an object of the present invention, medical waste, waste-flops La, construction waste, waste automobile shredder residue, municipal solid waste, in the case of the RPF, etc., of the RPF fuel to be used in cement kilns and boilers request of the standard From this point, the chlorine content is reduced to about 0.4 to 5% by mass, and it can be used as a regenerated solid fuel as it is.

  In addition, the chlorine contained in the waste is sufficiently removed, but other chemical components (carbon, hydrogen, etc.) that can become fuel are hardly removed, so the total calorific value when used as recycled solid fuel Is also expensive.

  In the present invention, the alkali introduced in the solid state, slurry state or liquid state is present by adhering to and adhering to the surface / surface vicinity of the solid content of the waste alone or alone. Hydrogen chloride generated by the decomposition of chlorine in the waste is immediately trapped by the alkali and produces alkali chloride particles. For this reason, by separating the generated alkali chloride particles and the solid content surface to which the alkali chloride particles adhere and adhere from the residual solids, the high chlorine concentration solids mainly composed of alkali chloride particles and the other low It can be separated into a solid content of chlorine concentration. At this time, the alkali can be separated efficiently by making the particle diameter of the alkali smaller than the particle diameter of the waste. This separation can be performed by the following crushing and classification processes.

  Prior to the water washing treatment, the solid content derived from the reaction vessel is crushed. For crushing solids, a dry crusher such as a food mixer, double roll crusher, hard crusher, impact shear mill or the like can be employed. When crushing the solid matter, it is not necessary to finely crush the entire solid content, and the crushing effect may be sufficient to remove the alkali chloride particles adhering or adhering to the surface or the vicinity of the solid content from the solid content.

  After crushing, the crushed solid content is classified. For classification of solid content, classifiers such as a vibration classifier, a cylindrical classifier such as a rotary cylinder type, a wind classifier such as a specific gravity sorting type, a gravity inertia type, etc. can be adopted. Is preferably used. By this classification treatment, it is separated into a solid content of fine particles mainly composed of alkali chloride particles and a solid content of low chlorine concentration other than that with a predetermined particle size. The predetermined particle size in the classification is appropriately adjusted according to the type and particle size of the waste to be treated, the type and particle size of the alkali to be introduced, the reaction conditions with superheated steam, or the crushing conditions. For example, a sieve classifier Is preferably classified with a sieve having a sieve pore diameter of 1 to 5 mm. It is preferable to use a sieve having a single pore diameter.

  After classification, the mass ratio of the residue remaining on the sieve of the sieving machine is preferably in the range of 40 to 70% with respect to the solid content before being passed through the sieving machine.

  In the present invention, only a solid matter having a high chlorine concentration (hereinafter referred to as an under sieve product) that has passed through the sieve screen is washed with water. The low chlorine concentration solid content (hereinafter referred to as sieve product) that does not pass through the sieve mesh and remains on the sieve does not have to be subjected to a water washing treatment. Since the sieved product is already finely divided, the water washing and desalting efficiency is high, and it can be directly subjected to the washing treatment without being pulverized again. Further, since the solid content remaining on the sieve is not subjected to the water washing treatment, the amount of water used for the water washing treatment can be reduced.

  The method of the water washing treatment is not particularly limited as long as it is a method in which the solid content is brought into contact with water. For example, the solid content powder is deposited in a pit having a drainage mechanism such as a wire mesh or a groove at the lower portion, and the upper portion thereof. For example, a method of spraying water, a method of suspending solid content in water in a washing tank equipped with a stirrer, and then removing water by filtration can be employed. Here, the filtration is preferably performed by a filter press, a centrifugal separator, or the like, and may be an ash extruder or a water drainage by natural flow at the time of stacking.

  In addition, a so-called cascade water washing method in which water washing is performed through two or more steps can be employed.

  In the case of washing with water, the solid-liquid ratio (mass ratio) is preferably in the range of 2 to 5, the washing time is preferably in the range of 10 to 60 minutes, and more preferably in the range of 20 to 40 minutes. . Moreover, it is preferable to make the temperature at the time of water washing into the range of 50 to 100 degreeC, and it is more preferable to set it as the range of 70 to 100 degreeC. Although it is preferably carried out at 100 ° C. or higher, it is necessary to carry out under pressure.

  Considering from a viewpoint other than the “desalting rate” by the water washing treatment, when the entire solid content derived from the reaction vessel is washed with water, 20 to 40% of water remains in the filtration residue. When it is put into a high-temperature furnace as a regenerated solid fuel, moisture is brought into the high-temperature zone and heat loss occurs. In order to prevent this, a drying process is required before charging the high temperature furnace.

On the other hand, when only the under sieve product is washed with water, 20 to 40% of water remains in the washing filtration residue, but the unwashed residue (sieved product) is almost completely dry. Even if it is put in a high temperature furnace as it is, the influence on heat loss can be minimized. In addition, in order to minimize the amount of moisture brought into the high-temperature furnace, when the drying treatment is performed only on the wet sieved product, the amount of drying treatment may be smaller than when the filtration residue washed with water is dried.

  The regenerated solid fuel obtained by the treatment of the present invention efficiently removes chlorine by washing the solid content after the superheated steam treatment with water, but almost removes other chemical components that can become fuel in the solid content. Since it is not done, a fuel of good quality can be obtained. In addition, the pulverization property of the solid content is also good. For example, as a condition that the solid fuel can be suitably used in the cement kiln, the ratio of the particle size of 1.5 mm or less is preferably 90% or more. The processed product of the invention can be pulverized to such a particle size.

  EXAMPLES Hereinafter, examples will be shown to describe the present invention more specifically, but the present invention is not limited to these examples.

[Examples 1 to 4]
(Test sample)
ASR (Automobile) having total chlorine concentrations of 2.85 (mass%) (Examples 1 and 2, Comparative Examples 1 and 2) and 3.50 (mass%) (Examples 3 and 4 and Comparative Examples 3 and 4 ) About the crushed goods which shredded Shredder Residue) to 10 mm or less, it processed on the following process conditions.

(Superheated steam generator: Sankei Engineering Co., Ltd.)
・ Batch processing reaction tank ・ Stainless steel mesh reaction vessel ・ Saturated steam and superheated steam continuous generator (Saturated steam at 100 ℃ is secondarily heated by IH heater to generate superheated steam)

(Processing conditions)
・ ASR crushed product filling amount: 20g
・ Saturated water vapor generation amount: 1.8 kg / hr (100 ° C.)
-Temperature of superheated steam: 260 ° C (degree of superheat: 160K)
・ Processing time: 60 minutes

(Alkali added)
A Ca compound was used as the alkali, and was introduced into the reaction vessel so as to be 6 molar equivalents relative to the total amount of chlorine in the waste. Specifically, solid Ca (OH) ₂ (150 μm or less) was used as the alkali, and 3.57 g was added to 20 g of waste having a total chlorine concentration of 2.85% by mass. 4.39 g was added to 20 g of waste having a total chlorine concentration of 3.50% by mass.

(Crushing conditions)
After the superheated steam treatment, the solid content taken out from the reaction vessel was crushed for 20 seconds using a miller (IFM-170G manufactured by Iwatani Corporation).

(Classification conditions)
The crushed solid content was sieved with a sieve having a sieve pore size of 1.0 mm and 2.0 mm, and small solid particles (referred to as an under sieve product) that passed through the sieve were collected.

(Washing conditions)
10 g of the sieving product recovered by crushing and classification in a 100 ml beaker was put, and distilled water was added so that the solid-liquid ratio (mass ratio) to the sample was 1: 4. After adding distilled water, the sample was washed with water for 30 minutes while stirring with a magnetic stirrer. A 100 ml beaker was covered with a heat insulating material, and the water temperature was kept at 50 ° C. After washing with water, the whole amount is filtered to collect the filtration residue.

(Analysis method)
The total chlorine concentration of the sieved product that has not been washed with water and the sieved product that has been washed with water is determined using the Eshka method (JIS M8813 “Coals and cokes—elemental analysis method” and JIS Z7302-6 “Waste solidified fuel—No. 6 parts: Total chlorine content test method "described in the explanation). In addition, the residual chlorine amount and the desalting rate of the solid content (hereinafter referred to as carbonized product) after the superheated steam treatment were calculated by the following formula.
・ Carbonized product residual chlorine = Total chlorine concentration of sieved products that have not been washed + Total chlorine concentration of sieved products that have been washed with water · Desalination rate = (Carbonized product total chlorine-Carbized product residual chlorine) / (Carbized product) Total chlorine) x 100

  The results of the obtained desalting rate are shown in Table 1. Since the desalination rate and the washing water amount reduction rate of each example exceeded the target values of 60% or more and 40%, respectively, a solid fuel with excellent fuel quality could be obtained.

[Comparative Example 1]
Solids crushing after overheating steaming, except that not carried out classification treatment to obtain a solid in the same manner as in Example 1. The washing water reduction rate was 0%, and the washing water amount could not be reduced.

[Comparative Example 2]
Except that the sieve hole diameter during the classification process after overheating steamed and 0.5mm, the solid parts in the same manner as in Example 1. Only those with a desalination rate below the target value of 60% could be obtained.

[Comparative Example 3]
Solids crushing after overheating steaming, except that not carried out classification treatment to obtain a solid in the same manner as in Example 3. The washing water reduction rate was 0%, and the washing water amount could not be reduced.

[Comparative Example 4]
Except that the sieve hole diameter during the classification process after overheating steamed and 0.5mm, the solid parts in the same manner as in Example 3. Only those with a desalination rate below the target value of 60% could be obtained.

  According to the waste processing method of the present invention, an excellent quality recycled solid fuel can be obtained from chlorine-containing waste.

DESCRIPTION OF SYMBOLS 1 Waste 2 Alkali 3 Fixed-quantity supply machine 4 Fixed-quantity supply machine 5 Reaction container 6 Exhaust gas 7 Superheated steam generator 8 Crushing process 9 Classification process 10 Water washing desalination process 11 Drainage process 12 Drainage 13 Water 14 Regenerated solid fuel

Claims (5)

A waste treatment method for decomposing and desalinating waste containing chlorine-containing plastic at high temperature,
While introducing a crushed product of waste containing plastic containing chlorine and a solid alkali metal compound or alkaline earth metal compound having a particle size of 10 to 500 μm smaller than the crushed product into the reaction vessel Supplying and discharging superheated steam to the reaction vessel,
Fixing the hydrogen chloride generated by the decomposition of the plastic in the waste in the reaction vessel to the solid phase by capturing the alkali metal compound or alkaline earth metal compound,
The solid content remaining in the reaction vessel is led out of the reaction vessel as a regenerated solid fuel,
After crushing the solid content led out of the reaction vessel, classification is performed using a sieve having a sieve pore size of 1 to 5 mm, and the alkali chloride particles and alkali chloride produced by the crushing and classification of the solid content are performed. and a solid surface in which the particles are adhered or fixed is separated from the solids of low chlorine concentration than these,
Washing only the fine solid content of high chlorine concentration that has passed through the sieve by the classification,
Waste disposal method.   The waste disposal method according to claim 1, wherein the crushed product of waste contains 80% by mass or more of particles having a particle size of 0.5 to 50 mm.   The waste processing method according to claim 1 or 2, wherein the amount of the alkali metal compound or alkaline earth metal compound to be introduced is 3 molar equivalents or more with respect to the amount of chlorine in the crushed product of the waste.   The waste disposal method according to any one of claims 1 to 3, wherein the temperature of the superheated steam is 210 to 350 ° C.   The method for treating waste according to any one of claims 1 to 4, wherein the superheated steam has a superheat degree of 80K or more and 250K or less.

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