JP5852491B2 - Waste treatment system and treatment method - Google Patents

Description

  The present invention relates to a waste processing system and a processing method. More specifically, the present invention relates to a treatment system and a treatment method for 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 lowered, and since various components are contained in the gas, a gas treatment step is necessary.

  In addition, a waste containing chlorine is introduced into the reaction vessel, superheated steam is supplied to and discharged from the reaction vessel, the waste is decomposed in the reaction vessel, and vaporized chlorine is heated by the superheated steam in the reaction vessel. There has been proposed a method for treating waste that is led out of the reaction vessel and uses the solid content remaining in the reaction vessel as a regenerated solid fuel (see, for example, Patent Document 2).

  However, in this method, there is a risk that a large amount of water vapor containing waste decomposition components such as hydrogen chloride (HCl) and hydrocarbons may be generated as exhaust gas.

  Examples of the method for treating the hydrogen chloride (HCl) -containing exhaust gas include a wet cleaning method using caustic soda, a dry method in which slaked lime or calcium carbonate is blown, and a semi-dry method in which a slaked lime slurry is sprayed. Examples of the method for treating the hydrocarbon-containing exhaust gas include an activated carbon adsorption method, a combustion method (including a method for blowing into a cement manufacturing process), a condensation recovery method, and the like.

  Since the exhaust gas is generated after the superheated steam treatment, the main component is steam, and when cooled in the course of the above treatment method, the water in the exhaust gas is condensed and a large amount of water is generated, and in addition to burning hydrocarbons When a low-temperature exhaust gas containing a large amount of moisture is introduced into a high-temperature furnace, heat loss that lowers the internal temperature of the high-temperature furnace occurs. Furthermore, since the exhaust gas contains hydrogen chloride (HCl), there is a concern about corrosion of the reaction vessel or the like.

  Although it depends on the chlorine content of the raw material waste, the processed product treated with superheated steam contains 0.4-5.0% by mass of chlorine. Etc. are required. However, efficient washing and desalting requires a large amount of washing water and heating.

JP 2000-96066 A JP 2011-255338 A

  Therefore, an object of the present invention is to provide a treatment system and a treatment method for treating waste containing chlorine by a simple method.

  As a result of various studies in view of such circumstances, the present inventors have made effective use of superheated steam generated as exhaust gas, thereby reducing exhaust gas treatment equipment, reducing heat loss, improving desalination efficiency during water washing and desalting treatment, and The present inventors have found that the washing water can be reduced and completed the present invention.

  That is, the present invention receives a waste containing chlorine and thermally decomposes the waste at a high temperature, a superheated steam generator for supplying superheated steam into the reaction container, and discharged from the reaction container A heat exchanger for exchanging heat between the hydrogen chloride-containing exhaust gas and the cooling medium, a scrubber for reducing the hydrogen chloride concentration in the hydrogen chloride-containing exhaust gas derived from the heat exchanger, and the heat exchanger and / or the scrubber It is equipped with a drain recovery device that recovers drain and a heat recovery device that recovers heat from the heat exchanger, and the recovered heat is used for preheating for the generation of superheated steam or for heating the washing water of the water washing treatment device. A waste treatment system is provided.

  Further, the present invention is a waste treatment method for decomposing and desalinating chlorine-containing waste at a high temperature, introducing chlorine-containing waste into a reaction vessel and supplying superheated steam to the reaction vessel. The hydrogen chloride generated by decomposing chlorine in the waste in the reaction vessel is discharged as exhaust gas, the exhaust gas is cooled by a heat exchanger, the hydrogen chloride concentration is reduced by a scrubber, and the heat exchange And / or the scrubber is used to recover the drain, and the recovered heat is used for preheating for the generation of superheated steam, or for the waste water used for heating the washing water of the washing treatment apparatus.

  According to the present invention, since the exhaust gas that has passed through the scrubber has reduced harmful components and moisture, the exhaust gas treatment device can be reduced as compared with the case where the exhaust gas generated from the waste is treated as it is. The heat recovered by the heat exchanger can be used for preheating for generation of superheated steam and for heating washing water for washing and desalting. Moreover, since the moisture in the exhaust gas is recovered as drainage by the heat exchanger and the scrubber, heat loss that occurs when exhaust gas containing a large amount of moisture is blown into a reaction vessel such as a high-temperature furnace can be reduced. Furthermore, since the recovered drain is hot water, it can be used as a part or all of the washing water for washing and desalting treatment of superheated steam-treated products. Since the water temperature is high, efficient washing and desalting is possible with a small amount of water. It has an excellent effect of becoming.

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

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a waste treatment system according to the present invention will be described with reference to the accompanying drawings.

  In FIG. 1, the chlorine-containing waste 1 targeted by the present invention includes chlorine-containing plastics, such as medical trash, waste bra, construction waste, scrap car shredder dust, city trash, etc. Waste (including RPF (Refuse Paper & Plastic Fuel) processed from these wastes).

  As shown in FIG. 1, the waste treatment system of this embodiment includes a reaction vessel 5, a superheated steam generator 7, a heat exchanger 14, a scrubber 15, a heat recovery device 17, and a drain recovery device 18. The inside of the waste treatment system is sucked and exhausted by, for example, one or a plurality of blowers (not shown) arranged on the downstream side. The entire waste treatment system is managed and controlled by a distributed control system (DCS) using a computer or the like (not shown).

  The shape of the reaction vessel 5 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, rotary kiln type, stoker type, fluidized bed furnace, vertical furnace, multistage type, paddle type stirring is used for continuous processing. Can be used.

  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.

  The superheated steam generator 7 generates superheated steam. Superheated steam means high-temperature steam in a state of 100 ° C. or higher under atmospheric pressure, and has characteristics such as high activity, heat radiation, reaction with ionic substances, and the like. Superheated steam is generated by generating saturated steam and then secondary-saturating the saturated steam using the superheater in the superheated steam generator 7 and supplied to 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, steam 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 superheated steam generator 7 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. It is also preferable to use waste heat recovered from the heat exchanger 14 by a heat recovery device 17 described later.

  The temperature of the superheated steam should be in the range of 210 ° C. or higher and 400 ° C. or lower from the viewpoint of sufficient carbonization of the waste and avoiding inconvenience when the waste is decomposed too much and used as a solid fuel. preferable.

  In order to obtain superheated steam, it is preferable to adjust the temperature of saturated steam to a range of 100 ° C. or higher and 130 ° C. or lower, which is a temperature range of a general low-pressure boiler, and the degree of superheating by secondary heating is in the range of 80K or higher and 300K or lower. It is preferable to adjust to. In the treatment system 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.

  The superheated steam is supplied into the reaction vessel 5 by a blower (not shown) or the like. When supplying superheated steam into the reaction vessel 5, the pressure is adjusted using a pressure regulating valve or the like (not shown). In the reaction vessel 5, the time for treating the waste 1 with superheated steam is preferably in the range of 10 minutes to 60 minutes, and 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.

  The organic chlorine in the waste 1 is thermally decomposed in the reaction vessel 5 by superheated steam treatment. Hydrogen chloride generated by the decomposition of the organic chlorine is led out to the reaction vessel 5 together with superheated steam as exhaust gas 6 whose main component is steam. The temperature of the exhaust gas 6 led out of the reaction vessel 5 is in the range of 150 to 300 ° C.

  In the present embodiment, the exhaust gas 6 led out from the reaction vessel 5 is circulated to the heat exchanger 14. At this time, the temperature of the exhaust gas 6 decreases due to heat exchange with cooling water or the like in the heat exchanger. The exhaust gas deprived of latent heat by the heat exchanger 14 is condensed and recovered as drain by the drain recovery device 18. As the heat exchanger 14, a commercially available tube heat exchanger, plate heat exchanger, plate fin heat exchanger, shell and plate heat exchanger, or the like can be used. Furthermore, a gas-liquid separator (not shown) that separates the exhaust gas and drain and a condenser (not shown) that completely liquefies the residual vapor in the exhaust gas can be disposed downstream of the heat exchanger 14.

  The heat recovery device 17 recovers the heat obtained from the heat exchanger 14 through the medium, and is used for preheating the generation of saturated steam in the superheated steam generator 7 or for heating the cleaning water in the water treatment apparatus 9. use. Moreover, when using water as a medium, it can supply to a superheated steam generator as water for superheated steam. Furthermore, it can be used as a part of washing water. In addition, the heat recovery apparatus 17 can use a commercially available heat exchanger or the like.

  The scrubber 15 reduces the hydrogen chloride concentration in the exhaust gas. As the scrubber 15, a commercially available packed tower, spray tower, cyclones scrubber, venturi scrubber, jet scrubber, fluidized bed scrubber, and wet wall tower can be used. Also, neutralizing and removing hydrogen chloride in exhaust gas by bringing gas-liquid contact between industrial water, washing water containing alkali slurry such as NaOH, slaked lime, etc. and hydrogen chloride-containing exhaust gas discharged from the heat exchanger Alternatively, other types of scrubbers that collect hydrogen chloride and the like can be used. The drain generated from the scrubber is recovered by the drain recovery device 18. Further, a part of the drain can be returned to the scrubber and recycled as cleaning water.

  Since the exhaust gas that has passed through the scrubber 15 has reduced harmful components such as hydrogen chloride and moisture, the equipment can be reduced as compared with the case where the exhaust gas generated from a reaction vessel such as a heating furnace is treated as it is. Furthermore, it is also preferable to detoxify the exhaust gas after passing through the scrubber using another exhaust gas treatment device 17.

  The drain recovery device 18 collects the drain generated by the heat exchanger 14 or the scrubber 15. This drain is warm water of 40 ° C. or higher, and is used as a part or the whole amount of the washing water of the washing treatment apparatus 9.

Alkali 2 can also be introduced into the reaction vessel 5. As the alkali, for example, an alkali metal compound, an alkaline earth metal compound, or the like can be used. As the alkali metal compound and alkaline earth metal compound, Ca (OH) ₂ , CaCO ₃ , NaOH, NaCO _{3 and the} like can be preferably used. Hydrogen chloride generated by the decomposition of chlorine in the waste by introducing an alkali is promoted to be fixed to the solid phase by the alkali, and it can be suppressed that hydrogen chloride is derived as exhaust gas. In addition, since the chlorine fixed to the alkali remains in the solid as a water-soluble inorganic chloride or the like, the inorganic chloride can be efficiently removed by washing with water after the superheated steam treatment. Since other chemical components that can be a fuel in the solid content are hardly removed, a fuel excellent in quality can be obtained.

  Further, a solid content outlet is provided at an appropriate position of the reaction vessel 5 so that the solid content remaining after the superheated steam treatment is discharged.

  This solid content is the target standard for RPF fuel used in cement kilns and boilers in the case of medical waste, waste bra, construction waste, scrap car shredder dust, municipal waste, RPF, etc. Thus, the chlorine content is reduced to about 0.4 to 5.0% by mass and can be used as a regenerated solid fuel as it is.

  When the superheated steam treatment is performed, there is also a drying effect, so that a drying step is not required as in the prior art, and a regenerated solid fuel desalted in one step can be produced. In the regenerated solid fuel, the drying step is important, but it is very advantageous from the viewpoint of energy saving to obtain a dried regenerated solid fuel without specially providing this step.

  In addition, the chlorine contained in the waste 1 is sufficiently removed by the superheated steam treatment, and other chemical components (carbon, hydrogen, etc.) that can be used as fuel are hardly removed. The total calorific value at the time of heating is also high.

  The water washing treatment device 9 is not particularly limited as long as it is a device for bringing the solid content into contact with water. For example, a solid powder is deposited in a pit having a water draining mechanism such as a wire mesh or a groove in 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.

  Moreover, the water-washing processing apparatus 9 can also employ a so-called cascade water-washing system in which the water-washing process is performed through two or more steps.

  It is preferable to adjust the temperature of the washing water at the time of washing to be in the range of 40 ° C. or more and 80 ° C. or less, and it is preferable to use the warm water collected in the drain recovery device 18 as a part or all of the washing water. . Although it is preferable that the heat of the drain be utilized to the maximum, an external heater may be used for the purpose of maintaining or heating the water temperature during cleaning.

  The crushing processing device 8 crushes the solid content derived from the reaction vessel 5 before the water washing treatment. As such a crushing processing device 8, a dry crusher such as a food mixer, a double roll crusher, a hard crusher, or an impact shear mill can be used.

  Next, an embodiment of the waste processing method according to the present invention will be described.

  That is, the waste processing method according to the present invention is a waste processing method in which waste containing chlorine is decomposed and desalted at high temperature. Then, waste containing chlorine is introduced into the reaction vessel, and superheated steam is supplied to the reaction vessel and discharged. Hydrogen chloride generated by the decomposition of chlorine in the waste in the reaction vessel is extracted from the reaction vessel as exhaust gas. The temperature of the derived exhaust gas is lowered by a heat exchanger. Furthermore, the scrubber reduces the hydrogen chloride concentration in the exhaust gas. On the other hand, drain generated in the heat exchanger and / or scrubber is collected, and the drain is used as a part or all of the washing water used for washing the solid content remaining in the reaction vessel. Using a heat recovery device or the like, the heat obtained by the heat exchanger is recovered. The recovered heat is used to heat superheated steam. Alternatively, the recovered heat is used for heating the washing water.

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 6, Comparative Examples 1 and 2]
(Test sample)

A crushed product obtained by crushing ASR (Automobile Shredder Residue) to 10 mm or less was processed under the following processing conditions.
(Superheated steam generator: Sankei Engineering Co., Ltd.)
・ Batch processing reaction tank ・ Stainless steel mesh reaction vessel ・ Saturated steam / Superheated steam continuous generation (Saturated steam at 100 ° C 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.)
・ 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, Ca (OH) ₂ was used as an alkali, and 3.14 g was added to 20 g of waste having a total chlorine concentration of 2.50% by mass.
(Analysis method)

The total chlorine concentration in the treated product after the superheated steam treatment was determined by the Eshka method (JIS M8813 “Coals and cokes—elemental analysis method” and JIS Z7302-6 “Waste solidified fuel—Part 6: Total chlorine content test method”. The method described in the explanation). The total chlorine concentration was 2.02% by mass. The moisture was 1% by mass. In the water washing treatment of the superheated steam-treated product, the solid-liquid ratio (mass ratio) of the superheated steam-treated product and distilled water (water temperature 15 ° C.) was 1: 3 or 1: 5, and the washing time was 15 minutes. Moreover, the water temperature at the time of the water washing process is 15 ° C., which is the same as the water temperature of distilled water, and 40 ° C., 60 ° C., and 80 ° C. assuming that the water is heated by a part or all of the drain recovered from the heat exchanger and scrubber Held in either. After washing with water, the whole amount was filtered using 5B filter paper, the total chlorine concentration in the filtration residue was measured by the Eschka method, and the desalting rate by the washing treatment was calculated by the following formula. The results of the obtained desalting rate are shown in Table 1.
Desalination rate = (2.02−total filtration residue chlorine) /2.02×100

  Each example has a high desalting rate of 70 to 90%, and when drainage of 40 to 80 ° C. is used as part or all of the washing water, it is possible to perform efficient washing and desalting with a small amount of water. An excellent effect was confirmed. Comparative Examples 1 and 2 in which washing was performed using washing water having the same water temperature (15 ° C.) as that of distilled water not heated by a part or all of the drain recovered from the heat exchanger and scrubber were removed. The salt ratio was as low as less than 70%.

  According to the waste processing system and the processing method of the present invention, it is possible to obtain an excellent quality recycled solid fuel from waste containing chlorine.

DESCRIPTION OF SYMBOLS 1 Waste 2 Alkali 3 Fixed supply machine 4 Fixed supply machine 5 Reaction container 6 Exhaust gas 7 Superheated steam generator 8 Crushing processing apparatus 9 Flushing processing apparatus 10 Drainage processing apparatus 11 Drainage 12 Water 13 Regenerated solid fuel 14 Heat exchanger 15 Scrubber 16 Water 17 Heat recovery device 18 Drain recovery device 19 Exhaust gas treatment device

Claims (5)

A reaction vessel that accepts waste containing chlorine and thermally decomposes the waste at high temperature;
A superheated steam generator for supplying superheated steam into the reaction vessel;
A heat exchanger for exchanging heat between the hydrogen chloride-containing exhaust gas discharged from the reaction vessel and the cooling medium;
A scrubber for reducing the hydrogen chloride concentration in the chlorine-containing exhaust gas derived from the heat exchanger;
A drain recovery device for recovering drain from the heat exchanger and / or the scrubber;
A heat recovery device for recovering heat from the heat exchanger ;
A solid treatment existing in the reaction vessel after the thermal decomposition is led out of the reaction vessel, and a water washing treatment device for washing the solid with water ,
Heat recovered by the heat recovery device is used to heat the washing water in the washing apparatus, and the temperature of the washing water, waste treatment system that will be adjusted in the range of 40 ° C. or higher 80 ° C. or less . Furthermore, waste treatment system according to claim 1, further comprising an exhaust gas treatment apparatus for treating an exhaust gas which has passed through the scrubber. A waste treatment method for decomposing and desalinating chlorine-containing waste at a high temperature,
While introducing waste containing chlorine into the reaction vessel, superheated steam is supplied to and discharged from the reaction vessel, and hydrogen chloride generated by decomposition of chlorine in the waste in the reaction vessel is derived as exhaust gas, The temperature of the exhaust gas is lowered by a heat exchanger, and the hydrogen chloride concentration is reduced by a scrubber, while the drain generated in the heat exchanger and / or the scrubber is recovered, and the drain remains in the reaction vessel. Use as part or all of the washing water for washing the solids, recover the heat obtained by the heat exchanger, use the heat for heating the superheated steam generation, or for heating the washing water Waste disposal method used. The waste treatment method according to claim 3 , wherein the superheated steam temperature is 210 to 400 ° C. The method for treating waste according to claim 3 or 4 , wherein the superheated steam has a superheat degree of 80K to 300K.

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