JP4243661B2 - Dust disposal method - Google Patents

Description

  The present invention relates to a method for recovering valuable metals, in particular non-ferrous metals, from dust such as shredder dust containing a mixture of valuable metal scraps and oxides, polymer compounds such as plastics, and the like.

  Solid waste such as automobiles, home appliances, and office automation equipment is made up of various materials such as valuable metals such as iron and non-ferrous metals, plastics, and ceramics. These members are also joined and compounded in various ways. Such solid waste is first disassembled and main parts, large metal materials, etc. are removed, then pressed, shredded, crushed and cut. Furthermore, by repeating the crushing process and the like, and separating each time by magnetic sorting, specific gravity sorting, cyclone, etc., it is separated and recovered into metal materials and plastics. As described above, the dust obtained through each stage has a size of 100 mm to several mm, and this dust contains a large amount of plastic or the like and a small amount of valuable metals.

Dust contains various kinds of polymer compounds such as metal scraps, oxides, and plastics. Therefore, when recovering valuable metals, the metal is made harmless while the product is made harmless. It is necessary to proceed with the collection.
As a method for treating such dust, there are a direct incineration method in which dust is incinerated directly in an incinerator by a complete combustion, and a wet method in which a contained metal is leached with mineral acid or the like and transferred into liquid. is there.

  In the method of incinerating dust, the dust is finally made harmless in the form of a complete oxide called slag. The recovery of metal from this slag requires a number of processes such as a pulverizer because the slag is hard, and various things are mixed in the form of oxides and composites. Although many steps are required for separation, it has hitherto been known that no detoxifying means other than slag has been known as a dust treatment method.

  However, as described above, the dust contains a large amount of polymer compounds such as plastics, and the amount of exhaust gas is large according to the direct incineration method. Since the incinerator is incinerated, non-ferrous metals and the like are sublimated, the oxides are scattered a lot, and the non-combustible material contains almost no valuable metals. In addition, in the wet method, dust contains a large amount of polymer compounds such as plastic, the metal content is low, and various components are contained in various amounts, increasing the number of processing steps for recovering valuable metals. Costs to ensure safety to the surrounding environment.

  In view of the above situation, the object of the present invention is to provide a method for recovering valuable metals from dust that is simple, can efficiently recover valuable metals, and has little impact on the surrounding environment due to emissions such as exhaust gas and wastewater. There is to do.

  In order to achieve the above object, the present invention firstly, a first step of heating a dust containing a metal and a polymer compound in a reducing atmosphere to obtain a vaporized gas and an incombustible material, A second step of recovering and smelting raw material, a third step of supplying oxygen or a gas containing oxygen to the vaporized gas and burning, and a fourth step of collecting fly ash from the exhaust gas after combustion. The dust treatment method according to claim 1, further comprising a fifth step of using the residue obtained by washing the collected fly ash as a smelting raw material, Third, the dust treatment method according to the first or second aspect, wherein the first step is performed at 450 to 700 ° C. and the third step is performed at 800 to 900 ° C., and fourth, the dust is shredder dust. The dust treatment method according to any one of the first to third, The dust treatment method according to any one of the first to fourth, wherein the first step is performed in a fluidized bed incinerator preliminarily charged with fluidized sand, sixthly, heat generated in the first step. The dust processing method in any one of 1st-5 which collect | recovers in a waste-heat boiler is provided.

  According to the present invention, valuable metals are easily and efficiently recovered as a smelting raw material from dust containing a mixture of valuable metal scraps, oxides, polymer compounds such as plastics, particularly shredder dust, In addition, it became possible to render the treated product harmless, and more efficient steam recovery.

  Shredder dust generated by shredding waste from automobiles, home appliances, office automation equipment, etc. contains oxides such as urethane, hard plastic, soft plastic, rubber, paper, fiber, metal, and glass. The composition is not constant, but generally 1-10% by weight of urethane (simply expressed simply as%), 1-20% of hard plastic, 1-10% of soft plastic, 1-10% of rubber, 1-30% of paper The composition is in the range of 1 to 30% fiber, 1 to 20% metal, and 20 to 60% oxide such as glass. Moreover, valuable metals, such as iron, aluminum, copper, lead, zinc, are contained as a metal.

A flowchart of the present invention is shown in FIG.
Moreover, this invention is demonstrated about the case where the fluidized-bed incinerator which shows the schematic longitudinal cross-sectional view in FIG. 2 is used as a furnace which performs a 1st process (heating process), a 3rd process (combustion process), etc. FIG.
The fluidized bed incinerator 1 includes, at the bottom of the furnace, an incombustible discharge port 2, a primary air supply port 3 that supplies primary air a into the furnace, and a fluidized bed b such as sand. In addition, a raw material charging port 4 and a secondary air supply port 5 are provided above, and further, a heat absorption part such as a water pipe of a waste heat boiler and a gas discharge port 6 are provided thereabove.

The primary air inlet 3 has a difference in the supply speed of the primary air a between the vicinity of the center and the peripheral part at the bottom of the furnace, and the fluidized bed b of the fluid medium such as silica sand introduced by this adjustment is provided. The shredder dust, which is the material to be processed supplied from the raw material inlet 4 to the fluidized bed b, is formed at the periphery of the furnace bottom by supplying the primary air a with an air ratio reduced to less than 1. A reducing atmosphere is maintained by the fluidized bed b in which a part of the plastic or the like is burned and heated in the central portion of the low oxygen state. The incombustible material c containing the metal in the object to be treated is discharged from the incombustible material outlet 2 to the outside of the furnace together with a part of the fluidized sand in an unoxidized state.
Further, the vaporized gas resulting from the thermal decomposition of the object to be treated is combusted by the secondary air e from the secondary air inlet 5 in the free board area d above the raw material inlet 4 to become the exhaust gas f after combustion, and the furnace together with fly ash The gas is discharged from the top gas discharge port 6 to the outside of the furnace.

  In the first step of the present invention, first, shredder dust as a raw material is charged from a raw material inlet 4 into a fluidized bed using silica sand as a fluid medium. When charging, it is desirable to unify the size in advance so that it flows by the primary air a and does not get caught by the charging device. The shredder dust often contains a large amount of plastic containing chlorine such as polyvinyl chloride, and usually contains 0.1 to 5% of chlorine. In this case, in order to fix chlorine or hydrogen chloride generated by incineration, it is desirable to charge a calcium compound at the same time.

  Next, heating is performed by burning a part of combustible material such as a polymer compound in the shredder dust. The primary air a heated from the primary air inlet 3 at the bottom of the furnace is blown to the fluidized bed in which the shredder dust in the furnace is mixed. The temperature in the fluidized bed is maintained at 450 to 700 ° C., preferably 550 to 650 ° C. by combustion using the heated primary air a in which the air ratio is controlled to a predetermined range of less than 1. At temperatures below 450 ° C, the thermal decomposition reaction of shredder dust by heating to obtain vaporized gas and incombustibles is insufficient, while at temperatures above 700 ° C, the sublimation of metals rapidly increases and adheres to the furnace wall. Or it is oxidized at a later stage and the recovery efficiency is lowered. Although air is used as the primary air a, it is not limited to air and any gas containing oxygen such as oxygen-enriched air may be used, and pure oxygen can also be used.

As described above, the air ratio, which is the ratio of the amount of air (inside oxygen) actually sent to the amount of air (inside oxygen) necessary for the combustion of the shredder dust, is set to less than 1. When the air ratio is less than 1, the shredder dust in the fluidized sand can be heated in a reducing atmosphere, the polymer compounds are decomposed and vaporized, and the metal is prevented from being oxidized and easily recovered. Therefore, an air ratio of 0.4 to 0.6 is preferable.
Next, as a second step, the incombustible material c that is not evaporated but remains is separated and recovered. That is, the incombustible material c containing a metal component is discharged from the incombustible material outlet 2 at the bottom of the furnace together with the fluidized sand in an unoxidized state to the smelting raw material.

  Further, the third step is a combustion step of vaporized gas, and the gas vaporized by heating the shredder dust in the fluidized bed of the first step is swirling secondary air from the secondary air inlet 5 in the free board area d. Combusted by stream e. In this case, the combustion temperature, that is, the temperature of the free board region d is preferably 800 to 900 ° C. At temperatures below 800 ° C, dioxins may be generated. At temperatures above 900 ° C, metal sublimation is promoted, and metals adhere to the furnace wall and become oxides and are contained in fly ash. It becomes difficult to recover the metal into c.

Furthermore, in the first process, if the temperature distribution is controlled separately in the vicinity of the hearth, the range slightly above the vicinity of the hearth and below the combustion part of the third process, and the combustion part of the third process, more metal recovery , Processing productivity is improved. Specifically, it is 700 ° C. or lower near the hearth, that is, near the upper layer of the fluidized bed, 900 ° C. or lower above the vicinity of the upper layer, and 950 ° C. or lower in the combustion section above it. By raising the temperature stepwise in this way, combustion becomes more efficient, and cracked gas generated in the fluidized bed above the fluidized bed and below the third process becomes a vortex below the third process. The amount of metal volatilization is not only moved upward but is also deposited on sand.
As described above, the temperature can be set to 600 to 700 to 900 ° C. in the first step and 950 ° C. or less in the third step, and the temperature distribution may be further divided into a plurality of regions and controlled.

In the third step, the compound formed by combining metal and calcium in the reducing atmosphere in the first step decomposes at temperatures exceeding 900 ° C. to form respective oxide molecules, but the temperature is 900 ° C. or lower. In this case, the compound becomes an oxide as it is, which contributes to recovery in a subsequent process and is considered advantageous. After combustion, the exhaust gas f after combustion accompanied with fly ash is discharged out of the furnace through the gas outlet 6 at the top of the furnace.
That is, by performing combustion in two stages of the first step and the third step, the metal in the shredder dust can be recovered in an unoxidized state and the reduction of the dust volume can be promoted.

  Further, a neutralizing agent is further added to the exhaust gas f after combustion accompanied by fly ash discharged from the gas outlet 6 to the outside of the furnace, and an acidic gas such as chlorine and hydrogen chloride contained in the exhaust gas f after combustion. Neutralizes ingredients. As this neutralizing agent, powdered and aqueous solutions such as slaked lime, baking soda and caustic soda can be used, but when using a bag filter (sometimes referred to as BF) in the latter stage, a powdered one is used. preferable. The neutralizing agent can be added by disposing a neutralizing device for spraying the alkaline chemical agent as a neutralizing agent in the exhaust pipe connected to the gas discharge port 6.

  Next, the exhaust gas f after combustion via the exhaust pipe is introduced from the gas discharge port 6 into a quenching and cooling tower, such as a jacket cooler that preferably does not directly contact the cooling water with gas and liquid. Preferably it cools to 180 degrees C or less. That is, the fly ash is easily collected by the bag filter at the latter stage.

  The fourth step is a fly ash collection and separation step. By passing the neutralized and reduced temperature exhaust gas containing fly ash, neutralized product, etc. through the bag filter, fly ash and neutralized product Can be collected. Fly ash and neutralized products collected by the bag filter contain metals such as iron, aluminum, copper, lead, and zinc, and also contain halogen elements such as chlorine, fluorine, and bromine. Each component varies depending on the composition of the original shredder dust, but iron 1-10%, aluminum 1-5%, copper 5-15%, lead 1-5%, zinc 1-5%, chlorine 1-15% , Fluorine + bromine is 0.1% or less.

  In addition, the above-mentioned bag filter having a stable separation efficiency is suitable for the apparatus for collecting and separating fly ash in the fourth step, but is not limited to this, and the solid fine powder entrained in the gas For example, a cotrel, a scrubber, or the like may be employed. If a cot rel is adopted, the rapid cooling and temperature reduction may be omitted, and if a scrubber is adopted, the rapid cooling and temperature reduction may be combined because of a gas-liquid contact method.

  Next, in the fifth step, the fly ash and neutralized material collected in the fourth step are added to water to perform a water washing treatment. The collected fly ash and neutralized products are concentrated in valuable metals and can be used as smelting raw materials as they are. Since the halogen element is also contained in a relatively large amount as described above, there is a possibility that the consumption of the inner bricks of the processing furnace may be accelerated when supplied to a processing furnace such as a flash smelting furnace used in the smelting process. For this reason, water is added to the fly ash and the neutralized product, followed by solid-liquid separation after stirring or mixing to recover the water washing residue. By separating the residue by this water washing, halogen elements such as chlorine can be transferred to the liquid side, and as a residue, a smelting raw material with a small amount of halogen elements such as chlorine and concentrated metal can be obtained. In addition, by setting the incineration temperature to 900 ° C. or less in the third step (combustion step), it is considered that the heavy metal is in a chemically stable form and the elution to the liquid side is suppressed.

  In addition, as described above, the mixture of fluidized sand and incombustible material that has been heat-treated in the first step to become incombustible material and discharged separately from the incombustible material discharge port 2 at the bottom of the furnace is further separated and smelted. Use as raw material. When quartz sand is used as fluidized sand, this mixture can be used as a raw material for smelting as it is. In addition, the fluid sand that accompanies incombustibles has metals such as iron, aluminum, and copper adhering to the dust, so this mixture of fluid sand and incombustible material is separated using the particle size difference and is different for each. It can also be used as a smelting raw material. Preferably, by using a 2 mm sieve, it can be sieved into non-combustible material over sieve and fluidized sand under sieve. Although fine metal adheres to the fluidized sand, when silica sand is used as the fluidized sand, it can be used as a raw material for the smelting process such as a copper smelting furnace as a slag-forming agent, and recovery of valuable metals adhering to the silica sand. Is also possible. In addition, when the specific gravity difference of an incombustible material and fluidized sand is large, it can replace with sieving or can also use together with a sieving, and can also employ | adopt a specific gravity separation system.

By the above dust treatment method, the metal in the shredder dust can be recovered in an uncombusted state in the incombustible material first by heat treatment, and the washing residue obtained by removing the halogen element from the fly ash in the exhaust gas from the combustion process is recovered. These can be used as smelting raw materials, respectively. Furthermore, the metal recovered by the neutralization treatment of the washing water, or the fluidized sand and incombustible material separated and discharged from the incombustible discharge port 2 at the bottom of the furnace. The recovered fluidized sand, to which fine metals further separated from the mixture, are attached as smelting raw materials.
The recovered smelting raw materials are separated into individual metals in the form of merging with metals from ordinary ore raw materials by charging them into the actual smelting process without further separation by metal. It will be collected.

Exhaust gas etc. discharged through each of the above steps is further released to the atmosphere through abatement equipment etc., but the exhaust gas from which halogen elements such as metals and chlorine have been removed by this treatment method has become harmless. Safety has been confirmed.
As mentioned above, although the form which performed each process, such as heating and combustion by a fluidized-bed incinerator, was shown as a dust treatment method of the present invention, it does not restrict to it, but a primary combustion furnace and a secondary combustion, respectively It can also be carried out in a furnace.

  Next, another flowchart of the present invention is shown in FIG. This is basically the same as in the case of the flowchart shown in FIG. 1, except that a 2 mm sieve is used for sieving the mixture of incombustible material obtained after the first step and fluid sand (silica sand). Incombustibles with high metal content such as copper can be recovered by separating sand (silica sand) with some metal such as copper from the dust as an underlayer. More efficient copper smelting can be performed by charging.

  Further, without providing a boiler water pipe in the fluidized bed incinerator itself, the exhaust gas after combustion generated in the third step of the fluidized bed incinerator is guided to the boiler to generate steam to perform heat recovery. The exhaust gas whose gas temperature has been reduced by heat recovery in the boiler is further rapidly cooled to Pass 1BF and collect fly ash. In this case, since the exhaust ash is before neutralization of exhaust gas, the obtained fly ash has a relatively low halogen content such as chlorine and can be supplied as it is to a smelting process such as a flash smelting furnace as a copper raw material. Next, no. The exhaust gas that passed through 1BF was neutralized. The neutralized ash is recovered by passing 2BF. This neutralized ash is concentrated in halogen content such as chlorine, but the residue with reduced halogen content such as chlorine obtained by wet processing such as water washing is used as a copper raw material for flash furnaces and the like. Can be supplied to the smelting process.

  As in the case of the flowchart of FIG. 1, even in the case of the flowchart of FIG. 3, the exhaust gas discharged through each step is further released into the atmosphere through a detoxification facility. Exhaust gas from which halogen elements such as metal and chlorine have been removed is rendered harmless and has been confirmed to be safe. In addition, safety is ensured by performing wastewater treatment on wastewater from which halogen such as chlorine has been transferred by performing wet treatment such as washing with water.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, it cannot be overemphasized that the technical scope of this invention is not limited by description of these Examples.

  [Example 1] A smelting raw material was recovered using the shredder dust having the material composition shown in Table 1 and the metal composition shown in Table 2 as treatment objects. Note that halogen elements such as chlorine, fluorine and bromine in the shredder dust are mainly contained in urethane and plastic.

In the fluidized bed incinerator 1 shown in FIG. 2, primary air a adjusted to have an air ratio of 0.4 from the primary air inlet 3 is blown upward from the lower part of the fluidized bed b and from the raw material inlet 4. The shredder dust having a size of 100 mm or less was charged on the fluidized bed at an average amount of 120 kg / h, and gasified in a reducing atmosphere while controlling the fluidized bed temperature at 650 ° C.
Moreover, the incombustible substance c which passed through the 1st process (heating process) with the fluid sand was extracted from the incombustible discharge port 2 of the furnace bottom. The metal content of the extracted mixture of fluid sand and incombustible material was as shown in Table 3 below.

The secondary air e is blown from the secondary air supply port 5 and the upflowing reducing vaporized gas which is gasified in the freeboard region d corresponding to the secondary combustion chamber is completely burned at 800 to 900 ° C. The later exhaust gas f was discharged out of the furnace through the gas discharge port 6.
After adding powdered slaked lime in the exhaust pipe part to the exhaust gas f after combustion accompanied with fly ash, it is introduced into a quenching and cooling tower, cooled to 170 to 180 ° C., and then neutralized from the exhaust gas by a bag filter. Dust containing fly ash (average generation of 16 kg / h) was collected.
The metal components of fly ash collected by the bag filter are as shown in Table 4, and those that can be smelted in the smelting process were obtained. The chlorine content and fluorine + bromine content in the fly ash were both 1% or less.

In order to further remove halogen elements such as chlorine contained in the fly ash, water is added to the fly ash so as to have a pulp concentration (referred to as PD) of 50, 100, 200 g / liter (represented by L). The mixture was stirred and washed with water, followed by solid-liquid separation with a filter press. The solid content obtained by solid-liquid separation (that is, a residue washed with water and referred to as a water washing residue) and the obtained liquid (that is, the liquid after washing and referred to as a water washing solution) are predetermined. Six samples were collected at time intervals.
The composition of the obtained water washing residue was as shown in Table 5, and the components contained in the water washing liquid were as shown in Table 6 and Table 7.

That is, the collected and collected fly ash can be washed with water to remove halogen elements such as chlorine, and the halogen load such as chlorine can be reduced, so that stable treatment in the smelting process is possible. Moreover, the content of valuable metals in the residue was not changed by washing with water.
Regarding the washing solution, Cu and Zn exceeded the regulation values of 0.5 mg / L and 4.0 mg / L, respectively, but the concentration of Cu was reduced by acidifying the washing solution and replacing it with Zn. Furthermore, by performing the neutralization process for the liquid after replacement, it was possible to remove Zn and clear the drainage regulation value.

About the incombustible material c including the fluidized sand extracted from the incombustible material outlet 2 of the fluidized bed incinerator 1 after the thermal decomposition by heating the shredder dust in the first step (that is, primary combustion and partial combustion). A sieving treatment was performed using a 5 mm sieve, and the product was separated into non-combustible material c over 5 mm (on the sieve) and fluid sand under 5 mm (under the sieve).
The composition of the incombustible material is as shown in Table 8, and the fluid sand had fine metal components attached as shown in Table 9.

  That is, an incombustible material that can be treated by smelting was obtained. By using silica sand as the fluidized sand, fluidized sand with fine valuable metals attached is used as a slag-forming agent in the smelting furnace of the smelting process to recover valuable metals, and other components are used as slag components. can do.

[ Reference Example 2] Using the shredder dust having the composition used in Example 1 as a raw material and silica sand as a fluid medium, the dust treatment method of the present invention was carried out on an operation scale according to the flowchart shown in FIG. The raw material was cut out at a rate of 3.2 ton / h with a chain feeder and charged into a fluidized bed incinerator. The primary air volume is blown at an air ratio of 0.51 and the secondary air volume is blown at an air ratio of 0.89. The temperature in the bed, the primary combustion chamber (1), the primary combustion chamber (2), and the temperatures of the secondary combustion chamber Was performed at each temperature described in Table 10.

[ Reference Example 3] As in Reference Example 2, the dust treatment method of the present invention was carried out on the operation scale according to the flowchart shown in FIG. 3 using the shredder dust having the composition used in Example 1 as a raw material and silica sand as a fluid medium. . The raw material was cut out at a rate of 3.2 ton / h with a chain feeder and charged into a fluidized bed incinerator. The primary air volume is blown at an air ratio of 0.54 and the secondary air volume is blown at an air ratio of 0.86, and the temperature in the bed, the primary combustion chamber (1), the primary combustion chamber (2), and the secondary combustion chamber temperatures. Was performed at each temperature described in Table 10.

The incombustible material obtained in the first step is classified with a 2 mm sieve, and the high-grade incombustible material is recovered as an overload, which is then loaded into the copper smelting process converter as a copper raw material. The collected sand (silica sand) was recovered and charged into a flash smelting furnace of a copper smelting process as a slagging agent. Further, the exhaust gas flow rate was about 35000 Nm ³ / h, and the number of CO peak occurrences was 0.
By maintaining the primary combustion chamber temperature at 800 ° C or lower and the secondary combustion chamber temperature at 950 ° C or lower in this way, heat recovery is performed while suppressing the generation of clinker in the furnace and preventing operational troubles. As in Example 1 and Example 2, incombustible material that can be processed by smelting can be obtained, and the fluidized sand with fine valuable metals attached is directly charged into the smelting furnace of the smelting process as a slagging agent. Valuable metals could be recovered.

  The present invention can be applied to recovering valuable metals, particularly non-ferrous metals, from dust such as shredder dust containing a mixture of valuable metal scraps, oxides, polymer compounds such as plastics, and the like.

It is a flowchart figure of the dust processing method which concerns on this invention. It is a schematic longitudinal cross-sectional view of the fluidized-bed incinerator used in the Example of the dust processing method which concerns on this invention. It is another flowchart figure of the dust processing method which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluidized bed incinerator 2 Incombustible discharge port 3 Primary supply port 4 Raw material inlet 5 Secondary supply port 6 Gas discharge port a Primary air b Fluidized bed c Incombustible material d Free board area e Secondary air f After combustion Exhaust gas

Claims (4)

In a fluidized bed in a fluidized bed furnace previously charged with a fluidized medium, shredder dust containing a metal and a polymer compound is combusted partially by supplying primary air with an air ratio of less than 1, and vaporized gas and non-combustible. the first step of obtaining and objects, the incombustible the second step of the smelting raw material was recovered by discharged outside the furnace, fully to supply secondary air to the vaporized gas in the freeboard zone of the furnace A third step for burning , a fourth step for discharging the exhaust gas after complete combustion to the outside of the furnace and collecting fly ash, and a residue obtained by washing the collected fly ash A dust treatment method comprising the fifth step . The dust treatment method according to claim 1 , wherein the first step is performed at 450 to 700 ° C., and the third step is performed at 800 to 900 ° C. The dust processing method according to claim 1 or 2 , wherein heat generated in the first step and the third step is recovered in a waste heat boiler. The dust processing method according to claim 1, wherein the fluid medium is silica sand .

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