JPH0459088A - Method for recovering valuable metal from shredder dust - Google Patents

Abstract

PURPOSE:To improve the efficiency in reducing the volume and to reduce the incineration cost by providing a first stage for again shredding dust with a shredder and magnetically separating the dust, a second stage for partially burning the dust in a fluidized-bed furnace and a third stage for separating and recovering valuable metals. CONSTITUTION:The supplied shredder dust is again shredded by a shredder into pieces having about 40mm size in the first stage. The shredded dust from the first stage as such or that magnetically separated, as required, is charged into a fluidized-bed furnace to partially burn the org. matter such as plastics and to decompose the org. matter into gas in the second stage. In the third stage valuable metals are recovered from the slag generated in the second stage by well-known beneficiation utilizing the physical properties of the slag or by the well-known refining method utilizing the chemical properties of the slag. The fluidized-bed furnace is efficiently and stably operated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a method for recovering valuable metals from shredder dust.

(b) Conventional technology A scrap car or a scrap home appliance, etc. is dismantled and its main parts removed, then soft pressed and shredded using a shredder.
Large metals are recovered, but at this time a large amount of dust is discharged, which is mainly composed of plastics and contains some valuable metals.

This dust is called "shredder dust", and its standard chemical components are shown in Table 1 below, and examples of metal components in the dust are shown below. As shown in Table 2.

In addition, in terms of size, it is usually cut with a blade width of 150 fiIm, but some of the dust is about 500 mm in length, so it is currently impossible to determine an unbiased value.

In addition, plastic scraps, metal pieces, metal wire scraps, glass scraps,
Sponge waste and other substances are intricately intertwined, making it almost impossible to separate them in this state.

As mentioned above, since shul/ladder dust contains various components and is intertwined with various shapes, there is no suitable treatment method in actual operation. For this reason, it is common practice to dispose of waste in landfills, but the bulk specific gravity of
．． 3, which is extremely small, and the volume of landfill is enormous, creating social problems such as securing land for landfill, and as a result, various disposal methods are currently being considered in various places.

The main processing methods that have been proposed to date are listed below.

■Here furnace type incineration method: 100 to 600 in the primary combustion furnace using a park furnace etc.
It is said that by suppressing combustion at °C and then completely burning the generated gas in a secondary combustion furnace, it is possible to reduce the volume of dust and the amount of hydrochloric acid gas in the exhaust gas.

■Double circulating incineration method: Two fluidized bed furnaces are used, hot sand is circulated between them to thermally decompose the dust, thermal energy is recovered from the exhaust gas, and the incineration dust is disposed of.

■Fluidized bed incineration method: Using one fluidized bed furnace, the dust is completely combusted, and then thermal energy from the furnace gas is converted into electrical energy and recovered. The incineration dust will be disposed of, but the hydrochloric acid in the exhaust gas will be fixed by putting lime etc. into the furnace.

■Rotary kiln incineration method: Since it is difficult to remove foreign materials from waste containing metal pieces in a fluidized bed furnace, the rotary kiln method is used. That is, after the dust is incinerated in a rotary kiln and the exhaust gas is combusted in a reburning chamber, thermal energy is converted into electrical energy and recovered in the next step.

■ Gravel bed incineration method: The dust is placed on the gravel bed of a gravel bed incinerator and incinerated while being moved, and thermal energy is recovered from the combustion exhaust gas in the same manner as in the above methods.

What these methods have in common is that the primary purpose is to reduce the volume of dust, and the secondary purpose is to fix hydrochloric acid in the combustion exhaust gas.
The second purpose is to recover heat from exhaust gas.The third purpose is to recover heat from exhaust gas. That is, by reducing the volume of dust through incineration and recovering thermal energy from the combustion exhaust gas, the cost of incineration is reduced.

The first and second objectives mentioned above are essential conditions for solving the problem, but the third objective is to recover thermal fuel to reduce incineration costs, and from the point of view of recycling redder dust. It can be highly evaluated in society.

However, recovering thermal energy requires significant capital investment as well as locational conditions for effective use of the recovered energy. Furthermore, in each of the above methods, recycling of the slag produced is not attempted, and the achievement rate of the first objective of volume reduction or weight reduction is low.

In addition, there are significant differences in the selection of combustion furnaces and their operating methods in the press method, and there are still problems that need to be resolved, such as the fact that the shrender dust itself is extremely difficult to handle and it is difficult to achieve stable combustion in the furnace. There are many.

(C) Disclosure of the Invention The main purpose of the present invention is to separate and recover valuable metals and glass from the slag after incinerating shredder dust, and further improve the volume reduction achievement rate, which is the first objective of the above conventional method. The aim is to improve this and reduce incineration costs.

Therefore, when recovering thermal energy, it is possible to add or use a process in combination as appropriate, but this is not the intention of the present invention.

That is, the present invention selects a fluidized bed furnace as an efficient and highly productive incinerator, performs pre-treatment to ensure stable incineration within the fluidized bed furnace, and limits the operating conditions of the fluidized bed furnace. This made it possible to operate the fluidized bed furnace stably and recover valuable metals.

When recovering valuable metals from shredder dust containing value-adding metals and organic substances, the present invention comprises a first step of shredding the dust again into pieces of 40 mm or less and performing magnetic beneficiation as necessary; The dust obtained in the process as it is or the dust after magnetic separation is heated at a furnace temperature of 400°C or higher, which is the decomposition temperature of organic matter, or lower than the melting point of aluminum, 650°C, and at a gas velocity of 50 to 150 cm/sec.
A second step in which combustion is suppressed in a fluidized bed furnace under the conditions of a combustion air ratio of 0.2 to 0.6, and the physical or chemical properties of the slag generated in the second step are utilized. The present invention provides a method for recovering valuable metals from shredder dust, which comprises a third step of separating and recovering valuable metals by known mining means or known smelting means.

FIG. 1 is a schematic process diagram showing an example of a method for reducing the volume of shredder dust and recycling it according to the invention. Next, the invention will be explained in the order of steps.

First, in the first step, the received Shredder Dass I is shredded again into small pieces of about 40 mm or less. Immediately after the dust is broken down into small pieces, it is separated into metal pieces, plastic pieces, sponge-like things, wire scraps, etc., so it is possible to use simple mineral beneficiation methods such as magnetic beneficiation. Due to the large volume, complicated one-mine methods cannot be used.

Next, in the second step, the dust as it is after being cut from the first step, or the dust subjected to beneficiation such as magnetic beneficiation as necessary, is charged into a fluidized bed furnace to partially remove organic matter such as plastics. Although combustion and decomposition gasification are performed, the following operating conditions are essential for recovery of metal components and stable operation of the fluidized bed furnace.

First, in order to prevent aluminum from melting, the maximum temperature of the fluidized bed furnace should be set at 650°C or higher, preferably 600°C or lower, and the minimum temperature should be set at 400°C or higher to promote the decomposition of organic matter. ℃ or higher, preferably 500℃ or higher. As a result of experiments, it was found that at an operating temperature of 650°C or higher, the aluminum content melts, and the contained metal becomes finer and oxidized, making it difficult to recover the metal in subsequent processes. The delay makes combustion unstable.

As a second condition, in order to prevent oxidation of metals, the amount of air blown into the fluidized bed furnace is set to 0.2 to 0.6, preferably 0.3 to 0.5, of the amount of air required for combustion of organic matter. suppress. The lowest air ratio (0,2) is necessary for continued combustion, and the highest air ratio (0,8) is necessary to prevent metal oxidation and chlorination.

The third condition is to stabilize the operation of the fluidized bed furnace.
The gas velocity in the furnace is 50-150 cm/s, preferably 8
It is necessary to adjust the speed between 0 and 120 cm/sec. As is well known, fluidized bed furnaces are used for materials with similar shapes and small aspect ratios, and when incinerating irregularly shaped and coarse materials such as shredder dust, the fluidized bed furnace deteriorates the flow of the medium in the furnace. However, there is a risk that the long-term stability of the situation may be undermined.
Coupled with the first step of cutting into small pieces, the flow state in the furnace is stabilized in correlation with the gas velocity in the furnace.

Further, coarse pieces and coarse particle slag are discharged from the lower part of the fluidized bed furnace, and gas accompanied by fine powder is discharged from a part of the furnace. The gas passes through a dust collector to separate and remove fine slag, and then the organic decomposition gas is combusted again (secondary combustion).
It becomes harmless and dissipates into the atmosphere.

In the third step, valuable metals are recovered from the slag generated in the second step described in L by means such as known beneficiation using the physical properties of the slag or known smelting using the chemical properties. An invention is not limited to its method or means.

However, when carrying out the present invention, the most effective recovery method is to collect coarse pieces and coarse grains from the slag by beneficiation means such as specific gravity beneficiation or magnetic beneficiation, or from the slag to fine powder. It is preferable to recover valuable metals by hydrometallurgical means such as leaching.

By satisfying the above-mentioned conditions in the second step, the coarse pieces and coarse particles of the slag can be discharged from the furnace without the valuable metals changing shape due to melting or being oxidized.
It is desirable to recover valuable metals by means of beneficiation that utilizes the physical properties of the slag.

In addition, fine sintered slag has small particles and a large surface area, so partial oxidation of the metal surface is unavoidable, making physical methods such as beneficiation alone unsuitable. It is desirable to recover the metal.

Next, the method of the present invention will be explained using examples.

(d) Examples The composition of the shredder dust used in the examples of the present invention is as shown in Tables 1 and 2.

Example 1 Shredder dust having the composition shown in Tables 1 and 2 was shredded again to pieces of 40 mm or less, and then subjected to magnetic beneficiation to recover only the iron content as a magnetic material.

The residue (non-magnetic material) after recovering the iron content is 40cmφ in diameter.
The mixture was charged into a fluidized bed furnace at a rate of 60 kg per hour. The operating conditions of this fluidized bed furnace are a temperature of 550°C and a gas velocity of 95°C.
am/sec and an air ratio of 0.4, and the temperature was regulated by water sparging.

Process 1 The metal in the coarse pieces and coarse particles discharged from the lower part of the furnace is oxidized and
No evidence of melting was observed, and it was easily recovered by physical means such as sieving, 9-gravity beneficiation, and table beneficiation.

On the other hand, the furnace exhaust gas containing fine particles was collected and removed by a dust collector, subjected to secondary combustion, and then cooled with gas and released into the atmosphere. The fine particles collected by the dust collector were slightly oxidized, so they were leached with dilute hydrochloric acid and then floated to recover copper, lead, and zinc concentrates.

- The recovered materials obtained from each of the collected treated culms in section F are iron scraps, aluminum scraps, copper scraps, glass scraps, and copper fist lead/zinc concentrate,
Their grades and actual yields are shown in Table 3.

In Table 3, it can be seen that the main component of the residue to be discarded is glass, and the amount generated is approximately 250 kg/T-raw material, indicating that the weight and volume have been significantly reduced.

Furthermore, Table 4 shows the measurement results of exhaust gas components after secondary combustion.

Pollution prevention regulatory values have been established for combustion gas emissions, and a comparison with the regulatory values is shown in Table 5.

HCu, NOx, and SOx are all well below regulation values, and there is no problem in terms of environmental pollution.

Example 2 Similar to Example 1, shredder dust with the composition shown in Tables 1 and 2 was tested, and the cutting conditions and operating conditions of the fluidized bed furnace (temperature, gas velocity, air ratio) were varied. The other conditions were the same as in Example 1.

The results are shown in Table 6. As can be seen from Table 6, the first
] [With No. 1, No. 2, without cutting, it is impossible to operate due to poor flow, and with cutting, No. 3, which has a high gas velocity and air ratio, cannot be operated for a long time due to the hearth scattering. Among No. 7, which has an extremely high ratio, and No. 10, which has a low air ratio, metal recovery is impossible in the former, and long-term operation is unstable in the latter, and No. 14 has a low furnace temperature.
For No. 15, long-term operation is unstable.

Other experimental examples No. 4, No. 5, No.
6, No.

8, No, 9, No, l 1, No,
12, No. 13, long-term operation is possible and metal recovery is possible, but the recovery rate is low;
13 (With cutting, gas velocity 95 cm/sec, air ratio 0
．． 4. When the temperature was 550 to 600°C, long-term operation was possible and valuable metals were recovered well.

(Blank below) (e) Effects of the invention - I - As mentioned above, the main purpose of the method of the present invention is to reduce the volume of shredder dust and recycle it, and to suppress shredder dust at low temperatures using a fluidized bed method with high efficiency. In addition to incineration using the combustion method, valuable metals are recovered from the generated slag, contributing to reducing the volume and weight of waste as much as possible.

Since the present invention is configured as described below, it has the following advantages.

a) Stabilization of fluidized bed incineration operation by JG pre-cutting: By performing pre-cutting and maintaining appropriate gas velocity, stable operation of the fluidized bed furnace can be achieved with high efficiency.

b) Increased efficiency of incineration through suppressed combustion: Because the fluidized bed suppressed combustion method is adopted, the amount of incineration per unit area of the hearth is approximately three times that of the conventional method.

C) Recovery of valuable metals by low-temperature suppressed combustion method: Because of low-temperature combustion in a reducing atmosphere, oxidation of metals can be prevented as much as possible, and valuable metals can be recovered from the slag.

d) Omission of gas cleaning process by fixing hydrochloric acid gas: Due to suppressed combustion at low temperatures, the chlorine content in the raw material is fixed in the incinerated ash, so the exhaust gas does not need dechlorination treatment, and the incinerated ash is collected. Afterwards, it can be released into the atmosphere through secondary combustion.

e) Minimization of waste: The residue after collecting valuable metals will be disposed of along with the incineration ash, but the volume reduction rate is approximately 95Vo.
A weight loss rate of 1% or more and a weight loss rate of about 70% or more can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic process diagram showing an example of the method for recovering valuables from shredder dust according to the present invention.

Claims (1)

[Claims] When recovering valuable metals from shredder dust containing valuable metals and organic substances, there is a first step in which the dust is shredded again to be cut into pieces of 40 mm or less, and if necessary magnetic beneficiation, and the raw material obtained in the first step is Alternatively, the dust after magnetic beneficiation is heated to a temperature of 400℃ or higher in the furnace to 650℃.
℃, a gas velocity of 50 to 150 cm/sec, and a combustion air ratio of 0.2 to 0.6 in a second step of suppressed combustion in a fluidized bed furnace, and from the slag generated in the second step A third step of separating and recovering valuable metals by known beneficiation means or smelting means using the physical or chemical properties of
A method for recovering valuable metals from shredder dust, comprising: