JP3602328B2 - Method and apparatus for recovering chlorine from shredder dust - Google Patents

Description

【００３１】
【表２】

【００３２】
【表３】

【００３３】
【表４】

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【発明の効果】
本発明によれば、シュレッダーダストを焼却して有用金属等の資源を回収するにあたり、その焼却排ガスに含まれる塩化水素態の塩素を排ガスの持つ燃焼熱を利用して、好ましくは入手し易い炭酸カルシウムの添加による石灰乳からなる吸収液と反応させて塩化カルシウムとすることができ、また、前記吸収液を循環的に燃焼排ガスと接触させることにより濃縮的に塩化カルシウム液を生成させることができ、燃焼排ガスに同時に含まれる硫黄分を石膏として、重金属を硫化物としてそれぞれ除去し、安全で、且つ、ＪＩＳ規定を満足する精製塩化カルシウム製造できるものであって、効率的に、従って経済的に回収できる比較的簡単な方法及び装置を提供できるという効果を奏するものである。
【図面の簡単な説明】
【図１】本発明のシュレッダーダストの焼却によって発生する排ガスから塩化カルシウムを生成するための工程を示すフローシートである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating shredder dust from waste automobiles, waste home appliances, construction waste materials, and the like, and more particularly, to a method for recovering chlorine contained in shredder dust.
[0002]
[Prior art]
When looking at solid waste such as automobile parts, home appliances and construction waste materials by material, various members made of ferrous metals, non-ferrous metals, plastics, ceramics, and the like are used. In shredder dust generated when these members are crushed and decomposed by shredder treatment, the above-mentioned various materials are bonded or combined in various forms. For such shredder dust, in order to recycle metal materials, organic substances such as plastics and flammable inorganic substances are incinerated, and ferrous metals are collected from the incineration residue by magnetic separation, and non-ferrous metals. Various recovery methods have also been attempted for system metals.
[0003]
By the way, the above-mentioned shredder dust contains a large amount of plastic as an organic substance, and at present, polyvinyl chloride containing chlorine is most contained as this plastic. Therefore, in the incineration treatment of shredder dust, chlorine or hydrogen chloride is directly generated in the exhaust gas in the process, so that it is necessary to clean the exhaust gas with lime milk as a post-treatment step, and the generated chlorine is involved. Very toxic and stable dioxins can be produced, and their release into the air poses a very serious problem in terms of general environmental pollution. The situation is a major obstacle.
[0004]
On the other hand, calcium chloride is a calcium compound containing chlorine as a useful component and stably. It is known that calcium chloride is recovered as a by-product in the ammonia soda method for producing sodium carbonate using salt and calcium carbonate (limestone) as raw materials. That is, ammonia and carbon dioxide are sequentially reacted with saturated saline to crystallize and recover sodium bicarbonate, which is the base of sodium carbonate, and then, to the separated mother liquor, lime milk is added to generate calcium chloride, This is a method in which salt is removed during the concentration process, and solid calcium chloride is obtained by standing to cool.
[0005]
[Problems to be solved by the invention]
However, in this conventional method, there is no effective method for recovering chlorine or hydrogen chloride gas generated in the incineration process of shredder dust, and the cleaning solution for cleaning exhaust gas generated by incineration of shredder dust contains many impurities such as heavy metals. Therefore, high-grade calcium chloride cannot be obtained by a method based on the ammonia soda method. Further, since the cleaning solution has a low chlorine concentration, there is a problem in economical efficiency, such as requiring a huge amount of heat energy for heat concentration. Shredder dust also contains sulfur, and combustion exhaust gas from incineration contains sulfur dioxide. Therefore, there is a problem that gypsum scale is inevitably generated and absorbed at the time of absorption of chlorine gas or hydrogen chloride gas and concentration of calcium chloride solution, and this gypsum obstructs equipment and remarkably hinders workability. Further, there is a problem that the combustion exhaust gas also contains heavy metals, which hinder the purification of calcium chloride together with gypsum.
[0006]
In view of such a problem, the present invention eliminates the need for ammoniacal soda solution in the process of incinerating shredder dust and recovering resources such as useful metals, and eliminates sulfur dioxide and heavy metals contained in the combustion gas of shredder dust. Efficient separation and recovery, and efficient enrichment and immobilization of hydrogen chloride chlorine contained simultaneously in the form of a purified calcium chloride compound that is safe and can be reused without consuming new heat energy It is intended to provide a processing method and an apparatus.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention incinerates shredder dust, makes the combustion exhaust gas come into contact with an absorbent consisting of calcium carbonate emulsion circulating between a neutralization tank in a concentration tower, By absorbing hydrogen chloride and sulfur dioxide to form calcium chloride and gypsum, and by increasing the concentration of calcium chloride in the absorbing solution to reduce the solubility of the formed gypsum, the gypsum is preferentially removed to obtain a high concentration chloride. A calcium solution is obtained, a sulfurizing agent is added to the high-concentration calcium chloride solution to separate contained metals as sulfides, and then the wastewater from the incinerator is used to concentrate the calcium chloride solution to obtain a solid chloride. A method for recovering chlorine from shredder dust for obtaining calcium is provided.
[0008]
Furthermore, an incinerator for incinerating shredder dust, a combustion furnace for burning exhaust gas from the incinerator, and a flue gas from the combustion furnace are introduced and brought into contact with an absorbent comprising calcium carbonate latex to form calcium chloride. A concentration tower for generating and concentrating, a neutralization tank for circulating the absorbing solution between the concentration tower, a centrifuge for separating and removing gypsum from the concentrated solution extracted from the neutralization tank, A sulfide tank for receiving the separated liquid from the separator and reacting with a sulfide agent to precipitate metal sulfide, a filter for filtering and separating the metal sulfide from the sulfide tank, and an incinerator for filtering the filtrate from the filter. From the shredder dust comprising a precipitation condenser for concentrating and precipitating calcium chloride by utilizing the exhaust heat of, and a filtration device for separating and recovering the precipitated calcium chloride from the precipitation condenser. To provide a chlorine recovery system.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention utilizes thermal energy of high-temperature flue gas generated by incineration of shredder dust to obtain lime milk from calcium carbonate in a calcium chloride producing step, and to add lime milk to hydrogen chloride in flue gas in the flue gas. Is to directly react the chlorine in the form to obtain calcium chloride and to concentrate the calcium chloride. In order to prevent clogging of the equipment with gypsum, 400 g / l of calcium chloride is used. The gypsum is set to 300 g / l, and heavy metals contained in the high-concentration calcium chloride solution after the separation of gypsum can be removed as sulfide.
[0010]
Further, an embodiment of the present invention will be specifically described with reference to a flow sheet of FIG.
[0011]
A large amount of shredder dust can be treated by using a rotary kiln as an incinerator for shredder dust. The fuel is burned using an auxiliary fuel such as heavy oil, and the shredder dust is heated to 800 ° C. or more and incinerated using the combustion heat of the organic matter itself. The incineration residue is separately supplied to the physical separation process for recycling and collecting metal.
[0012]
Since the exhaust gas from this incineration contains hydrocarbon gas and the like in an unburned state, the secondary combustion furnace or the tertiary combustion furnace further uses an auxiliary fuel to complete combustion to produce combustion exhaust gas.
[0013]
Combustion exhaust gas containing hydrogen chloride gas, carbon dioxide gas, and the like is introduced into the concentration tower, and the contained hydrogen chloride gas is brought into contact with the absorbing solution. When the gypsum becomes supersaturated, the absorption liquid becomes a scale in a pump or a pipe and is easily clogged. Circulate. Furthermore, since this gypsum has a property that the solubility decreases in accordance with the concentration of calcium chloride in the coexistence with calcium chloride, the gypsum is less likely to be supersaturated, and troubles can be prevented. Gypsum is efficiently replenished by the addition of calcium carbonate to the neutralization tank and the heat of reaction with the sulfur dioxide contained in the exhaust gas. Calcium carbonate is also an inexpensive raw material. Due to the contact with the combustion exhaust gas at a high temperature in the concentration tower, hydrogen chloride gas is absorbed by 90% or more and reacts with calcium to generate calcium chloride. The absorption liquid continuously concentrates by producing calcium chloride in the circulation.
[0014]
After being brought into contact with an absorption solution consisting of a calcium compound in a concentration tower, hydrogen chloride gas is separated, and the cooled combustion exhaust gas is sent to a high-order washing tower, which is sufficiently washed with an aqueous solution of caustic soda. And emits it as a clean gas from the chimney into the atmosphere.
[0015]
On the other hand, the circulating absorbent becomes a solution concentrated with calcium chloride as described above, and the concentrated liquid stays at the bottom of the neutralization tank. Further, the absorbing liquid also reacts with sulfur oxides in the combustion exhaust gas to form gypsum, and the gypsum is concentrated. The gypsum precipitates and blocks a circulation pump, piping, and the like. Therefore, the concentrated liquid is appropriately extracted from the neutralization tank, the concentrated liquid is appropriately extracted together with the precipitated gypsum, and introduced into a centrifugal separator, whereby the gypsum can be separated by solid-liquid separation. In addition, this retained concentrated liquid is extracted in an amount corresponding to the supply amount of the new absorption liquid or calcium carbonate to the neutralization tank so that the circulation amount can be maintained.
[0016]
The separation liquid, that is, the high-concentration calcium chloride liquid contains, in addition to calcium chloride, heavy metals such as copper, lead, and zinc as impurities. The heavy metal can be precipitated as a hardly soluble metal sulfide by introducing this high-concentration calcium chloride solution into a sulfidation tank and adding and reacting sodium sulfide, which is easily reactive and easily available as a sulfidizing agent, The metal sulfide can be filtered and separated by applying the high-concentration calcium chloride solution containing the metal sulfide to a filter such as a filter press. This metal sulfide has a high zinc quality and can be recycled as a zinc smelting raw material.
[0017]
Further, the filtrate is a high-concentration calcium chloride solution containing sodium chloride, and this solution is condensed and sufficiently crystallized by condensing the solution in a precipitation condenser for electrically heating the solution. Can be. In addition, solid sodium chloride can be separated and recovered by applying the solid-liquid mixture to a filter, and solid calcium chloride can be recovered by further concentrating and crystallizing the obtained high-concentration calcium chloride filtrate. The fixed calcium chloride is a calcium chloride dihydrate having a purity satisfying JIS K8124 (for drying) and 8125 (for moisture measurement). The filtrate after recovering the calcium chloride can be circulated and used as a mother liquor of the absorbing solution.
[0018]
【Example】
Hereinafter, the shredder dust was treated according to the method and apparatus of the flow sheet of FIG. 1 and the products in each step from the shredder dust combustion exhaust gas absorbing solution to the formation of calcium chloride were investigated.
[0019]
That is, shredder dust typified by the properties shown in Table 1 was incinerated by heating at 800 ° C. or more in a rotary kiln by using auxiliary fuel such as heavy oil by utilizing the heat of combustion of organic substances contained in the shredder dust itself.
[0020]
The exhaust gas contains unburned hydrocarbon gas and the like, which was completely burned in a secondary combustion furnace and a tertiary combustion furnace using an auxiliary fuel to obtain a combustion exhaust gas.
[0021]
Combustion exhaust gas containing hydrogen chloride gas, sulfur dioxide gas, etc. is introduced from a caster-lined SS duct (inner diameter 350 mm) into a quenching section (carbon pipe) of a SUS316 concentration tower (inner diameter 350 mm, length 9500 mm) and contained. The hydrogen chloride gas is brought into contact with the absorbing solution sprayed by the coreless spray nozzle. At this time, the concentration of calcium and chlorine in the liquid is concentrated to about 150 g / l and about 200 to 300 g / l, respectively, by evaporating the water in the absorbing liquid by the exhaust heat and adding calcium carbonate in the circulating neutralization tank. Is done.
[0022]
280 L of this concentrated solution was withdrawn, and the degaypsum process was performed, that is, a solid, withdrawn under solid content, and introduced into a manual scraping-type centrifuge, and 100 kg of (CaSO ₄ ) produced from SO ₂ in the exhaust gas was separated from the solution. did.
[0023]
The separated solution (240 L) is stored in a Teflon-lined SUS316L filtrate cushion tank and sent to the subsequent sulfurization step.
[0024]
In a SUS316L type sulfurizing tank lined with Teflon, 0.67 kg of sodium sulfide was added to the separator, and after the reaction, the mixture was filtered with a manually openable filter press having a filter area of 0.96 m ² to remove 10 kg of sulfurized residue. Obtained.
[0025]
The filtrate, that is, 200 L of a high concentration calcium chloride solution was heated and concentrated in a precipitation pot on a deposition electric furnace having an open top.
[0026]
As the concentration proceeds, sodium chloride precipitates first. In this test, when the calcium chloride became 40 wt% in the solution, heating was temporarily stopped at a liquid volume of 150 L, and sodium chloride was separated by a magnetic funnel type filter.
[0027]
The filtrate is again concentrated by heating on a deposition electric furnace, and the heating is stopped at about the remaining 8 L, and the precipitated calcium chloride and the filtrate are separated and collected by the filter.
[0028]
As described above, Table 2 shows a series of intermediate products from the concentrated solution to the formation of calcium chloride, the results of measuring the calcium concentration and the chlorine concentration of each process solution, and the amounts of calcium and chlorine.
[0029]
Table 3 shows the analytical values of the components of the sulfurized residue obtained in the sulfurization step, and Table 4 shows the grade of calcium chloride obtained as the final product.
[0030]
[Table 1]

[0031]
[Table 2]

[0032]
[Table 3]

[0033]
[Table 4]

[0034]
【The invention's effect】
According to the present invention, in recovering resources such as useful metals by incineration of shredder dust, hydrogen chloride chlorine contained in the incineration exhaust gas is utilized by utilizing the combustion heat of the exhaust gas, and carbon dioxide is preferably easily available. It can be reacted with an absorbing solution composed of lime milk by adding calcium to form calcium chloride, and the absorbing solution can be concentrated and produced by contacting the absorbing solution with combustion exhaust gas in a concentrated manner. It removes sulfur contained in the combustion exhaust gas simultaneously as gypsum and heavy metals as sulfides, and can produce purified calcium chloride that is safe and satisfies JIS regulations. This has the effect of providing a relatively simple method and apparatus that can be recovered.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing a process for producing calcium chloride from exhaust gas generated by incineration of shredder dust of the present invention.

Claims (2)

The shredder dust is incinerated, and the flue gas is brought into contact with an absorbent consisting of calcium carbonate latex circulating between the neutralization tank in the concentration tower to absorb hydrogen chloride and sulfur dioxide in the flue gas to form calcium chloride. Gypsum is produced, and the concentration of calcium chloride in the absorbing solution is increased to reduce the solubility of the produced gypsum, thereby preferentially removing the gypsum to obtain a high-concentration calcium chloride solution. A method for recovering chlorine from shredder dust, comprising adding a sulfurizing agent to separate contained metals as sulfides, and condensing by heating to obtain solid calcium chloride. An incinerator for incinerating the shredder dust, a concentrating tower for introducing the flue gas from the combustion furnace and bringing it into contact with an absorbing solution comprising calcium carbonate emulsion to generate and concentrate calcium chloride, and A neutralizing tank for circulating the absorbing solution, a centrifuge for separating and removing gypsum from the concentrated solution extracted from the neutralizing tank, and receiving the separated solution from the centrifugal separator and reacting it with a sulfurizing agent to form a metal sulfide. A sulfide tank for precipitating matter, a filter for filtering and separating the metal sulfide from the sulfide tank, a precipitation condenser for heating and concentrating a filtrate from the filter to precipitate calcium chloride, and And a filtration device for separating and recovering calcium chloride precipitated from the shredder dust.

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