JP4393915B2 - Method for treating substances containing zinc, lead and chlorine - Google Patents

Description

  The present invention relates to a method for treating a substance containing zinc, lead and chlorine such as molten fly ash or a mixture of molten fly ash and other dust (for example, incineration fly ash, steel dust, etc.).

Molten fly ash produced by melting incineration main ash (incineration residue), incineration fly ash, etc. of flammable waste (for example, combustible waste from general households) is composed of heavy metals such as zinc and lead, and chlorine Is contained at a high content. Moreover, the steel dust produced by processing steel scrap etc. with a steelmaking furnace contains much zinc other than iron.
Waste containing zinc, lead, etc., such as molten fly ash or a mixture of molten fly ash and steel dust, contains heavy metals such as zinc and lead. Therefore, it is necessary to dispose landfills after removing these heavy metals. is there.
Known methods for recovering heavy metals such as zinc and lead include wet recovery methods and dry recovery methods.
As a wet recovery method, for example, after adding water and a neutralizing agent to fly ash to adjust the pH of the solution to 8-11, water is added to the resulting residue after the first step of solid-liquid separation Repulping and adjusting the pH to 3 or less to elute heavy metals mainly composed of zinc and copper, and then filtering out residues containing heavy metals mainly composed of lead; Incineration comprising a third step of adding a neutralizing agent to the filtrate obtained in the step and the second step and neutralizing to pH 7 or higher to produce a heavy metal hydroxide mainly composed of zinc A method for treating fly ash from a furnace and a melting furnace has been proposed (Patent Document 1).
The wet recovery method has the advantage that various heavy metals can be recovered separately without using a heat source, but has a disadvantage that a large amount of water is required and the treatment process is complicated.

On the other hand, examples of the dry recovery method include a chloride volatilization method and a reduction volatilization method.
As a chlorination volatilization method, for example, incineration ash or fly ash is kneaded in the presence of chlorine, chlorine compounds or chloride ions, and chlorination is performed using chlorides of heavy metals and zinc compounds contained in the incineration ash or fly ash. Incineration ash or fly ash detoxification method comprising a step and a heat removal step of heating the incinerated ash or fly ash kneaded product to 600 to 900 ° C. to volatilize and remove chlorides of heavy metals together with zinc chloride and the like Has been proposed (Patent Document 2).
The chlorination volatilization method removes high boiling point metals by volatilizing them as low boiling point chlorides, and can recover heavy metals at a relatively low temperature and low energy load. It is widely used as a method for recovering harmful heavy metals from waste from the viewpoint that it can be volatilized and recovered.
As a reduction volatilization method, for example, when a carbonaceous reducing agent is added to steel dust containing zinc and subjected to reduction roasting, when zinc is volatilized and recovered as zinc oxide, a specific amount of sodium carbonate is added, A method for increasing the reduction volatilization amount of zinc oxide has been proposed (Patent Document 3).
The reduction volatilization method using a rotary kiln is known as the Welts method.
JP-A-8-141539 JP 2000-301103 A JP 2003-301226 A

When waste containing zinc, lead and chlorine such as molten fly ash is heated in a heating furnace having a predetermined temperature, exhaust gas containing volatile components containing zinc, lead and chlorine is generated. When this exhaust gas is guided from a heating furnace to a dry dust collector and dust in the exhaust gas is collected, dust containing zinc chloride, lead chloride and the like is obtained.
However, since zinc chloride contained in the dust has deliquescence, it causes clogging of a filter cloth or the like of a dry dust collector (for example, a bag filter). Zinc chloride also causes corrosion of processing equipment.
Therefore, the present invention is a method for dry treatment of substances containing zinc, lead and chlorine such as molten fly ash, and these zinc, lead and chlorine may adversely affect the operation of the dry dust collector or It is an object of the present invention to provide a method that can be recovered as non-deliquescent dust that does not promote corrosion.

As a result of intensive studies to solve the above problems, the present inventor has adjusted the content of chlorine and (alkaline metal + lead ) with respect to a specific treatment object that is a substance containing at least zinc, lead and chlorine. ) / Chlorine chemical equivalent ratio is adjusted, and a reducing agent is added to obtain a heating material. Then, the heating material is heated in a heating furnace at a predetermined temperature to obtain zinc, lead. If exhaust gas containing chlorine as a volatile component is generated, non-deliquescent dust consisting of zinc oxide, lead chloride, alkali metal chloride, etc. is generated in the exhaust gas, and this dust is collected by a dry dust collector. The present invention was completed by finding that it can be suitably recovered.
That is, the method for treating a substance containing zinc, lead and chlorine according to the present invention is (A) a treatment object which is a substance containing at least zinc, lead and chlorine, and is molten fly ash or incinerated with molten fly ash. Adjust the chlorine content and the chemical equivalent ratio of (alkali metal + lead) / chlorine to the treatment object consisting of a mixture of fly ash or steel dust , and add a reducing agent. A material preparation step of preparing a heating material having a chlorine content of 1 to 8% by mass and a chemical equivalent ratio of (alkali metal + lead) / chlorine of 1.2 or more ; (B) the heating material Is heated in a heating furnace at a temperature of 900 to 1,300 ° C. , and an exhaust gas containing zinc, lead and chlorine, a heating step for obtaining a fired product, and (C) a dry dust collector, from the exhaust gas, Collects dust mainly composed of zinc oxide and lead chloride Look containing a metal recovery process, removing the adjustment of the content of chlorine in the step (A) is a (a) by dividing the processing object into two at an appropriate ratio, chlorine and washing the one only Then, both are mixed to adjust the chlorine content to a desired value, (b) two kinds of substances having different chlorine contents are used as the object to be treated, and the chlorine content is A method of mixing a large substance and a substance having a small chlorine content at an appropriate ratio to obtain a mixture having a desired chlorine content, and (alkaline metal + lead in the step (A)) ) / Chemical equivalent ratio adjustment of chlorine is (a) waste glass, construction mixed waste including gypsum board generated when building is demolished, contaminated soil, alkali metal carbonate containing alkali metal A method of adding contained substances, (b) steel A method of adding the strike, characterized in that it is made by either.

  According to the treatment method of the present invention, zinc, lead and chlorine from substances containing zinc, lead and chlorine, such as molten fly ash, adversely affect the operation of the dry dust collector or promote corrosion of treatment equipment. It can be recovered as non-deliquescent dust (dust containing zinc oxide), and a fired product that can be used as a cement raw material with a low content of zinc, lead and chlorine can be obtained.

Hereinafter, the processing method of this invention is demonstrated in detail for every process.
[A. Material preparation process]
This process is a processing object that is a substance containing at least zinc, lead and chlorine, and for a processing object consisting of molten fly ash, or a mixture of molten fly ash and incineration fly ash or steel dust , Adjusting the chlorine content and adjusting the chemical equivalent ratio of (alkali metal + lead) / chlorine, and adding a reducing agent, the chlorine content is 1 to 8% by mass and (alkali metal + It is a step of preparing a heating material having a chemical equivalent ratio of (lead) / chlorine of 1.2 or more .
A substance containing zinc, lead and chlorine (hereinafter also referred to as “containing substance such as zinc”) which is the object of treatment of the present invention is molten fly ash, or a mixture of molten fly ash and incinerated fly ash or steel dust. It is .
The average component composition of the molten fly ash is 30% by mass of calcium, 9% by mass of sodium, 10% by mass of potassium, 2% by mass of lead, 5% by mass of zinc, 24% by mass of chlorine. The mass ratio is shown in FIG.
The content of chlorine of the heating material is 1-8 wt%, is adjusted preferably 1 to 7 wt%, more preferably 2 to 6% by weight, particularly preferably 3 to 5 mass%. If the content is less than 1% by mass, the volatilization of lead and alkali metals may not sufficiently proceed, and the content of lead and the like remaining in the fired product may increase. When the content exceeds 8% by mass, the dust in the exhaust gas collected in the subsequent process may exhibit deliquescence including zinc chloride, and may adhere to the filter cloth of the dry dust collector. There is a risk of accelerating the corrosion of the processing equipment by adversely affecting the operation of the dust collector or adhering to the inner wall surface of the exhaust gas flow passage.
The method for adjusting the chlorine content in the heating material is as follows: (a) Divide the zinc-containing material such as molten fly ash into two at an appropriate ratio, and wash only one of them with water to remove chlorine. After removing, mixing both to adjust the chlorine content to a desired value, (b) a substance with a high chlorine content such as molten fly ash, and a low chlorine content such as steel dust the material was mixed at an appropriate ratio, and method, and the like to obtain a mixture having the desired chlorine content.
In addition, when removing chlorine by washing with water, it is desirable to provide a preheating step before heating in the heating furnace to dry the heating material. In this case, it may be necessary to remove heavy metals contained in the filtrate after washing with water.

Chemical equivalent ratio of the heating material (alkali metal + Pb) / chlorine, 1.2 or more, preferably 1.3 or more, and more preferably is adjusted to 1.4 or more. When the chemical equivalent ratio is less than 1.2, the dust in the exhaust gas collected in the post-process may exhibit deliquescence including zinc chloride, which may adversely affect the operation of the dry dust collector or may be treated. May accelerate equipment corrosion.
The upper limit of the chemical equivalent ratio is preferably 3.0 or less, more preferably 2.5 or less, and particularly preferably 2.0 or less. If the chemical equivalent ratio exceeds 3.0, the amount of lead or alkali metal remaining in the fired product after heating increases, which may cause inconveniences such as requiring reprocessing.
The chemical equivalent means an amount of a substance that reacts with 0.5 mol of oxygen. For example, when 1 mol of alkali metal, 1 mol of lead, and 3 mol of chlorine are present, the chemical equivalent ratio of (alkali metal + lead) / chlorine is calculated as (1 + 2) / 3 = 1.
As a method for adjusting the chemical equivalent ratio, (a) a method of adding an alkali metal-containing material, small dust content of (b) chlorine (specifically, steel dust) method adding, but Can be mentioned.
Among these, as alkali metal-containing substances used in the method (a), waste glass, construction mixed waste (specifically, waste including gypsum board generated when the building is demolished), contamination (specifically, heavy metals, soil contaminated with dioxin) soil alkali metal-containing wastes, such as and, sodium carbonate, and alkali metal-containing agents such as an alkali metal-containing carbonate such as potassium carbonate. Among them, waste glass and construction mixed waste are preferably used from the viewpoints of cost reduction, promotion of waste recycling, and the like. In addition, the contaminated soil is preferably used from the viewpoint of removing harmful substances.

Examples of the reducing agent used in this step include carbonaceous reducing agents such as activated carbon, coke, and flammable waste (for example, waste plastics, shredder dust for home appliances and automobiles, solid waste fuel (RDF), etc.), and the like. It is done.
In addition, when using chlorine containing substances, such as a waste plastic and shredder dust, as a reducing agent, it is necessary to aim at adjustment of the above-mentioned chlorine content rate etc. also considering the chlorine contained in this reducing agent.
In the present invention, zinc oxide can be generated instead of zinc chloride in the exhaust gas generated by heating the heating material by adding a reducing agent to a substance containing zinc or the like that is the object to be treated. However, as described above, in order to produce zinc oxide, it is not sufficient to add a reducing agent alone, and adjustment of the chlorine content and the like is necessary.
The compounding amount of the reducing agent is preferably 5 to 40 parts by mass, more preferably 10 to 30 parts by mass, particularly preferably 15 to 100 parts by mass (dry mass) of all components of the heating material excluding the reducing agent. 25 parts by mass. If the blending amount is less than 5 parts by mass, zinc chloride may be mixed with dust in the exhaust gas collected by the dry dust collector, and deliquescence may be exhibited. If the blending amount exceeds 40 parts by mass, the amount of input heat becomes excessive, so that the volatilization of zinc, lead, and chlorine is inhibited by melting of the fired product, and the cost increases when the reducing agent is valuable. This is not preferable.

[B. Heating process]
In this step, the heating material obtained in step (A) is heated in a heating furnace at 900 to 1,300 ° C. , and exhaust gas containing zinc, lead and chlorine, and zinc, lead and chlorine are substantially added. This is a step of obtaining a fired product not contained in.
The heating material is usually charged into the heating furnace in the form of powder or granules.
As a heating furnace used at this process, the rotary kiln for cement clinker manufacture, etc. are mentioned. Thus, if the existing equipment is used, the cost required for the processing of the present invention can be suppressed.
The heating temperature in the heating furnace, 900~1,300 ℃, preferably 1,000~1,300 ℃, more preferably 1,100~1,250 ℃. When the temperature is less than 900 ° C., zinc, lead, alkali metal and chlorine are not sufficiently volatilized, and these components remain in the fired product. When the temperature exceeds 1,300 ° C., it is not preferable from the viewpoint of energy saving, and the heating material is melted to suppress volatilization of zinc, lead, alkali metal, etc., and these components remain in the fired product. Will do.
By heating in this step, zinc, lead, alkali metal, chlorine and the like contained in the heating material become volatile components and are led together with the exhaust gas from the heating furnace to the exhaust gas flow path and further to the dry dust collector.
On the other hand, the fired product produced in the heating furnace is a harmless inorganic substance containing calcium, silicon, aluminum, or the like as a main component and substantially free of zinc, lead, and chlorine, and therefore can be used as a cement raw material.
The contents of zinc, lead and chlorine in the fired product (wherein zinc and lead are values in terms of oxide) are each preferably 0.5% by mass or less, more preferably 0. It is 2% by mass or less, particularly preferably 0.1% by mass or less.

[C. Heavy metal recovery process]
In this step, dust containing zinc oxide and lead chloride as main components is collected from the exhaust gas generated in step (B) using a dry dust collector disposed outside the heating furnace via an exhaust gas flow passage. It is a process.
The dust collected in this step usually includes alkali metal chlorides such as sodium chloride and potassium chloride.
Examples of the dry dust collector include a bag filter. The temperature of the exhaust gas at the point where the dry dust collector is installed is usually 100 to 200 ° C.
If the chlorine content in the heating material in step (A) is not adjusted, the dust collected in step (C) will contain zinc chloride, and the filter cloth of the bag filter will be blocked. In addition, the corrosion of the processing equipment is accelerated. In the present invention, since the component-adjusted heating material is used, zinc chloride is not generated, and such a problem does not occur.
Whether the dust exhibits deliquescence can be easily determined by visual observation (color and properties) of the collected dust, changes in air pressure before and after the dust collector (filter cloth) of the dry dust collector, etc. it can.
If the collected dust is treated by, for example, a wet leaching method, it can be recovered by being separated into a liquid containing a soluble alkali metal chloride and a solid containing a heavy metal-containing compound such as zinc or lead. Of these, the liquid component can be recovered by separating sodium chloride, potassium chloride, etc. by utilizing the difference in solubility by cooling after heating. About solid content, after processing further and classifying for every metal, it can utilize as a nonferrous refining raw material.

Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited to these examples, and various modifications of the embodiments are possible within the scope of the claims.
[Examples 1 to 4, Comparative Examples 1 to 8]
Sample (mixed fly ash) mixed with molten fly ash and incinerated fly ash using a test kiln (inner diameter: 165 mm, length: 2,800 mm) and a bag filter connected to the test kiln through an exhaust gas flow passage An experiment was conducted to treat
Table 1 shows the contents of zinc and the like in the mixed fly ash. In addition, the value in Table 1 is an oxide conversion value except for chlorine.
The mixed fly ash was washed with water, waste glass (pulverized product having an average particle size of 15 μm; component composition is shown in Table 2), and activated carbon as a reducing agent were added to prepare a heating material.
At this time, the chlorine content in the heating material and the chemical equivalent ratio of (alkali metal + lead) / chlorine were adjusted as shown in Table 3. Moreover, the addition amount of activated carbon was 20 mass parts with respect to 100 mass parts of the mixture of mixed fly ash and waste glass in a dry state.
The prepared heating material was heated at 1,200 ° C. in a test kiln after granulation. The exhaust gas generated in the test kiln was guided to the bag filter and dust was collected. Whether the dust has deliquescence or not was evaluated by the magnitude of air pressure fluctuation before and after the bag filter and by visual observation. The evaluation results are shown in Table 3. Table 4 shows the analysis results of the components in the dust.
On the other hand, the components of the fired product (residue) produced in the test kiln were analyzed. The results are shown in Table 4.
From Table 3, a dust having no deliquescence can be obtained by satisfying the condition that the chlorine content is 8 mass% or less and the value of (alkali metal + lead) / chlorine is 1.2 or more. I understand that. Also, from Table 4, the main component of dust is zinc, lead, alkali metal and chlorine, and the main component of the firing residue in the kiln is calcium, silicon, aluminum, iron, etc., and zinc It can be seen that it contains almost no lead, alkali metal and chlorine.

Claims (1)

(A) Chlorine is a treatment object that is a substance containing at least zinc, lead and chlorine, and is composed of molten fly ash, or a treatment object comprising a mixture of molten fly ash and incineration fly ash or steel dust. And adjusting the chemical equivalent ratio of (alkali metal + lead) / chlorine, and adding a reducing agent, the chlorine content is 1-8 mass% and (alkali metal + lead) ) / Material preparation step of preparing a heating material having a chemical equivalent ratio of chlorine of 1.2 or more ;
(B) A heating step of heating the heating material at a temperature of 900 to 1,300 ° C. in a heating furnace to obtain an exhaust gas containing zinc, lead and chlorine, and a fired product,
With (C) a dry dust collector, from the exhaust gas, viewed contains a heavy metal recovery step for collecting dust composed mainly of zinc oxide and lead chloride,
Adjustment of the chlorine content in the step (A) is (a) dividing the object to be processed into two at an appropriate ratio, washing only one of them to remove the chlorine, and then mixing both. , A method for adjusting the chlorine content to a desired value, (b) two substances having different chlorine contents as the object to be treated, and a substance having a high chlorine content and a chlorine content A small amount of the substance is mixed in an appropriate ratio to obtain a mixture having a desired chlorine content.
Adjustment of the chemical equivalent ratio of (alkali metal + lead) / chlorine in the step (A) is (a) waste mixed glass, construction mixed waste including gypsum board generated when building is demolished, contaminated soil, alkali A method of treating a substance containing zinc, lead and chlorine, characterized in that it is carried out by any one of a method of adding an alkali metal-containing substance which is one of metal-containing carbonates, and (b) a method of adding steel dust .