JP2009269010A - Treatment method and treatment device for removing heavy metals from heavy metals-containing mineral powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method and a treatment device wherein, from heavy metals-containing mineral powder, particularly, from incineration ash, heave metals such as lead and cadmium are removed while the powder state of the mineral powder after treatment is retained. <P>SOLUTION: In the treatment method for removing heave metals from heave metals-containing mineral powder (incineration ash), heavy metals-containing mineral powder is brought into contact with a medium gas air current in the temperature range of 610 to 1,090°C in the presence of calcium chloride and/or magnesium chloride and/or sodium chloride and/or potassium chloride (hereinafter referred as calcium chloride or the like), so as to modify the heavy metals compound into the heavy metals chloride thereof by the reaction with the calcium chloride or the like, the heave metals chloride is moved into a medium gas as the stream thereof, and the mineral powder after the treatment and medium gas containing the chloride steam of the heavy metals are separated in the temperature range of 400 to 1,090°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for removing heavy metals from mineral powder. In particular, it relates to a technique for removing heavy metals from incineration ash.

  High-temperature melting method and eco-cement are used as technologies for detoxifying incinerated ash and recycling it. The former is treated at a high temperature of 1400 to 1800 ° C., and the latter is treated at a high temperature of 1400 to 1600 ° C. to separate heavy metals from the incinerated ash by evaporating to the exhaust gas side, and slag or ecocement obtained from the incinerated ash is removed. It is detoxified. However, the difficulty of these methods is that the treatment is performed at a high temperature of 1400 to 1800 ° C. or 1400 to 1600 ° C. Therefore, the amount of energy consumption is large.

  Japanese Patent No. 3108061 proposes a technique for processing and detoxifying incinerated ash at a relatively low temperature of 650 to 990 ° C., actually 750 to 850 ° C. However, this technique is a technique for insolubilizing and detoxifying heavy metals in incineration ash, and heavy metals are insolubilized and remain in the treated ash. On the other hand, the environmental standards related to soil contamination in the Decree No. 29 of the Ministry of the Environment dated December 26, 2002 require that the contents of heavy metals lead, cadmium, selenium and arsenic be reduced to 150 mg / kg or less. ing. According to the method of Japanese Patent No. 3108061, the elution of heavy metals in mineral powder or incinerated ash is suppressed by insolubilization, and environmental standards related to the elution of heavy metals of the same method or stricter than that " The environmental standards related to the elution of heavy metals of “Ministry of the Environment Notification No. 46” dated 23rd May have been fully achieved, but the heavy metals have not been separated and removed from the incineration ash. The content of heavy metals such as lead and cadmium, which are environmental standards related to the above, cannot be reduced to 150 mg / kg or less, which is the environmental standard of the ministerial ordinance, by the analysis method of the ministerial ordinance.

  As described above, the present inventor proposed a technique for treating and detoxifying incineration ash at a relatively low temperature of 700 to 990 ° C., actually 750 to 850 ° C., in Patent No. 380661, as described above. did. In this technology, heavy metals in incineration ash are insolubilized and rendered harmless, heavy metals remain insolubilized in the treated ash, and chlorides such as sodium chloride and calcium chloride remain as they are. . However, in the process of developing this technology, we found that the reaction between ash and gas was useful as a technology for detoxifying incineration ash, and continued research from various angles.

  In other words, by utilizing the reaction that occurs when chemical species evaporated in the gas collide with the chemical species on the surface of the ash, harmful substances contained in incineration ash etc. can be advantageously removed or detoxified. I thought and continued my research. The inventor has named a technique using this reaction as an AGR (Ash Gas Reaction) technique.

  Since the AGR technique uses diffusion in a gas, the reaction rate is generally high and industrially advantageous. Since the rate-determining step of the reaction rate is considered to be the movement rate of chemical species in ash (solid), the environmental temperature of the powder is maintained at a high level of 500 to 1100 ° C., and the particle size of the powder is reduced. The reaction rate is likely to be increased to an industrially useful level.

  Another useful point of the AGR technique is that this reaction works efficiently for removing harmful components from the incinerated ash in a temperature range of 500 to 1100 ° C. In this temperature range, the incinerated ash powder can be “handled as a powder” without melting, without being clinkered or consolidated. This not only is advantageous in terms of equipment because the process for treating incinerated ash is simplified, but also provides various advantages in recycling incinerated ash. For example, unlike slag obtained by the high-temperature melting method, mineral powder (treated ash) after treatment is obtained while retaining the state of the powder, so that it can be recycled as a raw material for cement and soil improvement materials. If this is the case, it may be possible to eliminate the need for pulverization that requires labor and energy.

  The present inventor has already proposed “detoxification technology of hexavalent chromium based on the AGR technology” in Japanese Patent No. 3676768. The present inventor has continued research on the AGR technology, and this time, as the present invention, proposes “a technology for removing heavy metals from mineral powder (incinerated ash) containing heavy metals based on the AGR technology”. is there. In parallel, “Technology based on AGR technology to remove chloride chlorine from mineral powder (incinerated ash) containing chloride” has been proposed.

  The problem of the present invention is that the powder after treatment (hereinafter referred to as “treated powder” or “treated ash”) remains in a powder state from a mineral powder (incinerated ash) containing heavy metals. It is providing the processing method and processing apparatus which remove heavy metals, such as lead and cadmium.

  That is, the problem of the present invention is that the heavy metals contained in the mineral powder (incinerated ash) are reduced to 610 to 1090 ° C., which is lower than 1400 to 1800 ° C. of the conventional high temperature melting method. And a method and apparatus for economically removing the treated powder (treated ash) while maintaining the powder state.

The gist of the present invention is that a mineral powder containing heavy metals is: (1) in the presence of calcium chloride and / or magnesium chloride and / or sodium chloride and / or potassium chloride (hereinafter referred to as “calcium chloride etc.”);
(2) In the temperature range of 610 ° C to 1090 ° C,
(3) Contact with the medium gas stream,
(4) By reaction with calcium chloride or the like, the heavy metal compound is converted to its heavy metal chloride,
(5) Move this heavy metal chloride into the medium gas as its vapor,
(6) By separating the treated powder and medium gas containing heavy metal chloride vapor in the temperature range of 400 to 1090 ° C.,
The purpose is to remove heavy metals from mineral powder containing heavy metals.

Or, mineral powder containing heavy metals (1) in the presence of calcium chloride,
(2) In the temperature range of 610 ° C to 1090 ° C,
(3) Contact with a medium gas stream containing carbon dioxide and / or water vapor,
(4) By reaction with calcium chloride or the like, the heavy metal compound is converted to its heavy metal chloride,
(5) Move this heavy metal chloride into the medium gas as its vapor,
(6) By separating the treated powder and medium gas containing heavy metal chloride vapor in the temperature range of 400 to 1090 ° C.,
The purpose is to remove heavy metals from mineral powder containing heavy metals.

Here, the mineral powder is a powder having a particle size of 3 mm or less, the main component of which is a mineral substance, for example, a substance mainly composed of SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO or the like. is there. For example, even if the particle size of the mineral-based powder is 4 mm or less, when the mineral-based powder having a particle size of 3 mm or less is included, it is regarded as the mineral powder of the present invention.

Typical mineral powders are general waste (garbage) and / or incineration ash of industrial waste. Incineration ash is representative of fly ash discharged from stoker-type incineration facilities and / or pulverized burner husks, and fly ash discharged from fluidized-bed incineration facilities, but is not limited to these. .

  Heavy metals are typically lead and cadmium, but also include zinc, copper, arsenic, selenium and the like. In addition, as compounds of heavy metals, oxides of these heavy metals such as lead oxide and cadmium oxide having a relatively low vapor pressure in a temperature range of 610 ° C. to 1090 ° C. are the main objects of the present invention. Such sulfates, phosphates, hydroxides and the like are also included.

The particle size of the mineral-based powder is 3 mm or less, but in order to reduce the amount of heavy metals remaining in the mineral-based powder, the finer particle size is preferably 1 mm or less, and more preferably 0.25 mm or less.
In addition, as shown in Comparative Example 3, as a result of testing the incineration ash burner with a particle size of 4 mm or more other than the particle size by the method of the present invention, the removal rate of heavy metals is greatly reduced. I understood.

The composition of the medium gas of the present invention is a gas mainly containing nitrogen, preferably containing carbon dioxide gas and water vapor, and may contain oxygen.
Water vapor and carbon dioxide gas produce sodium hydroxide and potassium hydroxide in the former and sodium carbonate and potassium carbonate in the latter when sodium chloride and potassium chloride, which are alkali metal chlorides, react with heavy metal oxides. And stabilizes the production system.

The range of the treatment temperature of the present invention is 610 ° C. to 1090 ° C., but the reaction rate is slow when the temperature is low, and the temperature is close to the melting temperature of the mineral powder, and “the powder is solidified”. There is a fear. Moreover, when temperature is high, it will become disadvantageous also in terms of the material of processing equipment. From such a viewpoint, the range of the treatment temperature is preferably 700 to 1050 ° C., more preferably 750 to 990 ° C. in consideration of the economical efficiency of the apparatus.
Data on the effect of processing temperature is shown in Example 1, Examples 3-8 and Comparative Example 2.

The temperature range for separating the treated powder (treated ash) and the medium gas containing heavy metal chloride vapor is 400 to 1090 ° C. based on the test data. In addition, it is preferable to set this temperature as 500-1090 degreeC, and it is more preferable to set it as 600-1090 degreeC.
Example 1, Example 2, and Comparative Example 1 are tests conducted to show the influence of the temperature at which the treated powder (treated ash) and the medium gas containing heavy metal chloride vapor are separated. From the data of Example 2, the temperature range for separating the medium gas containing the vapor of heavy metal chloride was set. In Comparative Example 1, when the temperature is lower than the temperature range defined in the present invention, the heavy metal chloride contained in the medium gas is re-adsorbed to the treated powder (treated ash), and the heavy metal in the treated powder (treated ash) An example has been shown in which the concentration of the species increases and their removal rate decreases significantly.

  The role of calcium oxide and / or magnesium oxide according to claim 4 is that when a gas containing heavy metal chloride vapor is separated from the treated powder (treated ash), a small amount of heavy metal chloride is treated ash. There is a possibility that these heavy metals will elute from the treated powder (treated ash) and exceed the environmental standards of “Ministry of the Environment Notification No. 46 dated August 23, 1991” So it is to prevent this. In other words, a small amount of heavy metal chloride re-adsorbed on the treated powder (treated ash) is changed to a small amount of heavy metal oxide to insolubilize and render it harmless.

  In order to confirm that chlorides such as calcium chloride, magnesium chloride, sodium chloride and potassium chloride are effective in principle by the treatment method of the present invention, a make-up sample was prepared and tested. Test results are shown in Examples 9-12. It was confirmed that calcium chloride, magnesium chloride, sodium chloride and potassium chloride have an effect as the chloride of the present invention.

  The equivalent ratio of the total chlorine content of chlorides such as calcium chloride to the total of heavy metals such as lead and cadmium contained in mineral powder is at what level of heavy metals such as lead and cadmium contained in mineral powder. Therefore, it is preferable to conduct a preliminary test in advance to determine the equivalent ratio of the total chlorine content of chloride to the total of heavy metals. In general, when the mineral powder is incinerated ash of general waste, the chlorine content of the incinerated ash contains heavy metals (lead, cadmium, arsenic, copper, zinc and other chlorine that can be removed by the present invention). The equivalent ratio is about 10 times the total amount of all heavy metals to be consumed, and there is often no need to add a new chloride.

In the following, the background to the present invention will be described, and the basic concept of “AGR technology” will be described.
In Japanese Patent No. 3108061, heavy metal chlorides such as water-soluble lead chloride and cadmium chloride evaporate in a reactor such as a rotary kiln, and efficiently react with calcium oxide and / or magnesium oxide to lead oxide and cadmium oxide. It was found to be fixed and insolubilized. However, as a result of detailed examination of the test results related to this patent, lead oxide and cadmium oxide decreased in the treated ash as well as heavy metal chlorides such as lead chloride and cadmium chloride, which are water-soluble and have high vapor pressure. As described above, the research of the present invention was obtained while pursuing the reason and pursuing the reason.

After many trials and errors, the inventor has discovered two important facts relating to the present invention.
One is that when performing AGR treatment (incineration ash is brought into contact with a medium gas stream in a temperature range of 610 ° C. to 1090 ° C.), a substance having a relatively low vapor pressure such as lead oxide and cadmium oxide is chlorinated. It is a phenomenon (hereinafter referred to as “discovery 1 of the present invention”) that is easily volatilized due to the presence of calcium or the like. This phenomenon has been confirmed by testing makeup powders in Examples 9 to 12 described later.

Another discovery is that heavy metal chloride vapor transferred from incineration ash into the medium gas in the reactor of AGR re-adsorbs to the low-temperature treated ash when it comes into contact with the low-temperature treated ash at the outlet of the reactor. (Hereinafter referred to as “discovery 2 of the present invention”).
Based on this fact, treated ash is proposed by “separating the treated ash and medium gas containing chloride vapor of heavy metals in a temperature range of 400 to 1090 ° C.” proposed in (6) of the gist of the present invention. It has been found that the amount of heavy metals can be greatly reduced.
The present invention has been reached by combining these “two discoveries” and “AGR technology”.

Here, the “AGR technology” which is the basis of the present invention will be described.
One of the features of the basic technology of AGR technology is that “mineral powder” and “medium gas stream” are brought into contact with each other, and the molecules of substance A that contribute to the reaction are moved to “medium gas” and contribute to this reaction. The molecules of the substance A to be moved at a high speed in the “medium gas” (hereinafter referred to as “AGR technology principle 1”), and the molecules of the substance A moved at the high speed are “mineral powder”. Is contacted with another substance B molecule that contributes to the reaction on the surface of the substrate (hereinafter referred to as “AGR technology principle 2”). Thus, by utilizing the fact that molecules of substances that contribute to the reaction move at a high speed in the “medium gas”, an industrially useful reaction speed as a whole is realized.

For this reason, it is necessary to use a reactor that performs the AGR technique with good contact between the mineral powder and the medium gas stream. As the reactor that satisfies the requirements, a kiln type reactor, a fluidized bed type reactor, a moving bed type reactor, etc. are preferably used.
Kiln type reactors are most suitable as reactors for performing AGR technology. The structure is simple, the contact efficiency between the mineral powder and the medium gas stream is good, and the piston flow property of the mineral powder is excellent, which is advantageous for increasing the reaction rate. However, the difficulty is that the volumetric efficiency of the reaction is poor and the reactor becomes large for the processing capacity.
The fluidized bed reactor has better contact efficiency between the mineral powder and the medium gas stream than the kiln reactor. However, the fluidized bed reactor is a fully mixed reactor, so it increases the reaction rate of mineral powder. It is disadvantageous. However, this is suitable when it is not necessary to increase the reaction rate. Although there is a problem in terms of equipment costs, the reaction rate can be increased by using a plurality of fluidized bed reactors connected in series.
Moving bed reactors require some effort to increase the contact efficiency between mineral powder and medium gas flow, but the piston flow of mineral powder is excellent, and the volumetric efficiency of the reaction can be increased. Is possible. In the moving bed type reactor, it is necessary to devise a mechanism for smoothly and continuously flowing mineral powder.

  Another feature of the basic technology of the AGR technology is that the moving speed by diffusion of molecules inside the powder particles is increased by a high temperature in a temperature range of 500 ° C. to 1100 ° C. (hereinafter referred to as “AGR technology principle 3”). Is used). This is because in Patent No. 3676768 described later, it was difficult to remove hexavalent chromium inside the incinerated ash particles by water washing in the temperature range from room temperature to 100 ° C., but the high temperature in the temperature range from 500 ° C. to 1000 ° C. It is shown that an industrially significant reaction rate is obtained by bringing a mineral powder (incinerated ash) into contact with a stream of medium gas (nitrogen gas) having a low oxygen concentration. In addition, a comparison between the "technology for removing chloride from chloride from mineral powder containing chloride (incinerated ash) based on AGR technology" and desalting by water washing, filed in parallel with the present invention But it is suggested. That is, the residual chlorine content of 1000 ppm is achieved in the temperature range of 650 ° C. to 1100 ° C. of “Technology for removing chloride chlorine from mineral powder (incinerated ash) containing chloride based on AGR technology”. However, it was suggested that the limit is 5000 ppm in the water washing performed at 100 ° C. or lower.

  In addition, another feature of the basic technology of the AGR technology is that the mineral powder (incinerated ash) is processed as it is in the temperature range of 500 ° C. to 1100 ° C. as described above. There is in point that can. By taking out the treated ash as powder, it is often advantageous when the treated ash is recycled.

The “AGR technique” will be further described below by taking the invention proposed by the present inventor as an example.
In Japanese Patent No. 3108061, in the temperature range of 650 ° C. to 980 ° C., chloride molecules of heavy metals such as lead chloride move from the incinerated ash particles to the surface of the particles at a high diffusion rate (the principle of AGR technology). 3). The lead chloride of the surface layer evaporates in the medium gas stream in contact with the particles, and the evaporated molecules such as lead chloride move at a high speed in the medium gas (AGR technology principle 1), A phenomenon (Principle 2 of AGR technology) that is adsorbed on the surface of the particles of calcium oxide or magnesium oxide in the surface layer of the particles and transformed into an oxide such as lead oxide and insolubilized is used here.
Although it is difficult for molecules such as lead chloride in the surface layer of the incinerated ash particles to move directly on the surface of the solid particles to reach calcium oxide etc. in the surface layer of the same particle, AGR technology is a medium. By using gas as an intermediary, the movement speed is remarkably increased (Principle of AGR technology 1) and the target reaction proceeds by contact with the molecule of the opposite chemical species on the surface of the powder particle (AGR) By utilizing the principle 2) of the technology, the overall reaction rate is increased to an industrially useful level.

Further, in Japanese Patent No. 3676768, by contacting “incinerated ash powder” and “medium gas stream composed of nitrogen containing almost no oxygen”, oxygen contained in hexavalent chromium in the incinerated ash powder particles Moves to the surface of the powder particles relatively quickly in the temperature range of 500 to 1000 ° C. (Principle 3 of AGR technology) and is dissipated from the surface into a medium gas composed of nitrogen having a low oxygen partial pressure. Using the phenomenon (AGR technology principle 1), the harmful hexavalent chromium inside the incinerated ash powder particles is deoxygenated at an industrially useful level of reaction rate to produce harmless trivalent chromium oxide Transformation to (Cr ₂ O ₃ ) has been achieved.
Incidentally, it was extremely difficult to sufficiently remove hexavalent chromium from a powder containing hexavalent chromium by washing with water at 100 ° C. or less, which started the invention of Japanese Patent No. 3676768.

Furthermore, the “technology to remove chlorine from chlorides from mineral powder (incinerated ash) based on AGR technology” proposed in parallel with this proposal is calcium chloride present in mineral powder. Chloride, magnesium chloride, sodium chloride, potassium chloride, etc., diffuse at a relatively high rate from the inside of the mineral powder to the surface in the temperature range of 650 ° C. to 1100 ° C. and reach the surface of the mineral powder. By the phenomenon (AGR technology principle 3) and the phenomenon that these chlorides evaporate in the medium gas and the chloride molecules move at a high speed in the medium gas (AGR technology principle 1). In the temperature range of 650 ° C. to 1100 ° C. and transformed into iron chloride having a very high vapor pressure (AGR technology principle 2), and this iron chloride in the medium gas Evaporate these salts The chlorine content of the object by combining the phenomenon of separation from the in mineral powder, and removing the chlorine component of chloride from mineral powders.
Here too, the three principles of the AGR technology, that is, “the high moving temperature in the temperature range of 500 ° C. to 1100 ° C. increases the moving speed due to molecular diffusion inside the powder particles” (the principle of the AGR technology) 3) “Fast moving speed of molecules in the medium gas” (Principle 1 of AGR technique) and “Molecules of the reaction component A in the medium gas are in contact with the molecules of the reaction component B on the surface of the powder particles. The phenomenon based on “transformation by the reaction that takes place” (Principle 2 of AGR technology) is the basis of the invention.

Three principles of AGR technology, “Fast movement of molecule of substance A by gas medium— Principle of AGR technique 1 ”, “Molecule of substance A that has moved at a high speed is applied to the surface of particles of mineral powder. Modification of substance AB caused by contact with molecule of substance B- AGR technology principle 2 "and" Diffusion rate of molecules from the inside to the surface of mineral powder in the temperature range of 500 ° C to 1100 ° C is high- The principle 3 "of AGR technology " is a well-known phenomenon. However, according to the present invention, in response to the problem to be solved, the problems are solved by finding a condition for performing a test and solving the problem by combining them well.

As described above, the present invention is a combination of the two discoveries found this time and the AGR technology. The details are as follows.
First, chloride molecules such as calcium chloride contained in mineral powder (incinerated ash) particles move through the particles of mineral powder at a relatively high speed in the temperature range of 610 to 1090 ° C. , Reaches the surface of the particles (AGR technology principle 3) and evaporates into the medium gas. In parallel with this, the main component of mineral powder heavy metals such as lead oxide and cadmium oxide contained in the particles of mineral powder, which has a low vapor pressure and hardly evaporates, has a temperature of 610 to 1090 ° C. It moves through the particles of mineral powder at a relatively fast speed in the range and reaches the surface of the particles (AGR technology principle 3). Molecules such as calcium chloride evaporated in the medium gas move in the medium gas at a high speed (AGR technology principle 1), and lead oxide, cadmium oxide, etc. reaching the surface of the mineral powder particles. In contact therewith, lead oxide, cadmium oxide and the like react with calcium chloride and the like to transform into lead chloride, cadmium chloride and the like having a high vapor pressure (AGR technology principle 2) (discovery 1 of the present invention). In general, chlorides of heavy metals have a high vapor pressure at high temperatures, so that they are efficiently evaporated into a medium gas, and lead, cadmium, and the like are separated from mineral powder particles. Further, by separating the medium gas containing the treated powder (treated ash) and heavy metal chloride vapor in the temperature range of 400 to 1090 ° C. (discovery 2 of the present invention), The heavy metal chloride vapor transferred from the mineral powder into the medium gas can be separated from the treated powder without being re-adsorbed by calcium oxide, magnesium oxide or the like in the low-temperature treated powder.

  As described above, the phenomenon of the present invention is that the calcium chloride and / or magnesium chloride and / or sodium chloride and / or potassium chloride present in the mineral powder (incinerated ash) is in the temperature range of 610 to 1090 ° C. In the medium gas, these chloride molecules collide with the oxides of heavy metals such as lead oxide and cadmium oxide present on the surface of the mineral powder. It is thought that this happens.

Examples of metathesis reactions:
When the medium gas does not contain carbon dioxide and water vapor (1) PbO + CaCl ₂ → PbCl ₂ + CaO
(2) CdO + MgCl ₂ → CdCl ₂ + MgO
▲ 3 ▼ PbO + 2NaCl → PbCl 2 + Na 2 O
When the medium gas contains carbon dioxide (4) CdO + CaCl ₂ + CO ₂ → CdCl ₂ + CaCO ₃
(5) PbO + MgCl ₂ + CO ₂ → PbCl ₂ + MgCO ₃
(6) CdO + 2NaCl + CO ₂ → CdCl ₂ + Na ₂ CO ₃
When the medium gas contains water vapor (7) CdO + 2NaCl + H ₂ O → CdCl ₂ + 2NaOH
(8) PbO + 2KCl + H ₂ O → PbCl ₂ + 2KOH

In reaction (3), Na ₂ O is produced, but Na ₂ O is unstable in the temperature range of 610 ° C. to 1090 ° C. in which the treatment of the present invention is carried out, so that the treated ash (treated ash) is stabilized. Further, it is preferable to use a medium gas containing carbon dioxide gas and / or water vapor. NaOH and KOH produced in the reactions (7) and (8) are stable and have a relatively high vapor pressure in the temperature range of 610 ° C. to 1090 ° C. in which the treatment of the present invention is carried out. Evaporates.

  As the processing apparatus for carrying out the present invention, as described above, a rotary kiln type reactor, a moving bed type reactor, and a fluidized bed type reactor are preferably used. As the moving bed type reaction apparatus, a blast furnace type reaction apparatus, a multi-stage type reaction apparatus such as a Helsov furnace type, and the like can be considered.

  In the rotary kiln type reactor and the moving bed type reactor, the flow of the mineral powder and the flow of the medium gas can be made counter-current or can be made co-current. Since the rotary kiln type reactor and the moving bed type reactor have high piston flow characteristics of the mineral powder flow, they are advantageous in increasing the reaction rate and lowering the chlorine concentration of the treated ash. On the other hand, the fluidized bed type reaction apparatus is advantageous in improving the contact between the medium gas and the mineral powder, but is a disadvantage in terms of increasing the reaction rate because it is a complete mixing type reaction apparatus. In order to increase the reaction rate, it is conceivable to use a two-stage or multi-stage fluidized bed reactor.

By the method proposed in the present invention, heavy metals can be removed from mineral powder (incinerated ash) containing heavy metals such as lead and cadmium.
Moreover, since the processing temperature of this invention is not the high temperature of 1400-1800 degreeC or 1400-1600 degreeC like a high temperature melting method and an eco-cement, it is a temperature range of 610 degreeC-1090 degreeC, Therefore processing powder (Processed ash) is not slag obtained by melting ash or semi-molten clinker, but can be obtained while maintaining the powder state. There are many useful aspects to recycle this. For example, when the treated ash subjected to the treatment according to the present invention is used as a soil improvement material or a cement raw material, the treated ash can be used without being pulverized.

  Further, the present invention is an energy-saving technology that consumes less energy because the processing temperature is significantly lower than that of the high temperature melting method and eco-cement, and is considered to contribute to the reduction of environmental loads such as carbon dioxide load.

  As an embodiment of the present invention, a case of a rotary kiln type reactor and a case of a fluidized bed type reactor will be described. However, embodiments of the present invention are not limited to these.

  As the mineral powder subjected to the treatment for removing heavy metals to be supplied to the reaction apparatus according to the present invention, waste incineration ash is representative. Here, processing of incineration ash by the processing method of the present invention will be described. Examples of the incineration ash of garbage include burning husk and fly ash coming out of a stoker furnace, and fly ash coming out of a fluidized bed furnace. Among these, the fly ash from the stoker furnace and the fly ash from the fluidized bed furnace can be treated as they are, but the burned husk from the stoker furnace needs to be pretreated. In the case of a burning husk, when the moisture is high, it is dried in advance. Next, iron is removed with a magnetic separator. The particle size is adjusted so as to be 3 mm or less by pulverization, or 1 mm or less, 0.25 mm or less, 0.1 mm or less, if necessary. Mix these fly ash and crushed burning husks, or use incinerated ash that is treated alone.

Next, the amount of heavy metals such as lead, cadmium, selenium, copper and zinc and the chlorine content of chlorides such as calcium chloride contained in the incineration ash are quantified, and the total chlorine content of chlorides relative to the total of heavy metals The equivalent ratio is calculated, and it is confirmed that this equivalent ratio is larger than a predetermined value. When this equivalence ratio is smaller than a predetermined value, it is adjusted by adding chloride. When the equivalence ratio is larger than a predetermined value, it is not necessary to add chloride.
In addition, since the predetermined value of an appropriate equivalence ratio changes with the property of incineration ash, the level of heavy metal removal requested | required, etc., it is necessary to test and determine the said incineration ash beforehand.

  The incinerated ash thus adjusted is supplied to the reactor and heated to a predetermined processing temperature determined within a temperature range of 610 ° C. to 1090 ° C. while flowing a medium gas, and after processing for a predetermined time, A medium gas containing chloride vapor of heavy metals is separated at a predetermined temperature determined within a temperature range of 400 to 990 ° C. Here, the predetermined treatment time and treatment temperature, and the temperature at which the medium gas containing the treated ash and heavy metal chloride vapor is separated vary depending on the properties of the incinerated ash and the level at which heavy metals are removed. The predetermined treatment time and treatment temperature and the temperature for separating the treatment gas and the medium gas containing the heavy metal chloride vapor must be determined in advance by testing the incineration ash.

The case of a rotary kiln reactor will be described with reference to FIG. The high temperature medium gas 3 obtained by burning the fuel 8 with the air 9 in the incineration ash 1 and the combustion furnace 12 to which sodium chloride or the like 1 'is added, if necessary, in the powder gas supply unit 13 of the rotary kiln type reactor. The two are supplied in parallel in the kiln rotating part 11 (although it can be made to flow countercurrently, FIG. 1 shows the case of cocurrent flow). A refractory brick 17 is lined on the inner surface of the rotating portion 11, and a lifter 16 is provided inside the refractory brick 17. The incinerated ash 1 flowing inside the kiln rotating part 11 is lifted by the lifter 16 and falls from above in the medium gas flow 3 ′ flowing perpendicular to the falling powder, and the incineration ash 1 and the medium gas flow 3 ′. Have good contact. The internal temperature of the rotary kiln reactor is maintained at a predetermined processing temperature by the high-temperature medium gas 3. Moreover, the gradient and rotation speed of the kiln rotation part 11 are adjusted so that the residence time of the incineration ash 1 becomes a predetermined time. The treated gas 2 and the reaction exhaust gas 4 are separated by the powder gas separation unit 14. The temperature of the powder gas separation unit 14 is adjusted by the powder gas separation unit-heating heat retention unit 15 so as to be a predetermined temperature in a temperature range of 400 ° C. to 1090 ° C. It is preferable that the heating and heat retaining unit 15 is provided with a heating device such as a sheathed heater and adjusted to a predetermined temperature. In a large apparatus, the temperature of the powder gas separation unit 14 may be maintained at a predetermined temperature or higher without providing a heating device.
The feature of the rotary kiln reactor is that the flow of the powder to be processed has high piston flow. This is advantageous in increasing the reaction rate.

The case of a fluidized bed reactor will be described with reference to FIG. The incinerated ash 1 to which sodium chloride or the like 1 ′ is added is supplied to the fluidized bed reactor main body 21 as necessary. A circulating gas 5 (hot circulating gas 5 ′) is supplied from the lower part to form a fluidized bed 6. The circulating gas 5 coming out from the upper part of the fluidized bed reactor main body 21 is separated and recovered from the cyclone recovered powder 7 by the cyclone 22 and then circulated to the lower part of the fluidized bed reactor 21 by the circulating gas blower 25. The reaction exhaust gas 4 is separated from the circulation gas 5 and discharged. The recovered powder 7 is recovered in the fluidized bed reactor 21 through the powder recovery tube 26. The temperature of the fluidized bed is maintained at a predetermined processing temperature by a high-temperature circulating gas 5 ′ obtained by mixing the high-temperature medium gas 3 obtained by burning the fuel 8 with the air 9 in the combustion furnace 12 and the circulating gas 5. The amount of powder extracted is adjusted by the rotary valve 24 so that the residence time of the powder becomes a predetermined value and the powder surface 29 of the fluidized bed has a predetermined height. In the powder extraction part 23 and the cyclone 22 and the recovery pipe 26, the medium gas (reaction exhaust gas 4) containing heavy metal vapor and the treated ash 2 are separated, so that the separation temperature becomes a predetermined separation temperature. There is a need. for that reason. In the powder extraction section 23, the powder extraction section heating and heat retaining section 27 heats and / or keeps the temperature so that the wall temperature becomes a predetermined separation temperature. Further, the cyclone 22 and the recovery pipe 26 are also circulated with the cyclone recovery powder 7 while being heated and / or kept warm by the cyclone and powder recovery pipe heating and warming unit 28 so that the wall temperature becomes a predetermined separation temperature. Gas 5 is separated.
The characteristics of the fluidized bed reactor are that the contact between the medium gas and the incinerated ash is good, and therefore the reaction rate is increased. On the other hand, since it is a complete mixing type, it is disadvantageous in terms of increasing the reaction rate. .

Example 1 : A kiln type electric furnace heating rotation type continuous test apparatus was used as a test apparatus. FIG. 3 shows a schematic diagram of the test apparatus, and FIG. 4 shows a flow sheet of the test apparatus. The effective volume of this reactor is 9 liters. The mineral powder used in the examples was incinerated ash.

  As shown in FIG. 3, this electric furnace heating rotary type continuous test apparatus is a rotary reaction cylinder-supporting roller receiver provided on the front and rear outer circumferences of a rotary reaction cylinder 31 made of SUS310 installed through the electric furnace 32. 33 is configured to rotate on the two-rotation reaction cylinder-support roller 34. The rotation speed is controlled to a predetermined value. The rotary reaction cylinder 31 is provided with a lifter 16 so as to improve the contact between the incineration ash 1 and the medium gas flow 3 '. The incinerated ash 1 to which sodium chloride or the like is added as needed is supplied from the powder supply hopper 36 to the rotary reaction cylinder 31 by the powder supply screw conveyor 37. The medium gas 3 is supplied to the rotary reaction cylinder 31 through the medium gas supply unit 38. The reaction exhaust gas 4 and the treated ash 2 are separated by a reaction exhaust gas treatment ash separation unit 39 provided with a reaction exhaust gas treatment ash separation unit-heat insulation unit 40. The reaction exhaust gas treatment ash separation unit-heat insulation unit 40 is heated to a predetermined temperature by a sheathed heater. A fixed part such as the medium gas supply unit 38 and the reaction exhaust gas treatment ash separation unit 39 and a rotary part such as the rotary reaction cylinder 31 and the rotary reaction cylinder-supporting roller receiver 33 are sealed by a rotary reaction cylinder-shaft seal 35. Yes. The entire apparatus is fixed on a continuous rotating electric furnace heating test reaction apparatus support base 41, and has a structure in which the gradient of the rotating reaction cylinder 31 can be changed. Further, the rotational speed of the rotary reaction cylinder 31 can be changed. The residence time of the powder is controlled by adjusting the rotational speed of the rotary reaction cylinder 31 and its gradient.

  As shown in FIG. 4, the incinerated ash 1 to which calcium chloride or the like 1 ′ is added as required has a predetermined composition and flow rate by controlling the flow rate of air 9, carbon dioxide gas 8 ′, and water vapor 9 ′ with a gas flow meter. After being continuously supplied to the electric furnace heating rotary continuous test apparatus 30 together with the medium gas 3 adjusted so as to be processed at a predetermined temperature for a predetermined residence time, the reaction exhaust gas treatment ash separation unit 39 determines a predetermined temperature. Thus, the reaction exhaust gas 4 and the treated ash 2 are separated.

  Ashes (mineral powder) is a mixture of 10 parts of fly ash of incineration ash of general waste (garbage) discharged from a stoker-type incineration facility and 20 parts of iron that has been crushed to 1 mm or less and removed. A sample (hereinafter referred to as “incinerated ash mixture”) was used. The heavy metals content of the incinerated ash mixture was 2470 mg / kg for lead, 60 mg / kg for cadmium, and 5 mg / kg (detection limit) for selenium as metals. Moreover, chromium was 560 mg / kg, copper was 1150 mg / kg, and zinc was 3040 mg / kg. The chlorine content of this ash was 6.1 w%. The chlorine content is considered to exist mainly in the form of sodium chloride, potassium chloride, calcium chloride, and magnesium chloride. Since the equivalent ratio of chlorine to heavy metals (lead, cadmium, arsenic, copper, zinc, etc.) is about 11 times, it is not necessary to add further chloride.

  The incinerated ash mixture was fed to the reactor at a feed rate of 1 kg / h. The residence time of ash was about 60 minutes. At the same time, a gas of 82% nitrogen, 6% oxygen, 6% carbon dioxide, and 6% water vapor was supplied as a medium gas at a flow rate of 20 liters / min. The treatment temperature of ash was 850 ° C., and the temperature for separating the treated ash 2 and the reaction exhaust gas 4 in the reaction exhaust gas-treatment ash separation unit 39 was kept at 800 ° C.

As a result of analyzing the obtained treated ash, lead was 140 mg / kg, cadmium was 8 mg / kg, and selenium was 5 mg / kg (detection limit) or less. At this time, the lead removal rate was 94.3%, and the cadmium removal rate was 86.7%.
In addition, the lead of the processing ash by the analysis method based on the environmental standard regarding the soil pollution of Ministry of the Environment Ordinance No. 29 was 120 mg / kg. Moreover, the elution of lead by the analysis method based on the environmental standards related to the elution of lead of Ministry of the Environment Notification No. 46 was 0.001 mg / L (detection limit) or less.

Example 2 and Comparative Example 1 : Using the same apparatus as in Example 1, the same sample as in Example 1 was tested under the same conditions as in Example 1. In Example 2, treated ash 2 of the reaction exhaust gas treated ash separation unit 39 was used. And only the temperature for separating the reaction exhaust gas 4 was kept at 600 ° C. In Comparative Example 1, this temperature was kept at 200 ° C.

As a result of analyzing the obtained treated ash, in Example 2, lead was 280 mg / kg, cadmium was 12 mg / kg, and selenium was 5 mg / kg (detection limit) or less. At this time, the lead removal rate was 88.7%, and the cadmium removal rate was 80%. In Comparative Example 1, lead was 1680 mg / kg, cadmium was 45 mg / kg, and selenium was 5 mg / kg (detection limit) or less. At this time, the lead removal rate was 32%, and the cadmium removal rate was 25%.
Table 3 shows the test conditions of Example 1, Example 2 and Comparative Example 1, and the residual amount of lead as a result of analyzing the obtained treated ash and the lead removal rate at this time.

  Table 1 shows the analysis results of the fly ash of incineration ash, the burning husk, and the incinerated ash mixture, and the analysis result of the treated ash of Example 1. Since the analysis results are shown as they are, the total value does not become 100 w%, and the total value is around 90 w%.

  Table 2 shows analysis methods of the mineral powder (incinerated ash) and the treated powder (treated ash).

Example 3 : A kiln type electric furnace heating rotary batch test apparatus was used as a test apparatus. FIG. 5 shows a schematic diagram of the test apparatus, and FIG. 6 shows a flow sheet of the test apparatus. The effective volume of this reactor is 3 liters. The mineral powder used in the examples was incinerated ash or make-up powder.

  As shown in FIG. 5, this electric furnace heating rotary batch test apparatus is provided with a rotary reaction cylinder-support provided on the outer circumference of a rotary reaction cylinder outer cylinder 51 made of SUS310 installed through the electric furnace 32. The roller receiver 33 is configured to rotate on the two rotary reaction cylinder-support rollers 34. The rotation speed is controlled to a predetermined value. A predetermined amount of mineral powder (incinerated ash) is charged into a ceramic rotary reaction cylinder 52. Both ends of the rotation reaction cylinder inner cylinder 52 are closed with a heat-resistant material having a hole through which the medium gas 3 flows in the center so that the mineral powder (incinerated ash) does not come out. The medium gas 3 is supplied from a medium gas supply unit 38. The outer side of the rotary reaction cylinder inner cylinder 52 is wound on a sheet of heat-resistant material and inserted into the rotation reaction cylinder outer cylinder 51 and set at a predetermined position, and the medium gas 3 is placed in the rotation reaction cylinder outer cylinder 51 and the rotation reaction cylinder inner cylinder 52. All the medium gases 3 are allowed to flow in the rotary reaction cylinder inner cylinder 52 without flowing between them. Further, a fixed part such as the medium gas supply unit 38 and the reaction exhaust gas outlet 53 and a rotating part such as the rotating reaction cylinder 31 and the rotating reaction cylinder-supporting roller receiver 33 are sealed by a rotating reaction cylinder-shaft seal 35. Yes. The rotary reaction cylinder inner cylinder 52 is provided with a lifter 16 to improve the contact between the mineral powder (incinerated ash) and the medium gas flow 3 '. The reaction exhaust gas 4 and the treated powder (treated ash) are separated inside the electric furnace at the outlet of the rotary reaction cylinder inner cylinder 52. Since this part is the same temperature as the processing temperature, the outlet of the rotary reaction cylinder outer cylinder 51 does not need to be heated. At the outlet of the rotary reaction cylinder outer cylinder 51, a heated reaction exhaust gas outlet 53 is provided, from which the reaction exhaust gas 4 is discharged.

  As shown in FIG. 6, in a state where the mineral powder (incineration ash) is charged in the rotary reaction cylinder inner cylinder 52, the rotation of the rotary reaction cylinder outer cylinder 51 is started, and air 9, carbon dioxide gas 8 ′, The supply of the medium gas 3 adjusted to have a predetermined composition and flow rate by controlling the flow rate of the water vapor 9 ′ with a gas flow meter is started to the medium gas supply unit 38. While the mineral powder (incinerated ash) and the medium gas stream 3 'are in good contact with each other inside the rotary reaction cylinder inner cylinder 52 due to the action of the lifter, the temperature of the electric furnace is increased so that the internal temperature reaches a predetermined temperature. When it reaches, the predetermined temperature is maintained for a predetermined time, and the mineral powder (incinerated ash) is processed. In this case, the temperature at which the treated powder (treated ash) and the reaction exhaust gas 4 are separated is the same temperature as the treatment temperature. After the processing is completed, the electric furnace is cooled, and then the rotary reaction cylinder inner cylinder 52 is taken out, and the treated powder (processed ash) is taken out from the rotary reaction cylinder inner cylinder 52.

  A sample 200 g of the incinerated ash mixture prepared in the same manner as in Example 1 was charged into the rotary reaction cylinder 52, and medium gas 3 (82% nitrogen, 6% oxygen, 6% carbon dioxide, water vapor having the same composition as in Example 1). 6% gas) was allowed to flow at 4 liters / minute, the temperature of the electric furnace was increased, and after treatment at 850 ° C. for 60 minutes, the electric furnace was cooled and the treated ash was taken out. In this case, the temperature at which the treated ash and the reaction exhaust gas 4 are separated is 850 ° C., which is the same as the treatment temperature.

  As a result of analyzing the obtained treated ash, lead was 120 mg / kg, cadmium was 6 mg / kg, and selenium was 5 mg / kg (detection limit) or less. At this time, the lead removal rate was 95.1%, and the cadmium removal rate was 90%. Table 3 shows the test conditions of Example 2, the remaining amount of lead as a result of analyzing the obtained treated ash, and the lead removal rate at this time.

Example 4 to Example 8 and Comparative Example 2 : Using the same test apparatus as in Example 3, the same sample as in Example 3 was tested in the same manner as in Example 3 except for the treatment temperature. Example 4 was 700 ° C., Example 5 was 750 ° C., Example 6 was 800 ° C., Example 7 was 950 ° C., Example 8 was 1050 ° C., and Comparative Example 2 was 500 ° C. In addition, the temperature which isolate | separates process ash and the reaction waste gas 4 is the same as process temperature.

  Table 3 shows the test conditions of Examples 4 to 8 and Comparative Example 2, and the residual amount of lead as a result of analyzing the obtained treated ash and the lead removal rate at this time.

Comparative Example 3 : A test was conducted to examine the influence of the coarse particle size of the mineral powder. The incinerated ash burner was sieved from the coarsely pulverized one, and the one with a particle size of 4 mm to 8 mm was separated to obtain coarse raw ash. The lead concentration of this sample was 1200 mg / kg, and the amount of chloride was 0.9% as the chlorine content. To this, 3.6% NaCl (2.2% as the chlorine content) was added so that the chlorine equivalent ratio was about 11 as in the other tests (the chlorine content in combination with the chlorine content of the raw ash was 3.1%) was used as a test sample.
This sample was tested by the same method as in Example 3 using the same test apparatus as in Example 3.

Table 3 shows the conditions of the test of Comparative Example 3, the residual amount of lead as a result of analyzing the obtained treated ash, and the lead removal rate at this time.
Lead removal rates have fallen significantly.

Example 9 to Example 12 : Using the same test apparatus as in Example 3, a makeup sample described below was processed in the same manner as in Example 3, the processing temperature was 850 ° C. in Example 9, and Example 10 was At 800 ° C, Example 11 was tested at 850 ° C and Example 12 was tested at 800 ° C.

  To make up the sample, Example 9 was sodium chloride, Example 10 was potassium chloride, Example 11 was calcium chloride, and Example 12 was lead oxide in the sand to see the effect of magnesium chloride. 5000 mg / kg, sodium chloride and the like were added and mixed well by adding 20 times the theoretical amount necessary for lead to convert to lead chloride.

Table 3 shows the test conditions of Examples 9 to 12 and the lead as a result of analyzing the obtained treated ash, the residual concentration and the lead removal rate at this time.
It has been confirmed that calcium chloride, magnesium chloride, sodium chloride, and potassium chloride are all effective as chlorides for removing the heavy metals of the present invention.

Kiln type reactor flow sheet Fluidized bed reactor flow sheet Outline diagram of electric furnace heating rotary continuous test equipment Electric furnace heating rotary continuous test equipment flow sheet Outline diagram of electric furnace heating rotary batch test equipment Electric furnace heating rotary batch test equipment flow sheet

Explanation of symbols

1: Mineral powder (incinerated ash)
1 ': calcium chloride, etc. 2: treated powder (treated ash)
3: Medium gas 3 ': Medium gas stream 4: Reaction exhaust gas 5: Circulating gas 5': High temperature circulating gas 6: Fluidized bed 7: Cyclone recovered powder 8: Fuel 8 ': Carbon dioxide 9: Air 9': Water vapor 11: Kiln rotating part 12: Combustion furnace 13: Powder gas supply part 14: Powder gas separation part 15: Powder gas separation part-Heat insulation part 16: Lifter 17: Refractory brick 18: Support roller 21: Fluidized bed type Reactor body 22: Cyclone 23: Powder extraction unit 24: Rotary valve 25: Circulation blower 26: Powder recovery tube 27: Powder extraction unit-Heating / warming unit 28: Cyclone and powder recovery tube-Heating / warming unit 29: Fluidized bed powder surface 30: Electric furnace heating rotary continuous test device 31: Rotating reaction cylinder 32: Electric furnace 33: Rotating reaction cylinder-supporting roller receiver 34: Rotating reaction cylinder-supporting roller 35: Rotating reaction cylinder-shaft seal 36 : Powder supply hopper 37: Powder Body supply screw conveyor 38: Medium gas supply unit 39: Reaction exhaust gas treatment ash separation unit 40: Reaction exhaust gas treatment ash separation unit-Heat insulation unit 41: Electric furnace heating rotary continuous test device support base 42: Gas flow meter 50: Electricity Furnace heating rotary batch test apparatus 51: Rotary reaction cylinder outer cylinder 52: Rotary reaction cylinder inner cylinder 53: Reaction exhaust gas outlet 54: Electric furnace heating rotary batch test apparatus support

Claims (7)

  A mineral powder containing heavy metals is contacted with a medium gas stream in the presence of calcium chloride and / or magnesium chloride and / or sodium chloride and / or potassium chloride in a temperature range of 610 ° C. to 1090 ° C. to obtain calcium chloride And / or by conversion with magnesium chloride and / or sodium chloride and / or potassium chloride, the heavy metal compound is converted to its heavy metal chloride, and the heavy metal chloride is transferred as vapor into the medium gas for treatment. A processing method for removing heavy metals from a mineral powder containing heavy metals, characterized in that a medium gas containing chloride powder of the mineral powder and heavy metals is separated in a temperature range of 400 to 1090 ° C.   The processing method for removing heavy metals from a mineral powder containing heavy metals according to claim 1, wherein the medium gas is a gas containing carbon dioxide and / or water vapor.   The temperature range in which the mineral powder containing heavy metals is brought into contact with the medium gas stream is 700 ° C. to 1050 ° C., and the medium gas containing the mineral powder after treatment and the chloride vapor of heavy metals is 400 to 1050 ° C. The processing method of removing heavy metals from the mineral powder containing heavy metals according to claim 1 or 2, wherein the separation is performed in a temperature range of   The processing method of removing heavy metals from the mineral powder containing heavy metals according to any one of claims 1 to 3, wherein the processing is performed in the presence of calcium oxide and / or magnesium oxide.   The processing method for removing heavy metals from a mineral powder containing heavy metals according to any one of claims 1 to 4, wherein the mineral powder is incinerated ash.   A mineral powder containing heavy metals, characterized in that the treatment device for performing the treatment according to any one of claims 1 to 5 is a kiln type treatment device, a moving bed type treatment device or a fluidized bed type treatment device. Processing equipment to remove heavy metals from water   It has a structure for keeping and / or heating so that the temperature of the wall of the portion separating the mineral powder after treatment and the medium gas containing chloride vapor of heavy metals is in the temperature range of 400 to 990 ° C. The processing apparatus which removes heavy metals from the mineral powder containing heavy metals of Claim 6 characterized by these

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