JP2011212530A - Method and apparatus for removing fluorine from fluorine-containing waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing fluorine from fluorine-containing waste which can be performed in a shorter time than heretofore.SOLUTION: The method for removing fluorine includes: an introduction process of introducing fluorine-containing waste into a heating furnace 31 by using the heating furnace 31, a water vapor supplying means and a waste gas treatment unit 4; a reaction process of supplying water vapor or water into the heating furnace 31 and bringing water vapor into contact with the waste at 850 to 1,300°C for 0.5 to 10 h; and a waste gas treating process of treating generated hydrogen fluoride gas with the waste gas treatment unit 4.

Description

  The present invention relates to a method for removing fluorine from waste containing fluorine such as steel slag.

In the steelmaking process, there are hot metal pretreatment slag, converter slag, electric furnace slag, secondary refining slag, etc. generated from electric furnaces, blast furnaces, etc., which are reused as roadbed materials and cement materials, or landfilled. However, since fluorite is used as a fluxing agent in the steelmaking process, these slags produced in the process contain fluorine, and if reused or discarded (hereinafter referred to as “reuse”, etc.) Can cause contamination.
As a conventional method for preventing outflow of fluorine contained in slag to the environment, a method of reducing fluorine content in slag by spraying water and water vapor to crushed slag to elute fluorine (Patent Document) 1) A method of suppressing the outflow of fluorine by stabilizing the slag using a fixing agent (Patent Document 2), adding an oxide containing a predetermined amount or more of SiO ₂ and / or iron oxide during scouring A method of adjusting slag with a small amount of fluorine elution (Patent Document 3) is known.

JP 2000-180073 A Japanese Patent No. 3620341 Patent No. 3935113

However, in the method of Patent Document 1, it takes time to process, and even when heated steam is used, 24 hours or more are required. Since both Patent Documents 2 and 3 require an additive, it is not economical because it causes the installation of an additive supply facility and an increase in running cost. Further, since the purpose is not to reduce the fluorine content itself in the slag, depending on the fluorine content in the slag, there are cases where the reuse or disposal of the slag is limited.
The subject of this invention is providing the fluorine removal processing method of a waste which can be implemented in a shorter time than before.

The present invention that has solved the above problems is as follows.
<Invention of Claim 1>
A fluorine removal treatment method for fluorine-containing waste using a heating furnace, a steam supply means, and an exhaust gas treatment means,
An introduction step of introducing the waste into the heating furnace;
A reaction step of supplying water vapor or water to the heating furnace and bringing the waste into contact with water vapor at 850 to 1300 ° C. for 0.5 to 10 hours;
An exhaust gas treatment process for treating the generated hydrogen fluoride gas in an exhaust gas treatment means.

(Function and effect)
According to the present invention, fluorine is scattered as hydrogen fluoride gas by aeration of water vapor under high temperature conditions for waste containing fluorine, and fluorine is removed from waste in a shorter time than before. Is possible. In the absence of water vapor, hydrogen fluoride is not generated and fluorine cannot be removed from the slag.
The “steam supply means” in the present invention is not limited to a means for directly supplying steam into the heating furnace, but means for supplying water into the heating furnace to generate steam in the furnace, and fuel and air in the heating furnace. Any means capable of supplying water vapor to the target substance in the furnace, such as means for generating water vapor by supplying and burning in a heating furnace, means for supplying gas containing water vapor generated from the factory, etc. are particularly limited. It is not a thing.

<Invention of Claim 2>
The method for removing fluorine from fluorine-containing waste according to claim 1, wherein the waste is slag generated in a steelmaking process.

<Invention of Claim 3>
The steam is a mixture of one or more of steam generated in combustion gas, steam generated from water supplied into the heating furnace, and steam supplied from outside the heating furnace. The fluorine removal processing method of the fluorine-containing waste of Claim 1 or 2 which is these.

<Invention of Claim 4>
The said water vapor | steam is mixed with gas previously, and is supplied to a heating furnace, The fluorine removal processing method of the fluorine containing waste in any one of Claims 1-3.

(Function and effect)
Water vapor is generated outside the heating furnace and upstream of the heating furnace, and mixed with gas, particularly air, to be supplied, whereby the water vapor and the slag can be efficiently contacted.

<Invention of Claim 5>
The method for removing fluorine from fluorine-containing waste according to any one of claims 1 to 4, wherein the waste is pulverized to a particle size of 10 mm or less and then supplied to a heating furnace.

(Function and effect)
By reducing the particle size of the fluorine-containing waste, the contact area with water vapor can be increased, and the fluorine removal treatment can be performed more efficiently.

<Invention of Claim 6>
The said heating furnace is a fluorine removal processing method of the fluorine-containing waste in any one of Claims 1-5 which is a rotary kiln or a fluidized bed.

(Function and effect)
Since the rotary kiln and the fluidized bed are heated while stirring the contents, the fluorine removal efficiency can be increased.

<Invention of Claim 7>
A heating furnace, steam supply means or water supply means, and exhaust gas treatment means,
Steam or water is supplied to the heating furnace, and the fluorine-containing waste and steam are brought into contact at 850 to 1300 ° C. for 0.5 to 10 hours,
Configured to treat the generated hydrogen fluoride gas in the exhaust gas treatment means,
An apparatus for removing fluorine from waste containing fluorine.

  According to the present invention, it is possible to remove fluorine from waste containing fluorine in a shorter time than before.

It is a flowchart at the time of using the internal combustion type heating furnace in the fluorine removal processing method which concerns on this invention. It is a flowchart at the time of using the external heating type heating furnace in the fluorine removal processing method which concerns on this invention. It is a flowchart which shows an example of the fluorine removal processing apparatus which concerns on this invention. It is a flowchart which shows an example of the waste gas processing equipment which concerns on this invention. It is a flowchart which shows an example of the reaction separation equipment which concerns on this invention. It is a flowchart which shows the fluorine removal processing apparatus of an Example. It is a graph which shows the relationship between the reaction temperature in Example, fluorine content of slag S 'from which fluorine was removed, and hydrogen fluoride partial pressure in the furnace (Kp = [pHF] ² / pH ₂ O). It is a graph which shows the relationship between the reaction time in an Example, and the fluorine content of slag S '.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present invention, “slag generated in the steelmaking process” means one kind or a mixture of two or more kinds of hot metal pretreatment slag, converter slag, electric furnace slag, secondary refining slag, etc., produced from an electric furnace or a blast furnace. Shall point to.
In the embodiment of the present invention, slag generated in the steelmaking process (hereinafter simply referred to as “slag”) is exemplified as the waste containing fluorine.

<Principle of fluorine removal treatment>
FIG. 1 shows a case where an internal combustion furnace 11 is used among the principles of the fluorine removal processing method according to the present invention. The slag S is put into the heating furnace 11 of the fluorine removing apparatus 1, and the fuel F and air A necessary for raising the furnace temperature are put into the heating furnace 11. By bringing slag S into contact with water vapor generated in the combustion gas by the combustion of fuel in the furnace, or water vapor V supplied from outside the furnace, and the fluorine in the slag S reacts as shown in the following equation: As a result, hydrogen fluoride is generated. In the absence of water vapor, hydrogen fluoride is not generated and fluorine cannot be removed from the slag.
CaF ₂ + H ₂ O → CaO + 2HF
The generated hydrogen fluoride gas is discharged from the heating furnace, and fluorine is collected by the exhaust gas treatment facility 12, detoxified, and then released into the atmosphere as exhaust gas W. On the other hand, the slag S ′ from which the fluorine has been removed is taken out from the furnace and reused.

  FIG. 2 shows a case where an external heating furnace 21 is used in the principle of the fluorine removal processing method according to the present invention. When using the external heating type heating furnace 21 in the fluorine removing apparatus 2, the slag S is charged into the heating furnace 21 and then reacted with the steam V supplied from outside the furnace while being heated. In order to discharge the generated HF gas from the furnace earlier, air A may be supplied into the furnace.

<Example of processing device>
〔heating furnace〕
FIG. 3 is a flowchart showing an example of the fluorine removal processing apparatus according to the present invention.
Any known firing furnace can be used as the heating furnace in the fluorine removal processing apparatus 3, but it is preferable to use an internal combustion type rotary kiln or an external heating type rotary kiln capable of uniform heat conduction to the slag charged. Further, although not shown in the illustrated example, a fluidized bed can also be preferably used. By using a rotary kiln or a fluidized bed, slag can be flowed, improving contact efficiency with water vapor and improving reaction efficiency. In the illustrated example, an internal combustion type rotary kiln 31 is used.

  The slag S introduced into the rotary kiln 31 is preferably pulverized to a particle size of 10 mm or less, more preferably 1 to 100 μm before introduction, in order to increase the subsequent heating efficiency and fluorine removal efficiency.

  Fuel A and air A from an air blower 32 as an air supply facility are supplied from the side opposite to the slag inlet of the rotary kiln, and heating is started. In addition, not only an air blower but well-known air supply means, such as an air compressor, can also be applied. When the temperature in the rotary kiln 31 reaches 500 to 800 ° C. or higher, the steam V is supplied, mixed with the combustion gas generated by burning the fuel, and supplied into the rotary kiln. When the internal heating furnace is used, it is preferable that the supply amount of the air A is an amount that enables combustion of the fuel F and enables the generated hydrogen fluoride to be sent out of the system. In addition, when using an external heating furnace (not shown), it is preferable that the supply amount of the air A is an amount that allows the generated hydrogen fluoride to be sent out of the system.

  In this example, the water vapor V is supplied from the outside, but it is also possible to generate hydrogen fluoride using only the water vapor in the combustion gas. When supplying the steam V from the outside, methods such as using a steam generating device such as an evaporator, or using steam generated in another process such as a steelmaking process can be used. Further, a means (not shown, for example, water spray) that can supply water into the heating furnace may be provided to generate water vapor directly in the furnace. It is preferable to use steam in the combustion gas in combination with steam V from outside the furnace because fluorine can be more efficiently removed. By continuing to supply a certain amount of water vapor V, fuel F, and air A, the temperature in the furnace can be efficiently raised to the reaction temperature.

  The reaction temperature is 850 to 1300 ° C, more preferably 1000 to 1200 ° C, which is the temperature at which the slag becomes a semi-molten state. The semi-molten state is a state before melting, which means a state in which solids are maintained and solids are in contact with each other, and JIS M 8801 “Coals—Test Method”. In the ash melting test method, the state immediately before the softening point is reached. The temperature at which the semi-molten state changes depends on the composition of the slag, but if the reaction temperature exceeds 1300 ° C., many slag S will be in a molten state and there will be no gaps between solids, resulting in poor contact efficiency with water vapor. End up. On the other hand, when the temperature is lower than 850 ° C., a sufficient reaction cannot be performed in a short time. That is, when the slag S is in a solid or semi-molten state, the water vapor and the slag S can be brought into contact with each other to efficiently remove fluorine.

  Slag is put into the furnace that has reached the reaction temperature, and water vapor and slag S are reacted for 0.5 to 10 hours, more preferably for 1 to 4 hours. The amount of water vapor supplied is at least the theoretical equivalent of the amount of fluorine removed from the slag, preferably 10 to 100 times the theoretical equivalent. If the supply amount of water vapor is small, the slag residence time is required to be long, and if it is too large, the efficiency becomes economically low.

  The fluorine removing device 3 is preferably provided with a furnace thermometer TI and a flow meter FI. This is because the flow rate is controlled according to the temperature in the furnace, and the water vapor supply and the fluorine removal reaction are performed more efficiently. Hydrogen fluoride generated by the reaction is taken out of the furnace together with the combustion gas, excess water vapor, and excess air, sent to the exhaust gas treatment facility 4, and then discarded from the exhaust facility 34 into the atmosphere.

[Exhaust gas treatment equipment]
FIG. 4 shows a flowchart of an example of the exhaust gas treatment facility 4.
The exhaust gas treatment facility illustrated in FIG. 4 includes a quencher 41, an absorption tower 42, an exclusion tower 43, and an incentive fan 44. The exhaust gas from the heating furnace 31 usually contains 0 to 50% of hydrogen fluoride. When the exhaust gas comes into contact with the water spray in the quencher, most of the hydrogen fluoride in the exhaust gas is dissolved in water to generate an aqueous hydrogen fluoride solution. Since the inlet temperature of the exhaust gas in the quencher is as high as 800 to 1000 ° C., the temperature of the water spray water to be contacted is preferably 0 to 50 degrees C. Hydrogen fluoride that has not dissolved in water is removed from the exhaust gas by being sent to the absorption tower and coming into contact with water. The exhaust gas that has passed through the absorption tower is sent to the exclusion tower, and the remaining hydrogen fluoride is neutralized and excluded by alkali F-1 such as caustic soda and separated into gas and liquid by the mist separator 44, and then through the trigger fan 45. Exhaust air from the exhaust system. If the concentration of hydrogen fluoride in the exhaust gas from the heating furnace is sufficiently low, removal of hydrogen fluoride in the absorption tower 42 may be omitted.

  The fluorine removed from the slag in the above process is recovered from the quencher 41 in the state of an aqueous hydrogen fluoride solution. At that time, the solution may be supplied to the reaction separation means 5 after being cooled by the quencher cooler 46 through the cooling medium F-2.

[Regeneration of calcium fluoride]
FIG. 5 shows a flow chart of an example of the reaction separation means 5 of the aqueous hydrogen fluoride solution. The reaction separation means 5 includes reaction vessels 51 and 52 and a separator 53. The aqueous hydrogen fluoride solution generated in the exhaust gas treatment facility 4 is sent to the reaction tank. Calcium fluoride is produced by adding calcium hydroxide or calcium carbonate F-3 to the reaction vessel and reacting with an aqueous hydrogen fluoride solution. As calcium to be added, use of a 1 to 10 g / L calcium hydroxide suspension is preferable because of excellent cost, calcium fluoride reaction efficiency, and the like. The formation reaction of calcium fluoride is as follows.
2HF + Ca (OH) ₂ → CaF ₂ + 2H ₂ O
2HF + CaCO ₃ → CaF ₂ + CO ₂ + H ₂ O
The precipitate after the reaction is subjected to sedimentation separation if necessary, and then subjected to solid-liquid separation with a centrifuge or the like. Calcium fluoride can be obtained by drying the obtained sludge. The recovered calcium fluoride can be used again in a steel making process or the like.

  A flow chart of the fluorine removal processing apparatus 6 used as an example is shown in FIG. A tubular electric furnace 61 was used as a heating furnace, an air compressor 62 was used as air supply means, a tank 63A, a pump 63B and an evaporator 63C were used as water vapor supply means, and a trap flask 65 was used as exhaust gas treatment means. A furnace thermometer TI was installed in the heating furnace, and a flow meter FI was installed in the air line.

  Slag S40g was installed in the center part of the tubular electric furnace 41, and heating was started while sending air. When the furnace temperature reached 500 ° C., the supply of water vapor from the water vapor supply means was started. The supply amounts of water vapor and air were 60 NL / h and 95 NL / h, respectively, and reached the predetermined reaction temperature and continued to be supplied until the reaction was completed.

FIG. 7 shows the fluorine content of the residual slag S ′ and the partial pressure of hydrogen fluoride relative to the water vapor pressure in the furnace gas when the slag S and the water vapor V are reacted for 4 hours after reaching the predetermined reaction temperature. The value was as shown. Note that Kp = [pHF] ² / pH ₂ O was used as an index of hydrogen fluoride partial pressure.

  The content of fluorine and fluorine compounds allowed when recycling slag, etc. is 4000 mg / kg or less (from Environmental Agency Notification No. 19 test). In the fluorine removing apparatus according to the present invention, it has been found that when the reaction temperature is 850 to 1300 ° C., fluorine removal of slag can be performed to a level that satisfies the environmental standards.

  Similarly, FIG. 8 shows the fluorine content of the remaining slag S ′ when the slag S and the steam V are reacted for 1, 2, and 3 hours, respectively, after reaching the reaction temperature of 1100 ° C. In addition, the fluorine content of the residual S ′ when the slag S is heated for 4 hours without supplying the steam V at 1000 ° C. and 1300 ° C. is shown. Even at a reaction time of 1 to 3 hours at 1100 ° C., it has been found that the amount of fluorine remaining in the slag is less than 4000 mg / kg, which is an acceptable standard for reuse. However, when no water vapor was supplied, the fluorine content was hardly reduced even after the reaction for 4 hours.

  The present invention can be used for the disposal and reuse of waste containing fluorine such as steel slag.

  DESCRIPTION OF SYMBOLS 1, 2, 3, 6 ... Fluorine removal processing apparatus, 11 ... Internal combustion heating furnace, 12 ... Exhaust gas processing equipment, 21 ... External heating type heating furnace, 31 ... Rotary kiln, 32 ... Air blower, 34 ... Exhaust equipment, 4 ... Exhaust gas Processing equipment 41 ... quencher 42 ... absorption tower 43 ... removal tower 44 ... mist separator 45 ... invitation fan 46 ... quencher cooler 5 ... reaction / recovery equipment 51, 52 ... reaction tank 53 ... Centrifuge 61, tubular electric furnace, 63A ... tank, 63B ... pump, 63C ... evaporator, 62 ... air compressor, 65 ... trap flask, A ... air, F ... fuel, S ... slag, S '... fluorine removal Slag, V ... steam or water, W ... exhaust gas, TI ... in-furnace thermometer, FI ... flow meter.

Claims (7)

A fluorine removal treatment method for fluorine-containing waste using a heating furnace, a steam supply means, and an exhaust gas treatment means,
An introduction step of introducing the waste into the heating furnace;
A reaction step of supplying water vapor or water to the heating furnace and bringing the waste into contact with water vapor at 850 to 1300 ° C. for 0.5 to 10 hours;
An exhaust gas treatment process for treating the generated hydrogen fluoride gas in an exhaust gas treatment means.   The method for removing fluorine from fluorine-containing waste according to claim 1, wherein the waste is slag generated in a steelmaking process.   The steam is a mixture of one or more of steam generated in combustion gas, steam generated from water supplied into the heating furnace, and steam supplied from outside the heating furnace. The fluorine removal processing method of the fluorine-containing waste of Claim 1 or 2 which is these.   The said water vapor | steam is mixed with gas previously, and is supplied to a heating furnace, The fluorine removal processing method of the fluorine containing waste in any one of Claims 1-3.   The method for removing fluorine from fluorine-containing waste according to any one of claims 1 to 4, wherein the waste is pulverized to a particle size of 10 mm or less and then supplied to a heating furnace.   The said heating furnace is a fluorine removal processing method of the fluorine-containing waste in any one of Claims 1-5 which is a rotary kiln or a fluidized bed. A heating furnace, steam supply means or water supply means, and exhaust gas treatment means,
Steam or water is supplied to the heating furnace, and the fluorine-containing waste and steam are brought into contact at 850 to 1300 ° C. for 0.5 to 10 hours,
Configured to treat the generated hydrogen fluoride gas in the exhaust gas treatment means,
An apparatus for removing fluorine from waste containing fluorine.

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