JP5023927B2 - Method for treating asbestos-containing material and fluoride sludge, and method for producing cement - Google Patents

Description

  The present invention relates to a treatment method for efficiently detoxifying simultaneously asbestos-containing materials such as asbestos waste and fluoride sludge containing phosphate ions discharged in the manufacturing process of semiconductor materials and the like. The present invention relates to a method for producing cement.

Asbestos (natural asbestos) is a naturally produced mineral fiber that has chemical stability and excellent heat resistance and strength. As materials, it was widely used for building walls, ceilings, floors, air-conditioning equipment, etc.
However, in recent years, this asbestos has no chemical toxicity, but its crystalline structure is acicular, so when inhaled by humans, it accumulates in the lung tissue without being excreted and accumulated for a long period of time. It has been pointed out that it causes serious illnesses.

Therefore, at present, measures are being taken to remove or remove asbestos sprayed on walls and ceilings that may be scattered and asbestos used as heat insulation materials in many buildings. Asbestos is generated as waste.
By the way, this kind of asbestos waste that may be scattered is designated as specially managed industrial waste in the “Waste Disposal and Cleaning Law”, and the processing standards from its discharge to collection, transportation and disposal are established. It has been.

  In addition, in the above processing standards related to collection and transportation, asbestos is stored in a container such as plastic and handled carefully so as not to be scattered due to breakage, etc. It is obliged to take measures. In addition, as a treatment standard related to the above disposal, double packing with water-resistant materials such as plastic bags and containers, or solidification with a sufficient amount of cement etc. and direct landfill disposal at a predetermined place It is stipulated that it is made harmless by a sufficient melting process using a melting method using a melting facility, and then treated as ordinary industrial waste.

  Of these asbestos disposal methods, the former direct landfill method requires a large amount of cement, and there is concern about the early depletion of the landfill site against the expected emissions. ing. Moreover, in the latter detoxification method by the intermediate treatment in the melting equipment, the melting point of asbestos is as high as around 1500 ° C., so it is difficult to completely detoxify asbestos depending on the melting temperature. There was a point.

  Therefore, in Patent Document 1 below, an asbestos detoxification method is proposed, which comprises mixing or kneading asbestos and a fluorocarbon decomposition product produced by decomposing and detoxifying the fluorocarbon, and then heating the mixture at a low temperature. Yes.

  And according to the conventional detoxification method, asbestos can be decomposed even at a heating temperature of 600 ° C. or less by using calcium fluoride produced by the detoxification treatment as a melting agent. It is said that asbestos can be detoxified with energy.

However, as described in Patent Document 1, in the asbestos detoxification treatment method, air is plasmatized by discharge using a chlorofluorocarbon decomposition detoxification device separately, and is subjected to ultrahigh temperature (about 10, 000 ° C.) arc is generated, and there chlorofluorocarbon [e.g., Freon 12 (CCl ₂ F _2)] and water vapor (H ₂ O), and must be decomposed by feeding, to process a large amount of asbestos waste However, there are problems that the process and equipment are complicated and the processing cost is increased.

On the other hand, in the manufacturing process of semiconductor materials and semiconductor devices, a large amount of used waste liquid containing hydrofluoric acid, silicic hydrofluoric acid, nitric acid, phosphoric acid and the like used as a cleaning liquid for etching a silicon wafer is discharged. In general, the used waste liquid is treated with a waste liquid neutralized with a calcium salt such as calcium hydroxide or calcium carbonate to form a slurry sludge containing fluoride (hereinafter referred to as fluoride sludge). However, there are many problems in the treatment of the fluoride sludge, and development of a simple treatment method and recycling is desired.
JP 2005-168632 A

  Therefore, as a result of intensive research on the detoxification treatment of the asbestos waste and the fluoride sludge as waste, the present inventors have found that the fluoride sludge contains calcium fluoride in the neutralization treatment. It is contained as a precipitate. Therefore, by mixing the fluoride sludge and the asbestos waste, the heating temperature required for the decomposition of the asbestos described above can be lowered, and the phosphorus contained in the fluoride sludge can be reduced. The inventors have found that the detoxification treatment can be performed more easily by causing cracks on the surface of the needle-like crystal structure and embrittlement by the acid ions.

  The present invention has been made on the basis of such knowledge. Asbestos-containing materials such as asbestos waste and fluoride sludge containing phosphate ions discharged in the manufacturing process of semiconductor materials and the like are simultaneously and low. It is an object of the present invention to provide a method for treating an asbestos-containing material and fluoride sludge that can be efficiently detoxified at a heating temperature, and a method for producing cement using the same.

In order to solve the above-mentioned problem, the asbestos-containing material and the treatment method of fluoride sludge according to claim 1 are obtained by mixing the asbestos-containing material and fluoride sludge containing calcium fluoride and phosphate ions. mixture was poured into a rotary kiln which definitive cement production facility with cement material, and is characterized in that the heat treatment of the mixture while firing the cement material.

The invention of claim 2 is the invention according to claim 1, it is characterized in that the heat treatment on the Symbol mixture was wet-milled.

The invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2 , at least one of incinerated main ash and lime is further mixed with the mixture.

Furthermore, the invention described in claim 4 is a method for producing cement using the method for treating asbestos-containing material and fluoride sludge according to any one of claims 1 to 3 , wherein the mixture is used together with a cement raw material. It is put into a rotary kiln, the cement raw material is fired to make cement, and the mixture is made part of the cement by the heat treatment.

According to the invention according to any one of claims 1 to 3 , fluoridation contained in the fluoride sludge by mixing asbestos-containing materials such as asbestos waste and fluoride sludge containing phosphate ions. With calcium (CaF ₂ ), the heating temperature required for decomposition of the asbestos can be lowered. In addition, the asbestos can be further easily decomposed by making the surface of the needle-like crystal structure crack by the phosphate ions contained in the fluoride sludge and making it brittle. Therefore, the the these asbestos compounds and fluoride sludge can be treated efficiently detoxified simultaneously and at a low heating temperature.

At this time, if the heat treatment is performed after the mixture is wet pulverized as in the invention described in claim 2 , scattering of the asbestos-containing material can be reliably prevented. In addition, the mixing of the asbestos-containing material and the fluoride sludge can be promoted, and the asbestos-containing material can be subdivided to decompose the asbestos during the heat treatment in a short time.

Moreover, the Rukoto be put into a rotary kiln for firing cement raw material in cement manufacturing facility, within the rotary kiln can be done because it is held in 900 ° C. to 1450 ° C., reliably detoxified.

In addition, moisture contained in the mixture can be instantly vaporized and discharged in the high temperature atmosphere, and calcium oxide (CaO), alumina (Al ₂ O ₃ ), iron ( Fe ₂ O ₃ ) and the like can be reused as part of the cement raw material. Incidentally, the calcium fluoride (CaF ₂ ) contained in the fluoride sludge is originally added for reducing the melting temperature at the time of firing the cement raw material. It is also possible to reduce the amount of calcium fluoride.

Furthermore, in recent years, in addition to the asbestos waste and the fluoride sludge, the main ash discharged from the incinerator has been requested to be detoxified. The main ash is mainly composed of components that are substantially the same as cement raw materials such as silicon dioxide (SiO ₂ ) and calcium oxide (CaO). Therefore, as in the invention described in claim 3 , if at least one of the incinerated main ash and lime is further mixed with the above mixture, the incinerated main ash as waste can be simultaneously detoxified, In particular, when heat treatment is performed in the rotary kiln, it can be effectively used as a part of the cement raw material.

In addition, as in the invention according to claim 4 , by charging the mixture together with the cement raw material into a rotary kiln, the cement raw material is fired into cement, and the mixture is heat treated to obtain an asbestos-containing material. By detoxifying the fluoride sludge, the mixture can be made part of the cement, and the cement can be produced efficiently.

(First embodiment)
Hereinafter, a first embodiment in which the method for treating asbestos-containing material and fluoride sludge according to the present invention is applied to a treatment method using a rotary kiln for firing cement raw materials in a cement production facility will be described.
FIG. 1 shows a treatment system used in the treatment method. First, the cement production facility will be described. Reference numeral 1 in FIG. 1 is a cement kiln for firing cement raw materials. This cement kiln 1 is a rotary kiln provided so as to be rotatable around an axis, and a preheater 3 for preheating the cement raw material is provided in a left kiln bottom portion 2 in the figure, and a right kiln in the figure. A main burner 5 for heating the inside is provided in front of the kiln 4. In addition, the code | symbol 6 in a figure is a clinker cooler for cooling the cement clinker after baking.

  Here, the preheater 3 is composed of a plurality of cyclones arranged in series in the vertical direction, and the cement raw material is supplied to the uppermost cyclone via the supply pipe 7, and the lowermost cyclone Connected to the bottom is a transfer pipe 3 a for sending the internal cement raw material to the kiln bottom part 2 of the cement kiln 1.

  On the other hand, the kiln bottom part 2 is provided with an exhaust gas pipe 3b for supplying the combustion exhaust gas discharged from the cement kiln 1 to the lowermost cyclone, and the exhaust gas discharged from the upper part of the uppermost cyclone is Exhaust air (not shown) is exhausted through the exhaust line 8.

And the processing equipment of the asbestos containing material and fluoride sludge is attached to the cement manufacturing equipment which consists of the said structure.
In FIG. 1, reference numeral 10 denotes a hopper into which an asbestos-containing material such as asbestos waste is charged. The lower discharge port of the hopper 10 is connected to the supply side of the wet mill 12 via a large-diameter opening / closing means 11. The wet mill 12 is connected to a fluoride sludge supply pipe 13 for introducing slurry fluoride sludge into the wet mill 12. In addition, when the fluidity in the mixture of these asbestos-containing materials and fluoride sludge is insufficient, a waste liquid, water, a fluidizing agent, etc. increase the fluidity separately from the solvent supply pipe (not shown) into the wet mill 12. It has come to be supplied as.

  On the other hand, one end of a transfer pipe 15 having a transfer pump 14 interposed is connected to the discharge side of the wet mill 12, and the other end of the transfer pipe 15 is connected to the front 4 of the cement kiln 1. And is introduced above the main burner 5.

  Further, a compressed air supply pipe 16 is connected to the upstream side of the transfer pipe 15 before the kiln 4. Here, the compressed air supply pipe 16 is arranged so that the compressed air is in the transfer pipe 15 and promotes the transfer of the slurry in the transfer pipe 15 to the cement kiln 1 side. The pipes are inclined so as to blow out.

Next, a first embodiment of the present invention using the processing system having the above configuration will be described.
First, the cement raw material supplied from the supply pipe 7 to the first-stage cyclone of the preheater 3 is preheated by the high-temperature exhaust gas from the cement kiln 1 that rises from below as it sequentially falls to the lower cyclone. In particular, the lowermost cyclone is introduced into the kiln bottom portion 2 of the cement kiln 1 through the transfer pipe 3a.

  And in this cement kiln 1, in the process gradually sent from the kiln bottom part 2 side to the kiln front 4 side, it is heated to about 1450 ° C. by the combustion exhaust gas from the main burner 5 and burned to become a clinker. Next, the clinker that has reached the front 4 is dropped into the clinker cooler 6 and sent to the right in the figure. At this time, the air is cooled to a predetermined temperature by the air supplied into the clinker cooler 6 and finally taken out from the clinker cooler 6.

  At the same time, the asbestos waste stored in the plastic container and carried into the cement manufacturing facility is directly fed into the hopper 10 together with the container, and the opening / closing means 11 is opened to supply the wet mill 12. . Further, in the wet mill 12, the valve 13a of the supply pipe 13 is opened to supply slurry fluoride sludge. Moreover, if necessary, waste liquid, sludge, water, or a fluidizing agent for separately providing fluidity is supplied.

  Here, the fluoride sludge will be described in detail. Among the fluoride sludge, a large amount of wastewater to be treated is hydrofluoric acid and nitric acid discharged from the wafer etching process in a semiconductor manufacturing factory or the like. It is a mixed acid wastewater mainly composed of In this wastewater, since fluorine is particularly subject to wastewater regulation, a treatment method is generally employed in which a calcium salt such as calcium carbonate or calcium hydroxide is added to agglomerate and precipitate the fluorine.

That is, the fluorine in the wastewater is a compound such as hydrofluoric acid (HF), ammonium fluoride (NH ₄ F), sodium fluoride (NaF), and hydrosilicofluoric acid (H ₂ SiF ₆ ). In addition, for example, calcium hydroxide (Ca (OH) ₂ ) is added as the above calcium salt to produce calcium fluoride CaF ₂ having low solubility.

FIG. 3 shows analysis results of components in a plurality of fluoride sludge samples discharged from this type of wafer etching process and subjected to calcium salt addition treatment. In the above analysis, thermal hydrolysis distillation and ion chromatography were used.
From FIG. 3, it can be seen that any fluoride sludge contains predetermined amounts of calcium, fluorine and phosphorus.

Then, in the present embodiment, a slurry-like fluoride sludge containing the calcium fluoride CaF ₂ as a precipitate, is it to introduce the wet mill 12 from the supply pipe 13. Then, in the wet mill 12, the asbestos waste is pulverized wet together with the container, and the pulverized asbestos waste and fluoride sludge are mixed.

Accordingly, the calcium fluoride contained in the fluoride sludge (CaF _2), while the lower heating temperature lower that required to decompose asbestos, the phosphate ions contained in the fluoride sludge, surface of the needle-like crystal structure By cracking and embrittlement, the asbestos can be further easily decomposed.

  In addition, in this case, in addition to the asbestos waste and fluoride sludge, incinerated main ash whose main component is a component substantially matching with cement raw materials such as silicon dioxide and calcium oxide is mixed in the wet mill 12. You can also. Moreover, it is preferable to adjust so that the viscosity of the slurry-like mixture of the asbestos waste after grinding | pulverization produced | generated in the wet mill 12, fluoride fluoride sludge, etc. may become 10,000 mPa * s or less.

Next, the slurry-like mixture discharged from the wet mill 12 is sent to the front 4 side of the cement kiln 1 through the transfer pipe 15 by the pump 14.
Then, by supplying compressed air from the compressed air supply pipe 16 into the transfer pipe 15, the slurry is jetted into the cement kiln 1 from the front 4 side of the kiln 1.

  Thereby, the mixture of asbestos waste and fluoride sludge is burned at a high temperature of about 2000 ° C. in the vicinity of the flame from the main burner 5 in the cement kiln 1. As a result, asbestos is instantly decomposed and made non-asbestos, thereby detoxifying. And the solid content in the said mixture is utilized as a part of cement raw material, the water | moisture content in the said mixture is vaporized instantaneously, it exhausts with combustion exhaust gas, and a cement is manufactured.

Therefore, according to the asbestos-containing material and fluoride sludge treatment method using the cement production facility having the above-described configuration, the fluoride sludge is mixed by mixing asbestos waste and fluoride sludge containing phosphate ions. the calcium fluoride contained in the heating temperature required for the decomposition of the asbestos can make lower. In addition, the asbestos can be further easily decomposed by making the surface of the needle-like crystal structure crack by the phosphate ions contained in the fluoride sludge and making it brittle.

  Furthermore, since the mixture of the asbestos waste and fluoride sludge is introduced into the cement kiln 1 from the front 4 side of the kiln 1 where a high temperature atmosphere of 1400 ° C. or higher is obtained, these asbestos-containing materials and fluorides are introduced. The sludge and the like can be detoxified at the same time and reliably.

  In addition, since the asbestos waste and fluoride sludge are wet pulverized and mixed by the wet mill 12, the asbestos waste that has been stored and transported in plastic containers to prevent scattering is also By putting the entire container into the wet mill 12 and crushing it wet, the asbestos can be pulverized while reliably preventing the asbestos from scattering.

  Moreover, since the mixture of the pulverized asbestos waste and fluoride sludge and the like is discharged as a slurry from the wet mill 12, it is discharged from the front 4 side of the cement kiln 1 through the transfer pipe 15 by the pump 14. By supplying inside, there is no possibility that asbestos is scattered in the transfer step after pulverization of asbestos waste. In addition, a general-purpose pump 14 can be used as the conveying means.

Further, since compressed air is supplied from the compressed air supply pipe 16 and the slurry in the transfer pipe 15 is ejected into the cement kiln 1, the slurry is supplied to a wide area in the cement kiln 1 and instantly burned. can do.
As a result, the rotary kiln can be detoxified easily and reliably without taking additional measures to prevent scattering.

(Second Embodiment)
FIG. 2 shows a treatment system used in the second embodiment of the method for treating asbestos-containing material and fluoride sludge according to the present invention. The same components as those shown in FIG. The explanation will be simplified.
In this processing system, a heating tank 17 is interposed in a transfer pipe 15 connected to the discharge side of the wet mill 12, and the discharge side of the heating tank 17 is introduced into the kiln bottom part 2 of the cement kiln 1. Yes.

  On the other hand, hot air of about 900 ° C. extracted from the kiln bottom portion 2 of the cement kiln 1 through the air supply pipe 18 is introduced into the heating tank 17 as a heat source. The high-temperature air introduced into the heating tank 17 is returned again to the kiln bottom portion 2 of the cement kiln 1 through the return pipe 19. In FIG. 2, the heating tank 17 is drawn away from the cement kiln 1, and as a result, the air supply pipe 18 and the return pipe 19 are routed. It is possible to install the tank 17 adjacent to the kiln bottom part 2 of the cement kiln 1.

  In the second embodiment using the processing system configured as described above, the mixture of asbestos waste and fluoride sludge and the like pulverized and mixed in the wet mill 12 is once sent to the heating tank 17. And in this heating tank 17, it heat-processes by the high temperature air of about 900 degreeC sent from the kiln bottom part 2 of the cement kiln 1. FIG. Then, since the decomposition temperature of asbestos is lowered to about 600 ° C. by the fluorine content contained in the fluoride sludge, the asbestos in the mixture is decomposed and rendered harmless in the heating tank 17.

Next, the slurry-like mixture discharged from the heating tank 17 is introduced into the interior from the kiln bottom portion 2 of the cement kiln 1 through the transfer pipe 15. And it burns in the cement kiln 1 by about 900 degreeC or more high temperature, and the solid content in the said mixture is utilized as a part of cement raw material similarly.
Therefore, also by the processing method shown in the second embodiment, it is possible to obtain the same effects as in the first embodiment described above.

It is a schematic block diagram which shows the processing system used for the 1st Embodiment of this invention. It is a schematic block diagram which shows the processing system used for the 2nd Embodiment of this invention. It is a graph which shows the analysis result of the component in the fluoride sludge discharged | emitted from the etching process of a wafer.

Explanation of symbols

1 Cement kiln (rotary kiln)
2 Kiln bottom part 4 In front of the kiln 10 Hopper for charging asbestos waste, etc. 12 Wet mill 13 Supply pipe for fluoride sludge 15 Transfer pipe 17 Heating tank

Claims (4)

A fluoride sludge containing asbestos compounds and calcium fluoride and phosphate ion are mixed, and charged into a rotary kiln definitive the resulting mixture to a cement production facility with a cement raw material, the mixture thereby firing the cement material A method for treating asbestos-containing material and fluoride sludge, characterized by subjecting to heat treatment. The method for treating asbestos-containing material and fluoride sludge according to claim 1, wherein the heat treatment is performed after the mixture is wet-pulverized . The method for treating asbestos-containing material and fluoride sludge according to claim 1 or 2, wherein at least one of incinerated main ash and lime is further mixed with the mixture . A method for producing cement using the asbestos-containing material and the fluoride sludge treatment method according to any one of claims 1 to 3, wherein the mixture is put together with the cement material into a rotary kiln, and the cement material is fired. And manufacturing the cement, wherein the mixture is made part of the cement by the heat treatment .

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