JP5170040B2 - HF-containing gas dry processing apparatus and processing method - Google Patents

Description

  The present invention relates to a dry processing apparatus and a processing method for removing HF from exhaust gas containing HF.

In semiconductor and liquid crystal manufacturing factories, PFC (Perfluoro compounds) is used as an etching agent and a cleaning agent. PFC is a generic term for CF ₄ , C ₂ F ₆ , C ₃ F ₈ , SF ₆ , NF _3, etc., and is a greenhouse gas with a high global warming potential and is therefore a regulated gas. In order to prevent PFC emission, decomposition methods such as a catalytic method, a combustion method, and a plasma method have been studied. When PFC is decomposed, gases such as HF and SOx are generated. HF and SOx are toxic gases and corrosive gases. For this reason, the PFC decomposition treatment also requires harmless treatment of these decomposition product gases.

  Although it is not HF detoxification treatment, it is known that hydrogen chloride, which is a halo acid, is removed by washing with an aqueous sodium hydroxide solution or using a reaction with slaked lime or calcium carbonate (for example, patents). References 1 and 2).

Japanese Patent Application Laid-Open No. 10-43546 (Claims, Prior Art) Japanese Patent Application Laid-Open No. 7-299327 (abstract, claims)

  The wet method in which a gas such as hydrogen chloride is absorbed and removed by a scrubber sprayed with water or an aqueous alkaline solution generates a large amount of acidic waste liquid, which requires this treatment.

  On the other hand, the dry process using slaked lime, calcium carbonate or the like has a lower reaction rate than the wet process, and the apparatus becomes larger.

  An object of the present invention is to provide a treatment apparatus and a treatment method suitable for removing HF from exhaust gas containing HF or exhaust gas containing HF and SOx by a dry method.

The present inventors use solid calcium hydroxide (hereinafter referred to as Ca (OH) ₂ ) in a fixed bed as a method for removing HF from a gas containing HF in a gas generated by decomposition of PFC. It was investigated. As a result, it was found that a high utilization rate can be obtained when about 4.0% of HF is brought into contact with Ca (OH) ₂ at a predetermined temperature under the PFC decomposition gas composition conditions. The PFC cracked gas composition contains about 1.0% CO ₂ , 5-15% H ₂ O, 3-6% O ₂ in addition to about 4.0% HF, and the rest is N ₂ . However, the strength of the Ca compound after the test decreased as the utilization rate increased. For this reason, it has been found that when used in a fixed bed, the calcium compound pulverized due to the strength reduction may block the pipe depending on the method of introducing exhaust gas and the structure of the Ca (OH) ₂ packed tower. Further, when the SOx with HF coexist, CaSO ₄ is produced on the surface by reaction with SOx and Ca (OH) _2, revealed that the Ca (OH) ₂ is inside the particles not effectively used for the reaction with HF It was.

According to the treatment apparatus of the present invention, it is possible to remove HF without clogging with the powdered calcium compound. The present invention proposes a method that can use almost 100% of Ca (OH) ₂ inside the particles even if SOx coexists with HF.

The present invention has a Ca (OH) ₂ packed tower through which gas is circulated, a mesh plate is provided in the packed tower, and a Ca (OH) ₂ layer is held thereon, and the lower part of the packed tower contains HF. An HF processing apparatus is proposed in which a gas inlet is provided and an exhaust port for discharging the gas after HF removal is provided at the top. It is desirable to provide a tank for recovering the waste calcium compound dropped from the mesh plate below the packed tower, and a blower or ejector for sucking and exhausting the gas in the packed tower at the exhaust gas outlet.

  Gases containing HF are released, for example, in semiconductor factories, liquid crystal factories, waste incinerators, and the like. Therefore, it is desirable to provide the HF treatment apparatus of the present invention in the exhaust gas line of these factories or furnaces.

It has been found that the apparatus can be miniaturized by providing a heat exchanger for lowering the HF-containing exhaust gas to a predetermined temperature in the front stage of the Ca (OH) ₂ packed tower.

Ca (OH) ₂ is filled in the packed column was Ca (OH) ₂ is gradually its function by reaction with a reactive and SOx of HF is required to be replaced because reduced. In order not to stop the operation of the HF removing device when replacing the used Ca (OH) _2, it is desirable to provide a plurality of packed towers so that they can be switched.

Reduce blower and ejector failures by providing a mesh plate that collects CaF ₂ powder entrained in exhaust gas in front of the blower or ejector that sucks and exhausts exhaust gas that has passed through the Ca (OH) ₂ layer. Can do.

Further, in the PFC decomposition by the catalytic method or the combustion method, since a water vapor component is contained in the exhaust gas, it is desirable to provide a condensed water reservoir for storing condensed water in the gas that has passed through the Ca (OH) ₂ packed tower. For example, in the PFC decomposition by the catalytic method, H ₂ O is used as a reactant. In this method, H ₂ O that has not been used for the decomposition reaction remains in the decomposition gas and condenses when the gas temperature decreases. By providing a tank for storing the condensed water, secondary waste can be minimized. In addition, there is also an advantage that a change in the form of Ca (OH) ₂ to CaO can be suppressed by passing the PFC decomposition product gas through a Ca (OH) ₂ packed tower while containing H ₂ O.

As the shape of Ca (OH) ₂ to be used, it can be used by molding into various shapes, for example, a granular shape, a pellet-like honeycomb shape, and the like, as in a normal catalyst, but a granular shape is desirable. Since commercially available granular Ca (OH) ₂ has a wide range of particle shape distribution, fine Ca (OH) ₂ is preferably removed in advance from the viewpoint of pressure loss. It is desirable to use granules Ca (OH) ₂ having a size of 0.5 mm or more. The shape factor of Ca (OH) ₂ is preferably 500 mm or more as the average pore diameter. In particular, 500 to 1500 mm is desirable. If it is 1500 liters or more, the strength is decreased, and the powder is pulverized during use with the load when the Ca (OH) ₂ is laminated, and the internal pressure loss increases. The specific surface area is preferably 20 m ² / g or more. If it is about 10 m ² / g, there is a possibility that the inside of Ca (OH) ₂ grains will not be used.

The PFC targeted in the present invention includes carbon, hydrogen, oxygen, sulfur, or a compound of nitrogen and fluorine. Specifically, a compound of carbon and fluorine, a compound of carbon, hydrogen and fluorine, carbon A compound composed of carbon, fluorine and oxygen, a compound composed of carbon, fluorine and oxygen, a compound composed of sulfur and fluorine, a compound composed of sulfur, fluorine and oxygen, a compound composed of nitrogen and fluorine, a compound composed of nitrogen, fluorine and oxygen , Compounds composed of nitrogen, fluorine, oxygen and hydrogen. Examples of compounds are CF ₄ , CHF ₃ , CH ₂ F ₂ , CH ₃ F, C ₂ F ₆ , C ₂ HF ₅ , C ₂ HF ₅ , C ₂ H ₂ F ₄ , C ₂ H ₃ F ₃ , C _2. H ₄ F ₂ , C ₂ H ₅ F, C ₃ F ₈ , CH ₃ OCF ₂ CF ₃ , C ₄ F ₈ , C ₅ F ₈ , SF ₆ , SO ₂ F ₂ , NF _{3 and the} like. Exhaust gas from semiconductor / liquid crystal manufacturing equipment contains chlorine compounds such as Cl ₂ , HCl and HOCl, bromine compounds such as HBr and Br ₂ , and iodine compounds such as HI and I _{2 in} addition to the above PFC. There is. These gases are contained in N ₂ , Air, N ₂ and O ₂ , or Ar.

The PFC decomposition gas may contain SOx (SO ₂ , SO _3, etc.) that is a decomposition product of SF _{6 at} the same time as HF. When the acidic gas in the cracked gas is only HF, it is possible to prevent Ca (OH) ₂ from undergoing a shape change in CaO by operating at 100 ° C. or higher and 460 ° C. or lower. However, it includes SOx with HF, Ca (OH) ₂ the surface of CaSO ₄ generated, Ca (OH) ₂ grains inside the utilization was found to be inhibited. When the utilization rate of Ca (OH) ₂ is low, the replacement frequency increases, and the amount of Ca (OH) ₂ to be filled increases, so that the processing apparatus becomes large.

As a countermeasure, it has been found that after SOx is removed in advance, HF is preferably removed by a Ca (OH) ₂ packed tower, whereby 90% or more of Ca (OH) ₂ can be used. Methods for removing SOx are generally known, such as using fine Ca (OH) ₂ in a fixed bed, fluidized bed, etc. to increase the removal rate, dry removal using CaO or CaCO ₃ , and electrostatic precipitating. What is necessary is just to use the method. Although it is desirable to completely remove SOx from the exhaust gas, it is expected that part of it will remain. In this case, it is desirable to Ca a (OH) ₂ in the working temperature to 100 ° C. or higher 310 ° C. or less, it has been found that thereby the Ca (OH) ₂ utilization to 90% or more. When the temperature is lower than 310 ° C., CaSO ₄ precipitates on the surface, and the Ca utilization rate decreases. The reason why the utilization rate of Ca (OH) ₂ is increased at a temperature of less than 310 ° C. is considered to be because the reactivity of Ca (OH) ₂ and SOx decreases and HF reacts preferentially.

In the SOx removal step, it is desirable to reduce the SOx concentration to about 1% with respect to the HF concentration to be processed. For example, when processing a gas having a 4% HF concentration, Ca (OH) ₂ can be used almost 100% by reducing the SOx concentration to 400 ppm or less. The SOx removal and the HF removal may be performed in the same reaction tower, or may be performed in a two-column system by dividing.

  According to the present invention, HF can be removed by a dry method. Since it is a dry type, water is not used and acidic drainage is not generated.

It is a figure which shows the processing system flow of PFC gas. It is the schematic of the basic test apparatus used in the Example. It is the schematic of the HF processing apparatus by one Example of this invention. It is the characteristic view which showed the influence which the temperature of Ca (OH) ₂ has on performance. It is the characteristic figure which showed the influence which the space velocity has on the performance of Ca (OH) ₂ . It is the figure which compared the performance of samples 1-3. It is a characteristic comparison figure before and behind using Ca (OH) ₂ . It is explanatory drawing of the method of switching a Ca (OH) ₂ packed tower.

  A system flow diagram of PFC processing including the HF processing apparatus of the present invention is shown in FIG. Semiconductors have many production lines, and the exhaust gas composition differs from line to line. The target exhaust gas line is an exhaust gas line containing HF and SOx.

In the exhaust gas from the semiconductor or liquid crystal production line, the exhaust gas containing PFC is decomposed by the PFC decomposition apparatus 10. All exhaust gases from the production line do not contain PFC, but some contain one of HF and SOx, some contain two at the same time, and some do not contain both. Of these, exhaust gas containing HF and SOx is selected using infrared absorption analysis, etc., and merged with the exhaust gas treated by the PFC decomposition apparatus 10, and in the SOx removal step 20, for example, CaO dry desulfurization and Remove SOx with a combination of electrostatic precipitator. The exhaust gas after the removal of SOx removes HF by a dry method using Ca (OH) ₂ in the HF removal step 30. The exhaust gas after this is exhausted. The feature of this system is that water or alkaline aqueous solution is not used for exhaust gas treatment.

Example 1
In this example, it was examined whether high concentration HF after decomposing CF ₄ which is a kind of PFC can be removed by Ca (OH) ₂ .

A system diagram of the basic test equipment used for the test is shown in FIG. In order to decompose PFC in the reaction tube 1, a PFC decomposition catalyst 2 made of Ni and Al is filled, and a commercially available Ca (OH) ₂ (Ca (OH) ₂ UCL-3 manufactured by Zude Chemie Co., Ltd.) is used in the subsequent stage. A Ca (OH) ₂ layer 3 made of this material was provided. Glass wool 4 was spread over the PFC decomposition catalyst 2 in the reaction tube, and an alumina wool 5 layer was provided between the PFC decomposition catalyst and the Ca (OH) ₂ layer and below the Ca (OH) ₂ layer. The exhaust gas that passed through the Ca (OH) ₂ layer was periodically collected in a Tedlar bag from the gas sampling port 6 and the HF concentration was measured. Except when measuring the HF concentration, the absorption water was passed through and exhausted. The reaction tube 1 was heated from the outside with an electric furnace 7, and a catalyst composed of Ni and Al (hereinafter referred to as Ni / Al catalyst) and Ca (OH) ₂ were heated to a predetermined temperature.

The reaction gas is composed of CF ₄ , Air, N ₂ and H ₂ O. Nitrogen was added to CF ₄ from the cylinder 8 to obtain a gas having a CF ₄ concentration of about 1.4%, and air was added to 1290 ml / min of 115 ml / min. Water vapor was supplied by introducing ion-exchanged water into the reaction tube at 0.30 ml / min and evaporating it at the top of the Ni / Al catalyst. This reaction gas was brought into contact with a Ni / Al catalyst. Temperature of the catalyst is 700 to 800 ° C., space velocity was 1000h ^-1 in CF ₄ + N ₂ based flow (space velocity (h ^-1) = flow rate of the reaction gas (ml / h) / amount of catalyst (ml)). The temperature of the catalyst was measured with a thermocouple inserted in the reaction tube.

When 1 mol of CF ₄ is decomposed, ₄ mol of HF is generated, and HF is present at a concentration of about 4% in the gas after passing through the Ni / Al catalyst. With the start of CF ₄ decomposition, the outlet gas was periodically collected in a Tedlar bag, and the HF concentration was measured. No HF was detected in the outlet gas for 60 minutes from the start of the test. The theoretical calcium utilization rate calculated as CaF ₂ was generated from the amount of HF calculated from the amount of CF ₄ charged and the amount of Ca (OH) ₂ filled was 95% or more. Further, only the diffraction pattern of CaF ₂ was detected from the X-ray diffraction analysis after the test, and it was confirmed that the utilization rate was 95% or more from the F analysis in Ca (OH) ₂ after the test.

From the above results, it was found that Ca (OH) ₂ can be used for high concentration HF treatment under PFC decomposition conditions.

  The preparation method of the Ni / Al catalyst used for the test is as follows.

  A commercially available boehmite powder is dried at 120 ° C. for 1 hour. An aqueous solution in which 210.82 g of nickel nitrate hexahydrate was dissolved was added to 200 g of this dry powder and kneaded. After kneading, it is dried for about 2 hours at a temperature of 250 to 300 ° C. in an air atmosphere, and further fired at a temperature of 700 ° C. for 2 hours in air. The fired product was pulverized and sieved to a particle size of 0.5-1 mm. The catalyst composition after completion was Ni / Al = 20/80 in terms of mol ratio.

Example 2
(A) The effect of the Ca (OH) ₂ use temperature on the removal of high-concentration HF after CF ₄ decomposition was examined.

The reaction tube temperature was changed in order to change the Ca (OH) ₂ temperature. For this reason, the PFC decomposition temperature of the Ni / Al catalyst also changed, but the HF supply amount to the Ca (OH) ₂ layer was calculated from the CF ₄ decomposition rate. Other conditions are the same as those in the first embodiment. The results of examining the temperature dependence are shown in FIG. The reaction temperature was varied from 250 to 460 ° C., but the time for detecting HF in the outlet gas was almost the same. That is, it was confirmed that there was no temperature dependence under the present test conditions and high removal performance was exhibited.

(B) Next, the space velocity SV dependence of Ca (OH) _{2 in} the case of removing high concentration HF after CF ₄ decomposition was examined.

The SV condition of Ca (OH) ₂ was increased by increasing the amount of reaction gas with the same composition. Other conditions are the same as those in the first embodiment. The results of examining the SV dependence are shown in FIG. The SV increased from 1000 to 2800 h ⁻¹ , but the time during which HF was detected in the outlet gas coincided with the time of 95% or more utilization rate calculated from the Ca (OH) ₂ amount and the HF supply amount. That is, it was confirmed that there was no SV dependency in this test condition and high removal performance was exhibited.

(C) Next, the shape dependence of Ca (OH) ₂ was examined. Table 1 shows specific surface areas and average pore diameters of various Ca (OH) ₂ . Moreover, the result of having investigated HF removal performance using those Ca (OH) ₂ is shown in FIG. High removal performance was exhibited when the specific surface area was 20 m ² / g or more and the average pore diameter was 500 mm or more. An average pore diameter of 577 mm but a specific surface area of 12 m ² / g has a sufficient diameter for HF to enter the pores, but the pore depth is not sufficient, and the inside of the Ca (OH) ₂ particles It is thought that it cannot be used enough.

(D) Next, the strength of Ca (OH) ₂ before and after use was examined. The strength was compared with the breaking weight of ₂ Ca (OH) grains. FIG. 7 shows the results of the relative strengths of the various Ca (OH) ₂ before and after the test when the fracture weight of the Ca (OH) ₂ used in Example 1 was taken as 100%.

  Sample 2 was about 1/10 after the test and had almost no strength. On the other hand, samples 1 and 3 had lower initial strength than sample 2, but the strength decrease after the test was small.

Example 3
In this example, the possibility of removing SOx and HF after decomposing SF ₆ which is a kind of PFC was examined. As the experimental apparatus, the apparatus shown in FIG. 2 was used.

The reaction gas is composed of SF ₆ , Air, N ₂ and H ₂ O. By adding nitrogen to the SF ₆ is about 1.4 percent SF ₆ concentration was added about 115 ml / min of air to the gas to about 1300 ml / min. Water vapor was supplied by introducing ion-exchanged water into the reaction tube at 0.30 ml / min and evaporating it at the top of the Ni / Al catalyst. This reaction gas was brought into contact with a Ni / Al catalyst. The temperature of the catalyst was changed to 600 to 700 ° C, and the temperature of Ca (OH) ₂ was changed to 310 to 670 ° C. The space velocity was about 1426～1440H ^-1 in SF ₆ + N ₂ based flow (space velocity (h ^-1) = flow rate of the reaction gas (ml / h) / amount of catalyst (ml)).

When 1 mol of SF ₆ is decomposed, ₆ mol of HF is produced and 1 mol of SOx is produced. Therefore, HF is present at a concentration of about 6% and SOx is present at a concentration of about 1% in the gas after passing through the Ni / Al catalyst. As the SF ₆ decomposition started, the outlet gas was periodically collected in a Tedlar bag, and the SO ₂ concentration and the HF concentration were measured.

At a Ca (OH) ₂ temperature of 460 ° C., the time during which SO ₂ and HF were detected in the outlet gas (breakthrough start time) was examined. SO ₂ was already detected 10 minutes after the start of the test. Moreover, mist which seems to be SO ₃ was detected after 30 minutes. HF was detected after 40 minutes. That is, under this condition, SO ₂ could hardly be removed with Ca (OH) ₂ . Moreover, HF was detected earlier than the estimated time, and Ca was not fully utilized. As a result of examining the test Ca (OH) ₂ by X-ray diffraction, diffraction patterns of CaSO ₄ and CaF ₂ were detected, but at the same time, unused Ca (OH) ₂ was also detected. Since HF alone has a high utilization rate, it is considered that CaSO ₄ has an influence. As a result of fluorescent X-ray analysis of the Ca (OH) ₂ granule cross section after the test, it was found that a large amount of S was present on the surface. That is, it was considered that CaSO ₄ was generated on the surface and the internal Ca (OH) ₂ was not used.

Therefore, in order to investigate the behavior of CaSO ₄ , the reaction temperature was lowered from 460 ° C. to 370 ° C. and 310 ° C., and the test was conducted. At 370 ° C., SO ₂ was detected 10 minutes after the start of the reaction. However, mist was detected after 40 minutes and HF was detected after 50 minutes, and it was expected that the utilization rate increased. Furthermore, at 310 ° C., SO ₂ was detected after 10 minutes and HF was detected after 50 minutes, but no mist was detected for 1 hour. As a result of examining the Ca (OH) ₂ tested at 310 ° C. by X-ray diffraction analysis, it was confirmed that unused Ca (OH) ₂ was not detected and almost 100% was used. That is, by setting the temperature of Ca (OH) ₂ to 310 ° C. or less, the generation of CaSO _{4 on} the surface can be suppressed, and Ca (OH) ₂ can be used effectively. As the reason why the low temperature surface CaSO ₄ generated is suppressed, the equilibrium reaction between SO ₂ and SO ₃ at low temperature side is shifted to SO ₃ side, the reactivity of SO ₃ as compared to SO _2, HF This is probably because HF is easy to react because it is low.

From the above, when processing a gas in which SOx and HF coexist, the Ca utilization rate can be increased by removing SOx in advance and then reacting HF with Ca (OH) ₂ . However, since it is difficult to completely remove SOx, it is desirable that the Ca (OH) ₂ use temperature is 310 ° C. or lower and 100 ° C. or higher. The reason why the temperature is 100 ° C. or higher is that H ₂ O in the exhaust gas is condensed.

Example 4
The apparatus configuration of the Ca (OH) ₂ packed tower is shown in FIG. This apparatus is a heat exchanger 100 for adjusting the temperature of exhaust gas containing HF, a Ca (OH) ₂ packed tower 101, a Ca (OH) ₂ layer 110, and a mesh that holds a Ca (OH) ₂ layer. A plate 102, a waste calcium compound recovery tank 103 connected to a Ca (OH) ₂ packed tower by a flange, and a blower (or ejector) 104 for sucking and exhausting exhaust gas are provided. Further, a switching valve 105 for switching exhaust gas introduction into another Ca (OH) ₂ packed tower and a switching valve 106 for switching between the packed tower and the bypass line between the heat exchanger 100 and the Ca (OH) ₂ packed tower 101. Have In addition, a mesh plate 107 that collects CaF ₂ powder entrained in the exhaust gas is provided in front of the blower (or ejector) 104, and a heater 108 for heating the Ca (OH) ₂ layer 110 is provided. The Ca (OH) ₂ packed tower 101 has a cylindrical shape with an inner diameter of about 300 mm and a height of 1 m.

Using this apparatus, the gas produced by the decomposition of CF ₄ was processed. For Ca (OH) ₂ , commercially available granular slaked lime (72 granular slaked lime from Yoshizawa Lime Industry) was screened and used only with a size of 1 mm or more, and 1.2 kg was filled. A mesh plate made of Inconel and having an aperture of 0.7 mm was used. A blower was used for exhaust gas suction.

The decomposition process of CF ₄ prior to the HF process by the apparatus of FIG. 3 is the same as in the first embodiment. A gas at about 750 ° C. containing about 4% of HF produced by the decomposition of CF ₄ was introduced into the Ca (OH) ₂ packed column 101 after the temperature was lowered to 350 ° C. by the water-cooled heat exchanger 100. Since the average temperature of the Ca (OH) ₂ layer was 310 ° C., heating by the heater 108 was not performed. An HF-containing gas was passed through the packed tower for 50 hours. It was confirmed that the HF concentration in the exhaust gas at the outlet of the blower was 0.5 ppm or less and was absorbed and removed with Ca (OH) ₂ . In addition, a part of CaF ₂ powder pulverized to 0.7 mm or less was recovered in the waste calcium compound recovery tank 103.

Example 5
An example of a method for switching the Ca (OH) ₂ packed tower is shown in FIG. The exhaust gas containing HF has a high temperature of 200 to 750 ° C. and contains HF from several thousand ppm to several percent. For this reason, if the gas flow path is changed with a normal valve, a heat and corrosion resistant material must be used, resulting in an increase in cost. There are also concerns about durability.

  Therefore, the gas flow path is changed by blowing compressed air. Air is blown at a higher pressure than the exhaust gas containing HF, and the Ca packed tower is switched from the first tower 101a to the second tower 101b. The gas after passing through the packed tower is cooled to 200 ° C. or lower by the heat exchanger 100 and the flow path is switched by the valve 106. Since the gas passing through the packed tower is a gas after HF is removed, the corrosion of the valve material can be reduced.

DESCRIPTION OF SYMBOLS 1 ... Reaction tube, 2 ... PFC decomposition catalyst, 3 ... Ca (OH) ₂ layer, 7 ... Electric furnace, 30 ... HF removal process, 100 ... Heat exchanger, 101 ... Ca (OH) ₂ packed tower, 102, 107 ... Mesh plate, 103 ... Waste calcium compound recovery tank, 104 ... Blower (or ejector), 108 ... Heater.

Claims (8)

An exhaust gas treatment method for a semiconductor or liquid crystal manufacturing plant, wherein an exhaust gas containing PFC is treated with PFC
The exhaust gas from the exhaust gas line containing HF and SOx is mixed with the exhaust gas discharged from the PFC decomposition device, and the SOx is removed from the exhaust gas containing HF and SOx.
The exhaust gas containing part of the remaining SOx is introduced into a Ca (OH) ₂ packed tower that holds a solid Ca (OH) ₂ layer as a fixed bed, and in the presence of H ₂ O in the exhaust gas, A dry treatment method for HF-containing gas, which comprises contacting the solid Ca (OH) ₂ at 310 ° C. to remove the remaining SOx and HF. _2. The dry treatment method for HF-containing gas according to claim 1, wherein H ₂ O in the exhaust gas is a water vapor component contained in the exhaust gas discharged from the PFC decomposition apparatus. 3. The dry treatment method for an HF-containing gas according to claim 1, wherein the Ca (OH) _{2 has} an average pore diameter of 500 to 1500 mm and a particle size of 0.5 mm or more. 4. The dry treatment method for an HF-containing gas according to claim 1, wherein the specific surface area of the Ca (OH) ₂ is 20 m ² / g or more. A Ca (OH) ₂ packed column through which SOx and HF-containing gas are circulated, an inlet for SOx and HF-containing gas provided at the lower portion of the packed column, and the inlet of the Ca (OH) ₂ packed column A Ca (OH) ₂ layer held by a mesh plate provided at the upper part, a gas outlet provided at the upper part of the packed tower from which SOx and HF have been removed, and the packing provided at the outlet. It passed through a blower or ejector for sucking and exhausting gas in the tower, a heater for heating the Ca (OH) ₂ layer in the packed tower to keep the temperature at 100 to 310 ° C., and a Ca (OH) ₂ packed tower. comprising a condensed water storing condensed water savings tank H ₂ O occurs condensed remaining in the gas, and the Ca (OH) SOx and HF containing introduced into the ₂ packed tower from the inlet gas was passed through the Ca (OH) ₂ layer in the presence of H ₂ O Turkey A dry processing apparatus for HF-containing gas.   The dry processing apparatus for HF-containing gas according to claim 5, further comprising a waste calcium compound recovery tank that recovers the calcium compound dropped from the mesh plate. In claim 5 or 6,
A dry processing apparatus for HF-containing gas, comprising a heat exchanger for adjusting a gas containing HF to a predetermined temperature in a stage preceding the Ca (OH) ₂ packed tower. 8. The dry processing apparatus for HF-containing gas according to claim 5, further comprising a mesh plate for collecting calcium compounds accompanying the gas at the gas discharge port.

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