JP4698201B2 - Fluorine-containing gas decomposition treatment apparatus and fluorine compound recovery method using the same - Google Patents

Description

  The present invention relates to a fluorine-containing gas decomposition treatment apparatus and a fluorine compound recovery method for treating a fluorine-containing gas and recycling a fluoride in the fluorine-containing gas.

SF ₆ gas, a fluorine-containing gas, has high insulation performance and arc-extinguishing performance, and is widely used in gas insulation equipment such as high voltage equipment and circuit breakers. It has reached 9,000 tons. However, the SF ₆ gas has an extremely high global warming potential of 23,900 times that of CO ₂ gas and has a high greenhouse effect, and is defined as a gas that requires emission reduction in the Kyoto Protocol. Therefore, the even maximum power industry is a consumer of the SF ₆ gas, the SF ₆ recovery improvement and recycling promotion of gas, steady efforts to reduce emissions into the atmosphere are deployed .

The electrical equipment or the like in which the SF ₆ gas is sealed as an insulating gas is used to remove impurities in the SF ₆ gas during operation, during assembly work at a manufacturing plant or installation site, and during a recovery process during periodic inspection. Mixing is inevitable. The SF ₆ gas that cannot be recycled due to contamination of impurities is disposed of. Further, in recent years, research and development of SF ₆ alternative gas has been energetically promoted, and therefore there is a possibility that a large amount of the SF ₆ gas is discarded when switching to the alternative gas.

In recent years, the SF ₆ gas to be discarded has been processed by a combustion wet method using water vapor by diverting a processing facility for fluorocarbon. Specifically, the SF ₆ gas is combusted, and the generated gas is absorbed with an aqueous sodium hydroxide solution, then reacted with calcium carbonate in a wet manner and recovered as fluorite.
However, since the product obtained by the treatment is in the form of fine particles, there is a problem that an aggregating agent is required for recovery. In addition, the recovered product is difficult to remove the flocculant and alkali components contained therein, and the wet reaction with the calcium carbonate is incomplete. There is a problem that it cannot be converted. Furthermore, there is a problem that the treatment apparatus is corroded by hydrofluoric acid generated by a wet reaction.

On the other hand, a method has been proposed in which the SF ₆ gas is injected into a TiO ₂ -based catalyst reactor together with air, nitrogen and water vapor and decomposed (see Patent Document 1). In the apparatus and method described in Patent Document 1, the gas generated by the decomposition is neutralized with an aqueous NaOH solution, the mist is removed, and then the desiccant is passed through and exhausted. In a fracture test at 800 ° C. with a SF ₆ gas concentration of 0.5% (throughput of 2.4 g / h), a fracture efficiency of 99.93% was achieved. However, the apparatus and method do not achieve the UN environmental standard of 99.99% or higher as the decomposition rate of SF ₆ and absorb and remove fluorine compounds and sulfur compounds at the same time. Is not intended to recycle fluorine compounds.

  Therefore, the fluorine-containing gas can be decomposed at a high decomposition rate, the handleability of the product after the decomposition treatment is excellent, the purity of the fluorine compound as the product is high, and it can be recycled. A fluorine-containing gas treatment apparatus that does not cause corrosion and a method for recovering a fluorine compound have not yet been provided, and the present situation is that further improved development is desired.

International Publication WO00 / 09258

An object of the present invention is to solve the conventional problems and achieve the following objects.
That is, the present invention is capable of decomposing the fluorine-containing gas at a high decomposition rate, has excellent handleability of the product after the decomposition treatment, has high purity of the fluorine compound as the product, and can be recycled. Another object of the present invention is to provide a fluorine-containing gas decomposition treatment apparatus and a fluorine compound recovery method that do not cause corrosion of the apparatus.

ただし、Ｆ_Ａ０は前記被処理ガスの処理量（ｍ^３／ｓ）、ｋは下記式（２）で表される分解反応速度定数（１／ｓ）、ε_Ａはδ_Ａ・ｙ_Ａ０、δ_Ａは分解反応前後におけるモル体積の増加分のフッ素化合物モル体積に対する割合、ｙ_Ａ０は反応開始時の前記被分解物のモル分率、ｘは前記被分解物の分解率を表す。

ただし、ｋ_０は分解反応の頻度因子（ｓ^−１）、Ｅは活性化エネルギー（Ｊ／ｍｏｌ）、Ｒは気体定数、Ｔは反応炉の絶対温度（Ｋ）を表す。

ただし、αは下記式（４）で表される設計係数（ｍ^３・ｍｉｎ／ｍｏｌ）、Ｇ_Ｃは分解ガスの流入量（ｍｏｌ／ｍｉｎ）を表す。

ただし、τは破過時間（ｍｉｎ）、ｂは量論係数、Ｑ_Ｃは固定化材料の前記分解ガス吸収容量（ｍｏｌ／ｍ^３−ｂｅｄ）を表す。
該＜１＞に記載のフッ素含有ガス分解処理装置においては、前記熱分解炉の体積Ｖ（ｍ^３）が、前記被分解物の熱分解特性に基づく前記式（１）から導出された体積であるため、前記熱分解において前記被分解物が所望の分解率で分解され、前記乾式固定化炉の反応帯の体積Ｖ_Ｃ（ｍ^３）が、前記分解ガスと前記固定化材料との固定化特性に基づく前記式（３）から導出された体積であるため、前記乾式固定化炉内で、前記分解ガス中のフッ素原子が全量固定される。
＜２＞ 熱分解炉が管状構造であり、該熱分解炉内に伝熱体を有する前記＜１＞に記載のフッ素含有ガス分解処理装置である。該＜２＞に記載のフッ素含有ガス分解処理装置においては、前記熱分解炉が管状構造であり、該熱分解炉内に伝熱体を有するため、加熱された前記伝熱体壁面との接触面積が大きく、前記フッ素含有ガス中の被分解物の分解が効率よく行われる。
＜３＞ 伝熱体が黒鉛製及びアルミナ製のいずれかであり、前記伝熱体の形状がチューブ状及びボール状のいずれかである前記＜２＞に記載のフッ素含有ガス分解処理装置である。
＜４＞ 乾式固定化炉が管状構造の反応管からなり、前記反応管の全長が、反応帯の長さの２倍以上である前記＜１＞から＜３＞のいずれかに記載のフッ素含有ガス分解処理装置である。該＜４＞に記載のフッ素含有ガス分解処理装置においては、乾式固定化炉が管状構造の反応管からなり、前記反応管の全長が、反応帯の高さの２倍以上であるため、反応管内において前記分解ガス中のフッ素原子を全量固定可能であり、再資源化可能な高純度のフッ素化合物を回収することができる。
＜５＞ 乾式固定化炉が、分解ガスが流通可能に接続された２以上の反応管からなり、前記分解ガスが前記２以上の反応管の内部を交互に通過するように設計された前記＜１＞から＜４＞のいずれかに記載のフッ素含有ガス分解処理装置である。該＜５＞に記載のフッ素含有ガス分解処理装置においては、乾式固定化炉が、分解ガスが流通可能に接続された２以上の反応管からなり、前記分解ガスが前記２以上の反応管の内部を交互に通過するように設計されているため、連続的に高純度のフッ素化合物を回収することができる。
＜６＞ 乾式固定化炉が、固定化材料として、Ｎａ、Ｌｉ、Ｋ、Ｃａ、Ｍｇ、及びＳｉから選択される少なくとも１種の炭酸塩、Ｎａ、Ｌｉ、Ｋ、Ｃａ、Ｍｇ、及びＳｉから選択される少なくとも１種の酸化物、及び炭酸水素ナトリウムのいずれかを含む前記＜１＞から＜５＞のいずれかに記載のフッ素含有ガス分解処理装置である。該＜６＞に記載のフッ素含有ガス分解処理装置においては、前記乾式固定化炉が、前記固定化材料として、Ｎａ、Ｌｉ、Ｋ、Ｃａ、Ｍｇ、及びＳｉから選択される少なくとも１種の炭酸塩、Ｎａ、Ｌｉ、Ｋ、Ｃａ、Ｍｇ、及びＳｉから選択される少なくとも１種の酸化物、及び炭酸水素ナトリウムのいずれかを含むため、前記分解ガス中のフッ素原子が、前記固定化材料に効率よく乾式固定され、再資源化可能なフッ素化合物として回収される。
＜７＞ 乾式固定化炉の下流側に、前記乾式固定化炉から排出される未固定の分解ガスを燃焼させる燃焼炉、及び前記未固定の分解ガスを洗浄するスクラバーの少なくともいずれかが配置された前記＜１＞から＜６＞のいずれかに記載のフッ素含有ガス分解処理装置である。該＜７＞に記載のフッ素含有ガス分解処理装置においては、乾式固定化炉の下流側に、前記乾式固定化炉から排出される未固定の分解ガスを燃焼させる燃焼炉、及び前記未固定の分解ガスを洗浄するスクラバーの少なくともいずれかが配置されているため、再資源化せず廃棄する成分を燃焼後湿式で無害化して処理することができる。
＜８＞ フッ素含有ガス中の被分解物がＳＦ_６（六フッ化硫黄）であり、水素含有化合物がＨ_２（水素）である前記＜１＞から＜７＞のいずれかに記載のフッ素含有ガス分解処理装置である。
＜９＞ フッ素含有ガス中の被分解物がＳＦ_６（六フッ化硫黄）であり、前記ＳＦ_６を９９．９９％以上分解する熱分解炉の体積Ｖ（ｍ^３）を式（１）より導出するのに際し、
前記式（１）中の分解反応速度定数ｋ（１／ｓ）が、式（２）において、頻度因子ｋ_０＝２．０８×１０^３（ｓ^−１）、活性化エネルギーＥ＝８．３１４×１０^４（Ｊ／ｍｏｌ）として導出される前記＜８＞に記載のフッ素含有ガス分解処理装置である。
＜１０＞ 熱分解炉の下流側に、硫黄成分除去フィルターが配置された前記＜８＞から＜９＞のいずれかに記載のフッ素含有ガス分解処理装置である。該＜１０＞に記載のフッ素含有ガス分解処理装置においては、前記熱分解炉の下流側に、硫黄成分除去フィルターが配置されているため、前記ＳＦ_６の熱分解において発生した前記分解ガス中の固体硫黄分を、乾式反応前に除去することができる。
＜１１＞ フッ素含有ガス中の被分解物がフルオロカーボンであり、水素含有化合物が水蒸気及び空気の少なくともいずれかである前記＜１＞から＜７＞のいずれかに記載のフッ素含有ガス分解処理装置である。 Means for solving the problems are as follows. That is,
<1> A gas to be treated comprising a fluorine-containing gas supplied from a fluorine-containing gas supply device and a hydrogen-containing compound supplied from a hydrogen supply device is heat-treated to thermally decompose a substance to be decomposed in the fluorine-containing gas. A pyrolysis furnace, and a dry immobilization furnace configured to dry-react the cracked gas discharged from the pyrolysis furnace and the immobilization material supplied from the immobilization material supply device, and immobilize a fluorine component in the decomposition gas. At least arranged,
The volume V (m ³ ) of the pyrolysis furnace was derived from the following formula (1), and the volume V _C (m ³ ) of the reaction zone of the dry fixation furnace was derived from the following formula (3) Is a fluorine-containing gas decomposition treatment apparatus characterized by

However, F _A0 is a processing amount of the gas to be processed (m ³ / s), k is a decomposition reaction rate constant (1 / s) represented by the following formula (2), ε _A is δ _A · y _A0 , δ _A is the ratio of the increase in the molar volume before and after the decomposition reaction to the fluorine compound molar volume, y _A0 is the molar fraction of the decomposition product at the start of the reaction, and x is the decomposition rate of the decomposition product.

However, _{k 0} is the frequency factor of the decomposition reaction ^(s -1), E is the activation energy (J / mol), R is the gas constant, T represents the absolute temperature of the reactor (K).

However, alpha design factor represented by the following formula ^{(4) (m 3 · min} / mol), G C represents the inflow of decomposition gas (mol / min).

However, tau is the breakthrough time (min), b is Ryoron coefficient, _{Q C} represents the decomposed gas absorption capacity of the immobilizing material ^(mol / m 3 -bed).
In the fluorine-containing gas decomposition treatment apparatus according to <1>, the volume V (m ³ ) of the pyrolysis furnace is a volume derived from the equation (1) based on the pyrolysis characteristics of the decomposition target. Therefore, in the thermal decomposition, the decomposition target is decomposed at a desired decomposition rate, and the volume V _C (m ³ ) of the reaction zone of the dry fixation furnace is the immobilization of the decomposition gas and the fixing material. Since the volume is derived from the formula (3) based on the characteristics, all the fluorine atoms in the cracked gas are fixed in the dry fixing furnace.
<2> The fluorine-containing gas decomposition treatment apparatus according to <1>, wherein the pyrolysis furnace has a tubular structure and has a heat transfer body in the pyrolysis furnace. In the fluorine-containing gas decomposition treatment apparatus according to <2>, the pyrolysis furnace has a tubular structure, and has a heat transfer body in the pyrolysis furnace, so that it is in contact with the heated heat transfer body wall surface. The area is large, and the decomposition target in the fluorine-containing gas is efficiently decomposed.
<3> The fluorine-containing gas decomposition treatment apparatus according to <2>, wherein the heat transfer body is made of graphite or alumina, and the shape of the heat transfer body is either a tube shape or a ball shape. .
<4> The fluorine-containing furnace according to any one of <1> to <3>, wherein the dry immobilization furnace includes a reaction tube having a tubular structure, and the total length of the reaction tube is at least twice the length of the reaction zone. This is a gas decomposition treatment apparatus. In the fluorine-containing gas decomposition treatment apparatus according to <4>, the dry immobilization furnace includes a reaction tube having a tubular structure, and the total length of the reaction tube is at least twice the height of the reaction zone. The whole amount of fluorine atoms in the cracked gas can be fixed in the tube, and a high-purity fluorine compound that can be recycled can be recovered.
<5> The dry immobilization furnace is composed of two or more reaction tubes connected so that the cracked gas can flow, and is designed so that the cracked gas alternately passes through the two or more reaction tubes. The fluorine-containing gas decomposition treatment apparatus according to any one of <1> to <4>. In the fluorine-containing gas decomposition treatment apparatus according to <5>, the dry immobilization furnace includes two or more reaction tubes connected to allow the decomposition gas to flow therethrough, and the decomposition gas includes the two or more reaction tubes. Since it is designed to alternately pass through the inside, a highly pure fluorine compound can be continuously recovered.
<6> The dry immobilization furnace is composed of at least one carbonate selected from Na, Li, K, Ca, Mg, and Si as an immobilization material, Na, Li, K, Ca, Mg, and Si. The fluorine-containing gas decomposition treatment apparatus according to any one of <1> to <5>, wherein the fluorine-containing gas decomposition treatment apparatus contains at least one selected oxide and sodium hydrogen carbonate. In the fluorine-containing gas decomposition treatment apparatus according to <6>, the dry immobilization furnace includes at least one carbonic acid selected from Na, Li, K, Ca, Mg, and Si as the immobilization material. Since at least one oxide selected from a salt, Na, Li, K, Ca, Mg, and Si and sodium hydrogen carbonate are included, fluorine atoms in the decomposition gas are contained in the immobilization material. Efficiently dry-fixed and recovered as a recyclable fluorine compound.
<7> At least one of a combustion furnace that burns unfixed cracked gas discharged from the dry fix furnace and a scrubber that cleans the unfixed cracked gas is disposed downstream of the dry fix furnace. The fluorine-containing gas decomposition treatment apparatus according to any one of <1> to <6>. In the fluorine-containing gas decomposition treatment apparatus according to <7>, a combustion furnace that burns unfixed cracked gas discharged from the dry fixation furnace downstream of the dry fixation furnace, and the unfixed Since at least one of the scrubbers for cleaning the cracked gas is disposed, the components to be discarded without being recycled can be treated by detoxification with a wet process after combustion.
<8> The fluorine-containing material according to any one of <1> to <7>, wherein the decomposition target in the fluorine-containing gas is SF ₆ (sulfur hexafluoride) and the hydrogen-containing compound is H ₂ (hydrogen). This is a gas decomposition treatment apparatus.
<9> The substance to be decomposed in the fluorine-containing gas is SF ₆ (sulfur hexafluoride), and the volume V (m ³ ) of the pyrolysis furnace that decomposes SF ₉ by 99.99% or more is calculated from the formula (1). In deriving,
The decomposition reaction rate constant k (1 / s) in the formula (1) is the frequency factor k ₀ = 2.08 × 10 ³ (s ⁻¹ ) and the activation energy E = 8.314 in the formula (2). × ¹⁰ 4 (J / mol) said derived as a fluorine-containing gas decomposition processor according to <8>.
<10> The fluorine-containing gas decomposition treatment apparatus according to any one of <8> to <9>, wherein a sulfur component removal filter is disposed on the downstream side of the thermal decomposition furnace. In the fluorine-containing gas decomposition treatment apparatus according to <10>, since a sulfur component removal filter is disposed on the downstream side of the thermal decomposition furnace, in the decomposition gas generated in the thermal decomposition of SF ₆ Solid sulfur can be removed prior to the dry reaction.
<11> The fluorine-containing gas decomposition treatment apparatus according to any one of <1> to <7>, wherein the decomposition target in the fluorine-containing gas is a fluorocarbon, and the hydrogen-containing compound is at least one of water vapor and air. is there.

<12> Using the fluorine-containing gas decomposition treatment apparatus according to any one of <1> to <11>, heat-treating the fluorine-containing gas and the hydrogen-containing compound, generating a decomposition gas, and fixing the decomposition gas A fluorine compound recovery method characterized by recovering a fluorine compound produced as a fixed product by dry reaction with a material. In the fluorine compound recovery method according to <12>, the recovery of the fluorine compound is performed using the fluorine-containing gas treatment device, and the pyrolysis of the fluorine-containing gas and the dry component of the fluorine component in the decomposition gas are performed. Fixing takes place in separate furnaces. As a result, the substance to be decomposed in the fluorine-containing gas is decomposed at a high decomposition rate, and the total amount of fluorine atoms in the decomposition gas is fixed. As a result, a high-purity fluorine compound is recovered.
<13> The fluorine compound recovery method according to <12>, wherein the hydrogen-containing compound contains hydrogen in a number of moles or more necessary for all the fluorine atoms in the fluorine-containing gas to be HF (hydrogen fluoride). In the fluorine compound recovery method according to <13>, the hydrogen-containing compound contains hydrogen in the number of moles or more necessary for all the fluorine atoms in the fluorine-containing gas to be HF. As a result, all the fluorine atoms in the fluorine-containing gas become HF. For example, the HF can be recovered as a fluorine compound by fixing the HF to the immobilization material by a dry reaction.
<14> The fluorine compound recovery method according to <12> to <13>, wherein the heat treatment temperature of the fluorine-containing gas and the hydrogen-containing compound is 700 ° C to 1200 ° C.
<15> The fluorine compound recovery method according to any one of <12> to <14>, wherein the dry reaction temperature between HF and the immobilization material is 150 to 500 ° C.
<16> The fluorine compound recovery method according to any one of <12> to <15>, wherein the recovery rate of the immobilized product is 90% or more, and the immobilized product is a fluorine compound having a purity of 97% or more. It is. In the fluorine compound recovery method according to <16>, the recovery rate of the immobilized product is 90% or more, and the immobilized product is a fluorine compound having a purity of 97% or more. The compound can be recycled, for example, for a fluorine raw material.

ただし、Ｆ_Ａ０は被処理ガスの処理量（ｍ^３／ｓ）、ｋは下記式（２）で表される分解反応速度定数（１／ｓ）、ε_Ａはδ_Ａ・ｙ_Ａ０、δ_Ａは分解反応前後におけるモル体積の増加分のフッ素化合物モル体積に対する割合、ｙ_Ａ０は反応開始時の前記被分解物のモル分率、ｘ_Ａは前記被分解物の分解率を表す。

ただし、ｋ_０は分解反応の頻度因子（ｓ^−１）、Ｅは活性化エネルギー（Ｊ／ｍｏｌ）、Ｒは気体定数、Ｔは熱分解温度の絶対温度（Ｋ）を表す。

ただし、αは下記式（４）で表される設計係数（ｍ^３・ｍｉｎ／ｍｏｌ）、Ｇ_Ｃは分解ガスの流入量（ｍｏｌ／ｍｉｎ）を表す。

ただし、τは前記固定化材料の破過時間（ｍｉｎ）、ｂは前記固定化材料の量論係数、Ｑ_Ｃは固定化材料の前記分解ガス吸収容量（ｍｏｌ／ｍ^３−ｂｅｄ）を表す。
該＜１７＞に記載のフッ素含有ガス分解処理装置の設計方法においては、前記熱分解炉の体積Ｖ（ｍ^３）が、前記式（１）から導出されるため、例えば、前記被処理ガスの処理量と熱処理温度とをパラメータとして、前記被分解物が所望の分解率で熱分解されるように前記熱分解炉の体積を算出し、該熱分解炉の体積に基づいて前記熱分解炉を設計することができる。また、前記乾式固定化炉の反応帯体積が、前記式（３）から導出されるため、前記固定化材料の固定化特性に応じて前記乾式固定化炉の反応帯体積を算出し、該体積に基づいて前記乾式固定化炉を設計することができ、この結果、前記分解ガス中のフッ素原子の全量を固定可能な前記乾式固定化炉を設計することができる。 <17> A heat treatment is performed on a gas to be treated including a fluorine-containing gas supplied from a fluorine-containing gas supply device and a hydrogen-containing compound supplied from a hydrogen supply device, and the decomposition target in the fluorine-containing gas is thermally decomposed. A pyrolysis furnace, and a dry immobilization furnace configured to dry-react the cracked gas discharged from the pyrolysis furnace and the immobilization material supplied from the immobilization material supply device to immobilize a fluorine component in the decomposition gas. Place at least,
The volume V (m ³ ) of the pyrolysis furnace is derived from the following formula (1), and the volume V _C (m ³ ) of the reaction zone of the dry fixation furnace is derived from the following formula (3). This is a method for designing a fluorine-containing gas decomposition treatment apparatus.

However, F _A0 is a processing amount of the gas to be processed (m ³ / s), k is a decomposition reaction rate constant (1 / s) represented by the following formula (2), ε _A is δ _A · y _A0 , δ _A Is the ratio of the increase in the molar volume before and after the decomposition reaction to the fluorine compound molar volume, y _A0 is the molar fraction of the decomposition product at the start of the reaction, and x _A is the decomposition rate of the decomposition product.

However, _{k 0} is the frequency factor of the decomposition reaction ^(s -1), E is the activation energy (J / mol), R is the gas constant, T represents absolute temperature (K) of the pyrolysis temperature.

However, alpha design factor represented by the following formula ^{(4) (m 3 · min} / mol), G C represents the inflow of decomposition gas (mol / min).

However, the immobilizing material breakthrough time τ (min), b is the stoichiometric coefficient of the immobilizing material, _{Q C} represents the decomposed gas absorption capacity of the immobilizing material ^(mol / m 3 -bed).
In the method for designing a fluorine-containing gas decomposition treatment apparatus according to <17>, since the volume V (m ³ ) of the pyrolysis furnace is derived from the equation (1), for example, Using the throughput and heat treatment temperature as parameters, the volume of the pyrolysis furnace is calculated so that the decomposition target is pyrolyzed at a desired decomposition rate, and the pyrolysis furnace is determined based on the volume of the pyrolysis furnace. Can be designed. Further, since the reaction zone volume of the dry immobilization furnace is derived from the equation (3), the reaction zone volume of the dry immobilization furnace is calculated according to the immobilization characteristics of the immobilization material, and the volume Thus, the dry immobilization furnace can be designed, and as a result, the dry immobilization furnace capable of fixing the total amount of fluorine atoms in the cracked gas can be designed.

  According to the present invention, conventional problems can be solved, the fluorine-containing gas can be decomposed at a high decomposition rate, the handleability of the product after the decomposition treatment is excellent, and the purity of the fluorine compound that is the product Therefore, it is possible to provide a fluorine-containing gas decomposition treatment apparatus and a fluorine compound recovery method that are high in recyclability and that do not cause corrosion of the apparatus.

ただし、Ｆ_Ａ０は前記被処理ガスの処理量（ｍ^３／ｓ）、ｋは下記式（２）で表される分解反応速度定数（１／ｓ）、ε_Ａはδ_Ａ・ｙ_Ａ０、δ_Ａは分解反応前後におけるモル体積の増加分のフッ素化合物モル体積に対する割合、ｙ_Ａ０は反応開始時の前記被分解物のモル分率、ｘ_Ａは前記被分解物の分解率を表す。

ただし、ｋ_０は分解反応の頻度因子（ｓ^−１）、Ｅは活性化エネルギー（Ｊ／ｍｏｌ）、Ｒは気体定数、Ｔは熱分解温度の絶対温度（Ｋ）を表す。

ただし、前記式（３）中、αは下記式（４）で表される設計係数（ｍ^３・ｍｉｎ／ｍｏｌ）、Ｇ_Ｃは分解ガスの流入量（ｍｏｌ／ｍｉｎ）を表す。

ただし、前記式（４）中、τは破過時間（ｍｉｎ）、ｂは量論係数、Ｑ_Ｃは固定化材料の前記分解ガス吸収容量（ｍｏｌ／ｍ^３−ｂｅｄ）を表す。 (Fluorine-containing gas decomposition treatment equipment)
The fluorine-containing gas decomposition treatment apparatus of the present invention is
A thermal decomposition furnace for heat-treating a gas to be processed comprising a fluorine-containing gas supplied from a fluorine-containing gas supply device and a hydrogen-containing compound supplied from a hydrogen supply device, and thermally decomposing a substance to be decomposed in the fluorine-containing gas And at least a dry immobilization furnace configured to dry-react the cracked gas discharged from the pyrolysis furnace and the immobilization material supplied from the immobilization material supply device to fix the fluorine component in the cracked gas. ,
The volume V (m ³ ) of the pyrolysis furnace is derived from the following formula (1), and the volume V _C (m ³ ) of the reaction zone of the fixed furnace is derived from the following formula (3).

However, F _A0 is a processing amount of the gas to be processed (m ³ / s), k is a decomposition reaction rate constant (1 / s) represented by the following formula (2), ε _A is δ _A · y _A0 , δ _A is the ratio of the increase in the molar volume before and after the decomposition reaction to the fluorine compound molar volume, y _A0 is the molar fraction of the decomposition product at the start of the reaction, and x _A is the decomposition rate of the decomposition product.

However, _{k 0} is the frequency factor of the decomposition reaction ^(s -1), E is the activation energy (J / mol), R is the gas constant, T represents absolute temperature (K) of the pyrolysis temperature.

However, the above formula (3), alpha design factor represented by the following formula ^{(4) (m 3 · min} / mol), G C represents the inflow of decomposition gas (mol / min).

However, the formula (4), tau is the breakthrough time (min), b is Ryoron coefficient, _{Q C} represents the decomposed gas absorption capacity of the immobilizing material ^(mol / m 3 -bed).

As the fluorine-containing gas decomposition treatment apparatus, for example, the decomposition target in the fluorine-containing gas supplied from the gas supply apparatus to be processed is SF ₆ and the hydrogen-containing compound supplied from the hydrogen supply apparatus is H ₂ . SF ₆ gas decomposition treatment apparatus, and fluorocarbon gas decomposition in which the substance to be decomposed in the fluorine-containing gas supplied from the gas supply apparatus to be processed is fluorocarbon, and the hydrogen-containing compound supplied from the hydrogen supply apparatus is water vapor and air A processing apparatus etc. are mentioned. An example of the SF ₆ gas decomposition treatment apparatus is shown in FIG.

<Pyrolysis furnace>
The pyrolysis furnace is not particularly limited as long as the volume of the pyrolysis furnace is derived from the equation (1), and can be appropriately selected according to the purpose. For example, the fluorine-containing gas supply device Provided with an inlet for fluorine-containing gas supplied from the above, an inlet for hydrogen-containing compound supplied from the hydrogen supply device, and an outlet for discharging the cracked gas after the reaction, and the inside penetrates through to allow gas to flow therethrough. Structure.

The pyrolysis furnace preferably has a tubular structure, and preferably has a heat transfer body disposed in the pyrolysis furnace so as to be in contact with the gas to be treated.
Examples of the shape of the heat transfer body include a tube shape and a ball shape. Further, when the heat transfer body is in a tube shape, a tubular structure or a spherical structure may be further provided in the heat transfer body in order to increase the contact area with the gas to be processed.
Moreover, there is no restriction | limiting in particular as the number of installation of the said heat exchanger, Although it can select suitably according to the objective, It is preferable that it is 2 or more.

The material of the heat transfer body is not particularly limited as long as it does not react with the gas to be processed and the decomposition gas under heat treatment conditions, and can be appropriately selected according to the purpose. For example, graphite, metal And ceramics.
Examples of the metal include copper, stainless steel, carbon steel, inconel, and nickel.
Examples of the ceramic include alumina, mullite, and silicon carbide.
Among these, graphite and alumina are preferable.

  The heating method of the heat transfer body in the pyrolysis furnace is not particularly limited and can be appropriately selected according to the purpose. For example, the method of indirectly heating the heat transfer body with an electric heater or the like, and the heat transfer For example, a method of energizing the heating element and generating heat by heating the electric resistance by electric resistance heating may be used.

<< Pyrolysis furnace design >>
As a method of designing the pyrolysis furnace, for example,
(1) Experimentally determining the decomposition rate as a thermal decomposition characteristic of the decomposition target using the concentration of the decomposition target in the fluorine-containing gas, the decomposition temperature, the residence time, and the addition amount of the hydrogen-containing compound as parameters. ,
(2) From the result of (1), the decomposition reaction rate constant of the decomposition product is obtained, and the frequency factor and activation energy of the decomposition reaction of the decomposition product are obtained from the Arrhenius plot of the decomposition reaction rate constant,
(3) Using the design formula for deriving the volume of the pyrolysis furnace, obtain the volume of the pyrolysis furnace capable of decomposing the material to be decomposed at a desired decomposition rate,
(4) The method of determining and designing the diameter and length of the said pyrolysis furnace is mentioned.
Hereinafter, SF ₆ gas as the fluorine-containing gas and hydrogen gas as the hydrogen-containing compound are thermally decomposed, and SF ₆ as a decomposition target is decomposed at a decomposition rate of 99.99% or more, which is a destruction standard of the United Nations Environment Program. A method for designing the pyrolysis furnace for the purpose will be specifically described.

-(1) Decomposition characteristics (decomposition rate)-
As the thermal decomposition characteristics (decomposition rate) of the substance to be decomposed in the fluorine-containing gas, the concentration, decomposition temperature, residence time, and addition amount of the hydrogen-containing compound can be obtained as parameters.
As the thermal decomposition characteristics of the SF ₆ (decomposition rate), for example, the SF ₆ SF ₆ concentration in the gas (6.6%, 13.8%), decomposition temperature (800 ° C., 900 ° C., 1000 ° C.), The residence time in the reaction tube (7.5 seconds, 10 seconds, 15 seconds) and the hydrogen gas addition amount (H / (F + S) ratio: 1.33, 1.6, 2.0) were examined as parameters. From the results, it can be seen that SF ₆ is decomposed by 99.99% or more at a temperature of 1000 ° C. or less by heat treatment with hydrogen gas.
FIG. 2 is a graph showing the relationship between the decomposition temperature and the decomposition rate when the SF ₆ concentration in the SF ₆ gas is 6.6% and the amount of hydrogen gas added is 1.33 as the H / (F + S) ratio. Shown in

ただし、前記式（５）中、ｋは分解反応速度定数（１／ｓ）、ｒ_Ａは分解反応速度（ｍｏｌｍ^−３ｓ^−１）、Ｃ_Ａ０は反応開始時の被分解物の濃度（ｍｏｌ／ｍ^３）を表す。
前記一次速度式（前記式（５））の、管形の反応器における積分形設計式としては、下記式（６）で表される。

ただし、前記式（６）において、τは滞留時間（ｓ）、ε_Ａはδｘ・ｙ_０（ただし、δは分解反応前後におけるモル体積の増加分のフッ素化合物モル体積に対する割合）、ｘ_Ａは被分解物の分解率、ｙ_０は被分解物のモル分率を表す。
前記分解反応速度定数ｋは、下記式（２）で表される。

ただし、前記式（２）中、ｋ_０は分解反応の頻度因子（ｓ^−１）、Ｅは活性化エネルギー（Ｊ／ｍｏｌ）、Ｒは気体定数、Ｔは分解温度の絶対温度（Ｋ）を表す。
さらに、前記分解反応速度定数のアレニウスプロットから、前記被分解物の分解反応の頻度因子及び活性化エネルギーを求める。 -(2) Decomposition rate constant-
As the decomposition reaction rate constant of the decomposition product in the fluorine-containing gas, from the result of the decomposition rate for each parameter obtained in the above (1), the decomposition reaction rate of the decomposition product is determined as the concentration of the decomposition product. And the first order velocity equation (the following equation (5)).

In the above formula (5), k is the decomposition reaction rate constant (1 / s), r _A is the decomposition reaction rate (molm ⁻³ s ⁻¹ ), and C _A0 is the concentration (mol) of the decomposition product at the start of the reaction. / M ³ ).
The integral design formula in the tubular reactor of the primary velocity formula (the formula (5)) is represented by the following formula (6).

However, in the formula (6), tau is the residence time (s), epsilon _A is δx · y 0 _(where [delta] is the ratio for the increment of the fluorine compound molar volume of molar volume before and after the decomposition reaction), x _A is decomposition rate of the degradation product, y ₀ represents the molar fraction of the decomposition products.
The decomposition reaction rate constant k is represented by the following formula (2).

However, the above formula (2), the frequency factor of _{k 0} is the decomposition reaction ^(s -1), E is the activation energy (J / mol), R is the gas constant, T is the absolute temperature (K) of the decomposition temperature To express.
Further, the frequency factor and activation energy of the decomposition reaction of the decomposition target are obtained from the Arrhenius plot of the decomposition reaction rate constant.

The decomposition reaction rate constant of the SF _6, the above (1) decomposition ratio of results for each parameter obtained in (3), the decomposition reaction rate of the SF _6, the first order kinetics (the equation (5 It is obtained by organizing with)).
In addition, from the Arrhenius plot of the decomposition reaction rate constant of SF ₆ (FIG. 4), 2.08 × 10 ³ (s ⁻¹ ) as the frequency factor (k ₀ ) of the decomposition reaction of SF ₆ , activation energy (E ), A value of 8.314 × 10 ⁴ (J / mol) is obtained.

ただし、前記式（１）中、Ｖは体積（ｍ^３）、Ｆ_Ａ０は前記被処理ガスの処理量（ｍ^３／ｓ）、ｋは前記式（２）で表される分解反応速度定数（１／ｓ）、ε_Ａはδ_Ａ・ｙ_Ａ０（δ_Ａは分解反応前後におけるモル体積の増加分のフッ素化合物モル体積に対する割合であり、下記反応式（Ｉ）で表されるＳＦ_６の分解反応においてδ_Ａ＝２）、ｙ_Ａ０は反応開始時の前記被分解物のモル分率、ｘ_Ａは前記被分解物の分解率を表す。

-(3) Volume of pyrolysis furnace-
The design equation for deriving the volume of the pyrolysis furnace is based on the integral design equation in the tubular reactor represented by the equation (6) and the decomposition reaction rate constant obtained in the above (2). It can represent with following formula (1).

However, the in formula (1), V is the volume ^(m _{3), F A0} is processing amount of the gas to be treated ^(m 3 / s), k is the decomposition reaction rate constant represented by the formula (2) ( 1 / s), ε _A is δ _A · y _A0 (δ _A is the ratio of the increase in the molar volume before and after the decomposition reaction to the fluorine compound molar volume, and the decomposition of SF ₆ represented by the following reaction formula (I) In the reaction, δ _A = 2), y _A0 represents the molar fraction of the decomposition product at the start of the reaction, and x _A represents the decomposition rate of the decomposition product.

In the equation (1), the decomposition rate x of the object to be decomposed from the value of the processing amount F _A0 of the gas to be processed and the value of the reaction rate constant k obtained by determining the heat treatment temperature T in the equation (1). The volume of the pyrolysis furnace for setting _A to 99.99% can be calculated.
A calculation example of the volume of the pyrolysis furnace in which the SF ₆ is pyrolyzed at a decomposition rate of 99.99% is shown in Table 1 below. Table 1 below is an example of calculating the volume of a pyrolysis furnace for decomposing 1 kg of SF _{6 at} a decomposition rate of 99.99% in one hour using the reaction temperature as a parameter.

-(4) Pyrolysis furnace design-
The pyrolysis furnace can be designed by calculating the cross-sectional area and length of the pyrolysis furnace from the volume of the pyrolysis furnace obtained in (3) above.
The pyrolysis furnace is preferably in the form of a tube. For example, when the volume V obtained by the formula (1) is 0.0061 m ³ , the pyrolysis furnace has a diameter of 0.12 m and a length. A shape of 0.54 m can be selected.
The volume V of the pyrolysis furnace derived from the equation (1) is the minimum space volume necessary for the pyrolysis. For this reason, when the said pyrolysis furnace has the said heat exchanger, the volume calculated from an external dimension becomes larger than the volume V derived | led-out by the said Formula (1). For example, FIG. 5 shows an example of the pyrolysis furnace having a volume derived from the equation (1) of 0.0061 m ³ and having two or more heat transfer bodies.

In the design of the pyrolysis furnace, the ratio of the diameter (a) to the length (b) ((a) / (b)) is preferably 0.05 to 0.3, 0.1 to 0 .2 is more preferable. When the ratio of the diameter (a) to the length (b) ((a) / (b)) exceeds 0.3, the gas to be processed passes through the pyrolysis furnace before being completely decomposed. If it is less than 0.05, the heating efficiency in the pyrolysis furnace and the heat generation efficiency of the heat transfer body may be reduced.
The diameter of the pyrolysis furnace is preferably less than 0.03 m and preferably less than 0.02 m. When the diameter of the pyrolysis furnace exceeds 0.03 m, the heat transfer efficiency to the gas to be treated may be lowered, and the cracking efficiency may be lowered.

  In designing the pyrolysis furnace, the ratio of the diameter (a) to the length (b) based on the volume derived from the equation (1) ((a ) / (B)) and the numerical range of the diameter are preferably designed, but if it is difficult to satisfy both, the heat transfer body in the pyrolysis furnace is set to 2 By providing as described above, heat transfer to the gas to be processed may be improved.

As the object to be decomposition products as SF ₆ and 99.99% or more degrades the volume of the pyrolysis furnace V ^{(m 3),} upon to derive by said volume V ^{(m 3)} of the formula (1), the formula The decomposition reaction constant k in (1) has the frequency factor (k ₀ ) of 2.08 × 10 ³ (s ⁻¹ ) and the activation energy (E) of 8.314 × 10 ^{4 in the} formula (2). It is preferably derived as (J / mol).

Further, as the said thermal cracking furnace to decompose 99.99% of SF ₆ as an object to be decomposition products, in order to remove the solid sulfur that occurs when the SF ₆ pyrolyzed with hydrogen gas, downstream It is preferable to arrange a sulfur component removal filter.
The sulfur component removal filter is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a Teflon (registered trademark) wool filter) and an alumina wool filter. Among these, Teflon A (registered trademark) wool filter is preferred.

On the other hand, the volume V (m ³ ) of the pyrolysis furnace that decomposes 99.99% or more of the fluorocarbon as the decomposition target is the same as the above-described pyrolysis furnace that decomposes SF ₆ by 99.99% or more. Can be derived.
Further, as the pyrolysis furnace for decomposing 99.99% or more of the fluorocarbon as the decomposition target, since the solid sulfur component to be removed in the decomposition reaction does not occur, except that the sulfur component removal filter is not necessary, It is preferably designed in the same manner as the above-mentioned pyrolysis furnace that decomposes SF ₆ by 99.99% or more.

<Dry immobilization furnace>
The dry immobilization furnace is not particularly limited as long as it contains the immobilization material inside and the volume of the reaction zone of the thermal dry immobilization furnace is derived by the equation (3). For example, the cracking gas is arranged downstream of the pyrolysis furnace, and the cracked gas discharged from the pyrolysis furnace is allowed to flow in. Further, the immobilization material supply means, and the immobilization Examples include a structure in which product recovery means are connected.

It is preferable that the dry immobilization furnace is a reaction tube having a tubular structure.
The total length of the reaction tube is preferably at least twice the length of the reaction zone designed based on the reaction zone volume derived from the equation (3), and preferably 2 to 10 times. More preferably, it is particularly preferably 3 to 5 times.
If the length of the reaction tube is less than twice the length of the reaction zone, the reaction between the fluorine component in the cracked gas and the immobilization material may be incomplete.

It is preferable that the dry immobilization furnace is composed of two or more reaction tubes connected so that cracked gas can flow therethrough. The cracked gas alternately passes through the two or more reaction tubes, whereby a high-purity fluorine compound can be recovered.
FIG. 6 shows an example of the dry immobilization furnace composed of two or more reaction tubes connected so that the cracked gas can flow.

The reaction zone is a region where the cracked gas and the immobilizing material react in the reaction tube to generate a fluorine compound, and the region is formed in the reaction tube from the gas inlet along with the flow of the cracked gas. It moves to the discharge port (FIGS. 6A to 6C).
Examples of the method for controlling the immobilization reaction in the dry immobilization furnace shown in FIG. 6 include the following methods.
The cracked gas flows into the first-stage reaction tube to form the reaction zone. The reaction zone moves toward the discharge port as the reaction between the fluorine component in the reaction gas and the immobilization material proceeds (FIG. 6A). After the immobilization material in the first stage reaction tube is completely fluorinated, the cracked gas flows into the second stage reaction tube to form a reaction zone (FIG. 6B). At this time, the cracked gas is controlled to flow only into the second-stage reaction tube, and the fluorine compound produced in the first reaction tube is recovered. Next, the first stage reaction tube is filled with the immobilization material, and the cracked gas discharged from the second stage reaction tube is controlled to flow (FIG. 6C).
By repeating this control procedure, a high-purity fluorine compound can be efficiently recovered.
The time required for the immobilization material in the reaction tube to be completely fluorinated is based on the detection (concentration) of hydrogen fluoride gas at the gas discharge ports (A and B in FIG. 6) of the reaction tube. Can be derived.

  In the dry reaction, no corrosive hydrofluoric acid is generated, so the material of the reaction tube is not particularly limited and can be appropriately selected according to the purpose. For example, ceramics such as alumina and mullite And metal materials such as copper and stainless steel.

<< Design of dry immobilization furnace >>
As a method of designing the dry-type fixing furnace, for example,
(1) Experimentally examining the dry reaction characteristics of the cracked gas and the immobilizing material, using the type of the immobilizing material, the reaction temperature, and the superficial velocity of the cracked gas as parameters,
(2) Experimentally determining the breakthrough time from the cracked gas breakthrough characteristics of the immobilization material,
(3) Obtain the cracked gas absorption capacity and stoichiometric coefficient of the immobilization material, determine the reaction zone volume of the dry immobilization furnace as a design coefficient together with the breakthrough time obtained in (2),
(4) The method of determining the diameter and length of the reaction zone of the dry fixation furnace, and designing the dry fixation furnace.

Hereinafter, SF ₆ gas as the fluorine-containing gas and hydrogen gas as the hydrogen-containing compound were pyrolyzed in the pyrolysis furnace, and the obtained SF ₆ was decomposed by 99.99% or more. The design method of the dry fixation furnace for fixing the cracked gas and obtaining the fluorine compound will be specifically described.

-(1) Dry reaction characteristics-
As the cracking gas used for examining the dry reaction characteristics, the composition before heat treatment in the pyrolysis furnace is SF ₆ : H ₂ : Ar (volume ratio) = 2: 9: 30, It is assumed that SF ₆ is decomposed by 99.99% or more.
The types of the immobilization material (NaHCO ₃ , CaCO ₃ ), reaction temperature (200 ° C., 250 ° C., 300 ° C.), and superficial velocity of the cracked gas (2.5 to 4.5 cm / s) are used as parameters. The dry reaction characteristics between the cracked gas and the immobilization material can be experimentally examined.
The cracked gas contains HF and H ₂ S, and each dry reaction characteristic can be confirmed from the concentration detected at the gas outlet of the dry fixing furnace during the reaction. Components that are not detected at the gas discharge port of the dry fixing furnace are fixed by a dry reaction with the fixing material, and components detected at the gas discharge port of the dry fixing furnace are fixed with the fixing material. Probably not reacting. FIG. 7 shows the measurement results of the detected concentration using the HF and H ₂ S detector tubes in the dry-type fixing furnace. FIG. 7 shows that HF can be recovered by separating HF and H ₂ S because HF is immobilized on the immobilizing material and H ₂ S is not immobilized.

-(2) Breakthrough time-
The breakthrough characteristic of the cracked gas is that the gas discharged from the gas outlet of the dry immobilization furnace is absorbed by deionized water, and the fluorine ion concentration contained in the absorbing liquid is continuously measured by the fluoride ion electrode. It can be examined by measuring. The results of examining the breakthrough characteristics of HF in the cracked gas are also shown in FIG. It can be seen from FIG. 7 that HF is detected in the absorbing liquid when HF breakthrough starts.
In this way, by measuring the time from the start of breakthrough until the HF concentration at the gas outlet of the dry immobilization furnace reaches the HF concentration of the cracked gas before the dry reaction, The HF breakthrough time can be obtained.

ただし、前記式（３）中、αは下記（４）で示される設計係数（ｍ^３・ｍｉｎ／ｍｏｌ）、Ｇ_Ｃは分解ガスの流入量（ｍｏｌ／ｍｉｎ）を表す。

ただし、前記式（４）中、τは破過時間（ｍｉｎ）、ｂは量論係数、Ｑ_Ｃは固定化材料の前記分解ガス吸収容量（ｍｏｌ／ｍ^３−ｂｅｄ）を表す。
前記固定化材の前記分解ガス吸収容量、量論係数、及び上記（２）において求めた破過時間とともに設計係数αを求めることができ、前記乾式固定化炉への前記分解ガスの流入量を設定し、前記式（３）により前記乾式固定化炉の反応帯体積を求めることができる。 -(3) Design factor-
The reaction zone volume of the dry immobilization furnace can be obtained from the following formula (3).

However, the above formula (3), alpha is the following (4) Design coefficients indicated by ^{(m 3 · min / mol)} , G C represents the inflow of decomposition gas (mol / min).

However, the formula (4), tau is the breakthrough time (min), b is Ryoron coefficient, _{Q C} represents the decomposed gas absorption capacity of the immobilizing material ^(mol / m 3 -bed).
The design coefficient α can be obtained together with the cracked gas absorption capacity, the stoichiometric coefficient of the immobilization material, and the breakthrough time obtained in the above (2), and the amount of the cracked gas flowing into the dry immobilization furnace can be determined. It is set, and the reaction zone volume of the dry immobilization furnace can be obtained from the equation (3).

-(4) Dry immobilization furnace design-
As a design of the dry-type fixing furnace, a cross-sectional area of the dry-type fixing furnace can be calculated from a processing flow rate of the cracked gas and a superficial velocity condition in the dry-type fixing furnace. From the reaction zone volume of the dry immobilization furnace obtained in 3), the length of the reaction zone can be calculated.
The length of the dry fixing furnace is preferably at least twice the length of the designed reaction zone, more preferably 2 to 10 times, and particularly preferably 3 to 5 times. preferable.
The length of the dry fixation furnace is preferably at least 3 times the inner diameter of the dry fixation furnace, more preferably at least 5 times. If the length of the dry immobilization furnace is less than three times the inner diameter of the dry immobilization furnace, the cracked gas and the immobilization material may not react uniformly, and the reaction zone is not formed as designed. Sometimes.

Preferably the dry immobilized furnace is tubular, for example, the formula volume V _C obtained by (3), 8.0 × 10 ^-4 when m is ^3, the reaction of the dry immobilized furnace A shape having a diameter of 0.12 m and a length of 0.07 m can be selected as the band, and a shape having a diameter of 0.12 m and a length of 0.4 m can be selected as the dry fixing furnace.

Moreover, it is preferable that the dry immobilization furnace is designed so that two or more reaction tubes are connected and arranged so that the cracked gas can flow therethrough.
When two or more reaction tubes are arranged, it is preferable to use an automatically controlled valve, valve, or the like in order to control the inflow of gas into each reaction tube.

-Immobilization material supply means-
There is no restriction | limiting in particular as a supply means of the said fixing material connected to the said dry-type fixation furnace, Although it can select suitably according to the objective, For example, a screw feeder, a parts feeder, etc. are mentioned.

-Immobilized product recovery means-
The means for recovering the immobilized product connected to the dry immobilization furnace is not particularly limited and may be appropriately selected according to the purpose. Examples thereof include recovery by a vibration method and recovery by a damper method. It is done.

<Other devices>
In the fluorine-containing gas decomposition treatment apparatus, it is preferable that a combustion furnace for burning unfixed decomposition gas discharged from the dry fixation furnace and a scrubber are disposed downstream of the dry fixation furnace. . By the combustion furnace and the scrubber, components that are components in the cracked gas and that are not recycled can be rendered detoxified by wet processing after combustion.

  There is no restriction | limiting in particular as said combustion furnace, According to the objective, it can select suitably, For example, a burner type combustion furnace, an electric heater type combustion furnace, etc. are mentioned.

  There is no restriction | limiting in particular as said scrubber, According to the objective, it can select suitably, For example, scrubbers, such as a stored water type, a pressurized water type, a packed bed type, and a rotary type, are mentioned.

Since the fluorine-containing gas decomposition treatment apparatus of the present invention thermally decomposes the gas to be treated, it is easy to start and stop the equipment as compared with the conventional combustion method. Further, since the amount of exhaust gas generated in the treatment process is small and the waste gas treatment facility can be made small, it is possible to reduce the size. Furthermore, since hydrofluoric acid is not generated in the immobilization reaction, it is not corroded.
The fluorine-containing gas decomposition treatment apparatus of the present invention can be suitably used for a fluorine compound recovery method described later.

(Fluorine compound recovery method)
The fluorine compound recovery method of the present invention is performed using the fluorine-containing gas decomposition treatment apparatus of the present invention described above, heat-treats the fluorine-containing gas and the hydrogen-containing compound, generates a decomposition gas, and fixes the decomposition gas to the fixed This is a method of recovering a fluorine compound produced as an immobilized product by dry-reacting with a chemical material, separating a fluorine component in the fluorine-containing gas from other components, and recovering only the fluorine component. is there.

The fluorine-containing gas treated by the fluorine compound recovery method is not particularly limited as long as it contains a fluorine atom as a component, and can be appropriately selected according to the purpose. For example, fluorine such as SF ₆ And compounds containing sulfur and fluorinated compounds (C, H, F compounds) such as fluorocarbons, and SF ₆ is particularly preferably treated.

  The hydrogen-containing compound is not particularly limited as long as it is a compound containing hydrogen in the number of moles or more necessary for all the fluorine atoms in the fluorine-containing gas to be HF, and may be appropriately selected according to the purpose. For example, it is preferable that the fluorine atom in the fluorine-containing gas and other atoms such as a sulfur atom and a halogen atom contain hydrogen in the number of moles or more necessary for becoming a hydrogen compound.

When the decomposition target is SF ₆ , the hydrogen-containing compound is a hydrogen gas containing hydrogen in the number of moles or more necessary for all of fluorine atoms and sulfur atoms to become HF and H ₂ S, respectively. Is preferred. By using such hydrogen gas, all the fluorine atoms in SF ₆ become HF and all the sulfur atoms become H ₂ S. Thereafter, for example, the high purity fluorine compound from which the sulfur component is separated can be recovered by dry fixing only the HF to the fixing material.

The heat treatment temperature of the fluorine-containing gas and the hydrogen-containing compound is preferably 700 to 1200 ° C, and more preferably 1000 to 1200 ° C.
If the heat treatment temperature is less than 700 ° C., the pyrolyzate may not be sufficiently decomposed. If the heat treatment temperature exceeds 1200 ° C., decomposition of H ₂ S gas is promoted, and single sulfur May occur and cause clogging of the sulfur removal filter.

The immobilization material is not particularly limited as long as it is a compound that is dry-reacted with HF in the cracked gas, immobilizes fluorine atoms in the HF, and is recovered as a solid fluorine compound. It can be selected appropriately.
Examples of the immobilization material include at least one carbonate selected from Na, Li, K, Ca, Mg, and Si, and at least one selected from Na, Li, K, Ca, Mg, and Si. A seed oxide, sodium hydrogencarbonate, etc. are mentioned, Among these, sodium carbonate, sodium hydrogencarbonate, calcium carbonate, and calcium oxide are preferable.

  The property of the immobilization material is not particularly limited as long as it is solid, and can be appropriately selected according to the purpose. However, it is preferably granular, and the particle size is 1 to 2 mm. preferable.

The dry reaction temperature between the cracked gas and the immobilization material is preferably 150 to 500 ° C, more preferably 150 to 300 ° C.
The dry reaction temperature is preferably a temperature at which only HF in the cracked gas reacts with the immobilization material. For example, when the decomposition target is SF ₆ , only HF in the cracked gas is It is preferable that the temperature reacts with the immobilization material and the other sulfur compounds do not react with the immobilization material.
When the dry reaction temperature is lower than 150 ° C., HF in the cracked gas becomes hydrofluoric acid, and the generated hydrofluoric acid may cause corrosion of the apparatus. When the dry reaction temperature exceeds 500 ° C., the chemical equilibrium concentration of HF gas in the cracked gas increases, and the immobilization rate may decrease.

FIG. 8 shows the chemical equilibrium composition of the solid component at 1 atm of H ₂ S1 mol, HF 6 mol, and Na ₂ CO ₃ 5 mol, and FIG. 9 shows the chemical equilibrium composition of the gas component.
From Figure 8, sodium carbonate as the immobilizing material, but the NaF reacts with HF in a wide temperature range of 200 to 800 ° C., hardly react with _{H 2} S, _{H 2} S gas shape It turns out that it is stable.
Moreover, from FIG. 9, since the HF density | concentration in a gaseous phase is 10 or less ppm in the temperature range of 500 degrees C or less, and is less than 1 ppm (10 < ^-6 > atm) in the temperature range of 300 degrees C or less, 150- It can be seen that at a dry reaction temperature of 300 ° C., HF can be selectively fixed to a low concentration by sodium carbonate as the fixing material.

FIG. 10 shows the chemical equilibrium composition of the solid component at 1 atm of H ₂ S1 mol, HF 6 mol, CaCO ₃ 10 mol, and O ₂ 4 mol, and FIG. 11 shows the chemical equilibrium composition of the gas component.
From Figure 10, calcium or calcium oxide carbonate as the immobilizing material is a CaF ₂ reacts with HF in a wide temperature range of 200 to 800 ° C., hardly react with _{H 2 S, H 2} S Shows that the gaseous state is stable.
Moreover, from FIG. 11, since the HF density | concentration in a gaseous phase is less than 10 ppm in the temperature range below 500 degreeC, and less than 1 ppm (10 < ^-6 > atm) in the temperature range below 300 degreeC, 150- It can be seen that at a dry reaction temperature of 300 ° C., HF can be selectively fixed to a low concentration by the calcium carbonate or calcium oxide of the fixing material.

In the said fluorine compound collection | recovery method, after fixing the said HF to the said fixing material, it is preferable to process the sulfur compound which is not fixed to the said fixing material.
There is no restriction | limiting in particular as a processing method of the said sulfur compound, According to the objective, it can select suitably, For example, a general acidic gas removal processing method can be applied.
Further, when the sulfur compound is H ₂ S, it can be recycled by burning H ₂ S to SOx, reacting it with a calcium carbonate solution or the like, and recovering it as gypsum (CaSO ₄ ).

A method for recovering the SF ₆ -containing gas using the fluorine-containing gas decomposition treatment apparatus (FIG. 1) of the present invention will be described.
SF ₆ supplied from the fluorine-containing gas supply device and H ₂ gas supplied from the hydrogen compound supply device are introduced into the pyrolysis furnace 3 and heat-treated. SF ₆ of the decomposition target is decomposed to generate a decomposition gas containing H ₂ S and HF, and sulfur. Sulfur is removed by a sulfur removal filter provided downstream of the pyrolysis furnace.
The generated cracked gas is introduced into the dry immobilization furnace, and dry-fixed under a temperature condition of 150 to 500 ° C. together with the immobilization material supplied from the immobilization material supply device. Here, only HF in the cracked gas is fixed to the fixing material, and becomes the fixed product (fluorine compound). The immobilized product is recovered in a recovery tank or the like.
On the other hand, H ₂ S that is not immobilized is discharged from the dry immobilization furnace and burned in the combustion furnace to become SOx. Thereafter, it is removed by wet scrubber or the like.
By the above treatment, for example, sodium fluoride and calcium fluoride are obtained as the immobilized product.

The immobilization product has a recovery rate of 90% or more because the immobilization material that is solid and granular is generated by a dry reaction with the cracked gas.
The immobilized product is a fluorine compound having a purity of 97% or more.

  There is no restriction | limiting in particular as a use of the said fixed product, According to the objective, it can select suitably, For example, industrial raw materials for HF manufacture, steel, etc., a reagent, etc. are mentioned.

In the fluorine compound recovery method of the present invention, the gas to be treated comprising the fluorine-containing gas and the hydrogen-containing compound is thermally decomposed by heating, and fluorine atoms in the generated decomposition gas are immobilized by a dry reaction. Since it is a method of fixing to a material and recovering the immobilized product, the amount of exhaust gas generated in the decomposition treatment step is small, and since the obtained immobilized product is a granular fluorine compound, it is excellent in handleability.
The fluorine compound recovery method of the present invention is suitable for recycling because the purity of the fluorine compound obtained by decomposing the fluorine-containing gas is 97% or more.

  Hereinafter, although the Example of this invention is described, this invention is not limited to this Example at all.

Example 1
An experiment was conducted in which a gas composed of Ar, SF ₆ , and H ₂ was used as a gas to be treated, and SF ₆ was decomposed by 99.99% or more to recover a fluorine compound. Ar is a component added for dilution.

ただし、式（１）中、Ｆ_Ａ０は前記被処理ガスの処理量（ｍ^３／ｓ）、ｋは分解反応速度定数（１／ｓ）、ε_Ａはδ_Ａ・ｙ_Ａ０（δ_Ａは分解反応前後におけるモル体積の増加分のフッ素化合物モル体積に対する割合であり、δ_Ａ＝２）、ｙ_Ａ０は反応開始時の前記被分解物のモル分率、ｘ_Ａは前記被分解物の分解率を表す。
前記分解反応速度定数は、頻度因子（ｋ_０）を２．０８×１０^３（ｓ^−１）、活性化エネルギー（Ｅ）を８．３１４×１０^４（Ｊ／ｍｏｌ）として下記式（２）を用いて算出した。

ただし、ｋ_０は分解反応の頻度因子（ｓ^−１）、Ｅは活性化エネルギー（Ｊ／ｍｏｌ）、Ｒは気体定数、Ｔは熱処理温度の絶対温度（Ｋ）を表す。 -Design and manufacture of pyrolysis furnace-
The pyrolysis furnace capable of decomposing SF ₆ by 99.99% or more was designed.
The decomposition rate of SF6 is set to 99.99%, and the processing amount of the gas to be processed is Ar: 5.0 × 10 ⁻⁶ m ³ / s, SF ₆ : 1.0 × 10 ⁻⁶ m ³ / s, H ₂ : 4.0 × 10 ⁻⁶ m ³ / s, the heat treatment temperature was set to 1000 ° C., and the volume V (m ³ ) of the pyrolysis furnace was calculated using the following formula (1).

However, in Formula (1), F _A0 is the processing amount (m ³ / s) of the gas to be processed, k is a decomposition reaction rate constant (1 / s), ε _A is δ _A · y _A0 (δ _A is decomposition) The ratio of the increase in the molar volume before and after the reaction to the molar volume of the fluorine compound, δ _A = 2), y _A0 is the molar fraction of the decomposition product at the start of the reaction, and x _A is the decomposition rate of the decomposition product Represents.
The decomposition reaction rate constant is defined by the following formula (2) where the frequency factor (k ₀ ) is 2.08 × 10 ³ (s ⁻¹ ) and the activation energy (E) is 8.314 × 10 ⁴ (J / mol). It calculated using.

However, _{k 0} is the frequency factor of the decomposition reaction ^(s -1), E is the activation energy (J / mol), R is the gas constant, T represents absolute temperature (K) of the heat treatment temperature.

As a result, a tubular pyrolysis furnace having a volume of 0.19 × 10 ⁻³ m ³ , an inner diameter of 0.02 m, and a length of 0.6 m was designed.
Based on the above design, a pyrolysis furnace having a tubular heat transfer body made of graphite was manufactured.

ただし、前記式（３）中、αは下記（４）で示される設計係数（ｍ^３・ｍｉｎ／ｍｏｌ）、Ｇ_Ｃは分解ガスの流入量（ｍｏｌ／ｍｉｎ）を表す。

ただし、前記式（４）中、τは破過時間（ｍｉｎ）、ｂは量論係数、Ｑ_Ｃは固定化材料の前記分解ガス吸収容量（ｍｏｌ／ｍ^３−ｂｅｄ）を表す。 -Design and manufacture of dry-type fixing furnaces-
Calcium carbonate was used as the immobilization material, the dry reaction characteristics of HF in the cracked gas and calcium carbonate of the immobilization material were examined, and the breakthrough time of HF was determined.
Moreover, the absorption capacity and stoichiometric coefficient of HF were calculated | required about the said fixing material.
Set the inflow of the decomposition gas to the dry immobilized furnace, using the following equation (3) to calculate the reaction zone volume V _C of the dry immobilized furnace.

However, the above formula (3), alpha is the following (4) Design coefficients indicated by ^{(m 3 · min / mol)} , G C represents the inflow of decomposition gas (mol / min).

However, the formula (4), tau is the breakthrough time (min), b is Ryoron coefficient, _{Q C} represents the decomposed gas absorption capacity of the immobilizing material ^(mol / m 3 -bed).

As a result, 0.023 × 10 ⁻³ m ³ was obtained as the value of the reaction zone volume of the dry immobilization furnace.
Since the dry immobilization furnace is designed so that the two reaction tubes are connected so that the cracked gas can flow therethrough, the reaction zone of the dry immobilization furnace has a diameter of 0.03 m and a length of 0.035 m. The dry fixing furnace was designed with a diameter of 0.03 m and a length of 0.15 m.
Based on the above design, a dry immobilization furnace comprising two reaction tubes made of alumina ceramic was manufactured.

-Fluorine gas decomposition equipment-
A fluorine gas decomposition treatment apparatus in which the designed and manufactured pyrolysis furnace and the dry fixing furnace were arranged as shown in FIG. 1 was manufactured.

-Recovery of fluorine compounds-
Using the fluorine gas decomposition treatment apparatus, SF ₆ gas decomposition treatment and fluorine compound recovery were performed.
A gas to be treated is sent to the pyrolysis furnace at 0.017 × 10 ⁻³ m ³ / s to perform a heat treatment at 1100 ° C. to generate a cracked gas, and then the cracked gas is supplied to the dry fixing furnace. It was sent at 0.02 × 10 ⁻³ m ³ / s, and dry-reacted at 100 ° C. with 100 g of calcium carbonate as the immobilization material, and the obtained immobilization product (fluorine compound) was recovered.
When the concentration of H ₂ S gas at the outlet of the dry fixed furnace was confirmed with a detector tube, the HF concentration could not be detected at all, although it showed an almost constant value within the range of analysis accuracy from the start of the reaction. From this, it was found that HF gas and H ₂ S were separated.

When the purity of the recovered fluorine compound (CaF ₂ ) was measured using thorium titration and fluorescent X-ray analysis, it was found to be 97%.
Further, the recovery rate is 99% from the stoichiometric weight when all the fixing materials filled in the dry-type fixing furnace become fluoride, the weight of the recovered fluorine compound, and the purity of the recovered fluorine compound. I found out that

(Example 2)
In Example 1, the SF ₆ -containing gas was thermally decomposed to obtain a fluorine compound in the same manner as in Example 1 except that the dry immobilization furnace was made of a single reaction tube.
When the purity of the recovered fluorine compound (CaF ₂ ) was measured using thorium titration and fluorescent X-ray analysis, it was found to be 90%.
The recovery rate was found to be 99%.

(Example 3)
In Example 1, the SF ₆ -containing gas was pyrolyzed in the same manner as in Example 1 except that the length of the reaction tube of the dry immobilization furnace was less than twice the length of the reaction zone. A compound was obtained.
When the purity of the recovered fluorine compound (CaF ₂ ) was measured using thorium titration and fluorescent X-ray analysis, it was found to be 60%.
The recovery rate was found to be 99%.

The design method of the fluorine-containing gas decomposition treatment apparatus of the present invention, the fluorine-containing gas decomposition treatment apparatus designed by the design method, and the fluorine compound recovery method using the same can decompose the fluorine-containing gas at a high decomposition rate. Yes, because it is easy to handle the product after the decomposition treatment, and the fluorine compound, which is the product, has high purity and can be recycled, it is suitable for disposal of SF ₆ gas and fluorocarbon gas. can do.

FIG. 1 is a schematic view showing an example of an SF ₆ gas decomposition treatment apparatus. Figure 2 is an example of a graph showing the degradation characteristics of SF _6. Figure 3 is an example of a graph for analyzing the decomposition reaction rate of the SF _6. Figure 4 is an example of Arrhenius plot of the rate constant of SF _6. FIG. 5 is a schematic diagram showing an example of a pyrolysis furnace. FIG. 6 is a schematic view showing an example of a dry-type fixing furnace. FIG. 7 is an example of a graph showing the dry separation characteristics of SF ₆ cracked gas. FIG. 8 is a chemical equilibrium diagram of solid components of H ₂ S, HF, and Na ₂ CO ₃ . FIG. 9 is a chemical equilibrium diagram of gaseous components of H ₂ S, HF, and Na ₂ CO ₃ . FIG. 10 is a chemical equilibrium diagram of solid components of H ₂ S, HF, CaCO ₃ , and O ₂ . FIG. 11 is a chemical equilibrium diagram of gaseous components of H ₂ S, HF, CaCO ₃ , and O ₂ .

Claims (10)

A thermal decomposition furnace for heat-treating a gas to be processed comprising a fluorine-containing gas supplied from a fluorine-containing gas supply device and a hydrogen-containing compound supplied from a hydrogen supply device, and thermally decomposing a substance to be decomposed in the fluorine-containing gas And at least a dry immobilization furnace configured to dry-react the cracked gas discharged from the pyrolysis furnace and the immobilization material supplied from the immobilization material supply device to fix the fluorine component in the cracked gas. ,
Fluorine volume V of the pyrolysis furnace (m ³⁾ can be derived from the following equation (1), the volume V _C of the reaction zone of the dry immobilized furnace _(m ³⁾ is derived from the following formula (3) Using the contained gas decomposition treatment device,
Heat treatment of the fluorine-containing gas and the hydrogen-containing compound to generate a decomposition gas;
A method for recovering a fluorine compound, characterized in that the decomposition gas is dry-reacted with an immobilization material to recover a fluorine compound produced as an immobilization product.

However, F _A0 is a processing amount of the gas to be processed (m ³ / s), k is a decomposition reaction rate constant (1 / s) represented by the following formula (2), ε _A is δ _A · y _A0 , δ _A is the ratio of the increase in the molar volume before and after the decomposition reaction to the fluorine compound molar volume, y _A0 is the molar fraction of the decomposition product at the start of the reaction, and x _A is the decomposition rate of the decomposition product.

However, k ₀ is the frequency factor (s ⁻¹ ) of the decomposition reaction determined from the Arrhenius plot of the decomposition reaction rate constant, and E is the activation energy (J / mol) determined from the Arrhenius plot of the decomposition reaction rate constant. , R is a gas constant, and T is the absolute temperature (K) of the thermal decomposition temperature.

However, alpha design factor represented by the following formula ^{(4) (m 3 · min} / mol), G C represents the inflow of decomposition gas (mol / min).

However, tau is the breakthrough time (min), b is Ryoron coefficient, _{Q C} represents the decomposed gas absorption capacity of the immobilizing material ^(mol / m 3 -bed). The fluorine compound recovery method according to claim 1, wherein the pyrolysis furnace has a tubular structure and has a heat transfer body in the pyrolysis furnace. The method for recovering a fluorine compound according to any one of claims 1 to 2, wherein the dry immobilization furnace comprises a reaction tube having a tubular structure, and the total length of the reaction tube is 2 to 10 times the length of the reaction zone. The dry immobilization furnace is composed of two or more reaction tubes connected so that cracked gas can flow therethrough, and the cracked gas passes through the two or more reaction tubes alternately. The method for recovering a fluorine compound according to any one of the above. The dry immobilization furnace is selected from at least one carbonate selected from Na, Li, K, Ca, Mg, and Si, Na, Li, K, Ca, Mg, and Si as the immobilization material. The method for recovering a fluorine compound according to any one of claims 1 to 4, comprising any one of at least one oxide and sodium hydrogen carbonate. A combustion furnace that burns unfixed cracked gas discharged from the dry fix furnace and at least one of a scrubber that cleans the unfixed cracked gas is disposed downstream of the dry fix furnace. The fluorine compound recovery method according to any one of 1 to 5. The fluorine compound recovery method according to any one of claims 1 to 6, wherein a substance to be decomposed in the fluorine-containing gas is SF ₆ (sulfur hexafluoride) and the hydrogen-containing compound is H ₂ (hydrogen). The substance to be decomposed in the fluorine-containing gas is SF ₆ (sulfur hexafluoride), and the volume V (m ³ ) of the pyrolysis furnace that decomposes SF ₉ by 99.99% or more is derived from the equation (1). On the occasion
The decomposition reaction rate constant k (1 / s) in the formula (1) is the frequency factor k ₀ = 2.08 × 10 ³ (s ⁻¹ ) and the activation energy E = 8.314 in the formula (2). The fluorine compound recovery method according to claim 7, which is derived as × 10 ⁴ (J / mol). The method for recovering a fluorine compound according to any one of claims 7 to 8, wherein a sulfur component removal filter is disposed downstream of the pyrolysis furnace. The method for recovering a fluorine compound according to any one of claims 1 to 6, wherein a substance to be decomposed in the fluorine-containing gas is a fluorocarbon, and the hydrogen-containing compound contains water vapor.

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