KR20180135134A - Device and Process for multi-stage of PFC treating reaction occurring in at least two reaction modules including catalytic reactor and acidic gas-removing reactor - Google Patents

Abstract

Provided is a device for treating a perfluorinated compound (PFC), in order to increase the catalytic reaction efficiency while lowering the reaction temperature in an endothermic reaction by equilibrium breakthrough while being compact, which comprises: (i) a reactor assembly in which a reactor module is serially connected in two or more stages, wherein the reactor module comprises a first reactor block for carrying out a hydrolysis reaction by a catalyst, for a PFC containing gas and a second reactor block removing acid gas from gaseous products discharged from the first reactor block; and (ii) a fluid flow guide dispersion plate made to increase the reaction efficiency by reducing a reaction deviation of a vertical section based on the central axis generated by the reaction of the PFC-containing gas with a part of a catalyst in the first reactor block.

Description

[0001] The present invention relates to an apparatus for treating an integrated multi-stage PFC and a PFC process using the same,

The present invention relates to a reactor module comprising, for a PFC containing gas, a reactor module comprising a first reactor block which performs a hydrolysis reaction by a catalyst and a second reactor block which removes acid gas from the gaseous product discharged from the first reactor block, An apparatus for treating perfluorocompound (PFC) with a reactor assembly and a fluid flow guide dispersion plate connected in series; A PFC treatment method using the apparatus, and a calcium fluoride production method from PFC.

Perfluoro compounds (PFCs) are carbon-containing perfluoro compounds (PFCs), nitrogen-containing perfluoro compounds (PFCs) and sulfur-containing perfluoro compounds (PFCs) .

The carbon-containing PFC include _{CF 4, CHF 3, CH 2} F 2, C 2 F 4, C 2 F 6, C 3 F 6, C 3 F 8, C 4 F 8, saturated and unsaturated aliphatic, such as C ₄ F ₁₀ aliphatic components as well as cyclic aliphatic and aromatic perfluorocarbons. Nitrogen-containing PFCs typically include NF ₃ , and sulfur-containing PFCs include SF ₄ , SF _6, and the like.

The harmful waste gas emitted from the semiconductor manufacturing process is discharged in a very wide variety depending on each process. Most of the harmful waste gas is volatile and is harmful to the human body or has a high global warming index. Among them, perfluorocompound (PFC), which is a perfluorocompound which is mainly discharged in the etching and CVD (chemical vapor deposition) process of a semiconductor process, is very stable and is not easy to remove. PFCs are more stable than CFCs (chlorofluorocompounds) used as refrigerants, and have a problem of not only being large in global warming index but also having a very long decomposition time and accumulating in the atmosphere when they are released. PFC emissions from semiconductor processes are increasing at an increasing rate each year. As the impact of PFC on global warming is increasing, countries are gradually strengthening regulations on PFC.

Several technologies for removing PFCs, especially carbon-based PFCs, are being developed, including PSA and membrane separation and recovery, and decomposition and removal using plasma, combustion, or catalysis. The decomposition and removal technology can be roughly classified into direct / indirect heat decomposition method, plasma decomposition method, and catalytic decomposition method. The direct / indirect heat decomposition method is a technology to decompose PFC by contacting with PFC with oxygen by direct heating with a high temperature combustion flame of 1000 or more and using an electric heating furnace. There are advantages. However, it has a disadvantage in that thermal NOx is generated because the efficiency is low and it must be operated at a high temperature of 1000 or more. The plasma decomposition method is a technique for generating a plasma of high energy state by using microwave or high frequency and then flowing a waste gas containing PFC to decompose it, and it is known to be very effective for PFC decomposition. However, when the gases are exposed to too high a state of the plasma, not only decomposition of the PFC to decompose but also stable gases such as N ₂ react with oxygen to produce excessive NO _x . The problem is that the plasma is generated well in the He or Ar atmosphere, but it is disadvantageous in that plasma generation is difficult under N ₂ , especially in the O ₂ environment, and the decomposition efficiency is rapidly deteriorated.

Sulfur hexafluoride (SF ₆ ) is a colorless, odorless, nontoxic, and nonflammable gas with a dielectric property that is known to be the largest of the six greenhouse gases with a global warming index of 23,900. It is mainly used as insulating medium for high voltage power equipment because of its excellent insulation at room temperature as well as at high temperature. It is used for etching process to remove the developed circuit pattern by chemical or physical method in semiconductor manufacturing process and cleaning process for treating impurities on the surface . It is also used as a gas to prevent oxidation or ignition in the magnesium smelting process. In addition, the inactivity of SF ₆ is used in small quantities to evaluate the efficiency of the ventilation system of the building, and fill materials such as tracer gas, soundproof window, and tire for air, ocean, and groundwater flow analysis. Like all other fluoride compounds, SF ₆ remains in the atmosphere for a long period of time (atmospheric lifetime: 800 to 3,200 yrs.).

There are problems such as separation, recovery, and decomposition of SF ₆ , which have limitations in the range and capacity of the process gas and generate secondary air pollutants such as SOx and SO ₂ F ₂ . It is necessary to develop SF ₆ treatment technology which can maximize effective treatment efficiency and energy efficiency.

Catalytic cracking is a technique to decompose PFC which is degradable at low temperature of 800 ℃ or lower by using catalyst and water vapor. By using the catalytic method, the decomposition temperature can be remarkably lowered, and the size of the scrubber can be greatly reduced due to the increase of the reaction activity, which makes it possible to miniaturize the scrubber. In addition, decomposition at a temperature as low as 800 ° C or less leads to a reduction in the operating cost due to continuous operation and easy maintenance of the durability of the system, and the generation of thermal NO _x due to N ₂ present in the exhaust gas It has the advantage of completely suppressing and greatly reducing device corrosion.

An object of the present invention is to provide a process for producing a PFC-containing gas, which comprises a first reactor block which performs a hydrolysis reaction by a catalyst and a second reactor block which performs a hydrolysis reaction of the gaseous product discharged from the first reactor block An apparatus for treating a perfluorocompound (PFC) with a reactor assembly and a fluid flow guide diffuser plate, the reactor modules comprising a second reactor block for removing acid gas, in two or more stages in series; And a method of treating PFC using the apparatus and a method of producing calcium fluoride from PFC.

A first aspect of the present invention is directed to a device for treating a perfluoro compound (PFC), comprising: (i) a cylindrical, tangential or polygonal tubular reactor assembly having a transverse center axis, A first reactor block for carrying out a hydrolysis reaction; And a second reactor block for removing acidic gas from gaseous products discharged from the first reactor block, wherein at least two of the first reactor blocks and at least two second reactor blocks are alternately connected The gaseous product fluid discharged from the first reactor block is introduced directly into the second reactor block adjacent to the first reactor block and discharged from the second reactor block at the previous stage A reactor assembly in which a gas fluid is introduced directly into a first reactor block at an adjacent rear end; (ii) an inlet pipe that feeds the PFC containing gas to be treated to the reactor assembly and has a vertical section perpendicular to the central axis smaller than a vertical section of the reactor assembly; (iii) a connection tube installed between the inlet tube and the reactor assembly and in the form of a tube that gradually expands along the fluid flow direction; And (iv) a distributor plate disposed inside the connection tube for guiding the flow of the fluid, wherein the PFC-containing gas introduced along the central axis through the inlet pipe is located at the upstream end of the first reactor block, Wherein a cycle of the PFC hydrolysis catalytic reaction and the acid gas elimination reaction is repeated twice or more in the reactor assembly, so that the forward catalytic reaction And the efficiency of the PFC treatment is improved.

A second aspect of the present invention is a method for treating an overburdened compound (PFC) in a PFC treating apparatus of the first aspect, wherein a hydrolysis reaction is carried out by a catalyst on a PFC containing gas in a first reactor block, And removing acidic gas from the hydrolyzate gas of the PFC in the first reactor block and the second reactor block.

A second aspect of the present invention is a method for producing calcium fluoride from a perfluorinated compound (PFC) in a PFC treating apparatus of the first aspect, characterized in that the PFC containing gas in the first reactor block is subjected to a hydrolysis reaction And reacting HF in the hydrolyzate gas of the PFC in the second reactor block with the solid phase HF remover to form calcium fluoride (CaF ₂ ).

Hereinafter, the present invention will be described in detail.

For example, the PFC treatment process by the catalytic cracking method is a process in which various gases discharged from a PFC collection duct are treated with an acidic gas through an alkali scrubber, and then hydrolyzed in a catalytic reactor, After the reaction, the PFC is removed.

CF ₄ + 2H ₂ O? CO ₂ + 4HF

CHF ₃ + (1/2) O ₂ + H ₂ O? CO ₂ + 3HF

C ₂ F ₆ + 3H ₂ O + (1/2) O ₂ → 2CO ₂ + 6HF

SF ₆ + 3H ₂ O - > SO ₃ + 6HF

SF ₆ + 2H ₂ O - > SO ₂ F ₂ + 4HF

Thus, the products of the PFC hydrolysis reaction include acidic gases such as HF, CO ₂ , SO ₃ and toxic gases such as SO ₂ F ₂ . Thus, toxic gases such as SO ₂ F ₂ can also be included in the example of acid gases in the present invention.

The acid gas is an acidic gas when it comes into contact with water, and examples thereof include halogen, hydrogen halide, nitrogen oxides (NOx), sulfur oxides (SOx), acetic acid, hydrogen sulfide, hydrogen sulfide and carbon dioxide. Acid gases cause serious corrosion problems in the downstream process, which usually requires a process configuration using expensive materials and SO ₂ F ₂ is a substance used as a fumigation insecticide and is highly toxic and desirably removed.

When the PFC hydrolysis reaction and the acid gas removal reaction occur consecutively, this corresponds to a catalytic reaction followed by a product removal reaction. Accordingly, the present invention relates to a catalytic reaction process for carrying out a hydrolysis reaction with a PFC-containing gas by a catalyst and a process for removing an acid gas in the hydrolyzate gas of PFC at the downstream of the catalytic reaction process, It is desired not only to accelerate the speed but also to lower the catalytic reaction temperature which is an endothermic reaction.

However, in a single reactor equipped with a catalyst and a solid acid gas removing agent, when the catalyst life and the lifetime of the solid acid gas removing agent are different, there arises a problem that the operation must be stopped to replace the catalyst and / or solid acid gas removing agent .

In order to solve this problem, the inventors of the present invention have proposed a method of separating the catalyst reaction-product elimination reaction into a reactor for reacting a catalyst and a reactor for removing a product, forming a single reactor module without heating / cooling, As a result of the computer simulation, it was found that a temperature reduction effect in the endothermic reaction expected in a shell-and-tube type integrated reactor in which a catalyst reaction occurs in a shell and a product removal reaction occurs in a tube is possible (FIG. FIG. 1 is a simulation result of the performance of a catalytic cracking apparatus in a case where the catalytic cracking-product elimination reaction is constituted by one stage or three stages. That is, when the apparatuses having a dual catalytic reaction for carrying out the hydrolysis reaction with the PFC-containing gas and a removal reaction for removing the acid gas in the hydrolyzate gas of the PFC are constructed in three stages, the catalytic reaction / Effect (equilibrium breakthrough) is possible. It has been confirmed that the addition of the reactor module stages simulates what happens in a single reactor environment.

From this, even if the reaction proceeds until the chemical reaction in which the gaseous product is formed from the gaseous reactant in the catalytic reactor at the front end proceeds to chemical equilibrium, the chemical equilibrium is removed through the reaction for removing a part or all of the gaseous product, The cycle in which the catalytic reaction occurs spontaneously in the reactor is turned at least once through the reactor module of the two or more catalytic reactor / product elimination reactor, so that as the number of cycles increases, the simultaneous reaction / Breakthrough) can occur.

Furthermore, since the absorption reaction for removing the product with the liquid absorbent is performed at room temperature or low temperature, additional heat supply is required to perform the post-end catalytic reaction of the cooled gas. However, according to the present invention, Can absorb / adsorb acidic gas at a high temperature, so that there is no need for additional heat supply to perform the catalytic reaction after the absorption / adsorption reaction.

For example, the hydrolysis reaction of the perfluorinated compound (g) and the reaction of forming calcium fluoride (CaF ₂ ) (s) from the hydrofluoric acid (HF) (g) (G) is consumed through the reaction of forming calcium fluoride (CaF ₂ ) (s) in one reactor as a result of performing equilibrium dissociation, the PFC It was found that the reaction of PFC hydrolysis can be improved by the dominant reaction of hydrolysis. The present invention is based on this.

Herein, the perfluorinated compound (PFC) can be extended to a compound capable of decomposing by a catalyst to form an acid gas such as HF, which is also within the scope of the present invention.

The PFC processing apparatus according to the present invention

(i) a cylindrical, tapered or polygonal tubular reactor assembly having a transverse center axis,

A first reactor block for carrying out a hydrolysis reaction with a catalyst for a PFC containing gas; And a second reactor block for removing acid gas from gaseous products discharged from the first reactor block, wherein the reactor modules are connected in series in two or more stages,

Two or more first reactor blocks and two or more second reactor blocks are alternately formed so as to be adjacent to each other,

In the direction of the central axis, the gaseous product fluid discharged from the first reactor block is introduced directly into the second reactor block adjacent to the first reactor block, and the gas fluid discharged from the second reactor block at the previous stage A reactor assembly directly introduced into the first reactor block;

(ii) an inlet pipe that feeds the PFC containing gas to be treated to the reactor assembly and has a vertical section perpendicular to the central axis smaller than a vertical section of the reactor assembly;

(iii) a connection tube installed between the inlet tube and the reactor assembly and in the form of a tube that gradually expands along the fluid flow direction; And

(iv) a dispersion plate installed inside the connection pipe for guiding the fluid flow,

And a fluid flow guide distribution plate having a shape designed to allow the PFC containing gas flowing along the central axis through the inlet pipe to reach the front face of the vertical section of the center axis of the first reactor block located at the upstream end of the reactor assembly,

The cycle of the PFC hydrolysis catalytic reaction and the acid gas removal reaction is repeated two or more times in the reactor assembly, so that the efficiency of the forward catalytic reaction is improved by the equilibrium breakthrough.

The reactor module used in the apparatus for treating PFC according to the present invention comprises: a first reactor for performing a hydrolysis reaction with a PFC-containing gas; And a second reactor for removing acid gas in the gaseous product discharged from the first reactor. Accordingly, the PFC treatment apparatus having the two or more stage reactor modules according to the present invention is a dry type PFC decomposition apparatus in which drainage is not generated.

Using the apparatus for treating PFC according to the present invention, calcium fluoride can be produced from PFC. At this time, the PFC containing gas in the first reactor is subjected to the hydrolysis reaction by the catalyst, and the HF The calcium fluoride (CaF ₂ ) can be formed by the solid acid gas removing agent in the PFC hydrolyzate gas containing PFC. FIG. 2 is a conceptual view schematically showing a reaction process when a reactor module including a PFC hydrolysis catalyst and a solid acid gas removing agent is used in two stages.

According to the present invention, in the PFC treatment device in which the reactor modules are connected in series in two or more stages, the cycle of the catalytic reaction and the product removal reaction is repeated twice or more, so that the efficiency of the catalytic reaction can be improved by the equilibrium breakthrough.

The present invention can be connected in series with two or more stages, preferably seven stages or less, more preferably three or five stages of reactor modules. In particular, in terms of economy and device compaction, it is preferable that the reactor modules are connected in series in three or four stages.

Further, the apparatus for treating a PFC according to the present invention is designed to perform 50 to 99%, preferably 65 to 95%, and more preferably 70 to 90% of the maximum catalytic treatment capacity of each catalytic reactor in each stage of the catalytic reactor Operation conditions can be set.

For example, when the reactor module has two stages and the catalyst treatment capacity of each stage is 80% of the maximum value, the sum of the catalyst treatment capacity (%) = the treatment capacity of the first stage (%) + = (100 X 0.8) + (20 X 0.8) = 80 + 16 = 96 (%).

For example, when the reactor module has three stages and the catalyst treatment capacity at each stage is 70% of the maximum value, the total catalyst treatment capacity (%) = the first stage treatment capacity (%) + the second stage treatment capacity (% The processing capacity (%) of the third stage is (100 X 0.7) + (30 X 0.7) + (9 X 0.7) = 70 + 21 + 6.3 = 97.3 (%).

The reactant conversion efficiency is a function of the reaction temperature, and when the reactant conversion efficiency is determined, the operating temperature of the catalyst layer is determined.

Therefore, when the reaction temperature (for example, 750 ° C) required to achieve the catalyst treatment capacity (for example, 97%) in the case of using the one-stage catalytic reactor and the catalytic reactor having two or more stages is used, 70%) is small, and the reaction temperature required for the catalytic reactor during the endothermic reaction can be lowered (e.g., 650 ° C). Further, although the thermal stability of the catalyst is deteriorated in a catalytic reaction performed at a high temperature, the present invention can prolong the lifetime of the catalyst by lowering the reaction temperature in an endothermic reaction using a two or more-stage catalytic reactor.

Further, when the catalyst component reacts with HF to form a metal fluoride, the specific surface area of the catalyst decreases and the decomposition activity decreases. Thus, the present invention reduces the catalyst poisoning problem by the reaction product of the catalyst (e.g., HF) by lowering the catalyst handling capacity (e.g., 70% of the maximum value) in each catalytic reactor, .

In addition, in order to compact two or more reactor modules, the present invention is designed such that each reactor can be blocked as shown in FIG. 3, and then the two or more first reactor blocks and the two or more second reactor blocks are alternately To provide a cylindrical, tapered or polygonal tubular reactor assembly having a central axis in the transverse direction.

Accordingly, the reactor assembly for PFC treatment according to the present invention comprises a catalytic reactor and a blocked acidic gas removal reactor which are blocked so that the reactor modules can be compactly assembled. At this time, the gaseous product discharged from the first reactor (104) is directly introduced into the second reactor (102) adjacent to the first reactor, and the gas discharged from the second reactor (102) And introduced directly into the first reactor 104 (Figure 3). In each of the blocked first reactors 104, the PFC-containing gas is subjected to a hydrolysis reaction by a catalyst, and in each of the blocked second reactors 102, the PFC hydrolyzate product is treated with an acid gas removing agent to perform PFC hydrolysis Some or all of the acid gas can be removed from the product.

In the case of the reactor assembly having the structure shown in FIG. 3, the first reactor 104 is all filled with a catalyst for hydrolysis reaction, the second reactor 102 is filled with a solid acidic gas removing agent, The gas is introduced into the first reactor 104, is converted into the hydrolyzate gas of the PFC while being brought into contact with the catalyst in the reactor, and the hydrolyzate gas of the PFC discharged from the first reactor is introduced into the first reactor 104 May be introduced directly into the second reactor 102 to remove the acid gas in the hydrolyzate of the PFC and then be discharged from the second reactor 102 and introduced into the first reactor 104 in the downstream stage.

At this time, the introducing portion of the at least one first reactor 104 and the introducing portion of the at least one second reactor 102 may be provided with a distributor plate 110 for guiding the fluid flow. The shape and / or structure of the dispersion plate is not limited as long as the fluid can be distributed evenly to the first reactor and the second reactor and allowed to react, or in the case of the second reactor to be distributed only to a part of the lower portion of the reactor, May have a plurality of nozzles disposed at the outlet, or may be in the form of a blower. In addition, the diffuser plate may be a rotator having a flow path or nozzle capable of evenly distributing the fluid to a desired area.

The upper portion of the first reactor block 104 is provided with a catalyst inlet 120a for hydrolysis reaction or the upper portion of the second reactor block 102 is provided with an acid gas eliminator inlet 120a Can be. Furthermore, a stopper 120b may be attached to the input port 120a.

The catalyst used in the first reactor for carrying out the PFC hydrolysis reaction according to the present invention may be prepared by molding the PFC in the waste gas as it is or in the form of spheres, A bed can be used in the reactor.

At this time, the first reactor block 104 can fill the catalyst particles between the supports of a mesh type having a size such that the gas can pass therethrough and the catalyst particles do not escape.

The catalyst for decomposing CF ₄ can decompose most of the PFC contained in the waste gas and can convert the carbon forming the PFC into CO _{2 so} that it can be mainly used for the waste gas generated in the semiconductor process. PFC can be usefully used in a process or a workplace where it is used or manufactured for the purpose of a cleaning agent, an etching agent, a solvent, a reaction raw material or the like.

Most of the catalysts applicable in catalytic cracking of PFC are solid acid catalysts, among which Al ₂ O ₃ catalysts are the most popular. As the catalyst for the hydrolysis reaction of the PFC, a spinel catalyst having an AB ₂ O ₄ composition and / or an aluminum phosphate catalyst may be used. As the metal A, Zn, Ni, Pd, Ti, Sn, Co, Zr, Ce and the like can be used. As the B metal, aluminum can be used.

The hydrolysis reaction between PFC and moisture is an endothermic reaction, and PFC decomposition proceeds rapidly because higher temperatures can induce spontaneous reactions that are easier to decompose. However, high temperatures degrade the thermal stability of the catalyst.

That is, the operation conditions of 500 to 800 ° C are the highest obstacle to maintaining the durability of the catalyst as a high temperature condition for maintaining the catalyst for a long time without physical or chemical change. In particular, the development of a catalyst having durability in a reaction atmosphere of 500 to 800 ° C. in which HF and water vapor generated as by-products are present at the same time is the key to commercialization.

In the present invention, the internal temperature of the first reactor during the catalytic decomposition of PFC may be preferably 600 to 750, more preferably 600 to 700 ° C, and most preferably 650 ° C.

In the conventional PFC treatment reactor, the reaction temperature in the hydrolysis reaction of PFC requires a temperature of 750 ° C as a temperature at which most PFCs can be hydrolyzed, that is, a decomposition rate of about 100%. However, according to the present invention, the hydrolysis reaction of PFC and the reaction of forming calcium fluoride (CaF ₂ ) from hydrofluoric acid (HF) formed from the hydrolysis reaction are continuously carried out, , The effect of consuming HF through the reaction of forming calcium fluoride (CaF ₂ ) in one reactor is exerted, and the efficiency of hydrolysis reaction is improved, resulting in a decomposition rate of 85% or more even at a temperature of 600 ° C , And a decomposition rate of 95% or more at 650 ° C (FIG. 1). Therefore, the present invention can lower the internal temperature of the reactor, and the energy saving effect can be exhibited by the reduction of the heat amount. As a result, RCS (Regenerative Catalytic System) can prevent the outflow of hydrofluoric acid, maximize RCS efficiency, and extend catalyst life.

In order to perform the hydrolysis reaction in the catalytic reactor, water may be heated in a heat exchanger before being introduced into the reactor and supplied in the form of steam. Preferably, pure water is used as the water to be supplied to the inside of the reactor, and the supply amount can be controlled in consideration of the hydrolysis reaction formula.

The water vapor contains a water / PFC molar ratio in the range of 1 to 100, and the PFC may be decomposed without deactivation of the catalyst by using 0 to 50% concentration of oxygen together with water vapor. If the content of water vapor is out of the above range, the reaction activity is decreased.

Meanwhile, since the PFC waste gas discharged from the semiconductor manufacturing industry using PFC contains process gases in addition to oxygen, nitrogen, moisture, etc., the waste gas treatment process can be constituted in several stages. Therefore, the process that can be included in the waste gas prior to removing the decomposition of PFC gases such as _{SiH 4, SiHCl 3, SiH 2} Cl 2, the silane gas component and HCl, a halogen gas, such as HF, HBr, F _2, Br _2, such as SiF ₄ The components can be separated or removed in advance using water. The waste gas containing PFC that can not be removed in the pretreatment process basically contains oxygen and nitrogen, and in some cases, moisture may be included.

Therefore, according to the present invention, in order to decompose and remove PFC under the atmosphere of steam and oxygen at a temperature of about 600 to 750 ° C. using a catalyst, the pretreated waste gas must be preheated to the reaction temperature. In this process, Can be added to adjust the amount of water vapor in the waste gas.

In the presence of water vapor, the waste gas is removed by hydrolysis of the PFC by the catalyst as it flows through the catalytic reactor. The fluorine (F) component constituting the PFC is converted mainly to fluoride such as HF and, depending on the kind of the perfluorinated compound, The nitrogen (N) or sulfur (S) components are converted to oxides such as CO ₂ , NO ₂ , and SO ₃ , respectively.

The solid acid gas removing agent for removing acidic gases such as HF, CO ₂ , NO ₂ , and SO ₃ may be in the form of a powder, a molded body having a predetermined shape, or a separator. The acid gas removing agent is preferably in the form of a pellet when considering ease of handling and the application of a packed reactor or cyclone. The pellet may be formed into a cylindrical shape or a spherical shape, but is not limited thereto. In addition, the solid acidic gas removing agent can absorb a part of the acid gas and change it into another compound, physically or chemically adsorb it, or selectively remove it through the separator.

As illustrated in FIGS. 3 (a) and 3 (b), an acidic gas eliminator inlet may be provided in the upper portion of the second reactor block 102, and an acidic gas eliminator outlet may be provided in each of the lower portions .

When the acidic gas removal reactor block is connected to the downstream of the PFC hydrolysis catalytic reactor block, the acid gas contained in the exhaust gas of the PFC hydrolysis catalytic reactor block reacts with the solid acid gas removing agent and can be removed as a solid reaction product . Therefore, drainage is not generated from the PFC decomposition apparatus.

Non-limiting examples of the solid phase remover may be a salt of an alkali metal or an alkaline earth metal, preferably a salt of a metal of the same group as Ca, or a salt of a metal of the same group as Mg.

Calcium salts such as calcium oxide (CaO), calcium carbonate (CaCO ₃ ) and calcium hydroxide (Ca (OH) ₂ ) can not only form water or carbon dioxide by reacting with HF but also form calcium fluoride (CaF ₂ ) To immobilize HF.

CaO + 2HF -> CaF ₂ + H ₂ O

CaCO ₃ + 2HF - > CaF ₂ + H ₂ O + CO ₂

_{Ca (OH) 2 + 2HF →} CaF 2 + H 2 O

In order to solve the problem that the catalytic lifetime of the catalytic reactor is different from the lifetime of the solid acid gas removing agent in the acid gas removing reactor, the solid acid removing agent in the acid gas removing reactor is continuously supplied to the acid gas removing reactor, The acidic gas removal reactor may be designed so that the solid acidic gaseous removal agent is discharged from the acidic gas removal reactor after the reaction is carried out. For example, the solid acidic degassing agent may be continuously fed to the upper portion of the second reactor and discharged to the lower portion of the second reactor while removing the acid gas from the hydrolyzate of the PFC. In terms of commercialization, the acid gas removal reactor or the second reactor block can be designed as a cyclone. When a cyclone is used, a powdery acidic gas removing agent can be used.

Calcium fluoride (CaF ₂ ) is also referred to as calcium fluoride, and is referred to as fluorite as a mineral. The calcium fluoride is pure white, and the fluorine exits from the lattice is purple because of the F-center. Such calcium fluoride has a property of transmitting infrared rays or ultraviolet rays well, and is widely used for manufacturing optical devices, and is also a useful resource material used as a raw material for solvents and fluorine compounds. Therefore, when the method for producing calcium fluoride according to the present invention is used, calcium fluoride, which is a useful resource material from a perfluorinated compound in an exhaust gas such as a semiconductor process, can be produced, which is advantageous in terms of efficient reuse of resources.

In addition, by treatment of calcium fluoride with an inorganic acid such as hydrochloric acid or sulfuric acid, the fluorine gas can be generated very easily.

In the present invention, the first reactor block and the second reactor block material may be made of stainless steel or inconel material in consideration of the high temperature of the PFC hydrolysis reaction and the acid gas removal reaction. However, It is possible to use a material having lower heat durability than the above.

Meanwhile, the apparatus for treating PFC according to the present invention supplies a PFC-containing gas to be treated to the reactor assembly and has a vertical cross-section perpendicular to the central axis smaller than that of the reactor assembly; And a connection tube disposed between the inlet tube and the reactor assembly and being in the form of a tube that gradually expands along the fluid flow direction,

Wherein the PFC containing gas flowing along the central axis through the inlet pipe is designed to reach the front surface of the vertical section perpendicular to the central axis of the first reactor block located at the upstream end of the reactor assembly Another feature is.

Generally, if the cross-sectional area of the reactor assembly is greater than the cross-sectional area of the inlet tube and the flow rate of the fluid reaching the reactor assembly is large, the flow inertia causes the fluid flow to be concentrated at the center of the reactor assembly front surface. This results in a decrease in the uniformity of flow in the reactor assembly, which causes the catalysts located outside of the first reactor block to function insufficiently, which is a major cause of degradation of the PFC hydrolysis catalytic reaction efficiency. The fluid flow guide distribution plate can act to smoothly diffuse the fluid flow while leading the PFC containing gas introduced through the inlet pipe to the top of the reactor assembly. Accordingly, the connecting pipe and the dispersing plate according to the present invention can improve the uniformity of the fluid flow in the first reactor block at the extreme end of the reactor assembly due to its structural characteristics, thereby solving the problems described above.

In consideration of this point, the fluid flow guide distribution plate of the present invention is designed so that the reaction efficiency of the vertical cross section based on the central axis generated by the reaction of the PFC containing gas with the part of the catalyst in the first reactor block is reduced, It may be designed.

Fluid flow guide The diffuser plate can be configured in a tubular shape that gradually expands along the fluid flow direction. The vertical section of the one or more diffuser plates may be circular, oval or polygonal, which is a vertical section of the reactor assembly.

The fluid flow guide diffusing plate of the present invention may be such that two or more resembling diffusing plates are superposed so that their central axes coincide. As an example of the fluid flow guide dispersion plate, it may be a guide vane having a shape as shown in FIG. The diffusing plate is installed in the inside of the connecting pipe and has a concentric circular shape on the cross section, and the shape of the conical portion of the cone may be opened. The dispersion plate may have a plurality of guide vanes having different diameters on a cross section. A drift may occur during the process of distributing the flow after the fast flow supplied from the inlet pipe collides with the guide vane center block (FIG. 8).

The ratio of the cross-sectional areas of the fluid channels formed between the respective cones of the guide vanes is made equal at the front end and the rear end of the guide vane, so that the fluid flow direction through the plurality of guide vanes can be evenly diffused, This can improve the uniformity of the gas flow in the first stage reactor block of the reactor assembly.

In one embodiment of the present invention, the vertical cross section of the fluid flow guide distribution plate may be similar to the vertical cross section of the connection pipe, and the center axis of the dispersion plate is aligned with the central axis of the connection pipe.

In one embodiment of the present invention, the vertical cross-section of the fluid flow guide distribution plate may be such that it resembles the vertical cross-section of the reactor assembly and the central axis of the dispersion plate is aligned with the central axis of the reactor assembly.

Preferably, the vertical section of the diffuser plate, the vertical section of the connecting tube, and the vertical section of the reactor assembly resemble one another and the diffuser plate is connected such that the central axis of the diffuser plate, the central axis of the connecting tube, It may be disposed inside the pipe.

In the PFC treatment apparatus of the present invention, the inflow pipe may include a nozzle for supplying or injecting the PFC-containing gas in the radial direction with respect to the central axis of the inflow pipe. The apparatus may further include an orifice ring disposed between the inlet pipe and the dispersion plate for temporarily expanding the fluid flow of the PFC containing gas prior to the fluid flow diffusion in the dispersion plate.

4 is a schematic diagram of a system for simulating gas flows and pressures in a PFC processing apparatus according to one embodiment of the present invention, including a guide vane and a polygonal tubular reactor assembly installed near an inlet tube for supplying a PFC- And the geometry of a PFC processing device. FIG. 6 shows a computational domain for computer simulation of the PFC processing apparatus, FIG. 7 shows a pressure distribution at the time of computer simulation of the PFC processing apparatus, FIG. 8 shows a PFC processing apparatus The flow of computer simulation is shown.

In the PFC processing apparatus of the present invention, the PFC-containing gas introduced along the central axis through the inlet pipe first reaches the first reactor block, which is the catalytic reactor of the reactor assembly.

According to the present invention, the dispersion plate installed inside the connection pipe and guiding the fluid flow can be designed so as to maximize the flow velocity of the gas flowing into the entire surface of the catalyst layer, so that a large part of the catalyst can be operated in a uniform load condition as much as possible 8). In addition, design changes of the fluid flow guide distribution plate may cause a rapid flow velocity through the reactor assembly center to disappear (FIG. 8). Furthermore, through the design modification of the fluid flow guide distributor plate, the flow flow in the catalytic reactor at each stage from at least the second module stage can be made relatively uniform and the flow uniformity at the cross section can be improved (FIG. 8).

As shown in FIG. 7, when the fluid flow guide dispersion plate is installed inside the connection pipe upstream of the first reactor block, the flow uniformity by the fluid flow guide distribution plate causes the upstream / downstream differential pressure of the catalyst reactor (330Pa - > 144Pa) as compared with the PFC treatment apparatus.

In the PFC treatment apparatus of the present invention, the PFC-containing gas introduced along the central axis through the inlet pipe reaches the first reactor block, which is the catalytic reactor of the reactor assembly, while receiving the resistance of the catalyst layer, (Fig. 8). Therefore, in order to reduce the back flow generated near the inlet pipe from the resistance of the catalyst layer located at the upstream end of the reactor assembly, the thickness of the first reactor block located at the upstream end of the reactor assembly, or the thickness of the catalyst layer filled therein, Can be adjusted to be smaller.

According to the present invention, when the catalytic reaction-product removal reaction is carried out by using a reactor for reactor for catalytic reaction and a reactor for product rejection, and one reactor module is connected in series, the catalytic reaction efficiency can be increased by equilibrium breakthrough . In addition, two or more blocked reactors and two or more blocked second reactors may be designed to be adjacent to each other so that two or more reactor modules can be compactly installed.

For example, according to the present invention, when a reactor module including a PFC hydrolysis catalytic reactor and a reactor for removing acidic gas from the hydrolyzate gas with a solid-phase remover is used in two or more stages, the decomposition temperature can be significantly lowered to 650 ° C or lower Therefore, it is advantageous in that it is easy to reduce the operating cost of the continuous operation and ensure the durability of the system, and to completely suppress the generation of thermal NO _x due to N ₂ present in the exhaust gas. In addition, as the hydrolyzate gas is consumed, the reaction of the hydrolysis is dominated by the equilibrium breakthrough, thereby improving the hydrolysis efficiency of the PFC and increasing the reaction activity. There is an advantage in terms of the energy utilization efficiency of the battery.

The apparatus for treating PFC according to the present invention further reduces the reaction deviation of the vertical section based on the central axis generated by the reaction of the PFC-containing gas with a part of the catalyst in the first reactor block through the design of the additional fluid flow guide dispersing plate So that the reaction efficiency can be increased.

FIG. 1 shows the results of computational simulation of the RCS performance of a single CF ₄ catalytic cracking reactor and a three-stage reaction-separation configuration.
FIG. 2 is a conceptual diagram schematically showing a reaction process when two stages of a reactor module having a PFC hydrolysis catalyst and a solid acid gas removing agent are connected in series.
FIGS. 3 (a), 3 (b) and 3 (c) are diagrams showing the results of a comparison between two or more blocked first reactors filled with a catalyst for hydrolysis reaction and two or more second reactors blocked with a solid acid gas- FIG. 2 is a schematic and exploded perspective view of a PFC processing apparatus connected in series with a PFC processing apparatus; FIG.
4 is a perspective view, a front view, and a side view showing a geometry of a PFC processing apparatus according to an embodiment of the present invention.
5 is a side view of a fluid flow guide distribution plate according to one embodiment of the present invention.
FIG. 6 illustrates a computational domain for computer simulation of a PFC processing apparatus according to an embodiment of the present invention.
FIG. 7 is a graph showing a pressure distribution during the simulation of the PFC treatment apparatus according to an embodiment of the present invention.
FIG. 8 is a graph showing the flow of the PFC processing apparatus according to one embodiment of the present invention during the computer simulation.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are intended to clearly illustrate the technical features of the present invention and do not limit the scope of protection of the present invention.

Example  1: Fabrication of four-stage reactor module for treating perfluorinated compound

As shown in FIG. 3 (a), the reactor modules having the PFC decomposition catalytic reactor and the HF elimination reactor were connected in series in four stages. At this time, a P / Al ₂ O ₃ commercial catalyst was filled in the catalytic reactor for PFC decomposition, and Si (40 wt.%) / CaO (60 wt.%) Beads were filled as a reducing agent in the HF elimination reactor.

Experimental Example  1: Operation efficiency of 4-stage reactor for treating perfluorinated compounds

In order to evaluate the operation efficiency of the four-stage reactor module for treating the perfluorinated compound prepared in Example 1, perfluorocompound hydrolysis reaction and HF solid phase reductant immobilization reaction were carried out in each of the above reactors, and CF ₄ was investigated. Specifically, as a condition of the hydrolysis reaction of the perfluorinated compound, the CF ₄ injection concentration was 3,000 ppm, the steam injection concentration was 8%, and the remaining gas was nitrogen (N ₂ ). The space velocity was 2,000 / h.

For comparison, the conversion of CF ₄ was investigated under the same reaction conditions using the same catalytic reactor and catalyst for PFC decomposition as in Example 1, without HF elimination reactor as a control.

The CF ₄ conversion rate represents the ratio of CF ₄ converted by the hydrolysis reaction of the initial CF ₄ and was calculated by the following equation.

As a result, when only the catalyst was constituted as the control, the conversion of CF ₄ was 90%, and the conversion of CF ₄ in Example 1 was 99%.

When a cycle consisting of a perfluorinated compound hydrolysis reaction and a HF elimination chemical reaction to form CaF ₂ from HF is carried out four times using the four-stage reactor module of Example 1, as if CaF ₂ is formed in one reactor The effect of consuming HF is exerted through the reaction, and the efficiency of the hydrolysis reaction is improved, and the decomposition rate can be 99% at 700 ° C. Therefore, the internal temperature of the reactor can be lowered and the energy saving effect can be exhibited by the reduction of the heat amount.

Claims (17)

An apparatus for treating a perfluoro compound (PFC)
(i) a cylindrical, tapered or polygonal tubular reactor assembly having a transverse center axis,
A first reactor block for carrying out a hydrolysis reaction with a catalyst for a PFC containing gas; And a second reactor block for removing acid gas from gaseous products discharged from the first reactor block, wherein the reactor modules are connected in series in two or more stages,
Two or more first reactor blocks and two or more second reactor blocks are alternately formed so as to be adjacent to each other,
In the direction of the central axis, the gaseous product fluid discharged from the first reactor block is introduced directly into the second reactor block adjacent to the first reactor block, and the gas fluid discharged from the second reactor block at the previous stage A reactor assembly directly introduced into the first reactor block;
(ii) an inlet pipe that feeds the PFC containing gas to be treated to the reactor assembly and has a vertical section perpendicular to the central axis smaller than a vertical section of the reactor assembly;
(iii) a connection tube installed between the inlet tube and the reactor assembly and in the form of a tube that gradually expands along the fluid flow direction; And
(iv) a dispersion plate installed inside the connection pipe for guiding the fluid flow,
And a fluid flow guide distribution plate having a shape designed to allow the PFC containing gas flowing along the central axis through the inlet pipe to reach the front face of the vertical section of the center axis of the first reactor block located at the upstream end of the reactor assembly,
Wherein a cycle of the PFC hydrolysis catalytic reaction and the acid gas elimination reaction is repeated twice or more in the reactor assembly so that the efficiency of the forward catalytic reaction is improved by the equilibrium breakthrough.
The fluid flow guide distribution plate according to claim 1, wherein the fluid flow guide distribution plate is designed to increase the reaction efficiency by reducing the reaction deviation of the vertical cross section with respect to the central axis generated by the reaction of the PFC containing gas with the part of the catalyst in the first reactor block In PFC treatment.
2. The method of claim 1 wherein the thickness of the first reactor block located at the upstream end of the reactor assembly or the thickness of the catalyst bed packed thereon is varied to reduce the back flow generated near the inlet tube from the resistance of the catalyst bed located at the upstream end of the reactor assembly Wherein the first reactor block is smaller than the first reactor block.
The PFC processing apparatus according to claim 1, wherein the vertical section of the dispersion plate is similar to the vertical section of the connection pipe, and the center axis of the dispersion plate is aligned with the center axis of the connection pipe.
The apparatus of claim 1, wherein the vertical section of the diffuser plate is similar to the vertical section of the reactor assembly and the central axis of the diffuser plate is aligned with the central axis of the reactor assembly.
The method of claim 1, wherein the vertical section of the diffuser plate, the vertical section of the connecting tube, and the vertical section of the reactor assembly are similar to each other so that the central axis of the diffuser plate, the central axis of the connecting tube, Wherein the dispersion plate is disposed inside the connection pipe.
2. The PFC processing apparatus according to claim 1, wherein the two or more resilient diffusers are superposed so that their central axes coincide with each other.
The method of claim 1, wherein the first reactor block is filled with a catalyst for hydrolysis reaction, the second reactor block is filled with a solid acidic gas scavenger,
The PFC-containing gas is introduced into the first reactor block, is converted into the hydrolyzate gas of the PFC while being in contact with the catalyst in the reactor, and the hydrolyzate gas of the PFC discharged from the first reactor block is introduced into the first reactor block Is introduced directly into the second reactor block to remove the acid gas in the hydrolyzate of the PFC and then discharged from the second reactor block and introduced into the first reactor block at the following stage.
2. The PFC processing apparatus according to claim 1, wherein the reactor modules are connected in series in three or four stages.
The PFC treatment apparatus according to claim 1, wherein a catalyst inlet for hydrolysis reaction is provided in an upper portion of the first reactor block, and an acid gas removing agent inlet is provided in an upper portion of the second reactor block.
The process of claim 1, wherein the solid acidic degassing agent is continuously fed to the top of the second reactor block and discharged to the bottom of the second reactor block while removing acidic gas from the hydrolyzate of the perfluorinated compound. Device.
2. The PFC processing apparatus according to claim 1, wherein operating conditions are set so that the first reactor block in each stage performs 50 to 99% of the maximum catalyst processing capacity of each reactor block.
The PFC processing apparatus according to claim 1, wherein the reaction temperature is lower than that in the case of using the reactor module having the same reactant conversion rate when the catalytic reaction is an endothermic reaction.
The method according to claim 1, wherein the second reactor for removing the acidic gas is a PFC which is characterized by the use of an acidic gas removing agent such as calcium oxide (CaO), calcium carbonate (CaCO ₃ ), calcium hydroxide (Ca (OH) ₂ ) Processing device.
The PFC treatment apparatus according to claim 1, wherein the second reactor for removing the acid gas is capable of absorbing HF using an acidic gas removing agent and chemically reacting to form calcium fluoride (CaF ₂ ).
A method for treating a perfluorinated compound (PFC) in a PFC treating apparatus according to any one of claims 1 to 15,
Characterized in that for the PFC containing gas in the first reactor block a hydrolysis reaction is carried out by means of a catalyst and in the second reactor block the acid gas in the hydrolyzate gas of the PFC is removed.
A method for producing calcium fluoride from a perfluorinated compound (PFC) in the PFC treatment apparatus according to any one of claims 1 to 15,
For the PFC containing gas in the first reactor block, a hydrolysis reaction is carried out by a catalyst, and in the second reactor block, HF in the PFC hydrolyzate gas is reacted with the solid phase HF remover to form calcium fluoride (CaF ₂ ) Characterized in that the calcium fluoride is produced.

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