JP2016075560A - Recombination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst type recombination device capable of miniaturizing the whole device.SOLUTION: A recombination device includes: a catalyst part 3 for introducing processing object gas containing hydrogen and oxygen, and recombining hydrogen and oxygen; and such a cylindrical part 2 that the processing object gas after being treated in the catalyst part 3 is circulated through the inner part thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a recombination apparatus for combining hydrogen and oxygen using a catalyst, and more particularly to a recombination apparatus installed in a nuclear-related facility such as a nuclear power plant.

  When a severe accident occurs at a nuclear power plant, the temperature of the fuel cladding tube becomes high due to a decrease in the cooling capacity of the core, and zirconium that is used as the cladding tube material reacts with the coolant (water)-Zirconium A large amount of hydrogen may be generated by the radioactive decomposition of water, which is decomposed by radiation from reaction, fission products, and the like.

  If this state is left unattended, the hydrogen concentration may reach the explosion limit and cause a hydrogen explosion. If the reactor containment vessel or reactor building is damaged by the hydrogen explosion, radioactive materials may be released into the environment. Therefore, a means for preventing a hydrogen explosion at the time of a severe accident is necessary.

  Conventionally, a recombination apparatus is known for recombining hydrogen generated by a water-zirconium reaction with oxygen to lower the hydrogen concentration in a containment vessel or a reactor building. As one of such recombination apparatuses, a catalytic recombination apparatus that can recombine hydrogen and oxygen at room temperature using a catalyst has been developed (Patent Documents 1 and 2).

  Catalytic recombination devices used in nuclear facilities are required to be able to operate independently without using a power source or external power in consideration of operational reliability. The buoyant force is used as the driving force.

  The catalytic recombination apparatus includes a catalyst structure including a catalyst carrier that supports a catalyst.

JP 2011-174773 A Japanese Patent Laid-Open No. 11-94992 Japanese Patent Laid-Open No. 10-227885

  The catalyst structure in the catalytic recombination apparatus of Patent Document 1 is configured by filling a granular catalyst in a (longitudinal) box-shaped cartridge, and arranging a plurality of cartridges filled with the catalyst vertically (see FIG. Bull filling type).

  In the pebble-filled catalytic recombination apparatus, since the catalyst surface area (reaction area) per unit volume can be increased, the reaction per unit volume is large, and there is a possibility that the size can be reduced. However, due to the non-uniformity of the voids between the catalyst particles, there are problems that the residence time distribution of the reactant flow, the drift, the blow-through, etc. occur, and the pressure loss of the catalyst layer increases. In particular, in order to secure natural convection against a large pressure loss, a large chimney is required to obtain a large chimney effect, and the recombination apparatus becomes large as a whole.

  Further, the catalyst structure in the catalytic recombination apparatus of Patent Documents 2 and 3 has a structure (plate type) in which a plurality of catalysts are formed into a plurality of plates and arranged vertically, and a gas to be treated flows between the plates. ).

  In the plate-type catalytic recombination apparatus, the gas to be treated flows between the plates arranged in parallel with an appropriate interval, so that the residence time distribution of the reactant flow, drift, blow-off, etc. occur, and the catalyst Problems such as pressure loss in the layer do not occur. However, in the plate-type catalytic recombination apparatus, since the catalyst is attached only to the surface of the plate, the surface area of the catalyst per unit volume is smaller than that of the pebble-filled type. If it is going to ensure, catalyst structure itself will enlarge.

  If there is a possibility that hydrogen generated during a severe accident at a nuclear power plant may accumulate in a relatively narrow place, a recombination device can be installed in the narrow place to efficiently reduce the hydrogen concentration. desirable. However, since the conventional recombination apparatus is large as described above, it has been difficult or impossible to install in a narrow place.

  The present invention has been made in view of the above-described problems of the prior art, and it is an object of the present invention to provide a catalytic recombination apparatus that can reduce the overall size of the apparatus.

  In order to solve the above-mentioned problem, the present invention according to the first aspect is a recombination device for combining hydrogen and oxygen using a catalyst, and has a large number of through-holes carrying the catalyst on the surface, A catalyst part that introduces a gas to be treated containing hydrogen and oxygen and recombines the hydrogen and oxygen; and a cylindrical part through which the gas to be treated after being treated by the catalyst part flows. , Comprising.

  The present invention according to a second aspect is characterized in that, in the present invention according to the first aspect, the catalyst part is formed by partitioning through holes adjacent to each other with a thin wall.

  The present invention according to a third aspect is characterized in that, in the present invention according to the first or second aspect, a cross section of the through hole is a polygon.

  According to a fourth aspect of the present invention, in the present invention according to any one of the first to third aspects, the buoyancy of the gas caused by the heat generated by the recombination reaction of the hydrogen and the oxygen in the catalyst unit The effective length of the cylindrical portion and the height of the catalyst portion are set so that the flow of the gas to be treated is generated in the through hole against the flow resistance in the through hole. To do.

  The present invention according to the fifth aspect is characterized in that, in the present invention according to the fourth aspect, the height of the catalyst portion is about 5 mm or less.

  The present invention according to a sixth aspect is characterized in that, in the present invention according to the fourth or fifth aspect, the flow path equivalent diameter of the through hole is 1 mm to 1.79 mm.

  According to a seventh aspect of the present invention, in the present invention according to any one of the first to sixth aspects, an intrusion for preventing intrusion of water or foreign matter into the cylindrical portion on the outlet side of the cylindrical portion. It further has a prevention means.

  The present invention according to an eighth aspect is the present invention according to the seventh aspect, wherein the intrusion prevention means includes an umbrella-shaped member that seals the upper end opening of the cylindrical portion, and the upper end portion of the cylindrical portion is A gas outlet is formed on the side surface.

  The present invention according to a ninth aspect is characterized in that, in the present invention according to any one of the first to eighth aspects, the catalyst structure is detachably attached to an inlet portion of the cylindrical portion. To do.

  According to the recombination apparatus according to the present invention, the entire apparatus can be downsized by downsizing the structure of the catalyst portion.

1 is a schematic configuration diagram of a catalytic recombination device according to an embodiment of the present invention. The arrow line view along the II-II line of FIG. FIG. 3 is an arrow view along the line III-III in FIG. 1. The arrow line view along the IV-IV line of FIG. The top view which expanded and showed the catalyst support member of the recombination apparatus shown in FIG. FIG. 6 is a longitudinal sectional view of the catalyst support member shown in FIG. 5. The bottom view of the catalyst support member shown in FIG. The top view which expanded and showed the catalyst holder of the recombination apparatus shown in FIG. The longitudinal cross-sectional view of the catalyst holder shown in FIG. The bottom view of the catalyst holder shown in FIG. It is a figure for demonstrating the structure of the catalyst part of the recombination apparatus shown in FIG. 1, (a) is the top view which showed the catalyst part typically, (b) is AA sectional drawing of (a). . (A) is the top view which expanded and showed the XIIa part of Fig.11 (a), (b) is the longitudinal cross-sectional view which expanded and showed the XIIb part of FIG.11 (b). The longitudinal cross-sectional view which expanded and showed the XIII part of FIG. The graph which showed the relationship between the thickness of a catalyst part, and the amount of hydrogen treatment. The schematic diagram which showed the flow-path structural model of the recombination apparatus shown in FIG. The graph which showed the optimal range of the recombination apparatus shown in FIG.

  Hereinafter, a catalytic recombination apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  The recombination apparatus according to this embodiment is an apparatus for combining hydrogen and oxygen using a catalyst, and is installed in a nuclear-related facility such as a nuclear power plant.

  As shown in FIGS. 1 to 4, the recombination apparatus 1 according to the present embodiment has a cylindrical portion 2 through which a processing target gas containing hydrogen and oxygen flows. The cylindrical part 2 is comprised with the cylindrical member. However, the member which comprises the cylindrical part 2 is not restricted to a cylindrical member, For example, the cylindrical member of a square cross section can also be used.

  At the lower end of the cylindrical portion 2, a catalyst structure 4 including a catalyst portion 3 having a large number of through holes (flow paths) carrying a catalyst on the surface is provided. The catalyst structure 4 has a disk-like or cylindrical outer shape and is fitted to the inner peripheral side of the circumferential protrusion on the upper surface of the structure support member 5 shown in FIGS. Attached to the lower end opening of the cylindrical portion 2 together with the member 5.

  The catalyst structure 4 includes the catalyst holder 6 shown in FIGS. 8 to 10 and the catalyst portion 3 shown in FIG. The catalyst holder 6 is composed of a substantially annular frame-shaped holding member that holds the peripheral edge portion of the catalyst portion 3, and the disc-shaped or cylindrical catalyst portion 3 is fitted into the concave portion of the catalyst holder 6. The catalyst holder 6 can be formed of, for example, a stainless material.

  A large number of through-holes (flow paths) provided in the catalyst unit 3 are polygons such as a triangle, a quadrangle, a pentagon, or a hexagon, and the flow paths adjacent to each other are partitioned by thin walls. (Honeycomb structure). The catalyst part uses a porous ceramic or stainless steel as a support. That is, a large number of through holes 7 are formed in the catalyst portion 3 as shown in FIG. The through-hole 7 extends along the direction in which the processing target gas is introduced into the cylindrical portion 2 (in this example, the axial direction of the cylindrical portion 2). Is distributed).

  A catalyst is applied to the catalyst portion 3 at least on the inner peripheral surface of each through hole 7. By adopting the honeycomb structure, the specific surface area (surface area per unit volume) of the catalyst part 3 can be increased, so that the contact efficiency between the gas to be treated and the catalyst can be greatly increased.

  As shown in FIG. 13, a bowl-shaped portion 2 </ b> A is formed at the lower end portion of the tubular portion 2. A peripheral portion 5A of the structure support member 5 is disposed between the flange-shaped portion 2A of the cylindrical portion 2 and the external support piece 8, and these members are fixed in a laminated state by bolts 9.

  As shown in FIG. 1, on the outlet side (upper end side) of the cylindrical portion 2, an intrusion prevention means 10 for preventing intrusion of water and foreign matter into the cylindrical portion 2 is provided. The intrusion prevention means 10 includes an umbrella-like member 11 that seals the upper end opening of the tubular portion 2. In response to an accident at a nuclear power plant, spray water may be sprayed inside the reactor containment vessel, but the umbrella-shaped member 11 can prevent the spray water from entering the tubular portion 2. . Thereby, it can prevent that basic reaction is inhibited by water adhering to a catalyst.

  A gas outlet 12 is formed on the side surface on the upper end side of the cylindrical portion 2, and the gas flowing through the cylindrical portion 2 is discharged to the side via the gas outlet 12. A mesh member 13 is provided at the gas outlet 12, and the mesh member 13 functions as an intrusion prevention means 10 that prevents intrusion of foreign matter (flying objects) into the cylindrical portion 2.

  The recombination device 1 according to the present embodiment does not require a power source for its operation, and uses natural convection in the cylindrical portion 2 as a driving force. That is, natural convection in the cylindrical portion 2 against the flow resistance in the plurality of through holes 7 of the catalyst portion 3 due to the buoyancy of the gas due to the heat generated by the recombination reaction of hydrogen and oxygen in the catalyst structure 4 The effective length of the cylindrical portion 2 (the length of the portion that contributes to the occurrence of natural convection) and the height of the catalyst portion 3 are set.

  That is, when the gas to be processed of the recombination apparatus 1 flows from the lower end inlet of the cylindrical portion 2 and passes through the catalyst structure 4, water vapor is generated by the recombination reaction of hydrogen and oxygen. In the presence of a catalyst, the recombination reaction occurs even at room temperature. The gas is heated by the heat generated by the recombination reaction to generate buoyancy due to the density difference, and natural convection is generated using this as a driving force (chimney effect). The treated gas containing the generated water vapor is discharged to the outside from the gas outlet 12 on the upper side surface of the cylindrical portion 2.

  FIG. 14 shows the relationship between the catalyst height (the height of the catalyst unit 3) and the hydrogen treatment amount in the case of a hydrogen concentration of 4 vol%, a reaction rate of 100%, and natural convection. The hydrogen processing amount indicates the processing amount (kg / h) per unit inflow area of the gas to be processed into the recombination apparatus 1.

As can be seen from FIG. 14, the amount of hydrogen treatment decreases as the catalyst height (the height of the catalyst unit 3) increases. Since the reaction between hydrogen and oxygen is very fast, the reaction is substantially completed immediately after the gas to be treated is introduced into the catalyst unit 3. For this reason, even if the catalyst height is increased, there is almost no contribution to reaction promotion. Rather, since the flow resistance in the catalyst unit 3 increases, the flow rate of the gas to be processed decreases, and as a result, the amount of hydrogen treatment decreases.
Therefore, even if the height of the catalyst part is larger than 5 mm, the hydrogen treatment capacity is reduced, while the recombination apparatus is enlarged. On the other hand, if the height of the catalyst part is smaller than 5 mm, the hydrogen treatment capacity is improved. And it turns out that a recombination apparatus can be reduced in size.

  Next, a practically desirable range (major part dimensions) for the coupling device in the present embodiment will be considered.

  FIG. 15 shows a flow path configuration model of the recombination device according to the present embodiment.

  The buoyancy accompanying heat generated by the catalytic reaction of hydrogen and oxygen is expressed by the following formula (1) when the flow is in a laminar flow region.

P _A = Δρ × g × h ₂ (1)
here,
P _A : Buoyancy due to heat generation by catalytic reaction [N / m ² ]
Δρ: density difference ρ _IN −ρ _OUT [kg / m ³ ]
ρ _IN : Inlet side gas density [kg / m ³ ]
ρ _OUT : outlet side gas density [kg / m ³ ]
g: Gravity acceleration [m / s ² ]
h ₂ : Chimney height [m]
The chimney height is an effective height corresponding to a portion where the chimney effect occurs in the cylindrical portion 2.

  The flow resistance in the catalyst part 3 is represented by the following formula (2).

P _B = 32 × μ × h ₁ × V _IN / d ₁ ² (2)
here,
P _B : Flow resistance [N / m ² ]
μ: Viscosity coefficient [Pa · s]
h ₁ : catalyst height [m]
V _IN : Inlet flow velocity [m / s]
d ₁ : catalyst channel equivalent diameter [m]
Assuming the flow resistance _{P B} in buoyancy _{P A} and the catalyst unit 3 due to heat generated by the catalyst are balanced with _(P A = _{P B),} and formula (1) from equation (2) becomes less.

h ₂ / h ₁ = 32 × μ × V _IN / d ₁ ² / (Δρ × g) (3)

When H = h ₁ + h ₂ , the following is obtained.

H / h ₁ = 32 × μ × V _IN / d ₁ ² / (Δρ × g) +1 (4)
FIG. 16 shows a practically desirable range (blacked portion in the graph) for the recombination device according to the present embodiment created based on the formula (4).

Since the upper limit of H is set to 300 mm for the downsizing of the recombination apparatus and the lower limit of h ₁ is set to 3 mm from the manufacturing limit, in FIG. 16, H / h ₁ is 100 for the upper limit and H = h for the lower limit. ₁ because it is the case of ₁ (h ₂ = 0 mm). The lower limit of _VIN is set to 0.3 m / s in consideration of the hydrogen treatment amount of the existing recombination apparatus. The upper limit of d ₁ is 1.79 mm based on the catalyst part that can be manufactured.

  As described above, according to the catalytic recombination device 1 according to the present embodiment, the catalyst unit 3 has through-holes 7 having a large number of cross-sections along the introduction direction of the gas to be processed into the cylindrical unit 2. Is formed and the height is small, it is possible to secure a small and high processing capacity by securing a large catalyst area, and to realize a reduction in pressure loss in the catalyst layer. The proposal for pressure loss in the catalyst layer is to ensure natural convection due to the chimney effect even with a relatively small cylindrical part, so the amount of hydrogen treated per unit volume of the catalyst is greatly increased compared to conventional recombination equipment. Can be increased.

  In the recombination apparatus 1 according to the present embodiment based on the above examination results, the catalyst height (thickness of the catalyst unit 3) is set to 5 mm in consideration of the hydrogen treatment amount of the existing recombination apparatus. The diameter of the catalyst unit 3 is 93 mm, and the overall dimensions of the entire apparatus are a diameter of 105 mm, a height of 420 mm, and a weight of about 2 kg. This is much smaller than the size and weight of the existing recombination apparatus.

  However, the thickness of the catalyst part and the overall dimensions of the recombination apparatus according to the present invention are not limited to these numerical values, and are appropriately selected and set within a practically desirable range as described above, for example. be able to. As a result, not only the catalyst structure 4 including the catalyst part 3 but also the entire recombination apparatus including the cylindrical part can be greatly reduced in size as compared with the case of the conventional catalytic recombination apparatus. Thereby, size reduction and weight reduction of the whole apparatus can be achieved.

  Due to the small size and light weight of the recombination device 1, the device can be easily installed and removed, and the exposure amount of the worker can be reduced by shortening the work time.

  Further, the downsizing and weight reduction of the recombination device 1 makes it possible to install the recombination device 1 in a narrow place where hydrogen can accumulate, or to easily increase a large number of bases depending on the required amount of hydrogen treatment. It becomes possible to install.

  Further, according to the recombination device 1 according to the present embodiment, since the catalyst structure 4 is detachably attached to the lower end portion of the cylindrical portion 2 with the bolt 9, the bolt 9 is removed and the catalyst is removed from the cylindrical portion 2. By removing the structure 4, the catalyst can be easily replaced.

DESCRIPTION OF SYMBOLS 1 Recombination apparatus 2 Cylindrical part 2A Cylindrical part of a cylindrical part lower end 3 Catalyst part (perforated plate-shaped member)
DESCRIPTION OF SYMBOLS 4 Catalyst structure 5 Structure support member 5A Peripheral part of structure support member 6 Catalyst holder 7 Through hole of catalyst part 8 External support piece 9 Bolt 10 Intrusion prevention means 11 Umbrella-shaped member 12 Gas outlet 13 Net-like member

Claims (9)

A recombination device for combining hydrogen and oxygen using a catalyst,
A catalyst part having a large number of through-holes carrying the catalyst on the surface, introducing a gas to be treated containing the hydrogen and oxygen, and recombining the hydrogen and oxygen;
A cylindrical part through which the gas to be treated after being treated by the catalyst part circulates;
A recombination device.   The recombination apparatus according to claim 1, wherein the catalyst part is formed by partitioning through-holes adjacent to each other with a thin wall.   The recombination apparatus according to claim 1, wherein a cross-section of the through hole is a polygon.   The flow of the gas to be treated is generated in the through hole against the flow resistance in the through hole by the buoyancy of the gas caused by the heat generated by the recombination reaction of the hydrogen and oxygen in the catalyst unit. The recombination apparatus according to any one of claims 1 to 3, wherein an effective length of the cylindrical portion and a height of the catalyst portion are set.   The recombination apparatus according to claim 4, wherein the height of the catalyst portion is about 5 mm or less.   The recombination apparatus according to claim 4 or 5, wherein a diameter corresponding to the flow path of the through hole is 1 mm to 1.79 mm.   The recombination device according to any one of claims 1 to 6, further comprising an intrusion prevention unit for preventing intrusion of water and foreign matter into the tubular portion on the outlet side of the tubular portion. The intrusion prevention means has an umbrella-like member that seals the upper end opening of the cylindrical portion,
The recombination apparatus according to claim 7, wherein a gas outlet is formed on a side surface of an upper end portion of the cylindrical portion. The recombination device according to any one of claims 1 to 8, wherein the catalyst structure is detachably attached to an inlet portion of the cylindrical portion.

Images