JP7344790B2 - Heat storage part structure of exhaust gas combustion treatment device and exhaust gas combustion treatment method - Google Patents

Description

The present invention relates to a heat storage part structure of a heat storage type exhaust gas combustion treatment apparatus, and an exhaust gas combustion treatment method performed using the heat storage part structure.

BACKGROUND ART A regenerative exhaust gas combustion treatment device is used as a device for combustion treatment of volatile organic compounds contained in exhaust gas from various factories. This is equipped with multiple heat storage parts that communicate with the combustion space, and has two modes: one in which untreated exhaust gas is introduced into the combustion space through the heat storage part, and the other in which the treated gas that has been combusted in the combustion space is introduced into the combustion space through the heat storage part. This is to switch each heat storage section to a mode in which heat is discharged to the outside. The treated gas, which has reached a high temperature in the combustion space, gives heat to a heat storage element placed in the heat storage section and is discharged as a low temperature, while the untreated exhaust gas is preheated by the high temperature heat storage element and then enters the combustion space. Since the exhaust gas is introduced, combustion treatment of exhaust gas can be performed with high thermal efficiency.

A ceramic honeycomb structure is generally used as a heat storage body disposed in a heat storage section of such a heat storage type exhaust gas combustion treatment device (see, for example, Patent Document 1). A honeycomb structure has cells partitioned by a large number of partition walls extending in a single direction, and exchanges heat with gas passing through the cells.

However, in the conventional heat storage type exhaust gas combustion treatment device, when the treated gas is discharged to the outside through the heat storage section, the combustion residue of volatile organic compounds is transferred to the gas inflow surface of the heat storage section, that is, when the treated gas is discharged to the outside through the heat storage section, It could accumulate on the surface in contact with the combustion space, causing the cells of the honeycomb structure to become clogged. When the cells become clogged, the gas flowability of the heat storage section decreases, and the honeycomb structure may be damaged due to an increase in pressure loss.

In particular, in recent years, as the uses of silicone resins have expanded, cases in which silicone resins are included in volatile organic compounds in exhaust gas are increasing. Silica produced by oxidative decomposition of silicone resin is acicular or fibrous, and becomes entangled to form a film that covers the cell openings of the honeycomb structure. Therefore, in exhaust gas combustion treatment equipment that processes exhaust gas containing silicone resin, there are problems such as a decrease in processing capacity in a short period of time due to clogging of the honeycomb structure, and frequent replacement of the honeycomb structure. There was a problem in that the treatment of exhaust gas had to be stopped.

Japanese Patent Application Publication No. 2002-195540

Therefore, in view of the above-mentioned circumstances, the present invention provides a heat storage type exhaust gas combustion treatment device in which the increase in pressure loss in the heat storage section is suppressed, and it is possible to perform combustion treatment of exhaust gas stably over a long period of time. An object of the present invention is to provide a heat storage structure and an exhaust gas combustion treatment method using the heat storage structure.

In order to solve the above problems, the heat storage section structure according to the present invention has the following features:
"Equipped with a plurality of heat storage parts communicating with a combustion space, exhaust gas containing volatile organic compounds is combusted in the combustion space, heat of the treated gas is recovered in the heat storage part, and the heat is supplied to the combustion space. Exhaust gas is preheated in the heat storage section, and each of the heat storage sections has an exhaust gas supply mode in which untreated exhaust gas is supplied, and a gas discharge mode in which combustion-treated gas in the combustion space is discharged; In a regenerative exhaust gas combustion treatment device that is switched to purge mode where purge gas is supplied,
Each of the heat storage parts is made up of multiple layers, and is connected to the lower part of the combustion space, and
The plurality of layers of the heat storage section includes a heat storage layer including a heat storage unit in which a solid ball-shaped heat storage body is irremovably housed in an air-permeable container made of an air-permeable material, and a honeycomb structure. equipped with both heat storage layers,
The heat storage layer constituted by the heat storage unit is provided so that only the uppermost layer of the heat storage section is in contact with the combustion space,
The heat storage body is a sphere having a size such that the number of heat storage bodies is N ³ when packed in the breathable container in the closest density, and (N-1) ³ of the heat storage bodies are filled in the breathable container. , which moves inside the breathable container by the pressure of the gas supplied in the purge mode, and has both the function of crushing the combustion residue of volatile organic compounds and the function of storing heat.

The material of the "solid ball-shaped heat storage body" is not particularly limited, and includes ceramics such as silicon carbide, aluminum titanate, alumina, and cordierite, metals such as aluminum, stainless steel, and copper, and composite materials of ceramics and metals. It can be done.

The heat storage unit structure of this configuration uses a heat storage unit in which a solid ball-shaped heat storage body is irremovably housed in an air-permeable container made of an air-permeable material. In the heat storage type exhaust gas combustion treatment device, a heat storage layer constituted by a heat storage unit is provided so as to be in contact with at least the combustion space. The ball-shaped heat storage body is easy to move, unlike the honeycomb structure used as a heat storage body in conventional exhaust gas combustion treatment equipment. Therefore, even if combustion residues of volatile organic compounds are deposited on the surface of the heat storage body, the combustion residues can be crushed by the movement of the heat storage body. The combustion residue that has been crushed into fine powder falls through the gaps between the heat storage bodies and passes through the heat storage section. Therefore, it is possible to effectively suppress an increase in pressure loss in the heat storage section due to the accumulation of combustion residues, and it is possible to stably perform combustion treatment of exhaust gas over a long period of time. In addition, since the solid ball-shaped heat storage body is housed in the breathable container in a non-removable manner, even if the heat storage body moves significantly so as to blow up, it will not fly out from the breathable container.

In addition to the above configuration, the heat storage structure according to the present invention has the following features:
“ The breathable container is a cube with a side of 10 cm to 30 cm, and the heat storage body has a diameter of 1 cm to 3 cm,
The filling rate of the solid ball-shaped heat storage body with respect to the air-permeable container may be 29% by volume to 68% by volume.

With this configuration, as will be described in detail later, a space suitable for the solid ball-shaped heat storage bodies to move inside the breathable container can be created between the heat storage bodies.

In addition to the above configuration, the heat storage structure according to the present invention has the following features:
"The solid ball-shaped heat storage body is a silicon carbide sintered body, the mass of each piece is 1.6 g to 15 g, and the diameter is 1.2 cm to 2.6 cm ,
The filling rate of the solid ball-shaped heat storage body with respect to the air-permeable container may be 34 % to 66 % by volume.

In the present invention, the ball shape adopted as a means for suppressing an increase in pressure loss in the heat storage section is the shape of the heat storage body itself. Therefore, it is desirable that this ball-shaped member has an excellent function as a heat storage body. Therefore, in the present invention, the ball-shaped heat storage body is made solid, and in this configuration, it is also made of a sintered body of silicon carbide, and the filling rate of the solid ball-shaped heat storage body with respect to the breathable container is 29% by volume. ~68% by volume. Since silicon carbide has high thermal conductivity, it can contribute to heat exchange up to the center of the solid ball-shaped heat storage body. In addition, by setting the filling rate within this range, as will be described in detail later, the heat capacity when the honeycomb structure used as a heat storage body in a conventional exhaust gas combustion treatment device is formed of silicon carbide sintered body, The heat capacity of the solid ball-shaped heat storage body accommodated in the air-permeable container of the same size as the honeycomb structure is made to be approximately the same, and the function as a heat storage body can be fully exhibited.

Next, the exhaust gas combustion treatment method according to the present invention includes:
``An exhaust gas combustion treatment method performed using the heat storage structure described above,
Recovering the heat of the treated gas by the solid ball-shaped heat storage body, and preheating the exhaust gas supplied to the combustion space with the heat of the solid ball-shaped heat storage body,
The solid ball-shaped heat storage body is blown up inside the breathable container by the gas pressure when gas is supplied from the outside to the combustion space via the heat storage unit, and the combustion residue of volatile organic compounds is blown up. By pulverizing and suppressing the accumulation of the combustion residue in the heat storage section, maintenance for suppressing an increase in pressure loss in the heat storage section is performed simultaneously with the combustion treatment of the exhaust gas.

One feature of the exhaust gas combustion treatment method of the present invention is that the member itself that exhibits the effect of suppressing the increase in pressure loss in the heat storage section is a heat storage body. In addition, maintenance to suppress the increase in pressure loss in the heat storage section is performed at the same time as the exhaust gas combustion process progresses.In other words, after detecting that the pressure loss has increased in the heat storage section, some kind of maintenance One of its major features is that it can maintain the desired state of the heat storage section while performing the original purpose of exhaust gas combustion treatment.

As described above, according to the present invention, in a heat storage type exhaust gas combustion treatment device, the increase in pressure loss in the heat storage part is suppressed, and the heat storage enables stable exhaust gas combustion treatment over a long period of time. It is possible to provide a heat storage section structure and an exhaust gas combustion treatment method performed using the heat storage section structure.

FIG. 1(a) is a perspective view of a breathable container, FIG. 1(b) is a perspective view of a breathable container formed of another material, and FIG. 1(c) is a perspective view of a breathable container with a different lid form. It is a schematic block diagram of a container. FIG. 2(a) is a schematic configuration diagram of a heat storage unit, and FIG. 2(b) is a schematic diagram illustrating how a heat storage body blows up in the heat storage unit. FIG. 3(a) is a longitudinal sectional view of the heat storage section structure of this embodiment, and FIG. 3(b) is a longitudinal sectional view of the heat storage section structure of a modification. FIG. 4 is a configuration diagram of a heat storage type exhaust gas combustion treatment device. FIG. 5 is an explanatory diagram of problems in a conventional heat storage structure using a honeycomb structure.

Hereinafter, a heat storage structure according to an embodiment of the present invention, a heat storage type exhaust gas combustion treatment device 100 employing this heat storage structure, and an exhaust gas combustion treatment method performed using the heat storage structure of this embodiment will be described. , will be specifically explained using drawings.

First, the schematic configuration of the exhaust gas combustion processing apparatus 100 will be described using FIG. 4. The exhaust gas combustion treatment device 100 includes a combustion furnace 90 and a plurality of heat storage units 60 each having a space communicating with a combustion space S, which is an internal space of the combustion furnace 90. The combustion furnace 90 includes a heating device 80 such as a burner for heating the combustion space S.

Here, as the plurality of heat storage units 60, a case where three heat storage units 60a, 60b, and 60c are successively arranged at the lower part of the combustion furnace 90 is illustrated. Untreated exhaust gas is supplied to each of the heat storage units 60a, 60b, and 60c from the exhaust gas supply pipe 21 via switching valves 31, 32, and 33, respectively. The untreated exhaust gas passes through the heat storage section 60 and is introduced into the combustion space S while rising. By heating the exhaust gas in the combustion space S, volatile organic compounds contained in the exhaust gas are combusted (oxidatively decomposed). When discharging the processed gas to the outside, the spaces of the heat storage units 60a, 60b, and 60c are communicated with the gas exhaust pipe 49 via the switching valves 41, 42, and 43, respectively. In addition, in order to expel the untreated exhaust gas staying inside the heat storage parts 60a, 60b, and 60c to the combustion space S, the purge gas supply pipe 22 is connected to the purge gas supply pipe 22 via the switching valves 51, 52, and 53, respectively. Gas is supplied to heat storage sections 60a, 60b, and 60c. As the purge gas, outside air or a treated gas discharged via the gas discharge pipe 49 can be used.

The plurality of heat storage units 60 are each switched between an exhaust gas supply mode in which untreated exhaust gas is supplied and a gas discharge mode in which treated gas is discharged, and some of the heat storage units 60 are in the exhaust gas supply mode. , the other heat storage units 60 are in the gas exhaust mode. Furthermore, when switching from the exhaust gas supply mode to the gas exhaust mode, the mode is switched to the purge mode in which purge gas is supplied to the heat storage section 60 prior to the gas exhaust mode. For example, the modes are switched such that one of the three heat storage units 60a, 60b, and 60c is in the exhaust gas supply mode, the other is in the gas exhaust mode, and the remaining one is in the purge mode. be exposed.

Note that the number of heat storage units 60 is not limited as long as it is plural. For example, if there are five heat storage units 60a to 60e, the mode switching is performed in the order of (1) to (5) as shown in Table 1. can be repeated.

As mentioned above, in the conventional exhaust gas combustion treatment device, the honeycomb structure H is used as a heat storage body, and as shown in FIG. A heat storage section 60 was configured. Then, in the exhaust mode in which the combustion-treated gas is discharged via the heat storage section 60, the combustion residue 70 of the volatile organic compound contained in the exhaust gas is transferred to the uppermost honeycomb structure H, that is, the combustion It is deposited on the honeycomb structure H in the layer that is in contact with the space S. The combustion residue 70 enters the cells of the honeycomb structure H and covers the openings of the cells, resulting in an increase in pressure loss in the honeycomb structure H.

Therefore, in this embodiment, at least a part of the heat storage section 60 is a heat storage unit 1 (in which a solid ball-shaped heat storage body B is irremovably housed in an air-permeable container 10 made of a material having air permeability). It consists of heat storage unit) . If there are multiple layers of heat storage bodies (heat storage layers) in the heat storage section 60, the uppermost layer in contact with the combustion space S is constituted by the heat storage unit 1 and is used as the heat storage layer. In other words, when the heat storage section 60 is composed of multiple layers of heat storage bodies, an example in which all the layers are composed of the heat storage unit 1 as shown in FIG. 3A is a reference example. In this embodiment, as shown in FIG. 3(b), only the uppermost layer in contact with the combustion space S is composed of the heat storage unit 1, and the other layers are composed of the honeycomb structure H. Since the combustion residue of volatile organic compounds accumulates when the treated gas flows from the combustion space S to the heat storage section 60, only one layer in contact with the combustion space S should be composed of the heat storage unit 1. If so, the desired effect can be fully obtained.

Note that although the illustration here shows a case in which one heat storage layer (one level of heat storage layer) is formed by arranging a plurality of heat storage units 1 in parallel in the horizontal direction, one heat storage layer is formed by a single heat storage layer. It is also possible to adopt a configuration consisting of one heat storage unit 1.

As illustrated in FIGS. 1(a), (b) and 2(a), the solid ball-shaped heat storage body B is housed in the air-permeable container 10 in a non-separable manner. The heat storage body B is accommodated in a container body 11 formed of material into a bottomed cylindrical shape, and the opening of the container body 11 is covered with a lid body 12 formed of a breathable material. I can do it. Alternatively, as illustrated in FIG. 1(c), the openings of a plurality of container bodies 11 each housing a heat storage body B are covered with one lid 12 made of a breathable material. It can be a mode.

Further, when a plurality of heat storage layers formed by the heat storage unit 1 are laminated, in the heat storage unit 1 constituting the uppermost layer, the opening of the container body 11 is set as above in order to irremovably accommodate the heat storage body B. However, in the second and subsequent heat storage layers, the opening of the container body 11 may be covered by the breathable container body 11 in the upper layer. can. Therefore, even if the air-permeable container 10 does not necessarily include the lid 12, the heat storage body B can be housed in the air-permeable container 10 in a manner that cannot be removed.

As the breathable material, a net body can be used as shown in FIG. 1(a). Alternatively, a punched metal sheet can be used, as shown in FIG. 1(b). Considering the temperature at which the combustion process is performed, it is desirable that the breathable material has a heat resistance of 700° C. or higher, and a mesh made of heat-resistant steel or a punched metal sheet can be used. In order to house the heat storage body B in the breathable container 10 in a non-separable manner, the size of the mesh of the mesh body and the size of the holes of the punched metal sheet are set smaller than the maximum diameter of the heat storage body B in the shape of a solid ball. Ru.

Note that a plurality of air-permeable containers 10 arranged in parallel in the horizontal direction or air-permeable containers 10 stacked vertically may be connected to each other by a hook-shaped member or wire.

Since the honeycomb structure H is formed by extrusion molding, it generally has a prismatic shape. Therefore, in the conventional heat storage unit in which a plurality of honeycomb structures H are arranged or stacked so that the cell directions match, the honeycomb structures H do not move even if some external force is applied. On the other hand, in the heat storage unit 1 of this embodiment, the heat storage body B is ball-shaped and therefore easy to move. Therefore, when supplying exhaust gas or purge gas to the heat storage section 60, the solid ball-shaped heat storage body B can be moved by the gas pressure. Therefore, even if the combustion residue of volatile organic compounds were to accumulate on the surface of the heat storage element B, the movement of the heat storage element B would crush the combustion residue and turn it into fine powder that would fall through the gaps between the heat storage elements B. Then, it passes through the heat storage section 60. Thereby, an increase in pressure loss due to clogging of the heat storage section 60 can be effectively suppressed.

As schematically shown in FIG. 2(b), the solid ball-shaped heat storage body B has a gas pressure (as shown by the arrow) when supplying exhaust gas to the heat storage section 60 or when supplying purge gas. It is desirable to move as if it were blowing up. For this purpose, it is desirable that the height of the breathable container 10 be at least five times the maximum diameter of the solid ball-shaped heat storage body B. As the solid ball-shaped heat storage element B moves upward, the combustion residue of the volatile organic compound is pulverized into finer particles due to the impact and friction when it rises and falls, and the voids between the heat storage elements B are crushed. Easy to fall through.

In this embodiment, clogging of the heat storage section is suppressed by making the shape of the heat storage body into a ball shape, but another feature is that "the member for suppressing clogging is itself a heat storage body". Therefore, it is desirable that the solid ball-shaped heat storage body has an excellent heat storage effect. For this purpose, the solid ball-shaped heat storage body can be made of a sintered body of silicon carbide. Generally, when a heat storage body is made into a solid ball shape, there is a drawback that the center portion thereof does not contribute to heat exchange. On the other hand, silicon carbide has a high thermal conductivity, so even if it is in the shape of a solid ball, it has the advantage that even the center part can contribute to heat exchange. In addition, silicon carbide has a small coefficient of thermal expansion, so it is susceptible to thermal shock due to repeated switching between the gas exhaust mode, which recovers heat from treated gas, and the exhaust gas supply mode, which preheats untreated gas. It also has the advantage of high resistance to

The density of the solid ball made of sintered silicon carbide is 1.7 g/cm ³ to 1.9 g/cm ³ . On the other hand, a typical honeycomb structure used as a heat storage body in conventional exhaust gas combustion treatment equipment has a cell density of about 100 cells/inch ² and a partition wall thickness of about 0.5 mm, and is made of silicon carbide. When formed from a sintered body, the density is 0.7 g/cm ³ to 0.9 g/cm ³ . Therefore, in order to make the heat capacity of a solid ball-shaped heat storage body housed in a breathable container to be about the same as that of a honeycomb structure of the same size as the breathable container, the masses of both are made to be about the same. In order to achieve this, the filling rate (volume percentage) of the solid ball-shaped heat storage body into the breathable container is set to 41% to 47%.

Also, considering only increasing heat capacity, it is desirable to house a large number of solid ball-shaped heat storage bodies in a breathable container, but in order for the solid ball-shaped heat storage bodies to move inside the breathable container, Instead of tightly packing the heat storage bodies into a breathable container, it is necessary to create appropriate gaps between the heat storage bodies. Therefore, in consideration of ease of handling, the size of the breathable container is assumed to be a cube with a side of 10 cm to 30 cm, and the solid ball-shaped heat storage body is assumed to be a true sphere with a diameter of 1 cm to 3 cm. , the filling rate (volume percentage) for the movement of the solid ball-shaped heat storage body was calculated.

The idea is to calculate the number of heat storage bodies housed in the breathable container from the filling rate (volume percentage) of 74% when the spheres are packed in the space closest to each other, and then calculate the number of heat storage bodies per side of the breathable container. Calculate the number (N) of heat storage bodies. As a result, the state when the heat storage bodies are most densely packed in the air-permeable container is approximated to the state where N layers of N×N heat storage bodies are laminated. Considering that the number of spheres in each direction must be at least (N-1) in order for the heat storage body to move by one space vertically and horizontally, the number of spheres in each direction must be at least (N-1). The number is (N-1) ³ , and the filling rate (volume percentage) in the breathable container is calculated from the total volume. The results of the calculation are shown in Table 2.

From this calculation result, when the size of the breathable container and the size of the solid ball-shaped heat storage body are set as above, in order for the solid ball-shaped heat storage body to move inside the breathable container, the filling rate (volume It can be said that it is sufficient to set the percentage) to 29% to 68%. Furthermore, in order to make the heat capacity of the solid ball-shaped heat storage body equal to or higher than that of the honeycomb structure, the mass of the solid ball-shaped heat storage body housed in the air-permeable container is reduced to a honeycomb structure of the same size as the air-permeable container. In order to make the mass greater than the mass of the structure, considering the above calculation results, it is said that the filling ratio (volume percentage) of the solid ball-shaped heat storage body to the breathable container should be 41% to 68%. be able to.

In addition, if the mass of the solid ball-shaped heat storage element is kept small, it will easily blow up due to the gas pressure when gas is supplied to the heat storage part, so the mass of each heat storage element should be 1.6g to 15g. is desirable. In this case, if the heat storage body is made of a sintered body of silicon carbide, the desirable diameter of the solid ball-shaped heat storage body is 1.2 cm to 2.6 cm based on the above density. When the diameter of the solid ball-shaped heat storage body is within this range, the filling rate calculated similarly to Table 2 is 34% to 66%.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to the above embodiments, and as shown below, various improvements can be made without departing from the gist of the present invention. and design changes are possible.

For example, in the above description, as an example of a breathable container including a lid, the lid is separated from the container body, but the lid is not limited to this, and is attached to the opening edge of the container body by a hinge. It can be used as a lid that opens and closes the opening of the container body by rotating around the hinge axis.

1 Heat storage unit 10 Breathable container 11 Container main body 12 Lid 60 Heat storage parts 60a, 60b, 60c Heat storage part 100 Exhaust gas combustion treatment device B Solid ball-shaped heat storage body H Honeycomb structure S Combustion space

Claims (4)

A plurality of heat storage parts communicating with a combustion space are provided, exhaust gas containing volatile organic compounds is combusted in the combustion space, heat of the treated gas is recovered in the heat storage part, and the exhaust gas is supplied to the combustion space. is preheated in the heat storage section, and each of the heat storage sections has an exhaust gas supply mode in which untreated exhaust gas is supplied, a gas discharge mode in which combustion-treated gas in the combustion space is discharged, and a purge mode. In a regenerative exhaust gas combustion treatment device that is switched to purge mode where gas is supplied,
Each of the heat storage parts is made up of multiple layers, and is connected to the lower part of the combustion space, and
The plurality of layers of the heat storage section includes a heat storage layer including a heat storage unit in which a solid ball-shaped heat storage body is irremovably housed in an air-permeable container made of an air-permeable material, and a honeycomb structure. equipped with both heat storage layers,
The heat storage layer constituted by the heat storage unit is provided so that only the uppermost layer of the heat storage section is in contact with the combustion space,
The heat storage body is a sphere having a size such that the number of heat storage bodies is N ³ when packed in the breathable container in the closest density, and (N-1) ³ of the heat storage bodies are filled in the breathable container. , a heat storage device that moves inside the breathable container by the pressure of the gas supplied in the purge mode, and has both the function of crushing combustion residue of volatile organic compounds and the function of storing heat. Department structure. The breathable container is a cube with a side of 10 cm to 30 cm, and the heat storage body has a diameter of 1 cm to 3 cm,
The heat storage part structure according to claim 1, wherein a filling rate of the solid ball-shaped heat storage body with respect to the air-permeable container is 29% by volume to 68% by volume. The solid ball-shaped heat storage body is a silicon carbide sintered body, each having a mass of 1.6 g to 15 g and a diameter of 1.2 cm to 2.6 cm,
The heat storage part structure according to claim 2, wherein a filling rate of the solid ball-shaped heat storage body with respect to the air-permeable container is 34% by volume to 66% by volume. An exhaust gas combustion treatment method performed using the heat storage structure according to any one of claims 1 to 3,
Recovering the heat of the treated gas by the solid ball-shaped heat storage body, and preheating the exhaust gas supplied to the combustion space with the heat of the solid ball-shaped heat storage body,
The solid ball-shaped heat storage body is blown up inside the breathable container by the gas pressure when gas is supplied from the outside to the combustion space via the heat storage unit, and the combustion residue of volatile organic compounds is blown up. An exhaust gas combustion treatment method, characterized in that maintenance for suppressing an increase in pressure loss in the heat storage section by pulverizing and suppressing the accumulation of the combustion residue in the heat storage section is performed simultaneously with the combustion treatment of the exhaust gas.

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