JPH0520641B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a waste heat recovery system using a fluidized bed heat exchanger.

(Prior Art) In a conventional waste heat recovery system of this type, a fluidized bed heat exchanger having the following configuration is interposed in the exhaust path of the exhaust gas led from the exhaust gas generation source.

That is, this fluidized bed heat exchanger includes a waste heat recovery medium layer that is fluidized by exhaust gas to form a fluidized bed, and a waste heat recovery pipe is introduced into the layer. Alumina sand or silica sand with an average particle size of about 0.2 to 3.0 mm is used as the waste heat recovery medium. Further, the waste heat recovery pipe is connected to a heat load section such as heating or hot water supply, so that an appropriate heat medium can be circulated between the fluidized bed and the heat load section.

Therefore, according to this waste heat recovery system, while the exhaust gas passes through the fluidized bed heat exchanger, the exhaust gas and the heat medium in the waste heat recovery pipe effectively transfer heat through the flowing waste heat recovery medium. As a result, heat is efficiently recovered from the exhaust gas, and this recovered heat can be used as a heat source for heating, etc.

By the way, the waste heat recovery medium such as alumina sand has no exhaust gas purification effect, and the fluidized bed heat exchanger merely has a waste heat recovery function.
Merely installing a fluidized bed heat exchanger in the exhaust gas exhaust route will not eliminate harmful substances in the exhaust gas, such as nitrogen oxides,
Hydrocarbons, carbon monoxide, etc. are not removed and are released into the atmosphere as they are, causing pollution problems.

Therefore, in conventional systems, in addition to a fluidized bed heat exchanger, an exhaust gas purification device such as a denitrification device or a desulfurization device is usually installed in the exhaust gas discharge path.

(Problem to be solved by the invention) However, when such an exhaust gas purification device is installed, in order to prevent performance deterioration of the exhaust gas purification device due to adhesion of soot and moisture in the exhaust gas, steam and high-pressure air are further added to the exhaust gas purification device. Coupled with the need for a cleaning device such as a soot blower using a soot blower, etc., there is a problem in that the structure of the entire system becomes unnecessarily complicated and large. Moreover, maintenance is not easy,
There is a problem in that the system down time required for maintenance and inspection, such as replacing the denitrification equipment, becomes long, resulting in extremely poor operational efficiency.

An object of the present invention is to provide a waste heat recovery system that can efficiently recover and purify exhaust gas heat without causing such problems.

(Means for Solving the Problems) In order to achieve the above object, the waste heat recovery system of the present invention has a fluidized bed heat exchanger having not only a heat recovery function but also an exhaust gas purification function. This is what I did.

That is, in the waste heat recovery system of the first invention, a waste heat recovery medium layer that is fluidized by the exhaust gas to form a fluidized bed is installed in the exhaust gas discharge path, and the waste heat recovery medium layer is disposed in the exhaust gas discharge path. A fluidized bed heat exchanger formed by guiding pipes is provided, and a plurality of types of granular ceramic catalysts capable of purifying and removing various harmful substances in exhaust gas are used as the waste heat recovery medium.

Further, in the waste heat recovery system of the second invention, a part of the exhaust gas exhaust route is configured to branch into a main route part and a bypass route part that merge at both ends, and the exhaust gas exhaust route passes through the main route part. A heat exchange section is equipped with a waste heat recovery medium layer that is fluidized by exhaust gas to form a fluidized bed, and a waste heat recovery pipe is introduced into the layer, and a heat exchange section that is fluidized by exhaust gas passing through a bypass route section. A fluidized bed heat exchanger consisting of an exhaust gas purification section having an internal exhaust gas purification medium layer that is forced to form a fluidized bed is installed, and the amount of exhaust gas introduced from the main path section to the heat exchange section and the bypass path. A plurality of types of granular ceramic catalysts are provided with an exhaust gas introduction amount control mechanism that controls the amount of exhaust gas introduced from the section to the exhaust gas purification section, and can purify and remove various harmful substances in the exhaust gas as the waste heat recovery medium and the exhaust gas purification medium. are using.

As the ceramic catalyst serving as the waste heat recovery medium and the exhaust gas purification medium, known ones can be used, and the most suitable one is selected depending on the properties of various harmful substances contained in the exhaust gas from which heat is to be recovered. For example, combustion catalysts include platinum supported on ceramic, ceramic catalysts for purifying nitrogen oxides, hydrocarbons, and carbon monoxide include platinum and rhodium supported on ceramic, or vanadium supported on ceramic. Preferably,

Further, each of the fluidized beds may be a single layer in which a plurality of types of ceramic catalysts are mixed, or a plurality of single-type ceramic catalyst layers each consisting of a different type of ceramic catalyst may be arranged in series along the exhaust gas passage direction. You may do so. For example, the first layer may be made of a ceramic catalyst that burns and purifies soot, hydrocarbons, carbon monoxide, etc. at low temperatures, and the second layer is made of a ceramic catalyst that reduces and purifies nitrogen oxides. In this case, the waste heat recovery pipe is arranged so as to pass through each layer in sequence.

(Operation) In the waste heat recovery system of the first invention, when the exhaust gas is brought to the fluidized bed heat exchanger, the kinetic energy of the exhaust gas causes the granular ceramic catalyst to flow, forming a fluidized bed. This fluidized bed effectively recovers heat from the exhaust gas. On the other hand, harmful substances in the exhaust gas are purified and removed by the action of the ceramic catalyst while the exhaust gas passes through the ceramic catalyst layer. Therefore, the exhaust gas that has passed through the fluidized bed heat exchanger does not contain harmful substances, and does not cause pollution problems such as air pollution even if it is discharged as is from a chimney or the like. Moreover,
Since the ceramic catalyst is constantly fluidized, it has a self-cleaning effect, and as a result, the adhesion of soot and the like can be reliably prevented.

Note that ceramic catalysts may lose their catalytic activity under high-temperature conditions above a certain temperature, but in the fluidized bed heat exchanger mentioned above, waste heat recovery
The temperature is maintained at approximately 500°C to 500°C, and the catalytic action is effectively carried out.

By the way, in order for a fluidized bed to be well formed and maintained by exhaust gas, it depends on the size and weight of the granular ceramic catalyst that is the constituent material, but it is necessary to control the amount of exhaust gas passing through the fluidized bed or the exhaust gas velocity. Below a certain point (fluidization start point), the fluidized bed components will no longer flow, and conversely, if it exceeds a certain point (terminal velocity), the fluidized bed components will scatter and will no longer form a good fluidized bed, so fluidization will begin. It is necessary to maintain the range above the terminal velocity and below the terminal velocity. Therefore, if a boiler or the like that is a source of exhaust gas is controlled proportionally depending on the load, the amount of exhaust gas introduced into the fluidized bed heat exchanger or the exhaust gas velocity will fluctuate, and in the system of the first invention, There is a possibility that a fluidized bed cannot be properly formed and maintained.

In the waste heat recovery system of the second invention, such inconveniences can be eliminated,
By controlling the amount of exhaust gas introduced from the main path section to the heat exchange section and the amount of exhaust gas introduced from the bypass path section to the exhaust gas purification section using the exhaust gas introduction amount control mechanism, the amount of exhaust gas discharged from the exhaust gas generation source or recovery can be controlled. This makes it possible to cope well with variations in heat load relative to the amount of heat.

That is, normally, the exhaust gas is introduced into the heat recovery section, and when the exhaust gas becomes below the fluidization starting point,
The exhaust gas is introduced into the exhaust gas purification section. In this exhaust gas purification section, when the exhaust gas exceeds the terminal velocity, the exhaust gas is introduced into the heat recovery section again.
Furthermore, in this heat recovery section as well, when the exhaust gas exceeds the terminal velocity, a portion of the exhaust gas is also introduced into the exhaust gas purification section.

By controlling the amount of exhaust gas introduced into the heat recovery section and the exhaust gas purification section in this way, it is possible to form and maintain a fluidized bed in good condition regardless of fluctuations in the amount of exhaust gas discharged from the exhaust gas generation source. . Further, in the same manner, the amount of waste heat recovery can be adjusted, and load fluctuations in the heat load section can be coped with. For example, when the heat load decreases, all or part of the exhaust gas is introduced into the exhaust gas purification section.

Note that the heat recovery action and the exhaust gas purification action are performed while the exhaust gas passes through the waste heat recovery section, and the exhaust gas purification action is performed when the exhaust gas passes through the exhaust gas purification section, as in the system of the first invention. It is.

(Example) Hereinafter, the structure of the present invention will be specifically explained based on each example shown in FIGS. 1 to 4.

In the system of the first embodiment shown in FIG.
1 is an exhaust gas generation source such as a boiler, engine, or gas turbine that is controlled ON/OFF; 2 is a chimney;
Reference numeral 3 designates an exhaust gas discharge path from the exhaust gas generation source 1 to the chimney 2, 4 a fluidized bed heat exchanger installed in the exhaust gas discharge path 3, and 5 a heat load section such as heating equipment or hot water supply equipment.

The fluidized bed heat exchanger 4 connects exhaust gas inlets and outlets 6a and 6b provided at the upper and lower parts of the main body container 6 to an exhaust gas exhaust path 3.
A waste heat recovery medium layer 7 is installed inside the main body container 6, and a waste heat recovery pipe 8 is guided into the layer 7.

The waste heat recovery medium layer 7 is constructed by stacking a plurality of types of granular ceramic catalysts on a perforated plate 11, which can purify various harmful substances such as nitrogen oxides contained in the exhaust gas 10. A fluidized bed is formed by the exhaust gas 10 passing through the main body container 6 from the exhaust gas outlet 6a to the exhaust gas outlet 6a. Ceramic catalysts are known and there are various types, but as the constituent material of the waste heat recovery medium layer 7, as mentioned above, ceramic catalysts are suitable for purifying various harmful substances contained in the exhaust gas 10 depending on their properties. Use the best one. Additionally, the average particle size of ceramic catalysts is similar to that of waste heat recovery media used in conventional fluidized bed heat exchangers.
It is desirable to keep it at around 0.2 to 3.0 mm.

The waste heat recovery medium layer 7, as shown in FIG.
It may be a single layer in which the plurality of types of ceramic catalysts described above are mixed, or such mixed layers may be arranged in an appropriate number of stages depending on the amount of heat recovery. Alternatively, a plurality of single-type ceramic catalyst layers, each consisting of a different type of ceramic catalyst, may be arranged in series in a plurality of upper and lower stages. For example, as shown in FIG. 3, the waste heat recovery medium layer 7 is separated into upper and lower three stages, and the first layer 7a is a combustion catalyst that burns and removes soot and dust, and the second layer 7b is a hydrocarbon and carbon monoxide layer. The third layer 7c is composed of a ceramic catalyst that reduces and removes nitrogen oxides. In this case, as the exhaust gas 10 passes through each layer 7a, 7b, and 7c, various harmful substances contained therein are sequentially removed, and in particular, the first layer 7a also functions as a filter. It will be fulfilled. Of course,
The number of stages of the single ceramic catalyst layer is appropriately set depending on the type of harmful substances contained in the exhaust gas, the type of catalyst required, the active temperature range of the catalyst, etc.

Note that the waste heat recovery pipe 8 is a heat transfer pipe that constitutes a part of a circulation closed circuit 9 that circulates an appropriate heat medium between the heat load section 5 and the heat load section 5 . Moreover, the porous plate 11
is for holding the ceramic catalyst layer 7, and in order to properly form a fluidized bed by the exhaust gas 10, the exhaust gas 10 flowing into the fluidized bed 7 is
It is also used to uniformly disperse the

In addition, in the system of the second embodiment shown in FIG. 4, a part of the exhaust gas discharge path 3 is configured to branch into a main path portion 3a and a bypass path portion 3b that merge at both ends, and a fluidized bed heat exchange The vessel 4 is divided into a heat exchange section 4a and an exhaust gas purification section 4b, and each section 4a, 4b is interposed in each path section 3a, 3b. That is, the main body container 6 is divided by the partition wall 12 into a heat exchange section 4a and an exhaust gas purification section 4b, and each section 4a,
A waste heat recovery medium layer 13a and an exhaust gas purification medium layer 13b are installed inside the waste heat recovery medium layer 13a and an exhaust gas purification medium layer 13b, respectively, and a waste heat recovery pipe 8 is guided into the waste heat medium layer 13a. The configuration of each layer 13a, 13b is the same as the waste heat recovery medium layer 7 in the first embodiment. The waste heat recovery medium layer 13a is made to flow by the exhaust gas 10 passing through the main path portion 3a to form a fluidized bed, and performs a heat recovery action and an exhaust gas purification action.
3b is a fluidized bed formed by the exhaust gas 10 passing through the bypass path portion 3b to form a fluidized bed and perform an exhaust gas purifying action. Note that the exhaust gas purification medium layer 13b is configured such that the amount of exhaust gas required to flow it well is smaller than the amount of exhaust gas required in the waste heat recovery medium layer 13a. Specifically, the exhaust gas purification medium layer 13b has a smaller capacity than the waste heat recovery medium layer 13a. It goes without saying that each layer 13a, 13b can have a configuration as illustrated in FIG. 2 or 3, similarly to the waste heat recovery medium layer 7. Further, the exhaust gas generation source 1 is a proportionally controlled boiler or the like.

Further, an exhaust gas introduction amount control mechanism 14 is provided to control the amount of exhaust gas introduced from the main path portion 3a to the heat exchange portion 4a and the amount of exhaust gas introduced from the bypass path portion 3b to the exhaust gas purification portion 4b. This exhaust gas introduction amount control mechanism 14 includes a first damper 15a provided in the main path portion 3a, a second damper 15b provided in the bypass path portion 3b, and a waste heat recovery medium layer 1.
A first differential pressure detector 16a detects the pressure difference between the upper and lower portions of the exhaust gas purification medium layer 13b, and a second differential pressure detector 16 detects the pressure difference between the upper and lower portions of the exhaust gas purification medium layer 13b.
b, and a control device 17 that controls the opening degree of each damper 15a, 15b based on the detected value by each detector 16a, 16b. That is, a change in the amount of exhaust gas is detected as a change in pressure loss (for example, when the amount of exhaust gas decreases, the pressure difference between the upper and lower parts of the layers 13a and 13b, that is, the pressure loss becomes smaller),
Based on this, the amount of exhaust gas introduced into the heat recovery section 4a or the exhaust gas purification section 4b is controlled as described above. Of course, such control can also be performed based on heat load fluctuations in the heat load section 5.

In the system of the second embodiment, a waste heat recovery pipe (not shown) for low heat load is introduced into the exhaust gas purification medium layer 13b, and the exhaust gas 10 is transferred to the layer 13b.
It may be configured so that a small amount of heat exchange can be performed even when passing through.

(Effects of the Invention) In the waste heat recovery system of the present invention, by using a fluidized bed heat exchanger as a fluidized bed constituent material, a ceramic catalyst having an exhaust gas purifying effect,
Since it is configured to have a waste heat recovery function and an exhaust gas purification function, there is no need to separately install a device for exhaust gas purification other than the fluidized bed heat exchanger as in conventional systems, and the overall system structure is therefore can be extremely simplified and miniaturized, and maintenance is also easy. In addition, since the ceramic catalyst is constantly flowing and has a self-cleaning effect, there is no need to provide a cleaning device and there is no risk of performance deterioration due to adhesion of soot, etc. In addition, by appropriately selecting a ceramic catalyst according to the type and properties of the harmful substances to be removed, any type of exhaust gas can be purified without changing the system structure or layout. Full of versatility.

Furthermore, in addition to the above-mentioned effects, the waste heat recovery system of the second invention always maintains a good fluidized bed to recover waste heat and purify exhaust gas, regardless of fluctuations in the amount of exhaust gas generated or heat load. This can be done more efficiently.

[Brief explanation of the drawing]

Figure 1 shows the first diagram of the waste heat recovery system according to the present invention.
A schematic longitudinal sectional side view showing the embodiment, FIG. 2 is an enlarged view of the same essential parts, FIG. 3 is an enlarged view similar to FIG. 2 showing a modification of the essential parts, and FIG. 4 shows the second embodiment. FIG. 2 is a schematic longitudinal sectional side view of the waste heat recovery system. 1...Exhaust gas generation source, 3...Exhaust gas emission route,
3a... Main route part, 3b... Bypass route part, 4... Fluidized bed heat exchanger, 4a... Waste heat recovery section, 4b... Exhaust gas purification section, 5... Heat load section,
7, 13a...Waste heat recovery medium layer, 8...Waste heat recovery pipe, 10...Exhaust gas, 13b...Exhaust gas purification medium layer, 14...Exhaust gas introduction amount control mechanism, 15a, 1
5b...Damper, 16a, 16b...Differential pressure detector, 17...Control device.

Claims (1)

[Claims] 1. A waste heat recovery medium layer that is made to flow by the exhaust gas to form a fluidized bed is installed in the exhaust path of the exhaust gas led from the exhaust gas generation source, and a waste heat recovery pipe is installed in the layer. A fluidized bed heat exchanger is installed in which the waste heat recovery medium layer is made of ceramic and platinum, which can purify and remove various harmful substances such as nitrogen oxides, hydrocarbons, and carbon monoxide in the exhaust gas. A waste heat recovery system comprising a plurality of types of granular ceramic catalysts, such as those carrying rhodium or vanadium, to purify exhaust gas while it passes through a waste heat recovery medium layer. . 2. The waste heat recovery medium layer is a single layer in which multiple types of ceramic catalysts are mixed.
A waste heat recovery system according to claim 1. 3. Claims characterized in that the waste heat recovery medium layer is formed by arranging a plurality of single type ceramic catalyst layers in series along the exhaust gas passage direction, each layer comprising a different type of ceramic catalyst. 1st
The waste heat recovery system described in Section. 4 A part of the exhaust gas exhaust route led from the exhaust gas generation source is configured to branch into a main route part and a bypass route part that join at both ends, and the exhaust gas passing through the main route part is made to flow into the exhaust gas exhaust route. a heat exchange section having a waste heat recovery medium layer therein which forms a fluidized bed and guiding a waste heat recovery pipe into the layer;
A fluidized bed heat exchanger is interposed between the exhaust gas purification section, which is equipped with an exhaust gas purification medium layer that is made to flow by the exhaust gas passing through the bypass path section to form a fluidized bed, and An exhaust gas introduction amount control mechanism is installed to control the amount of exhaust gas introduced into the heat exchange section and the amount of exhaust gas introduced into the exhaust gas purification section from the bypass path section, and the waste heat recovery medium layer and the exhaust gas purification medium layer are nitrogen oxides,
It is composed of multiple types of granular ceramic catalysts, such as ceramics supported with platinum, rhodium, or vanadium, which can purify and remove various harmful substances such as hydrocarbons and carbon monoxide, and converts exhaust gas into a waste heat recovery medium. A waste heat recovery system characterized in that the waste heat is purified while passing through a layer or an exhaust gas purification medium layer. 5. The waste heat recovery medium layer is a single layer in which multiple types of ceramic catalysts are mixed.
A waste heat recovery system according to claim 4. 6. The waste heat recovery system according to claim 4 or 5, wherein the exhaust gas purification medium layer is a single layer in which a plurality of types of ceramic catalysts are mixed. 7. Claim 4, characterized in that the waste heat recovery medium layer is a plurality of single-type ceramic catalyst layers, each of which is made of a different type of ceramic catalyst, arranged in series along the exhaust gas passage direction. or the waste heat recovery system described in paragraph 6. 8. Claim 4, wherein the exhaust gas purification medium layer is a plurality of single-type ceramic catalyst layers, each of which is made of a different type of ceramic catalyst, arranged in series along the exhaust gas passage direction. or the waste heat recovery system described in Section 5.