JPH06180115A - Waste heat recovery system - Google Patents

Abstract

PURPOSE:To effectively recover waste heat without using any expensive heat exchanger and keep stably the temperatures in a furnace by providing two exhaust lines respectively having heat storage bodies incorporated therein, making fresh air pass through the heat storage bodies alternatively and supplying the resulting heated air to a burner. CONSTITUTION:A first exhaust line 17 and a second air supply line 7 are controlled to open so as to allow a burner 2 to perform combustion, and combustion gas is made to pass through a first heat storage body 11 incorporated within the first exhaust line 17 so as to effect heat storage. Then, the second air supply line 7 is controlled to close, and a third air supply line 8 is controlled to open and close so as to keep the burner 2 effecting combustion. In this state, a second exhaust line 18 is controlled to open so as to make the second heat storage body 14 effect heat storage. In a state in which the first exhaust line 17 is controlled to close so as to make the heat storage body 14 effect heat storage, a first air supply line 6 is controlled to close with the third air supply line 8 being controlled to open so that fresh air, which is made to pass through the heat storage bodies so as to be heated, is supplied to the burner 2. The fresh air is made to pass through the heat storage bodies 11, 14 alternatively, and the heated air is supplied to the burner 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust heat recovery system for recovering exhaust heat of combustion gas generated when a burner installed in a furnace body operates to effectively use fuel.

[0002]

2. Description of the Related Art Conventionally, an exhaust heat recovery system for recovering exhaust heat of combustion gas generated during combustion operation of a burner installed in a furnace body and effectively using fuel is shown in, for example, FIG. 14 and FIG. There is such a system. The exhaust heat recovery system shown in FIG. 14 is a system that has been generally adopted conventionally. This system consists of one burner 5 in the furnace body 51.
2, the heat of the combustion gas is heat-exchanged during the process of passing the combustion gas through the exhaust passage 53 and the heat exchanger 54 when the gas and air are supplied to the burner 52 and burned. While the remaining combustion gas is exhausted to the atmosphere, the heat exchanged by the heat exchanger 54 raises the temperature of the fresh air supplied from the atmosphere, and the temperature of the air is raised.
Is supplied to the burner 52 through the air supply passage 55. In this system, when the temperature of the combustion gas is, for example, 1000 ° C., the heat exchanger 54
The temperature of the fresh air supplied from the atmosphere is raised from about 20 ° C. to 400 ° C. by the heat exchanged in (1) and is supplied to the burner 52. The exhaust temperature is as high as 600 ° C. because the efficiency of the heat exchanger 54 is limited.

Further, the heat storage type exhaust heat recovery system shown in FIG. 15 is provided with two burners 62A and 62B in a furnace main body 61, and supply and exhaust passages 63A and 6 are provided in the respective burners 62A and 62B.
3B are connected, and the respective ends of the supply / exhaust passages 63A, 63B are connected to the switching valve 64. When the valve body 65 of the switching valve 64 is switched to the position indicated by the solid line, the supply / exhaust passage 63B functions as the supply passage, and the burner 62B enters the combustion state, while the supply / exhaust passage 6 is provided.
3A functions as an exhaust passage. Further, when the valve body 65 is switched to the position indicated by the broken line, the supply / exhaust passage 63A functions as a supply passage and the burner 62A enters a combustion state, while the supply / exhaust passage 63B functions as an exhaust passage. It is configured. A heat storage body 66A is provided in the supply / exhaust passage 63A, and a heat storage body 66B is provided in the supply / exhaust passage 63B.
Is provided, and the heat of the combustion gas is stored in the heat storage bodies 66A and 66B in the process of exhausting the combustion gas generated by the combustion operation of the burners 62A and 62B.

The switching valve 64 has a fresh air
An intake port 64A and an exhaust port 64B are provided so that fresh air-air in the atmosphere-is sucked from the intake port 64A, while combustion gas after heat storage is exhausted from the exhaust port 64B.

According to the heat storage type exhaust heat recovery system having the above construction, the valve body 65 of the switching valve 64 is switched to the position indicated by the solid line, and the air in the atmosphere is fresh air-the intake port 64A.
From the heat storage body 66B through the air supply / exhaust passage 63B.
In the process of passing through the heat storage unit 66B, the air is heated to 900 ° C. by the heat stored in advance in the heat storage body 66B, for example.
When the temperature of the combustion gas supplied to the burner 62B by the combustion operation of the burner 62B reaches, for example, 1000 ° C., the combustion gas is exhausted from the burner 62A through the supply / exhaust passage 63A through the exhaust port 64B Then, when the heat of the combustion gas is stored in the heat storage body 66A by an amount corresponding to, for example, 800 ° C., the combustion gas is cooled to a temperature of about 200 ° C.
B is exhausted to the atmosphere.

After the burner 62B continues to burn for 20 seconds, for example, when the valve body 65 of the switching valve 64 is switched to the position indicated by the broken line, fresh air--air sucked from the suction port 64A--is in turn released. Since it is supplied to the burner 62A after passing through the heat supply / exhaust passage 63A and the heat storage body 66A, the burner 62B is extinguished, while the burner 62A is extinguished.
Becomes a combustion state, the heat of the combustion gas is stored in the heat storage body 66B, and then is exhausted from the exhaust port 64B through the supply / exhaust passage 63B. For example, when the switching valve 64 is switched at an interval of 20 seconds. , The burners 62A and 62B are in a combustion state alternately, and exhaust heat is stored in the heat storage body on the exhaust side.

[0007]

In the case of the conventional exhaust heat recovery system shown in FIG. 14, the heat exchanger 54 is made of a ceramic material or a metal material. A ceramic material can be used up to a relatively high temperature range, but has a problem that it is relatively expensive. On the other hand, although the metal material is relatively inexpensive, it has a problem that it cannot be used in a high temperature range. Further, the heat exchanger 54 has a problem that the heat exchange efficiency is relatively low.

In the case of the heat storage type exhaust heat recovery system shown in FIG. 15, at least two burners are required. Therefore, when it is applied to an existing furnace equipped with one burner, the size of the furnace body is greatly increased. However, since the burner has an alternating combustion method with two burners, there is a period of fire extinguishing, and the temperature inside the furnace may become unstable.

Therefore, in the present invention, the burner to be used can be installed in an existing furnace body without using an expensive heat exchanger having a problem in a high temperature region and without changing the existing furnace body. It is a technical issue to be solved to make it possible to provide a safe and inexpensive exhaust heat recovery system by stabilizing the temperature inside the furnace by making the system one and having no fire extinguishing period. is there.

[0010]

The technical means for solving the above-mentioned problems is to provide an exhaust heat recovery system for a burner provided in the furnace body and a burner for the burner. An air supply device that supplies air, an exhaust device that discharges combustion gas from the burner to the atmosphere, and an air supply device that is arranged between the air supply device and the burner. The air of the
A first air supply passage, a second air supply passage, and a third air supply passage that can be controlled to be opened and closed and that is provided between the furnace body and the exhaust device. Air flowing through the exhaust passage, the second exhaust passage, and the first air supply passage;
And a first heat storage body provided at a position where the combustion gas flowing through the first exhaust passage passes, the air flowing through the second air supply passage, and the combustion gas flowing through the second exhaust passage. And a second heat storage body provided at a position to be used.

[0011]

According to the exhaust heat recovery system having the above structure, the air supply device and the exhaust device are first operated, and the first exhaust passage and the second air supply passage are controlled to be opened to ignite the burner. The combustion temperature is raised and the temperature inside the furnace is raised. (1) In a state where the first exhaust passage and the second air supply passage are controlled to be open, the combustion gas generated by the combustion action of the burner passes through the first heat storage body provided in the first exhaust passage. In the process, the heat of the combustion gas is stored in the first heat storage body, and the combustion gas having a lowered temperature is discharged into the atmosphere by the exhaust device. (2) Next, in the state of (1), the third air supply passage is open-controlled. (3) Next, the second air supply passage is controlled to be closed to continue combustion of the burner by the air supply from the third air supply passage. (4) Next, the second exhaust passage is open-controlled while the first exhaust passage is open-controlled, so that the first heat storage body continues to store heat and the second heat storage body also starts to store heat. (5) Next, the first exhaust passage is controlled to be closed so that the combustion gas passes through the second exhaust passage and the heat storage of the second heat storage body is continued. (6) Next, the first air supply passage is open-controlled while the third air supply passage is open-controlled, and the fresh air is passed through the first heat storage body that has already sufficiently stored heat, so that the fresh air- Is supplied to the burner while being heated by the stored heat. That is, while the heat stored in the first heat storage body is recovered, the heat storage of the second heat storage body is continued. (7) Next, the third air supply passage is closed while the first air supply passage is open-controlled. (8) Next, the third air supply passage is open-controlled while the first air supply passage is open-controlled. (9) Next, the first air supply passage is closed and the combustion of the burner is continued by the air supply from the third air supply passage, and the second heat storage body continues to store heat. (10) Next, the first exhaust passage is also controlled to be opened while the second exhaust passage is being controlled to be opened, and the heat storage of the first heat storage body is started. (11) Next, the second exhaust passage is closed and controlled so that the combustion gas is passed through the first exhaust passage to store heat in the first heat storage body. (12) Next, the second air supply passage is controlled to be opened while the third air supply passage is being controlled to be open, and the fresh air is passed through the second heat storage body in which sufficient heat has already been stored. Is supplied to the burner while being heated by the stored heat. That is, the heat stored in the first heat storage body is continued while recovering the heat stored in the second heat storage body, and then the third air supply passage is closed and controlled to be in the state (1). Repeat the above steps. As described above, according to this exhaust heat recovery system, since there is no burner extinguishing period, the furnace temperature is stable and the exhaust heat can be recovered efficiently. The above step (1)
From (12) to (12), the step (1) is the main step of recovering the exhaust heat of the combustion gas stored in the second heat storage body, and the step (7) is the combustion gas stored in the first heat storage body. This is the main process of recovering the exhaust heat of. And the others are the switching process,
That is, it is a transitional process.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a systematic diagram schematically showing the overall configuration of an exhaust heat recovery system for recovering the heat of combustion gas due to combustion operation of a burner and effectively using the heat.
As shown in FIG. 1, the furnace body 1 is equipped with one burner 2 that uses gas as fuel. Further, an air supply device 3 for supplying fresh air from the atmosphere to the burner 2 is provided. An adjusting valve 4 is provided on the delivery side of the air supply device 3 for adjusting the delivery flow rate of air. On the other hand, an exhaust device 5 is provided for discharging the combustion gas generated by the burning action of the burner 2 into the atmosphere.

A bar is supplied from the air supply device 3 through an adjusting valve 4.
A first air supply passage 6, a second air supply passage 7, and a third air supply passage 8 are formed for supplying air to the air 2. A switching valve 10, a first heat storage body 11, and a switching valve 12 are provided in the first air supply passage 6. A switching valve 13, a second heat storage body 14, and a switching valve 15 are provided in the second air supply passage 7. Further, a switching valve 16 is provided in the third air supply passage 8.

Further, the combustion gas generated by the combustion action of the burner 2 is passed through the first heat storage body 11 or the second heat storage body 14, and the first heat storage body 11 or the second heat storage body 11 is stored. Since the combustion gas after the heat is stored in the body 14 is discharged into the atmosphere, the first part is provided between the furnace body 1 and the exhaust device 5.
The exhaust passage 17 and the second exhaust passage 18 are formed.

A switching valve 19 is provided in the first exhaust passage 17.
The first heat storage body 11 and the switching valve 20 are arranged. Further, a switching valve 21, the second heat storage body 14, and a switching valve 22 are arranged in the second exhaust passage 18.
Although not shown, the present system controls opening / closing of each of the switching valves to supply the air supply passages 6, 7, 8 and the exhaust passage 1
A control device for controlling opening / closing of 7, 18 is provided.

When only the first air supply passage 6 among the first air supply passage 6, the second air supply passage 7 and the third air supply passage 8 is controlled to be opened, the switching valve is controlled by the control device. 10, 12
Is controlled to be opened, and the other switching valves are controlled to be closed. Also,
When only the second air supply passage 7 is controlled to be opened, the switching valves 13 and 15 are controlled to be opened and the other switching valves are controlled to be closed by the control device. Further, when only the third air supply passage 8 is controlled to be opened, the switching device 16 is controlled to be opened and the other switching valves are controlled to be closed by the control device.

On the other hand, when only the first exhaust passage 17 of the first exhaust passage 17 and the second exhaust passage 18 is controlled to be opened, the switching valves 19 and 20 are controlled to be opened by the control device. The switching valves 21 and 22 of the second exhaust passage 18 are controlled to be closed. Further, when only the second exhaust passage 18 is controlled to be opened, the switching valves 21 and 22 are controlled to be opened, and the first exhaust passage 1 is controlled.
The switching valves 19 and 20 of 7 are controlled to be closed. When both the first exhaust passage 17 and the second exhaust passage 18 are open-controlled, the switching valves 19, 20, 21, 22 are open-controlled.

Next, the operation of the exhaust heat recovery system having the above configuration will be described with reference to FIGS. 2 to 13. 2 to 13, the route shown by the two-dot chain line shows the air supply path of the air supplied from the air supply device 3 to the burner 2, while the route shown by the broken line is. The exhaust path through which the combustion gas of the furnace body 1 is discharged from the exhaust device 5 into the atmosphere is shown.

First, the air supply device 3 and the exhaust device 5 are operated, and the first control is performed by the switching valve control by the control device.
The exhaust passage 17 and the second air supply passage 7 of the
The temperature of the inside of the furnace body 1 is raised by igniting the nozzle 2 to bring it into a combustion state. (1) Combustion by the combustion action of the burner 2 while the first exhaust passage 17 and the second air supply passage 7 are open-controlled by the switching valve control of the control device as shown in FIG. The heat of the combustion gas is stored in the first heat storage body 11 during the process of the gas passing through the first heat storage body 11 provided in the first exhaust passage 17, and the combustion gas whose temperature has dropped is discharged to the atmosphere by the exhaust device 5. Discharged inside.

(2) Next, as shown in FIG. 3, the third air supply passage 8 is controlled to be opened in the state of (1). (3) Next, as shown in FIG. 4, the combustion action of the burner 2 is continued by the closed control of the second air supply passage 7 and the air supply from the third air supply passage 8. (4) Next, as shown in FIG. 5, the second exhaust passage 18 is controlled to be opened while the first exhaust passage 17 is being controlled to be open, and the heat storage of the first heat storage body 11 is continued and the second heat storage body 11 is continuously stored. Heat storage body 1
Also start heat storage in 4.

(5) Next, as shown in FIG. 6, the first exhaust passage 17 is closed and controlled so that the combustion gas is discharged into the second exhaust passage 18.
And the heat storage of the second heat storage body 14 is continued. (6) Next, as shown in FIG. 7, the first air supply passage 6 is open-controlled while the third air supply passage 8 is open-controlled, and the first heat storage body 11 that has already sufficiently stored heat is freshly stored. By passing such a large amount of air, the air is supplied to the burner 2 while being heated by the accumulated heat. That is, the heat accumulated in the second heat storage body 14 is continued while recovering the heat stored in the first heat storage body 11.

(7) Next, as shown in FIG. 8, the third air supply passage 8 is controlled to be closed while the first air supply passage 6 is kept open, and the first heat storage body 11 is passed through. The hot air is supplied to the burner 2. (8) Next, as shown in FIG. 9, the third air supply passage 8 is open-controlled while the first air supply passage 6 is open-controlled. (9) Next, as shown in FIG. 10, the burner 2 is controlled by closing the first air supply passage 6 and supplying air from the third air supply passage 8.
To continue the burning action of.

(10) Next, as shown in FIG.
The first exhaust passage 17 is also opened while the exhaust passage 18 is kept open, and heat is also stored in the first heat storage body 11. (11) Next, as shown in FIG. 12, the second exhaust passage 1
8 is controlled to be closed to allow the combustion gas to pass through the first exhaust passage 17 and store heat only in the first heat storage body 11. (12) Next, as shown in FIG. 13, the third air supply passage 8
The second air supply passage 7 is opened while the open air is kept open, and the fresh air is passed through the second heat storage body 14 in which sufficient heat has been stored, so that the fresh air is heated by the stored heat. Supply to Na 2. That is, while collecting the heat stored in the second heat storage body 14, the first heat storage body 11
To continue the heat storage of the
The air supply passage 8 is closed and the above steps are repeated.

As described above, according to this exhaust heat recovery system, since the burner 2 has no extinguishing period, the furnace temperature is stable and the exhaust heat can be recovered efficiently. In addition, since air flows in both directions in the first heat storage body 11 and the second heat storage body 14 part, there is an effect that the adhesion of dust and the like generated during combustion is extremely small. It should be noted that, of the states of FIG. 2 to FIG. 13, the state of FIG. 1 is the main step of recovering the exhaust heat of the combustion gas stored in the second heat storage body 14, and the state of FIG. 8 is the first step. This is the main process of recovering the exhaust heat of the combustion gas stored in the heat storage body 11. And the others are switching steps, that is, transitional steps.

Since the durations of the states of FIG. 1 and FIG. 8 can be set arbitrarily, for example, 20 times each can be set.
It is desirable to set to 5 seconds or less for each of the transitional states of FIGS. 3 to 7 and the transitional states of FIGS.

[0026]

As described above, the present invention has the following effects. (1) Since only one burner is used, this exhaust heat recovery system can be applied to an existing furnace body without modifying the existing furnace body. (2) Since there is no burner extinguishing period, the temperature inside the furnace is stable and the quality of the heated object can be stabilized. (3) It is not necessary to use an expensive heat exchanger as in the related art, and the exhaust heat recovery efficiency can be improved as compared with a system using a heat exchanger. (4) In the conventional heat storage type system using two burners, the combustion air passage of the burner also serves as an exhaust passage.
Although restricted by the structure of the burner, the present invention is not restricted by this kind of structure.

[Brief description of drawings]

FIG. 1 is a system diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is an operation explanatory view.

FIG. 3 is an operation explanatory view.

FIG. 4 is an operation explanatory view.

FIG. 5 is an operation explanatory view.

FIG. 6 is an operation explanatory view.

FIG. 7 is an operation explanatory view.

FIG. 8 is an operation explanatory view.

FIG. 9 is an operation explanatory view.

FIG. 10 is an operation explanatory view.

FIG. 11 is an operation explanatory view.

FIG. 12 is an operation explanatory view.

FIG. 13 is an operation explanatory view.

FIG. 14 is a system diagram of a conventional exhaust heat recovery system.

FIG. 15 is a system diagram of another conventional exhaust heat recovery system.

[Explanation of symbols]

 1 Furnace Main Body 2 Burner 3 Air Supply Device 5 Exhaust Device 6 First Air Supply Passage 7 Second Air Supply Passage 8 Third Air Supply Passage 11 First Heat Storage Body 14 Second Heat Storage Body 17 First Exhaust passage 18 Second exhaust passage

Claims (1)

[Claims] 1. A burner installed in a furnace body, an air supply device for supplying combustion air to the burner, and combustion gas from the burner in the atmosphere. And a first air supply passage which is disposed between the air supply device and the burner and which supplies air from the air supply device to the burner and which can be controlled to open and close. , A second air supply passage, and a third
Air supply passage, a first exhaust passage provided between the furnace body and the exhaust device and capable of opening / closing control, a second exhaust passage, air flowing through the first air supply passage, and the first exhaust passage. The first heat storage body provided at a position where the combustion gas flowing through the first exhaust passage passes, and the position where the air flowing through the second air supply passage and the combustion gas flowing through the second exhaust passage pass through An exhaust heat recovery system, comprising: a provided second heat storage body.