JPS6246770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for recovering heat from combustion gas discharged from a boiler.

Conventionally, it has been proposed to recover heat from combustion gas discharged from a boiler.

For example, as shown in Japanese Patent Application Laid-open No. 54-81549, in a dual-effect absorption type water chiller/heater equipped with a boiler, a heat exchanger for heat recovery is installed in the exhaust gas passage of the boiler, and heating operation is performed. At the time, it is known that the heat exchanger is supplied with cold water generated in the evaporator or refrigerant liquid condensed in the condenser, and the heat of the exhaust gas is recovered by allowing the cold water or refrigerant liquid to absorb the heat of the exhaust gas. There is.

However, in such heat recovery technology, in order to avoid corrosion of the recovery heat exchanger and flue, it is necessary to keep the exhaust gas temperature at a temperature at which moisture in the exhaust gas does not condense. .

Therefore, it is necessary to control the exhaust gas temperature to a considerably high level, and it becomes impossible to maintain a large difference between the medium temperature of the heat recovery heat exchanger and the exhaust gas temperature, so that sufficient heat recovery cannot be expected.

An object of the present invention is to provide an exhaust gas heat recovery device that can recover almost 100% of the heat contained in combustion exhaust gas.

A feature of the present invention is that the temperature of the heat medium flowing through the heat exchanger for heat recovery is lower than the temperature at which moisture in the combustion gas condenses, and the moisture in the combustion gas is condensed and discharged. A dehumidifying heat exchanger that is placed between the combustion gas outflow side and the inflow side of the combustion gas chamber, absorbs moisture from the combustion gas on the combustion gas outflow side, and releases this moisture to the combustion gas on the combustion gas inflow side. It is.

As mentioned above, the dehumidifying heat exchanger absorbs the moisture in the combustion gas on the combustion gas outflow side, releases this moisture to the combustion gas inflow side, and prevents it from being thrown away into the atmosphere on the combustion gas outflow side. The heat held by the moisture in the gas is carried into the combustion gas inlet side (the inlet side of the heat exchanger for heat recovery), so it is about to be discarded into the atmosphere as moisture (fine droplets). can be recovered using a heat exchanger for heat recovery. This allows almost 100% of the combustion gas to be recovered.

Embodiments of the present invention will be described below with reference to FIGS. 1, 2, and 3.

FIG. 1 shows an embodiment of the present invention.

A temperature sensor 2 and a damper 3 are installed in the middle of an exhaust passage 1 for combustion gas discharged from a boiler (not shown), and a bypass passage 4 connecting both sides of the damper 3 is installed.

A corrugated matrix 5 (5a, 5b) made of Japanese paper impregnated with an aqueous lithium chloride solution spans the exhaust gas inlet and outlet of the bypass passage 4.
A dehumidifying heat exchanger 7 consisting of a drive unit 6 and a drive unit 6 is installed. The matrix 5 may be formed in an annular shape.

In the middle of the bypass passage 4, a heat exchanger 10 for heat recovery is installed, which consists of a heat exchanger tube 8 made of iron and a number of plate fins 9 made of aluminum fitted into the heat exchanger tube 8.

Bypass passage 4 at the bottom of the heat recovery heat exchanger 10
A condensed water receiving tray 11 is formed with, for example, an organic lining so that the metal material and the condensed water do not come into contact with each other as much as possible. This saucer 11
is equipped with a discharge pipe 12 for discharging condensed water and a trap 13 for preventing exhaust gas from flowing out.

Furthermore, a mist separator 14, a fan 15, and a temperature sensor 16 are installed downstream of the heat recovery heat exchanger 10.

A refrigerant conduit 17 is connected to the heat recovery heat exchanger 10, and a temperature sensor 18 and a flow switch 19 are disposed in the middle thereof.

Temperature sensors 2, 16, 18 and flow switch 19 are connected to control circuit 20, damper 3, fan 1
5 and the drive devices 6 of the dehumidifying heat exchanger 7 are each connected to a control circuit 20.

Next, the operation of this embodiment will be explained. Combustion exhaust gas from the boiler flows into the exhaust passage 1a, passes through the damper 3, and is discharged from the exhaust passage 1b. At this time, the exhaust gas temperature is detected by the temperature sensor 2 installed in the middle of the exhaust passage 1, and the control device 20 determines whether or not the heat can be recovered. Here, the control device 20
A signal indicating the supply of the heat medium to the heat recovery heat exchanger 10 by the flow switch 19 and a signal indicating the temperature of the heat medium by the temperature sensor 18 are sent. That is, heat recovery heat exchanger 1
If a heat medium is being supplied to the control device 20 and the temperature of the heat medium is low enough to condense moisture in the exhaust gas, and the temperature of the exhaust gas flowing into the exhaust passage 1 is high enough, the control device 20 At the same time, a signal is sent to switch the damper 3, the fan 15 is operated, and the exhaust gas from the boiler is passed through the exhaust passage 1a to the matrix 5a of the dehumidifying heat exchanger 7, the heat recovery heat exchanger 10, the mist separator 14, The air is discharged into the exhaust passage 1b through the bypass passage 4, which includes the fan 15 and the matrix 5b of the dehumidifying heat exchanger 7.

Further, the dehumidifying heat exchanger 7 is rotated by the drive device 6 by the control device 20, and the matrices 5a and 5b are alternately replaced. The exhaust gas flowing into the matrix 5a has a high temperature, so that the moisture absorbent, such as an aqueous lithium chloride solution, impregnated in the matrix 5a is heated, releases moisture, and dries. In this way, the exhaust gas to which moisture has been added flows into the heat recovery heat exchanger 10.

The heat medium introduced into the heat recovery heat exchanger 10 via the refrigerant pipe 17 flows inside the heat transfer tube group 8, exchanges heat with the exhaust gas flowing outside the heat transfer tube group 8 of the heat recovery heat exchanger 10, and generates heat. The medium gradually becomes hotter and recovers the heat contained in the exhaust gas.

On the other hand, the temperature of the exhaust gas is lowered to a temperature slightly higher than that of the heat medium by releasing heat to the heat medium passing through the heat exchanger tube group 8, so that the moisture contained in the exhaust gas is transferred to the fan 9 and the heat exchanger tube group 8. It condenses on the surface of the container and falls onto the saucer 11. The condensed water in the saucer 11 passes through the trap 13 and is discharged from the discharge pipe 12. The now low-temperature exhaust gas has condensed water droplets removed by the mist separator 14, is suctioned and pressurized by the fan 15, is dehumidified by the matrix 5b of the dehumidifying heat exchanger 7, and is discharged into the exhaust passage 1b. Here, the exhaust gas flowing into the matrix 5b is at a low temperature and contains moisture in a saturated state with a relative humidity of 100%, so the moisture absorbent impregnated into the matrix 5b absorbs the moisture. Therefore, the exhaust gas that has passed through the matrix 5a has a low relative temperature, and the exhaust gas passes through the exhaust passage 1b.
This prevents condensation on the aircraft wall even if it is slightly cooled while flowing inside.

Further, the matrices 5a and 5b are connected to the driving device 6.
Since the matrix in a dry state is sequentially sent to 5b and the matrix containing sufficient moisture is sent to 5a, the moisture in the exhaust gas is recovered by the matrix 5b and released into the exhaust gas again by the matrix 5a. be done.

Since the latent heat of condensation of moisture is as large as approximately 540 kcal/Kg, as described above, the matrix 5b that has absorbed moisture is moved to the position of the matrix 5a and released into the exhaust gas before it flows into the heat recovery heat exchanger 10. This corresponds to moving heat from the low temperature side to the high temperature side, and the transferred heat is eventually recovered by the heat medium flowing inside the heat recovery heat exchanger 10, so that the heat recovery is effective. The effect of being carried out can be obtained.

Note that the matrix 5b and the heat recovery heat exchanger 1
A temperature sensor 16 installed between the damper 3 and the damper 3 detects the temperature of the exhaust gas after heat recovery. The exhaust gas flow rate of the bypass passage 4 is adjusted by opening the opening of the bypass passage 4.

FIG. 2 shows another embodiment of the invention.

In this embodiment, a dehumidifying heat exchanger 7 and a heat recovery heat exchanger 10 are disposed in the middle of exhaust gas discharge passages 1a and 1b. The dehumidifying heat exchanger 7 is composed of a cross-flow matrix 5 in which a porous material is impregnated with a moisture absorbent, and high-temperature exhaust gas flowing into the heat recovery heat exchanger 10 from the exhaust passage 1a flows through one passage, and the porous material The low-temperature exhaust gas discharged from the heat recovery heat exchanger 10 with a relative humidity of approximately 100% flows through the other passage through a wall impregnated with a moisture absorbent, and is dehumidified through this wall and discharged from the discharge passage 1b. be done.

The exhaust gas that has absorbed moisture in the dehumidifying heat exchanger 7 is guided to the exhaust gas heat recovery heat exchanger 10, and is passed through the heat exchanger tube group 8.
It exchanges heat with the heat medium flowing inside. At this time, moisture in the exhaust gas condenses on the surfaces of the fins 9 and the heat exchanger tube group 8, and falls onto the saucer 11. The condensed water in the saucer 11 is discharged through a drap 13 and a discharge pipe 12. In addition, sulfur oxides, nitrogen oxides, carbon dioxide, etc. during combustion are dissolved in the condensed water in the saucer 11.
Since it is an acidic liquid, it requires neutralization treatment.

This embodiment has the advantage that since the dehumidifying heat exchanger 7 is not of the matrix rotation type, its rotational driving force can be omitted.

FIG. 3 shows another embodiment of the invention.

In this embodiment, an open absorption cycle is used as the dehumidification device. Exhaust gas discharge passage 1a
Then, the heat passes through the generator 21, the heat exchanger 10 for heat recovery, that is, the condenser heat transfer tube group 8a, and the heat transfer tube group 8b of the absorber 28, and is discharged from the discharge passage 1b. Mist separators 14a, 1 are provided on the downstream side of each exchanger.
4b and 14c are provided to prevent the solution and condensate from flowing out together with the exhaust gas flow.
A filling material 24 made of ceramic or glass, for example, is arranged inside the generator 21, and this filling material 24
A liquid moisture absorbent, such as an aqueous sodium hydroxide solution, is sprayed from a spraying device 22 located above. This moisture absorbent exchanges heat with the exhaust gas, is heated, releases moisture, and is concentrated. The concentrated liquid moisture absorbent is sent from the pump 25 to the dispersion device 26 of the absorber 28 .
The exhaust gas humidified by the generator 21 reaches the next heat recovery heat exchanger 10, exchanges heat with the heat medium flowing inside, and is cooled to a temperature almost close to the heat medium temperature.
Fins (not shown) in exhaust gas and heat exchanger tube group 8
It condenses on the surface of a and falls onto the saucer 11. saucer 1
The condensate of No. 1 is in this case almost neutral and contains only some carbonic acid. The reason is that the previous stage generator 2
1, it is a strong acid component. sulfur oxides and chlorine,
This is because NOx and the like react with the moisture absorbent NaOH to generate salt. Therefore, the condensed water in the saucer 11 is discharged through the trap 13 and the discharge pipe 12.
It can be reused as gray water in buildings.

The exhaust gas is then sent to absorber 28. The absorber 28 includes a heat transfer tube group 8 of the heat recovery heat exchanger 10.
b is disposed, and a thick liquid moisture absorbent is sprayed onto the heat transfer tube group 8b by the disposed spraying device 26, and fins (not shown) flow down the surface of the heat transfer tube group 8b. absorbs moisture. The heat of condensation generated at this time can be exchanged with the heat medium flowing within the heat transfer tube group 8b, and the heat can be further recovered by the heat medium. The liquid hygroscopic agent that has absorbed moisture and become thinner is sent from the pump 27 to the spraying device 22 of the generator 21 .

Note that in order to effectively operate the dehumidification cycle, the absorbents from pump 25 and pump 27 can also exchange heat with each other.

According to each of the above-mentioned embodiments, since the dehumidifying device is placed between the heat exchangers for heat recovery, it is possible to sufficiently recover the moisture in the exhaust gas, and furthermore, the relative humidity of the exhaust gas can be lowered. This has the effect of improving heat recovery efficiency and preventing moisture condensation within the flue. As described above, according to the present invention, it is possible to provide an exhaust gas heat recovery device that can recover almost 100% of the heat contained in combustion exhaust gas.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, and FIG.
3 are explanatory diagrams of other embodiments of the present invention. 1c, 1b... Exhaust passage, 2, 16, 18...
Sensor, 3...damper, 4...bypass passage,
5... Matrix, 7... Dehumidifying heat exchanger, 10
...Heat exchanger for heat recovery, 11...Saucer, 14...
Mist separator, 15...fan, 19...flow switch, 20...control circuit, 21...generator, 28...absorber.

Claims (1)

[Claims] 1 A heat exchanger is disposed in the combustion gas exhaust path of a boiler, and a heat medium is circulated through the heat exchanger to recover exhaust heat of the combustion gas, and the temperature of the heat medium flowing through the heat exchanger. is placed below the temperature at which moisture in the combustion gas condenses, condenses moisture in the combustion gas, and discharges the heat exchanger. An exhaust gas heat recovery device characterized by comprising a dehumidifying heat exchanger that absorbs moisture from combustion gas and releases this moisture to the combustion gas on the combustion gas inflow side.