JPH11153318A - Flue gas processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish an efficient gas reheating system with steam by utilizing heat of steam drain generating from steam used for heating flue gas in a flue gas processing system for processing combustion gas of a boiler or the like. SOLUTION: When a flue gas is heated by a heating medium supplied from a heat recovery device 24 to a GGH reheater 25 via a communication pipe 30, the heating medium is heated by a heating medium heater 17, and after being temporarily stored in a steam drain tank 5 via a steam drain line, heat retained by steam drain is used again to heat the waste gas by a group of steam drain heat transfer pipes 14 arranged in a waste gas passage 35. Thus, reheating of the waste gas and cooling of the steam drain are simultaneously carried out so that a heat exchanger such as a drain cooler or the like and a coolant such as water or the like become unnecessary. Because latent heat as well as sensible heat retained by the step as thermal energy is used, the amount of steam required can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flue gas treatment apparatus for treating combustion exhaust gas of a boiler or the like, and more particularly to a method for effectively utilizing steam drain generated in a gas reheating apparatus using steam and a suitable method for cooling exhaust gas. About.

[0002]

2. Description of the Related Art The mainstream of a flue gas desulfurization system in a boiler plant is a wet process. In the wet method, the exhaust gas is brought into contact with the absorbing liquid in the absorption tower of the desulfurization apparatus, so that the exhaust gas at the outlet of the absorption tower becomes a moisture-saturated gas, which causes corrosion by SO ₃ mist and purple smoke at the smoke outlet. To prevent this, a gas reheating device is generally installed at the outlet of the absorption tower to raise the temperature of the exhaust gas and discharge it from the chimney.

FIGS. 4 and 6 schematically show a conventional flue gas treatment system. As a method of reheating exhaust gas at the outlet of the absorption tower,
A steam gas heater (SGH) method using steam supplied from the boiler plant 18 shown in FIG. 4 and a gas gas heater (GGH) method using thermal energy of exhaust gas shown in FIG. 6 are mainstream.

In the SGH system shown in FIG. 4, steam is supplied from a boiler plant 18 to an SGH 22 disposed in an exhaust gas flow path on the downstream side of an absorption tower 21 via a steam supply line 3 to heat the exhaust gas. , And is returned to the boiler plant 18 from the steam drain line 4.

[0005] In the GGH system shown in FIG.
The GGH heat recovery unit 24 and the GGH reheater 25 connected by 31 each have a heat transfer tube for recovering the heat of the exhaust gas, and the GGH heat recovery unit 24 installed on the upstream side of the absorption tower 21 separates the exhaust gas from the exhaust gas. Using the recovered heat, the absorption tower 2
1 This is a system in which the exhaust gas is heated by the GGH reheater 25 installed on the downstream side. The heat transfer from the GGH heat recovery unit 24 to the GGH reheater 25 is performed by the heat medium filled in the communication tubes 30 and 31.

In the heat exchange system shown in FIGS. 4 and 6, an air preheater 19, an electric precipitator 20 and an absorption tower 21 are arranged in the exhaust gas flow path on the downstream side of the boiler plant 18 in order from the upstream side. The exhaust gas is heated by the SGH 22 or the GGH reheater 25 and the temperature is increased, and the exhaust gas is discharged from the chimney 23 to the atmosphere.

Next, FIG. 7 shows a detailed view of a conventional SGH type gas reheating apparatus shown in FIG. In the SGH method of FIG. 7, the SGH gas reheating device mainly includes an SGH reheater 22, a SGH heat transfer tube group 2, a steam supply line 3, a steam drain line 4, a steam drain tank 5, a steam drain pump 6,
Etc. The SGH inlet gas at the outlet of the desulfurization device is a water-saturated gas, and the exhaust gas is heated by exchanging heat with the SGH heat transfer tube group 2 installed in the exhaust gas passage 35. Depending on the request from the boiler plant 18 side, SGH
The outlet gas of No. 22 is usually about 70 to 90 ° C. The supply line 3 for the steam supplied from the boiler plant 18
By performing heat exchange with the gas at the outlet of the desulfurization device in the GH heat transfer tube group 2, the water becomes saturated water, and the steam drain line 4
It is collected in the steam drain tank 5. After the steam drain is once stored in the steam drain tank 5, the steam drain is returned to the boiler plant 18 via the drain flow control valve 10 by the steam drain pump 6.

The amount of steam supplied from the boiler plant 18 to the SGH 22 is measured by measuring the temperature of the outlet gas after passing through the SGH heat transfer tube group 2 by the temperature detector 11 so that the exhaust gas temperature of the outlet gas becomes equal to or higher than a set value. It is adjusted by a steam flow control valve 9 provided in the steam supply line 3.

Further, the GGH shown in FIG.
FIG. 9 shows a detailed view of the gas reheating apparatus of the system. The GGH gas reheating device includes a steam supply line 3, a steam drain line 4, a steam drain tank 5, a steam drain pump 6, a GGH heat recovery unit 24, and a heat recovery unit 24 from the boiler plant 18.
Heat recovery tube group 27 in GGH, GGH reheater 2
5. GGH reheat heat transfer tube group 16 in reheater 25, GG
The high-temperature side connection pipe 30 and the low-temperature side connection pipe 31 which are heat medium flow paths between the H reheating heat transfer pipe group 16 and the GGH heat recovery unit heat transfer pipe group 27, the steam supply line 3, the steam drain line 4, and the high temperature side connection pipe The heat medium heater 17 for exchanging heat between the low temperature side communication pipe 31 and the low temperature side communication pipe 31 is provided.

The control method of the supply amount of steam from the steam supply line 3 in the GGH gas reheating apparatus shown in FIG.
Similar to the GH method, the GG installed in the exhaust gas passage 35
The opening of the flow control valve 9 is adjusted based on the signal of the temperature detector 11 installed at the outlet of the H reheater 25.
In the H method, instead of directly heating the exhaust gas using steam, the heat medium in the high-temperature side connection pipe 30 that transfers heat from the heat recovery unit 24 installed in the exhaust gas channel 35 to the reheater 25 is heated. In this method, the exhaust gas is reheated by heating in the medium heater 17. The steam supplied from the boiler plant 18 to the heating medium heater 17 via the steam supply line 3 is used for heat exchange with the heat supply medium, and then is collected from the steam drain line 4 to the steam drain tank 5 and The water is returned to the boiler plant 18 again through the drain flow control valve 10 by the drain pump 6.

[0011]

In the above-mentioned prior art SGH and GGH gas reheating devices, it is necessary to transport steam drain, which is saturated water. When the saturated water is transported by the steam drain pump 6, the liquid temperature rises due to friction and the like due to the swirling flow in the steam drain pump 6, and the saturated water may be vaporized again. The temperature is often limited, and installation of a steam drain cooler or the like is essential. As a conventional system diagram with a steam drain cooler, S
FIG. 8 shows a case where the antenna is installed in the GH system, and FIG. 10 shows a case where the antenna is installed in the GGH system.

When the steam drain cooler 12 is installed on the downstream side of the steam drain line 4 shown in FIGS. 8 and 10, it is possible to cool the steam drain, but some kind of refrigerant (cooling water) is used to cool the steam. ) 13 must be supplied to the steam drain cooler 12. In addition, this requires not only the necessity of newly preparing the cooling water 13 but also discarding the thermal energy of the steam drain, which is not an economical method of using steam.

An object of the present invention is to provide a flue gas treatment system for treating a combustion exhaust gas of a boiler or the like, by utilizing the calorific value of a steam drain generated from steam used for raising the temperature of the exhaust gas, so that the gas generated by the efficient steam is used. Establish a reheating system.

[0014]

The above object of the present invention can be achieved by introducing a steam drain used for raising the temperature of exhaust gas into a steam drain heat transfer tube group provided in an exhaust gas flow passage to heat the exhaust gas. . The present invention relates to an SGH type gas reheating device, G
It includes the following three types of flue gas treatment devices in which a gas reheating device of the GH system and a gas reheating device using both the SGH system and the GGH system are arranged.

(1) A desulfurization device for removing sulfur oxides and dust in the exhaust gas, a gas reheating device for increasing the temperature of the exhaust gas, and In a flue gas treatment device provided with a chimney for discharging to the atmosphere, a steam gas heater provided with a heat transfer tube group to which steam is supplied, which is disposed in an exhaust gas passage as a gas reheating device, and a steam drain discharged from the steam gas heater And a steam drain heat transfer tube group to which the gas is supplied (see FIG. 1).

(2) A desulfurization device for removing sulfur oxides and dust in the exhaust gas, a gas reheating device for increasing the temperature of the exhaust gas, and In a flue gas treatment device equipped with a chimney that discharges to the atmosphere, as a gas reheating device, a heat recovery unit placed in the exhaust gas flow channel on the upstream side of the desulfurization device and the exhaust gas flow channel on the downstream side of the desulfurization device A reheater disposed, a gas gas heater connected between the heat recovery unit and the reheater by a circulation path of a heat medium, and heating the heat medium in the heat medium circulation path using steam. Smoke exhaust treatment device including a heat medium heater provided outside the exhaust gas flow path and a steam drain heat transfer tube group provided in the exhaust gas flow path and supplied with steam drain discharged from the heat medium heater (see FIG. 2) ).

(3) A desulfurization device for removing sulfur oxides and soot and dust in the exhaust gas, a gas reheating device for increasing the temperature of the exhaust gas, and a treated gas in order from the upstream side to the flow path of the exhaust gas discharged from the combustion device. In a flue gas treatment device equipped with a chimney that discharges to the atmosphere, a steam gas heater equipped with a heat transfer tube group to which steam is provided, which is arranged in the exhaust gas passage as a gas reheating device, and desulfurization as a gas reheating device A heat recovery device disposed in the exhaust gas flow path on the upstream side of the device and a reheater disposed in the exhaust gas flow path on the downstream side of the desulfurization device, and a heat medium between the heat recovery device and the reheater. A gas gas heater connected by a circulation flow path, a heat medium heater provided outside an exhaust gas flow path that heats the heat medium in the heat medium circulation flow path using steam, and the heat medium heater disposed in the exhaust gas flow path. Steam drain from heat medium heater Flue gas treatment apparatus having a steam drain heat transfer tube group steam drain discharged from the steam gas heater is supplied (see FIG. 3).

[0018]

The steam drain used for heating the exhaust gas passes through the steam drain heat transfer tube group provided in the exhaust gas flow path again, so that the steam drain exchanges heat with the exhaust gas. Drain cooling can be performed simultaneously. This eliminates the need for a heat exchanger such as a drain cooler, and eliminates the need for a coolant such as cooling water. In addition, since not only latent heat but also sensible heat is used as heat energy of the steam, the required steam amount can be reduced.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an SGH type gas reheating apparatus used in an SGH type flue gas treatment system shown in FIG. 4 which is disposed in a flue gas treatment system according to an embodiment of the present invention.

The SGH type gas reheating apparatus shown in FIG. 1 mainly includes an SGH reheater 22, a SGH heat transfer tube group 2, a steam supply line 3, a steam drain line 4, a steam drain tank 5,
It comprises a steam drain pump 6, a drain flow control valve 10, a steam drain heat transfer tube group 14, and the like. The SGH inlet gas at the desulfurizer outlet is a moisture-saturated gas, and the exhaust gas is heated by exchanging heat with the SGH heat transfer tube group 2 installed in the exhaust gas passage 35, and the outlet gas of the SGH 22 is usually 70 to 90 ° C. About. The steam supply line 3 supplied from the boiler plant 18 (FIG. 4) becomes saturated water by performing heat exchange with the inlet gas at the outlet of the desulfurization unit in the SGH heat transfer tube group 2, and becomes steam drain. The steam supply amount from the boiler plant 18 to the SGH 22 is measured by measuring the temperature of the outlet gas after passing through the SGH heat transfer tube group 2 by the temperature detector 11, and the steam is supplied so that the exhaust gas temperature of the outlet gas becomes equal to or higher than a set value. It is adjusted by a steam flow control valve 9 provided in the supply line 3.

The gas reheating device shown in FIG. 1 differs from the conventional gas reheating device in the method of using the steam drain.
The steam drain of the steam drain line 4 that has passed through the SGH heat transfer tube group 2 and has become saturated water is temporarily stored in a steam drain tank 5 and is discharged by a steam drain pump 6 on the downstream side of an absorption tower for flue gas desulfurization. The steam is sent to the steam drain tube group 14 installed in the flow path. In the steam drain tube group 14, the sensible heat of the steam drain is used to raise the gas temperature and cool the steam drain. The cooled steam drain is returned to the boiler plant 18 again. In addition, temperature detector 1
The supply amount of steam is adjusted by the steam flow control valve 9 so that the exhaust gas temperature of the outlet gas becomes equal to or higher than the set value at the measurement temperature of 1.

Although the steam drain heat transfer tube group 14 is installed in the exhaust gas passage 35 on the downstream side of the SGH heat transfer tube group 2 in FIG. 1, the steam drain heat transfer tube group 14 is installed in FIG. May be installed in the exhaust gas passage 35 between the upstream side of the heat transfer tube group 2 for SGH and the heat transfer device in the heat transfer tube group 2 for SGH. In the above gas reheating device, the heat transfer tube group 2
The state of existence of steam in the inside will be described in detail.

Here, as an example, a case where a certain superheated steam is supplied will be considered with reference to a TH diagram shown in FIG. The reheating of the gas using the superheated steam, that is, the process of cooling the steam, can be roughly classified into the states shown in FIG. First, the superheated steam supplied in a state is cooled to a state of saturated steam under an equal pressure. Then state →
In the process of the state, the latent steam is deprived of latent heat and becomes a state of saturated water. The process up to this point is performed in the tubes of the SGH heat transfer tube group 2 shown in the conventional gas reheating device, and the heat energy used is ΔH (1-3). On the other hand, in the embodiment of the present invention, the steam drain heat transfer tube group 1
The installation of 4 makes it possible to utilize the sensible heat of the steam drain up to the state →. That is, in the gas reheating device of the present embodiment, ΔH (1-4) can be used as the heat energy of the steam, and ΔH (3-4) is more than the conventional gas reheating device. It is possible to utilize the amount of heat.

The embodiment shown in FIG. 2 is an example in which the GGH-type smoke exhaust treatment system shown in FIG. 5 is used. G
In the GH method, the heat recovered by the GGH heat recovery unit 24 installed on the upstream side of the absorption tower 21 is used to heat the GGH installed in the downstream side of the absorption tower 21 by the heat medium filled in the connecting pipe 30.
This is a system for moving the exhaust gas to the reheater 25 to raise the temperature of the exhaust gas. At this time, when the signal from the temperature detector 11 installed in the exhaust gas passage 35 is equal to or lower than the set temperature, steam is supplied to the heat medium heater 17 by the steam flow rate regulating valve 9. The heat medium heater 17 exchanges GGH by heat exchange with steam.
The temperature of the medium supplied to the GGH heat transfer tube group 16 in the reheater 25 is increased, and GG is performed by the medium having the increased temperature.
The H heat transfer tube group 16 raises the gas temperature in the exhaust gas passage 35 to a set value. The steam used to raise the temperature of the medium in the heating medium heater 17 becomes a steam drain and the steam drain line 4
From the steam drain tank 5. After that, the steam is supplied to the steam drain heat transfer tube 14 by the steam drain pump 6, heat-exchanged again, and then sent to the boiler plant side.

The embodiment shown in FIG. 3 shows a case where the SGH 22 and the GGH reheater 25 are shared as a gas reheating method. The method of using steam for each is described above, and the description is omitted. However, the steam drain used in the SGH 22 disposed in the exhaust gas passage 35 and the steam drain used for raising the temperature of the medium in the heat medium heater 17 are steam The steam is sent from the drain 4 to the steam drain tank 5, where it is temporarily stored, supplied to the steam drain heat transfer tube 14 by the steam drain pump 6, heat-exchanged again, and then sent to the boiler plant side.

[0026]

According to the present invention, the heat energy of the steam drain can be reused, and the amount of steam used by the gas reheating device can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an SGH gas reheating device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a GGH gas reheating device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a gas reheating apparatus sharing SGH and GGH according to an embodiment of the present invention.

FIG. 4 is a system diagram of a flue gas treatment system including an SGH type gas reheating device.

FIG. 5 is a system diagram of a flue gas treatment system provided with a GGH type gas reheating device of the present invention.

FIG. 6 is a system diagram of a flue gas treatment system provided with a conventional GGH type gas reheating device.

FIG. 7 is a diagram showing an SGH type gas reheating apparatus according to the related art.

FIG. 8 is a view showing an SGH type gas reheating apparatus according to the related art.

FIG. 9 is a diagram showing a GGH type gas reheating apparatus according to the related art.

FIG. 10 is a diagram showing a GGH type gas reheating apparatus according to the related art.

FIG. 11 is a state diagram of steam.

[Explanation of symbols]

2 SGH heat transfer tube group 3 steam supply line 4 steam drain line 5 steam drain tank 6 steam drain pump 9 steam flow control valve 10 drain flow control valve 11 temperature detector 14 steam drain heat transfer tube group 16 GGH reheating heat transfer tube group 17 Heat medium heater 18 Boiler plant 19 Air preheater 20 Electric precipitator 21 Absorption tower 22 SGH 23 Chimney 24 GGH heat recovery unit 25 GGH reheater 27 GGH heat recovery unit heat transfer tube group 30, 31 Heat medium communication tube 35 Exhaust gas flow Road

Continued on the front page (72) Inventor Masayuki Yamamoto 6-9 Takaracho, Kure City, Hiroshima Prefecture Inside the Babcock Hitachi Kure Factory (72) Inventor Atsushi Uenozono 6-9 Takaramachi Kure City, Hiroshima Prefecture Babcock Hitachi Kure Co., Ltd. in the factory

Claims (6)

[Claims] 1. A desulfurization device for removing sulfur oxides and soot and dust in an exhaust gas, a gas reheating device for increasing the temperature of the exhaust gas, and an atmosphere for treating the treated gas in the order from the upstream side to the flow path of the exhaust gas discharged from the combustion device. In a flue gas treatment device provided with a chimney that discharges inside, a steam gas heater that is arranged in the exhaust gas channel as a gas reheating device and has a heat transfer tube group to which steam is supplied, and a steam drain discharged from the steam gas heater And a steam drain heat transfer tube group to be supplied. 2. A steam drain heat transfer tube group is provided between the communication gas flow passage from the desulfurization device outlet of the exhaust gas flow passage to the steam gas heater, between the heat transfer tubes in the steam gas heater heat transfer tube group,
The smoke exhaust treatment device according to claim 1, wherein the exhaust gas treatment device is disposed in any one of exhaust gas passages between the steam gas heater and the chimney. 3. A desulfurizer for removing sulfur oxides and soot and dust in the exhaust gas, a gas reheating device for increasing the temperature of the exhaust gas, and an atmosphere for treating the treated gas in the order from the upstream side to the flow path of the exhaust gas discharged from the combustion device. In a flue gas treatment device with a chimney that discharges inside, as a gas reheating device, it is placed in the exhaust gas channel on the upstream side of the desulfurization device and in the exhaust gas channel on the downstream side of the desulfurization device Gas heater connected between the reheater and the heat recovery unit and the reheater through a heat medium circulation channel, and an exhaust gas for heating the heat medium in the heat medium circulation channel using steam. A flue gas treatment apparatus, comprising: a heat medium heater provided outside the flow path; and a steam drain heat transfer tube group disposed in the exhaust gas flow path and supplied with a steam drain discharged from the heat medium heater. . 4. A steam drain heat transfer tube group is provided between the desulfurization device outlet of the exhaust gas passage and the gas gas heater reheater, between the heat transfer tubes in the gas gas heater reheat heat transfer tube group, and the gas gas heater reheater. The smoke exhaust treatment device according to claim 3, wherein the exhaust gas treatment device is disposed in any one of the exhaust gas passages between the chimneys. 5. A desulfurization device for removing sulfur oxides and dust in the exhaust gas, a gas reheating device for increasing the temperature of the exhaust gas, and an atmosphere for treating the treated gas in the order from the upstream to the flow path of the exhaust gas discharged from the combustion device. In a flue gas treatment device provided with a chimney that discharges steam, a steam gas heater that is provided in a flue gas passage as a gas reheating device and has a heat transfer tube group to which steam is supplied, and a desulfurization device as a gas reheating device A heat recovery unit disposed in the exhaust gas flow path on the upstream side of the reheater and a reheater disposed in the exhaust gas flow path on the downstream side of the desulfurization device A gas gas heater connected by a flow path; a heat medium heater provided outside an exhaust gas flow path for heating the heat medium in the heat medium circulation flow path using steam; and the heat source disposed in the exhaust gas flow path. Steam drain from the medium heater Flue gas treatment apparatus characterized by vapor drain discharged from team gas heater having a steam drain heat transfer tube group is supplied. 6. A steam drain heat transfer tube group is provided between the desulfurization device outlet of the exhaust gas passage and the gas gas heater reheater, between the heat transfer tubes in the gas gas heater reheat heat transfer tube group, and the gas gas heater reheater. The smoke exhaust treatment device according to claim 5, wherein the device is disposed between the steam gas heaters, between the heat transfer tubes in the steam gas heater heat transfer tube group, or between the steam gas heater and the chimney.