JPH0821618A - Exhaust gas treating device - Google Patents

Abstract

PURPOSE:To contrive to economize a makeup water, by forming at least a heat exchanging tube at a down stream side of a heat exchanger, by a carbon tube, in a case wherein an exhaust gas from a boiler and the like is cooled by the heat exchanger, a desulfurization by a wet type flue gas desulfurizating device is executed, and after a rising of a temperature of this is executed, an emission to an atmosphere is executed. CONSTITUTION:An exhaust gas from a boiler 1, after a denitration treatment by a denitration device 5, is cooled during passing through an air preheater 6, and a heat exchanger 8 in this order, and, after that, passes through a wet type flue gas desulfurizating device 9, and is exhausted from a chimney 3. In this occasion, at least heat exchanging tubes at a down stream side of a heat exchanger 8, are formed by carbon tubes. By this, the exhaust gas which is cooled to a low temperature is guided, as it is possible that the exhaust gas is cooled to 90 deg. or lower, for example, to about 50 deg.C without any worry about a corrosion of a tube. As a result, the decrease of the makeup water becomes possible at the wet type flue gas desulfurizating device 9, by making an evaporation quantity less, even if the gas and an absorption liquid execute a gas liquid contact in an absorption tower 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment apparatus for purifying exhaust gas from combustion equipment such as a boiler.

[0002]

2. Description of the Related Art Gas discharged from combustion equipment, such as a boiler, contains nitrogen oxides, dust, sulfur oxides, etc., and therefore, purification processing such as denitration, dedusting, desulfurization, etc. by an exhaust gas treatment device. After that, it is opened to the atmosphere.

As shown in FIG. 3, the exhaust gas treating apparatus includes a denitration device 5, an air preheater (GAH) 6, an electrostatic precipitator (E).
P) 7, a gas gas heater (GGH) 31, a wet flue gas desulfurization device 33, a gas gas heater (GGH) 34, etc., and the exhaust gas from the boiler 1 is denitrified by a denitration device 5, In the air preheater 6, for example, about 370
It is cooled from ℃ to about 130-140 ℃. Then, it is dedusted by the electric dust collector 7 and further cooled to, for example, about 90 ° C. by the gas gas heater 31, and then guided to the wet flue gas desulfurization device 33 to remove the sulfur content in the gas for desulfurization. . The gas after the desulfurization treatment is heated from, for example, about 50 ° C. to about 90 to 100 ° C. through the gas gas heater 34, and then released from the chimney 3 to the atmosphere.

[0004]

In the flue gas desulfurization apparatus 33, the exhaust gas is brought into gas-liquid contact in the absorption tower 35 with a slurry-like absorption liquid containing a calcium-based absorbent such as calcium carbonate. The sulfur oxide in the gas is absorbed and removed by the absorbing liquid to perform the desulfurization treatment of the exhaust gas. The absorption liquid that has absorbed the sulfur oxides is oxidized in the absorption tower 35, a part of this is appropriately extracted and sent to the separator 36, where it is subjected to solid-liquid separation and gypsum is recovered. A part of the filtrate is returned to the absorption tower 35 so that it can be effectively used. In the absorption tower 35,
For example, the exhaust gas from the gas heater 31 and the absorbing liquid at about 90 ° C. and the absorbing liquid are brought into gas-liquid contact with each other.
5 must be supplied. Therefore, the make-up water can be reduced by cooling the exhaust gas to a temperature of, for example, about 50 ° C by the gas gas heater 31, but since the heat exchange tube of the gas gas heater 31 is made of a material such as SUS or STB, the temperature is 90 ° C. Below that, the tube may corrode, so the exhaust gas can only be cooled to about 90 ° C.

Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide an exhaust gas treatment apparatus capable of reducing the makeup water of the wet flue gas desulfurization apparatus.

[0006]

In order to achieve the above-mentioned object, the exhaust gas treating apparatus of the present invention cools the exhaust gas from a combustion device with a heat exchanger and then desulfurizes it with a wet flue gas desulfurization apparatus. In an exhaust gas treatment device that heats up the heat exchanger and releases it to the atmosphere, at least the heat exchanger tube on the exhaust gas downstream side of the heat exchanger is formed of a carbon tube, or the heat exchanger and the wet flue gas in the exhaust gas duct. A gas cooler for further cooling the exhaust gas from the heat exchanger is provided between the desulfurizer and the carbon tube as the heat exchange tube (claims 1 and 3).

Further, the exhaust gas from the combustion equipment is cooled by exchanging heat with a heat exchange medium in a heat exchanger, and then desulfurized by bringing it into gas-liquid contact with an absorbent containing a calcium-based absorbent in a wet flue gas desulfurizer. Then, in the exhaust gas treatment device which is heated to the heat exchange medium from the heat exchanger and then opened to the atmosphere,
A heat exchange tube at least on the exhaust gas downstream side of the heat exchanger is formed of a carbon tube, and a vacuum belt filter is used as a device for solid-liquid separation of gypsum generated from the absorption liquid after desulfurization treatment of the flue gas desulfurization device, And, hot water is made by the heat component other than the heat component necessary for heating the gas after desulfurization of the heat exchange medium from the heat exchanger, and the hot water supplied to the vacuum belt filter to utilize this hot water for cake washing. A supply means is provided (Claim 2).

Further, after the exhaust gas from the combustion equipment is cooled by a heat exchanger, it is desulfurized by being brought into gas-liquid contact with an absorbent containing a calcium-based absorbent in a wet flue gas desulfurization apparatus, and then heated. In an exhaust gas treatment device opened to the atmosphere, between the heat exchanger of the exhaust gas duct and the wet flue gas desulfurization device, a gas cooler for further cooling the exhaust gas from the heat exchanger by using a carbon tube as a heat exchange tube is installed. With the use of a vacuum belt filter as a device for solid-liquid separation of the gypsum produced from the absorption liquid after desulfurization of the flue gas desulfurization device, and to use the water heated in the gas cooler for cake cleaning A means for supplying water to the vacuum belt filter is provided (Claim 4).

[0009]

The tube of the heat exchanger before desulfurization by the conventional wet flue gas desulfurization device is made of a material such as SUS and STB, so that the exhaust gas can be cooled only up to about 90 ° C. By forming at least the heat exchange tube on the exhaust gas downstream side of the heat exchanger with a carbon tube, the carbon tube has a high thermal conductivity and there is no risk of gas corrosion even when the exhaust gas is 90 ° C. or lower. Therefore, the exhaust gas can be cooled more than before,
It is possible to reduce the makeup water of the wet flue gas desulfurization device (Claim 1). Further, by providing a gas cooler having a carbon tube between the heat exchanger of the exhaust gas duct and the wet flue gas desulfurization apparatus, it is possible to further cool the exhaust gas to the wet flue gas desulfurization apparatus. It is possible to reduce the makeup water of the above (claim 3).

Further, hot water is produced by the heat components other than the heat components necessary for heating the gas after desulfurization of the heat exchange medium from the heat exchanger and the heat components recovered by the gas cooler, and this hot water is supplied to the flue gas desulfurization apparatus. By using it for cake cleaning of the vacuum belt filter, the water content of the recovered gypsum in the vacuum belt filter can be reduced (claims 2 and 4).

[0011]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a configuration diagram showing a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a boiler as a combustion device, and a fuel supply line for supplying fuel such as coal to the boiler 1. 2 is connected.

An exhaust gas duct 4 for guiding the exhaust gas discharged from the boiler 1 to the chimney 3 is connected to the boiler 1, and the exhaust gas duct 4 is sequentially arranged along the flow direction of the gas, for example, ammonia or alkaline ash in the exhaust gas. Denitration device 5 that removes nitrogen oxides in the gas by blowing air etc.
AH) 6, an electrostatic precipitator (EP) 7 for capturing dust such as dust in gas, a first gas gas heater (GGH) 8, an absorption tower 10 of a wet flue gas desulfurization device 9, a second gas gas heater (G
GH) 11 is provided.

The air preheater 6 indirectly exchanges heat between the exhaust gas of high temperature (for example, about 370 ° C.) after the denitration treatment and the air supplied to the boiler 1 and the like, and the exhaust gas is, for example, about 130 to 140.
It is cooled to ℃.

In the flue gas desulfurization apparatus 9, the exhaust gas is brought into gas-liquid contact with the slurry-like absorption liquid containing a calcium-based absorbent such as calcium carbonate in the absorption tower 10 to absorb the sulfur content in the gas into the absorption liquid. The gas is removed and the gas is desulfurized.

In the absorption tower 10, an absorption liquid line 12 for supplying an absorption liquid containing absorbent such as calcium carbonate and makeup water.
Is connected, and a liquid storage tank 13 for storing the absorbing liquid is provided below the inside thereof. Liquid reservoir 13
The absorption liquid is absorbed by the spray nozzle 14 in the upper part of the absorption tower 10.
Circulation line 1 having a circulation pump 15 for transferring to
6 is connected, and an air supply line 17 for supplying air for aerating (oxidizing) the absorbent after desulfurization to generate gypsum is connected. The circulation line 16 is connected to a liquid extraction line 19 for extracting a part of the absorbing liquid and sending it to a thickener 18, for example, a thickener 18, so that the liquid concentrated by the thickener 18 is sent to a vacuum belt filter 20 which is a solid-liquid separator. It has become.

The first gas heater 8 cools the gas by indirectly exchanging heat between the gas dedusted by the electrostatic precipitator 7 and a heat exchange medium such as water via a heat exchange tube. The tube is formed of a carbon tube and is configured so that the exhaust gas can be cooled to about 40 to 80 ° C, for example, 50 ° C. This is because the material of the tube of the heat exchanger before desulfurization by the conventional wet flue gas desulfurization equipment is SUS, STB, etc., so that the tube is corroded by the sulfur content in the gas when the exhaust gas is 90 ° C or less. Therefore, the exhaust gas could be cooled only up to about 90 ° C. Therefore, by forming the heat exchange tube from a carbon tube, there is no risk of corrosion by the gas even when the temperature of the exhaust gas is 90 ° C. or lower, so that the exhaust gas can be cooled to 90 ° C. or lower. Therefore, at least the heat exchange tube on the exhaust gas downstream side of the gas gas heater 8 (the tube of the portion that cools the exhaust gas to 90 ° C. or lower) may be formed of a carbon tube, and only that portion may be formed of the carbon tube. The entire structure may be formed of a carbon tube.

The second gas heater 11 exchanges heat between the gas of about 44 ° C. and the heat exchange medium (water) from the first gas heater 8 through the absorption tower 10 of the flue gas desulfurization apparatus 9 to generate the gas. The temperature is raised to about 90 ° C., and the heated gas is released from the chimney 3 to the atmosphere. Water, which is the heat exchange medium, is a common heat exchange medium for the first gas gas heater 8 and the second gas gas heater 11, and in order to cool the exhaust gas in the first gas gas heater 8, the exhaust gas in the second gas gas heater 11 is used. Acts to heat up. Further, in the water flow passage 21 which is a heat exchange medium, heat components other than the heat components necessary for heating the gas after desulfurization of the heat exchange medium are recovered and the makeup water is heated to, for example, about 70 ° C. The third heat exchanger 22 is provided.

In the third heat exchanger 22, a makeup water line 23 for guiding the heated makeup water to the vacuum belt filter 20.
Are connected to configure the hot water supply means 24.

The vacuum belt filter 20 collects gypsum by solid-liquid separation of gypsum (solid content) and liquid, and is connected to a return line 25 for returning the filtrate to the absorption tower 10. Specifically, the gypsum slurry liquid is supplied to the upper surface of the upper filter 26 while circulating the endless filter (a filter cloth composed of a belt) 26, and the gypsum slurry liquid is brought into close contact with the lower surface of the upper filter 26. The tray 27 provided in this manner is evacuated by a vacuum pump or the like, and the filter 26
While the solid content (gypsum) remains on the upper surface, the liquid content is sucked through the filter 26, and the sucked liquid content (filtrate) is supplied to the absorption tower 10 through the return line 25. R. The warm water from the makeup water line 23 is used for washing the cake. That is, the solid content (cake) remaining on the upper surface of the filter 26 is washed with warm water from the makeup water line 23, and the filtrate after cake washing is passed through the tray 27 and the return line 25 to the absorption tower 10. It will be supplied as makeup water to.

Next, the operation of the first embodiment will be described.

Exhaust gas at a high temperature, for example, about 370 ° C. from the boiler 1 is denitrified by the denitration device 5 and then cooled by the air preheater 6 to about 130 to 140 ° C. After being dedusted by the electric dust collector 7, it is cooled by the first gas heater 8 to about 50 ° C. by the heat exchange medium (water). At this time, since at least the heat exchange tube on the downstream side of the exhaust gas of the gas gas heater 8 (the tube of the part that cools the exhaust gas to 90 ° C or less) is formed of a carbon tube, the exhaust gas is heated to 90 ° C or less, for example, to about 50 ° C. Can be cooled without worrying about corrosion. Then, the cooled exhaust gas reaches the absorption tower 10 of the flue gas desulfurization apparatus 9, where it is desulfurized in gas-liquid contact with the calcium-based absorbent. in this way,
Since the exhaust gas cooled to near the exhaust gas temperature at the outlet of the absorption tower 10 is guided to the wet flue gas desulfurization device 9, even if the gas and the absorption liquid come into gas-liquid contact in the absorption tower 10, the amount of water evaporated is small, It is possible to reduce the makeup water of the wet flue gas desulfurization device 9.

After the desulfurization treatment, the absorption liquid is oxidized in the liquid storage tank 13 of the absorption tower 10 to produce gypsum, and a part of this is concentrated from the liquid extraction line 19 by the thickener 18,
It is guided to the vacuum belt filter 20 where the solid content (gypsum) is separated and collected. The filtrate is returned to the absorption tower 10.

The gas after desulfurization is heated from the temperature of about 44 ° C. to about 90 to 100 ° C. by the second gas heater 11 by the heat exchange medium (water) from the first gas heater 8 and then from the stack 3. Open to the atmosphere. At this time, the gas temperature is about 90 ~
Since it is 100 ° C, white smoke can be suppressed.

The heat exchange medium (water) from the first gas gas heater 8 guided to the second gas gas heater 11 has a heat component other than the heat component necessary for heating the gas after desulfurization treatment, which is the third heat exchanger 2.
Recovered at 2. The recovered heat heats the makeup water to, for example, about 70 ° C., and the hot water is supplied to the vacuum belt filter 20 via the makeup water line 23 and used for cake cleaning of the filter 20.

As described above, hot water is supplied to the vacuum belt filter 2
The water content of gypsum can be reduced by using it for cake washing of 0. That is, the vacuum belt filter 2
At 0, the water content can be reduced to 10% or less by washing with warm water, and if hot water is not used, the water content is about 15%, which is the guarantee limit. Further, other solid-liquid separators such as basket type and decanter type, which are generally used for solid-liquid separation of gypsum slurry liquid, have a better water content than the belt filter 20 when hot water is not used, but the water content is higher. Cannot be less than 10%. Therefore, even if the vacuum belt filter 20 is used as the solid-liquid separator for the gypsum slurry liquid, the water content is not inferior, and thus the basket-type solid-liquid separator is higher in cost than the vacuum belt filter 20 and installed. Since the space is large, the cost and the installation space can be reduced.

The hot water (filtrate) after cake washing is supplied to the absorption tower 10 as makeup water through the return line 25.

Therefore, the amount of makeup water in the wet flue gas desulfurization device 9 can be reduced, and the water content of the gypsum recovered in the wet flue gas desulfurization device 9 can be reduced.

Further, by using a carbon tube as the heat exchange tube of the first gas heater 8, the carbon tube has a higher thermal conductivity than SUS, STB, etc., so that the exhaust gas is heated from 135 ° C. to about 50 ° C., for example. Even if it is cooled, the first gas gas heater 8 does not increase in size, and only the heat exchange tube on the exhaust gas downstream side of the gas gas heater 8 (the tube for cooling the exhaust gas to 90 ° C. or less) is formed of a carbon tube. Even if the first gas heater 8
Does not become extremely large.

FIG. 2 is a constitutional view showing a second embodiment of the present invention. The difference from the first embodiment is that, as shown in FIG. The point is that a gas cooler 30 is used instead of the cooling. That is, the first gas heater (GGH) 3 of the exhaust gas duct 4
A gas cooler 30 is interposed between the absorption tower 10 of the wet flue gas desulfurization apparatus 9. 1st gas gas heater (GG
H) 31 is approximately 90% of the gas dedusted by the electrostatic precipitator 7.
It is the same as the conventional one (different from the first gas gas heater 8 of the first embodiment) that is cooled to 0 ° C., and includes a first gas gas heater (GGH) 31 and a second gas gas heater (GGH) 11
In terms of structure, any of heat pipe type, rottemure type, and Jungstrom type structures can be adopted.

The gas cooler 30 comprises the first gas gas heater 3
Exhaust gas from 1 (gas at about 90 ° C) and make-up water as a heat exchange medium are indirectly heat-exchanged via a carbon tube (heat exchange tube) to cool the gas to about 40-80 ° C, for example 50 ° C. To do.

The gas cooler 30 is connected with a make-up water line 32 for guiding the make-up water heated to, for example, about 70 ° C. by cooling the gas to the vacuum belt filter 20 in order to use it for cake washing.

Even with this structure, the make-up water for the wet flue gas desulfurization device 9 can be reduced.

That is, the high temperature from the boiler 1, for example, about 3
Exhaust gas at 70 ° C is denitrified and dedusted, and is then passed through the first gas heater 31 and the gas cooler 30 at about 40-80 ° C, for example 50 ° C.
After being cooled to 0 ° C., it reaches the absorption tower 10 of the flue gas desulfurization device 9, where it is desulfurized by gas-liquid contact with a calcium-based absorbent. In this way, since the exhaust gas cooled to near the exhaust gas temperature at the outlet of the absorption tower 10 is guided to the wet flue gas desulfurization apparatus 9, the moisture that evaporates even when the gas and the absorbing liquid come into gas-liquid contact in the absorption tower 10. Since the amount is small, the make-up water of the wet flue gas desulfurization device 9 can be reduced.

The gas after desulfurization is heated by the second gas heater 11 from, for example, about 44 ° C. to about 90 to 100 ° C.
The chimney 3 opens to the atmosphere.

The make-up water that contributes to the cooling of the exhaust gas in the gas cooler 30, recovers the heat of the gas and is heated to, for example, about 70 ° C., is supplied to the vacuum belt filter 20 through the make-up water line 32, and the filter 20 is supplied. Used to wash cakes. As described above, by using warm water for cleaning the cake of the vacuum belt filter 20, the water content of gypsum can be lowered. The warm water (filtrate) after cake washing is supplied as makeup water to the absorption tower 10 via the return line 25. Therefore, the amount of makeup water in the wet flue gas desulfurization device 9 can be reduced, and the water content of gypsum recovered in the wet flue gas desulfurization device 9 can be reduced.

[0037]

In summary, the present invention has the following excellent effects.

(1) At least the heat exchange tube on the exhaust gas downstream side of the heat exchanger is formed of a carbon tube, or as a heat exchange tube between the heat exchanger of the exhaust gas duct and the wet flue gas desulfurization device. By providing a gas cooler that further cools the exhaust gas from the heat exchanger using a carbon tube, it is possible to reduce the makeup water of the wet flue gas desulfurization device.

(2) Hot water is produced by the heat components other than the heat components necessary for heating the gas after desulfurization of the heat exchange medium from the heat exchanger or the heat components recovered by the gas cooler, and this hot water is flue gas desulfurization equipment The water content of the recovered gypsum can be reduced by using the vacuum belt filter for cake cleaning.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing an example of a conventional exhaust gas treatment apparatus.

[Explanation of symbols]

 1 Combustion equipment (boiler) 8 Heat exchanger (1st gas gas heater) 9 Wet flue gas desulfurization equipment

Claims (4)

[Claims] 1. An exhaust gas treatment device in which exhaust gas from a combustion device is cooled by a heat exchanger, desulfurized by a wet flue gas desulfurization device, heated, and then opened to the atmosphere, at least the heat exchanger. An exhaust gas treatment device characterized in that a heat exchange tube on the downstream side of the exhaust gas is formed of a carbon tube. 2. A desulfurization process in which the exhaust gas from a combustion device is cooled by exchanging heat with a heat exchange medium in a heat exchanger, and then brought into gas-liquid contact with an absorbing liquid containing a calcium-based absorbent in a wet flue gas desulfurization device. In the exhaust gas treatment device that heats it with the heat exchange medium from the heat exchanger and then releases it to the atmosphere, at least the heat exchange tube on the exhaust gas downstream side of the heat exchanger is formed of a carbon tube, and the exhaust gas is discharged. A vacuum belt filter is used as a device for solid-liquid separation of gypsum produced from the absorption liquid after desulfurization of the smoke desulfurization device, and the heat required for heating the gas after desulfurization of the heat exchange medium from the heat exchanger. An exhaust gas treatment device, characterized in that hot water is produced by heat other than heat, and hot water is supplied to the vacuum belt filter so as to use the hot water for cake washing. 3. An exhaust gas treatment device, wherein exhaust gas from a combustion device is cooled by a heat exchanger, desulfurized by a wet flue gas desulfurization device, heated, and then opened to the atmosphere. An exhaust gas treatment device comprising a gas cooler provided between a heat exchanger and a wet flue gas desulfurization device to further cool exhaust gas from the heat exchanger by using a carbon tube as a heat exchange tube. 4. After the exhaust gas from the combustion equipment is cooled by a heat exchanger, it is desulfurized by bringing it into gas-liquid contact with an absorbent containing a calcium-based absorbent in a wet flue gas desulfurizer, and after heating this. In an exhaust gas treatment device open to the atmosphere, between the heat exchanger of the exhaust gas duct and the wet flue gas desulfurization device,
A vacuum belt filter is provided as a device for solid-liquid separation of gypsum produced from the absorption liquid after desulfurization treatment of the flue gas desulfurization device, while providing a gas cooler for further cooling the exhaust gas from the heat exchanger using a carbon tube as the heat exchange tube. The exhaust gas treating apparatus is characterized in that water supply means for supplying the water heated by the gas cooler to the vacuum belt filter so as to be used for cleaning the cake is used.