JPH054022A - Flue gas desulfurization equipment - Google Patents

Abstract

PURPOSE:To lower the concentration of sulfurous acid gas in flue gas finally discharged to the atmosphere to increase desulfurization efficiency by taking off part of flue gas from between a heat exchanger for preheating the furnace and a reactor and providing a bypass flue supplying the gas to a region on the downstream side of the central part of the reactor and on the upstream side of the termination position. CONSTITUTION:From a flue 14 between a heat exchanger 16 and a reactor 18, branches off a bypass flue 28 which is connected to the place on time downstream side of the central part of the reactor 18 and on the upstream side of the termination part. Flue gas which is introduced into the reactor 18 through the main flue 14 is cooled by water sprayed with a nozzle 20 to a temp. corresponding to the dew point and mixed with hot flue gas introduced through the bypass flue 28 on the way to the termination. Thereby the flue gas is desulfurize with efficiency corresponding to the temp. of the mixed gas, so that the overall desulfurization efficiency of the reactor 18 is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas desulfurization device,
In particular, it relates to improvement of an exhaust gas desulfurization apparatus suitable for desulfurizing exhaust gas from a furnace that burns a sulfur-containing fuel such as coal or petroleum.

[0002]

2. Description of the Related Art Generally, when a fuel containing sulfur such as coal or petroleum is burned, harmful sulfur oxides, particularly sulfurous acid gas is generated. Therefore, desulfurization devices for purifying flue gas by reacting sulfurous acid gas with a calcium compound before releasing such exhaust gas to the atmosphere have been actively developed. This method is roughly classified into a wet method and a semi-dry method, and among them, the semi-dry method which does not require water treatment has been tried as an economical or simple method. In the semi-dry method, the generated dust is collected by a dry dust collector such as a filter dust collector or an electric dust collector.

By the way, the desulfurization efficiency in the semi-dry method is
Since the flue gas temperature can be maximized near the dew point, it is required to lower the gas temperature as close as possible to the dew point temperature in order to improve desulfurization efficiency. On the other hand, in the dry dust collector installed in the latter stage of the desulfurization device, prevention of dew condensation in the device is essential from the viewpoint of dust handling in the device and prevention of corrosion of the device. Therefore, it is required that the temperature at the entrance of the dust collector be as high as possible above the dew point temperature. As a method for solving this, for example, Japanese Patent Application Laid-Open No. 61-287421 discloses a system in which powdered alkali metal and water are supplied to the reaction zone, and high temperature flue gas is supplied to the end portion of the reaction zone. ing.

[0004]

However, although the conventional method has the effect of increasing the temperature of the gas after the end portion of the reaction zone, it removes the sulfurous acid gas in the high temperature flue gas supplied to the end portion of the reaction zone. However, the gas after the end of the reaction zone contains a high concentration of sulfurous acid gas, which is discharged to the atmosphere as it is.

In view of the above-mentioned conventional problems, the present invention has an object to provide an exhaust gas desulfurization apparatus which has a low concentration of sulfurous acid gas in the exhaust gas finally discharged to the atmosphere and has a high desulfurization efficiency.

[0006]

In order to achieve the above object, an exhaust gas desulfurization apparatus according to the present invention lowers the temperature of a flue gas of a furnace by water spraying, and gas sulfur in the gas in a low temperature region is reduced. In an exhaust gas desulfurization apparatus equipped with a reactor that reacts an oxide with a desulfurizing agent to form a dry solid compound,
A part of the flue gas was taken out from between the preheat heat exchanger of the furnace and the reactor, and a bypass flue was provided to supply the gas to a region downstream of the central part of the reactor and upstream of the end position. It is configured.

[0007]

According to the above construction, the gas temperature upstream of the bypass inflow position in the reactor can be made the dew point temperature, and the desulfurization efficiency of sulfurous acid in the gas inflowing from the reactor start point can be adjusted to the maximum. Further, the gas that has flown into the bypass is mixed with the gas that has flowed in from the reactor start point after the gas flow into the reactor until the end point of the reactor, and the desulfurization efficiency depends on the temperature of the mixed gas.
Therefore, the desulfurization efficiency of the reactor can be increased as a whole. Moreover, since the high temperature flue gas is supplied into the reactor from the downstream side of the heat exchanger, it is possible to obtain the effect of maintaining the maximum thermal efficiency on the upstream side of the heat exchanger.

[0008]

EXAMPLES Specific examples of the exhaust gas desulfurization apparatus according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the structure of a combustion facility equipped with an exhaust gas desulfurization apparatus according to an embodiment. The combustion furnace 10 burns using a sulfur-containing fuel such as coal or petroleum. Also combustion furnace 1
At 0, a flue 14 for discharging combustion exhaust gas is opened in a side wall on the furnace top side, and exhaust is performed from here. Flue 14
Is passed through a heat exchanger 16 installed on the way, where heat exchange with the combustion air supply pipe 12 is performed by the high temperature exhaust gas,
The combustion air is preheated. The flue 14 passing through the heat exchanger 16 is guided to the desulfurization reactor 18.

A flue 14 is connected to the starting end of the desulfurization reactor 18, that is, the lower end of the reactor in the illustrated example, to supply exhaust gas,
The exhaust gas is made to flow as an upward flow. As a desulfurizing agent for exhaust gas, for example, a desulfurizing agent of a calcium compound is used,
In the combustion furnace 10, the flue 14, or the reactor 18
In this, it is supposed to be added to the exhaust gas as powder.
In order to lower the exhaust gas to the dew point temperature inside the reactor 18, a water spray nozzle 20 is installed at the starting end inside the reactor 18, and along the flow of the introduced exhaust gas, that is, the gas flow. I am trying to spray toward the downstream of.

Further, an exhaust pipe 22 is opened at the most downstream end of the reactor 18, that is, at the top of the reactor 18 in the illustrated example, which is connected to a dry dust collector 24 in the subsequent stage, where dust is extracted from the exhaust gas. After being removed, the gas is guided to the chimney 26 at the final stage and released into the atmosphere.

In such an installation, in an embodiment, a bypass flue 28 is branched from the flue 14 between the heat exchanger 16 and the reactor 18, and the bypass flue 28 is connected to the reactor 18 by Downstream of the central part and in the reactor 18
It is configured to be connected to a position on the upstream side of the end portion of. In this bypass flue 28, the outlet 30 is directed to the downstream side inside the reactor 18, and the outlet 30 is branched into a plurality of outlets in order to improve mixing with the gas inside the reactor 18. I am trying to let you. Particularly, in this embodiment, the outlet 30 of the bypass flue 28 is set at the central position of the reactor 18 so that the temperature of the gas in the latter half of the reactor 18 is raised.

In the exhaust gas desulfurization apparatus according to the above embodiment, the temperature of the exhaust gas introduced through the main flue 28 is lowered to the dew point temperature by the water spray sprayed from the nozzle 20. When the gas temperature is near the dew point, the desulfurizing agent, which was calcium oxide in the upstream of the reactor 18, reacts with water to become calcium hydroxide. Since the reaction between calcium hydroxide and sulfurous acid gas has the highest gas temperature at the dew point, the desulfurization efficiency of the sulfurous acid gas in the gas flowing from the beginning of the reactor 18 is maximized.

Next, high temperature exhaust gas is introduced into the central portion of the reactor 18 from the downstream side of the heat exchanger 16 through the bypass flue 28, and is mixed with the dew point temperature gas until the end of the reactor 18. Due to this mixing action, the temperature of the mixed gas becomes higher than the dew point temperature. Therefore, the desulfurization efficiency of the sulfurous acid gas in the gas flowing in from the bypass flue 28 is lower than the desulfurization efficiency in the first half of the reactor 18, but the mixed gas is Desulfurization will be performed with efficiency according to the temperature.

FIG. 2 shows the distribution of changes in the desulfurization efficiency depending on the presence or absence of the bypass flue 28 in the lengthwise direction of the reactor 18, and the experimental results are shown in the following table.

[0016]

[Table 1] In Table 1, in Experiment 1, the bypass flow rate is 5
%, And the case where there is no bypass flow rate is shown in Experiment 2. In both cases, the water spray amount is adjusted so that the outlet temperature of the reactor 18 becomes constant at 65 ° C.

In Experiment 2, since the entire flow rate of the exhaust gas is introduced into the reactor 18, the reaction occurs at the dew point temperature or higher and the efficiency η is low. On the other hand, in Experiment 1, the introduced exhaust gas flow rate in the first half region of the reactor 18 was about 5% lower than in Experiment 2, so the exhaust gas temperature could be adjusted to near the dew point temperature.
The desulfurization efficiency η is large. In the latter half of the reactor 18, the gas temperature becomes higher than the dew point and the apparent desulfurization efficiency decreases due to the bypass flow, but the desulfurization reaction also proceeds in the latter half of the reactor 18, resulting in the desulfurization efficiency. η becomes large.

When the bypass flow is introduced into the reactor 18 and thereafter without being supplied to the reactor 18, the sulfurous acid gas contained in the bypass exhaust gas remains as it is and is discharged from the chimney to the atmosphere. Needless to say.

Next, FIG. 3 shows a cross-sectional structural view of an exhaust gas desulfurization apparatus according to another embodiment. This is different from the above-described embodiment in that when the exhaust gas on the downstream side of the heat exchanger 16 is introduced into the reactor 18 from the bypass flue 28, the outlet 30 of the exhaust gas is directed to the upstream side of the reactor 18. This has the advantage that the overall length of the reactor 18 can be shortened.

In the above embodiment, the case where the desulfurizing agent is separated from the water spray and added to the exhaust gas has been described, but the present invention can also be applied to the case where the desulfurizing agent is sprayed from the nozzle 20 and added.

[0021]

As described above, according to the present invention,
A part of the flue gas is taken out from between the heat exchanger for preheating of the furnace and the desulfurization reactor, and a bypass flue is provided to supply the gas to a region downstream of the central part of the reactor and upstream of the end position. With such a configuration, the exhaust gas desulfurization device having a low concentration of sulfurous acid gas in the exhaust gas finally released to the atmosphere and high desulfurization efficiency can be obtained. In particular, while maintaining the desulfurization action in the latter half of the desulfurization reactor where the bypass flow is introduced, it is possible to prevent dew condensation in the dust collector installed in the latter stage of the reactor and to reduce the efficiency of the heat exchanger. The overall desulfurization efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a combustion facility including an exhaust gas desulfurization device according to an embodiment.

FIG. 2 is a characteristic diagram of desulfurization efficiency of an exhaust gas desulfurization apparatus according to an example and desulfurization efficiency of a conventional reactor.

FIG. 3 is a cross-sectional configuration diagram of a desulfurization device according to another embodiment.

[Explanation of symbols]

 10 Combustion Furnace 12 Combustion Air Supply Pipe 14 Flue 16 Heat Exchanger 18 Desulfurization Reactor 20 Water Spray Nozzle 24 Dry Dust Collector 26 Chimney 28 Bypass Flue 30 Outlet

Claims (1)

Claim: What is claimed is: 1. A flue gas in a furnace is lowered in temperature by water spraying, and gaseous sulfur oxides in the gas are reacted with a desulfurizing agent in a low temperature region to form a dry solid compound. In the exhaust gas desulfurization device equipped with a reactor, a part of the flue gas is taken out between the preheat heat exchanger of the furnace and the reactor, and the flue gas is located in a region downstream of the central part of the reactor and upstream of the end position. An exhaust gas desulfurization device having a bypass flue for supplying gas.