JP3308286B2 - Dry flue gas desulfurization apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a combustion apparatus, and more particularly to a desulfurization method and apparatus suitable for reducing sulfur oxides in exhaust gas.

[0002]

2. Description of the Related Art In combustion devices such as thermal power plants, fossil fuels such as heavy oil and coal are often used, and the exhaust gas discharged therefrom usually contains acidic harmful substances such as sulfur compounds (SOx) and HCl. It is contained at a rate of 100 to 5000 ppm and is released into the atmosphere, causing acid rain and photochemical smog. A desulfurization device will be installed to treat these harmful substances, and this desulfurization device is roughly classified into a wet method and a dry method.
The wet method is represented by a limestone-gypsum method, and is particularly aimed at high-performance desulfurization. A major feature of the dry method is that there is no wastewater, and there are an adsorption method using activated carbon or the like and a reaction treatment method using an alkali metal or the like. In particular, the latter is the most economical method per unit weight of SO ₂ recovered, and has attracted attention in other countries.

A typical flow sheet of this method is shown in FIG.
Shown in The temperature of the exhaust gas from the boiler 1 is reduced by the air heater 3 and guided to the desulfurization tower 4. Desulfurizing agent 5 such as slaked lime
Is supplied by spraying into the flue 6 or the air heater outlet flue 13 or the desulfurization tower 4. At this time, the water pipe 14
And the air from the atomizing gas pipe 15 to the header 2
By spraying from the water spray nozzle 12, the temperature of the exhaust gas is lowered, the humidity is raised, and the desulfurization reaction is promoted.

[0004] At this time, water may be supplied separately from the desulfurizing agent 5, or may be supplied simultaneously with the desulfurizing agent 5 as a slurry. The reacted desulfurizing agent 5 is collected by the dust collecting device 8 together with the ash in the exhaust gas. At this time, a part of the collected particles including the unreacted desulfurizing agent collected by the dust collecting device 8 is supplied to the desulfurizing agent preparing device 37,
In some cases, it is supplied to the flue 13 or the desulfurization tower 4 again and used for the desulfurization reaction.

FIG. 19 shows the relationship between the relative humidity in the desulfurization tower 4 and the desulfurization rate when slaked lime particles are used as the desulfurizing agent 5.
Increasing the relative humidity increases the desulfurization rate for the following reasons. By increasing the humidity in the desulfurization tower 4, the amount of adsorbed water on the surface of the slaked lime particles blown into the desulfurization tower 4 increases. SO ₂ in the gas easily dissolves in this moisture to form acidic H ₂ SO ₃ . The H ₂ SO ₃ and Ca (O
H) The reaction of ₂ is a neutralization reaction, which proceeds rapidly,
It becomes SO ₃ and is fixed. At this time, if the amount of water in the slaked lime is large, the amount of dissolved SO ₂ also increases, so that high humidity conditions are desirable. Further, the generated CaSO ₃ expands. Therefore, CaSO ₃ covering the surface of slaked lime
Is destroyed and a new slaked lime surface inside appears, which has the effect of accelerating the reaction to the inside.

Therefore, it is desirable to increase the relative humidity as much as possible. However, in the case of an actual machine, if the relative humidity is increased, water condenses in the desulfurization tower 4 or in the subsequent dust collector 8 and a low temperature portion in the duct, and the drain is drained. This causes problems such as the generation of scale or the generation of scale and corrosion of the material due to H ₂ SO ₃ or H ₂ SO ₄ .

[0007] If the relative humidity is high, the temperature of the lower hopper of the desulfurization tower 4 drops, and the wall surface of the hopper condenses and the desulfurizing agent 5
Since the powder is moistened, the fluidity of the desulfurizing agent powder in the desulfurization tower 4 is reduced, and there is a problem that the desulfurizing agent 5 powder cannot be smoothly extracted from the lower hopper of the desulfurization tower 4. Therefore, conventionally, the lower hopper outlet temperature is controlled so as to maintain a value higher by about 10 ° C. than the saturation temperature. At this time, the relative humidity is about 60%, and it is currently impossible to increase the relative humidity further from the viewpoint of temperature control, and the desulfurization rate is lowered.

[0008]

In the prior art described above, the desulfurization performance is improved by increasing the relative humidity inside the desulfurization tower 4, but water condenses inside the desulfurization tower and the dust collector, and the duct in the gas is discharged. Also, the desulfurizing agent adheres to the inner wall of the device to cause scale, and furthermore, no consideration is given to the point of causing troubles such as material corrosion of the scale portion.Thus, long-term stable operation of the desulfurization tower cannot be performed. In some cases, the operation of the entire system was hindered. In addition, when the gas temperature of the desulfurization tower is increased (the relative humidity is decreased), scale formation and corrosion are suppressed to some extent, but the desulfurization performance is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry desulfurization method and apparatus which can prevent scale adhesion in the apparatus and corrosion of the apparatus while maintaining high desulfurization performance.

[0010]

The above object of the present invention is achieved by using the following means. Among the alkali metal compounds or alkaline earth metal compounds, a desulfurizing agent containing at least one or more compounds is supplied to a combustion furnace for burning a fossil fuel containing a sulfur compound such as petroleum or coal, or the desulfurizing agent is burned. Supply into the flue gas containing sulfur oxides discharged from the furnace, the furnace or
In a dry flue gas desulfurization method for spraying water from a desulfurization tower or a desulfurization tower inlet portion installed in an exhaust gas flue on the downstream side of the exhaust gas flue having the desulfurizing agent supply portion to remove sulfur compounds in the exhaust gas. A dry flue gas desulfurization method in which a vortex is generated in the middle of the gas flow direction in the desulfurization tower to form a region having a high relative humidity, and a desulfurizing agent containing the compound is mixed into the region having a high relative humidity.

Water is injected into the desulfurization tower or at the entrance of the desulfurization tower.
Desulfurization by atomization and vortex generation in the desulfurization tower
On the plane perpendicular to the gas flow in the area with high relative humidity in the tower
To form a high / low humidity gradient from the center to the tower wall, and
Keeping the tower outlet gas temperature above the saturation temperature
The water that has been deposited on the wall of the desulfurization tower 4 or the structure inside the desulfurization tower 4
To prevent dust adhesion due to contact and getting wet
desirable.

In the area where the water is sprayed, the liquid-gas ratio
(Ratio of water supply amount / sulfurous gas containing flue gas amount) is 0.0
Spray water in the range of 2 to 0.05 l / m ³ N
From 1 to 5 from the inlet of the desulfurization tower upstream of the gas in the desulfurization tower.
m and the gas superficial velocity in the desulfurization tower is 1 to
Spraying water-containing fluid in the range of 10m / s is desulfurizing
Desirable for higher performance.

At least one of an alkali metal compound and an alkaline earth metal compound is added to a combustion furnace for burning a fossil fuel containing a sulfur compound such as petroleum or coal or a flue gas containing sulfur oxides discharged from the combustion furnace. A desulfurization tower provided with a part for supplying a desulfurizing agent containing the above compound, and a desulfurization tower installed in an exhaust gas flue downstream of the furnace or the exhaust gas flue having the desulfurizing agent supply part , and inside or in the desulfurization tower In a dry flue gas desulfurization apparatus for removing sulfur compounds in exhaust gas comprising a water spray section provided at an inlet section, the water spray section includes a water ejection pipe disposed at a central portion, and the water ejection pipe.
Gas pipes for atomizing water placed around
The opening area of the tip portion, which is arranged around the gas pipe, is
A gas that is larger than those of the ejection pipe and the gas pipe by a predetermined amount.
A dry-type flue gas desulfurization unit equipped with a water jet nozzle having a pipe for jetting gas.

[0014] The water spray section of the above-mentioned dry flue gas desulfurization apparatus is water sprayed.
It is desirable that a dispersion plate is provided above the nozzle.
When a dispersing plate was installed just above the water spray nozzle,
Water droplets are blocked by this dispersion plate, bypassing and flowing downstream.
However, mixing with the exhaust gas violently on the dispersion plate
And at the same time a large amount of high-humidity gas vortices, namely Karman vortices
Occurs. The high humidity gas vortex keeps high humidity,
The reaction between O ₂ and the desulfurizing agent is promoted.

Further, the water spray angle of the water spray section is set to
When the angle is 40 to 180 degrees with respect to the flow direction, the water-containing fluid
Is blown countercurrent to the exhaust gas, and the water-containing fluid
Higher than in the case of
Sulfuric acid performance is obtained. In addition, in the dry flue gas desulfurization unit,
In addition, the heating fluid blowing means has an exhaust gas discharged from the furnace.
Connect the branch flue provided in the stack
It is desirable to connect the inlet channel.

At this time, a temperature detecting means is provided in the lower part of the desulfurization tower.
The temperature inside the lower part of the desulfurization tower detected by the temperature detecting means.
Heated fluid to maintain the exhaust gas saturation temperature + 5 ° C or higher
Means for controlling the amount of heated fluid blown from blowing means
Can be provided. Furthermore, the above-mentioned dry flue gas desulfurization equipment
Exhaust gas before introduction into the desulfurization tower and exhaust gas from the desulfurization tower.
Heat exchange between the desulfurized exhaust gas
It is desirable to provide a gas heat exchanger for the operation.

Exhaust gas before introduction into the desulfurization tower
Through heat exchange between desulfurized exhaust gases
By increasing the relative humidity in the sulfur tower, the desulfurization rate
High value can always be obtained and at the same time
Reduce the temperature at the desulfurization tower outlet to just above the adiabatic saturation temperature.
Dew condensation can occur in the dust collector and duct on the downstream side of the desulfurization tower.
Raw and corrosion prevention are achieved.

[0018]

The following actions are considered as reasons for improving the desulfurization performance. The desulfurization reaction with SO ₂ gas will be described here using slaked lime (hereinafter referred to as Ca (OH) ₂ ) as an example of the desulfurizing agent. The desulfurization reaction is as shown below.

H ₂ O + SO ₂ → H ₂ SO ₃ (1) Ca (OH) ₂ + H ₂ SO ₃ → CaSO ₃ + H ₂ O (2) As shown in the equation (1), SO ₂ is absorbed by water and (H ₂ SO ₃ ), and equation (2) is a reaction in which sulfurous acid reacts with slaked lime to generate calcium sulfite (CaSO ₃ ). When a high humidity region is formed in the desulfurization tower, the amount of water adhering to slaked lime particles increases, and the reaction of (1) is promoted.
The desulfurization rate in this high humidity area is improved. Areas other than the high-humidity area have low humidity, but at the outlet of the desulfurization tower, all supplied water evaporates, so the humidity rises and shows a predetermined desulfurization rate. become.

The water spray nozzle has a vortex separating gas
By adopting a configuration having piping (see FIG. 4),
A vortex containing fine water particles sprayed from the tip of the spill is a nozzle
Easy to separate from the tip. Also, from the gas pipe for vortex separation
Introduce gas such as air and spray from around the water spray nozzle
By doing so, this vortex can be separated from around the water spray nozzle.
You. Furthermore, the separated vortex rises in the exhaust gas flow
As a result, new high-humidity vortices are generated sequentially, and vortex separation
Although a certain amount of gas for use may always flow, intermittent flow is effective.
The result becomes clearer. Water is discharged into the high humidity vortex.
When sprayed against the flow of water, the jet of water
After being decelerated, it will reverse and ride on the exhaust gas flow.
You.

By the formation of the vortex, the desulfurizing agent and the sulfur oxide are converted.
It mixes well with the contained exhaust gas and enters the vortex. In this vortex
Has water droplets, which evaporate
Humidity values close to 100% are obtained. Vortex separation gas
The vortex separated from around the water spray nozzle is
Mixing with the exhaust gas stream is restricted while maintaining high humidity .
It flows downstream. Therefore, high desulfurization performance in this vortex
Will be shown. At the exit of the desulfurization tower, these high
Humidity vortex flows and the surrounding exhaust gas are mixed to achieve a uniform moisture concentration.
To improve the overall desulfurization performance.
Become. The desulfurizing agent blown into the exhaust gas becomes moist due to water spray in the desulfurization tower. Part of the desulfurizing agent is not transported to the dust collector and accumulates in the lower hopper of the desulfurization tower. Humidity of the desulfurizing agent decreases its fluidity, but when the temperature of the lower hopper of the desulfurizing tower decreases, the moisture in the gas further condenses on the surface of the desulfurizing agent and the wall surface of the lower hopper of the desulfurizing tower. And lowers the smooth discharge from the hopper.

On the other hand, a header that blows upward along the wall surface of the lower hopper is installed, and exhaust gas or heated air is blown in to remove the moisture of the accumulated desulfurizing agent. Keep the temperature above ℃ to prevent dew condensation on the hopper wall.

In order to increase the desulfurization rate, the relative humidity in the desulfurization tower
The desulfurization agent accumulates at the bottom of the desulfurization tower
The problem mentioned above is that by improving the fluidity of the deposited desulfurizing agent, the accumulated desulfurizing agent can be discharged smoothly .
Door can be. For this reason, the temperature of the hopper is detected, and the amount of exhaust gas or heated air supplied to the hopper is controlled.

Exhaust gas containing acidic harmful substances such as SO ₂ discharged from the combustion device is led to a gas heat exchanger, where the heat is exchanged with desulfurized exhaust gas discharged from a desulfurization tower to lower the temperature. The exhaust gas whose temperature has been lowered enters the desulfurization tower, and SO ₂ is removed by a desulfurizing agent containing fine particles of at least one of an alkali metal compound and an alkaline earth metal compound. At this time, in order to enhance the desulfurization performance, the temperature of the exhaust gas introduced into the desulfurization tower is cooled by the desulfurized exhaust gas discharged from the desulfurization tower. For this reason, the exhaust gas discharged from the desulfurization tower has the characteristic that the temperature can be raised by the gas heat exchanger before entering the dust collector. So the example
For example, in the sixth embodiment, the exhaust gas temperature at the outlet of the gas heat exchanger
Is about 90 ° C, which is about 30 ° C higher than the adiabatic saturation temperature.
There, in the dust collecting device be kept condensation absence
Wear.

Thus, it is possible to increase the relative humidity in the desulfurization tower.
And, as the desulfurization rate, at the same time to a temperature of adiabatic saturation temperature just above the desulfurization tower outlet it is possible to obtain very high values
Because it can be lowered, it is connected with a dust collector on the downstream side of the desulfurization tower with a duct.
Dew formation and corrosion prevention can be achieved.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the following examples, but is not limited to the following examples.

Embodiment 1 A case where slaked lime is used as a desulfurizing agent and the exhaust gas of a coal-fired boiler is desulfurized will be described using an example in which the apparatus according to the present invention is applied. FIG. 1 shows an embodiment for a boiler. Exhaust gas from boiler 1 is supplied to air heater 3
The temperature is lowered by the flue gas 6, and the gas is led to the desulfurization tower 4 through the flue 6. Slaked lime which is the desulfurizing agent 5 is supplied into the flue 13 from the desulfurizing agent introduction pipe 10. In the desulfurization tower 4, the water spray nozzle 1
The water spray nozzle 12 is supplied with water from a water pipe 14 and the atomized gas pipe 15 with air or steam. The water spray nozzle 12 is a two-fluid nozzle that atomizes water with air. The droplets sprayed from the water spray nozzle 12 come into contact with the boiler exhaust gas at about 150 ° C. and evaporate. A dispersion plate 16 is provided immediately above the water spray nozzle 12. FIG. 2A shows details around the water spray nozzle 12. The sprayed water droplets are interrupted by the dispersing plate 16 and bypassed to flow upstream.
On 6, a large amount of gas vortex 17, that is, Karman vortex, of high humidity is generated at the same time as violent mixing with the exhaust gas.

Although water droplets are trapped and evaporated in the vortex 17, the formation of the vortex 17 prevents mixing of the outside of the vortex 17 with the exhaust gas, so that the inside of the vortex 17 always maintains a high temperature. . Further, in the vortex 17, the dispersion plate 1
SO ₂ and desulfurizing agent 5 in the exhaust gas mixed on 6 are contained, and SO ₂ and desulfurizing agent 5 react under high humidity conditions, and exhibit high desulfurizing performance. The portion where the vortex 17 does not exist is a region where the humidity is low. However, as the vortex 17 disappears toward the outlet of the desulfurization tower 4, after all the water droplets evaporate,
Since the humidity increases to the average moisture concentration, a desulfurization reaction corresponding to this humidity is achieved. That is, since the reactivity in the vortex 17 can be increased by locally generating a high-concentration moisture region, that is, a high-humidity vortex region in the desulfurization tower 4, the overall desulfurization rate at the outlet of the desulfurization tower 4 is reduced. Will be improved.

This method is the reverse of the conventional method of improving the mixing of water droplets and exhaust gas to increase the evaporation rate and quickly obtaining a uniform water concentration, and can achieve high desulfurization performance.

Using this apparatus, coal A (SO in exhaust gas)
₍₂ concentration: 2000 ppm) was subjected to a desulfurization test. However, slaked lime is used as the desulfurizing agent 5, and slaked lime is twice the molar ratio of SO ₂ contained in the exhaust gas (hereinafter referred to as C).
a / S = 2). Water was sprayed from the water spray nozzle 12 so that the gas temperature at the outlet of the desulfurization tower was 70 ° C.

At this time, the liquid / gas ratio (ratio of water supply amount / sulfurous acid gas-containing exhaust gas duct gas amount) was 0.04 liter / m 2.
^{At 3} N, the average droplet diameter of the water spray was 30 μm, the position of the water spray nozzle 12 was 1.5 m from the gas upstream inlet of the desulfurization tower 4, the spray angle of the water spray nozzle 12 was 50 degrees, and the The gas superficial velocity in 4 was 2 m / s. However, the spray angle A of the water spray nozzle 12 is, as shown in FIG. 2B, an angle formed by a vertical cross section of the water spray that spreads divergently with respect to the water spray direction of the nozzle 12.

At the outlet of the boiler 1 and the outlet of the dust collector 8, after removing water in the gas, the SO ₂ concentration was measured to be 2000 ppm and 400 ppm, respectively. That is, 80% of the SO _{2 in} the exhaust gas has been removed. The Ca utilization of the desulfurizing agent particles recovered from the lower part of the dust collector 8 was 40%.

Second Embodiment FIGS. 3 to 5 show a second embodiment. The installation of the desulfurization tower 4 is the same as that of FIG.
A header 21 is provided so that water can be sprayed in a direction opposite to the gas flow. As shown in FIG. 4, in the water spray nozzle 12, the tip of the water pipe 14 faces the center, and the tip of the atomizing gas pipe 15 faces around the center, so that the water supplied from the water pipe 14 is supplied from the pipe 15. It is sprayed from the tip of the nozzle 12 while being atomized by the atomizing gas. Moreover, since the vortex separation gas pipe 18 is attached to the outside of the water spray nozzle 12, the vortex containing fine water particles sprayed from the tip of the nozzle 12 is easily separated from the tip of the nozzle 12.

Since the nozzle 12 is sprayed in a direction opposite to the flow of the exhaust gas, the vortex 17 'fixed around the water spray nozzle 12 as shown in FIGS. 5 (a) and 5 (b).
Is generated, and water droplets sprayed therein are confined to form a vortex 17 of high humidity. The example shown in FIG. 5A is a case where water spray is performed at an angle of 180 degrees to the gas flow, and the example shown in FIG. 5B is a case where water spray is performed at an angle of 135 degrees to the gas flow. is there. However, the nozzle angle here is an angle when the vertical direction of the exhaust gas in the desulfurization tower 4 is set to 0 degree with respect to the flow direction of the exhaust gas (here, the vertical upward direction).

Since the vortex 17 'is formed at the same place and is hardly mixed with the surroundings, a gas such as air is introduced from the gas pipe 18 for vortex separation, and the water spray nozzle 1
The vortex 17 ′ is sprayed from around the nozzle 1
2 can be separated from around. Further, the separated vortex 17 rises along with the flow of the exhaust gas, so that a new high-humidity vortex 17 is sequentially generated. The vortex separating gas may always flow a fixed amount, but the effect becomes more clear if it flows intermittently. The water is sprayed in the high-humidity vortex 17 in a state opposite to the flow of the exhaust gas, so that the jet is decelerated and thereafter,
It reverses and gets on the exhaust gas flow.

The formation of the vortex 17 causes the desulfurizing agent 5 and SO ₂
And mixed well with the exhaust gas containing the gas. Water drops are present in the vortex 17, and the relative humidity is close to 100% because the water drops evaporate. The vortex 17 separated from around the nozzle 12 by the vortex separating gas is restricted from mixing with the surrounding exhaust gas, and flows downstream of the exhaust gas flow while maintaining high humidity. Therefore, high desulfurization performance is exhibited in the vortex 17.

At the outlet of the desulfurization tower 4, the flow of the high-humidity vortex 17 and the surrounding exhaust gas are mixed to increase the uniform moisture concentration, so that the total desulfurization performance shows a high value. When the diameter of the desulfurization tower 4 is made larger than the diameter of the exhaust gas duct 13 in the desulfurization tower inlet structure, the enlarged portion 20 in FIG.
Although the flow velocity of the desulfurizing agent 5 decreases, the particles of the desulfurizing agent 5 supplied into the exhaust gas duct 13 enter into the reverse flow region, and float and stagnate, so that the particle concentration of the desulfurizing agent 5 is high. An area is created. This area extends from the inlet of the exhaust gas duct 13 to about one time the diameter of the desulfurization tower 4 in the desulfurization tower 4, and by spraying water within this range, the high-concentration desulfurizing agent 5 is turned into a high-humidity vortex 17. , So that higher desulfurization performance can be obtained.

Using this apparatus, coal A (SO in exhaust gas)
₍₂ concentration: 2000 ppm) was subjected to a desulfurization test. However, desulfurizing agent 5 uses slaked lime, and slaked lime is C
It was supplied under the condition of a / S = 2. Water was sprayed from the water spray nozzle 12 so that the gas temperature in the desulfurization tower 4 became 70 ° C.

The liquid / gas ratio at this time is 0.04 liter / m
^{At 3} N, the average droplet diameter of the water spray was 30 μm, the position of the water spray nozzle 12 was 1.5 m from the gas upstream inlet of the desulfurization tower 4, the spray angle of the water spray nozzle 12 was 50 degrees, and the The gas superficial velocity in 4 was 2 m / s.

At the outlet of the boiler 1 and the outlet of the dust collector 8, after removing water in the gas, the SO ₂ concentration was measured to be 2000 ppm and 400 ppm, respectively. That is, 80% of the SO _{2 in} the exhaust gas has been removed. The Ca utilization of the desulfurizing agent particles recovered from the lower part of the dust collector 8 was 40%.

Comparative Example 1 Using the apparatus shown in FIG. 18, a desulfurization test was performed on coal of coal A under the same conditions as in Example 1. The difference from the first embodiment is that water is sprayed from the water spray nozzle 12 in the desulfurization tower 4 through the water header 21 in the same direction as the exhaust gas in the same direction as that of the exhaust gas to lower the temperature in the exhaust gas.

At this time, the SO _{2 at} the outlet of the dust collector 8
The concentration was 800 ppm, and a desulfurization rate of 60% was obtained.
Further, the C of the desulfurizing agent particles collected from the lower part of the dust collector 8
a utilization was 30%.

Example 3 As in Example 2, water is sprayed in the desulfurization tower 4 in FIG. 3 so as to be directed in a direction crossing the flow of exhaust gas.
Using this apparatus, a desulfurization test was performed on the coal of coal A under the same conditions as in Example 1. However, the difference from the second embodiment is that, as shown in FIG. 6, water is sprayed from the water spray nozzle 12 in a direction crossing the exhaust gas flow, and then the vortex 1
A dispersing plate 16 is provided immediately above the water spray nozzle 12 in order to vigorously form 7. The sprayed water droplets are interrupted by the dispersion plate 16 and flow downstream by bypass. However, on the dispersion plate 16, a large amount of high-humidity gas vortices 17, that is, Karman vortices, are generated at the same time as vigorously mixing with the exhaust gas. I do.

As a result, the inside of the vortex 17 keeps high humidity,
The reaction between O ₂ and desulfurizing agent 5 is promoted. The SO ₂ concentration at the outlet of the dust collector 8 during the desulfurization test was 300 ppm,
A desulfurization rate of 85% was obtained. The Ca utilization of the desulfurizing agent particles recovered from the lower part of the dust collecting device 8 was 42.5%.

From the above, when water and gas were blown in countercurrent to the exhaust gas flow, a high-humidity region was present. Therefore, desulfurization tests were carried out under various conditions by changing each parameter. The apparatus was the same as in Example 2, except that the parameters were changed under the following conditions.

Spray angle of water spray nozzle (FIG. 2 (b))
Are 10, 20, 30, 50, 70, 120, 140, 1
Under the conditions of 60 and 180 degrees, the average droplet diameter of the water spray is 1
0, 20, 30, 50, 70, 100, 140, 17
The desulfurization test was performed under the conditions of 0 and 200 μm and the conditions of the gas superficial velocity in the desulfurization tower 4 of 0.5, 1, 3, 5, 7, 10, and 15 m / s.

The results are shown in FIGS. 7, 8 and 9.
As a result, it was found that when the water-containing fluid was blown in countercurrent under the following conditions, higher desulfurization performance was obtained as compared with co-current flow. Spray angle of water spray: 20 to 90 degrees Average of droplet diameter of water spray: 20 to 140 μm Gas superficial velocity in desulfurization tower: 1 to 10 m / s

Example 4 An example in which the apparatus shown in FIG. 5B is applied to the flow sheet shown in FIG. 1 will be specifically described. In order to examine what angle the water spray nozzle 12 should be attached to the gas flow, a desulfurization test was performed while changing the angle. Using this apparatus, a desulfurization test was performed on coal of coal A under the same conditions as in Example 2. However, the difference from the second embodiment is that FIG.
That is, the mounting angle of the water spray nozzle 12 was changed as shown in FIG.

FIG. 10 shows the result. When the water-containing fluid was blown at a mounting angle of the water spray nozzle 12 in the range of 40 to 180 degrees with respect to the gas flow, higher desulfurization performance was obtained as compared with the co-current flow.

S at the outlet of the dust collector 8 during the desulfurization test
The O ₂ concentration was 400 ppm, and a desulfurization rate of 80% was obtained. The Ca utilization of the desulfurizing agent particles collected from the lower part of the dust collecting device 8 was 40%.

The liquid / gas ratio (ratio of water supply amount / sulfurous acid gas-containing exhaust gas duct gas amount) is 0.02 liter / m ^3.
Below N, the exhaust gas temperature is high, the desulfurization performance is low, and it is not practical. If it is 0.05 liter / m ³ N or more, the exhaust gas temperature becomes close to the saturation temperature, and the moisture in the gas may reach the dew point, which is not practical. From this,
Liquid gas ratio (the ratio of the water supply quantity / sulfur dioxide containing exhaust gas duct gas amount) should be operated in the range of 0.02 to 0.05 liters / m ³ N.

With respect to the mounting position of the water spray nozzle 12, taking the desulfurization tower structure in FIG. 3 as an example, the sprayed water comes into contact with the wall of the desulfurization tower 4 or the structure in the desulfurization tower 4 and becomes dusty due to wetting. In order to prevent adhesion, a high / low humidity gradient is formed on the tower wall from the center on the gas flow orthogonal plane,
In addition, it is necessary to keep the temperature of the gas at the outlet of the tower higher than the saturation temperature. For this reason, the attachment position of the water spray nozzle 12 in the plane perpendicular to the gas flow and the attachment position of the lowermost part are determined so that the tower wall has the lowest possible humidity.
Also, when the water spray nozzle 12 is mounted at a high position,
Since it is necessary to keep the effective length of the desulfurization tower 4 downstream of the gas from the mounting position constant, the entire desulfurization tower 4 becomes high and is not economical. Therefore, the mounting position of the water spray nozzle 12 is desirably 1 time or less of L / D (water spray nozzle mounting position / desulfurization tower diameter), and in an actual apparatus having an exhaust gas treatment amount of tens of thousands m ³ N / h or more, the desulfurization tower 4 It must be within 5 m from the upstream inlet of the exhaust gas.

Fifth Embodiment FIG. 11 shows a fifth embodiment. FIG. 11 shows a method in which a group of water spray nozzles 12 are mounted so as to face each other in a desulfurization tower 4 similar to FIG. A vortex 17 flow fixed at the outlet of the water spray nozzle 12, especially on the downstream side of the exhaust gas flow, is generated. By colliding these jets, the pressure at the collision portion increases and the jets fluctuate vertically and horizontally. become. Vortex 17 fixed by this vibration
Rises separately from around the water spray nozzle 12, and vortices 17 are sequentially generated. The collision of the two jets has the effect of confining the sprayed water droplets in the vortex 17 flow, so that the overall desulfurization performance at the outlet of the desulfurization tower 4 can be enhanced as in the above embodiment.

Using this apparatus, a desulfurization test was performed on coal A under the same conditions as in Example 1. Dust collector 8 for desulfurization test
The SO ₂ concentration at the outlet of was 400 ppm, and a desulfurization rate of 80% was obtained. The Ca utilization of the desulfurizing agent particles collected from the lower part of the dust collecting device 8 was 40%.

The test results of each of the above examples are summarized as follows.
As shown in FIG. 12, the desulfurization performance according to the present invention is clearly higher than that of the conventional method.

This means that, as described in the present invention, a vortex 17 is generated in the middle of the gas flow direction in the desulfurization tower to form a maximum value of the relative humidity, and the desulfurizing agent 5 of the compound By being mixed in the relative humidity maximum value region (vortex), the reaction between SO _{2 in} the exhaust gas and the desulfurizing agent 5 is promoted, and high desulfurization performance is obtained.

Further, in order to effectively control the supply amount of water and the flow rate of the water dispersion fluid, the inside of the desulfurization tower 4 or the desulfurization tower 4 is controlled.
At least one of a temperature sensor, a humidity sensor, and a moisture concentration sensor may be attached to the outlet, and a signal from the sensor may be used to control the amount of supplied water and the flow rate of the water dispersion fluid.

Embodiment 6 FIG. 13 (Simplified illustration of the apparatus shown in FIG. 1)
Shows an example in which the present invention is applied to a commercial boiler.
Exhaust gas containing SOx from a coal-fired or heavy oil-fired boiler 1 is cooled down by an air heater 3 to about 150 ° C.
Temperature. At this time, the exhaust gas contains about 7 to 10% in the case of a coal-fired boiler, and about 12 to 15 in the case of a heavy oil-fired boiler.
Contains% water. The exhaust gas is led to the gas heat exchanger 30 and exchanges heat with the gas discharged from the desulfurization tower 4 to lower the temperature. The exhaust gas whose temperature has been lowered enters the desulfurization tower 4, where a desulfurizing agent 5 such as slaked lime and water are introduced, and SOx in the exhaust gas is removed. At this time, the temperature in the desulfurization tower 4 largely controls the desulfurization performance, that is, the difference between the temperature in the desulfurization tower 4 and the adiabatic saturation temperature. Desulfurization tower 4
Before exhaust gas from the desulfurization process, which enters the dust collector 8, can be heated in the gas heat exchanger 30.
In the present apparatus, the temperature at the outlet of the desulfurization tower 4 can be lowered to just above the adiabatic saturation temperature, so that a very high desulfurization rate can be obtained.

FIG. 14 shows the results of examining the relationship between the difference between the adiabatic saturation temperature and the desulfurization rate by changing the reaction gas temperature in an experimental apparatus capable of accurately controlling the humidity. FIG.
As shown in FIG. 4, it was found that the desulfurization rate was largely controlled by the difference from the adiabatic saturation temperature, and the desulfurization rate increased as the temperature approached the adiabatic saturation temperature.

Next, the result of an experiment using an experimental apparatus having the same system configuration as that of FIG. 13 will be described below. 200Nm ³ / h with about 10% moisture in heavy oil fired combustion furnace
Hot air is generated and 200O using a SO ₂ gas cylinder.
Simulated exhaust gas corresponding to boiler exhaust gas was prepared by mixing SO ₂ gas equivalent to ppm. The gas temperature was maintained at about 150 ° C. corresponding to the outlet of the air heater 3 using a cooler.

When the simulated exhaust gas having the above conditions was led to a regenerative gas heat exchanger (Jungstrom type air preheater), the temperature at the gas heat exchanger outlet dropped to 90 ° C. Next, the simulated exhaust gas was guided into a desulfurization tower, and slaked lime and water were supplied in the desulfurization tower. Slaked lime was supplied so that the molar ratio with SO ₂ gas was 2. While monitoring the thermometer provided in the center of the desulfurization tower, the water supply amount was determined aiming at the adiabatic saturation temperature plus 5 ° C (59 ° C in this case).

The S at the outlet of the desulfurization tower when the above desulfurization experiment was performed
The value of the O ₂ monitor was 350 to 360 ppm, and a value of about 83% was obtained as the desulfurization rate.

On the other hand, the temperature of the exhaust gas after leaving the gas heat exchanger was about 90 ° C., which was about 30 ° C. higher than the adiabatic saturation temperature. Immediately after the experiment, the inside of the dust collector was disassembled and inspected, and the presence or absence of dew condensation was visually checked, but no evidence was observed.

Comparative Experiment A comparative experiment was conducted in which the above-described experimental apparatus was directly supplied to the dust collecting apparatus by bypass without using the gas heat exchanger. At this time, the gas temperature at the outlet of the desulfurization reactor is equal to the adiabatic saturation temperature at which dew point corrosion in the dust collector can be prevented on an actual device scale plus 10
° C (in this case, 64 ° C), the water supply was gradually increased while watching the thermometer. The value of the SO ₂ monitor at the outlet of the desulfurization reactor at the time of performing the above desulfurization experiment was 85.
It was 0 ppm, and the desulfurization rate was as low as 58%.

Example 7 FIG. 15 (the introduction site of the desulfurizing agent of the desulfurization device of FIG. 1 was changed,
(Shown in simplified form) is a high-temperature desulfurization
In this example, high-temperature desulfurization is performed by blowing lime as a desulfurizing agent 5 therein, and water is sprayed to a desulfurization tower 4 provided in an exhaust gas flue to perform low-temperature desulfurization. At this time, a gas heat exchanger 30 is arranged in the flue 6 between the boiler 1 and the desulfurization tower 4, and heat exchange between the exhaust gas guided to the desulfurization tower 4 and the exhaust gas after desulfurization treatment discharged from the desulfurization tower 4 is performed. Done. Also in this embodiment, the reaction temperature in the desulfurization tower 4 can be lowered, and the same effect as in the sixth embodiment can be obtained.

According to Examples 6 and 7, when heat is exchanged between the exhaust gas before introduction into the desulfurization tower 4 and the exhaust gas discharged from the desulfurization tower 4, the temperature of the exhaust gas in the desulfurization tower 4 drops to just above the adiabatic saturation temperature. Even if it is performed, since the dew condensation in the dust collecting device 8 can be prevented, even if the dust collecting device 8 uses the integrated desulfurizing tower 4, the operation of the desulfurizing tower 4 is stopped due to the corrosion of the dust collecting device 8. Never. Further, since the desulfurization performance is governed by the relative humidity, the amount of water required to achieve the same relative humidity can be reduced by lowering the temperature at the inlet of the desulfurization tower 4, and the desulfurization rate can be improved.

Example 8 Slaked lime was used as a desulfurizing agent to remove exhaust gas from a coal-fired boiler.
In the case of sulfuric acid treatment, the apparatus according to the present invention was applied.
This will be described using an example. FIG. 16 shows an embodiment of the present invention.
In FIG. 16, the exhaust gas from the boiler 1 is
And the temperature is lowered to the desulfurization tower 4. The desulfurizing agent 5 is sprayed from the nozzle 11. The desulfurizing agent 5 is led into the desulfurization tower 4 via the flue 13. The temperature in the exhaust gas is lowered by spraying from the water spray nozzle 12 in the desulfurization tower 4, the reaction between the desulfurizing agent 5 and the sulfur oxide in the exhaust gas is promoted, and the sulfur oxide in the exhaust gas is removed. The reacted desulfurizing agent is collected by the dust collecting device 8 and discarded. The exhaust gas is then discharged from the chimney 9.

As described above, in the desulfurization system, the lower hopper temperature must be maintained at the exhaust gas saturation temperature + 5 ° C. or higher for the smooth extraction of the powder because the wet powder having poor fluidity is deposited at the lower portion of the desulfurization tower 4 as described above. is there. For this reason,
Part of the exhaust gas is supplied to the lower part of the desulfurization tower 4 by the branch line 23 and the pressure increasing fan 24. At this time, the ring header 26 is installed below the hopper, and blows upward along the hopper angle. At this time, the control of the amount of exhaust gas supplied to the ring header 26 is performed by a temperature sensor 27 provided below the hopper. That is, the lower hopper temperature is the exhaust gas saturation temperature + 5 ° C.
In order to maintain the above, the temperature of the hopper is
And the boosting fan 24 controls the exhaust gas blowing amount. The desulfurizing agent 5 deposited at the lower part of the desulfurization tower 4 is discharged from a discharge line 25.

This test was performed continuously for 100 hours, and the extraction of the powder from the lower hopper could be performed smoothly. When the desulfurization tower 4 was inspected inside after stopping the apparatus, no solid such as a desulfurizing agent was observed.

FIG. 17 shows an example in which an aeration system is used as a method for supplying exhaust gas to the lower hopper of the desulfurization tower 4.

[0071]

According to the present invention, higher desulfurization performance can be obtained as compared with the conventional method, the desulfurization apparatus can be reduced in size, and the desulfurizing agent used can be reduced for the following reasons.

Since a high humidity area can be partially formed in the desulfurization tower, the desulfurization performance can be improved.
In addition, the desulfurization equipment can be downsized, and the desulfurizing agent used
I'm done. By blowing part of the exhaust gas or heated air into the lower hopper of the desulfurization tower, it is possible to prevent condensation of moisture in the lower hopper of the desulfurization tower due to the desulfurization agent even if the relative humidity inside the desulfurization tower is high, and the moisture And the flowability can be improved, and the clogging of the hopper of the desulfurization tower stock is eliminated, so that the smooth removal of the accumulated desulfurization agent becomes possible,
High desulfurization performance can be maintained.

[Brief description of the drawings]

FIG. 1 is a flow sheet of a desulfurization apparatus according to a first embodiment.

FIG. 2 is a diagram showing a state of water spray in a desulfurization tower of Example 1.

FIG. 3 is a view showing an arrangement of a water spray nozzle in a desulfurization tower according to a second embodiment.

FIG. 4 is a view showing a structure in which a gas pipe for vortex separation in a desulfurization tower of Example 2 is attached around a water spray nozzle.

5 is a diagram showing a state of generation of a vortex when water is sprayed into exhaust gas using the water spray nozzle shown in FIG.

FIG. 6 is a view in which a dispersion plate is further attached to the water spray nozzle shown in FIG.

FIG. 7 is a view showing a desulfurization rate with respect to a spray angle of a water spray nozzle shown in FIG. 5;

FIG. 8 is a graph showing a desulfurization rate with respect to an average droplet diameter from a water spray nozzle shown in FIG.

FIG. 9 is a graph showing the desulfurization rate with respect to the superficial velocity of exhaust gas using the water spray nozzle shown in FIG.

FIG. 10 is a view showing a desulfurization rate with respect to a nozzle angle of exhaust gas using the water spray nozzle shown in FIG.

FIG. 11 is a view showing a state of water spray in a desulfurization tower according to a fifth embodiment.

FIG. 12 is a view showing a summary of test results of Examples 1 to 5.

FIG. 13 is a view showing a flow of a desulfurization apparatus of a sixth embodiment.

FIG. 14 is a diagram showing experimental data on adiabatic saturation temperature and desulfurization rate.

FIG. 15 is a view showing a flow of a desulfurization apparatus of a seventh embodiment.

FIG. 16 is a diagram showing a flow of an eighth embodiment.

FIG. 17 is a diagram illustrating a flow of a modification of the eighth embodiment.

FIG. 18 shows a flow sheet of a conventional desulfurization apparatus.

FIG. 19 is a diagram showing the relationship between relative humidity and desulfurization rate.

[Description of Signs] 1 boiler 3 air heater 4 desulfurization tower 5 desulfurizing agent 6, 13 flue, 8 dust collector, 9 chimney, 10
Desulfurizing agent introduction pipe, 12: water spray nozzle, 14: water pipe,
15: Atomized gas pipe, 16: Dispersion plate, 17: High humidity gas vortex, 18: Gas pipe for vortex separation, 20: Enlarged part, 2
DESCRIPTION OF SYMBOLS 1 ... Header, 22 ... Recycle line, 23 ... Branch line, 24 ... Booster fan, 25 ... Discharge line, 26 ... Ring header, 27 ... Temperature sensor, 30 ... Heat exchanger, 37 ...
Desulfurizer preparation equipment

──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. Hei 3-215059 (32) Priority date August 27, 1991 (27 August, 1991) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 3-217755 (32) Priority date August 29, 1991 (1991. August 29) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 3-262486 (32) Priority Date October 11, 1991 (Oct. 11, 1991) (33) Priority Claiming Country Japan (JP) (31) Priority Claim Number Japanese Patent Application No. 3-262487 ( 32) Priority Date October 11, 1991 (October 11, 1991) (33) Priority Country Japan (JP) (72) Inventor Koichi Yokoyama 3-36 Takaracho, Kure City, Hiroshima Pref. (72) Inventor Hiroyuki Nosaka 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Ltd. Kure Plant (72) Inventor Nakajima Noboru 3-36 Takara-cho, Kure City, Hiroshima Prefecture Inside the Kure Laboratory, Babcock Hitachi Ltd. (72) Inventor Seiji Takamoto 3-36 Takaracho, Kure City, Hiroshima Prefecture Inside the Kure Laboratory, Babcock Hitachi Ltd. (72) Inventor Takaharu, Kure City, Hiroshima Prefecture, No. 3-36, Babcock Incorporated Kure Research Institute Co., Ltd. (72) Inventor Yasuki Hashimoto 6-9, Takaracho, Kure-shi, Hiroshima Prefecture Babcock Incorporated Kure Plant (72) Inventor Hiroshi Ishizaka 3-36 Takara-cho, Kure-shi, Kumamoto Prefecture Inside the Kure Research Laboratory, Babcock Hitachi, Ltd. (72) Inventor: Satoshi Nishimura 6-9 Takaracho, Kure-shi, Hiroshima Prefecture, Kure Factory (72) Inventor Tadashi Nosaka, Kure, Hiroshima Prefecture, Japan No.36, Ichitakara-cho, Kure Research Laboratory, Babcock Hitachi Ltd. (56) References JP-A-60-90026 (JP, A) JP-A-59-120226 (JP, A) JP-A-56-31438 (JP, A) A) JP-A-49-9471 (JP, A) JP-A-56-119415 (JP, A) Actually open Showa 57-165226 (JP, U) Actually open 57-43820 (JP, U) JitsuHiraku Akira 61-868 (JP, U) (58 ) investigated the field (Int.Cl. ^7, DB name) B01D 53/34 B01D 53/04

Claims (11)

(57) [Claims] 1. A desulfurizing agent containing at least one or more compounds of an alkali metal compound or an alkaline earth metal compound is supplied into a combustion furnace for burning a fossil fuel containing a sulfur compound such as petroleum or coal, or The desulfurizing agent is supplied to a flue gas containing sulfur oxides discharged from a furnace of a combustion apparatus, and the exhaust gas containing the furnace or the desulfurizing agent supply portion is provided.
In a dry flue gas desulfurization method that removes sulfur compounds in flue gas by spraying water from the desulfurization tower installed at the flue gas flue downstream of the gas flue or from the inlet of the desulfurization tower, the gas flow in the desulfurization tower A dry flue gas desulfurization method, characterized in that a vortex is generated in the middle of the direction to form a region having a high relative humidity, and a desulfurizing agent containing the compound is mixed into the region having a high relative humidity. 2. Spraying water in the desulfurization tower or at the inlet of the desulfurization tower and generating a vortex in the desulfurization tower, from the center in the gas flow orthogonal plane in the high relative humidity area in the desulfurization tower. The dry flue gas desulfurization method according to claim 1, wherein a high / low humidity gradient is formed on the tower wall, and the temperature of the tower outlet gas is kept higher than the saturation temperature. 3. A liquid-gas ratio (ratio of water supply amount / sulfurous acid gas-containing flue gas amount) of 0.02 to 2 in an area where the water is sprayed.
The range of spraying water is 1 to 5 m from the inlet of the desulfurization tower upstream of the gas in the desulfurization tower, and the gas superficial velocity in the desulfurization tower is 1 liter / m ³ N. -10
The dry flue gas desulfurization method according to claim 1 or 2, wherein the water-containing fluid is sprayed in a range of m / s. 4. A combustion furnace for burning fossil fuels containing sulfur compounds such as petroleum and coal, or a flue gas containing sulfur oxides discharged from the combustion furnace, comprising at least one of an alkali metal compound and an alkaline earth metal compound. A desulfurization column provided with a part for supplying a desulfurizing agent containing one or more compounds, a desulfurization tower installed in an exhaust gas flue downstream of the exhaust gas flue with the furnace or the desulfurizing agent supply part , and inside the desulfurization tower or In a dry flue gas desulfurization apparatus for removing sulfur compounds in exhaust gas comprising a water spray section provided at the inlet of a desulfurization tower, the water spray section includes a water jetting pipe arranged at a central portion, and a water jetting pipe.
Gas pipe for atomizing water placed around the outlet pipe
And placed around the gas pipe, the opening area at the tip is
A predetermined amount larger than those of the water ejection pipe and the gas pipe
It has a water jet nozzle with gas jet piping.
Dry flue gas desulfurization equipment to be featured. 5. The dry flue gas desulfurization apparatus according to claim 4, wherein the water spray section has a dispersion plate installed above the water spray nozzle. 6. The dry flue gas desulfurization apparatus according to claim 4, wherein the water spray angle of the water spray section is 40 to 180 degrees with respect to the gas flow direction. 7. The dry flue gas desulfurization apparatus according to claim 4, wherein the water spray nozzles of the water spray section are respectively provided on both opposed wall surfaces of the desulfurization tower, and collide a water jet from the water spray nozzle. . 8. A gas heat exchanger for exchanging heat between the exhaust gas before being introduced into the desulfurization tower and the desulfurized exhaust gas discharged from the desulfurization tower is provided. The dry-type flue gas desulfurization apparatus according to the above. 9. The flue gas desulfurization apparatus according to claim 4, wherein a heating fluid blowing means is provided in a lower portion of the desulfurization tower. 10. The dry-type heating method according to claim 9, wherein a branch flue provided in an exhaust gas flue discharged from the furnace is connected to the heating fluid blowing means, or a heating air introduction flow path is connected. Flue gas desulfurization equipment. 11. A temperature detecting means is provided in a lower part of the desulfurization tower,
A means for controlling a heating fluid blowing amount from the heating fluid blowing means so that a temperature in a lower part of the desulfurization tower detected by the temperature detecting means can be maintained at an exhaust gas saturation temperature + 5 ° C or higher. 9. The dry flue gas desulfurization apparatus according to 9.