JPH06312118A - Dry exhaust gas desulfurization and its device - Google Patents

Abstract

PURPOSE:To obtain a dry exhaust gas desulfurization device which is capable of improving the desulfurization rate of a dry exhaust gas desulfurization device and reducing the consumption of a desulfurization agent, and at the same time, discharging a solid sticking to the wall surface of a desulfurization tower smoothly. CONSTITUTION:The exhaust gas desulfurization device consists of a desulfurization tower 19 with an inlet duct 1 for introducing an exhaust gas 8, an outlet duct 3 for allowing a treated exhaust gas to flow out and a solid discharge device 9 for discharging a solid, an absorbent atomization device 2a for spraying absorbent powder 2, e.g. NaCl, CaCl2 or KCl, to the exhaust gas 8 flowing in from the inlet duct 1, and a moistening water spray nozzle 4 for spraying an atomization water to the desulfurization part of a desulfurization tower 19 from an atomization water tank. In addition, this system is composed of an additive silo 6, an additive feeder 7 for feeding an additive from the additive silo 6 to the atomization water tank 5, a sensor 11 for detecting the thickness of the solid sticking to the inner wall of the desulfurization tower 19, and a hammering control device 12 for controlling a hammering device 10 based on a signal from the sensor 11 to peel the solid off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry exhaust gas desulfurization method and apparatus, and more particularly to a dry exhaust gas desulfurization method and apparatus for removing sulfur oxides in exhaust gas, which is for improving performance and maintaining stable operability of the apparatus. The present invention relates to a dry exhaust gas desulfurization method and apparatus suitable for contributing.

[0002]

2. Description of the Related Art As one of the methods for removing sulfur oxides in exhaust gas, after injecting absorbent powder (calcium-based absorbent such as slaked lime) into a duct, water for humidification is provided in a desulfurization tower in the subsequent flow. FIG. 8 shows an example of a dry flue gas desulfurization apparatus that sprays and absorbs and removes sulfur oxides in exhaust gas.

Exhaust gas 8 generated by combustion in a boiler, etc.
Is guided to the desulfurization tower 19 through the inlet duct 1. At this time,
The absorbent 2 is sprayed on the inlet duct 1 and introduced into the desulfurization tower 19 in a state of being suspended in the exhaust gas. A humidification water spray nozzle 4 is provided in the tower to complete vaporization of the sprayed fine droplets before reaching the tower outlet. In this process, sulfur oxides in the exhaust gas are absorbed through water. It is absorbed by Agent 2.

The reaction process of this dry desulfurization method is shown in FIG.
When the absorbent 20 that is sprayed and suspended in the exhaust gas 8 containing the sulfur oxides 21 as shown in FIG. 6 comes into contact with the spray water 22 in the desulfurization tower, the area around the absorbent 20 is covered with the spray water 22, and the surrounding area The sulfur oxide 21 in the exhaust gas is dissolved in the covered spray water 22. Further, the calcium in the absorbent 20 is dissolved in the spray water 22 and reacts with the sulfur oxide 21 dissolved in the spray water 22. The reaction product solid matter after the water 22 covering the surface of the absorbent 20 is evaporated is collected by the dust collector installed on the downstream side of the desulfurization tower.

This desulfurization reaction amount is governed by the evaporation time of the spray water 22, the solubility of calcium in the absorbent 20 in the spray water 22 and the solubility of the sulfur oxide 21 in the exhaust gas into the spray water 22. . Dissolution of sulfur oxides is promoted by the presence of chloride. Such a phenomenon is known in a wet desulfurization device using a spray dryer. However, in the dry desulfurization device that supplies the desulfurization agent in powder form, the ratio of the inner diameter to the length of the desulfurization tower is smaller than that of the wet desulfurization device that uses a spray dryer. Changes (changes in desulfurization rate) and blockages of the tower pose problems.

That is, in the desulfurization tower, it is unavoidable that a part of the sprayed water droplet 22 hits the wall of the tower during the process of vaporization to form a wetted surface at that portion to cause solid growth. As a means for removing the adhered matter, a large number of hammering devices are provided to the range where the adherence is concerned, and the wall surface is periodically vibrated to remove the solid matter.

[0007]

In the conventional water spray described above, the reaction proceeds in a model as shown in FIG. 9, but the sprayed water itself is neutral and has the ability to take up the sulfur oxides in the exhaust gas. Since the boiling point is low and the boiling point is low, the existence time as a liquid film covering the surface of the absorbent is short, so that the ability to absorb sulfur oxide is low. Further, since the calcium compound in the absorbent has a low solubility in water, the desulfurization reaction amount is small, and the desulfurization performance by water spray was not so good.
For this reason, a large amount of absorbent is required to maintain the required performance, resulting in high operating costs and reduced economic efficiency.

Further, as described above, the inside of the desulfurization tower is in an environment where the adhesive growth of the absorbent cannot be avoided. This adhesion is due to the collision of spray droplets on the tower wall,
Since the region changes due to the influence of the gas drift in the tower or the operating conditions, the degree of adhesion growth varies depending on the place even within a certain time. For this reason, there is a considerable variation in the size of solids that peel and fall when the hammering device provided on the tower wall is operated at regular intervals. There was a case where it interfered with the operation such as blocking the solids discharging device provided in the.

Also, as a measure to prevent the solids from growing too much, it was tried to shorten the operation interval of the hammering device, but in consideration of unnecessary vibration of the tower wall and noise generation, it is not always necessary. Not the preferred method. The present invention solves the above-mentioned problems of the prior art, improves the desulfurization rate in the desulfurization tower, reduces the amount of desulfurization agent used, and can smoothly discharge the solid matter generated in the desulfurization tower. An object is to provide a dry exhaust gas desulfurization method and apparatus.

[0010]

In order to achieve the above object, the first invention of the present application is to allow a powdered absorbent to flow into a desulfurization tower in a state of being suspended in exhaust gas, and from a humidification water spray nozzle at a desulfurization section. In a dry exhaust gas desulfurization method of spraying humidifying water to absorb and remove sulfur oxides in the exhaust gas until the fine droplets complete evaporation in the tower, and discharging the reaction product solid matter from the desulfurization tower, NaC in the humidifying water sprayed from the spray nozzle
l, CaCl ₂ , KCl, or a mixture containing at least one of the above chlorides is added to the dry exhaust gas desulfurization method.

A second invention is the same as the first invention,
The present invention relates to a dry exhaust gas desulfurization method, characterized in that NaCl as a chloride is added in an amount of 1 to 3% with respect to water. A third invention is an inlet duct for introducing a sulfur oxide-containing exhaust gas into a desulfurization tower, an outlet duct for discharging the exhaust gas treated in the desulfurization tower, and an absorbent for spraying an absorbent into the exhaust gas in the inlet duct. A spray device, a humidification water spray nozzle for spraying humidification water in a desulfurization tower, and a dry exhaust gas desulfurization apparatus equipped with a solids discharge device for discharging solid matter generated in the desulfurization tower, wherein chloride is added to the humidification water. The present invention relates to a dry-type exhaust gas desulfurization device, which is provided with a chloride addition device for adding.

A fourth invention is the same as the third invention,
Dry exhaust gas, characterized in that a plurality of sensors mounted at predetermined intervals on the tower wall of the desulfurization tower via insulators, and a hammering device that operates based on detection signals from the sensors are provided. Desulfurization equipment

[0013]

By adding the additive to the spray water, the boiling point of the water droplets after spraying rises and the existence time of the water droplets becomes long, so that the absorption time of sulfur oxide becomes long. Further, since the additive is a strong electrolyte such as NaCl, the action of dissolved cations facilitates the incorporation of sulfur oxides in the exhaust gas, and at the same time, the absorption covered with such sprayed water. Since the dissolution of, for example, a calcium compound in the agent is also promoted, the desulfurization reaction amount increases and the absorption performance improves.
As a result, the operating cost can be reduced.

Further, by arranging a plurality of sensors covered with an insulator of a predetermined length at a predetermined interval inside the desulfurization tower wall 30, the thickness of the solid matter adhered to the tower wall 30 is the above. When grown over the length (depth) of the insulator, electricity flows between the tips of the adjacent sensors. Therefore, by operating the hammering device based on this energization to peel off the solid matter, it is possible to prevent the adhered solid matter from growing beyond a certain thickness. Electric current is generated between the tips of the adjacent sensors because the above-mentioned strong electrolyte additive is mixed in the deposit, and the strong electrolyte is easily ionized in the surface water of the deposit to flow. .

[0015]

FIG. 1 shows an embodiment of the present invention. This dry type exhaust gas desulfurization apparatus is different from the conventional technique shown in FIG. 8 in that an additive supply feeder 7 for supplying an additive to the spray water tank 5 and
An additive silo 6 for storing the additive, a sensor 11 for detecting the thickness of the solid matter attached to the tower wall 30 of the desulfurization tower 19, and
The point is that a hammering device 10 for removing the adhered solid matter and a hammering control device 12 for controlling the hammering device 10 on the basis of a signal from the sensor 11 are provided. In addition, 1 is an inlet duct, 2 is an absorbent, 2a is an absorbent spraying device, 3 is an outlet duct, 4 is a humidifying water spraying nozzle, 8 is an exhaust gas, and 9 is a solid matter discharging device.

FIG. 5 is an explanatory view showing the sensor 11 portion of FIG. 1 in detail. In the figure, a plurality of sensors 11 covered with an insulator 31 up to a dimension of a depth T are provided on a desulfurization tower column wall 30. In such a configuration, the combustion exhaust gas 8 generated in the boiler, for example, flows into the desulfurization tower 19 together with the absorbent, for example, slaked lime powder 2, which is sprayed from the absorbent spraying device 2a. On the other hand, the additive stored in the additive silo 6, for example, NaCl is added to the additive supply feeder 7.
It is supplied to the spray water tank 5 via and is dissolved in the spray water. The spray water in which NaCl is dissolved is sprayed to the desulfurization section of the desulfurization tower 19 through the humidification water spray nozzle 4 and comes into contact with the combustion exhaust gas 8 accompanied with the absorbent 2. In this way, the combustion exhaust gas, the absorbent and the spray water to which NaCl is added come into contact with each other, and the sulfur oxides contained in the combustion exhaust gas 8 are absorbed by the absorbent.

The reaction process is shown in FIG. In the figure,
When the absorbent 20 that is sprayed and suspended in the exhaust gas 8 containing the sulfur oxide 21 comes into contact with the spray water 22 in the desulfurization tower 19, the spray water 22 covers the periphery of the absorbent 20 and the spray water 22 The sulfur oxide 21 in the exhaust gas dissolves. At this time, since the spray water 22 contains the anion 23 and the cation 24 in which the additive NaCl is dissolved, the dissolution of the sulfur oxide 21 in the exhaust gas 8 is promoted. Further, the calcium in the absorbent 20 is also dissolved in the spray water 22 in the same manner,
It reacts with the previously dissolved sulfur oxide 21. Absorbent 2
The reaction product solids after the spray water 22 covering the surface of No. 0 is evaporated are collected by a dust collector (not shown) downstream of the desulfurization tower.

While the desulfurization operation of the exhaust gas 8 proceeds in this manner, the solid matter 33 adheres to the tower wall 30 of the desulfurization tower 19. FIG. 6 is an explanatory diagram showing a state in which the solid matter 33 adheres to the tower wall 30. In the figure, when the thickness t of the adhered solid matter 33 due to the absorbent grows to be greater than or equal to the depth T of the insulator 31,
An electric current flows between the tips of the sensors 11 via the attached water 34. This current value changes as shown in FIG. Sensor 11
Detects a current value = A, for example, sends the signal to the hammering control device 12. The hammer control device 12, which has received the signal,
The hammering device 10 closest to the measurement position is operated at appropriate times to peel off the solid matter 33.

In this embodiment, the effect of adding the additive to the spray water is shown in FIGS. 3 and 4. In FIG. 3, the molar ratio of the absorbent and the molar ratio of the sulfur oxide in the exhaust gas (hereinafter referred to as Ca
/ S) is compared on the basis of a desulfurization rate of 70% in a desulfurization tower, Ca / S = 2 becomes Ca by adding an additive.
It was found that /S=1.5 can be reduced. Further, when the test was conducted by changing the concentration of the additive (NaCl), the results shown in FIG. 4 were obtained. In the figure, it can be seen that the additive amount when NaCl is used as the additive is 3 wt% or less, preferably around 1 wt%.

According to the present embodiment, by adding the additive to the spray water, the boiling point of the spray water rises and the droplet evaporation time becomes long, so that the sulfur oxide absorption time of the liquid droplet becomes long. In addition, compounds containing chloride as represented by NaCl and CaCl ₂ have a deliquescent property that is an ability to retain water, and after the spray water adheres to the absorbent, the droplets gradually evaporate. In addition, since the time that the water in the vicinity is taken in and the sprayed water covers the absorbent for a long time, the ability to absorb sulfur oxides is improved.

By spraying spray water containing a strong electrolyte such as chloride, an ion buffering action occurs between the spray water adhering to the absorbent and the surface of the absorbent, and calcium ions on the surface of the absorbent are easily dissolved. At the same time, the cations contained in the spray water promote the dissolution of the sulfur oxides in the exhaust gas, so that the desulfurization reaction is promoted and the desulfurization performance is improved. Furthermore, by adding a strong electrolyte such as chloride to the spray water, an electric current flows between the sensors 11 through the spray water in the solid matter grown on the inner wall of the desulfurization tower. The need for stripping can be detected. That is, by installing a plurality of sensors 11 that detect the thickness of the growing solid matter at appropriate positions on the desulfurization tower wall,
When the solid material reaches a predetermined thickness, the hammering device 10 can be activated and peeled.

According to this embodiment, since the sensor 11 for detecting the thickness of the solid matter, the hammering control device 12, and the hammering device 10 are provided, the solid matter 3 discharged from the lower part of the desulfurization tower 3
Since 3 can be maintained below a certain size, solid matter can be stably discharged from the discharging device 9. In this embodiment, for example, seawater can be used as an additive added to the spray water.

[0023]

According to the present invention, the amount of the desulfurization absorbent used can be significantly reduced by adding the additive to the spray water. For example, when the molar ratio of the absorbent to the sulfur oxide is expressed by Ca / S, when comparing on the basis of desulfurization rate = 70%, the value of Ca / S = 2.0 in the conventional method is C
It can be reduced to a / S = 1.5. As a result, the operating cost of this device for one year is reduced by about 20% compared with the conventional method even if the cost of the additive is taken into consideration.

Further, by controlling the hammering device, it is possible to improve the operating condition of the solids discharging device at the lower part of the tower and to ensure stable continuous operation of the desulfurization device.

[Brief description of drawings]

FIG. 1 is a flow chart of a dry exhaust gas desulfurization apparatus showing an embodiment of the present invention.

FIG. 2 is a model explanatory view of a desulfurization reaction in the present invention.

FIG. 3 is a performance curve diagram of a dry exhaust gas desulfurization device in an example.

FIG. 4 shows Na when Ca / S is constant in the example.
The figure which shows the relationship between Cl density | concentration and a desulfurization rate.

FIG. 5 is a diagram showing a sensor installed in a desulfurization tower.

FIG. 6 is a view showing a sensor installed in a desulfurization tower and a solid substance grown around the sensor.

FIG. 7 is a diagram showing the relationship between the amount of adhered solid matter and the value of current flowing between sensors.

FIG. 8 is a flow chart of a conventional dry exhaust gas desulfurization device.

FIG. 9 is a diagram showing a reaction model during water spraying.

[Explanation of symbols]

1 ... Inlet duct, 2 ... Absorbent, 2a ... Absorbent spraying device,
3 ... Exit duct, 4 ... Wet spray nozzle, 5 ... Spray water tank, 6 ... Additive silo, 7 ... Additive supply feeder, 8
... Exhaust gas, 9 ... Solids discharging device, 10 ... Hammering device, 11
... Sensor 12, 12 Hammering control device 19, 19 Desulfurization tower, 20 ...
Absorbent, 21 ... Sulfur oxide, 22 ... Spray water droplets, 23 ...
Anion in chloride, 24 ... Cation in chloride, 25
... calcium sulfate, 30 ... desulfurization tower tower wall, 31 ... insulator,
33 ... Solid matter, 34 ... Adhering water.

Claims (4)

[Claims] 1. A method in which a powdered absorbent is suspended in exhaust gas and flowed into a desulfurization tower, and humidification water is sprayed from a humidification water spray nozzle in the desulfurization section until fine droplets are completely evaporated in the tower. In the dry exhaust gas desulfurization method of absorbing and removing the sulfur oxides in the exhaust gas during the period and discharging the reaction product solid matter from the desulfurization tower, NaCl is added to the humidification water sprayed from the water spray nozzle.
A dry exhaust gas desulfurization method, comprising adding a mixture containing at least one of CaCl ₂ and KCl, or at least one of the above chlorides. 2. The NaC as chloride according to claim 1.
A method for desulfurization of exhaust gas of dry type, characterized in that 1 to 3% of 1 is added to water. 3. An inlet duct for introducing the sulfur oxide-containing exhaust gas into the desulfurization tower, an outlet duct for discharging the exhaust gas treated in the desulfurization tower, and an absorbent spray for spraying an absorbent into the exhaust gas in the inlet duct. Apparatus, a humidification water spray nozzle for spraying humidification water in the desulfurization tower, in a dry exhaust gas desulfurization apparatus equipped with a solid matter discharge device for discharging the solid matter generated in the desulfurization tower, chloride in the humidification water A dry-type exhaust gas desulfurization device, which is provided with a chloride addition device for addition. 4. The plurality of sensors mounted on the tower wall of the desulfurization tower at a predetermined interval via an insulator, and a hammering device which operates based on a detection signal from the sensors according to claim 3. A dry type exhaust gas desulfurization device characterized by being provided.