JP2015120102A - Flue gas desulfurizer and flue gas desulfurization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flue gas desulfurizer and a flue gas desulfurization method capable of preventing abrasion of an absorption column inner wall without the need for new operation power even if a desulfurization absorbing liquid containing abrasive components is used in a lime-gypsum process-based flue gas desulfurizer.SOLUTION: In a flue gas desulfurizer including an absorption column into which flue gas from a combustor including a boiler is introduced, spraying an absorbing liquid containing limestone or lime-containing slurry, and absorbing and removing sulfur oxides in the flue gas, a gutter 20 storing a liquid receiving the sprayed absorbing liquid and reducing a collision speed at which the sprayed absorbing liquid collides against an inner wall is provided in an inner wall portion against which the sprayed absorbing liquid directly collides. The collision speed of the sprayed liquid against the inner wall decreased by causing the sprayed liquid to strike on the liquid in the gutter 20 prior to the collision against the inner wall, thereby reducing an inner wall abrasion speed. The gutter 20 may be provided in a portion in which the sprayed liquid from spray nozzles 3a arranged horizontally in parallel and provided on both sides of an absorbing liquid pipe, respectively directly collides. Moreover, the abrasion suppression effect improves if a liquid level height in the gutter 20 is set such that the collision speed satisfies a predetermined abrasion speed.

Description

The present invention relates to a limestone-gypsum flue gas desulfurization apparatus and flue gas in which wear components such as SiO ₂ and Al ₂ O ₃ are contained in a limestone (calcium carbonate) used as a desulfurization absorbent or a slurry-like absorbent containing lime. The present invention relates to a desulfurization method, and more particularly, to a flue gas desulfurization apparatus and a flue gas desulfurization method suitable for improving wear resistance of an inner wall in a desulfurization absorption tower.

In thermal power plants and the like, calcium carbonate (CaCO ₃ ) contained in limestone is used as a device for removing sulfur oxides (SOx, mainly SO ₂ ) in exhaust gas generated by the combustion of fossil fuels in order to prevent air pollution. Limestone-gypsum flue gas desulfurization apparatus using) as a sulfur oxide absorbent has been widely put into practical use. FIG. 11 shows an absorption tower 1 (side view) in a conventional flue gas desulfurization apparatus, and FIG. 12 shows a plan view (part) of an absorption liquid piping portion of the absorption tower. FIG. 13 shows an enlarged view of the spray portion 4 in the vicinity of the inner wall of FIG.

  Exhaust gas containing sulfur oxides discharged from a combustion apparatus such as a boiler installed in a thermal power plant or factory flows through the inlet duct 12 in an arrow X direction (substantially horizontal direction) and is absorbed by a desulfurization fan (not shown). After being introduced into the tower 1, it rises and is discharged from the outlet duct 13 in the direction of arrow Y. During this time, an absorbent containing an absorbent such as a slurry containing limestone or lime is sprayed from a plurality of spray nozzles 3 attached to the absorbent pipe 2. The sprayed absorption liquid once accumulates in the circulation tank 6 at the bottom of the absorption tower 1 and is oxidized by oxygen in the air supplied from an air supply pipe (not shown) while being stirred by the oxidizing stirrer 7 to generate gypsum. To do. Part of the slurry-like absorption liquid in the circulation tank 6 is supplied to the absorption liquid pipe 2 in the upper part of the absorption tower 1 via the absorption liquid circulation pipe 8, and part is from an absorption liquid extraction pipe (not shown). It is sent to a waste liquid treatment / gypsum recovery system (not shown).

Limestone slurry (hereinafter referred to as absorption liquid slurry) used as a desulfurization absorption liquid is injected through the absorption liquid pipe 2 at a constant angle from a spray nozzle 3 installed in the absorption tower 1 at a constant interval, and is gas-liquid with exhaust gas. The contact causes the desulfurization reaction shown in the following (1) to (4).
SO ₂ + H ₂ O → H ₂ SO ₃ (1)
2H ₂ SO ₃ + CaCO ₃ → Ca (HSO ₃ ) ₂ + H ₂ O + CO ₂ (2)
Ca (HSO ₃ ) ₂ + O ₂ + 2H ₂ O → CaSO ₄ .2H ₂ O + H ₂ SO ₄ (3)
H ₂ SO ₄ + CaCO ₃ + H ₂ O → CaSO ₄ .2H ₂ O + CO ₂ (4)
In the absorbent slurry sprayed from the spray nozzle _{3, in} addition to CaCO ₃ which is a component contributing to the desulfurization reaction, gypsum generated by the desulfurization reaction, impurities such as silicon dioxide (SiO ₂ ) and aluminum oxide (Al ₂ ) in the limestone. O ₃ ) and the like are included. These SiO ₂ and Al ₂ O ₃ have high hardness, and become the main factor that the inner wall of the absorption tower where the absorbing liquid sprayed from the spray nozzle 3 collides is worn.

  In the example shown in FIG. 12, a plurality of absorbent liquid pipes 2 are arranged in parallel on the same horizontal plane in the absorption tower 1, and the spray nozzles 3a provided at both ends of each absorbent liquid pipe 2 are compared with other spray nozzles 3b. Since the spray liquid from these spray nozzles 3a is close to the inner wall, it can be said that the collision speed to the inner wall is much higher than the spray liquid from the other spray nozzles 3b. Therefore, taking measures against wear by the spray nozzle 3a close to the inner wall is useful for greatly reducing wear.

In general, in flue gas desulfurization equipment used in Japan, the total amount of wear components such as SiO ₂ and Al ₂ O ₃ contained in the slurry is about 0.5% (mass%, the same shall apply hereinafter). Measures are taken.

In FIG. 14, the example of the abrasion suppression method by a prior art is shown. In this example, compared to the case shown in FIG. 13, the spray nozzle 3a close to the inner wall is inclined and the collision angle of the absorbent slurry flow on the inner wall is changed from θ ₁ to θ ₂ (θ ₂ <θ ₁ ). Wear is suppressed by making it small. This is because the wear rate depends on the collision angle of the absorbent slurry flow against the wall material, and in stainless steel mainly used for the inner wall of the desulfurization tower, the wear rate is suppressed when the collision angle is smaller. By based on. In addition, lining construction with high wear resistance is also carried out to prevent damage due to wear.

  For example, in Patent Document 1 below, the inner wall of the desulfurization tower is reduced by reducing the spread angle of the sprayed absorbing liquid from the usual 90-100 degrees to 50-60 degrees by setting the spray nozzle installation interval equal to the spray effective range. A method is disclosed in which the collision angle with respect to is reduced so that the amount of the absorbing liquid that collides with the wall surface of the absorption tower does not increase.

  Patent Document 2 below has a configuration of a flue gas desulfurization apparatus in which a gas escape prevention material is installed on the entire inner circumference of the side wall of the absorption tower, and a weir is provided discontinuously along the circumferential direction of the gas escape prevention material. It is disclosed. The exhaust gas that is short-passed along the side wall of the absorption tower by the gas escape prevention material is directed toward the center of the absorption tower, thereby preventing the drift of the exhaust gas and the liquid film generated at the inner peripheral edge of the gas escape prevention material from the weir. Therefore, the liquid film can be prevented from being formed and an increase in pressure loss can be suppressed.

JP 2001-9237 A JP 2011-218273 A

In Southeast Asia, where demand for flue gas desulfurization equipment is increasing in recent years, the purity of mined limestone is low, and the concentration of wear components such as SiO ₂ and Al ₂ O ₃ in limestone is 25%. . In the absorbent slurry, the concentration decreases due to dilution, but the wear component concentration is around 5%. Therefore, the wear rate on the inner wall of the desulfurization tower will increase significantly compared to the conventional thermal power plant plant in Japan. Expected.

  In addition, in a limestone-gypsum flue gas desulfurization apparatus with a wear component concentration of 5%, the wear rate is about 1 mm per year even with a conventionally applied wear-resistant lining material (thickness of about 5 mm). (The conventional wear rate is 0.1 mm or less per year), and the dependence of the wear rate of the material on the collision angle is small. In the flue gas desulfurization apparatus and method described in Patent Document 1, Sufficient wear suppression effect cannot be expected.

  As a countermeasure, it is possible to make the structure of the portion of the absorption tower inner wall where the absorbent slurry collides easily replaceable, but it is not economical because a short-term maintenance is required. It is desired that the wear of the inner wall of the desulfurization tower can be suppressed without using expensive materials or new equipment.

  In the configuration described in Patent Document 2, the absorption liquid flows from the portion where the weir is provided to the portion where the weir is not provided, so that the liquid film generated at the inner peripheral end portion of the gas escape prevention material does not have a uniform thickness. For this reason, an increase in pressure loss can be suppressed. However, the gas escape prevention material and the weir simply collect and flow the absorbent slurry flowing down along the side wall, and no consideration is given to the problem of wear due to collision of the absorbent slurry with the inner wall of the desulfurization tower.

  An object of the present invention is to prevent exhaust gas from deteriorating the inner wall of an absorption tower without requiring new operating power even when a desulfurization absorbent containing a wear component is used in a limestone-gypsum flue gas desulfurization apparatus. A smoke desulfurization apparatus and a flue gas desulfurization method are provided.

  The above-described object of the present invention is achieved by providing a reservoir for storing liquid at a portion where the spray absorbing liquid directly collides with the inner wall of the absorption tower. Furthermore, it is more effective to set the storage height to be equal to or higher than the height at which the absorbing slurry slurry satisfies the predetermined wear rate.

Specifically, the object of the present invention can be achieved by adopting the following configuration.
The invention according to claim 1 introduces exhaust gas discharged from a combustion apparatus including a boiler, and sprays an absorption liquid containing slurry containing limestone or lime to absorb and remove sulfur oxides contained in the exhaust gas. In a flue gas desulfurization apparatus equipped with an absorption tower that stores the liquid, the spray absorption liquid on the inner wall of the absorption tower directly collides with the liquid that reduces the collision speed of the absorption liquid to the absorption tower inner wall by receiving the spray absorption liquid This is a flue gas desulfurization device provided with a section.

  The invention according to claim 2 is characterized in that the absorption tower includes a plurality of spray nozzles for spraying the absorbing liquid and a plurality of absorbing liquid pipes arranged in parallel on the same horizontal plane and having the plurality of spray nozzles. The flue gas desulfurization device according to claim 1, wherein the spray desulfurization device is provided at a portion where spray absorption liquid from spray nozzles installed at both ends of each absorption liquid pipe directly collides.

  According to the third aspect of the present invention, the relationship between the wear speed of the portion where the spray absorbent on the inner wall of the absorption tower directly collides with the collision speed of the absorbent and the liquid in the reservoir when the wear component concentration in the absorbent is a predetermined concentration From the relationship between the storage height of the liquid in the reservoir and the collision speed of the absorbing liquid, obtained from the relationship between the storage height of the liquid and the wear rate of the portion where the spray absorbing liquid indirectly collides with the inner wall of the absorption tower via the liquid 3. The flue gas desulfurization device according to claim 1, wherein a storage height of the liquid in the storage portion is set to a height equal to or higher than a collision speed that satisfies a predetermined wear rate.

  The invention according to claim 4 introduces exhaust gas discharged from a combustion apparatus including a boiler into an absorption tower having a configuration in which an absorption liquid containing slurry containing limestone or lime is sprayed, and is contained in the exhaust gas. In the flue gas desulfurization method that absorbs and removes sulfur oxides, the liquid is stored in the part where the spray absorption liquid directly collides with the absorption wall of the absorption tower, and the collision speed to the absorption tower inner wall by receiving the spray absorption liquid with the liquid This is a flue gas desulfurization method.

  According to a fifth aspect of the present invention, the absorption tower includes a plurality of spray nozzles for spraying the absorption liquid, and a plurality of absorption liquid pipes arranged in parallel on the same horizontal plane and having the plurality of spray nozzles. The exhaust gas desulfurization method according to claim 4, wherein the liquid is stored in a portion where the spray-absorbing liquid from the spray nozzles installed at both ends of the nozzle directly collides.

According to the sixth aspect of the present invention, the relationship between the wear rate of the portion where the spray absorbing liquid directly collides with the spray absorbing liquid on the inner wall of the absorber when the concentration of the wear component in the absorbing liquid is a predetermined concentration, and the liquid storage height. And the relationship between the wear speed of the portion where the spray absorbing liquid indirectly collides with the inner wall of the absorption tower via the liquid, and the relationship between the liquid storage height and the collision speed of the absorbing liquid is calculated from these relations, The flue gas desulfurization method according to claim 4 or 5, wherein the liquid is stored at a height equal to or higher than a collision speed that satisfies a predetermined wear rate.
(Function)
Wear caused by the collision of the absorbent slurry with the inner wall of the absorption tower is affected by the concentration of wear components such as SiO ₂ and Al ₂ O ₃ in the absorbent slurry, the collision speed, and the collision angle. On the other hand, since these conditions are affected by operating conditions such as the desulfurization rate in each plant and the purity of limestone used, it is not easy to change them.

  Table 1 compares the components of Southeast Asian limestone, which is an example of low-grade limestone, and domestic limestone, which is an example of high-grade limestone.

As is clear from Table 1, the content of SiO ₂ and Al ₂ O ₃ , which are wear components that affect stainless steel often used for the inner wall of the desulfurization tower, has been greatly increased compared to domestic products. I understand that. In the absorbent slurry, the concentration of these components decreases with dilution, but the wear component concentration in the absorbent slurry exceeds 1% compared to about 0.5% or less when high-grade limestone is used. .

  FIG. 4 shows the relationship between the wear component concentration in the absorbent slurry and the wear rate of stainless steel (SUS316L), which is an example of the wall surface material of the absorption tower inner wall. Using the apparatus shown in FIG. 5, the absorbent slurry was supplied from the slurry tank 21 to the spray nozzle 25 via the slurry line 27 by the pump 23 and sprayed onto the test piece 29. As the measurement conditions, the temperature of the absorbent slurry is room temperature (according to JIS), the test time is 24 hours (6 hours × 4 days), the flow rate (injection speed) of the absorbent slurry is 15 m / s, and the injection angle is 45 °. The wear rate was calculated from the wear depth after the 24-hour test. The wear depth was measured with a surface roughness meter.

  In the figure, the horizontal axis represents the wear component concentration, and the vertical axis represents the relative wear rate when the wear rate when the wear component concentration is 0.5% is 1. From this figure, when low-grade limestone mined in Southeast Asia etc. is used and the wear component concentration in the absorbent slurry is 1% or more, the wear rate is about twice that of high-grade limestone. It turns out that it becomes.

On the other hand, FIG. 6 shows the collision angle dependence of the wear rate when the wear component concentration in the absorbent slurry is 5%. The used apparatus and measurement conditions are the same as in the case of FIG.
In the figure, the horizontal axis represents the collision angle of the absorbent slurry flow, and the vertical axis represents the relative wear rate when the wear rate is 1 at a collision angle of 45 degrees. The reason why the collision angle is 45 degrees is that this angle is a normal injection angle.

  As is clear from this figure, even when the collision angle of the absorbent slurry is reduced, the wear rate hardly changes and the wear suppression effect is limited. In order to suppress the wear speed, it is effective to reduce the collision speed of the absorbent slurry flow to the inner wall of the absorption tower.

However, it is not easy to change the spray condition of the absorbent slurry because it is set to be optimal depending on the size of the absorption tower, the installation interval of the spray nozzles, and the like.
Although the absorption liquid slurry is sprayed throughout the absorption tower, most of the absorption liquid does not collide with the inner wall, and even when it collides with the inner wall, the absorption liquid often collides indirectly after collision. Moreover, even if it collides once with the inner wall, it flows down as it is, so that the inner wall portion where the absorbing liquid directly collides is limited. However, the portion where the spray absorbing liquid directly collides with the inner wall is particularly susceptible to wear.

  Therefore, according to the first or fourth aspect of the present invention, in order to prevent the spray absorption liquid from directly colliding with the inner wall of the absorption tower, a reservoir for storing the liquid is provided in that portion, and the absorption liquid slurry is added to the liquid. By causing the collision, the spray absorbing liquid indirectly collides with the inner wall. Therefore, it is possible to reduce the impact speed of spray absorption to the inner wall and reduce the wear speed of the inner wall without changing operating conditions such as the desulfurization rate in each plant.

  In the configuration described in Patent Document 2, although there are gas escape prevention materials and weirs, these simply act to collect and flow the absorbent slurry flowing down along the side wall. A weir or the like is installed on the inner wall portion where the spray absorbing liquid directly collides, and unless the liquid can be stored, the action of reducing the collision speed of the absorbing slurry on the inner wall cannot be expected.

  The liquid may be a liquid that may contain a solid material, including oil, seawater, industrial water, etc., but these liquids contaminate the gypsum produced, so use an absorbent slurry used for desulfurization. Is preferred. By using the absorbent slurry, it is possible to suppress the wear of the inner wall of the absorption tower without requiring new power.

  Also, among the plurality of spray nozzles provided in the absorption liquid pipes arranged in parallel on the same horizontal plane in the absorption tower, the spray nozzles installed at both ends of each absorption liquid pipe are the inner walls of the absorption tower as compared with other spray nozzles Therefore, it can be said that the wear speed of the inner wall of the absorption tower is greatly influenced by the spray liquid from the spray nozzle adjacent to the inner wall.

  Therefore, according to the invention of claim 2 or 5, in addition to the action of the invention of claim 1 or claim 4, in addition to the spray absorption from the spray nozzles installed at both ends of each absorbent liquid pipe. By providing the reservoir in the portion where the liquid directly collides, it is possible to effectively prevent the absorption tower inner wall from being worn.

  FIG. 7 shows the absorption liquid slurry flow rate dependence of the wear rate when the wear component concentration is 5%. In the figure, the horizontal axis represents the collision speed (impact velocity) of the absorbent slurry with the material, and the vertical axis represents the relative ratio of the wear speed when the collision speed is 15 m / s. The used apparatus and measurement conditions are the same as in the case of FIG. The collision speed was set to the injection speed.

  From this result, it is understood that the wear speed is proportional to the third power of the collision speed, and that the reduction of the collision speed is effective in suppressing wear. In other words, by providing a storage part that stores liquid on the inner wall part where the absorbing liquid slurry collides, the sprayed absorbing liquid slurry does not directly collide with the inner wall, but first, it collides with the liquid in the storing part. Decreases. Thus, the wear rate is greatly reduced. Further, if the collision speed is 5 m / s or less, the amount of wear decreases to a value that can be substantially ignored.

In general, it is known that there is a critical flow velocity in the occurrence of wear of stainless steel due to the absorbent slurry flow, and it can be expressed by the following equation (5).
W = k (Vsin θ−A) × (V cos θ−BV sin θ) (5)
Here, W: damage amount (same as wear amount) (mg / Kg), V: collision velocity (m / s) of particles (wear component particles), θ: collision angle (degree), k: constant, A: Threshold of vertical velocity required for the wear component particles to enter in the vertical direction (perpendicular to the material surface, direction P in FIG. 13), Bsin θ: horizontal direction (parallel to the material surface, Q in FIG. 13) This is the threshold of the horizontal velocity required to push the material in (direction).

  From the results of FIG. 7, it can be seen that the threshold value under the condition of containing 5% of wear components is around 5 m / s. If the amount of liquid in the reservoir is small and the reservoir height (liquid level height) is low, the effect of reducing the collision speed of the absorbed liquid slurry flow will decrease, but the collision speed will be reduced below this threshold collision speed. By storing at a height that can be reduced, the wear rate can be suppressed.

  The relationship between the liquid level height and the collision speed of the absorbing liquid can be obtained as follows. First, using the apparatus shown in FIG. 8, the relationship between the liquid level and the wear rate was determined. The test piece 29 is submerged in the slurry tank 31 and the liquid level height H (distance between the liquid level and the collision part 35 of the test piece 29) is changed so that the tip of the nozzle 25 coincides with the liquid level. The absorbent slurry was sprayed while the nozzle 25 was supported by a support member (not shown). FIG. 8A shows a front sectional view, and FIG. 8B shows a side sectional view. The liquid level height H was changed by changing the position of the test piece 29. As in the case of FIG. 4, the measurement conditions were as follows: the temperature of the absorbent slurry was normal temperature, the test time was 24 hours (6 hours × 4 days), the injection speed was 15 m / s, the injection angle was 45 °, and the wear rate was It was calculated from the wear depth after the 24-hour test. The wear depth was measured with a surface roughness meter. FIG. 9 shows the result.

Accordingly, by calculating the relationship between the storage height and the collision speed of the absorbing liquid from this relationship and the graph of FIG. 7, the storage height that achieves a collision speed of 5 m / s or less can be obtained.
The wall material of the inner wall of the absorption tower and the wear component concentration in the absorbent slurry vary depending on the use environment and operating conditions. If the liquid storage height is high, the collision mitigating action increases, and the collision speed of the absorbing liquid decreases. Therefore, the storage height satisfies the predetermined wear speed (not limited to almost zero, but within an allowable range). What is necessary is just to make it the height which becomes a collision speed or more.

  Therefore, according to the invention described in claim 3 or claim 6, in addition to the action of the invention described in claim 1 or claim 4, claim 2 or claim 5, the storage portion has a predetermined wear rate. By storing the liquid at a storage height that is equal to or higher than the collision speed that satisfies the above, an excellent wear suppression effect is exhibited.

  In the cylindrical desulfurization tower, the distance to the inner wall of the spray nozzle that is close to the inner wall differs depending on the site, but the structure of the reservoir is changed according to the maximum distance (for example, the protruding length from the inner wall is changed). This is possible.

  According to the present invention, in the limestone-gypsum flue gas desulfurization apparatus, there is a concern about severe wear damage, even when using low-grade limestone with low limestone purity, without changing the wall surface material of the absorption tower inner wall, High wear resistance can be imparted. In addition, since the annual wear rate of the inner wall of the absorption tower can be reduced, repair maintenance in a short period assumed at the time of lining construction becomes unnecessary.

  That is, according to the invention described in claim 1 or claim 4, the spray absorbing liquid does not directly collide with the inner wall, but the collision speed with respect to the inner wall is reduced by colliding after hitting the liquid in the storage portion. The wear rate can be reduced.

  According to the invention described in claim 2 or 5, in addition to the action of the invention described in claim 1 or 4, the collision speed of the spray liquid from the spray nozzle adjacent to the inner wall of the absorption tower is reduced. Thus, it is possible to effectively prevent wear of the inner wall of the absorption tower.

  According to the invention described in claim 3 or claim 6, in addition to the effect of the invention described in claim 1, claim 4, claim 2, or claim 5, the liquid storage height is set to a predetermined value. By setting the height to be equal to or higher than the collision speed satisfying the above wear speed, it is possible to further improve the effect of suppressing the wear of the inner wall of the absorption tower, and to make the collision speed such that the wear speed can be ignored.

It is a side view of the absorption tower of the flue gas desulfurization apparatus which is one Example of this invention. It is a top view of the absorption liquid piping part of the absorption tower of FIG. It is an enlarged view of the spray part of the inner wall vicinity of FIG. It is the figure which showed the relationship between the abrasion component density | concentration in an absorption liquid slurry, and the abrasion rate of the wall surface material of an absorption tower inner wall. It is a schematic diagram of the apparatus used in order to obtain | require the relationship between the wear component density | concentration in an absorption liquid slurry, and a wear rate. It is the figure which showed the collision angle dependence of the abrasion speed in case the abrasion component density | concentration in an absorption liquid slurry is 5%. It is the figure which showed the absorption liquid slurry flow rate dependence of the abrasion speed in case the abrasion component density | concentration in an absorption liquid slurry is 5%. It is a schematic diagram of the apparatus used in order to obtain | require the relationship between the liquid level height of a storage part, and a wear rate. It is the figure which showed the relationship between the liquid level height in a storage part, and a wear rate. It is the figure which showed the relationship between the liquid level height in a storage part, and the collision speed of absorption liquid slurry. It is a side view of the absorption tower of a flue gas desulfurization apparatus of a prior art. It is a top view of the absorption liquid piping part of the absorption tower of FIG. It is an enlarged view of the spray part of the inner wall vicinity of FIG. It is an enlarged view of another example of the spray part of the inner wall vicinity of FIG.

  Embodiments of the present invention are shown below.

  In FIG. 1, the side view of the absorption tower 1 of the flue gas desulfurization apparatus which is one Example of this invention is shown (the inside is also shown). 2 is a plan view (part) of the absorption liquid pipe 2 portion of the absorption tower of FIG. 1, and FIG. 3 is an enlarged view of the spray portion 5 near the inner wall of FIG.

  Exhaust gas containing sulfur oxides discharged from a combustion apparatus such as a boiler installed in a thermal power plant or factory flows through the inlet duct 12 in an arrow X direction (substantially horizontal direction) and is absorbed by a desulfurization fan (not shown). After being introduced into the tower 1, it rises and is discharged from the outlet duct 13 in the direction of arrow Y. During this time, an absorbent containing an absorbent such as a slurry containing limestone or lime is sprayed from the spray nozzle 3 installed at regular intervals in the absorption tower 1 through the absorbent pipe 2, and by gas-liquid contact with the exhaust gas, The desulfurization reaction shown in the above (1) to (4) occurs.

  By bringing the absorbent droplet sprayed as fine droplets from the spray nozzle 3 into contact with the exhaust gas, the SOx in the exhaust gas is absorbed by the spray nozzle 3 together with the soot and acid gases such as HCl and HF in the exhaust gas. It is absorbed and removed chemically at the surface.

  The absorbing solution that has absorbed SOx once accumulates in the circulation tank 6 at the bottom of the absorption tower 1 and is oxidized by oxygen in the air supplied from an air supply pipe (not shown) while being stirred by the oxidizing stirrer 7, Generate. The absorbent is supplied from an absorbent slurry (mainly limestone slurry) supply line (not shown) according to the amount of SOx contained in the exhaust gas from the boiler or the like. A part of the slurry-like absorption liquid in the circulation tank 6 in which calcium carbonate and gypsum coexist is pressurized by an absorption liquid circulation pump (not shown), and the absorption in the upper part of the absorption tower 1 is absorbed via the absorption liquid circulation pipe 8. It is supplied to the liquid pipe 2 and a part thereof is sent to a waste liquid treatment / gypsum recovery system (not shown) from an absorption liquid extraction pipe (not shown).

  Thus, although absorption liquid slurry is sprayed in the absorption tower 1 whole, most absorption liquid does not collide with an inner wall, but even when colliding with an inner wall, after absorption liquid collides, it collides indirectly There are many. Further, even if it collides once with the inner wall, it flows down as it is, so the inner wall portion where the absorbent slurry directly collides is limited. Easy to collide.

  In the example shown in FIG. 2, a plurality of absorbent liquid pipes 2 are arranged in parallel on the same horizontal plane in the absorption tower 1 (in the illustrated example, they are parallel), and spray nozzles provided at both ends of each absorbent liquid pipe 2. Since the colored spray nozzle 3a is closer to the inner wall than the other spray nozzles 3b, the spray liquid from these spray nozzles 3a collides with the inner wall compared to the spray liquid from the other spray nozzles 3b. Can be said to be very large.

  Therefore, in this embodiment, a soot (reservoir) 20 storing the absorbent slurry is provided on the inner wall portion where the absorbent slurry from the spray nozzle 3a collides, and sprayed from the spray nozzle 3 to the absorbent slurry in the kite 20. By applying the absorbing liquid slurry, the collision speed to the inner wall is lowered, and the wear speed of the inner wall is reduced. In this embodiment, the spray nozzles 3a provided at both ends of each absorption liquid pipe 2 are nozzles close to the inner wall of the absorption tower 1 for easy understanding, but the spray nozzles 3a at both ends of each absorption liquid pipe 2 are used. In addition to the spray nozzle 3b other than that, the collision speed to the inner wall portion near the inner wall is a reference collision speed (a speed at which wear is substantially negligible. For example, the wear component concentration 5% / s), the spray nozzle 3a (or 3b) is preferably the target.

  Moreover, since the absorption liquid piping 2 is installed in a plurality of stages (three stages in the illustrated example) in the vertical direction, it is preferable to install a gutter 20 in each stage. The position of the ridge 20 varies depending on the spray condition of the absorbent slurry. However, since the operation conditions in each plant are almost fixed, if installed in a position where the wear is predicted to be particularly severe for each plant. good.

  According to the present embodiment, the sprayed absorbent slurry does not directly collide with the inner wall, but first collides with the absorbent slurry in the tub 20 to reduce the flow velocity. Thereafter, the wear rate is greatly reduced due to the collision with the inner wall indirectly. For example, the flange 20 is formed of a member having an L-shaped cross section or a U-shaped cross section (may be a U-shaped cross section). The material may be polypropylene (PP) resin, silicon carbide (SiC), or the like.

  It is only necessary to store liquid in the tub 20, and liquids, oil, seawater, industrial water, etc. that may contain solids as liquids are also included, but considering the case where liquids flow into the circulation tank 6 In order to contaminate the gypsum produced, it is preferable to use an absorbent slurry used for desulfurization. In this case, it is possible to suppress wear of the inner wall of the absorption tower without requiring new power.

For example, when the wear component (SiO ₂ and Al ₂ O ₃ ) concentration in the absorbing liquid slurry is 5% (concentration assumed when low-grade limestone is used), The collision speed of the absorbing liquid slurry on the designed wall surface of the absorption tower 1 (the collision speed based on the previous reference) is 5 m / s or more. The reference collision speed is determined by a preliminary test performed in each predicted environment. That is, it is determined by the wear test using the wear component concentration in the slurry of each plant.

  In addition, the distance between the spray nozzle 3 and the inner wall differs depending on the site when installed in a cylindrical absorption tower. 3A shows the spray nozzle 3aa closest to the inner wall among the spray nozzles 3a at both ends of each absorbent liquid pipe 2, and FIG. 3B shows the spray nozzles at both ends of each absorbent liquid pipe 2. 3a shows the spray nozzle 3ab farthest from the inner wall, and both FIG. 3A and FIG. 3B show the case where the collision angle θ is 45 °.

First, the position in the height direction of the ridge 20 and the liquid level is based on the closest spray nozzle 3aa. The distance L ₃ between the spray nozzle 3aa and the liquid level is made smaller than the distance L ₂ between the wall surface 1a and the spray nozzle 3aa (L ₃ <L ₂ ). This is because when the collision angle θ is 45 ° and L ₃ is made larger than L ₂ , the injected slurry absorbing liquid does not reach the liquid level and directly collides with the wall surface 1a. The horizontal positions of the tub 20 and the liquid level are based on the farthest spray nozzle 3ab among the target spray nozzles 3a (in this example, the collision speed is 5 m / s or more). The protrusion length L ₁ at the top of the ridge 20 is set to be larger than the distance L ₄ between the position where the slurry absorbing liquid sprayed from the spray nozzle 3ab reaches the liquid level and the wall surface 1a (L ₄ <L ₁ ). . By setting L ₄ <L ₁ , it is possible to receive the slurry absorbing liquid injected with the liquid in the tub 20.

In the cylindrical desulfurization tower, since the distance to the inner wall of the spray nozzle 3 close to the inner wall differs depending on the part, the above L ₁ may be changed according to the maximum distance.
Further, as is apparent from FIG. 7, if the collision speed is 5 m / s or less, the amount of wear decreases to a value that can be substantially ignored. In FIG. 10, the relationship between the liquid level height in a storage part and the collision speed (collision flow velocity) of an absorption liquid slurry is shown. This graph is a result of experimentally evaluating the decrease in the liquid level and wear rate on the surface of the inner wall material (SUS316L) of the absorption tower 1. The horizontal axis indicates the liquid level height of the absorbing liquid slurry, and the vertical axis indicates the collision speed calculated from the wear speed under each liquid level condition. The wear rate under each liquid level condition is as shown in FIG. Although FIG. 9 shows only the liquid level height of up to about 17 mm, it can be obtained from predicted values thereafter.

In FIG. 3, there is a distance L ₃ between the spray nozzle 3aa and the liquid level, and actually there is a space between the spray nozzle 3a and the liquid level, but in the apparatus shown in FIG. 8, the tip of the nozzle 25 coincides with the liquid level. The condition was The reason for this is that even if there is the space portion, it flows into the liquid compared with the speed of the absorbing liquid that is decelerated or increased by the air resistance, exhaust gas flow, gravity, etc. received by the absorbing liquid sprayed from the spray nozzle 3a. Since the speed change that decelerates is larger, it is based on the premise that the speed change of the absorbing liquid due to the space can be ignored.

In addition, when the injected absorbent slurry bounces off the liquid surface and hits the wall surface 1a, it is considered that there is little influence on the wear because the degree of deceleration is large. Therefore, under this condition, it is assumed that the absorbing liquid slurry that has entered the liquid advances as it is and collides with the wall surface 1a. And in order to make the conditions of a collision angle uniform, the nozzle 25 of FIG. 8 used the nozzle injected right below instead of the nozzle which diffuses and injects. Since the distance between the tip of the nozzle 25 and the test piece 29 is sufficiently short, H in FIG. 8 substantially corresponds to the thickness of the liquid provided on the wall surface 1a (height in the direction perpendicular to the wall surface 1a). Since the collision angle of the slurry is 45 °, it is an idea that this thickness becomes the liquid level height H ₁ . Needless to say, when the injection angle of the absorbent slurry is changed, the data shown in FIG. 9 can be obtained if the conditions of the apparatus shown in FIG. 8 are also changed accordingly.

As can be seen from FIG. 10, in the case where the absorbent slurry is accumulated in the tub 20, in order to reduce the collision speed to a flow velocity of 5 m / s or less which is a wear suppression threshold, The height H ₁ needs to be 22.5 mm or more, but it is sufficient to ensure 25 mm or more in consideration of errors and the like. Therefore, by using the spear 20 having a height (reserved height) of 25 mm or more and storing the absorbent slurry so that the liquid level height H ₁ is 25 mm or more, the wear rate can be significantly reduced. is there. Since the absorbent slurry is always sprayed from the spray nozzle 3, if the absorbent slurry is stored in the tub 20 before the operation of the flue gas desulfurization apparatus, it is not necessary to replenish thereafter.

  As described above, the inner wall structure of the absorption tower 1 shown in the present embodiment stores the absorbing liquid slurry in a portion of the plurality of spray nozzles 3 where the absorbing liquid slurry from the spray nozzle 3a close to the inner wall directly collides. By forming the ridge 20, the collision speed of the absorbent slurry is reduced and wear is suppressed. According to this embodiment, damage due to wear of the inner wall is greatly reduced.

In this example, not only the use of low-grade limestone containing 1% or more of wear components SiO ₂ and Al ₂ O ₃ in the absorption liquid but also the discharge when high-grade limestone is used in the absorption liquid. It can also be applied to smoke desulfurization equipment and dust removal towers.

  The present invention is not limited to flue gas desulfurization devices but may be used for other flue gas exhaust devices.

DESCRIPTION OF SYMBOLS 1 Absorption tower 2 Absorption liquid piping 3 Spray nozzle 4,5 Spray part near inner wall 6 Circulation tank 7 Stirrer 8 Absorption liquid circulation piping 12 Inlet duct 13 Outlet duct 20 樋 21 Slurry tank 23 Pump 25 Spray nozzle 27 Slurry line 29 Test piece 31 Slurry Tank 35 collision site

Claims (6)

Smoke with an absorption tower that introduces exhaust gas discharged from a combustion device including a boiler, sprays an absorption liquid containing slurry containing limestone or lime, and absorbs and removes sulfur oxides contained in the exhaust gas In desulfurization equipment,
A flue gas desulfurization characterized in that a storage part for storing a liquid that reduces the collision speed of the absorbing liquid to the absorption tower inner wall by receiving the spray absorbing liquid is provided in a part where the spray absorbing liquid directly collides with the absorption tower inner wall apparatus. The absorption tower includes a plurality of spray nozzles for spraying an absorption liquid, and a plurality of absorption liquid pipes arranged in parallel on the same horizontal plane and having the plurality of spray nozzles,
2. The flue gas desulfurization apparatus according to claim 1, wherein the storage portion is provided in a portion where spray absorption liquid from spray nozzles installed at both ends of each absorption liquid pipe directly collides.   When the wear component concentration in the absorption liquid is a predetermined concentration, the relationship between the wear speed of the portion where the spray absorption liquid on the inner wall of the absorption tower directly collides with the collision speed of the absorption liquid, and the liquid storage height in the reservoir and the spray absorption liquid From the relationship between the storage height of the liquid in the reservoir and the collision velocity of the absorbing liquid, which is determined from the relationship between the wear rate of the portion that indirectly collides with the inner wall of the absorption tower via the liquid, the storage of the liquid in the reservoir is performed. The flue gas desulfurization apparatus according to claim 1 or 2, wherein the height is equal to or higher than a height at which a collision speed that satisfies a predetermined wear speed is obtained. The exhaust gas discharged from the combustion apparatus including the boiler is introduced into an absorption tower having a configuration in which an absorption liquid containing a slurry containing limestone or lime is sprayed to absorb and remove sulfur oxides contained in the exhaust gas. In the flue gas desulfurization method,
A flue gas desulfurization method characterized in that a liquid is stored in a portion of the inner wall of the absorption tower where the spray absorption liquid directly collides, and the collision absorption rate on the inner wall of the absorption tower is reduced by receiving the spray absorption liquid with the liquid. The absorption tower includes a plurality of spray nozzles for spraying an absorption liquid, and a plurality of absorption liquid pipes arranged in parallel on the same horizontal plane and having the plurality of spray nozzles,
5. The method of desulfurizing flue gas according to claim 4, wherein the liquid is stored in a portion where the spray absorbing liquid from the spray nozzles installed at both ends of each absorbing liquid pipe directly collides.   The relationship between the wear rate of the part where the spray absorption liquid collides directly on the inner wall of the absorption tower when the wear component concentration in the absorption liquid is a predetermined concentration and the collision speed of the absorption liquid, and the liquid storage height and the spray absorption liquid pass through the liquid. Thus, the relationship between the wear rate of the portion that indirectly collides with the inner wall of the absorption tower is obtained, and the relationship between the liquid storage height and the collision rate of the absorbing solution is calculated from these relationships, and the liquid is given a predetermined wear rate. The flue gas desulfurization method according to claim 4 or 5, wherein the flue gas is stored at a height equal to or higher than a height at which the collision speed is satisfied.

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