JP2004024945A - Absorption tower structure in wet flue gas desulfurization apparatus suitable for prevention of gas blow - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet flue gas desulfurization apparatus which can suppress gas blow in an absorption tower wall without largely increasing the apparatus cost, which can prevent decrease in the desulfurization performance and which can reduce the running cost. <P>SOLUTION: The apparatus is equipped with an absorption tower main body 1 having a circulation tank 6 to reserve an absorption liquid 5, an entrance duct 2 to introduce a waste gas discharged from a combustion apparatus such as a boiler into the upper side of the circulation tank, a spray absorbing part to allow the waste gas introduced from the entrance duct to flow in the vertical direction and to induce gas-liquid contact with the absorption liquid sprayed from spray nozzles 13 disposed in a plurality of stages along the gas flow direction, and an exit duct 3 to discharge the waste gas passed through the spray absorbing part. A porous diffusion plate (porous plate) 14 for the liquid flowing downward on the wall is installed on the plane perpendicular to the gas flow only near the tower wall in the spray absorbing part. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to an exhaust gas treatment device for removing harmful components in exhaust gas, and more particularly to a wet flue gas desulfurization device having a function of reducing gas drift and preventing a decrease in desulfurization performance in a gas absorption unit. is there.
[0002]
[Prior art]
FIG. 14 shows an absorption tower in a conventional wet flue gas desulfurization apparatus.
This wet flue gas desulfurization apparatus mainly includes an absorption tower main body 1, an inlet duct 2, an outlet duct 3, an absorption liquid circulation pump 4, a circulation tank 6, a stirrer 7, an air blowing pipe 8, a mist eliminator 9, and an absorption liquid discharge pipe. 10, a circulation pipe 11, a spray header 12, a spray nozzle 13, and the like. The stirrer 7 and the air blowing pipe 8 are installed in a circulation tank 6 in which the absorbing liquid 5 stays.
[0003]
Exhaust gas discharged from a boiler (not shown) is introduced into the absorption tower main body 1 substantially horizontally from an inlet duct 2 by a desulfurization fan (not shown), and discharged from an outlet duct 3 provided at the top of the tower. During this time, the absorption liquid 5 containing calcium carbonate sent from the absorption liquid circulation pump 4 is injected from the spray nozzle 13, and the absorption liquid 5 selectively absorbs SOx in the exhaust gas by gas-liquid contact between the absorption liquid 5 and the exhaust gas. . The absorbing solution that has absorbed SOx temporarily accumulates in the circulation tank 6 and is oxidized by oxygen in the air supplied from the air blowing pipe 8 while being stirred by the oxidizing stirrer 7 to generate calcium sulfate (gypsum).
[0004]
Part of the absorbent 5 in the circulation tank 6 in which calcium carbonate and gypsum coexist is sent to the spray nozzle 13 again by the absorbent circulation pump 4, and part of the waste liquid treatment / gypsum (not shown) is drawn from the absorbent extraction pipe 10. It is sent to the collection system. Among the absorbing liquids 5 atomized by the spray from the spray nozzle 13, those having a small droplet diameter are entrained in the exhaust gas, but are collected by the mist eliminator 9 provided in the outlet duct 3.
[0005]
In recent absorption towers, in order to achieve high performance and compactness, the tower diameter is often reduced and the gas flow velocity in the tower is increased. However, it has been found that when the gas flow velocity is increased, gas blow-through tends to occur near the tower wall.
[0006]
When gas blows through the tower wall in the absorption tower main body 1, the ratio between the flow rate of the absorbent and the flow rate of the exhaust gas in that part, that is, the liquid-gas ratio is extremely reduced. Desulfurization performance will be reduced. This tendency is more remarkable as the required desulfurization rate is higher. In the case of a boiler that burns oil coke with a high sulfur content, the SOx concentration at the inlet of the absorption tower becomes higher, so the effect of gas blow-through on the desulfurization performance Becomes larger. In order to compensate for the desulfurization performance reduced by gas blow-through, it is necessary to increase the circulating amount of the absorbing solution, and the power of the absorbing solution circulating pump 4 is increased. Also, if the liquid-gas ratio in the absorption tower is increased by increasing the absorption liquid circulation amount, the pressure loss in the spray section is increased, so that the power of a desulfurization fan (not shown) is also increased.
[0007]
[Problems to be solved by the invention]
The spray nozzles 13 installed in the absorption tower main body 1 are as close as possible to each other based on the restriction on the arrangement in the absorption tower main body 1 in consideration of the size, maintenance such as attachment and detachment, and the size of the spheader 12. They are arranged to be at intervals. Therefore, the number of spray nozzles 13 that can be arranged at each stage in the gas flow direction is determined, and the spray amount of the absorbing liquid is determined by dividing the liquid amount necessary for maintaining the desulfurization performance by the number of spray nozzles.
[0008]
If the amount of spray liquid required for maintaining the desulfurization performance of the exhaust gas cannot be maintained in one spray stage in the gas flow direction, usually two or more spray stages are installed in the gas flow direction. At this time, in the first and second spray stages, the arrangement positions of the spray nozzles 13 are usually changed along the gas flow direction. For example, the first stage is a center distribution method (a method in which the spray nozzles 13 are not disposed on the center line in the gas flow direction of the absorption tower, and the plurality of spray nozzles 13 are disposed uniformly on a plane orthogonal to the gas flow direction). ), A spray nozzle 13 is arranged on the center line of the absorption tower in the gas flow direction, and a plurality of spray nozzles 13 are arranged on a plane orthogonal to the gas flow direction with respect to the center line. Even if three or more spray stages are provided, the center distribution system and the center arrangement system are similarly alternately repeated for each spray stage.
[0009]
As the type of the spray nozzle 13 here, a hollow cone type spray nozzle is mainly used in which the inside of the spray nozzle 13 is hollow and solid matter is hardly clogged. The feature of the spray pattern of the spray droplets sprayed from the hollow cone type spray nozzle is a side view (FIG. 15A) and a bottom view (FIG. 15B) of the spray nozzle 13 during spray droplet spraying in FIG. As shown in FIG. 1), a droplet 20 is sprayed in a conical shape from the spray nozzle 13, and the spray droplet 20 is sprayed in the circumferential direction. This is a point having a spray pattern of the droplet 20 of FIG.
[0010]
In the above-mentioned conventional technique using a hollow cone type spray nozzle 13 as the spray nozzle 13 installed in the absorption tower main body 1, as shown in FIG. 13, a large number of spray nozzles are used due to the feature of the droplet spray pattern of the hollow cone type spray nozzle 13. At the center of the absorption tower main body 1 where the droplets 20 sprayed from 13 gather, the droplet density tends to be high, while around the tower wall of the absorption tower main body 1, spraying is performed from the center of the absorption tower main body 1. The droplet density tends to decrease.
[0011]
In the case of a cylindrical absorption tower, since the spray nozzles 13 are usually arranged in a grid pattern in the gas flow direction, the number of spray nozzles 13 around the tower wall tends to decrease. For this reason, the exhaust gas blows through the periphery of the tower wall, so that sufficient gas-liquid contact is not performed, and there is a problem that the SOx absorption performance is partially reduced, which may affect the overall desulfurization performance.
[0012]
Further, when exhaust gas flowing in the absorption tower main body 1 has a non-uniform flow with different densities in a cross section orthogonal to the gas flow direction, there is a problem that a pressure loss tends to increase due to generation of a vortex.
[0013]
In order to prevent such a phenomenon, if the gas flow rate in the absorption tower main body 1 is reduced, the tower diameter of the absorption tower itself needs to be increased, or the amount of the absorbing liquid sprayed into the absorption tower main body 1 becomes large. There was a problem that it was necessary to increase more than necessary.
[0014]
An object of the present invention is to suppress gas blow-through at the absorption tower wall without increasing the power of the absorption liquid circulation pump and the desulfurization fan, that is, without significantly increasing equipment costs, and to reduce the desulfurization performance. To obtain a wet-type flue gas desulfurization device having a low operating cost.
[0015]
Further, the object of the present invention is to increase the gas flow rate in the absorption tower to make the absorption tower compact, to prevent the drift of the exhaust gas flowing in the absorption tower, and to allow the exhaust gas to blow through the periphery of the absorption tower wall. And to prevent the pressure loss from becoming unnecessarily large due to the rectifying effect of the spray droplets.
[0016]
[Means for solving the problem]
The above object is achieved by the following.
(1) The invention according to claim 1 provides a circulation tank for storing an absorbing liquid, an inlet duct for introducing exhaust gas discharged from a combustion device such as a boiler above the circulation tank, and an exhaust gas introduced from the inlet duct. An absorption tower having a spray absorption section for flowing in a vertical direction and a gas-liquid contact with an absorbing liquid ejected from spray nozzles installed in a plurality of stages in a gas flow direction and an outlet duct for discharging exhaust gas passing through the spray absorption section is provided. Wet flue gas desulfurization system in which an open wall-shaped liquid dispersion plate (perforated plate, louver, etc.) is installed on the surface orthogonal to the gas flow only in the vicinity of the tower wall of the spray absorption section. It is.
[0017]
It is desirable to set the porosity of the above-mentioned wall falling liquid dispersion plate to 20 to 50%. When the porosity is less than 20%, the absorbing liquid hardly flows down from the holes, and most of the absorbing liquid flows down from the tip of the wall falling liquid dispersion plate. On the other hand, if the porosity exceeds 50%, the dispersion of the absorbing liquid becomes worse, and the absorbing liquid flows down only from some of the holes.
[0018]
When the diameter of the absorption tower is D and the width of the wall-flowing liquid dispersion plate is W, the W / D ratio is desirably 0.005 to 0.1.
[0019]
If the width W of the wall-flowing-down liquid dispersion plate is too small with respect to the tower diameter D of the absorption tower, the rectifying effect is weakened, and the gas flow rate variation coefficient is increased. Conversely, if the width W of the wall-flowing-down liquid dispersion plate is too large, gas tends to flow only at the center of the absorption tower, and the gas flow velocity variation coefficient is rather increased. Therefore, the width W of the wall-falling liquid dispersion plate has an appropriate range, the variation coefficient at which the desulfurization rate does not decrease is about 30%, and the condition is satisfied when the W / D is 0.005 to 0.1. Range.
[0020]
Furthermore, it is desirable to install a wall-falling liquid dispersion plate on at least the tower wall between the upper surface of the inlet duct and the lowermost spray nozzle so that exhaust gas immediately after entering the tower from the inlet duct does not blow through the vicinity of the absorber tower wall. .
[0021]
The absorption tower has an inlet duct and an outlet duct, and an exhaust gas channel is provided between the inlet duct and the outlet duct. A vertical partition plate having an opening is provided, and the exhaust gas introduced from the inlet duct at the partition plate is turned upward at the upward flow region and inverted at the opening on the ceiling side, and then downward toward the outlet duct. A two-chamber absorption tower having a spray nozzle in each of the above-mentioned regions so as to form a descending flow region through which exhaust gas flows, and to make the ejected absorbing liquid slurry come into countercurrent contact with the exhaust gas in the ascending flow region and co-currently contact in the descending flow region. And the wall-flowing liquid dispersion plate of the two-chamber absorption tower may be installed at least on the tower wall between the upper surface of the inlet duct and the lowermost spray nozzle.
[0022]
By using a two-chamber absorption tower, the desulfurization performance can be increased without increasing the size of the absorption tower, that is, by increasing the gas flow rate to be equal to or higher than the gas flow rate of a single-chamber absorption tower of almost the same size without increasing the equipment cost. Can be enhanced.
[0023]
(2) The invention according to claim 6 provides a circulation tank for storing an absorbing solution, an inlet duct for introducing exhaust gas discharged from a combustion device such as a boiler above the circulation tank, and an exhaust gas introduced from the inlet duct. An absorption tower having a spray absorption section for flowing in a vertical direction and a gas-liquid contact with an absorbing liquid ejected from spray nozzles installed in a plurality of stages in a gas flow direction and an outlet duct for discharging exhaust gas passing through the spray absorption section is provided. In the wet flue gas desulfurization apparatus, the plurality of spray nozzles are spray nozzles having a spray pattern of a solid type in which a spray nozzle installed near an absorption tower wall is a spray nozzle having a spray pattern of a hollow type. It is a wet type flue gas desulfurization apparatus characterized by the following.
[0024]
The absorption tower has an inlet duct and an outlet duct, and an exhaust gas channel is provided between the inlet duct and the outlet duct, and a ceiling is provided to divide the exhaust gas channel into two chambers on the inlet duct side and the outlet duct side. A vertical partition plate having an opening on the part side is provided, and the exhaust gas introduced from the inlet duct at the partition plate is turned upward at the upward flow region and turned over at the opening on the ceiling side, and then toward the outlet duct. It consists of a two-chamber absorption tower having a downward flow region where exhaust gas flows downward, and the spray nozzle installed near the tower wall and the partition plate of the two-chamber absorption tower is a spray nozzle having a solid type spray pattern, and other May be a spray nozzle having a spray pattern of a hollow type.
The effects of using a two-chamber absorption tower are as described above.
[0025]
(3) The invention according to claim 8 provides a circulation tank for storing an absorbent, an inlet duct for introducing exhaust gas discharged from a combustion device such as a boiler above the circulation tank, and an exhaust gas introduced from the inlet duct. An absorption tower having a spray absorption section for flowing in a vertical direction and a gas-liquid contact with an absorbing liquid ejected from spray nozzles installed in a plurality of stages in a gas flow direction and an outlet duct for discharging exhaust gas passing through the spray absorption section is provided. In a wet type flue gas desulfurization device, a solid type spray nozzle is disposed in a region where the gas flow rate is 1.1 times or more the average value of the gas flow rate when all the spray nozzles are spray nozzles having a hollow type spray pattern. Spray nozzles with a spray pattern of a hollow type are used as spray nozzles arranged in a region where the gas flow rate is less than 1.1 times the average value. Which is a wet flue gas desulfurization apparatus using a spray nozzle with a pattern.
[0026]
Also in this case, if the absorption tower adopts a configuration including the two-chamber absorption tower, the single-chamber type gas absorber having the same gas flow rate without increasing the size of the absorption tower, that is, without increasing the apparatus cost. The desulfurization performance can be increased more than before by setting the gas flow rate in the absorption tower or higher.
[0027]
(4) The invention according to claim 10 provides a circulation tank for storing an absorbent, an inlet duct for introducing exhaust gas discharged from a combustion device such as a boiler above the circulation tank, and an exhaust gas introduced from the inlet duct. An absorption tower having a spray absorption section for flowing in a vertical direction and a gas-liquid contact with an absorbing liquid ejected from spray nozzles installed in a plurality of stages in a gas flow direction and an outlet duct for discharging exhaust gas passing through the spray absorption section is provided. In a wet flue gas desulfurization device, a spray nozzle having a solid type spray pattern is used as a spray nozzle arranged in a region where the degree of drift is large for each stage of a plurality of spray nozzles arranged vertically in the absorption tower, This is a wet flue gas desulfurization apparatus using a spray nozzle having a spray pattern of a hollow type as a spray nozzle arranged in an area where the degree is not large.
[0028]
Also in this case, if the absorption tower adopts a configuration including the two-chamber absorption tower, the single-chamber type gas absorber having the same gas flow rate without increasing the size of the absorption tower, that is, without increasing the apparatus cost. The desulfurization performance can be increased more than before by setting the gas flow rate in the absorption tower or higher.
[0029]
[Action]
The problem with the prior art is that sufficient consideration is not given to rectification of the exhaust gas that is to be blown through the vicinity of the tower wall at high speed and to increase the SOx removal efficiency of the exhaust gas.
[0030]
According to the first aspect of the present invention, for example, an aperture-shaped wall falling liquid dispersion plate such as a perforated plate is provided only near the inner wall of the absorption tower where exhaust gas easily blows through. Since the wall-falling liquid dispersion plate itself is a resistor against the gas flow, part of the exhaust gas that has risen from near the tower wall from below passes through the wall-falling liquid dispersion plate, and the rest flows away from the wall-falling liquid dispersion plate. To try. Therefore, a local high flow velocity region of the exhaust gas is not formed.
[0031]
Also, a large amount of the absorbing liquid flows down on the inner wall of the absorption tower, and a part of the flowing liquid flows down from the hole of the wall-falling liquid dispersion plate, and the remainder flows down from the tip of the wall-falling liquid dispersion plate. Therefore, the absorbing liquid flowing down from the hole of the wall-falling liquid dispersion plate comes into contact with the exhaust gas that is going to pass through the wall-falling liquid dispersion plate, so that SOx in the exhaust gas can be removed. At this time, the contact time between the exhaust gas and the absorbing solution also becomes longer, so that high desulfurization performance is obtained. Further, the exhaust gas that is going to bypass the tip of the wall-falling liquid dispersion plate comes into contact with the absorbent flowing down from the tip of the wall-falling liquid dispersion plate. Can be removed.
[0032]
Therefore, according to the first aspect of the present invention, it is possible to simultaneously obtain a high gas rectification effect and a high desulfurization performance near the inner wall of the absorption tower.
[0033]
FIG. 16 (side view (FIG. 16 (a)) and bottom view (FIG. 16 (b)) of a spray nozzle portion during spray droplet spraying shows a full cone type spray nozzle 13 'having a solid type spray pattern. 5 shows a pattern of a spray droplet 20 ′. FIG. 17 shows a general structure of the hollow cone type spray nozzle 13 and the full cone type spray nozzle 13 ′.
A comparison of specifications between the hollow cone type spray nozzle 13 (FIG. 17A) and the full cone type spray nozzle 13 '(FIGS. 17B to 17D) shown in FIG. 17 is shown below.
[0034]
According to the invention as set forth in claim 6, in the cross section of the absorption tower, for example, the type of the spray nozzle installed around the tower wall of the absorption tower main body 1 is changed to a solid type capable of spraying liquid droplets directly below the spray nozzle. By using a full cone type spray nozzle 13 ′ having a spray pattern, it is possible to prevent exhaust gas blow-through, which is more likely to occur around the tower wall in the absorption tower, than when using a hollow cone type spray nozzle 13.
[0035]
The region where exhaust gas blow-through is likely to occur can be regarded as a region where the gas flow velocity is higher than the average gas flow velocity when all the spray nozzles are hollow cone type spray nozzles 13 having a hollow type spray pattern.
[0036]
Therefore, a spray nozzle arranged in a region where the gas flow velocity is 1.1 times or more as compared with the average gas flow velocity when all the spray nozzles are hollow cone spray nozzles 13 is a full cone type spray nozzle. By using the spray nozzle 13 ′ as a spray nozzle and the other spray nozzle as a hollow cone type spray nozzle 13, it is possible to prevent blow-through of exhaust gas.
[0037]
Further, as in the invention according to claim 10, a full cone having a solid type spray pattern as a spray nozzle arranged in a region where the degree of drift is large for each stage of a plurality of spray nozzles vertically arranged in an absorption tower. By using a hollow spray nozzle 13 ′ and a hollow nozzle 13 having a hollow spray pattern as a spray nozzle disposed in a region where the degree of drift is not large, blow-through of exhaust gas can be prevented.
[0038]
As described above, according to the first, sixth, eighth, and tenth aspects of the present invention, sufficient gas-liquid contact is performed, so that the phenomenon of lowering the SOx absorption performance does not occur.
According to the first, sixth, eighth, and tenth aspects of the present invention, by preventing the exhaust gas from flowing through, that is, by the gas-liquid contact between the spray droplets and the exhaust gas, the gas flows uniformly in the absorption tower. As a result, the gas flow is rectified, and the generation of a vortex which causes an increase in pressure loss can be suppressed. Therefore, in the spray portion, there is no longer a place where the pressure loss is increased due to local vortex generated due to the non-uniform flow of the gas, so that the pressure loss does not increase more than before.
[0039]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment according to the present invention, and shows a side surface of an absorption tower in which a perforated plate 14 is installed as a wall-falling liquid dispersion plate between an upper surface of an inlet duct 2 and a lowermost spray nozzle. In FIG. 1, the same members as those described with reference to FIG. 14 described above are denoted by the same reference numerals, and description thereof will be omitted.
[0040]
FIG. 2 is a view of the absorption tower taken along line AA ′ in FIG. FIG. 3 shows the flows of the gas and the absorbing liquid near the perforated plate 14 in FIG. FIG. 4 shows the relationship between the porosity (%) of the perforated plate 14 and the resistance coefficient, in which a support 15 (FIG. 3) is provided between the perforated plate 14 and the tower wall of the absorption tower body 1. It is. FIG. 5 shows the behavior of the liquid flowing down the wall when the porosity of the porous plate 14 is less than 20% and when it exceeds 50%. FIG. 6 shows the relationship between the ratio W / D of the width W of the perforated plate 14 to the diameter D of the absorption tower and the gas flow velocity variation coefficient. FIG. 7 shows another embodiment in which a louver 16 is used instead of the perforated plate 14 as the wall-flowing-down liquid dispersion plate. FIG. 8 shows another embodiment in which a perforated plate 14 is applied to the upflow area side of a two-chamber absorption tower.
[0041]
The embodiment shown in FIG. 1 differs from the prior art in that a perforated plate 14 is provided as a wall-falling liquid dispersion plate between the upper surface of the inlet duct 2 and the lowermost spray nozzle 13.
Exhaust gas introduced from the inlet duct 2 tends to flow toward the inner wall side of the absorption tower main body 1, but the perforated plate 14 installed only near the inner wall of the absorption tower serves as a resistor against gas flow, and is shown in FIG. 3. As described above, part of the exhaust gas that has risen from the bottom near the inner wall of the tower passes through the perforated plate 14, and the rest tends to flow while avoiding the perforated plate 14. Therefore, there is no local gas blow-through. In particular, gas blow-through near the bottom spray nozzle 13 is the most intense, and the greatest effect is obtained by installing the perforated plate 14 on the upstream side of the bottom spray nozzle 13, that is, between the upper surface of the inlet duct 2 and the bottom spray nozzle 13. Obtainable.
[0042]
The rectifying effect on the gas flow of the perforated plate 14 at this time largely depends on the resistance coefficient of the perforated plate 14, and the resistance coefficient is determined by the porosity of the perforated plate 14. FIG. 4 shows the relationship between the porosity of the perforated plate 14 and the resistance coefficient. The resistance coefficient required to prevent gas blow-through near the absorption tower wall is 2 or more, and if the porosity is 55% or less, the gas flow rectification effect is sufficient. Become.
[0043]
On the other hand, although a large amount of the absorbing liquid 5 flows down on the inner wall of the absorption tower body 1, a part of the flowing liquid flows down from the holes of the perforated plate 14 and the remaining Runs down from the tip of the Therefore, the absorbing liquid 5 flowing down from the holes of the perforated plate 14 comes into contact with the exhaust gas passing through the perforated plate 14, and it is possible to efficiently remove SOx in the exhaust gas. At this time, since the gas-liquid contact time is also long, high desulfurization performance is obtained. Furthermore, as with the prior art, the absorbent 5 flowing down from the tip of the perforated plate 14 comes into contact with the exhaust gas that is going to bypass the tip of the perforated plate 14, so that it is similar to the exhaust gas passing through the perforated plate 14. SOx can be removed.
[0044]
However, the behavior of the absorbent 5 on the perforated plate 14 depends on the porosity of the perforated plate 14. FIG. 5 shows the behavior of the absorbent 5 when the porosity of the perforated plate 14 is less than 20% and when it exceeds 50%. If the porosity of the perforated plate 14 is less than 20%, the absorbing liquid 5 becomes difficult to flow down from the holes, and most of the absorbing liquid 5 flows down from the tip of the perforated plate 14. On the other hand, if the porosity exceeds 50%, the dispersion of the absorbing liquid 5 becomes poor, and the absorbing liquid 5 flows down only from some of the holes. Therefore, in order to make the absorbing liquid 5 flow down uniformly from all the holes of the porous plate 14, it is necessary to set the porosity in the range of 20 to 50%.
[0045]
From the above, the uniform dispersion of the absorbing liquid 5 flowing down the inner wall of the absorption tower body 1 is more dominant than the gas flow rectification, and the porosity of the perforated plate 14 is set to 20 to 50%. It can be seen that the effects of the present invention can be utilized to the maximum.
[0046]
The rectifying effect of the perforated plate 14 is also greatly affected by the ratio of the width of the perforated plate 14 to the diameter of the absorption tower. FIG. 6 shows the relationship between W / D and the gas flow velocity variation coefficient when the diameter of the absorption tower body 1 is D and the width of the perforated plate 14 is W. The gas flow rate variation coefficient is an index representing the degree of deviation of the gas flow, and is based on the value of the gas flow rate distribution on the horizontal section (plane perpendicular to the gas flow) of the absorption tower spray section (standard deviation of gas flow rate) / (Average flow velocity). If the width W of the perforated plate 14 is too small with respect to the tower diameter D of the absorption tower, the rectifying effect is weakened, and the gas flow rate variation coefficient is increased. Conversely, if the width W of the perforated plate 14 is too large, the gas tends to flow only at the center of the absorption tower, and the gas flow velocity variation coefficient is rather increased. Therefore, it can be seen that there is an appropriate range for the width of the perforated plate 14. The coefficient of variation at which the desulfurization rate does not decrease is about 30%, and the condition can be satisfied when the W / D is in the range of 0.005 to 0.1.
[0047]
The embodiment shown in FIG. 7 differs from the embodiment shown in FIG. 1 in that a louver 16 is used instead of the perforated plate 14 as the wall-flowing-down liquid dispersion plate. Although it is slightly inferior to the embodiment shown in FIG. 1 in terms of the uniform dispersion of the liquid flowing down the wall, the rectification effect on exhaust gas that tends to blow through near the inner wall of the tower is almost the same as that in the embodiment shown in FIG. Is obtained.
[0048]
In the embodiment shown in FIG. 8, the lower end of the partition plate 17 is immersed in the circulation tank 6 to divide the gas flow path in the absorption tower main body 1 into two, and the gas ascending flow area 18 on the inlet duct 2 side. This is an example in which a perforated plate 14 of the present invention is attached to the inner wall of a two-chamber absorption tower that forms a gas descending flow area 19 on the side of the outlet duct 3. The embodiment shown in FIG. 8 can obtain substantially the same effect as the embodiment shown in FIG. 1, but the perforated plate 19 is provided in the downflow region 19 near the inner wall of the tower where gas is unlikely to flow through. There is no need for 14 installations.
[0049]
FIG. 9 is a layout view of a spray nozzle in an absorption tower according to another embodiment. In the figure, the black painted portion indicates a full cone type spray nozzle 13 ', and the other spray nozzles indicate the hollow cone type spray nozzle 13 as in the prior art. By installing a full-cone type spray nozzle 13 ′ that can spray droplets directly below the nozzle in a portion where the exhaust gas blows easily in the vicinity of the tower wall in the absorption tower main body 1, exhaust gas around the tower wall is installed. Since blow-through can be prevented, the flow velocity of the exhaust gas in the absorption tower main body 1 has a small deviation between the periphery of the tower wall and the center of the absorption tower as shown in FIG.
[0050]
The basic arrangement and specifications of the spray nozzles should be arranged at equal intervals as much as possible, based on internal spray piping size, nozzle size, and placement restrictions that take into account maintenance, such as nozzle installation and removal. Thus, the number of spray nozzles that can be arranged in one stage is determined, and the spray amount is obtained by dividing the amount of liquid necessary for maintaining the desulfurization performance by the number of spray nozzles.
[0051]
For each spray stage of the spray nozzles usually provided in the vertical direction in the absorption tower main body 1 in about 4 to 6 stages, it is comprehensively determined which spray nozzle is a full cone type spray nozzle 13 ′ and which spray nozzle is a hollow cone type spray nozzle 13. It is not necessary to provide both a full cone type spray nozzle 13 ′ and a hollow cone type spray nozzle 13 in all spray stages, and some of the spray stages are all constituted by hollow cone type spray nozzles 13. It may be something.
[0052]
The type of the spray nozzle around the inner wall of the absorption tower main body 1 is a full cone type spray nozzle 13 ′ that can spray droplets directly below the spray nozzle, so that the exhaust gas blow-through easily occurs in the prior art. Since the exhaust gas flow rate in the peripheral portion can be made uniform, exhaust gas does not blow out in the peripheral portion of the absorption tower tower wall in the related art, so that the gas-liquid contact becomes insufficient and the phenomenon that SOx absorption performance is reduced can be prevented. .
[0053]
Further, the gas flow in the absorption tower main body 1 is rectified, and the generation of a vortex which causes an increase in pressure loss can be suppressed, so that the pressure loss does not increase more than necessary.
[0054]
Specific examples of the hollow cone type spray nozzle 13 and the full cone type spray nozzle 13 'are as shown in FIG.
The swirl vane built-in type nozzle (FIG. 17 (b)) and the coreless type nozzle (FIG. 17 (c)) classified as the full cone type spray nozzle 13 'having a solid type spray pattern can obtain a full cone spray pattern. Thus, the spiral nozzle (FIG. 17 (d)) provides a pseudo-filled conical spray pattern in which hollow cones are continuously connected in a spiral.
[0055]
A feature of the appearance of the hollow cone nozzle 13 as shown in FIG. 17A is that it has a cylindrical swirling chamber, and the liquid inflow direction and the ejection direction are different by 90 degrees. Further, the liquid flows into the swirl chamber from the tangential direction, and there is a deviation of the width D between the liquid inlet and the central axis of the injection hole. Further, there is no special structure inside the swirling chamber, the spray liquid is a hollow conical spray, and the droplet diameter is smaller than that of the full cone.
[0056]
Next, among the full cone nozzles 13 ′, the nozzle with a built-in swirl vane shown in FIG. 17B has the most general full cone nozzle appearance shape, and the liquid inflow direction and the spray direction are the same. The swirl vanes are built in the nozzle. Generally, the swirling blade has two semicircular disks. The characteristic of the spray liquid is a filled conical spray, and the droplet diameter is slightly larger than that of the hollow cone type.
[0057]
The appearance of the coreless type nozzle shown in FIG. 17C is similar to the hollow cone nozzle 13 and does not have a swirl chamber. The liquid inflow direction and the injection direction are different by 90 degrees, and there is no axial displacement as in the hollow cone nozzle 13. Also, there is no structure inside, and an orifice (throttle) is characterized on the liquid inflow side. The spray liquid is a filled conical spray, and the droplet diameter is slightly larger than that of the hollow cone type.
[0058]
A feature of the appearance of the spiral nozzle shown in FIG. 17D is that it has a spiral spiral structure called a pigtail. The liquid inflow direction and the injection direction are the same, there is no structure inside, and there is an orifice in the liquid inflow section. The spray liquid belongs to a filled cone spray, but is not strictly a perfect filled cone, but has a pseudo filled cone shape in which a hollow cone type spray is continuously connected in a spiral shape. The droplet diameter is smaller than that of the hollow cone type.
[0059]
FIG. 11 shows another embodiment of the present invention. In this embodiment, a hollow chamber type spray nozzle 13 and a full cone type spray nozzle 13 'are used by applying the present invention to the two-chamber absorption tower main body 1 described in FIG. In this embodiment, the ratio of the length of the tower wall to the cross-sectional area of the absorption tower is larger than that of a normal absorption tower because the shape of the absorption tower body 1 is the partition plate 17 provided inside the absorption tower. For this reason, by applying the present invention, it is possible to prevent the exhaust gas from flowing around the inner wall of the absorption tower main body 1, so that the effect of rectifying the gas flow and the effect of preventing the SOx absorption performance from lowering are likely to appear.
[0060]
In the embodiment shown in FIG. 12, the exhaust gas flow simulation result inside the absorption tower main body 1 and the flow model test result show that the exhaust gas has a large degree of drift (at least a portion where the average gas flow velocity is 1.1 times or more). This shows that a full-cone type spray nozzle 13 ′ capable of spraying liquid droplets is provided immediately below the spray nozzle. Also in this embodiment, since the exhaust gas can be prevented from blowing around the inner wall of the tower in the absorption tower main body 1 and the exhaust gas flow can be rectified, the effects described in the above embodiment can be obtained.
[0061]
In addition, although not shown, a full cone type is provided in a portion where the degree of drift is large at each stage of the spray nozzles arranged vertically in the absorption tower (the exhaust gas flow simulation results and the flow model test results can also be used). By installing the spray nozzle 13 ', exhaust gas blow-through can be prevented over the entire area of the absorption tower from the exhaust gas inlet to the outlet.
[0062]
【The invention's effect】
According to the present invention, gas blow-through near the tower wall of the absorption tower can be prevented, and SOx gas in exhaust gas flowing near the tower wall can be positively removed. Can be reduced. In addition, since the amount of circulation of the absorbing liquid is small, the pressure loss in the spray portion is reduced, and the power of the desulfurization fan can be reduced.
[0063]
Further, since the desulfurization performance is maintained even when the exhaust gas flow rate in the absorption tower is increased, the pressure loss of the absorption tower can be prevented from becoming unnecessarily large, so that there is an effect that the equipment capacity can be reduced. .
[Brief description of the drawings]
FIG. 1 is an embodiment according to the present invention, showing a side surface of an absorption tower in which a perforated plate is installed as a wall-falling liquid dispersion plate between an upper surface of an inlet duct and a lowermost spray nozzle.
FIG. 2 shows a section taken along the line AA ′ of the absorption tower in FIG.
FIG. 3 shows flows of gas and absorbing liquid in the vicinity of a perforated plate in FIG.
FIG. 4 shows the relationship between the porosity of a perforated plate and the resistance coefficient.
FIG. 5 shows the behavior of the liquid flowing down the wall when the porosity of the perforated plate is less than 20% and when it exceeds 50%.
FIG. 6 shows the relationship between the ratio W / D of the width W of the perforated plate and the diameter D of the absorption tower and the gas flow velocity variation coefficient.
FIG. 7 is another embodiment using a louver instead of a perforated plate as a wall-falling liquid dispersion plate.
FIG. 8 shows another embodiment in which a perforated plate is applied to the upflow region side of a two-chamber absorption tower.
FIG. 9 shows a layout of a spray nozzle in an absorption tower according to another embodiment.
FIG. 10 is a diagram showing a flow rate of exhaust gas in a sectional direction at the center of an absorption tower in the wet desulfurization apparatus of the present invention.
FIG. 11 is a view showing another embodiment in which the present invention is applied to an absorption tower provided with a partition plate in the tower.
FIG. 12 is a view showing another embodiment in which the present invention is applied to a portion where exhaust gas drift is large.
FIG. 13 is a view showing a flow rate of exhaust gas in a sectional direction at the center of an absorption tower in a conventional wet desulfurization apparatus.
FIG. 14 shows a side view of a conventional exhaust gas treatment apparatus.
FIG. 15 is a diagram showing a droplet spray pattern of a hollow cone nozzle (FIG. 15 (a) is a side view, and FIG. 15 (b) is a bottom view).
FIG. 16 is a diagram showing a droplet spray pattern of a full cone nozzle (FIG. 16 (a) is a side view, and FIG. 16 (b) is a bottom view).
FIG. 17 shows a specific example of a hollow cone nozzle (FIG. 17A) and a specific example of a full cone nozzle (FIGS. 17B to 17D).
[Explanation of symbols]
1 Absorption tower body 2 Inlet duct
3 Outlet duct 4 Absorbent circulation pump
5 Absorbent 6 Circulation tank
7 stirrer 8 air blowing tube
9 Mist eliminator 10 Absorbent drain pipe
11 Circulation piping 12 Spray header
13, 13 'spray nozzle 14 perforated plate
15 Support 16 Louver
17 Partition plate 18 Gas rising flow area
19 Gas downflow area 20, 20 'Droplet
D diameter W width

Claims (11)

A circulation tank for storing the absorbing liquid, an inlet duct for introducing exhaust gas discharged from a combustion device such as a boiler above the circulation tank, and an exhaust gas introduced from the inlet duct flowing vertically, and a plurality of stages in the gas flow direction. In a wet-type flue gas desulfurization device including an absorption tower having a spray absorption section that makes gas-liquid contact with an absorbing liquid ejected from an installed spray nozzle and an outlet duct that discharges exhaust gas that has passed through the spray absorption section,
A wet-type flue gas desulfurization apparatus characterized in that an aperture-shaped wall falling liquid dispersion plate is provided on a surface orthogonal to a gas flow only in the vicinity of a tower wall of a spray absorption section. 2. The wet flue gas desulfurization apparatus according to claim 1, wherein the porosity of the wall falling liquid dispersion plate is set to 20 to 50%. The wet flue gas desulfurization according to claim 1 or 2, wherein the W / D ratio is 0.005 to 0.1, where D is the diameter of the absorption tower and W is the width of the liquid dispersion plate. apparatus. The wet flue gas desulfurization apparatus according to any one of claims 1 to 3, wherein the wall falling liquid dispersion plate is provided at least on a tower wall between the upper surface of the inlet duct and the lowermost spray nozzle. The absorption tower has an exhaust duct between the inlet duct and the outlet duct, and an exhaust duct between the inlet duct and the outlet duct. A vertical partition plate having an opening is provided, and the exhaust gas introduced from the inlet duct flows upward in the partition plate and the exhaust gas flows downward toward the outlet duct after being inverted at the opening on the ceiling side. From the two-chamber absorption tower provided with a spray nozzle in each region so that the ejected absorbing liquid slurry makes countercurrent contact with the exhaust gas in the ascending flow region and co-currently contacts in the descending flow region. The wet flue gas desulfurization according to any one of claims 1 to 4, wherein the wall falling liquid dispersion plate of the two-chamber absorption tower is installed at least on the tower wall between the upper surface of the inlet duct and the lowermost spray nozzle. apparatus. A circulation tank for storing the absorbing liquid, an inlet duct for introducing exhaust gas discharged from a combustion device such as a boiler above the circulation tank, and an exhaust gas introduced from the inlet duct flowing vertically, and a plurality of stages in the gas flow direction. In a wet-type flue gas desulfurization device including an absorption tower having a spray absorption section that makes gas-liquid contact with an absorbing liquid ejected from an installed spray nozzle and an outlet duct that discharges exhaust gas that has passed through the spray absorption section,
The plurality of spray nozzles are spray nozzles that are installed near the absorption tower tower wall, are spray nozzles having a solid type spray pattern, and the other spray nozzles are spray nozzles having a hollow type spray pattern. Smoke desulfurization equipment. The absorption tower has an exhaust duct between the inlet duct and the outlet duct, and an exhaust duct between the inlet duct and the outlet duct. A vertical partition plate having an opening is provided, and the exhaust gas introduced from the inlet duct flows upward in the partition plate and the exhaust gas flows downward toward the outlet duct after being inverted at the opening on the ceiling side. From the two-chamber absorption tower provided with a spray nozzle in each region so that the ejected absorbing liquid slurry makes countercurrent contact with the exhaust gas in the ascending flow region and co-currently contacts in the descending flow region. The spray nozzle installed near the tower wall and the partition plate of the two-chamber absorption tower is a spray nozzle with a solid type spray pattern, and the other spray nozzles have a hollow type spray pattern. Wet flue gas desulfurization apparatus according to claim 6, characterized in that the pre-nozzle. A circulation tank for storing the absorbing liquid, an inlet duct for introducing exhaust gas discharged from a combustion device such as a boiler above the circulation tank, and an exhaust gas introduced from the inlet duct flowing vertically, and a plurality of stages in the gas flow direction. In a wet-type flue gas desulfurization device including an absorption tower having a spray absorption section that makes gas-liquid contact with an absorbing liquid ejected from an installed spray nozzle and an outlet duct that discharges exhaust gas that has passed through the spray absorption section,
A spray nozzle having a solid type spray pattern is used as a spray nozzle arranged in a region where the gas flow rate is 1.1 times or more the average value of the gas flow rate when all the spray nozzles are spray nozzles having a hollow type spray pattern. And a spray nozzle having a hollow spray pattern is used as a spray nozzle disposed in a region having a gas flow rate less than 1.1 times the average value. The absorption tower has an exhaust duct between the inlet duct and the outlet duct, and an exhaust duct between the inlet duct and the outlet duct. A vertical partition plate having an opening is provided, and the exhaust gas introduced from the inlet duct flows upward in the partition plate and the exhaust gas flows downward toward the outlet duct after being inverted at the opening on the ceiling side. From the two-chamber absorption tower provided with a spray nozzle in each region so that the ejected absorbing liquid slurry makes countercurrent contact with the exhaust gas in the ascending flow region and co-currently contacts in the descending flow region. The spray nozzle arranged in a region where the gas flow rate is 1.1 times or more the average value of the gas flow rate when all the spray nozzles of the two-chamber absorption tower are spray nozzles having a hollow type spray pattern is medium. A spray nozzle with a type of spray pattern, a wet flue gas desulfurization apparatus according to claim 8, wherein the other spray nozzles are spray nozzles with a spray pattern of a hollow type. A circulation tank for storing the absorbing liquid, an inlet duct for introducing exhaust gas discharged from a combustion device such as a boiler above the circulation tank, and an exhaust gas introduced from the inlet duct flowing vertically, and a plurality of stages in the gas flow direction. In a wet-type flue gas desulfurization device including an absorption tower having a spray absorption section that makes gas-liquid contact with an absorbing liquid ejected from an installed spray nozzle and an outlet duct that discharges exhaust gas that has passed through the spray absorption section,
A spray nozzle having a solid type spray pattern is used as a spray nozzle arranged in a region where the degree of drift is large for each stage of the spray nozzle arranged in a plurality of stages in the vertical direction in the absorption tower, and is arranged in a region where the degree of drift is not large. A spray nozzle having a spray pattern of a hollow type as a spray nozzle. The absorption tower has an exhaust duct between the inlet duct and the outlet duct, and an exhaust duct between the inlet duct and the outlet duct. A vertical partition plate having an opening is provided, and the exhaust gas introduced from the inlet duct flows upward in the partition plate and the exhaust gas flows downward toward the outlet duct after being inverted at the opening on the ceiling side. From the two-chamber absorption tower provided with a spray nozzle in each region so that the ejected absorbing liquid slurry makes countercurrent contact with the exhaust gas in the ascending flow region and co-currently contacts in the descending flow region. In the two-chamber absorption tower, a spray nozzle having a solid type spray pattern is used as a spray nozzle arranged in a region where the degree of drift is large for each stage of a plurality of stages of spray nozzles arranged vertically in the two-chamber absorption tower. Wet flue gas desulfurization apparatus according to claim 10, wherein the use of spray nozzles having a spray pattern of a hollow type as spray nozzles disposed in the region is not large.

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