JP3486256B2 - Wet flue gas desulfurization equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tank oxidation in which bubbles blown into an absorption tower tank are caught in a pump and a so-called short path of a circulation slurry is reduced. The present invention relates to a wet-type flue gas desulfurization system. 2. Description of the Related Art In recent years, as a wet flue gas desulfurization apparatus, air is sent into a tank of an absorption tower, where it is brought into contact with a slurry solution (composed of a calcium compound such as limestone) absorbing sulfurous acid gas. The mainstream is to oxidize and eliminate the need for an oxidation tower (so-called tank oxidation method). In this case, how efficiently the air and the slurry solution are brought into contact in the tank depends on the amount of air consumed. In addition , power consumption is reduced, the processing speed is increased, and the size of the tank is reduced. As means for sending air into the tank and bringing it into contact with the slurry solution (that is, air supply means), there has been a method in which a vent pipe is fixed in the tank and mere bubbling is performed. In order to obtain contact, the applicant has developed and put into practical use a so-called arm-rotating type air supply means for supplying air to the back of a stirring rod rotating in a tank, and a wet desulfurization apparatus using the same. FIG. 6 is a view showing an example of a wet lime gypsum desulfurization apparatus to which the arm-rotating air supply means 7 is applied. This device uses a so-called gas-liquid contact device of the filling type (grid type), and its main structure is an absorbent slurry (calcium-containing slurry, in this case, limestone slurry).
1, an absorption tower 2 extending upward on one side of the tank 1, and a smoke exhaust outlet 3 formed on the other side of the tank 1 so as to rise upward. And a circulating pump 4 that sucks up the absorbent slurry in the tank 2 and sends it to the tower upper part 2a of the absorption tower 2, and an absorbent slurry provided in the tower upper part 2a of the absorption tower 2 and sent from the circulation pump 4. And a large gas-liquid contact area that is provided below the tower upper part 2a in the absorption tower 2 and holds the absorbent slurry flowing out from the nozzle 5a and flowing down from the nozzle 5a. After the sulfurous acid gas in the exhaust gas is brought into gas-liquid contact with the absorbent slurry and absorbed, the entire amount of the absorbent slurry is oxidized to obtain gypsum as a by-product. . That is, in this apparatus, untreated smoke exhaust gas A is guided to the tower upper portion 2a of the absorption tower 2, and is brought into gas-liquid contact with the absorbent slurry jetted from the nozzle 5a of the header pipe 5 by the circulation pump 4 so that the untreated exhaust gas A is discharged. The sulfur dioxide gas in the smoke A is absorbed and removed, and is discharged from the flue gas discharge section 3 as the treated flue gas B.
The absorbent slurry flowing out from the nozzle 5a and flowing down through the filler 6 while absorbing the sulfurous acid gas is oxidized in the tank 1 by the air supplied by the air supply means 7, and further causes a neutralization reaction. It becomes plaster. The arm rotation type air supply means 7 is supported by a hollow rotary shaft 8 in the tank 1 and is horizontally rotated by a motor (not shown), and an opening 10a extending from the hollow rotary shaft 8. Is provided with an air supply pipe 10 extended below the stirring rod 9, and a rotary joint 11 for connecting the base end side of the hollow rotary shaft 8 to an air source,
By rotating the hollow rotary shaft 8 while pressurizing the air C from the rotary joint 11, the air C is supplied from the air supply pipe 10 to the gas phase region generated on the back side in the rotation direction of the stirring rod 9,
The vortex force generated by the rotation of the stirring rod 9 causes the end of the gas phase region to shred, causing a large number of substantially uniform fine bubbles to be generated. Is efficiently contacted. Also,
The main reactions occurring during these processes are the following reaction formulas (1) to (3). (Absorption tower) SO ₂ + H ₂ O → H ⁺ + HSO ₃ ⁻ (1) (Tank) H ⁺ + HSO ₃ ⁻ + 1 / 2O ₂ → 2H ⁺ + SO ₄ ²⁻ (2) 2H ⁺ + SO ₄ ²⁻ + CaCO ₃ + H ₂ O → CaSO ₄ .2H ₂ O + CO ₂ (3) In the tank 1, gypsum and a small amount of limestone as an absorbent are suspended or dissolved, and these are sucked out by the extraction pump 12. The gypsum E is supplied to the solid-liquid separator 15 and filtered, and is extracted as gypsum E having a low water content (usually, a water content: about 10%). On the other hand, the filtrate from the solid-liquid separator 15 is sent to a filtrate tank 16, where limestone G is added and supplied to the tank 1 again by a slurry pump 17 as an absorbent slurry. FIG. 6 shows a desulfurization apparatus without a dust removing section. However, the filling type gas-liquid contacting apparatus itself has almost no dust removing action. Therefore, when high dust removing performance is required, the absorption tower is required. A dust removing unit having a pipe formed with a plurality of nozzles for injecting water is provided on the upstream side of 2. In addition, as a gas-liquid contact device conventionally used in this type of desulfurization device,
For example, there is a so-called liquid column type as disclosed in Japanese Utility Model Laid-Open No. 59-53828. In this method, an absorbent slurry is ejected from a nozzle in a liquid column manner without using a filler, thereby performing gas-liquid contact. Although the desulfurization apparatus shown in FIG. 6 is provided with one so-called co-current type absorption tower, the applicant assigns co-current flow to the flue gas introduction side and the discharge side of one tank. It has been proposed a desulfurization device consisting of a so-called hybrid type gas-liquid contactor, which is equipped with a type absorption tower and a counter-current type absorption tower, respectively. In addition, the size of the apparatus can be reduced and power consumption can be reduced. In the above-mentioned conventional desulfurization apparatus, a large flow containing bubbles as indicated by an arrow N1 in FIG. The flow N2 generated and branched from the outer periphery of the flow N1 is directly and smoothly
From the outlet opening connected to the pump 12. For this reason, a large amount of air bubbles are directly contained in the flow N2 and flow into the circulation pump 4 and the withdrawal pump 12, resulting in performance deterioration and damage of each pump, or increase in noise and vibration. Also, a large amount of flow N3 (that is, a short path) in which the slurry that has fallen from the absorption tower 2 in contact with the flue gas is directly sucked into the circulation pump 4 or the like without coming into contact with the air bubbles occurs, which hinders improvement in desulfurization performance and the like. There was also a problem. In the single-column desulfurization apparatus as shown in FIG. 6, the outlet opening of the pump is provided on the side opposite to the side where the absorption tower is located, so that the outlet opening is kept away from the slurry drop position. You can avoid short passes,
In this case, there is a problem that the degree of freedom of design is deteriorated. Also, in the above-mentioned hybrid type desulfurization apparatus, even if the outlet opening of the pump is provided on any side, since the slurry in contact with the exhaust gas falls on the upper part, the flow N3
Such short paths are inevitable, which also hinders performance improvement. In this type of tank oxidation type desulfurization apparatus, as a technique for preventing gas from being sucked into a pump, for example, as shown in Japanese Patent Publication No. 5-26525, a partition wall is provided at the bottom of the tank. There has been proposed a technique in which a liquid reservoir is formed upright and a pump outlet is provided in the liquid reservoir. This is to prevent the suction of bubbles by setting the cross-sectional area of the liquid reservoir so that the flow velocity generated in the liquid reservoir according to the withdrawal amount of the pump is lower than the rising speed of the bubbles, For example, if the air supply means is based on simple bubbling (a so-called fixed type air sparger), it is considered to be effective in reducing air bubble suction. However, with this configuration, it is not possible to suppress a flow in which the slurry that has fallen near the upper portion of the liquid reservoir is directly sucked into the pump, that is, a short path. Furthermore, as in the above-described arm-rotating type air supply means,
In the case of generating a large flow N1 rising at the center of the tank and descending at the side wall of the tank, it may not be practically possible to adjust the flow velocity of the liquid reservoir only by its step area. However, it is not possible to effectively reduce air bubble suction. [0013] In view of the above, the present invention employs an air supply means (or a stirrer) in which a flow including air bubbles descending along the side wall of the tank is employed. It is an object of the present invention to provide a wet flue gas desulfurization apparatus that suppresses the incorporation of air bubbles into a pump and the short path even when a simple absorption tower configuration (or arrangement of a pump outlet opening) is used. In order to achieve the above object, a wet flue gas desulfurization apparatus of the present invention comprises an absorption tower in which a slurry containing a calcium compound is supplied to a bottom tank, and a slurry in the tank. Tank having a circulating pump for sending air to the upper part of the absorption tower and contacting it with flue gas, air supply means for supplying air for oxidation into the tank, and an extraction pump for extracting slurry in the tank In a wet flue gas desulfurization device of an oxidation system, in a slurry liquid, obliquely downward from the inner surface of the side wall of the tank so as to cover at least the upper side of the outlet opening for the circulation pump or the extraction pump in the side wall of the tank. elongation, characterized in that the descending flow of the slurry liquid in the tank near the side wall provided with the inclined plate for guiding a direction away from the outlet opening for the pump. Further, in the wet flue gas desulfurization apparatus according to the present invention , a perforated plate is erected on the bottom surface of the tank so as to partition between a lower end of the inclined plate and the bottom surface of the tank. . According to the present invention, even if there is a flow descending along the inner surface of the tank side wall, this flow is guided by the inclined plate in a direction away from the outlet opening of the pump, and is branched from this flow. Therefore, the generation of the flow directly and smoothly flowing into the outlet opening is prevented, and the bubble separation is realized. Also, the slurry that falls above the outlet opening of the pump flows along the inclined plate toward the center of the tank, so that it passes through at least a region where a large amount of air bubbles are present, and the short path is reduced. Further, since the porous plate for dividing between the tip and the tank bottom of the inclined plate is erected, the flow entering the outlet opening, bubble separation is further promoted by the action of the porous plate . An embodiment of the present invention will be described below with reference to FIGS. Note that the same elements as those of the conventional wet flue gas desulfurization apparatus shown in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 1, the wet flue gas desulfurization device of the present embodiment is a gas-liquid contact device for bringing the absorbent slurry into gas-liquid contact with flue gas, and also with air for oxidation.
Hybrid-type gas-liquid contact device 1 as shown in FIG.
00. The gas-liquid contact device 100 is provided with a tank 101 to which an absorbent slurry (calcium-containing slurry, in this case, limestone slurry) is supplied, and extends upward from one side (the left side in the figure) of the tank 101 to perform untreated discharge. A flue gas introduction section 111 for introducing smoke A is formed at the upper end thereof, and extends upward from the introduction-side absorption tower 110 through which the flue gas flows downward, and from the other side (the right side in the figure) of the tank 101. A flue gas deriving section 121 for deriving the treated flue gas is formed at the upper end thereof, and the flue gas flowing through the upper absorption tower 110 and passing through the upper portion of the tank 101 flows upward. And a side absorption tower 120. Each of the absorption towers 110 and 120 is provided with a spray pipe 112 and 122, respectively. The spray pipes 112 and 122 have a plurality of nozzles 113 and 123 for jetting the absorbent spray upward in a liquid column shape. Is formed. Also, on both sides of the tank 101, circulating pumps 11 for sucking up the absorbent slurry in the tank 101 are provided.
4 and 124 are provided, and the absorbent slurry is sent to the respective spray pipes 112 and 122 via the circulation pipes 115 and 125 and is jetted from the respective nozzles 113 and 123. Furthermore, in this case, the outlet side absorption tower 12
A mist eliminator 130 for collecting and removing accompanying mist is provided at the upper end of the zero. The mist collected by the mist eliminator 130 is dropped, for example, into the outlet-side absorption tower 120 so that the mist is collected directly into the tank 1.
01. 2 is an air blower that supplies air to the air supply means 7 via the rotary joint 11. Reference numeral 102 denotes an inner surface of the side wall of the tank 101 so as to cover the upper side and the front side of each outlet opening 105 (shown in FIG. 3) of each of the pumps 114 and 124 on the side wall of the tank 101. It is an inclined plate provided to extend obliquely downward from. In this case, as shown in FIG. 2, the inclined plate 102 is disposed over the entire length of the tank 101 in the depth direction, and is provided collectively with respect to the outlet openings of the pumps. A perforated plate 103 (mostly not shown) is provided between the tank and the bottom surface of the tank 101 so as to divide this portion over the entire length in the depth direction. This perforated plate 103 is, for example, a punching metal having an aperture ratio of 50%.
By providing such an inclined plate 102 and a perforated plate 103, suction of air bubbles into each pump and a so-called short path are suppressed as described later. Although FIG. 2 shows a state in which the partition 104 is provided, this is unnecessary in the present embodiment, and an aspect in which the partition 104 is provided will be described later. Next, the operation of the desulfurization apparatus configured as described above will be described. The absorbent slurry in the tank 101 is circulated by circulation pumps 114 and 124 respectively.
5,125 to the spray pipes 112,122. On the other hand, the flue gas first passes through the flue gas introduction section 111 and is introduced into the introduction-side absorption tower 110 and descends. The absorbent slurry supplied to the spray pipe 112 is applied to the spray pipe 11.
The absorbent slurry ejected upward from the second nozzle 113 and sprayed upward is dispersed at the top and then descends, and the descending slurry and the ejected slurry collide with each other to form fine particles, resulting in fine particles. Particulate slurries are generated one after another, and the particulate slurries are dispersed and present in the tower, and eventually fall slowly. In this way, the flue gas containing sulfurous acid gas flows down in the tower where the particulate slurry is present, so that the gas-liquid contact area per volume increases. In addition, since the exhaust gas is effectively entrained in the jet of the slurry near the nozzle 113, the slurry and the exhaust gas are effectively mixed, and first, a considerable amount of sulfur dioxide gas is supplied to the cocurrent absorption tower 110. Removed. For example, even if the circulating flow rate and the liquid column height of the absorbent slurry in the introduction-side absorption tower 110 are set lower than before, it is possible to absorb and remove sulfurous acid gas at a desulfurization rate of about 60 to 70%. (Conventionally, 90-
95% desulfurization rate has been achieved). Next, the flue gas flowing down the absorption tower 110 flows laterally in the upper part of the tank 101 and then from the lower part in the absorption tower 1.
Enter 20 and ascend the absorption tower 120. In the absorption tower 120, the absorbent slurry is supplied to the nozzle 123 of the spray pipe 122.
From the upper side, becomes fine particles like the absorption tower 110, slowly falls, and comes into contact with the exhaust gas flowing oppositely. In addition, since the exhaust gas is effectively entrained in the slurry jet flow near the nozzle 123, the slurry and the exhaust gas are effectively mixed, and furthermore, the countercurrent type absorption tower 120 is used.
Finally, most of the remaining sulfur dioxide gas is removed. For example, sulfur dioxide is finally absorbed and removed at a desulfurization rate of 90 to 95% or more. In the tank 101, as described in the conventional example, the air C flows from the air blower 11a through the rotary joint 11, the hollow rotary shaft 8, and the open end 10a of the air supply pipe 10, and the air C The vortex force generated by the rotation of the stirring rod 9 is supplied to the above-mentioned gas phase region on the back side, and the end portion of the gas phase region is cut off to generate a large number of substantially uniform fine bubbles. The absorbent slurry that has absorbed sulfur dioxide gas and flowed down in the towers 110 and 120 is in contact with the air and is oxidized, and gypsum is obtained as in the conventional case. At this time, a large circulating flow is generated in the tank 101 by the action of the arm-rotating air supply means 7 as shown by an arrow N5 in FIG. A descending flow is constantly occurring. However, even if there is such a flow descending along the inner surface of the tank side wall, this flow N5 is generated by the inclined plate 102 as shown in FIG.
The flow which is guided in a direction away from the flow path 05 and which branches off from this flow and flows directly and smoothly into the outlet opening 105 is prevented. In other words, the flow N6 that flows into the outlet opening 105 so as to branch off from the flow N5 is a flow that detours on the tip side of the inclined plate 102.
Further, the flow N6 is prevented from flowing smoothly by the perforated plate 103 below the tip of the inclined plate 102, so that the flow N6 is further twisted and bent while disturbing the flow direction. For this reason, bubbles in the tank 101 (bubbles contained in a large amount in the flow N5) are separated from the flow N6 at this detour portion on the tip side of the inclined plate 102 and further before the perforated plate 103, and Hardly flows into the side space (ie the outlet opening). On the other hand, the absorbent slurry falling above the pump outlet opening 105 is dragged by the large flow N5 by the arm-rotating air supply means 7 and becomes a flow N7 along the side wall of the tank 101 and descends. I do. However, this flow N7 is also guided by the inclined plate 102 in a direction away from the outlet opening 105 of the pump as shown in FIG.
From flowing directly and smoothly into the outlet opening 105 (that is, a short path) is avoided. That is,
The flow N7 containing the dropped absorbent flows toward the center of the tank along the inclined plate 102, and flows into the space below the inclined plate 102 while disturbing the flow direction by the perforated plate 103. After passing through a large area, most of which reacts with air bubbles (air), the outlet opening 1
05 sucked. As described above, according to the desulfurization apparatus having the gas-liquid contact device 100 of the above embodiment, gas-liquid contact (absorption of sulfurous acid gas) can be performed in two stages in one tank. For this reason, while maintaining the lateral dimensions of the apparatus (mainly the area occupied by the tank 101) at the same level as before, and setting the height of each absorption tower and the circulating flow rate of the slurry at the same level or lower than the conventional level, A higher gas-liquid contact efficiency (desulfurization rate) can be obtained. Then, the above-described inclined plate 102
Of the pumps 114 and 12 by the action of
The inflow of air bubbles into 4, 12 is significantly reduced compared to the past,
There is an effect that deterioration or damage of the pump, or noise or vibration is reliably avoided. Further, even if the hybrid-type gas-liquid contact device 100 is employed as in the above-described embodiment and the outlet opening 105 of the pump cannot be moved away from the position where the absorbent slurry falls, the above-described inclined plate 1 can be used.
02 and the perforated plate 103, the short path can be almost avoided, so that the desulfurization rate can be further improved and the purity of gypsum as a by-product can be improved while reducing the size of the apparatus. The perforated plate 1 shown in FIG.
03 not provided configuration, also be configured to provide a tilting plate 102a having a shape tip of FIG. 5 is refracted downward, the tank side walls
Direct the flow descending along the inner surface away from the pump outlet opening
There is an effect of guiding in a zigzag direction or the tank center side. Further, in the above embodiment, the outlet opening 10 of each pump is used.
5 are arranged side by side in the depth direction of the tank 101, but the oblique plate 102 and the perforated plate 103 are separated so that a horizontally long space defined by the inclined plate 102 and the perforated plate 103 is partitioned by each of these outlet openings. The partition 104 as shown in FIG.
May be erected at predetermined intervals. In this way, the circulating pumps 114 and 124 suck up the absorbent slurry containing a large amount of unreacted limestone by the action of the partition wall 104. That is, the discharge side of the slurry pump 17 is connected to a space partitioned by the partition wall 104 corresponding to the outlet openings of the circulating pumps 114 and 124, and is partitioned for each outlet opening of the circulating pumps 114 and 124. When a new absorbent slurry is supplied into the space, the absorbent slurry containing a large amount of unreacted limestone is supplied to the circulation pump 114,
It is sucked up by 124. Further, in this case, an outlet opening for sucking slurry in the tank 101 to produce gypsum (an outlet opening connecting the suction side of the extraction pump 12) is connected to an outlet opening of each of the circulation pumps 114 and 124. Is separated by the respective walls 104, so that a slurry containing a large amount of gypsum is efficiently extracted by absorbing and flowing down and oxidizing sulfur dioxide gas. Further, the introduction-side absorption tower 2 in the above embodiment is used.
Although the zero and outlet side absorption towers 30 are of the liquid column type, they may be grid type absorption towers (contact processing towers). However, in the case of the grid type, it is preferable to provide a dust removing section because the dust removing action is small, and a pump and piping for this are also required. Therefore, the liquid column type which does not require these is superior. Further, the desulfurization apparatus of the present invention is not limited to the system employing the hybrid type gas-liquid contact device as in the above-described embodiment, and it goes without saying that, for example, a conventional single-column system may be employed. According to the present invention, even if there is a flow descending along the inner surface of the tank side wall, this flow is guided by the inclined plate in a direction away from the outlet opening of the pump, and is branched from this flow. As a result, the generation of the flow flowing directly and smoothly into the outlet opening is prevented. Also, the slurry falling above the outlet opening of the pump flows along the inclined plate toward the center of the tank, and at least passes through a region where a large amount of bubbles are present. Therefore, it is possible to prevent a large amount of air bubbles from flowing into the outlet opening of the pump, thereby reducing or damaging the performance of the pump, reducing noise and vibration, and reducing the short path. Further, since the porous plate for dividing between the tip and the tank bottom of the inclined plate are erected, flow entering the outlet opening will be further twists and turns in front of the perforated plate . Therefore, air bubbles are almost prevented from flowing into the outlet opening of the pump, and the performance of the pump is reduced, and damage and noise are significantly reduced, and the short path is further reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of a wet flue gas desulfurization apparatus according to one embodiment of the present invention. FIG. 2 is a perspective view of an essential part of a wet flue gas desulfurization apparatus according to an embodiment of the present invention. FIG. 3 is a side view of a main part of a wet flue gas desulfurization apparatus according to one embodiment of the present invention. FIG. 4 is a side view of a main part of a wet flue gas desulfurization apparatus according to a reference example of the present invention. FIG. 5 is a side view of a main part of a wet flue gas desulfurization apparatus as another reference example of the present invention. FIG. 6 is an overall configuration diagram of a conventional wet flue gas desulfurization device.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noboru Ishii 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Heavy Industries, Ltd. (72) Inventor Masakazu Onizuka 4-2-2 Kanonshinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture No. Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratories (56) References Japanese Utility Model No. 7-9427 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 53/34-53/80

Claims (1)

(57) [Claims 1] An absorption tower in which a slurry containing a calcium compound is supplied to a tank at the bottom, and a circulation for sending the slurry in the tank to the upper part of the absorption tower to make contact with flue gas. In a tank oxidation type wet flue gas desulfurization device comprising a pump, an air supply means for supplying air for oxidation into the tank, and an extraction pump for extracting slurry in the tank, the so as to cover at least the upper side of a circulation pump or the withdrawal outlet opening of the pump, extending from the inner surface of the side wall of the tank to the slurry liquid obliquely downward, the flow of descending slurry liquid tank side wall near Guide away from pump outlet opening
While providing an inclined plate, the lower end of the inclined plate and the
On the tank bottom so as to separate it from the tank bottom
A wet flue gas desulfurization device characterized by having a perforated plate installed upright .