JP2004321868A - Wet flue gas desulfurization method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly flexible wet flue gas desulfurization method which can well achieve a required degree of desulfurization without increase in cost even in the case of a flue gas varying in properties, and to provide an apparatus therefor. <P>SOLUTION: The flue gas fed into a first absorption zone 4 in an absorption tower is brought into contact with an absorbent and is turned and fed into a second absorption zone 5. The resulting flue gas is brought into contact with an absorbent in the zone 5 and is turned and fed into a third absorption zone 6. The resulting flue gas is brought into contact with an absorbent in the zone 6 and is discharged out of the absorption tower. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４４】
表１に示すように、図９に示す従来方式の湿式排煙脱硫装置では、仕切板６１で仕切られた入口側および出口側のゾーンがともに向流気液接触方式であり、ガスの圧力損失が大きいが、本発明方式の湿式排煙脱硫装置は、並流→向流→並流による気液接触方式であり、並流による気液接触部が多いのでガスの圧力損失が小さい。しかも、脱硫率は、従来方式と同等以上のレベルである。
【００４５】
以下の表２は、図１に示す本発明の湿式排煙脱硫装置と図９に示す従来の湿式排煙脱硫装置において、排ガス中の硫黄酸化物濃度が高い場合（入口濃度が１０００ｐｐｍ 超）における運転データの一例を示す。
【００４６】
【表２】

【００４７】
表２に示すように、図９に示す従来方式の湿式排煙脱硫装置は向流による気液接触方式であるから、ガスの圧力損失が大きいが、本発明方式の湿式排煙脱硫装置は、並流→向流→並流による気液接触方式であり、並流による気液接触部が多いのでガスの圧力損失が小さい。本例は、排ガス中の硫黄酸化物濃度が高濃度の場合であるから、本発明方式および従来方式ともに吸収液循環量は表１の場合より多いが、本発明方式は硫黄酸化物を吸収するための３つの吸収ゾーンを有しており、各吸収ゾーンのＬ／Ｇ比率を適正に設定することにより、脱硫率は従来方式と比べて遜色ないレベルを維持しつつ、吸収液循環量を従来方式より少なくすることができる。従って、吸収液を送給するポンプのモータ動力を低減することができる。
【００４８】
【発明の効果】
本発明は、上記のとおり構成されているので、次の効果を奏する。
（１）請求項１記載の発明によれば、変化する排ガス性状に対しても充分に要求脱硫率を満足することができるフレキシビリティに優れた湿式排煙脱硫方法を提供することができる。特に、ガス中の硫黄酸化物濃度が高い場合には、本発明の特徴である３吸収ゾーン方式による効果（動力コスト低減メリット）は大きくなる。
（２）請求項２記載の発明によれば、ガスの圧力損失と吸収液の流れに対する抵抗を少なくすることができるので、排ガスを送給するブロワーや吸収液を送給するポンプの動力コストを低減することができる。
（３）請求項３記載の発明によれば、脱硫装置を連続運転しつつ吸収液供給機器の洗浄と脱硫操作を同時に実行することができる。
（４）請求項４記載の発明によれば、請求項１記載の方法を実施するに好適である、運転操作条件の幅が広くて非常にフレキシビリティに富んだコンパクトな湿式排煙脱硫装置を提供することができる。
（５）請求項５記載の発明によれば、請求項２記載の方法を実施するに好適である、設備コストの低い湿式排煙脱硫装置を提供することができる。
（６）請求項６記載の発明によれば、請求項３記載の方法を実施するに好適である、設備コストの低い湿式排煙脱硫装置を提供することができる。
（７）請求項７記載の発明によれば、さらにフレキシビリティに優れた動力コストの低い湿式排煙脱硫装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の湿式排煙脱硫装置の一実施例の概略構成を示す透視斜視図である。
【図２】本発明の湿式排煙脱硫装置の別の実施例の概略構成を示す透視斜視図である。
【図３】本発明の湿式排煙脱硫装置に使用するスプレー噴霧段のスプレーヘッダーの配置の一例を示す平面図である。
【図４】本発明の湿式排煙脱硫装置に使用するスプレー噴霧段のスプレーヘッダーの配置の別の例を示す平面図である。
【図５】上下方向に伸縮可能である仕切板の斜視図である。
【図６】図５の仕切板を本発明のスプレー型吸収塔に配置した一例を示す平面図である。
【図７】従来の湿式排煙脱硫装置の概略構成図である。
【図８】従来の別の湿式排煙脱硫装置の概略構成図である。
【図９】従来のさらに別の湿式排煙脱硫装置の概略構成図である。
【符号の説明】
１…スプレー型吸収塔
２…仕切板
３…排ガスダクト
４…第一吸収ゾーン
４ａ、４ｂ、４ｃ…スプレー噴霧段
５…第二吸収ゾーン
５ａ、５ｂ、５ｃ…スプレー噴霧段
６…第三吸収ゾーン
６ａ、６ｂ、６ｃ…スプレー噴霧段
７…排ガス出口
８、９、１０…循環液ライン
１１…ポンプ
１２…洗浄液貯留タンク
１３、１４、１５、１６、１７、１８…バルブ
１９、２１、２２…スプレーヘッダー
２０、２３、２４…分岐スプレー管
２５ａ、２５ｂ…仕切板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wet flue gas desulfurization method for removing sulfur oxides in flue gas discharged from a thermal power plant and the like, and a wet flue gas desulfurization apparatus used for carrying out the method.
[0002]
[Prior art and background]
Since a large amount of sulfur is contained in the gas discharged from a thermal power plant or the like, an exhaust gas treatment facility called a flue gas desulfurization device is generally required. The required desulfurization rate differs for each area where the desulfurization equipment is installed, and it is necessary to design the desulfurization equipment so that the required desulfurization rate does not fall below the required desulfurization rate even for a moment. Therefore, in the case of equipment having a narrow range of operating conditions and low flexibility, it is necessary to provide an excessively large processing capacity more than is normally required. However, in the case of a desulfurization facility, especially when the size of the desulfurization facility is increased in the height direction, the total extension of the auxiliary facilities such as gas pipes becomes longer accompanying the main body desulfurization facility.
[0003]
In addition, the required desulfurization rate not only varies from region to region, but also varies depending on various circumstances after the operation of the equipment, and the type of coal used for thermal power generation must use coal types that were not initially planned. Yes, different coal types usually have different sulfur contents. However, due to a rapid increase in the sulfur content in coal, there is a case where the required desulfurization rate cannot be satisfied only by changing the operating conditions of the equipment. In such a case, it is necessary to add new auxiliary equipment to satisfy the required desulfurization rate, and the equipment cost is greatly increased. Therefore, desulfurization equipment with a wide range of operating conditions and great flexibility is preferable so that the required desulfurization rate can be satisfied by changing the operating conditions as much as possible.However, as described above, the sulfur content in the coal Undesirable coal raw materials may come out in the case of a desulfurization facility with a narrow range of operating conditions and low flexibility depending on the species.
[0004]
Therefore, various types of wet flue gas desulfurization apparatuses have been proposed for the purpose of efficiently contacting gas and liquid and improving the desulfurization rate of exhaust gas containing sulfur oxides (for example, Patent Document 1 and Patent Document 2).
[0005]
According to the wet flue gas desulfurization device disclosed in Patent Document 1, as shown in FIG. 7, the sulfur oxide-containing exhaust gas 31 flows from the upper part of the cylindrical tank 32 through the duct 33 that flows tangentially to the cylindrical surface. The absorption liquid, such as limestone slurry, supplied into the double pipe discharge duct 35 from the liquid suction duct 34 by flowing into the cylindrical tank 32 to form a swirling flow is sprayed on the outer wall of the double pipe in a large number in the radial direction. The gas ejected from the nozzle 36 becomes a mist-like absorbing liquid, absorbs the sulfur oxides in the swirling gas stream, and the gas that has absorbed the sulfur oxides is discharged through the duct 35.
[0006]
According to the wet flue gas desulfurization apparatus disclosed in Patent Document 2, as shown in FIG. 8, a sulfur oxide-containing exhaust gas 41 is a liquid column provided above a tank 42 to which an absorbent such as limestone slurry is supplied. The gas that has come into gas-liquid contact with the absorption liquid in the tank 42 in the introduction-side absorption tower 43 of the type, and the gas discharged from the introduction-side absorption tower 43 is discharged from the tank in the liquid-column-type extraction-side absorption tower 44 provided above the tank 42. After coming into gas-liquid contact again with the absorbing liquid in 42, it is discharged through outlet 45.
[0007]
Further, according to the wet flue gas desulfurization apparatus shown in FIG. 9, the sulfur oxide-containing exhaust gas 51 is introduced into the spray type absorption tower 52, and the gas is supplied to the circulating liquid lines 54, 55 from the bottom tank 53 in the lower part of the absorption tower. , 56, the absorbing liquid such as limestone slurry is sprayed from spray spraying stages 57, 58, 59 to absorb the sulfur oxides in the exhaust gas, and the gas having the sulfur oxides absorbed is discharged through outlet 60. .
[0008]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 8-28055 [Patent Document 2]
JP-A-10-5524
[Problems to be solved by the invention]
As described above, the range of operating conditions required for desulfurization equipment is wide, and equipment that can flexibly respond to changes in local circumstances and raw material circumstances is required, but conventional desulfurization equipment is as follows. There are drawbacks.
[0010]
Since the wet flue gas desulfurization apparatus shown in FIG. 7 has only one sulfur oxide absorption zone, the range of operating conditions for changing exhaust gas properties is narrow, and the specific method for changing the amount of sulfur oxide in the exhaust gas is specific. The only operation method is to increase or decrease the amount of the mist-like absorbent ejected from the spray nozzle 36.
[0011]
The wet flue gas desulfurization apparatus shown in FIG. 8 has two absorption zones, and the range of operating conditions for changing exhaust gas properties is wider than that of the apparatus shown in FIG. 7, but specific for the variation in the amount of sulfur oxides in the exhaust gas. The only practical operation method is to increase or decrease the amount of the absorbing liquid injected from the spray pipes 46 and 47 of the inlet-side absorption tower 43 and the outlet-side absorption tower 44. Because of this method, it is difficult to greatly change the gas-liquid contact area.
[0012]
Further, in the wet flue gas desulfurization apparatus shown in FIG. 9, the inside of the absorption tower 52 is divided into two by a partition plate 61, but similarly to the apparatus shown in FIG. 7 and FIG. On the other hand, in order to secure the required desulfurization rate, the amount of the absorbing liquid sprayed from the spraying stages 57, 58, 59 in the left and right parts separated by the partition plate 61 must be increased or decreased, and the exhaust gas properties which change Operating conditions are not wide.
[0013]
The present invention has been made in view of such problems of the conventional technology, and has as its object to sufficiently increase the required desulfurization rate even for changing exhaust gas properties without increasing equipment costs. An object of the present invention is to provide a wet flue gas desulfurization method and an apparatus therefor which are satisfactory and have excellent flexibility.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is to introduce the exhaust gas introduced into the second absorption zone by inverting the exhaust gas introduced into the first absorption zone in the absorption tower after being brought into contact with the absorbent, and the exhaust gas in the second absorption zone It has three sulfur oxide absorption zones such that it is inverted after being brought into contact with the absorption liquid and introduced into the third absorption zone, and the exhaust gas is brought into contact with the absorption liquid in the third absorption zone. The required desulfurization rate can be satisfied by skillfully using the functions of the first to third absorption zones flexibly in response to the change in exhaust gas properties.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
That is, in the wet flue gas desulfurization method of the present invention, the sulfur oxides contained in the exhaust gas are absorbed by spraying limestone slurry, which is an absorbing liquid, from the spray spray stage onto the sulfur oxide-containing exhaust gas introduced into the spray type absorption tower. In a wet-type flue gas desulfurization method in which liquid is absorbed and stored in the bottom of the absorption tower, and the absorption liquid stored in the bottom of the tower is pumped to a spray spray stage via a circulating liquid line and circulated, the first absorption in the absorption tower is performed. The exhaust gas introduced into the zone is reversed after being brought into contact with the absorbing liquid and introduced into the second absorption zone, and the exhaust gas is reversed after being brought into contact with the absorbing liquid in the second absorption zone and introduced into the third absorption zone, Further, the exhaust gas is discharged outside the absorption tower after being brought into contact with the absorption liquid in the third absorption zone.
[0016]
For example, in the first absorption zone, 50 to 60% of the required desulfurization rate is achieved, in the second absorption zone, 60 to 95% of the required desulfurization rate, and in the third absorption zone, 95% of the required desulfurization rate. In order to achieve the above, the function of each absorption zone can be properly used. These values of the desulfurization rate are merely examples, and since there are three absorption zones, the equipment can be operated flexibly in response to changes in the exhaust gas properties and the required desulfurization rate.
[0017]
Since the content of sulfur oxides in the exhaust gas of the first absorption zone in which the sulfur oxides are first absorbed is the largest among the three zones, the flow direction of the exhaust gas and the flow direction of the absorbing liquid are opposite to each other. In the case of flow gas-liquid contact, each spray nozzle in the spray spray stage may be blocked by precipitated solids (calcium sulfite or calcium sulfate) in the exhaust gas. However, if the flow direction of the exhaust gas and the flow direction of the absorbing liquid are the same, that is, so-called co-current gas-liquid contact, each spray nozzle of the spray spray stage is less likely to be clogged by solids. Moreover, since the first absorption zone originally has a very high concentration of sulfur oxides in the exhaust gas, the absorption effect of sulfur oxides by parallel gas-liquid contact is comparable to that of countercurrent gas-liquid contact. Can be expected.
[0018]
Therefore, in the first absorption zone, the exhaust gas and the absorbent are brought into contact in a co-current manner, the exhaust gas is reversed, and the exhaust gas and the absorbent are brought into contact in a counter-current manner in the second absorption zone. If the exhaust gas and the absorbing liquid are brought into contact in the zone in a co-current manner, each spray nozzle of the spray spray stage of the first absorption zone, which is a co-current gas-liquid contact, is not blocked by solids, and A considerable amount of sulfur oxide is absorbed by the absorbing solution, and the concentration of sulfur oxide in the gas is greatly reduced.
[0019]
In the subsequent second absorption zone, sulfur oxides in the exhaust gas are absorbed by the absorption liquid by countercurrent contact, which can be expected to be more efficient gas-liquid contact than co-current contact, enabling a wide range of requirements for the required desulfurization rate become.
[0020]
Since the third absorption zone, which is a cocurrent contact, is provided, the required desulfurization rate can be achieved even when the sulfur oxide concentration in the exhaust gas increases rapidly.
[0021]
As described above, the required desulfurization rate can be rationally satisfied by selecting appropriate operating conditions by utilizing the characteristics of each absorption zone in the order of parallel flow → counter flow → parallel flow. Furthermore, the countercurrent gas-liquid contact method has a larger exhaust gas pressure loss than the parallel current gas-liquid contact method, but the exhaust gas pressure loss is large due to the large number of cocurrent gas-liquid contact systems, such as cocurrent → countercurrent → cocurrent. Since the number is reduced, it is possible to reduce the power cost of the blower for supplying the exhaust gas. Further, in the countercurrent gas-liquid contact, the gas flow flowing in the opposite direction has a large resistance to the flow of the absorbing liquid, so that it is necessary to increase the supply pressure of the absorbing liquid in order to ensure good gas-liquid contact. Therefore, since there are many co-current gas-liquid contact systems such as co-current → counter-current → co-current, it is possible to reduce the supply power of the absorbing liquid.
[0022]
However, when each spray nozzle in the spray spray stage is clogged by solids, maintenance work such as stopping the operation of the desulfurization device and cleaning the clogged nozzle to eliminate the clogging is required. Therefore, the washing liquid for washing the spray spray stage is supplied to the circulating liquid line that pumps the absorbing solution stored in the bottom of the tower to the spray spray stage, and it is possible to spray either the absorbing solution or the washing solution from the spray spray stage. By adopting such a system, it is possible to clean the absorbing liquid supply device while operating the desulfurization device. For example, when the spray nozzle of the spraying stage of the first absorption zone is closed, a cleaning liquid (for example, water or hydrochloric acid) is supplied to the spraying stage of the first absorption zone, and the second absorption zone and the third absorption zone are supplied. By supplying the absorbing liquid to the spray spray stage of the first absorption zone, removing the sulfur oxides in the exhaust gas so as to secure the required desulfurization rate in the second and third absorption zones, It is possible to remove the blockage by washing the spray nozzle. In this way, the washing and desulfurization operation of the absorbent supply device can be simultaneously performed while the desulfurization device is continuously operated.
[0023]
As described above, according to the present invention, by incorporating three sulfur oxide absorption zones having different functions into one tower, a compact facility with a wide range of operating conditions and a very high flexibility is realized. it can. In addition, since the required desulfurization rate can be achieved by selecting the operation control method of each of the three sulfur oxide absorption zones so as to adapt to the changing exhaust gas properties, a surplus spray nozzle is provided more than necessary. No need.
[0024]
As a desulfurization device having first, second and third absorption zones with a spray spray stage in a spray type absorption tower, the interior of the absorption tower is vertically partitioned except for near the top of the upper space in the absorption tower. A partition plate is arranged and divided into two into an exhaust gas introduction part consisting of the first and second absorption zones and an exhaust gas discharge part consisting of the third absorption zone, and penetrating through the top of the absorption tower so as to form the first absorption zone. An exhaust gas duct is introduced so as to reach the upper part in the absorption tower, a spray spray stage is installed in the exhaust gas duct, and a spray spray stage is installed so as to surround the exhaust gas duct to form a second absorption zone, It is possible to adopt a configuration in which a spray spray stage is installed in the exhaust gas discharge section so as to form three absorption zones and an exhaust gas outlet is formed on the side of the absorption tower.
[0025]
By providing three absorption zones in a spray-type absorption tower, many advantages can be obtained as described above. On the other hand, a fixed partition plate for partitioning the absorption zone also has a large resistance to gas flowing in the tower. There is an inconvenience of becoming. Therefore, by employing a retractable partition plates in the vertical direction, processing of properties that are not requires three absorption zones exhaust gas (e.g., sulfur oxide concentrations of low gas SO ₂ concentration in the exhaust gas is 500ppm or less) In this case, the partition plate is contracted into two absorption zones, so that the required desulfurization rate is secured and the pressure loss of the exhaust gas is reduced, so that the power cost can be reduced.
[0026]
【Example】
Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and can be appropriately changed and modified without departing from the technical scope of the present invention.
[0027]
FIG. 1 is a perspective view showing a schematic configuration of a wet flue gas desulfurization apparatus according to one embodiment of the present invention. A partition plate 2 is arranged so as to vertically partition the inside of the absorption tower while leaving the vicinity of the top of the upper space inside the spray type absorption tower 1, and the inside of the tower is divided into an exhaust gas introduction section and an exhaust gas discharge section. . The exhaust gas introduction section includes first and second absorption zones described later, and is formed on the left side of the partition plate 2. The exhaust gas discharge section includes a third absorption zone described later, and is formed on the right side of the partition plate 2.
[0028]
That is, the exhaust gas duct 3 is introduced so as to pass through the top of the spray type absorption tower 1 and reach the upper part in the absorption tower, and spray spray stages 4a, 4b and 4c are installed in the exhaust gas duct 3, and these exhaust gas ducts 3 The first absorption zone 4 is formed by the spraying stages 4a, 4b and 4c installed therein. Further, spray spray stages 5a, 5b and 5c are provided so as to surround the exhaust gas duct 3, and the second absorption zone 5 is formed by the spray spray stages 5a, 5b and 5c installed around the exhaust gas duct 3. You.
[0029]
Spray spray stages 6a, 6b and 6c are provided in the exhaust gas discharge section on the right side of the partition plate 2, and these spray spray stages 6a, 6b and 6c form a third absorption zone 6. An exhaust gas outlet 7 is formed on the side of the absorption tower below the lowermost spraying stage 6c.
[0030]
All of the above spraying stages spray the absorbing liquid downward. In the first absorbing zone 4, the exhaust gas descending in the exhaust gas duct 3 and the absorbing liquid are brought into parallel contact, and the second absorbing zone 5 rises. The exhaust gas and the absorbing liquid are brought into countercurrent contact with each other, and the descending exhaust gas and the absorbing liquid are brought into parallel contact in the third absorption zone 6.
[0031]
Absorbent liquid (limestone slurry which is a mixture of limestone granules and water) stored at the bottom of the absorption tower 1 is passed through circulating liquid lines 8, 9, and 10 to the first, second and third absorption zones 4, respectively. , 5 and 6, respectively. Reference numeral 11 denotes an absorption liquid supply pump.
[0032]
According to the wet flue gas desulfurization apparatus configured as described above, the sulfur oxide-containing exhaust gas introduced into the exhaust gas duct 3 by the suction blower (not shown) located to the right of the exhaust gas outlet 7 is sprayed into the spray spray stages 4a and 4b. From 4c and 4c, limestone slurry as an absorbing solution is sprayed to absorb the sulfur oxides in the exhaust gas into the absorbing solution and stored in the bottom of the absorption tower 1. The absorbing liquid sprayed from the spray spray stages 4a, 4b and 4c is directed downward and is in a gas-liquid contact by co-current which coincides with the flow direction of the gas introduced from the exhaust gas duct 3. It is unlikely that the spray nozzles 4a, 4b and 4c will be blocked. Moreover, since the first absorption zone 4 has the largest amount of sulfur oxide in the exhaust gas among the three absorption zones, the sulfur oxide is efficiently absorbed by the absorbing solution. In addition, since the gas-liquid contact is caused by the co-current flow, the pressure loss of the exhaust gas is small, the suction power of the blower is reduced, and the absorption liquid supply power of the pump 11 can be reduced.
[0033]
Next, the exhaust gas is reversed in a direction opposite to the introduction direction, and is introduced into the second absorption zone 5. The absorbing liquid sprayed from the spraying stages 5a, 5b and 5c is directed downward and is in gas-liquid contact by countercurrent which is opposite to the flow direction of the gas flowing upward, so that the sulfur in the exhaust gas is efficiently removed. Oxides can be absorbed, and it is possible to respond to a wide range of required desulfurization rates.
[0034]
Further, the exhaust gas is reversed and introduced into the third absorption zone 6. The absorbing liquid sprayed from the spray spray stages 6a, 6b and 6c is directed downward, and is in a gas-liquid contact by co-current which coincides with the flow direction of the gas flowing downward, and the spray spray stages 6a, It is unlikely that the spray nozzles 6b and 6c will be blocked. Since the gas-liquid contact is caused by the cocurrent, the pressure loss of the exhaust gas is small and the resistance to the supply of the absorbing liquid is small. By providing such a third absorption zone, the required desulfurization rate can be satisfied even if the concentration of sulfur oxides in the exhaust gas suddenly increases.
[0035]
Further, since the absorbent stored at the bottom of the absorption tower 1 is divided into two by the partition plate 2, the types and concentrations of the left and right absorbents can be changed as necessary. For example, a thick limestone slurry can be stored on the left side and a thin limestone slurry can be stored on the right side.
[0036]
As described above, the gas that has reached the predetermined cleanliness level by absorbing the sulfur oxides in the gas into the absorbing liquid is discharged from the outlet 7 and, if necessary, is additionally processed by another gas processing facility. Processing is performed.
[0037]
FIG. 2 is a perspective view showing a schematic configuration of a wet flue gas desulfurization apparatus according to another embodiment of the present invention.
[0038]
In this embodiment, when each of the spray nozzles in the spray spray stage is clogged by the solid content, the clogging nozzle can be cleaned and the clogging can be eliminated without stopping the operation of the desulfurization device. That is, the tank 12 storing the cleaning liquid (water, hydrochloric acid, or the like) for cleaning each spray nozzle in the spray spray stage is connected to each of the circulating liquid lines 8, 9, and 10. Spraying either the absorbing liquid or the cleaning liquid from each spraying stage of the first, second or third absorption zone 4, 5, 6 by opening and closing valves 13 and 14, 15 and 16 and 17 and 18; Can be. For example, when the spray nozzles of the spray spray stages 4a, 4b and 4c of the first absorption zone 4 are closed, the cleaning liquid is supplied to the spray spray stages 4a, 4b and 4c by closing the valve 13 and opening the valve 14. While cleaning the spray nozzles, the valves 15 and 17 are opened and the valves 16 and 18 are closed to supply the spray liquid to the spraying stages of the second absorption zone 5 and the third absorption zone 6, so that the second and first spray nozzles can be cleaned. It is possible to absorb the sulfur oxides in the exhaust gas so that the required desulfurization rate is secured in the three absorption zones 5 and 6, and the washing and desulfurization operations of the absorption liquid supply equipment are simultaneously performed while the desulfurization unit is continuously operated. can do.
[0039]
FIG. 3 is a diagram showing an example of the arrangement of the spray headers of the spray spray stages in the first absorption zone, and FIG. 4 is a diagram showing the arrangement of the spray headers of the spray spray stages in the second absorption zone and the third absorption zone. It is a figure showing an example.
[0040]
In FIG. 3, 19 is a spray header, and 20 is a branch spray tube. In FIG. 4, reference numerals 21 and 22 denote spray headers, and reference numerals 23 and 24 denote branch spray tubes. The spray headers 19, 21, 22 are connected to circulating fluid lines 8, 9, 10, respectively.
[0041]
FIG. 5 shows a partition plate which can expand and contract in the vertical direction. This partition plate is composed of two parts, an upper part 25a and a lower part 5b. A receiver is embedded in the upper partition plate 25a, and when receiving a signal from the outside of the desulfurization device, the upper partition plate 25a is sandwiched between the guide members 26, 26 and can expand and contract in the vertical direction. For example, if the sulfur oxide concentration in the exhaust gas is low (≦ 500 ppm) and a sufficient desulfurization rate can be ensured even in the two absorption zones, the upper partition plate 25a is contracted and the spray type absorption is performed. Two sulfur oxide absorption zones in the tower 1 (the first absorption zone in the exhaust gas duct 3 and the absorption zone excluding the exhaust gas duct 3) can be provided. If the upper partition plate 25a is contracted, there is no partition plate that becomes a gas flow resistance, so that the power cost can be reduced. FIG. 6 is a plan view showing an example in which the extendable partition plate of FIG.
[0042]
Table 1 below shows that, in the wet flue gas desulfurization apparatus of the present invention shown in FIG. 1 and the conventional wet flue gas desulfurization apparatus shown in FIG. 9, the sulfur oxide concentration in the exhaust gas is normal (the inlet concentration is 1000 ppm or less). 4 shows an example of the operation data in FIG. In Table 1 and Table 2 below, the SO ₂ concentration is a numerical value on a dry basis.
[0043]
[Table 1]

[0044]
As shown in Table 1, in the conventional wet flue gas desulfurization apparatus shown in FIG. 9, both the inlet and outlet zones separated by the partition plate 61 are of the countercurrent gas-liquid contact type, and the gas pressure loss However, the wet flue gas desulfurization system of the present invention is of the gas-liquid contact type using co-current → counter-current → co-current, and the gas-liquid contact part due to co-current has a small pressure loss of gas. Moreover, the desulfurization rate is at a level equal to or higher than that of the conventional method.
[0045]
Table 2 below shows that, in the case of the wet flue gas desulfurization apparatus of the present invention shown in FIG. 1 and the conventional wet flue gas desulfurization apparatus shown in FIG. 9, when the sulfur oxide concentration in the exhaust gas is high (the inlet concentration exceeds 1000 ppm). 4 shows an example of operation data.
[0046]
[Table 2]

[0047]
As shown in Table 2, since the conventional wet flue gas desulfurization apparatus shown in FIG. 9 is a gas-liquid contact system by countercurrent, the pressure loss of the gas is large. It is a gas-liquid contact method by co-current → counter-current → co-current. Since there are many gas-liquid contact parts by co-current, gas pressure loss is small. In this example, the sulfur oxide concentration in the exhaust gas is high, and therefore, the circulation amount of the absorbent is larger than that in Table 1 in both the method of the present invention and the conventional method, but the method of the present invention absorbs the sulfur oxide. By setting the L / G ratio of each absorption zone properly, the desulfurization rate can be maintained at a level comparable to that of the conventional method and the absorption liquid circulation amount can be reduced. It can be less than the system. Therefore, it is possible to reduce the motor power of the pump for supplying the absorbing liquid.
[0048]
【The invention's effect】
The present invention is configured as described above, and has the following effects.
(1) According to the first aspect of the present invention, it is possible to provide a wet flue gas desulfurization method having excellent flexibility and capable of sufficiently satisfying a required desulfurization rate even with changing exhaust gas properties. In particular, when the sulfur oxide concentration in the gas is high, the effect (power cost reduction merit) of the three-absorption zone method, which is a feature of the present invention, becomes large.
(2) According to the second aspect of the invention, the pressure loss of the gas and the resistance to the flow of the absorbing liquid can be reduced, so that the power cost of the blower for supplying the exhaust gas and the pump for supplying the absorbing liquid is reduced. Can be reduced.
(3) According to the third aspect of the invention, the washing and desulfurization operation of the absorbent supply device can be simultaneously performed while the desulfurization device is continuously operated.
(4) According to the fourth aspect of the present invention, there is provided a compact wet flue gas desulfurization apparatus which is suitable for carrying out the method of the first aspect, has a wide range of operating conditions and is very flexible. Can be provided.
(5) According to the fifth aspect of the invention, it is possible to provide a wet flue gas desulfurization apparatus which is suitable for carrying out the method of the second aspect and has a low equipment cost.
(6) According to the invention of claim 6, it is possible to provide a wet flue gas desulfurization apparatus which is suitable for carrying out the method of claim 3 and has a low equipment cost.
(7) According to the invention as set forth in claim 7, it is possible to provide a wet flue gas desulfurization apparatus having excellent flexibility and low power cost.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of an embodiment of a wet flue gas desulfurization apparatus of the present invention.
FIG. 2 is a perspective view showing a schematic configuration of another embodiment of the wet flue gas desulfurization apparatus of the present invention.
FIG. 3 is a plan view showing an example of an arrangement of a spray header of a spray spray stage used in the wet flue gas desulfurization apparatus of the present invention.
FIG. 4 is a plan view showing another example of the arrangement of the spray header of the spray spray stage used in the wet flue gas desulfurization apparatus of the present invention.
FIG. 5 is a perspective view of a partition plate that can expand and contract in the vertical direction.
FIG. 6 is a plan view showing an example in which the partition plate of FIG. 5 is arranged in the spray type absorption tower of the present invention.
FIG. 7 is a schematic configuration diagram of a conventional wet flue gas desulfurization device.
FIG. 8 is a schematic configuration diagram of another conventional wet flue gas desulfurization device.
FIG. 9 is a schematic configuration diagram of still another conventional wet flue gas desulfurization device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Spray absorption tower 2 ... Partition plate 3 ... Exhaust gas duct 4 ... First absorption zone 4a, 4b, 4c ... Spray spray stage 5 ... Second absorption zone 5a, 5b, 5c ... Spray spray stage 6 ... Third absorption zone 6a, 6b, 6c spray spray stage 7 exhaust gas outlets 8, 9, 10 circulating fluid line 11 pump 12 cleaning fluid storage tanks 13, 14, 15, 16, 17, 18 valves 19, 21, 22 spray Headers 20, 23, 24: Branch spray tubes 25a, 25b: Partition plate

Claims (7)

The limestone slurry, which is the absorbing liquid, is sprayed from the spray spray stage onto the sulfur oxide-containing exhaust gas introduced into the spray type absorption tower, and the sulfur oxide in the exhaust gas is absorbed by the absorbing liquid and stored at the bottom of the absorption tower. In a wet flue gas desulfurization method in which the absorbent stored at the bottom of the tower is pumped up to a spray spray stage through a circulating liquid line and circulated, the exhaust gas introduced into the first absorption zone in the absorber is brought into contact with the absorbent. It is inverted and introduced into the second absorption zone later, the exhaust gas is brought into contact with the absorbent in the second absorption zone, then inverted and introduced into the third absorption zone, and the exhaust gas is further absorbed into the third absorption zone. A wet flue gas desulfurization method, wherein the flue gas is discharged outside of the absorption tower after contact with the flue gas. In the first absorption zone, the exhaust gas and the absorbent are brought into contact in a co-current manner, in the second absorption zone, the exhaust gas and the absorbent are brought into contact in a counter-current manner, and in the third absorption zone, the exhaust gas and the absorbent are brought into contact in a co-current manner. The wet flue gas desulfurization method according to claim 1, wherein: The washing liquid for washing the spray spray stage is supplied to the circulating fluid line that pumps up the absorbing solution stored in the bottom of the tower to the spray spray stage, and that either the absorbing solution or the washing solution can be sprayed from the spray spray stage. The wet flue gas desulfurization method according to claim 1 or 2, wherein: Spray limestone slurry, which is an absorbing liquid, is sprayed onto the sulfur oxide-containing exhaust gas introduced into the upper space inside the spray type absorption tower from the spray spray stage installed in the absorption tower, and the sulfur oxides in the exhaust gas are absorbed by the absorption liquid In the wet flue gas desulfurization unit, where the liquid stored at the bottom of the absorption tower is pumped to the spray spray stage through the circulating liquid line and circulated, the absorbent stored at the bottom of the tower remains near the top of the upper space inside the absorption tower. A partition plate is arranged so as to partition the inside of the absorption tower in the vertical direction, and is divided into an exhaust gas introduction section composed of the first and second absorption zones and an exhaust gas discharge section composed of the third absorption zone to form a first absorption zone. As such, an exhaust gas duct is introduced so as to penetrate the top of the absorption tower and reach the upper part of the absorption tower, a spray spray stage is installed in the exhaust gas duct, and the spray spray stage is surrounded by the exhaust gas duct. A flue gas desulfurization unit, wherein a spray spray stage is installed in the exhaust gas discharge section so as to form a second absorption zone and a third absorption zone is formed, and an exhaust gas outlet is formed on the side of the absorption tower. . The first, second and third absorption zones are sprayed with the absorption liquid downward from the spraying stage provided in each of the absorption zones.In the first absorption zone, the exhaust gas descending in the exhaust gas duct and the absorption liquid are brought into parallel contact. 5. The wet flue gas desulfurization apparatus according to claim 4, wherein the rising exhaust gas and the absorbing liquid are brought into countercurrent contact with each other in the second absorption zone, and the falling exhaust gas and the absorbing liquid are brought into parallel contact with each other in the third absorption zone. . Connect the container that stores the washing liquid to wash the spray spray stage and the circulating fluid line that pumps up the absorbent stored at the bottom of the tower to the spray spray stage, and spray either the absorbing solution or the washing liquid from the spray spray stage The wet flue gas desulfurization apparatus according to claim 4 or 5, wherein the apparatus is capable of being used. The wet flue gas desulfurization device according to claim 4, 5 or 6, wherein the partition plate is vertically expandable and contractable.

Images