HK1029543B - Wet type flue gas desulfurization equipment - Google Patents

Description

Wet type smoke discharging and desulfurizing device

Technical Field

The invention relates to a method for washing combustion exhaust generated by a boiler and the like by using alkali-containing absorption liquidSO in gas₂To improve a wet flue gas desulfurization apparatus for desulfurization.

Technical Field

When a fuel containing a sulfur component is burned, the solid matter in the ash is removed and used as sulfurous acid gas (SO)₂) When discharged into the atmosphere, the acid rain drops on the ground, causing a great adverse effect on the environment as well as a severe adverse effect on human bodies and animals.

Therefore, in the past, large-scale combustion facilities and factories have been equipped with flue gas desulfurization devices, most of which are wet flue gas desulfurization devices.

The wet desulfurization method is a method of removing SO by bringing an alkaline absorption liquid containing lime or the like into gas-liquid contact with an exhaust gas₂While, at the same time, absorbing SO from the exhaust gas₂In the oxidation method, air is blown into the absorbent, and sulfite is generated in the absorbent and oxidized to form stable sulfate.

Conventionally, various techniques have been developed for blowing air into the absorption liquid, for example, the technique employed in the absorption tower 101 shown in FIG. 13A is an air blowing technique (A) for blowing air 10 into the whole liquid bath section 102 by a plurality of fixed blowing pipes 116, the air blowing technique (B) for blowing air 10 into the whole liquid bath section 102 while rotating each by a plurality of rotating blowing pipes 115 as shown in FIG. 13(B), the air blowing technique (C) for combining a plurality of fixed blowing pipes 117 with the diffusion stirring function of a stirrer 119 as shown in FIG. 13(C), a circulating pump 118B is separately attached to the outside of the liquid bath section 102 as shown in FIG. 14, an independent pipe 118 for circulating the absorption liquid is disposed in the pipe 118, an air-blowing pipe 118a is disposed in the pipe 118, and a gas-liquid mixture is formed in advance in the pipe 118, and (D) an air blowing technique of blowing the air 10 into the whole liquid bath section 102 by using the diffusion function of the stirrer 119 in combination with the spray-like blowing.

Further, instead of the independent absorbent circulation duct 118 in the air blowing technique (D), a branched absorbent circulation duct 110c branched by the absorbent dispersion duct 103 for dispersing the absorbent into the exhaust gas is used (see fig. 12), and the air blowing technique (E) of the stirrer 119 is not used.

Among the various air blowing methods described above, the air blowing technique (B) shown in fig. 13(B) does not require a separate pipe for circulating the absorption liquid, or a stirrer, and although the oxidation performance is high, it is difficult to install the convection absorption tower, which is currently the mainstream, in terms of its shape. In the present situation of fig. 13(a), the air blowing technique (a) using a plurality of fixed blowing pipes 116 is not suitable because the size of the tank used is increased and the oxidizing ability of the tank is limited, which is unavoidable.

As a means for solving the above-mentioned problems, various proposals have been made, and there is a strong desire to realize an air blowing technique in which the oxidation performance can be made equal to that of the air blowing technique B by providing the side surface of the tank and increasing the degree of freedom of arrangement.

Further, the provision of the agitator 119 according to the air blowing techniques (C) and (D) is necessary in view of maintaining the high oxidation performance and preventing the deposition and accumulation of the products generated by the oxidation, but it has a problem that the provision of the agitator not only increases the cost of the equipment but also excessively increases the size of the equipment.

Examples of the conventionally used apparatus include the apparatus described in JP-A-62-194423.

In the wet flue gas desulfurization apparatus disclosed in the above publication, the exhaust gas introduction section is connected to the absorption tower, and the absorption liquid dispersion pipe of the absorption liquid dispersion device attached to the upper part of the absorption tower is connected from the liquid tank at the bottom of the absorption tower.

A more specific structure of the air blowing method (air blowing device) shown in this publication is described below with reference to fig. 10.

As seen in fig. 10, this scheme should belong to the air blowing method E described above.

The absorption liquid in the liquid tank part 102 at the bottom of the absorption tower 101 is introduced into an exhaust gas passage not shown in the figure and dispersed by a circulation pump 104 and an absorption liquid dispersion pipe 103, and the dispersion liquid absorbs and dissolves SO in the exhaust gas₂Thereafter, the reflux is stored in the tank portion 102.

In this embodiment, as a method for oxidizing the absorption liquid in the liquid tank section 102, the following method of blowing air can be used.

That is, a branch pipe 110a for circulating the absorption liquid is provided downstream of the circulation pump 104 of the absorption liquid distribution pipe 103, and one end thereof is connected to the circulation pump 104 and the other end thereof is communicated with the liquid tank portion 102. Further, an air intake pipe 105 having a smaller diameter than the branch pipe 110a is provided in the branch pipe 110a, and the end 105a is inserted, and the axial center of the end 105a is bent and provided at a position in the axial center of the branch pipe 110 a. The blowing air flow 10 and the absorbent 11 flowing through the branch pipe 110a are caused to flow in the same direction, and join at the axial center thereof to flow toward the downstream opening. Further, an air blowing blower 106 for blowing air is connected to the air blowing pipe 105.

However, in addition to the above-mentioned air blowing device, another method of promoting oxidation of the absorbent by blowing air, another method of making the blowing air fine, and a method of not requiring a stirrer have been proposed.

For example, according to the proposal disclosed in Japanese patent application laid-open No. 8-257347, as shown in FIGS. 11A and B, the absorbent is sprayed from the upper part of a liquid bath part (circulation tank) 102 provided at the lower part of an absorption tower 101 through a circulation pump 104 and an absorbent spraying pipe 103 by a not-shown spraying nozzle, and a falling flow of the absorbent containing sulfurous acid at a high concentration is formed after contacting with the exhaust gas during the falling, and is directly introduced into the bottom of the liquid bath part 102 through an introduction pipe 110B, and an ascending flow of the absorbent is formed in the liquid bath part 102 by the falling pressure of the falling flow, thereby constituting a diffusing function of preventing the sedimentation of particles such as gypsum.

In the process of introducing the absorbent 11 into the bottom of the liquid tank section 102, the air 10 for oxidation is blown in, or blown into the introduction pipe 110b, and brought into contact with the absorbent containing sulfurous acid at a high concentration to increase the oxidation reaction rate, and then the air 10 is finely bubbled and uniformly dispersed in the liquid flow section 102 through the disc-like dispersion pipe 111 having the blow-out holes 111a in the bottom.

That is, in the above-mentioned embodiment, as a method for promoting the oxidation of the absorbing solution, air is blown into the absorbing solution containing sulfurous acid at a high concentration after contacting with the exhaust gas, and a high oxidation reaction rate can be obtained. As a method for obtaining effective gas-liquid contact to make blown air fine, air is blown into an absorbent flowing in a conduit based on the pressure at the time of dropping, and a gas-liquid mixed fluid is ejected from the end of an introduction pipe through an annular dispersion pipe 111 having a large number of blowing holes, and the blown air can be made fine. Also, by providing the dispersion pipe at the bottom of the whole liquid bath portion, air can be blown into the whole area.

However, there arises a problem that particles settle to the air blowing holes 111a to be scaled, and particularly, there is a problem in maintenance.

As another means for dispersing the blown air and preventing the adhesion and deposition of scale of products such as gypsum without providing a stirring device, there has been proposed a method of imparting fluidity to the stock solution in the liquid tank portion having the above-mentioned structure, in which, as shown in FIG. 12, a plurality of spray nozzles 112 for blowing a jet stream are provided at a predetermined angle in the normal direction of the liquid tank portion (circulation tank) 102, the absorption liquid in the liquid tank portion 102 is caused to flow along the inner wall of the liquid tank portion 102 in the direction of the arrow A to thereby stir the absorption liquid, an independent tube 110c for circulating the absorption liquid is provided between the base of the spray nozzles 112 and the liquid tank portion 102 via a spray pump 113, and an air blowing tube 114 is provided near the base of the spray nozzles 112. This case has a problem that a considerable space is required around the absorption tower in the liquid tank section 102, which inevitably leads to an increase in the size of the apparatus, and further improvement in the refinement of the oxidizing air bubbles and dispersion into the absorption liquid is still required.

In addition, in the above-described method of fig. 10, the air is blown into the branch pipe for circulating the absorbing liquid 110a in advance, and the air is blown into the liquid tank portion 102 as dispersed fine bubbles, which has the following problems.

That is, in one aspect, the blown air 10 concentrates at a high pressure on the branch pipe, so that a negative pressure cavity is formed in a part of the branch pipe, and the pressure of the absorbing liquid is liable to fluctuate, to be unstable, and to be liable to cause corrosion on the inner surface of the branch pipe. Another problem is that after the gas and liquid are merged in the branch pipe, the dispersed bubbles are homogenized, and a considerable distance is required for the flow, and the length of the branch pipe from the gas and liquid merging portion to the liquid groove portion must be long, so that it is necessary to solve the problem of downsizing the apparatus and reducing the apparatus cost.

DISCLOSURE OF THE INVENTION

The present invention has been made to solve the above problems, and an object of the present invention is to provide an air blowing device in a wet flue gas desulfurization apparatus which is space-saving, compact in size, low in equipment cost, easy to maintain, and low in cost and can be operated under low power. It is constituted by a gas-liquid mixing method which maintains the low cost and miniaturization of an effective oxidation apparatus and utilizes air blowing of water flow stratification without using a blower, and a jet forming method of a gas-liquid mixture without using a stirrer.

In order to achieve the above object, the present invention is characterized in that sulfur oxide gas (SO) in combustion exhaust gas is cleaned with an alkali-containing absorbing solution₂，SO₃Etc.), in a wet flue gas desulfurization apparatus for performing desulfurization, an absorption liquid having one end opened as an outlet into a liquid tank of an absorption towerAn air blowing pipe is disposed in the circulation pipe, and the installation position of the air blowing pipe is taken at the upstream side of 3D-10D measured from the end of the pipe when the inner diameter of the absorption liquid circulation pipe is D.

In this case, the pipe is provided downstream of the circulation pump in the main pipe connecting the tank portion and the absorbent dispersion device, and is a branch pipe branching off from the main pipe, so that a separate circulation pump is not required on the branch pipe side.

According to the above configuration, since the installation position of the air blowing pipe is set to 3D to 10D from the end of the absorbent circulation duct having an inner diameter D, the cavity of the negative pressure region in the duct caused by the blowing of the air is stabilized at the outlet of the duct, and the blown air is dispersed in a finely dispersed state in the absorbent trough portion, so that the oxidation of the absorbent can be efficiently performed.

When the gas-liquid ratio exceeds 10D, the gas bubbles after the gas-liquid mixture disappears, and the desired effect of the present invention cannot be obtained.

In the present invention, when air is blown into the absorbent circulating tube, the end of the air blowing tube is inserted into the tube, and the end of the air blowing tube is directed downstream to form an opening surface having a half-open shape.

According to the above invention, the blown air is allowed to form a water flow layer in the absorbing liquid circulating pipe, and the air is blown into the layer portion to form gas-liquid mixture with the absorbing liquid.

That is, when the air blowing pipe is attached to the absorbent circulating pipe, the end of the air blowing pipe is formed into a half-open shape, the opening surface of the half-open is directed in the downstream direction of the branch pipe, the back surface of the half-open back part in the streamline shape is formed for the flowing water flow, and the air is blown into the cavity part having a large opening in accordance with the back part of the streamline shape, so that the cavity part caused by the blown air in the pipe is rapidly ended, and a stable state is achieved. Therefore, the pressure fluctuation of the absorbing liquid is small, and the corrosion in the pipe can be suppressed.

That is, as shown in fig. 4, since the interface layer is fixed at the half-opening 4a of the air blowing pipe, the pressure of the absorbent 11 and the air 10 is stabilized, and since the opening surface of the half-opening 4a is large, the pressure of the blown air is also reduced.

As a result, the hollow portion 41a is stabilized, and air is finely divided at the end of the hollow portion 41a and dispersed in the absorbent.

Further, according to the above invention, the pressure of the air merged in the absorbent in the duct is low, and after the merging, the air is finely divided at the end of the hollow portion 41a to form fine bubbles and dispersed in the surrounding absorbent, so that the supply pressure of the air can be reduced, and by this reduction in pressure, the running cost can be saved.

Further, since the gas bubbles are made uniform and the flow distance is shortened after the gas and liquid are merged in the pipe, the length of the pipe from the gas-liquid merging portion to the liquid groove portion is also reduced, and therefore, the downsizing of the apparatus can be effectively achieved and the cost of the apparatus can be reduced.

In still another aspect of the present invention, when the air blowing pipe is attached to the duct, an orifice is provided upstream of the place where the air blowing pipe is attached, and a negative pressure region formed by the orifice is an outlet opening of the air blowing pipe. According to the above invention, the orifice plate for generating the compressed fluid is disposed in the pipe line, the water flow generated by the orifice forms a negative pressure region (hollow portion) by layers, air is sucked (self-priming) and supplied, a hollow vortex is generated in the hollow portion, gas and liquid are mixed, and the contracted fluid expands and is pressurized, so that the gas-liquid mixture is cut off and dispersed into fine bubbles at the discharge port, and is discharged in a jet flow into the liquid tank portion.

In this case, in order to satisfactorily achieve the above-described effects, the aperture of the orifice is set to 2/3 to 3/4 with respect to the diameter of the branch pipe, and the flow rate of the absorbing liquid passing through the orifice, that is, the flow rate at the orifice is preferably set to 8 to 14 m/sec.

Also according to the present invention, the liquid mixture discharged in a jet flow can be put in a stirred state in the liquid sump portion, and a high oxidizing ability can be obtained without providing a stirrer.

That is, in the present invention, since the negative pressure in the cavity provides the air with self-priming capability, it is not necessary to provide a blower for supplying air, and the gas-liquid mixture fluid is ejected from the liquid tank part by the discharge port which forms fine bubbles by shearing and dispersion in the process of flowing and expanding to generate high pressure after contracting the fluid, so that the agitation power can be generated in the liquid tank, and the high oxidizing property can be obtained without providing an agitator.

In the above invention, the form of the orifice is only required to clamp an orifice plate separately prepared in the pipe, which can reduce the cost of the equipment greatly. The required high-efficiency oxidation performance can be obtained at the absorption liquid branching from the absorption liquid circulating pump, and the absorption liquid circulating pipeline for installing the air blowing pipe is formed into an independent pipeline, so that a low-pressure pump is not needed.

In addition, the gas-liquid mixing method capable of forming fine bubbles can reduce corrosion on the inner surface of the conduit (inner surface of the pipe) at the gas-liquid mixing position even in long-term operation, which saves space, miniaturizes equipment, reduces equipment cost, is easy to maintain and low in cost, and operates at low power.

Brief description of the drawings

FIG. 1 is a partial longitudinal sectional view showing an important structure of an air blowing device in a wet flue gas desulfurization apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged schematic view of the relationship between the branched pipe for circulating an absorbing liquid and the air blowing pipe in FIG. 1, wherein (A) is a longitudinal sectional view and (B) is a front view.

FIG. 3 is a schematic view showing the relationship between a branched pipe for circulating an absorbing liquid and an air blowing pipe in the 2 nd embodiment of the present invention, (A) is a longitudinal sectional view, and (B) is a front view.

FIG. 4 is an enlarged view showing the relationship between the branched pipe for circulating an absorbing liquid and the air blowing pipe in FIG. 2 according to the present invention.

Fig. 5 is a partial vertical sectional view showing the main structure of an air blowing device in a wet flue gas desulfurization apparatus according to embodiment 3 of the present invention.

FIG. 6 is a schematic view of a main part of a spray nozzle including a branch pipe and an air blowing pipe.

Fig. 7(a) is a schematic diagram showing a negative pressure region formed by the orifice of the injection nozzle of fig. 6 and a state in which cavity vortices are generated in the region, and (B) is a schematic diagram showing a state in which the pressure changes in the negative pressure region of the injection nozzle.

FIG. 8A is a graph showing the relationship between the ratio of the amount of air sucked to the opening area of the orifice and the flow rate of the liquid discharged from the orifice, as the relationship between the air suction flow rate and the orifice diameter, and FIG. 8B is a graph showing the relationship between the flow rate of the liquid discharged from the orifice and the miniaturization capability. In the figure, the relationship is shown by the ratio of the flow rate of the fine air to the area of the orifice throttling part.

Fig. 9(a) is a schematic diagram showing the relationship between the jet arrival point, the ratio of the distance to the nozzle (branch pipe) diameter, and the dynamic pressure of the jet from the nozzle (branch pipe), and (B) is a schematic diagram showing the relationship between the liquid flow rate and the discharge pressure when aeration is performed by the blower and when aeration is performed by suction through the 100mm orifice.

Fig. 10 is a schematic view of a main part of an air blowing device in a conventional wet flue gas desulfurization device.

Fig. 11 is a schematic view of an air blowing device in another example of a conventional wet flue gas desulfurization device.

Fig. 12 is a schematic view of an air blowing device in another example of a conventional wet flue gas desulfurization device.

Fig. 13 is a schematic diagram showing the basic classification of an air blowing device in a conventional wet flue gas desulfurization device, wherein (a) is a schematic diagram showing a case where a plurality of fixed blowing pipes are arranged, (B) is a schematic diagram showing a case where a plurality of rotary blowing pipes are used, and (C) is a schematic diagram showing a case where a plurality of air blowing pipes with an agitator are provided.

FIG. 14 is a schematic view showing another classification of the air blowing device of the conventional wet flue gas desulfurization device shown in FIG. 13, in which an air blowing pipe is provided in an independent pipeline for circulating an absorbent and a stirrer is provided.

Fig. 15 is an overall configuration diagram of a wet flue gas desulfurization apparatus applied to the present invention.

In general, as the explanation of the symbols in the above figures, 1 is an absorption tower, 2 is a liquid tank part, 3 is a branch pipe for circulating an absorption liquid, 4 is an air blowing pipe, 4a is an end part, 5 is an orifice, 6 is a negative pressure region, 10 is air, 11 is a circulating absorption liquid, and 12 is a gas-liquid mixture.

Best mode for carrying out the invention

The present invention will be described in detail below with reference to examples shown in the drawings. However, the shapes of the components and other relative arrangements described in the embodiments are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples.

Fig. 1 and 2 show a 1 st embodiment, fig. 3 shows a 2 nd embodiment, fig. 5 shows a 3 rd embodiment, and fig. 15 shows an overall configuration diagram of a wet flue gas desulfurization apparatus to which the present invention is applied.

In fig. 1, 2 and 15, reference numeral 2 denotes a liquid tank portion provided at the lower part of the absorption tower 1 in the wet flue gas desulfurization apparatus, and the liquid tank portion 2 stores an aqueous absorption liquid containing an alkaline component such as lime. In the absorber 1, as is well known, as for the combustion exhaust gas a introduced from a combustion facility such as a boiler,

the absorbing liquid supplied from the liquid tank part 2 is dispersed by a dispersing device 52 such as a shower to absorb SO in the exhaust gas₂The oxide gas of sulfur is absorbed in the absorption liquid. Also containing captured SO₂The absorption liquid in the absorption tower is dropped or flows down and returns to the liquid tank part 2. Removal of SO₂The exhaust gas of the oxide gas of sulfur is demisted by the demister 50, and then discharged to the exhaust gas treatment part of the next process or discharged to the atmosphere through the exhaust gas lead-out part 51.

On the other hand, since the absorption liquid in the liquid bath section 2 contains sulfite, it is necessary to oxidize it and take it out as stable sulfate, and therefore an air blowing device is additionally provided to supply sufficient air 10 to the liquid bath section 2 of the wet flue gas desulfurization device.

In the air blowing device of this embodiment, as shown in fig. 1 and 15, a pump 53 is installed on the upstream side, a branch pipe 3 branching off an absorbing liquid scattering pipe 55 is inserted into the liquid tank 2 from the side wall through a valve 56, and the outlet end 3a thereof is opened as a discharge port in the liquid tank part 2.

Similarly, an end 4a of an air blowing pipe 4 is inserted from the duct 3 near the side wall of the liquid tank 2 near the branch pipe 3, and as shown in FIG. 4, the inserted end 4a is formed in a half-open shape and flows downward toward the duct 3, thereby forming a hollow portion 41 a. In other words, the cross section of the end portion 4a is formed into a semicircular concave shape toward the downstream direction, and the hollow portion 41a is formed toward the downstream direction. Similarly, the free end of the half-open end 4a is inserted to the inner peripheral surface position opposite to the branched pipe for absorbent circulation 3.

In the example of FIG. 1, the position of confluence with respect to the air blowing pipes 4 in the branched pipes for circulating the absorption liquid 3, that is, the mounting position, is set outside the liquid tank part 2, and needless to say, the position of confluence is also set inside the liquid tank part 2.

As shown in FIGS. 2 and 3, the branch pipe for circulating an absorbent solution 3 at the insertion end 4a is installed at a position where the merged position is formed, and when the inner diameter of the pipe 3 is D, the branch pipe is installed on the upstream side of the pipe 3 at a distance of 3D to 10D from the end, and the air pressure merged with the absorbent solution in the pipe 3 is dispersed as fine bubbles after the merging even at a low pressure, thereby improving the gas-liquid contact effect.

Further, the inner diameter of the end portion 4a formed in the semi-open shape is, in any case, smaller than the inner diameter D of the branch pipe 3, and as shown in fig. 2(B) and 3(B), a compressed fluid is formed by the gaps 3C formed at the upper and lower or left and right end sides of the end portion 4a, and it is preferable that the inner diameter is 0.4D to 0.7D in order to allow the absorption liquid to smoothly pass therethrough.

As shown in fig. 2(B), the pipe shape shown by the axial direction cut of the end portion 4a is such that the axial direction cut surface coincides with a horizontal cross section running through the center axis when viewed from the front side facing the branch pipe 3. As shown in fig. 3B, the arrangement may be made to coincide with a vertical (vertical) cross section passing through the center axis of the branch pipe 3. Or may be formed to coincide with another inclined surface passing through the center axis. The angle formed by the central axis of the end portion 4a and the central axis of the branch pipe 3 may be a substantially right angle as shown in fig. 2(a), or may be another angle as shown in fig. 3 (a).

Therefore, according to the present embodiment, the end 4a of the air blowing pipe 4 is formed in a half-open shape, the back 41 in the direction opposite to the water flow in the branched pipe for absorbing liquid circulation 3 is formed in a substantially streamlined shape, the opening surface 40 on the downstream side in the liquid flow direction is formed in a half-open shape, and the opening surface is formed in a large diameter width of the pipe, so that the hollow portion 41a caused by the air in the branched pipe 3 is very stable, and the pressure fluctuation of the absorbing liquid is small, thereby providing an effect of suppressing the occurrence of corrosion in the pipe.

In the embodiment of fig. 2 and 3, the air merged with the absorbent in the branched pipe 3 is dispersed by forming fine bubbles immediately after merging even at a low pressure, so that the supply pressure of the air can be reduced, and the running cost can be reduced by reducing the pressure.

Further, since the opening surface 40 is large and the air pressure is low, the flow distance when the bubbles after the gas-liquid confluence in the branch pipe 3 are made uniform is short, and the pipe length from the end 4a to the liquid tank portion 2 can be made smaller to be 3D to 10D. It is needless to say that the branch pipe 3 is not branched by the absorbing liquid scattering pipe, and a separate pipe of the circulation pump is not separately provided.

Fig. 5 and 6 show a schematic configuration of embodiment 3 of the present invention, in which fig. 7(a) is a schematic diagram of a situation in which an absorbent 11, which has changed from a compressed fluid state to an expanded state, and sucked air immediately form an air-liquid mixture 12 in a negative pressure region 6 generated by an orifice 5, and fig. 7(B) is a schematic diagram of a pressure change situation in the negative pressure region 6.

In this example, as an air blowing means for supplying sufficient air 10 into the liquid tank part 2 storing the aqueous absorption solution containing the alkaline component such as lime in fig. 5 and 6, a spray nozzle structure using an orifice in the branch pipe 3 shown in fig. 15 is employed in this example.

That is, the branched pipe 3 branched at the downstream side of the circulation pipe 53 of the absorption liquid dispersion pipe 55 is inserted into the liquid tank part 2 to circulate and discharge the absorption liquid from the discharge port 3a thereof to the liquid tank part 2, and the branched pipe 3 is provided with an orifice 5 in a straight pipe part extending from the discharge port 3a to the upstream side, and an air blowing pipe 4 opened toward a negative pressure region 6 formed by the orifice 5 immediately after the outlet of the orifice 5.

In this case, the position (opening position) of the air blowing pipe 4 is arranged at the upstream position of 3D to 10D from the downstream outlet 3 a. The air 10 for oxidation is self-sucked by suction force in the negative pressure region 6 through the air blowing pipe 4, and the self-sucked air 10 is merged with the absorption liquid 11 in an expanded state after contraction flow by hollow vortex formed in the negative pressure region 6 to form a gas-liquid merged fluid 12.

As shown in fig. 7(B), the absorption liquid 11 passing through the orifice 5 starts to expand after the negative pressure region 6 is formed, the pressure reaches the rising point 7 once, and returns to the original positive pressure state, while the self-priming air 10 is sheared and fine bubbles are formed, and the gas-liquid mixture 12 is discharged from the discharge port 3a in a jet flow state to the liquid tank portion 2. Similarly, the discharged jet reaches a predetermined position in the liquid bath section 2, and then, an upward flow is formed, and the storage liquid is stirred, thereby not only having a high oxidation performance but also preventing the deposition and accumulation of the oxidation products.

The following is a spray nozzle of the air blowing device in this embodiment, using a branch pipe with a diameter of 150 mm and a circulation flow rate of 100 to 350m³The flow rate of ventilation is 60-600 m³The results of the nozzle performance tests performed under the operating conditions of/h are shown in FIGS. 8 to 9.

It is known that the amount of air sucked by a small-diameter orifice generating a large negative pressure even with the same amount of liquid injected is large by sucking air (self-priming) with the suction pressure of the orifice and examining the relationship between the amount of liquid flow and the amount of self-priming air of orifices of different diameters. In fig. 8(a), the relationship between the air suction flow rate and the orifice diameter can be obtained by sorting the relationship between the ratio of the air suction amount to the orifice opening area and the liquid discharge flow rate at the orifice.

As can be understood from the figure, the flow velocity at the orifice is about 8 to 14m/s, and the orifice diameter is preferably 2/3 to 3/4 relative to the branch pipe diameter.

The relationship between the time of suction ventilation and the minute air flow rate was examined below.

The sucked air is blown off into fine bubbles by the liquid flow rate, and the relationship between the capability of such a fine control (the limit of the ventilation flow rate at the time of air suction) and the liquid flow rate tends to increase the amount of the fine air as the orifice diameter becomes smaller even at the same amount of the blown liquid. Fig. 8(B) shows the relationship between the liquid ejection flow rate of the orifice and the miniaturization capability. The relationship was examined and the ratio of the flow rate of the fine air to the orifice sectional area was used.

The solid line calculation formula in fig. 8(B) has the following equation.

U_Bair＝4.5(U₁₀-3.3)²2g … … (1) wherein: u shape_Bair: fine air flow/orifice opening area [ m ÷³/m².sec]

U₁₀: flow rate of liquid discharged from orifice [ m/sec ]]

According to the formula (1), the jet flow velocity at the orifice must be 3.3m/sec or more for the air refinement. Therefore, it can be understood that the orifice diameter is 2/3 to 3/4 relative to the branch pipe diameter to satisfy this requirement.

The distance reached by the jet was investigated as follows.

Although the stirring effect can be obtained by the jet flow, the distance of arrival of the jet flow must be considered as an effective index for evaluation. Fig. 9(a) shows a relationship between the distance and the diameter of the nozzle (branch pipe) and the dynamic pressure of the jet from the nozzle (branch pipe), where the curved point is the arrival point of the jet, and the ratio of the distance to the diameter of the nozzle (branch pipe) is shown.

According to the figure, the distance L reached by the jet is_iAnd the ejection dynamic pressure Pdn are summarized as the following formula (2).

L_j＝Dn×(0.72Pdn+12)……(2)

Lj: distance [ m ] reached by jet from nozzle

Dn: jet nozzle caliber (m)

Pdn: dynamic pressure of jet stream ejected from jet nozzle [ KPa ]

In addition, although the above is a result of using water, it is considered that the distance reached tends to be longer when salt is mixed in the liquid.

Therefore, the oxidation load is relatively low when the aperture of the orifice is 2/3 to 3/4 relative to the aperture of the branch pipe, and the oxidation can be performed by using the sucked air at a position 3m deep into the liquid, and the oxidation blower can be omitted. Further, the relationship between the flow rate of air which can be made fine and the flow rate of liquid at the orifice was 1.3 times as large as the flow rate of the ejection liquid at 8 to 10m/sec, or at 12 m/sec. Therefore, the flow velocity at the orifice is preferably 8m/sec or more, and the upper limit thereof may be 14m/sec or less for obtaining a desired fine size.

If the oxidation performance is increased in proportion to the reference superficial velocity of the bed area of the tank in the range of the fine air, the effect is hardly obtained if the aeration amount exceeds the above range. Although the self-priming performance and the miniaturization performance vary with the orifice diameter, the orifice diameter is preferably 2/3 to 3/4 with respect to the branch pipe diameter, and accordingly, the distance of arrival of the jet flow can be set to 15 or more depending on the operating conditions, and the jet flow force can be generated from the discharge port into the liquid tank. When the jet flow jetted from the end of the branched pipe inclined downward reaches a certain distance (the distance reached above), the jet flow is bent at a sharp angle to form an upward flow, and an agitation flow is generated in the retention liquid.

Fig. 9(B) shows the relationship between the liquid flow rate and the discharge pressure when the self-priming ventilation is performed by the blower ventilation and the 100mm orifice.

As can be seen, as the ventilation increases, the liquid discharge pressure tends to increase, but no substantial pressure increase is obtained. Even if the distance to be reached is almost the same by blowing air with a blower or by self-priming, the effect of the present invention can be confirmed.

Industrial applicability of the invention

As described above, according to the present invention, the occurrence of corrosion on the inner surface of the guide pipe of the branched pipe for circulating an absorbing liquid can be suppressed even in a long-term operation. The length of the pipe from the end 4a of the air blowing pipe to the liquid flow portion 2 is set to a small value of 3D to 10D, so that the apparatus can be miniaturized and the cost of the apparatus can be reduced.

In particular, according to the invention described in claim 5, the suction system is used without using the power for air blowing, and the bubble-refining capability is improved, so that the value is excellent in terms of power consumption as compared with any conventional system, and high oxidation performance equivalent to that of the arm rotation type (air blowing device B) can be obtained without providing a stirrer, and the side mounting system having a high degree of freedom of arrangement can be established by spraying the gas-liquid mixed phase fluid from the side of the tank for oxidation.

Claims (7)

1. Cleaning SO in fuel exhaust gas by using alkali-containing absorption liquid₂A wet flue gas desulfurization apparatus for desulfurizing an oxide gas of sulfur or the like, wherein an opening at one end of an absorption liquid circulation pipe is provided as a discharge port in a liquid tank of an absorption tower, characterized in that an air blowing pipe is installed in the absorption liquid circulation pipe, and the position of the opening at the outlet of the blowing pipe is provided at an upstream position in the range of 3D to 10D as measured from the end of the pipe when the inner diameter of the absorption liquid circulation pipe is D.

2. A wet flue gas desulfurization apparatus according to claim 1, wherein the duct according to claim 1 is a branch pipe branched from a downstream side of a circulation pump provided in a main duct connected between the liquid tank part and the absorption liquid dispersion device.

3. The wet flue gas desulfurization apparatus according to claim 1, wherein when the air blowing pipe is installed in the duct, an end portion of the air blowing pipe is inserted into the duct, and an opening surface having a semi-open shape is formed on a downstream side of the end portion.

4. The wet flue gas desulfurization apparatus according to claim 1, wherein the inner diameter of the end of the air blowing pipe is set to 0.4D to 0.7D with respect to the inner diameter D of the duct.

5. The wet flue gas desulfurization apparatus according to claim 1, wherein when the air blowing pipe is installed in the duct, an orifice is provided upstream of the installation position of the air blowing pipe, and the position of the outlet opening of the air blowing pipe is located in a negative pressure region formed by the orifice.

6. The wet flue gas desulfurization apparatus according to claim 3, wherein the orifice has a diameter set to 2/3 to 3/4 relative to the diameter of the branch pipe.

7. The wet flue gas desulfurization apparatus according to claim 3, wherein the flow velocity of the absorption liquid passing through the orifice is set to 8 to 14 m/sec.