JP4094694B2 - Jet bubbling reactor for flue gas desulfurization - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas-liquid contact method in which a gas and a liquid are brought into contact with each other with high contact efficiency, the gas and the liquid are reacted, the gas is absorbed into the liquid, or the gas is humidified and cooled with the liquid, and the method More particularly, the present invention relates to a gas-liquid contact device utilizing a novel jet bubbling system, that is, a jet bubbling reactor.
[0002]
[Prior art]
The main components of the gas-liquid contact mechanism that have been used in the past when absorbing gas into liquid or reacting gas with liquid are the gas-liquid contact mechanism of the packed bed system and the gas-liquid of the spray system. It is a contact mechanism.
In a packed bed type gas-liquid contact mechanism, a packed bed is formed by filling a tower or tank with a packing material, and usually a liquid flows downward from the upper part of the packed bed and a gas flows upward from the lower part of the packed bed. The gas-liquid contact is made in the packed bed.
In the spray-type gas-liquid contact mechanism, a spray nozzle is provided in the upper part of the tower, and gas flows upward from the lower part of the tower, while the liquid is sprayed from the spray nozzle toward the gas, and the sprayed liquid and gas are vaporized in the tower. Liquid contact.
[0003]
However, the gas-liquid contact mechanism of the packed bed system has a relatively high gas-liquid contact efficiency, but is not suitable for a large-scale apparatus due to problems such as drift. On the other hand, although the spray-type gas-liquid contact mechanism has a simple structure, it has a drawback in that the volume of the gas-liquid contact portion increases because of the low efficiency of gas-liquid contact.
In addition, both require a large liquid feed pump because the liquid needs to flow down at a large flow rate per area of the packed bed, or the liquid must be sprayed at a large flow rate per area of the gas-liquid contact area, Equipment costs and power costs increase, and when slurry is used as a liquid, troubles due to wear tend to occur.
[0004]
Therefore, in order to achieve a high gas-liquid contact efficiency, unlike a gas continuous-phase gas-liquid contact mechanism such as a spray-type or packed-bed-type gas-liquid contact mechanism, a jet characterized by the liquid side being a continuous phase. The present inventors have developed and put into practical use a bubbling gas-liquid contact mechanism.
Hereinafter, a reactor having a jet bubbling type gas-liquid contact mechanism, that is, a jet bubbling reactor (hereinafter simply referred to as JBR) will be described as an example. As shown in FIG. 7, the JBR 10 is divided into a gas outlet chamber 12 and a gas inlet chamber 14 provided so as to cross the tank body in order from the top, and a lower liquid storage chamber 16 for storing a liquid. Yes.
The gas outlet chamber 12 and the gas inlet chamber 14 are partitioned by an upper deck plate 18 that extends horizontally across the tank body, and the gas inlet chamber 14 and the liquid storage chamber 16 extend substantially parallel to the upper deck plate 18. It is partitioned by the lower deck plate 20. The lower deck plate 20 is located above the liquid level of the liquid 22 and forms a gas outflow space 24 therebetween.
[0005]
The gas outlet chamber 12 is connected to an outlet duct 26 and the gas inlet chamber 14 below it is connected to an inlet duct 28. In addition, as a gas riser that causes a gas (hereinafter referred to as a liquid contact gas) after contact with the liquid to flow into the gas outlet chamber 12 from the space portion 24, a plurality of pipe-shaped communication pipes 30 (in FIG. (Only this is shown) penetrates the gas inlet chamber 14 and allows the space 24 and the gas outlet chamber 12 to communicate with each other.
A large number of gas blowing pipes (gas spargers) 32 communicate with the gas inlet chamber 14 at the upper end and descend downward from the lower deck plate 20 so as to be immersed in the liquid 22 at the lower end. A number of small openings are provided at the lower end.
[0006]
The gas is blown into the liquid from the gas blowing pipe 32 through the gas inlet chamber 14, flows out as fine bubbles into the liquid outside the gas blowing pipe 32, and is a liquid continuous phase gas-liquid contact region. A jet bubbling layer is formed where gas-liquid contact is made. Thereafter, the gas flows out of the system via the gas riser 30 and the gas outlet chamber 12.
[0007]
[Problems to be solved by the invention]
By the way, in order to make the reactor that advances the reaction with gas-liquid contact and the absorption tower that advances the absorption with gas-liquid contact more compact, develop a gas-liquid contact mechanism with higher gas-liquid contact efficiency. It is necessary.
Accordingly, an object of the present invention is to provide a jet bubbling reactor equipped with a gas-liquid contact mechanism that further increases the gas-liquid contact efficiency as compared with the prior art.
[0008]
[Means for Solving the Problems]
As a result of repeated research and experiments, the present inventors have developed a novel jet bubbling method with high gas-liquid contact efficiency and have completed the present invention.
[0009]
  According to the present inventionFor flue gas desulfurizationThe jet bubbling reactor (hereinafter referred to as JBR)
  A deck plate that extends across the tank body and divides the interior of the tank body vertically,
  The tank body accommodates the liquid downward from the deck plate so as to secure a space portion between the deck plate and the liquid surface, and is connected to the space portion so that the gas flows into the space portion and the liquid. A liquid storage chamber having an inlet of the above and a deck plate, having a gas-liquid separation space and a gas outlet, and partitioned by a deck plate into a gas-liquid separation chamber for separating entrained liquid from the gas,
  In addition, the pipe body has openings in the upper and lower parts, penetrates the deck plate in the upper part, communicates with the gas-liquid separation chamber, and is immersed in the liquid in the lower part to extend the space part of the liquid storage chamber in the vertical direction. The liquid is introduced into the inside of the tube body, and the gas flows into the liquid inside the tube body from the outside of the tube body through the lower opening, and the gas and the liquid are intimately mixed to form the upper gas. A jet bubbling tube that forms a super jet bubbling layer in which the gas flowing out into the zone entrains the liquid,
  The outermost row of jet bubbling pipes is formed from a cylindrical body disposed in the space between the side wall of the tank body and the outermost row of jet bubbling pipes so as to surround the outermost row of jet bubbling pipes from the side. A gas introduction ring with a hole therethrough;
  The upper end communicates with the gas-liquid separation chamber through the deck plate, and the lower end is formed with a pipe body arranged vertically so as to be immersed in the liquid deeper than the jet bubbling pipe. A liquid downcomer for returning the entrained liquid separated from the liquid to the liquid storage chamber;
  WithThe entrainment velocity of the gas in the super jet bubbling layer is 6 to 8 m / s, and the average bubble hold-up in the super jet bubbling layer is 0.4 to 0.6. Opening diameter is 10-15mmIt is characterized by that.
[0010]
  According to the present inventionFor flue gas desulfurizationIn jet bubbling reactor,spiritBy bringing the body and liquid into gas-liquid contact, depending on the purpose, the gas and liquid react, the gas is absorbed into the liquid, the gas is humidified and cooled, and the gas is reduced with the liquid. Moisten.
  In the present invention, a super jet bubbling layer is formed in the pipe by introducing gas from the outside of the jet bubbling pipe containing the liquid through the opening at the bottom of the pipe at a higher speed than in the prior art.
  A suitable gas flow rate in the tube is 4,000 Nm per unit cross-sectional area of the tube.³/ M 2 / h to 15,000 Nm³/ M²/ H range.
  Since the gas flowing out from the region where the super jet bubbling layer is formed into the upper gas region is accompanied by the liquid, the liquid is separated from the gas in the upper gas region, and the gas is sent out of the system. On the other hand, the separated liquid is returned to the liquid layer.
[0011]
The gas introduction ring is preferably connected at its upper end to the deck plate and has its lower end extending below the lower end of the jet bubbling tube so as to be immersed in the liquid during operation. The cross-sectional shape may be circular or polygonal. The distance between the gas introduction ring and the tank body side wall may be determined in consideration of the flow velocity of the gas. Preferably, the distance between the gas introduction ring and the tank body side wall becomes narrower as the distance from the gas inflow port increases. Further, there is no particular restriction between the gas introduction ring and the outermost jet bubbling pipe as long as there is no problem in the flow of gas into the outermost jet bubbling pipe.
As for the size, number and distribution of the through holes, it is sufficient that the gas flows in the radial direction toward the jet bubbling pipe as viewed in the circumferential direction of the tank body, and the through holes are not necessarily distributed uniformly. There is no need to provide holes. The position of the through hole in the vertical direction of the gas introduction ring is not limited, and may be determined in consideration of the gas-liquid separation function of the space, the quality of the inflow to the jet bubbling pipe, and the like. The shape of the through hole is not limited, and may be circular, elliptical, or square.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described specifically and in detail with reference to the accompanying drawings.
【Example】
Overall configuration
The JBR according to the present invention causes gas-liquid contact in a liquid continuous phase by blowing gas into a liquid at a higher speed (super) than in the past (jet bubbling).
Below is an example of JBR configuration when boiler flue gas is gas and limestone slurry is gas-liquid contacted as liquid (hereinafter referred to as absorption reaction liquid) to remove harmful substances such as sulfurous acid gas in the flue gas The JBR according to the present invention will be described.
As shown in FIG. 1, the JBR 50 contains a super jet bubbling absorption part 54 (hereinafter simply referred to as an absorption part 54) that absorbs harmful substances such as sulfurous acid gas in the flue gas, and an absorption reaction liquid. An absorption reaction liquid part 56 (hereinafter simply referred to as reaction liquid part 56) that neutralizes and oxidizes the sulfurous acid absorbed by the absorption part 54 and converts it into gypsum, and a gas-liquid separation part 58 are provided.
[0013]
The absorption part 54 is composed of a number of jet bubbling pipes 66 which are attached at an upper end to a deck plate 64 provided on the surface of the absorption reaction liquid and vertically arranged so that the lower end is immersed in the absorption reaction liquid. These jet bubbling pipes 66 are provided with openings 68 at the lower ends thereof.
The flue gas flows from the space 62 outside the jet bubbling pipe 66 through the opening 68 to the absorption reaction liquid inside the jet bubbling pipe 66 at a high speed, and a large number of bubbles are generated in the inside to generate a high-performance gas-liquid contact region. A super jet bubbling layer is formed inside the jet bubbling tube 66.
Hazardous substances such as sulfurous acid gas in the flue gas are absorbed and removed by this super jet bubbling layer. As shown in FIG. 1, the flue gas becomes bubbles and rises in the vicinity of the tube wall in the jet bubbling tube 66, as will be described in detail later with reference to FIG. 5 and FIG. 6. At the upper end of 66, it is separated from the super jet bubbling layer and is discharged out of the JBR 50 as a clean gas through the gas-liquid separation chamber 58.
[0014]
On the other hand, the absorbed reaction liquid containing the absorbed sulfurous acid is separated from the cleaning gas in the gas-liquid separation chamber 58 and descends in the central portion in the jet bubbling pipe 66 and the liquid downcomer pipe 70 as shown by arrows in FIG. Then, the reaction liquid part 56 is returned.
The reaction liquid part 56 is a solid suspension layer having an appropriate stirring means 72, in which limestone slurry is supplied as an absorbent via a limestone slurry supply pipe 71 by a limestone slurry pump (not shown). The Furthermore, air is supplied from the air blowing pipe 74 in the form of bubbles as an oxidant. The sulfurous acid absorbed in the absorption reaction liquid from the flue gas is neutralized and oxidized by limestone and air in the absorption reaction liquid accommodated in the reaction liquid section 56 to form gypsum. Continues to grow while gently flowing in the suspension layer.
[0015]
Details of each part
Space
The space 62 refers to a space between the deck plate 64 and the surface of the absorbing reaction solution, the ceiling surface is the deck plate 64, the side surfaces are the side walls of the JBR 50 and the jet bubbling tube, and the lower surface is the absorbing reaction solution. The jet bubbling pipe 66 (hereinafter, in principle, the reference numeral 66 is omitted) extends vertically through the space 62.
The flue gas flowing in via the flue gas introducing duct 34 is dispersed in a uniform flow velocity distribution with respect to each jet bubbling pipe by the space portion 62, and the high-speed gas is discharged from the opening 68 at the lower end of the jet bubbling pipe to the inside of the jet bubbling pipe. And then bubble out into the tube to form a super jet bubbling layer.
[0016]
Gas introduction ring
When introducing smoke into the jet bubbling pipe 66 from the inlet duct 34 through the space 62, in order to distribute the smoke as uniformly as possible to the horizontal cross section of the JBR, the smoke is made ring-shaped from the outer periphery of the JBR. It is desirable to guide it into the JBR and make it flow evenly from several places toward the jet bubbling pipe.
Therefore, in this embodiment, as shown in FIGS. 2A and 2B, a cylindrical gas introduction ring 76 having a circular through-hole 78 surrounds the jet bubbling tube group, and the upper end is connected to the deck plate 64. It is connected and provided in the space 62 between the tank body and the outermost jet bubbling pipe so as to be immersed in the absorption reaction liquid at all times during operation at the lower end.
The shape of the gas introduction ring is not limited to this, and may be a polygonal cross section, or may be provided with a larger number of through holes.
[0017]
Gas cooling section
When the flue gas is hot, a gas cooling unit 52 is provided between the inlet duct 34 and the flue gas introduction port of the JBR 50, and the flue gas can be pre-humidified and cooled there. The gas cooling section 52 is formed of a gas conduit whose cross-sectional area gradually increases, and includes a spray nozzle 60 for spraying the slurry-like absorption reaction liquid into the conduit. In the gas cooling unit 52, the high-temperature flue gas contacts with the sprayed absorption reaction liquid, and the water in the absorption reaction liquid evaporates in the flue gas, so that the flue gas increases to a saturation temperature of 40-60 ° C. Wet cooled.
The smoke exhausted after being humidified and cooled flows into the space 62 along with the remaining absorption reaction liquid that has not evaporated.
The remaining absorbed reaction liquid is separated from the flue gas in the space 62 and falls, and immediately mixed with the absorption reaction liquid layer of the reaction liquid section 56, and only the cooled flue gas enters the absorption section 54. Since the absorption reaction liquid containing solids does not flow on the horizontal deck plate as in the prior art, it flows down directly to the reaction liquid section 56, so that solids adhere and deposit on the deck plate as in the conventional case. The problem does not arise.
[0018]
Gas-liquid separation chamber
In order to perform gas-liquid separation more effectively in the gas-liquid separation chamber 58, as shown in FIG. 2 (a), a gas-liquid separation plate 79 such as a cap is disposed above the jet bubbling tube, and the gas is separated by gravity. It is also possible to perform gas-liquid separation by collision before liquid separation. The shape of the gas-liquid separation plate is not limited to this, and may be a flat plate or an umbrella shape. Further, the position and size of the gas-liquid separation plate are not limited.
As shown in FIG. 1, a cleaning device 59 provided with a number of spray nozzles is provided on the ceiling of the gas-liquid separation chamber 58, and the horizontal deck plate 64 is cleaned with a clear liquid to obtain solids (if the (If any) is made into a slurry, fluidized, and poured into the liquid downcomer 70.
The lower part of the liquid descending pipe 70 reaches below the opening 68 of the jet bubbling pipe, and during operation, it is immersed in the absorption reaction liquid and is liquid-sealed.
The clean gas exiting the gas-liquid separation chamber 58 of the JBR 50 is finally removed through the mist eliminator, finally removing droplets in the gas, sent to the chimney, and released to the atmosphere.
[0019]
Jet bubbling tube
The jet bubbling pipe disposed vertically inside the space 62 is formed of an open pipe at both the upper and lower ends.
By the way, in a state where the exhaust gas does not flow into the space portion 62, the absorption of the liquid amount is such that the lower part of the jet bubbling pipe, preferably the part up to about 100 to 600 mm in height from the lower end is immersed in the absorption reaction liquid. Since the reaction liquid is accommodated in the reaction liquid part 56, the lower end of the jet bubbling pipe is closed in terms of fluid, and the liquid levels inside and outside the jet bubbling pipe are equal.
Next, as the flue gas fills the space 62, the liquid level of the absorbed reaction liquid in contact with the space 62 is pushed downward, the liquid level outside the jet bubbling pipe is lowered, and the liquid level in the pipe is raised.
Furthermore, when the pressure of the flue gas in the space 62 increases and the pressure reaches the immersion depth in units of the absorption reaction liquid, the flue gas starts to flow inward from the opening 68 at the lower part of the jet bubbling pipe (in FIG. 1). (See the leftmost jet bubbling tube). At this time, the depth of the liquid column existing in the jet bubbling pipe, that is, the immersion depth at the time of gas bubbling, Hb (see FIG. 5B) is expressed by the following equation.
Hb = (1 + Ao / Ai) Hs (1)
Here, Hs = immersion depth at rest (see FIG. 5A), Ai = total cross-sectional area of the entire jet bubbling pipe, and Ao = cross-sectional area of the space 62.
In addition, the pressure of smoke required at this time, Po,
Po = ρl (1 + Ai / Ao) Hs (2)
It becomes. Here, ρl = the density of the absorbing reaction solution.
[0020]
Further, when the pressure of the flue gas in the space 62 increases, the liquid level is pushed downward from the lower end of the jet bubbling pipe, the flue gas passage depth is secured, and the flue gas of a predetermined flow rate flows. At this time, the gas jet flow rate from the lower end opening of the jet bubbling pipe to the liquid column side in the pipe, that is, the gas flow rate Q from the outer side to the inner side of the jet bubbling pipe has a uniform gas inlet velocity distribution along the periphery of the lower end opening. Is expressed by the following equation.
Q = {(ρl−ρv) / ρv)}^0.5∫ c {2g (H−X)}^0.5Lp (x) dx (3)
Where ρl = density of absorbed reaction liquid, ρv = density of flue gas, c = constant, g = gravity acceleration, H = gas flow path depth, X = X distance from the lower end of the pipe in the gas flow path, Lp ( x) = gas channel width (a function of x), and the integration range is 0 to H when the gas channel is open at the lower end, and hs (skirt height) to when the lower end has a skirt. H + hs.
[0021]
Formation of intimately mixed jet bubbling layer
Now, in order to form a stable jet bubbling layer (hereinafter referred to as “stable jet bubbling layer”, which is intimately mixed, intimately mixed) that is intimately mixed in the jet bubbling pipe. First, the flue gas must have enough energy to push back the absorbing reaction solution from the inside of the high-pressure pipe to the outside of the pipe through the opening. That is, it is necessary that the pressure of the flue gas in the space 62 is higher than Po in the equation (2).
As a result of continuing the experimental study, as a condition for forming a stable jet bubbling layer, in addition to the above-described pressure condition of flue gas, the first condition found by the present inventors is the porous condition as in the prior art. Rather than generating small bubbles from the beginning using a diffuser plate, it is the stable jet that blows off the flue gas as a large gas lump and collides with the absorbing reaction liquid to disperse it into many small bubbles. This is the key to obtaining a bubbling layer. In particular, it can be easily understood that this jet bubbling method, in which a small gas-liquid is generated despite the large opening area, is effective when a gas is blown into a liquid containing solids such as slurry. I will.
The diameter of the gas lump depends to some extent on the properties of the gas and liquid, but in the case of flue gas desulfurization, since the dispersed bubble diameter is generally about 2 to 3 mm, the gas lump is naturally a diameter several times larger than this. It becomes. That is, it is only necessary to have a diameter five times that of bubbles, that is, an opening diameter of about 10 to 15 mm.
[0022]
In the jet bubbling phenomenon, not only bubbles but also fine particles of the absorbed reaction solution are generated. Therefore, in order to form a stable jet bubbling layer, the second condition is that fine droplets that try to return to the outside of the tube from the difference in specific gravity. The smoke must have the energy to return from the outside into the pipe.
The energy that satisfies the second condition is known as the gas droplet entrainment speed of 6-8 m / s.
[0023]
Jet bubbling tube opening
Now, assuming that the gas opening is constituted by the lower end port of the circular jet bubbling pipe as shown in FIG. 3 (d), theoretically, the gas opening extends along the entire peripheral length of the lower end opening of the jet bubbling pipe. A donut-like gas mass having a flow path depth H is generated. When the lower end opening is configured at the tube opening, the above two conditions are almost satisfied according to the calculation, so the shape of the circular tube that forms the lower end opening at the tube opening is the simplest jet bubbling mechanically. It can be said that it is a tube.
[0024]
Actually, since the donut-shaped gas mass is unstable, it is desirable that the gas flow path width is in the same order as the gas flow path depth, and the lower end opening is formed as a so-called comb-shaped opening. Is desirable.
There are a wide range of flue gas properties and absorption reaction liquid properties to handle, especially when using slurry as an absorption reaction liquid. The lower end opening depth of the jet bubbling pipe, H (see FIG. 3A), is preferably about H = 0.025 m.
[0025]
The shape and size of the opening of the jet bubbling tube may satisfy the first condition and the second condition described above. Preferably, the opening diameter has an equivalent diameter of 10 to 15 mm as described above. As long as it can generate a jet bubbling phenomenon due to flue gas, there is no particular limitation in the present invention.
Regarding the shape, in addition to the so-called comb-shaped slot-shaped opening 68a (see FIG. 3A) in which the bottom of the tube is opened, for example, a through-hole-shaped opening 68b provided so as to penetrate the tube wall (FIG. 3). (See (b)), and may have a skirt 68c (see FIG. 3C) below the opening 68b. As shown in FIG. 3 (d), the opening may be simply a tube cut.
If the length L of the skirt 68c is appropriately lengthened to, for example, 100 to 500 mm so that the exhaust gas does not flow out from the lower end of the jet bubbling pipe, the exhaust speed of the exhaust gas is the above critical value even at the lower end of the opening. It is possible to exceed the speed (6-8 m / s) (note that the comb-shaped slot shape has a quadratic curve distribution in the horizontal gas flow velocity, and the flow velocity is zero at the lower end of the opening. ), There is an advantage that liquid oscillation such as sloshing does not occur in the jet bubbling layer. However, since the skirt portion becomes a dead zone, there is a disadvantage that solid matter is deposited in the long term, so it is necessary to consider a trade-off.
In the case of slot-like comb-shaped openings and through-hole shaped openings, the shape of the opening itself is a long hole, and it is practical to use an appropriate rounded corner, but round holes and triangles (with a rounded upper part) (Including trapezoidal) holes, square holes, etc. In addition to the single stage on the top and bottom, two or three stages, etc. In addition to the equidistant pitch arrangement on the left and right, the use of multiple pitches, etc. However, these are within the scope of selection by those skilled in the art and are not particularly limited in the present invention.
[0026]
When the lower end opening depth H of the jet bubbling pipe (see Fig. 3 (a)) is 25 mm, the flue gas becomes a flue gas mass about 25 mm deep from the opening at the lower end of the jet bubbling pipe. In the pipe filled with the absorption reaction liquid, it is inverted in the vertical direction by the buoyancy of the smoke. Therefore, a gas mass having a diameter of about 25 mm exists at the lower part inside the tube.
This gas mass breaks up and disperses into many bubbles while rising along the tube wall in the tube by buoyancy. The bubble diameter is determined by the surface tension, viscosity, etc. of the liquid, and most of them are about 2 to 3 mm. The shape of is shown.
[0027]
Jet bubbling layer height
Many of the generated bubbles are driven by their own buoyancy or by the pressure of flue gas and blow up in the tube with the absorbing reaction solution. Since the height of the liquid in the tube is dynamically expanded by the amount of bubbles, the height of the jet bubbling layer, Hj,
Hj = Hb / (1-Ф) (4)
It becomes. Here, Hb = immersion depth at the time of gas bubbling, and Ф = bubble hold-up. The average soot is 0.4 to 0.6 in the jet bubbling layer.
At this time, the pressure Po of the flue gas required outside the jet bubbling pipe is continuously liquid phase even if the jet bubbling layer in the pipe is dynamically expanded.
Po = ρl {(1 + Ai / Ao) Hs + (Ai / Ao) H} + HjФρv (5)
It becomes a little larger than when foaming.
[0028]
Flow state of jet bubbling phase
The approximately 25mm flue gas that flowed into the pipe in the horizontal direction turns upward by buoyancy in the pipe filled with the absorption reaction liquid, and has a jet bubbling with a diameter 2 to 3 times larger than the diameter of the original flue gas. It blows up as a lump (about 50-75 mm) and then breaks up into bubbles of 2 mm diameter. When the bubbles reach the height Hj of the in-tube jet bubbling layer, the bubbles are separated from the jet bubbling phase and collected in the gas-liquid separation chamber 58 above the jet bubbling layer.
The absorption reaction liquid entrained in the bubbles separates from the bubbles here and flows downward with a specific gravity difference. It is necessary for the liquid flow to give a flow cross-sectional area of about 10% of the jet bubbling flow for smooth descent of the liquid. For that purpose, when a circular part having a width of 50 to 75 mm along the wall surface of the jet bubbling pipe is a jet bubbling body as seen in the cross section of the jet bubbling pipe, a circular part having a diameter of about 50 mm inside the circular ring is used as the liquid flow part. Function (see FIG. 4). Therefore, considering the jet bubbling main body and the liquid flow portion, the diameter of the jet bubbling pipe is preferably about 150 to 200 mm.
[0029]
Cross section of jet bubbling tube
In general, the cross-sectional shape of a jet bubbling tube is circular, but this is the reason why the material is readily available and economical, and the present invention does not limit the jet bubbling tube to a specific shape. . In the present invention, for example, the cross section of the jet bubbling tube is not only a circle but also an elliptical or oval curved contour cross section, a polygonal contour cross section such as a triangle, square, pentagon, hexagon, or a trough shape. Any shape such as a flat plate structure can be adopted.
When the cross-sectional area of the jet bubbling pipe is not circular, it can be handled in the same manner as the circular pipe by setting the equivalent pipe diameter (= 4 × cross-sectional area / immersion side length) to the diameter of the circular pipe. For example, a flat-plate structure having a width W has an equivalent tube diameter of 4 × W / 2 = 2W, and can be said to be a rough basic gas-liquid contact means in terms of performance compared to a circular tube having the same gap.
[0030]
Standard dimensions of jet bubbling pipe
From the above description, the unit means of the basic gas-liquid contact mechanism of the present invention, that is, the jet bubbling pipe is typically a circular pipe having a diameter of about 150 to 200 mm, and the gas flow path depth is 25 mm downward from the lower end. In addition, the flue gas is ejected horizontally into the absorption reaction liquid in the pipe at a flow rate of about 10 Nm / s.
A practical scale flue gas desulfurization apparatus requires a large number of jet bubbling pipes, and these jet bubbling pipes are arranged on the deck board so as to extend downward from the deck board.
The jet bubbling pipe is held through the horizontal deck plate at the upper end thereof, and the gas-liquid separation chamber 58 is formed on the deck plate.
[0031]
Arrangement of jet bubbling pipe
In order to arrange a jet bubbling pipe made of a circular pipe on a horizontal deck board, there are two standard arrangements, an equilateral triangle and a square arrangement.
Deck plate diameter Ds and pipe placement pitch P_TAnd the number N of pipes have the following relationship in consideration of a dead space when arranging the pipes.
N = C (D_S/ P_T)²                                     (6)
Here, C = 0.86 (regular triangle arrangement) and 0.75 (square arrangement).
P when the tube is placed close_T= Dj (the diameter of the jet bubbling pipe), but there is also a limitation in installation, so that such arrangement is difficult in practical use._T= 1.25Dj is common.
P_TThe ratio of the total area of the jet bubbling pipe to the cross-sectional area of JBR when = 1.25 Dj is 0.48 to 0.55 from a simple calculation.
[0032]
Gas-liquid contact action in a jet bubbling tube.
Hereinafter, the gas-liquid contact action inside the jet bubbling pipe will be described in detail by taking the simplest jet bubbling pipe using a cylindrical pipe having a diameter of 200 mm opened at the upper and lower ends as an example.
FIG. 5A shows the state of the absorption reaction liquid inside and outside the jet bubbling pipe before the introduction of flue gas (the amount of flue gas inflow, Gs is Gs = 0). The liquid surface inside and outside the cylindrical tube is at the same height, and the lower end of the jet bubbling tube is at a depth of Hs from the liquid surface.
FIG. 5B shows a small amount of smoke (Gs = about 60 Nm).^Three/ M² / H) shows the state in the pipe when introduced. The liquid level on the outside of the tube is pushed down to a height of several millimeters above the lower end of the tube by the pressure of the flue gas, and the flue gas once dives in the absorption reaction liquid, and a group of bubbles with a diameter of about several millimeters from the lower end. It rises in the pipe. The bubble group swirls around the inner wall surface from the lower end of the tube, and rises slowly in the absorption reaction solution independently of each other, so that the absorption reaction solution in the tube is almost stationary. Hb indicates the difference in liquid level between the inside and outside of the tube.
[0033]
FIG. 6C shows the case where the gas amount is further increased (Gs = about 400 Nm).^Three/ M² / H) in the pipe. The liquid level on the outside of the tube is pushed down several centimeters below the lower end of the tube, and the flue gas is blown into the tube as a bubble mass having a diameter of several centimeters from a part of the peripheral length of the lower end. The bubble mass is crushed by pressure at the lower end surface of the tube and becomes a group of bubbles in which many bubbles with a diameter of several millimeters are collected. The bubble group sucks the absorbing reaction liquid while turning around the inner wall surface of the tube wall and rising.
The liquid flow of this absorption reaction liquid is L = about 500 m.^Three / M² At the flow rate L per unit cross-sectional area of about / h, as shown by the arrow, the gas first rises in the tube together with the bubbles, and then turns downward as the bubbles separate into the upper gas layer, to the center in the tube A liquid descending flow is formed. The descending liquid flow is again sucked into the ejected bubble group to form a liquid circulation circuit in the pipe. This state is a flow close to a conventional bubble layer.
[0034]
FIG. 6 (d) shows a case where the gas amount is further increased (Gs = about 4,200 Nm).^Three/ M² / H) in the pipe. The liquid level outside the tube is pushed down several centimeters below the lower end of the tube, and the flue gas is blown into the tube as a bubble mass with a diameter of about several centimeters from almost the entire length around the lower end. The bubble mass is crushed by pressure at the lower end surface of the tube to form a bubble group having a diameter of several mm. The bubble group rapidly rises near the inner wall surface of the tube wall. The rising bubbles are attracted more strongly by the liquid, while the bubbles collide with the flow of the liquid and the bubbles break up even smaller. At this time, some bubbles are united, but again collide with the liquid flow and re-divide.
The flow of liquid is L = about 8,400m^Three / M² At a flow rate L per unit cross-sectional area of about / h, the liquid is disturbed due to the collision with the bubble, and the liquid rises and falls repeatedly in the bubble group, so that a clear liquid circulation circuit is not formed. On the other hand, bubbles are also accompanied by a liquid flow in which a part of the bubbles descend. Therefore, the gas-liquid circulation in the pipe is irregular. A small amount, eg about 200 mg / Nm^ThreeAlthough a certain amount of liquid droplets are accompanied by the flue gas, they are separated in the gas-liquid separation chamber 58 and returned to the reaction liquid section 56 from the liquid descending pipe 70 opened in the deck plate 64.
The gas-liquid contact phenomenon at this stage is almost the same as the conventional jet bubbling phenomenon.
[0035]
FIG. 6 (e) shows a further increase in gas flow rate (Gs = about 14,100 Nm).^Three/ M² / H) in the pipe. The liquid level of the absorption reaction liquid is pushed down to several centimeters below the lower end of the pipe, and the flue gas is blown into the pipe as a gas column-like or continuous gas mass flow from almost the entire length around the lower end. The air column mass is crushed by pressure at the lower end surface of the tube and becomes a bubble mass of several centimeters. The bubble mass rises rapidly in the tube. The rising bubble mass collides with the absorbing reaction solution and breaks up into a large amount of bubbles. On the other hand, the absorption reaction liquid is further sucked by a large amount of bubbles, and L = about 53,400 m.^Three / M² The flow rate L per unit cross-sectional area is about / h. The bubbles collide with this liquid flow, and the bubbles break up even smaller. At this time, some bubbles are united, but again collide with the liquid flow and re-divide.
The flow of the absorbed reaction liquid is disturbed due to the collision with the bubbles, but because the rising speed of the bubbles is large, the liquid does not descend in the pipe, and most of the liquid rises in the pipe together with the flue gas. It flows out to the liquid separation chamber 58.
In the gas-liquid separation chamber 58, the flow rate of the flue gas rapidly decreases. Therefore, the absorption reaction liquid accompanying the flue gas is separated from the flue gas flow, partly flows down from the liquid downcomer 70, and the remaining part is jet bubbling. Returning to the lower part of the pipe, a large liquid circulation circuit is formed as shown by arrows. This is the super jet bubbling phenomenon of the present invention.
[0036]
The state of the mixed layer of the absorption reaction liquid and the exhaust gas is mainly determined by the exhaust gas flow rate Gs, but is also affected by the shape of the gas inlet at the lower end of the pipe.
If the opening edge of the opening through which the flue gas flows into the pipe is a simple straight line as described above, it is easy to form a large bubble mass, and after the large bubble mass rises, the absorbed reaction liquid enters the space and smoke is exhausted. Since the outlet of the exhaust gas is closed, the way of exhausting smoke into the pipe becomes intermittent, and the jet bubbling layer in the pipe tends to move periodically. This phenomenon tends to be mitigated by making the opening edge comb-shaped, creating a small bubble mass from the beginning, and further increasing the flow rate of the flue gas at the opening.
By the way, in the super jet bubbling layer constrained in the jet bubbling pipe of the present invention, the wavelength of this periodic movement is limited to about twice the diameter of the jet bubbling pipe, so there are many jet bubbling pipes. In a certain JBR, the vibration frequency as a whole increases, and metastable fluidity is achieved. On the contrary, since the gas-liquid movement becomes intense due to this vibration, there is an advantage that the contact efficiency of the gas-liquid is improved.
[0038]
Desulfurization rate by this JBR
As described above, the super jet bubbling gas-liquid contact mechanism of the present invention has excellent gas-liquid contact efficiency. Next, the improvement of the desulfurization rate by the super jet bubbling gas-liquid contact mechanism will be described.
The desulfurization rate η in the liquid-phase continuous gas-liquid contact layer as in the present invention is, for example, January 1996 when the reaction in the absorption reaction solution layer is fast and the absorption rate of sulfurous acid gas from the gas phase is rate-limiting. It can be obtained by the following formula (7) described on page 342 of “Chemical Reaction and Reactor Design” published by Maruzen Co., Ltd. (this description is cited as a reference in this specification).
η ≒ 1-exp {-(K_Gaπ / G_MZ_f} (7)
Where K_G= Overall gas capacity factor (kgmol / m² / H / atm), a = specific surface area (m² / M^Three ), Π = total pressure (atm), G_M= Gas flow rate (kgmol / m² / H), Z_f= Gas-liquid contact layer height (m).
K_GDepends on the diffusion coefficient of the substance inherent to the gas / liquid, the properties of the gas and liquid, and the film thickness affected by the flow state._MThe larger the is, the larger G_MThis is because the thickness of the boundary film decreases as the thickness increases. In the case of the present invention, K_G∞G_M ^0.5Has been measured. a represents the ratio of the gas-liquid contact area in the unit volume, which is proportional to the bubble volume in the unit volume, that is, the porosity Φ, and inversely proportional to the bubble diameter Dp. G_MIs small, for example G_M≦ 50Nm^Three/ M²/ H, the porosity increases proportionally as the gas is fed in, while the bubble diameter is kept almost constant, so a∞G_MIt will be about. In the super jet bubbling layer of the present invention, since bubbles having a small diameter already exist in the jet bubbling pipe close to the maximum density, a itself is a large value._MThe dependence on is not so great. According to the measurement, a∞G_M ^0.32It is about, and as a whole, K_Ga∞G_M ^0.82Degree. (K) in equation (7)_Gaπ / G_M) Term is G_M ^-0.17And gradually decreases as the gas flow rate increases.
On the other hand, in the case of the present invention, the jet bubbling layer fills up the jet bubbling pipe and communicates with the gas-liquid separation chamber at the top._fCorresponds to the height of the jet bubbling tube. The pressure loss on the gas side is calculated by multiplying the height of the jet bubbling pipe by the porosity Φ._MIndicates a constant value that does not depend on. Arbitrary gas flow rate G_MIn order to obtain a predetermined η, the height of the jet bubbling pipe may be changed according to the equation (7).
[0039]
The flue gas desulfurization apparatus equipped with the JBR of this example is actually operated, and the temperature of 120 ° C. containing 1,200 ppm of sulfurous acid gas is 1,50,000 Nm.^Three/ H flue gas was treated, as calculated, the desulfurization rate reached about 96%, and the pressure loss of flue gas was about 260 mmH₂ O.
Industrial water used for humidifying and cooling smoke is about 50m^Three / H, extraction amount of gypsum slurry is about 60m^Three / H, supply of limestone slurry is about 30m^Three / H. Oxidation air is 16,000 Nm using a wet (Nash type) air compressor with a motor power of 420 kW.^Three/ H was inserted into JBR in a water saturated state. Further, a slurry containing gypsum crystallized at a concentration of about 200 g / l is extracted from the lower part of the JBR by a pump 36 and continuously supplied to the JBR from a limestone slurry supply pipe 71 by a limestone slurry pump (not shown). .
As a result of continuous operation for about 11 months using this JBR82, there was almost no increase in the gas loss of the flue gas, and in the open inspection after one year, the accumulation of solids in the JBR82 Little deposits and blockages were observed.
[0040]
Effect of JBR of this embodiment
As described above, the JBR 50 of this embodiment brings gas and liquid into contact with each other with a gas-liquid contact efficiency that is significantly higher than that of the conventional gas-liquid contact mechanism. For example, when applied to flue gas desulfurization treatment High desulfurization rate can be achieved with a compact tank.
In addition, by providing the gas introduction ring 76, it is possible to introduce flue gas toward the jet bubbling pipe at a uniform radial flow rate when viewed in the circumferential direction of the tank body, so that the gas-liquid contact efficiency of the jet bubbling pipe is improved over the entire JBR. Uniformly high efficiency can be maintained.
Further, since the gas-liquid contact region is limited to the jet bubbling pipe 66 and is independent from each other, there is little fluctuation and a stable desulfurization rate can be achieved.
Furthermore, when the flue gas is cooled in advance by the absorption reaction liquid or the like, the flue gas is first introduced into the space portion 62 (the space between the deck plate and the liquid surface of the absorption reaction liquid) that functions as a gas-liquid separation space. As in the prior art, there is no problem that solid matter accumulates on a horizontal deck board and the like, and the flow path of the flue gas becomes narrow and the pressure loss of the flue gas increases.
[0041]
【The invention's effect】
As is clear from the above detailed description regarding the present invention including the description of the present embodiment, the JBR of the present invention has a jet bubbling mechanism with a novel configuration, and has the following advantages and effects. .
First, unlike conventional spray towers and packed towers, it does not require a large liquid circulation pump, and the features of the jet bubbling method are low in gas-liquid contact area and high in volumetric efficiency. It can be demonstrated. In other words, it is possible to increase the smoke introduction speed per unit cross-sectional area (opening width x gas lump depth) when blowing exhaust gas into the absorption reaction liquid, and to further increase the smoke introduction speed. Thus, a super jet bubbling layer with high gas-liquid contact efficiency can be formed, so that the cross-sectional area of the JBR tank can be made smaller than before. Moreover, since the height of the super jet bubbling layer is increased from about 1 to 2 m to about 3 to 5 m of the conventional jet bubbling layer, the residence time and contact time of gas and liquid are increased accordingly, and a good small immersion depth Thus, high gas-liquid contact efficiency can be obtained, the pressure loss of the gas can be reduced, and thus the required power of the gas blower can be reduced accordingly.
Secondly, in this JBR, since the super jet bubbling layer is formed inside the jet bubbling tube, the liquid flow region is localized in the jet bubbling tube, and the flow region is spread over the entire surface of the JBR. Compared with the conventional JBR, it is significantly narrower, and swinging, that is, sloshing (even if it is caused by an earthquake or the like) is suppressed to an extremely small level as compared with the conventional case. In addition, since there is fluid stability of the liquid, there is an advantage that the fluctuation of the gas-liquid contact efficiency is reduced.
Thirdly, by providing a gas introduction ring, smoke can be introduced toward the jet bubbling pipe at a uniform radial flow velocity when viewed in the circumferential direction of the tank body, so that the gas-liquid contact efficiency of the jet bubbling pipe can be reduced to JBR. High efficiency can be maintained uniformly throughout.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of an example of a jet bubbling reactor according to the present invention.
2 (a) is a schematic longitudinal sectional view of a JBR having the same configuration as the JBR of FIG. 1 and having an introduction ring and a gas-liquid separation plate, and FIG. 2 (b) is a view of FIG. 2 (a). It is a cross-sectional view of JBR in the arrow I-I.
FIGS. 3A to 3D are perspective views showing examples of a lower opening of a jet bubbling pipe, respectively.
FIG. 4 is a pipe cross-sectional view showing a liquid descending region in a jet bubbling pipe.
5 (a) and 5 (b) are schematic longitudinal sectional views showing a state in the jet bubbling pipe during operation of the JBR shown in FIG.
6 (c) to 6 (e) are schematic longitudinal sectional views showing a state in the jet bubbling pipe during the operation of the JBR shown in FIG. 1, following FIG. 5 (b).
FIG. 7 is a schematic diagram showing a configuration of a conventional JBR.
[Explanation of symbols]
10 Conventional jet bubbling reactor
12 Gas outlet chamber
14 Gas inlet chamber
16 Liquid chamber
18 Upper deck board
20 Lower deck board
22 Liquid
24 Space
26 Outlet duct
28 Inlet duct
30 Riser
32 Gas blowing pipe
50 Jet bubbling reactor
52 Cooling unit
54 Super Jet Bubbling Absorber (Absorber)
56 Absorption reaction liquid part (reaction liquid part)
58 Gas-liquid separator
59 Cleaning equipment
60 spray nozzle
62 Space
64 deck boards
66 Jet bubbling tube
68 opening
70 Liquid downcomer
71 Limestone slurry supply pipe
72 Stirring means
74 Air blowing pipe
76 Gas introduction ring
78 Through hole
79 Gas-liquid separator

Claims (3)

Tank body,
A deck plate that extends across the tank body and divides the interior of the tank body vertically,
The tank body accommodates liquid downward from the deck plate so as to secure a space portion between the deck plate and the liquid surface, and communicates with the space portion to allow gas to flow into the space portion and the liquid. A liquid storage chamber having an inlet of the above and a deck plate, having a gas-liquid separation space and a gas outlet, and partitioned by a deck plate into a gas-liquid separation chamber for separating entrained liquid from the gas,
In addition, the pipe body has openings in the upper and lower parts, penetrates the deck plate in the upper part, communicates with the gas-liquid separation chamber, and is immersed in the liquid in the lower part to extend the space part of the liquid storage chamber in the vertical direction. The liquid is introduced into the inside of the tube body, and the gas is allowed to flow into the liquid inside the tube body from the outside of the tube body through the lower opening. A jet bubbling tube that forms a super jet bubbling layer in which the gas flowing out into the zone entrains the liquid,
The outermost row of jet bubbling pipes is surrounded by a cylindrical body disposed in the space between the side wall of the tank body and the outermost row of jet bubbling pipes. A gas introduction ring with a hole therethrough;
At the upper end, it penetrates the deck plate and communicates with the gas-liquid separation chamber. At the lower end, it is formed of a pipe body that is arranged vertically so as to be immersed in the liquid deeper than the jet bubbling pipe. A liquid downcomer that returns the entrained liquid separated from the liquid to the liquid storage chamber, the gas droplet entrainment speed in the super jet bubbling layer is 6 to 8 m / s, and the average bubble hold-up in the super jet bubbling layer is A jet bubbling reactor for flue gas desulfurization , characterized in that the opening diameter of the lower portion of the jet bubbling pipe is 10 to 15 mm . Flow rate of the gas jet bubbling tract, according to claim 1, characterized in that in the range of unit cross-sectional area per ^{4,000Nm 3 / m 2 / h~15,000Nm 3} / m 2 / h of the jet bubbling tube Jet bubbling reactor for flue gas desulfurization . The jet bubbling reactor for flue gas desulfurization according to claim 1 or 2, wherein a stirring means for stirring the liquid is provided in the liquid storage chamber.

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