JPH06126128A - Method and apparatus for wet desulfurization of exhaut gas - Google Patents

Abstract

PURPOSE:To provide a method and an apparatus for desulfurization of an exhaust gas wherein the exhaust gas flow is equalized in an absorption tower without producing a large increase in pressure loss and desulfurization performance is improved. CONSTITUTION:An exhaust gas flow path being located on the downstream of an exhaust gas inlet 3 provided on the side wall of an absorption tower 1 and on the upstream region of a gas absorption part 10 is divided into a number of small flow paths 26 by means of flow path dividing members 21 and an auxiliary nozzle 24 is provided on each of these small flow paths and an absorption liq. is fed into the auxiliary nozzle 24 through an auxiliary nozzle pipe 22 being branched from an absorption liq. circulation system and a flow adjusting valve 23 and is sprayed. The exhaust gas flow rate passing through each small flow path is adjusted and equalized by adjusting the amt. of spray and the flow rate distribution of the exhaust gas flowing in the absorption part 10 is equalized. It is possible thereby to prevent the exhaust gas flow from being biased in the absorption part 10 in the absorption tower without increasing pressure loss caused by passing of the exhaust gas and to improve desulfurization performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet exhaust gas desulfurization method and apparatus, and more particularly to a wet exhaust gas desulfurization method and apparatus equipped with a gas absorption tower capable of preventing uneven flow of exhaust gas with low pressure loss.

[0002]

2. Description of the Related Art Exhaust gas discharged from a device for burning a fuel containing sulfur such as a boiler or a heating furnace contains harmful sulfur oxides. At present, as a general apparatus for removing sulfur oxides in exhaust gas, there is a wet exhaust gas desulfurization apparatus. An example of a conventional wet exhaust gas desulfurization apparatus is shown in FIG. The gas absorption tower 1 has a gas absorption section 10 therein, and the exhaust gas 16 containing the sulfur oxides flowing from the exhaust gas inlet 3 is
Sulfur oxides are removed while passing through the gas absorption unit 10, and the purified gas 17 is discharged from the exhaust gas outlet 4. The lower part of the gas absorption tower 1 is an absorption liquid storage tank 2 having a stirrer 15 and an air injection pipe 13, and is made of a mixture of an absorbent such as limestone or slaked lime and an absorption product such as gypsum or calcium sulfite. The absorbing liquid 12 in the form of a slurry is stored. While the absorbing liquid 12 is guided to the gas absorbing portion 10 by the absorbing liquid circulation system including the absorbing liquid withdrawing pipe 5, the pump 6, the nozzle pipe 34, the nozzle 35, etc., the absorbing liquid 12 is sprayed from the nozzle 35 and drops as the droplet 11. First, the sulfur oxides in the exhaust gas 16 are absorbed and removed. Air is blown into the absorbent storage tank 2 as an oxidant from an air injection pipe 13 in order to convert calcium sulfite, which is an absorption product, into gypsum. Further, a part of the absorbing liquid 12 is sent from the circulation system to the dehydration line 9 to separate gypsum. Further, a stirrer 15 is provided near the air inlet of the air injection pipe 13 in the absorbent storage tank.

[0003]

The exhaust gas inlet 3 is usually provided on the side wall of the absorption tower 1 located above the liquid surface of the absorbent storage tank 2. Therefore, the exhaust gas changes its flow direction from the exhaust gas inlet 3 to the gas absorption section 10 in the absorption tower, and the gas flow rate distribution of the gas absorption section 10 is significantly biased as shown in FIGS. 11 and 12. It becomes a thing. Normally, the flow rate on the wall surface side of the absorption tower facing the exhaust gas inlet 3 is large, and backflow may occur near the wall surface on the exhaust gas inlet side. Since the spray flow rate of the absorbing liquid is determined according to the exhaust gas flow rate and the sulfur oxide concentration in the exhaust gas, the deviation of the process gas flow rate as described above may be caused by the deterioration of the absorption performance in the absorption tower, that is, the desulfurization performance, or the spray flow rate. This will be accompanied by an increase in equipment costs such as pumps and operating costs associated with the increase in

As a conventional technique for preventing such a situation,
As shown in FIG. 13, there is one in which a perforated plate 20 is arranged in a portion located downstream of the exhaust gas inlet 3 and upstream of the gas absorption portion 10 when viewed from the average flow direction of the exhaust gas. However, in order to prevent the uneven flow of exhaust gas by the perforated plate 20, the aperture ratio of the perforated plate 20 is inevitably decreased, which inevitably causes a large increase in pressure loss. An increase in pressure loss leads to an increase in equipment cost and operating cost. Further, the absorbing liquid 12 sprayed from the nozzle 35
There is a case in which a part of the gas stays on the perforated plate 20 in an unbalanced manner, which promotes uneven flow of the exhaust gas. Further, the staying place may move irregularly, and the exhaust gas flow will be accompanied by irregular fluctuations. As described above, the conventional technique cannot sufficiently prevent the drift of the exhaust gas in the absorption tower.

An object of the present invention is to provide a wet exhaust gas desulfurization method and apparatus capable of improving the desulfurization performance by equalizing the flow of exhaust gas in the absorption tower without causing a large increase in pressure loss. is there.

[0006]

In order to achieve the above object, a first invention of the present application is to introduce exhaust gas from an inlet provided on a side wall of an absorption tower and guide the introduced exhaust gas to an absorption section in the absorption tower, Absorbing liquid is sprayed on this to bring it into gas-liquid contact to absorb the sulfur oxides in the exhaust gas into the absorbing liquid, and the treated exhaust gas is discharged from the absorption tower discharge port, and the absorbing liquid is collected in a storage tank and collected. In the wet exhaust gas desulfurization method in which the absorbed liquid is recirculated and sprayed to the absorption part, a plurality of small flow paths are formed in the absorption tower exhaust gas passage downstream of the exhaust gas inlet and upstream of the absorption part by a dividing member. The present invention relates to a wet exhaust gas desulfurization method characterized in that the exhaust gas is divided into two parts, the fluid is sprayed in each small channel, and the flow rate of the exhaust gas in the small channel is adjusted by adjusting the flow rate of the sprayed fluid. .

A second aspect of the present invention is an absorption tower having an exhaust gas inlet and an exhaust port, which has an absorption section for spraying an absorbing liquid to the exhaust gas introduced through the inlet to absorb and remove sulfur oxides in the exhaust gas. An absorption liquid storage tank provided inside or outside the absorption tower for collecting and storing the absorption liquid sprayed in the absorption section,
In a wet exhaust gas desulfurization apparatus having an absorbent circulation system that recirculates the absorbent in a storage tank to the absorption section, in the absorption tower exhaust gas passage downstream of the exhaust gas introduction port in the absorption tower and upstream of the absorption section. The present invention relates to a wet exhaust gas desulfurization device, characterized in that a member for dividing the fuel cell into a plurality of small channels and an auxiliary nozzle for spraying a fluid are provided in the divided small channels.

[0008]

According to the present invention, the exhaust gas flow flowing in the divided small flow passages is dragged by the liquid droplets sprayed from the auxiliary nozzle 24 so as to substantially face the gas flow, as shown in FIG. , Its rapid flow is hindered. The droplet immediately after being sprayed from the auxiliary nozzle 24 has a high speed and a large momentum, so that the exhaust gas is caused to flow in the same direction as the droplet, and a swirl region is usually generated in the vicinity of the auxiliary nozzle 24.
The magnitude of the flow inhibition is closely related to the momentum of the spray flow, that is, the flow rate and the flow velocity. By changing the spray flow rate from the auxiliary nozzle 24, it is possible to change the flow rate of the exhaust gas flowing through each small flow path 26. it can. In other words, by controlling the spray flow rate of the auxiliary nozzle in the small flow path, the exhaust gas flow rate distribution in the cross section of the absorption tower can be equalized and uneven flow can be prevented. Such an operation is performed by the auxiliary nozzle 2 in the small flow path 26.
It is possible to surely happen by arranging 4. The wall surface of the small flow path 26 has a role of stably holding the vortex flow region 31 near the auxiliary nozzle 24, and when there is no wall surface, the vortex flows of the adjacent auxiliary nozzles 24 interfere with each other and are extremely unstable. It becomes a flow, and the function of preventing drift is greatly reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. A wet exhaust gas desulfurization apparatus according to the present invention is shown in FIGS. The absorption tower 1 of the present embodiment is a vertical type, has a gas absorption part 10 inside thereof, and has a bottom part serving as an absorption liquid storage tank 2.
The exhaust gas inlet 3 is arranged on the side wall of the absorption tower so as to be located above the liquid surface of the absorbing liquid in the absorbing liquid storage tank 2. A main nozzle 8 is arranged above the gas absorbing section 10, and an absorbing liquid 12 is sprayed from an absorbing liquid circulation system including an absorbing liquid withdrawing pipe 5, a pump 6, a main nozzle pipe 7 and the like to form droplets 11 into gas. The absorber 10 is dropped. The exhaust gas outlet 4 is provided above the main nozzle 8, that is, downstream from the flow of the exhaust gas. At a position downstream of the exhaust gas inlet 3 and upstream of the gas absorption unit 10,
A flow path dividing member 21 for dividing the absorption tower flow path cross section into a plurality of small flow paths 26 is arranged, and an auxiliary nozzle 24 is arranged in the small flow path 26. The absorption liquid is supplied to each auxiliary nozzle 24 from the absorption liquid circulation system through auxiliary nozzle pipes 22 (a plurality of lines) and a flow rate adjusting valve 23 for adjusting the amount of spray liquid. Small channel 26
For example, as shown in FIG. 4, it is configured by assembling flat or corrugated flow path dividing members 21a and 21b in a lattice shape. The distance L of the small flow path 26 in the exhaust gas flow direction is preferably about 3 times or more the hydraulic diameter of the small flow path 26 (4 × small flow path cross-sectional area ÷ small flow path perimeter). The flow rate adjustment amount 23 may be obtained by dividing the plurality of auxiliary nozzles 24 into several blocks and disposing one in each block. The cross section of the absorption tower channel is divided into a plurality of small channels downstream of the exhaust gas inlet 3, and the auxiliary nozzles 2 are provided in the respective small channels.
4 may be arranged and a flow rate adjusting valve may be provided for each auxiliary nozzle 24. However, even if it is not so far, if the flow rate of the auxiliary nozzle 24 is adjusted so that there is no significant deviation when installing the device, The flow rate adjusting valve can be omitted.

The present invention has such a structure and operates as follows. The exhaust gas flow containing the sulfur oxides introduced from the exhaust gas inlet 3 flows into the small flow path 26 having the auxiliary nozzle 24 according to the present invention while being significantly biased as described above due to the abrupt change in the flow direction. From each auxiliary nozzle 24, a droplet of the absorbing liquid 12 is sprayed. That is, a large amount of droplets are sprayed on the small flow path 26 with a large exhaust gas flow rate, and a small amount of droplets are sprayed on the small flow path 26 with a small exhaust gas flow rate. As shown in FIG. 6, the exhaust gas flow flowing in the small flow path 26 is dragged by the liquid droplets, and its rapid flow is obstructed. The degree of flow inhibition is closely related to the momentum of the spray flow, that is, the flow rate and the flow velocity, and the flow rate of the spray from the auxiliary nozzle 24 is changed by the flow rate adjusting valve 23 so that the flow rate of the exhaust gas flowing through each small flow path 26 is equalized. Turn into This makes it possible to equalize the cross-sectional flow rate distribution of the exhaust gas flowing into the gas absorption unit 10, so that a high absorption performance, that is, a high desulfurization rate can be obtained.

The liquid sprayed from the auxiliary nozzle 24 is not limited to the absorbing liquid, and may be water that also serves as a cooling and dust removing agent. Since absorption occurs, the amount of absorbing liquid supplied to the main nozzle 8 can be reduced, the gas absorbing portion 10 can be reduced, that is, the height of the absorption tower can be shortened, and the effect peculiar to the embodiment can be achieved.

The arrangement of the flow path dividing members forming the small flow paths 26 is not limited to the grid shape, and as shown in FIG. 5, the flow path dividing members are divided only in one direction where the deviation of the exhaust gas flow rate distribution in the cross section of the absorption tower is large. May be. Since the structure of this embodiment is simplified,
This will lead to lower equipment costs. The auxiliary nozzle pipe group does not have to be arranged in the same stage, and may be divided into a plurality of stages as shown in FIG. 7. Here, if the split auxiliary nozzle pipe 22a of one stage and the split auxiliary nozzle pipe 22b of the other stage are arranged so as to be substantially orthogonal to each other, the flow rate adjusting valve 23
The exhaust gas flow rate distribution can be adjusted more finely with a and 23b.

As shown in FIG. 8, a flat plate or corrugated flow path dividing member 28a is arranged in a comb shape in the cross section of the absorption tower flow path, and the flow path dividing member 28a is arranged substantially upstream or downstream thereof in the arrangement direction. The small channels 26 may be formed by arranging the channel dividing members 28b in a comb shape so as to be orthogonal to each other. In this embodiment, the assembly of the flow path dividing member and the mounting process of the auxiliary nozzle are facilitated. The flow path dividing member is not limited to a flat plate shape, and as shown in FIG. 9, the small flow path 26 can be configured by using a plurality of tubular members 33, which simplifies the assembly of the flow path dividing member. To be done.
In addition, although the example in which the absorbent storage tank is installed at the bottom of the absorption tower is shown in the above-mentioned embodiment, the absorbent storage tank may be installed outside the absorption tower in the present invention.

[0014]

INDUSTRIAL APPLICABILITY The present invention is a method of directly changing the flow of exhaust gas by the movement of droplets, rather than the prevention of uneven flow utilizing pressure drop due to a structure such as a perforated plate. In comparison, it is possible to prevent the exhaust gas from drifting in the absorption tower very efficiently, that is, with a low pressure loss, and prevent the desulfurization performance from decreasing.

[Brief description of drawings]

FIG. 1 is an embodiment diagram of a wet exhaust gas desulfurization apparatus according to the present invention.

FIG. 2 is a sectional view taken along the line AA ′ of FIG.

FIG. 3 is a sectional view taken along line BB ′ of FIG.

FIG. 4 is a diagram showing an embodiment of a flow path dividing member according to the present invention.

FIG. 5 is a diagram of another embodiment of the flow path dividing member according to the present invention.

FIG. 6 is a diagram illustrating a flow of exhaust gas in a small flow path according to the present invention.

[FIG. 7]

FIG. 8

FIG. 9 is a diagram showing another embodiment of the present invention.

FIG. 10 is a diagram showing a conventional wet exhaust gas desulfurization device.

FIG. 11 is a diagram illustrating a flow of exhaust gas in a conventional wet exhaust gas desulfurization apparatus absorption tower.

FIG. 12 is a diagram showing a velocity distribution in a CC ′ cross section of FIG. 11.

FIG. 13 is a diagram showing another example of a conventional wet exhaust gas desulfurization device.

[Explanation of symbols]

1 ... Absorption tower, 2 ... Absorption liquid storage tank, 3 ... Exhaust gas inlet, 4 ...
Exhaust gas outlet, 5 ... Absorbing liquid extraction pipe, 6 ... Pump, 7 ...
Main nozzle piping, 8 ... Main nozzle, 10 ... Gas absorption section, 11
... Droplets, 12 ... Absorption liquid, 13 ... Air injection pipe, 14 ... Bubbles, 15 ... Stirrer, 16 ... Exhaust gas, 17 ... Purification nozzle,
21, 21a, 21b ... Flow path dividing members, 22, 22a,
22b ... Auxiliary nozzle piping, 23, 23a, 23b ... Flow control valve, 24 ... Auxiliary nozzle, 26 ... Small flow path.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigehito Takamoto 3 36 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Ltd. Kure Research Institute (72) Hirofumi Yoshikawa 3 36 36 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Stock Company Kure Research Institute (72) Inventor Shigeru Nozawa 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Ltd. Kure Factory

Claims (2)

[Claims] 1. Sulfur oxides in exhaust gas introduced by introducing exhaust gas from an inlet provided on the side wall of the absorption tower, guiding the introduced exhaust gas to an absorption section in the absorption tower, spraying the absorption liquid on the absorption part, and making gas-liquid contact therewith. In the absorption liquid, the treated exhaust gas is discharged from the absorption tower discharge port, the absorption liquid is collected in a storage tank, and the collected absorption liquid is recirculated to the absorption part and sprayed to obtain a wet exhaust gas desulfurization method. In the downstream of the exhaust gas inlet, and the exhaust gas passage in the absorption tower in the upstream region from the absorption part is divided into a plurality of small channels by a dividing member to divide the exhaust gas, and the fluid is in each small channel. A wet exhaust gas desulfurization method characterized in that the flow rate of exhaust gas in a small flow path is adjusted by spraying and adjusting the flow rate of the sprayed fluid. 2. An absorption tower having an exhaust gas introduction port and an exhaust port, the absorption tower having an absorption unit for absorbing and removing sulfur oxides in the exhaust gas by spraying an absorption liquid on the exhaust gas introduced from the introduction port, and the absorption unit. A wet type including an absorption liquid storage tank provided inside or outside the absorption tower for collecting and storing the sprayed absorption liquid, and an absorption liquid circulation system for recirculating the absorption liquid in the storage tank to the absorption unit. In the exhaust gas desulfurization device, a member that divides the exhaust gas passage in the absorption tower into a plurality of small flow paths downstream of the exhaust gas introduction port in the absorption tower and upstream of the absorption section, and a fluid is sprayed into the divided small flow paths. A wet exhaust gas desulfurization apparatus, which is provided with an auxiliary nozzle for