JPH0957055A - High-performance horizontal flow-type stack gas desulfurizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the high-performance desulfurizer made compact without increasing the running cost and low in equipment cost and construction cost. SOLUTION: Plural gas flowing plates 13 each having almost the same width as the widthwise length of a gas passage in an absorption tower and having a height shorter than the length of the gas passage in the height direction are set on the downstream side of a spary part orthogonally to the gas flow in plural stages. Consequently, the droplet of a liq. absorbent is collected with the flowing plate 13 to form a liq. film on the plate 13 and divided by the kinetic energy of a waste gas, the inside of the liq. is violently mixed, and the SO2 absorption rate is increased. The divided droplet is collided again with the flowing plate 13 on the downstream side without absorbing SO2 , the SO2 absorption on the plate surface and the SO2 absorption when the droplet flows down from the plate 13 and is divided are repeated, and the droplet flows down gradually onto the tower bottom. The utilization rate of the absorbent is increased, and hence the desulfurization performance is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet flue gas desulfurization apparatus for removing sulfur dioxide (SO ₂ ) in boiler exhaust gas, and in particular, in a horizontal flow type absorption tower with an increased gas flow velocity, a sprayed absorption apparatus is used. The present invention relates to a wet flue gas desulfurization device capable of improving desulfurization performance by effectively utilizing a liquid, reducing the amount of scattered mist at the outlet of an absorption tower, and further significantly reducing operating costs.

[0002]

2. Description of the Related Art Sulfur oxides in flue gas generated by combustion of fossil fuels in thermal power plants, etc., especially S
O ₂ is one of the main causes of environmental problems such as air pollution and acid rain, and in recent years, the spread of flue gas desulfurization devices has been desired on a global scale.

The main current desulfurization system is a wet method based on the limestone-one-gypsum method, and the spray method, which has the most achievement and has the highest reliability, is widely adopted all over the world. This spray type wet flue gas desulfurization device has high desulfurization performance,
It is technically well established.

FIG. 3 shows an example of a horizontal type wet flue gas desulfurization apparatus in which the direction of the exhaust gas flow is not vertical according to the conventional spray method. This desulfurization apparatus mainly comprises an absorption tower body 1, an inlet duct 2, an outlet duct 3, a spray nozzle 4, an absorbing liquid circulation pump 5, a circulation tank 6, a stirrer 7, an air blowing pipe 8, a mist eliminator 9 and the like. To be done. A plurality of spray nozzles 4 are installed in a direction substantially orthogonal to the gas flow, and a plurality of spray nozzles 4 are installed in the gas flow direction. Further, the agitator 7 and the air blowing pipe 8 are installed in the circulation tank 6 in the lower part of the absorption tower main body 1 where the absorbing liquid stays, and the mist eliminator 9 is installed in the outlet duct 3.

Exhaust gas discharged from a boiler (not shown) is introduced into the absorber main body 1 from the inlet duct 2 and discharged from the outlet duct 3 by a desulfurization fan (not shown). During this time, the absorption liquid containing calcium carbonate sent from the absorption liquid circulation pump 5 is sprayed from the plurality of spray nozzles 4 to the absorption tower body 1, and the absorption liquid and the exhaust gas are brought into gas-liquid contact. At this time, the absorbing liquid selectively absorbs SO ₂ in the exhaust gas and forms calcium sulfite. The absorbing solution that has generated calcium sulfite is temporarily stored in the circulation tank 6, and while being stirred by the oxidizing stirrer 7, the calcium sulfite in the absorbing solution is oxidized by the oxygen in the air supplied from the air blowing pipe 8, and calcium sulfate is added. Produces (gypsum). Circulation tank 6 in which calcium carbonate and gypsum coexist
A part of the absorbing liquid therein is sent again to the spray nozzle 4 by the absorbing liquid circulating pump 5, and a part is sent from the absorbing liquid extracting pipe 10 to a waste liquid treating / gypsum collecting system (not shown).
Further, of the absorbing liquid sprayed from the spray nozzle 4 and atomized, those having a small droplet diameter are entrained in the exhaust gas, but are recovered by the mist eliminator 9 provided in the outlet duct 3.

However, since the current wet flue gas desulfurization equipment is expensive, its penetration rate in developing countries is still low. Therefore, in order to increase the penetration rate of desulfurization equipment worldwide, it is important to significantly reduce the equipment cost and operating cost of the desulfurization equipment. As a concrete means for reducing the cost, as shown in FIG. 3, an absorption tower (hereinafter referred to as a horizontal flow type absorption tower) in which the absorbing liquid is sprayed by a part of a duct through which the exhaust gas flows in a non-vertical direction can be considered. . Since the horizontal flow type absorption tower is low in height and compact, the facility cost can be significantly reduced, but it is difficult to expect high desulfurization performance. The possible causes are as follows.

As shown in FIG. 4, when the absorbing liquid is sprayed in the direction counter to the gas flow, that is, in the counterflow direction, the absorbing liquid immediately after being ejected from the spray nozzle 4 has a large inertial force, and therefore the relative velocity with the gas. Keeps a high value and the mixing state inside the droplets is good, but the inertia of the droplets gradually weakens and they become entrained in the gas flow. If it is entrained in the gas flow, the contact time with the gas becomes longer, but the relative velocity sharply decreases, so that the mixing inside the droplets deteriorates and the SO ₂ absorption performance significantly decreases. Especially when the SO ₂ concentration of the exhaust gas is high, this tendency is remarkable, and it becomes more difficult to improve the performance. However, if the amount of spray per unit gas, that is, the liquid gas ratio is increased, the desulfurization performance can be easily improved, but problems such as an increase in pressure loss in the spray portion and an increase in the amount of scattered mist occur.

[0008]

In the above-mentioned prior art, no consideration is given to improving the performance of a horizontal flow type wet desulfurization apparatus. In order to obtain high desulfurization performance with the conventional horizontal flow type absorption tower structure and gas-liquid contact method, it is necessary to increase the liquid circulation ratio of the absorbing liquid to increase the liquid-gas ratio. There has been a problem that the operating cost is increased due to the increase in the amount of the pump and the power of the fan as the volume increases.

An object of the present invention is to obtain a desulfurization device having a high desulfurization performance which is compact without increasing the operating cost, has a low equipment cost and a low construction cost.

[0010]

The above object of the present invention can be achieved by the following means. That is, by contacting the absorbing liquid ejected from a plurality of spray nozzles and the exhaust gas discharged from the combustion device such as a boiler, the absorption tower in which the exhaust gas flows in a direction other than the vertical direction for processing the sulfur oxides in the exhaust gas. In a horizontal flow type flue gas desulfurization device equipped with, inside the absorption tower, having a width almost the same as the width direction length of the gas passage in the absorption tower, the length direction in the height direction of the gas passage in the absorption tower. It is a flue gas desulfurization device in which a plurality of liquid flow down plates having a height shorter than the height are installed in a direction orthogonal to the gas flow and in a plurality of stages in the gas flow direction so as not to block the gas flow.

The liquid flow-down plate of the present invention is positioned in the gas flow direction so that the position of the side end near the gas flow downstream is higher than that of the side end near the gas flow upstream. It is preferable that the liquid flow lower plate is inclined and a weir is provided at a side end portion of the liquid flow lower plate near the downstream side of the gas flow. Further, it is preferable to install the liquid flow-down plate on the downstream side of the position of the spray nozzle.

According to the present invention, the absorption liquid immediately after being ejected from the spray nozzle has a high SO ₂ absorption speed because the mixing inside the droplets is vigorous and the relative speed with the gas is high.
When the inertia of the droplet is weakened and the droplet is entrained in the gas flow, the relative velocity decreases, the mixing state inside the droplet deteriorates, and the SO ₂ absorption rate rapidly decreases. This tendency becomes more remarkable when the SO ₂ concentration is high.

However, in the present invention, the width of the gas passage in the absorption tower is approximately the same as the width of the gas passage in the downstream side, and is shorter than the length of the gas passage in the absorption tower in the height direction. Since a plurality of liquid lower plates having a height are installed in a direction orthogonal to the gas flow and a plurality of stages in the gas flow direction so as not to block the gas flow, the liquid of the absorbing liquid whose SO ₂ absorption performance has begun to deteriorate. The droplets collide with the liquid flow lower plate and form a liquid film on the surface of the liquid flow lower plate.
When flowing down on the liquid flow plate, it is split by the kinetic energy of the exhaust gas. Similar to the spray nozzle, when the liquid is split, the inside of the liquid is vigorously mixed, so that the SO ₂ absorption rate becomes high. Split droplets collide again with another liquid flows down plate downstream while absorbing SO _2, and SO ₂ absorption in the above-mentioned liquid flows down plate surface, and flows down from the liquid flow down plate, S when dividing
While repeating O ₂ absorption, it gradually flows down to the bottom of the column. Therefore, the desulfurization performance is improved by improving the utilization rate of the absorbent. Further, since the scattered mist is also collected by this liquid flow-down plate, it can contribute to the reduction of the amount of scattered mist at the tower outlet.

Further, the liquid flow lower plate is inclined with respect to the gas flow direction so that the position of the side end of the liquid flow lower plate closer to the gas flow downstream side is higher than the position of the side end of the liquid flow lower plate closer to the gas flow upstream side. Then, when a weir is provided at the side end portion of the liquid flow lower plate near the gas flow downstream side, the absorbing liquid that collides with the liquid flow lower plate and forms a liquid film on the surface of the liquid flow lower plate accompanies the gas flow. Ascend the flow board,
Attempts to overflow from the downstream end, but since the liquid flow lower plate has a weir at the downstream end, the liquid is blocked here,
It will flow down from the upstream end on the opposite side. At this time, a strong shearing force is generated on the surface of the liquid film, and the liquid film flows down toward the upstream end while wavy, so that the SO ₂ absorption rate is increased and the utilization rate of the absorption liquid is further improved.

[0015]

1 shows a horizontal flow type flue gas desulfurization apparatus according to an embodiment of the present invention. Similar to the conventional desulfurization apparatus shown in FIG. 3, the absorption tower body 1, the inlet duct 2, the outlet duct 3, the spray nozzle 4, the circulation pump 5, the circulation tank 6,
Although it is composed of a stirrer 7, an air blowing pipe 8, a mist eliminator 9, etc., the spray nozzle 4 is not installed in the tower, but a nozzle box 12 is installed on the wall surface of the tower and is installed therein. Further, in the embodiment according to the present invention, a plurality of liquid flow lower plates 13 having a width substantially the same as the width of the inside of the absorption tower body 1 are provided downstream of the spray portion to which the spray nozzle 4 is attached in a direction orthogonal to the gas flow, Install multiple stages in the direction.

Then, as shown in FIG.
Inclining the liquid flow down plate 13 so that the position of the end closer to the gas outlet duct 3 is higher than the end closer to the inlet duct 2 of
A weir 16 is provided at the end of the liquid flow-down plate 13 near the outlet duct 3. Therefore, the spray droplets 14 whose SO ₂ absorption performance has started to deteriorate collide with the liquid flow lower plate 13 and form a liquid film on the surface of the liquid flow lower plate 13. The liquid film is entrained by the gas, and the liquid flow-down plate 13
To overflow from the downstream end, but since the liquid flow down plate 13 has a weir 16 at the downstream end, the liquid is dammed here by the weir 16 and flows down from the upstream end on the opposite side. Will be done. At this time, a strong shearing force is generated on the surface of the liquid film, and the liquid flows down toward the upstream end while wavy, so that the absorbing liquid is sufficiently mixed and the SO ₂ absorption speed on the surface of the liquid film is increased. Further, when the absorbing liquid overflows from the upstream end of the liquid flow-down plate 13 and flows down, it is split by the kinetic energy of the exhaust gas. Similar to the spray nozzle, when the liquid is split, the inside of the liquid is vigorously mixed, so that the SO ₂ absorption rate becomes high. SO when split droplets collide again on the downstream side of the liquid flows down plate 13 while absorbing SO _2, and SO ₂ absorption in the above-mentioned liquid flows down plate 13 surface, to divide flows down from the liquid flow down plate 13 ₂ Gradually flow down to the bottom of the tower while repeating absorption.

Therefore, the desulfurization performance can be improved by increasing the utilization ratio of the absorbing liquid without increasing the liquid-gas ratio. In addition, the scattered mist is also the liquid flow down plate 13
The amount of scattered mist at the tower outlet is also reduced because it is collected at.

In the embodiment shown in FIG. 1, the spray nozzle 4
Is not installed in the tower, but is installed in the nozzle bock 12 on the wall surface of the tower, and is installed therein. However, as in the prior art of FIG.
1 is arranged as shown in FIG. 1, an effect substantially similar to that of the embodiment shown in FIG. 1 can be obtained.

As described above, according to the present invention, the liquid flow lowering plate is installed in the spray portion, and the absorbing liquid whose SO ₂ absorption performance has started to deteriorate is collided with the liquid flow lowering plate to thereby make the liquid flow lowering plate. The absorbing liquid is sufficiently mixed on the surface of the plate, absorbs SO ₂ while flowing down on the plate surface, overflows from the liquid lower plate, and absorbs SO ₂ again when atomizing, so the following excellent effects are obtained. Obtainable.

A) The utilization rate of the absorbing liquid is improved, and high desulfurization performance can be obtained with a low liquid-gas ratio. b) Since the liquid is collected by the liquid flow-down plate, the amount of scattered mist can be reduced. c) By reducing the liquid-gas ratio, the pressure loss in the absorption section can be reduced. d) Since the horizontal flow type absorption tower can achieve high performance, the desulfurization equipment becomes very compact, and the equipment cost and construction cost can be significantly reduced. e) With the reduction of the liquid gas ratio, it becomes possible to reduce the power of the absorption liquid circulation pump. f) The power of the desulfurization fan can be reduced as the pressure loss is reduced. As described above, the facility cost, construction cost, and operating cost of the flue gas desulfurization device can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a wet flue gas desulfurization apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a state of absorbing liquid in the vicinity of the liquid flow-down plate of FIG.

FIG. 3 is a schematic cross-sectional view of a conventional horizontal flow type wet desulfurization apparatus.

FIG. 4 is a diagram showing a relationship between a track of droplets and a relative velocity in a horizontal flow type absorption tower of a conventional technique.

[Explanation of symbols]

1 absorption tower main body 2 inlet duct 3 outlet duct 4 spray nozzle 5 circulation pump 6 circulation tank 7 stirrer 8 air blowing pipe 9 mist eliminator 10 absorbing liquid discharge pipe 12 nozzle box 13 liquid lower plate 16 weir

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hirofumi Yoshikawa 3-36 Takaracho, Kure City, Hiroshima Prefecture Babcock-Hitachi Co., Ltd., Kure Research Institute (72) Atsushi Shigemi 6-9 Takaramachi, Kure City, Hiroshima Prefecture Babcock-Hitachi Kure Factory Co., Ltd.

Claims (3)

[Claims] 1. The exhaust gas flows in a non-vertical direction for treating sulfur oxides in the exhaust gas by bringing the absorbing liquid ejected from a plurality of spray nozzles into contact with the exhaust gas discharged from a combustion device such as a boiler. In a horizontal flow type flue gas desulfurization device equipped with an absorption tower, the width of the gas flow path inside the absorption tower is approximately the same as the width of the gas flow path inside the absorption tower, and the height of the gas flow path inside the absorption tower is high. High-performance horizontal flow type characterized by installing a plurality of liquid flow lower plates having a height shorter than the length of the direction in the direction orthogonal to the gas flow and in multiple stages in the gas flow direction so as not to block the gas flow. Flue gas desulfurization equipment. 2. The liquid flow lower plate is inclined with respect to the gas flow direction so that the position of the side end of the liquid flow lower plate closer to the gas flow downstream side is higher than the position of the side end of the liquid flow lower plate closer to the gas flow upstream side. Let
The high-performance horizontal flow type flue gas desulfurization apparatus according to claim 1, wherein a weir is provided at a side end portion of the liquid flow-down plate near the gas flow downstream side. 3. The high-performance horizontal flow type flue gas desulfurization apparatus according to claim 2, wherein the liquid flow-down plate is installed on the downstream side of the position of the spray nozzle.