JP2012239922A - Seawater flue gas desulfurization apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aeration apparatus and a seawater flue gas desulfurization apparatus having the same where oxidation reaction is accelerated and good processing is achieved.SOLUTION: The seawater flue gas desulfurization apparatus include: a flue gas desulfurization absorption tower 102 which allows exhaust gas 101 and seawater 103 to be in gas-liquid contact to desulfurize SOinto sulfurous acid (HSO); a dilution mixing tank 105 which is disposed under the flue gas desulfurization absorption tower 102 and which dilutes and mixes used seawater 103A containing sulfur with diluting seawater 103; and an oxidation tank 106 having the aeration apparatus 120 which is disposed downstream of the diluting-mixing tank 105 to carry out water quality recovery of diluted and used seawater 103B. In the seawater flue gas desulfurization apparatus, microbubble 151 is supplied by a microbubble generator 150 to the seawater 103 which is supplied to the flue gas desulfurization absorption tower 102.

Description

  The present invention relates to wastewater treatment of flue gas desulfurization devices applied to power plants such as coal-fired, crude oil-fired, and heavy oil-fired, and more particularly, wastewater of exhaust gas desulfurization devices that use the seawater method (used seawater). The present invention relates to a seawater flue gas desulfurization apparatus provided with an aeration apparatus for decarbonating (aeration) by aeration.

Conventionally, in a power plant using coal, crude oil or the like as fuel, combustion exhaust gas (hereinafter referred to as “gas”) discharged from a boiler is sulfur such as sulfur dioxide (SO ₂ ) contained in the exhaust gas. The oxide (SOx) is removed and then released to the atmosphere. As a desulfurization method of a flue gas desulfurization apparatus that performs such a desulfurization treatment, a limestone gypsum method, a spray dryer method, a seawater method, and the like are known.

Among these, the flue gas desulfurization apparatus (hereinafter referred to as “seawater flue gas desulfurization apparatus”) employing the seawater method is a desulfurization system that uses seawater as an absorbent. In this system, for example, by supplying seawater and boiler exhaust gas into a desulfurization tower (absorption tower) having a cylindrical shape such as a substantially cylindrical shape, a wet-based gas-liquid contact is generated using seawater as an absorption liquid. To remove sulfur oxides.
The desulfurized seawater (spent seawater) used as an absorbent in the desulfurization tower described above, for example, flows and drains through a long waterway (Seawater Oxidation Treatment System; SOTS) with an open top. The carbon dioxide is decarboxylated (explosion) by aeration that causes microbubbles to flow out from the aeration apparatus installed in the apparatus (patent documents 1 to 3).

JP 2006-055779 A JP 2009-028570 A JP 2009-028572 A

2. Description of the Related Art Conventionally, an aeration nozzle used in an aeration apparatus is one in which a large number of small slits are provided in an air diffuser film made of rubber or the like covering the periphery of a substrate, and is generally called a “diffuser nozzle”.
Such an aeration nozzle causes many micro bubbles (for example, about 1 to 5 mm) of substantially equal size to flow out from the slit due to the pressure of supplied air, but the aeration apparatus has many aeration nozzles on the bottom surface of the apparatus. The shape (water channel shape) is determined mainly by the amount of air generated by the aeration nozzle and the bubble diameter with respect to the predetermined seawater properties after desulfurization.
For this reason, in order to reduce the construction cost and operation cost of the aeration channel, it is essential to reduce the shape of the channel and reduce the amount of air to be supplied.
In addition, when aeration is continuously performed in seawater using such an aeration nozzle, precipitates such as calcium sulfate in seawater are deposited near the slit wall surface of the diffuser membrane and in the vicinity of the slit opening. As a result, the pressure loss of the diffuser membrane increases and the discharge pressure height of the discharge means such as the blower and compressor that supplies air to the diffuser is generated, resulting in the blower and compressor. There is a problem that load is applied.

  In view of the above problems, the present invention provides a seawater flue gas desulfurization apparatus equipped with an aeration apparatus that promotes an oxidation reaction and can perform good processing, and also provides a blower and a compressor for supplying aeration air to a SOTS. The problem is to solve the problem of load increase.

A first invention of the present invention for solving the above-described problem is a flue gas desulfurization absorption tower that makes a gas-liquid contact between exhaust gas and seawater to desulfurize SO ₂ to sulfurous acid (H ₂ SO ₃ ), and flue gas A dilution mixing tank that is provided below the desulfurization absorption tower and dilutes and mixes used seawater containing sulfur with dilution seawater, and is provided downstream of the dilution mixing tank. The seawater flue gas desulfurization apparatus includes an oxidation tank having an aeration apparatus that performs the above and supplies ultrafine bubbles to seawater supplied to the flue gas desulfurization absorption tower using an ultrafine bubble generator.

  A second invention is the seawater flue gas desulfurization apparatus according to the first invention, characterized in that oxygen is supplied to the ultrafine bubble generator and oxygen-containing ultrafine bubbles are supplied.

  A third invention is the seawater flue gas desulfurization apparatus according to the first or second invention, wherein the ultrafine bubbles are either one or both of microbubbles and nanobubbles.

  According to the present invention, by introducing ultrafine bubbles into the seawater supplied to the seawater flue gas desulfurization apparatus, the ultrafine bubbles remain in the diluted used seawater, so that they are installed in the water channel (SOTS). The aeration device can be replaced with a diffuser pipe that generates bubbles to generate convection of seawater, reducing the total amount of air required for the seawater flue gas desulfurization device, simplifying and simplifying the aeration device and aeration nozzle, It is possible to shorten the SOTS water channel length or to omit the SOTS water channel.

FIG. 1 is a schematic view of a seawater flue gas desulfurization apparatus according to the present embodiment. FIG. 2 is a relationship diagram between the bubble diameter and the rising speed.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

An aeration apparatus and a seawater flue gas desulfurization apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a seawater flue gas desulfurization apparatus according to the present embodiment.
As shown in FIG. 1, a seawater flue gas desulfurization apparatus 100 includes a flue gas desulfurization absorption tower 102 that makes a gas-liquid contact between exhaust gas 101 and seawater 103 to desulfurize SO ₂ to sulfurous acid (H ₂ SO ₃ ), A dilution mixing tank 105 is provided below the smoke desulfurization absorption tower 102 to dilute and mix the used seawater 103A containing sulfur with the seawater 103 for dilution, and is provided downstream of the dilution mixing tank 105 for use in dilution. An oxidation tank 106 having an aeration device 120 for performing a water quality recovery process of the finished seawater 103B, and supplying the microbubbles 151 to the seawater 103 supplied to the flue gas desulfurization absorption tower 102 by the microbubble generator 150 It is.

In the seawater flue gas desulfurization apparatus 100, a part of the seawater 103 for absorption in the seawater 103 supplied through the seawater supply line L ₁ in the flue gas desulfurization absorption tower 102 is brought into gas-liquid contact with the exhaust gas 101, thereby SO ₂ in 101 is absorbed by seawater 103. Then, the used seawater 103 </ b> A that has absorbed the sulfur content in the flue gas desulfurization absorption tower 102 is mixed with the seawater 103 for dilution supplied to the dilution mixing tank 105 provided in the lower part of the flue gas desulfurization absorption tower 102. The diluted used seawater 103B mixed and diluted with the dilution seawater 103 is supplied to the oxidation tank 106 provided on the downstream side of the dilution mixing tank 105, and the air 122 supplied from the oxidation air blower 121 is supplied. Is supplied by an aeration nozzle 123 to restore water quality, and then discharged into the sea as drainage 124.
1, reference numeral 102a is a spray nozzle for the liquid pillar jetting seawater 103 upwardly, 120 aeration device, 122a bubbles, L ₁ is seawater supply line, L ₂ is diluted seawater supply line, L ₃ is desulfurized seawater A supply line, L ₄ is an exhaust gas supply line, L ₅ is an air supply line, L ₆ is a discharge line for purified gas 101A, and L ₇ is a discharge line for drainage 124.

  At the time of this oxidation treatment, by supplying ultrafine bubbles 151 from the ultrafine bubble generator 150 to the seawater 103 in advance, ultrafine bubbles remain in the seawater introduced to the diluted used seawater 103B. Then, the oxidation treatment with microbubbles from the aeration apparatus 120 is promoted.

  That is, when microbubbles are introduced into seawater, the diameter of the bubbles is extremely small, so that they are difficult to escape from seawater. Therefore, even after contributing to seawater desulfurization in the flue gas desulfurization absorption tower 102, the microbubbles 151 remain in the diluted used seawater 103B and are transported to the oxidation tank 106. Will contribute to the oxidation treatment in the oxidation tank 106.

  Here, in the present invention, the microbubble 151 refers to a microbubble having a bubble diameter of 10 to several tens of micrometers, or a nanobubble having a diameter of several hundred nm or less. A state in which bubbles having an intermediate size are mixed is called a micro / nano bubble.

FIG. 2 is a relationship diagram between the bubble diameter and the rising speed. FIG. 2 shows the relationship between the bubble diameter and the rising speed when the seawater temperature is 35 ° C., but in the case of normal bubbles (for example, 2.0 mm), the rising speed is about 222 mm / s. is there.
On the other hand, those having a bubble diameter of 0.1 mm or less have an ascending speed of 6.4 mm / s or less, and most of them stay.

  Therefore, most of the microbubbles 151 remain even when the diluted used seawater 103B reaches the oxidation tank 106. Therefore, in the oxidation tank 106, the gas-liquid contact area in the oxidation reaction is wide. It is supposed to be. As a result, the oxidation reaction of the diluted used seawater 103B in the oxidation tank 106 becomes efficient.

  In the present invention, since the aeration nozzle only needs to have a function of convection of seawater by the air lift effect in the oxidation tank 106, an aeration tube such as a jet jet nozzle that does not use an aeration film may be used. .

  According to the present embodiment, since the ultrafine bubbles 151 are supplied to the seawater 103 supplied to the flue gas desulfurization absorption tower 102 by the ultrafine bubble generator 150, the diluted used seawater after contributing to flue gas desulfurization is used. Even in 103B, since the microbubbles 151 remain, the oxidation reaction in the oxidation tank 106 can be promoted.

  As a result, the length of the water channel can be shortened compared with the conventional case where only seawater is used, and the amount of air supply is reduced due to the generation of extremely minute air. The operating cost can be greatly reduced.

  For example, the amount of air supplied (air amount of microbubbles and air of convection bubbles) to a conventional aeration apparatus using a diffuser membrane (as an example, the length of a water channel is 150 m, the width of a water channel is 20 m, and the water depth is 4 m). If the amount) is reduced by 1/2, the width and depth of the water channel are the same as the conventional one, and the length of the water channel is 75 m, which is 1/2 of the length of the conventional water channel. Further, for example, the width and depth of the water channel may be changed in addition to the change of the water channel length so that the construction cost is minimized.

  In addition, oxygen may be further included in the microbubbles 151 to improve the oxidation treatment efficiency.

  As described above, in the present embodiment, seawater has been described as an example of water to be treated. However, the present invention is not limited to this, and can be applied to, for example, an aeration apparatus that performs aeration on contaminated water in a contamination process.

DESCRIPTION OF SYMBOLS 100 Seawater flue gas desulfurization apparatus 102 Flue gas desulfurization absorption tower 103 Seawater 103A Used seawater 103B Diluted used seawater 105 Dilution mixing tank 106 Oxidation tank 120A-120B Aeration apparatus 150 Very small bubble generator 151 Very small bubble

Claims (3)

A flue gas desulfurization absorption tower for desulfurization reaction of SO ₂ to sulfurous acid (H ₂ SO ₃ ) by gas-liquid contact between exhaust gas and seawater;
A dilution mixing tank that is provided below the flue gas desulfurization absorption tower and dilutes and mixes used seawater containing sulfur with seawater for dilution;
An oxidation tank provided on the downstream side of the dilution mixing tank and having an aeration apparatus for performing water quality recovery processing of diluted used seawater,
A seawater flue gas desulfurization apparatus, wherein ultrafine bubbles are supplied to seawater supplied to a flue gas desulfurization absorption tower by an ultrafine bubble generator. In claim 1,
A seawater flue gas desulfurization apparatus, characterized in that oxygen is supplied to the ultrafine bubble generator and oxygen-containing ultrafine bubbles are supplied. In claim 1 or 2,
The seawater flue gas desulfurization apparatus, wherein the ultrafine bubbles are one or both of microbubbles and nanobubbles.

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