JP2005230678A - Exhaust gas treatment apparatus and exhaust gas treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment apparatus that is capable of being loaded on a ship and of efficiently removing toxic substances in a high temperature exhaust gas. <P>SOLUTION: The exhaust gas treatment apparatus has an exhaust gas intake 2a, a dust collecting device 2 to remove the toxic substances in the exhaust gas taken in and discharging means 2b, 6 to discharge the exhaust gas from which the toxic substances have been removed. The dust collecting device 2 is characterized in that a pretreatment device having a number of ceramic filters 10 and a tubular wire gauze 11 accounting for 1-4% of the total number of these ceramic filters 10 arranged therein is connected with a SOx removing device at the downstream side of the pretreatment device, which is provided with an absorption tower 13 to contact an absorption liquid comprised of polyethylene glycol dimethyl ether as a main component, which is able to absorb the SOx in the exhaust gas, with the exhaust gas, an evaporating means 17 to evaporate the SOx in the absorption liquid which has absorbed the SOx sent from the absorption tower 13 and a recovering means of the SOx as H<SB>2</SB>SO<SB>4</SB>by oxidizing the evaporated SOx and causing the SOx to react with water. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust gas treatment apparatus and an exhaust gas treatment method, and more particularly to an exhaust gas treatment apparatus and an exhaust gas treatment method that can be mounted on a ship and the like and can efficiently remove harmful substances such as dust in high-temperature exhaust gas.

  As a method for purifying harmful substances such as NOx, SOx and dust in the exhaust gas by an absorption method, the overall equipment cost is low, the apparatus is also relatively small in installation area, and is often used. Using this method, removal of exhaust gas containing a relatively large amount of organic solvent having a low concentration, removal of high concentration solvent gas (Patent Document 1), and the like are known.

  However, a dry method using a heat-resistant filter is adopted for harmful substances such as dust in the exhaust gas heated to a high temperature. The dry method generally requires a large-scale device, but the removal of harmful substances discharged from ships and the like requires the development of a device that is as compact and efficient as possible. Is difficult to use.

In general, as a fuel for marine engines, in general, poor and inexpensive C heavy oil is often used. In addition, the exhaust gas from the engine may reach a high temperature of about 500 ° C., and it contains many harmful substances and is released into the air as it is. However, from an environmental viewpoint, it is necessary to remove harmful substances contained in such exhaust gas.
JP-A-7-171335

  In order to remove such high-temperature exhaust gas, we considered a hazardous substance removal device with a heat-resistant ceramic filter in the dust collection, but it is prone to clogging due to the presence of soot in the exhaust gas, and maintenance work is required. It was necessary to perform it frequently and the removal efficiency was poor. Moreover, as long as it is installed in a ship, it cannot be a large-scale device, and development of a device that efficiently removes harmful substances in exhaust gas is strongly desired while making the removal device as compact as possible. Yes.

  Therefore, in view of the above-mentioned problems of the prior art, the present inventor has intensively studied and as a result, used a heat-resistant ceramic filter and replaced a part of the ceramic filter with a porous material having air permeability. We have succeeded in developing an exhaust gas treatment device and an exhaust gas treatment method that can remove harmful substances in exhaust gas efficiently and reduce the maintenance frequency with a relatively inexpensive method.

  An object of the present invention is to provide an exhaust gas treatment apparatus and an exhaust gas treatment method that can be mounted on a ship or the like and can efficiently remove harmful substances such as dust in high-temperature exhaust gas.

The above object can be achieved by the invention described in the claims. That is, the characteristic configuration of the exhaust gas treatment apparatus according to the present invention includes an exhaust gas inlet, a dust collector that removes harmful substances in the incorporated exhaust gas, and a discharge means that discharges the exhaust gas from which harmful substances have been removed. The precipitator in which the dust collector is arranged with a large number of ceramic filters and a porous body occupying 1 to 4% of the total number of the ceramic filters, and the downstream side of the pretreatment apparatus In addition, an absorption tower capable of absorbing SOx in the exhaust gas and contacting an absorption liquid mainly composed of polyethylene glycol dimethyl ether with the exhaust gas, and SOx in the absorption liquid sent from the absorption tower and absorbing SOx are evaporated. The SOx removal device having the evaporation means and the means for oxidizing the evaporated SOx and reacting with water to recover it as H ₂ SO ₄ is connected.

  According to this configuration, even if the exhaust gas supply amount per unit time is increased and the processing amount by the dust collector is increased, the pressure applied to the engine exhaust outlet side (hereinafter, back pressure) or The pressure difference between the front and back of the ceramic filter (hereinafter referred to as differential pressure) can be reduced, and dust and other harmful substances in the exhaust gas can be efficiently and reliably removed. Therefore, the overall apparatus configuration can be made compact and the number of maintenance can be reduced. If the number of porous bodies arranged is less than 1% of the total number of ceramic filters, it is difficult to effectively reduce the back pressure, so the number of maintenance can not be reduced reliably. Conversely, the number of porous bodies arranged However, if it exceeds 4% of the total number of ceramic filters, the dust removal effect is not sufficient even if the back pressure can be lowered, which is not preferable. More preferably, the number of disposed porous bodies is 2-3% of the total number of ceramic filters.

Moreover, according to the above-described configuration, SOx in the exhaust gas can be effectively absorbed and removed without requiring particularly large equipment, and not only can it be released into the atmosphere as clean exhaust gas, but also like a ship. Even when there is a strong demand for compactness, it can be applied very effectively and has high practicality. Moreover, the means for recovering the H ₂ SO _4, enables reuse the recovered H ₂ SO _4, it is possible to reduce the running cost of the equipment.

  As a result, it is possible to provide an exhaust gas treatment apparatus that can be efficiently mounted on a high-temperature exhaust gas and can remove harmful substances such as dust in a case where downsizing is required, such as a ship.

  It is preferable that the porous body is formed of a substantially cylindrical wire net having a size of 400 to 800 mesh.

  According to this configuration, harmful substances can be reliably removed efficiently and reliably with a cheaper device configuration.

  The dust collector is preferably provided with an automatic backwash mechanism.

  According to this configuration, when the ceramic filter disposed in the dust collector reaches a predetermined differential pressure, the ceramic filter is automatically cleaned, so that the capacity can be recovered in a short time and the processing efficiency can be increased.

Further, the exhaust gas treatment method according to the present invention is characterized in that the exhaust gas treatment apparatus according to claim 1 is used to remove soot and dust in the exhaust gas, and then the exhaust gas is introduced into an absorption tower so that the SOx in the exhaust gas is removed. The exhaust gas is brought into contact with an absorption liquid containing polyethylene glycol dimethyl ether as a main component, and SOx in the absorption liquid that has absorbed SOx is evaporated by an evaporation means, and the evaporated SOx is oxidized and then reacted with water. And a step of recovering as H ₂ SO ₄ .

  According to this configuration, it is possible to provide an exhaust gas treatment method that can be mounted on a ship or the like and can efficiently remove harmful substances such as dust in high-temperature exhaust gas.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an exhaust gas treatment apparatus according to the present embodiment, and shows a schematic overall structure that mainly performs dust treatment. As this exhaust gas treatment apparatus, an apparatus mounted on a ship is cited as an example.

  In FIG. 1, D is a heavy oil-fired auxiliary engine, and exhaust gas generated therefrom passes through a damper device 1 that can be controlled to open and close, and a total of 100 or more ceramic filters and the total number of these ceramic filters. A porous body occupying 1 to 4% is fed to a dust collector 2 which is a pretreatment means arranged in three upper and lower stages. The ceramic filter and the porous body will be described later.

  Hazardous substances such as dust collected by the dust collector 2 are discharged to the dust collecting can 5 by the screw type unloader 3 via the open / close damper device 4. Further, the dust collector 2 is provided with an automatic backwashing mechanism. That is, a ceramic filter disposed in the dust collector 2 and a compressed air introduction mechanism for cleaning the porous body are attached, and the compressed air is passed through the valve 8 and the ceramic filter and the porous body are appropriately returned. The ceramic filter is fed in the opposite direction to clean the inside of the ceramic filter. Reference numeral 9 is a pulse control box equipped with a differential pressure gauge for controlling the supply of compressed air. For example, when the differential pressure in the dust collector 2 becomes a certain level or higher, the valve 8 is automatically opened to introduce compressed air. However, this operation may be performed manually.

  On the other hand, the exhaust gas from which harmful substances have been removed by the dust collector 2 is discharged to the SOx treatment apparatus shown in FIG. 2 by the blower 6 via the exhaust gas discharge path 2b which is an exhaust gas discharge means. However, when using a fuel with a small amount of SOx emission, it is not always necessary to use this SOx processing apparatus, but it is preferable to use the SOx processing apparatus in order to enhance environmental purification. Reference numeral 7 represents a measurement port for measuring the dust concentration in the exhaust gas.

FIG. 2 shows a schematic overall configuration of an absorption-type SOx processing apparatus. This apparatus absorbs and removes harmful substances such as SOx in the supplied exhaust gas, and an evaporation tower 17 which is an evaporation means for volatilizing an absorption liquid sent from the absorption tower 13 and absorbing SOx. And an oxidation catalyst tank 18 which is a means for oxidizing and recovering the evaporated SOx, a water reaction tank 22 and the like, and high concentration H ₂ SO ₄ is obtained from the water reaction tank 22.

  That is, the exhaust gas is fed into the lower portion of the substantially cylindrical scrubber type absorption tower 13. In the absorption tower 13, the absorption liquid 20 is sprayed by a spray 21 provided in the upper part of the absorption tower. When the absorption liquid 20 wets the absorption tower packing 14 and flows downward, the exhaust gas comes into contact with the liquid film formed on the surface of the absorption tower packing 14 so that SOx in the exhaust gas is absorbed by the absorption liquid. The exhaust gas (process gas) from which SOx has been absorbed and removed is discharged from the top of the absorption tower 13. A mist catcher or an activated carbon packed bed may be provided on the top of the absorption tower 13.

  The absorbing liquid that has absorbed SOx in contact with the exhaust gas is sent to the heat exchanger 15 by the pump P, heated, sprayed from the upper part of the evaporating tower 17, and flows down through the evaporating tower filler layer 23. Evaporated and stored in the lower part of the evaporating tower 17 to form the regenerated absorbent 20. The stored regenerated absorbent is cooled by the cooler 16 and then supplied to the absorption tower 13 by a pump (not shown) or the like.

  When supplying the regenerated absorbent 20 to the absorption tower 13, a flow meter and a supply amount adjusting means may be provided to control the supply amount.

The exhaust gas expelled from the absorbent in the evaporating tower 17 is sent to the oxidation catalyst tank 18. The oxidation catalyst tank 18 includes an oxidation catalyst layer 18a, and SO ₂ contained in the exhaust gas is oxidized to SO ₃ through the oxidation catalyst layer 18a. Further, SO ₃ is sent to the water reaction tank 22 and a small amount of water is sprayed by the spray 21 or the like, and SO ₃ is oxidized to H ₂ SO ₄ . The water reaction tank 22 is provided with a catalyst layer 22a in which SO ₃ is changed to H ₂ SO ₄ to improve efficiency. As the catalyst used in the catalyst layer 22a, activated carbon or the like can be used.

Thereafter, the generated H ₂ SO ₄ is stored and concentrated in the receiving tank 19. The concentrated and recovered H ₂ SO ₄ is recycled because of its high concentration. The remaining gas components in the exhaust gas sent to the receiving tank 19 are exhausted by the exhaust fan 33. But the receiving tank 19 is not necessarily required and may be directly recovered from the water reaction tank 22.

As the oxidation catalyst in the oxidation catalyst tank 18, V ₂ O ₅ or the like can be used, but other oxidation catalysts may be used. In short, as long as SO ₂ can be oxidized to SO ₃ , it is limited to these. is not.

  The absorption liquid 20 brought into contact with the exhaust gas in the absorption tower 13 is an SOx absorption liquid mainly composed of polyethylene glycol dimethyl ether represented by the following chemical formula 1 (for example, trade names sold by Clariant Japan Co., Ltd., Clariant GmbH). Genosolve 1900) is used.

[Chemical 1]
CH ₃ (OCH ₂ CH ₂ ) _n OCH ₃
n = 4-6
By contacting this SOx absorbent with exhaust gas, 90% or more of SO ₂ , SO _{3 and} other SOx components in the exhaust gas can be absorbed and removed.

Various known fillers can be used as the filler filled in the scrubber type absorption tower. In particular, a hollow cylinder having ribs and voids that can pass through the fluid standing upright on both sides of the bowl-shaped flap, and ribs, having a surface area of 75 m ² / m ³ or more and a space ratio of 95% or more. A resin molded product (for example, trade name HI-LEX (manufactured by Toyo Tire & Rubber Co., Ltd.) can be used. In particular, since this filler has a large surface area and a thin film of absorbing liquid is formed on the surface, High removal efficiency can be achieved by combination with an absorbing solution having high absorption efficiency.

  Next, a number of ceramic filters (hereinafter sometimes simply referred to as filters) and porous bodies arranged in the dust collector 2 will be described with reference to FIGS.

  The filter 10 has an opening 10a at one end and has a substantially cylindrical shape with the other end closed. The opening 10a is formed with a gutter 10b for mounting in the dust collector 2. Yes. A large number of these filters 10 are densely arranged in the dust collector 2, and the exhaust gas introduced from the exhaust gas inlet 2a of the dust collector 2 passes through the filter 10 and is collected via the exhaust gas discharge path 2b. It is discharged to the outside of the dust device 2.

  A 400-mesh metal mesh 11 having a substantially cylindrical shape, which is a kind of porous body having substantially the same shape as that of the filter 10, is mixed with a large number of these filters 10 into a punching metal 12 having a cylindrical shape having a diameter of 60 mm and a hole diameter of 1 mm. The external fitting and the number corresponding to 1 to 4% of the total number of the filters 10 are arranged. By the arrangement of the wire mesh 11, an increase in the differential pressure is avoided and dust is also removed. Accordingly, a metal mesh 11 with a small mesh and a large hole diameter is not preferable because the dust removal ability is low, and conversely, if the hole diameter is too fine, the differential pressure increases, which is not preferable. After all, the roughness of the wire mesh 11 is preferably about 400 to 1200 mesh, more preferably 400 to 800 mesh. Although the punching metal 12 is not always necessary, the metal mesh 11 can maintain its function for a long time and can be reinforced because the relatively large diameter dust particles can be removed.

(Example 1)
In the dust collector shown in FIG. 1, a total of 211 cordierite ceramic filters (commercially available) with an inner diameter of about 60 mm and a length of about 1000 mm are arranged in three upper and lower stages, and the ceramic filters arranged in these three upper and lower stages. A 400-mesh metal mesh having a total of two, one, two, and a total of five from the top is arranged at a substantially central position of the above-mentioned by inserting a cylindrical punching metal plate on the inner periphery thereof. An exhaust gas of about 380 ° C. discharged from one auxiliary engine of 800 kW was passed through this dust collector at a flow rate of about 64 m / s and about 3000 m ³ N / h. When the pressure on the dust collector outlet side was measured, it was 0.30 kPa, the increase in the differential pressure was not large, and the frequency required for cleaning was not high. In addition, the dust in the exhaust gas input to the dust collector was about 0.1 g / m ³ N. On the outlet side, the amount of dust was reduced to 0.033 g / m ³ N. If it can be reduced to the above, there is substantially no problem in discharging, and no problem occurs in the processing of the next process.
(Example 2)
Exhaust gas was allowed to flow in the same manner as in Example 1 except that five substantially cylindrical 800 mesh metal nets were attached as the porous body. As a result, when the pressure on the filter outlet side was measured, it was 0.28 kPa, and the amount of dust in the exhaust gas charged into the bag filter was 0.030 g / m ³ N.
(Comparative Example 1)
Similarly to Example 1, 216 filters were arranged in the dust collector, but exhaust gas was allowed to flow without arranging a porous body. As a result, the amount of dust was 0.032 g / m ³ N, but the pressure on the filter outlet side was as high as 0.53 kPa, and clogging was large, which was not preferable.
(Comparative Example 2)
Exhaust gas was allowed to flow in the same manner as in Example 1 except that 10 cylindrical 400-mesh wire meshes of Example 1 were installed in the dust collector. As a result, when the pressure on the filter outlet side was measured, it was 0.28 kPa, but the amount of dust was 0.060 g / m ³ N, which was not sufficient, and the wire mesh surface was darkened, especially with large particles. It was found that dust removal was not sufficient.
(Comparative Example 3)
Exhaust gas was allowed to flow in the same manner as in Example 1 except that five cylindrical 200-mesh wire meshes were installed in the dust collector. As a result, the static pressure on the outlet side of the filter was measured and found to be 0.16 kPa. However, the amount of dust was as high as 0.060 g / m ³ N, which was not sufficient, and the wire mesh surface was darkened. It was found that the removal of large soot was not sufficient.

  The results are summarized in Table 1.

〔別実施の形態〕
（１）集塵装置内に配置されるセラミックフィルターの数は上記した例に限定されるものではなく、装着される船舶などの規模に応じて適宜変更可能である。また、セラミックフィルターのサイズ、仕様なども適宜選択できる。
（２）上記実施形態では、多孔体として略円筒状をした金網とパンチングメタルの組み合わせを用いた例を示したが、金網あるいはパンチングメタルのみから構成されていてもよく、更に、他の耐熱材料で４００〜８００メッシュ金網相当程度の通気性を有している多孔体を使用してもよい。
（３）上記実施形態では、吸収塔において吸収液を上部から散布し、排ガスを下部から充填材層を通過させて吸収塔上部から排出する、いわゆるスクラバー方式のものを例に挙げて説明したが、吸収塔の構成としてはこれに限定されるものではなく、同じ縦型でも、吸収液を充填した筒状吸収塔であって、下部から排ガスをバブリングさせる方式や、横方向に移動する横型方式、例えばミキシングパイプ方式のような構成であってもよい。
（４）上記実施形態ＳＯｘ処理装置に接続して、排ガス中の他の有害成分を除去する吸収塔あるいは除去装置などを組み合わせて使用してもよい。

[Another embodiment]
(1) The number of ceramic filters arranged in the dust collector is not limited to the above-described example, and can be appropriately changed according to the scale of a ship to be installed. In addition, the size and specifications of the ceramic filter can be appropriately selected.
(2) In the above embodiment, an example using a combination of a substantially cylindrical wire mesh and punching metal as a porous body has been shown, but it may be composed only of a wire mesh or punching metal, and other heat resistant materials. Alternatively, a porous body having air permeability equivalent to 400 to 800 mesh wire net may be used.
(3) In the above embodiment, the absorption liquid is sprayed from the upper part in the absorption tower and the exhaust gas is passed through the filler layer from the lower part and discharged from the upper part of the absorption tower. The structure of the absorption tower is not limited to this, and even in the same vertical type, it is a cylindrical absorption tower filled with an absorption liquid, and a method of bubbling exhaust gas from the lower part or a horizontal type that moves in the horizontal direction For example, a configuration such as a mixing pipe system may be used.
(4) An absorption tower or a removal device that removes other harmful components in the exhaust gas may be used in combination with the SOx treatment device of the above embodiment.

  In the said embodiment, although the example mounted in a ship was shown, it is not limited to this, It can mount and utilize for various vehicles.

Schematic overall configuration diagram of an exhaust gas treatment apparatus according to the present invention Schematic overall configuration diagram of SOx processing equipment Partial enlarged configuration diagram showing the exhaust gas intake location of the bag filter of FIG. Perspective view of porous body

Explanation of symbols

2 Dust collector 2a Exhaust gas inlet 2b, 6 Exhaust gas discharge means 10 Ceramic filter 11 Porous body 13 Absorption tower 17 Evaporation means

Claims (2)

An exhaust gas inlet, a dust collector for removing harmful substances in the taken-in exhaust gas, and a discharge means for discharging the exhaust gas from which harmful substances have been removed, wherein the dust collector includes a number of ceramic filters, A pretreatment device in which a porous body occupying 1 to 4% of the total number of ceramic filters is disposed, and polyethylene glycol capable of absorbing SOx in the exhaust gas downstream of the pretreatment device An absorption tower in which an absorption liquid mainly composed of dimethyl ether is brought into contact with the exhaust gas, an evaporation means for evaporating SOx in the absorption liquid sent from the absorption tower and absorbing SOx, and reacting with water while oxidizing the evaporated SOx An exhaust gas treatment apparatus to which an SOx removal apparatus having a means for recovering as H ₂ SO ₄ is connected. Absorption mainly composed of polyethylene glycol dimethyl ether capable of absorbing SOx in the exhaust gas by introducing the exhaust gas into an absorption tower after removing dust in the exhaust gas using the exhaust gas treatment device of claim 1 An exhaust gas treatment method comprising a step of bringing the exhaust gas into contact with a liquid, evaporating SOx in an absorbing solution that has absorbed SOx by an evaporation means, oxidizing the evaporated SOx, and subsequently reacting with water to recover H ₂ SO ₄ .

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