KR101829655B1 - Method for purifying polluted wash water used for cleaning exhaust gas of SCRUBBER for ship - Google Patents

Abstract

An exhaust gas washing apparatus, which is a closed-loop washing water scrubber, and an exhaust gas recirculation (EGR) scrubber, which is used as an NOx reduction apparatus of a ship engine, generate contaminated washing water. A chemical reaction between a sulfuric acid (H_2SO_4) in the contaminated washing water and sodium hydroxide (NaOH) can generate sodium sulfate (Na_2SO_4) salt. When a circulation washing operation is continued, the salt concentration increases while increasing the content of residue such as soot. The increased residue content and salt concentration can cause the degradation of the washing effects of the scrubbers. To increase the washing effects, the contaminated washing water is cooled primarily and secondarily to discharge sodium sulfate decahydrate (Na_2SO_4, 10H_2O) precipitated therefrom. The dissolving rate rapidly decreases as the temperature drops, thereby increasing the amount of the sodium sulfate (Na_2SO_4) salt being discharged therefrom. The precipitated salt and coagulated combustion residue can be separated by a centrifugal separator to reduce the concentration rate of the sodium sulfate (Na_2SO_4) salt and the contamination degree of the washing water. Accordingly, the amount of bleed-off water and make-up water can be reduced to increase the cost efficiency while reducing the space limitations in a ship.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for purifying contaminated cleaning water used for cleaning exhaust gas SCRUBBER

The present invention relates to an exhaust gas cleaning apparatus (closed-loop clean water SCRUBBER) for a marine engine and a boiler using a fuel of high sulfur content, and a SCRUBBER for exhaust gas recirculation (EGR) (Na2SO4) salt formed by neutralizing the contaminated washing water containing H2SO4 and combustion residues with sodium hydroxide (2NaOH) and the coagulated contaminants are first cooled with seawater and then cooled with a separate cooling device to obtain an aqueous solution (Na2SO4) salts and aggregation residues by centrifuging the precipitated sodium sulfate (Na2SO4) by lowering the solubility of water (contaminated washing water).

The present invention relates to a method for purifying polluted washing water used in an exhaust gas cleaning apparatus for a marine engine and a boiler, and a SCRUBBER for exhaust gas recirculation (EGR) which is a NOx reducing apparatus of a marine engine.

As a result of the application of the air pollution regulation of MARPOL Annex VI, the exhaust gas of marine engines and boilers using high-sulfur marine fuel oil is reduced by SCRUBBER equipment and the technology to reduce the sulfur oxides to 0.1% Respectively.

However, this technology is already limiting the discharge of washing water in some US states because the SCRUBBER washing water (seawater) containing soot and sulfur oxides is discharged into the sea and damages the marine environment and lowers the alkalinity of coastal seawater. , Far East Asia, etc., are considered.

HYDRID SCRUBBER, which mixes open-loop seawater SCRUBBER method with closed-loop clean-water SCRUBBER method, is applied more and more because of strengthening emission regulation of polluted wash water.

Closed loop clean water SCRUBBER method, cleaning water scrub the SCRUBBER contact with exhaust gas, organic and inorganic combustion residue is generated.

A method for eliminating this is disclosed in Patent Registration No. 10-1421856 (Publication No. 10-2012-0125504), which is an exhaust gas cleaning equipment for a diesel engine, which comprises an exhaust gas cleaning And a scrubber fluid cleaning device connected to the gas scrubber (1) for scrubbing the contaminated scrubber fluid, wherein the scrubber fluid cleaning device is adapted to remove at least contaminant particles from the contaminated scrubber fluid A centrifugal separator 9 for separating the contaminant phase and the flushed cleaner fluid, the centrifugal separator 9 comprising a rotor 11 surrounding a separation space 12 having a stack of separation discs 13, A separator inlet 8 for the contaminated scrubber fluid extending into the separating space 12, a first separator outlet 14 for the scrubbed scrubber fluid extending from the separating space 12, And a second separator outlet (15) for the contaminant phase extending from the separator space (12), the scrubber fluid cleaner being adapted to deliver a contaminated scrubber fluid from the gas scrubber (1) to the separator inlet Means for transferring the flushing washer fluid from the first separator outlet 14 to the scrubber 1 and a buffer tank 6 for separating the gas scrubber 1 from the first separator outlet 14, Is arranged to deliver the scrubber fluid that has been washed from the first separator outlet 14 to the gas scrubber 1 via the buffer tank 6 and from the gas scrubber 1 The means for delivering the contaminated scrubber fluid to the separator inlet 8 comprises an exhaust gas scrubber 1 arranged to deliver contaminated scrubber fluid from the gas scrubber 1 to the separator inlet 8 via a buffer tank 6, . The process of providing a contaminated scrubber fluid containing contaminant particles from an exhaust scrubber as a method for cleaning a contaminated scrubber fluid, separating the contaminant phase containing contaminant particles from the contaminated scrubber fluid in the disk stack centrifuge A method for cleaning a contaminated scrubber fluid, comprising the steps of providing a scrubbed scrubber fluid, providing the scrubbed scrubber fluid to an exhaust scrubber, a disk stack separating the scrubbed scrubber fluid, The present invention also proposes a method of cleaning a contaminated scrubber fluid by a process further comprising a centrifugal separator.

However, even if the contaminated washing water is centrifuged and then reused, the increase of the sulfuric acid and sulfuric acid in the washing water continues to increase, thereby deteriorating the cleaning effect of the SCRUBBER.

Sodium hydroxide (NaOH) is added to the contaminated wash water in the SCRUBBER due to combustion of the high sulfur fuel oil of the marine engine and the boiler to neutralize it by increasing sulfuric acid and sulfuric acid contents.

At this time, the sodium sulfate (Na2SO4) salt is formed by the chemical reaction, and when the circulation washing is continued, the concentration of the salt is increased, and the saturated aqueous solution washing water is formed and precipitation of sodium sulfate (Na2SO4) salt is progressed and the cleaning effect of SCRUBBER is remarkably decreased.

Bleed off water and make-up water are required to increase the cleaning effect of the SCRUBBER at the concentration of the sodium sulfate (Na ₂ SO ₄ ) salt of the washing water.

Therefore, the concentration of sodium sulfate in the contaminated wash water of SCRUBBER is determined by the low solubility of the wash water, which is determined by the wash water temperature.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above problems, and it is an object of the present invention to solve the above problems and to provide a method and apparatus for removing sulfuric acid (H ₂ SO ₄ ) and sodium hydroxide (2NaOH) contained in contaminated washing water of an exhaust gas scrubber (closed loop fresh water SCRUBBER) When the sodium sulfate (Na ₂ SO ₄ ) salt is formed and the circulation washing is continued, the concentration of the salt increases and the content of residues such as soot increases in the washing water. When the contaminated washing water is first and secondly cooled, sodium sulfate _{(Na 2 SO 4. 10H 2} O) to precipitate there is more the temperature is lowered solubility is drastically lowered amount sodium sulfate (Na ₂ SO ₄₎ salt is precipitated, the precipitated sodium sulfate (Na ₂ SO ₄₎ salt, and The separation of the coagulated combustion residue by a centrifugal separator is intended to provide a method for purifying scrubber water which can reduce the amount of bleed off water and make-up water by reducing the salt concentration and pollution degree of the wash water The.

The present invention relates to a method of cleaning after neutralization by supplementing sodium hydroxide (NaOH) to a contaminated acidified washing water of a closed loop fresh water SCRUBBER, wherein the washing water of the circulating tank 4 is supplied to the SCRUBBER 3 The contaminated washing water in which the exhaust gas containing sulfur oxides in the SCRUBBER is washed is collected in the settling tank 4-1. The sodium hydroxide (NaOH) supply of the alkaline supply unit 16 causes the settling tank 4-1, (Na ₂ SO ₄ ) salt, and the concentration gradually becomes thicker.

Conventional techniques use a method of separating contaminated washing water by a centrifuge and purifying the washing water by make-up water and bleed off water by supersaturated washing water in the salt.

However, according to the present invention, the primary cooling (20 ° C-40 ° C) is performed in the seawater cooling cooler 5 through the feed pump 2 14 and the coagulant is supplied from the coagulant injector 17 to the secondary cooling cooler built- (1 ° C-19 ° C) in the solution (6), 10 sodium hydroxide (Na ₂ SO ₄ .10H ₂ O) precipitates and adheres to the cooling surface.

This salt can be scraped off with a scraper device 6 and removed with a centrifuge to reduce the salt concentration of the wash water.]

Sulfuric acid (H ₂ SO ₄ ) and sodium hydroxide (2NaOH) contained in the contaminated washing water of the exhaust gas scrubber (closed loop fresh water SCRUBBER) generate a sodium sulfate (Na ₂ SO ₄ ) salt by chemical reaction, The concentration increases and the residue content such as soot increases in the washing water. At this time, when the contaminated washing water is first and secondly cooled, 10 sodium hydroxide (Na ₂ SO ₄ .10H ₂ O) is precipitated. As the temperature becomes lower The solubility is drastically lowered and a large amount of sodium sulfate (Na ₂ SO ₄ ) salt is precipitated. When the precipitated sodium sulfate (Na ₂ SO ₄ ) salt and the coagulated combustion residue are separated by a centrifuge, the salt concentration and contamination degree of the washing water are reduced, There is a significant effect of reducing the amount of water (Bleed off water) and make-up water.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an apparatus for separating washing water contaminated with the SCRUBBER apparatus of the present invention into a decanter and a disk centrifuge (three-phase)
FIG. 2 is a schematic view of an apparatus for separating salts and residues into two disk-type centrifuges (two-phase / three-phase) via the first and second cooling apparatuses of contaminated washing water in the SCRUBBER apparatus of the present invention
FIG. 3 is a view showing a state in which the washing water contaminated with the SCRUBBER apparatus of the present invention is separated into one disk type centrifuge (two-phase) through the first and second cooling apparatuses and the salt and the residue are taken out through an absorption filter Device Schematic

(EN) The present invention relates to a scrubber cleaning water purification method, in which cleaning water connected to a circulation tank (4), a supply pump (13) and a SCRUBBER (3) in an exhaust gas cleaning apparatus for a ship is used for cleaning exhaust gas containing sulfur oxides in SCRUBBER In the closed loop fresh water SCRUBBER SYSTEM connected to the settling tank 4-1 and the circulating tank 4 and the SCRUBBER SYSTEM for EGR (Exhaust Gas Recirculation) which is a NOx abatement device of the marine engine, sodium hydroxide (2NaOH ) Is chemically reacted with sulfuric acid (H2SO4) in the wash water to form a salt (Na2SO4)

The contaminated washing water is firstly cooled (20 ° C-40 ° C) by the seawater cooling cooler (5) by the feed pump 2 (14) and coagulant is supplied from the coagulant feeder (17) (Na ₂ SO ₄ .10H ₂ O) precipitates and adheres to the cooling surface when cooled (1 ° C-19 ° C) in the cooler built-in scrubber device .

Further, the precipitated sodium hydroxide 10 Na ₂ SO ₄ .10H ₂ O is scraped off by the scraper device 6.

Further, the 10 scratched sodium sulfate (Na ₂ SO ₄ .10H ₂ O) scraped with the scraper device 6 and the coagulated combustion residue are firstly separated from the decanter centrifuge 78, The fine particles and a minute amount of oil are separated by the separator (three-phase separation) 8-1 and returned to the circulation tank 4 or bleed off.

It is also possible to replace the decanter centrifuge 78 with an automatic cleaning disc centrifuge (biphasic separator) 8 where it is first separated and sent to the circulation tank 4, or an automatic cleaning disc centrifuge (Three-phase separation) 8-1, and a part thereof is taken out (Bleed off).

In place of the decanter centrifuge 78 and the automatic swab disk centrifuge (three-phase separator) 8-1, only an automatic swab disk centrifugal separator (two-phase separator) 8 is installed and centrifugally separated Is circulated to the circulation tank 4 and a part thereof is blown off to a separate absorption filter 88 arranged in series.

The present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic view of an apparatus for separating washing water contaminated with the SCRUBBER apparatus of the present invention into a decanter and a disk-type centrifugal separator (three-phase) through a first and second cooling apparatus, FIG. 3 is a schematic view of a device for separating salts and residues into two disk type centrifuges (two-phase / three-phase) through the first and second cooling devices, FIG. , Separating the salt and the residue into a single disk centrifuge (two-phase) through a secondary cooling device, and taking out a part thereof through an absorption filter.

Sodium sulfate (Na ₂ SO ₄ ) salt is a sodium sulfate (Na ₂ SO ₄ ) salt produced by neutralization of sulfuric acid (H2SO4) and sodium hydroxide (2NaOH).

As the cleaning process of closed loop fresh water SCRUBBER increases over time, the concentration of salt increases and it becomes saturated aqueous sodium acid salt solution.

At this time, when the contaminated washing water is cooled, an anti-acid sodium salt is precipitated. The salt is a 10-hydroxysulfate (Na ₂ SO ₄ .10H ₂ O), and the lower the temperature, the lower the solubility is drastically reduced.

example)

@ 32.4 ° C solubility 49.7 g / 100 ml @ 30 ° C solubility 38 g / 100 ml,

@ 20 ° C Solubility 17g / 100ml @ 10 ° C Solubility 9g / 100ml @ 5 ° C Solubility 5g / 100ml

Sulfur content (sulfuric acid content of fuel oil): 3.5%

Fuel consumption: 1,200 kg / h

Sulfur (production of sulfuric acid per hour during combustion): about 42 kg / h

Na2SO4 (salt formation in sodium hydroxide neutralization): about 186 kg / h

Water At a maximum solubility of 50 kg / m3 (Na2SO4) at 5 ° C, sodium chloride (Na ₂ SO ₄ ) salt of about 136 kg (186 kg-50 kg) is precipitated and the salt concentration of the wash water is reduced. There is an effect that is not necessary.

The sodium sulfate (Na ₂ SO ₄ ) salt is formed by the chemical reaction between the sulfuric acid (H ₂ SO ₄ ) and the sodium hydroxide (2NaOH) in the wash water, and the salt precipitated by the cooling effect and the combustion residue aggregated by the flocculant are removed by a centrifuge It is purified by a physical method.

The present invention relates to a method of cleaning after neutralization by supplementing sodium hydroxide (NaOH) to a contaminated acidified washing water of a closed loop fresh water SCRUBBER, wherein the washing water of the circulating tank 4 is supplied to the SCRUBBER 3 The contaminated washing water in which the exhaust gas containing sulfur oxides in the SCRUBBER is washed is collected in the settling tank 4-1. The sodium hydroxide (NaOH) supply of the alkaline supply unit 16 causes the settling tank 4-1, (Na ₂ SO ₄ ), and the concentration of the salt gradually increases.

Here, the circulation tank 4 and the settling tank 4-1 are integral and both form a balanced conduit and a baffle plate. When the fluid in the settling tank 4-1 flows into the circulation tank 4, give.

The polluted wash water is firstly cooled (20 ° C-40 ° C) in the seawater cooling cooler 5 by the feed pump 2 14 and the polymer electrolyte is added to improve the separation efficiency of combustion residues in the coagulant input device 17 Coagulant in the system is added.

The cooler built-in scrubber device 6 is a secondary cooling device for lowering the solubility of contaminated washing water which is not sufficient in the primary cooling. When the cooling device is suddenly cooled (1 ° C-20 ° C) 10 sodium hydroxide ₂ SO ₄ .10H ₂ O) precipitates and sticks to the cooling surface and accumulates in the inner tube of the cooling device.

In order to scrape off this, a device 6 with a scraper must be additionally installed in the inner wall of the conical cooler. This device 6 is directly cooled by a separate cooling device 7.

The 10 crystals of sodium sulfate (Na ₂ SO ₄ .10H ₂ O) precipitated at this time and the coagulated combustion residue were first separated in a decanter centrifuge (78) and secondarily separated into an automatic cleaning disc centrifuge (3-phase separation) The fine particles and the minute amount of oil are separated by the centrifugal separator 8-1 and sent to the circulation tank 4 through the three-way valve 11 by the turbidity meter 10 or taken out to the storage tank 99 .

(2-phase separation) 8 at the position of the decanter centrifugal separator 78 where they are sent to the circulation tank 4 for primary separation and are sent to the automatic cleaning disc centrifuge 3 Phase separation) 8-1 and a part of the separated water is sent out to the storage tank 99 by bleed off.

Also, only an automatic cleaning disc type centrifugal separator (two-phase separation) 8 is installed in place of the decanter centrifuge 78 and the automatic cleaning disc centrifuge (three-phase separation) 8-1, And is sent to the storage tank 99 by blowing off the water to another absorption filter 88 arranged in series.

1: Hull 2: SEA CHEST (Seawater intake)
3: SCRUBBER device 4: circulation tank
4-1: Settling tank 5: Seawater cooling cooler
6: Scraper device with built-in cooler 7: Cooling device (CHILLER)
8: Automatic cleaning disc centrifuge (2 phase separation)
8-1: Automatic cleaning disc centrifuge (3 phase separation)
9: Sludge tank 10: Turbidity measuring device
11: 3-way valve 12: Seawater pump
13: Feed pump 1 14: Feed pump 2
15: makeup water supply device 16: alkaline supply device
17: coagulant injector 21: three way valve
78: Decanter centrifuge 88: Absorption filter
99: Holding tank (holding tank)

Claims (6)

The washing water connected to the circulation tank 4, the feed pump 1 13 and the SCRUBBER 3 in the ship exhaust gas cleaning apparatus is used to wash the exhaust gas containing sulfur oxides in the SCRUBBER and to circulate the sedimentation tank 4-1, 4) and a SCRUBBER SYSTEM for EGR (Exhaust Gas Recirculation), which is a NOx abatement device for marine engines.
Alkali supply salt to sodium (2NaOH) hydroxide wash water reaction sulfuric acid (H ₂ SO ₄₎ and of the chemical _{(16) (Na 2 SO 4} ) is generated,
The contaminated washing water is first cooled in the seawater cooling cooler 5 by the feed pump 2 14 and supplied with the flocculant from the flocculant feeder 17 to form a cooler built-in scrubber device 6), 10-hydroxysulfuric acid (Na ₂ SO ₄ .10H ₂ O) precipitates and adheres to the cooling surface when the water is cooled further.
The method according to claim 1, characterized in that the precipitated decahydrate (Na ₂ SO ₄ .10H ₂ O) is scraped off with a cooler built-in scrubber device (6) How to purify
3. The method according to claim 2, wherein the 10 scratched sodium sulfate (Na ₂ SO ₄ .10H ₂ O) scraped with the cooler built-in scraper device (6) and the coagulated combustion residue are firstly separated from the decanter centrifuge (78) (3-phase separation) 8-1 separates the fine particles and a minute amount of the oil from the circulation tank 4 and bleeds off the marine exhaust gas SCRUBBER To clean contaminated wash water used in
The method according to claim 3, wherein the decanter centrifuge (78) is replaced with an automatic swab disk centrifuge (2-phase separator) (8), where it is primarily separated and sent to the circulation tank (4) A method of purifying the polluted washing water used for washing of the exhaust gas SCRUBBER for marine, characterized in that a secondary separation is carried out by a disk type centrifugal separator (three-phase separation) 8-1 and a part is taken out
The centrifugal separator according to claim 3, wherein the decanter centrifuge (78) and the automatic swarf disk centrifuge (3-phase separator) (8-1) are replaced with an automatic swab disk centrifuge And then centrifugally separated and sent to the circulation tank 4 and a part thereof is bleed off by a separate absorption filter 88 arranged in series. The polluted water used in the cleaning of the SCRUBBER How to purify the wash water
The apparatus according to any one of claims 3, 4, and 5, wherein the circulation tank (4) and the settling tank (4-1) are integral and both form a balanced conduit and a baffle plate, Wherein the flow of the fluid to the circulation tank (4) is prevented from moving when the fluid of the circulating fluid flows into the circulation tank (4).

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