JP2002001042A - Wet dust collecting method for exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet dust collecting method by which it is possible to capture dust efficiently from an exhaust gas containing the dust at a low installation cost, and especially remove even the dust with low wetting properties such as unburnt carbon or an unburnt oil content present in the exhaust gas discharged from a diesel engine to an aqueous solution, at a high uptake efficiency, and further, by which it is possible to easily treat the captured dust after its uptake process. SOLUTION: In the wet dust collecting method by which the dust present in the exhaust gas containing the dust is brought into contact with the aqueous solution to capture the dust, a surfactant and if necessary, a defoaming agent are added to the aqueous solution and this mixture is used to capture the dust from the exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet dust removing method for collecting dust in exhaust gas containing dust by bringing the dust into contact with an aqueous solution, and in particular, contains dust such as unburned carbon and unburned oil. The present invention relates to a wet dust removal method suitable for removing dust in exhaust gas discharged from a diesel engine such as a diesel power generation facility.

[0002]

2. Description of the Related Art Heretofore, as a dust removing method for removing dust in exhaust gas containing dust, a ceramic filter method, an eliminator method, an aqueous solution spraying method, an aqueous solution contacting method, and the like have been used.

In the above ceramics filter method, a ceramics porous filter is installed in a flue to filter and collect dust, and further, the filter is heated to collect collected unburned carbon and unburned oil. This is an effective method for removing dust having a relatively large particle size. In addition, the eliminator method is a method in which an eliminator having a zigzag flow path formed of plastic or the like is disposed at the top of a flue gas desulfurization unit or at a later stage to adhere and collect dust and remove the dust. This method is suitable for removing mist in exhaust gas, and is a method for removing dust secondarily. In addition, the aqueous solution spraying method is a method in which water or flue gas desulfurization absorbent is sprayed into exhaust gas from a spray nozzle, and dust is collected in liquid particles thereof. In this method, dust is collected in the water layer by contact with the water layer.

[0004]

In the above-mentioned conventional method for removing dust from exhaust gas, the ceramic filter method uses several μm.
Dust having the following small particle size, such as unburned carbon in exhaust gas discharged from diesel engines, has low collection efficiency, and if the amount of dust is large, the filter is likely to be clogged. However, there is also a problem that the energy cost and equipment cost for heating are increased.

[0005] In the eliminator method, dust is only collected as a by-product, so that the dust collection efficiency is low.
When unburned oil in exhaust gas discharged from diesel engines is collected and adheres to the surface of plastics, etc., there is no accurate method to remove it, so there is the trouble of manually cleaning and removing the accumulated oil. If left as it is, there is a risk of slipping in the exhaust gas after treatment, and there is also a problem that the equipment cost increases.

In wet dust removal methods such as an aqueous solution spray method and an aqueous solution contact method, dust having good wettability to an aqueous solution has a high collection efficiency, but unburned dust in exhaust gas discharged from a diesel engine. Dust having low wettability with respect to an aqueous solution such as bon or unburned oil has a problem of low collection efficiency.

The present invention has been made in view of the above-mentioned problems, and can efficiently collect dust in exhaust gas containing dust at a low cost of equipment, and in particular, discharges dust from diesel engines. Wet dust removal method that can remove dust with low wettability to aqueous solution, such as unburned carbon and unburned oil in exhaust gas, with high collection efficiency and easy treatment after collection The purpose was to provide.

[0008]

The gist of the present invention for achieving the above object is as follows.
In a wet dust removal method of contacting and collecting dust in exhaust gas containing dust with an aqueous solution, the wet dust removal method for exhaust gas is characterized by adding a surfactant to the aqueous solution. The wettability of dust having low wettability is improved by the action of the surfactant, and the dust is easily collected in an aqueous solution.

Further, in the invention according to claim 2,
A wet dust removal method for exhaust gas containing dust, wherein a dust and a defoaming agent are added to an aqueous solution in a wet dust removal method for collecting dust by contacting the dust with an aqueous solution. With this configuration, the wettability of dust is improved, and foaming at the time of collection or the like can be suppressed.

Further, in the invention according to claim 3,
In the method for wet dust removal of exhaust gas according to claim 1 or 2, the exhaust gas containing dust is exhaust gas discharged from a diesel engine. By applying the present invention to exhaust gas discharged from a diesel engine containing a large amount of dust having low wettability with respect to an aqueous solution such as an oil component, the effect can be effectively exhibited.

Further, in the invention according to claim 4,
4. The method according to claim 1, wherein the aqueous solution is a desulfurization absorbing solution for removing sulfur oxides in the exhaust gas, and the facility is provided with a flue gas desulfurization device. In this case, since it is not necessary to particularly provide a collection facility, the facility cost is reduced.

[0012]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of a flue gas desulfurization apparatus to which a wet dust removal method for exhaust gas according to an embodiment of the present invention is applied.

Reference numeral 1 denotes a packed bed type desulfurization column having a packed bed 2 formed therein. A liquid storage tank 4 is provided at the bottom of the tower, and a treatment gas discharge flue 5 is provided at the top of the tower. Above the packed bed 2, an eliminator 3 for mainly separating mist is provided. An inlet a for the gas to be treated is connected below the packed bed 2, and between the packed bed 2 and the eliminator 3, an absorption liquid supply pipe d for supplying a desulfurization absorption liquid onto the packed bed 2.
Although not shown, a spray nozzle for uniformly spraying the absorbing liquid on the packed bed 2 is provided.

The apparatus to which the wet dust removal method of the present invention is applied is not limited to the above configuration. The desulfurization tower
Instead of a packed bed type, a desulfurization tower of an appropriate type such as a spray type, a liquid film type, or a perforated plate type may be used, and a denitrification tower may be used instead of a desulfurization tower. You may.

Reference numeral 6 denotes an absorbent tank, reference numeral 7 denotes a surfactant tank, and reference numeral 8 denotes an antifoaming tank. In addition,
The defoaming agent tank 8 does not need to be provided particularly for the type of surfactant used and dust removal with little foaming. In an independent dust removing tower or the like instead of a desulfurization tower, the absorption liquid tank 6 is naturally a water tank for industrial water or the like.

Next, an operation of removing dust in exhaust gas discharged from diesel power generation equipment by using the dust removing method of the present invention using the flue gas desulfurization apparatus having the above-described structure will be described. From the spray nozzle of the absorption liquid supply pipe d connected to the desulfurization tower 1, the absorption liquid is uniformly sprayed on the packed bed 2. The absorption liquid is supplied from the liquid storage tank 4 by extracting the desulfurization absorption liquid by the circulation pump P1 and supplied through the absorption liquid circulation flow path c. If necessary, the absorption liquid is supplied from the absorption liquid tank 6 through the absorption liquid supply pump P2. It is mixed with a new desulfurization absorption liquid supplied through the absorption liquid supply passage e, and is supplied through the absorption liquid supply pipe d.

Gas to be treated discharged from diesel power generation equipment containing dust and sulfur oxides such as unburned carbon and unburned oil is charged into the desulfurization tower 1 through an inlet a for the gas to be treated. It is introduced below the bed 2 and rises in countercurrent contact with the absorbent flowing down the packed bed 2 while flowing countercurrently. During the countercurrent contact, sulfur oxides are absorbed by the desulfurization absorbent and dust is collected. And dispersed in the desulfurization absorption liquid. The gas to be treated from which the sulfur oxides and dusts have been removed rises, the mist is mainly separated by the eliminator 3, and is discharged into the atmosphere via the exhaust flue 5 at the top of the tower as a purified treatment gas. You.

The desulfurized absorbing liquid that has collected the dust descends and is stored in the liquid storage tank 4 at the bottom of the tower, and a part is sent from the absorbing liquid discharge pipe b to a wastewater treatment device outside the system, and a part is discharged. It is withdrawn by the circulation pump P1 and circulated as an absorbent.

The desulfurization absorption liquid contains a surfactant tank 7
The surfactant and the defoamer are added via the respective supply pipes g and f by the surfactant supply pump P3 and the defoamer supply pump P4 from the defoamer tank 8. As the desulfurization absorbing solution, an aqueous solution of magnesium hydroxide is used, and as the surfactant, it is preferable to use a nonionic surfactant. However, in the dust removal method of the present invention, the absorbing solution and the surfactant are used. Not limited.

In the above, by adding a surfactant to the desulfurization absorbing solution, even wet dust having low wettability to an aqueous solution, such as unburned carbon or unburned oil, has improved wettability and is trapped. Since the particles are easily collected and dispersed, the collection efficiency is increased. In addition, by adding an antifoaming agent to the absorbing liquid, the wettability of dust is improved, and foaming of the desulfurizing absorbing liquid, which is easily foamed by the surfactant, can be suppressed.

The amount of the surfactant added is 50 to 20.
0 ppm is preferable, and 70-100 pp is more preferable.
If it is less than 50 ppm, the effect of collecting and dispersing dust is small, and if it is more than 200 ppm, the COD in the purge liquid increases, and the burden on the wastewater treatment apparatus increases. Further, the addition amount of the defoaming agent is preferably from 1 to 20 ppm, more preferably from 4 to 10 ppm. If it is less than 1 ppm, the defoaming effect is small, and if it is more than 10 ppm, a significant improvement in the defoaming effect cannot be expected, However, there is a problem that the cost of chemicals increases.

The desulfurized absorbing solution extracted from the absorbing solution discharge pipe b is treated by a wastewater treatment device (not shown) and discharged to a river or the like. Dust dispersed in the desulfurized absorbing solution is discharged to the wastewater treatment device. Separation processing can be easily performed using an attached filter or the like.

(Example) In order to confirm the effects of a surfactant and an antifoaming agent, 500 ml of a magnesium hydroxide aqueous solution (Mg (OH) 2: 2 wt% solution) was used as a desulfurization absorption solution, and diesel exhaust gas was used. 13 mg of the collected dust was mixed and stirred at a temperature of 60 ° C. for 15 seconds to observe a dust dispersion effect. 1. No surfactant and no defoamer added: no dispersion. 2. Nonionic surfactant added at 70 ppm: has a dispersing effect but remarkably foams. 3. Addition of 50 ppm of nonionic surfactant: It has a dispersing effect, but remarkably foams. 4. Nonionic surfactant 70ppm + defoamer 4ppm
Addition: Dispersion effect, foam suppression effect. 5. Nonionic surfactant 70ppm + antifoamer 10pp
m addition: COD160, although there is a dispersing effect and a foam suppressing effect
In ppm, the COD increase is about 1.6 times the amount of surfactant added.
It was twice.

[0024]

According to the present invention, dust in exhaust gas containing dust can be efficiently collected at low equipment cost.
In particular, dust having low wettability with respect to an aqueous solution, such as unburned carbon and unburned oil in exhaust gas discharged from a diesel engine, can be removed with high collection efficiency. Is also an easy wet dust removal method.

[Brief description of the drawings]

FIG. 1 is a system diagram of a flue gas desulfurization apparatus to which a wet dust removal method for exhaust gas according to an embodiment of the present invention is applied.

[Explanation of symbols]

 1: Desulfurization tower 2: Packed bed 3: Eliminator 4: Liquid storage tank 5: Flue gas for discharging treated gas 6: Absorbent tank 7: Surfactant tank 8: Defoamer tank

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G091 AA06 AA18 AB15 BA13 CA15 4D002 AA02 AC01 AC10 BA02 BA14 BA16 CA01 CA02 CA04 CA07 DA06 DA12 DA64 DA70 EA02 4D032 AB03 BB05 BB07 DA01

Claims (4)

[Claims] 1. A wet dust removal method for collecting dust by contacting dust in an exhaust gas containing dust with an aqueous solution, wherein a surfactant is added to the aqueous solution. 2. A wet dust removal method for collecting dust by contacting dust in exhaust gas containing dust with an aqueous solution, wherein a surfactant and an antifoaming agent are added to the aqueous solution. 3. The exhaust gas containing dust is exhaust gas discharged from a diesel engine.
Or the wet dust removal method for exhaust gas according to claim 2. 4. The desulfurization absorbing solution for removing sulfur oxides in exhaust gas as an aqueous solution.
The wet dust removal method for exhaust gas according to any one of the above.