JPH0938453A - Treatment of flue gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove SOx and dust with high efficiency by a combination of a simple equipment and mist catcher by wet-desulfurizing a waste combustion gas and then jetting high-pressure air into the waste gas to remove mist and dust. SOLUTION: An absorbing solution B contg. limestone in a circulating tank 2 is sprayed into an absorption tower 1 by a pump 3, a waste gas A is brought into contact with the absor bent B, desulfurized and freed from dust, and the mist of the absorbing solution B is removed by a mist catcher 4 to obtain a treated waste gas A'. The treated waste gas A' is passed through a flue 5, and the compressed air C compressed by a compressor 10 and then cooled by a cooler 11 is injected from a nozzle 6. The waste gas is further passed through a mist catcher 7 and discharged as a treated waste gas A". When high-pressure air is injected in this way into the waste combustion gas saturated with moisture in wet desulfurization, the temp. is lowered due to the adiabatic expansion, and the gas is supersaturated with moisture. The supersaturated moisture is condensed with the dust as a nucleus, and the dust is thickened.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flue gas treatment method for removing sulfur oxides and soot from combustion exhaust gas from a boiler or the like.

[0002]

2. Description of the Related Art Conventionally, sulfur oxides and soot contained in combustion exhaust gas from boilers and the like are first treated by removing soot and dust by a dry electrostatic precipitator and then absorbing liquid containing alkali such as limestone. It is general that the exhaust gas is washed with and is subjected to wet desulfurization. Generally, most of the soot dust that is not collected by the dry electrostatic precipitator is removed at the same time as the sulfur oxides in the wet desulfurization process, so that a high dust removal performance is obtained overall. Further, in the wet desulfurization step, it is general that mist is removed and smoke is exhausted in order to prevent the absorbing solution mist generated during gas-liquid contact from scattering and becoming soot. If higher dust removal performance is required, a high-level dust removal may be performed by installing a wet electrostatic precipitator in the downstream of the wet desulfurization process.

[0003]

In recent years, with the increase of environmental problems, the concentration of soot and dust that can be discharged in combustion exhaust gas tends to decrease, and in the future, a wet electrostatic precipitator will be installed downstream of the wet desulfurization process. The need is growing. However, since the wet electrostatic precipitator is expensive equipment and requires a large installation area, a high-quality dust removing equipment by an inexpensive and simple method is demanded instead.

[0004]

Means for Solving the Problems The present invention comprises a step of wet desulfurization of combustion exhaust gas containing sulfur oxides and dust, a step of injecting high pressure air into the wet desulfurized exhaust gas, a mist of exhaust gas injected with high pressure air, and And a step of removing soot and dust.

[0005]

According to the present invention, by injecting high-pressure air into the combustion exhaust gas saturated with water in the wet desulfurization step, the temperature of the combustion exhaust gas is lowered by the adiabatic expansion of the injected air, Water in the combustion exhaust gas becomes supersaturated. Supersaturated water condenses with soot as the nucleus and enlarges the soot. Enlarged soot dust has an increased inertial force, so it can be easily collected using an inertial collision or the like.

[0006]

EXAMPLES Hereinafter, specific examples of the present invention will be shown in comparison with a conventional method (comparative example) to clarify the effects of the present invention.

(Example) The present invention will be specifically described with reference to FIG. In FIG. 1, a combustion exhaust gas A of 1,000 m ³ N per hour was used as a diameter: 35
It was led to an absorption tower 1 having a height of 6 cm and a wet desulfurization of 6 m.
The conditions of the combustion exhaust gas A led to the absorption tower 1 are shown in Table 1 below.

[0008]

[Table 1]

In the absorption tower 1, the absorption liquid B containing limestone stored in the circulation tank 2 is pumped up to 20 m ³ per hour by the pump 3, and the exhaust gas A is brought into gas-liquid contact with the absorption liquid B for cooling and desulfurization. In addition, remove dust, and absorb liquid B with mist catcher 4.
The spray mist was removed to obtain the treated exhaust gas A '. The SOx concentration and soot concentration of the treated exhaust gas A ′ were as shown in Table 2 below.

[0010]

[Table 2]

The treated exhaust gas A'passes through a 25 cm square flue 5.
7kg / cm with compressor 10 on the way ²Compressed into a cooler 1
Compressed air C cooled in 1 is 10m / h^ThreeN injection nozzle 6
Was injected into the treated exhaust gas A '. Next, inject compressed air C
The emitted exhaust gas A ′ is processed and discharged through the mist catcher 7.
It was discharged as gas A ″.

The mist catcher 7 shown in FIG. 2 has a height of 25 cm and a thickness of 3 mm, and is made up of 13 vinyl chloride folding plate type collision plates 8 refracted at 90 °. Two stages were used in series in the gas flow direction. The SOx concentration and the soot concentration in the treated exhaust gas A ″ were as shown in Table 3 below.

[0013]

[Table 3]

(Comparative Example) As a comparative example, the SOx concentration in the treated exhaust gas A ″ when the compressed air is not injected under the same conditions as in the embodiment,
The soot and dust concentrations are shown in Table 4 below.

[0015]

[Table 4]

The present invention has been specifically described above with reference to the examples and measurement results of FIGS. 1 and 2. As is clear from comparison with the comparative example, according to the present invention, the dust concentration is clear. A significant reduction was seen.

[0017]

As described above, according to the present invention, it is possible to collect the dust particles, which are difficult to collect, with high removal efficiency by combining the simple equipment for producing compressed air and injecting it into the exhaust gas and the mist catcher.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining an embodiment of the present invention.

FIG. 2 is an explanatory view of an example of a structure of a mist catcher according to the present invention.

Claims (1)

[Claims] 1. A process of wet desulfurizing combustion exhaust gas containing sulfur oxides and soot, a process of injecting high-pressure air to the wet desulfurized exhaust gas, and a process of removing mist and soot of exhaust gas injected with high-pressure air. A flue gas treatment method characterized by: