KR20200048608A - High-throughput two-stage dry apparatus for removing acidic gas - Google Patents

Abstract

The present invention relates to a method for removing acidic gas included in exhaust gas and an apparatus thereof. According to the present invention, the method comprises: a first removing step of injecting an acidic gas reactant into exhaust gas including acidic gas to remove the acidic gas; a first trapping step of trapping an unreacted acidic gas reactant from the acidic gas reactant used in the first removing step by fly ash and discharging the exhaust gas from which the acidic gas is removed; a second removing step of injecting an acidic gas reactant into the exhaust gas discharged from the first trapping step to remove the remaining acidic gas; a second trapping step of trapping the unreacted acidic gas reactant from the unreacted acidic gas reactant used in the second removing step by the fly ash and discharging the exhaust gas from which the remaining acidic gas is removed; and a reuse step of mixing the fly ash of the first and second tramping steps with water to reuse the mixture as the acidic gas reactant for the first and second removing steps, respectively. Accordingly, while acidic gas removing efficiency is maintained at an equal level to that of an existing acidic gas removing method and apparatus, the use amount of acidic gas reactant and active charcoal is remarkably reduced.

Description

High-throughput two-stage dry apparatus for removing acidic gas

The present invention provides a two-stage dry acid gas removal method and apparatus with high acid gas removal efficiency.

Existing dry acid gas removal apparatus dryly sprays CaCO ₃ or sodium bicarbonate onto contaminated gas to react with HCl, SOx, etc. in the gas, and then react the reactants in the form of ash in a bag filter at the rear end. It is a way to collect and remove. The above methods are SOx removal rate 60%, HCl removal rate 80%, SDA (Spray Dry Absorption, SOx removal rate 85% or higher, HCl removal rate 90% or higher) and WS (Wet Scrubber, SOx removal rate 95% or higher, HCl removal rate 95% or higher ) Compared to the method, acid gas and reaction efficiency are inferior.

In addition, the relatively high removal efficiency and the economically superior SDA method have insufficient acid gas removal rates in regions with enhanced emission standards compared to other regions such as the metropolitan area, and the current acid gas removal method consists of two stages of the existing dry + WS method. A method of increasing processing efficiency is applied. However, the WS has high treatment efficiency, but requires a large amount of process water, needs to treat a large amount of alkaline wastewater reacted with acid gas, is installed adjacent to a sewage treatment plant, and must be applied to a facility where water supply and wastewater treatment are smooth. , There are limitations in operation, and the SDA and WS have a problem in that the facility is excessive and the site needs to be secured.

Furthermore, as disclosed in Patent Publication No. 2016-0077378, an acid gas removal method and apparatus using a wet scrubber and an ion exchange scrubber are being studied, but minimize the problems of the conventional acid gas removal apparatus, and react reagents reacting with acid gas. Research to significantly reduce is still insufficient.

The present invention provides an acid gas removal method and apparatus. More specifically, the present invention uses a significantly less amount of acid gas reactant and activated carbon than the conventional acid gas removal method and apparatus, and is a high-efficiency two-stage dry acid gas capable of maintaining an efficiency equal to or higher than that of the existing dry + WS method. It is to provide a removal method and apparatus.

According to one aspect of the present invention, the present invention is a first removal step of removing the acid gas by injecting an acid gas reactant to the flue gas containing the acid gas; A first collecting step of collecting unreacted reagents among the acid gas reactants used in the first removal step with fly ash and discharging the exhaust gas from which the acid gas has been removed; A second removal step of removing residual acid gas by injecting an acid gas reactant into the exhaust gas discharged in the first collecting step; And a second collecting step of collecting unreacted reagents among the acidic gas reactants used in the second removal step with fly ash and discharging the residual acid gas from which the remaining acidic gas is removed, and the first and second collecting steps. It provides an acid gas removal method comprising a reuse step of mixing the ash of the water with the acid gas reactants of the first and second removal steps, respectively.

According to another aspect of the present invention, the present invention includes an acid gas reactant, a first removal unit for removing acid gas from flue gas generated during sludge incineration; A first collection unit for collecting unreacted reagents among the acid gas reactants used in the first removal unit with fly ash; A first circulation unit for mixing the ash of the first collection unit with water and injecting it into the first removal unit; A second removing part comprising an acid gas reactant and removing acid gas from the gas discharged from the first collecting part; A second collecting portion for collecting unreacted reagents among the acidic gas reactants used in the second removing portion with fly ash; A second circulation part in which the ash of the second collection part is mixed with water and injected into the second removal part; And a selective catalytic reduction unit through which gas discharged from the second collecting unit is injected.

The present invention can lower the temperature of the exhaust gas injected into the acid gas removal method and apparatus than the conventional SDA method acid gas removal method and apparatus, so that the heat recovery amount of the waste heat boiler can be increased, and the conventional dry + WS method acid gas While maintaining an acidic gas removal rate equivalent to that of the removal method and apparatus, a remarkably low amount of acidic gas reactant and activated carbon can be used.

1 shows a schematic flow diagram of a method for removing acidic gases of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention provides an acid gas removal method and apparatus capable of significantly reducing the amount of an acid gas reactant used while showing an acid gas removal rate equivalent to that of a conventional acid gas removal method and apparatus.

Specifically, the present invention is a first removal step of removing the acid gas by injecting an acid gas reactant to the flue gas containing the acid gas; A first collecting step of collecting unreacted reagents among the acid gas reactants used in the first removal step with fly ash and discharging the exhaust gas from which the acid gas has been removed; A second removal step of removing residual acid gas by injecting an acid gas reactant into the exhaust gas discharged in the first collecting step; And a second collecting step of collecting unreacted reagents among the acidic gas reactants used in the second removal step with fly ash and discharging the residual acid gas from which the remaining acidic gas is removed, and the first and second collecting steps. It provides an acid gas removal method comprising a reuse step of mixing the ash of the water with the acid gas reactants of the first and second removal steps, respectively.

In addition, the present invention includes an acid gas reactant, a first removal unit for removing acid gas from flue gas generated during sludge incineration; A first collection unit for collecting unreacted reagents in the form of fly ash among the acid gas reactants used in the first removal unit; A first circulation unit for mixing the ash of the first collection unit with water and injecting it into the first removal unit; A second removing part comprising an acid gas reactant and removing acid gas from the gas discharged from the first collecting part; A second collecting portion for collecting unreacted reagents in the form of a fly ash among the acidic gas reactants used in the second removing portion; A second circulation part in which the ash of the second collection part is mixed with water and injected into the second removal part; And it provides an acidic gas removal apparatus including a selective catalyst reduction unit is injected with the gas discharged from the second collecting portion.

The exhaust gas includes at least one selected from the group consisting of sulfur oxides and HCl.

At this time, in the case of the conventional SDA (Spray Dry Absorption) method, it is carried out near 220 ° C., which is 80 ° C. or higher, higher than the saturation temperature of the acid gas reactant, and is not performed at 200 ° C. or lower due to problems such as dioxin resynthesis. In addition, the conventional SDA method uses a lot of water because it removes the acid gas through a chemical reaction, but the present invention uses little water because it removes the acid gas through an adsorption reaction. Therefore, the exhaust gas of the acidic gas removal apparatus of the present invention has a smaller amount of water injected than the conventional SDA method, and thus may be injected at 120 to 170 ° C when the exhaust gas is injected into the first removal unit. Therefore, it is possible to recover more waste heat than the conventional acid gas removal method and apparatus.

In addition, the acid gas reactant includes at least one selected from the group consisting of sodium hydrogen carbonate (NaHCO ₃ ), calcium carbonate (CaCO ₃ ), calcium hydroxide (Ca (OH) ₂ ) and sodium carbonate (Na ₂ CO ₃ ). .

A first removal step and a second removal step of the acid gas removal method; And the first and second removers of the acid gas removal device, which react an acid gas reactant and an acid gas. As the acid gas reactant increases, more acid gas can be removed, but an excessive amount of acid gas reactant is injected. Doing so has the problem of reduced economic efficiency. Therefore, the acid gas removal method and apparatus of the present invention can increase the acid gas removal efficiency, and can significantly reduce the amount of the acid gas reactant used.

A first collecting step and a second collecting step of the acid gas removal method; And the first collection portion and the second collection portion of the acid gas removal device is not limited, it may be implemented as a bag filter (Bag Filter), may include activated carbon. For example, the first collection portion including activated carbon may collect unreacted reagents in the form of fly ash among the acid gas reactants used in the first removal portion.

The reuse step of the acid gas removal method and the first circulation portion and the second circulation portion of the acid gas removal device may reuse the acid gas reactant in a slurry form by mixing ash with water.

Due to the reuse step of the acid gas removal method and the first circulation section and the second circulation section of the acid gas removal apparatus, the unreacted acid gas reactant in the ash is reused, so it is used compared to the existing dry acid gas removal apparatus. The amount of acid gas reactants to be reduced can be as low as 70%. Furthermore, since it is injected into the first removal portion and the second removal portion in the form of a slurry, the removal efficiency of acid gas can be improved up to 90%.

The present invention may include the step of performing a second removal step by mixing a part of the exhaust gas discharged from the second capture step with the exhaust gas discharged from the first capture step in the acid gas removal method. The gas removal device may further include a gas circulation part that injects some of the gas discharged from the second collection part into the second removal part.

In the acid gas removal method, a part of the exhaust gas discharged in the second capture step is mixed with the exhaust gas discharged in the first capture step to perform the second removal step, so the final acid gas treatment efficiency is the same as the existing acid gas treatment method. Equal levels can be shown. Likewise, by mixing the gas injected into the second removal unit through the gas circulation unit of the acidic gas removal unit and the gas processed in the first collection unit (Back-mixing), the acidic gas concentration is lowered and then the acidity is removed from the second removal unit. Since the gas is treated, the final acid gas treatment efficiency may be equivalent to that of the existing acid gas treatment device.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are only examples for helping the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

Example 1

In removing the acid gas contained in the flue gas generated during incineration of the sewage treatment plant sludge, an acid gas removal device as shown in FIG. 1 was used. The specific acid gas removal process is as follows.

First, the flue gas is injected into the first removal portion containing the acid gas reactant, and unreacted reagents among the acid gas reactants reacted in the first removal portion are collected in the first collection portion in the form of fly ash. do. The ash is mixed with water and circulated through the first circulation portion to the first removal portion.

The unreacted flue gas from the first removal part passes through the first collection part, is injected into the second removal part containing the acidic gas reactant, and the fly ash is removed from the unreacted reactant among the acid gas reactants reacted by the second removal part. It is collected in the second collecting part in the form. The ash is mixed with water and circulated through the second circulation portion to the second removal portion.

Some of the unreacted flue gas that has passed through the second collection portion is injected into the second removal portion through the gas circulation portion, whereby unreacted flue gas that has passed through the first collection portion and unreacted flue gas injected through the gas circulation portion are mixed ( Back-mixing) to lower the acid gas concentration of the exhaust gas injected into the second removal unit.

At this time, the exhaust gas injected into the first removal unit was 8,912 Nm ³ per hour, the concentration of sulfur oxide in the exhaust gas was 820 ppm, and the concentration of HCl was 450 ppm, and the exhaust gas temperature before the injection of the first removal unit (after the economizer) Was 170 ° C.

In addition, powdery lime (Ca (OH) ₂ ) was used as the acid gas reactant, and activated carbon was used in the first and second collection portions, respectively. The powdered lime and activated carbon were used so that the removal rate of sulfur oxides was 99% or more, and the removal rate of HCl was 98% or more.

Comparative Example 1

An acidic gas removal device using a conventional dry + wet scrubber (WS) method was used.

At this time, the exhaust gas injected into the acidic gas removal device by mixing the conventional dry + wet scrubber (WS) method was used the same exhaust gas as in Example 1.

In addition, the powdered lime and activated carbon used in the conventional dry method and NaCl used in the wet scrubber (WS) method were used so that the removal rate of sulfur oxides was 99% or more and the removal rate of HCl was 98% or more.

<Measurement of acid gas concentration in acid gas removal system>

Table 1 shows the concentration of acidic gases in the front end of the first removal unit, the rear end of the first collection unit, the front end of the second removal unit, the rear end of the second collection unit, the gas circulation unit, and the selective catalyst reduction unit of Example 1.

division Flue gas volume per hour (Nm ³ / hr) Sulfur oxide (SO _x ) HCl Concentration (ppm) Concentration (ppm) Front end of the first removal part (rear end of the economizer) 8,912 820 450 Rear end of the first collection part 8,912 82 85 Second removal part shear 15,846 48 53 Rear end of the second collection part 15,846 5 10 Gas circulation 6,934 5 10 Selective catalyst reduction department 1,978 5 10

As shown in Table 1, Example 1 was able to remove about 90% of the initial exhaust gas from the first removal unit and the first collection unit, and HCl was able to remove about 81.1%. In addition, it was found that in the second removal unit and the second collection unit, sulfur oxides were able to remove about 99.4% of the initial flue gas, and HCl could remove about 97.8%.

Furthermore, the degree of acid gas removal in Example 1 and Comparative Example 1 was compared, and the amount of acid gas removed and the amount of acid gas reactant and activated carbon used in each device are shown in Table 2 below.

Comparative Example 1 Example 1 Initial sulfur oxide concentration (ppm) 820 820 Initial HCl concentration (ppm) 450 450 Sulfur oxide concentration after processing (ppm) 5.0 5.0 HCl concentration after processing (ppm) 10.0 10.0 Powdered lime used per hour (kg / h) 79.6 60.9 Activated carbon used per hour (kg / h) 1.5 1.0 NaCl used per hour 76.7 - Sulfur oxide removal rate (%) 99.4 99.4 HCl removal rate (%) 97.8 97.8

As shown in Table 2, it was found that Example 1 of the present invention showed the same level of acid gas removal rate as Comparative Example 1. Furthermore, it was found that Example 1 of the present invention does not use NaCl as compared to Comparative Example 1, but uses a significantly smaller amount of powdered lime per hour and activated carbon.

For a more specific comparison, the acid gas removal rate from Example 1 to the first collection part of the present invention and the acid gas removal rate of the dry acid gas removal device in Comparative Example 1 were compared in Table 3 below.

Dry acid gas removal device in Comparative Example 1 A device consisting of a first removal unit, a first collection unit, and a first circulation unit in Example 1 Initial sulfur oxide concentration (ppm) 820 820 Initial HCl concentration (ppm) 450 450 Sulfur oxide concentration after processing (ppm) 246 82.0 HCl concentration after processing (ppm) 180 85 Powdered lime used per hour (kg / h) 79.6 54.2 Activated carbon used per hour (kg / h) 1.5 1.0 Sulfur oxide removal rate (%) 70 90.0 HCl removal rate (%) 60 81.1

As shown in Table 3, the acidic gas removal efficiency of the dry acidic gas removal device in Comparative Example 1 showed 70% and 60%, respectively, of sulfur oxides and HCl, whereas the first removal unit of Example 1 of the present invention, The acid gas removal efficiency of the device consisting of the first collection part and the first circulation part was 90% and 81.1%, respectively, of sulfur oxides and HCl, and it was found that the acid gas removal rate was significantly higher than that of the conventional dry acid gas removal device. Table 4 summarizes the drug costs used when Example 1 of the present invention is operated for 20 years and when Comparative Example 1 is operated for 20 years.

division Slaked lime cost for one year (ⓐ) Cost of activated carbon used for one year (ⓑ) NaCl cost for one year (ⓒ) Pharmaceutical expenses during the operation period (20 years) (KRW, (ⓐ + ⓑ + ⓒ) * 20) Unit price (won / kg) 120 4,400 358 - Uptime (h) 24 Yearly 330 Comparative Example 1 (①) 75,651,840 52,272,000 217,472,112 6,907,919,040 Example 1 (②) 57,831,840 34,151,040 0 1,839,657,600 Difference (①-②) 17,820,000 18,120,960 217,472,112 5,068,261,440

As shown in Table 4, the acid gas removal apparatus according to Example 1 of the present invention can significantly reduce the slaked lime, activated carbon and NaCl used in operation for 20 years compared to the acid gas removal apparatus according to Comparative Example 1 .

Although the embodiments of the present invention have been described in detail above, the scope of rights of the present invention is not limited thereto, and it is possible that various modifications and variations are possible without departing from the technical spirit of the present invention as set forth in the claims. It will be apparent to those of ordinary skill in the field.

Claims (9)

A first removal step of removing the acid gas by injecting an acid gas reactant into the flue gas containing the acid gas;
A first collecting step of collecting unreacted reagent from among the acid gas reactants used in the first removal step with fly ash and discharging the exhaust gas from which the acid gas has been removed;
A second removal step of removing residual acid gas by injecting an acid gas reactant into the exhaust gas discharged from the first collection step; And
And a second collecting step of collecting unreacted reagent from the acidic gas reactant used in the second removing step with fly ash and discharging the exhaust gas from which the remaining acidic gas is removed,
And a reuse step of mixing the ash of the first and second collecting steps with water and reusing the acid and gas reactants of the first and second removal steps, respectively.
The method of claim 1, wherein a second removal step is performed by mixing a part of the exhaust gas discharged in the second capture step with the exhaust gas discharged in the first capture step.
The method of claim 1, wherein the exhaust gas comprises at least one selected from the group consisting of sulfur oxides and HCl.
The method of claim 1, wherein the acid gas reactant is one selected from the group consisting of sodium hydrogen carbonate (NaHCO ₃ ), calcium carbonate (CaCO ₃ ), calcium hydroxide (Ca (OH) ₂ ) and sodium carbonate (Na ₂ CO ₃ ). A method for removing acidic gas, comprising the above.
It includes an acid gas reactant, a first removal unit for removing acid gas from the flue gas generated during sludge incineration;
A first collection unit for collecting unreacted reagents among the acid gas reactants used in the first removal unit with fly ash;
A first circulation unit for mixing the ash of the first collection unit with water and injecting it into the first removal unit;
A second removing part comprising an acid gas reactant and removing acid gas from the gas discharged from the first collecting part;
A second collection portion for collecting unreacted reagents among the acid gas reactants used in the second removal portion with fly ash;
A second circulation part in which the ash of the second collection part is mixed with water and injected into the second removal part; And
Acidic gas removal apparatus including a selective catalyst reduction unit is injected with the gas discharged from the second collecting portion.
The apparatus for removing acidic gases according to claim 5, comprising a gas circulation part for injecting some of the gas discharged from the second collecting part into the second removing part.
According to claim 1, The exhaust gas comprises at least one selected from the group consisting of sulfur oxides and HCl, acid gas removal device.
The method of claim 1, wherein the acid gas reactant is one selected from the group consisting of sodium hydrogen carbonate (NaHCO ₃ ), calcium carbonate (CaCO ₃ ), calcium hydroxide (Ca (OH) ₂ ) and sodium carbonate (Na ₂ CO ₃ ). An acid gas removal device comprising the above.
According to claim 1, The exhaust gas is injected at 120 to 170 ℃, acidic gas removal device.

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