KR100646712B1 - Method and apparatus for removing acidic noxious gas using sodium bicarbonate - Google Patents

Abstract

The present invention relates to a method and a device for removing acidic harmful gas using sodium hydrogen carbonate, and injecting sodium hydrogen carbonate to the front of the bag filter in an air pollution prevention facility including an incinerator and a bag filter. Removal of acidic harmful gases, characterized in that the neutralization reaction with acidic harmful gases in the combustion gas generated in the process, and the removal of acidic harmful gases, including sodium hydrogencarbonate supply unit and activated carbon supply unit installed in front of the bag filter Provide the device.

The removal method and the removal device of acidic harmful gas according to the present invention are complementary to the conventional dry method, and the construction cost and operation cost are low, there is no generation of waste water, and no installation space is required, and the control device is simple, The removal efficiency is also excellent.

Sodium bicarbonate, noxious acid gases, activated carbon, wheat

Description

Method and apparatus for removing acidic noxious gas using sodium bicarbonate

1 is a schematic diagram of an acidic noxious gas removal apparatus according to an embodiment of the present invention.

FIG. 2 shows the mass balance of the removal device of FIG.

Figure 3 is a schematic diagram of the acidic noxious gas removal apparatus according to another embodiment of the present invention.

4 is a process chart of the removal apparatus of FIG.

5 is a detailed view of a sodium bicarbonate supply apparatus according to the present invention.

6 is a graph showing the removal rate of HCl according to the stoichiometric ratio of NaHCO ₃ / HCl.

7 is a graph showing the removal rate of SO ₂ according to the stoichiometric ratio of NaHCO ₃ / SO ₂ .

<Description of the symbols for the main parts of the drawings>

10: incinerator 20: waste heat boiler

30: electrostatic filter 40: contact reactor

50: bag filter (filtration dust collector) 60: stack

61: HCl / SOx analyzer 70: sodium bicarbonate silo

71: wheat 72: dosing hopper

73: metering supply 74: supply pan

75: supply nozzle 80: activated carbon silo

90: cyclone 100: cooling tower

The present invention relates to a method and an apparatus for removing acidic harmful gas generated in an air pollution prevention facility, and more particularly, by supplementing an existing process in an air pollution prevention facility and using sodium hydrogen carbonate, A method and apparatus for removing SOx / HCl are provided.

General methods of removing acidic harmful gases generated from power plants, municipal waste incinerators, waste incinerators, and designated waste incinerators can be broadly classified into dry absorption method, semi-dry absorption method, and wet cleaning method as follows.

end. Dry Adsorption Process

The system consists of an evaporation cooler, a neutralizer input and a bag filter or electrostatic precipitator. The combustion gas passing through the incinerator waste heat boiler is injected with water through the evaporative cooler to lower the gas temperature and increase the water content of the gas. At this time, the temperature of the combustion gas is cooled but is still maintained higher than the thermal insulation saturation. In this state, when alkaline chemicals (eg Ca (OH) ₂ ) are sprayed into a fine powder, acidic harmful gas and alkali powder are reached while forming a solid filter cake on the surface of the bag filter. This chemical reaction forms a neutral salt. The reaction neutral salt formed is separated by a filter bag cleaning mechanism and collected in the lower hopper and discharged. The neutralization reaction occurs as follows.

CaO + 2HCl → CaCl ₂ + H ₂ O

CaO + SOx → CaSOx

I. Semidry Adsorption Process

Alkaline chemicals are evaporated into a liquid phase in a mist in a chamber to react with an acidic noxious gas to form a crystalline state, and the solid product is collected in a downstream bag filter or electrostatic precipitator and discharged. At this time, the final combustion gas temperature is still higher than the insulation saturation.

This semi-dry absorption method is more efficient than the pure dry absorption method, so that the neutralizer consumption is low, and compared to the normal wet cleaning method, there is no investment cost and no neutralization treatment, so that it can be treated at a low running cost. As dust removal, a bag filter or an electrostatic precipitator can be used. The neutralization reaction occurs as follows.

Ca (OH) ₂ + 2HCl → CaCl ₂ + 2H ₂ O

Ca (OH) ₂ + SOx → CaSO ₄ + H2O

All. Wet Scrubbing Process

Generally, a solution such as caustic soda (NaOH) is used to maximize the treatment of harmful gases. The combustion gas is cooled below the dew point and passes through a scrubber while saturated. The performance of this system depends on the method of collecting droplets in the scubar and designing the re-heating exhaust gas prior to discharge into the stack.

However, these removal methods have the following problems.

end. Dry Adsorption Process

The dry method is cheap in terms of construction cost and operation cost, no waste water, no installation space and simple control device, but the removal efficiency is as low as 50%.

The sulfur oxide and hydrogen chloride treatment facilities of the municipal waste incineration plant and the industrial waste incineration plant were used alone to remove them below the allowable emission limit.

I. Semidry Adsorption Process

The semi-dry method has a high abatement efficiency of up to 98%, no waste water treatment, and the construction cost is more expensive than the dry method but cheaper than the wet method.

Since lime should be supplied in the form of slurry, a slurry supply facility is required, and skilled operating personnel are required for maintenance and repair.

Recently, this method has been widely used for the removal of sulfur oxides and hydrogen chloride in municipal waste incinerator.

All. Wet Scrubbing Process

The wet method has a very high abatement efficiency of up to 98%, but it is expensive in construction and operating costs, and requires a separate wastewater treatment facility.

In the present invention, among the above methods used to remove acidic harmful gas in the combustion gas, the dry method is low in construction and operating costs, there is no generation of waste water, does not require a lot of installation space, but the control device has a simple feature, but the removal It is suggested to make up for the problem of not being commercialized due to poor efficiency.

Accordingly, an object of the present invention is to provide a method and a device for removing acidic harmful gas, which is low in construction cost and operating cost, does not generate waste water, does not require much installation space, and has a simple control device, and also has excellent removal efficiency of acidic harmful gas. It is.

The present invention, in order to achieve the above object, in the air pollution prevention facility including an incinerator and a bag filter (injection of sodium hydrogen carbonate to the front end of the bag filter) and the acidic harmful gas in the combustion gas generated in the incinerator; It provides a method for removing acidic harmful gas, characterized in that the neutralization reaction.

Preferably, the removal method is characterized in that the activated carbon is added to the front end of the bag filter together.

In the present invention, sodium bicarbonate and activated carbon react with acid noxious gas (SOx / HCl) in combustion gas and form a filter layer of sodium bicarbonate / activated carbon on the filter surface in the bag filter to remove adsorption to dust, heavy metals, dioxins, and furans. Characterized in that.

In order to increase the removal efficiency of the acidic harmful gas in the present invention, it is preferable to first inject the sodium hydrogen carbonate into a particle size of 10 to 20 ㎛ using a mill, and secondly, the sodium hydrogen carbonate at least Preferably, the reaction is carried out in contact with an acidic noxious gas for 2 seconds. Third, the temperature of the combustion gas is preferably maintained at 140 to 200 ° C. Fourth, the stoichiometric ratio (molar ratio) of the sodium hydrogencarbonate / acidic noxious gas is 1; It is preferable to add sodium bicarbonate so as to be 2 to 2.

In addition, the present invention is a conventional acid harmful gas removal device including an incinerator and a bag filter, the acid harmful gas comprising a sodium hydrogen carbonate supply device and an activated carbon supply device installed in front of the bag filter Provide a removal device.

The sodium bicarbonate supply apparatus is a silo for storing sodium bicarbonate, a hopper and a metering feeder installed at the bottom of the silo to control the amount of sodium bicarbonate according to the concentration of acidic harmful gas, the bottom of the metering feeder And a mill installed in the mill for finely pulverizing sodium hydrogen carbonate to a particle size of 10 to 20 μm, and a supply fan connected to the mill to supply the finely ground sodium bicarbonate to the front end of the bag filter. do.

Acid harmful gas removal equipment according to the present invention is applicable to power plants, municipal waste incinerator, waste incinerator, designated waste incinerator and the like.

The present invention is characterized in that the sodium bicarbonate (NaHCO ₃ ) (Sodium Bicarbonate) powder is made into fine particles using a mill and introduced into the front of the bag filter (B / F: Bag Filter) as activated carbon, and the carbonic acid thus added Sodium hydrogen and activated carbon react with harmful substances (SOx / HCl) in the combustion gas and form a filter layer of NaHCO ₃ / activated carbon on the filter surface in the bag filter to adsorb and remove dust and dioxins.

SOx / HCl removal efficiency by the removal method of the present invention is more than 95%, it is higher in reactivity than the dry method (50% removal rate) using a conventional powdered lime.

The process of removing the acidic harmful gas according to the present invention has the advantage of lower investment and operating costs than the semi-dry absorption method and the wet cleaning method, and in particular, a small amount of money is spent in processing the final output.

Above all, the important point in this process is that the sodium bicarbonate, which is introduced at a high temperature of about 180 ° C, is vaporized into carbon dioxide (CO ₂ ) and water (H ₂ O) to change into sodium carbonate (Na ₂ CO ₃ ), and the mass is 25-30. By reducing the%, the amount of flyash discharged is significantly reduced compared to the semi-dry type slaked lime, which can reduce the amount of fly ash currently designated as designated waste, contributing to environmental protection and saving the cost of treating designated waste. Can be.

The slaked lime used in the semi-dry reaction tower requires a reaction time of 10 seconds or more, but a separate reaction tower should be used. Sodium bicarbonate used in the present invention has good reactivity, so a reaction time of about 2 seconds is sufficient. Since the high removal efficiency can be obtained even by reacting with acidic harmful gas by injecting into the duct, the installation site of the equipment can be minimized, and the existing operating equipment can be applied only by simple modification.

In addition, since sodium bicarbonate is a substance used for food, even operators operating on-site can perform safe operation, and there is also an excellent health and safety because it is harmless to the body even after a long exposure.

In addition, heavy metals and organic compounds contained in the final output can be separated. Complementing these facilities can reuse the final output, further reducing the amount of final ash that is thrown into the landfill and recycling resources. It is also suitable for the purpose.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic view of an acidic noxious gas removal apparatus according to an embodiment of the present invention, the apparatus is an incinerator 10, waste heat boiler 20, electrostatic filter 30, the contact reactor 40, the bag filter 50 ), Stack 60, sodium hydrogen carbonate silo 70, and mill 71.

The treatment of the combustion gas by the treatment facility is as follows. Acid noxious gas is generated in the incinerator 10 and flows into the contact reactor 40 through the waste heat boiler 20 and the electrostatic filter 30. Sodium hydrogen carbonate is stored in a silo 70, which is a storage tank, and crushed to an optimal fine particle size by a grinder such as a mill 71. The sodium hydrogen carbonate powder that has undergone this process is injected into the contact reactor 40 installed between the electrostatic filter 30, which is an electrostatic precipitator, and the bag filter 50, which is a precipitator. Here, the neutralization reaction of acidic noxious gas occurs as shown in Equation 3 below, the minimum temperature is 140 ℃ to 200 ℃.

HCl + NaHCO ₃ → NaCl + H ₂ O + CO ₂ (HCl Removal)

₂ NaHCO ₃ + H ₂ SO ₄ → Na ₂ SO ₄ + H ₂ O + CO ₂ (SO ₃ Plume Removal)

2NaHCO ₃ → Na ₂ CO ₃ + H ₂ O

Na ₂ CO ₃ + SO ₂ → (1 / 2O ₂ ) → Na ₂ SO ₄ + CO ₂ (SO ₂ Removal)

The reaction products formed during the neutralization are sucked into the bag filter 50, and when a certain thickness is reached, precipitates of the reaction products are dropped from the filter bag and collected under the bag filter 50. Fly ash dropped into the bag filter 50 hopper is discharged through a conveyor and a rotary valve installed in the lower portion. The treated combustion gas is discharged into the atmosphere through the stack 60.

Figure 2 shows the mass balance of the removal device of Figure 1, when incinerator 10 incineration of 1 ton of waste, 200 to 300 kg of slag (slag) is generated, passing through the waste heat boiler 20 One combustion gas produces 6 to 7 kg of HCl, 1 to 1.5 kg of SO ₂ , and 20 to 30 kg of flyash containing heavy metals and organic compounds (dioxin, furan), respectively.

Injecting 0.25 to 1 kg of activated carbon (AC) together with 25 to 30 kg of sodium bicarbonate (BICA) to the acidic combustion gas adsorbs and removes 0.25 to 1 kg of heavy metals, dioxins and furans, and 18 to 21 kg. The final output of is collected in a dry state at the bottom of the bag filter 50. Combustion gases undergoing this process are released to the atmosphere under stringent emission standards.

In this case, the neutralization reaction may be performed in a duct connecting the electrostatic filter 30 and the bag filter 50 without a separate contact reactor 40.

Figure 3 is a schematic diagram of the acidic harmful gas removal apparatus according to another embodiment of the present invention, the device is an incinerator 10, waste heat boiler 20, bag filter 50, stack 60, sodium hydrogen carbonate silo ( 70), the activated carbon silo 80, the cyclone 90, and the cooling tower 100.

The apparatus is an example of a combustion gas treatment plant using sodium hydrogen carbonate, and is a combustion gas treatment plant installed to remove sulfur oxides, nitrogen oxides, dust, and dioxins contained in combustion gases generated during incineration of industrial waste.

FIG. 4 is a process diagram of the removal apparatus of FIG. 3, and the process of treating combustion gas by this treatment facility is similar to the case of using the removal apparatus of FIG. 1.

In order to use sodium hydrogen carbonate, there are operating conditions that must be preceded. In other words, in order to react sodium hydrogen carbonate with the acidic harmful gas in the combustion gas, it is necessary to consider the optimum particle size, reaction time and temperature.

First, sodium bicarbonate must be ground to an optimal particle size. For proper particle size, sodium bicarbonate is pulverized through a mill 71 prior to injection into the flue gas treatment plant. Suitable particle size of sodium hydrogen carbonate is 10-20 μm, preferably 15 μm. The consumption of sodium hydrogen carbonate depends on the component or type of bag filter 50 used, but generally 25 to 30 kg is consumed per ton of industrial waste.

Second, sodium bicarbonate should be in contact with acidic noxious gases for at least 2 seconds. Finely pulverized sodium hydrogen carbonate particles are injected together with activated carbon at the front of the bag filter 50, and a reaction time of at least 2 seconds is required to react with the acidic harmful gas in the combustion gas. This becomes a factor in determining the duct length before the combustion gas reaches the bag filter 50.

Third, the combustion gas temperature must be at least 140 ° C. for proper neutralization. That is, the temperature at which the neutralization reaction occurs should be at least 140 ℃. Suitable temperatures for the neutralization reaction are 140 to 200 ° C.

Fourth, the final dust removal should be carried out in the bag filter 50.

Fifth, activated carbon is injected (100 mg / m 3) into the injection position of sodium hydrogen carbonate to remove heavy metals, dioxins, and furans.

When the optimum reaction and operating conditions as described above are satisfied, not only HCl (99%) but also SOx (95%) can obtain high removal efficiency.

According to the amount of HCl / SOx discharged through the HCl / SOx analyzer 61 installed in the stack 60, the amount of sodium hydrogen carbonate is adjusted through the quantitative hopper 72 and the quantitative feeder 73 to obtain the optimum reactivity. Reflect the design to meet the stability of the equipment.

The dosing hopper 72 quantifies sodium hydrogen carbonate according to the concentration of HCl / SOx measured in the stack 60, and supplies it to the quantitative feeder 73, and the carbonate milled to an optimum particle size through the mill 71. Sodium hydrogen is supplied to the bag filter 50 facility by the supply fan 74, and injected and mixed into the combustion gas through the supply nozzle 75 at the front of the bag filter 50 to react with the harmful acid gas in the combustion gas. do.

Sodium hydrogen carbonate and activated carbon injected into the precipitator 50 of the filter dust collector 50 through the supply nozzle 75 as shown in part A of FIG. 4 form a sodium bicarbonate / activated carbon filter layer in the filter dust collector 50 as shown in the portion B, respectively. The target reactant is desorbed and the like, and the final reactant is discharged to the outside through the bag filter hopper, which can be recycled and used as an industrial raw material.

5 is a detailed view of a sodium bicarbonate supply apparatus according to the present invention, wherein the supply apparatus is installed in a silo 70 for storing sodium bicarbonate and at a lower end of the silo 70 according to the concentration of an acidic noxious gas. A metering hopper 72 and a metering feeder 73 for adjusting a supply amount of sodium bicarbonate, and a mill installed at the lower end of the metering feeder 73 to pulverize sodium bicarbonate to a particle size of 10 to 20 ㎛ (71) And a supply fan 74 connected to the mill to supply the finely ground sodium hydrogen carbonate to the front end of the bag filter.

The sodium hydrogen carbonate supply apparatus is preferably installed at the front end of the bag filter, but may be installed at the electrostatic precipitator (ESP), the desulfurization facility, and the front end of the cyclone.

6 is a graph showing the removal rate of HCl according to the stoichiometric ratio of NaHCO ₃ / HCl, Figure 7 is a graph showing the removal rate of SO ₂ according to the stoichiometry of NaHCO ₃ / SO ₂ , the sodium hydrogen carbonate / acid harmful gas As the stoichiometric ratio (molar ratio) increases, it can be seen that the removal rate also increases. When the stoichiometric ratio is about 1, a high removal rate can be achieved, and the maximum removal rate reaches 99% and 95% at the stoichiometric ratio 1.5, respectively, and above that, even if the stoichiometric ratio increases, the removal rate no longer increases.

The removal method and removal device of acidic noxious gas according to the present invention are complementary to the conventional dry method, and are excellent in removal efficiency of acidic noxious gas, and the equipment is simple, no waste water is generated, and the amount of fly ash is reduced to reduce designated waste. The operating cost is also reduced by reducing the cost of phosphoric acid treatment.

Claims (9)

In an air pollution prevention facility including an incinerator and a bag filter, sodium hydrogen carbonate is introduced to the front of the bag filter to neutralize the acidic harmful gas in the combustion gas generated in the incinerator. Injecting activated carbon together in front of the bag filter, The sodium bicarbonate and activated carbon react with the acidic noxious gas (SOx / HCl) in the combustion gas and form a filtration layer of sodium bicarbonate / activated carbon on the filter surface in the bag filter to adsorb and remove dust, heavy metals, dioxins and furans, The sodium bicarbonate was pulverized into a particle size of 10 to 20 ㎛ using a mill, and then added. Reacting the sodium bicarbonate with an acidic noxious gas for at least 2 seconds, Maintaining the temperature of the combustion gas at 140 to 200 ℃, Sodium hydrogen carbonate is added so that the reaction stoichiometric ratio (molar ratio) of the said sodium bicarbonate / acid noxious gas is 1-2, The removal method of the acidic noxious gas. delete delete delete delete delete delete A conventional acid noxious gas removal apparatus including an incinerator and a bag filter, the apparatus comprising a sodium hydrogen carbonate supply device and an activated carbon supply device installed in front of the bag filter, The sodium bicarbonate supply apparatus is a silo for storing sodium bicarbonate, a hopper and a metering hopper to be installed at the bottom of the silo to control the amount of sodium bicarbonate according to the concentration of acidic harmful gas, the bottom of the metering feeder And a mill installed in the mill for finely pulverizing sodium hydrogen carbonate to a particle size of 10 to 20 μm, and a supply fan connected to the mill to supply the finely ground sodium bicarbonate to the front end of the bag filter. To remove acidic harmful gas. delete

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