JP2010201427A - Method of treating gas - Google Patents

Abstract

A gas containing a SO ₃ component, for example in the gas generated by the combustion of fuel containing sulfur in a boiler or the like, the sulfuric acid mist derived from causative SO ₃ component and SO ₃ component such as white smoke or tobacco smoke Providing a cheap, efficient, simple and safe removal method.
SOLUTION: A method of treating a gas produced by burning fuel in a boiler 1 and sent to an air preheater 2, a desulfurization device 4, and then a chimney 5 through a flue, having an average particle diameter of 20 μm or less, Sodium bicarbonate powder having an angle of repose of 65 ° or less and a dispersity of 10% or more is decomposed using a gaseous medium heated to 60 ° C. or more, and contains SO _{2 in an amount} of 500 ppm by volume or more in at least one flue. further by spraying the gas containing SO ₃ component, the processing method of the gas for removing SO ₃ component in the gas.
[Selection] Figure 1

Description

The present invention relates to a gas processing method for neutralizing SO ₃ components contained in a gas or the like generated by combustion of a fuel containing sulfur in a boiler or the like at low cost, efficiently, simply and safely.

When fuels containing sulfur such as heavy oil, coal and coke are burned, or when raw materials containing sulfur such as iron ore are burned, SO ₃ and H ₂ SO ₄ are contained in the exhaust gas, and the equipment is corroded. Cause air pollution. SO ₃ or H ₂ SO ₄ reacts with water vapor contained in the exhaust gas to become sulfuric acid mist, and when discharged into the atmosphere, it causes white smoke or purple smoke.

Therefore, in order to remove SO ₃ , H ₂ SO ₄ and sulfuric acid mist (hereinafter collectively referred to as SO ₃ components), oxides or hydroxides of calcium and magnesium are used. the dispersed slurry in an organic solvent, has previously or prevent the formation of SO ₃ component is added to the fuel, and a method of neutralizing additives or to SO ₃ component in the gas after combustion is used. However, in these methods, the additive easily accumulates in the heat exchanging portion of the boiler, and if it is deposited in a large amount, the operation of the boiler is hindered, so that it is difficult to use a large amount of the additive.

In addition, in order to actively neutralize the SO ₃ component in the flue, the exhaust gas is preheated with air from a powder of calcium hydroxide, magnesium oxide, magnesium hydroxide, etc., or a slurry in which the powder is dispersed in water. A method of injecting into the flue after passing through the vessel is also used. However, when the powder itself is injected in this method, a fine powder having poor fluidity is injected by a screw feeder or the like, so that the quantitative property is poor and it is difficult to obtain a stable effect. Furthermore, since these powders are likely to aggregate, they are difficult to uniformly disperse in the gas and have a low effect as a neutralizing agent. Moreover, when inject | pouring in the state of a slurry, the powder contained in a slurry accumulates on the transfer line for inject | pouring a slurry, and it is easy to clog, and it is difficult to use it stably by a fixed quantity.

  Further, for example, when magnesium oxide is used, excessive addition of magnesium oxide powder is required because magnesium oxide has low reaction efficiency. In this case, unreacted magnesium oxide remains in the flue, but since magnesium oxide has low solubility in water, there may be a problem in the post-treatment of magnesium oxide. Furthermore, there is a problem that it is difficult to quantify the injection amount because of the fine powder and poor fluidity.

On the other hand, there is also a method of injecting ammonia into the flue, but there are problems in the regulations and operating temperature of handling high-pressure gas and the like, and a separate large-scale facility is required. Further, in the case of removing SO ₃ with ammonia, acidic ammonium sulfate is generated unless a sufficient injection amount is maintained. If acidic ammonium sulfate adheres to the apparatus, it causes trouble, so ammonia must be injected excessively, and excess ammonia is released into the atmosphere, which is a problem for environmental conservation.

In operation of boilers and the like, in order to prevent a reduction in operating rate and perform stable operation, by neutralizing and removing sulfur oxides, particularly SO ₃ components, it is possible to prevent the formation of sulfuric acid mist due to exhaust gas cooling, It is necessary to prevent acid corrosion, flue blockage, and the like in each process until flue gas is discharged and on the flue side walls.

Further, when the SO ₃ component is cooled and reacts with water vapor, sulfuric acid mist is generated, and when discharged from the chimney, white smoke is generated. This white smoke is observed as purple smoke, brown smoke or black smoke depending on the weather, but the flicker does not disappear easily. The sulfuric acid mist that becomes white smoke, etc., damages the human body, animals and plants at the descending point. Further, the dust accumulated in the flue and the like is discharged as an acid smut containing a large amount of sulfuric acid due to load fluctuations and the like, resulting in acid falling dust and worsening the environment. These damages are particularly large in the vicinity of the chimney compared to the case where SO ₂ is contained in the exhaust gas. Therefore, suppressing these by neutralizing and removing the SO ₃ component is very effective for environmental measures.

Therefore, it is necessary to remove gas containing SO ₃ component, such as combustion exhaust gas of fossil fuel, gas generated by using fuel containing sulfur content in boilers, etc., and SO ₃ component as impurities. There is a need for a method of neutralizing and removing SO ₃ components more efficiently and safely in a certain gas. In addition, SO ₃ components can also be removed in the treatment of exhaust gas such as combustion of waste liquid, waste oil, waste gas and solid waste in steel making, iron making, non-ferrous metal refining, glass melting, sulfuric acid production, surfactant production, etc. There is a need for an efficient and safe neutralization method for SO ₃ components. Therefore, an object of the present invention is to provide a method for efficiently, simply and safely removing SO ₃ components from the gas as described above.

The present invention is a method for treating gas produced by combustion of fuel in a boiler and sent to an air preheater, a desulfurizer, and then to a chimney through a flue, having an average particle diameter of 20 μm or less and an angle of repose of 65 °. or less and a degree of dispersion of 10% or more of sodium bicarbonate powder, and digested with gaseous medium heated to 60 ° C. or higher, at least one flue, the SO ₂ contained more than 500 vol ppm, further SO ₃ by spraying into a gas containing components, it provides a method of treating a gas containing a SO ₃ component, and removing the SO ₃ component in the gas.

In the present invention, sodium hydrogen carbonate powder is sprayed into a gas to be treated by a gaseous medium heated to 60 ° C. or higher, and sodium hydrogen carbonate powder is in a gas of 60 ° C. or higher, for example, acid (SO ₃ component). In the gas heated above the dew point, it decomposes into sodium carbonate, carbon dioxide and water. At this time, the portion from which carbon dioxide and water are removed becomes pores, and becomes sodium carbonate particles having a porous structure with a high porosity and a large specific surface area. When the particles have a porous structure, the adsorption power of SO _{3 and the} like is increased, and the SO ₃ component can be removed by rapid neutralization.

According to the present invention, the SO ₃ component in the gas and the sulfuric acid mist derived therefrom can be removed inexpensively, efficiently, simply and safely. Therefore, colored smoke such as white smoke and purple smoke in the exhaust gas discharged from the boiler or the like can be suppressed. Also, in gases containing SO ₃ components as impurities other than exhaust gas, it is meaningful in industrial production to perform removal of SO ₃ components inexpensively, efficiently, simply and safely.

The figure which shows the method of processing the waste gas burned with the boiler.

The sodium hydrogen carbonate powder in the present invention has an average particle diameter of 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less. Sodium hydrogen carbonate having an average particle diameter of 20 μm or less has a large specific surface area of the particle itself and a large diameter of pores formed during thermal decomposition. Therefore, the apparent diffusion rate of the SO ₃ component is increased, and as a result, the reactivity is considered to be increased. Since the average diffusion rate of the particle diameters of smaller the SO ₃ component apparent sodium bicarbonate powder is fast Preferably, the lower limit thereof is not limited in terms of the effect of removing SO ₃ component, and cost required for pulverization of the powder, Considering the ease of handling of the produced fine powder, it is preferably 1 μm or more.

The sodium bicarbonate powder added to the gas to be treated preferably has an angle of repose of 65 ° or less, particularly 60 ° or less, as a powder physical property. Sodium bicarbonate powder with an angle of repose within this range has good fluidity, for example, it can maintain a good spraying state even when sprayed into a flue, and is also stable because it can be easily discharged from a storage tank or pneumatically transported. It is discharged from the storage tank, and a predetermined amount can be quantitatively injected into the gas to be treated, and it reacts efficiently with SO ₃ . Therefore, the amount of sodium bicarbonate sprayed can be reduced, and handling and control as a powder is easy. In addition, the repose angle of sodium hydrogencarbonate powder here is the total powder (mixture) added when adding an anti-caking agent or coarse particles to sodium hydrogencarbonate and adding it to the gas as described later. Indicates the angle of repose.

  Here, the angle of repose can be measured using a powder tester PT-D manufactured by Hosokawa Micron. In other words, the angle of repose is determined when the powder sample is passed through a sieve having a diameter of 80 mm and an aperture of 710 μm while vibrating and then gently dropped onto a table having a diameter of 80 mm from a funnel having a height of 160 mm on a horizontal surface. Is a numerical value defined by measuring the angle formed by the generatrix and the horizontal plane of the cone.

Sodium hydrogencarbonate powder is preferably added in an amount of 1 to 16 times mol, particularly 4 to 10 times mol for the SO ₃ component contained in the gas. If the amount is less than 1 mole, the SO ₃ component cannot be removed sufficiently, and the effect of removing white smoke or purple smoke may be insufficient. However, since sodium hydrogen carbonate in the present invention has a higher reaction efficiency than magnesium hydroxide and the like, if it is present at 16 times mole, SO ₃ components other than those adsorbed in the dust can be removed, so no further addition is necessary. is there.

Here, in the observation with the naked eye of the exhaust from the chimney in the test by the actual power plant boiler of the inventors, if the SO ₃ component is converted to SO ₃ and is 2 ppm by volume or less, white smoke or purple smoke can be prevented. The effect could be confirmed meaningfully. Therefore, good results can be obtained by adding an amount of sodium bicarbonate that can maintain this level.

In the method of the present invention, the SO ₃ component is selectively selected from a gas containing a small amount of SO _{3 of} about 20 volume ppm in a gas containing high volume SO ₂ exceeding 500 volume ppm or even 1000 volume ppm. Can be removed. Conventionally, many techniques for removing SO ₂ have been disclosed as SO _X removal methods, but no technique for easily and selectively removing SO ₃ components has been disclosed.

In the present invention, sodium hydrogen carbonate is used as a neutralizing agent for removing the SO ₃ component, and therefore, compared with ammonia that is handled as a high-pressure gas and is regulated by deleterious poisons, or sodium hydroxide that is a deleterious substance. Therefore, the worker can handle it safely. Moreover, since it can implement only with simple spray apparatuses, such as an ejector, an expensive capital investment is unnecessary for implementation. Since the SO ₃ component is removed by neutralization in the method of the present invention, it can be easily replaced with the conventional method of injecting ammonia, which is also removed by neutralization, and can be used in combination with the conventional method.

In the present invention, in order to remove the SO ₃ component in the gas more efficiently, it is preferable to mix a sodium hydrogen carbonate anti-caking agent in the sodium hydrogen carbonate and add it to the gas. Sodium hydrogen carbonate tends to agglomerate and solidify due to the presence of a small amount of water, resulting in poor fluidity. Therefore, if it is stored in a state of being pulverized to 20 μm or less, it tends to solidify at the time of storage or the dispersibility at the time of use. However, since the aggregation of sodium hydrogen carbonate can be suppressed by the presence of the anti-caking agent, the high fluidity of sodium hydrogen carbonate can be maintained, and fine powder of sodium hydrogen carbonate can be well dispersed in the gas. As a result, a high reaction efficiency, that is, a high SO ₃ removal effect can be maintained.

  The average particle diameter of the anti-caking agent is preferably 0.005 to 5.0 μm, particularly preferably 0.005 to 2.0 μm. When fine particles having an average particle diameter in this range are added as an anti-caking agent, the anti-caking agent particles can be prevented from adhering to the surface of the sodium hydrogen carbonate particles and aggregation of the sodium hydrogen carbonate particles can be prevented. Even if the average particle diameter of the anti-caking agent is less than 0.005 μm, the anti-caking effect is not enhanced and it cannot be obtained as an inexpensive industrial product. Moreover, since the anti-caking agent is interposed between sodium hydrogen carbonate particles and prevents sodium hydrogen carbonate particles from contacting with each other, the caking of sodium hydrogen carbonate particles is prevented, so that the average particle diameter exceeds 5.0 μm. In the case of large particles, even if the same mass ratio as in the case of fine particles is added, the anti-caking effect is reduced because the number of anti-caking agents is small.

  As the anti-caking agent, magnesium carbonate, silica, alumina, aluminosilicate, artificial or natural zeolite, stearate, etc., generally known as substances added for the purpose of preventing caking of powder and improving fluidity. Can be used, and a plurality of substances can be mixed and used. Of these, silica is preferable, and fumed silica is particularly preferable among silicas because of its fine average particle diameter, anti-caking effect, and availability.

  When fumed silica is used, hydrophilic fumed silica having good dispersibility in water is preferable depending on the injection position of sodium hydrogen carbonate into the apparatus. Hydrophobic silica is effective in improving the flowability of sodium hydrogen carbonate, but in boilers, for example, when sodium hydrogen carbonate and its anti-caking agent are added upstream of the flue gas desulfurizer, the absorption of the flue gas desulfurizer Hydrophobic silica aggregates in the tower to form a film at the gas-liquid interface. If the film is stirred under the influence of air or the like, foaming may occur.

  Silica has hydrophilicity unless it is hydrophobized and can be suitably used as an anti-caking agent. Since hydrophilic fumed silica does not float in water but disperses in water, there is no problem with foaming as described above. On the other hand, in the process where an electrostatic precipitator is installed between the location where sodium hydrogen carbonate and its anti-caking agent are added and the flue gas desulfurization device, the above-mentioned troubles such as foaming do not occur. The inhibitor can be used regardless of hydrophobicity or hydrophilicity.

  Moreover, zeolite can also be preferably used as the anti-caking agent. Zeolite can be suitably used because it has an effect of neutralizing by reacting with an acidic component, although the effect as an anti-caking agent is inferior to fumed silica. In particular, synthetic zeolite called 4A-type zeolite has an average particle diameter as small as about 1 to 5 μm and contains sodium, so that neutralizing action of acidic components is strongly preferred. Further, since this zeolite can also be used as a desiccant, it is possible to further suppress the caking of sodium hydrogen carbonate, and it is more effective when used together with fumed silica.

  In this invention, when adding a caking inhibitor, it is preferable to add 0.1-5.0 mass% with respect to sodium hydrogencarbonate, especially 0.3-2.0 mass%. If the content is less than 0.1% by mass, the effect of improving the fluidity of sodium hydrogen carbonate is low. Even if the addition amount of the anti-caking agent exceeds 5.0% by mass, the effect is not increased and only the cost is increased.

  In addition, when using sodium hydrogen carbonate powder stored in a storage tank, in order to improve its discharge, mixed with sodium hydrogen carbonate or sodium carbonate coarse particles with an average particle diameter of more than 20 μm, especially 50 μm or more It is preferable to do. The upper limit of the average particle diameter of the coarse particles is preferably 400 μm or less in view of availability for industrial use. It is effective to mix 20 to 50% by mass of sodium hydrogen carbonate having an average particle diameter of 20 μm or less in sodium hydrogen carbonate and 13 to 50% by mass in sodium carbonate. Further, coarse particles of sodium hydrogen carbonate and coarse particles of sodium carbonate may be mixed and used.

By mixing the coarse particles in the above proportion, it is possible to prevent a phenomenon called a rat hole, where only the central portion of the powder in the storage tank is discharged and the powder remains in the vicinity of the wall. This effect is physically obtained by mixing large particles, but considering the effect of removing acidic components, it is preferable to use sodium hydrogen carbonate or sodium carbonate coarse particles. When using coarse grains of sodium carbonate, it is preferable to use porous sodium carbonate called light ash from the effect of removing SO ₃ components.

  Here, when sodium carbonate is used, since it is highly hygroscopic, it is important to package with a moisture-proof packaging material in order to store it in a packaged form for a long period of time.

  In the present invention, the temperature of the gas to be treated is not particularly limited. Since the gaseous medium supplied into the gas together with sodium hydrogen carbonate is heated to 60 ° C. or more in order to spray sodium hydrogen carbonate, sodium hydrogen carbonate is decomposed into sodium carbonate immediately before spraying on the gas to be treated. Sprayed into the gas.

In the present invention, since the sodium hydrogen carbonate powder having high fluidity is preferably added together with the anti-caking agent and / or coarse particles in the gas, unlike the slurry, it is easy to handle without precipitation. Further, the apparatus is not clogged, sodium bicarbonate can be quantitatively injected, and the SO ₃ component can be removed by stable and accurate neutralization. Furthermore, since it is supplied in a dry system rather than an aqueous solution, problems such as corrosion of equipment do not occur, the management of the apparatus and operation is easy, and stable operation can be maintained.

  Next, the method of the present invention will be specifically described with reference to FIG. 1, taking as an example a method of treating exhaust gas generated by burning fuel in a boiler. FIG. 1 is a diagram illustrating a method for treating exhaust gas burned in a boiler.

The hot exhaust gas burned in the boiler 1 is sent to the air preheater 2 through the first flue 6. Here, heat is exchanged with the combustion air sent to the boiler 1 in order to improve the fuel consumption rate, and the temperature of the combustion air is raised. Next, the exhaust gas is sent to the electrostatic precipitator 3 through the second flue 7, and dust contained in the exhaust gas is removed by static electricity. Here, a bag filter may be used instead of the electric dust collector 3, and the electric dust collector 3 may be omitted depending on the components contained in the exhaust gas. Exhaust gas passing through the electrostatic precipitator 3, is sent to the desulfurizer 4 through a third flue 8, SO ₂ and the like are removed by a magnesium hydroxide slurry and the like. Next, the exhaust gas is sent to the chimney 5 through the fourth flue 9 and discharged from the chimney 5.

Even if the exhaust gas containing the SO ₃ component is, for example, about 20 ppm by volume in terms of SO ₃ , a phenomenon in which white smoke or purple smoke is long flowing from the chimney 5 appears. The main cause is considered that SO ₃ component contained in the exhaust gas reacts with water vapor contained in the atmosphere in the flue and desulfurization apparatus 4 to form sulfuric acid mist. Therefore, the generation of colored smoke such as white smoke or purple smoke can be prevented by removing the SO ₃ component and sulfuric acid mist by adding sodium hydrogen carbonate powder to the exhaust gas. If the SO ₃ component concentration in the gas is lowered to 2 volume ppm or less in terms of SO ₃ , white smoke or purple smoke can be prevented until almost no observation is possible with the naked eye.

In the above process, in the present invention, sodium hydrogen carbonate powder is added by a gaseous medium such as heated air in at least one flue between the first flue 6 and the fourth flue 9. The flue to be used is appropriately selected according to the purpose. In the present invention, sodium hydrogen carbonate is sprayed using a heated gaseous medium and is supplied into the gas as sodium carbonate. Therefore, SO ₃ is effective in both the _{third and} fourth flues 8 and 9. Components can be removed.

[Example 1] In order to confirm the removal effect of SO ₃ component in the gas by the addition of sodium hydrogen carbonate, a test was conducted using the exhaust gas generated by burning the fuel in the boiler of an actual power plant. Here, the construction of the equipment is the same as that of FIG. 1 except for the electric dust collector 3 and the second flue 7, and sodium hydrogen carbonate is in the fourth flue 9 where the gas temperature is 50 ° C. Sprayed on. Specifically, exhaust gas is treated in the following steps, and in the fourth flue 9 between the desulfurization apparatus 4 and the chimney 5, each amount shown in Table 1 using air at 25 ° C. and heated air at 200 ° C. A mixture obtained by adding 1.0% by mass of hydrophilic fumed silica having an average particle diameter of 0.01 μm to sodium hydrogen carbonate powder having an average particle diameter of 9 μm was sprayed.

Then, the SO ₃ component in the gas discharged from the chimney 5 was quantified and evaluated. Further, the flickering of white smoke (including purple smoke) caused by the SO ₃ component discharged from the chimney 5 was visually observed and evaluated. The results are shown in Table 1. Table 1 also shows the case where sodium bicarbonate powder was not added as a comparison.

In addition, the addition amount of the sodium hydrogencarbonate powder in Table 1 is shown by the molar ratio with respect to the SO ₃ component contained in the exhaust gas before being sent to the desulfurization apparatus (before being contacted with water vapor and forming sulfuric acid miss). .

Step: The high-temperature exhaust gas burned in the boiler is sent to the air preheater 2 through the first flue 6 to exchange heat with the combustion air, and then the exhaust gas is sent to the desulfurization device 4 through the third flue 8. The SO _{2 and the} like are removed by magnesium hydroxide slurry, and then sent to the chimney 5 through the fourth flue 9 and discharged from the chimney 5.

The boiler equipment specifications and exhaust gas composition at the time of implementation were as follows.
<Boiler specification> Model: Forced once-through type Benson boiler, Evaporation amount: 83 t / hr, Steam temperature: 520 ° C., Steam pressure: 137 × 10 ⁵ Pa.
<Exhaust gas composition> O ₂ : 4.5 vol%, SO ₂ : 1400 vol ppm, converted concentration of SO ₃ component: 17 vol ppm.

In addition, the pure content of sodium hydrogen carbonate in Table 1 is an analytical value of sodium hydrogen carbonate in the solid substance sucked and collected in the middle of the pipe for injecting sodium hydrogen carbonate into the fourth flue 9 and neutralized. It was measured by a titration method. From Table 1, when spraying using air at 25 ° C., decomposition of sodium hydrogencarbonate did not proceed, so removal of the SO ₃ component was insufficient. Therefore, when white smoke discharged from the chimney is sprayed using air at 25 ° C, the concentration of white smoke flickers is halved compared to the case where sodium bicarbonate is not added, but there is no difference in the flutter length. It was. On the other hand, the concentration of white smoke fluttering when sprayed using 200 ° C. air was discernable with caution, and the length was also significantly reduced compared to the case where no sodium bicarbonate was added.

  [Example 2] In a flue 7 between the air preheater 2 and the desulfurizer 4, a sodium hydrogencarbonate powder having an average particle diameter of 9 µm and a hydrophilic fumed silica having an average particle diameter of 0.01 µm are used as sodium hydrogencarbonate powder. The mixture added at 1.0% by mass with respect to each was spray-injected in the amounts shown in Table 2 using air at temperatures of 25 ° C. and 200 ° C., respectively. That is, the test was performed in the same manner as in Example 1 except for the injection position, and the evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

In addition, the pure content of sodium hydrogen carbonate in Table 2 is an analytical value of sodium hydrogen carbonate in a solid substance sucked and collected in the middle of a pipe for injecting sodium hydrogen carbonate into the flue 7, and is determined by a neutralization titration method. It was measured. From Table 2, the direction of spraying using air at 200 ° C. sufficiently removes the SO ₃ component. When air at 200 ° C is used, sodium hydrogen carbonate is decomposed in advance and then injected into the flue, whereas when air at 25 ° C is used, sodium hydrogen carbonate is decomposed in the flue 7. Therefore, it is estimated that the reaction time with the SO ₃ component has decreased by the time required for the decomposition. Further, it was confirmed that the fluttering disappeared when the SO ₃ component was 2 ppm.

  [Example 3] The following test was conducted to confirm the effect of improving the fluidity and dispersibility of sodium hydrogencarbonate powder by the addition of an anti-caking agent. That is, nothing added to sodium hydrogen carbonate powder having an average particle diameter of 9 μm, 1% by mass of hydrophilic fumed silica added as an anti-caking agent to the sodium hydrogen carbonate powder, and hydrogen carbonate The physical properties of each of sodium powders with 1% by mass of zeolite added as an anti-caking agent were evaluated.

  The physical properties were evaluated by measuring the angle of repose as an index of fluidity and the degree of dispersion as an index of dispersibility. In general, if the angle of repose exceeds 65 °, the fluidity deteriorates and the discharge from the storage tank becomes difficult to handle, and if the degree of dispersion is less than 10%, the jet property deteriorates and sprays into the air stream. It can be judged that the scattering state at the time of the deterioration.

  Here, the angle of repose was measured by the method described above. The degree of dispersion was measured using a powder tester PT-D type manufactured by Hosokawa Micron. That is, 10 g of the powder sample is dropped from a height of 61 cm onto a watch glass with a diameter of 10 cm installed so that the concave surface is on top, and outside the watch glass with respect to the total mass of the dropped powder sample. It is the numerical value prescribed | regulated as 100 fraction of the mass of the scattered powder sample.

  From this result, it can be seen that the repose angle and dispersity of sodium hydrogen carbonate are changed by the addition of hydrophilic silica and zeolite, and the fluidity and dispersibility as a powder are improved.

  Next, each powder shown in Table 3 was used, and a test was carried out by spraying with air and supplying it to the flue. As a result, the anti-caking agent was added to the powder with no anti-caking agent added. It was difficult to supply a predetermined amount stably compared to the added powder.

  [Example 4] A test for confirming improvement in dischargeability of sodium hydrogen carbonate powder from a storage tank by adding coarse particles was performed. That is, to the sodium hydrogencarbonate powder having an average particle diameter of 9 μm added with 1% by mass of hydrophilic fumed silica as an anti-caking agent, no sodium hydrogen carbonate coarse particles were added (Sample 1) Then, 30% by mass of sodium hydrogen carbonate coarse particles having an average particle diameter of 98 μm (sample 2) and 19% by mass of sodium carbonate coarse particles having an average particle diameter of 98 μm (sample 3) were prepared.

  Next, a storage tank was prepared in which the bottom of a cone having an apex angle of 60 degrees and a bottom diameter of 1 m was connected to the bottom of a cylinder having an inner diameter of 1 m and a height of 2 m, and a discharge portion having an inner diameter of 20 cm was connected to the apex of the cone. . In addition, a damper was installed in this discharge part. Using the above samples 1 to 3, 600 kg of sodium carbonate was added to the storage tank, the damper was opened, and the discharge from the storage tank was observed. In the case of Sample 1 and Sample 2 in which coarse particles were mixed, almost the entire amount could be discharged, but in the case where no coarse particles were added, only the central portion was discharged, and about half of the whole remained.

1: Boiler 2: Air preheater 3: Electric dust collector 4: Desulfurization device 5: Chimney 6: First flue 7: Second flue 8: Third flue 9: Fourth flue

Claims (7)

A method of treating gas generated by combustion of fuel in a boiler and sent to an air preheater, a desulfurizer, and then to a chimney through a flue, having an average particle diameter of 20 μm or less, an angle of repose of 65 ° or less, and dispersion A gas containing 10% or more of sodium hydrogen carbonate powder is decomposed using a gaseous medium heated to 60 ° C. or higher, and contains SO _{2 in an amount} of 500 ppm by volume or more in at least one flue, and further contains a SO ₃ component. spray by the processing method for a gas containing a SO ₃ component, and removing the SO ₃ component in the gas inside. The gas treatment method according to claim 1, wherein the sodium hydrogencarbonate powder is added in an amount of 1 to 16 moles relative to the SO ₃ component in the gas. A method of treating a gas produced by burning fuel in a boiler and passing through a flue to an air preheater, a desulfurizer, and then to a chimney, wherein sodium bicarbonate powder having an average particle diameter of 20 μm or less is obtained at 60 ° C. decomposed using a gaseous medium which has been heated to above, at least one flue, by the SO ₂ contained more than 500 vol ppm, further sprayed into the gas containing SO ₃ component, SO ₃ component in the gas In addition to the sodium hydrogen carbonate powder, 0.1-5 mass% anti-caking agent was added to the sodium hydrogen carbonate powder, and the anti-caking agent was added to the sodium hydrogen carbonate powder. A method for treating a gas, wherein the angle of repose of the mixture is 65 ° or less and the degree of dispersion of the mixture is 10% or more.   The gas treatment method according to claim 3, wherein the anti-caking agent has an average particle diameter of 0.005 to 5 μm.   The gas treatment method according to claim 3 or 4, wherein the anti-caking agent comprises silica and / or zeolite. A method of treating a gas produced by burning fuel in a boiler and passing through a flue to an air preheater, a desulfurizer, and then to a chimney, wherein sodium bicarbonate powder having an average particle diameter of 20 μm or less is obtained at 60 ° C. decomposed using a gaseous medium which has been heated to above, at least one flue, by the SO ₂ contained more than 500 vol ppm, further sprayed into the gas containing SO ₃ component, SO ₃ component in the gas Together with the sodium hydrogen carbonate powder having an average particle diameter of 20 μm or less, 20-50 mass% of the sodium hydrogen carbonate coarse particles having an average particle diameter of more than 20 μm or 13-50 with respect to the powder. A method for treating a gas comprising adding mass% of sodium carbonate coarse particles having an average particle diameter of more than 20 μm. The gas containing SO ₃ component is produced by combustion of fuel containing sulfur and contains SO ₂ in a volume of 500 ppm by volume or more. The concentration of SO ₃ component in the gas is 2 ppm by volume in terms of SO _3. The gas processing method according to any one of claims 1 to 6, which is reduced to the following.

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