JPH09141049A - Method for producing desulfurization agent and flue gas desulfurization method - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a desulfurizing agent with improved utilization, a method for producing the same, and a flue gas desulfurizing method using the same. SOLUTION: Slaked lime (Ca (OH) ₂ ) or quick lime (CaO) is dispersed in water or an aqueous methanol solution so as to be a slurry of 1 to 60% by weight, and stirred and mixed while introducing a CO ₂ -containing gas. As a desulfurizing agent, the desulfurizing agent is slurried or dried and then blown into the exhaust gas flue in the combustion furnace or in the subsequent flow to react with SOx in the combustion exhaust gas.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a desulfurizing agent and a flue gas desulfurizing method, and more particularly to a method for producing a desulfurizing agent and a flue gas desulfurizing method in which the utilization rate and desulfurization rate of the desulfurizing agent are improved.

[0002]

2. Description of the Related Art Sulfur oxides (hereinafter referred to as SO
x)) as a flue gas desulfurization method, for example, a dry flue gas desulfurization method in which a calcium (Ca) -based desulfurizing agent is blown into a combustion furnace or an exhaust gas flue, and a slurry-like desulfurizing agent such as slaked lime slurry. A semi-dry flue gas desulfurization method of blowing in air, or introducing the exhaust gas into the absorption tower and bringing it into contact with a desulfurizing agent slurry, for example, limestone slurry, to remove SO in the exhaust gas.
A wet flue gas desulfurization method that absorbs x is known, and the dry or semi-dry flue gas desulfurization method is widely adopted because the equipment cost is low and a certain degree of desulfurization rate can be obtained.

However, the desulfurization agent has a low utilization rate in the above-mentioned dry or semi-dry desulfurization method. For example, in the dry flue gas desulfurization method, when limestone is used as the desulfurization agent, the amount of the desulfurization agent used is 5 to 5% of the sulfur content to be removed. You need 8 times.
On the other hand, even when slaked lime (Ca (OH) ₂ ) which is relatively expensive but has a high desulfurization activity is used as the desulfurizing agent, there is a problem that a desulfurizing agent of several times the sulfur content to be removed is required. is there. Therefore, it has been desired to develop a desulfurizing agent manufacturing method and a flue gas desulfurizing method using the manufactured desulfurizing agent, which have a high utilization rate of the desulfurizing agent and are inexpensive.

[0004]

The object of the present invention is to solve the above-mentioned problems of the prior art and improve the desulfurizing agent utilization rate.
It is to provide an inexpensive method for producing a desulfurizing agent. Another object of the present invention is to provide a flue gas desulfurization method capable of increasing the utilization rate of a desulfurization agent and improving the desulfurization rate.

[0005]

In order to achieve the above object, the present inventor has conducted extensive studies on the relationship between the type of desulfurizing agent and the desulfurizing agent utilization rate in a dry or semi-dry flue gas desulfurization method, and as a result, slaked lime (Ca (OH) ₂ ) or quick lime (Ca
O) is poured into water or an aqueous methanol solution to form a slurry, and the mixture is stirred and mixed in an air atmosphere or while blowing CO ₂ to obtain a desulfurizing agent having a significantly improved Ca utilization rate during desulfurization. And has reached the present invention. Further, the present inventor, by blowing the obtained desulfurization agent into the combustion furnace or into the exhaust gas flue, or by mixing with the fuel in advance to produce a desulfurization agent-containing fuel and then burning, the sulfur oxidation in the combustion exhaust gas They have found that they can effectively remove matter and have reached the present invention.

That is, the invention claimed in the present application is as follows. (1) A method for producing a desulfurizing agent, characterized in that slaked lime or quick lime is dispersed in water or an aqueous methanol solution so as to be a slurry of 1 to 60% by weight, and stirred and mixed in an air atmosphere. (2) The method for producing a desulfurizing agent as described in (1) above, which comprises stirring and mixing while blowing a CO ₂ -containing gas. (3) The method for producing a desulfurizing agent according to (2) above, wherein combustion exhaust gas is used as the CO ₂ -containing gas. (4) The method for producing a desulfurizing agent according to any one of (1) to (3) above, which comprises stirring, mixing, draining, and drying. (5) The desulfurizing agent produced by any of the above (1) to (4) is blown into the combustion furnace and / or the exhaust gas flue of the downstream of the combustion furnace as a desulfurizing agent as a slurry to produce combustion exhaust gas. A flue gas desulfurization method, characterized by reacting with sulfur oxides therein. (6) The desulfurizing agent produced by any of the above (1) to (4) is mixed with a fuel as a slurry or as a desulfurizing agent to obtain a desulfurizing agent-containing fuel, and the desulfurizing agent-containing fuel is burned to produce exhaust gas. A flue gas desulfurization method comprising reacting the sulfur oxide therein with the desulfurizing agent.

In the present invention, slaked lime (Ca (OH) ₂ ) or quick lime (CaO) is put into water or an aqueous solution of methanol (hereinafter also simply referred to as "methanol") to form a slurry, which is then subjected to an air atmosphere or CO. ₂ This is a method for producing a highly active desulfurizing agent, which comprises stirring and mixing while blowing a gas containing ₂ therein. Further, the present invention is a highly active desulfurizing agent as a slurry,
Or it is blown into a combustion furnace and / or an exhaust gas flue as a desulfurizing agent to desulfurize, or pulverized coal, coal-
A fuel such as water slurry (CWM) or heavy oil is mixed with the highly active desulfurizing agent to obtain a desulfurizing agent-containing fuel, which is burned, and exhaust gas generated is desulfurized in the furnace by the desulfurizing agent. It is a smoke desulfurization method.

Slaked lime (Ca (OH) ₂ ) used in the present invention
Alternatively, quick lime (CaO) powder has a particle size of 0.01 to 20.
It is 0 μm, preferably 0.01 to 20 μm.
If it is less than 0.01 μm, it is highly active because it is originally fine particles, and the effect of the present invention is small, and if it exceeds 200 μm, only the surface of the particle is activated and a sufficient effect cannot be obtained. When the particle size is 0.01 to 20 μm, the effect of the present invention is great, which is preferable.

Water or methanol is used as a solvent for dispersing the powder of slaked lime, but methanol is more preferable.
It is preferable because the Ca utilization rate of the desulfurizing agent is further improved. The methanol concentration is 1 to 100 vol%, preferably 10
It is 100 vol%. If it is less than 1 vol%, the effect of using methanol is not exhibited. A water-soluble alcohol such as ethanol may be used instead of methanol.

The slaked lime or quick lime in the water or methanol slurry is 1 to 60% by weight, preferably 2 to 50% by weight. If it is less than 1% by weight, the equipment for stirring and mixing becomes excessively large, and if it exceeds 60% by weight, the efficiency of the stirring and mixing operation is lowered due to an increase in slurry viscosity. If it is 2 to 50%, the stirring and mixing operation can be efficiently performed, which is preferable. The slurry temperature during stirring is 0 to 80 ° C, preferably 20 to 60
° C. The stirring and mixing time is 1 to 20 hours, preferably 2 to 20 hours, when CO ₂ is not introduced. If it is less than 1 hour, the amount of carbon dioxide taken up will be insufficient and the desulfurization activity will be insufficiently improved. On the other hand, if it is 20 hours or more, it is not practical. When introducing a CO ₂ -containing gas,
The stirring time can be shortened, for example, 0.05 to 5 hours. If it is less than 0.05 hours, the carbon dioxide gas is not taken up sufficiently, and even if it is carried out for 5 hours or more, the superiority does not appear. Note stirring time, different hydrated lime or quicklime having a particle size, slurry concentration, stirring intensity, the CO ₂ concentration of the CO ₂ containing gas.

The CO ₂ concentration of the CO ₂ containing gas is 0.02.
It is -100 vol%, preferably 5-100 vol%. If it is 0.02 vol or less, the effect of introducing CO ₂ is not sufficiently exhibited. When the CO ₂ concentration is in the range of 5 to 100 vol%, the effect of introducing CO ₂ can be sufficiently obtained, the cost is advantageous, and the handling is easy. As the CO ₂ -containing gas, combustion exhaust gas discharged from a combustion furnace or exhaust gas after desulfurization thereof can be used. For example, when using combustion exhaust gas having a CO ₂ concentration of 8 to 16 vol%, 0.1 to 3 is used. A highly active desulfurizing agent can be obtained by stirring and mixing for about an hour. Air can also be used as the CO ₂ -containing gas.

In the present invention, slaked lime or quick lime is introduced into water or methanol by introducing a CO ₂ -containing gas,
Alternatively, the reason why the desulfurization activity of the desulfurization agent is improved by stirring and mixing without introducing is that a part or all of the desulfurization agent is highly active fine-grained calcium carbonate (CaCO ₃ ).
Or, it is thought that it changes to its approximation. A desulfurizing agent with higher desulfurization activity is obtained when methanol is used than when water is used as a solvent, because the finer carbonated desulfurizing agent is generated in methanol. Presumed to be.

FIG. 1 shows that slaked lime (Ca (OH) ₂ ) was put into water or methanol and stirred in the atmosphere for 20 hours.
It shows the thermal decomposition characteristics of the desulfurizing agent activated by mixing. For comparison, the thermal decomposition characteristics of slaked lime (Ca (OH) ₂ ) and calcium carbonate (CaCO ₃ ) are shown at the same time. In the figure, Ca (OH) ₂ activated in water is
It has almost the same thermal decomposition characteristics as CaCO _3, and when it is stirred and mixed in water, Ca (OH) ₂ absorbs CO ₂ in the atmosphere and most of it is converted into fine particles of CaCO ₃ . I understand. On the other hand, the thermal decomposition pattern of Ca (OH) ₂ activated in methanol did not always coincide with that of CaCO ₃ by differential thermal analysis, and showed a unique behavior. Therefore, other components besides CaCO ₃ were generated. Is also expected.

FIG. 2 shows the results of X-ray diffraction of slaked lime and a desulfurizing agent which was dried after stirring slaked lime in water or methanol while blowing carbon dioxide gas. In the figure, slaked lime (Ca (OH) ₂ ) stirred and mixed in water shows a diffraction peak similar to that of CaCO _3, and by stirring while introducing a CO ₂ -containing gas in water, Ca (OH) ₂ Mostly fine-grained CaC
It can be seen that it has been converted to O ₃ . On the other hand, C in methanol
Stirring while introducing O ₂ containing gas, mixed Ca (O
H) ₂ does not show a clear diffraction peak, and it is speculated that a finer crystalline desulfurizing agent was prepared.

In the flue gas desulfurization method of the present invention, the desulfurizing agent prepared above is blown into the combustion equipment, that is, in the combustion furnace or / and its exhaust gas flue to react with SOx in the exhaust gas to remove it. is there. In addition, another flue gas desulfurization method of the present invention, the desulfurization agent obtained above is mixed with a combustion fuel in advance to obtain a desulfurization agent-containing fuel, and the desulfurization agent-containing fuel is burned to generate SOx in the generated exhaust gas. It is to be removed by reacting with the desulfurizing agent contained in the fuel.

[0016]

Next, the present invention will be described in more detail by way of examples. Example 1 5 g of commercially available slaked lime (Ca (OH) ₂ ) having an average particle size of 3 μm
Is put into water to make a slurry of 2% by weight, and a laboratory medium speed mixer is used as an agitator in an air atmosphere at 25 ° C. for 1 hour.
Stir, mix for hours, then filter using a suction filter,
Then, it was dried at 105 ° C. for about 1 hour using a dryer to obtain a desulfurizing agent.

About 10 to 100 mg of the obtained desulfurizing agent
Using a thermobalance, at 900 ℃, SO _TwoConcentration 0.3%
(O_Two: 5%, N_Tworeact with gas for 2 hours)
Then, from the weight change, the calcium (Ca)
The usage rate (hereinafter referred to as Ca conversion rate) was determined.

[0018]

(Equation 1)

Example 2 A desulfurizing agent was prepared in the same manner as in Example 1 except that the stirring and mixing time was 20 hours.
A reactivity test with ₂ was performed. Comparative Example 1 Commercially available slaked lime was used as a desulfurizing agent without treatment,
A reactivity test with SO ₂ was conducted in the same manner as in Example 1.

The Ca conversion rate measurement results in Examples 1 and 2 and Comparative Example 1 are shown in FIG. From FIG. 3, the desulfurization agent treated in water (Examples 1 and 2) was untreated Ca (OH) ₂
It can be seen that the Ca conversion rate was improved as compared with (Comparative Example 1), and particularly the Ca conversion rate of the one treated for 20 hours (Example 2) was significantly improved. Example 3 A desulfurizing agent was prepared in the same manner as in Example 1 except that a 20% aqueous methanol solution was used instead of water, and a reactivity test with SO ₂ was conducted in the same manner.

Example 4 A desulfurizing agent was prepared in the same manner as in Example 3 except that the stirring time was 20 hours, and the reactivity test with SO ₂ was conducted in the same manner. The Ca conversion of the desulfurizing agent obtained in Examples 3 to 4 was
It is shown in FIG. 4 together with the result of Comparative Example 1.

From FIG. 4, the Ca conversion of the desulfurizing agents of Examples 3 to 4 treated by stirring in methanol is untreated.
H) ₂ compared to H) ₂ , and it can be seen that the Ca conversion rate was remarkably improved especially after stirring for 20 hours (Example 4). Example 5 At the time of stirring, CO ₂ containing gas having a CO ₂ concentration of 15% was blown as carbonation at 0.4 liter / min while stirring and mixing, and stirring and mixing time were 0.5.
A desulfurizing agent was prepared in the same manner as in Example 1 except that the time was set, and a reactivity test with SO ₂ was conducted in the same manner.

[0023] Example 6 during stirring, stirring while blowing CO ₂ concentration of 15% CO ₂ containing gas as carbonated at 0.4 l / min, with mixing, stirring, mixing time 1.0
A desulfurizing agent was prepared in the same manner as in Example 1 except that the time was set, and a reactivity test with SO ₂ was conducted in the same manner.

[0024] Example 7 upon stirring, stirring while blowing CO ₂ concentration of 15% CO ₂ containing gas as carbonated at 0.4 l / min, with mixing, stirring, mixing time 2.0
A desulfurizing agent was prepared in the same manner as in Example 1 except that the time was set, and a reactivity test with SO ₂ was conducted in the same manner.

The Ca conversion rates of Examples 5 to 7 are shown in FIG. 5 in comparison with Comparative Example 1. From FIG. 5, it can be seen that the Ca conversion rates of Examples 5 to 7 in which carbonation was performed during stirring were significantly improved. Further, it is understood that by using carbonation in combination, the Ca conversion rate could be sufficiently improved even by the stirring process for a short time. Example 8 At the time of stirring, while stirring and mixing a CO ₂ -containing gas having a CO ₂ concentration of 15% at a rate of 0.4 l / min as carbonation, the stirring and mixing time was 0.5.
A desulfurizing agent was prepared in the same manner as in Example 3 except that the time was set, and a reactivity test with SO ₂ was conducted in the same manner.

[0026] when Example 9 stirring, stirring while blowing CO ₂ concentration of 15% CO ₂ containing gas as carbonated at 0.4 l / min, with mixing, stirring, mixing time 1.0
A desulfurizing agent was prepared in the same manner as in Example 3 except that the time was set, and a reactivity test with SO ₂ was conducted in the same manner.

[0027] Example 10 during stirring, stirring while blowing CO ₂ concentration of 15% CO ₂ containing gas as carbonated at 0.4 l / min, with mixing, stirring, mixing time 2.0
A desulfurizing agent was prepared in the same manner as in Example 3 except that the time was set, and a reactivity test with SO ₂ was conducted in the same manner.

The Ca conversions of Examples 8 to 10 are shown in FIG. 6 in comparison with Comparative Example 1. From FIGS. 6A and 6B, in Examples 8 to 10 in which methanol was used as a solvent and carbonation was carried out at the time of stirring, the Ca conversion rate was remarkably improved by stirring and mixing for a short time. It can be seen that each is larger than the case where carbonation is used together with water.

Next, a specific example of the flue gas desulfurization method of the present invention will be described. Example 11 FIG. 7 is a conceptual diagram showing an example of the flue gas desulfurization method of the present invention. This desulfurization method is a dry desulfurization method in which a desulfurizing agent is blown into a combustion facility, that is, a combustion furnace or / and an exhaust gas flue. For example, 24 kg of slaked lime 1 is added to methanol 2
It is introduced together with (20% aqueous methanol solution) into the stirring facility 3 to obtain, for example, a 6 wt% slurry 8, and the slurry 8
As a CO ₂ -containing gas, the combustion exhaust gas (CO
₂ 14.4%) 7 at 0.9 Nm ³ / min while stirring and stirring, for example, for 2 hours by rotating the stirrer 4 at, for example, 360 rpm, and then introducing it to a downstream dehydration / drying facility 5 for dehydration. For example, the activated desulfurizing agent was dried by drying at 105 ° C. for about 1 hour. This activated desulfurizing agent is used as fuel, for example, pulverized coal having a high sulfur content (S content 2.4 wt%).
In a combustion furnace 6 in which 100 kg / Hr is burned.
Although the desulfurization treatment of the exhaust gas was performed by blowing in at a rate of 3 kg / Hr (ca content is about 1.5 times the sulfur content to be removed ... molar ratio), the desulfurization rate varies depending on the combustion conditions.
0-90%. 9 is energy taken out as superheated steam, for example.

In this embodiment, it is also possible to prolong the stirring and carbonation time and use water as a solvent instead of methanol. Further, the desulfurizing agent can be used as it is without drying it. Comparative Example 2 A similar exhaust gas desulfurization operation was performed in the same manner as in Example 11 except that the slaked lime of Comparative Example 1 (untreated) was used as the desulfurizing agent blown into the combustion furnace and / or its exhaust gas flue. The desulfurization rate was 30 to 50%.

Embodiment 12 FIG. 8 is a conceptual diagram showing another embodiment of the flue gas desulfurization method of the present invention. In this desulfurization method, a desulfurizing agent is mixed in advance with a fuel to obtain a desulfurizing agent-containing fuel, which is then introduced into a combustion furnace and burned, and SOx generated is removed by the desulfurizing agent in the fuel. The desulfurization agent was adjusted in the same manner as in Example 11, and the obtained activated desulfurization agent 10 was dehydrated and concentrated, for example, as a slurry, and then, for example, heavy oil having a high sulfur content (S content 3.2 wt%). ) 13, the desulfurizing agent content is 1
2.4 wt% (Ca content 1.4% sulfur to be removed)
The mixture is mixed so as to have a double amount ... molar ratio), and is mixed and homogenized in the fuel / desulfurization agent mixing facility 11 to obtain the desulfurization agent-containing fuel 12. When the desulfurizing agent-containing fuel 12 was introduced into the combustion furnace 6 at 100 kg / Hr and burned, the desulfurization rate of the exhaust gas was 60 to 90% although it varied depending on the combustion conditions. 9 is energy taken out as superheated steam, for example.

Comparative Example 3 Exhaust gas desulfurization was carried out in the same manner as in Example 12 except that the slaked lime of Comparative Example 1 (untreated) was used as the desulfurizing agent. The desulfurization rate was 30 to 60%. there were.

[0033]

According to the invention of claim 1 of the present application, slaked lime or quick lime is dispersed in water or methanol,
A desulfurizing agent having a high Ca conversion rate can be prepared by mixing in an air atmosphere. According to the invention of claim 2 of the present application, slaked lime or quick lime is dispersed in water or methanol and stirred while blowing a CO ₂ -containing gas,
By mixing, a desulfurizing agent having a high Ca conversion rate can be prepared in a short time.

According to the invention of claim 3 of the present application, CO
By using the combustion exhaust gas as the ₂ content gas, it is possible to effectively utilize the exhaust gas to prepare a desulfurization agent having a high Ca conversion rate without requiring a new CO ₂ source. According to the invention of claim 4 of the present application, the desulfurizing agent produced is deliquored and dried to obtain a dry desulfurizing agent having a high Ca conversion rate.

According to the invention of claim 5 of the present application, the highly active desulfurizing agent is blown into the combustion furnace and / or the exhaust gas flue of the subsequent flow as it is after slurry (after dehydration concentration if necessary) or after drying. By reacting with sulfur oxides in the combustion exhaust gas, the desulfurization rate can be improved, for example, by about 1.5 to 2.0 times as compared with the case of using the conventional desulfurizing agent. .

According to the sixth aspect of the present invention, the highly active desulfurizing agent is slurry or dried, and then mixed with the fuel to prepare a desulfurizing agent-containing fuel, and the desulfurizing agent mixed fuel is burned. Since the sulfur oxides generated at this time can be removed by reacting with the desulfurizing agent contained in the fuel, the desulfurization rate is improved as compared with the case of using the conventional desulfurizing agent.

[Brief description of the drawings]

FIG. 1 is a diagram showing the thermal decomposition characteristics of various desulfurizing agents.

FIG. 2 is a diagram showing the results of X-ray diffraction of various desulfurizing agents.

FIG. 3 is a graph showing the Ca conversion rates of Examples 1 and 2.

FIG. 4 is a graph showing Ca conversion rates in Examples 3 to 4.

FIG. 5 is a graph showing Ca conversion rates in Examples 5 to 7.

FIG. 6 is a graph showing Ca conversion rates of Examples 8 to 10.

FIG. 7 is a conceptual diagram showing an embodiment of a flue gas desulfurization method of the present invention.

FIG. 8 is a conceptual diagram showing another embodiment of the flue gas desulfurization method of the present invention.

[Explanation of symbols]

1 ... slaked lime or quick lime, 2 ... methanol, 3 ... stirring equipment (carbonation equipment), 4 ... stirring machine, 5 ... dehydration / drying equipment,
6 ... Combustion furnace (and / or exhaust gas flue), 7 ... Combustion exhaust gas after desulfurization, 8 ... Slurry, 9 ... Energy, 10 ... Activated desulfurizing agent, 11 ... Fuel / desulfurizing agent mixing facility, 12 ... Desulfurizing agent mixing Fuel, 13 ... Fuel.

Claims (6)

[Claims] 1. A method for producing a desulfurizing agent, which comprises dispersing slaked lime or quick lime in water or an aqueous methanol solution so as to be 1 to 60% by weight, and stirring and mixing in an air atmosphere. 2. Agitating while blowing a CO ₂ -containing gas,
The method for producing a desulfurizing agent according to claim 1, wherein the method is mixed. 3. The method for producing a desulfurization agent according to claim 2, wherein combustion exhaust gas is used as the CO ₂ -containing gas. 4. The method for producing a desulfurizing agent according to any one of claims 1 to 3, which comprises stirring, mixing, deliquoring and drying. 5. The desulfurizing agent produced according to any one of claims 1 to 4 is blown into a combustion exhaust gas flue as a slurry or as a dry desulfurizing agent into a combustion furnace and / or into an exhaust gas flue of a downstream of the combustion furnace. A flue gas desulfurization method characterized by reacting with sulfur oxides of. 6. The desulfurizing agent produced according to any one of claims 1 to 4 is mixed with a fuel as a slurry or as a dry desulfurizing agent to produce a desulfurizing agent-containing fuel, and the desulfurizing agent-containing fuel is burned to produce an exhaust gas. A flue gas desulfurization method, characterized in that the sulfur oxide of (1) is reacted with the desulfurizing agent.