JP3896639B2 - Activated carbon catalyst and flue gas desulfurization method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an activated carbon catalyst for recovering and removing sulfur oxides contained in exhaust gas as sulfuric acid by catalytic sulfation reaction, and a flue gas desulfurization method using the same.
[0002]
[Prior art]
Conventionally, sulfur oxides such as sulfurous acid gas contained in exhaust gas are finally converted into sulfuric acid by oxidizing with oxygen coexisting at low temperature, and this is directly used as sulfuric acid or by reacting this with calcium compounds. The process of recovering as gypsum is well known.
As such a catalyst for oxidizing sulfurous acid gas or the like in exhaust gas, activated carbon is most preferable. That is, when a ceramic carrier such as alumina, silica, titania, or zeolite is used as the catalyst, the activity is insufficient by itself, so it is necessary to add a metal or metal oxide as a catalyst species to the catalyst. is there. However, these catalyst species have the disadvantage that they cannot maintain stable activity for a long time because they are dissolved or altered by the attack of the sulfuric acid produced. On the other hand, the activated carbon has the characteristics that the activity is expressed without supporting any catalyst species, and that it continues without deterioration for a long time.
[0003]
However, in the industrial use as a flue gas desulfurization apparatus, when using commercially available activated carbon as it is, the catalytic activity in the catalytic sulfation reaction is low, so that the catalyst filling amount is extremely high in order to obtain a desired desulfurization effect. Therefore, compared to other desulfurization processes such as a wet flue gas desulfurization process, there is a problem that it cannot be economically compared.
By the way, the adsorption and oxidation activity (hereinafter simply referred to as “activity”) of sulfur dioxide gas of activated carbon is very large if there is no moisture in the exhaust gas. However, since the product sulfuric acid is very hygroscopic, it absorbs moisture on the activated carbon surface in the presence of water vapor to form dilute sulfuric acid, which fills the pores of the activated carbon and diffuses sulfurous acid gas. As a result, the surface activity of the activated carbon is not sufficiently exhibited.
Therefore, various methods have been proposed in which the activated carbon is imparted with water repellency and the generated sulfuric acid is quickly discharged from the pores of the activated carbon to maintain the high activity of the activated carbon.
[0004]
For example, in Chem. Eng. Comm. Vol. 60 (1987), P253, a dispersion of polytetrafluoroethylene (hereinafter abbreviated as PTFE) is sprayed on activated carbon having an average diameter of 0.78 mm. An example is disclosed in which the rate constant of adsorption and oxidation reaction of sulfurous acid gas is increased by a factor of 3 in an added amount of 8 to 20%.
JP-A-59-36531 discloses that the activated carbon is subjected to water repellency treatment to increase the adsorption and oxidation activity of sulfurous acid gas. Specifically, a PTFE dispersion is applied to granular activated carbon of 5 to 10 mm. It is disclosed that, when impregnated and heat-treated at 200 ° C. for 2 hours, the activity is much higher than that of a catalyst with a simple activated carbon.
[0005]
[Problems to be solved by the invention]
The present inventors conducted the following confirmation experiment in order to verify the effectiveness of a measure for increasing the activity of activated carbon as such a conventional catalyst.
First, based on the conventional water repellent technology described above, PTFE was supported on various commercially available activated carbons in the particle size range of 2.8 to 4.0 mmφ by spraying or impregnation, and the activity was measured. Compared with a simple catalyst for activated carbon, a certain degree of activity improvement and long-lasting durability were observed.
However, when considering large-scale industrial practice, this level of activity is still not sufficient as a catalyst to outperform other competing flue gas desulfurization processes, further improving catalytic activity. Recognized that is necessary.
[0006]
Thus, as a result of various studies, the present inventors have found that it is effective to make the activated carbon macropores (pores having a pore diameter exceeding 5 nm) water repellent in order to improve the catalytic activity. In a separate patent application filed on the same day, a method of impregnating and supporting a water repellent material such as polystyrene having a sphere equivalent diameter of 10 to 100 nm, water repellent macropores and finely pulverizing activated carbon, and an average sphere such as commercially available PTFE A method of forming a macropore having a water repellent property by mixing with a fluorine resin having an equivalent diameter of 100 nm or more was shown. However, the macropores remaining in the finely pulverized activated carbon particles have a problem that they are not sufficiently water-repellent.
Therefore, finely pulverized activated carbon particles are impregnated and supported with a water repellent material having a sphere equivalent diameter of 10 to 100 nm, and then mixed with a fluororesin such as commercially available PTFE to repel all macropores of the catalyst. As a result, it was confirmed that the catalytic activity was further improved, and the present invention was solved in which the above-mentioned problems were solved.
[0007]
That is, the development process will be described in detail below. In order to further improve the activity of the activated carbon by making the water repellent, the present inventors can effectively make any part of the activated carbon water repellent. I checked if there was.
First, the fluorine distribution in an activated carbon catalyst prepared by a conventional method in which a PTFE dispersion was sprayed or impregnated on activated carbon was subjected to surface analysis by EPMA. As a result, it was found that the PTFE particles did not penetrate into the activated carbon particles at all, and all adhered to the outer surface of the particles. This is because commercially available activated carbon has almost no pores of 1 μm or more, and resistance is too high for PTFE particles having a diameter in the range of 0.2 to 0.4 μm to enter the pores. This is probably because of this. Incidentally, similar experimental results were obtained when a dispersion of polystyrene particles having an average particle size of 0.3 μm was used instead of the PTFE dispersion. Then, an activity test was performed on the activated carbon catalyst supporting these two types of water-repellent particles. As a result, it was found that the catalyst supporting PTFE was slightly more active than the activated carbon catalyst supporting polystyrene particles. However, none of them exhibited high activity as expected.
[0008]
Therefore, the present inventors expect that the discharge of the generated sulfuric acid will be greatly promoted by uniformly repelling the entire surface of the activated carbon including the vicinity of the active site, and pores of 5 nm or less in the activated carbon. It was decided to perform the water repellency treatment on the entire surface including pores having a diameter (hereinafter abbreviated as micropores).
As a first method, various activated carbon catalysts having different surface fluorination degrees were prepared by flowing an appropriate amount of fluorine gas at 100 to 400 ° C. through activated carbon.
As a second method, after dissolving stearic acid, a styrene oligomer (average molecular weight of about 320), a fluorine-containing oil (average molecular weight of about 500), etc., which are water-repellent substances having a low molecular weight, in an appropriate low boiling point solvent, Activated carbon was immersed in this under reduced pressure, these solutions were sufficiently infiltrated into the pores, dried under reduced pressure, and the solvent was blown off to coat the inside of the pores of the activated carbon with a water repellent substance.
The specific surface area of the activated carbon catalyst prepared in this way is within an apparent decrease range due to the increase in weight accompanying the loading of the water-repellent substance, and these loaded materials may block or destroy the pores. Not confirmed.
[0009]
Subsequently, a sulfurous acid gas reaction activity test was performed using various activated carbon catalysts having a fluorination rate of 1 to 20% obtained by the first method. As the fluorination rate increased, water was increased. Water surface floating time test (this is the average value of the sedimentation start time and sedimentation end time by gently floating the water-repellent activated carbon particles on the water surface. However, it was found that the adsorption and oxidation activity of sulfurous acid gas decreased rather in inverse proportion to the increase in the fluorination rate.
Further, in the activated carbon catalyst carrying stearic acid, styrene oligomer, fluorinated oil, etc. obtained by the second method, as the loading amount increases, the water repellency by the water surface floating time test is similarly applied. Although an increase in water content is observed, the adsorption and oxidation activities of sulfurous acid gas are only slightly exceeding the catalytic activity of the activated carbon alone in the addition range of 0.5 to 2%, and the activity rapidly increases as the addition amount increases. It turned out to go down.
[0010]
From the above, it was estimated that the entire water repellency including the micropores of the activated carbon could not provide a sufficient activity improvement effect to cover or destroy the oxidation active sites of the activated carbon.
Therefore, the present inventors do not make the micropores that contribute most to the activity in activated carbon water repellent, but only make the macropores (pores having a pore diameter of more than 5 nm) that serve as a discharge flow path for the generated sulfuric acid. I tried to do that. First, polyethylene and polystyrene powder having a molecular weight of 100,000 or more are dissolved in toluene heated to 60 to 70 ° C. by several percent, activated carbon particles are immersed in this under reduced pressure, and then dried under reduced pressure while heating to thoroughly remove toluene. Was scattered. The activated carbon catalyst thus obtained showed a significant improvement in activity when the water-repellent substance was supported in a range of 0.3 to 1.5 wt% with respect to the starting activated carbon.
[0011]
This means that if polyethylene and polystyrene with a molecular weight of 100,000 or more are spherical and dispersed in a toluene solvent, the diameter will be 7 nm or more even if not swollen in the solvent, and this will penetrate into the micropores of the activated carbon. Not the size you can. Therefore, this activated carbon catalyst should be considered to make the macropores and the outer surface of the activated carbon particles water repellent. And as mentioned above, in this reaction system, the water repellency of the outer surface of the activated carbon does not contribute so much to the improvement of the reaction activity. It is inferred that it contributes to
[0012]
Then, next, in order to obtain the knowledge of how much pore size of the macropores in the raw activated carbon contributes to the activity improvement, each polystyrene (hereinafter abbreviated as PS). ) Prepare 5 types of latex (particles with relatively uniform PS spherical particles dispersed in water, about 10 wt% in water) whose average diameter is different from 10, 28, 55, 102, and 300 nm. After diluting to 0.1 to 5 wt%, the activated carbon catalyst was prepared by immersing the raw material activated carbon under reduced pressure and then drying under reduced pressure, and each was subjected to an activity test. As a result, in any activated carbon catalyst, the optimum addition amount of PS exhibiting the highest activity is in the vicinity of 1 wt%, the average diameters of 28 nm and 55 nm show high activity, and those of 10 nm and 102 nm It was found that the activity was slightly lower than that, and that the average diameter of 300 nm was not much different from that of untreated activated carbon.
SEM observation of the catalyst particle fracture surface for these five types of activated carbon catalyst revealed that PS particles with an average diameter of 55 nm or less uniformly penetrated into the activated carbon particles, whereas 102 nm PS particles Many of the activated carbon particles were present near the surface of the activated carbon particles, and PS particles of 300 nm adhered only to the outer surface of the activated carbon particles.
[0013]
The reason why the activated carbon catalyst impregnated with PS particles having an average diameter of 10 nm is lower in activity than those impregnated with 55 nm and 102 nm PS particles is beyond the scope of estimation, but the PS particles become smaller in diameter. It is considered that this is because the micropores of the raw material activated carbon are easily blocked. Therefore, from the above experimental results, it seems that it is sufficient to make the macropores having a diameter larger than the minimum diameter in which PS particles having an average diameter of 28 nm can penetrate water repellent.
In this way, it was confirmed by the above-mentioned activity test that water repellency of the macropores of the starting activated carbon greatly contributes to the improvement of the activity.
[0014]
Further, as the water repellent substance for making the macropores water repellent, it is preferable to use a fluorine resin such as PTFE having a higher water repellency than PS or polyethylene. However, as described above, since the average particle size of commercially available fluororesin is relatively large, 0.2 to 0.4 μm, it hardly penetrates into the macropores of the raw material activated carbon.
Accordingly, the present inventors have previously crushed raw material activated carbon as a method for making the macropores of activated carbon water repellent easily and reliably using a fluorine resin having a relatively large average particle size, and the PTFE particles or the A method was adopted in which the dispersion was mixed and molded again.
[0015]
Activated carbon is fragile in terms of material, and when it is pulverized, it first begins to break from a portion having a relatively large pore diameter. As the pulverization further proceeds, the smaller hole portion is destroyed. Therefore, after thoroughly pulverizing the activated carbon and erasing all the macropores that the original activated carbon had, after mixing the PTFE particles and molding again, all the initial macropores in the activated carbon were made of PTFE particles. Will be qualified.
Based on this concept, the inventors of the present invention can improve the macropore modification rate by PTFE and obtain higher activity if the activated carbon is first pulverized to the finest particles and mixed with the PTFE dispersion. I thought. Therefore, commercially available activated carbon was pulverized to an average particle size of 10 μm to prepare an activated carbon catalyst.
[0016]
However, even if the amount of PTFE supported was variously changed within the range of 2 to 30 wt%, a highly active activated carbon catalyst could not be obtained. This is considered to be because if the raw material activated carbon is pulverized too finely, the gap between the activated carbon particles that should be the discharge flow path of the generated sulfuric acid becomes extremely narrow, and further, the gap is blocked by PTFE. .
Therefore, when pulverizing, it is thought that there is an optimum value for the particle size of the activated carbon, and the average particle size of the activated carbon powder is variously changed from 10 to 3,000 μm while the amount of PTFE added is constant. As a result, it was possible to obtain a highly active activated carbon catalyst in the range of 12 to 600 μm. There are various reasons why a highly active activated carbon catalyst was obtained in this way. However, a fluororesin such as PTFE has a higher water repellency than PS and the like. It is thought that it contributed.
[0017]
By the way, when the activated carbon is pulverized to an average particle diameter of 12 to 600 μm in this way, the macropores in the raw material activated carbon are considerably reduced. Nevertheless, considerable macropores remain.
Therefore, the present inventors made the remaining macropores of the activated carbon powder after pulverization water-repellent in advance with a water-repellent substance having a particle size capable of entering the macropores, and dispersed the obtained activated carbon powder and fluorine resin. It was thought that if the mixture was formed by mixing the liquid, higher activity could be obtained than the activated carbon catalyst obtained by simply mixing and molding the activated carbon powder and the fluororesin dispersion.
[0018]
From this viewpoint, first, activated carbon powder pulverized and classified into a particle size range of 106 to 212 μm is loaded with about 1 wt% of 28 nm PS spherical particles by the above-described method, and then PTFE dispersion is applied to the activated carbon. On the other hand, an activated carbon catalyst was obtained by mixing and molding so that the PTFE was 10 wt%. Then, when an activity test was performed using this activated carbon catalyst, it showed higher activity than any of the above-mentioned activated carbon catalysts without any mistake, and thus the present invention was completed.
The present invention has been made on the basis of such knowledge, and an activated carbon catalyst capable of effectively and easily repelling pores having a desired diameter and exhibiting high activity, and uses the same. Accordingly, it is an object of the present invention to provide a flue gas desulfurization method that enables flue gas desulfurization that is inferior in desulfurization efficiency as compared with other flue gas desulfurization processes and thus has excellent economic efficiency.
[0019]
[Means for Solving the Problems]
The activated carbon catalyst according to the present invention as set forth in claim 1 is an activated carbon catalyst for adsorbing and oxidizing the sulfur oxide by being brought into contact with exhaust gas containing sulfur oxide, and recovering and removing it as sulfuric acid. A water-repellent substance that has a contact angle with water of 90 ° or more and cannot penetrate into pores of 5 nm or less in the activated carbon is added to the activated carbon powder having a particle diameter of 12 to 600 μm with respect to the activated carbon. After loading 2 to 3.0 wt%, add fluororesin particles or dispersion thereof so that the fluororesin becomes 2 to 20 wt%, and mix and support, and shape this into a predetermined shape. It is a feature.
[0020]
Here, the invention according to claim 2 is characterized in that the activated carbon powder has an average particle diameter in the range of 15 to 400 μm, and the invention according to claim 3 further comprises the activated carbon powder. Is characterized in that the average particle size is in the range of 20 to 200 μm. The invention according to claim 4 The water repellent material, The activated carbon is supported at 0.5 to 1.5 wt% with respect to the activated carbon, and the invention according to claim 5 is characterized in that the fluororesin in the dispersion is 5 to 15 wt% with respect to the activated carbon. % Range.
[0021]
The invention according to claim 6 is characterized in that the fluororesin is polytetrafluoroethylene, perfluoroalkoxy resin, tetrafluoroethylene hexafluoride propylene copolymer, or trifluoroethylene chloride resin. It is what.
Next, the flue gas desulfurization method according to the present invention described in claim 7 is obtained by bringing the exhaust gas containing sulfur oxide into contact with the activated carbon catalyst according to any one of the above claims 1 to 6 in the exhaust gas. The sulfur oxide is adsorbed and oxidized on the activated carbon catalyst and recovered and removed as sulfuric acid.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the activated carbon catalyst according to the present invention will be specifically described.
The activated carbon catalyst according to the present invention is for oxidizing and recovering as sulfuric acid by oxidizing the sulfurous acid gas in the exhaust gas with coexisting oxygen. The activated carbon powder having a certain range of average particle diameter is preliminarily treated with a water-repellent substance. The main feature is that a predetermined amount of is carried, and then a predetermined range of highly water-repellent fluororesin particles or a dispersion thereof is mixed and molded into a desired shape.
Here, as the activated carbon to be used, since there is a difference in activity depending on the type of coal based on the difference in raw materials, it is preferable to select activated carbon having the highest activity. For example, changes in activity before and after the water repellent treatment performed by the present inventors on 15 types of activated carbon such as those using coal as a raw material, those using coconut shells, and those using peat and petroleum pitch as a raw material. According to the comparative experiment, activated carbon catalyst using coal as a main raw material exhibited a high activity as compared with other activated carbon catalysts using coconut shell, peat, petroleum pitch or the like as raw materials.
[0023]
Although the reason why activated carbon mainly made of coal shows superiority when treated with water repellency is not clear, originally activated carbon based on coal is originally compared with activated carbon made of other raw materials, Adsorption of sulfurous acid gas, the number of oxidation active sites is large, but it is inferior in hydrophobicity. Therefore, it is considered that the excellent activity in the original coal-based activated carbon appears remarkably by applying water repellent treatment. . However, in the present invention, a water-repellent substance that has an average particle size of 12 to 600 μm and has a contact angle with water of 90 ° or more in advance and cannot penetrate into pores of 5 nm or less in the activated carbon. Is added to the activated carbon in an amount of 0.2 to 3.0 wt%, and then a dispersion containing 2 to 20 wt% of a fluorine resin is added and mixed. Even if it is a kind of activated carbon, the activity is greatly improved.
[0024]
The first important point that greatly affects the activity improvement by water repellency is the preparation of the particle size of the activated carbon powder as a raw material. When the particle size of the activated carbon powder is too coarse, no high activity will be exhibited regardless of the amount of fluorine resin added. On the contrary, if the particle size is too fine, as described above, the gap between the activated carbon particles that should be the discharge flow path of the generated sulfuric acid becomes extremely narrow, and further, the gap is blocked by PTFE. Regardless of the amount of fluorine resin added, the activity is rapidly reduced.
According to the knowledge of the present inventors, the particle size range of the activated carbon powder for obtaining high activity is 12 to 600 μm, preferably 15 to 400 μm, more preferably as seen in the examples described later. It is the range of 20-200 micrometers (refer FIG. 2).
[0025]
Next, an important point is that the activated carbon powder is loaded with a water-repellent substance in advance. Here, the water repellent material must have a contact angle with water of 90 ° or more, and from the viewpoint of making the remaining macropores of the activated carbon powder water repellent, the micropores in the activated carbon powder, that is, 5 nm or less. It is necessary that it cannot penetrate into the pores. As a water-repellent substance that satisfies these requirements, there is generally a hydrocarbon-based resin or a fluorine resin.
Examples of the method of supporting the water repellent substance on the activated carbon powder include, for example, dissolving the water repellent substance in an organic solvent, impregnating the activated carbon powder with the water repellent substance, and then removing the organic solvent to remove the activated carbon powder. It is possible to apply a method of supporting the activated carbon powder or a method of supporting the activated carbon powder in a form in which the water-repellent substance is dispersed in water. When dispersed in water and supported on activated carbon powder, the diameter of the water-repellent substance particles is in the range of 5 to 100 nm so as not to penetrate into the micropores of the activated carbon powder and sufficiently penetrate into the remaining macropores. The more preferable range of the average particle diameter is 10 to 70 nm.
[0026]
Further, the amount of the water repellent material previously supported on the activated carbon powder is in the range of 0.2 to 3.0 wt%, more preferably in the range of 0.5 to 1.5 wt% with respect to the activated carbon powder. Yes (see FIG. 3).
Next, as the fluorine resin used for the water repellent treatment, commercially available resins can be used, but it is preferable to select one having a high fluorine content, that is, one having excellent water repellency. Examples of such a fluorine resin include polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA), tetrafluoroethylene hexafluoropropylene copolymer (FEP), and trifluoroethylene chloride resin (PCTEF). Is preferred. These fluorine resins have higher water repellency than polystyrene, polyethylene, etc., and the average particle size of these fluorine resins in the dispersion is relatively large at 0.2 to 0.4 μm. Therefore, the desired activated carbon catalyst in which even the macropores are water repellent can be obtained by kneading and molding them.
[0027]
Here, the third important point having a great influence on the activity improvement by water repellency is the addition amount of these fluorine resins. When the addition amount of this fluororesin is 2 wt% or less, the activity rapidly decreases. Conversely, when the amount added exceeds 20 wt%, the activity gradually decreases. According to the results of experiments by the present inventors, the range of the optimum addition amount that maintains higher activity is 2 to 20 wt%, more preferably 5 to 20 wt%, as the weight of the fluororesin with respect to the activated carbon powder. Yes (see FIG. 4).
This optimum addition amount is remarkable in that the tendency is almost the same even if the average particle size is variously changed in the range of the average particle size of 12 to 600 μm of the raw material activated carbon powder necessary for obtaining high activity. The features were confirmed.
[0028]
In this way, when molding the kneaded activated carbon powder and the fluororesin, various molding methods such as extrusion molding, tableting molding, and forced granulation can be applied. Incidentally, when it is desired to obtain an activated carbon catalyst having high strength, tableting molding in which the mixed powder is pressed into a fixed shape is preferable. Further, when it is desired to suppress the generation of differential pressure due to dust or the like in exhaust gas, the mixed powder can be formed into a plate shape or a honeycomb shape. As described above, in the present activated carbon catalyst, the activated carbon powder can be made into an arbitrary shape using the raw material as a raw material, and an excellent effect can be obtained from the viewpoint of manufacturing cost in addition to the above-described improvement in activity.
[0029]
【Example】
Next, the present invention will be described more specifically with reference to examples.
Example 1
Six types of commercially available activated carbon were each fired at 800 ° C. for 1 hour in a nitrogen stream.
Next, about 100 g of the obtained activated carbon was crushed with a commercially available grinder, and then classified using a sieve shaker for 2 hours using a stainless steel sieve (106 μm to 212 μm). It was. The activated carbon obtained by repeating such operations is hereinafter referred to as finely divided activated carbon, and is represented by the average value of the mesh of each sieve combined with the representative diameter of the obtained finely divided activated carbon particles (hereinafter referred to as the pulverized particle diameter). It was. That is, in the case of the above operation, the pulverized particle diameter of the obtained finely powdered activated carbon is 159 μm.
[0030]
Next, deionized water was added to a commercially available spherical PS dispersion (10 wt%) having an average particle size of 28 nm to dilute it 50 times, and then 20 g of the activated carbon was immersed in 100 cc of the spherical PS dispersion and reduced in pressure with a rotary evaporator. Impregnation and drying were performed. Thereafter, this was dried in a dryer at 45 to 50 ° C. for 12 hours to prepare finely powdered activated carbon having a spherical PS loading of about 1 wt%. Next, water was added to a commercially available PTFE dispersion (60 wt%) to dilute it 6-fold, and the above-mentioned fine activated carbon carrying spherical PS was kneaded with the PTFE dispersion, respectively, and then the molding pressure was 500 kgf / cm ² The activated carbon catalyst according to the present invention containing 1 wt% spherical PS and 10 wt% PTFE was obtained. Next, this activated carbon catalyst was dried at 45 to 50 ° C. for 12 hours, and then roughly crushed and classified to obtain a granular activated carbon catalyst having a diameter of 2.8 to 4.0 mmφ.
[0031]
As another activated carbon catalyst according to the present invention, a commercially available PS is first dissolved in about 100 c of toluene heated to 50 to 70 ° C. to prepare a PS solution, and a fine powder having a pulverized particle size of 159 μm obtained by the above operation is used. 50 g of activated carbon was immersed in the PS solution and impregnated under reduced pressure and dried with a rotary evaporator. Thereafter, drying was performed under reduced pressure for 12 hours in a dryer at 45 to 50 ° C. to prepare finely powdered activated carbon having a PS loading of about 1 wt%. Subsequently, water was added to a commercially available PTFE dispersion (60 wt%) and diluted 6-fold. Similarly, the finely divided activated carbon carrying PS was kneaded with the PTFE dispersion, and then the molding pressure was 500 kgf / cm using a compression molding machine. ² To obtain a mixed molded catalyst containing 1 wt% dissolved PS and 10 wt% PTFE. Next, this mixed molded catalyst was dried at 45 to 50 ° C. for 12 hours and then pulverized and classified to obtain a granular activated carbon catalyst having a diameter of 2.8 to 4.0 mmφ.
[0032]
Next, as Comparative Example 1 with respect to Example 1, an equivalent amount of deionized water or water was added to the above 6 types of fine activated carbon having a pulverized particle diameter of 159 μm, and the resulting fine activated carbon was similarly molded at a molding pressure of 500 kgf / cm ² The resulting activated carbon catalyst having a PS and PTFE content of 0 wt% was coarsely crushed and classified to obtain a granular activated carbon catalyst having a particle size of 2.8 to 4.0 mmφ.
[0033]
Subsequently, the activity test was performed using the two types of activated carbon catalysts according to the present invention thus obtained and the activated carbon catalyst of Comparative Example 1 in a catalytic sulfation reaction test apparatus. Each catalyst is filled with 40 ml in a jacketed glass reactor with an inner diameter of 16 mmφ, and SO ₂ ; 1000 vol ppm, O ₂ ; 4vol%, CO ₂ ; 10 vol%, N ₂ A gas with a composition of balance and relative humidity of 100% was put into this reactor at 50 ° C. and 400 dm ³ / hr (SV = 10,000 hr-1), SO ₂ Outlet SO using a meter (ultraviolet / infrared) ₂ Was measured to evaluate the catalytic activity.
FIG. 1 shows the desulfurization performance of each activated carbon catalyst after 100 hours from the start of the test. From FIG. 1, the granular activated carbon catalyst according to the present invention in which spherical activated carbon or dissolved PS is contained in 6 kinds of activated carbon and 10 wt% of PTFE is compared with the activated carbon catalyst of Comparative Example 1 that does not contain PTFE. As a result, it can be seen that the desulfurization performance is greatly improved. Incidentally, in the two types of activated carbon catalysts according to the present invention, Dissolved PS Higher activity was obtained with the spherical PS loaded than with the loaded PS. Therefore, when carrying PS in advance, it is preferable to use spherical PS rather than dissolved PS. However, as long as a PS having a shape other than a spherical shape can be manufactured, the PS may be used and is not limited to a spherical shape.
[0034]
(Example 2)
In Example 1, activated carbon A fired at 800 ° C. for 1 hour in a nitrogen stream was pulverized and classified in the same manner as in Example 1. At this time, by using a combination of sieves having different meshes (0 to 20 μm, 20 to 53 μm, 53 to 106 μm, 106 to 212 μm, 212 to 300 μm, 2800 to 4000 μm), four types of the present invention having different pulverized particle diameters are used. The finely divided activated carbon (36.5, 79.5, 159, 256) μm and the finely divided activated carbon (10, 3400 μm) as two types of Comparative Example 2 for Example 2 were obtained.
Next, deionized water was added to a commercially available spherical PS dispersion (10 wt%) with an average particle size of 28 nm to dilute it 50 times, and 20 g of the activated carbon was immersed in 100 cc of the spherical polystyrene dispersion and impregnated under reduced pressure with a rotary evaporator. And drying. Thereafter, drying was performed in a dryer at 45 to 50 ° C. for 12 hours to prepare finely powdered activated carbon having a spherical PS loading of about 1 wt%.
Subsequently, water was added to a commercially available PTFE dispersion (60 wt%) to dilute it 6 times, and the same operation (kneading / molding / drying / roughing) was performed on the fine activated carbon having the above-mentioned 6 pulverized particle sizes. By crushing and classifying), a granular activated carbon catalyst having a particle size of 2.8 to 4.0 mmφ containing 1 wt% spherical PS and 10 wt% PTFE was obtained.
[0035]
In order to obtain an activated carbon catalyst carrying dissolved PS, first, a PS solution was prepared by dissolving commercially available PS in about 100 cc of toluene warmed to 50 to 70 ° C., and the four kinds of books obtained by the above operation. The finely powdered activated carbon according to the invention and two kinds of finely powdered activated carbon as Comparative Example 2 and 50 g of each were immersed in the PS solution, and subjected to vacuum impregnation and drying with a rotary evaporator. Thereafter, drying was performed under reduced pressure for 12 hours in a dryer at 45 to 50 ° C. to prepare finely divided activated carbon having a PS loading of about 1 wt%.
Furthermore, after adding water to a commercially available PTFE dispersion (60 wt%) and diluting it 6 times, the finely divided activated carbon carrying the dissolved PS was kneaded with the PTFE dispersion, and similarly, the molding pressure was 500 kgf / cm ² 6 kinds of mixed molded catalysts having different pulverized particle diameters containing 1 wt% dissolved PS and 10 wt% PTFE were obtained. Next, this mixed molded catalyst was dried at 45 to 50 ° C. for 12 hours, and then coarsely crushed and classified to obtain a granular activated carbon catalyst having a diameter of 2.8 to 4.0 mmφ.
[0036]
Next, the reaction test apparatus described in Example 1 was used for the activated carbon catalyst according to the present invention having four types of pulverized particle diameters and the activated carbon catalyst of Comparative Example 2 having two types of pulverized particle diameters. The catalytic activity was evaluated under the same conditions.
FIG. 2 shows the desulfurization performance of each activated carbon catalyst 100 hours after the start of the test. As shown in FIG. 2, the activated carbon catalyst containing 1 wt% dissolved PS or spherical PS and 10 wt% PTFE has a pulverized particle diameter of the raw material activated carbon of 12 to 600 μm (preferably 15 to 400 μm, more preferably 20 to 200 μm). In some cases, it shows very high desulfurization performance. Therefore, Dissolved PS Alternatively, when obtaining a highly active activated carbon catalyst by kneading and molding finely divided activated carbon supporting spherical PS and PTFE, the finely divided activated carbon powder has a pulverized particle size range of 12 to 600 μm (preferably 15 to 400 μm, more preferably 20 to 200 μm). ) Range is the optimum diameter. Further, as in Example 1, it is understood that it is preferable to use spherical PS rather than dissolved PS when supporting PS in advance.
[0037]
(Example 3)
In Example 1, activated carbon A calcined at 800 ° C. for 1 hour in a nitrogen stream was pulverized and classified in the same manner as in Example 1 to obtain finely powdered activated carbon having a pulverized particle size of 159 μm.
Next, a commercially available spherical PS dispersion (10 wt%) having an average particle size of 28 nm is diluted by adding deionized water to prepare various concentrations (0 to 3 wt%). It is immersed in 100 cc of each spherical PS dispersion, impregnated under reduced pressure with a rotary evaporator and dried, then dried for 12 hours in a dryer at 45 to 50 ° C., and fine activated carbon with a spherical PS loading of 0 to 3 wt% Was prepared.
Furthermore, commercially available PTFE dispersion (60 wt%) is diluted by adding water to prepare PTFE dispersion (0 to 15 wt%) having different concentrations, and the fine activated carbon carrying spherical PS is kneaded with the PTFE dispersion. Molded (molding pressure 500kgf / cm ² ), A mixed molded catalyst impregnated with 0 to 3 wt% of spherical PS and 0 to 15 wt% of PTFE was obtained. Next, this mixed molded catalyst was dried at 45 to 50 ° C. for 12 hours and then roughly crushed and classified to obtain a granular activated carbon catalyst according to the present invention having a diameter of 2.8 to 4.0 mmφ.
[0038]
Further, as Comparative Example 3 with respect to Example 3, activated carbon A fired at 800 ° C. for 1 hour in a nitrogen stream in Example 1 was pulverized and classified by the same method to obtain finely powdered activated carbon having a pulverized particle size of 159 μm. It was.
Next, water is added to a similar spherical PS dispersion (10 wt%) having an average particle size of 28 nm to dilute to prepare spherical PS dispersions (0 to 3 wt%) having different concentrations. This spherical polystyrene dispersion was immersed in 100 cc of each and subjected to vacuum impregnation and drying with a rotary evaporator. Thereafter, drying was performed in a dryer at 45 to 50 ° C. for 12 hours to prepare finely powdered activated carbon having a spherical PS loading of 0 to 3 wt%. Next, 20 g of water was added to the activated carbon and kneaded, and the molding pressure was similarly 500 kgf / cm in a compression molding machine. ² To obtain a mixed molded catalyst containing 0 to 3 wt% of spherical PS. Next, this mixed molded catalyst was dried at 45 to 50 ° C. for 12 hours, and then coarsely crushed and classified to obtain a granular activated carbon catalyst having a diameter of 2.8 to 4.0 mmφ.
[0039]
Subsequently, the catalytic activity of the activated carbon catalyst according to the present invention thus obtained and the activated carbon catalyst of Comparative Example 3 was evaluated under the same conditions using the reaction test apparatus described in Example 1.
3 and 4 show the desulfurization performance of each activated carbon catalyst 100 hours after the start of the test. FIG. 3 shows that the amount of spherical PS suitable for obtaining high activity is in the range of 0.2 to 3 wt%. Further, it can be seen from FIG. 4 that the amount of PTFE kneaded at this time is in the range of 2 to 20 wt% (preferably 5 to 15 wt%).
[0040]
【The invention's effect】
As described above, in the activated carbon catalyst according to any one of claims 1 to 6, the activated carbon powder having an average particle size of 12 to 600 μm, preferably 15 to 400 μm, more preferably 20 to 200 μm, The water-repellent substance that has a contact angle of 90 ° or more and cannot penetrate into pores of 5 nm or less in the activated carbon is 0.2 to 3.0 wt% with respect to the activated carbon, more preferably 0. After loading 5 to 1.5 wt%, add fluororesin particles or a dispersion thereof so that the fluorine resin is 2 to 20 wt%, preferably 5 to 15 wt%, and mix and support it. The residual macropores of the activated carbon powder can be made water repellent by the water repellent material, and the macropores generated between the activated carbon powders can be made water repellent by fluorine resin. Therefore, excluding the micropores that contribute most to the catalytic sulfation reaction, the highly active activated carbon catalyst in which the macropores that serve as the flow path for the generated sulfuric acid are efficiently water-repellent is easily manufactured in any shape. The effect that it can do is acquired.
Therefore, according to the flue gas desulfurization method according to claim 7 using the activated carbon catalyst according to any one of claims 1 to 6, there is no inferior desulfurization efficiency as compared with other flue gas desulfurization processes, and thus economical. Exhaust flue gas desulfurization with excellent properties becomes possible.
[Brief description of the drawings]
FIG. 1 is a graph showing the results of an activity test in Example 1 of the present invention.
FIG. 2 is a graph showing the results of an activity test of Example 2 in the same manner.
FIG. 3 is a graph showing the results of an activity test of Example 3 in the same manner.
4 is a graph showing the results of an activity test of Example 3 in the same manner. FIG.

Claims (7)

An activated carbon catalyst for adsorbing and oxidizing the sulfur oxide by contacting with an exhaust gas containing sulfur oxide to recover and remove it as sulfuric acid, wherein the activated carbon powder having an average particle size of 12 to 600 μm is mixed with water. After a water repellent material having a contact angle of 90 ° or more and which cannot penetrate into pores of 5 nm or less in the activated carbon is supported on the activated carbon in an amount of 0.2 to 3.0 wt%, a fluororesin An activated carbon catalyst obtained by adding fluororesin particles or a dispersion thereof so as to be 2 to 20 wt%, mixing and supporting the resulting mixture, and molding the resultant into a predetermined shape. The activated carbon catalyst according to claim 1, wherein the activated carbon powder has an average particle size in the range of 15 to 400 µm. The activated carbon catalyst according to claim 1, wherein the activated carbon powder has an average particle size in the range of 20 to 200 µm. The activated carbon catalyst according to any one of claims 1 to 3, wherein the water-repellent substance is supported at 0.5 to 1.5 wt% with respect to the activated carbon. The activated carbon catalyst according to any one of claims 1 to 4, wherein the fluorine resin in the dispersion is in a range of 5 to 15 wt% with respect to the activated carbon. 6. The fluororesin is polytetrafluoroethylene, perfluoroalkoxy resin, tetrafluoroethylene hexafluoride propylene copolymer, or trifluoroethylene chloride resin. The activated carbon catalyst described. By contacting the activated carbon catalyst according to any one of claims 1 to 6 with an exhaust gas containing sulfur oxide, the sulfur oxide in the exhaust gas is adsorbed and oxidized on the activated carbon catalyst to be recovered and removed as sulfuric acid. A flue gas desulfurization method.

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