JP4017380B2 - Gas treatment method using water-resistant spherical silica as an adsorbent - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas treatment method for removing a water-soluble compound from a gas to be treated containing a water-soluble compound discharged from a factory or the like, and more particularly to a gas treatment method using water-resistant spherical silica as an adsorbent.
[0002]
[Prior art]
As an apparatus for removing and recovering an organic solvent from exhaust gas containing an organic solvent discharged from a factory, etc., there is a fluidized bed type gas processing apparatus having an adsorption tower, a desorption tower and a recovery device, and using spherical activated carbon as an adsorbent. Are known.
[0003]
In this conventional apparatus, first, exhaust gas containing an organic solvent is introduced into an adsorption tower and brought into countercurrent contact with flowing spherical activated carbon. Thereby, the organic solvent in the exhaust gas is adsorbed and removed by the spherical activated carbon. The exhaust gas from which the organic solvent has been removed is discharged from the adsorption tower. On the other hand, the spherical activated carbon adsorbing the organic solvent is transferred from the adsorption tower to the desorption tower. In the desorption tower, the organic solvent adsorbed by the desorption gas is desorbed, and the regenerated spherical activated carbon is returned to the adsorption tower for reuse. The desorbed organic solvent is recovered by a recovery device.
[0004]
[Problems to be solved by the invention]
By the way, when trying to apply such a fluidized bed type gas treatment device using activated carbon as an adsorbent to an exhaust gas containing a water-soluble compound such as methanol, the adsorption capability of activated carbon for water-soluble compounds is low. The amount of use increases and the apparatus becomes large-scale.
[0005]
On the other hand, silica gel is known as one having a high adsorbing ability for such water-soluble compounds. To solve the above problem, for example, a method of using granular silica gel having excellent fluidity as an adsorbent is conceivable. However, in this case, moisture contained in the exhaust gas is simultaneously adsorbed on the silica gel, which may cause the silica gel particles to be crushed. If it becomes like this, fluidity | liquidity will fall, the stable operation | movement of an apparatus will become difficult, and processing efficiency will fall. Further, there is a problem that fine powder and dust are generated by crushing silica gel particles, and the fine powder is discharged from the apparatus along with the gas.
[0006]
Therefore, the present invention has been made in view of such circumstances, and when the water-soluble compound such as methanol and ethanol contained in the gas to be treated is removed using the adsorbent, the adsorbent can be prevented from being crushed and efficiently An object of the present invention is to provide a gas treatment method capable of good and stable operation.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the gas treatment method according to the present invention comprises contacting a gas to be treated containing a water-soluble compound with an adsorbent to adsorb the water-soluble compound in the gas to be treated to the adsorbent. The water-soluble compound adsorbed on the catalyst is desorbed by heating to regenerate the adsorbent, and the treated gas is continuously treated while the regenerated adsorbent moves again to contact the treated gas. The gas to be treated is continuously processed while moving the adsorbent through a fluidized bed, and the adsorbent has a specific surface area of 200 to 900 m ² / g and a particle diameter of 0.5 to 1.4 mm. And the following formula (1);
N = (W / W ₀ ) × 100 (1),
It is characterized by using water-resistant spherical silica having a water resistance N defined by the formula of 45% or more. Here, in the formula, N represents the water resistance (%) of the adsorbent, W ₀ represents the total number (particles) of the adsorbent immersed in water, and W represents cracking in W _0. The number of items that did not exist is shown.
[0008]
In the present invention, “the adsorbent is spherical” does not necessarily mean a true sphere, and the adsorbent particles are placed on a steel plate having a smooth surface so as not to overlap. It means that 90% by mass or more of the adsorbent is in a shape of falling from the steel sheet when it is tilted.
[0009]
In such a gas treatment method, when the gas to be treated comes into contact with the adsorbent, the water-soluble compounds in the gas to be treated are effectively adsorbed and removed. When the water-resistant spherical silica having a water resistance N of 45% or more is used as the adsorbent, the present inventors can suppress the adverse effect of moisture adsorption contained in the gas to be treated. And the generation of fine powder was found to be sufficiently prevented.
[0010]
In addition, as the water-resistant spherical silica, those having a specific surface area of 200 to 900 m ² / g are used. If the specific surface area of the water-resistant spherical silica is set to a value within such a range, sufficient water resistance can be imparted while suppressing a decrease in the adsorption amount of the water-soluble compound.
[0011]
Furthermore, it is more preferable to use an adsorbent that further contains spherical activated carbon. In this way, even if the gas to be treated contains hydrophobic compounds, these hydrophobic compounds can be removed together with the water-soluble compounds.
[0012]
More specifically, in the present invention, the gas to be processed is continuously processed while the adsorbent is moved by the fluidized bed . In this case, it is useful to use an adsorbent having a particle diameter of 0.5 to 1.4 mm. In the present invention, the expression that the particle diameter of the adsorbent is “lower limit value to upper limit value” means that the upper limit value is obtained when the adsorbent is sieved with a sieve having openings corresponding to the lower limit value and the upper limit value. It means that the mass of the material that passes through the sieve with the mesh openings corresponding to and remains on the sieve with the mesh openings corresponding to the lower limit is 90% or more with respect to the total mass.
[0013]
When an adsorbent having a particle diameter in such a range is used, it becomes easy to maintain the flow velocity of the gas to be treated in countercurrent contact with the adsorbent within a suitable range, and the components to be removed in the gas to be treated are sufficient. It is possible to suppress a decrease in processing capacity while adsorbing and removing.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail. The positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.
[0015]
The gas treatment method according to the present invention treats a gas to be treated containing a water-soluble compound. Here, the water-soluble compound refers to a compound having a solubility in water at 25 ° C. (the maximum mass (g) of a solute dissolved in 100 g) is 50 or more. Examples of such water-soluble compounds include organic compounds such as methanol and ethanol.
[0016]
The water resistant spherical silica used in the present invention needs to have a water resistance N defined by the above formula (1) of 45% or more, preferably 50% or more. When the water resistance is less than 45%, when a gas to be treated containing moisture is treated, silica is crushed by moisture adsorption, making it difficult to form a stable fluidized bed and to transfer silica. Further, in addition to this, fine powder is likely to be generated, and there is a risk that this fine powder is accompanied by the treated gas and discharged to the outside of the processing apparatus.
[0017]
Furthermore, the specific surface area of the water-resistant spherical silica is 200 to 900 m ² / g , preferably 300 to 800 m ² / g. When the surface area is less than 200 m ² / g, the amount of water-soluble compound adsorbed is undesirably reduced. On the other hand, when the specific surface area exceeds 900 m ² / g, the water resistance of the water-resistant spherical silica decreases. It tends to be prominent.
[0018]
Such water-resistant spherical silica can be produced, for example, by the method described in Japanese Patent Publication No. 7-64543. That is, the water-resistant spherical silica used in the present invention is a spherical silica xerogel obtained by drying a silica hydrogel obtained by neutralizing an alkali silicate aqueous solution at a temperature of 100 to 1000 ° C. with superheat steam, and a 500 to 1000 It can be produced by baking at a temperature of 0 ° C.
[0019]
In addition, when the gas to be treated contains a water-soluble compound and a hydrophobic compound that is difficult to adsorb on water-resistant spherical silica such as n-hexane, toluene, etc., in order to remove these hydrophobic compounds at the same time as the water-soluble compound It is preferable to use a mixture of water-resistant spherical silica and spherical activated carbon as an adsorbent, that is, use a mixed adsorbent of water-resistant spherical silica and spherical activated carbon. In this case, the mixing ratio of the water-resistant spherical silica and the spherical activated carbon can be appropriately determined in consideration of the type of the component to be removed, the allowable residual component amount in the treated gas, and the like. Examples of the spherical activated carbon used here include spherical activated carbon activated by steam after granulating petroleum pitch into a spherical shape, but are not limited thereto.
[0020]
In addition, as a gas processing apparatus for effectively carrying out the gas processing method according to the present invention, a gas processing apparatus that contacts a gas to be processed while moving a fluidized bed type adsorbent is adopted, for example, as shown in FIG. A fluidized bed continuous gas treatment device is preferred.
[0021]
In FIG. 1, a gas processing apparatus 100 is a multistage fluidized bed type continuous gas processing apparatus, and includes an adsorption tower 10, a desorption tower 20, and a recovery unit 30. The adsorption tower 10 has a plurality of trays 12 made of perforated plates inside, and a gas to be treated 1 containing a component to be removed including a water-soluble compound is supplied from below. The gas 1 to be treated is in countercurrent contact with an adsorbent 11 (water-resistant spherical silica described above or a mixture of this and spherical activated carbon) that sequentially moves to the lower tray while forming a fluidized bed on the tray 12. . At this time, the component to be removed in the gas to be treated 1 is adsorbed and removed by the adsorbent 11. The treated gas 2 from which the components to be removed are removed is discharged from the upper part of the adsorption tower 10. On the other hand, the adsorbent 11 that has adsorbed the component to be removed W is extracted from the lower part of the adsorption tower 10 and supplied to the upper part of the desorption tower 20.
[0022]
The desorption tower 20 is, for example, a heating unit 21 configured by a heating unit using steam, an electric heater or the like as a heat source, and a cooling unit disposed below the heating unit 21 and configured by a cooling unit using water or the like as a refrigerant. A portion 22 is provided. A carrier gas G is introduced into the lower part of the desorption tower 20, and the carrier gas G sent from the upper part of the heating unit 21 is introduced into the recovery unit 30.
[0023]
The adsorbent 11 that has adsorbed the component to be removed W supplied from the upper part of the desorption tower 20 moves downward by gravity and is heated to, for example, 100 to 250 ° C. in the heating unit 21 to desorb the component to be removed W. To do. The to-be-removed component W desorbed from the adsorbent 11 is conveyed to the recovery device 30 by the carrier gas G, separated from the carrier gas G by a method such as cooling by the cooling device 40, and then sent to the recovery system 50 for recovery. Is done.
[0024]
On the other hand, the adsorbent 11 from which the component W to be removed has been desorbed and regenerated by the heating unit 21 is cooled to, for example, 20 to 60 ° C. by the cooling unit 22, and then extracted from the lower part of the desorption tower 20. 10 is supplied to the top. In this way, the adsorbent 11 circulates and moves between the adsorption tower 10 and the desorption tower 20 and repeats the adsorption / desorption of the components to be removed in the gas to be treated 1, whereby the gas to be treated 1 is continuously treated.
[0025]
Here, when a fluidized bed type apparatus such as the gas processing apparatus 100 is used, the particle diameter of the adsorbent 11 is 0.5 to 1.4 mm .
[0026]
When the particle size of the adsorbent 11 exceeds 1.4 mm, it is necessary to excessively increase the flow rate of the gas to be processed 1 for forming the fluidized bed in the adsorption tower 10. And the adsorbent 11 contact time becomes inconveniently short. Moreover, in order to avoid this and to secure a sufficient contact time, measures such as increasing the number of fluidized bed stages and increasing the bed height of the fluidized bed are required.
[0027]
【Example】
Specific examples according to the present invention will be described below, but the present invention is not limited thereto.
[0028]
<Method for evaluating water resistance of adsorbent>
(1) Collect 100 samples of adsorbent in a 10 ml sample bottle.
(2) Inject 5 ml of room temperature water into the sample bottle to immerse the sample, cover it and leave it at room temperature for 30 minutes.
(3) Tilt the sample bottle to drain the water, and dry for 3 hours in a constant temperature dryer set at 80 ° C.
(4) Take out the dried sample and count the number of samples with no cracks.
(5) The water resistance of the adsorbent is calculated according to the relationship of the following formula (1).
N = (W / W ₀ ) × 100 (1)
As described above, N represents the water resistance (%) of the adsorbent, and W ₀ is the number of samples first collected in the procedure (1) (= total number of particles immersed in water; 100 particles). Is the number of cracks that did not occur as counted in step (4).
[0029]
<Measurement of specific surface area of adsorbent>
It was measured by the t-plot method of JIS K1150.
[0030]
In the following examples and comparative examples, the gas flow rate is a value converted to a standard state, and ppm is based on volume.
<Example 1>
Air having a temperature of 30 ° C. and a relative humidity of 30% containing 1000 ± 100 ppm of methanol as a component to be removed was continuously supplied at a flow rate of 60 m ³ / h to the gas processing apparatus 100 having the configuration shown in FIG. Further, the inner diameter of the adsorption tower 10 was set to 155 mm, and a multistage fluidized bed type configuration having six stages of perforated plate trays 12 was adopted. Here, as the adsorbent 11, water-resistant spherical silica (CA RiACT Q-3 manufactured by Fuji Silysia Chemical Co., Ltd.) having a water resistance of 48%, a specific surface area of 550 m ² / g, and a particle diameter of 0.71 to 1.18 mm is used. The circulation rate was 2 kg / h.
[0031]
On the other hand, the inner diameter of the desorption tower 20 was 155 mm, and an electric heater was used as the indirect heating source for the heating unit 21. The desorption temperature at this time was 150 ° C., and nitrogen gas was circulated as a carrier gas G at 0.4 m ³ / h. Further, the adsorbent 11 was cooled to 40 ° C. in the cooling unit 22. Further, chiller water having a temperature of 5 ° C. was circulated through the collector 30 as a refrigerant, and the desorbed component W to be removed was cooled and liquefied.
[0032]
As a result, the methanol concentration in the treated gas 2 (treated air) at the outlet of the adsorption tower 10 was about 50 ppm. At this time, the recovery device 30 recovered methanol at a rate of 0.08 kg / h and water at a rate of 0.24 kg / h. Further, the gas treatment apparatus 100 was able to operate stably for 40 days continuously, and the methanol removal rate maintained a sufficiently high removal efficiency of about 95%.
[0033]
<Example 2>
Except for using water-resistant spherical silica having a water resistance of 62%, a specific surface area of 300 m ² / g, and a particle diameter of 0.71 to 1.18 mm (CAriACT Q-10, manufactured by Fuji Silysia Chemical Co., Ltd.) as the adsorbent 11. Exhaust gas treatment was performed in the same manner as in Example 1.
[0034]
As a result, the methanol concentration in the treated gas 2 (treated air) at the outlet of the adsorption tower 10 was about 70 ppm. At this time, the recovery device 30 recovered methanol at a rate of 0.08 kg / h and water at a rate of 0.24 kg / h. Moreover, the gas treatment apparatus 100 was able to operate stably for 40 days continuously, and the methanol removal rate maintained a sufficiently high removal efficiency of about 93%.
[0035]
<Example 3>
Air having a temperature of 30 ° C. and a relative humidity of 30% containing 1000 ± 100 ppm of methanol and 1000 ± 100 ppm of toluene as components to be removed is continuously supplied to the same fluidized bed type gas treatment apparatus 100 as used in Example 1. It was supplied at a flow rate of 60 m ³ / h. Further, as the adsorbent 11, water-resistant spherical silica having a water resistance of 48%, a specific surface area of 550 m ² / g, and a particle diameter of 0.71 to 1.18 mm (CA RiACT Q-3 manufactured by Fuji Silysia Chemical Ltd.) and a particle diameter of 0 A mixed adsorbent in which a petroleum pitch-based spherical activated carbon (manufactured by Kureha Chemical Industry Co., Ltd .; G-BAC) of 60 to 1.00 mm was mixed at a mass ratio of 50:50 was used, and the circulation rate was 4 kg / h. Further, the desorption temperature in the desorption tower 20 was set to 150 ° C., nitrogen gas was circulated at 0.8 m ³ / h as the carrier gas G, and the adsorbent was cooled to 40 ° C. in the cooling unit 22.
[0036]
As a result, the methanol concentration in the treated gas 2 (treated air) at the outlet of the adsorption tower 10 was about 100 ppm, and the toluene concentration was about 2 ppm. At this time, the recovery unit 30 recovered methanol at a rate of 0.07 kg / h, toluene at 0.25 kg / h, and water at 0.24 kg / h. Moreover, the gas treatment apparatus was able to operate stably for 40 days continuously, maintaining a sufficiently high removal efficiency with a methanol removal rate of about 90% and a toluene removal rate of about 99.8%. As described above, it is confirmed that by using the mixed adsorbent, these compounds can be stably removed at a high removal rate from the gas to be treated 1 containing both the water-soluble compound and the hydrophobic compound. It was done.
[0037]
<Comparative example 1>
Exhaust gas treatment was performed in the same manner as in Example 1 except that the petroleum pitch-based spherical activated carbon used in Example 2 was used alone as the adsorbent. As a result, it was found that the methanol concentration in the treated gas 2 (treated air) at the outlet of the adsorption tower 10 was about 900 ppm, and methanol in the air supplied to the adsorption tower 10 was hardly removed.
[0038]
<Comparative example 2>
Example 1 except that general-purpose spherical silica gel (Fuji Silica Chemical Co., Ltd. Fuji Silica Silica A type) having a water resistance of 20%, a specific surface area of 650 m ² / g, and a particle diameter of 0.85 to 1.70 mm was used as the adsorbent. Exhaust gas treatment was performed in the same manner as described above.
[0039]
As a result, generation of dust was frequently confirmed from the upper exhaust port of the adsorption tower 10, but the methanol concentration in the treated gas 2 (treated air) at the outlet of the adsorption tower 10 was about 40 ppm. In addition, when the gas processing apparatus 100 is continuously operated for about 7 days, the fluidized state of the fluidized bed of the adsorption tower 10 becomes unstable, and the quantitative circulation of the adsorbent becomes impossible, so the operation of the gas processing apparatus is stopped. did.
[0040]
<Comparative Example 3>
As an adsorbent, general-purpose spherical silica gel (Fuji Silica Chemical A type manufactured by Fuji Silysia Chemical Ltd.) having a water resistance of 20%, a specific surface area of 650 m ² / g, and a particle diameter of 0.85 to 1.70 mm, and the water resistance used in Example 1 were used. Exhaust gas treatment was performed in the same manner as in Example 1 except that a water-resistant 37% mixed adsorbent in which spherical spherical silica was mixed at a mass ratio of 40:60 was used.
[0041]
As a result, the methanol concentration in the treated gas 2 (treated air) at the outlet of the adsorption tower 10 was about 50 ppm. However, when the gas processing apparatus 100 is continuously operated for about 15 days, the fluidized state of the fluidized bed of the adsorption tower 10 becomes unstable and the quantitative circulation of the adsorbent becomes impossible, so the operation of the gas processing apparatus is stopped. did.
[0042]
【The invention's effect】
As described above, according to the gas treatment method of the present invention, water-resistant spherical silica having a water resistance of 45% or more is used as an adsorbent, and a gas to be treated containing a water-soluble compound is adsorbed in a fluidized bed type. By continuously processing using a gas processing device that moves while moving the agent, it is possible to sufficiently suppress crushing of the adsorbent due to moisture adsorption in the gas to be processed, such as methanol, ethanol, etc. contained in the gas to be processed It becomes possible to remove the water-soluble compound continuously for a long time with a high removal rate.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a fluidized bed gas processing apparatus suitable for carrying out the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Processed gas, 2 ... Processed gas, 10 ... Adsorption tower, 11 ... Adsorbent, 12 ... Tray, 20 ... Desorption tower, 21 ... Heating part, 22 ... Cooling part, 30 ... Recovery machine, 100 ... Gas treatment apparatus.

Claims (2)

A treated gas containing a water-soluble compound is brought into contact with an adsorbent to adsorb the water-soluble compound in the treated gas to the adsorbent, and the water-soluble compound adsorbed on the adsorbent is desorbed by heating. The adsorbent is regenerated, and the treated gas is continuously treated while moving so that the regenerated adsorbent comes into contact with the treated gas again.
The gas to be treated is continuously processed while the adsorbent is moved by a fluidized bed,
As the adsorbent,
The specific surface area is 200 to 900 m ² / g,
The particle diameter is 0.5 to 1.4 mm, and the following formula (1);
N = (W / W ₀ ) × 100 (1),
N: water resistance (%) of the adsorbent,
W ₀ : the total number (particles) of particles of the adsorbent immersed in water,
W: Number of W ₀ that did not crack (number),
A gas treatment method characterized by using a water-resistant spherical silica having a water resistance N defined by (1) of 45% or more. Examples adsorbent used and further comprising a spherical activated carbon, gas processing method according to claim 1, wherein.

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