JP2526597B2 - Ceramic Filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ceramic filter regenerated by a backwashing operation, which is designed to efficiently remove soot and dust from high-temperature dust-containing gas.

“Prior art and its problems” Conventionally, it has been proposed to use porous ceramics having excellent heat resistance when removing soot and dust from dust-containing gas, particularly high-temperature dust-containing gas (for example, Kaisho 59-
See 225721). When such a ceramics filter is used, dust adheres to and accumulates on the dust-containing gas side surface of the filter over time, which increases ventilation resistance and gas pressure loss. Therefore, after a certain period of time, a backwashing airflow is made to flow from the clean gas side toward the dust-containing gas side, and the dust accumulated on the dust-containing gas side surface is removed to restore the air permeability.

However, when the dust-containing gas is actually treated for a long period of time, depending on the type of dust, fine particles penetrate into the inner part of the filter and they are not completely removed even by backwashing. The ventilation resistance also gradually increases. For this reason,
The power cost of the air blowing means for passing the dust-containing gas increases, or the dust-containing gas processing capacity decreases. When the ventilation resistance becomes extremely high, the filter must be replaced, which causes an increase in maintenance cost.

In order to solve such a problem, in Japanese Utility Model Laid-Open No. 61-64315, a precoat layer made of a mixture of heat-resistant fibers and inorganic particles is formed on the dust-containing gas side surface of the filter prior to the dust removing operation. However, it has been proposed to capture most of the dust with a precoat layer to reduce clogging of the filter due to the dust.

However, in this filter, the precoat layer is peeled off during backwashing, and therefore it is necessary to re-add the precoat material after the backwashing to regenerate the precoat layer. In this way, since the precoat material is added each time the backwash is performed, the operation becomes complicated, the cost of the precoat material increases, and when the collected dust is useful, the amount of impurities mixed in increases and the collected dust becomes unnecessary. In this case, the amount of waste will increase.

"Object of the invention" The object of the present invention is to solve the above-mentioned problems of the prior art, to prevent dust from entering the inner part of the filter to cause clogging, and to extend the life of the filter as much as possible. The purpose is to eliminate the need to add precoat material each time backwashing.

"Structure of the Invention" The present invention is used for dust removal of high-temperature dust-containing gas, and in a porous ceramics filter for which backwashing operation is performed, the surface layer of at least one surface of the filter has a powder of a cleavable substance. The ceramic filter is characterized in that a retained filter layer is formed.

The powder of such a cleavable substance is in the form of scales, and if such powder gets into the pores of the filter, it will be difficult to come out even by backwashing. Further, even if such powders enter the pores of the filter, they are deposited while maintaining a gap between them, that is, forming a large number of gas passages, so that air permeability is ensured.

Therefore, it is possible to form a filter layer by holding powder of the cleavable substance on the surface layer of at least one surface of the filter, particularly the surface on the side that comes into contact with the dust-containing gas. It is possible to prevent invasion into the inner part of the interior, to improve the restoration of air permeability by backwashing, and to maintain the life of the filter for a long time.

In addition, the dust accumulated on the surface of the filter due to the continuation of the dust removal operation is separated and removed during the backwash, but the powder of the cleavable substance that has entered the pores of the filter surface layer is not removed even during the backwash. Since it is retained, it is not necessary to coat the powder of the cleavable substance with each backwash. That is, the filter layer formed by the powder of the cleavable substance plays the role almost semipermanently.

In the present invention, as the cleavable substance, a cleavable mineral such as talc, mica, graphite or the like is preferably used. Among them, talc has a good cleaving property and has a remarkable scale shape, which can be said to be particularly preferable in the present invention. Since graphite is oxidized at 600 to 700 ° C. in an oxidizing atmosphere, it is preferable to use it only in a non-oxidizing atmosphere or at 500 ° C. or less.

The average particle size of the powder of the cleavable substance is preferably several tens of μm or less, more preferably 0.5 to 5 μm. Average particle size is 0.5 μm
When it is less than 100%, the powder easily enters the inside of the filter, and the ventilation resistance of the filter, that is, the pressure loss tends to increase. If the average particle size exceeds 5 μm, it becomes difficult to form the filter layer on the surface layer of the filter, and the dust removal effect on the surface layer of the filter tends to decrease.

As a method of holding the powder of the cleavable substance on the surface layer of the surface of the ceramic filter that is in contact with the dust-containing gas, the gas containing the powder is added to the dust-containing gas flow of this filter prior to the dust removal operation by the ceramic filter. A method of passing the powder from the road side to the clean gas flow path side to capture the powder with this filter, or the surface of the ceramics filter to which the dust-containing gas is to be contacted, use a cloth or felt-like tool to remove the powder. A method of rubbing in can be adopted.

The ceramic filter according to the present invention preferably has a tubular shape, but other various shapes such as a plate can be adopted.

"Embodiment of the Invention" FIG. 3 shows an example of a dust remover using a ceramics filter according to the present invention.

That is, in the can body 11, a plurality of tubular porous ceramic filters 12 are arranged and accommodated substantially in parallel, and the upper and lower end portions and the intermediate portion of the filter 12 are held by a plurality of metal tube sheets 13. Has been done. Both sides of the tube sheet 13 are covered with heat insulating material 14.

A dust-containing gas inlet 15 is formed in the upper portion of the can body 11 and
The lower part of the is a hopper 17 for storing the separated dust 16. The dust 16 stored in the hopper 17 is intermittently opened by opening the valve 18 and taken out from the dust take-out port 19.

A plurality of clean gas outlets 20 are formed on the side wall of the can body 11. In this example, each clean gas outlet 20 is formed one by one in correspondence with each section partitioned by the tube sheet 13. .
The clean gas outlet 20 is connected to a pipe 21 for taking the clean gas out of the system, and the pipe 21 is provided with a suction fan 22. Ejectors 23 for backwashing are arranged at each clean gas outlet 20, and these ejectors 23 are connected to a compressed gas introduction pipe 24 connected to a compressor 25 via a solenoid valve 26. The dust-containing gas inlet 15 is connected to the dust-containing gas generation source 27 via a dust-containing gas introduction pipe 28, and a hopper 29 for feeding a cleavable substance powder is installed in the middle of the dust-containing gas introduction pipe 28. .

In the above configuration, before starting the dust removal operation, first, the operation of holding the powder of the cleavable substance on the inner surface of the filter 12 is performed. That is, the suction fan 22 is operated to suck air or clean gas, pass through the dust-containing gas inlet 15 into the pipe of each filter 12, pass through the wall of the filter 12, and pass from the clean gas outlet 20 to the pipe line 21. Generate a flow of gas that flows out. At this time, the flow velocity in the direction perpendicular to the surface of the filter 12 is
2.5 to 30 cm / s is preferable. In this state, the powder of the cleavable substance is introduced from the hopper 29, and the powder of the cleavable substance is placed on the flow of the gas and introduced into the filter 12. The powder of the cleavable substance is trapped on the inner surface of the filter 12 as the gas passes through the wall of the filter 12. The amount of the above powder input is 1.2 to before the pressure loss.
The amount is preferably about 5 times.

Then, the charging of the powder is stopped, the electromagnetic valve 26 is opened, the compressed gas is sent from the compressor 25 to the ejector 23, the compressed gas is ejected from the ejector 23, and backwashing is performed. By this backwashing, most of the powder adhering to the inner surface of the filter 12 is removed and falls into the hopper 17, but a part of the powder enters the pores of the inner surface of the filter 12 and is captured, so the pressure loss is powder. Slightly higher than before body insertion.

The treatment with the cleavable substance powder may be completed by performing the above operation only once, but if the above operation can be performed multiple times,
It is more preferable to repeat about 10 times. As a result, a filter layer, which holds the cleavable substance powder, is formed on the surface layer of the inner surface of the filter 12 (the surface in contact with the dust-containing gas).

Next, as a dust removal operation, the dust-containing gas from the dust-containing gas generating source 27 is introduced into the dust-containing gas inlet 15 through the dust-containing gas introduction pipe 28. The dust-containing gas flows into the filter 12, passes through the wall of the filter 12 to become clean gas, and is taken out of the system through the clean gas outlet 20 and the pipe line 21. Further, the dust in the dust-containing gas is separated when the dust-containing gas passes through the wall of the filter 12, and most of it is dropped and collected in the hopper 17.

However, if the dust removal operation is continued, the amount of dust that adheres to and accumulates on the inner wall of the filter 12 increases, and the pressure loss for passing the gas gradually increases. Therefore, it is necessary to perform the backwash operation regularly during the dust removing operation.

For backwashing operation, open the solenoid valve 26 and remove the ejector from the compressor 25.
Compressed gas is introduced into 23, and the compressed gas is ejected from the ejector 23. As a result, the backwash airflow flows from the outer surface to the inner surface of the filter 12, and the dust that has adhered to and accumulated on the inner surface of the filter 12 is blown off and removed. It should be noted that the backwashing operation is sequentially performed for each of the compartments partitioned by the tube sheet 13, and the dust removal operation is continued in the non-backwashing compartment so that the operation of the apparatus is not completely interrupted. It is preferable.

Next, the effect of using the ceramics filter 12 according to the present invention will be described with reference to FIGS. 1 and 2. First
The figure shows a cross section of a ceramic filter according to the present invention in which a powder of a cleavable substance is held, and Fig. 2 shows a cross section of a conventional ceramic filter. In FIGS. 1 and 2, 12 is a ceramics filter, 31 is a dust-containing gas passage, 32 is a clean gas passage, 33a, 33b and 33c are pores, 34 is a cleavable substance powder, and 35 is dust. The arrow A indicates the gas passage direction.

In the ceramic filter shown in FIG. 1, by passing the gas containing the powder 34 before the dust removing operation,
Pores 33a, 33b in which the powder 34 is located on the surface layer on the dust-containing gas side
Get in. Since the powder 34 is in the form of flakes, it is likely to be caught by the pore structure of the filter 12, has a small penetration into the inside of the filter 12, and does not easily enter the pores 33c inside. At the same time, even if the force to remove by backwashing acts, it becomes difficult to remove. Therefore, once the cleavable substance powder 34 is held, its characteristics are maintained almost semipermanently without deterioration. Further, since the powder 34 is in the form of flakes, even if the powder 34 is deposited on the surface pores 33a and 33b, many passages are formed and air permeability is ensured.

In this state, when the dust-containing gas is passed in the direction of the arrow A in the figure, the dust 35 contained in the dust-containing gas is prevented from entering the internal pores 33c by the filter layer of the powder 34, and most of the dust 35 is blocked. Are captured by the pores 33a closest to the surface layer. Therefore, when the backwash airflow is sprayed from the clean gas flow path 32,
The captured dust 35 is released from the pores 33a, and the filter 12
Removed from Therefore, recovery of the air permeability by backwashing becomes good, and the air permeability of the filter 12 can be maintained in a good state for a long period of time.

On the other hand, when the dust-containing gas is passed through the ceramics filter shown in FIG. 2 in the direction of arrow A in the figure, the dust 35 contained in the dust-containing gas is not limited to the surface pores 33a and 33b but to the internal pores 33c. It invades and gradually accumulates as the dust removal operation continues. Even if backwashing is performed when the pressure loss increases, the dust 35 that has penetrated to the internal pores 33c is difficult to remove even by backwashing, and the air permeability is not completely restored. Therefore, even if backwashing is regularly performed, the pressure loss gradually increases as the dust removing operation continues, and finally becomes unusable.

[Example] The effect of the ceramics filter according to the present invention was tested using a simulated dust remover shown in FIG.

In this simulated dust removing device, one canister 11 contains a filter 12 made of porous ceramics. A dust-containing gas introduction pipe for introducing dust-containing gas into the filter 12 is provided on the upper portion of the can body 11.
28 is connected.

The dust-containing gas introduction pipe 28 has a heater 41, a dust supply hopper 42,
Cleavable substance powder supply hopper 43, dispersion ejector 44, valve 45
Are connected in sequence. The heater 41 receives the signal from the temperature sensor 46 and raises the temperature of the inflow gas to a predetermined temperature. A branch pipe 47 leading to a bag filter 49 via a valve 48 is connected between the can body 11 of the dust-containing gas introduction pipe 28 and the valve 45.

The side wall of the can body 11 is connected to a clean gas take-out pipe 21 which communicates with a clean gas flow path.
Backwash ejector 23, valve 50, orifice 51, flow control valve 5
2. A suction fan 53 is provided in sequence. Flow control valve 52
Receives a signal from the orifice 51 and adjusts the flow rate to a predetermined value. The ejector 23 has a compressed gas introduction pipe from the compressor 25.
24 is connected via a solenoid valve 26. Between the ejector 23 of the clean gas extraction pipe 21 and the valve 50, there is a backwash air introduction pipe.
54 is connected, and a valve 55 is provided in the backwash air introduction pipe 54.

In this device, the flow at the time of forward flow is shown by the solid line arrow, and the flow at the time of reverse flow is shown by the broken line arrow.

In the above apparatus, as the filter 12, a tube body made of β-cordierite and having a porosity of 42%, an average pore diameter of 60 μm, an inner diameter of 140 mm, an outer diameter of 170 mm, and a length of 309 mm was used. As the cleavable substance powder, talc having an average particle size of 2.5 to 3 μm was used.

First, the valves 45 and 50 were opened, the other valves were closed, the suction fan 53 was operated, and the air flow indicated by the solid line arrow in the figure was generated. At this time, the flow velocity through the filter 12 was set to be 20 cm / s. In this state, about 20 g of the talc powder was charged from the hopper 43. The talc powder was dispersed by the ejector 44, flowed into the air flow into the filter 12, and part of it adhered to the inner surface of the filter 12. As a result, the pressure drop rose from the initial 220 mmAq to 380 mmAq.

Here, the valves 45 and 50 were closed, the valves 48 and 55, and the solenoid valve 26 were opened, and the compressed gas was ejected from the nozzle of the ejector 23 to generate the backwash airflow indicated by the broken line arrow in the figure. The ejection of the compressed gas from the ejector 23 was performed twice in 0.4 seconds. The pressure loss after backwashing was 250 mmAq. The same operation was repeated 10 times, and the pressure loss after the 10th backwash was about 500 mmAq.

In this way, after the talc powder was held by the filter 12, the dust removing operation was performed. First, the valves 45 and 50 were opened, the other valves were closed, the suction fan 53 was operated, and the air flow indicated by the solid line arrow in the figure was generated. In this state, the heater 41 was operated to set the inflow air temperature to 150 ° C. Further, blast furnace dust having an average particle diameter of 10 μm is charged from the dust supply hopper 42, dispersed by the ejector 44 and placed on the air flow,
Introduced into filter 12. The dust concentration is 7.3 g / m ³ , the flow velocity through the filter 12 is about 8 cm / s,
I adjusted each.

The dust was carried by the air flow into the filter 12, and when the air flow passed through the filter 12, the dust was separated and removed by the inner wall of the filter 12. A part of the dust adhered to the inner wall of the filter 12 and accumulated, so that the pressure loss gradually increased. Therefore,
Open the solenoid valve 26 every 7.5 minutes to remove the ejector 23 from 6 to 7 kg / cm ²
The backwash was performed by ejecting the compressed gas of G twice for 0.4 seconds.

If this operation is continued, the pressure loss before backwashing when backwashing at regular intervals continues to rise gradually, but it stabilizes about 140 hours after the start of the dust removal operation, and 1330 mmA immediately before backwashing.
q, 1230mmAq immediately after backwashing. After that, the pressure loss did not increase, and this state could be maintained until 720 hours later.

On the other hand, instead of talc powder, the average particle size without cleavage is 4.0μ
m alumina powder was held in the same way and the dust removal operation was performed in the same way. As a result, after about 150 hours, it reached 2100 mmAq immediately before backwashing, 1900 mmAq immediately after backwashing, and then continued to rise gradually, so after 200 hours The experiment was stopped.

In addition, the filter 12 not subjected to the pretreatment for holding the powder was used.
As a result of performing the same dust removing operation as above, after about 150 hours, 1700 mmAq immediately before backwash and 148 immediately after backwash.
Since it reached 0 mmAq and continued to rise gradually thereafter, the experiment was stopped after 200 hours.

As described above, it is understood that the filter that holds the cleavable substance powder such as talc is stable in a place where the pressure loss is low as a whole, and the difference in pressure loss before and after backwashing can be suppressed to be small.

"Effects of the Invention" As described above, according to the ceramics filter of the present invention, the surface layer of at least one surface of the filter,
Since the filter layer that holds the powder of the cleavable substance is formed, most of the dust in the dust-containing gas is captured by this filter layer, and the dust is less likely to enter the pores inside the filter. .

As a result, during backwashing, dust accumulated on the surface of the ceramics filter is easily removed, and recovery of air permeability is improved. Then, in the case of continuous operation, the pressure loss at the time of steady stabilization is suppressed to be lower than that of the one in which the non-cleavable substance powder is held and the one in which the powder holding pretreatment is not performed. Moreover, since the powder of the cleavable substance is in the form of flakes, even if it is deposited on the surface layer of the ceramic filter, sufficient air permeability is ensured. Furthermore, once the powder is held on the surface layer of the ceramic filter, it is difficult to remove it even by backwashing, and its characteristics are maintained almost semipermanently.

The ceramic filter of the present invention removes dust from high-temperature dust-containing exhaust gas generated in a blast furnace, a converter, an electric furnace, a cupola, a radioactive waste incinerator, etc., and converts the exhaust gas into a clean gas to effectively utilize its thermal energy. It is suitable for various uses.

[Brief description of drawings]

FIG. 1 is a partial sectional view schematically showing a ceramics filter according to the present invention, FIG. 2 is a partial sectional view schematically showing a conventional ceramics filter, and FIG. 3 is a dust removing apparatus to which the ceramics filter according to the present invention is applied. FIG. 4 is a vertical sectional view showing an example, and FIG. 4 is a schematic sectional view showing a simulated dust remover for testing the effect of the ceramics filter according to the present invention. In the figure, 12 is a ceramics filter, 31 is a dust-containing gas passage,
32 is a clean gas flow path, 33a, 33b and 33c are pores, 34 is a powder of a cleavable substance, and 35 is dust.

Claims (3)

(57) [Claims] 1. A porous ceramics filter, which is used for dust removal of high-temperature dust-containing gas and is subjected to backwashing operation, in which powder of a cleavable substance is held on the surface layer of at least one surface of the filter. A ceramics filter having a layer formed therein. 2. A ceramic filter according to claim 1, wherein the cleavable substance is selected from talc, mica and graphite. 3. A ceramics filter according to claim 1 or 2, wherein the powder of the cleavable substance has an average particle size of 0.5 to 5 μm.