JPH0811168B2 - Backwash method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a backwashing method in an apparatus for removing dust-containing gas through a porous partition wall.

“Prior Art and Its Problems” As a device for removing dust from high-temperature dust-containing gas, a device using a tubular body made of porous ceramics is known. For example, as shown in FIG. 3, a plurality of porous tubular bodies 12 made of ceramics are arranged and accommodated in a can body 11 substantially in parallel, and the porous tubular body 12 has upper and lower end portions and an intermediate portion. The part is held dust-tight by a plurality of tube plates 13.
A dust-containing gas inlet 14 is formed in the upper part of the can body 11, and a lower part of the can body 11 stores a dust 16 separated from the dust-containing gas.
It is 15. The dust 16 stored in the hopper 15 is taken out from the take-out port 18 by opening the valve 17 at a predetermined time. A plurality of clean gas outlets 19 are formed on the side wall of the can body 11, and in this example, each clean gas outlet 19 is formed one by one in correspondence with each section partitioned by the tube sheet 13. There is. Clean gas outlet pipe 20 connected to clean gas outlet 19
An ejector 21 is provided in the. The ejector 21 is configured such that the inner diameter of the clean gas take-out pipe 20 is made thin in the middle and a backwash nozzle 22 is arranged from this thinned portion toward the clean gas take-out port 19.

In this device, when the dust-containing gas is fed from the dust-containing gas inlet 14, the dust-containing gas is introduced into the plurality of porous pipes 12, passes through the walls of the porous pipes 12 to become a clean gas, and is cleaned. It flows out from the gas outlet 19 through the clean gas outlet pipe 20.
At this time, the dust contained in the dust-containing gas is the porous tube body 12
Cannot pass through the wall of the hopper 15
It is stored inside.

As the dust removing operation is performed by this device, dust adheres to and accumulates on the inner wall of the porous tube body 12, so that clogging gradually occurs and ventilation resistance increases. Therefore, gas is periodically ejected from the backwash nozzle 22 to perform backwash. When the gas is ejected at high speed from the backwash nozzle 22 toward the clean gas outlet 19, the clean gas around the backwash nozzle 22 is also included in the ejector 21 having a narrow inner diameter, and these gases are used as the backwash gas. It will flow toward the partition. Then, this backwash gas is blown to the outside of the porous pipe body 12, passes through the wall of the porous pipe body 12 from the outside to the inside, and the dust accumulated on the inner wall of the porous pipe body 12 is removed, Prevent jams. This apparatus is provided with a clean gas extraction pipe 20 and an ejector 21 one by one in each section partitioned by the tube sheet 13, and the backwashing operation can be sequentially performed in each section, while in other sections, The dust removal operation can be continued.

However, in this dust removing apparatus, the flow velocity of the dust-containing gas becomes slower as it flows downward in the porous pipe body 21, and the flow velocity becomes almost zero at the lower end portion of the porous pipe body 12. For this reason, particularly when backwashing is performed in the lowermost section partitioned by the tube sheet 13, the backwash gas passes through the wall of the porous tube body 12 from the outside to the inside and then moves downward in the porous tube body 12. A state occurs in which the fluid does not flow into the chamber and stays or rises. In such a state, the dust blown off from the inner wall of the porous tubular body 12 is less likely to fall downward, and while floating, adheres to the inner wall of the porous tubular body 12 in the upper section during the dust removal operation. Or, when the backwashing is finished and the dust removing operation is started again, the dust is again adsorbed on the inner wall of the porous tube body 12. Therefore, there is a problem that the backwashing effect is reduced and continuous operation becomes difficult.

"Object of the Invention" The object of the present invention is to enhance the backwashing effect by allowing the dust blown off from the inner wall of the porous partition wall by the backwashing gas to quickly fall downward without floating or rising. The purpose is to provide a backwashing method.

"Structure of the invention" The present invention, a dust-containing gas is fed from the upper part of the space partitioned by the porous partition wall arranged substantially vertically, clean gas is passed through the partition wall, and taken out of the space, And, in the backwashing method of the partition wall, using a dust remover adapted to take out the separated dust from the lower part of the space, and feeding backwash gas toward the partition wall from outside the space during predetermined backwashing, A circulation path that communicates from the lower part of the space to the upper part of the space and is provided with an ejector is provided, and the ejector is operated to extract at least part of the gas from the lower part of the space at the time of the backwash, and to the upper part of the space. It is characterized by circulation.

Thus, by extracting at least a part of the gas from the lower part of the space partitioned by the partition wall and circulating it to the upper part of this space, the downward flow of the gas in this space also flows in the lower part of this space. It can be maintained. For this reason,
The dust blown off from the inner wall of the partition by the backwash gas,
The downward flow of gas in this space is quickly dropped and collected. Therefore, the dust that has been blown off is prevented from rising and adhering to the upper partition wall portion, or floating and re-adhering after the backwashing is completed, and the backwashing effect can be enhanced.

In the present invention, the gas circulation from the lower part of this space to the upper part of this space may be continuously carried out irrespective of the dust removing operation or the backwashing operation, but in a preferred embodiment of the present invention, the backwashing operation is performed. Only occasionally do gas circulation.

That is, for gas circulation, an ejector provided in the circulation path is operated. When the gas circulation is always performed continuously, the compressed gas is ejected from the nozzle of the ejector. However, the constant circulation requires a high-capacity high-pressure compressor, resulting in an increase in equipment cost.

On the other hand, if the gas circulation is performed only during backwashing, the backwashing only removes the dust adhering to the inner wall of the porous partition wall.
The purpose can be achieved by performing backwashing for a relatively short period of time, such as at regular intervals, the power cost required for gas circulation during that time is not so large, and the wear resistance and heat resistance required for the ejector are also low. The tolerance is widened and the equipment cost can be reduced. Further, the compressor required for the ejector has a relatively small capacity, which is sufficient and the facility cost can be reduced.

When the gas circulation is not performed during the dust removing operation, even if the flow velocity in the lower part of the space partitioned by the partition wall is zero, the dust can be collected by the downward inertial force of the dust, and there is almost no practical problem.

In a preferred aspect of the present invention, the partition wall is tubular,
The inside of this pipe is defined as the space. The tubular shape makes it possible to easily produce a filter medium having sufficient strength, and by disposing a plurality of the tubular partition walls, the filtration area can be increased. Ceramics are preferable as the material of the partition walls. Porous ceramics have excellent heat resistance and wear resistance, and can be applied to treatment of high temperature dust-containing gas.

A fan or the like can be used as the blowing means, but the heat-resistant structure of the fan becomes complicated when treating high-temperature dust-containing gas. In this respect, since the ejector simply arranges a simple circulation nozzle in the flow path, it is easy to take heat resistance measures.Furthermore, the gas ejected from the circulation nozzle may be at room temperature, in which case the circulation nozzle is cooled from the inside. No special heat resistance measures are required. Further, the amount of gas ejected from the circulation nozzle is much smaller than the flow rate of the circulation line, so that the blower means is downsized and simplified.

Further, in another preferred aspect of the present invention, the circulation path is provided with a dust remover by filtration, inertial force or centrifugal force. Although the gas extracted from the lower part of the space is often accompanied by a considerable amount of dust, by removing the dust with the dust remover and circulating the dust in this way, the adverse effect of dust on the ejector can be prevented.

"Embodiment of the Invention" FIGS. 1 and 2 show an example of a dust remover for carrying out the present invention. In the figure, the third
The substantially same parts as those of the dust removing device in the figure are designated by the same reference numerals, and the description thereof will be omitted.

In this dust remover, one end of the circulation pipe 23 is connected so as to communicate with the inside of the hopper 15 in order to extract the dust-containing gas from below the porous pipe body 12, and the other end of the circulation pipe 23 rises upward. Is connected to the dust-containing gas inlet 14. Circulation pipe 23
A dust filter 24 is attached to a portion of the hopper 15 that opens. As shown in FIG. 2, the dust removing filter 24 is constructed by holding a filter medium 25 made of sand, ceramic powder or the like with a wire mesh 26. The dust-containing gas G passes through the dust-removing filter 24 to be dust-removed and flows in the circulation pipe 23. Instead of the dust filter 24, a dust remover by inertia, centrifugal force, or the like may be attached.

An ejector 27 as an air blower is provided in the middle of the circulation pipe 23. The ejector 27 is formed by reducing the inner diameter of the circulation pipe 23, and is provided with a circulation nozzle 28 that opens in the flow direction of the circulation gas. When the pressurized gas is ejected from the circulation nozzle 28, the flow velocity is increased at the reduced diameter portion, and the dust-containing gas located below is also entrained to flow upward. A valve 29 is attached to the upper portion of the circulation pipe 23. The valve 29 is designed to open only during backwashing and close during normal operation.

Next, the backwashing method of the present invention using this dust removing device will be described.

First, the dust removal operation is no different from the conventional example, and the dust-containing gas is introduced from the dust-containing gas inlet 14 and circulated in each porous tube body 12. The dust-containing gas passes through the wall of the porous tube body 12 to remove dust, and becomes clean gas and is taken out from the clean gas take-out pipe 20. Further, the dust contained in the dust-containing gas falls downward, is stored in the hopper 15, and is taken out by periodically opening the valve 17. The flow rate of the dust-containing gas becomes slower as it flows downward in the porous tube 12, and becomes almost zero at the lower end of the porous tube 12, but due to the inertial force of the dust, the dust remains as it is. Fall within 15

Then, when the dust removing operation is continued, dust gradually adheres to and deposits on the inner wall of the porous tube body 12, the ventilation resistance of the porous tube body 12 increases, and the processing capacity decreases. Therefore, after a predetermined dust removal operation time or after reaching a predetermined ventilation resistance value,
Compressed air is ejected from the backwash nozzle 22 of the ejector 21, and the backwash gas is blown to the outside of the porous pipe body 12 from the clean gas outlet 19. As a result, the dust accumulated on the inner wall of the porous tube body 12 is removed, the ventilation resistance of the porous tube body 12 is reduced, and the processing capacity is restored.

The backwashing may be performed from all the clean gas outlets 19 at the same time, but in that case, the dust removing operation must be temporarily stopped, which may cause inconvenience in the operation of the system using the dust removing device. Therefore, it is preferable that the backwash is sequentially performed for each of the compartments partitioned by the tube sheet 13, and the dust removal operation is performed for the other compartments where the backwash is not performed.

The feature of the present invention is that during the above-mentioned backwashing operation, a part of the dust-containing gas is extracted from below the porous tubular body 12 and the porous tubular body is removed.
To circulate above 12. That is, at the time of the backwash operation, the valve 29 is opened and the compressed air is ejected from the circulation nozzle 28 of the ejector 27. As a result, an upward blowing air force is generated, and the dust-containing gas existing in the hopper 15 can be sucked and introduced into the circulation pipe 23, and can be sent to the vicinity of the dust-containing gas inlet 14 through the circulation pipe 23. In this case, since the dust-containing gas is introduced into the circulation pipe 23 after the dust is removed by the dust removing filter 24, it is possible to prevent the ejector 27 and the valve 29 from being damaged or blocked by the dust.

As described above, by extracting the dust-containing gas gas from the lower side of the porous pipe body 12 and circulating the dust-containing gas gas above the porous pipe body 12, a downward flow of the dust-containing gas also occurs in the lower portion of the porous pipe body 12. Therefore, for example, when backwashing is performed in the lowermost section partitioned by the tube sheet 13, the dust blown off from the inner wall of the porous tube body 12 by the backwash gas does not float or rise. That is, they will be quickly collected in the hopper 15 along with the flow of dust-containing gas. Thus, the dust washed off by the backwash is prevented from adhering again to the inner wall of the porous tube body 12, and the backwash effect can be enhanced.

The flow velocity of the dust-containing gas at the lower end portion of the porous pipe body 12 can be increased as the circulation amount of the dust-containing gas taken out from the circulation pipe 23 is increased, that is, as the wind force sent by the ejector 27 is increased. However, if the flow velocity of the dust-containing gas at the lower end of the porous tube body 12 is increased more than necessary, turbulent flow will be generated in the hopper 15 and the dust will rather float rather. Therefore, it is preferable to adjust the gas circulation rate such that the downward flow velocity of the dust-containing gas near the lower end of the porous tube body 12 is 0.3 to 4 m / sec.

As mentioned above, gas circulation is preferably performed only during the backwash operation. That is, the valve 29 is opened and the compressed air is ejected from the circulation nozzle 28 of the ejector 27 only during the backwash operation. As a result, the power required to drive the ejector 27 can be reduced, and the equipment such as a compressor that supplies compressed air to the circulation nozzle 28 can be made small. Also, when there are a plurality of compartments above and below, the gas circulation is particularly effective when backwashing in the lowermost compartment partitioned by the tube sheet 13, so only during backwashing in the lowermost compartment. The dust-containing gas may be circulated.

A preferred example of the time mode of dust removal and backwash will be described by taking as an example a dust remover which is divided into three sections of an upper stage, a middle stage and a lower stage by a tube sheet as shown in FIG.
The present invention is not limited to such temporal modes.

First, dust removal operation is performed for several tens of minutes in the upper, middle, and lower sections. Then, backwash operation is performed for about 0.2 seconds in the upper stage, while the dust removal operation is continued in the middle and lower stages. After a lapse of about 1 to several seconds, the same backwashing operation is performed in the middle stage, and the dust removing operation is performed in the upper and lower stages during this period. After a lapse of about 1 to several seconds, the same backwashing operation is performed on the lower stage, while the dust removing operation is performed on the upper and middle stages. The above dust removal / backwash cycle is repeated periodically. Therefore, the above-mentioned gas circulation is about 0.2 seconds plus alpha at the time of backwashing the bottom in a cycle of several tens of minutes, and about 5 seconds in total even if the gas is circulated during each backwashing,
The ratio of the gas circulation time to one cycle is extremely small.

In the above embodiments, the example in which the porous tubular body is used as the porous partition wall, but a porous plate-like body or the like can be used instead of the tubular body. Also, as the material of the partition wall,
Various materials such as ceramics, glass, carbon, and sintered metal can be used, but ceramics are preferable because they are generally excellent in heat resistance, wear resistance, and corrosion resistance.

[Advantages of the Invention] As described above, according to the present invention, at the time of the backwash operation, at least a part of the dust-containing gas is extracted from the lower part of the space partitioned by the porous partition wall and circulated to the upper part of this space. As a result, downward flow of dust-containing gas occurs even in the lower part of the porous partition wall, and the dust washed off from the inner wall of the partition wall by backwash does not float or rise, Since it falls, it is possible to prevent reattachment of dust and enhance the backwash effect. Therefore, the interval for performing the backwashing process can be lengthened and the operation rate of the dust removing device can be improved. In addition, since the ejector only has a simple circulation nozzle in the flow path, it is easy to take heat-resistant measures.The gas ejected from the circulation nozzle may be at room temperature. In that case, the circulation nozzle is cooled from the inside, so additional heat-resistant measures can be taken. Is unnecessary. Further, since the gas ejected from the circulation nozzle is much smaller than the flow rate of the circulation line, it is possible to configure a blower means that is downsized and simplified. Further, if the gas is circulated only during the backwash operation, the time for operating the circulation path can be extremely short, so that the power cost can be reduced and the frequency of failure occurrence due to dust in the circulation device can be suppressed. Further, even when the circulating gas has to be cooled due to the limitation of the heat resistant temperature of the circulation device, the heat loss can be suppressed to be extremely small.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an example of a dust remover for carrying out the present invention, FIG. 2 is a partially enlarged sectional view showing a dust remover provided in a circulation path of the same, and FIG. 3 is a conventional dust remover. FIG. 3 is a vertical cross-sectional view showing an example of a device. 12 is a porous tube body, 13 is a tube plate, 15 is a hopper, 19 is a clean gas outlet, 21 is an ejector, 22 is a backwash nozzle, 23 is a circulation pipe,
24 is a dust filter, 27 is an ejector, 28 is a circulation nozzle.

Claims (4)

[Claims] 1. A dust-containing gas is fed from the upper part of a space defined by porous partitions arranged substantially vertically, and a clean gas is passed through the partitions to be taken out of the space and separated. In the backwashing method of the partition wall, in which a backwashing gas is sent from the outside of the space toward the partition wall at the time of predetermined backwashing, a lower part of the space is used. To a top of the space and a circulation path having an ejector is provided, and the ejector is operated to extract at least a part of the gas from the bottom of the space and circulate the gas in the top of the space. A characteristic backwash method. 2. The backwashing method according to claim 1, wherein the partition wall is tubular and the space is inside the tube. 3. The backwashing method according to claim 1 or 2, wherein the partition wall is made of ceramics. 4. The backwashing method according to claim 1, wherein a dust remover by filtration, inertia or centrifugal force is provided in a circulation path from a lower part of the space to an upper part of the space.