KR830000347B1 - Low pressure filter - Google Patents

Abstract

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Description

Low pressure filter

1 is a cross-sectional view of a filter device having two low pressure filters.

2 is a partial sectional view of an air purification tank having a valve and a nozzle.

3 is a cross-sectional view taken along line II-II of FIG. 2 of the transition detail from the air purification tank to the nozzle.

4 is a pressure lapse diagram at a plurality of locations of filter hoses between counter flows.

5 is a cross-sectional view of the filter hose expanded inward in the case of dust separation.

6 is a sectional view of the same hose in the case of flush cleaning.

In the industry for purifying air having extremely high dust concentrations, filters having counter cleaning devices have been remarkably implemented. This device is retroactive to the basic idea disclosed in German patent specification 1228130 (Mikropal).

The dust-containing air enters the dust air chamber from below. This dust is detained (detained) by a plurality of individual filter hoses in the dust chamber, so that the purified air proceeds to the exhaust chamber through the plurality of free openings and is returned to the working process from the exhaust chamber or discharged to the atmosphere. .

A plurality of rims, i.e., nozzles, are provided at the top of each free opening or a plurality of filter hoses, and these nozzles are connected to high pressure via a piping member and a controllable valve. The valve opens in a short time at a selectable interval and inflates the filter hose by compressed air impact.

By slowing down the bonding of the dust layer adhering to the outer side of the filter hose, the filter cloth can be purged and fully effective. It is actually shown that this device is still suitable today.

Following the above idea, German Patent Specification No. 1021560 (Buhler) discloses a low pressure filter in which an appropriate counter cleaning device is provided. The low pressure filter acts as an oil removal dry cleaning air and does not require compressed air. In this case, the plurality of filter hoses in the dust chamber are connected to the exhaust chamber above the dust chamber through various free openings. Of course, in the case of the filter of this paper, since a plurality of Laval nozzles are provided on the free opening, the purified air passes through the Laval nozzles and flows into the exhaust chamber as rain. The cleaning is continuously maintained at 0.3 to 0.5 atm or less in the air purification tank, while the air purification tank has the necessary capacity to give the compressed air impact necessary to clean the filter hose. It is connected to the air distribution chamber through a pipe connecting the material valve. The rims of these valves are oriented with a short distance inside these filter hoses along the centers of the Laval nozzles, respectively, via a plurality of Laval nozzles. In the air distribution chamber, there is a small amount of air mother liquor of the filter itself. However, this reserved portion does not perform a feedback washing action alone. If the air distribution chamber that expands from 04 at 4.0 atmospheres to 40 liters has a capacity of 40 liters (l), for this reason, it is considered that the air phone works effectively only 4 liters. Do not.

However, in the case of the known low pressure filter, effective air purification has been considered as 40 to 80 liters. The filter casing cannot already insert a suitable volume. Therefore, in case of individual products, the air generator itself is integrated into the filter head or directly connected to the air generator. The air required for cleaning, i.e., during the effective cleaning process, is thus continuously supplied directly from the air generator, the rotary piston compressor, and the like.

In order to adequately secure the air replenishment during cleaning, an air generating device or an air source is often connected as close as possible to the air distribution chamber.

The main problem in the case of low pressure filters is that they can only compress the air purification relatively little, and thus can not produce inherent compressed air shocks. Nevertheless, however, this air purifying pressurized shock needs to reverse the flow of air to be purified to the opening even in the case of 0.5 atm or less, and thus perform counter-cleaning, that is, return washing.

This object has been achieved in the case of the above-described design of the applicant as follows. Instead of an air purge impact, an air purge is generated, which, via the Laval nozzle, climbs a remarkable amount of purge air from the exhaust chamber, thus doubling the air purge and doubling it back into this volume of air. Therefore, it brings about a remarkable clean effect. The above purification method of controlling each hose individually and in particular at adjustable time intervals is now carried out by the applicant over a period of approximately 15 years, in particular in terms of air volume and dust content such as, for example, the separation and recovery of powdery residues in the case of milling. It was effectively used because of its extremely high load.

Again many similar solutions are known and their methods are either incompletely used with secondary supplemental air or already made air, or none at all. In this type of low pressure filter, the rim of the valve passes through the opening of the filter hose so that only a small ring gap remains in the air purified by the filter. As is further demonstrated, this solution is of relatively low cleaning effect. In this case, the allowable filter load is substantially relatively low, so that the entire purification apparatus is necessarily large.

The Applicant has studied to improve the purifying action even in the case of other embodiments by directly connecting the rim of the valve by a pipe member which mechanically moves the free opening of the filter hose. This design can preserve the flow loss small, but the techniques used so far have not been able to achieve uniform cleaning even after years of effort. In the case of relatively low filter loads, the action of this filter is excellent, and in the case of high loads, a large difference is observed in the purification of individual hoses. According to the conventional knowledge, it cannot be solved enough to satisfy the above problem because it is measured in the case of mechanical operation when the shock pressure rise is counter-washed. This pressure, of course, is concentrated at a constant low value. Relatively good results of the filter initially described by the applicant of the present application are generally obtained with respect to the mechanical concept described last, and therefore are preferred to those originally described in the sale.

The main object of the present invention is to improve the filter having the counter-cleaning device and to prevent the above-mentioned partial defects from appearing in particular. In this invention, it was surprisingly found that the practical improvement of the purification effect and the simplification of the substantial structure are also achieved.

The present invention is a method of purifying an elongated filter hose using an opposite washing shock that counters a known flow that is purified through a filter hose, and is characterized in that the opposite washing has a first compressed air shock and a relatively low strength. And furthermore, it is carried out by a second post-cleaning shock which is carried out directly over a long period of time.

An object of the present invention is to blow off dust particles from the filter bag to the outside in a post-cleaning step in which the dust layer is scattered from the filter bag (forge).

It has been found for the first time as this new method that the purification process has been introduced in practice today, but this has not been done.

German patent 1228130, described earlier, states that the duration of the pressure cleaning process with regard to the purging action is clearly not extreme, as indicated in many of the experimental examples thereafter. However, according to the present invention, the first impact scatters only the dust layer. However, it was then proved that the strength of the cleaning operation was relatively low, causing the filter cloth to expand slowly, thus returning to a constant gauge and contacting it. At this time, the dust part of the filter cloth is slowed and blown out of the paper by the post-cleaning.

In each case (undyed door), after each cleaning process, which can be determined by the naked eye as a dust cloud in pure air, the intrusion of dust into the hose is now completely eliminated, at least conventionally accepted as a natural law, at least as usual. Is not already weighed.

This new method can certainly be converted into various implementations.

An obvious solution is to control the air purification valve from a high pressure source with a constant air volume in time or by a new method, or for example, a valve with two openings, a valve with two types and a special structural design. Is used for the connection part.

Until now, studies have shown that the late cleaning process is 3 to 20 times the length of the first compressed air impact process, preferably 3 to 7.5 times the length, and the average pressure generated by the filter hose during the late cleaning process is the first compressed air. The best results were obtained when about two to six quarters lower than the corresponding pressure peak of the impact.

The most important point is to cause the overpressure and re-start of the filter process during the filter hose forefront cleaning process, and in the case of the above filter process, almost without exception, the air to be filtered can be sucked through the filter forage without loss. In addition, the filter hose acts on the dust chamber surrounded by the vacuum. It is advantageous that the duration of the counter-cleaning impact should be adjusted without permission in order to obtain a determined status for the re-cleaning process, in particular the transition to the filter process, and especially to consume as little energy or air purification as possible with low effective air purification. .

Depending on what kind of apparatus the present invention is implemented, it may be possible to adjust the strength of the opposing air purification simultaneously or independently in the case of the first compressed air impact and in the case of the post-cleaning impact, respectively. The effective air purification amount is almost equal to the capacity of one filter hose, and the water column of 2000 to 8000 mm in the immediate vicinity of the free opening of the filter hose is preferably prepared at a pressure of 4000 to 6000 mm. The best results are obtained when the valve is discharged directly through the large-area valve with the driving nozzle and the cleaning time is adjusted to close the low-area valve again at a pressure higher than the water column of 2000 to 3000 mm. have. Therefore, this method is particularly fully advantageous for cleaning the low pressure filter, and the air purification amount is large in the air purification tank such as the capacity of the filter hose having an average overpressure of water column of 8000 mm but at least 3000 mm for the low pressure filter. It discharges to the nozzle which is oriented freely in this filter hose via a valve. As an alternative use, it has been found to be reasonable to bring the air pressure of the air purification tank prior to cleaning to a water column of 4000 to 6000 mm and to drop it to a water column of 2000 to 3000 mm of the air purification tank during cleaning.

4 shows the pressure loss measured at various locations of the filter hose having a length of approximately 2 m or more, wherein the air pressure of the air purification tank at the start of cleaning is about 5000 mm with the water column and 3500 mm with the water column at the end of the cleaning. do. These curves are taken as piezo crystal and cathode oscillation graphs, and the vertical axis shows the pressure passage, and the horizontal axis shows time, starting from 0 to the right. These curves are stacked on top of each other at regular intervals for better visibility.

Pressure curve A is measured at the free opening of the filter hose and curve E is measured above the closed end of the filter hose. Thus, the E curve and the adjacent D curve are equally determined by the edge effect (reflection of the pressure wave) and at the initial (0.05 second) already indicate the first steep rise in pressure and continue to the peak. We can clearly recognize post-cleanings lasting almost 3/10 seconds with relatively little strength or pressure. The representative B and C curves for about two-thirds of the length of the filter hose at the center clearly show the characteristics of this new method. In both cases, the first pressure rise lasts about 1/100 second and then appears shocking. Then, after 3/100 second, the 1st cleaning process is complete | finished.

In the case of a clean filter hose which is not used, it is necessary to pay attention again after performing the pressure measurement. If there is a dust layer in the filter hose, the pressure rise in the first and the purification process will be more substantial. Curves B and C again show a gentle transition from the first impact process to the second late wash process. This transition from the first to the second process, at the same time, determines whether the great advantages of this new method are fully used or not.

In other words, if a short time of rest (pause) is put in the same shape between the first process and the second process, the filter material is dragged to the support gauge, and thus there is a risk of penetrating and pressing the fine dust inward.

The post-cleaning process is relatively quiet but is characterized by a low pressure process. During the post-cleaning process, the average pressure is almost 1/6 to 1/2 less than the pressure peak corresponding to the first cleaning process, depending on which curve is observed. The temporal ratio from the first acceleration process to the return cleaning process is between 1: 3 and 1: 7.5. Optimal values have only been obtained for a few products in the past. Depending on the product, it is necessary to lengthen the washing time up to 20 times or more than the first step. The other limit may be that the pressure drop occurs approximately slowly so that the Peterforge turns to the support gauge moderately smoothly without repulsion.

In other words, the curve is extremely interesting with respect to the measuring point A provided at the initial end of the filter hose above. If the pressure passage is again followed from right to left, it should be noted that the first pressure peak is steeper and larger than all of the other pressure values of the filter hose. This is the first compressed air impact to the clean air coming from the filter hose which flows against it. The time for the first pressure rise is not more than 5/1000 seconds. It is natural that damage to the filter cloth does not occur by such a short action time. It is conceivable that an overpressure peak will occur in the first collision of the two arms facing each other. It is conceivable that an overpressure peak will occur in the first collision of the two arms facing each other. After 1/100 second or less, this overpressure is reversed into a vacuum.

The curve indicates a relatively rapid negative pressure rise when neglecting the overlapping microscopic vibrations, which are then often resolved until the end of the feedback cleaning process. Therefore, the following conclusions are drawn. In other words, the air flow of the fras flows from the inside of the hose to the outside of the hose from the beginning to the end of the pre-feedback washing process, and as described several times, the smooth transition from the return cleaning to the normal operation of the dust purification begins.

Thus, a number of teachings can be captured from the description so far.

○ Shocking pressure rises with counter cleaning

A pressure peak that acts for a short time (extracting dust on the outside of the forge does not require only a short time, and the extension of this time already brings nothing except large air losses)

It is particularly important to maintain a slightly delayed delivery to the second late cleaning process, in this case from the inside of the filter towards the outside.

○ Since the pressure of the filter hose drops frequently, the air flow reversal from the counter cleaning to the normal dust purification process is performed smoothly, and the filter forge does not contact the support gauge properly and thus expands inward.

It is desirable that a complete counter cleansing process is shorter than normal and usually less than 1 second and even less than 1/2 second.

Furthermore, the present invention relates to a low pressure filter having a counter cleaning device for purifying air containing dust,

○ In the true room,

○ Exhaust chamber for purifier air

○ and air purification tank

And an air purifying tank having a plurality of edges connected to the exhaust chamber via a plurality of filter hoses having a plurality of free openings of the dust chamber, and wherein the counter cleaning device is oriented in a direction to the interior of the filter hose. It has a valve of material.

According to the present invention, since the air purifying tank is disposed on the dust chamber in the low pressure filter at a predetermined interval with respect to the chamber, and the valve is connected to the air purifying tank, the amount of air required for counter cleaning with a predetermined pressure is controlled. It is characterized in that the discharge to the rim metal directly from the air purification tank at time intervals.

In practice, two points of view are important: the first point of view shows that the filter hose gives a short impact to the filter hose.

According to the second view, counter-rectifications of at least several seconds and of moderately low intensity and long-lasting need to be prepared in advance to further purify the filter cloth. However, it is known in the art that this purification process is always only influenced and controlled in the partial pipe. According to this novel invention, counter-cleaning is strongly introduced and effectively completed, thereby enabling a substantially high filter load and displaying an excellent purifying action.

For example, a small filter of 24 filter hoses is cleaned by counter-cleaning as it passes through each individual hose to the other hose. This action is repeated during the roll up time.

According to the present invention, it is advantageous when the two times can be adjusted as much as possible during the counter washing, so that a relatively thick dust layer from several mm to 1 cm is attached on the outside of the filter. This dust layer itself is at least a product specific filter material which is better than any filter cloth as it is known because many of the holes in this dust layer are smaller than the dust portion to be cleaned. The dust layer is slightly fixed by the flowing air, and constitutes the dust abdomen attached to the circumference of the whole hose. Since the filter forge is folded over and folded over the gauge for each hose, the filter forge maintains the pipe shape from the outside to the inside even in the case of strong airflow, ie corresponding air pressure. On each free surface of the wire gauge, the filter pouch swells inward and the dust layer is adapted to this shape. The opening of the large-area male valves suddenly results in a first cleaning air shock which acts directly toward the interior of the filter hose. Compresses the air column in the filter hose by the first impact, generates an overpressure relative to the pressure outside the filter forks, and inflates this filter forged with a dust layer by shock wave energy, thus discharging the dust layer. (投 出)

In the conventional filter, this is omitted. This is because the filter cloth is moved inward from the outside at about the same speed in the known embodiment. In fact, even in the case of a relatively small pressure difference, the filter forge is again pressed against the inside or generates a force from 50 to 100 kg.

Therefore, in the case of the known filter, the return motion can be regarded as the impact shape as well. For this reason, the dust component in the inside of this filter cloth is similarly pressed toward inside through many pore holes in which the relatively large component of the dust component floating around a hose is fully opened.

However, it is wrong to conclude that the cleaning shock must last for a relatively long time because, for example, it is necessary not only to press air again and again with respect to the inner hose volume, but also to strain the filter forge with great force. This leads to premature failure.

According to the present invention, it has been found that the optimum value for the load of the air consumption paper and the filter process itself is achieved if the forge is completely retaken with the swelling shape inwardly if the post-washing is performed on the first impact part. In this case, the tapered paper is likewise beaten to only one side, that is, to the outside.

Even in the case of the low pressure filter, the overpressure of the water volume of at least 3000, but higher than 8000 mm, which is almost the same as the content of one filter hose, is discharged through the nozzle which is freely oriented in the filter hose via a large area valve directly into the air tank. In case of good late cleaning is guaranteed. In the case of 20 L of filter hose contents, the best results were obtained with 15 to 30 L of cleaning air. The best value can be achieved when the pressure of the air purifying tank before cleaning becomes a water column of 4000 to 6000 mm and when the water column during cleaning does not exceed 2000 to 3000 μ. Therefore, in the case of a low pressure filter, a sufficiently strong post-cleaning is ensured. Because. If the initial pressure (initial pressure) is too high, excess air is consumed. In the case of high-pressure adjustment for a long time, it was necessary to separately control the strength of the post-cleaning in two opening stages, for example, by designing a special valve.

According to this novel invention, such an accessory is obsolete in the case of a low pressure filter due to a particularly advantageous embodiment.

One of the most important measures in the case of the low pressure filter is considered to be that the effective cleaning air amount is directly supplied to the valve. This cleaning air has almost complete energy and is discharged directly into the drive nozzle. This drive nozzle is arranged a little distance on the free opening of the filter hose, and is orientated inside the hose. The pressurized energy is converted to subsequent later cleaning in accordance with the first impact cleaning for the first time in the case of a hose.

According to the method according to the present invention, after the first pressure peak is reached, a post-cleaning step of the target difference controlled with respect to the time of the air purification and the post-cleaning strength is introduced, and the target intensity lowered and substantially maintained during the step is obtained. If this is followed, follow-up washing is performed afterwards, which is not completely dependent on the pressure shock of the preceding sudden.

The present invention will be clarified with reference to the examples and the spirit of the preferred embodiments will be described.

Hereinafter, embodiments according to the present invention will be described with reference to FIGS. 1, 2 and 3.

1 shows the use of two low pressure filters. The filter 1 on the left side and the filter 2 on the right side are connected to the common air blower device 6 for air purification via pipe pipes 3, 4, and 5. The blower device 6 starts from the drive motor 7, the rotary piston blower 8 and the silencer 9 acting on the suction and supply sides.

Since these blowers generally generate noise, dozens of unit blowers have been improved in recent years so as to be attached to the silenced blower chamber. In particular, this corresponds to the case of milling, and this is because milling generally uses a plurality of blowers for the feeding device. As indicated by the branch connection part 10, the air of a blower can be supplied to another air consumption apparatus.

The filter 1 has a large dust air chamber 11 and blocks the air chamber toward the outside by the filling valve 12. This filter 1 again has an inlet connection 13 for the air containing the dust to be cleaned and a filter hose 14 and 15 which are fixed by an upper cover. In practice, for example, only two filter hoses are used in special cases for filters installed in a cyclo. In contrast, in the engineering industry, filters with a number of hoses of about 20 to 100 are often used.

In the case of the filter hose 14, the tubular filter cloth 16 is covered over the support optical fiber 17, and the basket itself is composed of a plurality of vertical wires 18 and a spiral winding 19. The supporting light ribbon 17 is removed from the connection with the lid 27 of the dust chamber 11, as with the filter wrap 16 or only the filter wrap 16.

Each of the filter hoses 14 or 15 has an opening 21 that is open toward the top, and through which the filter hose 14 or 15 can freely flow the air purifying the filter cloth, as in the case of the filter 2. It is obvious. All the air flows into the exhaust chamber 22 via the free opening 21 and is formed by the lower casing 23 and the lid 24 filter 1 of the exhaust chamber and through the suction pipe 25. Alternatively, it can be connected to an intermediate suction, where the air can be guided back to the atmosphere or to the work process. Since the air purifying tank 26 can be installed at regular intervals in the upper part of the dust chamber 11, this exhaust can be sucked through the open opening 21 without being disturbed in the exhaust chamber 22. The air purification tank 26 is fully integrated with the exhaust chamber 22 in the case of the filter 1 and is supported on the lid 27 by the intermediate member 28. In the case of the filter 2, the air purification tank 26 is open at the top.

In FIG. 2, the air purification tank 26 is shown on the upper part of the free opening 21 like the nozzle 30 and the valve 31. As shown in FIG. The air purification tank 26 has a flat upper and lower sides, and this means that the plurality of nozzles 30 are guided through the air purification tank 26 and can be connected to the two corresponding tank planes with high tight sealing by upper and lower parts. So it becomes possible. As the filter has a large number of filter hoses, the air purification tank 26 becomes larger in size, and the support for both tank surfaces is also increased.

The valve 31 has the same structure as the design shown in West German Patent Application No. 1021560. So-called large area valves are important and these valves are suitable for the special needs of low pressure filter counter cleaning. The large area thin film 32 is pressed by the valve casing 33 to be airtight on the air purification tank 26 via the bolt 34. The thin film 32 of the illustrated design moves away from and toward the nozzle only by specifically forming an intermediate chamber corresponding to the thin film 32 and the sealing edge 35, the nozzle 30 and the valve casing 33. Can be brought into the open or closed position. Since the thin film 32 has a plurality of completely small holes 36, the air pressure acting in the air purification tank 26 is also adjusted on the upper side of the thin film 32.

The nozzle 30 may be pressurized when the thin film 32 is closed, or may be vacuumed depending on the pressure of the exhaust chamber 22 as appropriate. Therefore, the thin film acts as compressed air in the upper part with a larger area than in the lower part. On the other hand, the thin film 32 is pressed downward by the spring 37 so that the thin film 32 is closed in the normal driving and further closed by a relatively large force.

The space above the membrane 32 is controlled by an electrically actuated valve 31. When the solenoid valve 31 is opened, the compressed air is released on the thin film 32 through a larger area than a large number of holes, and the pressure suddenly drops to zero, correspondingly by the pressing pressure of the air purification tank acting underneath. This results in a shock release of the large passage cross section 38 on the free annular (annular) surface.

The compressed air is guided into the nozzle 30 through the large breaking portion 39 between the lid of the air purification tank 26 and the passage cross-sectional area 38 by the container piezoelectric body. The nozzle itself is constituted as a drive nozzle 41 having a relatively long cylindrical pipe member 40 and a lower end thereof having a drive opening 42. The compressed air of the induction nozzle rushing toward the center of the nozzle 30 through the large cross-sectional area of the large air purification tank 26 having a tapered end of the drive nozzle 41 is almost completely used in the area of the point 43. Compressed again to atmospheric pressure.

The cross-sectional areas 39, 38, and 42 are gradually reduced in the flow direction.

Since the best value is obtained when the guide nozzle 41 is at a certain distance above the free opening 21, the cross-sectional area of the free opening 21 used for the purified air is constant from the lower part to the upper part through the above point. . An important particularity lies in the structural design of the part that determines the air flow. Thus, for example, connecting the lower and upper bases by the nozzles 30 and configuring the passage cross-sectional area 39 in the shape of a plurality of single holes provided in a predetermined circle are considered inadequate in the early stages of air technology. have. Nevertheless, the experiments conducted at that time result in the opposite of finding a valid optimal solution that results in structural cost and configuration of the maximum pressure at point 43, and thus the maximum effect of the opposite cleaning of the filter hose. It turned out.

In FIG. 1, the filter hose 14 is a fresh hose which has not been operated yet. The filter 1 and the hose 15 of FIG. 5 have a thick dust layer highlighted in the figure after prolonged, dust air filtration.

In FIG. 6, the dust layer is scattered as the hose which deposited the dust expands. The hose 50 of the filter 2 shows the state approximately in the middle of counter cleaning when it moves from impact cleaning to late washing. I can shake the main volume dust off the forge. By post-cleaning, it is considered to take sufficient time to remove the dust floating around the filter again, instead of immediately pulling it on the filter, and to drop it downward. Therefore, the overall cleaning process is said to be forcibly making an intermediate break after the impact cleaning. In the case of the hose 51, counter washing is completely closed and dust cleaning is started again, but it is performed for the first time after this hose is inflated toward the inside.

In FIG. 1 and FIG. 2, the valve 31 is used as the solenoid valve 53, and this solenoid valve is connected to the control apparatus 55 via the electrical control wiring 54. As shown in FIG.

The controller 55 has a time switch 56, and the time interval for the cleaning process is selected by this switch. It is conceivable that each filter hose is sequentially counter-cleaned individually when a counter-cleaning is performed after a predetermined interval via a control wiring by a suitable electrical member, and when a small filter is instructed.

For example, whether or not to individually clean hoses capable of cleaning 30 and more hoses simultaneously or a plurality of lakes simultaneously depends on the entire suction device. Since the controller 55 is provided in duplicate, the filters 1 and 2 can be adjusted independently. Of particular importance is another adjustment device in this case, that is, a time-based cleaning length adjustment device 57. Moreover, the above-described structural specificity makes it possible to optimally solve an extremely large number of special cases for dust cleaning by using the simplest means, such as adjusting the spacing and duration of the counter cleaning coalescing.

Although the entire control method of the valve can be solved mechanically, it can be seen that it requires a high structural expense up to 8.9 of 10.

On the contrary, as with the electric control device, the fluid control device is known to be functionally good.

It is apparent that the present invention can be further improved in various details even under pressure monitoring such as cleaning air of dusty air.

Again, different values can be obtained for a given amount of cleaning air and cleaning air because the strength of the counter-cleaning can be controlled not only by its pressure, but also by the amount of air. For a given value, the optimal value is important, at least when studying dust problems.

Claims (1)

Low pressure with counter-cleaning device for purifying air containing dust carried out at a slight intensity but over a relatively long time, with counter-cleaning being the first compressed air shock and the post-cleaning shock immediately following the second. In the filter. The scavenging tank is installed in the low pressure filter above the low pressure filter and spaced apart from the dust air chamber, and the valve is connected to the air purifying tank, whereby the amount of air required for counter cleaning is adjustable at a predetermined time interval. Low pressure filter, characterized in that configured to be blown into the rim directly from the air purification tank.

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