DE2717329A1 - SYSTEM FOR THE REMOVAL OF PARTICLES FROM A GAS - Google Patents

Description

PATENT LAWYERS A. GRÜNECKER

Ot-KG

H. KINKELDEY

DRNQ

W. STOCKMAIR K. SCHUMANN

CKRBtNW-OFL-FHn

P. H. JAKOB

G. BEZOLD

DR FBtM

8 MUNICH

MAXUMJANSTRASSE

P 11504

April 19, 1977

Brunswick Corporation

One Brunswick Flaza, Skokie, 111.60076, USA

System for removing particles from a gas

The invention "relates to a filtration system, * that is to say a system for removing particles from a gas.

A serious hazard to the environment and health are the emissions of fine. Laws or law-related regulations are particles "or particles of large industrial plants are. As a result thereof been adopted to set the maximum emission of particles for each particular plant or factory. One way to meet these regulations, is one with particles

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TEIESRAMME MONAPAT

TELECOPER

Filter laden gas "before releasing it to the atmosphere is delivered. Large filtration systems are currently being grounded are used, which have several compartments or separate rooms containing filter elements. Both from technical as well as for economic reasons, these filter elements have to be repeatedly cleaned and used again will,

In general, all filtration systems are designed to that they remove particles emitted by cyclical processes. For example, can the gas temperature, the flow velocity, the particle size and the so-called "grain load" change. The "grain load" is the total mass of particles expressed in grains contained in one standard cubic foot of gas. So this is what it is the particle mass present per unit volume of gas. For any particular plant, the grain load in the contaminated gas based on previous experience. The filtration system will then designed to allow this type of particulate contaminated gas to be purified.

Because only with considerable capital or operating costs the fans for the gas can be replaced and the output for the operation of the fans can be increased, there must be a maximum pressure drop across the filtration system to be selected. Because the system continues to process a minimal volume of gas over a period of time the minimum flow rate through the system must be determined. The system must continue to do so designed to handle gas at a specified maximum temperature. Are these parameters known or selected, the system is engineered to purify a gas

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can to meet the requirements placed on the submitted To meet grain loading without exceeding the desired pressure drop or the maximum permissible flow rate can be achieved.

On the other hand, the aim is to keep such a system as small as possible in order to reduce costs do. The factors that affect size include:

1. The speed of the gas at the entry surface of the filter element, that is, the Superficial velocity of the gas;

2. the Schinutsaufnahmeacity of the filter element it at the maximum value of the pressure drop across the system that can be achieved due to the design; and

3. The "Effective Inlet Grain Load" as they are is defined below.

In order to explain what is meant by "effective inlet grain load", the re-entrainment or Reentrainment effect will be explained. In short is Reentrainment the fragmentation or splintering and redistribution in the gas of particle agglomerates, that have accumulated in the filter. When all particle agglomerates are fragmented into pieces of one size that is equal to that of the particles in the gas, the system never achieves the desired separation of the particles from the gas. With large filtration systems it is unavoidable that a certain part of the collected Particles are simply distributed back into the gas to be cleaned or are entrained there. So that is the "effective Inlet Grain Load "the actual inlet grain load plus the grain load due to particulate eeentrainment. The bigger the particle re-entrainment,

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the larger and the more expensive is the filtration system.

The gas temperature can also have an effect on the size of the Systems have. Very hot gases must be cooled by either diluting the gas with cold air or by diluting it cooled in an auxiliary device. In either case, the cost of the system increases. So if a filtration system can process gas at a high temperature, its cost can be reduced. FiI-tration systems, that can process hot gases offer additional advantages. So, for example In the case of coal gasification, fine particles are removed from the hot gas. So far it is not a satisfactory one technical solution for this high temperature separation occurring problems have been found.

In many industries, voluminous or large bag houses or bag filter devices are used on a large scale, to remove particles from escaping gases. In such bag filters, tubular, Bags made of cloth are used as filter media. Cloth bags are surface filters that consist of yarns that are tightly woven into a fabric; as an alternative, the surface filters also consist of fibers that are intertwined with each other, so that a dense, fleece-like or non-woven fabric results. Such fabrics have many small channels running through one surface of the fabric run to the opposite surface of the fabric. When a particulate-laden gas hits an exposed When it hits the surface of the cloth filter, the gas flows through these channels, while the exposed one The fabric surface is coated with particles at the beginning, which adhere to the yarn and tend to close the openings

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to clog the ducts. This initial coating then serves as the filter medium. If more filters collected, "a cake forms on the exposed surface of the fabric, and the pressure drop across the Fabric increases. The bag filters are cleaned periodically by breaking apart the surface cake will. For example, the bag filter can be subjected to mechanical or pneumatic vibration which creates a ripple effect or a certain waviness in the sack; this is what makes it solid Material shaken off the surface of the bag.

If the superficial velocity of the particle-laden gas is too high, the particles penetrate deeply into it the fabric and cannot be removed during cleaning. This leads to a failure of the filter, known as "blinding". The substances currently used cannot be used as cleanable filter media serve when the superficial velocity of the gas is greater than about 10.2 cm / sec. To big To be able to handle the volume of the gas laden with particles at high flow velocities must be considered As a result, the filter bags are relatively large so that they can filter the gas without causing an excessively high surface velocity is produced. In other words, a large area of fabric is used during filtering to avoid high surface speed, so that the bag filters are large and expensive. Often the bag filter has to be even bigger and still be more expensive if hot gases are filtered because most substances have temperatures of more than approx. / 260 C cannot withstand. As a result, the hot gas is often diluted with cooler air so that the total volume of the gas to be filtered increases. So if the desired surface speed is

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keep ν / he should, the filter area must be increased.

The overall size of the filtration system could be made public can be reduced if depth filters are used instead of the surface filters used in bag filters. Deep filters offer in comparison with surface filters. several advantages, because they also at high surface speeds · with comparable pressure drops can work and a greater dirt holding capacity than fabric filters to have. As a result, a system using depth filters would become smaller and therefore less expensive as a surface filter system designed for the same capacity is. One reason why depth filters have not previously been used in large filtration systems is in the fact that so far no practical way has been found to repeatedly clean such filters in situ.

In contrast to surface filters, depth filters usually contain thick, but relatively open or porous Fiber layers. In a typical depth filter, there are discrete, randomly oriented fibers with small filters processed into an open matrix or mat. Essentially all of the collected particles are stored in the Inside the mat and will not form a cake on the surface of the mat. If the particles are in the depth filter collect, the pressure drop across the file is for one certain amount of precipitation smaller than with a corresponding surface filter. The reason for that is the particles deposited in the depth filter form an open matrix with a comparatively low flow resistance offers. If the same amount of particles is to be collected by a surface filter, then so these particles would form a cake and offer high flow resistance. So that means that

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a larger volume of gas can be passed through a depth filter before the pressure drop occurs due to the design expected maximum value reached.

Of course, depth filters remove the particles from a gas stream through a mechanism other than surface filter. When the gas flows into the depth filter, so the particles collide with the fibers deep in the filter and adhere to the fibers. First a particle adheres on an uncoated paser, then a second particle adheres to the previously deposited particle, and so on, the particles forming chain-like structures when they collect in the filter. These chain-shaped particle structures are referred to as "dendrites". The dendrites extend far into the gas flow into it. As a result, the dendrites act as very effective particle collectors and continue to grow, when additional particles are deposited on them.

During filtration, a certain dendrite continues to grow as long as new particles are deposited on it, until one of the following two events occurs. Either the dendrite is detached from the fiber by tensile forces separated when the dendrite grows larger, or the dendrite grows outward until it connects with an adjacent fiber or a nearby dendrite growing on the same or an adjacent paser comes into contact with it recorded. In the first-mentioned case, the detached dendrite is likely to be attached again to one in the direction of the flow When viewed further back, fibers adhere. However, it is possible that a dendrite is coming out of the filter migrates, i.e. leaves the filter. In the last-mentioned pail an agglomeration or a lump grows from deposited particles gradually to a rather voluminous or bulky deposit. in the

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In the following, the term "agglomerate" will be used to include the dendrites and / or the voluminous deposits describe.

The invention relates to a system for filtering a high-speed, particle-laden gas using a depth filter element which can be repeatedly cleaned without the filter element tearing or being destroyed prematurely and / or without massive or severe re-entrainment of the collected particles occurs. This system can be operated at high temperatures (above 260 ^° C.) and in corrosive environments and is particularly suitable for small, compact filtration units.

In this system, fine particles, that is, particles with an average diameter of about 15 microns, become fine or less, removed from the gas by a depth filter, which fibers with a mean diameter of about Contains 10 microns or less. Depending on the environment, these fibers can be metallic or ceramic or organic material. According to a preferred embodiment, the fiber mass has a graduated packing density, so that the gas laden with the particles first flows through a fiber mass with a low density and then encounters masses of fibers with increasing densities. A typical depth filter contains two masses of fiber. The denser mass is twice as large as the less dense mass. There is also an intermediate layer provided of fibers that separates these masses and serves as a transition zone in which the density of the fiber masses gradually increasing. In a typical case, the low density mass has a density that is in the range is between 0.2 and 1 vol .- $, while the high density mass has a density ranging between

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2 and 5 vol.? ". A thin filter with a large surface, such as a board or a wall or a plate, is preferred. Such a "panel" is flat or just slightly convex.

According to an essential feature of the present invention exceeds the surface velocity of the particle-laden gas 15.2 cm / sec. The preferred one Surface speed ranges from about 50.8 cm / sec to about 76.2 cm / sec. A surface speed greater than about 127 cm / sec should generally be avoided because of the pressure drop on the filter element becomes too large and some particles are pressed through the filter element. Since with high When working at surface speed, the filtration system of the present invention is smaller and considerably less expensive than a conventional bag filter designed for the same capacity.

In this system, the depth element is repeated, cleaned as required. In practice, cleaning is initiated before the filter element gets that far has been loaded that across the filter element a pressure drop of 38.1 cm of water at a surface velocity of the gas laden with particles, which at a gas temperature of 260 C is equal to 50.8 cm / sec is. The cleaning is carried out by interrupting the flow of the particle-laden gas and the Depth filter element with simultaneous introduction of a reverse flow of cleaning gas is subjected to shrinkage. The agglomerates are formed by the vibrations separated from the fibers, while the reverse flow of the cleaning gas removes the detached agglomerates the filter is moved in a direction opposite to the direction of flow of the particle-laden Gas is. 709845/0837

The vibrations of the filter element can be caused by several Process can be achieved, for example, by mechanical, sonic or electromagnetic methods. A "special Appropriate technique is the entire piIterelement using a mechanical vibrator coupled to the element to vibrate. It one or more vibrators can be used. According to a preferred embodiment, impact vibrators are grounded used.

The vibrators can be attached directly to the filter element; alternatively, you can log into large distance from the element outside of the aggressive environment prevailing in the vicinity of the element. In the latter case, a rod or equivalent element can be used to support the To transmit vibrations to the filter element. Care must be taken that the vibrator is mounted in this way that the damping of the vibrations is minimal.

The duration of the oscillations depends on the thickness and density of the filter medium, the properties of the particles, the Surface velocity of the gas as well as other parameters. In most use cases, at metallic fibers the required duration of the vibrations 50 seconds or less, according to a preferred one Embodiment from 5 to 10 seconds.

The frequency of the vibrations can vary over a wide range and does not appear to be a critical variable to represent. The energy emitted by the vibrators should cover a wide frequency range so that the Formation of node zones in the element is as low as possible.

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The period of time in which the cleaning gas flows is longer than the duration of the oscillations. In detail should the flow of the cleaning gas according to a preferred embodiment shortly before the introduction of the vibrations begin and end shortly after the point in time at which the oscillations have ended. This reverse Gas flow flushes the detached and broken agglomerates out of the filter element when it vibrates. Most Agglomerates that leave the filter element are much heavier and larger than the incoming particles and fall under the action of gravity as they exit the filter element. Because of her Size and weight, these agglomerates are not too far from the filter element due to the reversed gas flow carried away. It is therefore an essential property of this system that most of it consists of the filter element distant agglomerates precipitate quickly.

In this system, the cleaning gas does not have the function of separating the particles from the fibers. As a result, its speed is relatively slow and usually less than or approximately equal to the speed of the particle-laden gas stream which hits the surface of the filter element. In this system, the purge gas velocity does not exceed 76.2 cm / sec, and is normally in the range of about 25 _f 4 to 50.8 cm / sec.

According to a further essential feature of the present invention, the excitation caused by the vibrations and the cleaning gas is applied to the filter, adjusted so that it is insufficient to the IV & sse of the detached agglomerates on the finely divided Reduce the condition of the particles to be removed from the gas. It cannot be avoided that

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some agglomerates will be fragmented into pieces with dimensions approximately equal to those of the particles fed. Nevertheless, the greater proportion of the mass of the detached agglomerates remains relatively large, that is to say the agglomerates have, for example, an average diameter which is greater than 15 microns, with the majority of the particles having an average diameter which is greater than 50 microns. As a result, most of the agglomerates removed are relatively heavy and therefore precipitate quickly. The maximum acceptable re-entrainment of the fine particles is approximately 50 °. In other words, in cleaning, no more than 50% by weight of the detached agglomerates will be fragmented into parts with dimensions equal to those of the particles in the gas to be cleaned, that is, 15 microns. Investigations have shown that depth filters with metallic fibers can be cleaned with a reentrainment of less than 30 °.

Another key feature is the relationship between the length of time the filter element is cleaned, and the length of time in which the filtration is carried out. In general, the filtration cycle is essential longer than the cleaning cycle. As a result, the size of the system is kept relatively small. In the In most cases, the filter element operates in a period of time that is at least an order of magnitude (10 times) greater than the length of time the filter element is cleaned. For example, a typical filter cleaning cycle is about 3 minutes of filtration \ md 12 seconds of reverse flow of cleaning gas Direction, during which time the filter element is exposed to strong vibrations for 8 seconds will. In investigations, a filter element was continuously alternated for 100,000 cycles or more

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subjected to filtration and purification without noticeable damage to the metallic fibers or the filter element occurred.

Because the filter element is repeatedly cleaned and high gas velocities are used, this can System can be much smaller than conventional bag filters of equivalent capacity. Based on these By reducing the size, this system can be installed at a lower cost than using a bag filter same capacity. In addition, because fibers can be used that are resistant to the influences from high temperatures and corrosion, such a system can be used to hot and / or To clean strongly corrosive gases that cannot be processed with conventional bag filters. In one typically, such a system has a capacity of 169.9 cm (6,000 cubic feet) per minute or more.

A preferred thought lies in a system that is solid, in one flowing at high speed Particles entrained in the gas stream are removed. The gas flows through a depth filter that catches the particles. The depth filter used has a fiber mass that is temperature and corrosion resistant. At least part of the fiber mass has a graduated packing density, so that the contaminated gas in its flow through this graded fiber mass meets fiber masses with increasing densities. The filter is cleaned by subjecting it to vibration while a cleaning gas is blown through the filter at the same time. The direction of flow of the cleaning gas is opposite to the direction of flow of the contaminated gas. The excitation that is exerted on the filter by the vibrations and the cleaning gas is

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laid that particle reentrainment is less than $ 50. The system is relatively small and less expensive than a conventional filtration system of equal capacity.

The invention is illustrated below with the aid of exemplary embodiments explained in more detail with reference to the accompanying schematic drawings.

Show it:

Fig. 1 is a representation of the Filtration system according to Invention;

FIG. 2 is a plan view of the filter element according to FIG Invention;

3 shows, on an enlarged scale, a fragmentary view of the filter element, with portions broken away, en are shown;

4 shows a section through the filter element before the screens or screens of the element with one another be attached;

Fig. 5 is a section through the filter element along the Line V-V of Figure 2;

6 shows a section through the filter element on a greatly enlarged scale, the transition zones between two different sections of the element are shown;

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Pig. 7 shows a graphic illustration to explain the transition zone;

8 shows a side view of one way of attaching the vibrators to the filter element;

Figure 9 ι- ¹¹¹ enlarged scale a section along the line IX-IX of Figure 8.

10 shows, on an enlarged scale, a cross-sectional view of one of those shown in FIGS. 1, 7, 8 and 11 Vibrators;

11 shows a plan view of a filter element with a second possibility, the vibrators on the filter element to fix;

12 shows a photomicrograph or a KL insert image or micrograph with 100-fold magnification of a mass of metallic fibers, used in the filter element, showing the collected fine particles, which form agglomerates adhering to the fibers; and

13 is a 100-fold photomicrograph Enlargement of the same mass of metallic fibers shown in FIG. 11, but with this Mass has been cleaned by the cleaning method according to the present invention.

Figure 1 shows the filter system 1O according to the invention, the two filter compartments or separate filter spaces 12 and 14 contains. Although only two separated in the system 1O Rooms are shown, it is usual for large units

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borrowed to use a lot of such filter liquids, "for example from 10 to 100 or more piIter rooms.

The two filter spaces 12 and 14 are identical, so that Identical components have been given the same reference numerals, but the components of the space 14 by a Are marked with a dash. Each filter space 12 and 14 is through a filter plate 16, 16 »in an inlet area 18, 18 "and an outlet area 20, 20" divided; each of these spaces contains an inlet 22, 22 ", two Outlets 24, 24 'and 26, 26' as well as a tapered one Bottom 28, 28 "which ends in a trough or container 30, 30" in which a screw 32, 32 "is used for removal the collected solids is arranged. The outlet areas 20, 20 »of each space 12 and 14 are closed Structures that are separate from each other. In contrast to this, the inlet areas 18, 18 »protrude through one another a line 38 in connection.

The filter plates 16, 16 'are at their edges on suitable Attachments 36 attached so that the plates 16, 16 »are arranged at an angle which is in the range between 45 and is 85 ° with respect to the horizontal. Since the plates 16, 16 'are inclined, larger particles and particle agglomerates fall generally down into the floor 28, 28 'of rooms 12 and 14, where they are fed by augers 32, 32' be removed from the rooms. Seals (not shown) are provided around the edges of the plates 16, 16 ', which are intended to prevent the gas laden with particles from bypassing the plates. This is the way that flows all gas from the inlet sections 18, 18 'through the plates 16, 16' into the outlet sections 20, 20 '.

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In the filter system 1O, a filter plate 16 is used, as shown in detail in FIGS. This plate 16 contains a rectangular Frame 62 (see Figure 2) with an appropriate size, for example 0.76 m 0.9H4 m χ 1.27 cm (2_1 / 2ft χ 3ft x 1/2 inch) or 0.9H4m χ 1.524m χ 1.27cm (3ft χ 5ft χ 1/2 inch). The frame 62 holds two sections 64 and 66 of metal fiber mats in place. As shown in Figure 5, these sections 64 and 66 formed by sieves 68,

69 and 70 have been placed one on top of the other, with the filter medium 72 (metallic fibers) being located between adjacent screens. Sections 64 and 66 are approximately 3.18 mm (1/8 inch) thick, but have different packing densities, with section 6G having a substantially higher density than section 64.

The edges of screens 68-70 are fitted into frame 62, folded over the screens and secured by links or fasteners 74, such as bolts and Pop rivets is attached. At intervals of Additional fasteners 76 extending through washers are provided approximately each 10.16 cm (4 inches) or washers 78 (see FIG. 5). These connecting elements 76 connect the screens 68 to

70 with each other and also ensure an almost uniform thickness of the two sections 64 and 66 of the filter plate

As can be seen in particular in FIG. 1, the filter plate 16 can have a bulge 80 in the vicinity of its center with the maximum height of the bulge approximately 2.5 cm (1 inch) above the level of the lower side 62a of the Frame 62 is. During the filter operation, the gas flow loaded with the particles hits the underside the plate 16, so that the plate is in the flow direction of the gas flow, which is indicated by the arrows a

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want to weigh. Since the plate, however, with a curvature is provided, this deflection of the plate 16 does not lead to serious channeling or corrugation of the gases. That means the following: An expansion or enlargement of the thickness of the two sections takes place due to the bending approximately uniformly so as to avoid open or low density areas that could channel of the gas flow were made possible.

The filter medium 72 forming the sections 64 and 66 has statistically, that is to say randomly oriented, strong, metallic fibers. These fibers have a length ranging from 1.2γ to 5.1 cm and a diameter ranging from 2 to 8 microns. Nickel-chromium fibers are preferred because they have a high resistance to corrosion and can withstand high temperatures. The density of section 64 is 1/2 fo _f while the density of section 66 is 2.5 ^. This construction allows AC fine particles to be filtered as indicated by the following table.

Particle size (microns) weight-7

0-5 39 5-10 18th 10-20 16 20 - 40 18th 40-80 9

W} .e shown in Figure 1, the plate 16 is so in the filter chamber 12 arranged that when filtering the gas flow first through the section 64 with lower Density must flow. When the filter media 72 removes the particles catches, agglomerates are in the section 64 with

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low packing density. This particle build-up do not form a continuous cake, so the gas flow can continue to flow into the high density section 66 without excessive pressure drops. the small particles that are not trapped in the low density section 64 will normally be trapped in the high density portion 66.

FIG. 4 shows the two sections 64 and 66 on an enlarged scale. It can be seen that the higher density portion 66 has a density which is substantially greater than the density of the lower density portion 64; the sieves 68 and 70 serve to compress the fiber mats. This different density required for a higher dust holding capacity can vary depending on the type of particles that are caught in the filter medium 7 ^ and on other conditions of the system 10. Normally, however, the higher density portion 66 should have a density at least two times the density of the lower density portion 64; the two sections should be connected to each other by a transition layer with a density increasing from the lower value to the higher value.

FIG. 6 shows such a transition layer 67 made of fibers, which is formed where the two sections 64 and 66 meet. The density of this layer 67 increases from left to right as shown in FIG. The two sections 64 and 66 are therefore only apparently separated by a sharp, clear boundary formed by the sieve 69; in practice this is not the case. Instead, the density of layer 67 gradually increases from left to right . When the particle-laden gas passes through section 64 and into the

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Section 66 flows, it must as a consequence of this first the Transition layer 67 pass, taking it on gradually denser masses of fibers meets. This increases the dust holding capacity, and it becomes the training of a compacted, i.e. compressed, particle cake avoided deep in the filter element.

The layer 67 has several intermediate layers or fillings 67a »these are fibers that are between the wires of the screen 69 protrude. These fills 67a have a density value that is between the density values for sections 64 and 66 lies. The density of the fillings 67a is smallest near the center of the fill and greatest on the bands of filling near the wires of screen 69. Between the pairs of links 76, the flexible screen 69 bends slightly. As a result, the fillings 67a have the closest lie at the midpoint between the connections 76, a slightly lower density than the fillings in the Find the connections 76.

FIG. 7 shows a graphical representation, the abscissa being the distance between the dirty side of the Plate 16 and the clean side of the plate is applied, while the ordinate shows the density of the fiber mass is applied at points between the dirty or clean side of the plate 16. Set the curves A and B. represents the density of the fibers encountered by a particle-laden gas while it is along two different ones Paths that are labeled A and B in FIG. 6 flows. First of all, curve A will be discussed. When the gas passes through the plate 16 along the through the Line A is flowing, it first encounters a fiber mass with a relatively low density until it reaches the Transition layer 67 reached. Since the path A through a

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In the region of the transition layer where the transition layer has its smallest thickness and its density is almost equal to the density of the section 66 , the gas experiences a relatively abrupt change in the paser density as it passes between the sections 64 and 66. The curve A therefore has a relatively steep slope a. If in contrast hierzx '. as the gas follows the path B, it encounters masses of fibers of gradually increasing density as it moves through the transition layer 67. The curve B therefore has a relatively small or gradual slope b.

Due to its structure, the filter plate 16 can be operated at temperatures of more than 260 ^° C.? in addition, their construction and structure are not affected by vibrations and high-speed gas flows. The screens 68 to 70 represent an essential feature of the plate 16. These screens 68 to 70 fulfill a double function. First of all, they transmit vibrations over the entire fiber mass. In addition, they keep the mass intact and maintain their graduated density even with vibrations and gas flows at high speed. Since the screens are formed from interwoven wires, gripping sections 68a, 69a and 70a (see FIG. 6) arise at the points of intersection between these wires. These gripper sections 68a, 69a and 70a serve to hold the fiber race in place.

The attachment of the vibrators will be explained below. An example of a suitable vibrator arrangement is shown in FIGS. 8 and 9. As can be seen from these figures, there are two impact vibrators 82 and 84 of different sizes (see Figure 8) by a carrier 85 on impact plates 86a and 86b attached by fasteners 88 with the center of the filter plate 16 are connected. These

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Vibrators 82 and 84 are at right angles to each other and arranged offset relative to one another. Suitable vibrators 82 and 8'4 v / ground from the Branford vibrator Company, New Britain, Conn. Details of the larger vibrator 82 (2.5 cm diameter) are in Figure 10 shown. The small vibrator 84 (diameter 15.8 mm) has essentially the same structure; the The difference is that its piston part has a smaller cross-sectional area.

As shown in FIG. 10, the vibrator 84 includes a hexagonal block 90 with a central bore 92 along its longitudinal axis. Through the side walls the bore has a threaded inlet opening 94 extending therefrom which receives an air conduit, and a pair of air outlet ports 96 and 98. At the ends of the bore 92 are threaded portions IOO and 1o2 provided, each adjustable Pick up plugs or closures 104 and 106. Every closure 104 and I06 has a threaded one End that is screwed into the threaded receiving sections IOO and 1o2. Compared to with Threaded ends of each closure are flanged or flanged attachment ends I08 and 110 respectively. The ends I08 and 1 TO each have hexagonal nuts or nut connecting pieces 112 and II4 formed integrally therewith.

A piston member 116 extends the length of the bore 92. This piston member 116 includes two spaced apart enlarged pistons 118 and 120 which fit tightly, that is, non-slipping, against the side wall of the bore 92, and a pair of piston heads 122 and 12 / [ _f, which are each formed in one piece with the piston 118 and 12o, as well as a designed

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saved circular ring 126 in the middle area of the piston element. The piston heads 122 and 124 have diameters which are substantially smaller than the diameter of the cylindrical ones Items 118 and 120 are. The volume that is passed through the piston head 118, the side wall of the bore 92 and the Shutter I04 is defined, forms a left pressure chamber 128. In a similar way, the volume created by the other piston head 124 forms the side wall of the Hole and the other, closure I06 is defined, a right pressure chamber 130. Two air ducts 132 and 134 are provided along the side wall of the bore, which connect the pressure chambers 128 and 130 to one another.

The piston element 116 is normally biased towards the closure 104 by a spring 136, which is looped around the piston head 1-4. As a result, the piston element 116 is initially positioned so that one air opening 98 is open and the other air opening 96 is closed. When compressed air or compressed air emerges from the line 94, it flows through the left and right air ducts 132 and 134, ¹ with the chambers 128 and 130 alternating! be filled. Since opening 96 is closed and opening 98 is open at the beginning, a pressure builds up in the left pressure chamber 128, so that the piston element 116 is forced to move to the right as shown in FIG is depressed. As a result, the left air port 96 is opened and the right air port 98 is closed, reducing the pressure in the left chamber 128 and increasing the pressure in the right chamber 130. As a result, the direction of movement of the piston element 116 is reversed. This cycle repeats itself continuously as long as compressed air flows into the pressure chambers 128 and 130.

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As can be seen in particular in FIGS. 8 and 9, the vibrators 82 and 84 are connected to the supports 85 with L-shaped elements 140 and 142. The base 142a of element H ² , which is substantially longer than the other element 140, is attached to striking plates 86a and 86b by bolts H4. The upwardly extending leg 142a of this element 142 is welded to the base 140a of the other element 140. A hole is through the leg 142abzw. the base 140a is drilled in members 142 and 140, respectively, and the wear or plug 146 of the larger vibrator 82 is attached to the bracket 85 by a bolt 148 which passes through the hole.

Essentially because of the different sizes of the vibrators, the vibrators vibrate at very different rates Frequencies. For example, the piston element (not shown) also vibrates in the large vibrator 82 a speed of 180 cycles per second, while the piston element 116 in the other vibrator 84 with a Swings at a speed of 130 cycles per second. These Arrangement of vibrators 82 and 84 causes simultaneous lateral, longitudinal and torsional displacement of the filter plate 16 when the pistons perform their oscillatory motion. The following results in detail How it works: When the piston elements of the two Vibrators 82 and 84 strike against their adjustable latches, the latches, the carrier 85, the Impact plates 86a and 86b, the sieves 68 to 70, the Pahinen 62 and the individual fibers of the filter medium 72 asynchronously or out of phase with each other so that a sequence of waves of different frequencies is generated.

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An alternative vibration system is shown in FIG. Two one-inch Branford vibrators 84a, as shown in FIG. 10, are attached to carriers 1 ^ 1, that along the longitudinal axis of the plate 16a approximately midway between the center of the plate and the edges of the plate are arranged. Each carrier I5I is attached to a striking plate 153 which is attached to the Plate 16a is attached. The vibrators are generally parallel to the plane of the plate 16a and are driven to operate at different frequencies swing.

Since the vibrators are piston vibrators, strike them with great weight like someone hitting an anvil Hammer on the plate, creating a wave that propagates through the plate. This wave generates inertial forces that exceed the adhesive forces, which hold the agglomerates in the pulp; however, these forces are not so strong that they Break fibers or damage the filter plate 16. Since the system shown in Figure 1 contains two vibrators, which are mounted at right angles relative to one another, the filter plate also moves relative to the plane the filter plates inwards and outwards. It was observed that there are some hot spots in the plate form; due to the careful arrangement of the vibrators and the asynchronous generation of vibration by the vibrators However, the formation of such hot spots can be minimized.

When examining the vibratory movements of the filter plate 16, the acceleration was measured. Of course there is no known way of measuring the actual acceleration of the fiber agglomerate units. However, acceleration measurements were carried out

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which are correlated with your acceleration measurement would have to. These measured values for the acceleration are hereinafter referred to as "apparent acceleration" designated. The acceleration measurements were carried out in connection with the filter plate shown in FIG. The measurements were made on the fasteners the plate made because of these convenient attachment points for the measuring device and a stable reference grid for comparisons between the plates. In the cases mentioned, only the acceleration was in measured along the axis perpendicular to the plate surface. The measuring device consisted of a piezoelectric Accelerometer and a readable tip voltmeter or an oscilloscope. The one used Accelerometer was made by pcb Piezotronics, Buffalo, N.Y. manufactured. It generates an output voltage that is proportional to the amount of acceleration it experiences. The readout device measures this voltage, The voltage values are converted into acceleration values by means of a calibration curve supplied with the accelerometer. To carry out the measurement was the accelerometer on one of the fasteners attached, the vibration source actuated, and the voltage signal from the accelerometer was read on the voltmeter or oscilloscope. When the data was processed, the read voltage values converted into acceleration values. Although this procedure allows an appropriate determination of the acceleration values, care should be taken it should be noted that the measurements at mass concentration points (Fastener plus accelerometer). So one should expect that the measured acceleration values are smaller than the values actually in the areas of Plate occur between the fastenings.

709845/0837

It has been observed that the majority of the metallic fibers have what appears to be a minimal acceleration of about 10 g (g is the acceleration due to gravity) with the minimum input energy. In general it was maximum apparent acceleration of the fibers 250 g. While this is convenient, it was not essential that all fibers have an apparent acceleration in the range of 10 to 250 g. Had some fibers an apparent acceleration with values that are substantial were larger than 250 g; others had values of less than 10 g. By far the majority of the fibers, however, had an apparent acceleration in the area from 10 to 250 g.

The functionality of the system is explained below will.

As can be seen again from Figure 1, each filter chamber 12 and Η can be operated in two different ways, namely in the filter operation and in the cleaning operation. In filter operation, the particles are removed from the gas flow; During the cleaning operation, the filter plates 16, 16 are cleaned around those caught in the plates To remove agglomerates. Each filter room 12 and Η constantly changes between filter operation and cleaning operation, one room works in filter mode, while the other room works in cleaning mode.

In the following it should be assumed that the room 12 operates in filter mode. In this operating mode the particle-laden gas stream, which leaves a coal-burning power station, for example, flows through the main line 38, a branch line 40 and an open valve 42 into the inlet 22. The gas flow normally contains at least 2.3 to 45.8 grams / standard cubic meter of solid particles, with the majority of

709845/0837.

Particle has an average diameter of less than 25 microns. If metallic fibers are used, the temperature may, of the gas stream in continuous operation in the range of ambient temperature, up to 427 ⁰ C and for intermittent operation of up to 593 ⁰ C.

A fan 44 induces or generates a flow of gas that carries the particulate-laden gas into the inlet area 18 of the filter chamber 12, through the filter plate 16 in the From laßbereich 2o and from there out of the outlet 24 out line 46 and a normally open valve 43 sucks. A considerable part of the larger particles fall out of the particle-laden gas directly under the influence of gravity down to the container 3o, since the gas velocity on entry into the inlet region 18 is greatly reduced. The flow rate of the gas is controlled so that the velocity of the gas approaching the filter plate is in the range is between about 30.5 to 66 cm / sec. If room 12 is working in filter mode, room I4 is in cleaning mode, with a valve 50 at the inlet 22 'and a valve 43 in the line 24a closed and one valve 52 · are open in line 58a. The reason for that results from the explanation of the cleaning company.

When the gas laden with the particles flows through the mass of metallic fibers, the particles themselves adhere directly on the fibers or on other previously deposited particles. Agglomerates gradually grow in the Metallic fiber matrix. Figure 12 shows in a ί

Microscope image of the fibers loaded with collected agglomerate-forming particles. Here was AC fine dust in gas with an obvious resp. Surface velocity of 50.8 cm / sec carried away. The microscope picture was taken when the pressure dropped at the filter was 13 cm of water column. While

709845/0837.

During cleaning, these agglomerates have to be separated or detached and removed from the matrix of metal fibers. FIG. 13 shows a microscopic image of the status of pasers after they have been cleaned. A small number of particles remain even after cleaning still adhere to the fibers. This is even useful because it improves the filtration efficiency. To After cleaning, the pressure drop across the filter is 2.8 cm water column. The two microscope images were taken with the same magnification (100 x). Because of the The agglomerates can be removed after cleaning look far into the filter.

To the functioning of the room 12 from the filter operation on the cleaning company and room H from the cleaning company To switch to filter operation, the open valves 42, 43 and 52 'are closed while the closed ones Valves 43 ', 50 and 52 are opened. If so the valves are in their respective positions, a second fan 56 is switched on to To draw in air from the atmosphere through line 53 and blow it into outlet 24. With this movement flows the air in the Auslaßbereica 2o of the space 12 through which Plate 16 into inlet area 18 and then out through outlet 26. Any, through re-training in the cleaning gas Entrained particles are mixed with the particle-laden gas which now flows into the ravun 14.

With the new cleaning method, the plate is now set in vibration by the vibrators 82 and 84, if the reverse air flow passes through the filter plate 16. Screens 68, 69 and 70 and connections 76 transmit the vibrations on the entire plate 16. These vibrations ground the agglomerates from the fibers replaced. Because of the pressure difference between the inlet

709845/0837

areas 18, 18 * of the rooms 12 and 14, the gas does not flow from the Ravun 14 into the room 16 if the room 14 rubbed in the filter and the room 12 is in the cleaning mode and vice versa. The speed of the reverse air flow impinging on the filter plate 16 is normally in the range between 25 _f 4 cm / sec and 50.8 cm / sec. The agglomerates are flushed out of the plate 16 by the cleaning air, large and heavy agglomerates falling onto the floor 28 of the space 12 into the container 30 before they are carried out of the outlet 26 by the cleaning air flow. The auger 32 then removes these collected agglomerates from the chamber 12.

It has been observed that the high velocities generated in spaces 12 and H during filtration create turbulent flows which exert high forces and thereby blow the dust collected in container 30 back into spaces 12 and H. In order to avoid this problem, the containers 30, 30 ^{f are} covered with baffle walls 81, 81 »during the filtration operation. The baffle walls 81, 81 'are opened during the cleaning operation (by a device not shown), as shown for the room H during the cleaning operation, and are closed during the filtration operation, as is indicated for the room 12 during the filtration operation.

With the arrangement of the vibrators shown, the plates 16 and 16a can be used for about 4 minutes during filter operation when the particle _{load of} the gas flow is 22 t gg / m and the surface velocity of the particle-laden gas is about 50.8 cm / sec. Under these conditions the pressure build-up increases to approximately 17.8 cm. Water column in 4 minutes. The panels will then be approximately 8 seconds long

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cleaned and then work again for about 4 minutes in piIter mode. This alternating filtering and cleaning can be repeated practically indefinitely until the filter plates are finally completely worn out. The life of the plate, the cleaning cycle and the filter cycle can vary depending on the size the plates, the density of the filter medium, the type of particles, the particle size distribution in the gas stream, the grain load in the gas flow, the temperature conditions, the existence or absence of corrosive materials in the gas stream and other variables. In the cleaning process discussed here, however, the pressure drop across the plate eventually reaches after each Cleaning cycle has a constant value and the period between cleaning cycles remains essentially the same constant. This means that a high level of stability for the filter element and the filtration system can be achieved can.

In any particular system, each individual chamber will be switched between filter operation and cleaning operation in progressive order. For example, if a system contains 10 rooms labeled A to J, then room A operates for a certain period of time in cleaning mode, while rooms B to J operate in filter mode. At the end of the cleaning cycle for room A, this room is switched to filter operation. Room B can then be switched to cleaning mode immediately at the end of the cleaning cycle of room A, or a period of time (T) can elapse before room B is switched to cleaning mode. The longer the time interval (T), the better it is; this depends on the grain load and the dust holding capacity of the filter element.

709845/0837

In the following a system with 10 rooms is to be considered, which is designed to handle 708 m / min of gas at a grain load of 22.9 g / m; have along all filter elements have a maximum dust absorption capacity

2
of 2153 g per m surface on the dirty side per cycle at the maximum allowable pressure drop. Assume that each space has 4 filter elements

2
with a surface of 0.557 πι per filter and that 12 seconds are required to clean each filter element. Then the cycle time (CT) for a system with 10 chambers going through a full filter Z-cleaning cycle and the time interval (T) between cleaning cycles of each chamber can be calculated based on the following equations:

/ Filter capacity \ / filter unit- ^ / number of] / number of \ I capacity) X upper- JX I filter] XI spaces in the \ V lbs / ft cycle / V area / ^l "'» ™ - · ---- ----- '

C.T. = -

\ _per room / I put inherited / \ '\ operated /

/ Flow rate
J speed / inditude]

( ^0001428

Grains

C.T. = Minutes / cycle

C.T. -

/ number of \ I seconds J I to filter /. \ cleaning /

I number of rooms |

I in FiIterbe- /

X \ drove J

[Total number of rooms

For the system defined above, the following applies:

70984 5/08 3

-33-

27-329

(ο, 44) χ (β) χ (4) χ (9)

CT = = 2.66 minutes /

(25,000) X (1O) X (.000H28) cycle

² · ⁶⁶ - [-Bot ^x 9]

T. = = 0.086 minutes

10

2 A dust absorption capacity of 215 3 g / m per cycle "at the selected maximum filter pressure difference is typical of the depth filter that is used in such System is used. In contrast, if a cloth filter with a typical dust holding capacity of

215 g / m 2 is used per cycle, the cycle time (T) for the explained system with 10 spaces would be 0.267 minutes per cycle and the time interval - 9.2 seconds. This means that the inlet grain load is too high or the piIterflache is insufficient. As a result, the filter system could not operate stably, the pressure drop across the system would exceed the design limit, the flow rate through the system would decrease ¹ UId below the design limit, and eventually the system would totally collapse. This could be avoided by increasing the number of rooms in the system so that the velocity of the gas impinging on the surface of the cloth filter is reduced to a value which does not exceed 10.2 cm / sec. However, this greatly increases the cost of the system.

709845/0837

In the middle of page 18 and in the fourth from the last line "AC fine particles" are mentioned on page 28 of the description, ie AC fine particles or AC fine dust. at AC fine dust is a standardized test dust that is used in the American industry for filtration tests is used. This dust is distributed through the AC Spark Plug Division of General Motors Corporation and is sold and offered both as "AC fine" and "AC coarse" dust, i.e. as fine or coarse dust. This dust is an "air cleaner test dust", which is made from natural Dust supplied by General Motors Phoenix Laboratories and sorted by size is made up of AC Spark Plug Division of General Motors Corporation, Flint, Michigan.

The AC fine dust has the following particle distribution;

Particle size percentage amount

0-5 microns 39 % + 2%

5-10 microns 18 WJJ.

10-20 microns 16 I ± 3t

20 - 40 microns 18 % + _ 3%

40 - 80 microns 9 1 + 3%

70984 5/0837

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Claims (1)

Pat ent claims 1. PiItration system for removing particles from a gas, characterized by a space (12, I4), which has a depth filter (16, 16 ·) with a Fiber assembly (72) contains, by a device for Movement of the particle-laden gas through the Space (12, 14) that the surface speed of the with Particles laden gas exceeds 15.2 cm / sec, wherein the particles collect on the fiber surfaces and between the fibers to form particle agglomerates in the fiber element (72) to form, further by means of the element (72) for loosening the agglomerates of the Fibers vibrate and a cleaning gas is sent through the space (12, I4) in a direction that is opposite to the direction of flow of the gas laden with particles, further through a device for Switchover of the room (12, I4) between the filtration mode, in which the gas laden with particles passes through the Filter element flows and removes the particles from it be, and the cleaning operation in which the flow 709845/0837 TtILtPON {O TELEnflAMMG WIONAPAT ORIGINAL INSPECTED of the gas loaded with bar particles can be interrupted by a chamber and the filter element (72) cleaned by actuating the vibrating and loading device, whereby the agglomerates are detached from the fibers and the cleaning gas from the filter element (72) flushes away the detached agglomerates which when leaving the filter element (72) sediment quickly and _{collect on the floor of the room (12 f} H) and through a device (3 ² , 32 ·) for removing the accumulated agglomerates from the floor of the room (12, H). 2. Filtration system according to claim 1, characterized in that at least part of the mass of fibers is one has an average diameter of 10 microns or less. 3. Filtration system according to one of claims 1 or 2, characterized in that the filter element (72) has a Has device which keeps the fiber mass intact at high gas velocities and in addition serves to transmit the vibrations over the entire mass. 4. Filtration system according to one of claims 1 to 3, characterized in that the surface speed the particle-laden gas between 15.2 cm / sec and I27 cm / sec. 5. A filtration system according to any one of claims 1 to 4, characterized in that the temperature of the particle-laden gas exceeds 260 ⁰ C. 6. Filtration system according to one of claims 1 to 5, characterized in that the barticle reerrfcrainment does not exceed $ 50. 709345/0837 7. Filtration system according to one of claims 1 to 6, characterized in that the filter element (72) is cleaned before it is loaded so / eit that a pressure drop of 38.1 cm water column at a surface velocity of the particle laden on the filter element Gas of 50.8 cm / sec at a gas temperature of 260 ⁰ C exists. 8. Filtration system according to one of claims 1 to 7, characterized in that the surface velocity of the cleaning gas does not exceed 76.2 cm / sec. 9. Filtration system according to claim 8, characterized in that the surface velocity of the cleaning gas in the range between 25.4 cm / sec and 50.8 cm / sec lies. 10. Filtration system according to one of claims 1 to 9, characterized in that the fibers are made of metallic material. 11. Filtration system according to one of claims 1 to 9, characterized in that the fibers are made of ceramic jfeterial. 12. Filtration system according to one of claims 1 to 9, characterized in that the fibers are made of organic Bfeterial are manufactured, 13. Filtration system according to one of claims 1 to 12, characterized in that the time span in which the filter element (72) operates in the filter mode is at least is an order of magnitude greater than the period of time in which the filter element (72) is cleaned. 709 8 4 5/0837 H. Pil entered ions system according to one of claims 1 "to 13, characterized in that the density of the fiber mass is graded so that the particle-laden and to filtering gas first in a fiber terrace with lower Density flows and then meets fiber masses with increasing densities. 15. Filtration system according to one of claims 1 to I4, characterized by first and second fiber masses having different densities, the second fiber mass has a density which exceeds the density of the first mass of fibers by at least two times, and furthermore the two masses are separated by an intermediate layer of fibers which forms a transition zone (67), and wherein the density of the fibers in the transition zone (67) increases from the first mass to the second mass. 16. Filtration system according to claim I5, characterized in that that the density of the first fiber mass in the range between 0.2 and 1 $ and the density of the second fiber mass ranges between $ 2 and $ 5. 17. Filtration system according to one of claims 1 to 16, characterized in that a shock vibrator (82, 84) is used to vibrate the filter element (72) to move. 18. system for removing particles from a gas, wherein the particles have a mean diameter of 15 Microns or less are characterized by a device for filtering the gas by passing it through a depth filter element (72), with particles charged gas has a surface velocity greater than 15.2 cm / sec, and by a device that periodically interrupts the flow of the gas charged with particles 709845/0837 the filter element (72) cleans by removing the filter element (72) is exposed to vibrations while at the same time a cleaning gas through the filter element (72) into a Is pressed in the opposite direction to the flow direction of the particle-laden gas, the cleaning gas having a superficial velocity not exceeding 76.2 cm / sec. 19. System according to claim 18, characterized in that the surface velocity of the gas loaded with particles is in the range between 15.2 cm / sec and I27 cm / sec. 20. System according to claim I9, characterized in that the surface velocity of the cleaning gas is in the range between 25.4 cm / sec and 50.8 cm / sec. 21. System according to one of claims 18 to 20, characterized in that the particle reentrainment does not exceed 50 i °, 22. System for cleaning a depth filter element with Fibers that have a mean diameter of 10 microns or less, characterized by a device which subjects the depth filter element (72) to vibrations, to detach the adhering fiber agglomerates while at the same time a cleaning gas with a surface speed not exceeding 76.2 cm / sec the depth filter (72) is printed. 23. System according to claim 22, characterized in that that the surface velocity of the cleaning gas is in the range of 25.4 cm / sec to 50.8 cm / sec. 709845/0837 27-329 24. System according to one of claims 22 or 23 _f, characterized in that the fibers are made from a metallic Ifeterial. 25. System according to one of claims 22 or 23, characterized characterized in that the Pasern is made of a ceramic Material are made. 26. System according to one of claims 22 or 23, characterized in that the Pasern consists of an organic IY & terial are made. 709845/0837