WO2018149544A1

WO2018149544A1 - Method for filtration of gases loaded with particles, and filter device for carrying out such a method

Info

Publication number: WO2018149544A1
Application number: PCT/EP2018/000032
Authority: WO
Inventors: Viktor Josef Lauer; Jörg Michael Wendels; Daniel Kleemann; Edwin Koch; Jan Weber; Christophe Hainka
Original assignee: Hydac Fluidcarecenter Gmbh
Priority date: 2017-02-14
Filing date: 2018-01-24
Publication date: 2018-08-23
Also published as: DE102017001372A1

Abstract

A method for filtration of fumes produced in the context of selective production methods in a production chamber (2), such as welding fumes of 3D printers, having the following steps: guiding the fumes from the production chamber (2) to the raw gas inlet (18) of a filter housing (20) which accommodates at least one filter element (54; 80), the filter material (56) of which separates, during a filtration procedure, the raw gas inlet (18) from a clean gas outlet (50); establishing a flow through the filter material (56) and discharging the gas via the clean gas outlet (50) and regenerating the filter element (54; 80) by moving the filter element in order to dislodge particles accumulated on the incident flow side of the filter material (56).

Description

Process for the filtration of particulate-laden gases and filter device for carrying out such a process

The invention relates to a method for the filtration of particulate-laden gases, in particular resulting from selective manufacturing processes in a production room flue gases, such as welding smoke of SD printers. Furthermore, the invention relates to a filter device for carrying out such a method.

The filtration of particulate-laden gases requires considerable technical and economic effort when there is a high particulate load, as is very often the case with flue gases. Large amounts of particles deposited on the filter material of the filter element used cause a rapid blocking, so that no sufficiently long filter service life can be achieved. Increased occur such problems with flue gases, such as the resulting in 3 D printers for metal welding fume. In the selective laser sintering, as it is known as SLS method (DE 10 2015 01 7 026), powdered, chemically pure metal particles are applied in layers and then fused with a high-power laser under a protective gas atmosphere. The welding fumes produced in such processes, which operate in the manner of powder pressure, are conducted out of the building space containing a protective gas atmosphere to the filter device and consist of protective gas with heavy exposure to powder particles. The rapid access occurring here Setting the filter material forces frequent filter changes, which complicates the economic operation related printers.

A well-known in the filtration of fluids of a general nature procedure for extending filter life is the regeneration of the filter materials involved. In the filtration of welding fumes, as is the case in selective production methods using protective gas, the regeneration is usually carried out in such a way that particles deposited on the upstream side of the filter material of respective filter elements located in the filter housing pass through recirculated, filtered gas Blowing off to be detached. In the filter housing for this purpose a blower-generating blower for the supply of several nozzles is required. Because of the consequent device-side effort and the high gas consumption, which can be up to 8l / m ² filter surface per backwash, also high operating costs.

In view of this problem, the invention has the object to provide a method which allows the filtration of flue gases, as they arise in selective, working with inert gas manufacturing process, in a particularly economical manner.

According to the invention, this object is achieved by a method having the steps specified in claim 1. As indicated, the invention provides a regeneration for the filter element through which the flue gas flows in the filter housing in such a way that the filter element is moved to detach particles deposited on the inflow side of the filter material. In contrast to the usual regeneration, in the method according to the invention, no clean gas is returned to the filter housing in order to detach particles as purge gas in the return flow through the filter material by emitting deposited particles by blowing the filter material through clean gas. When moving by moving the filter element In contrast, separation does not result in a loss of purge gas, so that the method according to the invention can also be used economically and cost-effectively for the filtration of welding fumes in 3D printers, where comparatively expensive shielding gases, such as argon, are used.

In a particularly advantageous manner, the movement can be carried out by compressing a collapsible filter element. In order to effect a particularly effective shaking off during this movement, the compression and return of the filter element to the original shape can be carried out intermittently.

With filter elements having a filter material surrounding a filtrate side forming inner filter cavity, which is connected to the clean gas outlet of the filter housing, the method can be carried out with particular advantage so that the clean gas outlet of the filter housing kept closed from the beginning to the end of the compression of the filter element becomes. As a result, when compressed in the inner filter cavity, a pressure surge arises from the inside to the outside, which acts on the particles in addition to the acceleration forces generated by the movement to detach the particles from the particles.

Advantageously, the method according to the invention can also be carried out in such a way that the filter element is rotated during the movement. The centrifugal force generated during the rotation causes an effective separation of the deposited particles.

Advantageously, the filter element is separated from the clean gas outlet of the filter housing prior to rotation, so that the filter element is freely rotatable and the housing connection of the filter element does not have to be formed by a rotary bearing. According to claim 7, the subject of the invention is also a filter device for the filtration of particulate-laden gases, such as flue gases, which arise in selective production processes, in particular in SD printers, in a production space. As indicated in claim 7, the filter device according to the invention comprises a filter housing having a raw gas inlet and a clean gas outlet and accommodating at least one filter element, the filter material of which separates the raw gas inlet from the clean gas outlet during filtration, a drive being provided by which Filter element is a detachment of deposited on the upstream side of the filter material particles causing movement mediated.

In advantageous embodiments of the filter device according to the invention, a filter element is provided with a collapsible filter material in the form of a kind of bellows, which is closed except for an end connected to the clean gas outlet end, being provided as a drive linear drive for compressing the filter material. The compression of the bellows of the filter material leads to a shaking off of deposited particles.

In advantageous embodiments of the clean gas outlet of the filter housing by means of a valve is releasable and lockable. When the clean gas outlet is closed, the compression of the bellows of the filter material results in a pressure surge, through which the internal gas volume of the bellows is pressed outwards as backwash gas through the filter material and deposits are blasted off. For the compression, a linear drive, for example in the form of a working cylinder, can be provided as drive, which can be actuated for compressing and pulling the bellows into the original shape. For a regeneration by acting on the filter material centrifugal force can be provided as a drive a rotary drive with a motor through which the filter element for a regeneration process is set in rotation.

Advantageously, the arrangement can also be made such that a combination of motor and linear drive is provided as the drive of the filter element. By simultaneous collapse and rotation a particularly effective regeneration is achievable.

In the filter housing more than one filter element can be arranged, which can be collapsed by means of its own linear drive, wherein the filter housing for each filter element has its own clean gas outlet, each with an associated valve. In an advantageous manner, this allows a regeneration process to be carried out on a selected filter element without interrupting the filtration operation.

In embodiments of the filter device in which the raw gas inlet of the filter housing is connected to a shielding during operation with welding smoke emitting output of the production space of a 3D printer, may be particularly advantageous the clean gas outlet of the filter housing with the protective gas inlet of the production space in combination. The filter device thereby forms part of the protective gas supply of the relevant 3 D printer.

In the case of such a use, it is advantageously possible for a further filter device arranged downstream of the filter device to be provided as a postfilter in the connection leading to the protective gas inlet. Furthermore, the arrangement can be made so that in the

Protective gas inlet leading connection a suction fan is provided which sucks the gas stream for the filtration process through the filter housing of the filter device, as well as a gas cooler is provided to cool back the heated during the previous welding inert gas before re-entering the production room to the desired working temperature.

In the case of the abovementioned variants of the regeneration, the detached contaminants fall off into the bottom region of the filter housing, which serves as a collecting space from which the retentate can be discharged.

The invention with reference to embodiments shown in the drawings will be explained in detail.

1 shows, in a highly schematically simplified representation, the production space of a 3D printer with a protective gas cycle shown in a symbolic representation, which is provided with a filter device according to the invention; Fig. 2 is a schematically simplified longitudinal section of a first

Embodiment of the filter device according to the invention, wherein the filtration mode is shown;

Fig. 3 a of FIG. 2 corresponding longitudinal section, wherein the

Regeneration mode is shown;

Fig. 4 is a schematically simplified longitudinal section of a second

Embodiment of the filter device according to the invention, wherein the filtration mode is shown; a corresponding longitudinal section of Figure 4, wherein the regeneration mode is shown. a simplified schematic longitudinal section of a second embodiment, wherein the filtration mode is shown; a corresponding longitudinal section of Figure 6, wherein the regeneration mode is shown. in the manner of a simplified, sketch-like functional representation of a third embodiment with two filter elements in the filter housing, wherein the regeneration mode is shown; and a representation corresponding to FIG. 8, wherein the one filter element in the filtration mode and the other filter element in the regeneration mode are shown.

With reference to the accompanying drawings, the invention is illustrated by examples of the use of the filtering device for welding fume-containing protective gas discharged from the space of a 3D printer for metal. Such printers operate on the principle of selective laser sintering (abbreviated: SLS-Ver ears). It is a type of powder pressure, in which powdered, chemically pure metal particles are used, which are applied in layers and then fused with a high-power laser under a protective gas atmosphere. This makes it possible to produce metal objects with very high precision. The resulting welding fume, which together with the protective Gas is discharged from the space of the printer is charged to a very large extent with particles of the metal powder. This leads to a blocking of the filter material after short periods of operation. In order to avoid the labor and cost expenditure for correspondingly frequent filter changes and to enable economical operation, it therefore makes sense to allow longer filter service lives by regeneration.

The inventive 3D printer, of which only the installation space 2 is schematically indicated in FIG. 1, is therefore associated with a regenerable filter device according to the invention as a prefilter 4. The installation space 2 has, in the manner customary in such printers, a lowerable printing table 6 on which an object 8 is formed by fusing applied powder layers by means of the radiation of a high-power laser 10. This is done under the atmosphere of a protective gas, such as argon, which is supplied to the space 2 via a protective gas inlet 12 and discharged via a protective gas outlet 14. From the output 14, the protective gas, together with the welding fume produced during the printing process, passes as raw gas via a crude gas line 16 to the raw gas inlet 18 of the filter housing of the prefilter 4, which is designated 20 in FIGS. From the pre-filter 4, the filtered clean gas passes via a clean gas line 22 to a secondary filter 24, the output of which leads via a suction line 26 to a suction fan 28. This creates a negative pressure for the operation of the filters 4 and 24 as a suction filter. From the suction fan 28, the clean gas passes through a gas cooler 30 and a return line 32 to the protective gas inlet 12 of the installation space 2, after the heated by the previous welding gas in the gas cooler 30 is cooled back to the desired operating temperature. At the return line 32, a protective gas reservoir 34 and a pressure relief valve 36 are connected. The pressure limiting valve 36 serving as overpressure protection of the protective gas circuit is followed by a filter 38 for gas escaping via the valve 36. Figs. 2 and 3 show a first embodiment of the filter device according to the invention, which forms the regenerable pre-filter 4 of the system shown in Fig. 1. At the filter housing 20 forming a hollow circular cylinder, the raw gas inlet 18 is located near the bottom area 40 of the housing 20, which is closed except for a central passage 42 for a lifting cylinder 44. This extends coaxially to the housing longitudinal axis 46 in the interior 20, wherein the inner end of the lifting cylinder 44 is located approximately one third of the height of the housing 20. On the upper housing cover 48 is coaxially with the axis 46, the clean gas outlet 50, from which a connecting piece 52 extends into the interior of the filter housing 20. In the embodiment shown in FIGS. 2 and 3, a collapsible filter element 54 is provided in the filter housing 20. This has a filter material 56, which has the form of a kind of bellows, which is closed except for the end 58 in FIGS. 2 and 3 above. This open end is attached with a tight connection to the connecting piece 52 of the clean gas outlet 50 so that it is in communication with the interior of the bellows formed by the filter material 56. With its closed, lower end 60 of the bellows with the piston rod 62 of the lifting cylinder 44 is connected. The filter material 56 used is advantageously an air filter medium of class F9, which has an applied PTFE membrane on the upstream side. The membrane ensures that the filter is a surface filter in which the dirt does not penetrate into the depth of the filter material and thus can be easily peeled off.

FIG. 2 shows the exemplary embodiment in filtration mode, in which valves, not shown, are open at the raw gas inlet 18 and at the clean gas outlet 50. During the filtering process, the raw gas flows from the line 16 through the raw gas inlet 18 and flows through, as indicated in Fig. 2 with non-quantified flow arrows, the filter material 56 of the filter element 54 from the outside into the interior of the bellows, which in Filtrations- Operation, as shown in Fig. 2, in a fully developed form. From the inner cavity of the filter element 54, the cleaned filtrate flows out via the clean gas outlet 50. To carry out the regeneration mode, the lift cylinder 44 is actuated such that the piston rod 62 extends and compresses the collapsible filter element 54, so that the bellows formed from the filter material 56, as shown in Fig. 3, is folded. The acceleration forces acting on rapid movement lead to detachment of accumulated particles, in particular when shaking takes place by intermittent compression and extraction. The detached during the regeneration particles fall off into the bottom portion 40 of the filter housing 20, which serves as a collecting space from which the contaminants are occasionally removed by means of a discharge device 68 (FIG. 1) having a shut-off device 70 and a retentate 72. 4 and 5 show a further embodiment in which a rotary drive with an electric motor 74 is provided as a drive for the movement in place of the linear drive forming a lifting cylinder 44 whose axis 46 coaxial shaft 76 connected to the lower end cap 78 of a filter element 80 is. This is formed in conventional construction with hollow cylindrical filter material extending from lower end cap 78 to upper end cap 82. In this is a coaxial passage which forms the connection of the inner filter cavity with the clean gas outlet 50 in the regeneration mode shown in Fig. 4. Serving as a rotary drive electric motor 74 is connected to a coaxial to the axis 46 lifting cylinder 84 through which the motor 74 and thus the filter element 80 in the filtration mode (Fig. 4) is raised such that the passage at the upper end cap 82 in close contact with Connecting piece 52 of the clean gas outlet 50 is. When the electric motor 74 is stopped, the filtration process takes place with the valves open at the raw gas inlet 18 and at the clean gas outlet 50 in the case of this position of the filter element 80. As shown by non-quantified flow arrows in FIG. 4, In this case, the raw gas entering via the inlet 18 flows from the outside inwards into the filter element 80 and exits the internal filter cavity via the clean gas outlet 50 as clean gas. FIG. 5 illustrates the regeneration mode that takes place at the raw gas inlet 18 and the clean gas outlet 50 when the valves are closed (not shown). The electric motor 74 and thus the filter element 80 are lowered by retracting the lifting cylinder 84, so that the upper end cap 82 of the filter element 80 is released from the connecting piece 52 of the clean gas outlet 50 and the filter element 80 is freely rotatable. The actuated electric motor 74 now sets the filter element 80 in rotation so that particles deposited on the outside by centrifugal force are thrown off and, as in the previous variants, fall off to the bottom region 40 of the filter housing 20 and can be discharged on a case-by-case basis.

6 and 7 show a third embodiment in which, in correspondence with the first embodiment, a filter element 54 is provided in the form of a collapsible bellows, which is compressible and extendable as in the first embodiment by means of a lifting cylinder 44. The difference from the first embodiment is merely that a shut-off valve 88 in the form of a plate or poppet valve is provided at the outlet nozzle 86 of the clean gas outlet 50, which can be actuated by an actuator 90 in the closed position or passage position. In the filtration state shown in Fig. 6, the valve 88 is in the on state, so that the filter element 54, as indicated by non-numbered flow arrows, flows through in the same manner, as shown in Fig. 2 for the first example. For the regeneration process shown in Fig. 7, the shut-off valve 88 is closed. As a result, when the bellows are compressed into the shape shown in FIG. 7, the internal gas volume of the bellows is pressed outward through the filter material 56 in a pressure surge, thereby breaking off the deposited particles. As in the first example of FIGS. 2 and 3, the detached particles fall off into the bottom region 40 of the filter housing 20.

FIGS. 8 and 9 show a fourth exemplary embodiment which, like the third exemplary embodiment, provides a shut-off valve 88 on clean gas outlets 50. In the filter housing 20, however, more than one filter element 54 is arranged, in the example of FIGS. 8 and 9 two filter elements 54, which are each formed by a collapsible bellows. The filter elements 54 can be pressed and pulled together independently of each other by their own linear drive 44. The clean gas outlet 50 of each filter element 54 is connected via its shut-off valve 88 to a common clean gas space 92, at the outlet of which the clean gas line 22 (see FIG. At the bottom area 40 of the filter housing 20 there is a funnel-like collecting space 94 for fallen-off dirt particles, which settle in a retentate container 96.

Fig. 8 shows the filtration mode for both filter elements 54, wherein the shut-off valve 88 of both filter elements 54 in the passage position and the filtration takes place at each extended bellows. FIG. 9 shows one filter element 54 with the shut-off valve 88 open in the filtration mode, while the other filter element 54 is in the regeneration mode. The associated shut-off valve 88 is closed and the filter element 54 collapsed to produce the backwash pressure surge. In this way, this embodiment allows a continuous operation by each blocked filter elements 54 are regenerated with continued filtration operation of a respective other filter element 54.

Claims

Patent claims

1. A method for the filtration of in a production room (2) produced by selective manufacturing processes flue gases, such as welding smoke of 3D printers, with the steps:

Guiding the flue gas from the production space (2) to the raw gas inlet (18) of a filter housing (20) which accommodates at least one filter element (54, 80) whose filter material (56) separates the raw gas inlet (18) from a clean gas outlet (50) during the filtration process ;

Flow through the filter material (56) and discharge of the gas via the clean gas outlet (50) and

- Regenerating the filter element (54; 80) by this is moved to detachment of on the upstream side of the filter material (56) deposited particles.

2. The method according to claim 1, characterized in that the movement is carried out by compressing a collapsible filter element (54).

3. The method according to claim 1 or 2, characterized in that the compression and a return of the filter element (54) are carried out intermittently in the original form.

4. The method according to any one of the preceding claims, characterized in that the clean gas outlet (50) of the filter housing (20) from the beginning to the end of the compression of the filter element (54) is kept closed.

5. The method according to any one of the preceding claims, characterized in that the filter element (80) is set in the movement in rotation.

6. The method according to any one of the preceding claims, characterized in that the filter element (80) before the rotation of the clean gas outlet (50) of the filter housing (20) is separated.

7. Filter device for the filtration of particulate-laden gases, such as welding gases produced in selective manufacturing processes, especially in 3D printers, in a production space (2), with a filter housing (20) having a raw gas inlet (18) and a clean gas outlet (50) and receives at least one filter element (54; 80) whose filter material (56) separates the raw gas inlet (18) from the clean gas outlet (50) during filtration, and a drive (44; 74) through which the filter element (54; 54, 80) a detachment of on the upstream side of the filter material (56) deposited particles causing movement can be mediated.

8. Filter device according to claim 7, characterized in that a filter element (54) is provided with a collapsible filter material (56) in the form of a kind of bellows, which is closed except for one with the clean gas outlet (50) end (58), and in that a linear drive (44) is provided as drive for compressing the filter material (56).

9. Filter device according to claim 7 or 8, characterized in that the clean gas outlet (50) of the filter housing (20) by means of a valve (88) is releasable and lockable.

10. Filter device according to one of claims 7 to 9, characterized in that a rotary drive with a motor (74) is provided as drive, by means of which the filter element (80) is set for a regeneration process in rotation.

1 1. Filter device according to one of claims 7 to 10, characterized in that a combination of motor (74) and linear drive (84) is provided as the drive of the filter element (80).

12. Filter device according to one of claims 7 to 11, characterized in that in the filter housing (20) more than one filter element (54) is arranged, each by means of a separate linear drive (44) are collapsible, and that the filter housing (20) for each filter element (54) has its own clean gas outlet (50), each with an associated valve (88).

13. Filter device according to one of claims 7 to 12, characterized in that the raw gas inlet (18) of the filter housing (20) is connected to a protective gas during operation with welding smoke emitting output (14) of the production space (2) of a 3D printer.

14. Filter device according to one of claims 7 to 13, characterized in that the respective clean gas outlet (50) of the filter housing (20) with the protective gas inlet (12) of the production space (2) of the 3 D printer is in communication.

15. Filter device according to one of claims 7 to 14, characterized in that in the protective gas inlet (12) leading connection a filter housing (20) downstream further filter means (24) is provided.

16. Filter device according to one of claims 7 to 15, characterized in that in the protective gas inlet (12) leading connection, a suction fan (28) and a gas cooler (30) are provided.