Device for separating pollutants and / or particles from a process exhaust gas stream

Abstract

Device for separating pollutants and / or particles from a process exhaust gas stream, in which a process raw gas flows by means of a compressor towards at least one filter element and through the at least one filter element; wherein the at least one filter element is arranged in a chamber and a metering device for a powdered additive is arranged upstream of the at least one filter element in the flow direction of the process raw gas, with which the additive can be supplied to the process raw gas. characterized in that wherein a storage container (A) for the powdered additive is arranged on the dosing device such that the powdered additive is dispensed onto a surface of at least one sieve (D) and that at least one sieve (D) can be set into vibration by means of a device (B) and / or vibrations can be coupled into the sieve (D) that act on the sieve (D); wherein characterized by the fact that The mesh size of the at least one sieve (D) and the particle size of the powdered additive are selected such that particles of the powdered additive only pass through the sieve (D) if the at least one sieve (D) has been set into vibration or the sieve (D) is vibrating and particles that have passed through the at least one sieve (D) can be fed into the process raw gas stream and are deposited as part of a filter cake on the at least one filter element, wherein two sieves (D) are arranged decoupled from each other so that independent, unhindered vibration of one of the two sieves (D) or both sieves (D) is possible.

Description

[0001] The invention relates to a device for separating pollutants and / or particles from a process exhaust gas stream. In particular, it is intended to remove pollutants or particles from process exhaust gas streams that are released and carried along with the process raw gas during an additive manufacturing process in which powdered material is locally solidified using an energy beam. Examples of such processes include selective laser sintering or laser melting.

[0002] The invention can also be used to separate liquid or gaseous components from a process raw gas before they pass through a filter element.

[0003] In additive manufacturing processes, the particles carried in the process raw gas are a critical factor. Firstly, their high chemical reactivity can pose a risk. Secondly, they pose a danger to the filter material of filter elements, which they can easily damage due to their higher energy and momentum, and even penetrate, thus reducing the effectiveness of the separation action and consequently the usable service life of the filter element.

[0004] If damaged, such particles can even be returned to a processing chamber where the additive manufacturing process takes place, which negatively impacts quality. Process gas is often recirculated to minimize costs due to the use of inert process exhaust gases.

[0005] For example, an extraction device for exhaust gas containing pollutants is known from DE 10 2013 008 233 A1.

[0006] DE 1 186 829 A relates to a dosing device for dry filter aids.

[0007] A method for dust separation from a gas stream is described in DE 30 03 124 A1.

[0008] US 2002 / 0060230 A1 describes a vibration classifier for powders.

[0009] DE 102 26 989 A1 discloses a method for filling micronized powders in very small quantities.

[0010] It is therefore an object of the invention to provide possibilities for improving the separation effect while simultaneously extending the service life of filter elements.

[0011] According to the invention, this problem is solved with a device having the features of claim 1. Advantageous embodiments and further developments of the invention can be realized with features specified in dependent claims.

[0012] For filtering process gas-borne pollutants or particles, the invention provides a novel "dosing unit" for powdered additive material. A specific amount of powdered additive material is added to the process to achieve improved filtration efficiency and longer filter service life.

[0013] In the device according to the invention, a raw process gas flows by means of a compressor towards and through at least one filter element. The at least one filter element is arranged in a chamber, and upstream of the at least one filter element, in the flow direction of the raw process gas, a metering device for a powdered additive is arranged, by which the powdered additive can be supplied to the raw process gas.

[0014] The dosing device has a storage container for the powdered additive such that the powdered additive is dispensed onto the surface of at least one sieve. The sieve can be set into vibration by a device and / or vibrations can be coupled into the sieve, acting upon it.

[0015] The mesh size of the at least one sieve and the particle size of the powdered additive are selected such that particles of the powdered additive only pass through the sieve if the at least one sieve has been set into vibration or the sieve is vibrating, and particles of the powdered additive that have passed through the at least one sieve can be fed into the process raw gas stream and are deposited as part of a filter cake on the at least one filter element.

[0016] The particles can thus be metered into the raw process gas by means of the sieve's vibrations and carried along with this raw process gas stream to at least one filter element, where they are deposited, forming part of the filter cake. During periods when the system is switched off and the sieve is not vibrating, no particles of the powdered additive can enter the raw process gas.

[0017] The device used to vibrate or couple vibrations into the sieve should include at least one sonotrode. The sonotrode may be located at the edge or on an outer frame of the sieve.

[0018] At least a portion of the raw process exhaust gas stream should flow along the side of the at least one sieve that is located opposite the storage container, so that particles of the powdered additive or powdered additive can be carried along with this portion of the raw process gas stream to the at least one filter element as a result of the Venturi effect.

[0019] It is not absolutely necessary to route the entire volume flow of the raw process gas to the metering device. It may be sufficient to route only a portion of the raw process gas to the metering device. This can be achieved, for example, via a bypass line that can be opened and closed by means of at least one valve, so that the raw process gas only temporarily flows through the metering device to the at least one filter element and can carry particles of the powdered additive.

[0020] Advantageously, the device used to set the at least one sieve into vibration, or to couple vibrations into the sieve, can be connected to an electronic control unit. The electronic control unit should be designed to influence, or allow to influence, the activation time of the device used to set the at least one sieve into vibration, the duration of its activation, and the frequency and / or amplitude of the vibrations.

[0021] The storage container for the powdered additive can be arranged so that the powdered additive is conveyed to the sieve by gravity. This conveyance can be assisted by at least one additional element that can couple vibrations into the wall of the storage container or that can set the storage container into oscillating motion.

[0022] The powdered additive can be a dry, mineral powder that is chemically inert with the process exhaust gas and pollutants and particles contained in the raw process gas, particularly calcium carbonate or activated carbon. White calcium carbonate, commercially available from Bassermann minerals GmbH, Mannheim, Germany, under the trade name "Omycarb 15-GU", is particularly suitable. Activated carbon can be advantageously used if liquid or gaseous pollutants are present in the raw process gas.

[0023] If two sieves arranged one behind the other in the conveying direction of the powdered filler material or powdered additive are used in a device according to the invention, it is advantageous not to set them into vibration synchronously and / or to couple vibrations with different, preferably opposite, propagation directions into the sieve.

[0024] Two sieves are arranged in a decoupled manner, so that independent, unhindered oscillation of one or both sieves is possible.

[0025] Vibrations with a frequency in the range of 25 Hz to 100 kHz, at a power of up to 4000 W and / or particle sizes of the powdered filler material or powdered additive in the range of 1 µm to 100 µm can be used.

[0026] The invention involves influencing a sieve with a specific mesh size using ultrasound and / or vibrations. The mesh size is designed, taking into account the particle size of the powdered additive, such that no powdered additive passes through the sieve without excitation. Using at least one sonotrode and optionally a generator, the ultrasound or vibration energy can be converted into mechanical energy and transferred to the sieve by means of the device that sets the sieve into vibration or couples vibrations into the sieve.

[0027] As soon as the sieve is activated, a defined quantity of powdered additive passes through it, depending on the duration, amplitude, and frequency of the respective vibrations. The powdered additive can then be conveyed via a suction port into a filter unit by means of the pressure differential achieved by the compressor. The powdered additive settles on the surface of the at least one filter element and, at least as part of the filter cake, leads to improved performance.

[0028] The invention makes it possible to add a powder that is otherwise difficult to convey to a process raw gas in a very simple way and in the correct dosage.

[0029] The respective storage container can hold a corresponding quantity of powdered additive or filler material. Activating the sieve introduces a defined quantity of the powdered additive or filler material into the raw process gas flow. A bypass circuit allows the storage container to be changed without any unwanted leakage of untreated raw process gas.

[0030] The invention will be explained in more detail below by way of example.

[0031] This shows: Fig. 1 in schematic form the arrangement of a device according to the invention in a bypass line through which at least part of the process raw gas flows.

[0032] A connection fitting C is attached to the bypass line E. Above the connection fitting C are a device B, with which the at least one sieve can be set into vibration or with which vibrations can be coupled into the sieve, and at least one sieve D. Above the sieve D is a storage container A, open towards the sieve D, in which powdered calcium carbonate with an average particle size d is stored. 50 is available in the range of 20 µm to 90 µm.

[0033] The sieve D has a mesh size of 250 µm, so that the calcium carbonate particles, as a powdered additive, can only pass through the mesh if the sieve D has been vibrated and / or vibrations are coupled into the sieve. For this purpose, the device B comprises at least one sonotrode and a generator. The device is connected to an electronic control unit (not shown), as described in the general section of the description. The control can be carried out analogously to the description already given there.

[0034] The powdered additive material is forced to the surface of the sieve D by gravity. Using the vibrational energy, particles can pass through the sieve D and, aided by the suction effect of the raw process gas flowing past the connection nozzle C, are carried along with the raw process gas through the rest of the bypass line E to the filter element (not shown).

[0035] A valve F is located at the beginning and end of the bypass line E. If at least one of the valves F is closed, no powdered filler material or powdered additive reaches the filter element.

[0036] If both valves F are closed, the storage container A can be replaced safely and without problems.

Claims

[1] Device for separating pollutants and / or particles from a process exhaust gas stream, in which a process raw gas flows by means of a compressor towards at least one filter element and through the at least one filter element; wherein the at least one filter element is arranged in a chamber and a metering device for a powdered additive is arranged upstream of the at least one filter element in the flow direction of the process raw gas, with which the additive can be supplied to the process raw gas, characterized by , that whereby a storage container (A) for the powdered additive is arranged on the dosing device such that the powdered additive is dispensed onto a surface of at least one sieve (D) and that at least one sieve (D) can be set into vibration by means of a device (B) and / or vibrations can be coupled into the sieve (D) that act on the sieve (D); wherein characterized by , that The mesh size of the at least one sieve (D) and the particle size of the powdered additive are selected such that particles of the powdered additive only pass through the sieve (D) if the at least one sieve (D) has been set into vibration or the sieve (D) is vibrating and particles that have passed through the at least one sieve (D) can be fed into the process raw gas stream and are deposited as part of a filter cake on the at least one filter element, wherein two sieves (D) are arranged decoupled from each other so that independent, unhindered vibration of one of the two sieves (D) or both sieves (D) is possible. [2] Device according to claim 1, characterized bythat the device (B) has at least one sonotrode. [3] Device according to any one of the preceding claims, characterized by , that at least a part s of the process raw gas stream flows on the side of the at least one sieve (D), so that particles of the powdered additive or powdered additive are carried along with this part of the process raw gas stream to the at least one filter element as a result of the Venturi effect. [4] Device according to any one of the preceding claims, characterized by , that the process raw gas flow or part of the process raw gas flow is routed through a bypass line (E). [5] Device according to any one of the preceding claims, characterized bythat the device (B) is connected to an electronic control and / or regulating unit and the electronic control and / or regulating unit is designed in such a way that the time of switching on the device (B), the duration of the switched-on state of the device (B), the frequency and / or the amplitude of the vibrations is / are influenced. [6] Device according to any one of the preceding claims, characterized by , that the storage container (A) for the powdered additive is arranged in such a way that the powdered additive is drawn to the sieve (D) by gravitational force. [7] Device according to any one of the preceding claims, characterized bythat the powdered additive is a dry mineral powder, in particular calcium carbonate or activated carbon, that does not chemically react with the process exhaust gas, and pollutants and particles contained in the raw process gas. [8] Device according to any one of the preceding claims, characterized by that two sieves (D) arranged one behind the other in the conveying direction of the powdered additive or powdered additive are not set into synchronous vibration and / or vibrations with different, preferably opposite, propagation directions are coupled into the sieve (D). [9] Device according to any one of the preceding claims, characterized by , that vibrations with a frequency in the range of 25 Hz to 100 kHz and / or particle sizes of the powdered additive or powdered admixture in the range of 1 µm to 100 µm are used.

Images