Filter device for cleaning a gas flow carrying foreign bodies

Abstract

The present invention relates to a method for the dry filtration of a gas flow that carries foreign bodies, in particular in a filter device (10) for cleaning waste gas produced in additive manufacturing techniques, said method comprising the following steps: conducting a raw gas flow containing foreign bodies into a raw gas space of a filter unit which has at least one filter element separating a raw gas side from a clean gas side, said filter element having a filter surface facing the raw gas side; cleaning material from the filter surface; and supplying oxidant to a reaction region (22) such that foreign bodies contained in the material cleaned from the filter surface react with the oxidant in the reaction region (22) to form oxide-containing foreign bodies. In the method, material cleaned from the filter surface is comminuted in a treatment space (19) such that by supplying oxidant to the reaction region (22) foreign bodies contained in comminuted, cleaned material are oxidised. The present invention also relates to a filter device designed to carry out the method.

Description

[0001] Filter device for cleaning a gas stream containing foreign matter

[0002] The invention relates to a filter device for cleaning a gas stream containing foreign matter.

[0003] When cleaning gases containing highly flammable or pyrophoric foreign bodies, such as those found in systems for the additive manufacturing of metal workpieces (e.g., during laser sintering of workpieces made of titanium or aluminum alloys), there is a risk of uncontrolled fires. This risk is particularly high when such highly flammable foreign bodies accumulate on the filter surfaces of the filter device, because the accumulated material, after being cleaned from the filter surface, easily comes into contact with atmospheric oxygen upon removal from the filter device. Attempts have been made to counteract these risks by pre-coating the filter surfaces with inert filtration aids such as CaOCh or by adding such aids to the raw gas to be cleaned, similar to the setup shown in WO 2012 / 032003 A1.

[0004] The object of the invention is to prevent fires in material removed from the filter device, in particular when removing material that arises when cleaning filter surfaces and is collected, for example, in a dust collection container.

[0005] A filter device according to the invention for cleaning raw gas containing foreign bodies comprises at least one filter element with at least one filter surface separating a raw gas side from a clean gas side in a raw gas chamber to which a raw gas stream containing foreign bodies can be fed; a cleaning device for cleaning material from the filter surface and an oxidizing agent supply device designed to feed an oxidizing agent to a reaction zone such that foreign bodies contained in the material cleaned from the filter surface and / or the raw gas stream react with the oxidizing agent in the reaction zone to form oxide-containing foreign bodies;wherein a comminution device is provided which is designed to comminute material cleaned from the filter surface in a treatment chamber such that foreign bodies contained in the comminuted, cleaned material are oxidized by supplying oxidizing agent to the reaction region;

[0006] In the filter device according to the invention, material cleaned from the filter surface is additionally comminuted in a treatment chamber such that foreign bodies contained in the comminuted, cleaned material are oxidized by supplying oxidizing agent to the reaction area.

[0007] The filter device according to the invention makes it possible to suppress or even prevent fires in material cleaned by filter elements, which can occur particularly when the cleaned material is removed from the filter device and the resulting contact with atmospheric oxygen. The risk of such fires exists, for example, when using dry filters to filter raw gases containing flammable foreign matter, such as those that can occur when filtering exhaust gases generated in additive manufacturing technologies, such as laser sintering of metal workpieces, using a dry filter.

[0008] With the filter device according to the invention, it is particularly possible to deliberately initiate a spontaneous oxidation of foreign bodies, which leads to their inerting or passivation. During spontaneous oxidation, the desired reaction(s) for the formation of oxide-containing foreign bodies proceed essentially without the provision of activation energy by supplying energy from an energy source, such as an ignition source or a heat source. Oxidation can be initiated simply by the oxidizing agent coming into contact with material present in the reaction zone or entering the reaction zone, which material falls off the filter surface during cleaning.

[0009] The oxidizing agent can be air or an oxygen-containing gas. Other substances, for example inert gases such as nitrogen or noble gases, can be admixed with the oxidizing agent to form an oxidizing agent stream. For example, air can be used to form the oxidizing agent stream, or an oxygen-depleted mixture with an oxygen content of 2 to 21 percent by volume, in particular an oxygen content of 5 to 21 percent, or even an oxygen-enriched mixture with an oxygen content of up to 30 percent by volume, in particular up to 50 percent by volume, or even more if necessary. The oxygen content can be suitably selected, particularly depending on the application or economic conditions.The concentration of oxidant in the oxidant stream is selected to be sufficiently high to enable a spontaneous reaction of foreign matter-containing material in the reaction zone to form oxide-containing foreign matter. Generally, it can be assumed that, with the same chemical composition, the oxygen content can be lower the more the material is comminuted, i.e., the smaller the size of the comminuted particles or residual agglomerates, because then the effectively available surface area of ​​the comminuted material is larger and the oxidation reaction proceeds more quickly.

[0010] Comminution results in a measurable reduction in the size of the material removed from the filter surface, particularly by breaking down agglomerates contained in the removed material into smaller fragments. These fragments can themselves be (smaller) agglomerates or particles containing foreign matter that cannot easily be further crushed.

[0011] The comminution of material cleaned from the filter surface can occur, in particular, during a comminution period. The comminution period is the period in which a measurable comminution of material cleaned from the filter surface is taking place or is still taking place, in particular, agglomerates are broken down into smaller fragments.

[0012] The treatment chamber is a space in which the comminution of cleaned material takes place. In the reaction zone, foreign bodies contained in the cleaned material react with the oxidizing agent to form oxide-containing foreign bodies. The treatment chamber can largely overlap with the reaction zone or even be identical to the reaction zone. However, there can also be zones in which only comminution of cleaned material takes place, but no oxidation of foreign bodies. Likewise, there can also be zones in which oxidation of foreign bodies (still) takes place, but no comminution (anymore). The present invention provides a filter device in which improved, controlled oxidation of reactive or even highly reactive foreign bodies in exhaust gases, such as metal-containing particles in the exhaust fumes from additive manufacturing systems such as laser sintering, is enabled.The reaction can, in particular, be a spontaneous reaction that essentially requires no activation energy. Nevertheless, the comminution provided by the invention allows for highly efficient conversion of reactive foreign bodies into largely inert and thus inertized or passivated oxidized foreign bodies. The high reactivity of such foreign bodies with oxidizing agents such as oxygen or air—the actual reason why dry filtration of exhaust gases containing such foreign bodies is problematic—is exploited to specifically trigger a controlled spontaneous reaction of the foreign bodies with the oxidizing agent.

[0013] Extensive experiments have shown that the mere addition of a fluid containing an oxidizing agent is not sufficient to achieve the desired controlled oxidation of reactive or even highly reactive foreign bodies. However, surprisingly, the additional measure of comminuting material cleaned from the filter surface that contains reactive or self-igniting foreign bodies, such that the foreign bodies contained in the comminuted, cleaned material are oxidized by supplying an oxidizing agent to the reaction zone, leads to improved control of the oxidation process and thus to an improved adjustment of the degree of conversion of reactive foreign bodies to inert, oxidized foreign bodies.

[0014] The additional measure of comminution thus decisively ensures that the proportion of reactive foreign bodies in material to be removed from the filter device (for example by replacing a collecting container in which material removed from the filter device is collected) remains below a maximum specified threshold.

[0015] The comminution of material cleaned from the filter surface can be carried out both before the addition of oxidizing agent and during the addition of oxidizing agent, provided that it is ensured that the oxidizing agent at least also comes into contact with comminuted cleaned material containing reactive foreign bodies and thus the oxidation of reactive foreign bodies takes place through contact of oxidizing agent with such comminuted cleaned material.

[0016] Further investigations into the surprising finding that the material cleaned from the filter surface can be oxidized more effectively when it is crushed have shown that the cleaned material is often in the form of agglomerates containing a large number of cohesive foreign particles. The agglomerates have a relatively small surface area, which means that the oxidizing agent has a small area of ​​attack, meaning that the reactive foreign particles in the agglomerates cannot be completely oxidized. Furthermore, the size of such agglomerates as well as their proportion in the crushed material can vary greatly. During crushing, such agglomerates in particular are broken down into their constituents. Therefore, crushing gives the cleaned material a larger surface area and thus a larger area of ​​attack for the oxidizing agent, which in turn should lead to improved oxidation.In addition, comminution results in a much more uniform particle size distribution because the agglomerates are largely broken down into the components (particles) of which they were composed.

[0017] In the context of the present invention, the term "body" should be generally understood as a generic term for "particles" and "agglomerates." Material removed from the filter surface essentially consists of agglomerates. Agglomerates are composite bodies and comprise a plurality of simple bodies or particles that are interconnected or held together to form a coherent body. The term "particles" refers to simple bodies that cannot be easily broken down further. Particles can be foreign bodies entrained in the gas stream (e.g., metal particles) or particles of a filtration aid with which the filter surface is precoated before filtration begins. Common filtration aids include calcium carbonate or rock flour.

[0018] Comminution means a reduction in the size of cleaned material. This comminution particularly affects agglomerates composed of a large number of interconnected or cohesive particles. During comminution, these agglomerates are broken apart into smaller fragments composed of fewer particles and thus become smaller. After comminution, the majority of the cleaned material should no longer be in the form of agglomerates. In a particular embodiment, at the end of the comminution period, essentially only particles (simple bodies) remain, because essentially all agglomerates (composite bodies) have been broken down as far as possible into their constituent parts (particles).

[0019] The term "comminution" as used here means breaking agglomerates into smaller fragments. This process ends when the fragments themselves are no longer agglomerates and therefore can no longer be easily broken down into smaller fragments using physical separation processes.

[0020] Furthermore, it is possible to specifically initiate the spontaneous reaction of cleaned material containing foreign bodies with oxidizing agent by appropriately controlling the supply and / or discharge of oxidizing agent and, if necessary, other measures and to keep its course well under control, so that an uncontrolled reaction of the foreign bodies with the oxidizing agent can be avoided.

[0021] In principle, highly flammable foreign bodies contained in the raw gas should be rendered harmless by deliberately converting them into an oxidized configuration. In the oxidized configuration, these foreign bodies are generally inert and no longer hazardous, so that further handling of these oxidized foreign bodies no longer requires any special precautions. To further support this implementation, a suitable supply and / or removal of oxidizing agent to a predetermined reaction zone containing material cleaned from the filter surface and thus containing foreign bodies can be provided, and / or further measures for removing oxidizing agent from the reaction zone can be provided.In particular, the course of the usually highly exothermic oxidation reaction can be well controlled if the oxidant is not just fed to the reaction zone, but rather flows through the reaction zone. The oxidant is then fed to the reaction zone at a first point or in a first region (inlet) and flows through the reaction zone until it leaves the reaction zone again at a further point or in a further region (outlet), at least provided it has not been consumed by reaction with material containing foreign bodies while flowing through the reaction zone. In this way, it is possible to specifically provide an excess of oxidant in the reaction zone, as required to spontaneously initiate the desired reaction for the formation of oxide-containing foreign bodies or to maintain it at a controlled rate. The flow allows the course of the oxidation reaction to be controlled.This occurs spontaneously but in a controlled manner as soon as the oxidant flow starts and can be well controlled by adjusting the strength of the oxidant flow and, if necessary, also by adjusting the composition of the oxidant flow.

[0022] In particular, material cleaned from the filter surface can be crushed in the treatment chamber before foreign bodies contained in the cleaned material are oxidized by supplying oxidizing agent to the reaction area.

[0023] The comminution of cleaned material then precedes the oxidation of foreign bodies. In particular, in a first phase, at least a portion of the cleaned material is to be comminuted without the addition of an oxidizing agent, thereby initiating an oxidation reaction. Thus, in this first phase, only the cleaned material, in particular agglomerates containing a plurality of cohesive foreign body particles, is comminuted, but no oxidation of foreign bodies occurs. It is entirely possible, and even desirable, that after the first phase, the two aforementioned processes of comminution of cleaned material and oxidation of foreign bodies take place in parallel in a second phase.

[0024] In particular, the comminution of filter surface cleaned material can take place in an inert environment, at least in a first phase at the beginning of a comminution period.

[0025] An environment is considered "inert" in which the proportion of oxidizing agent is so low that no significant oxidation of foreign bodies occurs, or at least this oxidation occurs so slowly that the temperature in the reaction zone increases only slightly, in particular by a maximum of 5 °C, preferably by a maximum of 1 °C. In particular embodiments, an environment with a proportion of 2 volume percent or less of oxygen, based on the amount of substance, can be considered inert.

[0026] The comminution of filter surface cleaned material can, based on the comminution period, take place in an inert environment for at least 50% of the comminution period, in particular for at least 75%, preferably for at least 90%, more preferably for at least 95%, particularly preferably for at least 98%.

[0027] In one embodiment, comminution can take place in an inert environment throughout the entire comminution period. In this case, the first phase lasts throughout the entire comminution period.

[0028] In a preferred embodiment, the comminution can take place in a second phase following the first phase in an oxidizing environment.

[0029] The cleaned material can be shredded to such an extent within the shredding period that after the end of the shredding period individual

[0030] Bodies are no longer visible to the human eye. After the end of the comminution period, the cleaned material can have an average body size of at most 0.3 mm. After the end of the comminution period, at least 50 percent by weight of the cleaned material can have a body size of 1 mm or less, in particular a body size of 0.5 mm or less, in particular a body size of 0.1 mm or less and preferably a body size of 0.05 mm or less. In further embodiments, even after the end of the comminution period, at least 75 percent by weight of the cleaned material can have a body size of 1 mm or less, in particular a body size of 0.5 mm or less, in particular a body size of 0.1 mm or less and preferably a body size of 0.05 mm or less.In still further embodiments, even after the end of the comminution period, at least 90 percent by weight of the cleaned material may have a body size of 1 mm or less, in particular a body size of 0.5 mm or less, in particular a body size of 0.1 mm or less, preferably a body size of 0.05 mm or less. The proportion of cleaned material with a body size of 1 mm or less, 0.5 mm or less, 0.1 mm or less, and 0.05 mm or less in relation to the total mass of cleaned material may be determined by successively sieving cleaned material through a set of sieves, each with a standardized mesh size of 1 mm, 0.5 mm, 0.1 mm, or 0.05 mm.

[0031] Comminution can be achieved using a pneumatic device. The pneumatic device can have at least one pressurized fluid line, in particular a pressurized gas line, which opens into the treatment chamber, wherein an inert pressurized fluid, in particular an inert pressurized gas, is injected into the treatment chamber through the pressurized fluid line, at least during the first phase, in order to comminute material cleaned from the filter surface. The pneumatic device can, in particular, be a pneumatic conveying device, which is designed, for example, as a solids injector or jet pump. In addition to comminuting cleaned material by applying pressurized fluid, such a pneumatic conveying device designed as a solids injector or jet pump can, in particular, be designed to generate a negative pressure in order to convey cleaned material into and / or through the treatment chamber and / or into or through the reaction zone.In addition to the primarily desired transport of cleaned material, the desired comminution of cleaned material and / or reaction of cleaned material with oxidizing agent can also be supported in a very efficient manner.

[0032] The treatment chamber can be in fluid communication with the raw gas chamber during the first phase.

[0033] During the first phase, inert pressurized fluid, in particular inert pressurized gas, can be injected into the treatment chamber so that agglomerates are crushed there, but no oxidation (at least no noticeable oxidation) of foreign bodies takes place.

[0034] The treatment chamber can also be the raw gas chamber itself or include the raw gas chamber as a subsection of the treatment chamber. This facilitates precoating the filter surface with fluidized, shredded material.

[0035] The inert pressurized fluid, in particular the inert pressurized gas, can be injected into the treatment chamber in such a way that material located in the treatment chamber is swirled up and deposits as a precoat layer on the filter surface.

[0036] During a second phase, a pressurized fluid containing an oxidizing agent, in particular a pressurized gas containing an oxidizing agent, can be injected into the treatment chamber.

[0037] An oxidant-containing fluid or gas can be generated in the pressurized fluid line by adding an oxidant-containing fluid or gas to the inert fluid or gas, or by switching from an inert fluid or gas to an oxidant-containing fluid or gas. It is also conceivable to provide an additional pressurized fluid line to inject the oxidant-containing pressurized fluid or gas into the treatment chamber.

[0038] During the second phase, the raw gas chamber can be sealed fluid-tight from the treatment chamber. This prevents the raw gas chamber from becoming contaminated with an unacceptably high oxidant concentration due to the injection of fluid or gas containing an oxidant into the treatment chamber.

[0039] During a third phase following the second phase, the treatment chamber can then again be in fluid communication with the raw gas chamber and pressurized fluid or pressurized gas can be injected into the treatment chamber in such a way that material in the treatment chamber is swirled up and deposits as a precoat layer on the filter surface.

[0040] The pressurized fluid or pressurized gas injected during the third phase is also preferably an inert fluid or gas. In this way, excessive entry of oxidizing agent into the raw gas chamber during the third phase can be prevented, and no special measures are required to inertize the raw gas chamber. With regard to the conditions for an inert fluid or gas, the above statements apply accordingly. This means that the proportion of oxidizing agent in the pressurized fluid or pressurized gas should be so low that no significant oxidation of foreign bodies occurs in the treatment chamber during the third phase, or at least this oxidation occurs so slowly that the temperature in the treatment chamber increases only slightly, in particular by a maximum of 5 °C, preferably by a maximum of 1 °C.In particular embodiments, a proportion of 2 volume percent or less of oxygen in the pressurized fluid or pressurized gas injected during the third phase may be considered inert.

[0041] During the third phase, further shredding of the cleaned material is not necessarily required. Further shredding of the cleaned material during the third phase can be helpful in some cases. In this case, the shredding period will also include the third phase. In many cases, however, sufficient shredding of the cleaned material can already be achieved during the first and second phases. In this case, no further shredding of the cleaned material will take place in the third phase; instead, only the resuspension of shredded cleaned material and, if desired, precoating of the filter surface.

[0042] The comminution can be carried out using a mechanical comminution tool that exerts a conveying, mixing, and / or vibrating motion on the cleaned material and is located in the treatment chamber. The mechanical comminution tool can comprise at least one of the following mechanical comminution tools: auger; rotary valve; counter-rotating rollers; mixer; fluidizer; vibrator; vibrating screen.

[0043] The reaction area may comprise areas located downstream of the treatment chamber, in particular downstream lines, conveyors and / or containers.

[0044] A pneumatic conveying device can be assigned to the treatment chamber, in particular a conveying device operating as a solids injector or jet pump. The pneumatic conveying device is designed to convey solid-containing material, in particular material cleaned from the filter surface and comminuted. In particular, the reaction zone can be located downstream of the treatment chamber, so that cleaned material, after at least partial comminution in the treatment chamber, is conveyed to the reaction zone and there exposed to a fluid containing an oxidizing agent. Comminution does not have to be completely finished when the cleaned material reaches the downstream reaction zone. It is sufficient if a certain breakdown of large aggregates has taken place before the fluid containing an oxidizing agent is applied and the reaction begins.If desired, further comminution of cleaned aggregates can also take place in the reaction area.

[0045] A first pneumatic conveying device can be assigned to the treatment chamber. The first pneumatic conveying device can be designed, in particular, as a solids injector or jet pump. The treatment chamber can be subjected to negative pressure, in particular by the first pneumatic conveying device, in order to remove cleaned material from the treatment chamber. Applying negative pressure to the treatment chamber can, in particular, occur downstream of the comminution of cleaned material.

[0046] In particular, the first pneumatic conveying device can be designed to generate a negative pressure in order to convey cleaned material into and / or through the treatment chamber.

[0047] In particular, the first pneumatic conveying device can be supplied with inert fluid in order to suppress a reaction of cleaned foreign bodies with oxidizing agent at least in a first phase of comminution.

[0048] In a further embodiment of the filter device according to the invention, a second pneumatically operated conveying device can be assigned to the reaction zone. The second pneumatically operated conveying device can also be designed, in particular, as a solids injector or jet pump. The second pneumatically operated conveying device transports the cleaned material into or through the reaction zone. The second pneumatically operated conveying device can, in particular, be supplied with a fluid containing an oxidizing agent in order to initiate and / or promote the conversion of foreign bodies into oxidized foreign bodies in addition to transporting the cleaned material in the reaction zone.

[0049] The second pneumatically operated conveying device can apply negative pressure to the treatment chamber to convey cleaned material from the treatment chamber into the reaction zone. Additionally or alternatively, the second pneumatically operated conveying device can be designed to generate negative pressure to convey cleaned material into and / or through the reaction zone.

[0050] In particular, the pneumatic conveying device can be designed to generate a negative pressure in order to convey cleaned material both into and / or through the treatment chamber and to convey cleaned material into and / or through the reaction zone. In such embodiments, only one pneumatic conveying device needs to be provided, which assumes both the function of the above-described first pneumatic conveying device, which is assigned to the treatment chamber, and the function of the second pneumatic conveying device, which is assigned to the reaction zone. Such a configuration of the filter device with only one pneumatic conveying device, which is assigned to both the treatment chamber and the reaction zone, is particularly suitable when the treatment chamber and / or the reaction zone are designed as a circuit.The pneumatic conveying device will then be designed in particular in such a way that it can be operated either with inert fluid (in order to only effect comminution of cleaned material without oxidation) or with fluid containing an oxidizing agent (in order to support oxidation of cleaned material and, if necessary, also to effect further comminution of cleaned material).

[0051] The reaction zone and / or the treatment chamber can in particular be designed as a circuit in which cleaned material is selectively conveyed in one or more reaction cycles and / or treatment cycles in a circuit. This can be achieved, for example, by conveying cleaned material, after passing through the reaction zone for the first time, if desired after separating the fluid phase, for example by a filter unit, back to an upstream point in the reaction zone and there being again subjected to oxidizing agent-containing fluid by the second pneumatically operated conveying device. In this way, cleaned material can pass through the circuit in the reaction zone several times, with each pass through the circuit resulting in increasingly more extensive oxidation of foreign bodies.Likewise, the treatment chamber can be designed as a circuit in which cleaned material is conveyed in a circuit, optionally in one or more treatment cycles, and is progressively reduced in size. This can be achieved, for example, by conveying cleaned material back to an upstream location in the treatment chamber after passing through the treatment chamber for the first time, if desired after separation of the fluid phase, for example, by a filter unit, and there being again subjected to fluid, particularly an inert fluid, by the first pneumatically operated conveying device.The reaction zone and the treatment chamber can be formed by the same section of the circuit if the circuit is optionally supplied with inert fluid (then this section of the circuit forms the treatment chamber in which only comminution of cleaned material takes place) or with fluid containing an oxidizing agent (then this section of the circuit forms the reaction zone in which cleaned material reacts with oxidizing agent; in addition, comminution of cleaned material can also take place).

[0052] A secondary filter unit can be assigned to both the treatment chamber and the reaction zone, into which cleaned material from the treatment chamber and / or the reaction zone is conveyed. It can even be provided, particularly if the reaction zone is designed as a circuit, that a common secondary filter unit is assigned to the treatment chamber and the reaction zone.In this case, by appropriately controlling shut-off devices in the treatment chamber and the reaction zone, it is possible to ensure that the raw gas chamber of this secondary filter unit is either fluidically connected to the treatment chamber, so that purified material from the treatment chamber is conveyed into the raw gas chamber of the secondary filter unit (where largely inert ambient conditions then prevail), or that the raw gas chamber is fluidically connected to the reaction zone, so that purified material conveyed in the reaction zone reaches the raw gas chamber of the secondary filter unit. From the raw gas chamber of the secondary filter unit, the purified and now oxidized material can then either be discharged into a collection container or be conveyed further in the reaction zone in a circuit where it is again exposed to fluid containing an oxidizing agent.Since the reaction zone is usually subject to ambient conditions containing oxidizing agents, the treatment zone will generally be sealed off from the raw gas zone of the secondary filter unit if the latter is in fluid communication with the reaction zone.

[0053] A first shut-off device can be assigned to the reaction area and / or the treatment chamber, which is designed to shut off the treatment chamber from the raw gas chamber. The first shut-off device can be designed, in particular, to shut off the reaction area and / or the treatment chamber or the specific area of ​​the reaction area and / or the treatment chamber from the raw gas chamber when non-inert ambient conditions prevail in the reaction area and / or the treatment chamber or in a specific area of ​​the reaction area and / or the treatment chamber.The first shut-off device can in particular be controlled in such a way that, if non-inert ambient conditions prevail in the reaction area and / or in the treatment chamber or in a specific area of ​​the reaction area and / or the treatment chamber, it shuts off the reaction area and / or the treatment chamber or the specific area of ​​the reaction area and / or the treatment chamber from the raw gas chamber.

[0054] By closing the first shut-off device, in particular the raw grass chamber can be shut off from the reaction chamber and / or the treatment chamber or a specific region of the reaction chamber and / or the treatment chamber after addition of fluid containing an oxidizing agent, for example compressed gas containing an oxidizing agent, into the reaction chamber and / or the treatment chamber or into the specific region of the reaction chamber and / or the treatment chamber after sufficient comminution of cleaned material, at least until the proportion or concentration of oxidizing agent in the reaction chamber and / or the treatment chamber or in the specific region of the reaction chamber and / or the treatment chamber has fallen sufficiently, in particular is at most as high as a maximum permissible threshold value for the proportion or concentration of oxidizing agent in the raw gas chamber.

[0055] The treatment chamber may contain a lock chamber designed to receive and store material cleaned from the filter surface. In particular, foreign bodies or agglomerates containing foreign bodies that have accumulated on the filter surface are collected and stored in the lock chamber after cleaning, where they are subsequently crushed and then, if necessary, oxidized. In particular, the crushing can already take place in the lock chamber.

[0056] In particular, the first shut-off device can be assigned to the lock chamber and be designed to shut off the treatment chamber or a specific area of ​​the treatment chamber (in particular the lock chamber) from the raw gas chamber after the cleaned material has been received in the lock chamber, in particular if non-inert ambient conditions prevail in the treatment chamber or the specific area of ​​the treatment chamber.

[0057] Material cleaned from the filter surface can be conveyed from the lock chamber to a downstream discharge area (which in particular contains at least part of the reaction zone), for example, by a pneumatic conveying device such as a solids injector. In such cases, oxidizing agent can be supplied to the lock chamber and / or the discharge area by means of the pneumatic conveying device.

[0058] The conveyance of cleaned and shredded material, in particular the conveyance of cleaned and shredded material from the lock chamber to the discharge area, can be carried out in particular by the pneumatic conveying device. In the case of a pneumatic conveying device designed as a solids injector, the solids injector can, for example, be operated with air or an oxygen-containing gas, so that by applying air or oxygen-containing gas to a compressed air connection of the solids injector, the lock chamber is subjected to a negative pressure, and the shredded, cleaned material is drawn from the lock chamber and conveyed through a conveying line of the solids injector to a disposal area, for example, a collection container.The cleaned material removed from the lock chamber may already be fully or partially oxidized by reaction with an oxidizing agent and thus converted into an inert configuration (inerted or passivated). If the material removed from the lock chamber contains foreign bodies that have not yet been inerted (passivated) and / or foreign bodies that have not yet been sufficiently inerted (passivated), further passivation of the cleaned material containing foreign bodies may occur in the conveying line of the solids injector and / or other downstream areas.

[0059] In addition to the first shut-off device, a second shut-off device can also be provided, which is designed to shut off the treatment chamber or a specific region of the treatment chamber (in particular the lock chamber) from downstream regions. In particular, the second shut-off device can be designed to shut off the treatment chamber or the specific region of the treatment chamber from downstream regions when the treatment chamber or the specific region of the treatment chamber is in fluid communication with the raw gas chamber (i.e., when the first shut-off device is open). In some embodiments, the second shut-off device can be designed to shut off the reaction region or a sub-region of the reaction region from downstream regions, such that the reaction region or the sub-region of the reaction region lies between the first shut-off device and the second shut-off device.

[0060] The treatment chamber may contain a collection area designed to receive and hold material cleaned from the filter surface. In particular, foreign bodies or agglomerates containing foreign bodies that have accumulated on the filter surface are collected and held in the collection area after cleaning, where they are subsequently crushed and then, if necessary, oxidized. In particular, the crushing can already take place in the collection area. In particular, the collection area can be formed at the bottom of the raw gas chamber.

[0061] Fluid or gas, especially pressurized gas in the treatment chamber, can be led out of the treatment chamber and returned, in whole or in part, to the treatment chamber. The fluid or gas, especially pressurized gas, can be fed from the treatment chamber to a downstream filter stage.

[0062] The application of fluid or gas, in particular compressed gas, to the treatment chamber and, if necessary, the actuation of the first shut-off device and / or the second shut-off device can be controlled / regulated in such a way that, if a non-inert environment is present in the treatment chamber, the raw gas chamber is sealed off fluid-tight from the treatment chamber.

[0063] With regard to the conditions for an inert environment, the above statements also apply here accordingly. This means that inert conditions prevail in the treatment room, the proportion of oxidizing agent in the treatment room should be so low that no significant oxidation of foreign bodies occurs in the treatment room, or at least this oxidation should occur so slowly that the temperature in the treatment room increases only slightly, in particular by a maximum of 5 °C, preferably by a maximum of 1 °C. In special embodiments, a proportion of 2 volume percent or less of oxygen in the treatment room can be considered inert.

[0064] In particular, a non-inert environment may exist in the treatment room if the concentration of oxidant in the treatment room reaches or exceeds a maximum permissible threshold value for the concentration of oxidant in the raw gas room.

[0065] In all variants of the filter device according to the invention described herein, it is conceivable in a further embodiment, and even advantageous, that material cleaned from the filter surface of the at least one filter element, which material has been completely or at least partially converted into cleaned material containing oxide-containing foreign bodies by reaction of foreign bodies with the oxidizing agent in the reaction region, is returned to the raw gas space for precoating the filter surface of the at least one filter element facing the raw gas side.For this purpose, the filter device can be provided with at least one precoating line via which cleaned material, after the desired extent of conversion of foreign bodies to oxidized foreign bodies, can be removed from the reaction zone, a collecting container for oxidized cleaned material and / or from an area connecting the reaction zone to the collecting container and can be returned to the raw gas chamber of the filter device. The precoating line can have various branches that branch off from the collecting container for oxidized cleaned material, the reaction zone and / or the area between the reaction zone and the collecting container and open into a common precoating line that ultimately leads to the raw gas chamber. It is understood that not all of the branches mentioned are absolutely necessary and it may be sufficient to provide just one of these branches.Each of the aforementioned branches, as well as the common precoating line leading into the raw gas chamber, can be equipped with shut-off devices that allow the branches to be selectively opened or closed, thus adjusting the flow of cleaned material used for precoating in each branch as desired. The precoating of the filter surface of the at least one filter element in the raw gas chamber is then carried out in a conventional manner by blowing the cleaned material from the precoating line 70 into the raw gas chamber, usually at recurring intervals immediately after the filter surface has been cleaned.

[0066] The invention and particular embodiments of the invention are explained in more detail below using exemplary embodiments.

[0067] Figures 1a and 1b show a simplified schematic side view of a filter device according to an embodiment of the present invention.

[0068] Figures 1c, 1d and 1e show, in simplified schematic side views, filter devices according to further embodiments of the present invention.

[0069] Figure 2a shows a simplified schematic side view of a filter device according to an embodiment of the present invention, in which the comminution device comprises a mechanical comminution tool provided in the treatment chamber with the configuration of a rotary valve.

[0070] Figure 2b shows a simplified schematic side view of a filter device according to an embodiment of the present invention, in which the comminution device comprises a mechanical comminution tool provided in the treatment chamber with the configuration of a sieve.

[0071] Figure 2c shows a simplified schematic side view of a filter device according to an embodiment of the present invention, in which the comminution device comprises a mechanical comminution tool with the configuration of a vibrator provided in the treatment chamber.

[0072] Figure 2d shows a simplified schematic side view of a filter device according to an embodiment of the present invention, in which the comminution device comprises a mechanical comminution tool provided in the treatment chamber with the configuration of a mixer.

[0073] Figure 2e shows a simplified schematic side view of a filter device according to an embodiment of the present invention, in which the comminution device comprises a mechanical comminution tool provided in the treatment chamber with the configuration of two counter-rotating rollers.

[0074] Figure 2f shows a simplified schematic side view of a filter device according to an embodiment of the present invention, in which the comminution device comprises a mechanical comminution tool provided in the treatment chamber with the configuration of a conveyor screw.

[0075] Figure 2g shows a simplified schematic side view of a filter device according to embodiments of the present invention, in which the comminution device comprises a mechanical comminution tool provided in the treatment chamber with the configuration of a fluidizing device.

[0076] Figures 3a to 3d show simplified schematic side views of various filter devices according to embodiments of the present invention, in which the comminution device comprises a pneumatic device through which pressurized fluid or pressurized gas is injected into the treatment chamber in such a way that cleaned material located in the treatment chamber is comminuted. It should be noted that in all figures, the same reference numerals refer to the same or similar components. To avoid repetition, each of these components is described only once, generally with reference to the embodiment for which the component is first shown in the figures. For all other embodiments, express reference is made to the description of this embodiment, which applies equally to the respective embodiment unless otherwise stated.

[0077] Figures 1a, 1b, 1c, 1d, and 1e show, in simplified schematic side views, different embodiments of a filter device 10 for dry filtration of a raw gas containing foreign matter. The filter devices 10 shown in Figures 1a, 1b, 1c, 1d, and 1e serve to illustrate embodiments of the filter device according to the invention. The following statements apply to each of the embodiments shown in Figures 1a, 1b, 1c, 1d, and 1e, unless otherwise stated.

[0078] The filter device 10 comprises at least one (primary) filter element (not shown) separating a raw gas side from a clean gas side, having at least one filter surface facing the raw gas side. The (primary) filter element is arranged in a (primary) raw gas chamber, to which a raw gas stream carrying foreign matter can be supplied (also not shown). The raw gas stream can contain, for example, exhaust gas or exhaust air from a process chamber of a system for the additive manufacturing of workpieces, in particular workpieces made of metal such as metals containing titanium or aluminum. From the (primary) raw gas chamber, a fluid phase (in particular gas) of the raw gas stream, after passing through the (primary) filter element, reaches the clean gas side as clean fluid, in particular as clean gas, and is discharged from there.Foreign matter entrained in the raw gas stream accumulates on the filter surface of the (primary) filter element facing the raw gas side and forms a filter cake there, which is cleaned from time to time (for example, by subjecting the respective (primary) filter element to a pressure pulse). It is understood that several (primary) filter elements can be arranged in the raw gas chamber. To simplify the description, reference is made below only to one (primary) filter element, with the proviso that the same applies if several (primary) filter elements are provided in the raw gas chamber. The same applies to all other embodiments shown in Figures 2a to 2g and 3a to 3d. Whenever the terms filter element or raw gas chamber are mentioned below without further suffix, it is understood that this refers to the primary filter element or the primary raw gas chamber of the filter device 10.

[0079] When the filter element is cleaned, the cleaned material falls downwards and is collected by a cleaning arrangement 11 arranged below the filter element. For this purpose, the cleaning arrangement 11 has an upper funnel-shaped collecting area 12 into which the material that has accumulated on the raw gas side of the filter element falls after a filter element has been cleaned (for example, by subjecting the filter element to a pressure pulse). The funnel-shaped collecting area 12 can, for example, form a lower area of ​​the raw gas chamber. The material cleaned from the filter surface passes from the collecting area 12 into a lower area 13 arranged below, which includes a first closure device with a first shut-off element 14 and a second shut-off element 15.The two shut-off devices 14 and 15 form a lock 60 with a lock chamber 60a, which allows cleaned material to be discharged from the raw grass chamber and transported further to downstream areas in the raw gas chamber, in particular to a treatment chamber 19 of a comminution device 16 located downstream of the raw gas chamber, without creating a direct fluid connection between the raw gas chamber and the treatment chamber 19. In embodiments in which exclusively inert conditions prevail in the treatment chamber 19, it may also be sufficient not to provide a first shut-off device between the raw gas chamber and the treatment chamber 19. In particular, instead of the lock realized by the two shut-off devices 14 and 15, a first closure device with only one shut-off device (which is located downstream of the treatment chamber, in particular) can be provided.As already mentioned, this is particularly relevant for embodiments in which the treatment chamber 19, or at least a region of the treatment chamber 19 which directly adjoins the raw gas chamber, is supplied exclusively with inert fluid.

[0080] The shut-off devices 14, 15, like other shut-off devices described here, can be designed as a shut-off valve, a flap, a lock, a disk valve, or a pinch valve. The treatment chamber 19 of the comminution device 16 comprises a comminution line 17, which is connected to the lower region 13 and opens into a downstream secondary filter unit 18, as well as an inlet 38 through which the treatment chamber 19 can be supplied with a gas, in particular an inert gas such as argon or nitrogen. Depending on the design, the comminution device 16 can also include a raw gas chamber 18a of a secondary filter unit 18, which then, together with the comminution line 17, forms the treatment chamber 19, in which material cleaned from the filter surface is comminuted.In the comminution device 16 shown in Figures 1a, 1b, 1c, 1d, and 1e, the material cleaned from the filter surface is generally comminuted with the aid of a pneumatic conveying device, in particular with the aid of a pneumatic conveying device operating as a jet pump or solids injector. For this purpose, the material cleaned from the filter surface is exposed to fluid, in particular gas, preferably an inert gas such as argon or nitrogen, in the comminution line 17 via the inlet 38.Figures 1a, 1b, 1c, 1d and 1e show, by way of example, an arrangement in which the treatment chamber 19 is supplied with inert gas by an injector having the configuration of a jet pump operated at the inlet 38, so that the fluid flow, in particular gas flow, injected into the comminution line 17 via the inlet 38 also creates a suction which assists in conveying cleaned material through the first closure device (in Figures 1a to 1d through the open second shut-off device 15) or second closure device (in Figure 1e through the open fourth shut-off device 21) into the treatment chamber 19.However, it would also be conceivable to inject pressurized fluid or pressurized gas (in particular an inert pressurized fluid or an inert pressurized gas such as argon or nitrogen) into the comminution line 17 through the inlet 38, so that the conveyance of cleaned material through the first or second closure device into the treatment chamber 19 occurs essentially only under the effect of gravity, and the further conveyance of cleaned material and gas in the comminution line 17 occurs essentially by means of the injected pressurized fluid or pressurized gas, for example in the manner of a fluidizing device. In the embodiments according to Figures 1a, 1b, 1c, and 1d, the cleaned material conveyed from the raw gas chamber via the first closure device into the treatment chamber 19 is conveyed via the comminution line 17 into the raw gas chamber 18a of the secondary filter unit 18 and is comminuted during transport.Oxidation of foreign matter does not occur during this process because the treatment chamber 19 is only exposed to an inert fluid, particularly gas. Thus, in a first phase at the beginning of a comminution period, material cleaned from the filter surface is comminuted in an inert environment.

[0081] The embodiment shown in Figure 1e has the special feature compared to the embodiments according to Figures 1a to 1d that cleaned material conveyed from the raw gas chamber via the first closure device reaches the raw gas chamber 18a of the secondary filter unit 18 via a removal line 58, which can be designed as a downpipe, for example, and / or which can be equipped with suitable conveying tools (e.g. a conveyor screw), without any significant comminution. Only after being discharged from the raw gas chamber 18a does the cleaned material reach the treatment chamber 19 of the comminution device 16 via the second closure device. The treatment chamber 19 in this case has a comminution line 17 downstream of the second closure device, which is supplied with fluid, in particular gas, via the inlet 38.The comminution line 17 is designed as a circuit, and its downstream end opens into the raw gas chamber 18a of the secondary filter unit. After the cleaned material has entered the comminution line 17, at least in a first phase at the beginning of a comminution period, the comminution line 17 is supplied with inert fluid via the inlet 38, so that the cleaned material is comminuted in the comminution line 17 in an inert environment.

[0082] In the embodiment according to Figure 1e, cleaned material is conveyed from the raw gas chamber via the first closure device, the line 58, the raw gas chamber 18a of the secondary filter unit 18 and the second closure device into the treatment chamber 19, where it is then crushed during transport through the crushing line 17 and conveyed in a circuit back into the raw gas chamber of the secondary filter unit 18.

[0083] After passing through the comminution line 17, the now-comminuted, cleaned material again enters the raw gas chamber 18a of the secondary filter unit. From there, the comminution material can be conveyed through the second closure device into the comminution line 17, and a further comminution cycle can be performed by supplying the comminution line 17 with inert fluid via the inlet 38, provided that comminutable, cleaned material is still present.

[0084] However, it is also possible, in a subsequent cycle, to supply the comminution line 17 with a fluid containing an oxidizing agent via the inlet 36. The treatment chamber 19 with its comminution line 17 thus becomes the reaction zone 22 with its reaction line 23.

[0085] Inlet 36 can be a separate inlet from inlet 38, which is supplied with oxidant-containing fluid, while inlet 38 is supplied with inert fluid. However, it is simpler to use one and the same inlet, which is optionally supplied with inert fluid as inlet 38 or with oxidant-containing fluid as inlet 36. This design variant allows only a single injector to be operated at the common inlet, which is optionally operated with inert fluid (and then supplies the comminution line 17 with inert fluid at inlet 38) or with oxidant-containing fluid (and then supplies the reaction line 23 with oxidant-containing fluid at inlet 36).Depending on whether the common injector is operated with inert fluid or with oxidant-containing fluid, the common inlet is then the inlet 38 for applying (inert) fluid to the cleaned material for comminution of the cleaned material in the treatment area 19 or the inlet 36 for applying an oxidant-containing fluid to the cleaned material in the reaction area 22. It should be noted at this point that even when the cleaned material is applied with oxidant-containing fluid (via the inlet 36), further comminution of the cleaned material can still take place in the reaction area 22 (in particular in the reaction line 23).

[0086] In the embodiment according to Figure 1e, the treatment area 19 of the comminution device 16 (with comminution line 17) and the reaction area 22 (with reaction line 23) are each provided in the same section of a circuit. The cleaned material is conveyed through the circuit in several cycles, with this section of the circuit forming the comminution line 17 of the treatment area 19 or the reaction line 23 of the reaction area 22 in each of the cycles.In Figure 1e, this dual role is indicated by the fact that the reference numerals 19 and 16 for treatment chamber and comminution device are appended in parentheses after the reference numeral 22 for the reaction area, the reference numeral 17 for the comminution line is appended in parentheses after the reference numeral 23 for the reaction line and the reference numeral 38 for the inlet for supplying the comminution line 17 with (inert) fluid for comminution of cleaned material is appended in parentheses after the reference numeral 36 for the inlet 36 for supplying the reaction line 23 with fluid containing oxidizing agent.

[0087] The secondary filter unit 18 comprises at least one secondary filter element, which separates the raw gas chamber 18a of the secondary filter unit 18 from a clean gas chamber 18b. Gas filtered by the secondary filter unit 18 (essentially the inert gas injected into the treatment chamber 19) is discharged from the clean gas chamber 18b via a line 26. The raw gas chamber 18a of the secondary filter unit 18 has a collecting area in its lower region, which is connected to a downstream reaction area 22 via a second closure device designed as a lock with a third shut-off device 20 and a fourth shut-off device 21.

[0088] Any comminuted, cleaned material located in the collection area of ​​the raw gas chamber 18a of the secondary filter unit 18 is transported via the second closure device with the shut-off devices 20, 21 into the reaction area 22. In the embodiments according to Figures 1a, 1b and 1c, the comminuted, cleaned material in the reaction area 22 is transported from an upstream initial area to a downstream discharge area by blowing in fluid containing an oxidizing agent through an injector operated at the inlet 36, and from there transferred to a discharge filter unit 24. In the embodiments designed with a circuit according to Figures 1d and 1e, the comminuted, cleaned material, if applicable.After previously passing through the aggregate shredding circuit one or more times, the waste material in the reaction zone 22 is returned from the upstream initial zone to the raw gas chamber 18a of the secondary filter purity unit 18 and blown into the raw gas chamber 18a, where it is deposited on the filter surface of the at least one secondary filter element 18 facing the raw gas chamber and / or on the walls or floor of the raw gas chamber 18a. A renewed cleaning cycle on the at least one secondary filter element can ensure that this cleaned material, which has now been at least partially converted into oxidized material by reaction with oxidizing agent in the reaction zone 22, collects in the collection zone of the secondary filter unit 18.From there, the cleaned material can be transported again via the second closure device with the shut-off devices 20, 21 into the reaction zone 22 and, if desired, undergo another reaction cycle by again blowing in fluid containing an oxidizing agent through the inlet 36. This cycle can be repeated several times until sufficient conversion of cleaned material to oxidized cleaned material has taken place. Once the cleaned material collected in the collection area of ​​the secondary filter unit 18 has been sufficiently converted into oxidized material, the cleaned material is transported via the second closure device with the shut-off devices 20, 21 into the initial area of ​​the reaction zone 22 and from there conveyed into a collection container 25 by opening the discharge flap 26. It is understood that during this discharge process, the inlet 36 is not supplied with fluid.

[0089] The reaction zone 22 comprises a reaction line 23, the upstream initial region of which is connected via the second closure device to the collection region of the raw gas chamber 18a of the secondary filter unit 18, and the downstream discharge region of which, in the embodiments according to Figures 1a, 1b, and 1c, opens into a raw gas chamber 24a of the downstream discharge filter unit 24, or, in the embodiments according to Figures 1d and 1e, opens into the raw gas chamber 18a of the secondary filter unit 18, to form a circuit. Located at the upstream initial region of the reaction line 23 is the inlet 36, through which the reaction zone 22 can be supplied with a fluid, in particular a gas, in particular a gas containing an oxidizing agent, such as air or an oxygen-containing gas. Depending on the design, the raw gas chamber 24a of the discharge filter unit 24 orthe raw gas chamber 18a of the secondary filter unit 18.

[0090] In the reaction zone 22 shown in Figures 1a to 1e, the material cleaned from the filter surface and completely or at least partially comminuted in the comminution device 16 is generally conveyed through the reaction zone 22 with the aid of a pneumatic conveying device, in particular with the aid of a pneumatic conveying device designed as a solids injector. Foreign bodies contained in the comminuted, cleaned material are oxidized by reaction with the oxidizing agent. For this purpose, the comminuted, cleaned material is exposed to fluid, in particular gas, preferably a gas containing an oxidizing agent, such as air or oxygen, via the inlet 36.Figures 1a to 1e show, by way of example, an arrangement in which the reaction line 23 is supplied with oxidant-containing fluid, in particular gas, by a solids injector having the configuration of a jet pump operated at the inlet 36, so that the fluid or gas flow injected into the reaction line 23 via the inlet 36 creates a suction which drives or at least supports the conveyance of comminuted, cleaned material through the second closure device into the reaction region 22.It would also be conceivable in principle to inject pressurized fluid or pressurized gas (in particular pressurized fluid containing an oxidizing agent or pressurized gas containing an oxidizing agent, such as air or oxygen-containing gas) into the reaction line 23 through the inlet 36, so that the conveying of comminuted, cleaned material through the second closure device into the reaction line 23 takes place essentially only under the effect of gravity, and the further conveying of comminuted, cleaned material and gas in the reaction line 23 to the discharge filter unit 24 or to the raw gas chamber 18a of the secondary filter unit 18 takes place essentially by means of the injected pressurized fluid or pressurized gas, for example in the manner of a fluidizing device. The comminuted, cleaned material conveyed from the raw gas chamber 18a of the secondary filter unit 18 via the second closure device into the reaction chamber 22 is thereby conveyed via the reaction line 23 into the discharge filter device 24 orto the raw gas chamber 18a of the secondary filter unit 18, wherein foreign bodies contained in the crushed, cleaned material are oxidized during transport.

[0091] Depending on the design, it is conceivable that comminution of material cleaned from the filter surface takes place exclusively, or essentially exclusively, in an inert environment. This would be the case, for example, if the treatment chamber 19 only includes the comminution line 17 and, if applicable, the raw gas chamber 18a of the secondary filter unit 18. Such a design can be provided, for example, if the processes taking place in the comminution line 17 and, if applicable, the raw gas chamber 18a already lead to a configuration of cleaned material in which the agglomerates originally still present have already been practically completely broken down into fragments having the configuration of particles.

[0092] However, embodiments are also conceivable in which comminution also takes place under oxidative ambient conditions, such as those present after the at least partially comminuted, cleaned material has been exposed to a fluid containing an oxidizing agent, in particular in the reaction zone 22, which in the example shown comprises the reaction line 23 and possibly the raw gas space 24a of the discharge filter unit 24 or the raw gas space 18a of the secondary filter unit 18. In such embodiments, in a first phase at the beginning of the comminution period, material cleaned from the filter surface is comminuted in an inert environment, but not yet oxidized (in the comminution line 17 and possiblyin the raw gas chamber 18a of the secondary filter unit 18, which then belong to the treatment chamber 19, but not to the reaction zone 22), and during a subsequent second phase of the comminution period, material cleaned from the filter surface is comminuted and oxidized in an oxidative or reactive environment (in the reaction line 23 and, if applicable, in the raw gas chamber 24a of the discharge filter unit 24 or in the raw gas chamber 18a of the secondary filter unit, which then form the reaction zone 22). In this case, the treatment zone 19 comprises both the comminution line 17 and, if applicable, the raw gas chamber 18a of the secondary filter unit 18, thus also the reaction zone 22, or at least parts of the reaction zone 22.

[0093] In the example shown, the secondary filter unit 18 and, if present, the discharge filter unit 24 have a cuboid-shaped filter housing with a funnel-shaped outlet at the lower end of the filter housing. It is also possible for the filter housings of the filter units 18 and 24 to have a different shape, for example a cylindrical shape. In the embodiments according to Figures 1a, 1b, 1c, a discharge collection area is formed at the funnel-shaped outlet of the filter housing of the discharge filter unit 24, to which, for example, a collecting container 25 is connected. In the embodiments according to Figures 1d and 1e, a discharge collection area is formed at the funnel-shaped outlet of the filter housing of the secondary filter unit 18, to which, for example, the collecting container 25 is connected via a discharge shut-off device 26. The oxide-containing foreign bodies, which are now inert (i.e.inerted or passivated) are collected in this collecting container 25 and can be removed safely, for example by replacing the collecting container 25.

[0094] In the embodiments according to Figures 1a and 1c, the fluid phase still present after passing through the reaction zone 22 is filtered by means of at least one discharge filter element 51 in the discharge filter unit 24 and is discharged via line 27 from the clean gas chamber 24b of the discharge filter unit 24. Each of the discharge filter units 24 can comprise at least one discharge filter element 51, which filters the fluid phase still present after passing through the reaction zone 22, which can then be transported away via line 27.

[0095] In the embodiments according to Figures 1d and 1e, the fluid phase still present after passing through the reaction region 22 is filtered by means of the at least one filter element in the secondary filter unit 18 and led out of the clean gas chamber 18b of the secondary filter unit 18 via the line 27. For the sake of completeness, it should be noted that in the embodiments according to Figures 1d and 1e it is also possible to return the fluid phase filtered in the secondary filter unit 18 from the clean gas chamber 18b via a return line 52 and a conveying device 54, for example a blower or a conveying pump, to the comminution line 17 or the removal line 58, as shown in Figure 1b and described in more detail below. As a rule, it will be noted that the concentration of oxidizing agent in the fluid phase returned from the clean gas chamber 18b via the return line 52 has a value that is sufficient for the comminution line 17 orthe extraction line 58 does not exceed the tolerable threshold.

[0096] In the described embodiment with inert fluid, in particular inert compressed gas, being applied to the inlet 38, the components located in the area highlighted in gray in Figure 1a, namely the cleaning arrangement 11, the comminution line 17, the secondary filter unit 18, and the third shut-off device 20 of the second closure device, are always under inert ambient conditions (inert gas atmosphere). In the area highlighted in gray in Figure 1a upstream of the third shut-off device 20, inert ambient conditions therefore prevail at all times (according to a common definition, the presence of inert ambient conditions can, for example, be defined such that the oxygen concentration is always less than 2 percent by volume based on the amount of substance).In the area shaded in Figure 1a between the third shut-off device 20 and the fourth shut-off device 21, ambient conditions may occur that contain an oxidizing agent at least temporarily. It is therefore possible for comminution to take place under inert ambient conditions throughout the entire comminution period if care is taken to ensure that no further comminution takes place in the areas downstream of the third shut-off device 20, particularly in the reaction area 22. For the sake of completeness, it should be mentioned that ambient conditions containing an oxidizing agent generally prevail in all other areas not shaded.

[0097] It should also be noted that in all other figures, areas where inert ambient conditions prevail at all times are shaded gray, while areas where oxidizing agent-containing ambient conditions prevail at least temporarily are shaded. Areas not shaded in the figures generally have oxidizing agent-containing ambient conditions.

[0098] Figure 1b shows a similar structure to the filter device shown in Figure 1a). In contrast to the embodiment shown in Figure 1a, in the embodiment according to Figure 1b, the comminution device 16 has a pneumatic conveying device in which the fluid (gas) for comminution of material cleaned from the filter surface is circulated in the comminution device 16. For this purpose, the gas filtered in the secondary filter unit 18 is returned from the clean gas chamber 18b to the comminution line 17 via a return line 52 and a conveying device 54, for example a blower or a conveying pump.In this way, the inert gas returned from the clean gas chamber 18b of the secondary filter unit 18 can be redirected past the area where the material cleaned from the filter surface passes from the first closure device into the comminution device 16, and in the downstream area of ​​the circuit line, which forms the comminution line 17, can be used to break up agglomerates in the cleaned material into smaller fragments. With a sufficiently high conveying capacity in the circuit 52, 17, the returned inert gas can even serve as an injector to assist in conveying material cleaned from the filter surface through the first closure device into the comminution device 16. This creates a closed circuit for the inert gas for comminution of material cleaned from the filter surface in the comminution device 16.In the return circuit, in particular in the return line 52, a tank for temporarily storing returned fluid, in particular gas, may also be provided (as shown, for example, in Fig. 3b, see reference numeral 56). The tank may be located upstream or downstream of the conveying device 54.

[0099] Furthermore, in the embodiment according to Figure 1b, a fluid inlet 40 and a fluid outlet 41 are located in a region between the third shut-off device 20 and the fourth shut-off device 21 of the second closure device. A fluid, in particular a gas, e.g. air, a gas containing an oxidizing agent, or even an inert gas, can be injected via the fluid inlet 40 and discharged again through the fluid outlet 41. If an oxidizing agent-containing gas is supplied to the comminuted material when it is located in the region between the shut-off device 20 and the shut-off device 21, a conversion of reactive foreign bodies into inert foreign bodies can be initiated in this region, if desired. The reaction chamber 22 in this case comprises the region between the shut-off device 20 and the shut-off device 21, as well as downstream regions, if desired.In this case, it is recommended to keep the third shut-off device 20 closed at least as long as oxidant-containing gas is supplied via the fluid inlet 40, in order to isolate upstream areas, in particular the treatment chamber 19 and / or the raw gas chamber, from the reaction chamber 22. Alternatively or additionally, the oxidation can be carried out by supplying an oxidant-containing gas into the reaction line 23, as described above.

[0100] The area between the third shut-off device 20 and the fourth shut-off device 21 can also be supplied with an inert fluid, in particular an inert gas, via the fluid inlet 40 in order to flush this area. The inert fluid, in particular an inert gas, serving as the flushing fluid can then preferably be withdrawn via the fluid outlet 41, so that the flushing fluid flows through the area between the third shut-off device 20 and the fourth shut-off device 21, efficiently displacing the fluid, in particular gas, present in this area. The third shut-off device 20 and the fourth shut-off device 21 are preferably kept closed during this flushing process.Such a rinsing process can be carried out, for example, after the discharge of cleaned material from the area between the third shut-off device 20 and the fourth shut-off device 21 into a downstream area, in particular if the cleaned material has already come into contact with an environment containing an oxidizing agent and therefore an environment containing an oxidizing agent temporarily prevails in the area between the third shut-off device 20 and the fourth shut-off device 21.

[0101] In the area between the shut-off device 20 and the shut-off device 21, additional comminution of material cleaned from the filter surface can take place, either additionally or alternatively—with the addition of an inert fluid (gas) through the fluid inlet 40. This area then also belongs to the treatment chamber 19.

[0102] It should be noted that the previously described conceivable configurations for the fluid inlet 40 and the fluid outlet 41 are also possible in the other embodiments according to Figures 1a, 1b, 1c, 1d, 2a to 2e, and 3a to 3d. The above description of the fluid inlet 40 and the fluid outlet 41 applies equally to these embodiments.

[0103] In the embodiments shown in Figures 1c, 1d and 1e, a precoating line 70 is also shown, via which at least partially oxidized, cleaned material from the collection container 25 and / or from an area located between the third and fourth shut-off device 20, 21 of the second closure device can be returned to the raw gas space of the (primary) filter unit of the filter device 10. This material returned to the raw gas space through the precoating line 70 is used there as precoating material, with which the surfaces of the filter elements are coated before and / or during operation of the filter device 10. As a rule, precoating material is used for the precoating of the filter elements of the (primary) filter unit that is sufficiently inertized so that the pyrophoric properties of foreign bodies to be separated from the raw gas can be reduced or eliminated by precoating.An excessive increase in such pyrophoric properties during operation can be slowed down if foreign bodies accumulate on the filter surface by adhering to it. Depending on the degree of conversion of cleaned material to oxidized cleaned material in the reaction zone, material suitable for precoating can be taken from the collection container 25 and / or the discharge zone of the secondary filter unit 18, in particular between the third and fourth shut-off devices 20, 21 of the second closure device. The quantity and composition of the material returned to the raw gas chamber via the precoating line 70 can be adjusted by controlling shut-off devices 72, 74 in the respective branches of the precoating line 70.

[0104] It should also be noted that it is even conceivable for the precoating line 70 to branch off from the reaction line 23, so that the injector acting on the reaction line 23 through the inlet 36 or the pressurized fluid acting on the inlet 36 can be used to return purified material, which is at least partially oxidized, to the raw gas chamber of the primary filter unit. To support this recirculation, the raw gas chamber 18a of the secondary filter unit 18 can also be separated from the reaction line 23 by closing an associated shut-off device 76.

[0105] The aforementioned variants of branching the precoating line 70 from the collecting container 25, branching the precoating line 70 from the area between the third and fourth shut-off devices 20, 21 of the second closure device, and branching the precoating line 70 from the reaction line 23 can be operated jointly or individually. In phases in which precoating of the filter elements of the primary filter unit is not desired, the corresponding branches of the precoating line 70 will be shut down by closing the corresponding shut-off devices 72, 74. In phases in which precoating of the filter elements of the primary filter unit is desired, one or more of the shut-off devices 72, 74 will be fully or partially opened, or the shut-off device 76 will be closed.

[0106] Figures 2a to 2g show various embodiments of the filter device according to the invention, in which the treatment chamber 19 comprises a mechanical comminution tool, in particular a mechanical conveying tool, vibrating tool, mixing tool, and / or screening tool. This mechanical comminution tool can be designed such that, in addition to or as an alternative to the pneumatic device described above, it contributes to the comminution of material cleaned from the filter surface or even takes over this task entirely (without the need for a pneumatic device). The filter devices 10 according to Figures 2a to 2g also serve to illustrate further embodiments of the filter device according to the invention.

[0107] In the filter device 10 shown in Figure 2a, the lower region 13 of the cleaning device 11 has a rotary valve 28 arranged between the first shut-off device 14 and the second shut-off device 15 of the first closure device. The rotary valve 28 is designed such that, in addition to conveying cleaned material, it can also break down agglomerates contained in the cleaned material into smaller fragments, thus serving to crush material cleaned from the filter surface. The region in which the rotary valve 28 is located forms the treatment chamber 19 in this embodiment.The rotary valve 28 can serve as the sole comminution tool (in which case, the treatment chamber 19 comprises only the area in which the rotary valve 28 is located) or in addition to a pneumatic device as described above (in which case, the treatment chamber 19 comprises the area in which the rotary valve 28 is located and the area in which the pneumatic device is located, for example, a downstream comminution line 17). The rotary valve 28 can also be arranged in a different area, for example, in the comminution line 17 described above.

[0108] Furthermore, the filter device 10 comprises a reaction line 23 and a discharge filter 24 with a collecting container 25, for a more detailed description of which reference is made to the preceding explanations.

[0109] Between the first shut-off device 14 and the rotary valve 28 there is also an optional fluid inlet 40 and a likewise optional fluid outlet 41. The explanations given above with reference to Figure 1b apply accordingly to the fluid inlet 40 and the fluid outlet 41. A fluid, in particular a gas, e.g. air, oxygen or inert gas, can be injected via the fluid inlet 40 and discharged again through the fluid outlet 41. Thus, after the cleaned material has passed through the shut-off device 14 and reaches the rotary valve 28, an oxidizing agent-containing fluid, in particular gas, can be supplied. The material cleaned from the filter surface is oxidized by the oxidizing agent-containing fluid, in particular gas, while it is comminuted and transported further through the rotary valve 28. Thus, oxidation and comminution can take place in parallel.Alternatively or additionally, an inert fluid can also be introduced as a flushing fluid via the fluid inlet 40 and the fluid outlet 41 in order to flush the area in which the rotary valve 28 is located after the cleaned material has been discharged. The shut-off device 14 will advantageously always be closed when oxidant-containing fluid is supplied via the inlet 40 or when an oxidant-containing environment prevails in the area in which the rotary valve 28 is located, in order to seal off the treatment chamber 19, in which, in this case, oxidant-containing ambient conditions temporarily prevail, from the raw gas chamber. Thus, inert ambient conditions prevail in the raw gas chamber arranged upstream of the shut-off device 14 at all times when the first shut-off device 14 is closed synchronously with the addition of oxidant-containing fluid through the inlet 40.In the area between the first shut-off device 14 and the second shut-off device 15, or in the area of ​​the rotary valve 28, the ambient conditions can alternate between inert ambient conditions and ambient conditions containing oxidizing agents. Thus, comminution can take place, at least temporarily, in an oxidizing environment.

[0110] After comminution in the rotary valve 28, the comminuted, cleaned material is transported through the open shut-off device 15 via the reaction line 23 to the discharge filter unit 24. Alternatively or additionally, the oxidation of comminuted, cleaned material in the reaction line 23 can take place by supplying an oxidant-containing gas via an oxidant supply device, for example in the manner described above with reference to Figures 1a and 1b by operating a solids injector at the connection 36 of the reaction line 23. In the reaction line 23, the comminuted material cleaned from the filter surface then reacts with the oxidant-containing fluid, in particular gas, to form oxide-containing foreign bodies. The comminuted material cleaned from the filter surface is transported via the reaction line 23 to the discharge filter 24 and from there to the collection container 25.Further comminution of the cleaned material can also take place in the reaction line 23, if desired. Instead of the rotary valve 28, a sieve 29, as shown in Figure 2b, or a vibrator 30, as shown in Figure 2c, a mixer 31, as shown in Figure 2d, an arrangement of counter-rotating rollers 32, as shown in Figure 2e, a conveyor screw 33, as shown in Figure 2f, and / or a fluidizing device 34, as shown in Figure 2g, can be used as mechanical comminution tools. The tools mentioned can also be combined with one another in any desired manner, for example, arranged one after the other. For example, the vibrator 30 can have the configuration of a vibrating sieve.

[0111] Figures 3a to 3d show simplified schematic side views of filter devices 10 according to various embodiments of the present invention. The filter devices 10 according to Figures 3a to 3d serve to illustrate further embodiments of the filter device according to the invention. In the embodiments according to Figures 3a to 3d, the comminution device 16 has a pneumatic device through which pressurized fluid, in particular pressurized gas, is injected into the treatment chamber 19. The pressurized fluid or pressurized gas is injected into the treatment chamber 19 in such a way that cleaned material located in the treatment chamber 19 is comminuted. In particular, the embodiments shown in Figures 3a to 3d also enable material located in the treatment chamber 19 to be swirled up after comminution and to deposit as a precoat layer on the filter surface, if desired.

[0112] In the filter devices 10 according to Figures 3a to 3d, the cleaned material that accumulates during cleaning of the filter element also falls downwards and is collected by a cleaning arrangement 11 arranged below the filter element. For this purpose, the cleaning arrangement 11 has an upper funnel-shaped collecting area 12 that forms a bottom area of ​​the raw gas chamber and into which the material that has accumulated on the raw gas side of the filter element falls after cleaning of the filter element (for example, by subjecting the filter element to a pressure pulse). The material cleaned from the filter surface passes from the collecting area 12 into a lower area 13 arranged below, which comprises a first closure device with a first shut-off element 14 and a second shut-off element 15.The two shut-off devices 14 and 15 form a lock 60 with a lock chamber 60a located between the two shut-off devices 14 and 15, which allows the purified material to be discharged from the raw gas chamber. By closing the first shut-off device 14, the raw gas chamber can be sealed fluid-tight from the lock chamber 60a formed between the first shut-off device 14 and the second shut-off device 15, which forms the treatment chamber 19 or belongs to the treatment chamber 19, when the purified material is located in the treatment chamber 19. This makes it possible, when the first shut-off device 14 is open or closed, to supply the treatment chamber 19 with an inert fluid, in particular an inert gas such as argon or nitrogen, or - when the first shut-off device 14 is closed - to supply the treatment chamber 19 with a fluid containing an oxidizing agent, in particular with air or oxygen-containing gas.When the first shut-off device 14 is open, the lock chamber 60a belonging to the treatment chamber 19 forms an extension of the raw gas chamber. This makes it possible to swirl up material located in the treatment chamber 19 after it has been crushed, possibly even after it has been completely or at least partially oxidized, with the first shut-off device 14 open, so that this swirled-up material deposits as a precoat layer on the filter surfaces of the primary filter unit (precoating of the primary filter unit by at least partially oxidized, cleaned material). As described above, the shut-off devices 14, 15 can also be designed as a flap, a lock, a disc valve, or a pinch valve.

[0113] Here, too, in configurations in which exclusively inert conditions prevail in the treatment chamber 19 (which in this case spatially corresponds to the lock chamber 60a), it may be sufficient not to provide a first shut-off device 14 between the raw gas chamber and the treatment chamber 19 (lock chamber 60a). In particular, instead of the lock 60 realized by the two shut-off devices 14 and 15, a first closure device with only one shut-off device (which is in particular located downstream of the treatment chamber 19 and therefore functions as the second shut-off device 15) can be provided. The lock chamber 60a belonging to the treatment chamber 19 then forms an extension of the raw gas chamber. As already mentioned, this is particularly relevant for embodiments in which the treatment chamber 19, or at least a region of the treatment chamber 19 which directly adjoins the raw gas chamber (lock chamber 60a), is supplied exclusively with inert fluid.In contrast to the embodiments shown in Figures 1a and 1b, the treatment chamber 19 of the comminution device 16 does not have its own comminution line 17. Instead, the treatment chamber 19 is formed by the lock chamber 60a formed between the first shut-off device 4 and the second shut-off device 15. The raw gas chamber can also belong to the treatment chamber 19, as in the embodiments shown in Figures 3c and 3d, for example. In some embodiments, the treatment chamber 19 can also comprise further downstream regions that also belong to the reaction chamber 22. When the lock chamber 60a is supplied with inert fluid, the upper shut-off device 14 can even remain open, so that in this case too, the treatment chamber 19 extends into the raw gas chamber as long as the first shut-off device 14 is open.

[0114] In the embodiments according to Figures 3a and 3b, a fluid inlet 40 and a fluid outlet 41 each open into the area between the first shut-off device 14 and the second shut-off device 15 of the first closure device, which forms the lock chamber 60a and belongs to the treatment chamber 19. A fluid, in particular a gas such as an inert gas (argon, nitrogen, other noble gases), but also air or a gas containing an oxidizing agent, can be injected into the treatment chamber 19 via the fluid inlet 40. Fluid, in particular gas, can be discharged from the treatment chamber 19 again through the fluid outlet 41. The fluid or gas discharged from the lock chamber can be passed through a secondary filter unit 18 in order to retain any foreign bodies entrained therewith, as shown, for example, in Figures 3a, 3b and 3c.Figure 3d shows a variant in which the fluid or gas discharged from the lock chamber 60a is guided over the discharge filter unit 24 to retain any entrained foreign matter. For further details, reference is expressly made to the preceding description of the fluid inlet 40 and the fluid outlet 41, which applies equally to the embodiments shown in Figures 3a to 3d.

[0115] Cleaned material located in the lock chamber 60a between the first shut-off device 14 and the second shut-off device 15, which has a high proportion of agglomerates consisting of a large number of particles adhering to one another or bonded together, can be exposed to a pressurized inert fluid, in particular an inert gas, via the fluid inlet 40 according to the embodiments shown in Figures 3a and 3b. In this way, efficient comminution (i.e., breaking down into smaller fragments) of the material cleaned from the filter surface can already take place in this lock chamber 60a.At sufficiently high pressure, even a complete, or at least largely complete, comminution of agglomerates can be achieved, in which the existing agglomerates are practically completely broken down into fragments which only, or at least largely only, consist of foreign body particles and / or filtration aid particles which can no longer be easily broken down into even smaller fragments.

[0116] If the previously described pressurization of the lock chamber with pressurized fluid, in particular compressed gas, occurs with the first shut-off device 14 closed (and normally also the second shut-off device 15 closed) in order to build up sufficient pressure to crush agglomerates in the lock chamber, the first shut-off device 14 can be opened after comminution has taken place, and the lock chamber can then be subjected to one or more pressure pulses via the fluid inlet 40. In response to such pressure pulses, the crushed, cleaned material is swirled up and also enters the raw gas chamber. There, it can then redeposit as a new precoat layer on the filter surfaces of the primary filter unit.Since the size of the agglomerates originally formed on the filter surface has become much smaller as a result of the comminution, the comminutioned, cleaned material is well suited as new precoat material, particularly if this material has been at least partially converted into oxidized material. Instead of one or more pressure pulses with a short duration (in particular less than 10 s or even less than 1 s), the cleaned material can also be dispersed for precoating by blowing in a fluid, in particular gas, over one or more longer periods of time. For example, the fluid or gas can be blown in for a period of up to 1 minute, in particular over a period of up to 30 seconds. The blowing in can be carried out once or several times in succession, if desired. Generally, when fluid is blown in over a longer period of time (i.e.longer than 10 seconds) operate with a lower pressure of the injected fluid than when subjected to pressure pulses. Once sufficient precoating of the filter surface(s) has been achieved, the first shut-off device 14 is closed again. As soon as the raw gas chamber is fluid-tightly sealed off from the lock chamber 60a, the comminuted, cleaned material still located in the lock chamber 60a can be conveyed from the lock chamber 60a into downstream areas by opening the second shut-off device 15, in particular into the reaction region 22, which has a reaction line 23 as described above with reference to the embodiment shown in Figures 1a and 1b.A solid injector operated at a connection 36 of the reaction line 23 can be used to convey comminuted, cleaned material from the lock chamber 60a into the reaction area 22, as also described above with reference to the embodiment shown in Figures 1a and 1b, to which reference is hereby expressly made.

[0117] It is also conceivable to carry out the previously described application of inert pressurized fluid, in particular inert pressurized gas, to the lock chamber 60a for comminution of cleaned material with the first shut-off device 14 open. In this case, the application of pressurized fluid, in particular pressurized gas, will lead both to comminution of agglomerates and to turbulence, through which both already crushed and not yet crushed or only slightly crushed agglomerates can enter the raw gas chamber and deposit as a precoat layer on the filter surface. Such a more irregular precoat layer may be entirely sufficient in some cases. The advantage of this configuration is that comminution and precoating can take place in a single step. The application of pressurized fluid can take place in the same way as described above.

[0118] When opening the second shut-off device 15 for further conveying comminuted, cleaned material into the reaction zone 22, the first shut-off device 14 should be closed in order to avoid a direct fluid connection between the reaction zone 22, in which ambient conditions containing oxidizing agents normally prevail, and the raw gas space, in which inert ambient conditions must be maintained at all times.

[0119] When the first shut-off device 14 is closed, for a faster and / or more effective conversion of reactive foreign bodies into oxidized and therefore less reactive foreign bodies, the lock chamber 60a can also be exposed to a fluid containing an oxidizing agent, such as air or an oxygen-containing gas, thus initiating the controlled spontaneous oxidation of reactive foreign bodies while the comminuted, cleaned material is still in the lock chamber 60a. This can occur simultaneously with or slightly before the opening of the second shut-off device 15. In such embodiments, the lock chamber 60a belongs not only to the treatment chamber 19, but also temporarily to the reaction area 22.

[0120] Depending on whether the lock chamber 60a is exposed to an inert fluid or a fluid containing an oxidizing agent, either inert ambient conditions or ambient conditions containing an oxidizing agent prevail in the lock chamber 60a and thus also in the treatment chamber 19. This is indicated in Figures 3a to 3e by the hatched background of the lock chamber 60a located between the first shut-off device 14 and the second shut-off device 15.

[0121] Figure 3b shows a similar structure to the filter device shown in Figure 3a. In contrast to the embodiment shown in Figure 3a, in the embodiment shown in Figure 3a, the fluid (gas) for comminuting material cleaned from the filter surface is circulated in the comminution device 16. For this purpose, the gas filtered in the secondary filter unit 18 is returned from the clean gas chamber 18b to the fluid inlet 40 via a return line 52, a conveying device 54, for example a blower or a conveying pump, and a tank 56. The tank 56 is optional and could also be omitted, as can be seen in the embodiment shown in Figure 1b.

[0122] In the embodiments shown in Figures 3c and 3d, a fluid inlet 42 opens directly into the raw gas chamber. Analogous to the fluid inlet 40 in the embodiments according to Figures 3a and 3b, a fluid, in particular a gas such as an inert gas (argon, nitrogen, other noble gases), can be injected via the fluid inlet 42, but into the raw gas chamber instead of the lock chamber 60a formed between the first shut-off device 14 and the second shut-off device 15. The fluid inlet 42 has the configuration of an injector lance directed from above toward the collection area 12.In the embodiments according to Figures 3c and 3d, cleaned material located in the collection area 12 formed at the bottom of the raw gas chamber, which has a high proportion of agglomerates consisting of a large number of adhering or interconnected particles, is exposed to a pressurized inert fluid, in particular an inert gas (for example, argon or another noble gas; in this variant, it is recommended to inject the same inert gas used to create a protective gas atmosphere in the raw gas chamber) via the fluid inlet 42. In this way, efficient comminution (i.e., breaking down into smaller fragments) of material cleaned from the filter surface can take place in the raw gas chamber.Here, too, with sufficiently high pressure, even complete, or at least largely complete, comminution of agglomerates can be achieved. The existing agglomerates are practically completely broken down into fragments that now consist only, or at least largely only, of foreign body particles and / or filtration aid particles, which can no longer be easily broken down into even smaller fragments. Since the size of the agglomerates originally formed on the filter surface has become much smaller as a result of comminution, the crushed, cleaned material is well suited as a new precoat material.

[0123] The embodiments shown in Figures 3c and 3d are similar to the above-described variant of the embodiments according to Figures 3a and 3b, in which the pressurization of the lock chamber 60a with inert pressurized fluid, in particular inert pressurized gas, for comminution of cleaned material is carried out with the first shut-off device 14 open. Also in the case of the embodiments according to Figures 3c and 3d, the pressurization of pressurized fluid, in particular pressurized gas, will lead both to the comminution of agglomerates and to the swirling up of cleaned material in the raw gas chamber, as a result of which both already crushed and not yet crushed or only slightly crushed agglomerates accumulate on the filter surface as a precoat layer. The result is a more irregular precoat layer because even incompletely crushed agglomerates may be incorporated into the precoat layer.However, the direct injection of inert pressurized fluid, particularly inert pressurized gas, into the raw gas chamber via the fluid inlet 42 also offers the advantage that comminution and precoating can be performed in a single step. Once sufficient precoating of the filter surface has been achieved, the first shut-off device 14 is opened to discharge any remaining comminuted, cleaned material from the raw gas chamber into the lock chamber 60a formed between the first shut-off device 14 and the second shut-off device 15, and is then closed again.As soon as the raw gas chamber is fluid-tightly sealed from the lock chamber 60a, the comminuted, purified material located in the lock chamber 60a can be conveyed from the lock chamber 60a into downstream areas by opening the second shut-off device 15, in particular into the reaction zone 22, which has a reaction line 23, as described above with reference to the embodiment shown in Figures 1a and 1b. A solids injector operated at a connection 36 of the reaction line 23 can be used to convey comminuted, purified material from the lock chamber 60a into the reaction zone 22, as also described above with reference to the embodiments shown in Figures 1a, 1b, 3a, 3b, to which express reference is hereby made.

[0124] It is also conceivable in the embodiments according to Figures 3a, 3b, 3c, or 3d to provide a precoating line 70 that branches off from the collection container 25, from a discharge lock provided between the discharge filter unit 24 and the collection container 25, and / or from the reaction line 23 and opens into the raw gas chamber of the primary filter unit, as described with reference to Figures 1c and 1d. Express reference is made to the relevant explanations regarding Figures 1c and 1d.

[0125] Finally, it should be mentioned that even in the case of the embodiments shown in Figures 3a to 3d, the pneumatic device shown in the figures and described above for comminuting material cleaned from the filter surface by means of injection of pressurized fluid, in particular pressurized gas, can be combined with one or more of the mechanical comminution devices shown in Figures 2a to 2g, for example by providing one or more of these mechanical comminution devices in the lock chamber formed between the first shut-off device 14 and the second shut-off device 15.

Claims

Claims 1. A filter device (10) for cleaning raw gas containing foreign bodies, comprising: at least one filter element with at least one filter surface separating a raw gas side from a clean gas side in a raw gas chamber to which a raw gas stream containing foreign bodies can be fed; a cleaning device for cleaning material from the filter surface; an oxidizing agent supply device designed to supply an oxidizing agent to a reaction region (22) such that foreign bodies contained in material cleaned from the filter surface and / or in the raw gas stream react with the oxidizing agent in the reaction region (22) to form oxide-containing foreign bodies;wherein a comminution device (16) is provided which is designed to comminute material cleaned from the filter surface in a treatment chamber (19) such that foreign bodies contained in the comminuted, cleaned material are oxidized by supplying oxidizing agent to the reaction region (22); 2. Filter device (10) according to claim 1, wherein the comminution device (16) is designed such that material cleaned from the filter surface is comminuted in the treatment chamber (19) before foreign bodies contained in the cleaned material are oxidized by supplying oxidizing agent to the reaction region (22).

3. Filter device (10) according to claim 2, wherein the comminution device (16) is designed such that the comminution of filter surface cleaned material takes place at least in a first phase at the beginning of a comminution period in an inert environment.

4. Filter device (10) according to claim 3, wherein the comminution device (16) is designed such that the comminution of material cleaned from the filter surface is at least 50% in relation to the comminution period takes place in an inert environment, in particular at least 75%, preferably at least 90%, particularly preferably at least 98%.

5. Filter device (10) according to claim 3 or 4, wherein the comminution device (16) is designed such that the comminution takes place in an inert environment during the entire comminution period.

6. Filter device (10) according to claim 3 or 4, wherein the comminution device (16) is designed such that the comminution takes place in an oxidizing environment in a second phase following the first phase.

7. Filter device (10) according to one of claims 1 to 6, wherein the comminution device (16) is designed such that the cleaned material is comminuted within the comminution period to such an extent that after the end of the comminution period, individual bodies are no longer visible to the human eye.

8. Filter device (10) according to claim 7, wherein the comminution device (16) is designed such that after the end of the comminution period, the cleaned material has an average body size of at most 0.3 mm.

9. Filter device (10) according to claim 7 or 8, wherein the comminution device (16) is designed such that after the end of the comminution period at least 50 percent by weight of the cleaned material has a body size of 1 mm or less, in particular a body size of 0.5 mm or less, in particular a body size of 0.1 mm or less and preferably a body size of 0.05 mm or less.

10. Filter device (10) according to claim 7 or 8, wherein the comminution device (16) is designed such that after the end of the comminution period at least 75 percent by weight of the cleaned material has a body size of 1 mm or less, in particular a body size of 0.5 mm or less, in particular a body size of 0.1 mm or less and preferably a body size of 0.05 mm or less.

11. Filter device (10) according to claim 7 or 8, wherein the comminution device (16) is designed such that after the end of the comminution time- at least 90 percent by weight of the cleaned material has a body size of 1 mm or less, in particular a body size of 0.5 mm or less, in particular a body size of 0.1 mm or less and preferably a body size of 0.05 mm or less.

12. The filter device (10) according to one of claims 1 to 11, wherein the comminution device (16) is configured such that comminution is performed with the aid of a pneumatic device.

13. The filter device (10) according to claim 12, wherein the pneumatic device comprises at least one pressurized fluid line (40; 42) opening into the treatment chamber (19), wherein, at least during the first phase, an inert pressurized fluid is injected into the treatment chamber (19) through the pressurized fluid line (40; 42) in order to comminute material cleaned from the filter surface.

14. Filter device (10) according to claim 13, wherein the comminution device (16) is designed such that the treatment chamber (19) is in fluid communication with the raw gas chamber during the first phase.

15. Filter device (10) according to claim 14, wherein the comminution device (16) is designed such that the inert pressure fluid is injected into the treatment chamber (19) in such a way that material located in the treatment chamber (19) is whirled up and deposits as a precoat layer on the filter surface.

16. The filter device (10) according to any one of claims 13 to 15, wherein the filter device (10) is configured such that, during a second phase, an oxidizing agent-containing gas is injected into the treatment chamber (19).

17. The filter device (10) according to claim 16, wherein the filter device (10) is configured such that, during the second phase, the raw gas chamber is sealed fluid-tight from the treatment chamber (19).

18. Filter device (10) according to claim 16 or 17, wherein the filter device (10) is designed such that during a third phase following the second phase, the treatment chamber (19) is in fluid communication with the raw gas chamber and preferably inert pressurized fluid is injected into the treatment chamber (19) in such a way that material located in the treatment chamber (19) is whirled up and deposits as a precoat layer on the filter surface.

19. Filter device (10) according to one of claims 1 to 18, wherein in the treatment chamber (19) a mechanical comminution tool (28; 29, 30; 31; 32; 33; 34) is provided, which exerts a conveying, mixing and / or shaking movement on the cleaned material and is located in the treatment room.

20. Filter device (10) according to claim 19, wherein the mechanical comminution tool (28; 29, 30; 31; 32; 33; 34) comprises at least one of the following mechanical comminution tools: screw (33); rotary valve (28); counter-rotating rollers (32); mixer (31); fluidizing device (34); shaker (30); sieve (29).

21. Filter device (10) according to one of claims 1 to 20, wherein the reaction region (22) comprises regions located downstream of the treatment chamber (19), in particular downstream lines, conveying devices and / or containers.

22. Filter device (10) according to one of claims 1 to 21, wherein the reaction region (22) is arranged downstream of the treatment chamber (19), so that cleaned material, after at least partially being crushed in the treatment chamber (19), is conveyed into the reaction region (22) and is there exposed to fluid containing an oxidizing agent.

23. Filter device (10) according to one of claims 1 to 22, which has at least one pneumatic conveying device, which is designed in particular as a solid injector or jet pump.

24. Filter device (10) according to claim 23, wherein a first pneumatic conveying device is assigned to the treatment chamber (19), wherein the first pneumatic conveying device is designed in particular as a solid injector or jet pump.

25. Filter device (10) according to claim 23 or 24, wherein the first pneumatic conveying device (38) is designed such that the treatment chamber (19) is subjected to negative pressure by the first pneumatic conveying device in order to withdraw cleaned material from the treatment chamber (19), wherein the first pneumatic conveying device is designed in particular such that the application of negative pressure to the treatment chamber (19) takes place downstream of the comminution of cleaned material.

26. Filter device (10) according to claim 22 or 23, wherein the first pneumatic conveying device is designed to generate a negative pressure in order to convey cleaned material into and / or through the treatment chamber (19).

27. Filter device (10) according to one of claims 23 to 26, wherein the first pneumatic conveying device is designed such that it is supplied with inert fluid.

28. Filter device (10) according to one of claims 22 to 27, wherein a second pneumatically operating conveying device is assigned to the reaction region (22), which is in particular supplied with fluid containing an oxidizing agent, wherein the second pneumatic conveying device is designed in particular as a solids injector or jet pump.

29. Filter device (10) according to claim 28, wherein the second pneumatically operating conveying device is designed such that the treatment chamber (19) is subjected to negative pressure by the second pneumatically operating conveying device in order to convey cleaned material from the treatment chamber (19) into the reaction region (22) and / or wherein the second pneumatically operating conveying device is designed to generate a negative pressure in order to convey cleaned material into and / or through the reaction region (22).

30. Filter device according to one of claims 22 to 29, wherein the pneumatic conveying device is designed to generate a negative pressure in order to convey cleaned material both into and / or through the treatment chamber (19) and to convey cleaned material into and / or through the reaction region (22).

31. Filter device (10) according to one of claims 1 to 30, wherein the reaction region (22) and / or the treatment chamber (19) is designed as a circuit in which cleaned material is selectively conveyed in one or more reaction cycles in a circuit, wherein in particular the circuit has at least one secondary filter unit.

32. Filter device (10) according to one of claims 1 to 31, wherein the treatment chamber (19) and / or the reaction region (22) is assigned a secondary filter unit (18, 24) into which cleaned material from the treatment chamber (19) and / or the reaction region (22) is conveyed.

33. Filter device (10) according to one of claims 1 to 32, wherein the treatment chamber (19) is assigned a first shut-off element (14) which is designed to shut off the treatment chamber (19) from the raw gas chamber; wherein the first shut-off element (14) is designed in particular to shut off the treatment chamber (19) or regions of the treatment chamber (19) from the raw gas chamber when non-inert ambient conditions prevail there.

34. Filter device (10) according to one of claims 1 to 33, wherein the treatment chamber (19) contains a lock chamber (60a) which is designed to receive and hold material cleaned from the filter surface.

35. Filter device (10) according to claim 34, wherein the lock chamber (60a) is assigned a downstream discharge area into which material cleaned from the filter surface is conveyed, wherein oxidizing agent can be supplied to the lock chamber (60a) and / or the discharge area.

36. Filter device (10) according to one of claims 33 to 35, wherein a second shut-off element (21; 15) is provided which is designed to shut off the treatment chamber (19) or regions of the treatment chamber (19) from downstream regions.

37. Filter device (10) according to one of claims 1 to 36, wherein the treatment chamber (19) contains a collecting area (12) which is designed to receive and / or Holding material cleaned from the filter surface, wherein the collecting area (12) is formed on a bottom of the raw gas space.

38. Filter device (10) according to one of claims 1 to 37, wherein the filter device (10) is designed such that fluid, in particular gas, is returned from the treatment chamber (19) in whole or in part to the treatment chamber (19).

39. Filter device (10) according to one of claims 1 to 38, further comprising a control / regulation for controlling / regulating the admission of fluid, in particular gas, to the treatment chamber (19) and optionally an actuation of the first shut-off element (14) and / or the second shut-off element (21; 15) such that, in the presence of a non-inert environment in the treatment chamber (19), the raw gas chamber is shut off fluid-tight from the treatment chamber (19).

40. Filter device (10) according to one of claims 1 to 39, which is designed such that material cleaned from the filter surface, which has been completely or at least partially converted into cleaned material containing oxide-containing foreign bodies by reaction of foreign bodies with the oxidizing agent in the reaction region (22), is returned to the raw gas space for precoating the filter surface of the at least one filter element facing the raw gas side.

41. Filter device (10) according to claim 40, wherein the filter device (10) has at least one precoating line (70) which branches off from a collecting container (25) for oxidized, cleaned material, the reaction region (22) and / or a region located between the reaction region (22) and the collecting container (25) and opens into the raw gas space.

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