Method for dry-filtering a fores-containing gas flow and filter device for cleaning a fores-

Abstract

The invention relates to a method and a filter device for dry-filtering a gas stream carrying foreign matters, in particular in a filter device for cleaning off gases produced in additive manufacturing technology, comprising: introducing a raw material gas stream (44) containing foreign matters into a raw material gas chamber (15) of a filter unit (12), the filter unit (12) has at least one filter surface separating a raw material gas side from a clean gas side; an oxidizing agent is fed into a reaction zone (24) located on the raw material gas side downstream of the filter surface such that foreign matters contained in substances cleared from the filter surface and / or in the raw material gas flow react with the oxidizing agent within the reaction zone (24) to form oxide-containing foreign matters.

Description

[0001] This application is a divisional application of the application with the filing date of January 14, 2021, application number 202180019471.5, and invention title "Method for Dry-Filtering a Gas Stream Carrying Foreign Matter and Filter Device for Cleaning a Feed Gas Carrying Foreign Matter". Technical Field

[0002] The present invention relates to a method for dry-filtering a gas stream carrying foreign matter and to a filter device for cleaning a feed gas carrying foreign matter. Background Art

[0003] When purifying a gas carrying highly flammable foreign matter or foreign substances, such as in a system for additive manufacturing of workpieces made of metal (for example, in laser sintering of workpieces made of titanium alloy or aluminum alloy), there is a risk of an uncontrolled fire in the exhaust gas. This risk is particularly high when such highly flammable foreign matter deposits on the filter surface and accumulates during the process. Similar to the design shown in WO 2012 / 032003 A1, attempts have been made to address these risks by pre-coating the filter surface with an inerting filtration aid (such as CaCO3) or adding such an aid to the feed gas to be purified. Summary of the Invention

[0004] The object of the present invention is to prevent or suppress the combustion of the feed gas by means of a dry filter when filtering a feed gas containing flammable foreign matter, such as especially when filtering the exhaust gas generated in additive manufacturing technology.

[0005] According to the present invention, in a method for dry-filtering a gas stream carrying foreign matter, which method is particularly used in a filter device for removing exhaust air or exhaust gas generated in additive manufacturing technology, a feed gas stream containing foreign matter is supplied to the feed gas space of a filter unit, which filter unit has at least one filter surface separating the feed gas side from the clean gas side. Furthermore, an oxidant is supplied to a reaction zone on the feed gas side of the filter surface downstream of the filter surface. The oxidant is supplied such that the foreign matter contained in the substances removed from the filter surface and / or the foreign matter contained in the feed gas stream reacts with the oxidant in the reaction zone to form foreign matter containing oxides.

[0006] The present invention proposes a method and provides a filter device with a corresponding design, in which, in particular, the spontaneous oxidation of reactive or even highly reactive foreign substances in the exhaust gas (such as metal-containing particles in the exhaust gas from an additive manufacturing device such as a laser sintering device) is caused. The high reactivity of such foreign substances with oxidants such as oxygen or air - which is actually the reason for the problem of dry filtration of such exhaust gas - is thus particularly used to trigger the spontaneous reaction of the foreign substances with the oxidant. Surprisingly, the spontaneous reaction can be particularly initiated and its progress kept well under control by appropriately controlling the supply and / or discharge of the oxidant and, if necessary, also by other measures, such that an uncontrolled reaction of the foreign substances with the oxidant can be avoided. By using the method proposed herein, the heat generated during the reaction can be well dissipated, such that there is no need to worry about uncontrolled fires or explosions.

[0007] The basic idea of the present invention is not to render the flammable foreign substances contained in the feed gas inert, but rather to render them harmless by purposefully initiating and performing a controlled transfer (i.e., by means of a chemical reaction) of these combustible foreign substances into an oxidized configuration. In the oxidized configuration, these foreign substances are generally of low reactivity or inert and no longer combustible, such that no special precautions are required for the further treatment of these oxidized foreign substances.

[0008] However, care must be taken to ensure that the spontaneous oxidation reaction proceeds in a controlled manner. This can be achieved by appropriately supplying an oxidant to a predetermined reaction zone containing the substances removed from the filter surface and thus containing foreign substances and / or further by measures to remove oxides from the reaction zone. It has been found that if the oxidant is not only supplied to the reaction zone but also flows through the reaction zone, the progress of the often strongly exothermic oxidation reaction can be well controlled. The oxidant is then supplied to the reaction zone at a first location or in a first region (the inlet) and flows through the reaction zone until it leaves the reaction zone again at another location or in another region (the outlet), in any case provided that it is not consumed by reaction with the substances containing foreign substances while flowing through the reaction zone. In this way, in particular, an excess of oxidant can be provided in the reaction zone, since a desired reaction for forming foreign substances containing oxides needs to be spontaneously initiated or the desired reaction maintained at a controlled level. The flow of oxidant through the reaction zone allows for precise control of the progress of the oxidation reaction. Once the oxidant flow is started, the oxidation reaction proceeds spontaneously but in a controlled manner and can be well controlled by adjusting the intensity of the oxidant flow and also by adjusting the composition of the oxidant flow.

[0009] In the case of spontaneous oxidation, the desired reaction to form foreign matter containing oxides occurs substantially without the supply of activation energy by the energy supply from an energy source such as an ignition source or a heat source. Oxidation may have been initiated by the contact of an oxidant with substances that are present in or enter the reaction zone and that have detached from the filter surface during the cleaning process.

[0010] The oxidant can be air or an oxygen-containing gas. Other substances such as inert gases like nitrogen or noble gases can be mixed with the oxidant to form an oxidant stream. For example, air can be used to form an oxidant stream, or a lean oxygen mixture with an oxygen content of 5 - 21 vol%. An oxidant or an oxidant concentration in the oxidant stream is selected to be high enough to allow the spontaneous reaction of the foreign matter-containing substances in the reaction zone to form foreign matter containing oxides.

[0011] The wording "on the raw gas side of the filter surface downstream of the filter surface" is intended to express that the reaction zone is downstream of the raw gas space with respect to the transport of foreign matter that has accumulated on the filter surface and has been removed from the filter surface during the cleaning cycle (e.g., by applying a pressure pulse to the filter surface). Thus, the substances removed from the filter surface are transported to the reaction zone. In particular, the reaction zone is separated from the raw gas space, in particular from the downstream of the raw gas space. If the oxidant is first supplied downstream of the reaction zone but not to the raw gas space or the regions upstream of the raw gas space (i.e., these regions remain free of oxidant), the oxidation treatment of the removed foreign matter-containing substances does not affect the process environment of the actual filtration of the raw gas by the introduction of the oxidant. In particular, this filtration process or the working process that generates the exhaust gas to be filtered can occur under mostly inert conditions and is not disturbed by the oxidation treatment. When the oxidant is supplied, the maintenance of the inert environment in the raw gas space can be additionally ensured by temporarily separating the reaction zone from the raw gas space, in particular by separating the raw gas space in an airtight manner.

[0012] As explained, it is advantageous to actively remove the unconsumed oxidant from the reaction zone when the substances removed from the filter surface react with the oxidant. In this way, an appropriate excess of oxidant can be provided and thus a controlled course of the oxidation reaction can be achieved. This means that the aim is not necessarily to remove only the reaction products formed during the reaction, in particular the foreign matter containing oxides and, where applicable, the untransformed or incompletely transformed removed substances, from the reaction zone after more or less complete chemical conversion has occurred. Instead, during the course of the oxidation reaction, any unconsumed oxidant in the reaction should be removed, usually to the same extent as new oxidant is added. In this way, the oxidation reaction in the reaction zone can proceed substantially under constant environmental conditions, in particular at a constant concentration of oxidant.

[0013] Once a sufficient proportion of the foreign-matter-containing substance has been converted into oxide-containing foreign matter in the reaction zone or at least in a partial zone belonging to the reaction zone, and / or a sufficient amount of the foreign-matter-containing substance has been removed from the reaction zone or at least from a partial zone belonging to the reaction zone, it can be considered that the oxidation reaction has stopped at least in a partial zone belonging to the reaction zone. In this case, the supply of additional oxidant to the reaction zone or to a partial zone belonging to the reaction zone is stopped. Then, the reaction product or reaction residue is usually removed from the reaction zone or from a partial zone belonging to the reaction zone. It is generally considered that substantially all of the reaction product or reaction residue is removed from the reaction zone or from a partial zone belonging to the reaction zone. It is also sufficient to remove only a part of the reaction product or reaction residue. The reaction product or reaction residue remaining in the reaction zone or in a partial zone belonging to the reaction zone can subsequently be additionally oxidized together with the fresh substance entering the reaction zone or a partial zone belonging to the reaction zone, if necessary, after adding additional oxidant. After the oxidant remaining in the reaction zone or in a partial zone belonging to the reaction zone after the reaction has stopped or has occurred has been removed, the reaction zone or a partial zone belonging to the reaction zone can be placed in fluid communication with the raw gas space without the risk of oxidant entering the raw gas space.

[0014] In particular, the oxidant can be sucked out or withdrawn from the reaction zone or from a partial zone belonging to the reaction zone. For this purpose, the reaction zone can be subjected to a negative pressure in order to suck out the oxidant still present in the reaction zone. It is also possible to suck out the reaction product and / or other reaction residues from the reaction zone by applying a negative pressure to the reaction zone. The application of a negative pressure to the reaction zone can occur during and / or after the reaction of the substance removed from the filter surface with the oxidant.

[0015] An oxidant inlet can be provided for supplying the oxidant to the reaction zone or to a partial zone belonging to the reaction zone. An oxidant outlet can be provided for removing the oxidant from the reaction zone or from a partial zone belonging to the reaction zone. In the simplest case, the oxidant inlet can also be used as the oxidant outlet at the same time. However, it is generally provided that the oxidant outlet is different from the oxidant inlet, in particular such that an oxidant stream is formed between the oxidant inlet and the oxidant outlet, which oxidant stream crosses the reaction zone or a partial zone belonging to the reaction zone as large a part as possible.

[0016] The oxidant outlet can be a specially provided outlet for discharging gases, in particular the oxidant. However, the unconsumed oxidant is discharged through the oxidant outlet together with the oxide-containing foreign matter formed during the reaction and, if applicable, the unreacted removed substance. In this case, the oxidant outlet is designed to discharge both gaseous substances and solid-containing substances.

[0017] It is conceivable, but not absolutely necessary, that all reactions of the substance containing foreign matter with the oxidant occur in the upstream region of the oxidant outlet. Except that the oxidant stream may be recycled to the oxidant inlet, the oxidant discharged through the oxidant outlet or the mixture of the oxidant and other (e.g., inert) fluids is then no longer used for further oxidation. However, it is also conceivable that the reaction zone includes a region located downstream of the oxidant outlet, in particular a pipe or pipeline, a conveying device and / or a container located downstream of the oxidant outlet. It will be particularly worth considering whether the unconsumed oxidant is discharged through the oxidant outlet together with the foreign matter containing oxides formed during the reaction process and the foreign matter that may not have been converted or reacted yet.

[0018] In a possible embodiment, the oxidant outlet can be connected to a pneumatic conveying device. In particular, the pneumatic conveying device can be a conveying device operating as a solid syringe or a jet pump. Alternatively, a suction fan can be conceived. The pneumatic conveying device can be connected to the oxidant outlet through a conveying connection and thus exert a suction effect on the reaction zone or a part of the reaction zone. The suction effect causes the oxidant or the mixture of the oxidant and other (e.g., inert) fluids containing oxygen introduced into the reaction zone or a part of the reaction zone to flow towards the oxidant outlet as the oxidant, thus passing through the reaction zone or a part of the reaction zone and causing the oxidant to react with the substance containing foreign matter to form a foreign matter containing oxides.

[0019] The foreign matter containing oxides formed during the reaction process and the foreign matter that may not have reacted yet can also be discharged via the pneumatic conveying device, in particular a conveying device operating as a solid syringe or a jet pump. The pneumatic conveying device can also be used to further transport such a solid-containing substance to a collection container or a disposal container through a pipeline, for example. The transported solid-containing substance can contain the foreign matter containing oxides generated by the reaction with the oxidant, or the unreacted scavenged substance. The pneumatic conveying device can be particularly arranged to remove the solid-containing substance from the reaction zone or a part of the reaction zone. However, it is also conceivable that the pneumatic conveying device is arranged to extract the solid-containing substance from the reaction zone or a part of the reaction zone and to extract the gaseous substance from the reaction zone or a part of the reaction zone and / or to add the oxidant to the transported solid-containing substance. For example, in a solid syringe, a fluid or an oxygen-containing gas mixture containing an oxidant such as air can be used as the conveying fluid. In this way, when the conveying fluid and the transported solid-containing mixture are transported through the downstream part of the solid syringe of the conveying pipeline, the mixing of the conveying fluid and the transported solid-containing substance causes the desired oxidation reaction to occur effectively.

[0020] By controlling the pneumatic conveying device, the suction intensity acting on the substances in the reaction zone or a partial zone of the reaction zone can be adjusted. At a lower suction intensity, (at least substantially) only gaseous substances are withdrawn from the reaction zone or a partial zone of the reaction zone, such that the opening (suction opening) of the conveying connection piece connected to the pneumatic conveying device forms an oxidant outlet. In the case of a stronger suction intensity, both solid-containing substances and gaseous substances are withdrawn from the reaction zone or from a partial zone of the reaction zone. In this case, the suction opening forms an outlet for further conveying the solid-containing substance in the reaction zone or in a partial zone of the reaction zone, and at the same time, forms an oxidant outlet and / or arrangement for supplying the oxidant to the further conveyed solid-containing substance. The latter is achieved, for example, by mixing the oxidant-containing conveying fluid in the solid syringe with the solid-containing substance.

[0021] Furthermore, the reaction zone or a partial zone of the reaction zone is acted upon by an inert fluid, in particular an inert gas. By mixing the inert gas, for example, the concentration of the oxidant in the oxidant stream can be appropriately adjusted, and if necessary, the progress of the oxidation reaction can be accelerated or slowed down. Using an inert fluid that does not contain an oxidant, the action on the reaction zone or a partial zone of the reaction zone can be used, for example, to stop the further reaction process of the scavenged substance with the oxidant in the reaction zone or a partial zone of the reaction zone. The inert fluid can also be used to expel any residual oxidant in the reaction zone or a partial zone of the reaction zone to create a sufficient inert atmosphere in the reaction zone or a partial zone of the reaction zone to allow the formation of a fluid contact between the reaction zone or a partial zone of the reaction zone and the raw material gas space. For example, the reaction can be stopped after a certain amount or a certain proportion of the scavenged substance has reacted with the oxidant.

[0022] For example, it can be set that the reaction of the substance removed from the filter surface with the oxidant takes place in a reaction stage, where the oxidant is applied to the reaction zone or a partial zone of the reaction zone, which occurs during the corresponding reaction stage, and after the corresponding reaction stage, the reaction zone or the partial zone of the reaction zone is subjected to an inert fluid without added oxidant. In this way, the reaction process can be managed in a very controlled manner because the reaction will stop after the oxidant supply is cut off, and then, any substance in the reaction zone or the partial zone of the reaction zone, whether solid or gas, can be removed from the reaction zone or the partial zone of the reaction zone either completely or partially. By simultaneously purging the reaction zone or the partial zone of the reaction zone with an inert fluid, the concentration of the oxidant can then be reduced to the extent that fluid contact between the reaction zone or the partial zone of the reaction zone and the raw gas space becomes possible again, at which level there is no risk of the oxidant entering the raw gas space. Then, the reaction zone or the partial zone of the reaction zone is ready to receive another batch of substances removed from the filter surface.

[0023] Introducing an inert gas into the reaction zone or a partial zone of the reaction zone can be achieved in a simple manner, for example, by supplying an inert fluid thereto via a cleaning port of a solid syringe.

[0024] To support the described measures, it can be stipulated that the inert fluid is supplied to the reaction zone or a partial zone of the reaction zone via a further fluid inlet different from the oxidant inlet. For example, such a further fluid inlet can be arranged near the opening connecting the reaction zone or a partial zone of the reaction zone to the raw gas space in order to selectively flush out the oxidant from near this opening. It is also conceivable to provide a plurality of such further fluid inlets.

[0025] It can also be beneficial when the inert fluid and / or the oxidant are discharged from the reaction zone or a partial zone of the reaction zone through one or more further outlets provided other than the oxidant outlet. For example, it can be stipulated that a plurality of oxidant outlets are arranged on the housing surrounding the reaction zone or a partial zone of the reaction zone such that a widely distributed oxidant flow fully covering the volume of the reaction zone is distributed in the reaction zone or a partial zone of the reaction zone. It is also possible to provide a specific arrangement of one of a number of outlets for the inert fluid relative to the corresponding coupling inlet opening for the inert fluid in order to flush out the oxidant from certain regions of the reaction zone or a partial zone of the reaction zone in a particularly effective manner.

[0026] When the reaction of the material removed from the filter surface with the oxidant occurs, an inert fluid may already have been started to be applied to the reaction zone or a part of the reaction zone. In particular, then, the inert fluid can also be used to remove heat. For example, this often occurs when the oxidant stream is a mixture of an oxidant (e.g., oxygen) and an inert gas (e.g., nitrogen) containing only a small amount of oxidant.

[0027] The reaction zone or a part of the reaction zone can be traversed by a heat transfer fluid for removing the heat generated during the reaction of the material removed from the filter surface with the oxidant. Where appropriate, the heat transfer fluid stream can flow through the reaction zone or a part of the reaction zone together with the oxidant stream. The oxidant itself can also act as a heat transfer fluid, especially when only part of the oxidant reacts, because an excess of oxidant is added to accelerate the reaction. The heat transfer fluid can also act as an inert fluid for flushing out the oxidant remaining after the reaction in the reaction zone or in the part of the reaction zone where the reaction has been completed. Then, it can be convenient to use an inert fluid without added oxidant as the heat transfer fluid.

[0028] The reaction zone can include an agglomerate collection area adapted to receive the material removed from the filter surface, whereby foreign matter or agglomerates containing foreign matter that have accumulated on the filter surface are removed and collected and retained in the agglomerate collection area. The agglomerate collection area then particularly constitutes a part of the above-mentioned reaction zone. The agglomerate collection area can be designed such that the material removed from the filter surface directly falls from the raw gas space into the agglomerate collection area without being pre-collected at a position between the filter element and the agglomerate collection area (e.g., in the bottom area of the filter housing surrounding the raw gas space).

[0029] The agglomerate collection area can have a first closing device with a first cut-off member coupled thereto. The first closing device can be designed such that it can enable the material falling from the filter surface during the cleaning process to be collected in the agglomerate collection area (especially only briefly), and after the removed material has been collected in the agglomerate collection area, the reaction zone is closed off from the raw gas space (especially in an airtight manner), at least until the concentration of the oxidant in the reaction zone has decreased to a sufficient extent.

[0030] Reducing to a sufficient degree means, in particular, until it can be assumed that the concentration of the oxidant in the reaction zone has been reduced below a predetermined threshold. This may be the case when the reaction for forming the foreign matter containing the oxide has been completed, the oxidant has been substantially consumed and / or all substances have been removed from the reaction zone or the agglomerate collection zone. In fact, as long as the rate at which the reaction proceeds is well known (e.g., from tests), this state can be assumed by waiting a predetermined time from the start of the oxidation reaction. However, generally, this condition will be reached in any case when, after the reaction has been completed, especially by means of suction and / or evacuation with an inert fluid, the oxidant has been removed from the reaction zone or the agglomerate collection zone.

[0031] In particular, the first cut-off member can be designed such that when the first cut-off member is open, it does not significantly impede, in any case, the received substances removed from the filter surface in the agglomerate collection zone. In particular, the first cut-off member opens during and / or immediately after the cleaning process of the filter element and remains open in any case until the substances detached from the filter surface on the raw gas side during the cleaning process have been substantially collected in the agglomerate collection zone. In particular, after the reaction for forming the foreign matter containing the oxide in the reaction zone has been completed, once the concentration of the oxidant in the reaction zone has dropped to a sufficient degree and there is no longer any reason to fear that the oxidant will enter the raw gas space from the reaction zone to an extent that will interfere with the process conditions prevailing there, the first cut-off member can be opened again.

[0032] The substances removed from the filter surface can be transported from the agglomerate collection zone to a downstream discharge zone. The discharge zone can be located downstream of the reaction zone, in the sense that no further oxidation of the foreign matter takes place in the discharge zone itself. However, it is conceivable and, in fact, preferred that the reaction zone also at least partially includes the discharge zone and, depending on the presence of the oxidant, the foreign matter is still oxidized in the discharge zone. In this case, the oxidant can be supplied not only to the agglomerate collection zone but also to the discharge zone or even specifically to the discharge zone.

[0033] The discharge area may have a second closing device having a cut-off member that can cut off the discharge area from the downstream area, in particular in an airtight manner. The second closing device is not absolutely necessary, especially if the aim is to achieve a substantial complete conversion of combustible foreign matter into foreign matter containing oxides before the substances introduced into the discharge area reach the downstream end of the discharge area. In the absence of the second closing device or when the second closing device is open, the desired oxidation reaction in the discharge area can occur very effectively while transporting the substances being conveyed forward rapidly. When the second closing device is provided, the associated cut-off member can be designed to form an airtight partition in its closed position. However, this feature is not crucial either; in many cases, a cut-off function only for particles larger than a certain size will be effective. In particular, the reaction zone can be located between the first and the second closing devices. The discharge area may further include a collection container. In the collection container, substances containing solids can be collected, in particular oxide-containing products resulting from the oxidation of substances removed from the filter surface, and ultimately disposed of.

[0034] After leaving the reaction zone, especially when reaching the downstream part of the discharge area, it can be useful for any oxidant not consumed in the reaction zone and, if applicable, any additional fluid produced as an excess fluid or waste liquid (especially in the case of a gaseous fluid, as exhaust gas) to be returned to the reaction zone in whole or in part. For example, the waste liquid outlet or the exhaust gas outlet can be connected to the collection container, and the fluid flow leaving the waste liquid outlet can be returned or recycled to the reaction zone in whole or in part. In particular, the fluid recirculation of the type mentioned here can significantly limit the amount of fluid consumed, whether as an oxidant, a heat transfer fluid, a cleaning fluid, and / or a conveying fluid. In particular, an inert fluid is generally not consumed during conveyance through the reaction zone and can be retained in the circuit formed in this way indefinitely. If necessary, fresh oxidant can be added to the recirculating fluid flow to compensate for the oxidant consumption in the reaction zone.

[0035] If fluid recirculation is provided, in particular, a control / regulation system can be provided that is designed such that the fluid pressure within the circuit, in particular within the reaction zone, does not exceed and / or does not fall below a predetermined value, in particular remains within a predetermined range. As a control variable for controlling the fluid pressure, it can be stipulated, for example, that only a part of the fluid flow accumulating as waste liquid returns to the reaction zone, while the other part is discharged to the environment or an external waste liquid treatment system, and the returning fluid flow is always regulated such that the fluid pressure in the circuit, in particular in the reaction zone, remains constant, in particular does not exceed a predetermined value and / or does not fall below another predetermined value, in particular remains within a predetermined range.

[0036] In the reaction zone, a conveying member may be provided for conveying the substances removed from the filter surface. Preferably, the conveying member may be a conveying fluid. For example, when a solid syringe is provided for removing substances from the agglomerate collection container into the discharge line, the fluid used to create a negative pressure or vacuum at the conveying port of the solid syringe may serve as the conveying fluid for further conveying the substances conveyed from the agglomerate collection container downstream of the solid syringe. The conveying member can be used to further quickly and effectively convey the solid-containing substances. In addition, the conveying member can improve the mixing or loosening of the solid-containing substances, making such substances more easily accessible to the oxidant. Alternatively or additionally, the conveying member may also include a screw conveyor, a rotary valve, an incline or slope, and / or a fluidizing device. In particular, the conveying member can be designed such that the conveying direction of the substances removed from the filter surface can be reversed.

[0037] Other embodiments of the above-described method and the filter device described in further detail below will be described:

[0038] The reaction zone may include a collection container. At least one member for moving the substances removed from the filter surface may be provided in the collection container, in particular a screw conveyor, a fluidizing device, a pivoting device, and / or a mixer for the collection container.

[0039] The reaction zone can be designed to be temperature-controlled, in particular heated and / or cooled. Different from the above, various designs can be envisioned, in which an ignition device and / or a heating device are assigned to the reaction zone in order to actively initiate the reaction of the foreign matter with the oxidant. Then, the conversion of the removed substances into foreign matter containing oxides does not depend on the start of spontaneous oxidation. In all other respects, the foregoing and the following also apply to this alternative embodiment of the invention. The applicant reserves the right to direct claims to such alternative embodiments, for example, in a divisional application.

[0040] The foreign matter may, for example, contain or be a metal and have a granular, in particular flaky, powdery, or smoky configuration. In particular, the foreign matter may have a configuration that is not fully oxidized or even not oxidized at all. In particular, the foreign matter may be titanium powder or titanium flakes. The foreign matter may not be an oxidized metal foreign matter or not entirely an oxidized metal foreign matter. For example, during the additive manufacturing process of a metal workpiece, when the workpiece is built layer by layer from a powder bed, such foreign matter is generated by using a powdery metal substance. Typical metals used in such a process that can result in the discharge of combustible foreign matter into the air are titanium, aluminum, magnesium, and their alloys, as well as various steels such as structural steel, quenched and tempered steel, and high-alloy stainless steel.

[0041] The method may further include the step of adding a filter aid to the feed gas stream, the filter surface, the reaction zone, and / or the discharge zone. The filter aid may be configured to inhibit the reaction of foreign matter and / or substances removed from the filter surface with an oxidizing agent, particularly oxygen. If necessary, a flame retardant additive may be added to the exhaust gas so that agglomerates of foreign matter and the filter aid are formed. The addition of a SiO2-based filter aid has proven particularly suitable for inhibiting the combustion of the feed gas in additive manufacturing processes using titanium and / or aluminum-magnesium alloys. For example, the laser sintering method is known as an additive manufacturing process that generates exhaust gas prone to spontaneous combustion.

[0042] The filter aid may be, for example, an inorganic substance. In particular, inorganic substances such as silica-based inorganic substances or calcium carbonate-based inorganic substances may be used as the filter aid. In particular, the filter aid may be used to ensure that the oxidation occurring in the reaction zone does not get out of control.

[0043] When added, the filter aid may have a granular, particularly powder-like configuration. This allows the filter aid to be metered precisely into the feed gas stream and / or the filter device, particularly for coating the filter surface (precoating). In addition, suitable filter aids allow the use of simple supply mechanisms such as flap valve supply or pressurized gas supply. When fine-grained filter aids are added, the formation of flame-retardant agglomerates is more efficient.

[0044] The filter aid may be configured to bind metal-containing foreign matter in the agglomerates in a granular configuration, particularly at a temperature of 600 °C or higher, particularly at a temperature of 650 °C or higher, particularly at a temperature of 1220 °C or higher, particularly at a temperature of 750 °C or higher, particularly at a temperature of 1320 °C or higher. Depending on the filter aid, temperatures up to 1000 °C, particularly up to 1250 °C, particularly up to 1500 °C can be reached without overly inhibiting the formation of agglomerates and / or causing the decomposition or disintegration of the agglomerates to an undesired large extent. The formed agglomerates are non-combustible or only have poor flammability within the mentioned temperature range, so that a higher operating safety is possible compared to conventional filter devices. Many SiO2 glasses start to soften at temperatures starting from 600 °C and can then form agglomerates with foreign matter. Depending on the configuration of the SiO2 material, for example by adding additives or forming it into a glass foam, the temperature at which softening starts can be varied in a suitable manner.

[0045] The agglomerates mixed with the filter aid can turn into a flowable configuration similar to a glass melt upon strong heating and turn into a vitreous configuration after cooling to below the glass transition point. The filter aid melts and thereby entraps foreign substances in the melt, such that inerting has occurred in this state. Once the melt solidifies, a vitreous or glassy configuration is formed. The formation of the flowable configuration can occur especially after heating to a temperature of 600 °C or higher, especially 650 °C or higher, especially 1220 °C or higher, especially 750 °C or higher, especially 1320 °C or higher. During this process, the agglomerates can have a vitreous configuration after cooling to below the glass transition temperature. This can prevent oxidants from coming into contact with metal-containing foreign substances.

[0046] In particular, the filter aid can be a substance having a vitreous configuration or that can be transformed into a vitreous configuration under the influence of heat.

[0047] Silica-based substances having a vitreous configuration are made of solids and have an amorphous structure or at least a partially crystalline structure. Such glasses have silica as their main component and their network structure is mainly formed by silica. In particular, such glasses include so-called silicate glasses. Silicate-based glasses can exist in a pure form, such as silica glass. If a higher softening temperature is desired, quartz glass is also conceivable. In addition to silicate-based glasses, other components can be present, such as phosphates, borates, etc.

[0048] The filter aid can have at least one of the following substances as a main component: expanded glass beads, glass powder, silica particles (SiO2 particles), quartz powder, or a mixture of at least two of these substances. In particular, very suitable glass substances are those made from recycled waste glass (recycled glass), such as expanded glass or foamed glass. Expanded glass is produced by grinding waste broken glass and adding a binder and / or an expanding agent thereto. This produces roughly round grains with small air-filled pores. Expanded glass with a grain size of 0.04 - 16 mm can be produced. These fine particles have a closed pore structure. Foamed glass, especially foamed glass ballast, is produced in a similar manner. Glass or foamed glass can be produced such that the temperature at which the softening range begins and / or the lower limit of the glass transition temperature takes a value between 600 °C and 750 °C.

[0049] In the event of a fire, the initially formed agglomerates of filter aid and metal powder, which are still in powder or granular form, soften or melt under the action of heat. The flowable glass melt surrounds the foreign matter containing metal and renders them inert. After the melt solidifies, a glassy structure is formed, in which the foreign matter containing metal is permanently enclosed in or surrounded by the filter aid. Once a flowable configuration is formed, the individual self-igniting particles of the metal are bound (vitrified) by the filter aid. In the vitrified state, the reaction with oxidants, especially with oxygen (O2), is difficult or impossible. In particular, this type of vitrification process occurs at those locations where the filter aid agglomerates accumulate. In particular, when heat is generated (e.g., in the event of a fire), a filter cake that has been formed on the raw gas side of the filter surface and that also consists entirely or mainly, in any ratio, of filter aid agglomerates can exhibit such a phase change from a powder or granular configuration to a flowable and ultimately to a glassy configuration. This vitrification process can also occur on the surface of the bulk cone formed in the agglomerate collection area during operation, resulting in the effective inerting of the substances contained in the agglomerate collection area. This vitrification process can be assisted by periodically coating the surface of the bulk material cone formed in the agglomerate collection area with a layer of filter aid.

[0050] The formed agglomerates can remain chemically stable in the event of a fire, i.e., in the presence of an oxidant (usually oxygen), at temperatures up to 650 °C, especially at temperatures up to 750 °C, especially at temperatures up to 850 °C, especially at temperatures up to 1000 °C, especially at temperatures up to 1250 °C, especially at temperatures up to 1500 °C.

[0051] The filter aid can also have a gaseous configuration. In this case, the filter aid can also be used as a heat transfer fluid after the oxidation of foreign matter and / or substances removed from the filter surface has occurred.

[0052] When the filter element has been cleaned and the substances removed from the filter surface have been deposited in the agglomerate collection area and / or the discharge area and / or the reaction area, the filter aid and / or an oxidant can be applied to the agglomerate collection area and / or the discharge area and / or the reaction area.

[0053] The application of the oxidant to the agglomerate collection area and / or the discharge area and / or the reaction area can be carried out in a timed relationship with the application of the filter aid to the agglomerate collection area and / or the discharge area, especially before the application of the filter aid to the agglomerate collection area and / or the discharge area and / or the reaction area, or after the application of the filter aid to the agglomerate collection area and / or the discharge area and / or the reaction area.

[0054] A filter device for cleaning a raw material gas carrying foreign matter according to the present invention includes at least one filter element having at least one filter surface in a raw material gas space, and a raw material gas stream containing foreign matter can be supplied to the at least one filter element. Further, an oxidant supply device is provided, which is adapted to supply an oxidant to a reaction zone on the raw material gas side of the filter surface downstream of the filter surface. The oxidant supply facility is designed such that foreign matter contained in the substances removed from the filter surface and / or in the raw material gas stream reacts with the oxidant in the reaction zone to form foreign matter containing oxides.

[0055] The explanations given above with reference to the method according to the present invention also apply analogously to the filter device according to the present invention. For the sake of avoiding repetition, the previous explanations are specifically noted.

[0056] In particular, the oxidant can be air or an oxygen-containing gas. In particular, the reaction zone can be located downstream of the raw material gas space. In particular, the reaction zone can be adapted to be cut off with respect to the raw material gas space when the oxidant is supplied. These measures help to ensure that the raw material gas space remains substantially free of the oxidant.

[0057] The filter device can be designed such that, during the reaction of the substances removed from the filter surface with the oxidant, unconsumed oxidant can be removed from the reaction zone. This can enable particularly good control of the reaction occurring in the reaction zone.

[0058] The filter device can have an oxidant inlet and an oxidant outlet. The oxidant inlet is designed to supply the oxidant to the reaction zone or a part of the reaction zone, and the oxidant outlet is designed to discharge the oxidant from the reaction zone or from a part of the reaction zone. The oxidant outlet is particularly different from the oxidant inlet.

[0059] The filter device can be further configured to discharge, in particular suck away, unconsumed oxidant through the same oxidant outlet as the foreign matter containing oxides (and, if applicable, unreacted foreign matter) formed during the reaction.

[0060] The reaction zone can include a region downstream of the oxidant outlet, in particular a downstream pipeline, a conveying device, and / or a container.

[0061] It is particularly suitable when the oxidant outlet is connected to a pneumatic conveying device, in particular to a conveying device operating as a solid syringe or a jet pump and / or to an extraction fan. The filter device may also have a pneumatic conveying device, in particular a conveying device operating as a solid syringe or a jet pump, which is arranged to discharge foreign substances containing oxides and any unreacted foreign substances formed during the reaction. The pneumatic conveying device can also be used to remove the oxidant or other gaseous substances from the reaction zone or from a part of the reaction zone.

[0062] The filter device can be designed to apply a negative pressure to the reaction zone or a part of the reaction zone, in particular during and / or after the reaction of the substances removed from the filter surface with the oxidant. Additionally or alternatively, the filter device can be configured to act on the reaction zone or a part of the reaction zone with an inert fluid, in particular with an inert gas.

[0063] The filter device can also have a control system arranged such that the reaction of the substances removed from the filter surface with the oxidant takes place in a reaction stage, in which oxygen is arranged to be applied to the reaction zone or a part of the reaction zone during the reaction stage, and / or after the corresponding reaction stage, an inert fluid without added oxidant is applied to the reaction zone or a part of the reaction zone.

[0064] The filter device can have a further fluid inlet for introducing an inert fluid into the reaction zone or a part of the reaction zone, different from the oxidant inlet.

[0065] The filter device can include a further outlet in addition to the oxidant outlet for discharging the inert fluid and / or the oxidant from the reaction zone and / or from a part of the reaction zone.

[0066] In any case, after the reaction of the substances removed from the filter surface with the oxidant has occurred, the reaction zone or a part of the reaction zone can be acted upon by an inert fluid, in particular an inert gas, and / or a negative pressure. In this case, the inert fluid displaces the oxidant from the reaction zone or from a part of the reaction zone, so that uncontrolled oxidation no longer occurs. This effect can also be achieved by applying a negative pressure to the reaction zone or a part of the reaction zone, i.e., sucking or extracting the oxidant from the reaction zone or a part of the reaction zone. In this regard, the two measures can also be combined and support each other.

[0067] The filter device may further comprise an oxidant inlet through which an oxidant can be supplied to the reaction zone or a partial zone of the reaction zone. The oxidant inlet may be provided with a shut-off device to allow the oxidant to enter the reaction zone or a partial zone of the reaction zone in a controlled manner. The filter device may also have an outlet, particularly an outlet different from the oxidant inlet, through which the oxidant still present in the reaction zone or a partial zone of the reaction zone can be discharged after the reaction between the substance removed from the filter surface and the oxidant has taken place.

[0068] Preferably, the oxidant inlet may be arranged at the top of the reaction zone or a partial zone of the reaction zone, which top is arranged on the side of the reaction zone or a partial zone of the reaction zone facing the raw gas space. In particular, the outlet may be arranged at the bottom end of the reaction zone or a partial zone of the reaction zone, which bottom end is arranged on the side of the reaction zone or a partial zone of the reaction zone facing away from the raw gas space. This arrangement allows the oxidant to be supplied to the reaction zone efficiently and reliably, and also allows the substances removed from the filter surface to be reliably emptied from the reaction zone or a partial zone of the reaction zone together with the oxidant stream through the outlet.

[0069] The filter device may also be provided with a common outlet through which residues of the reaction between the substance removed from the filter surface and the oxidant, in particular foreign substances containing oxides formed, completely or partially unreacted substances, and excess oxidant can be removed from the reaction zone or from a partial zone of the reaction zone. This results in a simple structure of the filter device, particularly of the reaction zone. The reaction zone or a partial zone of the reaction zone may have a heat transfer fluid flowing through it for removing the heat generated during the reaction.

[0070] The reaction zone may further comprise an agglomerate collection area which is designed to receive the substances removed from the filter surface, whereby foreign substances or agglomerates containing foreign substances that have accumulated on the filter surface after the removal can be collected and stored in the agglomerate collection area. Then, in particular, the agglomerate collection area forms a partial zone of the above-mentioned reaction zone.

[0071] The agglomerate collection area may have a first closing device coupled thereto, which first closing device has a first cut-off member and is designed such that the substances that can fall off from the filter surface during the cleaning process, particularly only briefly, can be collected in the agglomerate collection area, and after collecting the cleaned substances in the agglomerate collection area, in any case cut off the reaction zone from the raw gas space, at least until the concentration of the oxidant in the reaction zone has dropped to a sufficient extent.

[0072] In addition, the filter device may have a discharge area downstream of the agglomerate collection area into which the material removed from the filter surface can be transported. In particular, the reaction area includes at least a part of the discharge area, and specifically, an oxidant can be supplied into the agglomerate collection area and / or the discharge area.

[0073] The discharge area may have a second closing device, where in particular, the reaction area is arranged between the first closing device and the second closing device.

[0074] In the reaction area, a conveying member may be provided, which is configured to convey the material removed from the filter surface. Specifically, the conveying member includes a conveying fluid. For example, when a solid syringe is provided for discharging the material from the agglomerate collection container into the discharge pipeline, the fluid used to generate a negative pressure at the conveying port of the solid syringe can act as the conveying fluid for further conveying the material transported from the agglomerate collection container downstream of the solid syringe.

[0075] Regarding the advantages and benefits of the individual features, reference is made to the description of the method and other features according to the present invention.

[0076] The oxidant may be air or an oxygen-containing gas, in particular an oxygen-containing gas with an oxygen content of 1 - 21 vol%. In the reaction area, the oxidant can cause the foreign matter and / or material removed from the filter surface to react spontaneously. The reaction area may be located downstream of the raw material gas space.

[0077] The filter device may be arranged to supply a heat transfer fluid to the reaction area and discharge the heat transfer fluid after flowing through the reaction area or a part of the reaction area, for removing the heat generated during the oxidation process and the foreign matter containing oxides and the excess oxidant.

[0078] A conveying member for conveying the material removed from the filter surface, in particular a screw conveyor, a rotary valve, an incline or an inclined plane, and / or a fluidizing device, may be provided in the reaction area. In particular, the conveying member may be designed such that the transport direction of the material removed from the filter surface is reversible. In particular, the conveying member may be a pneumatic conveying facility, such as a solid syringe.

[0079] The discharge area may include a waste liquid outlet area through which the fluid substances produced after passing through the process can be discharged. If, as described herein, the substances removed from the filter surface are oxidized by means of a gaseous fluid, in particular by means of a gaseous oxidant, a heat transfer fluid, a cleaning fluid and / or a transport fluid, the gaseous effluent (exhaust gas) will mainly be produced in the waste liquid outlet area. In the present application, the terms "exhaust gas" or "exhaust gas outlet area" are also used for simplicity, regardless of whether the fluid accumulated at the end of the process is mainly gaseous or liquid. The exhaust gas outlet area may have a filter unit with at least one filter element and an exhaust gas outlet. In particular, the exhaust gas outlet area may include a pressurized gas removal device. The pressurized gas removal device may be configured to apply a pressure pulse to at least one filter element. Alternatively, the filter unit may have at least one filter element with a storage filter. The exhaust gas outlet area may be designed such that in particular the mixture of residues and excess oxidant formed during the reaction process can be filtered therein and discharged from the filter device through the exhaust gas outlet.

[0080] In particular, the filter device may have a fluid recirculation unit which is designed such that after leaving the reaction area, the unconsumed oxidant in the reaction area and, if applicable, additional fluids accumulated as waste liquid or exhaust gas are completely or partially returned to the reaction area. In particular, a control / regulation system may be provided which is designed such that the fluid pressure in the resulting circuit, in particular in the reaction area, does not exceed a predetermined upper limit value and / or does not fall below a predetermined lower limit value, and in particular is maintained within a predetermined range.

[0081] The discharge area may include a collection container for substances containing solids, where substances containing solids, in particular foreign substances containing oxides, can be collected. Once the collection container is filled, it can be removed by the operator and replaced with an empty collection container. Thus, interruptions in the filtration process can be avoided. In particular, the discharge area may include a collection container for isolating substances containing solids, the collection container having an outlet for fluids, in particular gaseous substances (exhaust gas outlet). In this case, the outlet may have a filter unit coupled thereto for cleaning the fluid substances from foreign substances of the above type. In addition, a fluid recirculation unit of the above type may be coupled to the outlet.

[0082] An arrangement for temperature control, in particular for heating and / or cooling the reaction area or a part of the reaction area, may be coupled to the reaction area or a part of the reaction area. In an alternative embodiment, the reaction area or a part of the reaction area may include an ignition device and / or a heating device for actively initiating the reaction of the foreign substances with the oxidant.

[0083] Furthermore, the filter device may include a filter aid supply arrangement having a filter aid supply line leading into the raw gas space, into the raw gas stream upstream and / or downstream of the raw gas space, and / or into the reaction zone and / or into the discharge zone, in particular into a collection container, for supplying a filter aid. Thereby, the filter aid may be configured to inhibit further reaction of foreign matter with an oxidant, in particular with oxygen, once the first oxidation of the material removed from the filter surface has occurred. Description of the Drawings

[0084] The present invention and specific embodiments thereof will be explained in more detail below by way of exemplary embodiments.

[0085] Figure 1 A side view of a filter device according to the present invention is shown.

[0086] Figure 2 In a side view rotated 90 degrees relative to Figure 1 a view of Figure 1 the filter is shown.

[0087] Figure 3 A schematic view of an embodiment of the reaction zone is shown.

[0088] Figure 4 A schematic view of another embodiment of the reaction zone is shown.

[0089] Figure 5 A schematic view of another embodiment of the reaction zone is shown.

[0090] Figure 6 A schematic view of an exemplary discharge zone, in particular a collection container for substances containing solids, is shown. Detailed Description of the Embodiments

[0091] Figure 1 and Figure 2 Side views rotated 90 degrees relative to each other show a filter device 10 for cleaning a raw gas carrying foreign matter according to an embodiment of the present invention. The filter device 10 includes a filter unit 12 having at least one filter element 14 (not shown in Figure 1 and not shown in Figure 2One of the filter elements 14 in the filter unit 12 is shown). The filter unit 12 is mounted above the raw gas inlet opening 16 in the upper part of the housing 18. For the sake of clarity, the raw gas inlet opening 16 is partially omitted. The filter unit 12 includes a plurality of filter elements 14 in the form of dry filters, and each of the filter elements 14 is configured as a rigid body filter. This is intended to show that the walls of the filter elements 14 have sufficient rigidity to keep the filter elements 14 upright without the help of other support structures. In this sense, the filter elements 14 are inherently stable. The filter elements 14 are suspended on a horizontally extending common holder and extend parallel to each other in the vertical direction. This is schematically shown in Figure 2 and is schematically shown in Figure 2 One of the filter elements 14 in approximately its installed position is shown. It should be noted that different installations of the filter elements 14 in the housing 18 are also possible, for example, horizontal installation, in which the filter elements extend in the horizontal direction and are attached to a vertical holder. Each of the filter elements 14 has at least one filter surface on which the raw gas acts. In Figure 1 and Figure 2 the filter surface on which the raw gas acts is located on the outside (raw gas side) of one of the respective filter elements 14. After the purified gas passes through the wall of the filter element 14, it flows from the raw gas side to the clean gas side, and the purified gas faces the internal space surrounded by the wall of the filter element 14. The filter elements 14 are open towards the top, so that the clean gas space 17 extends from the internal space to the area above the filter unit 12.

[0092] In Figure 1 and Figure 2 in the lower region 18b shown, the housing 18 takes the form of a funnel with downwardly tapering side walls. Adjacent to the lower region 18b is the reaction region 24. The foreign matter-containing substances that have accumulated at the filter elements on the raw gas side fall into the reaction region 24 after the removal of the corresponding one of the filter elements 14 (for example, by applying a pressure pulse to the corresponding filter element 14, see the pressurized gas removal unit 58 schematically shown in Figure 2 ). In particular, the substances entering the reaction region 24 contain foreign matter-containing substances from the raw gas stream and / or from the substances removed from the filter surface. The reaction region 24 is located downstream of the housing 18 and is connected via a channel 28 to the lower region 18b of the housing 18 surrounding the raw gas space 15. A first closing device having a first cut-off member 30 is arranged in the channel 28. The first cut-off member 30 can be designed as a shut-off valve, a flap valve, a disk valve, or a pinch valve, just like the other cut-off members described herein.

[0093] In the illustrated example, the reaction zone 24 has a funnel-shaped container 32 that forms an agglomerate collection zone 33. In the illustrated example, the container 32 has sidewalls that taper downwardly away from the feed gas space 15. The container 32 may alternatively take another shape, such as a cylindrical shape or a rectangular shape. The container 32 has an optional additional fluid inlet 38 and an additional fluid outlet 40 at its top end 34 (i.e., the end of the container 32 facing the feed gas space 15), through which excess fluid (such as excess oxidant, excess cleaning fluid, heat transfer fluid for removing heat generated during the reaction, or a mixture of the above fluids) can leave the container 32. It should be noted that if desired, multiple additional fluid inlets 38 and multiple additional fluid outlets 40 can be provided, and the arrangement of these additional inlets or additional outlets on the container 32 can be selected as needed.

[0094] The container 32 has an oxidant inlet 36 in its lower region or at its bottom end 42 (i.e., at the end of the container 32 away from the feed gas space 15). The oxidant inlet 36 is configured to allow an oxidant stream to be introduced into the agglomerate collection zone 33. In addition to an oxidant such as oxygen, other fluids (such as an inert fluid, especially an inert gas such as nitrogen) can also be introduced through the oxidant inlet 36 into the container 32 surrounding the agglomerate collection zone 33. A mixture of the additional fluid and the oxidant can be used to adjust the appropriate concentration of the oxidant for cleaning purposes and / or for removing heat. If the additional fluid is used as a heat transfer fluid and / or a cleaning fluid, the additional fluid can alternatively or additionally be introduced into the container 32 via one or more additional fluid inlets (such as the above-mentioned additional fluid inlet 38). In particular, the oxidant inlet 36 can be configured as a fluidizing device such as having a fluidizing disk, so that when the oxidant stream is introduced, loosening or fluidization of the solid-containing material in the agglomerate collection zone 33 can also be achieved.

[0095] The container 32 further includes an outlet 39 for discharging the solid-containing material, which is located in the lower region of the container 32 in the illustrated embodiment. Preferably, such solid-containing material will include foreign matter containing oxides formed during the oxidation process. However, it is not necessary that all foreign matter and / or material that has entered the agglomerate collection zone 33 and has been removed from the filter surface has been completely oxidized when removed from the container 32 via the outlet 39. It is also possible that the oxidation of oxidizable foreign matter can still occur downstream of the outlet 39.

[0096] The process environment in an additive manufacturing process that produces oxidizable or combustible residues should generally be inert and not changed or at least not overly changed. This also applies to the treatment of the exhaust gas generated in the process, especially if the clean exhaust gas is recycled into the process in a loop or circuit. If combustible foreign matter in the exhaust gas can be removed by a dry filter, an inert mixture of an inert carrier gas and particulate foreign matter will typically enter the source gas space, where the proportion of oxygen and other substances that can act as oxidants is below a predetermined threshold. Therefore, the filtration of the source gas carrying combustible foreign matter is carried out under inert conditions, and it is not desirable to introduce oxygen or other substances with an oxidizing effect into the source gas space. This complicates the possibility of rendering harmless the solid-containing substances that accumulate on the filter surface by oxidation.

[0097] In Figure 1 shown schematically by arrow 44 and carrying foreign matter to be separated by device 10, the source gas stream enters the source gas space 15 surrounded by the housing 18 via the source gas supply line 54 through the source gas inlet opening 16. After entering the source gas space 15, the source gas stream 44 is conveyed to the filter unit 12. A filter aid supply opening 20 is provided on the side of the housing 18 opposite to the source gas inlet opening 16, through which a filter aid (such as a solid such as CaCO3 or SiO2-based with flame retardant properties) can be supplied from a storage container into the source gas space 15. The filter aid can be introduced into the source gas space 15 before the source gas stream 44 is charged into the source gas space 15. Then, the introduced filter aid accumulates particularly on the filter surface of the filter element 14 and / or on the wall of the source gas space 15, where each filter aid forms a filter aid layer (precoating layer). The flow of the filter aid entering the source gas space 15 through the filter aid supply opening 20 is indicated by Figure 1 arrow 45 in

[0098] Alternatively or additionally, the filter aid supply opening 52 can be arranged in the source gas supply line 54. The source gas supply line 54 is connected to the source gas inlet opening 16. This allows the filter aid to be introduced into the source gas stream 44 before the source gas stream 44 enters the source gas space 15 of the filter device 10. This results in a favorable mixing of the foreign matter contained in the source gas stream 44 with the filter aid in order to increase the autoignition threshold of the source gas. Optionally, a baffle or distributor plate 56 can be provided near the filter aid supply opening 52 so that the filter aid is evenly distributed in the source gas stream 44.

[0099] In Figure 2As schematically shown, a pressurized gas scavenging unit 58 is coupled to the filter unit 12 and is located in the clean gas space 17 of the filter unit 12 above the filter element 14. At certain time intervals, the pressurized gas scavenging unit 58 pressurizes the corresponding filter element 14 such that the filter element 14 is subjected to a pressure shock from the clean gas space 17. The pressure shock causes foreign matter such as easily combustible foreign matter and, in some cases, also filter aids, which have accumulated on the filter surface on the raw gas side of the corresponding filter element 14, to fall off from the filter element 14 and to drop downward due to their gravity. The substances removed from the filter surface then fall through the channel 28 together with the foreign matter and the filter aids into the agglomerate collection area 33 in the reaction area 24.

[0100] The first shut-off member 30 is normally open, such that there is a fluid connection between the raw gas space 15 and the reaction zone 24. This is maintained in particular at the start and during the purging cycle of the filter element 14. In this way, the substances falling from the filter surface during purging can fall unhindered or at least substantially unhindered into the agglomerate collection zone 33 of the reaction zone 24 and do not deposit significantly on the base plate or the walls of the housing 18 surrounding the raw gas space 15. Once the purging has been completed and the oxidation cycle has started in the reaction zone 24, the first shut-off member 30 is closed, such that the agglomerate collection zone 33 of the reaction zone 24 is fluid-tightly separated from the raw gas space 15 for at least a period of time during which an oxidant-containing environment prevails in the agglomerate collection zone 33. Then, an oxidant is introduced via the oxidant inlet 36 into the agglomerate collection zone 33 to cause spontaneous oxidation of the substances entering the agglomerate collection zone 33. The oxidant inlet 36 is designed such that the oxidant flows through or mixes with the solid-containing substances (in particular the oxidizable substances removed from the filter surface) in the agglomerate collection zone 33 and thus spontaneously initiates the oxidation of this substance, i.e., without additional input of energy via a heating device, an ignition device, etc. Then, the oxides formed by oxidation (now inert foreign matter), the excess oxidant and other substances can be transported via the outlet 39 along the discharge line 60 to the discharge zone 62 downstream of the agglomerate collection zone 33. After this discharge process has been completed, the concentration of the oxidant in the agglomerate collection zone 33 has dropped to a level where contamination of the raw gas space 15 is no longer a concern, and the shut-off member 30 can then be opened again. To assist in discharging the oxidant from the container 32 surrounding the agglomerate collection zone 33, a purge fluid in the form of nitrogen, a noble gas or another inert gas can be introduced into the container 32 via an optional additional fluid inlet 38. This allows the residual oxidant still present in the container 32 to be removed from the container 32 via the additional fluid outlet 40 and thus from the agglomerate collection zone 33 to create an inert environment in the container 32 or in the agglomerate collection zone 33. When the shut-off member 30 is open, foreign matter from the raw gas stream 44 and the substances removed from the filter surface can enter the reaction zone 24 again without intermediate storage. By not collecting foreign matter in the lower region 18b of the housing 18, dust bridges are effectively avoided, which would otherwise strongly impair the subsequent sliding of the foreign matter into the reaction zone 24.

[0101] As a variant, it is conceivable that a continuous flow of an inert fluid (such as nitrogen or a noble gas) passes at least temporarily through the container 32 via the oxidant inlet 36 and / or via a further fluid inlet 38. This continuous flow passes through the agglomerate collection area 33 of the reaction zone 24, flows to the outlet 39 and leaves the container 32 again through the outlet 39. Once the cleaning of the filter element 14 or the plurality of filter elements has taken place and the shut-off member 30 is closed, a sufficient amount of oxidant can be added to this fluid flow so that the substances located in the agglomerate collection area 33 can react or be transformed by oxidation. Once the transformation has occurred to the desired extent, the supply of oxidant to this fluid flow can be stopped, and the foreign matter containing oxides or the re-reacted foreign matter can be conveyed with this fluid flow from the agglomerate collection area 33 or from the container 32 via the discharge line 60 to the discharge area 62.

[0102] The coordination between the start of the pressurized gas purge unit 58, i.e., the cleaning of the one or more respective filter elements 14 of the substances adhering to the filter surface, and the opening and closing of the shut-off member 30 is carried out by the control unit 59. The control unit 59 can be configured such that the shut-off member 30 is open as a default setting, whereby foreign matter in the raw material gas that does not reach the filter element 14 or detaches from the filter element surface outside the cleaning cycle directly falls into the agglomerate collection area 33 of the reaction zone 24. Even during the cleaning of the filter element 14, the shut-off member 30 remains open to allow the substances removed from the filter surface to be discharged into the reaction zone 24 without intermediate storage. As soon as the cleaning is completed, the control unit 59 closes the shut-off member 30 for a short time so that oxidant can be admitted into the reaction zone 24, in particular, into the container 32 surrounding the agglomerate collection area 33, and the reaction zone 24 is now separated from the raw material gas space 15. After a predetermined time, it can be assumed that the substances removed from the filter surface in the agglomerate collection area 33 have been oxidized to an extent sufficient to form foreign matter containing oxides. To the extent that the oxidant added in the reaction is not consumed, the excess oxidant is then removed from the agglomerate collection area 33 so that an inert environment reappears in the reaction zone 24, i.e., the oxidant concentration is so low that even if foreign matter or substances removed from the filter surface enter the agglomerate collection area 33, no further oxidation occurs. Then, the control unit 59 can reopen the shut-off member 30 to again allow foreign matter and substances removed from the filter surface to enter the agglomerate collection area 33.

[0103] In some embodiments, the container 32 can be arranged to be movable or acted upon by a stirring device and / or a tapping device to produce a corresponding rocking motion, vibration, shaking motion, etc. of the container 32 in order to facilitate the subsequent or continued downward sliding of the solid-containing substances through the outlet 39. In this way, it is possible to achieve as complete an emptying of the agglomerate collection area 33 as possible.

[0104] In addition to the discharge line 60, the discharge area 62 preferably further includes a collection container 64, in which foreign matter containing oxides is collected. The fluid substance, in particular the gaseous substance, reaching the collection container 64 via the discharge line 60 is discharged again from the collection container 64 via the exhaust gas outlet 130.

[0105] Optionally, a second closing device having a second cut-off member 66 may be provided in the discharge line 60 in an area, for example, near the collection container 64. Thus, the second closing device is also coupled to the discharge area 62. The second closing device is designed to separate the upstream part of the discharge area 62 from the downstream part. The upstream part still belongs to the reaction area 24 and the oxidation of the substance containing foreign matter still occurs therein, while the oxidation no longer occurs in the downstream part. However, it is not essential to provide the second closing device. It has been found that the desired oxidation reaction can occur completely in the discharge area 62, in particular in the discharge line 60, and in particular can be completed before the substance transported through the discharge line 60 reaches the downstream end of the discharge line 60, where the discharge line 60 leads, for example, into the collection container 64.

[0106] The downstream end of the discharge line 60 leads into the collection container 64. When reaching the collection container 64, the solid-containing substance, in particular the foreign matter containing oxides formed during oxidation, falls into the collection container 64 of the discharge area 62 and can thus be disposed of. At the top, the exhaust gas outlet area 120 (see Figure 6 ) leads into the collection container 64. In the exhaust gas outlet area 120, there is an exhaust gas outlet 130, through which the excess fluid substance, in particular the oxidant, the cleaning fluid, the transport fluid, the heat transfer fluid and other fluids, can be discharged from the discharge area 62. If necessary, the excess fluid substance (hereinafter also simply referred to as exhaust gas) can be discharged to the environment or the exhaust system via the cut-off valve 78. Alternatively, as Figure 2 shown, all or part of the excess fluid substance can be returned to the reaction area 24, in particular to the oxidant inlet 36. Also in this case, optionally, a cut-off valve 78 can be provided. The arrangement shown Figure 2 will be described in more detail below.

[0107] Figure 3 Another embodiment of the container 32 is shown. Only the features different from the container 32 of Figure 1 and Figure 2 will be described in more detail below. For the description of the additional features in Figure 3 , reference is made to the description of Figure 1 and Figure 2 , in which the same or corresponding features are denoted by the same reference numerals. InFigure 3 In an embodiment, a pneumatic conveying device (configured as a solid syringe 80 in this case) is arranged to convey a substance from a container 32. In this embodiment, a hollow nozzle 68 extends from the top end 34 of the container 32 into the interior of the container 32. The tip of the hollow nozzle 68 extends to a position near the root or bottom end 42 of the container 32. The hollow nozzle 68 includes one or more openings in a region adjacent to its tip, through which the substance can be discharged from the container 32, and the hollow nozzle 68 is connected to the conveying port 74 of the solid syringe 80.

[0108] Alternatively or in addition to the solid syringe, a suction fan can be provided to convey a substance, in particular a gaseous substance, from the container 32. Like the solid syringe, the suction fan can be connected to the container 32 via the hollow nozzle 68 and can be particularly arranged to extract or suck away oxidants and other gaseous fluids from the agglomerate collection area 33.

[0109] In addition to the conveying port 74, the solid syringe 80 also has a conveying fluid inlet 70 and a substance discharge port 76. The conveying fluid inlet 70 can be supplied with a conveying fluid (such as air). The substance discharge port 76 is in communication with the conveying fluid inlet 70 and the conveying port 74. The conveying port 74 connects the hollow nozzle 68 to a passage that connects the conveying fluid inlet 70 to the substance discharge port 76. The conveying fluid inlet 70 generally has a shape that tapers towards the substance discharge port 76 so as to accelerate the conveying fluid in the passage when acted upon by the conveying fluid, thereby creating a negative pressure in the hollow nozzle 68 and thus sucking out the solid-containing substance from the container 32 through the hollow nozzle 68. The substance discharge port 76 of the solid syringe 80 is connected to a discharge line 60. When the conveying fluid inlet 70 is acted upon, the conveying fluid is conveyed from the conveying fluid inlet 70 to the discharge line 60 via the substance discharge port 76, thereby creating a negative pressure in the hollow nozzle 68. Due to this negative pressure, the solid-containing substance present in the container 32 (in particular, the oxide-containing foreign matter formed during the reaction) together with the gaseous substance (in particular, the unconsumed oxidant) is sucked into the hollow nozzle 68 and conveyed through the hollow nozzle 68 to the substance discharge port 76. During this process, the sucked-in substance is mixed with the conveying fluid and is conveyed through the substance discharge port 76 into the discharge line 60 of the discharge area 62.

[0110] Depending on the conveying fluid entering the conveying fluid inlet 70, the suction intensity of the solid syringe 80 can be adjusted, so that the corresponding amounts of the solid-containing substance and the gaseous substance conveyed from the container 32 can be adjusted, or the mixing ratio between the substance conveyed from the container 32 and the mixed conveying fluid can be adjusted. Ultimately, this allows precise control of the oxidation reaction occurring in the container 32 and also any oxidation reaction that may occur downstream of the solid syringe 80 in the discharge line 60.

[0111] Foreign objects containing oxides can also be sucked out of the container 32 in an alternative manner. For this purpose, a negative pressure can be generated in the discharge area 62, for example, by means of a blower or a suction device, whereby the foreign objects containing oxides are sucked into the discharge pipeline 60 of the discharge area 62 through the hollow nozzle 68. In addition to the foreign objects containing oxides, for example, excess oxidant and / or additional substances or fluids can also be sucked out of the container 32. Once the extraction is complete, that is, as long as little or no oxidant remains in the agglomerate collection area 33, the cut-off member 30 can release the passage 28 from the raw gas space 15 to the agglomerate collection area 33. In such an arrangement, the transport fluid inlet 70 is not necessary, but can be optionally provided to assist in removing the oxide-containing impurities.

[0112] Instead of or in addition to using negative pressure to extract the foreign objects containing oxides, a transport fluid (especially a transport gas) can be introduced into the container 32 via the fluid inlet 38. The transport fluid is under positive pressure and then pneumatically forces the foreign objects containing oxides through the hollow nozzle 68 into the discharge pipeline 60 to the discharge area 62. For assistance, the transport fluid can be introduced into the discharge pipeline 60 through the transport fluid inlet 70 to further transport the foreign objects containing oxides and prevent the formation of dust bridges. The transport fluid can be an inert fluid such as nitrogen. The transport fluid can also include an oxidant such as oxygen. In this way, it can be ensured that the oxidation reaction continues to occur when the substance is transported from the container 32 to the discharge area 62. For example, if it is necessary to add an oxidant to the transport fluid, it is convenient to use air as the transport fluid. If necessary, an inert fluid can also be used as the transport fluid and the oxidant can be introduced into the container 32 through a separate inlet.

[0113] In order to safely remove the excess oxidant from the agglomerate collection area 33 or the container 32 of the reaction area 24, the excess oxidant can be removed from the interior of the container 32 via the fluid outlet 40 after removing the foreign objects containing oxides, preferably by allowing an inert fluid (such as nitrogen or an inert gas) to pass through the fluid inlet 38 or the oxidant inlet 36, and the inert fluid displaces the excess oxidant from the agglomerate collection area 33 or the container 32 of the reaction area 24.

[0114] In addition, after the substance has been removed from the container 32 through the solid syringe 80, it is also possible to supply an inert fluid (such as an inert gas like nitrogen) to the container 32 through the solid syringe 80. The solid syringe 80 has an additional port 72 which can act together with the cleaning fluid to restore a potentially blocked fluid connection between the hollow nozzle 68 and the substance discharge port 76. By applying the inert fluid to the cleaning port 72 and, if necessary, closing the substance discharge port 76, the inert fluid can be easily introduced into the container 32 to flush or clean any oxidant that still remains in the agglomerate collection area 33.

[0115] Figure 4 Another embodiment of the container is shown, in which, similar to Figure 3 , a pneumatic conveying device (configured as a solid syringe 80 in this case) is provided to convey the substance from the container 32. Only those features of the container 32 that are different from Figure 1 , Figure 2 and Figure 3 will be described in more detail below. To describe Figure 4 other features in, reference is made to Figure 1 , Figure 2 and in particular Figure 3 's description, in which the same or corresponding features are provided with the same reference numerals.

[0116] Different from the embodiment of Figure 3 , according to Figure 4 's embodiment, the solid syringe 80 is arranged at the lowest point of the container 32. In the shown variant, the side walls of the container 32 converge downwardly, where these side walls are closest to each other. An opening is formed at the bottom of the container 32, which communicates with the conveying port 74 of the solid syringe 80, and the substance can be sucked out of the container 32 through this opening. It can be understood that a plurality of such openings can also be formed at the bottom of the container 32. In this embodiment, the conveying fluid inlet 36 of the solid syringe 80 (which can be acted upon by a conveying fluid (such as air)) also serves as the oxidant inlet 36 of the container 32 and is thus denoted by the reference numeral 36.

[0117] The material discharge port 76 is further connected to the discharge pipeline 60. Generally, the conveying fluid inlet 36 communicates with the material discharge port 76 via a passage having a shape that tapers towards the material discharge port 76, so as to accelerate the conveying fluid in the passage when the conveying fluid is applied to the conveying fluid inlet 36. When the conveying fluid is applied to the conveying fluid inlet 36, the conveying fluid is introduced from the conveying fluid inlet 36 into the discharge pipeline 60 via the material discharge port 76, thereby generating a negative pressure, which causes the solid-containing material (especially the oxide-containing foreign matter formed during the reaction) and the gaseous material (especially the unconsumed oxidant) present in the container 32 to be sucked or drawn in together and conveyed to the material discharge port 76. During this process, the inhaled material is mixed with the conveying fluid and transported through the material discharge port 76 into the discharge pipeline 60 of the discharge area 62.

[0118] When only a slight positive pressure is applied to the conveying fluid inlet 36, the acceleration of the conveying fluid in the passage leading to the material discharge port 76 is not sufficient to generate a significant negative pressure. In this case, the conveying fluid is introduced into the container through the conveying port 74. This effect can be further enhanced by closing the material discharge port 76. Therefore, if the conveying fluid inlet 36 of the solid syringe 80 is acted upon by a conveying fluid (such as air) containing an oxidant under a slight positive pressure, the final effect is to supply the oxidant to the container 32 or the agglomerate collection area 33. Additionally, Figure 4 the operation of the solid syringe 80 in Figure 3 is the same as the operation of the solid syringe 80 shown in

[0119] Figure 4 The solid syringe 80 shown in also has a port 72, which can act together with the cleaning fluid to restore the potentially blocked fluid connection between the conveying port 74 and the material discharge port 76. By applying an inert fluid to the cleaning port 72 and, if necessary, closing the material discharge port 76, the inert fluid can be easily introduced into the container 32 to clean any oxidant remaining in the agglomerate collection area 33. By applying the inert fluid containing the oxidant to the port 72 in this way, the oxidant can also be introduced into the agglomerate collection area 33 if necessary.

[0120] Figure 5 The agglomerate collection area 33 of the reaction area 24 located in the container 32 is shown, where the first cut-off member 30 is upstream in the flow direction of the cleared material. Figure 5Schematically shows how the material 89 removed from the filter surface falls into the container 32 in the direction of the cutting member 30. When doing so, the falling material removed from the filter surface straddles the oxidant stream 90 flowing from the oxidant inlet 92 to the oxidant outlet 94. When the oxidant stream 90 passes through, the material removed from the filter surface spontaneously reacts with the oxidant, thereby converting into poorly reactive or inert and / or oxide-containing foreign matter 91. The oxide-containing foreign matter formed during oxidation is mainly discharged via the discharge line 60 ( Figure 5 not shown in the figure) to the discharge area 62 downstream of the container 32. The oxidation of the unoxidized foreign matter can also continue in the discharge line 60. The heat generated by the reaction can be dissipated together with the oxidant stream 90 through the oxidant outlet 94, and the oxidant stream 90 is usually a mixture of an oxidant (such as oxygen) and an inert component (such as nitrogen or an inert gas).

[0121] Figure 6 Shows an embodiment of the exhaust gas outlet area 120 leading to the collection container 64. The exhaust gas outlet area 120 includes an additional filter unit 122 mounted on the partition 124. The additional filter unit 122 may include one or more filter elements. The partition 124 separates the exhaust gas outlet area 120 into a raw gas space 126 and a clean gas space 128. A mixture of solid-containing substances (especially oxide-containing foreign matter, unoxidized foreign matter, possible filter aids, other solids and aggregates of such substances) and fluid-phase substances, especially gaseous substances (especially excess oxidant, transport fluid, cleaning fluid, cooling fluid, etc.) enters the raw gas space 126. The additional filter unit 122 is configured to filter the mixture reaching the raw gas space 126 to remove particulate oxidation residues and other particulate foreign matter. Then, the filtered mixture of the fluid phase is present in the clean gas space 128 and is discharged through the exhaust gas outlet 130 located in the clean gas space 128. In particular, the mixture of the fluid phase is gaseous, so it is hereinafter referred to in a simplified form as exhaust gas. This exhaust gas can be discharged into the environment or into an external exhaust gas system via a cut-off device, for example. Alternatively, as Figure 6 shown, this exhaust gas can also be returned to the reaction area 24, for example, to the oxidant inlet 36. It is conceivable that a part of this exhaust gas is discharged to the surroundings or an external exhaust gas system, and another part of this exhaust gas is returned to the reaction area 24, for example, to the oxidant inlet 36. In this case, the ratio of the exhaust gas stream returned to the reaction area 24 to the discharged exhaust gas stream can be controlled. In particular, this control can be arranged such that only so much exhaust gas always returns to the circuit, especially to the reaction area 24, such that the fluid pressure (especially the gas pressure) in the circuit system (especially in the reaction area 24) does not exceed a predetermined upper limit value and is especially maintained within a predetermined range.

[0122] In addition, a pressurized gas purging unit coupled to the additional filter unit 122 is arranged in the clean gas space 128. The pressurized gas purging unit is designed to generate pressure pulses acting on the filter element for purging. The pressure pulses reach the clean gas space 128 from the pressurized gas reservoir 134 via the pressurized gas opening 132 and reach the filter element of the additional filter unit 122 from the clean gas space 128. The pressurized gas reservoir 134 can preferably be filled with pressurized gas via the pressurized gas line 136. Once the filter performance of the additional filter unit 122 deteriorates, the pressurized gas purging is used to purge the additional filter unit 122. In this case, the pressurized gas is introduced into the clean gas space 128 in the form of pressurized gas pulses, whereby the filter element wall is subjected to the pressure pulses and foreign matter that has accumulated on the raw gas side of the additional filter unit 122 is purged from the additional filter unit 122. These foreign matters then fall from the exhaust gas outlet region 120 through the passage 138 into the collection container 64. A cut-off member 140 is optionally arranged in the passage 138 to separate the discharge region 62 from the exhaust gas outlet region 120. It should be noted that it is not necessary to equip the additional filter unit 122 with a cleanable filter element, and for example, a storage filter in the additional filter unit 122 can be used very well, and this storage filter must be replaced from time to time.

[0123] To achieve the recirculation of the fluid, in particular the recirculation of the transport fluid and / or the unconsumed oxidant, it can be arranged that the exhaust gas outlet 130 is connected to the reaction zone 24, in particular to the oxidant inlet 36, as schematically shown as the exhaust gas recirculation line 150 in Figure 2 It should be understood that, as shown in Figure 2 and Figure 6 the cut-off valve 78 in the exhaust gas recirculation line 150 is optional, and an exhaust gas recirculation line 150 without a cut-off valve is also possible. This recirculation generates a closed loop, whereby the inert fluid added as the transport fluid and / or the cleaning fluid and / or the heat dissipation fluid to the aforementioned dry filtering process can be recirculated in this process via the exhaust gas recirculation line 150 after passing through this process. In this way, a significant saving of the required inert fluid can be achieved.

[0124] Since the oxidant (especially oxygen) is consumed when passing through the described process of oxidizing the filter residue, it makes sense to add the oxidant again to the fluid returning from the exhaust gas outlet 130 to the reaction zone 24, in particular to the oxidant inlet 36, to the extent that the oxidant is consumed when passing through this process. For this purpose, a sensor 142 can be provided in the exhaust gas recirculation line 150, for example between the exhaust gas outlet 130 and the oxidant inlet 36, to determine the loss of the oxidant in the fluid stream leaving the exhaust gas outlet 130 relative to the desired concentration of the oxidant in the oxidant stream entering the vessel 32 at the oxidant inlet 36. In addition, a device 144 can be provided for supplying the oxidant to the recirculation fluid stream based on the loss of the oxidant determined by the sensor 142.

[0125] In Figure 2 the example shown, the sensor 142 is located at the oxidant inlet 36 and detects the actual concentration of the oxidant in the oxidant stream when the oxidant stream enters the agglomerate collection zone 33 of the vessel 32 or the reaction zone 24. The device 144 for supplying the oxidant to the recirculation fluid stream leads to the exhaust gas recirculation line 150 at a position upstream of the sensor 142 and is controlled such that the oxidant concentration sensed at the sensor 142 is maintained at a predetermined value or within a predetermined range around this predetermined value.

[0126] For example, the amount of fluid carried in this process can be kept constant by monitoring the fluid pressure in the recirculation fluid stream. For example, this can be achieved by sensing and controlling or regulating the pressure at the exhaust gas outlet 130, at the oxidant inlet 36, or in the exhaust gas recirculation line 150. As Figure 2 shown, for this purpose, a pressure reducing valve 146 can be arranged in the exhaust gas recirculation line 150, for example. By means of the pressure reducing valve, a predetermined pressure can be set in the exhaust gas recirculation line 150, and thus ultimately the mass flow rate of the fluid phase in the circuit (i.e., the sum of the oxidant and other fluids such as the feed fluid, the cleaning fluid, the heat transfer fluid) can be kept constant.

[0127] With an arrangement of the type described, the mass flow rate of the fluid carried in the circuit and the concentration of the oxidant in this circuit can be controlled or regulated in a simple manner. Thus, the intensity of the oxidation reaction occurring during the treatment of the filter residue can be very well controlled or regulated in a closed control loop in such a way that sufficient effective oxidation of the combustible substances is achieved while not generating too much reaction heat.

Claims

1. A method for dry-filtering a gas stream carrying foreign matter, the method comprising: introducing a raw gas stream (44) containing foreign matter into a raw gas space (15) of a filter unit (12), the filter unit (12) having at least one filter surface separating the raw gas side from the clean gas side; removing the foreign matter that has accumulated at the at least one filter surface during a cleaning cycle and transporting the removed foreign matter to a downstream reaction zone (24); supplying an oxidant to the reaction zone (24) through a pneumatic conveying device (80); causing the foreign matter contained in the material removed from the filter surface and / or contained in the raw gas stream to react with the oxidant in the reaction zone (24) to form foreign matter containing oxides.

2. The method according to claim 1, Among them, wherein the pneumatic conveying device (80) is a conveying device operating as a solid syringe or an ejector pump.

3. The method according to claim 1 or 2, Among them, wherein the reaction zone is downstream of the raw gas space with respect to the transport of the foreign matter that has accumulated on the filter surface and has been removed from the filter surface during the cleaning cycle.

4. The method according to claim 1 or 2, Among them, removing the unconsumed oxidant from the reaction zone (24) during the reaction of the material removed from the filter surface with the oxidant.

5. The method according to claim 1 or 2, Among them, supplying the oxidant to the reaction zone (24) via an oxidant inlet (36) and removing it via an oxidant outlet (39).

6. The method according to claim 5, Among them, wherein the oxidant outlet (39) is different from the oxidant inlet (36).

7. The method according to claim 5, Among them, the unconsumed oxidant, the foreign matter containing oxides formed during the reaction, and, if applicable, the unreacted foreign matter are discharged through the same oxidant outlet (39).

8. The method according to claim 7, Among them, wherein the reaction zone (24) includes a region downstream of the oxidant outlet (39).

9. The method according to claim 5, Among them, wherein the oxidant outlet (39) is connected to the pneumatic conveying device (80).

10. The method according to claim 1 or 2, Among them, wherein the reaction zone (24) has a negative pressure applied thereto.

11. The method according to claim 10, Among them, applying a negative pressure to the reaction zone (24) during and / or after the reaction of the material removed from the filter surface with the oxidant.

12. The method according to claim 1 or 2, Among them, withdrawing the unconsumed oxidant from the reaction zone (24) through the pneumatic conveying device during the reaction of the material removed from the filter surface with the oxidant.

13. The method according to claim 1 or 2, Among them, wherein the reaction zone (24) is acted upon by an inert fluid.

14. The method according to claim 13, Among them, The reaction of the substance removed from the filter surface with the oxidant takes place in the reaction stage, and after the corresponding reaction stage, the reaction zone is acted upon by an inert fluid to which no oxidant is added.

15. The method according to claim 13, Among them, An inert fluid is supplied into the reaction zone via a further fluid inlet (38) different from the oxidant inlet (36).

16. The method according to claim 13, Among them, The inert fluid and / or the oxidant is / are discharged from the reaction zone through a further outlet (40) provided in addition to the oxidant outlet (39).

17. The method according to claim 1 or 2, Among them, The reaction zone (24) has a heat transfer fluid flowing through the reaction zone (24) for removing the heat generated during the reaction of the substance removed from the filter surface with the oxidant.

18. The method according to claim 1 or 2, Among them, The reaction zone (24) includes an agglomerate collection zone (33) configured to receive the substance removed from the filter surface, wherein foreign matter or agglomerates containing foreign matter that have accumulated on the filter surface are removed, collected, and stored in the agglomerate collection zone (33).

19. The method according to claim 18, Among them, The substance removed from the filter surface is transported from the agglomerate collection zone (33) into a downstream discharge zone (62), wherein the discharge zone (62) includes at least a part of the reaction zone (24); and an oxidant is supplied to the agglomerate collection zone (33) and / or the discharge zone (62).

20. The method according to claim 19, Among them, A first closing device having a first shut-off member (30) is coupled to the agglomerate collection zone (33), the closing device being designed such that it enables the substance shed from the filter surface during the cleaning process to be collected in the agglomerate collection zone (33) and, after the removed substance has been collected in the agglomerate collection zone (33), closes the reaction zone (24) relative to the raw gas space (15), at least until the oxidant concentration in the reaction zone (24) and / or the agglomerate collection zone (33) has dropped to a sufficient extent.

21. The method according to claim 20, Among them, The discharge zone (62) includes a second closing device (66), wherein the reaction zone (24) is located between the first closing device and the second closing device; and / or, wherein the discharge zone (62) includes a collection container (64) for substances containing solids.

22. The method according to claim 1 or 2, Among them, After leaving the reaction zone (24), the unconsumed oxidant in the reaction zone (24) and, if applicable, also any additional fluid accumulating as an excess flow volume, is / are recycled completely or partially to the reaction zone (24).

23. The method according to claim 22, Among them, A control / regulation unit is provided, which is arranged such that the fluid pressure within the reaction zone (24) does not exceed a predetermined upper limit value or remains within a predetermined pressure range.

24. A filter device (10) for cleaning a raw material gas carrying foreign matter, comprising: At least one filter element (14), which has at least one filter surface that separates a raw material gas side from a clean gas side in a raw material gas space, and a raw material gas stream (44) containing foreign matter can be supplied to the raw material gas space; A cleaning device, which is adapted to clean the foreign matter that has accumulated at the at least one filter surface during a cleaning cycle and convey the cleaned foreign matter to a downstream reaction zone (24); An oxidant supply device, which is adapted to supply an oxidant to the reaction zone (24) through a pneumatic conveying device (80); So that the foreign matter contained in the material removed from the filter surface and / or the raw material gas stream (44) reacts with the oxidant within the reaction zone (24) to form foreign matter containing oxides.

25. The filter device (10) according to claim 24, Among them, The pneumatic conveying device is configured to operate as a solid syringe or an ejector pump.

26. The filter device (10) according to claim 24 or 25, Among them, The reaction zone is downstream of the raw material gas space with respect to the conveyance of the foreign matter that has accumulated on the filter surface and has been removed from the filter surface during the cleaning cycle.

27. The filter device (10) according to claim 24 or 25, Among them, During the reaction of the material removed from the filter surface with the oxidant, unconsumed oxidant can be removed from the reaction zone (24).

28. The filter device (10) according to claim 24 or 25, including an oxidant inlet (36) and an oxidant outlet (39), the oxidant inlet (36) being arranged to supply oxidant to the reaction zone (24), the oxidant outlet (39) being arranged to remove oxidant from the reaction zone (24), wherein, The oxidant outlet (39) is different from the oxidant inlet (36).

29. The filter device (10) according to claim 28, The filter device (10) is designed to discharge unconsumed oxidant, together with the foreign matter containing oxides formed during the reaction and, if applicable, unreacted foreign matter, through the same oxidant outlet (39).

30. The filter device (10) according to claim 28, Among them, The reaction zone (24) includes a region downstream of the oxidant outlet (39).

31. The filter device (10) according to claim 28, Among them, The oxidant outlet (39) is connected to the pneumatic conveying device (80).

32. The filter device (10) according to claim 24 or 25, The filter device (10) is arranged to apply a negative pressure to the reaction zone (24) during and / or after the reaction of the material removed from the filter surface with the oxidant.

33. The filter device (10) according to claim 24 or 25, The filter device (10) is arranged to act on the reaction zone (24) with an inert fluid.

34. The filter device (10) according to claim 33, comprising a control unit (59) arranged such that the reaction of the substance removed from the filter surface with the oxidant takes place in a reaction stage, wherein, After the corresponding reaction stage, an inert fluid without added oxidant is applied to the reaction zone (24).

35. The filter device (10) according to claim 34, Further comprising an additional fluid inlet (38) leading into the reaction zone (24), the additional fluid inlet (38) being different from the oxidant inlet (36) for introducing an inert fluid and / or a heat transfer fluid.

36. The filter device (10) according to claim 33, Further comprising an additional outlet (40) for discharging the inert fluid and / or the oxidant, the additional outlet (40) being provided in addition to the oxidant outlet (39).

37. The filter device (10) according to claim 24 or 25, Among them, The reaction zone (24) includes an agglomerate collection zone (33) arranged to receive the material removed from the filter surface, wherein foreign matter or agglomerates containing foreign matter that have accumulated on the filter surface can be collected and stored in the agglomerate collection zone (33) after being removed.

38. The filter device (10) according to claim 37, Further includes an emission area (62), the emission area (62) being located downstream of the agglomerate collection area (33), and the material removed from the filter surface can be transported into the emission area (62), wherein, The discharge zone (62) includes at least a part of the reaction zone (24), and An oxidant can be supplied to the agglomerate collection zone (33) and / or the discharge zone (62).

39. The filter device (10) according to claim 38, Among them, The agglomerate collection zone (33) has a first closing device coupled thereto, the first closing device having a first cut-off member (30), and the first closing device is designed such that the first closing device can cause the material shed from the filter surface during the cleaning process to be collected in the agglomerate collection zone (33), and after the removed material is collected in the agglomerate collection zone (33), the reaction zone (24) is closed relative to the raw material gas space (15), at least until the oxidant concentration in the reaction zone (24) has dropped to a sufficient extent.

40. The filter device (10) according to claim 39, Among them, The discharge zone (62) includes a second closing device, wherein the reaction zone (24) is located between the first closing device and the second closing device.

41. The filter device (10) according to claim 40, Among them, The discharge zone (62) includes a collection container (64) for separating the solid-containing material, wherein the collection container (64) has an outlet for the fluid material, and an additional filter unit (122) for removing foreign matter from the fluid material is coupled to the outlet.

42. The filter device (10) according to claim 24 or 25, Further comprising a fluid recirculation unit (150), the fluid recirculation unit (150) being arranged such that, after leaving the reaction zone (24), oxidant not consumed in the reaction zone (24), and, if applicable, also additional fluid accumulating as an excess stream, is fully or partially recirculated to the reaction zone (24), wherein, A control / regulation unit is provided, the control / regulation unit being arranged such that the fluid pressure in the reaction zone (24) does not exceed a predetermined value or remains within a predetermined range.

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