Patent Application
20230079987
The invention relates to a method for the dry filtration of a gas flow carrying foreign objects, and to a filter device for cleaning raw gas carrying foreign objects.
WO 2012/032003 A1 shows a method for the dry filtration of gases carrying foreign bodies or objects, e.g. exhaust air from a paint shop, in which filter surfaces are coated with limestone powder (CaCO3) as filtration aid before charging with raw gas containing foreign objects. In this way, clogging of pores of the filter by sticky foreign substances can be suppressed. This coating of filter surfaces with limestone powder before they come into contact with foreign objects is known as precoating. Precoating is typically used in the cleaning of exhaust air from wet paint shops.
It is an object of the invention to prevent or suppress raw gas fires when filtering raw gases containing flammable foreign objects by means of a dry filter, in particular at high operating temperatures.
In the method for the dry filtration of a gas flow carrying foreign objects according to the invention, in particular in a filter device for cleaning off exhaust air produced in additive manufacturing technologies, a raw gas flow containing foreign objects is fed into a raw gas space of a filter unit which has at least one filter surface separating a raw gas side from a clean gas side. Furthermore, an oxidant is fed to a reaction region located on the raw gas side of the filter surface downstream of the filter surface. The oxidant is fed such that foreign objects contained in material cleaned off from the filter surface and/or in the raw gas flow react with the oxidant in the reaction region to form oxide-containing foreign objects.
The oxidant may be, for example, air or an oxygen-containing gas.
The basic idea of the present invention is to render foreign objects contained in the raw gas, which are readily combustible, harmless by specifically initiating and carrying out a controlled transfer of these combustible foreign objects into an oxidized configuration (i.e by chemical reaction). In the oxidized configuration, these foreign objects are generally poorly reactive or inert and no longer combustible, so that further handling of these oxidized foreign objects no longer requires special precautions. However, care has to be taken to ensure that the oxidation reaction proceeds in a controlled manner and, in particular, that the thermal energy generated during oxidation does not lead to the formation of flames or fires. This is achieved by suitable supply of oxidant to a predetermined reaction region and/or further measures for removing the thermal energy generated during the reaction from the reaction region.
For example, the reaction region may be downstream of the raw gas space with respect to the transport of foreign objects that have accumulated on the filter surface and have been cleaned off from the filter surface. Thus, the reaction region is located on the raw gas side, but downstream of the filter surface. If the oxidant is first supplied to the downstream reaction region, but not to the raw gas space or a region upstream of the raw gas space, the raw gas space remains free of oxidant, so that the actual filtration of the raw gas can proceed under largely inert conditions. Maintaining an inert environment in the raw gas space can be further ensured by closing off the reaction region from the raw gas space—at least when oxidant is supplied.
In addition, a heat transfer fluid may flow through the reaction region to remove heat generated during the reaction. The heat transfer fluid may be a fluid flow separate from the oxidant, for example an inert gas such as nitrogen, which is introduced into the reaction region and discharged from the reaction region after flowing through the reaction region. Such a heat transfer fluid can be maintained in a circulating flow if, after discharge of the heat transfer fluid from the reaction region, suitable heat exchangers are provided in which the heat transfer fluid can release its heat. It is also conceivable and indeed preferred that the heat transfer fluid also contains the oxidant. For example, air or a gas mixture of an inert gas with a predetermined content of oxygen can flow through the reaction region. The heat transfer fluid flows through the reaction region, i.e. a certain amount of heat transfer fluid is supplied to the reaction region per unit of time and heat transfer fluid is removed from the reaction region to the same extent.
Furthermore, an agglomerate collection region may be provided, which is designed to receive material cleaned off from the filter surface, which in the following will be referred to as cleaned-off material. Foreign objects accumulated on the filter surface or agglomerates containing foreign bodies, after cleaning off from the filter surface, are collected in the agglomerate collection region and stored therein. It may be provided that the agglomerate collection region has a first closure means which is controlled such that it closes off the raw gas space with respect to a discharge region downstream of the raw gas space for the removal of material cleaned off from the filter surface or establishes a connection between the raw gas space and the discharge region. The first closure means may, for example, comprise a first closure member provided in a boundary of the raw gas space relative to its surroundings. By controlling the first closure means, the amount of material passing from the raw gas space to the discharge region per unit of time can be controlled such that a predetermined amount of oxidizable material is always present in the reaction region and thus a predetermined amount of oxidizable material is transported through the reaction region per unit of time. As a result, suitable control of the first closure means can be used to ensure that the amount of heat generated in the reaction of the oxidizable material remains within a tolerable range such that the temperature in the reaction region does not exceed a predetermined threshold value.
In certain embodiments, the reaction region may be located within the discharge region such that the discharge region contains the reaction region. In particular, the reaction region may then be located downstream of the first closure means so that, when the first closure means is closed, the oxidation occurring in the reaction region does not affect the ambient conditions prevailing in the raw gas space.
In particular, it may be provided that the oxidant is fed to the discharge region. This allows the raw gas space to remain free, at least largely free, of oxidant because the oxidant is fed downstream of the raw gas space in the direction of flow of material cleaned off from the filter surface. In particular, it may be provided that the raw gas space remains closed with respect to the discharge region when oxidant is fed to the discharge region.
In further embodiments, the discharge region may comprise a second closure means arranged downstream of the first closure means in the direction of flow of material cleaned off from the filter surface. The reaction region may then be located between the first closure means and the second closure means. In this way, a fairly well-defined location of the reaction region can be obtained. In particular, it can be ensured by controlling the first and second closure means that the oxidation of combustible foreign objects taking place in the reaction region does not have a major impact on upstream regions (such as the raw gas space) or downstream regions (such as a collecting container for material cleaned off from the filter surface). In particular, the second closure means may comprise a second closure member configured to delimit the reaction region of the discharge arrangement with respect to a downstream agglomerate collecting container. In particular, the first closure means may be configured to have a lock function. If desired, the second closure means may additionally or alternatively be designed to have a lock function. To this end, the first closure means and/or the second closure means can have two closure members arranged one after the other or one closure member with lock function.
In a further embodiment, a conveying member may be provided in the reaction region for transporting material cleaned off from the filter surface. Mechanical conveying members, in particular a screw conveyor, a rotary valve or the like, can be used as conveying members. In particular, the conveying member can be designed such that a transport direction of material cleaned off from the filter surface can be reversed in order to better mix the cleaned-off material with oxidant and thus to safely inertize the cleaned-off material. It is also conceivable to implement a conveying member by gravity by providing a slope or gradient in the reaction region through which the cleaned-off material will fall. A further measure for promoting the transport of cleaned-off material can be that the cleaned-off material in the reaction region is acted upon by means of a fluidizing device. These measures can, of course, also be combined.
The discharge region may comprise an agglomerate collecting container. The agglomerate collecting container may be located immediately downstream of the raw gas space, optionally with the interposition of a first closure means. It is also conceivable that a transport section constituting the discharge region or part of the discharge region is interposed between the first closure means and the agglomerate collecting container in addition. Such a transport section may, for example, constitute or contain the reaction region as described above. For such embodiments in which the transport section comprises all or at least part of the reaction region, the paraphrase that the reaction region constitues a reaction section will be used hereinafter. A second closure means may then be provided between the transport section and the agglomerate collecting container, by means of which the further transport section can be closed off from the agglomerate collecting container.
In further embodiments, as an alternative or in addition to the embodiments described above, it may be provided that the agglomerate collecting container comprises the reaction region. The oxidation of combustible foreign objects then takes place either exclusively in the agglomerate collecting container or both in the agglomerate collecting container and in the further transport section.
To support the course of the oxidation reaction and/or to improve the removal of resulting reaction heat, at least one member for moving material cleaned off from the filter surface can be provided in the agglomerate collecting container. Such a member may operate mechanically, in particular in the manner of a screw conveyor or mixer. Such a member may also operate pneumatically, for example in the manner of a fluidizing device. It is also conceivable to provide an arrangement for pivoting, rocking or moving the agglomerate collecting container. Of course, these designs can also be combined with each other, for example by providing a fluidizing tray in the agglomerate collecting container, pivotable mounting of the agglomerate collecting container and/or additional provision of one or more mixer arms.
In addition, the reaction region can be temperature-controlled, both when designed as a reaction section and when arranged in the agglomerate collecting container. This can be effected, for example, by means of the heat transfer fluid already mentioned. In addition or alternatively, corresponding heating elements and/or cooling elements may be associated with a wall surrounding the reaction region for this purpose. On the one hand, it may be favorable if the reaction region can be heated in order to quickly reach or maintain a certain activation temperature for the oxidation. On the other hand, it will often be helpful if the reaction region can be cooled in order to be able to efficiently dissipate the thermal energy generated during the oxidation. In addition, it may be provided that the reaction region includes an ignition device to initiate the reaction of foreign objects with the oxidant.
In further embodiments, it may be provided that filtration aid is fed to the raw gas flow, the filter surface and/or the reaction region. The filtration aid is designed to suppress a reaction of foreign objects with oxidant, in particular with oxygen. For this reason, the filtration aid will also be referred to as extinguishing agent in the following. Besides, the filtration aid can also serve to bring the reaction region to a suitable temperature, in particular to supply or dissipate heat.
The filtration aid may be, for example, an inorganic material, in particular a silicon oxide-based inorganic material or a calcium carbonate-based inorganic material can be used as filtration aid.
The filtration aid can serve in particular to ensure that the oxidation taking place in the reaction region does not get out of control.
The addition of a filtration aid pursues a similar objective to that of the conventional precoating process, in which limestone powder (CaCO3) is added. The precoating process is to be modified to the effect that a substance is added as filtration aid which is selected with regard to suppressing a reaction of spontaneously flammable or self-igniting foreign objects with oxidant, in particular with oxygen, during filtration. In this way, it can be achieved that fires do not occur or that, in any case after ignition, the further spread of flames is effectively hindered. The filtration aid is easy to dose. In particular, the filtration aid is suitable for forming agglomerates containing foreign objects. The addition of the filtration aid does not interfere with the operation of the filter during normal operation (i.e. without fire). In particular, this includes the fact that the filtration aid forms a filter cake on filter surfaces after contact with the gas flow containing foreign objects, which adheres well but is also just as easily removed by means of pressurized gas pulses.
The raw gas is an uncleaned gas, which thus carries foreign objects, and has not yet passed through a filter device. For example, the raw gas can be a smoke or gas (aerosol) carrying metal particles. The term smoke is intended to denote an aerosol of dust particles and/or liquid droplets in finely distributed form carried in an air flow or gas flow. In the case of smoke, the particle diameter is usually 800 nm or smaller. In the case of a raw gas carrying combustible foreign objects, it may be provided that the carrier gas is an inert gas, i.e. that the proportion of oxygen and other components that can act as oxidants is kept below a predetermined threshold in the carrier gas. In such a case, filtration of the raw gas also takes place under inert conditions, i.e. the proportion of oxygen and other components that can act as oxidants is also kept below a predetermined threshold in the raw gas space. Foreign objects do not come into contact with oxidants such as oxygen before material is discharged from the raw gas space.
An inorganic material is in particular a material that consists mainly of carbon-free compounds, in particular is free of organic chemical compounds of carbon. Certain carbon compounds such as carbon monoxide, carbon dioxide, carbon disulfide, carbonic acid, carbonates, carbides, ionic cyanides, cyanates and thiocyanates shall also be considered inorganic materials. Inorganic materials include, in particular, silicon dioxide.
In the context of the present invention, silicon dioxide (SiO2)-based or based on silicon dioxide means that the filtration aid comprises silicon dioxide or a silicon dioxide compound as its main constituent. The filtration aid may further comprise other materials present in lower mass proportions than silicon dioxide.
The raw gas space is a portion of the filter device into which the raw gas is introduced. Agglomerates containing foreign objects are formed by the accumulation of foreign objects on filtration aid. Such agglomerates can be formed in the raw gas flow or raw gas space, but in particular when foreign objects from the raw gas flow accumulate on or attach to filter surfaces as the raw gas flow passes through the filter surface of the filter unit into a clean gas space.
The addition of SiO2-based filtration aid is particularly useful when the raw gas to be filtered contains foreign objects that are self-igniting or combustible. Such foreign objects or foreign particles tend to ignite spontaneously. This ignition can often occur without additional thermal energy input from the outside. When foreign objects have a small particle size, the foreign objects have a relatively large surface area relative to their volume, which makes the foreign objects particularly easy to ignite. It can be sufficient for the foreign objects to rub against each other as a result of movement in the raw gas flow. Frequently, the foreign objects are also electrostatically charged when they rub against each other, which leads to an additional ignition source due to electrical discharges. The addition of filtration aids on the basis of silicon dioxide, according to the invention, reliably suppresses such self-ignition in the raw gas.
The foreign objects may, for example, contain metals or be metals and have a granular, in particular chip-like, powder-like or smoke-like, configuration. In particular, the foreign objects may have a configuration that is not completely oxidized or even not oxidized at all. In particular, the foreign objects may be titanium powder or titanium chips. The foreign objects may be metallic foreign objects that are not oxidized or not completely oxidized. Such foreign objects are created, for example, during additive manufacturing of metallic workpieces, by using powdery metallic materials when building up workpieces layer by layer from a powder bed. Typical metals used in such processes, which can lead to combustible foreign objects in the exhaust air, are titanium, aluminum, magnesium and their alloys, as well as many steels such as structural steel, quenched and tempered steel, high-alloy stainless steels. The addition of a filtration aid based on SiO2 proposed herein has proven to be particularly suitable for suppressing raw gas fires in additive manufacturing processes in which titanium and/or aluminum-magnesium alloys are used. Known, for example, is the laser sintering process as an additive manufacturing process that produces waste gases that tend to self-ignite.
When added, the filtration aid can have a granular, in particular powdery, configuration. This allows precise metering of the filtration aid into the raw gas flow and/or into the filter device, in particular for coating filter surfaces (precoating). In addition, an appropriate filtration aid allows a simple feed mechanism, such as a flap or a pressurized gas feed, to be used. The finer-grained the filtration aid is when added, the more efficient the formation of ignition-retardant agglomerates.
The filtration aid may be configured to bind metal-containing foreign objects with a granular configuration in agglomerates, in particular at temperatures of 600° C. or more, in particular at temperatures of 650° C. or more, in particular at temperatures of 700° C. or more, in particular at temperatures of 750° C. or more, in particular at temperatures of 800° C. or more. Depending on the filtration aid, temperatures of up to 1000° C., in particular up to 1250° C., in particular up to 1500° C., can be reached without inhibiting the formation of agglomerates too much and/or causing decomposition or disintegration of agglomerates to an undesirably large extent. The agglomerates formed are not flammable or only with difficulty flammable in the temperature ranges mentioned, so that higher operational safety is possible compared with conventional filter devices. Many SiO2 glasses begin to soften at temperatures starting from 600° C. and can then form agglomerates with foreign objects. Depending on the configuration of the SiO2 material, e.g. by adding additives or forming it as a glass foam, the temperature at which softening begins can be varied in suitable manner.
The agglomerates can change to a flowable configuration resembling a glass melt when heated strongly, and to a glass-like or vitreous configuration after cooling below the glass transition point. The filtration aids melt and thereby trap the foreign objects in the melt, so that inerting already occurs in this state. Once the melt has solidified, a vitreous configuration is formed. The formation of a flowable configuration can occur in particular after heating to temperatures of 600° C. or more, in particular 650° C. or more, in particular 1220° C. or more, in particular 750° C. or more, in particular 1320° C. or more. In this process, the agglomerates may have a vitreous configuration after cooling below the glass transition temperature. This can prevent oxidant from coming into contact with the metal-containing foreign objects.
In particular, the filtration aid can be a material that has a vitreous configuration or can be converted to a vitreous configuration under the influence of heat.
Materials based on silicon dioxide with a vitreous configuration are made from a solid and have an amorphous or at least partially crystalline structure. Such glasses have silicon dioxide as their main constituent and their network is formed mainly of silicon dioxide. These include, in particular, so-called silicate glasses.
The silicate base glass can be present in pure form, for example as silica glass. Quartz glass is also conceivable if higher softening temperatures are desired. In addition to the silicate base glass, additional components may be present, for example phosphate, borate, and the like.
The filtration aid may have as a main constituent at least one of the following materials: expanded glass beads, glass powder, silicon dioxide particles (SiO2 particles), quartz powder, or a mixture of at least two of these materials. In particular, well-suited glass materials are those made from recycled waste glass (recycling glass), such as expanded glass or foamed glass. Expanded glass is produced by grinding waste glass cullet and adding binding and/or expanding agents thereto. This produces roughly round grains with small, gas-filled pores. Expanded glass can be produced in grain sizes from 0.04-16 mm. The granules have a closed pore structure. Foamed glass, in particular foamed glass ballast, is produced in a similar way. Expanded glass or foamed glass can be produced such that the lower limit for the temperature at which the softening range begins and/or the glass transition temperature assumes a value between 600° C. and 750° C.
In the event of fire, the still powdery or granular agglomerates of filtration aid and metal powder initially formed soften or melt under the action of heat. The flowable glass melt surrounds the metal-containing foreign objects and inerts the same. After solidification of the melt, a glass-like structure is formed, with metal-containing foreign objects permanently enclosed in the filtration aid or surrounded by the filtration aid. As soon as the flowable configuration is formed, the individual self-igniting particles of the metal are bound (vitrified) by the filtration aid. A reaction with oxidants, in particular with oxygen (O2), is only possible with difficulty or is no longer possible at all in the vitrified state. A vitrification process of the type described occurs in particular at those locations where filtration aid agglomerates accumulate. In particular, a filter cake which has formed on the raw gas side on a filter surface and which also consists entirely or at any rate largely of filtration aid agglomerates, can exhibit such a phase transition from a powder-like or granular configuration to a flowable and finally glass-like configuration when heat is generated (for example in the case of a fire). Such a vitrification process can also take place at bulk cone surfaces formed in an agglomerate collection region during operation, leading to efficient inerting of the material contained in the agglomerate collection region. This vitrification process can be assisted by coating the surface of the cone of bulk material forming in the agglomerate collection region with a layer of filtration aid from time to time.
The agglomerates formed can remain chemically stable in the event of fire, i.e. in the presence of an oxidant (usually oxygen), at temperatures of up to 650° C., in particular at temperatures of up to 750° C., in particular at temperatures of up to 850° C., in particular at temperatures of up to 1000° C., in particular at temperatures of up to 1250° C., in particular at temperatures of up to 1500° C.
It is possible to selectively or specifically apply an oxidant to the agglomerate collection area, in particular the reaction section and/or the agglomerate collecting container, or to introduce oxidant into the agglomerate collection region, in particular the reaction section and/or the agglomerate collecting container. The introduction of oxidant can take place automatically, in particular in accordance with a control system or software. Alternatively or additionally, manual introduction of oxidant can also be provided. In particular, gases or gas mixtures with a sufficiently high proportion of oxygen can be used as oxidants. In the simplest case, the oxidant introduced can be air. The introduction of oxidant into the agglomerate collection region, in particular into the reaction section and/or into the agglomerate collecting container, has the effect that material stored in the agglomerate collection region, in particular in the reaction section and/or in the agglomerate collecting container, can react with the oxidant. This specifically initiates the reaction that actually needs to be suppressed or at any rate controlled. The heat of reaction generated during oxidation leads to an increase in temperature of the filtration aid. When the temperature reaches or even exceeds the vitrification temperature of the filtration aid, the filtration aid changes into a flowable vitreous phase, thereby enclosing the already oxidized and possibly still existing non-oxidized agglomerates. The thus effected phase change of filtration aid thus causes vitrification of the material in the agglomerate collection region, in particular in the reaction section and/or in the agglomerate collecting container, and thus renders this material insensitive to further oxidation processes and thereby harmless. After vitrification has taken place, the risk of uncontrolled ignition of material stored in the agglomerate collection region, in particular in the reaction section and/or in the agglomerate collecting container, can thus be avoided when the agglomerate collection region, in particular the agglomerate collecting container, is removed from the filter device. This measure allows the material stored in the agglomerate collection region to be transferred from a reactive configuration to an inert configuration in targeted and controllable manner. The amount of material stored in the agglomerate collection region, in particular in the reaction section and/or in the agglomerate collecting container, that is allowed to react with the oxidant, can be controlled by the amount of filtration aids and/or oxidant added in each case. This increases the safety of personnel when handling the agglomerate collection region, in particular when changing containers for receiving cleaned-off material.
The application, or charging, of oxygen to the agglomerate collection region, in particular the reaction section and/or the agglomerate collecting container, can take place in timed relationship with the application, or charging, of filtration aid to the agglomerate collection region, in particular the reaction section and/or the agglomerate collecting container. In particular, the application of filtration aid to the agglomerate collection region (24; 92) and/or the discharge region and/or the reaction region can precede the oxidant, or the agglomerate collection region, in particular the reaction section and/or the agglomerate collecting container, may have the oxidant applied thereto after filtration aid has been applied to the bulk cone or to the material stored in the agglomerate collection region, in particular in the agglomerate collecting container. In particular, the agglomerate collection region, in particular the reaction section and/or the agglomerate collecting container, may have the oxidant applied thereto before an agglomerate collecting container associated with the agglomerate collection region is detached from its holder and removed. Then, when the material in the agglomerate collection region comes into contact with atmospheric oxygen after the agglomerate collecting container has been removed, the combustible materials or mixtures are rendered harmless by vitrification or transfer to an inert oxidized configuration so that the risk of uncontrolled oxidation or fire no longer exists.
After exposure to heat, the agglomerates formed from filtration aid and foreign objects exhibit a shell enclosing foreign objects and having a glass-like configuration, so that no contact of foreign object(s) with oxidant occurs. This reliably prevents a fire in the raw gas space, in a raw gas supply line upstream of the raw gas space of the filter device and/or in a region downstream of the filter device, in particular in an agglomerate collection region or a line leading to an agglomerate collection region.
In this case, a chemically resistant substance can form from the filtration aid, which can hermetically enclose or trap the self-igniting foreign objects before they can ignite. The chemically resistant substance formed from the filtration aid can even become flowable under heat, thus smothering flames after foreign objects have ignited. In particular, silicon dioxide glasses remain chemically stable as a melt up to high temperatures and do not decompose when exposed to oxygen or other oxidants. In particular, silicon dioxide glasses do not split off oxygen-containing functional groups even at high temperatures.
The filtration aid may be designed such that it does not split off members or compounds that may act as oxidants when it is heated to temperatures of 600° C. or more, in particular to temperatures of 650° C. or more, in particular to temperatures of 700° C. or more, in particular to temperatures of 750° C. or more, in particular to temperatures of 800° C. or more. In particular, the filtration aid can be designed to remain chemically stable up to temperatures of 1000° C., in particular up to temperatures of 1250° C., in particular up to temperatures of 1500° C., in particular not to split off any elements or compounds that can act as oxidants.
The filtration aid may have an average particle size of 10 to 30 μm, preferably between 15 and 25 μm. An average particle size is understood to the effect that a major part of the particles of the filtration aid have a diameter that is between 10 and 30 μm. All data refer to the X50 value, i.e. that 50% of the particles have diameters in the range mentioned in each case.
Depending on the raw gas to be filtered, the filtration aid may have a softening point or glass transition temperature of 600° C. or more, in particular of 650° C. or more, in particular of 700° C. or more, in particular of 750° C. or more, in particular of 800° C. or more, and up to 1000° C., in particular up to 1250° C., in particular up to 1500° C. In the event of fire, this permits a phase change of the filtration aid, i.e. a transition of the filtration aid to a flowable state, and thus vitrification of the foreign objects. Thus, a fire can be reliably avoided or stopped.
The method may further comprise distributing or atomizing the filtration aid in the raw gas space and/or in the reaction region, in particular uniform distribution on components arranged in the raw gas space and/or in the reaction region, such as filter elements and raw gas space walls or walls in the discharge region of the filter device; in particular in the region of the reaction section and/or in the agglomerate collecting container.
In the method, agglomerates that contain foreign objects and have accumulated on the filter surface can be cleaned off and collected and stored in an agglomerate collection region. It can be provided that the agglomerate collection region is charged with filtration aid.
The charging of the agglomerate collection region can take place when the agglomerate collection region stores a predetermined amount of agglomerates. This prevents the amount of agglomerates adjacent each other from exceeding a predetermined amount, thereby reducing the risk of ignition of the agglomerates.
Prior to removing an agglomerate collecting container associated with the agglomerate collection region, the agglomerate collection region may be charged with filtration aid such that the foreign body-containing agglomerates collected in the agglomerate collection region or agglomerate collecting container are covered with a layer of filtration aid. After the agglomerate collection region has been charged with filtration aid, the agglomerate collection region may additionally be charaged with an oxidant, in particular after filtration aid has been applied to material stored in the agglomerate collection region and before the agglomerate collecting container is removed.
The agglomerate collecting container can be a disposable container intended for single use only. After the agglomerate collection region has been charged with filtration aid and oxidant, the agglomerate collecting container can be removed and disposed of. Since, after addition of oxidant, vitrification of the cleaned-off material in the agglomerate collection region has already taken place before the agglomerate collecting container is removed from its holder, it is ensured that all material is bound in the agglomerate collecting container and that it can be safely disposed of in the usual manner.
The method and the device according to the invention, respectively, may be used in cleaning off foreign objects from a gas flow in a filter device, in particular in a device of one of the following types:
A filter device for cleaning raw gas carrying foreign objects, according to the invention, comprises at least one filter element having at least one filter surface in a raw gas space, to which a raw gas flow containing foreign objects can be fed. Further, an oxidant supply means is provided which is adapted to feed an oxidant to a reaction region located on the raw gas side of the filter surface downstream of the filter surface. The oxidant supply means is designed such that foreign objects contained in material cleaned off from the filter surface and/or in the raw gas flow react with the oxidant in the reaction region to form oxide-containing foreign objects.
The explanations given above with reference to the method according to the invention also apply analogously to the filter device according to the invention.
In particular, the oxidant may be air or an oxygen-containing gas. In particular, the reaction region may be located downstream of the raw gas space. In particular, the reaction region may be adapted to be shut off or closed off with respect to the raw gas space when the oxidant is supplied. These measures help to ensure that the raw gas space remains largely free of oxidant.
Moreover, the filter device may have an arrangement for supplying a heat transfer fluid to the reaction region and discharging the heat transfer fluid after flowing through the reaction region. Such an arrangement assists in dissipating thermal energy generated by the reaction in the reaction region. In this regard, the heat transfer fluid may also contain the oxidant, for example, in the form of air or in the form of a gas mixture of an inert gas having a predetermined content of oxygen. The heat transfer fluid flows through the reaction region, i.e. it is supplied to the reaction region and discharged from the reaction region.
Furthermore, the filter device may comprise an agglomerate collection region adapted to receive material cleaned off from the filter surface. The filter device comprises a cleaning-off arrangement, for example a pressurized-gas cleaning-off arrangement, by means of which foreign objects or agglomerates containing foreign objects, which have accumulated on the filter surface, are cleaned off from time to time. This cleaned-off material is collected and stored in the agglomerate collection region.
The agglomerate collection region can have, in particular, a first closure means which can be controlled such that it closes off the raw gas space with respect to a discharge region downstream of the raw gas space for the removal of material cleaned off from the filter surface, or establishes a connection between the raw gas space and the discharge region. The first closure means may comprise, for example, a first closure member provided in a boundary of the raw gas space relative to its surroundings.
By controlling the first closure means, the amount of material passing from the raw gas space to the discharge region per unit of time can be controlled such that a predetermined amount of oxidizable material is always present in the reaction region. As a result, the amount of heat generated during the reaction of the oxidizable material can be maintained within a tolerable range.
In certain embodiments, the discharge region may contain the reaction region. In that case, the reaction region will as a rule be located downstream of the first closure means.
The oxidant supply means may be configured to open into the discharge region.
In this way, it can be ensured that the raw gas space remains largely free of oxidant, because the oxidant is supplied downstream of the raw gas space in the direction of flow of material cleaned off from the filter surface. In particular, in support hereof, it may be provided that the raw gas space remains closed to the discharge region when oxidant is supplied to the discharge region.
In further embodiments, the discharge region may include a second closure means disposed downstream of the first closure means in the direction of flow of material cleaned off from the filter surface. The reaction region may then be located between the first closure means and the second closure means.
In particular, the second closure means may comprise a second closure member configured to delimit the reaction region of the discharge arrangement with respect to a downstream agglomerate collecting container.
In further embodiments, a conveying member may be provided in the reaction region for transporting material cleaned off from the filter surface. Such a conveying member may be a mechanically operating conveying member, in particular a screw conveyor or a rotary valve. Alternatively or additionally, a slope or gradient may be provided in the reaction region through which the material cleaned off from the filter surface will fall. Furthermore, it is conceivable to provide a fluidizing device in the reaction region as a conveying member. All these measures mentioned can be combined with each other. The conveying member can be designed such that a transport direction of material cleaned off from the filter surface can be reversed.
In further embodiments, the discharge region may comprise an agglomerate collecting container. In particular, it may be provided that the agglomerate collecting container comprises the reaction region.
For example, at least one member for moving material cleaned off from the filter surface may be provided in the agglomerate collecting container. Such a member may be, for example, a mechanically operating member, in particular a screw conveyor or a mixer. It is also conceivable that such a member is designed as a fluidizing device or that such a member comprises a fluidizing device.
Furthermore, it is conceivable to support the agglomerate collecting container movably, for example pivotably, rotatably or rockably. The aforementioned embodiments may also be combined.
In addition, in certain embodiments, temperature control devices can be provided by means of which the reaction region can be temperature-controlled, in particular heated and/or cooled. Furthermore, it may be provided that the reaction region comprises an ignition device for starting the reaction of foreign objects with the oxidant.
In further embodiments, a filtration aid feed arrangement may be provided with a filtration aid feed line for feeding filtration aid, which opens into the raw gas space and/or into the raw gas flow upstream and/or downstream of the raw gas space. The filtration aid is designed to suppress a reaction of foreign objects with oxidant, in particular with oxygen. The filtration aid may be, for example, an inorganic material, in particular an inorganic material based on silicon dioxide or calcium carbonate.
The filtration aid may be supplied to the raw gas flow upstream of the raw gas space, to the raw gas space, the filter surface, the discharge region, in particular to the reaction region and/or a collection region for material cleaned off from the filter surface (hereinafter also referred to as agglomerate collection region).
The filtration aid feed arrangement can be designed such that the filtration aid forms a glass-like protective layer under the effect of heat, on filter surfaces facing the raw gas space or the reaction region and/or on raw gas space walls or reaction region walls and/or can be distributed in the raw gas flow in such a way that glass-like agglomerates of filtration aid and foreign objects are formed in the raw gas flow upstream and/or downstream of the filter surface, in particular in the discharge region, or on the filter surface under the effect of heat.
The filter device may further comprise an agglomerate collecting container associated with the agglomerate collection region and disposed on a bottom side of the filter device, the agglomerate collecting container having a filtration aid entry opening through which the filtration aid may be fed into the agglomerate collecting container. The agglomerate collecting container may thereby form the agglomerate collection region.
The filter device can have a first line, through which oxidant can be delivered from an oxidant reservoir and/or filtration aid from a filtration aid reservoir into the raw gas space and/or into a raw gas line opening into the raw gas space and/or into a reaction region or into a reaction section, and in particular a second line, through which oxidant can be delivered from the oxidant reservoir and/or filtration aid from the filtration aid reservoir into the agglomerate collecting container. The oxidant may be air or an oxygen-containing gas mixture, wherein the oxidant, when introduced into the agglomerate collecting container, subjects material located in the agglomerate collecting container to oxidant. If desired, the introduction of oxidant may also be take place via a third line that is different from the second line.
The reaction region, or reaction section, can be defined as the part of a filter device that connects the raw gas space with the agglomerate collecting container. This reaction region is designed to allow reaction of the material cleaned off from a filter surface with oxidant in order to allow a controlled and thus safe reaction to take place there. For this purpose, the reaction region can be formed with an oxidant inlet through which oxidant can be introduced into the reaction region. The filtration aid or the extinguishing agent can also be introduced into the reaction region via the same inlet or via a separate inlet. The reaction region may be designed to be closable, for example by one or more shut-off valves or a shut-off device such as a rotary valve, so that the amount of cleaned-off material can be appropriately controlled such that the reaction in the reaction region does not exceed a predetermined strength. Furthermore, the reaction region may have a waste gas outlet through which excess oxidant including oxidation residues, such as soot and other foreign matter particles, may be discharged from the reaction region. The reaction region may also include a transport member, such as a screw conveyor, a fluidizing tray, or a conveyor belt. The screw conveyor rotates to convey the cleaned-off material through the reaction region. The fluidizing tray is, for example, a sheet or grid through which a gaseous conveying medium can be passed so that the cleaned-off material located on or above the fluidizing tray is transported to a reaction region outlet. The conveyor belt has the same function, but enables this function in a different manner.
The filter device may include a material diverter connecting the second line to the first line. This allows selective introduction of the filtration aid into both the raw gas space and the agglomerate collecting container. This increases safety for operators when operating filter devices according to the invention.
The material diverter can be controllable such that a filtration aid flow can be selectively passed through the first line and/or through the second line. Preferably, an automatic control device can be used for this purpose. Alternatively, the material diverter can also be actuated by operating personnel that manually manipulates the material diverter and thus introduces the filtration aid flow into the first line and/or the second line.
The agglomerate collecting container may include an oxidant entry opening through which oxidant, in particular air or an oxygen-containing gas mixture, may be introduced into the agglomerate collecting container. By adding oxidant, oxidizable material stored in the agglomerate collecting container can be selectively activated to render the oxidizable material harmless by vitrification with filtration aid and/or conversion of the oxidizable material into poorly reactive or inert oxidized material. This enhances the safety of service personnel when replacing the agglomerate collecting container.
The filter device may comprise furthermore an oxidant line that opens into the oxidant entry opening of the agglomerate collecting container. Oxidant may be selectively delivered to the agglomerate collecting container automatically or manually through the oxidant line. Automatic is understood to mean that a control unit takes over the feeding of oxidant. In the case of manual feeding, this is done by service personnel operating a switch or lever to introduce the oxidant into the agglomerate collecting container. In certain embodiments, the second line may serve as an oxidant line at the same time. For example, the introduction of filtration aid into the agglomerate collecting container may take place simultaneously with the application of oxidant to the material in the agglomerate collection region. It is also possible to carry out the introduction of filtration aid into the agglomerate collecting container and the application of oxidant to the material located in the agglomerate collecting container in terms of time one after the other, for example by means of additional valves in the second line. For example, oxidant could be introduced into the agglomerate collecting container first, followed by the filtration aid.
The filter device may comprise furthermore a metering device configured to adjust a predetermined amount of filtration aids. This allows precise delivery of filtration aids into the filter device, thereby increasing the operational safety of the filter device.
The aforementioned embodiments and advantages of the method according to the invention also apply to the use according to the invention and the filter device according to the invention.
The invention and specific embodiments of the invention will be explained in more detail below by way of exemplary embodiments.
In the lower part of the housing 18 shown in
Since the raw gas carries combustible foreign objects, it may be provided that an inert gas is used as carrier gas for the raw gas, i.e. that the proportion of oxygen and other substances that can act as oxidants is kept below a predetermined threshold in the carrier gas. Therefore, the proportion of oxygen and other substances that can act as oxidants is also kept below a predetermined threshold in the raw gas space 15. Thus, filtration of the raw gas carrying combustible foreign objects takes place under inert conditions, i.e. foreign objects do not come into contact with oxidants such as oxygen until material is discharged from the raw gas space 15.
The disposal funnel 28 can be closed at its lowest point by a valve 34, which is opened only briefly when material containing foreign bodies is to be discharged from the collection region 24. In order to ensure disposal of the foreign objects collected in the collection region 24, which are generally readily self-igniting in the absence of filtration aids, an inclined fluidizing tray 36 is located in the collection region 24, to which gas is supplied via a port 38. Connected to the port 38 is a blower, only schematically designated 40, through which pressurized gas or inert gas is conducted into the fluidizing tray 36. The gas flow generated in the blower 40 is adjusted such that, on the one hand, the material collected in the collection region 24 is loosened to such an extent that it is readily free-flowing and can thus be easily removed via the disposal opening 26, but that, on the other hand, this material cannot get back out of the collection region 24 into the housing 18 or into the raw gas space 15.
The raw gas flow schematically indicated by the arrow 44, which carries foreign objects that are to be separated by the device 10, enters the raw gas space 15 enclosed by the housing 18 via a raw gas feed line 54 through the raw gas inflow opening 16, said raw gas space 15 being bounded on its upper side by the raw gas side of the filter unit 12. After entering the raw gas space 15, the raw gas flow 44 is transported to the filter unit 12. On the opposite side of the housing 18 from the raw gas inlet opening 16 is the filtration aid feed opening 20 through which filtration aids can be fed from a reservoir or storage container 72 into the raw gas space 15. The filtration aids can be introduced into the raw gas space 15 before the latter is charged with the raw gas flow 44. The filtration aids introduced then accumulate, in particular, on filter surfaces of the filter elements 14 and/or on walls of the raw gas space 15, where they each form a layer of filtration aid (precoat layer). The flow of filtration aids entering the raw gas space 15 through the filtration aid feed opening 20 is indicated by an arrow 45 in
Alternatively or additionally, a filtration aid feed opening 52 may be arranged in the raw gas feed line 54. The raw gas feed line 54 is connected to the raw gas inflow opening 16. This allows the filtration aid to be introduced into the raw gas flow 44 before it enters the raw gas space 15 of the filter device 10. This results in advantageous mixing of foreign objects contained in the raw gas flow 44 and the filtration aid so as to raise the self-ignition threshold of the raw gas. Optionally, a baffle plate or distributor plate 56 may be disposed near the filtration aid feed opening 52 such that the filtration aid is uniformly distributed in the raw gas flow 44. For this purpose, the filtration aid flow is directed onto the distributor plate 56, whereby particles of the filtration aid bounce off the distributor plate 56 “chaotically”, i.e. in non-predetermined paths, and are distributed in the raw gas flow 44. A corresponding distributor plate may also be arranged in the raw gas space 15 at the filtration aid feed opening 20 or 20′, which enables a uniform distribution of the filtration aid, in particular on a filter surface of the filter elements 14. In this case, the distribution plate can be arranged at the filtration aid feed opening 20 such that particles of the filtration aid bouncing off from the same are passed in the direction of the filter elements 14 and adhere to the filter surface of the filter elements 14.
In a lower portion of the funnel-shaped housing region 18b. there is a port 48 communicating with a ring line 46 extending horizontally through the housing 18b. The ring line 46 is located above the collection region 24 and, in particular, always above the material collected in the collection region 24. Connected to the port 48 is a further blower 50, which is also indicated only schematically in
Associated with the filter unit 12 is a pressurized-gas cleaning-off unit (not shown in the figures) that is located on the clean gas side of the filter unit 12 above the filter elements 14. At certain intervals in time, the pressurized-gas cleaning-off unit acts upon a respective filter element 14 such that the filter element 14 experiences a pressure surge from its clean gas side. The pressure surge causes foreign objects, such as filtration aids and readily self-igniting foreign objects, which have accumulated on the filter surface on the raw gas side of the respective filter element 14, to detach from the filter element 14 and fall down as a result of their gravity.
In particular, the filtration aid may be a material having a glass-like or vitreous configuration or capable of being converted to a vitreous configuration under the action of heat. Silicon dioxide-based materials with a glass-like configuration are made from a solid and have an amorphous or at least partially crystalline structure. Such glasses have silicon dioxide as their main constituent and their network is formed mainly of silicon dioxide. These include, in particular, so-called silicate glasses. The silicate base glass can be present in pure form, for example as quartz glass or silica glass. In addition to the silicate base glass, additional components may be present, for example phosphate, borate, and the like.
A solids injector 80 is disposed at the outlet 76 and is controllable to transport the filtration aid from the solids injector 80 to a valve 84 via a connecting line 82 and then to one or more of the filtration aid feed openings 20, 20′ and 52. The solids injector 80 may be pneumatically operated so that the filtration aid is transported through the connecting line 82 by means of pressurized gas. In
Preferably, the valves 84, 94 may be flap valves or disc valves.
Alternatively, the agglomerate collecting container 92 may itself have a feed opening, not shown, which is connected to the feed line 88 and the valve 94. Alternatively, the feed line 88 may be connected directly to the storage container 72 through a further solids injector not shown. In that case, the filtration aid could be introduced at different pressures and simultaneously into both the raw gas flow 44 and the agglomerate collection region 92. This allows for more efficient control of the filter device and further enhances safety during operation of the filter device 10.
Furthermore, an oxidant line 114 opens into an oxidant entry opening 118 of the agglomerate collecting container 92. The oxidant line 114 can be used to introduce an oxidant, such as air or an oxygen-containing gas, schematically designated 112 in
In particular, it may be provided to supply oxidant 112 to the agglomerate collection region 92 in timed relationship with the introduction of filtration aid into the agglomerate collecting container 92. In particular, it may be provided to supply oxidant to the agglomerate collecting container 92 after filtration aid has previously been introduced into the agglomerate collecting container 92. It may also be provided to supply oxidant to the agglomerate collecting container 92 before the agglomerate collecting container 92 is removed from the docking plate 98, for example for replacing a full agglomerate collecting container 92 with a new agglomerate collecting container. By supplying oxidant to the agglomerate collecting container 92, oxidation of material present in the agglomerate collecting container 92 is specifically promoted. This has the effect, on the one hand, that some of the combustible foreign objects present in the agglomerate collecting container 92 are converted into an inert oxidized form and, on the other hand, that the filtration aid is converted into a vitreous phase as a result of the heat generated during oxidation, whereby material still present in the agglomerate collecting container 92—whether combustible or not—is enclosed or trapped in a vitreous coating. This vitrification prevents the remaining combustible foreign objects from further contact with oxidant, thus converting the material in the agglomerate collecting container 92 to a harmless chemically inert configuration.
Alternatively or additionally, it is also possible to introduce oxidant 112 into the agglomerate collecting container 92 via the feed line 88, for example by way of an appropriate branch in the feed line 88 upstream of the agglomerate collecting container 92, in which case a separate oxidant entry opening 118 in the agglomerate collecting container 92 may not be required.
With the addition of oxidant 112, oxidation of filtered-off foreign objects in the agglomerate collecting container 92 can be purposefully triggered or initiated. The severity of this purposefully triggered oxidation reaction can be well controlled via the quantity and composition of oxidant 112 added. In addition, the filtration aid—which can be added in large quantities if necessary—absorbs excess heat energy and thereby vitrifies the existing reactive material in the agglomerate collecting container 92. In this manner, an effective and well-controllable possibility of converting combustible material into poorly reactive or inert and harmless material in the agglomerate collecting container 92 can be achieved. This increases the safety during operation of the filter device.
When the filter elements 14 are cleaned off, a pressurized gas is introduced into the filter elements 14 in a direction opposite to the direction of flow of the raw gas flow, whereby foreign objects are blasted off the filter element 14 by means of the pressure surge and fall into the agglomerate collecting container 92 via the lower housing region 18b. Once the filling level sensor 100 indicates that the agglomerate collecting container 92 has reached a predetermined maximum level, the discharge flap 96 is closed. Then, manually or by means of the control unit 110, the valve 94 is opened, the material diverter 86 is actuated, and the solids injector 80 is activated so that the filtration aid is transported from the storage container 72 into the agglomerate collecting container 92 via the connecting line 82, the material diverter 86, the feed line 88, the valve 94, and the docking plate 98. A supply of filtration aid into the agglomerate collecting container 92 takes place until a predetermined amount of filtration aid has been introduced into the agglomerate collecting container 92, which is ascertained on the basis of a decrease in weight of the storage container 72 as determined by the weight sensors in the holder 78. Preferably, the amount corresponds to a barrier layer of filtration aid of predetermined thickness, for example a barrier layer of filtration aid approximately 2 cm high in the agglomerate collecting container 92. Subsequently, the valve 94 is closed. Thereafter, an oxidant 112 may be introduced into the agglomerate collecting container 92 via an oxidant line 114 and an oxidant entry opening 118. When combustible foreign objects react with the oxidant 112, the filtration aid is heated to vitrify the foreign objects, thereby preventing further reaction of the foreign objects. The agglomerate collecting container 92 can be removed from the filter device 10 without the foreign objects in the agglomerate collecting container 92 self-igniting. The barrier layer of filtration aid ensures that the foreign objects in the agglomerate collecting container 92 do not self-ignite.
This is particularly true when the barrier layer has assumed a vitreous configuration, such as after exposure to heat in a fire. The agglomerate collecting container 92 can be lowered from the filter device 10 by a lifting and lowering device 99.
Another sequence for supplying filtration aid and oxidant is also possible, namely that oxidant is first introduced into the agglomerate collecting container 92 to cause the foreign objects to oxidize, and subsequently, when the oxidation reaction has occurred, a barrier layer of the filtration aid is applied to the oxidized foreign objects.
It may also be provided to introduce filtration aid and oxidant into the agglomerate collecting container 92 through a common opening. In other words, the filtration aid feed opening 90 as well as the oxidant entry opening 118 may be combined into a common opening. This results in a reduced number of inlet openings into the agglomerate collecting container 92.
The control unit 110 is connected via data lines or control lines, in particular, to the weight sensors 79, the solids injector 80, the valves 84, 94, the material diverter 86, and the discharge flap 96 in order to actuate or manipulate the same.
In this case, the raw gas flow 44 contains self-igniting foreign objects, such as powdery or chip-shaped metal dusts that tend to self-ignite when establishing contact with oxygen or under the action of mechanical energy. In a step 104, the filtration aid is supplied to the raw gas flow 44 and/or the filter element 14 via at least one of the filtration aid feed openings 20, 20′ and 52, the filtration aid mixing with the foreign objects in the raw gas flow 44, thereby reducing the tendency to self-ignite. The softening point of the filtration aid is 500° C. or more. Once the softening point is exceeded, the filtration aid changes to a glassy or vitreous configuration and vitrifies the foreign objects through the associated phase change from an agglomerate of loosely accumulated solids to a uniform solid with a vitreous configuration. In other words, the filtration aid encloses the foreign objects with a glass layer, so that agglomerates of filtration aid and foreign objects are formed. A supply of oxidant to the foreign object(s) is thus effectively prevented.
Optionally, an oxidant inlet 212 may be disposed in the reaction section 120 in the region of the screw conveyor 122. Through this oxidant inlet 212, oxidant can be introduced into the reaction section 120, i.e. into the region of the screw conveyor 122, where it is mixed with the cleaned-off material 139 transported by the screw conveyor 122 and causes an oxidation reaction of the cleaned-off material 139. This oxidizes the cleaned-off material 139 into a poorly reactive or inert material 141. In addition to the oxidant, a poorly reactive or inert fluid (e.g. nitrogen (N2)) may also be introduced via the oxidant inlet 212, primarily to remove heat generated during the reaction. A waste gas outlet 218 is disposed at the downstream end of the screw conveyor 122 through which excess oxidant is discharged from the reaction section 120 along with heat, oxidant residues such as soot, and other substances generated during oxidation. Introducing the oxidant into the screw conveyor 122 has the advantage that no fluidization by an oxidant flow is necessary, because the mixing of the cleaned-off material 139 with the oxidant occurs mechanically through the screw conveyor 122. Thus, no batchwise metering of the cleaned-off material 139 is necessary, since only a small portion of the cleaned-off material 139 can react with the oxidant at any given time. In other words, continuous oxidation can be realized hereby. Furthermore, a filtration aid inlet 214, which may also be referred to as a filtration aid entry, may be arranged in the reaction section 120 such that filtration aid or extinguishing agent may be introduced into the reaction section 120 in the region of the screw conveyor 122. In the embodiment shown in
The shut-off members 124, 126, 128 allow the flow of cleaned-off material 139 passing through the reaction section at any given time to be controlled and thus influence the heat generated when cleaned-off material 139 reacts with oxidant 142. In some embodiments, control of the shut-off members and/or the heat transfer fluid flow may be sufficient in itself to control the temperature generated, thereby eliminating the need for further addition of filtration aid. A further aspect of the shut-off members, in particular shut-off members 124 and optionally 126, is that no oxidant can enter the filter device 10, in particular the raw gas space 15, from the reaction section 120.
In
The shut-off members 124, 126, 128 allow the reaction section 120 to be delimited from the collection region 24 and the agglomerate collecting container 92. In particular, they enable specific control of the amount of oxidizable material present in the reaction region per unit of time and thus of the heat of reaction generated per unit of time. As soon as the shut-off members 124, 126, 128 ensure that at least the first closure means and optionally also the second closure means is closed, oxidant can be introduced into the reaction section 120 through the oxidant inlet 212. The shut-off members 124, 126, 128 may preferably be in the form of a shut-off valve, a flap, a slide, a door, or a pinch valve. A pinch valve has an elastic tube which, for reducing flow through the tube, is compressed or squeezed, thereby reducing a diameter of the elastic tube. For example, the screw conveyor 122 may be formed like an Archimedes screw.
It is particularly favorable if the shut-off members 124, 126 at the upstream end and/or the shut-off members 128, 126 at the downstream end of the reaction section 120 are configured to have the function of a lock. Then, the reaction section 120 can become independent of the operating state of the first closure means at the upstream end and the operating state of the second closure means at the downstream end, respectively, with respect to the passage of oxidant into the raw gas space 15 or into an agglomerate collecting container 92 arranged downstream, respectively. This allows oxidants to be continuously introduced into the reaction section 120 without the need for synchronization with the shut-off member of the first and second closure means, respectively. Such a lock function is particularly advantageous for the first closure means at the upstream end of the reaction section 120, because oxidant can thus be prevented from entering the raw gas space 15. The lock function can be realized, for example, by the first closure means and/or the second closure means having in the instant case two shut-off members 124, 126 and 126, 128, respectively, arranged one after the other.
As is also shown in
The reaction section 120 and the agglomerate collecting container 92 each form part of a reaction region. This reaction region may be located in portions of both the reaction section 120 and the agglomerate collecting container 92, or may be located in only one portion thereof.
In
The rotary valve 140 allows control of the material flow of the cleaned-off material 139, and thus control and/or influence the amount of heat generated when the cleaned-off material reacts with air or oxidant. The rotary valve 140 has an axis of rotation about which a blade wheel is rotatable, the rotation of the blade wheel being controllable by the control unit 110. In the embodiment, the axis of rotation is oriented horizontally. However, other orientations of the axis of rotation are possible as well.
Furthermore, the reaction section 120 may include the oxidant inlet 212, the filtration aid inlet 214, and the waste gas outlet 218, see also
The reaction section 120 of
The reaction section 120 may also be referred to as the waste reaction section. This means that in this section cleaned-off material reacts with oxidant in controlled manner, such that uncontrolled ignition of the cleaned-off material is avoided.
The conditioning device 147 comprises a container having the configuration of the agglomerate collecting container 92. The container further includes two or more feet 164 attached to a bottom side of the container.
With these exemplary embodiments, good mixing of the oxidant with the cleaned-off material is possible.
The cover 137 includes two stirring blades 188 extending from a bottom side of the cover 137 to the bottom 172 of the agglomerate collecting container 92, but preferably not contacting the bottom 172. The stirring blades 188 are configured to agitate the cleaned-off material 139 that has accumulated in the agglomerate collecting container 92, thereby enabling better mixing of the cleaned-off material 139 with the oxidant and/or filtration aid. In particular, the filtration aid may be an extinguishing agent and will also be referred to as extinguishing agent in the following. To enable mixing of the oxidant with the cleaned-off material 139, additionally or alternatively, a motor not shown and adapted to move the stirring blades 188 may be disposed in the cover to move the agglomerate collecting container 92 about the axis of rotation 186. The heat of reaction generated by the reaction of the cleaned-off material with the oxidant is discharged or dissipated from the gas outlet 136 with the oxidant flow. In addition, it may also be provided here that filtration aid is supplied.
Preferably, the temperature control element 236 may be disposed about the material outlet 242. However, it is also possible to arrange the temperature control element 236 at another location in the reaction section 120. It fulfills the same function here as in
In addition, the waste gas outlet 218 is arranged in the ceiling 238, through which the mixture of oxidant and oxidation residues as well as heat can be discharged from the reaction section 120.
The oxidant inlet 212 is arranged in the upstream portion of the reaction section 120, for example in a front half of the central part 143 of the reaction section 120. Through this oxidant inlet 212, the oxidant 143 can be introduced into the transport section 123 of the screw conveyor 122, where it is mixed with the cleaned-off material 139 transported by the screw conveyor 122 and causes an oxidation reaction of the cleaned-off material 139. This converts the cleaned-off material 139 into a poorly reactive or inert material 141. Introducing the oxidant 143 into the transport section 123 has the advantage that fluidization by an oxidant flow is not necessary, because mixing of the cleaned-off material 139 with the oxidant 143 occurs mechanically by the screw conveyor 122. Downstream of the oxidant inlet 212 in the direction of material flow, in particular in a rear half of the central part 143, the filtration aid inlet 214 or extinguishing agent inlet is arranged, through which the filtration aid or extinguishing agent can be introduced into the reaction section 120, in particular into the transport section 123. In addition, the ignition source 144 may also be arranged here.
A waste gas outlet region 258 is arranged at the rear end of the screw conveyor 122, in the present embodiment opposite the opening formed at the bottom of the transport section 123. The waste gas outlet region 258 comprises a filter unit 260 supported on a partition 262. The filter unit 260 may comprise one or more filter elements. The partition 262 divides the waste gas outlet region 258 into a raw gas space 259 and a clean gas space 261. A mixture 146, which is formed from residues formed during the oxidation occurring in the reaction section 120, as well as excess proportions of the oxidant flow and optionally the filtration aid flow, enters the raw gas space 259. The filter unit 260 is configured to filter the mixture 146 to remove particulate oxidation residues therefrom. The clean gas space 261 then contains a filtered gaseous mixture that can be discharged via the waste gas outlet 218, which is arranged at the clean gas space 261, and can be discharged into the environment, for example. A pressurized-gas cleaning-off unit associated with the filter unit 260 is also arranged in the clean gas space 261, which is arranged to generate pressurized gas pulses that act on the filter element or elements for cleaning-off. The pressurized gas pulses pass through a pressurized gas opening 263 from a pressurized gas storage unit 264 into the clean gas space and from there to the filter element or elements. The pressurized gas storage 264 can preferably be filled with pressurized gas via a pressurized gas line 266. The pressurized gas serves to clean-off the filter unit 260 as soon as the filter performance of the filter unit 260 deteriorates. In that case, the pressurized gas is introduced into the clean gas space 261, whereby foreign objects that have settled on the raw gas side of the filter unit 260 are cleaned off from the filter unit 260. These foreign objects then fall out of the waste gas outlet region 258, through the opening in the transport section 123, through the rear part 132 of the reaction section 120, and after opening the shut-off member 128, through the shut-off member 128 into the agglomerate collecting container 92, which is not shown. This is particularly advantageous because both the inert material 141 and the cleaned-off foreign objects can be collected in the agglomerate collecting container 92 and subsequently disposed of. At the rear part 132 of the reaction section, the temperature control element 236 may be arranged. For the function of the temperature control element, see
The transport member may be a paddle mixer instead of a screw conveyor. A paddle mixer has an axis from which a plurality of paddles extend in radial direction, the paddles being distributed, preferably uniformly distributed, in the axial direction along the axis. These paddles can both move the cleaned-off material along the transport path 123, and allow advantageous mixing of the cleaned-off material with the oxidant. This can ensure that preferably all of the cleaned-off material is oxidized, thereby preventing subsequent oxidation.
The transport member may rotate in different directions. For example, the transport member may rotate to transport the cleaned-off material 139 to the rear part 132 of the reaction section 120 so that it can be discharged therefrom into the agglomerate collecting container 92, which is not shown. The transport member may also be rotated in alternating directions to allow good mixing of the cleaned-off material 139 with the oxidant 142 or the extinguishing agent. This may alternatively ensure that the complete cleaned-off material 139 oxidizes with the oxidant 142.
It should be expressly noted that the variants described above with reference to the individual figures may be combined with each other and are not limited to the figure in which the corresponding variant is described. For a better understanding, the same reference numerals have been used in all figures for like components in each case. It is understood that the description belonging to a reference numeral in a particular case also refers to all other figures in which the reference numeral occurs.
The operation of the discharge arrangement, in particular the reaction section 120, can be continuous, in particular when shut-off members with a lock function are used. The provision of suitable transport devices in the reaction section also favors continuous operation for oxidation of foreign objects, in particular the provision of a screw conveyor, a conveying fluid and/or a rotary valve in the reaction section. Batch or intermittent operation is possible, in particular when valves are used as shut-off members.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 102 036.8 | Jan 2020 | DE | national |
| 10 2020 103 982.4 | Feb 2020 | DE | national |
| 10 2020 112 856.8 | May 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/050704 | 1/14/2021 | WO |
