Device for generating an aerosol from a liquid medium with particle classification

Abstract

Device for generating an aerosol from a liquid reservoir (17) with a classification of the particles of the aerosol to maintain controlled conditions of a filter test with regard to the aerosol, wherein a default value and a maximum permissible deviation from this default value can be specified for each aerosol parameter, with a single-substance nozzle generating droplets from the liquid reservoir (17) in a reaction chamber (19) above the liquid reservoir (17) of a container (18), with an annular gap (2) connected to the reaction chamber (19) with an annular gap suction (3) for diverting the gas flow so that droplets follow the gas flow according to their inertia or reach an aerosol outlet of the device, and with a drying chamber (12) in the flow direction of the droplets not extracted by the annular gap suction (3) for forming and / or drying the particles of the aerosol.

Description

[0001] The invention relates to devices for generating an aerosol from a liquid medium with a classification of the particles.

[0002] Aerosols, i.e., gas-borne particles, are becoming increasingly important both industrially and environmentally. The interplay of these aspects is evident, for example, in filters for air conditioning systems. They are designed to remove particulate contaminants from the air while achieving the highest possible energy efficiency. As with most filtration tasks, separation must at least reach a certain level.

[0003] This performance of a filter is determined through a filtration process under controlled conditions. Controlled conditions for such a filter test are necessary to achieve comparable test results. Comparable test results allow, for example, the classification of filters into filter classes or efficiency classes. These serve to facilitate the targeted selection of filter products for a specific application. The controlled conditions of the filter test are defined in standards for important filter application areas. Examples include filters for vacuum cleaners, engine air intake, vehicle interior ventilation, and air conditioning systems.

[0004] Controlled conditions for filter testing affect both the flowing fluid in terms of volume flow and condition parameters, as well as other parameters, as well as the aerosol. The aerosol decisively influences the outcome of the filtration process for a given filter, assuming all other parameters remain unchanged. The filtration process represents a highly complex interaction between particles, the active elements of the filter, and the particles already separated. The interactions can be of mechanical origin or, among other factors, of electrical origin, in this case, electrostatic charging.

[0005] In addition to the aerosol material, the complex interaction mentioned is significantly influenced by the parameters of the aerosol particles: size distribution, concentration and charge state.

[0006] For example, when spraying a liquid, a higher energy input results in a reduction in the average particle size but also an increase in the number of particles produced per unit of time. The two factors are generally not adjustable separately.

[0007] Aerosols that meet the requirements for filter testing under controlled conditions are referred to as test aerosols. The specifications for the aerosol can either consist of defining its parameters or specifying the aerosol generation process and its parameters.

[0008] Non-defined parameters of the aerosol can then be controlled in such a way that the most meaningful filter test is achieved.

[0009] For example, highly efficient filters for breathing air filtration are tested for very small particle sizes. Since these are the least removed, the removal efficiency for all other particle sizes always shows better values ​​than that determined in the test conducted this way. When testing a filter, material from the test aerosol is necessarily deposited in the filter. The mass increases significantly if the test aerosol contains larger particles than required for the test. This can be highly problematic during subsequent use of the filter. An advantageous aerosol for this application therefore contains as few larger particles as possible.

[0010] In contrast, filters for air conditioning systems, for example, tend to trap larger particles. Smaller particles pass through the filter because energy efficiency is paramount. Testing these filters must therefore be conducted using a test aerosol containing these large particles. If the test aerosol also contains a significant proportion of smaller particles, particle counting methods used for filter testing are regularly overloaded in terms of the dynamic range of the concentration measurement range.

[0011] Document 10 2017 219 370 A1 discloses a device for generating an aerosol of solid particles from a liquid reservoir by means of cold atomization. For this purpose, a compressed air generating and / or compressed air supply device is / are connected to a vortex tube, so that the compressed air is divided into a cooled air stream and a heated air stream. Furthermore, the outlet of the vortex tube with the cooled air stream is connected to an atomizing nozzle, and the outlet of the vortex tube with the heated air stream is connected to a drying device for the atomized reservoir. The atomizing nozzle is also connected to the drying device, so that the aerosol with solid particles from the liquid reservoir is present downstream of the drying device.

[0012] Document 20 2015 105 630 U1 describes an aerosol generator comprising a container containing the liquid to be atomized, an outlet for the aerosol, a two-component nozzle in the liquid, a compressor, at least one sensor, and a control device. This allows even small amounts of aerosol to be provided.

[0013] A very simply constructed, well-known dispersing nozzle is the Laskin nozzle. Its special feature is that the point of action—the meeting point of the accelerated propellant gas jet and the liquid to be dispersed—is not located inside the nozzle or in the free space immediately adjacent to the nozzle, but rather below the surface of the aerosol liquid reservoir. In the simplest case, the point of action is formed at a wall hole located below the liquid surface, through which the propellant gas flows and the liquid in contact there. Scaling the aerosol quantity to achieve higher particle production rates is easily possible by increasing the number of holes, their diameters, or the propellant gas pre-pressure. However, the potential change in the particle size distribution must be considered when scaling.Such a nozzle type is known from the document DE 198 21 552 C1 as an aerosol generator, wherein a transition from a larger number of holes to an annular gap is provided to achieve even higher particle production rates.

[0014] From the publication DE 10 2012 203 011 A1, a device for generating an aerosol is known, comprising an atomizing device operated with a pressurized gas for a solution or suspension contained in a container. For this purpose, a device for cooling the carrier gas is arranged upstream of the atomizing device, so that the atomization temperature is greater than the melting temperature of the solution or suspension and lower than room temperature. Furthermore, a heating device for the aerosol consisting of the carrier gas and the solution or suspension is arranged downstream of the atomizing device, so that the aerosol is warmed to room temperature. By spraying a saline solution or a suspension at a reduced temperature and subsequently heating the aerosol to room temperature, a solid aerosol can be generated without the need for a downstream drying unit.

[0015] US 2014 / 0196440 A1 describes a mixing device for an exhaust aftertreatment device comprising an elbow pipe that changes the flow direction of an exhaust gas, an injector attached to the elbow pipe and injecting a reducing agent solution into the elbow pipe toward the straight pipe. Furthermore, a mixing tube with openings in its peripheral wall serves as a cover for the aqueous reducing agent solution.

[0016] US Pat. No. 8,006,961 B1 discloses a process fluid supply arrangement comprising an ejector arrangement fluidically connected to a process fluid supply arrangement. The arrangement has an annular nozzle and a fluid supply for providing a mixture.

[0017] WO 2007 / 076064 A2 discloses a method and system for delivering high-dose inhalable solid aerosols, wherein the aerosols originate from an aqueous or non-aqueous solution and contain the desired therapeutic agents. For this purpose, an aerosol generator, an aerosol vaporizer, an aerosol concentrator, and an aerosol flow controller are provided.

[0018] Classification of particles in an aerosol to be generated with these particles is not provided for in the solutions of the above-mentioned publications.

[0019] The invention defined in claim 1 is based on the object of realizing a device for generating an aerosol from a liquid medium in such a way that a simple classification of the particles also takes place.

[0020] This problem is solved with the features listed in patent claim 1.

[0021] The devices for generating an aerosol from a liquid medium are characterized in particular by the fact that, when the aerosol is generated, the particles of the aerosol are simultaneously classified to ensure compliance with controlled conditions of a filter test with regard to the aerosol, whereby a default value and a maximum permissible deviation from this default value can be specified for each aerosol parameter.

[0022] For this purpose, the device comprises a single-component nozzle that generates droplets from the liquid in a reaction chamber above the liquid in a container. Furthermore, an annular gap connected to the reaction chamber is provided with an annular gap extraction system for redirecting the gas flow so that droplets, depending on their inertia, either follow the gas flow or reach an aerosol outlet of the device. This redirection leads to a classification determined by the gas flow. A drying chamber is connected in the flow direction of the droplets not extracted by the annular gap extraction system, so that aerosol particles are formed and / or dried.

[0023] The device thus combines a liquid circuit for generating a primary aerosol with a downstream gas flow circuit for classifying the droplets and providing a secondary aerosol with classified particles. The result is a secondary aerosol optimized for a specific application. This allows controlled filter test conditions to be maintained with regard to the aerosol, with a specified value and a maximum permissible deviation from this specified value being defined for each aerosol parameter. The device thus represents an aerosol generator that provides an optimized secondary aerosol.

[0024] The gas flow circuit features an annular gap with an annular gap extraction system for redirecting the gas flow, which classifies the droplets of the primary aerosol generated by atomization. The small droplets undesirable for use in the aerosol, as well as the small particles otherwise created or present during drying, are recirculated and do not leave this process step. The nearly saturated carrier gas also does not leave this process step. The advantages are, firstly, that drying of the larger particles, which are then transferred to the next process step, is easier, and secondly, the water removal from the liquid phase is proportional. This is ensured by the fact that no vaporous water leaves the process chamber.

[0025] The large droplets that are not diverted in the gas stream are carried away by a laminar flow of dry gas and dried in the process. Drying is facilitated by the fact that they are separated from their original carrier gas, which contains water vapor, at the point of diversion.

[0026] Advantageous embodiments of the invention are specified in patent claims 2 to 6.

[0027] According to the embodiment of claim 2, the container comprises the liquid reservoir and the reaction chamber for the droplets arranged above it. To generate the droplets, the liquid reservoir in the container is connected via a conveyor device to an atomizer nozzle in the reaction chamber of the container. This provides a compact implementation of the liquid circuit.

[0028] According to the embodiment of claim 3, the annular gap is connected to the reaction chamber of the container via a fan for generating circulating air. The resulting gas flow circuit is thus connected to the liquid circuit via the reaction chamber.

[0029] According to the embodiment of patent claim 4, the drying chamber is a pipe section that has pores for the passage of air. An air supply chamber surrounding the pipe section is connected to an air supply fan. Furthermore, the aerosol outlet is located in the flow direction of the droplets and formed and / or dried particles not extracted by the annular gap extraction. The tendency for particles to deposit on the walls of the pipe section can be counteracted by a low-impulse and laminar addition of the drying air in such a way that the particle flow is concentrated on the rotation axis of the pipe section, away from the wall.

[0030] According to the embodiment of patent claim 5, the annular gap is formed from a tube with a flow guide arranged therein.

[0031] According to the development of patent claim 6, the device has a liquid circuit with the liquid reservoir in the container, the conveying device and the atomizing nozzle in the reaction chamber above the liquid reservoir in the container and an independent gas circuit with the reaction chamber in the container, the annular gap, the annular gap suction and the blower.

[0032] An embodiment of the invention is shown in principle in the drawing and is described in more detail below.

[0033] It shows the Fig. 1 a device for generating an aerosol from a liquid medium with a classification of the particles.

[0034] Using this device, an aerosol consisting of, for example, salt particles with increased particle size can be produced in a technically cost-effective manner. Atomizing a salt solution produces airborne droplets. The water is then evaporated from the droplets by adding dry air or removing water vapor, so that the salt forms a solid particle.

[0035] The droplets are generated by a single-component nozzle acting as an atomizer nozzle 9. For this purpose, a suction line 7 connects the liquid reservoir 17 to the conveying device 8 acting as a liquid pump, which is further connected to the atomizer nozzle 9 in a reaction chamber 19 of the container 18. The reaction chamber 19 is located above the liquid reservoir 17. In the reaction chamber 19, larger droplets are deposited back into the liquid reservoir 17 by gravity and inertia, while medium-sized and small droplets remain suspended in the reaction chamber 19. This creates a liquid circuit, whereby the pressurized gas-free generation in this way makes it possible to achieve a volume flow-neutral circuit for the liquid reservoir 17 in the container 18 with respect to the outlet of the reaction chamber 19.

[0036] An independent gas circuit has an annular gap 2 and an annular gap extraction system 3, which is also connected to the reaction chamber 19. Droplets from the reaction chamber 19 are drawn in, passing through the annular gap 2. The annular gap 2 consists of a riser pipe 1 in which a flow guide 10 is arranged. In the upper area of ​​the annular gap 2, opposite the reaction chamber 19, there is an opening 3 serving as an annular gap extraction system 3, to which an extraction chamber 4, a fan 5, and a recirculation line 6 leading to the reaction chamber 19 are connected in succession. The pressure for the extraction can be adjusted and / or controlled by means of the fan 5. The gas circuit thus realized has only one opening at the transition of the annular gap 2 to a downstream drying chamber 12. The volume flow that is sucked in by means of the annular gap suction 3 is identical to the volume flow that enters the drying chamber 12.This means that no gas escapes at the transition point between the annular gap 2 and the annular gap exhaust 3, as the system is otherwise sealed to the environment of the facility. The gas circuit can be controlled independently of the liquid circuit.

[0037] When the gas circuit is activated, droplets from the reaction chamber 19 are sucked into the annular gap 2 through the annular gap extraction system 3. At the transition point, formed by the opening in the annular gap 2, the gas flow is sharply deflected, allowing only small droplets to follow. These droplets return to the reaction chamber 19 via the extraction chamber 4, the fan 5, and the recirculation line 6, forming a circuit they cannot leave. The large droplets are separated from their carrier gas flow because they cannot follow the deflection. Their inertia moves them into the drying chamber 12. There, dry air is added via an air supply filter 16, an air supply fan 15, and a sintered body, a pipe section 11 with pores for the air to pass through. The dry air causes the water in the droplets to evaporate, and solid salt particles form.The dry air is added laminarly through the sintered body, so that the drying air keeps the particles away from the walls in the drying chamber 12 to prevent unwanted deposits. For this purpose, the sintered body is surrounded by an air supply chamber 14, which is connected to the air supply fan 15. This makes the aerosol containing the particles available at the outlet 13 of the device. Reference symbol 1 riser pipe 2 Annular gap 3 Annular gap extraction 4 Suction chamber 5 fans 6 Recirculation duct 7 Suction line 8 Conveyor system 9 atomizer nozzle 10 Flow guidance 11 Pipe section 12 Drying chamber 13 Exit 14 Supply air chamber 15 supply air fans 16 supply air filters

Claims

[1] Device for generating an aerosol from a liquid source (17) with a classification of the particles of the aerosol to comply with controlled conditions of a filter test with respect to the aerosol, wherein a target value and a maximum permissible deviation from this target value can be specified for each aerosol parameter, with a single-component nozzle generating droplets from the liquid source (17) in a reaction chamber (19) above the liquid source (17) of a container (18), an annular gap (2) connected to the reaction chamber (19) with an annular gap suction (3) for diverting the gas flow so that droplets follow the gas flow according to their inertia or reach an aerosol outlet of the device, and a drying chamber (12) in the direction of flow of the droplets not suctioned by the annular gap suction (3) for forming and / or drying the particles of the aerosol. [2] Device according to claim 1, characterized by, that the container (18) has the liquid reservoir (17) and the reaction chamber (19) arranged above it for the droplets, and that to generate the droplets the liquid reservoir (17) in the container (18) is connected via a conveying device (8) to an atomizing nozzle (9) in the reaction chamber (19) of the container (18). [3] Device according to claim 1, characterized by , that the annular gap (2) is connected to the reaction chamber (19) of the container (18) via a blower (5) to generate a recirculated air. [4] Device according to claim 1, characterized by , that the drying chamber (12) is a pipe section (11) which has pores for the passage of air, that an air supply space (14) surrounding the pipe section (11) is connected to an air supply blower (15) and that the aerosol outlet is connected in the direction of flow of the droplets and dried and / or formed particles not extracted by the annular gap extraction (3). [5] Device according to claim 1, characterized by , that the annular gap (2) is formed from a pipe with a flow guide (10) arranged therein. [6] Device according to claims 1, 2 and 3, characterized by , that the device has a liquid circuit with the liquid reservoir (17) in the container (18), the conveying device (8) and the atomizing nozzle (9) in the reaction chamber above the liquid reservoir (17) in the container (18) and an independent gas circuit with the reaction chamber in the container (18), the annular gap (2), the annular gap extraction (3) and the blower (5).

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