Liquid thermal nebulization device

Abstract

The invention relates to a thermal fogging device for generating fog from a liquid aerosol, applicable to the treatment of plants such as potatoes. The device comprises a control unit 1, a hot gas flow production assembly 2, an ejection duct 4 having an outward fog discharge zone 5, first and second liquid sources 6, 7, injection means 8 into an injection zone 9 of the ejection duct from the first source, connection means 10 from the second source to the injection zone, and first and second temperature probes 11, 12 in the injection and ejection zones. The control unit is configured to control the connection means based on the difference between the temperatures measured by the second and first probes. (See Figure 1 for abbreviations.)

Description

Title of the invention: Device for thermal fogging of a liquid

[0001] The present invention relates to a thermal fogging device, allowing the generation of a fog from a liquid aerosol. It finds particular application in the treatment of certain plants, such as potatoes.

[0002] When potatoes are harvested by a farmer, they are generally stored in a storage room, under conditions, in particular temperature, humidity and light, provided for this purpose.

[0003] One of the problems posed by the storage of potatoes is that of germination, particularly in the case of storage periods which can be long. To prevent this germination, the potatoes are treated with an anti-germination product, which is applied by thermal fogging using a device provided for this purpose.

[0004] Thermal fogging therefore consists of applying a product in the form of a mist of droplets, generally a few microns in diameter, from a liquid aerosol. The fog is generated by a device in the storage space, and diffused into it by means of a ventilation system internal to the storage building.

[0005] Known devices combine the generation of a gas flow, generally air, at a relatively high speed, with the heating of this flow, to a temperature that is also relatively high. The generation of the gas flow can be obtained by a blower system using one or more electric fans. The heating of the generated gas flow can be obtained by one or more electric resistors, or even a combustion chamber with a gasoline engine.

[0006] These systems provide injection means for injecting the liquid dosed with active product into the hot air flow, so as to allow the evaporation of the liquid into droplets forming a mist which is then conducted towards the end of a gun or exhaust channel and diffused at the outlet.

[0007] It is very important to be able to control the evaporation temperature of the liquid in the hot air flow, in order to be able to correctly regulate the liquid flow rate and avoid accidents linked to excessively high temperatures. Indeed, depending on the product applied, the temperature and the speed of the air flow, an optimum flow rate makes it possible to obtain the desired evaporation without the risk of ignition. Beyond this optimum flow rate, the risk of ignition constitutes a risk of damage to the device, and a danger for the user. Indeed, such devices allow the evaporation of products at high temperatures, above 370 °C, using heating means which heat the blown air to a high temperature also, above 600 °C. These high temperatures combine with the highly flammable nature of the product present in the dosed liquid, to constitute the aforementioned risk.

[0008] This is why a temperature probe is generally provided at the injection zone of the metered liquid, and possibly a temperature probe at the heating means. These temperature probes are connected to a control system which makes it possible to adapt the injection flow rate.

[0009] An example of such a device is known for example from document EP 2 186 573. In this device, in the event of an increase in the temperature measured by a probe arranged in the ejection duct due to the absence of product injected from a main reservoir, the supply of product switches to a secondary reservoir with a secondary injection circuit, to avoid the rise in temperature in the ejection duct due to the absence of product injected.

[0010] However, such a device does not allow the injection of product, aimed at cooling the ejection duct, in the event of untimely shutdown of the device, for example in the event of a power cut.

[0011] Furthermore, flames may appear at the outlet of the ejection duct without the evaporation temperature in the injection zone of the ejection duct triggering the switch to the secondary tank.

[0012] One of the aims of the invention is therefore to solve the aforementioned problems in particular. Thus, the invention aims in particular to propose a safer thermal fogging device.

[0013] The invention thus relates to a device for thermo-nebulizing a liquid, comprising a control unit connected to a source of energy, preferably electrical, an assembly for producing a flow of hot gas under pressure connected to the control unit and to a source of energy, preferably electrical, and having a hot gas outlet, an ejection duct having a hot gas inlet connected to the hot gas outlet and a zone for ejecting a mist of liquid towards the outside of the ejection duct.

[0014] The device also comprises a first source of liquid intended to receive a treatment liquid, and a second source of liquid intended to receive a pressurized cooling liquid, as well as injection means for injecting into an injection zone of the ejection conduit a flow of liquid from the first source, connected to a source of energy, preferably electrical, and connected to the control unit, and means for connecting the second source to the injection zone connected to the control unit.

[0015] The device further comprises a first temperature probe arranged in the injection zone so as to measure the evaporation temperature of the liquid in the injection zone, and connected to the control unit, and a second temperature probe arranged in the ejection area so as to measure the temperature in this ejection area, and connected to the control unit.

[0016] The control unit is configured to receive a first temperature measured by the first probe and a second temperature measured by the second probe, and to control the connection means so as to prevent the arrival of liquid in the injection zone from the second source when the difference between the second temperature and the first temperature is less than a threshold value, and to authorize the arrival of liquid in the injection zone from the second source when the difference between the second temperature and the first temperature is greater than or equal to said threshold value.

[0017] According to certain embodiments, the device further comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations: - the control unit is configured to allow modification of the threshold value depending on the type of liquid contained in the first source; - the control unit is configured to enable operation of the device with a given list of liquid types, each of said liquid types being associated with a corresponding threshold value; - the device comprises a selector connected to the control unit and configured to allow an operator to select a type of liquid; - the injection means comprise a pump controlled by the control unit, connected to a source of energy, preferably electric, and hydraulically connected on the one hand to the first source and on the other hand to the injection zone; - the control unit is configured to receive a temperature value measured by the first probe and to control the flow rate of the pump according to the temperature value received from the first probe; - the connection means comprise a valve controlled by the control unit and hydraulically connected on the one hand to the second source and on the other hand to the injection zone; - the control unit is configured to receive a first temperature value measured by the first probe and a second temperature value measured by the second probe, and to control the opening and closing of the valve depending on the difference between the temperature values ​​respectively received from the first probe and the second probe; - the control unit is configured to open the valve at least for a specified period of time in the event of the device stopping operation; - the assembly comprises a unit for blowing a gas flow, such as one or several fans, connected to means for heating the gas flow generated by the blowing unit, such as one or more electrical resistors, the blowing unit and the heating means being connected to the control unit; - the device comprises a third temperature probe arranged in the assembly, so as to measure the temperature of the heating unit; - the device comprises a pressure sensor arranged to measure the pressure in, or at the outlet of, the second source, and connected to the control unit; - the control unit is configured to receive a pressure value from the pressure sensor and to stop operation, or prevent start-up, of the device if the pressure value received from the sensor is lower than a determined pressure value; - the device comprises liquid level measuring means arranged so as to measure the liquid level in the second source, and connected to the control unit. - the control unit is configured to receive a liquid level value from the measuring means and to stop operation, or prevent start-up, of the device if the level value received from the measuring means is lower than a determined level value.

[0018] Thus, the system of the invention makes it possible in particular to effectively and securely control the injection of product into the injection zone, and therefore the evaporation of the product in this zone, while making it possible to detect the rise in temperature and / or the formation of a flame at the outlet of the ejection duct, all without depending on the power supply of the device.

[0019] The characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of example, and not limiting, with reference to the appended [Fig.l], corresponding to a schematic representation of an example of a device of the invention.

[0020] The device thus comprises a control unit 1, an assembly 2 for producing a flow of hot gas under pressure, an ejection duct 4, a first source 6 of liquid, a second source 7 of liquid, means 8 for injecting the liquid contained in the first source 6 into the ejection duct 4, means 10 for connecting the second source 7 to the ejection duct 4, as well as first and second temperature probes 11, 12.

[0021] The control unit 1 is connected to a power source, such as an electrical power source.

[0022] The assembly 2 is connected to the control unit 1. It is also connected to a power source, such as an electrical power source. It has a hot gas outlet 3.

[0023] The ejection duct 4 has a hot gas inlet connected to the hot gas outlet 3 of the assembly 2, and, opposite the hot gas inlet, an ejection zone 5 of a liquid mist towards the outside of the ejection duct 4.

[0024] The first source 6 of liquid takes the form of a reservoir intended to contain a treatment liquid, for example of the anti-germination type. The second source 7 of liquid also takes the form of a reservoir intended to contain liquid kept under pressure, this liquid being capable of cooling the ejection pipe 4, such as water possibly mixed with an additive. This second source 7 is configured to allow the pressurization of the contained liquid. This pressurization can be carried out manually before starting the device, for example by manual pumping.

[0025] The injection means 8 are intended to allow the injection of a flow of liquid coming from the first source 6, into the ejection conduit 4, precisely in an injection zone 9 thereof. The injection means 8 are also connected to an energy source, such as an electrical energy source, as well as to the control unit 1.

[0026] The connection means 10 make it possible to connect the second source 7 to the ejection conduit 4, precisely to the injection zone 9 thereof. They are also connected to the control unit 1.

[0027] The first probe 11 is arranged in the injection zone 9 of the ejection conduit 4. It thus makes it possible to measure the evaporation temperature of the liquid in this injection zone 9. It is also connected to the control unit 1.

[0028] The second temperature probe 12 is arranged in the ejection zone 5 of the ejection duct 4. It thus makes it possible to measure the temperature in this ejection zone 5. It is also connected to the control unit 1.

[0029] The control unit 1 is configured to control the device, in particular as a function of the difference between the temperature values ​​that it receives from the first and second probes 11, 12. Thus, the control unit 1 is in particular configured to control the connection means 10 so as to prevent or allow the arrival of liquid contained under pressure in the second source 7, in the injection zone 9.

[0030] Specifically, when the difference between the temperature measured by the second probe 12 and the temperature measured by the first probe 11 is less than a threshold value, the control unit 1 controls the connection means 10 so as to prevent the liquid contained under pressure in the second source 7 from arriving in the injection zone 9 of the ejection conduit 4. Conversely, when the difference between the temperature measured by the second probe 12 and the temperature measured by the first probe 11 is greater than or equal to the threshold value, the control unit 1 controls the connection means 10 so as to allow the liquid contained under pressure to enter the injection zone 9 of the ejection conduit 4. pressure in the second source 7 to arrive in the injection zone 9 of the ejection conduit 4.

[0031] Preferably, the control unit 1 is configured to allow the modification of the only one depending on the type of liquid contained in the first source 6. Indeed, depending on the type of liquid used for the treatment, the temperature difference from which it is necessary to trigger the injection, in the injection zone 9 of the ejection pipe 4, of the cooling liquid from the second source 7, varies.

[0032] Provision may be made to configure the control unit 1 to enable operation of the device with a given list of liquid types, each of the liquid types being associated with a corresponding threshold value.

[0033] For example, the device may include a selector connected to the control unit 1, this selector being configured to allow an operator to select a liquid type from the liquid types in the given list of liquid types.

[0034] This selector can be part of a control interface, directly integrated into the control unit 1, or remote.

[0035] The injection means 8 comprise for example a pump 13. This pump 13 is connected to the control unit 1 so that it can be controlled by the latter. It is supplied with energy by an energy source, such as an electrical energy source. It is arranged between the first source 6 and the injection zone 9 of the ejection pipe 4, hydraulically connected to this first source 6 and this electrical injection zone 9. Thus, when the system is started, the pump 8 controlled by the control unit 1 according to a certain setpoint, makes it possible to inject liquid from the first source 6 into the injection zone 9 of the ejection pipe 4, therefore into the flow of hot air coming from the outlet 3 of the assembly 2.

[0036] The control unit 1 is configured to receive a temperature value measured by the first probe 11, i.e. the probe arranged in the injection zone 9 of the ejection conduit 4. Depending on this received temperature, the control unit 1 automatically controls in particular the flow rate of the pump 13. If the temperature is too high, this may be due to a flow rate of injected liquid that is too low, and this flow rate is then adjusted automatically by the control unit 1. Thus, the operator does not need to constantly adjust the flow rate to obtain an appropriate evaporation temperature in the injection zone 9.

[0037] The control unit 1, the first probe 11, and the pump 13, form a circuit for regulating the injection flow rate of the liquid contained in the first source 6.

[0038] The connection means 10 comprise for example a valve 14, such as a solenoid valve 14. It is arranged between the second source 7 and the injection zone 9 of the ejection conduit 4, hydraulically connected to this first source 6 and this electrical injection zone 9. When the valve is open, since the liquid contained in the second source 7 is under pressure, this is brought into the injection zone 9 of the ejection conduit 4. The opening and closing of the valve 14 is controlled by the control unit 1.

[0039] Specifically, the control unit 1 is configured to control the valve 14, in particular as a function of the temperature values ​​that it receives from the first and second probes 11, 12. When the difference between the temperature measured by the second probe 12 and the temperature measured by the first probe 11 is less than the corresponding threshold value, the control unit 1 keeps the valve 14 closed so as to prevent the liquid contained under pressure in the second source 7 from arriving in the injection zone 9 of the ejection conduit 4. Conversely, when the difference between the temperature measured by the second probe 12 and the temperature measured by the first probe 11 is greater than or equal to the corresponding threshold value, the control unit 1 opens the valve 14 so as to allow the liquid contained under pressure in the second source 7 to arrive in the injection zone 9 of the ejection conduit 4.

[0040] It is considered that, for a given type of liquid, the risk of a flame appearing at the ejection zone 5 of the ejection duct 4 is significant for a given temperature difference between the temperature measured by the second probe 12 and the temperature measured by the first probe 11. Also, the threshold value, associated with the type of liquid contained in the first source 6, is determined so that the triggering of the injection of the liquid contained in the second source 7, into the injection zone 9 of the ejection duct 4, occurs before a flame appears in the ejection zone 5 of the ejection duct 4.

[0041] The control unit 1, the first and second probes 11, 12 and the valve 14 form a safety circuit.

[0042] Furthermore, it is provided that the control unit 1 can detect the stopping, in particular the untimely stopping, of the device, for example due to a power supply cut. In this case, the control unit 1 controls the opening of the valve 14, at least for a certain duration, in order to inject into the ejection conduit 4 (via the injection zone 9) liquid contained under pressure in the second source 7, with the effect of cooling the ejection conduit 4.

[0043] The assembly 2 for producing a flow of hot gas, here hot air, comprises a unit 15 for blowing a flow of gas and means 16 for heating the flow of gas produced by the blowing unit 15. The blowing unit 15 comprises for example one or more fans 15. The heating means (16) comprise for example one or more electrical resistors 16. Both the blowing unit 15 and the heating means 16 are connected to the control unit 1.

[0044] A third temperature probe 17 is also provided, arranged in the assembly 2, for example at the outlet 3 of the heating means 16, so as to measure the temperature of this heating unit 16.

[0045] Furthermore, the device can be equipped with a pressure sensor 18, arranged so as to measure the pressure in, or at the outlet of, the second source 7, and connected to the control unit 1. Preferably, as shown in [Fig. 1], this sensor 18 is arranged in the hydraulic circuit between the outlet of the second source 7 and the valve 14. Alternatively, the pressure sensor could be arranged against the external wall of the second source 7, or inside it.

[0046] The control unit 1 can then receive a pressure value measured by the sensor 18, and control the device according to this information. Thus, if the pressure value received by the control unit 1 is lower than a determined pressure value, the control unit 1 stops the operation of the device if it is in operation or prevents it from starting up otherwise. In this way, the risk of insufficient pressure of the liquid contained in the second source 7 which would prevent it from arriving in the injection zone 9 when the valve 14 is open is avoided.

[0047] It is also possible to provide means 19 for measuring the liquid level in the second source 7, for example of the capacitive type, connected to the control unit 1.

[0048] The control unit 1 can then receive a liquid level value measured by the measuring means 19, and control the device according to this information. Thus, if the liquid level value received by the control unit 1 is lower than a determined level value, the control unit 1 stops the operation of the device if it is in operation or prevents it from starting up otherwise. In this way, the risk of an insufficient liquid level contained in the second source 7 which would not allow the arrival of a sufficient quantity of liquid from the second source 7 when the valve 14 is open is avoided.

[0049] The control unit 1 may be provided with an input-output device, for example a keyboard and a screen, or a touch screen, allowing an operator to enter operating instructions for the device and to receive messages relating to the operation of the device.

[0050] Preferably, the control unit 1, or at least its input-output device, are located in a separate electrical control box, which increases the operator's comfort in terms of noise pollution or treatment product emissions.

[0051] The input-output device, or at least the output portion enabling information to be displayed, is orientable, which allows the operator to orient it to reduce light-related effects such as glare or obscuration.

[0052] In the event of the temperatures measured by one or other of the first, second and third probes 11, 12, 16 being exceeded, compared to given threshold values, provision may be made for the emission of an audible signal and / or a light signal, controlled by the control unit 1, for a determined duration, to warn the operator, alterna tively to, or in combination with, the emission of a message on a screen. These audible or visual alert devices are connected to a battery, which preferably recharges automatically when the device is under electrical power, so as to remain operational even in the event of a power failure.

[0053] The present description is given by way of example and is not limiting of the invention.

[0054] In particular, the invention is not limited to the use of specific heating means 16 or blowing means 15, nor to a specific valve type means 14 (tap, solenoid valve, etc.).

Claims

Claims

1. - Device for thermal nebulization of a liquid, the device including, - a control unit (1) connected to a power source, preferably electrical, - an assembly (2) for producing a flow of hot gas under pressure connected to the control unit (1) and to an energy source, preferably electrical, and having a hot gas outlet (3), - an ejection duct (4), having a hot gas inlet connected to the hot gas outlet (3) and an ejection zone (5) of a liquid mist towards the outside of the ejection duct (4), - a first source (6) of liquid intended to receive a treatment liquid, and a second source (7) of liquid intended to receive a pressurized cooling liquid, - injection means (8) for injecting into an injection zone (9) of the ejection conduit (4) a flow of liquid from the first source (6), connected to a source of energy, preferably electrical, and connected to the control unit (1), - means (10) for connecting the second source (7) to the injection zone (9), connected to the control unit (1), - a first temperature probe (11) arranged in the injection zone (9) so as to measure the evaporation temperature of the liquid in the injection zone (9), and connected to the control unit (1), - a second temperature probe (12) arranged in the ejection zone (5) so as to measure the temperature in this ejection zone (5), and connected to the control unit (1), the control unit (1) being configured to receive a first temperature measured by the first probe (11) and a second temperature measured by the second probe (12), and to control the connection means (10) so as to prevent the arrival of liquid in the injection zone (9) from the second source (7) when the difference between the second temperature and the first temperature is less than a threshold value,and to allow the arrival of liquid in the injection zone (9) from the second source (7) when the difference between the second temperature and the first temperature is greater than or equal to said threshold value.,

2. Device according to claim 1, characterized in that the unit of control (1) is configured to allow modification of the threshold value depending on the type of liquid contained in the first source (6).

3. Device according to claim 2, characterized in that the control unit (1) is configured to allow operation of the device with a given list of liquid types, each of said liquid types being associated with a corresponding threshold value.

4. Device according to claim 3, characterized in that it comprises a selector connected to the control unit (1) and configured to allow an operator to select a type of liquid.

5. 5. Device according to any one of claims 1 to 3, characterized in that the injection means (8) comprise a pump (13) controlled by the control unit (1), connected to a source of energy, preferably electrical, and hydraulically connected on the one hand to the first source (6) and on the other hand to the injection zone (9).

6. 6. Device according to claim 5, characterized in that the control unit (1) is configured to receive a temperature value measured by the first probe (11) and to control the flow rate of the pump (13) as a function of the temperature value received from the first probe (11).

7. 7. Device according to any one of claims 1 to 6, characterized in that the connection means (10) comprise a valve (14) controlled by the control unit (1) and hydraulically connected on the one hand to the second source (7) and on the other hand to the injection zone (9).

8. 8. Device according to claim 7, characterized in that the control unit (1) is configured to receive a first temperature value measured by the first probe (11) and a second temperature value measured by the second probe (12), and to control the opening and closing of the valve (14) as a function of the difference between the temperature values ​​respectively received from the first probe (11) and the second probe (12).

9. 9. Device according to any one of claims 1 to 8, characterized in that the control unit (1) is configured to open the valve (14) at least for a determined duration in the event of the device stopping operation.

10. 10. Device according to any one of claims 1 to 9, characterized in that the assembly (2) comprises a unit (15) for blowing a gas flow, such as one or more fans (15), connected to heating means (16) for the gas flow generated by the blowing unit. (15), such as one or more electrical resistors (16), the blowing unit (15) and the heating means (16), being connected to the control unit (1)

11. 11. Device according to claim 10, characterized in that it comprises a third temperature probe (17) arranged in the assembly (2), so as to measure the temperature of the heating unit (16).

12. 12. Device according to any one of claims 1 to 11, characterized in that it comprises a pressure sensor (18) arranged so as to measure the pressure in, or at the outlet of, the second source (7), and connected to the control unit (1).

13. 13. Device according to claim 12, characterized in that the control unit (1) is configured to receive a pressure value from the pressure sensor (18) and to stop the operation, or prevent the start-up, of the device if the pressure value received from the sensor (18) is lower than a determined pressure value.

14. 14. Device according to any one of claims 1 to 13, characterized in that it comprises liquid level measuring means (19) arranged so as to measure the liquid level in the second source (7), and connected to the control unit (1).

15. 15. Device according to claim 14, characterized in that the control unit (1) is configured to receive a liquid level value from the measuring means (19) and to stop the operation, or prevent the start-up, of the device if the level value received from the measuring means (19) is lower than a determined level value.

Images