IN-LINE SPRAYING SYSTEM VIA ULTRASOUND, WHICH CAN BE USED IN THE DISPENSING OF AGROCHEMICAL AGENTS FOR POST-HARVEST FRUIT

Abstract

An in-line spraying system via ultrasound, which can be used in the dispensing of agrochemical agents for post-harvest fruit, which has a spray chamber formed by a closed tank containing the liquid to be sprayed, an agitator, two ultrasound transducers and a fan; a chamber for applying the mist to the fruit, formed by a closed chamber disposed on the processing line, which has gates with slats for allowing the fruit in and out, a cylindrical applicator for the agrochemical, which is connected to the spray chamber via a duct; and a chamber for recovering the mist, formed by a closed tank coupled to the application chamber, below the Processing line, which is connected to the spray chamber via a duct, and wherein the recovered mist is moved by the fan. A process for operating the system is also disclosed.

Claims

1. An in-line spraying system via ultrasound, useful in the dispensing of agrochemical agents for post-harvest fruit, comprising at least the following components: a. a spray chamber composed of a closed tank containing the liquid to be sprayed, an agitator disposed in the upper section of the tank formed by a rotor with blades, which must be immersed in the liquid to be sprayed at a height of at least ⅓ of the liquid level; at least two ultrasound transducers of different frequency operating between 0.75 and 1.0 MHz and between 0.9 and 1.7 MHz, with an power between 5 and 60 W, immersed in the liquid at a distance of between 10 and 20 cm from the base, with an equidistant distribution with respect to the center of the base of the chamber; and a fan that moves the steam towards the outlet of the tank; b. a chamber for applying the mist to the fruit, composed of a closed chamber disposed on the processing line, which has gates with slats for the entry and exit of the fruit, a cylindrical applicator of the agrochemical agent located at the top and parallel to the processing line with perforations of 2 mm in diameter in the lower area, to distribute the mist homogeneously, which is connected to the spray chamber by means of a duct; and c. a mist recovery chamber, composed of a closed tank coupled to the application chamber, below the processing line which is connected to the spray chamber by a duct, where the recovered mist is moved by the fan.

2. The in-line spraying system via ultrasound, useful in the dispensing of agrochemical agents for post-harvest fruit according to claim 1, wherein the duct of the mist application chamber has a diameter between 0.2-3.2cm.

3. The in-line spraying system via ultrasound, useful in the dispensing of agrochemical agents for post-harvest fruit according to claim 1, wherein the duct of the mist recovery chamber has a diameter between 1 and 2 cm.

4. The in-line spraying system by ultrasound, useful in the dispensing of agrochemical agents for post-harvest fruit according to claim 1, wherein, optionally, the mist recovery chamber contains a line for returning condensed liquids to the spraying chamber, connected by means of a self-priming suction pump.

5. The in-line spraying system via ultrasound, useful in the dispensing of agrochemical agents for post-harvest fruit according to claim 1, wherein the spray, application and recovery chambers are made of an insulating material of the food-grade plastic type.

6. A process for operating the in-line spraying system of claim 1, comprising at least the following steps: i. arranging the liquid to be sprayed in the closed tank and keep under agitation using the rotor at a speed of between 0.8 to 4 m/s; ii. activating the transducers according to the particle size to be sprayed, applying the following frequencies: frequencies of between 1.0 and 1.75 MHz and power between 1 and 10 W for compounds with a particle size of between 3 and 10 μm; or frequencies of between 0.5 and 0.9 MHz and power between 5 and 60 W for compounds with a particle size of between 11 and 100 μm; iii. applying the spayed solution to the fruits by regulating the speed of the fan: applying a fan speed of between 2000 and 3000 rpm to generate a flow rate of between 10 and 16 m3/min, for fruits smaller than 2.2 cm in equatorial diameter; or applying a fan speed of between 250 and 1000 rpm to generate a flow rate of between 2 and 6 m3/min, for fruits larger than 7 cm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1: Diagram of the in-line spraying system via ultrasound.

[0013] FIG. 2: Experimental spraying system via ultrasound.

[0014] FIG. 3: Images of sprinkling (3a and 3b) and spraying (3c) assays for Kiwi.

[0015] FIG. 4: Images of the sprinkling (4a and 4b) and spraying (4c) assays for blueberries.

DISCLOSURE OF THE INVENTION

[0016] The present technology corresponds to an in-line spraying system via ultrasound transducers, useful in the dispensing of agrochemical agents for post-harvest fruit with prune and/or hair, more specifically, for fruits of the peaches, kiwis, plums and blueberries type. This spraying system can be installed directly on the post-harvest fruit selection process lines, allowing their mobility, without requiring modification to adapt and avoiding alterations in the structure of the plant.

[0017] Advantageously, the spraying system makes it possible to generate different droplet sizes to adapt to the particle size of the agrochemical agent to be applied, and thus allow the complete coating of the particles and avoid excess water. The agrochemical agents may be present in liquid form or as suspended solids between 0.3 μm and 100 μm in size.

[0018] This spraying system comprises at least three chambers, which are described below, taking as reference FIG. 1:

[0019] a. a spray chamber composed of a closed tank (1) containing the liquid to be sprayed (2), an agitator disposed in the upper section of the tank (3) formed by a rotor with blades, which must be immersed in the liquid to be sprayed (2) at a height of at least ⅓ of the liquid level; at least two ultrasound transducers (4) of different frequency operating between 0.75 and 1.0 MHz and between 0.9 and 1.7 MHz, with an adjustable power between 5 and 60 W, immersed in the liquid at a distance of between 10 and 20 cm from the base, with an equidistant distribution with respect to the center of the base of the chamber; and a fan (5) that moves the steam towards the outlet of the tank (6). Optionally, this chamber may contain more than one transducer of equal frequency to increase the mist formation rate, allowing more fruits to be processed per minute.

[0020] b. a chamber for applying the mist to the fruit, composed of a closed chamber (7) disposed on the processing line (8), which has gates with slats (9) for the entry and exit of the fruit, a cylindrical applicator (10) of the agrochemical agent located at the top and parallel to the processing line with perforations of 2 mm in diameter in the lower area (11), to distribute the mist homogeneously, which is connected to the spray chamber by means of a duct (12) of diameter between 0.2-3.2 cm.

[0021] c. a mist recovery chamber, composed of a closed tank (13) coupled to the application chamber, below the processing line (8) which is connected to the spray chamber by a duct (14) of diameter between 1 and 2 cm, where the recovered mist is moved by the fan (5). Optionally, this chamber may contain a line for returning condensed liquids (15) to the mist chamber, for which it must be connected to a self-primming suction pump (16). The latter makes it possible to recover the product that was not used or not adhered to the fruit and can be reused. The spray, application and recovery chambers may be made from insulating material, preferably, but exclusively of food-grade plastic, to prevent condensation of the mist due to heat transfer by conduction.

[0022] On the other hand, the process for operating the selective spraying system of agrochemical agents comprises at least the following steps:

[0023] i. Arrangement of the liquid to be sprayed in the closed tank (1) and keep under agitation using the rotor (3) at a speed of between 0.8 to 4m/s;

[0024] ii. Activation of transducers (piezoelectric crystals), which depending on the particle size to be sprayed the following frequencies can be applied:

[0025] Frequencies of between 1.0 and 1.75 MHz and power between 1 and 10 W for compounds with a particle size of between 3 and 10 μm; or

[0026] Frequencies of between 0.5 and 0.9 MHz and power between 5 and 60 W for compounds with a particle size of between 11 and 100 μm;

[0027] iii. Application of the spayed solution to the fruits in line by regulating the speed of the fan (5):

[0028] applying a fan speed of between 2000 and 3000 rpm to generate a flow rate of between 10 and 16 m3/min, useful on fruits smaller than 2.2 cm in equatorial diameter; or

[0029] applying a fan speed of between 250 and 1000 rpm to generate a flow rate of between 2 and 6 m.sup.3/min, useful in fruits larger than 7 cm.

[0030] The regulation of the flow rate depending on the fruit size, allows to obtain the concentration of the chemical agent necessary to perform its effect.

[0031] The spraying system and the process for the selective spraying of compounds allows the application of agrochemical agents of various molecular weights, without damaging the pruina of waxy fruits and in fruits with hairs allowing the passage of the agent easily through the cilia barrier. Selective nebulization keeps the fruit dry and ensures rapid evaporation of water, which is used as a vehicle for transmitting the chemical substance.

APPLICATION EXAMPLES

Example 1

Determination of the Frequency of Operation to Spray Iprodione®

[0032] The experimental spraying system via ultrasound was used (see FIG. 2), where it was worked with frequencies of 0.5 to 1.75 MHz to spray Iprodione® and obtain a concentration of 2 ppm of chemical agent on the surface of kiwis. This chemical agent corresponds to a fungicide and has a molecular weight of 330.17 g/mol and a water solubility of 13.9 mg/L

[0033] The frequency of the transducers was evaluated, using a power of 30W, which generated a mist at a rate of 4 m.sup.3/min, a flow rate of 0.1 m.sup.3/min and a processing speed of 50 kiwis per minute with a residence time of 5 s; the surfaces of the kiwis were subsequently analyzed to determine the concentration of fungicide by HPLC method.

[0034] 10 liters of a solution with a concentration of 15% (w/v), equivalent to 150 g/L solution, were used, obtaining the results shown in Table 1,

TABLE-US-00001 TABLE 1 Concentration in ppm, as a function of cavitation frequency. Cavitation Fruit concentration frequency (MHz) (ppm) 0.5 5.1 0.75 301 1.0 1.95 1.25 1.1 1.5 0.54 1.75 0.1

[0035] From these results it can be concluded that, in order to achieve a concentration greater than 2 ppm for this compound, it is necessary to use transducers with low cavitation frequencies to generate larger droplets and coat this molecule having a high molecular weight.

Example 2

Determination of Operating Conditions of the Spraying System

[0036] With the results of Table 1, the operating conditions of the spraying system were determined to obtain a concentration of 2 ppm of Iprodione® on the surface of Kiwis. The flow rate of cold mist and dilution of the chemical agent were evaluated, where 3 concentrations were used: 0.3% w/v; 3% w/v and 15% w/v.

[0037] Considering the molecular weight, the equipment was configured to work with the transducers of 0.7 MHz applying a power of 30 W to a volume of 10 L of solution, this allowed to generate a cold mist with a formation rate of 4 m.sup.3/min. The fruit was transported through the application chamber at a rate of 50 fruits per minute with a residence time of 5 seconds, which corresponds to the time it takes to turn twice the fruit on the conveyor belt.

[0038] The determination of the concentration of chemicals deposited in the fruit was performed through specific residue analysis in HPLC (mass/mass). The ppm results by fruit of the application of Iprodione® in kiwis are presented in Table 2,

TABLE-US-00002 TABLE 2 Concentration of Iprodione ® in fruits in using different dispersion flows of cold mist. Solution Fruit concentration (ppm) Concentration (w/v) Flow rate of 1 m.sup.3/min Flow rate of 0.1 m.sup.3/min .sup. 15% 0.19 3.09   3% 0.02 0.38 0.30% 0.01 0.13

[0039] From these results it follows that the coating value equal to or greater than 2 ppm Iprodione® was achieved, using a low flow rate (0.1 m.sup.3/min) since this flow allowed the mist to remain suspended for a longer time and, therefore, the density and concentration of the mist was also higher. It was also possible to estimate by simple interpolation that in order to obtain 2 ppm of Iprodione® on the surface of kiwis it was necessary to use a solution of 10.18% (w/v).

Example 3

Comparison of Application of Iprodione® by Spraying v/s Ultrasound

[0040] The application of Iprodione® in 50 Kiwi fruits and blueberries was compared by ultrasound method and 50 fruits with air pressure atomization with 10 liters of solution at a concentration of 10.18% (w/v), using a Sony H300 brand 20.1 mp HD camera. High-speed images were taken in the application of the solution in both sprinkling and spraying, and the results were subsequently analyzed by HPLC for the quantification of the residue in the fruit.

[0041] The application of the sprinkling was carried out at 15 cm and 30 cm from the sprinkler to the fruit, and the nebulization at 30 cm from the fruit. FIG. 3 shows the spraying assay for kiwi (3a and 3b) and FIG. 4 for blueberry (4a and 4b), where it can be seen that the skin of both fruits suffers damage by the droplet size; opposite case to that presented by the spraying technique (FIG. 3c for kiwi and FIG. 4c for blueberry), where better impregnation was achieved. These samples were allowed to stand for 24 hours and the amount of fungicide present in the fruit was analyzed, the results are shown in Table 3,

TABLE-US-00003 TABLE 3 Concentration of Iprodione ® in fruits in using dispersion of cold mist and sprinkling at 15 and 30 cm. Fruit concentration (ppm)/ Flow rate of Flow rate of Flow rate of 1 m.sup.3/min, 1 m.sup.3/min, 1 m.sup.3/min, Ten Fruit Average Spraying Sprinkling 15 cm Sprinkling 30 cm Kiwi Group 1 2.1 2.5 2.3 Kiwi Group 2 1.9 2.7 2.1 Kiwi Group 3 2 2.6 2.3 Kiwi Group 4 1.9 2.5 2.4 Kiwi Group 5 2 2.7 2.3 Blueberry Group 1 1.3 1.5 1.4 Blueberry Group 2 1.1 1.6 1.3 Blueberry Group 3 1.2 1.6 1.4 Blueberry Group 4 1.1 1.5 1.4 Blueberry Group 5 1.2 1.6 1.4

[0042] As shown in Table 3, the spraying application was not uniform and exceeded the expected levels. Although we worked with kiwi and blueberry which are very complex fruits due to their skin and the presence of wax, the ultrasound application could be applied successfully and this can be extended to other fruits.