FR2487638A1 - Fumigation plants to treat prod. with pesticidal gas, esp. phosphine - having exhaust gas scrubber and gas chamber in laminated plastic - Google Patents

Abstract

The installation is of the type in which the prod. is contacted by the gas inside a gas-tight fumigation chamber. In addn. to the fumigation chamber, the installation comprises a generator for poison gas and a neutralising vessel in which gas is decontaminated. Controls are provided to regulate gas flow between generator and fumigation chamber and the diffusion of gas within the chamber. Gas flowing from the generator and/or the fumigation chamber can be directed into the neutralising vessel for decontamination. Pref. the fumigation chamber gas inlet is fitted with fan blowing into the chamber and the gas outlet with a fan extracting from the chamber. Pref. the walls of the fumagation chamber and/or of the gas generator are in laminated plastic sheet material comprising a centre sheet of expanded polyurethane sandwiched between two layers of isophthalic polyester resin reinforced with glass fibres. The installation is for fumigating food prods., e.g. cocoa beans, coffee beans, to destroy pests such as insects and parasites likely to harm the keeping properties of the prod. In addn. to very thorough fumigation, the plant can be reloaded quickly because dangerous exhaust gases are safely decontaminated before release.

Description

The present invention relates to a plant for the treatment of products with gases, for example toxic gases, in view of the destruction of insects, parasites and other pests and in the preservation of the products.

The current technique consisted in diffusing a gas in an enclosed space in which the products to be treated are stored.

One of the methods used consisted in introducing directly into the mass of the product to be treated, tablets of a solid pesticide which hydrolyzed on contact with ambient humidity to produce a toxic gas.

The introduction of the pesticide into the massa of the product to be treated must be carried out quickly to avoid that the gas emissions reach a dangerous threshold for the personnel employed at this spot and for the environment.

According to this method, it is not possible to treat a large mass of product without jeopardizing the safety of personnel, taking into account the brief time taken to hydrolyze the product.

In addition, the reaction of the pesticide produces wastes which must be evacuated as a whole from the mass of the product after fumigation so as not to harm its purity and which in some cases are themselves toxic.

To eliminate these drawbacks, another method as set out in French patent NP 79 15797 consists of placing strips of product on the mass of the stock having a succession of cells each receiving a tablet of solid pesticide.

These cells or the strip is covered with a gas permeable fabric and capable of retaining the waste products from the reaction.

This bende can receive only one kind of solid pesticide producing a gas of great diffusibility to treat in depth the mass of the product in the case where it is stored in bulk as is the case for grain stored in silos or in boat holds.

According to this method, the most commonly used pesticide is a metal phosphide producing by hydrolysis of hydrogen phosphide or phosphine.

This toxic sorted gas must be contained in a perfectly sealed enclosure for obvious safety reasons.

Experience has denied that phosphine has the power to diffuse through concrete, wood and certain metals such as aluminum, which limits its field of application to enclosures of a particular design.

Another treatment method implemented consists in placing the products under a tarpaulin forming an enclosure into which the is introduced or produces a toxic gas.

The disadvantage of this procedure results from the difficulty of obtaining a perfectly sealed enclosure which represents a real danger for the staff employed and for the environment.

In addition to compensate for the gas losses, users are obliged to produce a significant quantity of it without being certain of obtaining total destruction of the pests in the mass of the products stored, taking into account the irrational distribution of the product. toxic.

One of the drawbacks of this method resides in the fact that, due to the irrational distribution of the toxic product, the surviving pests gradually become desensitized to the treatment.

In general, the methods set out above do not make it possible to control at any time the concentration and the diffusion of toxic gas inside the storage enclosure according to data specific to the conditions of the product (hygrometry, temperature) and ambient air conditions, or to stop an ongoing treatment in the event that this stop is justified by safety measures.

At the end of the treatment, the toxic gases are in most cases discharged as such into the atmosphere, and this very slowly so as not to harm the safety of the personnel and the environment of the enclosure.

As is easily understood, the methods set out above do not make it possible to release the storage enclosures in a safe and rapid manner, which poses numerous problems in the case of the use of gases of great toxicity such as phosphine.

it should be noted that some of the toxic gases used from a concentration threshold within the enclosure form an explosive mixture with its atmosphere.

The absence of control of their concentration and the conditions of their reaction can present in some cases a real danger which limits their jobs.

In many cases to overcome these drawbacks, gases are used which make it possible to soften the safety measures, but which harm the entire product treated, which is a drawback in the case where it is a food product such as than "coffee", "cocoa", or others.

it has been found that the phosphine which requires rigorous safety conditions for its use allows the product to be treated in depth due to its great diffusion capacity and its downward diffusion and does not subsequently leave any trace.

None of the methods mentioned allow industrial application of this gas while respecting the safety conditions that its use requires.

The object of the present invention is to overcome the drawbacks stated above by using a product treatment plant using a gas, for example phosphine, on an industrial scale while respecting strict safety conditions.

Another object of the present invention is the implementation of a treatment plant making it possible to control the concentration of the gas, its diffusion and to ensure its decontamination after treatment or after rapid degassing.

To this end, the central processing unit according to the invention is essentially characterized in that it consists of at least one sealed cell for storing the products to be treated, at least one chamber for producing a toxic gas, at least one toxic gas decontamination center, at least one control and command center acting on means enabling the communication of the chamber and the cell and the diffusion of the toxic gas therein, or the communication of the cell and / or the room with the decontamination center to neutralize toxic gases.

Other advantages and characteristics of the invention will appear on reading the description of a preferred embodiment with reference to the appended drawings in which: - Figure 1 is a diagram of the central processing unit; - Figure 2 is an exploded view of the storage cell; - Figure 3 is a sectional view of the chamber 2; - Figure 4 is a top view of a tray; - Figures 5 to 7 are explanatory diagrams of how it works
central station.

As shown, the central processing unit for products using a gas, for example phosphine, consists of at least one cell 1 for storing the products to be treated in which the phosphine produced in a hydrolysis chamber 2 in communication with the cell is dispersed. storage 1, of a gas decontamination center 3 in communication with said cell i and / or said chamber 2 after treatment or after rapid degassing and means for monitoring and controlling the various stages of treatment.

As shown by way of example in FIG. 1, the storage cell consists of a horizontal base wall 4, two vertical side walls 5, a horizontal cover wall 6 of a door 1A, a bottom 7 can be replaced by a door of the same type as the door lA.

Each of the components of the cell is made of a synthetic material which is impermeable to the treatment gas and resistant to corrosion which may result from the use of such a specific gas.

Advantageously, each component of the cell is obtained by molding and consists of a central core 8 of expanded polyurethane sandwiched between two layers 9 of isophthalic polyester resin reinforced with glass fibers. The central core 8 is intended to provide the cell with good thermal insulation to prevent the temperature of the medium outside the cell from adversely affecting the quality of the treatment.

The layers 9 of reinforced polyester resin give the cell good mechanical resistance and ensure that it has good aging resistance whatever the climatic conditions.

Advantageously, the base plate 4 is provided with two plywood plates 4A disposed respectively between a layer 9 and the central core 8. Between these two plates 4A are disposed at equal distance in the core 8 of the crosspieces 4B, for example made of wood 4 as shown in section BE of Figure 2.

This configuration makes it possible to increase the mechanical resistance of the base plates and in particular their resistance to crushing or to punching under the effect of the loads exerted by the stored products.

The base plates and covers each have two vertical wings 10 and are arranged during mounting opposite one another.

The side walls 5 of square shape come ee have during assembly against the internal faces of the vertical wings 10 and are fixed against them by gluing or other method.

On the base plate 4 is disposed a wear plate 11 fixed by gluing. This wear plate formed with the same materials and processes as the cell but with the addition of a silicon carbide such as for example that sold commercially under the brand "CARBORUNDUM" to reinforce its wear resistance and improve its characteristics mechanical.

At each end of the cell there is a nozzle, the base, side and cover plate of which is fixed by a frame, for example of polyester, at the bottom of which has been placed an in-cert consisting of a profile of preferably rectangular cross section in steel.

To ensure the seal, the cell has at each corner internally a polyester angle type joint preferably fixed by gluing.

The bottom 7 is constituted by a substantially square plate fixed by gluing or other method respectively to the side walls 5 to the base plate 4 and to the cover plate 6. The bottom 7 can advantageously be replaced by a door lA in order to facilitate the cell loading.

The door 1A is advantageously provided with two leaves mounted on hinges embedded respectively in the respective leaf and in the side walls or in the frame.

The airtightness of the cell at the door is ensured by a seal made of a synthetic material capable of withstanding the corrosive power of toxic ga, for example phosphine.

 advantageously these seals are "Water-proof" tpa or similar.

According to an alternative embodiment as can be seen in FIG. 1, the storage cells consist of unit cells placed end to end in order to increase the quantity of product to be treated.

In this case, each end unit cell will be provided with a door 1A in order to facilitate the loading or unloading of the storage cell.

At the anointing of each hase cell are arranged joint covers fixed by gluing or other process. Preferably the glue used to fix the covers, anointed is of the same type as the material with which they are made in order to achieve perfect sealing.

The cover anointed cover 12 ensuring the sealing at the junction of two cover plates is in the form of a rectangular plate provided at the end with two vertical wings 13 directed downwards coming to be pressed against the external face of the wings 10. In order to stiffen the assembly, the joint cover 12 is provided with a longitudinal rib 14 f @ isent c.oI - on its outer face. The base anointed cover 15 ensures the watertightness at the junction of the base plates 4. This joint cover of substantially rectangular shape with a thickness equal to that of the wear plates is placed inside the cells between each side wall and between each wear plate.

The lateral joint covers 16 seal between each side plate of two adjoining cells. These joint covers are also constituted by a vertical rectangular plate which is fixed on the external faces of the side walls and comes to be disposed between a wing 10 of a cover plate 6 and a wing 10 of a base plate 4.

According to another embodiment not shown, the storage cells are constituted by a cylindrical silo constituted as described above by two layers of polyester resins reinforced with glass fibers sandwiching a central core of expanded polyurethane.

Each cell 1 is provided with two orifices for communicating with the chamber 2 for producing the toxic gas by means of two pipes 17 and 18 connected in leaktight manner to said cell and to said chamber. Preferably, the two orifices are formed in the cover plate due to the power of downward diffusion of the gas used, but it goes without saying that they may also be formed in the side walls.

The gas production chamber 2 is placed above the cell and consists of a sealed box 19 provided with a hatch 20 with hermetic closure allowing the introduction, for example, of a charge of aluminum phosphide into the case of phosphine use.

The box 19 made of any suitable material, for example of the type constituting the cell has a circular orifice with a conical surface 21 cooperating with the hatch 20.

This hatch also has a conical portion covered with a teflon seal which is applied to the conical surface 21. As is easily understood, this arrangement makes it possible to obtain a perfect seal of the chamber 2.

The hatch 20 is associated with a closing system known per se, for example of the type formed by a horizontal arm movable in the vertical direction by any known system for cooperating with ears secured to the box. In the case where the hydrolysis chamber receives a load of a solid hydrolyzable pesticide such as, for example, aluminum phosphide, there are arranged therein several superimposed plates 2A spaced apart from each other and removably mounted on a structure 2B.

Each tray has a series of 2C cells spaced from one another, each receiving a pellet of an aluminum phosphide
The tray cells allow the hydrolysates or reaction waste to be retained during the treatment
The fact of spacing the trays and the cells makes it possible to avoid excessive overheating during the reaction and results in better evolution of the gas during the hydrolysis. The air of the storage cell 1 is directed into the chamber 2 via the pipe 18 and an extractor 22 housed in the said pipe. Thanks to its humidity, this air in contact with the metallic phosphide will cause the hydrolysis of the latter with a view to the release of the phosphine.

This phosphine-laden air will be introduced into cell 1 through line 17 using a blower 23 housed therein (fig.5).

This arrangement makes it possible to ensure the distribution and the diffusion of phosphine inside the cell in a homogeneous manner.

To permanently control the release of toxic gas, the temperature and humidity inside cell 1 and / or chamber 2, the concentration of toxic gas in the chamber and / or in the cell, the control unit is equipped with ZD remote sampling probes of any known type sending their information to the control and command center.

Depending on the data it receives, the control center will slow down or accelerate the hydrolysis of aluminum phosphide by acting on the extractor and the blower to decrease or increase the flow rate of air charged with phosphine or will control the degassing of the cell and / or the bedroom.

Preferably the 2D probes are arranged in the hatch 20 and open into the hydrolysis chamber 2 but it goes without saying that they can be housed in the cell 1.

According to another embodiment, the 2D probes consist of a glass tube provided with a reagent which is housed for the measurement in a removable pumping device which is placed in a valve for communicating the atmosphere of the bedroom 2 or cell 1.

In the pipe 17 is arranged between the blower 23 and the chamber 2 a valve 24 hydraulically controlled from the control and command center to interrupt during its closing the path of the toxic gas between the cell and the chamber 2 in view of the 'stop treatment.

In the pipe 18 to 11 entering the chamber 2 is disposed a two-way valve 1A authorizing either the communication of the pipe 18 with the chamber 2 being treated, or the communication of the pipe 18 with the decontamination center 3 by via a pipe 25 comprising an extractor 26 in the event of treatment stopping to degas the cell 1
If the control unit is equipped with several cells 1
The pipe 25 opens into a manifold 27 fitted with the extractor 26 intended to pulsate the toxic gas towards the decontamination unit 3 via a pipe 28.

To the line 17 is connected a suction line 29 provided with a valve 30 hydraulically controlled from the control and command center.

The purpose of this valve, open only during degassing of the cell 1, is to put the line 17 in communication with the air outside the cell.

To degas cell 1, the power supply to blower 23 and extractor 22 is cut off, valve 24 is closed, valve 18A is closed to put line 18 into communication with line 25, valve is opened 30, the extractor 27 is started up in the case of several cells and the extractor 22 and the blower 23 are actuated (FIG. 6).

To degas the hydrolysis chamber (fig. 7) it is placed in communication with the outside air by means of a suction pipe 31 provided with a valve 32 open in this case in communication with the line 25 or the manifold 27 via a line 33 provided with a valve 34 open during degassing.

The other valves in this case being closed.

it should be noted that the degassing of cell 1 and of chamber 2 can be carried out simultaneously, which increases the safety of the personnel employed on the power station.

In this case only the valve 24 will be closed and the valve 18A will allow the communication of the pipe 18 with the pipe 25.

The decontamination center known per se consists of a scrubler or a washing tower 35, a pump 36 sending a sprayed liquid in the form of a curtain into the scrubler or the tower, an extractor pulsing the gas to decontaminate in the scrublater or tower against the current of the liquid jet.

This liquid advantageously consists of water added with sodium chloride or other detergent. It should be noted that the scrublisher extractor can advantageously replace the extractor 26.

The central equipment, such as extractors, blowers and valves are of the explosion-proof type or are controlled by an electro-hydraulic or hydro-pneumatic circuit.

The cenrale as described allows, thanks to its excellent sealing, a minimum concentration of toxic gas for the destruction of all insects whether larvae or adults.

In the case of the use of phosphine, the concentration per cell can be maintained between 710 and 800 PPM obtained by the hydrolysis of a charge of 1,800 gr to 2,400 gr of metallic phosphide without affecting the quality of the treatment.

In most cases, the products are treated with phosphine which behaves as an insecticide and fungicide.

The plant as described can also be used for long-term storage of products.

In this case, the products can be stored under an atmosphere charged with phosphine in proportions of 40 PPD4 cubic meter with permanent control.

In addition, an ambient air conditioning unit can be added to the central processing unit, for example, to dry products to increase the processing capacity.

The central unit as described constitutes a fixed unit, but it goes without saying that it can be mounted on the platform of a towing vehicle and that its different members can be mobile, for example for treating several cells from the same unit.

It goes without saying that the present invention can receive all modifications and variations without departing from the scope of this patent.

Claims (1)

 R1 / Central treatment of products with toxic gases charac  terized in that it consists of at least one cell i  waterproof storage of the products to be treated, at least one  chamber (2) for producing a toxic gas, of at least one  toxic gas decontamination center (3) of at least one  control center for measurement and control acting on  means for connecting the room and  of the cell and the diffusion of the toxic gas in it  or the communication of the cell (1) and / or the room (2)  with the decontamination center (3) to neutralize the  toxic gas. R2 / Processing unit according to claim 1 characterized  in that the cell (1) and the chamber (2) are joined together  sealingly by at least two pipes (17) and (18) provided  respectively an extractor (22) and a blower (23) for  aspirate the gaseous atmosphere of the cell (1), direct it into  the chamber (2) where it is charged with toxic gas and for intro  reduce and diffuse the gaseous atmosphere charged with toxic gas  in the cell (1). R3 / Central processing unit according to claim 1 and the return  dication 2 characterized in that the blower (23) and ltextrac  (22) have a variable diet controlled by the  control and command based on the data it receives  transmit through at least one cham  bre (2) so that depending on the concentration of  toxic gas registered we can vary the flow of  toxic gas mixture circulating between said cell  and the so-called room which also makes it possible to slow down or  to accelerate the hydrolysis of a solid pesticide in the case  for example from the use of phosphine produced from  of a metallic phosphide. R4 / Central processing unit according to claims 1 and 2 charac  terized in that the line (17) between the blower (23) and  the chamber (2) is provided with a valve (24) controlled by  the control and command center to allow the cir  culation of the toxic gas mixture between the cell and the  said room or to interrupt this circulation in case  stopping treatment. R5 / Central processing unit according to claim 1 characterized  in that the pipe (18) between the chamber (2) and the extractor  tor (22) is equipped with a two-way valve (18A) allows  both the communication of the pipe (18) with the  room (2), during processing or either communication of  the pipe (18) and a pipe (25) connected to a collec  tor (27) during degassing of the cell by suction of  the outside air in it using an ace line  piration (29) connected to the pipe (17) and equipped with a valve  (30) open in this case and by discharge into the pipe  (25) and in the collector (27) of the gaseous atmosphere of the  cell. R6 / Central processing unit according to claim I characterized  in that the chamber (2) is equipped with an ace line  outside air and pipe (33)  connecting said chamber with the collector (27) equipped  respectively a valve (32) and a valve (34) open  during the degassing of said chamber. R7 / Central processing unit according to claim 1 character  sée in that the collector (27) is equipped with a blower  (26) allowing the toxic gas mixture to be pulsed from the  cell and / or chamber during degassing to the center  decontamination (3) via a pipe  (28). R8 / Processing unit according to claim 1 characterized  in that the cell (1) and / or the chamber (2) are made up  by molding a layer (8) of expanded polyurethane  sandwiched between two layers (9) of resin  isophthalic polyester reinforced with glass fibers.  R9 / Central processing unit according to claims 1 and 8 char  terized in that between each layer (9) and the layer (8) is  arranged a plywood plate (4A) and that between each  plate (4A) in the layer (8) are arranged at equal distance  this sleepers (4B) preferably in wood. R10 / Central processing unit according to claim i characterized  in that in the case of using a solid pesticide  producing a toxic gas by chemical reaction, the chamber  (2) is equipped with several removable trays (2A) super  placed mounted on a structure (2B) spaced from each to  very and each comprising a series of spaced cells (2C)  each other receiving a plate of pesti  solid cide, in order to avoid overheating during  reaction and ensure better diffusion of the toxic gas.