FI67013B - FOERFARANDE FOER BEHANDLING AV EN AGRIKULTURELL PRODUKT MED OSFORVAETE - Google Patents

Description

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(32) (33) (31) Requested interest * —Begird prtorttet (71) Degesch GmbH, Weismillererstrasse 32-40, Frankfurt am Main, Federal Republic of Germany Förbundsrepubliken Tyskland (DE) (72) James S. Cook, Houston, Texas, USA (US) (74) Oy Koister Ab (54) The present invention relates to a process for the chemical treatment of stored agricultural products, such as cereals, in a phosphorus hydrate. The invention relates in particular to a treatment method in which phosphorus water is applied without recirculation.

Agricultural products, such as grain, are often stored for a period of time, such as the time between harvesting and further processing of the products. This storage can take considerable periods of time. As a result, in order to maintain the quality of the stored product, certain storage procedures have been followed to keep the product in good condition and to prevent contamination.

For example, the temperature and humidity of the stored product must be kept within certain limits to prevent contamination. This standardization is sometimes accomplished by physically turning the grain in a storage facility. Temperature and humidity control is also implemented using large fans to vent the product through a valve system in the storage tank, typically including an air distribution manifold under the stored product and valves in the roof or superstructure of the storage facility (commonly known as the "top"). In this way, outdoor air can be forced up and down through the mass of stored product.

In addition to problems caused by unreasonable temperature or humidity conditions, stored agricultural products are also susceptible to damage by various living pests, such as insects that eat the product, lay eggs on it, etc. As soon as such products are stored, measures must be taken to prevent significant contamination. Various liquid chemicals have been applied to stored agricultural products to kill these pests and to prevent them from damaging the stored product. Such liquid gas treatment agents are applied to the top of the stored product and the gas is to flow down into the product and through the entire volume of the product to achieve contaminants at each location. However, such liquid applications are an expensive means of control and are difficult to apply in such a way as to ensure an even distribution of the chemical throughout the stored product, which is necessary to eliminate an acceptable high percentage of contamination.

Gaseous substances have also been used for this purpose. The gas can be distributed through a compressed air ventilation system to circulate the gas through the stored product and then out through the exhaust system. This method is known as "single pass" gas treatment. In an effort to further improve the efficiency of gas treatment and the uniformity of gas distribution, a method was developed in the art to apply gas by continuous air recirculation. In this method, any of the valves in the storage tank are closed to the outside air. The air duct is attached to the tank above the surface of the product (the "top" of the warehouse) and connected to the intake of a fan or blower which supplies air to the aeration system under the stored product. The gas is fed into a duct or tank, after which air and gas are passed through the stored product using a fan or blower. The mixture of air and gas is then led to the fan intake by means of an air duct and recirculated through the product, and the recirculation is continued for a sufficient period of time to achieve a uniformly distributed gas concentration in the mass of stored product.

6701 3 3

When implementing such recycling treatment methods, the total amount of gas is generally released over a relatively short period of time, about 10-40 minutes. These short release times make it necessary to use air flow rates in this technique that are relatively high in order to achieve a uniform gas distribution. The gas distribution is still affected by the properties of the gases used in each case. These chemicals are prone to sorption by the stored product, i.e. the chemical can be absorbed into the grain or adsorbed on the surface of the grain. In addition, some gases decompose into other compounds after application. These factors tend to cause an uneven concentration of the gas, with the highest concentrations occurring at the points closest to the gas inlet. When such compelling factors are taken into account, the air flow rates required in recirculation processes are generally 0.00848-0.1696 m / min.

3 3 in / min./m stored product), which flow rates correspond to providing one complete ventilation through the stored product in 2.5 to 50 minutes. Lower airflow rates have not been used, as it has been found that lower airflows provide less than fully effective pest control.

Relatively high capacity ducts and fans must therefore be used in the conventional implementation of this method, with duct diameters ranging from 205 to 915 mm and the fans used requiring 5 to 100 horsepower motors. Such large ducts are relatively expensive and the size of the fans makes it necessary to use a large amount of energy during such traditional gas treatment methods.

As mentioned above, the flow rate is normally expressed in units of cubic meters per minute per cubic meter of product stored. In this terminology, agricultural products such as cereals can be dried at approximately 0.424 m / min. at a flow rate (corresponding to a total ventilation of 10 minutes), cooling and conditioning are carried out at a flow rate of about 0.1666-0.0424 m / min. (2.5-10 minute ventilation) and gas treatment using the recirculation or single run compressed air method have traditionally been performed at flow rates ranging from approximately 0.00848 to 0.3392 m / min, and are generally 0.0212 m / min. min (corresponding to 20 minutes of ventilation).

6701 3

One particular gas treatment agent, aluminum phosphide, which can be described as a solid gas treatment agent, is available in the form of tablets, granules or powder. Gaseous hydrogen phosphide (phosphorus hydrogen) is developed from solid aluminum phosphide in the presence of ambient humidity. Hydrogen phosphide has previously been used as a gas treatment agent in static systems, but those skilled in the art have argued that it should not be used in compressed air systems. In its solid form, it is applied to the grain after the grain has been transferred from one container to another, divided into the top or top and bottom of the grain in the container, and inserted into the grain to different depths. Each of these gas treatment methods has relied on the penetration capacity of phosphine gas and conventional flows in the storage facility to provide distribution throughout the stored product. Occasionally, aeration systems with high airflows have been used in an attempt to help hydrogen phosphorus penetrate. Although other gas treatment agents are released and reach peak gas concentrations in approximately 10-40 minutes, aluminum phosphide requires a much longer time, 16-30 hours, to release the phosphorus hydrogen contained therein and the relationship between this release time and the appropriate air flow rate has not been realized.

Therefore, there is a need for a method of treating cereals and other agricultural products that provides an even distribution of chemicals with airflows that are proportional to gas release and uniformly high destruction rates without the need for large and expensive air recycling equipment and oversized chemicals.

It is a general object of the present invention to provide an improved method for handling stored agricultural products.

The invention relates to a method for treating an agricultural product stored in a container with hydrogen phosphorus. The process is characterized in that hydrogen phosphorus is fed into the tank and that hydrogen phosphorus and air are circulated through the product at such a flow rate that the air in the product is not completely changed until after about 1.5 hours at the earliest.

The process can be performed using a one-run technique by (a) placing the product in a closed tank, (b) connecting an air duct to the tank, (c) feeding hydrogen phosphorus to the tank, and (d) passing air and hydrogen phosphorus through the recycle system at a very low flow rate for sufficient time. to distribute evenly throughout the product.

The process can also be performed using a recirculation technique by (a) placing the product in a closed vessel, (b) connecting an air duct between the top and bottom of the tank, (c) feeding hydrogen to the tank, and (d) passing air through the air duct at a very low flow rate; recirculate air and chemical for sufficient time to distribute the chemical evenly throughout the product.

In a preferred embodiment, the hydrogen phosphorus is derived from aluminum phosphide.

To achieve the optimum benefits of this method, the air in the tank must be recirculated at a flow rate of approximately 3 0.005 m / min. (1.5 hour ventilation). Particularly advantageous results are obtained using a flow rate low enough to provide complete ventilation only after 3.5 days.

This method is particularly useful for treating starchy products such as flour and whole or processed cereal grains.

Reference is now made to the attached Figure 1.

Figure 1 shows a typical container arrangement for agricultural products that can be used to implement the method of the present invention.

Figure 1 shows a grain storage system. The agricultural product 10 is stored in tank 12. A fan or fan 14 is connected to the bottom of tank 12 via air supply duct 16 and aeration manifold 18, while return air duct 20 is connected to tank 12 near tank top and directs air from tank to intake fan 14 for recirculation. and through the stored product 10.

In a single run technique, using phosphorus hydrogen is fed to the product 10 using a blower 14 and either duct 16 or duct 20 to force air and hydrogen phosphorus either up or down through the product and out of the outlet to the outside air.

When carrying out the treatment with the recycling technique, all the outlets leading to the outside air in the tank 12 are closed first. A recirculation system consisting of a fan 14 and associated feeds from return ducts 16 and 20 is attached to the tank to provide a recirculating airway that passes through the tank and the stored product 10. Hydrogen phosphorus is then added to the closed system.

Typically, the chemical in these methods can be applied to the top surface of the agricultural product 10, although the treatment material can be fed into any closed system, such as a supply line 16 or a return line 20, as is best suited for the particular application. The blower 14 is then operated for a suitable period of time to achieve an even distribution of the gas throughout the mass of the agricultural product 10. After the fan has been running for a sufficient period of time to achieve the desired even distribution, the fan is disconnected and no further air movement is required before the tank is vented to aerate the agricultural product and remove gas.

Such treatment methods by compressed air recirculation have heretofore been well known in the art. Prior to the present invention, however, the compressed air treatment method has been implemented with much higher air flows than are required in the practice of the present invention.

The blower 14, supply duct 16, and return duct 20 are schematically enlarged to show the relatively large size of these components as they are typically constructed to dry, standardize, and process the product 10 by conventional methods. Figure 1 also shows a low flow return duct 22, a low flow fan 24 and a low flow supply duct 26 which are relatively small in size and capacity and may be specially equipped to implement the method of the present invention.

The method of the present invention can be accomplished by the one-run technique of introducing hydrogen phosphorus into the area 28 of the top of the tank 12. With the tank vented to the outside air, gas is drawn down through the product by a fan 24 at a very low flow rate. The fan is then switched off and the outlets are closed. Alternatively, the chemical can be fed to the bottom of the tank 12 and a blower 24 used to force the gas upward through the product 10, again at a very low flow rate.

The single run technique of the present invention can also be implemented using higher capacity recirculation equipment such as blower 7 6701 3 14, supply duct 16 and return duct 20. When using larger conventional equipment, the very small airflows necessary to practice this invention can be achieved using a larger blower such as blower 14, 1 -5 minutes every 3-4 hours. However, when using higher capacity systems, extreme caution must be exercised as such systems operate at much higher pressures, which requires that all leaks in the system be blocked.

The method of the present invention can be similarly implemented using a recirculation technique in which the outlets leading out of the tank 12 are closed and the blower 24 and ducts 22 and 26 are used to recycle phosphorus hydrogen at a very low flow rate for a sufficient time to achieve uniform distribution. As with the single run method, the recirculation technique can be implemented in accordance with the present invention using conventional higher capacity airflow systems when the fan is cycled to very short time intervals and when appropriate precautions are taken in view of the higher pressures.

It is an essential feature of this invention to provide a circulating chemical treatment process that requires much lower air flow rates than previously known methods. In the method carried out according to the previous method, flow rates of, for example, 0.00848 3 m / min or more are generally used, so that a complete exchange of air in the product is achieved in 50 minutes or less.

However, it has been found that more efficient results with slow-developing or slow-fed, poorly sorbed chemicals are achieved more efficiently at flow rates much lower with a suitably selected treatment chemical.

In previous methods in the art, the flow rate must be kept relatively high because it has been found that at lower flow rates, the grain or other crop product absorbs the treatment chemical primarily at the point where the gas is fed to the storage tank. For example, hydrogen cyanide, ethylene dibromide, and ethylene dichloride, chemicals commonly used as a gas treatment agent for agricultural products, tend to be highly sorbable in agricultural products. This high sorbability property results in an uneven distribution of the gas treatment agent in the mass of the product.

8 67013 Consequently, in order to achieve effective pest control throughout the stored product, prior art methods require the use of high capacity airflow equipment and long application times so that all parts of the stored product receive sufficient concentrations of gas treatment agent to achieve desired control, resulting in increased costs and stored product to remove residual concentrations of gas treatment agent. An additional effect of the higher flow rates is the increased gas leakage under the associated greater pressure differences, which further results in the additional volumes of gas required by prior art methods, along with the associated hazards.

However, it has now been found that by selecting phosphorus hydrogen, which is only very little or not sorbable in agricultural products and by releasing this chemical slowly, the circulating air flow rate can be significantly reduced while achieving better results at lower material and energy costs.

In a preferred embodiment of the process of this invention, the hydrogen phosphorus is obtained from aluminum phosphide, which is available in the form of tablets, granules or powder. Aluminum phosphide can be added at various points in the air recirculation system in the manner best suited to the particular application.

The following examples illustrate the invention.

Example I

Three similar steel welded grain tanks, about 12 m high and 35 m in diameter, were filled and leveled to a depth of about 11 m with 10,670 m 2 of long-grain raw rice. All containers were tightly closed. A two-horsepower blower with a 152 mm inlet and an 86 mm outlet was used for the latter two tanks. A 152 mm sheet metal return pipe was erected from the top of each tank to the fan inlet. A 1.8 m long hose with a diameter of 100 mm was connected from the fan outlet to a central collection system at the bottom of the tank. An air flow rate of 0.0011 3 m / min was obtained, corresponding to an air exchange of about eight hours in the rice pulp.

As a control, the first container was disinfected according to Phostox® (trademark quality of aluminum phosphide) label label 6701 3 without air circulation. Two boxes of Phorstoxin® tablets = 14,400 tablets (approximately 40 tablets per 33.35 cubic meters of rice) were spread evenly on the surface of the rice. The gas treatment was considered complete and the experiment was terminated after 500 hours (21 days).

High concentrations above 2,400 ppm were recorded in the first tank. The gas required five days to penetrate the bottom of the tank at lethal concentrations of 10-15 ppm. After 21 days, the base concentration had not exceeded 20 ppm, although a minimum concentration of 50 ppm would have been recommended.

The second tank was treated using an air recirculation system. Two boxes of Phostoxin (approximately 40 tablets per 33.35 cubic meters) were evenly sprinkled on the surface of the rice. After about three hours, when the concentrations above the gas treatment agent had reached 490 ppm, the fan was turned on and, except for a short interruption, it was run continuously for about 13 hours. After a standstill period of 10 hours, the fan was switched on again for about eight hours, for a total of about 21 hours for the test. The fan was then turned off and the experiment terminated after 201 hours (8.3 days). A complete distribution of 450 ppm was obtained throughout the tank within eight hours of application. Steady and lethal concentrations were maintained, resulting in complete extermination of pests with 5.5-8 days of exposure.

The third container was treated using one box of Phostoxin tablets (approximately 20 tablets per 33.35 cubic meters) without recirculation. The tablets were pulverized and blown into the space above the rice from one point. After 1 1/2 hours of exposure with a reading above 650 ppm rice, the fan was turned on and run continuously for another 18 1/2 hours. The analysis was stopped and the gas treatment was considered complete in 135 hours (5.67 days). At half of the previous dose, complete gas distribution was achieved within eight hours. Complete destruction was achieved in 5.67 days.

Example II

The steel-walled horizontal warehouse building, 27.5 m wide, 110 m long and 12 m high, contained four 27.5 x 27.5 3 m lairs with a capacity of 36,850 m. Each parcel was loaded with 24,120 m of paddy rice to a leveled depth of about 10.8 m.

3 10 6701 3 3 80 tablets of aluminum phosphide per 33.35 m were blown into the upper end of the building in a 32 mm diameter pipe connected to a 1 1/2 horsepower instantaneous fan. One fan was connected to the lower aeration manifold under each bay. Air flow rate 3 3

was calculated to be approximately 0.0012 m / min. m (six-hour full-female ventilation). The natural distress caused by rice weevils and, to a lesser extent, grain worms was repelled and the rice was transported away in about four months free of all living pests. Complete distribution was achieved within six months with concentrations within good control limits. Example III

Two identical grain storage tanks made of corrugated steel with a diameter of 22 m, a eaves height of 3 15.5 m and a peak of 22 m and a calculated capacity of 6,633 m were loaded with 6,578 m of yellow millet No. 2. 152 mm PVC pipe was installed on the ceiling 0.6-0.9 m above the eaves line and led down along the outer wall 1.5 m from the ground. The manifold of the PVC pipe and the flexible hose connected the return line with a 2-horsepower fan, whereby the fan was connected to the aeration system at the bottom of the tank 3 under the grain. Barometric pressure calculations showed approximately 0.021 m / min. (3.5 hour ventilation) without flow rate. Both containers were gas treated with similar doses of approximately 80 tablets per 33.35 m 2 using two boxes (14,400 tablets) of Phostoxin ® tablets per container.

In the first container, the entire dose was applied to the surface of the grain on the opposite side of the return air tube. The fan system was turned on shortly after all the tablets were fed and allowed to run for 12 hours. Seven hours later, it was restarted for another 5 1/2 hours, which meant a total ventilation time of 17 1/2 hours, or 24 hours after the gas exposure had occurred. A steady and complete distribution was achieved in 3.5 hours and complete results were achieved.

In the second container, 9,600 tablets (2/3 of the dose) were applied to the upper area and the remaining 4,800 tablets were treated in the four aeration channels at the bottom of the container. No air flow was used. Varying disinfectant concentrations were recorded at various points from the top of the tank to the bottom. It took 2.5 days for the gas to penetrate the center of the tank.

The advantages of the present invention can be summarized by comparing different handling parameters for a typical compact steel storage tank with a capacity of 6,700 m 2. Aeration and conditioning can be carried out in 3 such tanks at 0.0848 m / min. at a flow rate of 20 horsepower in a duct with a diameter of 1,220 mm reaches 34,000 m "Vh. Conventional recirculation gas treatment methods generally use a flow rate of 0.0212 m / min m, which can be achieved with a 3-5 horsepower fan In contrast, the gas treatment process of the present invention can be carried out in such a tank at a flow rate of 0.000848 m / min, requiring only a 1/3 horsepower fan and a 114 mm diameter duct. The method can be efficiently 3 implemented even at lower flow rates of 0.0006 m / min with even lower equipment.

The advantages of the present invention can be further demonstrated by comparing the dosage amounts required to apply aluminum phosphide. The name 3 label guidelines recommend 180 tablets per 33.35 m, while 3 common practice in the industry has been 40-80 tablets per 33.35 m, resulting in effective controls in 8-10 and 8-21 days, respectively. However, when using the method of the present invention, 3 need be used only 20-40 tablets per 33.35 m to achieve effective control in 5.5-6 days.