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PS6-2 – 6146

Large scale grain fumigations using pure cylinderized phosphinetogether with the HORN DILUPHOS SYSTEM

P. Horn1, F. Horn2

1 Dipl. Eng., Fosfoquim S.A., Chile. Marchant Pereira 367, of 901, Providencia, Santiago, Chile. phorn@fosfoquim.cl2 Dr., Fosfoquim S.A., Chile. Marchant Pereira 367, of 901, Providencia, Santiago, Chile. phorn@fosfoquim.cl

Since the Horn Diluphos System was developedin the year 2001, the number and size of thefumigations has increased considerably. The HornDiluphos System uses a patented method for directblending of phosphine with air.

The first model of phosphine blending device,developed in 2001, has a phosphine dispensingcapacity of 1.2 kg/hour. The second model,developed in 2003, has a capacity of or 3 kg/hour.

Since year 2002, this method has been usedin Chile, Australia, the United States andArgentina, with great success.

As this technology has proven to be veryefficient and effective, the size of the fumigationshas increased, and thus the time required forfumigations. In Chile, many fumigations usemore than 10 kg of phosphine on one site. InAustralia these numbers are even larger. In somesites more than 100 kg of phosphine have to beapplied for one fumigation.

In order to reduce the time required for largefumigations, a new model was developed in theyear 2005. This model is able to dispense 200 g/minute or 12 kg/hour of phosphine.

The first large fumigation made with thisequipment was in the port of Kwinana in Perth,Australia in July 2005.

In 12 hours, 144 kg of phosphine were appliedon one large flat storage with approx. 300,000tons of grain. Great results in gas distributionand insect control were obtained.

After this great success, more than 1,400,000tons of grain have been fumigated and more than

700 kg of pure cylindered phosphine have beenapplied since July 2005 with one HDS 800 inAustralia.

Since April 2006, one of these phosphinedispensing units is also being used in Chile forlarge fresh fruit fumigations. This reduced thetime required for standard fumigations from 4hours to less than 1 hour.

In the year 2001, FOSFOQUIM developed theHorn Diluphos System (HDS), a patented methodfor the blending of pure cylindered phosphinewith air.

The system dilutes pure phosphine with airwithout risk of ignition, using a patented dilutiondevice developed by Fosfoquim. The unitcontrols the different parameters with a PLC,indicating to the operator the steps to followthrough an LCD screen. The unit has severalsafety measures to ensure that the phosphine- airmixture will not burn, even in case of powerfailure.

The first model of phosphine blending device,had a phosphine dispensing capacity of 1.2 kg/hourof pure phosphine, which means 19 g ofphosphine per minute.

This unit was used in silos and grainwarehouses up to 5,000 tons, but even thoughthe labor required for the grain fumigations wasreduced and the safety increased considerablycompared to other alternatives of phosphinefumigation, since the gas could be easily appliedfrom outside the facility, the time required to applythe gas for large fumigations was still of several hours.

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For that reason, and knowing the beauty andadvantages of the system, FOSFOQUIMdeveloped the second model in the year 2003.This model had a capacity of 3 kg/hour or 47 -50 grams per minute of pure phosphine.

The capacity of this unit was larger than thecapacity of all the available alternatives ofphosphine dispensing equipment, going fromgenerators and other cylindered mixtures.

Since the year 2002, the great advantages ofthis fumigation method and equipment, haveallowed its use in Chile, Australia, the UnitedStates and Argentina for different applications,as for example grain fumigations, empty spacefumigation, mill fumigation, nut fumigations andfresh fruit fumigations among others.

The advantage for grain fumigations is the fastdistribution of the fumigant achieved through theuse of this technology combined with the H-System, a fumigation method developed byFOSFOQUIM, in which the interstitial air of thegrain storage is replaced by a mixture of gas andair at a concentration close to the requiredconcentration. The source of gas used for thisphosphine air mixture, comes from the HornDiluphos System and if required, gas concentrationcan be adjusted using an additional fan fordilution. This permits getting an immediate evengas distribution, shortening the time of thefumigation, depending on the type of facility,several days.

On the other hand, the capacity of thisfumigation system to control exactly the amountof gas added to the structure to be fumigated,allows applying phosphine to empty space andflour mill fumigations, controlling the risk ofcorrosion. Using the HDS system, a controlled,low but effective concentration of gas can beadded to the mill in a short period of time,obtaining immediate gas distribution, and thusreducing the shut off time, killing the insects andcontrolling corrosion. In Chile and Argentina thissystem is applied in different mills and factoriesseveral times a year with excellent results. Oneof the advantages of the system is that the air forthe dilution of the gas can be taken from theinside of the facility to be fumigated, avoiding

in that way the build up of a positive pressurethat would increase the gas leaks to the atmosphere.

As this is a clean method, where only purephosphine is applied, and no residues are leftbehind, this is an excellent method for thefumigation of high value stored food commoditieslike nuts and dried fruits, that cannot befumigated with products that leave residues afterfumigation, and where the content of ammoniaproduced by other alternatives of phosphinegenerating fumigants, can damage the productand change its color and value.

Going further and looking for alternatives tomethyl bromide, Fosfoquim developed andpatented in the year 2003 a method for fresh fruitfumigation using pure phosphine free fromammonia. This method allows fumigating fruitsusing the Horn Diluphos System, applying highconcentrations of gas at low temperature tocontrol insects and pests on fruits, withoutproducing damage or changes to the fruits andcontrolling effectively the pests. This method isapplied now in Chile commercially for the exportof fruits to different countries worldwide.

The advantages of this technology are:� The fumigator does not need to enter into

the facility to be fumigated� An even gas distribution is achieved shortly

after the beginning of fumigation� No need to collect or deactivate spent

material after fumigation� Reduced labor for gas application� The exact required amount of gas can be

applied� Only pure phosphine is appliedWith these advantages, this technology has

proven to be very efficient and cost effective, forthe control of pests in stored food, commoditiesand empty spaces.

Since this technology was developed in theyear 2001, Fosfoquim has performed more than2500 fumigations only in Chile using the HDStechnology. Large volumes are being fumigatedalso in Australia, Argentina, and the United Statesof America.

This has caused that the size of thefumigations, where this technology is applied,

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has increased in the past years, from silos varyingfrom 5,000 cubic meters up to 50,000 cubicmeters or more, and for that reason the timerequired for fumigations has also increasedconsiderably compared to the use of thistechnology some years ago.

Only in Chile, more than 15 kg of phosphineare often applied on one site. In Australia andArgentina these numbers are even larger. In thesetwo countries, as also in other countries off theworld, more than 150 kg of phosphine have tobe applied sometimes only for one simplefumigation.

Considering the amount of cylinders requiredfor these fumigations, if there were usedphosphine - nitrogen or phosphine - carbondioxide mixtures, with 1.5 to 2 % of phosphine,it would not be possible to make thosefumigations, since more than 200 cylinderswould be required for each fumigation.

But using the HDS (Horn Diluphos System)technology, the number of cylinders is reducedby several times. One pure phosphine cylinderhas a content of 18 to 22 kg of pure gas, whilethe mixtures contain less than 1 or 0.5 kg of purephosphine.

Grain handling companies are trying to buildlarger and larger grain storage facilities, in orderto reduce the unitary storage cost for theirproduct. When the engineers design thosemonster grain storages, normally they do notconsider fumigation as one of their key aspects.For that reason, as fumigation cannot be avoided,the grain handling companies have to spend largeamounts of money for fumigation in equipmentand labor.

Considering the traditional fumigationmethods, several people have to be employed foreach fumigation in order to place the fumigant,and after fumigation collect and deactivate spentmaterial, using several hours of labor.

In metal phosphide fumigation, additional riskhas to be considered because workers are enteringinto a confined space, where gas is being liberatedand where other risks are constantly present.

In order to reduce the time required for largefumigations, a new model was developed in the

year 2005. This large model, called the HDS 800(Figure 1), is able to dispense 200 g/minute or12 kg/hour of pure phosphine (Table 1).

Figure 1. Horn Diluphos System, model HDS 800.This unit uses four phosphine cylinders and 1 nitrogencylinder for purging and I able to dispense 12 kg ofpure phosphine per hour.

Table 1. Specifications of HDS 800.

Air Flow 800 Cubic meter /hourPhosphine flow 200 Grams/minutePH3 concentration 10.000 ppmWeigth 500 kgPhosphine cylinders used 4Nitrogen cylinders 1

After manufacturing, testing, and calibratingthe unit in Chile, the first unit of this model wassent to Perth in Australia to fumigate the largestflat grain store worldwide.

In 12 hours, 144 kg of phosphine were appliedon one large flat storage with approx. 300,000tons of grain in the port of Kwinana in Perth,Australia in July 2005 (Figure 2).

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Great results in gas distribution and insect controlwere obtained. The 300 meter long, 70 meter wideand 28 meter high storage was put completely undergas with an even gas concentration in less than 20hours, only a couple of hours after finishing gasinjection (Figures 3, 4 and 5).

The gas was added through one of 18recirculation ducts into the headspace of thestorage, by disconnecting the aeration fan. Thefresh air used to dilute the phosphine gas, wastaken from the tunnel under the storage, to whichthe recirculation fan was connected. The other17 recirculation fans were used during gas injectionand then 12 hours after gas injection to distributethe gas evenly, taking the fresh air from the tunnelinto the headspace. After achieving an evendistribution, the recirculation was turned of.

In order to reestablish gas concentration inthose low concentration spots caused by smallleaks, like for example behind doors, therecirculation fans were turned on once a day inorder to move the gas inside the storage.

Labor required for the fumigation of this storagewas reduced several times and the risk of exposureto high phosphine concentrations of the fumigatorscontrolled, since the fumigators did not require toenter into the bin to place the fumigant. Twenty years

ago, fumigators in Germany where asked to use 10or more tablets per ton of grain. This means that fora storage like the above named, 9,000 kg of metalphsophides would be required, and it is easy toimagine the labor and worker exposure involved inthe distribution of the tablets and after fumigationthe collection of the spent product.

After this great success in July 2005 and untilJuly 2006, more than 1,500,000 tons of grainhave been fumigated and more than 800 kg ofpure cylindered phosphine have been appliedwith one unit of the HDS 800 in Australia.

The unit is being used with success in bunkerstorages, where the gas is distributed in less than24 hours in storage sizes varying from 20,000 to60,000 tons. The unit is used also for flatwarehouses and silos, where the possibility ofadding large amounts of gas in a short period oftime has interesting advantages for the grainhandling companies.

One of the great advantages for the grain handlingcompanies is the reduction in time required forfumigation, which saves and increases their existingcapacity for fumigations and thus avoids the needfor construction of new storages and fumigationfacilities.

Figure 2. Port Kwinana, Perth, Australia, 300,000 ton flat storage first fumigated wit the HDS 800in 2005. 144 kg applied for one fumigation

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Figure 3. Fumigation van used byFOSFOQUIM in Chile for itsfumigation. This unit has one HDS800 installed inside and travels tothe different locations where gashas to be applied.

Figure 4. Fumigation of a bunkerstorage with the HDS 800. Thephosphine-air mixture is appliedinto the headspace that is generatedbetween the tarp and the grainwhile the gas is injected.

Figure 5. Detail of bunker storagefumgation with the HDS 800. Thephosphine-air mixture is appliedinto the headspace that is generatedbetween the tarp and the grainwhile the gas is injected, anddiluted with an additional fan.

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The fast distribution of the gas obtained with theuse of the HDS technology, allows reducingfumigation time several days.

Considering the success of this new model,new units are being built, to be used in Chile,Argentina, Australia and the USA.

Since April 2006, one of these large phosphinedispensing units is being used in Chile for largescale fresh fruit fumigations. This great toolallowed to reduce the time required for standardfumigations from 4 hours to less than 1 hour,increasing the response capacity of Fosfoquim’sfumigation branch Fosfoquim FumigacionesS.A.

In Chile, more than 20 fumigations per dayare being performed by Fosfoquim, during almostthree quarters of the year using the Horn DiluphosSystem.

This new tool will allow opening the doors toa whole list of new markets for the purecylindered phosphine business.

As for example ship fumigations with grain,where large amounts of gas have to be deliveredin short periods of time in order to avoid demurragecosts to the shipping companies. Until this largecapacity unit was developed, the best availablealternative for ship fumigation was metalphosphides with recirculation.

This traditional method for ship fumigationusing metal phosphides has a series ofdisadvantages like:

� Residues in the grain� The need to collect, deactivate and dispose

of spent material after fumigation.� Long time for gas generation, which means

that the method cannot be used for short tripfumigations as for example ships traveling fromthe US to Mexico or New Zealand or Australiato South Asia.

� No control of gas concentration.On the other hand, there are a series of

advantages of the HDS System for ship fumigations,like:

� Reduced gas injection and distributiontime, which allows starting to control pestsimmediately after gas injection.

� Method can be applied for short voyage in

transit fumigations.� No residues are left behind after

fumigation.� The gas can be applied to a sealed structure

from outside, avoiding people entering intoconfined spaces.

For several countries, phosphine is applied forin transit timber fumigation. Until the HDStechnology was developed, only metal phosphidescould be applied for those fumigations, but thisfumigation method had a series of disadvantages.

Timber and log fumigation require highdosages of gas to be able to control the pests.This is obtained normally overdosing metalphosphides in order to achieve on one side a fastgeneration of lethal gas concentrations, andadditionally avoid concentration reductions dueto leakage. But this practice has a great risk ingenerating gas explosions, since often these shipholds contain liquid water. When metalphosphides get in contact with water theygenerate high concentration of phosphine that canignite spontaneously and explode.

As the HDS system applies a controlledmixture of air and phosphine, where theconcentration is always below 10,000 ppm, thisrisk is eliminated.

Also the same advantage for grain ship intransit fumigation, of reduced gas distributiontime, acquires importance where voyage time istoo short as to allow the gas generation from mealphosphides.

This means also that much less gas can beapplied since it is not necessary to overdose inorder to achieve a fast gas distribution.

A third new market for pure cylinderedphosphine is the fumigation of empty space andflour mill fumigation. Since in Chile andArgentina it is not allowed to apply methylbromide or other gases, different than phosphine,to empty space fumigations, mills have startedto apply pure cylindered phosphine since itbecame available through the HDS technology.The beauty of this method is that corrosion canbe avoided if concentration is maintained belowcertain limits, which depends on temperature andmoisture content of air.

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As mills have not too much down time, it is ofgreat importance to achieve a fast gas distribution,which at this time can be done with the HDS 800 ina very short period of time.

In large facilities, natural distribution bydiffusion, convection and other natural airmovements, are very slow to distribute the gas,and it can take sometimes several days to get aneven distribution in very large or tall storages, andin some cases gas never is distributed completely.

Fort that reason researchers have developeda series of different gas distribution methods, likethe J-System, the SCIRO-Flow, SCIRO-Circ, themethod where the metal phosphide tablets aredispensed to the belt while loading the grainstorage among others. But the larger the storage,the harder it is to distribute the gas and the morelabor and time are involved for fumigation. In

some cases large storages are tremendous technicalchallenges for the grain handling companies. Andespecially for those cases it is of great importanceto count with a method like the HDS system, andspecifically the model HDS 800, able to dispenselarge amount of gas in only a short time.

As conclusion it is recommended that in the future,when building new facilities where any product hasto be fumigated, fumigation is considered as one ofthe key points in design. Materials have to be chosenin order to facilitate sealing labor, but it is of mostimportance to look for available technologies likethe Horn Diluphos System and install the systems inorder to allow applying these technologies effectively.At this time, existing facilities have to be adaptedand modified in order to apply this new method,but in the future this application should beconsidered from the conception of the projects.