PROCESS, INSTALLATION AND CHAMBER FOR REDUCING BIOLOGICAL ACTIVITY IN AN ENCLOSURE, PARTICULARLY FOR A STORAGE SPACE

Abstract: The present invention relates to the preservation of stocked products, in particular cereal grain, by extracting the air contained in a silo (1) or the like, introducing air to the interior of a chamber (3) suitable for the oxidation of microorganisms suspended in the air, said chamber being equipped internally with heating means, ultra-violet lamps or catalysers. Downstream of the chamber there may be installed a heat exchanger (4) or an ozone decomposition system. The processed air is once more introduced to the silo by means of a propeller device. The electrostatic charge formed on the product may be dissipated by means of anodes provided above blocks that act as the heating means.

Description: Specification of the Patent of Invention for: "PROCESS, IN¬ STALLATION AND CHAMBER FOR REDUCING BIOLOGICAL ACTIVITY IN AN ENCLOSURE, PARTICULARLY FOR A STORAGE SPACE" FIELD OF THE INVENTION The present invention refers to a process, an in¬ stallation and a chamber for reducing the biological activity in storage spaces, such as silos, storage sheds, grain stores, cargo holds in grain transport ships or the like, and partic¬ ularly for the storage and preservation of grains or other perishable foodstuffs. STATE OF THE ART The storage of large quantities of agricultural pro¬ ducts and principally cereals is problematic with regard to the preservation of the product throughout the period of stor- age. Losses due to the deterioration of stored grains has been a considerable problem on a worldwide scale and it should be observed that losses of this nature are presently of the order of 30% of the total product stocked in Brazil, about 12% in the USA and as high as 50% in some countries of the African continent. Cereals are characterized by a high potential energy content. Their availability in thousands of tons makes storage locations an excellent nutrition medium for fungi, bacteria, acarids and insects, provided that the ambient conditions such as temperature and humidity (absolute humidity of the grain and relative humidity of the atmosphere) are favorable. The processes used up to the present involve a storage system which controls such parameters so as to reduce biological ac- tivity to a minimum. The controls act on the following vari¬ ables: - Reduction of the absolute humidity of the grain by previous drying. Constant airing of the storage ambient so as to reduce the fungi population by entrainment of the spores and to reduce the temperature increased as a result of biological activ¬ ity. - Utilization of gases such as nitrogen (N2), caτbon dioxide (C02) and other gases with the basic purpose of reducing the concentration of oxygen and thus producing a reduction in the aerobic organisms population as well as the metabolism of the grain itself. - Use of toxic chemical products to reduce the amount of microorganisms and insects by intoxication. All these processes have limited efficiency and some present health risks to the consumers, particularly those re¬ lated to the use of toxic chemical products. According to the most recent scientific works re¬ garding the inter-relation of the various variables within a mass of cereals, fungi have been identified as one of the most important elements in the matrix of the echo-system. The fol¬ lowing works can be cited as being of special importance: 1) Sinha R.N., Van Bronswijk J.E.M.H., Wallace H.A.H. , CM.A. Journal, August 1, 1970, Vol. 103, 300 - 301 2) Sinha R.N. , Van Bronswijk J.E.M.H., Environ . Entomology 2: 142, 1973 3) Sinha R.N., Journal of Economic Entomology, Vol 64, 1, 3 - 6. 4) Mori M., Onoue Y., Takahashi T., Chounan S., Moriya K., J Antibact. Antifung. Agents Vol. 15 N° 12, P 601 - 605, 1987. 5) Griffiths A.D., Hodson A.C., Christensen CM., Journal of Economic Entomology, Vol. 52, N° 3, page 516 - 518. 6) Sinha R.N., Harasymek L., Environmental Entomology Vol 3, N° 2, pages 244, 246. 7) Tadros, M.S., Vestnik Ceskolovenske Spolecnosti Zoologicke, Svazek XXXIX, Cislo 4, 1975, Str. 293 The above works show that the elimination of fungi in the stored mass results in the reduction over a period of time of the population of insects and acarids. It is important to note that not only fungivorous organisms depend on fungi but also all larva which, after hatching of the eggs, need fungi to be able to create their digestive systems. A device for oxidizing particles in suspension in air is already known from Brazilian patent PI 8302255 (US 4,877,990) and European patent 281.551 of the present inven- tor. Such device creates the generation of high power density within ducts provided in a refractory ceramic block by means of a resistance wire passing through such ducts. These de¬ vices are suitable for small and medium sized ambients but are not specially adequate for large areas, such as large stores for the stocking of grain. Brazilian patent application PI 8502832 of the pres¬ ent inventor discloses a system for the preservation of agri¬ cultural products by sterilizing the air. That system uses U-shaped pipes or tubes inside silos, each tube being formed with various orifices in both of its vertical arms and one of the arms having in its interior an apparatus of the type dis¬ closed in Brazilian patent PI 8302255 (US 4,877,990). Such a system, however, was found to have the following disadvan¬ tages: - reduced preservation capacity per apparatus: the maximum amount with which satisfactory results of air sterilization were obtained is limited to about 200 kg of stocked product per apparatus; - grain damage: heat generation within the silo tends to dehy- drate the stocked grain, thus prejudicing its preservation; and - necessity to adapt the interior of the silos: the same num¬ ber of U-shaped pipes as of the necessary apparatuses has to be installed within the silos. Another disadvantage of the prior art grain storage systems is related to the generation of static electricity in view of friction between individual grains, in particular at the time of storage, and this may generate discharges that can cause explosions should there be any inflammable gases in the silo or shed, or even serious injury or death to persons within the silo. OBJECTS OF THE INVENTION Considering the prior art, the object of the present invention is to eliminate fungi from storage ambients so as to permit agricultural products to be preserved without the use of chemicals, as well as to permit the storage of the product with high absolute humidity content, in a totally new manner and without damaging the stored grain. A further object of the invention consists in elimi¬ nating the electrostatic charge in the stored product so as to avoid the resulting disadvantages and risks. BRIEF DESCRIPTION OF THE INVENTION The process by which the above objects may be reached is characterized by the following steps: - gradually extracting the air from the ambient; - oxidating air within a chamber located outside the ambient; - forcing the processed air into the ambient. The above process may be applied in closed , open or mixed circuit, that is to say, the air may circulate perma¬ nently without exchange with the atmosphere, or fresh proc¬ essed air may be admitted to the ambient together with total removal of the air previously within the ambient, or further, part of the air may be circulated and the rest admitted from outside. The use of a closed circuit, however, has the advan¬ tage that the air of the storage ambient is gradually steri¬ lized with respect to the presence of microorganisms until almost total sterilization is obtained. Apart from this, a closed circuit permits one to obtain a hydrostatic balance be¬ tween the air and the stored product. The new concept presently proposed consists in in¬ troducing to the storage ambient regular volumes of sterilized air, sterilization being obtained by subjecting the air to el- evated temperatures, of the order of 500°C and subsequently cooling the air before it is pumped into the storage ambient. The air is heated in such a manner that heat is not dissipated within the storage ambient, so as to permit temperature and humidity conditions to be maintained within the desired param¬ eters. The installation of the invention comprises: - an air line; a chamber provided with an air entrance and an air exit, connected to the enclosure through said air line, said cham¬ ber including means for oxidizing air; - propelling means connected to said air line for introducing the air processed in said chamber to said enclosure. Preferably, the air line establishes a closed cir¬ cuit leaving an upper region of the storage enclosure, passing through the chamber, a heat exchanger and the propelling means and re-entering the storage enclosure at a lower region thereof, thus creating air circulation through the stored product. In a preferred embodiment of the invention, the chamber is provided with one or more ceramic blocks therein having a series of capillaries through which a resistance wire passes to act as a heating filament. According to the invention, it is possible to neu¬ tralize the electrostatic charge on the stored grains by suit¬ able polarization of the heating filaments of the ceramic element. This polarization is obtained by using the thermionic emission effect which favors the neutralization of the posi¬ tive electrostatic charges generated by friction between the individual grains, thus eliminating the risks resulting from the accumulation of such charges. In an alternative system, the chamber is equipped with ultra-violet (UV) lamps. This embodiment makes the heat exchanger unnecessary, but it is then advisable to include a system for decomposing the ozone generated by the UV gener¬ ation downstream of the chamber. Such a system may comprise an ozone trap or an air heating chamber for heating air to about 70 to 80°C Obviously, however, there will be no necessity to decompose the ozone if the stored product is ozone-resistant or, for any reason, the presence of ozone is desirable. Ultra-violet oxidation is indirect, that is to say, ultra-violet radiation degrades the protean casing of microorganisms or spores by ionization. The radicals thus lib¬ erated react with the components of the air to effect the neutralization. DESCRIPTION OF THE EMBODIMENTS The invention will now be described in more detail with reference to an embodiment illustrated in the drawings. The figures show schematically: Figure 1 - a microbiological activity reducing in¬ stallation in accordance with the present invention; Figure 2 - a cross sectional view of a first embod¬ iment of the chamber for oxidizing particles in the air; Figure 3 - a perspective view of a detail of the chamber of Figure 2; Figure 4 - a schematic representation of an elec- trical circuit for the embodiment illustrated in Figures 2 and 3; Figure 5 - a cross section of a second embodiment of the chamber for oxidizing particles in the air; Figure 6 - a cross section of a third embodiment of the air particle oxidizing chamber. Figure 1 shows a silo 1 in the upper portion of which there is an air outlet 9 to which an air line 2 is con¬ nected. The air line passes consecutively through an adiabatic heating chamber 3, a heat exchanger 4 and propelling means 5 which promotes the circulation of the air through line 2, be¬ fore returning to the silo 1 through an air inlet 10 in a lower portion thereof. Between the air inlet in silo 1 and a storage chamber, there is a plenum chamber 7 and a perforated base or screen 8. Sterilized air is uniformly distributed in the plenum chamber 7 below the stored grain and it penetrates upwardly the storage compartment through the perforated base 8 so that the complete mass of grain is permeated by processed air. The air inside silo 1 is sucked through air outlet 9 and, after processing, returns through inlet 10. The portion 2' of air line that is upstream of blower 5 represents the low pressure section of the line, whereas portion 2" is its high pressure section. Air is heated in heating chamber 3 to a sufficiently elevated temperature to oxidize any microorganisms suspended in the air. This oxidation may be effected by heating, radi¬ ation or catalysis and chamber 3 may comprise a plurality of blocks of ceramic provided with heating elements, as will be described later with reference to Figure 2, a series of ultra¬ violet lamps (Figure 4) or a platinum catalyst (Figure 5) for oxidizing viable particles or, furthermore, it may make use of available steam or any other heated fluid from local utili- ties. Such embodiments are only mentioned by way of exam¬ ple, it obviously being possible to use other oxidation means. The heat exchanger 4 may be conventional with a coil through which air flows and around which flows cooling water. Naturally, provided they are suitably dimensioned, any other suitable types of known heat exchanger may be used, for exam¬ ple finned air cooled exchangers. The propelling device 5 may comprise a known air pump, compressor or the like. Reference number 6 indicates an electronic processor or control circuit for activating and deactivating the propeller device in dependence upon the conditions detected by a detector 16 (Figure 2) provided within the heating chamber 3. The electronic control and the detector are known compo- nents. Figure 2 shows a heating chamber 3 provided with refractory ceramic blocks 11 and anodes 12 fixed to flow sepa¬ rating walls 13. Chamber 3 has an air inlet 14 and an air out¬ let 15, the separating walls 13 causing the air the follow an extended tortuous path so as to increase its residence time within the chamber. A greater residence time of the air within the chamber 3 favors a more complete elimination of the microorganisms in suspension. It should be noted that not all of the air flowing within heating chamber will forcibly pass inside one of the refractory ceramic blocks 11, therefore ena¬ bling a greater volume of air to pass by the chamber. Detector 16, which is shown only schematically, may be a thermo-couple type temperature sensor, or a suspended particle detector or, furthermore, an electrostatic charge de- tector. Known particle sensors comprise, for example, a semi¬ conductor laser device (infra-red), a suspended viable parti¬ cle monitor (Tyndall effect) or a plate capacitor (variable capacitance) . The walls of chamber 3 are preferably thermally in¬ sulated from the atmosphere so that the air heats more rapidly and at a greater intensity and so that there are no signif¬ icant heat losses. Figure 3 shows in greater detail one of the ceramic blocks 11 and its corresponding anode 12. According to a prin¬ ciple analogous to that in the above mentioned Brazilian pat¬ ent PI 8302255 (US 4,877,990) and European patent 281.551, the ceramic block has a series of capillaries 17 through which a heating filament 18 passes. The terminals of the filament are indicated by reference 19. The temperature of the air flowing through the capillaries reaches about 500°C However, temper¬ atures above 100°C are already capable of destroying living organisms. According to a preferred embodiment, anode 12 which is positioned immediately above the ceramic block, is polarized . positively with respect to the filaments of the block and comprises a metallic net with a 5 mm mesh, mounted on an insulating support 20 of Teflon. The anode voltage should be chosen so as to avoid any corona effect, 1 kv being suitable for the desired purpose. The corona effect is partic¬ ularly undesirable due to the resulting formation of ozone (03). The heat generated in the capillaries generates electron emission, this occurring as from about 300°C, anode 12 accel¬ erating the electrons emitted. Figure 4 is an electric circuit exemplifying a man¬ ner of interconnecting filament 18 and anode 12 and showing how the latter may be polarized with respect to the former. Figure 5 shows an embodiment in which a chamber 3' is equipped with a series of ultra-violet lamps 21. In this embodiment, the flow separating walls may comprise a material having reflective properties, such as a polished metal or mir¬ ror, so as to increase the incidence of ultra-violet radiation on the particles suspended in the air flowing through the said chamber. The embodiment shown in Figure 6 comprises a plural¬ ity of catalysers 22 as oxidation elements. Such catalysers 22 may be platinum pads and are connectable to an electric energy source (not shown). DESCRIPTION OF AN EXPERIMENT A model Kepler-Weber silo was loaded with 70 tons of recently harvested corn without any type of prior treatment and having an absolute humidity of 18%. Under such conditions, the normal expectation is for the corn to be totally fermented in two weeks. The system for the reduction of biological activity, comprising a heating chamber with refractory ceramic blocks, a water-cooled coil type heat exchanger and a propeller device, was regulated to process the total volume of air within the silo once every three hours, that is to say, the air was totally processed eight times a day. Measurements were taken at 16 different points twice a day, and microbiological analysis was carried out in the fungus laboratory of the University of Sao Paulo (USP) by Dr. Valderez Gambali, vice-president of the Brazilian Society of Microbiology, whereas the analysis of the temperature, pres¬ sure and humidity within the system was carried out by the Kepler-Weber team. 40 days after the start of the experiment, the sys- tern was still functioning and the corn was in a perfect condi¬ tion with the same average degree of 18% humidity, the maximum temperature within the silo being about 21°C, contrary to all the most conservative predictions. An increase of temperature due to biological activity in the mass of grain and loss of humidity due to heating would have been expected. This result was obtained without the customary prior drying of the grains of corn which would have consumed more energy, nor the appli¬ cation of any toxic or atoxic chemical product. In Brazil, the fungus normally present in harvested corn is of the Fusarium type and during the period of storage, one would expect that this flora would change from Fusarium to a high incidence of Piniscilum and Aspergillus Flavus. In the above described experiment, no Piniscilum or Aspergillus was observed, and only a reduction in Fusarium and the total ab- sence of insects, without the formation of any woodworm or the like, was observed. CONCLUSION The proposed system is modular and is easily adapted to any type of storage location, such as silos, warehouses, grain stores or ships' cargo holds, the choice of parameters such as flow rate, power consumption of the sterilization sys¬ tem, the type of heat exchanger, the static pressure of the propeller means and the polarization voltage, being selected basically as a function of the mass of material to be pre¬ served as well as of the nature of the material and the de¬ sired absolute humidity. The tests carried out showed that the ratio power consumption to mass of product is in the region of 10 Watts/ton.

Claims: CLAIMS 1. Process for reducing the biological activity in an enclo¬ sure, particularly for a storage location, characterized by the steps of: - extracting air gradually from the enclosure; - submitting air to oxidation within a chamber located outside said enclosure, thereby oxidizing the particles suspended in the air; and - forcing the processed air into the enclosure. 2. Process according to claim 1, characterized in that the oxidation of the particles is obtained by heating the air after which the air is cooled in a subsequent stage. 3. Process according to claim 1, characterized in that the oxidation of the particles is obtained by ultra- violet radiation. 4. Process according to claim 3, characterized in that, after the oxidation step, the air is submitted to a step of decomposition of ozone which is generated by the ultra¬ violet radiation. 5. Process according to claim 4, characterized in that the ozone decomposition step comprises heating the air to a temperature of 70 to 80°C 6. Process according to claim 1, characterized in that the oxidation of the particles is obtained by catalysis. 7. Process according to any of claims 1 to 6, char¬ acterized in that the air is submitted to a tortuous path within the oxidation chamber. 8. Installation for reducing biological activity in enclosures, particularly for storage locations, characterized in that it comprises: - an air line; a chamber provided with an air inlet and an air outlet, con¬ nected to the enclosure through said air line, said chamber having means for oxidizing air; and - propelling means connected to the air line and capable of introducing to said enclosure air processed in said chamber. 9. Installation according to claim 8, characterized in that the chamber is provided with means for heating air to an elevated temperature, a heat exchanger suitable for cooling the air that leaves the chamber being connected downstream of said chamber and having an air inlet and an air outlet. 10. Installation according to claim 8, characterized in that the chamber is equipped with ultra-violet lamps. 11. Installation according to claim 10, character¬ ized in that the chamber is provided with an ozone decompos¬ ition system. 12. Installation according to claim 8, characterized in that the chamber is equipped with catalysers. 13. Installation according to one of claims 8 to 12 , characterized in that the chamber is provided with a tortu¬ ous path. 14. Installation according to one of claims 8 to 13, characterized in that the air line establishes a closed cir¬ cuit leaving the enclosure, passing through the chamber and the propelling means and penetrating the enclosure once more. 15. Installation according to claim 14, character- ized in that a heat exchanger is provided between the chamber and the propelling means. 16. Installation according to claim 11, character¬ ized in that the the ozone decomposition system is provided between the chamber and the propelling means. 17. Installation according to claim 8, characterized in that the the enclosure is a silo with a lower chamber, a storage compartment and a perforated base, the lower chamber being situated below the storage compartment and the perfo¬ rated base being provided between the lower chamber and the storage compartment. 18. Installation according to claim 8, characterized in that the a detector is provided within the chamber and con¬ nected to an electronic control circuit capable of controlling the propelling means in dependence upon the conditions moni- tored within the chamber. 19. Installation according to claim 18, character¬ ized in that the detector is a temperature sensor. 20. Chamber for reducing biological activity in en¬ closures, particularly for storage locations, for an installa- tion according to claim 8, the chamber containing in its interior at least one block provided with capillaries, a heating filament connectable to an electric energy source passing through said capillaries, the block being so arranged between said inlet and outlet of the chamber that, when in use, at least part of the air that circulates in the interior of the chamber passes through the capillaries, characterized in that above the block is provided an anode that is polarizable with respect to the filament by means of the ap- plication of an electric voltage. 21. Chamber according to claim 20, characterized in that the anode comprises a metallic screen mounted on an insu¬ lating support. 22. Chamber according to claim 21, characterized in that the metallic screen of the anode has a mesh of about 5 mm. 23. Chamber according to claim 21, characterized in that the insulating support is manufactured from Teflon. 24. Chamber according to claim 20, characterized in that the voltage applied to the anode is about 1 kv. 25. Chamber for reducing biological activity in en¬ closures, particularly for storage locations, for an installa¬ tion according to claim 8, characterized in that the chamber contains in its interior at least one ultra-violet lamp. 26. Chamber according to claim 25, characterized in that a mirror is provided around the ultra-violet lamp. 27. Chamber for reducing biological activity in en¬ closures, particularly for storage locations, for an installa¬ tion according to claim 8, characterized in that the chamber contains in its interior a catalyser to which electric current may be applied. 28. Chamber according to any one of claims 20 to 27, characterized in that various oxidation elements are provided, the chamber being provided internally with flow separating walls, as to provide a tortuous path for the air flow. AMENDED CLAIMS [received by the International Bureau on 12 March 1993 (12.03.93); original claims 3-6,10-12,16 and 25-27 cancelled; claims 1 and 2 replaced by new claim 1; claim 7 replaced by new claim 2; claims 8 and 9 replaced by new claim 3; claims 13-15,17-24 and 28 replaced by new claims 4-15 (2 pages)] 1. Process for reducing the biological activity in a storage enclosure and keeping it low, for preserving stuff against deterioration, characterized by the following steps: - introducing air into a chamber which is located outside a storage enclosure - oxidizing the air in said chamber by heating the air; - cooling the air before entering said storage enclosure; - propelling the oxidized air from said chamber to said .storage enclosure; and - releasing air from said storage enclosure. 2. Process according to claim 1, characterized in that the air is submitted to a tortuous path within the oxidation chamber. 3. Installation for reducing biological activity in a stor¬ age enclosure and keeping it low, for preserving stuff against deterioration, comprising: - a chamber which is outside a storage enclosure; - means for introducing air into said chamber; - means located inside said chamber for oxidizing air in said chamber; - means for propelling oxidized air from said chamber to a storage enclosure; and - means for releasing air from said storage enclosure; characterized in that said means for oxidizing air comprises means for heating air to an elevated temperature, a heat exchanger means suitable for cooling the air that leaves the chamber being connected downstream of said means for heating air and between the same and said storage enclosure. 4. Installation according to claim 3, characterized in that the chamber is provided with a tortuous path. 5. Installation according to claim 4, characterized in that a closed circuit is provided for circulating air from said storage enclosure, through said chamber, said heat exchanger and said propelling means and back to said storage enclo¬ sure. 6. Installation according to claim 5, characterized in that said heat exchanger means is provided in a flow path between the chamber and the propelling means. 7. Installation according to claim 4 characterized in that said storage enclosure is a silo with a lower chamber, a storage compartment and a perforated base, the lower chamber being situated below the storage compartment and the perfo¬ rated base being provided between the lower chamber and the storage compartment, an air inlet leading air treated in said chamber to said lower chamber, an air outlet being pro- vided on the storage compartment to allow air to leave the storage compartment. 8. Installation according to claim 4, characterized in that a detector is provided within the chamber and connected to an electronic control circuit capable of controlling the propelling means in dependence upon the conditions monitored within the chamber. 9. Installation according to claim 8, characterized in that said detector is a temperature sensor. 10. Chamber for reducing biological activity in storage en¬ closures and keeping it low, to preserve stuff against dete¬ rioration, characterized in that it comprises in its interior at least one block as oxidation element which is provided with capillaries, a heating filament connectable to an electric energy source passing through said capillaries, said block being so arranged between said inlet and outlet of the chamber that, when in use, at least part of the air that circulates in the interior of the chamber passes through the capillaries, wherein above the block is provided an anode, which is polarizable with respect to the filament by means of the application of an electric voltage. 11. Chamber according to claim 10, characterized in that the anode comprises a metallic screen mounted on an insulating support. 12. Chamber according to claim 11, characterized in that the metallic screen of the anode has a mesh of about 5 mm. 13. Chamber according to claim 12, characterized in that the insulating support is manufactured from Teflon. 14. Chamber according to claim 10, characterized in that the voltage applied to the anode is about 1 kv. 15. Chamber according to claim 10, characterized in that various oxidation elements are provided, the chamber being provided internally with flow separating walls, as to pro¬ vide a tortuous path for the air flow. STATEMENT UNDER ARTICLE 19(1) Having studied the result of the international search, applicant has cancelled claims 3-6, 10-12, 16 and 25-27 directed to the oxidation obtained by means of ultra¬ violet radiation and catalysis, bearing in mind cited WO 90/02572. Therefore, applicant has limited the new claims 1 to 15 to the embodiments of Figures 1 to 4 in which the oxidation is obtained by a heat means (block 11 with capillaries and heating filament). As one can observe from the original application, the applicant considers as the best mode the embodiment according to which the oxidation of liven organisms is obtained by a heating means (e.g. of the type disclosed in US-PS 4.877.990). This embodiment has already proved to be very efficient on experiments held by the appli¬ cant, as described on page 9 of the description.

Inventors: ALINTOR FIORENZANO JR, ALINTOR, FIORENZANO, JR.
Applicants: CLOVER ELETRONICA LTDA, CLOVER ELETRONICA LTDA.
Application year: 1991
Main classification: A23B9
IPC codes: A23B9, A23L3, A61L9