Regenerative Vapor/Particle Generator

- GroupAg LLC

The present invention discloses a regenerative particle/vapor separator to thermally convert various liquids used to treat stored agricultural products into vapor by: 1) Entraining the liquid in a turbulent mist and then effectuating a change of the liquid into a vapor intermixed with the mist; and, 2) Separating the vapor out of the mist while retaining the remaining mist for subsequent conversion to vapor. Some liquids used to treat stored agricultural products undergo the further step of thermally decomposing into beneficial gaseous byproducts which are also separated out of the mist. The vapor and/or gaseous byproducts are then applied to a stored mass of agricultural products to variously sanitize, clean, and chemically and biologically alter them.

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Description
CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

FIELD OF THE INVENTION

The present invention deals generally with a device for thermally converting various liquids used to treat stored agricultural products into vapor by: 1) Entraining the liquid in a turbulent mist and then effectuating a change of the liquid into a vapor intermixed with the mist; and, 2) Separating the vapor out of the mist while retaining the remaining mist for subsequent conversion to vapor. Some substances used to treat stored agricultural products undergo the further step of thermally decomposing into beneficial gaseous byproducts which are also separated out of the mist. The vapor and/or gaseous byproducts are then applied to a stored mass of agricultural products to variously sanitize, clean, and chemically and biologically alter them.

BACKGROUND OF THE INVENTION

The ability to store harvested agricultural products for extended periods of time is an important element in ensuring an adequate food supply because cyclical growing seasons are asynchronous with the steady demand for staple foodstuffs. Globally, conventional and cold storage techniques are well known techniques for the long term storage of pome fruit, onions, potatoes, and the like even in relatively poorly developed nations. See e.g. K. Moazzem & K. Fujita, The Potato Marketing System and Its Changes in Bangladesh: From the Perspective of a Village Study in the Comilla District, 42 The Developing Econ. 63-94 (March 2004). Wherever such agricultural products are stored, the process of treating these agricultural products to sanitize, clean, and chemically and biologically alter the exterior surfaces of the product is a common process.

Traditionally such treatments were made by dipping, drenching or spraying the agricultural product with the desired chemicals. This is wasteful and inefficient and has the further disadvantage of creating a significant amount of contaminated post-treatment effluent that must be disposed of safely. Further, such methods require that the agricultural product must be physically transported into, and out of, a treatment device “assembly line” style. To address these limitations, more efficient and cost-effective methods of treating agricultural products directly in situ in the storage facility have been developed. These rely on devices that generate a mist containing the chemical to be deposited on the agricultural product and then allowing or causing the mist to permeate the stored mass of product. Mists, however, suffer from the disadvantage of insufficiently penetrating the deeper layers of piled agricultural product to which they are applied. As a result, some devices have been created that use heat to vaporize at least some of the chemical. These devices all share the same shortcoming: they are incapable of completely ensuring that only vapor is generated. As a result, larger non-vaporous particles remain intermixed with vapor particles and thus distribution throughout a pile of stored agricultural product, while improved, is still uneven. It is thus a first goal of the present invention to provide a device that ensures the complete vaporization of chemicals subjected to it without the creation residual droplets and mist in the delivered hot gaseous stream.

Furthermore, in the case of peroxyacetic acid (PAA), a commonly used post-harvest sanitizing agent, a mere physical change from liquid to vapor is not all that occurs. As it is heated, PAA thermally decomposes into a number of intermediate byproducts, a significant fraction of which are hydroxyl radicals and elemental oxygen. These substances are powerful oxidizers and are known to eliminate a number of common surface pathogens from various surfaces. Unfortunately, vaporous PAA works best when applied at higher temperatures because the antimicrobial components created when PAA thermally decomposes (hydroxyl ions and elemental oxygen) are highly reactive with other substances in the environment and as such the vapor must be relatively hot so that free hydroxyl ions and elemental oxygen are formed directly on, or very close to, the surface to be sanitized. While it is possible to create such a vapor and apply it at relatively low temperatures, the resulting concentration of antimicrobial hydroxyl ions and elemental oxygen is comparatively low on, or near, the surface to be sanitized thus necessitating a longer application time. However, by selectively increasing the concentration of hydroxyl ions and elemental oxygen relative to other substances in the generated vapor, higher concentrations of both substances remain when applied. By this means PAA vapor may be applied to agricultural products that otherwise would be damaged by the higher vapor temperatures called for when using other methods extant in the prior art. Co- pending U.S. Provisional App. 61/619894 describes such a process. U.S. Pat. NO. 6,596,231 describes a related process used to sterilize PET bottles. However, this invention comprehends a lengthy tubular heating chamber in which the PAA is transported linearly down the heating chamber where it is terminally injected into passing PET bottles. Because of its size and mode of use, such a device is not portable and is thus unusable in conventional agricultural applications where treatments must occur where agricultural products are temporarily stored. It is thus a second goal of the present invention to provide a highly compact, portable device that may be transported to various agricultural storage facilities, wherein the device creates a PAA vapor that contains a relatively high concentration of hydroxyl ions and elemental oxygen for application on a stored mass of agricultural product at relatively low temperatures.

SUMMARY OF THE INVENTION

The present invention is comprised of: 1) A metal heating vessel; 2) A vapor collector; 3) A heating assembly; 4) An air blower; and, 5) A pump for delivering liquid to the heating vessel for vaporization/dissociation.

The metal heating vessel is in the general form of a hollow double-walled cylinder with a closed top and bottom. Formed in the closed top are one or more first circular openings and through each of these first circular openings a metal vaporizing unit is installed. Each vaporizing unit is in the form of an open top cylinder and is installed in the closed top such that the edges forming the open top of the vaporizing unit are both: 1) Flush with the first circular opening; and, 2) Lie in the plane of the closed top. By this means the cylindrical body of each vaporizing unit extends into the interior of the heating vessel. Each vaporizing unit is in turn perforated around its circumferential periphery by a series of heating slits each of which is formed at a level about 1 cm from the bottom of the vaporizing unit. Each of these heating slits is oriented so that forced air entering from the bottom of the vaporizing unit is directed radially along the lower portion of the curved outer wall of the vaporizing unit to form a whirling vortex inside the vaporizing unit.

Into the open top of each vaporizing unit a metal vapor separator is installed. Each vapor separator is the general form of a funnel or truncated cone and is installed in its associated vaporizing unit such that the edges forming the wider, open top of the vapor separator are both: 1) Flush with the open top of the vaporizing unit; and, 2) Lie in the plane of the closed top of the heating vessel. Each vapor separator thus seals the interior of its associated vaporizing unit such that the only exit path for particles generated in the vaporizing unit is through the smaller, open bottom of the vapor separator and thence out of its larger, open top.

Surmounting the closed top of the heating vessel is an inverted conical vapor collector. Affixed to the smaller opening of this conical vapor collector is a vapor distribution duct. This vapor distribution duct is used to transport generated vapors to a remote, stored mass of agricultural product. It will be readily apparent that the conical vapor collector and vapor distribution duct may be omitted and the closed top of the heating vessel may be exposed directly to the interior aspect of the storage facility.

Extending into the bottom part of the heating vessel and proceeding up and to the closed top are one or more chemical supply lines: one for each vaporizing unit. Each chemical supply line proceeds into each vaporizing unit such that chemical provided through the chemical supply line rests on the bottom of the vaporizing unit. The amount of chemical pumped through each chemical supply line is controlled to ensure that the amount of chemical in each vaporizing unit never rises to the level of the circumferential row of heating slits in the lower portion of each vaporizing unit.

One or more apertures allowing heated air from one or more heating assemblies perforate the wall of the heating vessel near its closed bottom. The heating assemblies are attached to the heating vessel and the air blower is in turn attached to the heating assemblies such that output air from the air blower passes through the heating assemblies entering the heating vessel.

The invention is used to apply peroxyacetic acid (PAA) in the following manner: First, the heating unit and the blower are activated and together they provide heated air to the interior of the heating vessel. The heated air circulates inside the heating vessel, and begins to warm the vaporizing units. The heated air accelerates through the circumferentially disposed heating slits in the bottom of each vaporizing unit, forms a vortex inside the vaporizing unit, and exits from the vaporizing unit and heating vessel through the smaller, open bottom of the vapor separator. Second, a supply of PAA to be applied to a stored mass of agricultural product is pumped through the chemical supply lines and comes to rest in the bottom of each vaporizing unit. Here, the PAA becomes entrained as droplets and mist in the swirling vortex of hot air. Third, as the temperature in the bottom of the vaporizing unit rises, the PAA mist in the vaporizing unit undergoes a state change from liquid mist to gas. As the gas heats further, the PAA begins to thermally decompose into a number of intermediate byproducts, a significant fraction of which are relatively light hydroxyl radicals and elemental oxygen. Being relatively less massive than most of the other byproducts, these substances remain closer to the central axis of the rotating air vortex in the vaporizing unit and preferentially exit through the smaller, open bottom of the vapor separator while heavier, more massive particles remain inside the vaporizing unit repeatedly reforming and dissociating into a new population of transitory byproducts. This process continues ensuring a relatively steady output of a stream of vapor containing a high concentration of hydroxyl radicals and elemental oxygen. Fourth, the vapor that exits each heating vessel is collected by the aforementioned inverted conical vapor collector and routed by means of the aforementioned vapor distribution duct to the stored mass of agricultural product. Finally, as the PAA is consumed in the vaporizing unit, additional PAA is supplied to the vaporizing unit and the cycle continues.

The invention is used to apply 1,4-dimethylnaphthalene (1,4-DMN) in the following manner: First, the heating unit and the blower are activated and together they provide heated air to the interior of the heating vessel. The heated air circulates inside the heating vessel, and begins to warm the vaporizing units. The heated air accelerates through the circumferentially disposed heating slits in the bottom of each vaporizing unit, forms a vortex inside the vaporizing unit, and exits from the vaporizing unit and heating vessel through the smaller, open bottom of the vapor separator. Second, a supply of 1,4-DMN to be applied to a stored mass of agricultural product is pumped through the chemical supply lines and comes to rest in the bottom of each vaporizing unit. Here, the 1,4-DMN becomes entrained as droplets and mist particles in the swirling vortex of hot air. Third, as the temperature in the bottom of the vaporizing unit rises, the 1,4-DMN mist in the vaporizing unit undergoes a state change from liquid mist to gas. Being relatively less massive, the gaseous vapor remains closer to the central axis of the rotating air vortex in the vaporizing unit and preferentially exits through the smaller, open bottom of the vapor separator while heavier, more massive liquid mist particles remain inside the vaporizing unit until they too change state and are discharged from the vaporizing unit. This process continues ensuring a relatively steady output of a nearly pure stream of 1,4-DMN vapor. Fourth, the vapor that exits each heating vessel is collected by the aforementioned inverted conical vapor collector and routed by means of the aforementioned vapor distribution duct to the stored mass of agricultural product. Finally, as the 1,4-DMN is consumed in the vaporizing unit, additional 1,4-DMN is supplied to the vaporizing unit and the cycle continues.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cut-away view of the interior of the heating vessel and conical vapor collector showing internal details.

FIG. 2 is a detail view of a cross section of the interior of the heating vessel showing a vaporizing unit, its air entry ports and slits, and its associated vapor separator.

FIG. 3 is a partial elevation view of a cross section of the heating vessel showing internal details.

FIG. 4 is a partial schematic view of the present invention.

FIG. 5a is an elevation view of the interior of one vaporizing unit with associated vapor separator showing how air enters a vaporizing unit.

FIG. 5b is an elevation view of the interior of one vaporizing unit with associated vapor separator showing the circulating vortex in a vaporizing unit.

FIG. 6a is an elevation view of the interior of one vaporizing unit with associated vapor separator showing path less massive particles describe as they circulate in, and ultimately escape from, a vaporizing unit.

FIG. 6b is an elevation view of the interior of one vaporizing unit with associated vapor separator showing path more massive particles describe as they circulate in, and largely remain confined within, a vaporizing unit.

 DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1, 2, and 3, heating vessel 100 is in the general form of a hollow cylinder having a closed top 101 and closed bottom. Except for closed top 101, heating vessel 100 is double walled; the resulting space between the inner and outer walls being filled with high-temperature insulating material 102 such as fiberglass cloth, vermiculite fiberglass cloth, refractory silica fabric, or the like. At least the inner walls of heating vessel 100 and closed top 101 are formed of steel or aluminum or some other suitable metallic material capable of withstanding heat in excess of about 600° C. Apertures 103 are formed through the inner and outer walls of heating vessel 100 and any interposed insulating material 102 allowing for the introduction of forced hot air into the enclosed space inside heating vessel 100. Surmounting heating vessel 100 and enclosing it, is removable conical vapor collector 200. Affixed to the smaller open top of conical vapor collector 200 is vapor collection duct 201. Vapor collection duct 201 is used to adapt conical vapor collector 200 to distribution ductwork 202 used to distribute vaporized/dissociated particles for deposition on a mass of stored agricultural product.

Formed in closed top 101 are first circular openings 104 and through each first circular opening 104 a vaporizing unit 105 is installed. Each vaporizing unit 105 is in the form of an open top cylinder and is installed in closed top 101 such that the circumferential edges forming the open top of vaporizing unit 105: 1) Are flush with first circular opening 104; 2) Lie in the plane of closed top 101; and, 3) Circumferentially seal closed top 102 and vaporizing unit 105 together along first circular opening 104. By this means the cylindrical body of each vaporizing unit 105 extends into the closed lower part of heating vessel 100. Each vaporizing unit 105 is also formed of steel or aluminum or any other suitable metallic, ceramic, or vitreous material capable of withstanding heat in excess of about 600° C. Each vaporizing unit 105 is perforated around its circumferential periphery by a series of air entry ports 106 each of which is formed at a level about 1 cm from the bottom of vaporizing unit 105. Air entry ports 106 may be created in many forms—punched louvers and “cheese grater” beveled slits being two—but in this exemplary embodiment of the present invention air entry ports 106 are formed using a punch such that when viewed from the outside of vaporizing unit 105, each air entry port 106 is an inward-dimpled, semi-circular depression wherein the air entry slit 107 is formed along the depressed linear edge of the semi-circular depression. Each air entry port 106 is further oriented such that the linear edge of the aforementioned semi-circle depression and its associated air entry slit 107 forms an angle ranging between about 0° and about 135° with respect to the plane of closed top 101 preferably in the range of about 60° to about 90°. In this exemplary embodiment of the present invention, this angle is about 75° and as such forced air admitted into vaporizing unit 105 proceeds radially along the curved inner surface of vaporizing unit 105 forming a rotating vortex of air inside vaporizing unit 105 such that the greatest turbulence and highest pressure is generally localized in the lower part of vaporizing unit 105. This turbulence initiates the vaporization process by first causing a physical conversion of the liquid into a more easily vaporized liquid mist.

Into the open top of each vaporizing unit 105 a metal vapor separator 108 is installed. Each vapor separator 108 is the general form of a truncated funnel and is installed in its associated vaporizing unit 105 such that the edges forming the wider, open top 110 of vapor separator 108: 1) Are flush with the open top of vaporizing unit 105; 2) Lie in the plane of closed top 101; and, 3) Circumferentially seal vaporizing unit 105 and vapor separator 108 together. Each vapor separator 108 thus seals the interior of its associated vaporizing unit 105 such that the only exit path for particles generated in the vaporizing unit 105 is through the smaller, open bottom 111 of vapor separator 108 and thence out of its larger, open top 110. Each vapor separator 108 is also formed of steel or aluminum or any other suitable metallic, ceramic, or vitreous material capable of withstanding heat in excess of about 600° C.

The static and dynamic pressure head encountered when air is forced into a particular vaporizing unit 105 is controlled by the ratio of the area of the smaller, open bottom 111 of vapor separator 108 and the sum of the open areas of the multiplicity of air entry slits 107 in the vaporizing unit 105 and friction loss. This ratio varies between about 0.50 and about 2.00, preferably in the range of about 0.80 and about 1.25. In this exemplary embodiment of the present invention this ratio is about 1.00.

Extending into the closed bottom part of heating vessel 100 and proceeding up toward the bottom (inside surface) of closed top 101 are one or more chemical supply lines 109—one for each vaporizing unit 105. By routing chemical supply lines 109 through the open interior of heating vessel 100, transported chemicals are preheated before being deposited in vaporizing unit 105. Each chemical supply line 109 is preferably routed through the bottom of each vaporizing unit 105 and extends up slightly to provide a shallow pool of chemical in each vaporizing unit 105. Alternative arrangements in which each chemical supply line 109 penetrates through the side, and proceeds immediately down to the bottom of, each vaporizing unit 105 are equally effective. Chemical supply lines 109 are preferably formed of steel or aluminum or any other suitable metallic material capable of withstanding heat in excess of about 600° C. The amount of chemical supplied through each chemical supply line 109 is adjustable to ensure that the amount of chemical in each vaporizing unit 105 never rises to the level of the circumferential row of air entry ports 106 in the lower portion of each vaporizing unit 105.

Turning now to FIG. 4, heating units 300 are preferably linear flow, electrically powered hot air generators like the Forsthoff Type 7500. Such units are adjustable and capable of heating forced air to temperatures as high as about 700° C. Those having skill in the art will recognize that equivalent heating units are readily available from other manufacturers. Similarly, equivalent units are available using other sources of energy, including but not limited to various hydrocarbon fuels such as propane, natural gas, kerosene, and other organic gases and liquids. In this exemplary embodiment, the output ports of heating units 300 are physically insinuated trough apertures 103 in the double wall of heating vessel 100 such that air forced through heating units 300 is injected into heating vessel 100.

Air blower 400 is preferably a regenerative, side channel radial blower like the Rietschle- Thomas HB-229. Such units are capable of supplying about 100 m3/h of ambient air at 0 mbar pressure differential when supplied with 240 VAC at 60 Hz and about 84 m3/h of ambient at 0 mbar pressure differential when supplied with 240 VAC at 50 Hz. Those having skill in the art will recognize that equivalent air blowers or compressors are readily available from other manufacturers. Similarly, equivalent units are constructed using a variety of technologies, including, but not limited to, axial flow, rotary screw, and rotary vane. In this exemplary embodiment, the output port of air blower 400 is bifurcated and supplies half of its output air to each of heating units 300. Air blower 400 is preferably connected to mains power by means of variable frequency drive 401. By this means, the operator can vary the frequency of the AC voltage supplied to air blower 400 and thus its speed and output.

Chemical pump 500 is preferably a peristaltic metering pump like the Heidolph Pumpdrive 510x with a multichannel head capable of independently supplying chemical to each chemical supply line 109. Those having skill in the art will recognize that equivalent chemical pumps are readily available from other manufacturers. Similarly, equivalent units are constructed using a variety of technologies, including but not limited to diaphragm, gear, and piston pumps. In this exemplary embodiment, each chemical supply line is placed in a single reservoir 501 containing one liquid, but it will be readily apparent that each of chemical lines 109 may be placed in a different reservoir containing a different liquid. Also, it will be readily apparent that chemical supply lines 109 may be connected and fed by the same single channel pump. Similarly, separate single or multi-channel chemical pumps 500 may be used to supply different liquids to different chemical supply lines 109 at different rates. By this means a multiplicity of chemicals may be simultaneously vaporized and/or dissociated and applied to a mass of stored agricultural product.

Referring now to FIGS. 1, 2, 3, and 4, a first exemplary embodiment of the present invention is configured with: 1) A heating vessel 100 having an inner shell approximately 34 cm deep and 34 cm in diameter (approximately 10,000 cc); 2) Six vaporizing units 105 measuring approximately 8 cm deep and 7 cm in diameter (approximately 300 cc) with approximately 20 air entry ports 106 and associated air entry slits 107; and, 3) Six concentrically mounted conical vapor separators 108 measuring approximately: a) 7 cm in diameter at the larger, open top 110; b) 2 cm in diameter at the smaller, open bottom 111; and, c) 4 cm deep.

This first exemplary embodiment of the present invention is used to apply peroxyacetic acid (PAA) to stored potatoes in the following manner:

  • 1) A commercially available preparation of 4 liters of 5% PAA is diluted with water in a ratio of 1:4 to form 20 liters of 1% aqueous PAA solution;
  • 2) Heating units 300 are activated and set to generate heated air at a temperature of about 280° C.;
  • 3) Air blower 400 is activated and its associated variable frequency drive 401 is set to deliver 240 VAC line voltage at 50 Hz. Since the ratio of the sum of the open areas of the six smaller, open bottoms 111 of the six vapor separators 108 and the sum of the open areas of the 120 air entry slits 107 circumferentially disposed around the periphery of all six vaporizing units 105 approximates unity, heating vessel 100 presents a combined static and dynamic pressure head of less than about 10 mbar under normal operating conditions. Since the system is preferably mounted on a cart or other conveyance such that when used it may be placed in close proximity to the stored mass of agricultural product to be treated, distribution ductwork 202 can be kept short enough that the combined static and dynamic pressure head presented to air blower 400 by heating vessel 100, vapor collection duct 201, and distribution ductwork 202 is no greater than about 20 mbar. As such, air blower 400 is capable of delivering about 75 m3/h of superheated air into the center cavity of heating vessel 100. When operated this way, the temperature of the air in heating vessel 101 fluctuates in a range between about 245° C. and about 300° C., preferably about 275° C. Similarly, the air inside the vaporizing units 105 fluctuates in a range between about 260° C. and about 280° C., preferably about 270° C.
  • 4) Referring now to FIGS. 4, 5a, 5b, 6a, and 6b, the superheated air provided by heating units 300 and air blower 400 finds its way into vaporizing units 105 by means of air entry ports 106 each with an associated air entry slit 107. In this exemplary implementation of the present invention, air entry ports 106 and their associated air entry slits 107 are oriented such that as the hot air in heating vessel 100 enters each vaporizing unit 105 it is directed into the bottom of vaporizing unit 105 and along its curved inner wall as shown by arrow 120. By this means, a constant rotating vortex of hot air 122 circulates in each vaporizing unit 105.
  • 5) When the air inside vaporizing units 105 has stabilized at the proscribed temperature, chemical pump 500 begins to deliver about 0.26 ml of 1% aqueous solution of PAA to each vaporizing unit 105 per second of operation. This amount represents the observed maximum steady state consumption of 1% aqueous PAA using vaporizing units 105 of the size described above and with the invention operating at the temperature and air flow rates described above. The operator must ensure that the pool of 1% aqueous PAA solution 121 in each vaporizing unit 105 does not rise to the level of the open areas of air entry slits 107 circumferentially disposed around the periphery of vaporizing units 105. The top layer of the pool of 1% aqueous PAA solution becomes entrained as droplets and mist particles in the vortex of hot air circulating in the vaporizing unit. These droplets and mist particles quickly change state to a true vapor containing gaseous PAA and superheated steam. The PAA then dissociates via two main reactions:


CH3CO2—OH→CH3CO2−+OH−→CH3+CO2+OH−  (i)


CH3CO2—OH→CH3COOH+O   (ii)

The intermediate acetic acid decomposes via a third independent reaction:


CH3COOH→(CH3CO)2O+C2H2O+H2O   (iii)

The heavier components in this gaseous mixture, specifically the remaining droplets and mist particles of 1% aqueous PAA solution, the acetic anhydride (CH3CO)2O, acetic acid CH3COOH, acetate anions CH3CO2−, ethenone C2H2O, and CO2 tend to segregate towards the outer aspect of the vortex near the curved wall of vaporizing unit 105 as shown by arrow 124 while the lighter CH3 molecules, oxygen atoms, OH− ions, and H2O molecules tend to remain closer to the spinning core of the vortex as shown by arrow 123. As a result, these lighter components selectively pass up and out through the lower, open area 111 of vapor separator 108 while the heavier components tend to remain behind.

  • 6) The vapor generated by all six vaporizing units 105 is collected by means of vapor collector 200 and vapor collection duct 201 and sent via associated distribution ductwork 202 to a storage facility for a period of 3.5 hours. This process consumes all 20 liters of diluted 1% aqueous solution of PAA.

Referring again to FIGS. 1, 2, 3, and 4, this first exemplary embodiment of the present invention is used to apply the sprout inhibitor 1,4-dimethylnaphthalene (1,4-DMN) to stored potatoes in the following manner:

  • 1) In the United States, 1,4-DMN is usually applied to stored potatoes to achieve a concentration in the potato ranging from about 5.0 ppm to 10.0 ppm. Generally, 3.79 liters (one U.S. gallon) of 1,4-DMN if properly vaporized will treat the following potato weights achieving the associated concentration of 1,4-DMN in the potatoes:

Potato Weight (cwt) 1,4-DMN Air Concentration (ppm) 17,000 5.0 11,250 7.5 8,500 10.0

Assuming a storage facility with 100,000 cwt of potatoes is to be treated to achieve a 1,4-DMN concentration of 5.0 ppm in the potatoes, approximately 22.3 liters (5.9 U.S. gallons) of commercially available 1-4-DMN solution containing approximately 97% 1,4-DMN must be vaporized and introduced into the storage facility.
  • 2) Heating units 300 are activated and set to generate heated air at a temperature of about 280° C.;
  • 3) Air blower 400 is activated and its associated variable frequency drive 401 is set to deliver 240 VAC line voltage at 50 Hz. Since the ratio of the sum of the open areas of the six smaller, open bottoms 111 of the six vapor separators 108 and the sum of the open areas of the 120 air entry slits 107 circumferentially disposed around the periphery of all six vaporizing units 105 approximates unity, heating vessel 100 presents a combined static and dynamic pressure head of less than about 10 mbar under normal operating conditions. Since the system is preferably mounted on a cart or other conveyance such that when used it may be placed in close proximity to the stored mass of agricultural product to be treated, distribution ductwork 202 can be kept short enough that the combined static and dynamic pressure head presented to air blower 400 by heating vessel 100, vapor collection duct 201, and distribution ductwork 202 is no greater than about 20 mbar. As such, air blower 400 is capable of delivering about 75 m3/h of superheated air into the center cavity of heating vessel 100. When operated this way, the temperature of the air in heating vessel 101 fluctuates in a range between about 245° C. and about 300° C., preferably about 275° C. Similarly, the air inside the vaporizing units 105 fluctuates in a range between about 260° C. and about 280° C., preferably about 270° C.
  • 4) Referring again to FIGS. 4, 5a, 5b, 6a, and 6b, the superheated air provided by heating units 300 and air blower 400 finds its way into vaporizing units 105 by means of air entry ports 106 each with an associated air entry slit 107. In this exemplary implementation of the present invention, air entry ports 106 and their associated air entry slits 107 are oriented such that as the hot air in heating vessel 100 enters each vaporizing unit 105 it is directed into the bottom of vaporizing unit 105 and along its curved inner wall as shown by arrow 120. By this means, a constant rotating vortex of hot air 122 circulates in each vaporizing unit 105.
  • 5) When the air inside vaporizing units 105 has stabilized at the proscribed temperature, chemical pump 500 begins to deliver about 0.35 ml of 1,4-DMN to each vaporizing unit 105 per second of operation. This amount represents the observed maximum steady state consumption of 1,4 DMN using vaporizing units 105 of the size described above and with the invention operating at the temperature and air flow rates described above. As before, the operator must ensure that the pool of 1,4-DMN 121 in each vaporizing unit 105 does not rise to the level of the open areas of air entry slits 107 circumferentially disposed around the periphery of vaporizing units 105. The top layer of the pool of 1,4-DMN becomes entrained as droplets and mist in the vortex of hot air circulating in the vaporizing unit. These 1,4-DMN droplets and mist particles quickly change state to a true vapor containing gaseous 1,4-DMN. The heavier droplets and mist particles tend to segregate towards the outer aspect of the vortex near the curved wall of vaporizing unit 105 as shown by arrow 124 while the lighter 1,4-DMN molecules tend to remain closer to the spinning core of the vortex as shown by arrow 123. As a result, the essentially pure 1,4-DMN vapor selectively passes up and out through the lower, open area 111 of vapor separator 108 while the heavier droplets and mist particles tend to remain behind where they too are subsequently converted to molecules of 1,4-DMN.
  • 6) The vapor generated by all six vaporizing units 105 is collected by means of vapor collector 200 and vapor collection duct 201 and sent via associated distribution ductwork 202 to a storage facility for a period of about 3.0 hours. This process consumes all 5.9 liters of 1,4-DMN.

It will be readily apparent to the those skilled in the art that the above disclosed exemplary embodiment of the present invention can be altered in numerous obvious ways, /including for example, merely scaling the size of the unit up or down to incorporate a lesser or greater number of vaporizing units 105, associated vapor separators 108, heating units 300, and air blowers 400.

Similarly, increasing or decreasing the volume of each vaporizing unit 105 and associated vapor separator 108 while simultaneously increasing or decreasing the air flow through heating vessel 100 and adjusting the output of heating units 300 to maintain the temperature of the air inside vaporizing units 105 within a proscribed range to vary the maximum output of the device is also within the spirit and scope of the present invention.

Similarly, increasing or decreasing the volume of hot air pumped through heating vessel 100 while maintaining the volume of each vaporizing unit 105 and associated vapor separator 108 while increasing the flow rate of liquid to be vaporized by each vaporizing unit 105 to increase or decrease the output derived from each vaporizing unit 105 is also within the spirit and scope of the present invention.

Similarly, supplying more than one chemical to different vaporizing units 105 and supplying different chemicals to different vaporizing units is also within the spirit and scope of the present invention.

Similarly, while the preferred embodiment of the present invention has been described in connection with application of various chemicals to a stored mass of agricultural product, it will be readily apparent that the device may be used to apply one or more chemical vapors to other surfaces and products.

Moreover, although only a few exemplary embodiments of the present invention have been described in detail, those skilled in the art will readily appreciate that numerous minor modifications and rearrangements of the exemplary embodiments are readily conceivable. Accordingly, all such modifications and rearrangements are intended to be included within the scope of this invention as defined in the following claims.

Claims

1. A regenerative vapor/particle generator comprising:

a. a heating vessel with a hollow interior cavity enclosed by a top surface and bottom surface;
b. at least one air blower unit atmospherically connected to at least one heating unit wherein said heating unit is atmospherically connected to said interior cavity capable of providing hot air into said interior cavity;
c. at least one cylindrical vaporizing unit installed in said heating vessel: i. wherein said vaporizing unit is perforated around its circumferential periphery by a multiplicity of heating slits; ii. wherein the exterior aspect of said vaporizing unit extends into said hollow interior cavity such that said multiplicity of heating slits are enclosed within said interior cavity; iii. wherein said heating slits are oriented such that hot air admitted into said vaporizing units flows substantially unidirectionally along the curved inner surface of said vaporizing unit forming a vortex inside said vaporizing unit;
d. a funnel-shaped vapor separator in the general form of an inverted, truncated cone installed through the top of said vaporizing unit; i. wherein said vapor separator has an open, larger end and an open, smaller end and the central axis of said vapor separator is aligned with the central axis of said vaporizing unit in which it is installed; ii. wherein the open, smaller end of said vapor separator is situated inside said vaporizing unit and the outer surface of said vapor separator substantially seals the open top of said vaporizing unit such that the only exit path for vaporized and dissociated materials generated in said vaporizing unit is through the open, smaller end of said vapor separator and upwardly though the open, larger end of said vapor separator.

2. A regenerative vapor/particle generator of claim 1 further comprising a vapor collector wherein the open, larger end of said vapor collector covers the open, larger end of said vapor separator and seals it from the atmosphere and said vapor collector is atmospherically connected to a distribution duct for transferring vaporized and dissociated materials to an enclosed space.

3. A regenerative vapor/particle generator of claim 1 wherein said heating unit generates heat from electricity.

4. A regenerative vapor/particle generator of claim 1 wherein said heating unit generates heat by burning hydrocarbon fuel.

Patent History
Publication number: 20130152878
Type: Application
Filed: Feb 17, 2013
Publication Date: Jun 20, 2013
Applicant: GroupAg LLC (Rexburg, ID)
Inventor: Kent Wasden (Rexburg, ID)
Application Number: 13/769,352
Classifications
Current U.S. Class: Interior Of Boilers (122/491)
International Classification: F22B 37/00 (20060101);