U.S. patent number RE39,636 [Application Number 09/735,186] was granted by the patent office on 2007-05-22 for agricultural methods with superheated steam.
Invention is credited to Claude Brown.
United States Patent |
RE39,636 |
Brown |
May 22, 2007 |
Agricultural methods with superheated steam
Abstract
Methods for treating plants and fields in agricultural
applications are provided by selective delivery of superheated
steam. Particularly preferred applications include delivery
adjacent to grape vine leaves in order to defoliate basal leaves
and to kill localized insect pests, and by injecting superheated
steam in strawberry beds prior to planting to kill nematodes. The
superheated steam is delivered at temperatures in excess of about
250.degree. F.
Inventors: |
Brown; Claude (Lodi, CA) |
Family
ID: |
25500566 |
Appl.
No.: |
09/735,186 |
Filed: |
December 15, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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08642534 |
May 3, 1996 |
5867935 |
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Reissue of: |
08958073 |
Oct 27, 1997 |
05848492 |
Dec 15, 1998 |
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Current U.S.
Class: |
47/1.44;
47/58.1R |
Current CPC
Class: |
A01G
11/00 (20130101); A01G 17/02 (20130101); A01M
19/00 (20130101) |
Current International
Class: |
A01M
15/00 (20060101) |
Field of
Search: |
;47/1.44,1.01R,58.1R
;43/130 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2738669 |
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Sep 1976 |
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DE |
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3922022 |
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Jan 1991 |
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DE |
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2423132 |
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Dec 1979 |
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FR |
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2752145 |
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Feb 1998 |
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FR |
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2030434 |
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Apr 1980 |
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GB |
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1188128 |
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Dec 1987 |
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IT |
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240568 |
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Dec 1994 |
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NZ |
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264258 |
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Feb 1996 |
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NZ |
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2002400 |
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Nov 1993 |
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RU |
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1012829 |
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Apr 1983 |
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SU |
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1780676 |
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Dec 1992 |
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SU |
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WO 00/22926 |
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Apr 2000 |
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WO |
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Other References
Anonymous. 1992. Grape Pest Management. 2d. ed., Flaherty et al.,
eds., University of California, Division of Agricultural and
Natural Resources, Publication 3343, pp. xi-xii and 290. cited by
examiner .
Sass et al., Dubbels Taschenbuch fur den Maschinenbau, 1966, p. 37,
paragraph d., New York (2 pages) (with accompanying English
Translation, 2 pages). cited by other.
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Primary Examiner: Gellner; Jeffrey L.
Attorney, Agent or Firm: Vosen; Steven R.
Parent Case Text
This is a continuation-in-part of Ser. No. 08/642,534, filed May 3,
1996 .[.pending.]. .Iadd.now U.S. Pat. No. 5,867,935.Iaddend..
Claims
It is claimed:
1. An agricultural method for in the field use, comprising:
generating steam in a first steam generator, the steam having water
droplets therein; removing substantially all the water droplets
from the steam so as to form saturated steam substantially free of
water droplets; heating the .[.supersaturated.]. .Iadd.saturated
.Iaddend.steam to at least about 300.degree. F. in a second steam
generator to form superheated steam; and, selectively delivering
sufficient of the superheated steam to soil in a field to kill
undesired organisms.
2. The method as in claim 1 wherein the superheated steam is
delivered at a temperature above about 250.degree. F.
3. The method as in claim 1 wherein the selective delivery includes
penetrating the soil to a depth in a range of about two inches to
about twenty inches to deliver the superheated steam therein.
4. The method as in claim 2 wherein the undesired organisms are
weeds.
5. The method as in claim 2 wherein the undesired organisms are
insects or worms.
6. The method as in claim 2 further comprising turning over an
upper soil layer while selectively delivering the superheated steam
thereto.
7. The method as in claim 1 wherein the undesired organisms are
nematodes.
8. The method as in claim 3 wherein the selective delivery is prior
to planting a crop.
9. A preplant treatment method for fields, comprising: generating
steam in a first steam generator, the steam having water droplets
therein; removing substantially all the water droplets from the
steam so as to form saturated steam substantially free of water
droplets; heating the .[.supersaturated.]. .Iadd.saturated
.Iaddend.steam to at least about 300.degree. F. in a second steam
generator to form superheated steam; and, selectively delivering
sufficient of the superheated steam to soil in the field prior to
planting to kill nematodes therein, the superheated steam being
delivered at a temperature above 250.degree. F.
10. The preplant treatment method as in claim 9 wherein the field
is for planting strawberries.
11. A method for defoliating grape vines comprising: generating a
flow of superheated steam; and.[.,.]. delivering the flow of
superheated steam to basal leaves adjacent to developing grape
berries.
12. The method as in claim 11 wherein the superheated steam
delivered contacts the basal leaves and is in a temperature range
of about 250.degree. F. to about 500.degree. F.
13. The method as in claim 11 wherein the flow of superheated steam
is generated to be from about 300.degree. F. to about 800.degree.
F. and is at a pressure of from about 5 psi to about 60 psi.
14. The method as in claim 11 wherein the superheated steam is
substantially free of water droplets.
15. The method as in claim 11 wherein the generation of flow of
superheated steam includes initially forming steam in a first steam
generator followed by generating superheated steam in a second
steam generator, wherein water droplets in the steam from the first
steam generator are substantially removed before treatment in the
second steam generator.
16. A method for treating raisin grapes or prune plums in the
field, comprising: generating a flow of superheated steam, the
superheated steam having a drying adjuvant entrained therein; and,
delivering the flow of superheated steam to the raisin grapes or
prune plums.
17. The method as in claim 16 wherein the adjuvant is methyl oleate
or ethyl oleate.
18. The method as in claim 16 wherein the flow of superheated steam
delivered is effective to increase moisture evaporation from the
raisin grapes or prune plums.
.Iadd.19. An agricultural method comprising: generating a flow of
superheated steam in which substantially all of the water droplets
are removed from the steam prior to generating said superheated
steam; and delivering the flow of superheated steam to a plant
having a graft, where said delivering is sufficient to inhibit a
growth of suckers or canes on said plant..Iaddend.
.Iadd.20. The method of claim 19, wherein said plant is a fruit
plant. .Iaddend.
.Iadd.21. The method of claim 19, wherein said plant is a cotton
plant..Iaddend.
.Iadd.22. The method of claim 19, wherein said plant is a vine, a
tree, or a shrub. .Iaddend.
.Iadd.23. The method of claim 22, wherein said vine is a grape
vine..Iaddend.
.Iadd.24. The method of claim 22, wherein said tree is a nut
tree..Iaddend.
.Iadd.25. The method of claim 19, wherein said delivering delivers
said flow adjacent to said graft. .Iaddend.
.Iadd.26. The method of claim 19, wherein said delivering delivers
said flow to the root stock of said graft..Iaddend.
.Iadd.27. The agricultural method of claim 19, wherein said
generating said flow of superheated steam includes: generating
steam in a first steam generator, the steam having water droplets
therein; removing substantially all the water droplets from the
steam so as to form a steam substantially free of water droplets;
and heating the steam substantially free of water droplets to at
least about 300.degree. F. in a second steam generator to form said
superheated steam..Iaddend.
.Iadd.28. An agricultural method comprising: generating a flow of
superheated steam in which substantially all of the water droplets
are removed from the steam prior to generating said superheated
steam; and delivering the flow of superheated steam adjacent to a
graft sufficient to inhibit a growth adjacent to said
graft..Iaddend.
.Iadd.29. The method of claim 28, wherein said graft is the graft
of a fruit plant. .Iaddend.
.Iadd.30. The method of claim 28, wherein said graft is the graft
of a cotton plant. .Iaddend.
.Iadd.31. The method of claim 28, wherein said graft is the graft
of a vine, a tree, or a shrub. .Iaddend.
.Iadd.32. The method of claim 31, wherein said vine is a grape
vine..Iaddend.
.Iadd.33. The method of claim 31, wherein said tree is a nut
tree..Iaddend.
.Iadd.34. The method of claim 28, wherein said growth is a leaf, a
sucker or a cane. .Iaddend.
.Iadd.35. The agricultural method of claim 28, wherein said
generating said flow of superheated steam includes: generating
steam in a first steam generator, the steam having water droplets
therein; removing substantially all the water droplets from the
steam so as to form a steam substantially free of water droplets;
and heating the steam substantially free of water droplets to at
least about 300.degree. F. in a second steam generator to form said
superheated steam..Iaddend.
.Iadd.36. An agricultural method comprising; generating a flow of
superheated steam in which substantially all of the water droplets
are removed from the steam prior to generating said superheated
steam; and delivering the flow of superheated steam to a plant
sufficient to fumigate said plant..Iaddend.
.Iadd.37. The method of claim 36, wherein said plant is a fruit
plant..Iaddend.
.Iadd.38. The method of claim 36, wherein said plant is a cotton
plant..Iaddend.
.Iadd.39. The method of claim 36, wherein said plant is a vine, a
tree, or a shrub..Iaddend.
.Iadd.40. The method of claim 39, wherein, said vine is a grape
vine..Iaddend.
.Iadd.41. The method of claim 39, wherein said tree is a nut
tree..Iaddend.
.Iadd.42. The agricultural method of claim 36, wherein said
generating said flow of superheated steam includes: generating
steam in a first steam generator, the steam having water droplets
therein; removing substantially all the water droplets from the
steam so as to form saturated steam substantially free of water
droplets; and heating the steam to at least about 300.degree. F. in
a second steam generator to form said superheated steam..Iaddend.
Description
FIELD OF THE INVENTION
The present invention generally relates to superheated steam for
agricultural uses, and more particularly relates to delivering
superheated steam in the field in fumigating, weeding, defoliating,
and drying applications where the superheated steam is selectively
delivered above and/or below the soil such as with a portable
apparatus.
BACKGROUND OF THE INVENTION
Selective defoliation of a field growing crop such as grape vines
has long been known as a desirable practice. Thus, for example,
U.S. Pat. 2,865,135, issued Dec. 23, 1958, inventors Gamboni et al.
discloses a grape leaf stripping mechanism to strip the leaves from
grape vines by a mechanical apparatus rather than manual
defoliation. The apparatus disclosed by this patent uses a pair of
heaters to effect the defoliation.
More recently, the University of California publication on Grape
Pest Management (2nd Edition, 1992, publication 3343) notes that
among the practices for disease control are the removal of basal
leaves from vines approximately two weeks after bloom. This
practice reduces Botrytis bunch rot and produces a superior wins
grape in many North Coast vineyards, and has also been reported to
reduce first-generation leaf hoppers. The publication notes that
most leaf removal is presently done by hand, but that mechanical
systems are being developed and used by several growers. (Supra,
xi.)
Removal of basal leaves on grape vines also permits the grape
clusters to hang free and allows light penetration for coloring and
budwood development, and allows air and chemical spray penetration
for reducing molds, moisture, and insect infestation. Leaf removal
has proven to produce a better acid/sugar ratio in ripening
berries, and thus results in better quality wines and/or
juices.
Manual defoliation is, obviously, labor intensive and thus tends to
be costly. In addition, manual defoliation when performed shortly
after fruiting tends to bruise the very small berries in the fruit
cluster. Further, manual defoliation leads supply to displace pests
such as leaf hoppers to the adjacent, remaining leaves where they
can continue to wreak their damage and subsequently can return to
the fruit cluster.
The presently known mechanical means for defoliating are
disadvantageous because those that blow air or pull a vacuum tend
to damage the berries by bruising or removing the berries
themselves.
Another problem area for cultivated fields and crop maintenance
such as vineyards particularly in California are that typical soils
contain nematodes that feed on roots, which reduce root efficiency.
Nematode infestation of vineyards are manifested by reduced vigor
and yield with a light yellowing of leaves because
nematode-infected vine roots are unable to meet above-ground
demands for nutrients and water.
Preplant fumigants such as methyl bromide profoundly affect
nematodes, and current advice for preparing a new vineyard includes
the application of a nematicide such as methyl bromide (Grape Pest
Management, supra, p. 290). However, methyl bromide bas been
implicated in harming the ozone layer. As a consequence,
considerable environmental pressure has been building against its
use. Nevertheless, in February 1996, the California Senate voted to
delay a proposed ban on the ozone-depleting fumigant, methyl
bromide, until the end of 1997. A reason for delaying the proposed
ban was due to lack of effective alternatives for agriculture in
soil pest control, particularly for crops such as strawberries.
On small scale soil treatments, nurseries have been able to use
steam as a sterilant for minimizing fungal infections. Thus,
bedding plant nurseries have been able to grow seedlings in steam
sterilized soils. But such small scale soil treatments are not
presently practical or possible for in the field use. Further the
steam used is not a very efficient process, since it involves for
example, temperatures close to 212.degree. F.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a side view of a superheated steam delivering
apparatus useful in practicing aspects of the invention;
FIG. 2 shows a block diagram of the superheated steam delivery
portion of the superheated steam delivery apparatus;
FIG. 3 shows a cross-sectional view of a steam generator;
FIG. 4 shows a cross-sectional view of a steam separator;
FIG. 5 shows a top view of the steam separator shown in FIG. 4;
FIG. 6. shows a cross-sectional view of a superheated steam
generator and control system;
FIG. 7 shows a cross-sectional view of a nozzle as a means for
distributing superheated steam as embodied in the invention;
and
FIG. 8 shows a perspective view of knives as another means for
distributing superheated steam as embodied in the invention.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide in the field
agricultural uses of superheated steam that may be selectively
delivered for applications such as fumigation, weeding,
defoliation, and drying. These objects are achievable through use
of a portable apparatus capable of delivering superheated steam at
selected locations to plants or soil in agricultural fields.
Superheated steam may be delivered to trellised plants, such as,
for example, grapes and berries, while delivery to soil is useful,
for example, for a wide variety of plant cultures, including
strawberry fields and vineyards.
In one aspect of the present invention, an agricultural method for
in the field use comprises the selective delivery of sufficient
superheated steam to soil in a field to kill undesired organisms.
The undesired organisms can be insects, whether in adult or larval
form, and worms, such as nematodes. The undesired organisms can
also be weeds. The superheated steam is preferably delivered at a
temperature above about 250.degree. F., and can be delivered
adjacent to the soil surface (above ground) or can be by
penetrating the soil to deliver the superheated steam therein.
In another aspect of the present invention, a method for
defoliating plants, preferably grape vines, is provided whereby
superheated steam is delivered to basal leaves. When treating grape
vines, the superheated steam is preferably delivered adjacent to
developing grape berries within a desired volume, or envelope. The
desired envelope has a characteristic dimensional size within which
the treating steam has a temperature range sufficient for
defoliation, but which surprisingly does not damage the grape
berries themselves.
In yet another aspect of the present invention, a method for
treating raisin grapes or prune plums is provided to decrease time
of drying on the cane or tree prior to harvest.
Other objects and advantages of the invention will become apparent
upon reading the detailed description and as set out in the
appended claims.
Detailed Description of the Preferred Embodiment
Broadly, the invention involves the selective delivery of
superheated steam for a variety of agricultural applications. This
selective delivery of superheated steam has been made possible by a
particularly preferred apparatus, which will the illustrated as the
best mode contemplated for carrying out the present invention;
however, other apparatus capable of generating superheated steam
may be used so long as the superheated steam is delivered at the
temperature or temperature ranges necessary for practicing aspects
of the invention.
The preferred apparatus for use in practicing the invention
includes a portable frame, a water reservoir mounted on the frame
and defining an upstream end of a fluid passageway carried by the
frame, a first chamber disposed along the fluid passageway
downstream of the reservoir, which includes, a beater operable to
convert water being flowed from the reservoir and through the
chamber into steam, a second chamber disposed along the, fluid
passageway and of a construction sufficient to receive steam at a
first temperature range downstream of the first chamber and to heat
the received steam to within a second (elevated) temperature range
so that steam is superheated, and an outlet adapted to deliver a
flow of superheated steam from the second chamber.
One particularly preferred application in accordance with the
invention is to defoliate ;grape vines. Because the heat of
superheat can be generally transformed into work without forming
moisture, the use of superheated steam efficiently permits
application of high temperature but relatively low velocity flows
in the vicinity desired for such application, such as adjacent to
developing grape berries without bruising or damaging the berries
themselves, yet while accomplishing efficient defoliation. By
contrast, were one to use steam that was not superheated, then the
developing berries would be subjected to bruising and other damage.
Further, normal (wet) steam cools rapidly so that were one to try
to direct wet (not superheated) steam towards foliage, little or no
leaf removal would be achieved.
The preferred apparatus for superheated steam delivery has a
portable frame that is of sufficiently small dimensions and not
overly heavy so as headily to be moved over a field of growing
plants (where the agricultural application is to deliver
superheated steam adjacent to leaves of above-ground plants, for
example). Present day vineyards on the west coast of the United
States typically grow grape vines on trellises (e.g. cordon trained
grapes). Vine rows are frequently spaced about 8-12 feet apart in
the United States (and more narrowly in Europe). Grape growers pull
various apparatus down the vine roves by tractor during the growing
season and at harvest. Thus, a preferred apparatus embodiment
typically has the frame width designed to fit vineyard rows down to
about 8 feet wide, which are analogous to the dimensions of frames
used for grape gondolas and machine grape harvesters
Preferred embodiments of the invention include a rail, or ski,
extending from the frame and adjustably moveable against field
growing plants in a manner analogous to a horizontal picking rail
of grape harvester truck shakers, which move along the trellis and
address the trunk and grape stakes below the cordon height level. A
defoliation embodiment of the invention will first be described,
followed by a description of some alternative embodiments, useful
as for treating soft in accordance with the invention.
FIG. 1 illustrates a superheated steam delivery apparatus 10 as
embodied in the invention being used, for example, to defoliate a
vine 2, tree, shrub or the like. The apparatus 10 generally
comprises a superheated steam delivery portion 12 mounted on a
hitch or portable frame 14, wherein said frame engages the ground
through wheels 16 or by other similar means such as track type
treads. The frame 14 can be hitched with a tractor (not shown), for
example, to move the superheated steam delivery portion along a row
of foliage for superheated steam treatment purposes. Although as
shown the superheated steam delivery portion 12 is mounted on a
trailer, it shall be understood that such portion can be an
integral part of a tractor, truck or moving vehicle. The portable
frame 14 may also include a rail, or ski, (not illustrated)
extending from the frame which can be adjustably moved against the
field growing plants 2 of a construction and in a manner analogous
to that known for the rails of grape harvesters.
The superheated steam delivery portion 12 of the apparatus 10
includes a means for selectively distributing superheated steam to
a desired location, such as nozzle 20 which has a pattern of
orifices through which the superheated steam is distributed and
thus delivered to a particular plant for which treatment is
desired. The nozzle is generally held a selected distance from the
foliage 2 such that the foliage is exposed to the flow of the
superheated stream. The characteristics of the superheated steam
are important if optimum defoliation is desired while damage to the
berries or other fruit avoided, but optimum characteristics of the
superheated steam will vary and depend on the type of plant and the
time of leaf growth to which treatment is being applied.
For example, if defoliation of grapevines is desired soon after
berries are forming while the adjacent leaves are young and thus
tender, it is preferable that the superheated steam flowing
outwardly from the nozzle be delivered approximately 12 to 15
inches in height and within a temperature range of 250.degree. F.
to 500.degree. F. at such height but at a flow less than 60 psi.
This requires that the temperature of superheated steam be raised
in the second chamber (a superheating steam generator) to higher
than the 250.degree. F. to 500.degree. F. range of actual delivery.
In order that the selective delivery of superheated steam to the
desired location be at this range, the superheated steam emerging
from the superheated steam generator 28 should be at a temperature
of at least about 300.degree. F., typically in a temperature range
of from about 300.degree. F. to about 800.degree. F., and at a
pressure range of about 5 PSI to about 60 PSI.
This technique of applying a flow of superheated steam having
desired characteristics to a field of grapevines has many benefits.
For instance, defoliating of basal leaves allows grape dusters to
hang free so that developing fruits are free of wind damage and the
bloom is not rubbed away. Leaf removal also allows more light
penetration for coloring and budwood development. Leaf removal
further facilitates penetration of air and chemical spray for
reducing molds, moisture and insect infestation. Moreover,
defoliating of leaves has resulted in producing better acid/sugar
ration in ripening berries, thus resulting in better quality wines
and juices.
Although the lust described apparatus is particularly useful for
defoliation of basal leaves on grape vines, it can readily be used
to direct superheated steam adjacent to the area where root stock
has been grafted to the desired grape variety. Stray suckers or
canes sometimes tend to grow from the root stock below the graft
point, and the inventive apparatus can be used to remove these
undesirable suckers by application of the superheated steam. The
number, size and shape of distributing orifices in nozzle 20 thus
will vary for such different uses.
Other applications include applying the superheated steam to the
soil surface to kill undesired organisms such as weeds and to the
upper layers of soil as it is turned over to fumigate the soil. In
this application, the nozzle 20 will preferably be replaced by one
or a plurality of tines, or knives in which orifices may be
vertically aligned for superheated steam distribution. Particularly
in the latter (or latter two) applications, one can admix another
soil or weed treatment agent with the superheated steam, since many
insecticides, fumigants, and the like are already applied in vapor
form and thus can be combined, such as entrained, with the flow of
superheated steam.
FIG. 2 represents a block diagram of the superheated steam delivery
portion 12 of the superheated steam delivery apparatus 10. The
superheated steam delivery portion 12 generally comprises a water
reservoir 22, a steam generator 24, a steam separator 26, a
superheated steam generator 28 and nozzle 20. The superheated steam
delivery portion 12 also includes an electrical power supply 30 and
a fuel tank 32 for supplying the necessary power to run the various
components of the superheated steam delivery portion 12.
The superheated steam generating process begins at the water
reservoir 22 which holds the water supply necessary to generate
the: required quantity of superheated steam for treating the
foliage 2. The water reservoir should have a capacity to produce
sufficient superheated stream so that a desired portion of a field
of plants is superheated steam treated while maintaining
portability. In a preferred embodiment, for example, the water
reservoir 22 has the capacity to hold 300 gallons of water, which
permits treatment of about 1-4 acres per hour when the apparatus is
moved at a rate of about 1-2 miles per hour through rows about 12
feet wide.
In the first step of the superheated steam generating, process,
water along line 34 is pumped into the steam generator 24 so that a
sufficient amount of steam is produced at the output of the steam
generator 24 The rate of flow of water from the water reservoir 22
to the steam generator 24 should be sufficient in order for the
steam generator 24 to continuously produce steam at its output
without coming to a dry state. In the preferred embodiment, for
example, water from the water reservoir 22 is pumped at about a
rate of 45 gallons per hour (gph) to the steam generator 24. This
rate results in the steam generator 24 continuously converting
about 33 gph out of the 45 gph of water into steam. Of the 12 gph
surplus water, about 11 gph is recycled back to the water reservoir
22 along line 36 so that an efficient use of water results.
As will be discussed more in detail later, the steam generator 24
performs a heat exchange process upon the incoming water so that
steam is generated at its output. Briefly, the steam generator 24
receives fuel from the fuel tank along line 40 and combusts it with
pressurized air to form a hot gas, mixture. The steam generator 24
also receives electrical power from the power supply 30 along line
38 in order to run an air blower. The air blower forces the hot gas
mixture to flow within the steam generator thus exposing the water
therein to the heat from the continuously flowing hot gas mixture.
As a result, steam is generated at the output of the steam
generator. In the preferred embodiment, steam at the superheated
steam generator output is at a temperature of about 300.degree. F.
to 700.degree. F. (or higher) and at a pressure of about 5 to 60
PSI.
Although in the preferred embodiment the vapor produced at the
output of the steam generator 24 is at a relatively high
temperature, typically about 80 percent of it is steam and about 20
percent is water droplets by weight. It is preferred to remove most
of the water droplets before the vapor undergoes a superheating
steam process. Hence, the vapor from the steam generator output is
fed to the steam separator 26 along line 42. Water droplet removal
is preferred because one can more efficiently heat the steam
without using energy to vaporize the water droplets. Although
removal of the water droplets from the vapor flowing from the steam
generator 24 is preferred, it shall be understood that such removal
is not necessary and that the vapor from the steam generator can be
directly fed into the superheated steam generator 28. As will be
explained in more detail later, the steam separator 26 preferably
uses a centrifugal and condensation process to remove most, if not
all, of the water droplets from the vapor flowing from the steam
generator 24 which results in a high quality saturated steam vapor
at the steam separator output. Most of the water droplets removed
from the vapor is recycled back to the water reservoir 22 along
line 36 so that an efficient use of the water supply is
achieved.
The steam at the output of the steam separator 36 is thereafter fed
to the superheated steam generator 28 along line 44 so that
superheated steam is produced at the output thereof. The
superheated steam generator performs essentially the same heat
exchange process as the steam generator 24 does, but typically on a
smaller scale. Briefly, the superheated steam generator receives
fuel from the fuel tank 32 along line 46 and combines it with air
to form a hot gas mixture. The superheated steam generator 28 also
receives electrical power from the power supply 30 along line 48 to
run an air blower. The air blower forces the hot gas mixture to
flow within the superheated steam generator so that the low
moisture (dry) steam therein is exposed to the heat of the
continuously flowing hot gas mixture. As a result, superheated
steam is produced at the output of the superheated steam generator
28. Thus, in the preferred embodiment, the superheated steam at the
outlet of the superheated steam generator 28 is at a temperature of
about 800.degree. F. and at a pressure of about 50 PSI.
The superheated steam at the output of the superheated steam
generator is subsequently fed to the nozzle 20 along line 50 so
that the superheated steam can be selectively applied to the plant
for treatment. The nozzle receives the superheated steam from the
superheated steam generator 20 and directs, or distributes, it such
that the flowing superheated steam from the orifices of the nozzle
20 has a desired envelope shape. As will be understood, actual
patterns of distribution and nozzle sizes and shapes will vary
depending upon the desired applications. In a preferred embodiment
for vine defoliation, the superheated steam flowing outwardly from
the outlet nozzle 20 may provide a vertical or horizontal envelope
of approximately 12 to 15 inches in height and within a temperature
range of about 250.degree. F. to 500.degree. F. at such height. It
has been found that such characteristics obtain optimum defoliation
of grapevines, at least in the vineyards located in the Northern
part of California. It shall be understood that the optimum
envelope and characteristics of the outwardly flowing superheated
steam will depend on the particular type of foliage being
treated.
Referring now to FIG. 3, a cross-sectional view of the steam
generator 24 is shown. The steam generator 24 generally operates as
a heat exchanger whereupon incoming water from the water reservoir
22 is continuously exposed to the heat of a hot gas mixture flow to
convert the water into steam. The steam generator 24 can generally
be divided into three portions: a burner portico 52, a heat
exchanging portion 54 and an exhaust portion 56. A cylindrical
metal housing 58, preferably made from a heavy gauge corrosion
resistant aluminized steel and having a side wall 59a, a top wall
59b and a bottom wall 59c, encases the heat exchanging portion 54
and the exhaust portion 56. The burner portion 52 sits over the top
wall 59b of the metal housing 58. The steam generator 24 further
includes an external pump 60 for pumping in water from the water
reservoir 22 which is delivered along; flowline 34 and also
includes an electric motor 62 for driving the pump 60 and for
driving a component of the burner 52. Preferably, the pump 60 is a
positive displacement multi-cylinder pump.
The burner portion 52 is the portion of the steam generator 24
which produces the hot gas mixture needed for the heat exchanging
process. It generally comprises an air blower 64, a fuel inlet
pipe: 66, a burner head 68 and an elongated fire tube 70. The air
blower 64 is coupled to the electric motor 62 by way of a drive
train (not shown) and drives the blower such that pressurized air
72 is forced downward towards the fire tube 70. The fuel inlet pipe
66 is coupled to a valve 62 which selectively allows fuel to flow
from flowline 40 towards the burner head 68 byway of the fuel inlet
pipe 66. The burner head 68, which is situated within the elongated
fire tube 70, ignites the flowing fuel using the pressurized air 72
to form a downward-flowing, hot gas mixture 74. The hot gas mixture
74 is forced downward into the elongated fire tube 70 for complete
combustion. The elongated fire tube 74 extends coaxially into the
metal housing 58 by way of an aperture in the top wall 59b.
The heat exchanging portion 54 is the portion of the steam
generator 24 where most, if not all, of the heat exchanging process
occurs. The heat exchanging portion 54 generally comprises a pair
of concentric spirally wound pipes, i.e. an outer spirally wound
pipe 76 and an inner spirally wound pipe 78. Preferably, the pipes
are 1/4 inch IPS schedule 80 pipes. The outer spirally wound pipe
76 preferably comprises 85 feet of pipe and measures 14 inches in
outside diameter and 35 inches in length after coiling. The inner
spirally wound pipe 78 preferably comprises 45 feet of pipe and
measures 11 inches in outside diameter and 18 inches in length
after coiling. The outer and inner pipes 76 and 78 are joined at
the bottom of the heat exchanging portion 54, and in the preferred
embodiment, the outer and inner wound pipes form a continuous
single pipe that has been serpentined to form the outer and inner
spirally wound pipes 76 and 78, and has a total length of 1.30
linear feet.
The heat exchanging portion 54 further includes outer, top and
bottom ceramic refractorics 56a-56c which generally encase the
outer and inner spirally wound pipes 76 and 78 and insulates the
heat exchanging portion 54 from cooler ambient temperatures. The
outer ceramic refractory 56a is cylindrical in shape, concentric
with the outer and inner spirally wound pipes and snugly covers the
outer surface of the outer spirally wound pipe 76. The outer
ceramic refractory's cylindrical shape is preferably smaller in
diameter and in height than the metal housing 58, and is mounted
generally near the upper portion of the housing and tangentially
along a portion of the inner surface of the side wall 59a. The top
ceramic refractory 56b is a circular disk in shape with a centrally
located aperture extending therethrough and situated between the
top coil of the outer spirally wound pipe 76 and the top wall 59b
of the metal housing 58. The aperture of the top ceramic refractory
is generally concentric with the aperture of the top wall 59b,
wherein the fire tube 70 extends therethrough. The bottom ceramic
refractory 56c is generally a circular disk in shape and is joined
to the bottom two coils of the inner spirally wound pipe 78, thus
sealing off the lower end of the inner coil 78. Such a construction
results in three heat exchanging compartments within the heat
exchanging portion 54: a lower compartment 80 defined by the
cylindrical space within the inner spirally wound pipe 78 and
sealed at the lower end by the bottom ceramic refractory 56c; an
upper compartment 82 defined as the space between the upper
spirally wound pipe 76 and the fire tube 70 and extending from the
top ceramic refractory 56b to the top of the inner spirally wound
pipe 78; and a corridor compartment 84 defined as the space between
the outer and inner spirally wound pipes 76 and 78.
The outer spirally wound pipe 64 is fluidly coupled to the pump 60
at the top coil thereof, whereby water from the water reservoir 22
is pumped into the steam generator 24 initially into the outer
spirally wound pipe 78. The outer spirally wound pipe 64 is also
fluidly coupled to the inner spirally wound pipe 78 at the bottom
coil of both pipes 76 and 78. An outlet pipe 86 is fluidly coupled
to the inner spirally wound pipe 78 at the top coil thereof and
extends downward within the lower compartment 80 through an
aperture within the lower ceramic refractory 56c and radially
outward within the exhaust portion 56 and exits the metal housing
58 through an aperture into flowline 42. In the preferred
embodiment, the outlet pipe 86 is also part of the continuous wound
pipe that makes up the outer and inner spirally wound pipes 76 and
78.
The exhaust portion 56 of the steam generator 24 is generally a
duct for allowing the cooled hot gas mixture 74 exiting the heat
exchanging portion 54 to flow out of the steam generator 54 to the
atmosphere. The exhaust portion 56 generally comprises the space
between the heat exchanging portion 54 and the bottom and side
walls 59c and 59b of the metal housing 58. Thus, exhaust gas
flowing out of the bottom of the heat exchanging portion 54 flows
into the exhaust portion in the space between the heat exchanging
portion 54 and the bottom wall 59c of the metal housing 58, and
then subsequently flows upwardly in the space between the heat
exchanging portion 54 and the side wall 59a of the metal housing
58. The exhaust gas mixture 74 thereafter exits the steam generator
24 through aperture 88 at the top wall 59b of the metal housing
58.
In operation, the steam generator's pump 60 continuously delivers
water from the water reservoir 22 into the steam generator 54
initially by way of the outer spirally wound pipe 76. At the same
time, fuel is delivered to the burner head 68 from the fuel tank 32
by way of flowline 40, valve 62 and fuel inlet line 66. The burner
head 68 ignites the fuel using the pressurized air 72 from the air
blower 64 and forms a downward-flowing hot gas mixture 74.
Combustion of the hot gas mixture 74 occurs while the gas 74 is
flowing downward through the fire tube 70. The hot gas mixture 74
subsequently exits the fire tube 70 and flows into the heat
exchanging portion 54; and specifically, flows initially into the
inner compartment 80, wherein heat from the hot gas mixture 74
exchanges with the fluid flowing through the inner spirally wound
pipe 78. The flowing hot gas mixture 74 thereafter encounters the
lower ceramic refractory 56c and changes direction flowing upwardly
into the upper compartment 82, wherein heat from the hot gas
mixture 74 exchanges with the fluid flowing through the outer
spirally wound pipe 76. The flowing hot gas mixture 74 next
encounters the upper ceramic refractory 56b and changes direction
flowing downward towards the corridor compartment 84, wherein the
heat from the hot gas mixture 74 exchanges with the fluid flouring
through the outer and inner spirally wound pipes 76 and 78.
Thereafter, the flowing hot gas mixture 74 flows out of the heat
exchanging portion at the lower end of the corridor compartment 84
and into the exhaust portion 56 of the steam generator 24, whereby
the gas mixture subsequently exits the steam generator 24 as
waste.
The steam generator 24 is enclosed so that the hot gas mixture 74
is under pressure and forced at relatively high velocity past the
pipe coil surface, therefore maximizing the heat exchanging
process. Of the 35.75 square feet of coiled pipe surface in the
complete coil, only 24 square feet of pipe surface provides the
actual heat exchange. The remaining 11.75 feet of surface are on
the outside of the outer spirally wound pipe and are not in contact
with the hot gas mixture. As a result, the heat exchange process
typically delivers a vapor to the flowline comprising of 80 percent
steam and 20 percent water droplets by weight.
FIGS. 4 and 5 illustrate a steam separator 26 for removing the
undesired water droplets and for delivering steam substantially
free of unvaporizcd water to the superheated steam generator 28.
The steam separator 26 preferably operates to remove the water
droplets from the vapor produced by the steam generator 24 by a
centrifugal separating method. Thus, the steam generator 26 may
comprise a metal housing 122 having a top wall 124a, a side wall
124b and a bottom wall 124c, and whose boundaries define a chamber
128 within the metal housing 122. The top wall 124a has a centrally
located aperture 114 and a cylindrical outlet stack 124 extending
vertically and outwardly therefrom and being concentric with the
aperture 114. A vertical insulated separating cylinder 110 having;
an opened top and bottom is mounted to the inner surface of the top
wall 124a and preferably situated such that its longitudinal axis
is coaxial with that of the outlet stack 126.
The steam separator 26, further has an inlet tube 112 extending
outwardly from the metal housing 122 to flowline 42, wherein steam
from the steam generator 24 is brought into the steam separator 26
by way of flowline 24 and inlet tube 112. The inlet tube 112 also
extends inward into the chamber 128 and tangential to the side wall
of the separating cylinder 110. Located near the bottom of the
chamber 128 is a drain pipe 116 extending radially outward from the
side wall 124b of the metal housing 122. The steam separator 26
further includes an external condensate trap 120 which is fluidly
coupled to the chamber 128 by way of dip tube 118. The dip tube 118
extends vertically upward within the chamber lab from about 3
inches above the bottom wall 124c and then radially outward around
the center of the chamber to the external condensate 120 by way of
an aperture on the side wall 124b of the metal housing 122.
In operation, vapor and liquid from the steam generator 24 is
delivered into the steam separator 26 by way of flowline 42 and
inlet tube 112. These vapor and water droplets circulate around the
cylindrical separator 110, whereupon the heavier droplets arc
centrifugally separated from the steam to leave a high quality
saturated steam. The saturated steam thereafter flows upwardly
through the separating cylinder 110, through the outlet stack 126
and exits the steam separator 26 into flowline 44.
The superheated steam generator 28 is similar to the already
described steam generator 24 in construction, but on a smaller
scale. For example, a preferred embodiment apparatus has a total
hourly heat release in a "steady state condition" (defined for the
present purposes as superheated steam discharging from the
superheated steam generator 28 at 800.degree. F. while being
supplied with about 240 lbs. of steam 50 PSI) of approximately
350,000 BTU/hour. Larger systems, of course are feasible. Of the
350,000 BTU/hour heat release, about 70% is provided by the steam
generator 24 while about 30% is provided by the super-heated steam
generator 28. Both burners of the respective steam generator 24 and
superheated steam generator 28 include conventional temperature
controllers based on the steam output desired so that the steam
flow is regulated to be continuous during use of the apparatus. For
example, the superheated steam generator 28 preferably has a high
firing rate so as to produce in short time intervals the elevated
temperature required, yet to be able to quickly respond when the
maximum temperature level of the process is reached. This may be
achieved by the use of a bi-metallic sensing unit operating a pilot
valve which in turn controls a modulating diaphragm gas valve on
the fuel supply line so as to provide quick response and to control
the outlet temperatures at about .+-.15.degree. F. To achieve such
quick response, the available heat input of the superheated is
about 1.5 times the heat required to operate at the defined "steady
state condition." The thermostatic recontrolled pilot valve is
preferably water-cooled by the feed water pump on the steam
generator 24, and is isolated from the elevated temperatures
adjacent to it. The superheated burner system will not fire unless
an adequate supply of steam is being fed into the superheated coil
through a flow responsive control system, which responds to a
differential pressure valve on the coil inlet and transmits this
difference in pressure to a control which opens or closes the
circuit to the fuel valve on the burner.
Turning to FIG. 6, a cross-sectional view of the super-heated steam
generator 28 is shown in conjunction with a suitable superheated
steam control system. In order for the superheated steam generator
28 to generate superheated steam at the "steady state condition,"
fuel along flowline 46 is initially fed into a modulating control
valve 132 by way of a controllable valve 130. The modulating fuel
valve 132 has a main fuel outlet coupled to flowline 133 which
feeds fuel to the main burner of the superheated steam generator
28. The modulating valve also has a secondary fuel outlet coupled
to flowline 134 which allows fuel to flow to the burners pilot
ignition system (not shown). Pilot fuel line 134 is coupled to a
thermostatic recontrolled pilot valve 136 which is cooled by
flowing cooling water in T-flowline 138. The thermostatically
controlled pilot valve 136 senses the temperature of the
superheated steam exiting the superheated steam generator 28 and
controls the modulating fuel valve 132 such that the superheated
steam flowing out of the superheated steam generator 28 is
maintained at "steady state condition" with a temperature variance
of .+-.15.degree. F. Such temperature can be verified by
temperature indicator 140 which is situated within the path of
flowline 50 at the superheated steam generator output.
With the modulating fuel valve 132 and the thermostatic
recontrolled pilot valve 136 controlling the flow of fuel into the
burner of the superheated steam generator 28 such that "steady
state condition" is maintained, a continuous flow of saturated
steam from the steam separator 26 is fed into the superheated steam
generator 28 by way of flowline 44, valve 42 and differential
pressure valve 146. The differential pressure valve 146 has an
upstream and downstream outlet for sensing the pressure of the
incoming saturated steam. Both the upstream and downstream outlets
are coupled to a differential pressure responsive control 148 by
way of flowlines 147a and 147b, respectively. Both flowlines 147a
and 147b have water seal loops 149a and 149b to prevent any water
droplets present in the saturated steam from flowing to the
differential pressure responsive control 148. The pressure of the
incoming saturated steam is sensed by the differential pressure
responsive control 148, which in turn controls the controllable:
valve 130 such that when the pressure of the incoming saturated
steam is above a selected level the differential pressure
responsive control 148 opens the controllable valve to allow fuel
to flow to the modulating valve 132. On the other hand, when the
pressure of the incoming saturated steam is less than the selected
level, the differential pressure responsive control 148 shuts the
controllable valve 130 so that fuel is prevented from flowing into
modulating valve 132. Thus, only when the pressure of the incoming
saturated steam is above the selected level, will the superheated
steam generator 28 be operable.
Once the superheated steam exits the superheated steam generator
28, it flows into the nozzle 20 by way of flowline 50. The
superheated steam so delivered typically will consist essentially
of water vapor and air (e.g. is without combustion gases generated
from the burner). However, insecticides, fumigants, drying aids, or
the like can be combined with, or entrained in, the flow of
superheated steam so as to efficiently treat the desired soil or
organism in one operation. Thus, agents to be entrained in the flow
of superheated steam will typically be injected into flowline 50
after exiting; the steam generator 28.
The nozzle 20 is designed so that the superheated steam flowing out
of the nozzle 20 provides for equal distribution of the discharged
steam across the height of the nozzle exit and at a velocity
sufficient to carry the superheated steam out to the desired
distance and desired temperature without undue infusion of cooling
ambient air. The temperature of the discharge from the superheated
can be varied to elevate or lower the superheated stream
temperature conditions and still achieve the desired temperature at
the desired distance.
Referring to FIG. 7, a cross-sectional view of the nozzle 20 is
shown. The nozzle 20 comprises an inlet tube 150 for allowing
superheated stream to flow into the outlet nozzle 20 from flowline
50. The outlet nozzle 20 further has a housing 152 having walls
defining a space within which has been partitioned into four
separate chambers by a manifold 154 and a pair of perforated
baffles 156 and 158.
In operation, superheated steam enters the nozzle 20 into the first
chamber 160 by way of the inlet tube 150. The first chamber 160 is
defined as the space bounded by the walls of the housing 152 and
the manifold 154. The manifold 154 has a series of orifices 168,
preferably equally spaced along the manifold, to allow equal
distribution of superheated steam to flow from the fiat chamber 160
to the second chamber 162.
The second chamber 162 is defined as the space bounded by the
manifold 154, the housing 152 and the first perforated baffle 156.
Superheated steam entering into the second chamber subsequently
flows into the third chamber by way of perforations 170 on the
first perforated baffle 156. The perforations 170 on the first
perforated baffle 156 are preferably spaced throughout the entire
surface of the first perforated baffle 156 to allow equal
distribution of superheated stream to flow into the third
chamber.
The third chamber 164 is defined as the space bounded by the first
perforated baffle 156, the housing 152 and the second perforated
baffle 158. Perforation 172 on the second perforated baffle 158 are
similar to that of the first separated baffle 156 so to allow equal
distribution of superheated steam to flow into the exiting chamber
166.
The exiting chamber is defined as the space bounded by the second
perforated baffle 158 and the housing 152, and has an opening 174
at one end where superheated steam flows out of the nozzle 20 where
it is applied to the desired foliage 2. The sizes of the orifices
168, the perforations 170 and 172, and the opening 174 allow for
the desired BTU release, temperature and velocity of the treating
superheated steam.
In defoliation applications of the superheated steam delivery
apparatus 10 for grape vines, the nozzle 20 preferably tracks on
the vine 2 in such a way that the superheated steam of
approximately 250.degree. F. to 500.degree. F. envelopes the vine 2
at the desired distance. Thus, it is desirable to connect the
nozzle 20 so that it can easily move in and out to track the vine 2
at the desired distance from the vine. Therefore, in a preferred
embodiment, all connecting lines of the superheated steam delivery
apparatus 10 are flexible; this includes the water lines 34 and 36,
the steam lines 42, 44 and 50, the power lines 38 and 48, and the
fuel fines 40 and 46.
So that the nozzle 20 may be easily positioned for treating the
foliage 2, the use of hydraulic sensing or mechanical sensing to
move the nozzle in and out can be employed. For example, a parallel
link arm assembly holding a ski along the vine trunk to correctly
position the nozzle can be used. Such an assembly is known to the
art in connection with grape harvesters.
Returning to FIG. 1, the nozzle 20 is illustrated for selectively
delivery of superheated steam above the soil, such as adjacent to
leaves of above-ground plants; however, as already described,
superheated steam can be used to kill undesired organisms such as
weeds on the surface of the soil or undesirable nematodes within
the soil. When killing weeds above ground, one can position nozzle
20 several inches above the soil surface and permit the superheated
steam to be delivered adjacent to the soil surface. Post-emergent
weed control in accordance with the invention has experimentally
demonstrated with such recalcitrant weeds as Bermuda grass and
morning glory. Surface rhizomes and seeds of these weeds were also
killed or their ability to grow retarded.
Turning to FIG. 8 where the inventive apparatus is used to kill
insects or their larvae within soil, then the apparatus can include
another means for distributing superheated steam, such as a
plurality of knives 200 mounted on a bar 202 and spaced from each
other, such as by a four inch spacing. Bar 202 as illustrated may
be a standard A-frame toolbar conventionally known and used with
apparatus such as a cultivator and fertilizer side dressing sled.
These knives can be drawn through soil to a depth, for example, of
about 24 inches, while emitting superheated steam delivered through
a tube to orifices (not illustrated) along one side of the knives.
More shallow injections than a depth of 24 inches, of course, may
be found suitable, and the spacing between the knives may be
adjusted as desired. For example, strawberry beds would typically
only need soil penetration and superheated steam injection in a
range of about two inches to about ten inches, although for
fumigating applications in general one may wish to penetrate the
soil and inject superheated steam in a range of about 2 inches to
about 20 inches.
By increasing the temperature at which the superheated steam is
selectively delivered to in the field plants, one can also increase
efficiency for fruits intended to dry (or partially dry) in the
field before harvest, e.g. prune plums and raisin grapes. For
example, by contrast to use of superheated steam in grape vine
defoliation where damage to the young grape berries must be
avoided, one can selectively deliver higher temperature superheated
steam, usually more slowly, to raisin grapes to assist them in
drying. In such a drying application, one preferably entrains a
drying aid (such as methyl or ethyl oleate) in the flow of
superheated steamy which assists in moisture evaporation across the
usual waxy barrier on the fruit's skin.
Aspects of the invention will now be illustrated by the following
examples which are intended to illustrate but not limit the
invention.
EXAMPLE 1
A prototype of the superheated steam apparatus as described for
grape defoliation was pulled by a tractor moving about 1-2 miles
per hour through grape vine rows spaced 12 feet apart. With a 300
gallon water reservoir, superheated steam was applied to about 1-2
acres per hour. Within minutes of application, the treated leaves
shriveled. The leaves were dry within an hour, followed by leave
drop over the next several days. Further, leave hoppers on those
directly treated leaves and adjacent leaves were killed and
observed to have fallen from the growing vines; however, the
developing grape berries were not harmed at all.
EXAMPLE 2
The top four inches of a worked soil bed had superheated steam
applied. Samples of the soil were then inspected and were shown to
be substantially sterilized.
EXAMPLE 3
The prototype of the superheated steam apparatus had the steam
nozzle :placed facing down to the row berm of orchard and vineyard
rows at a distance 2 inches to 3 inches above the ground and was
moved parallel to the ground at between 1/4 mph and 11/2 mph,
depending upon the amount of vegetation to be killed. The
superheated steam that was so delivered was in a temperature range
of 500.degree. F.-700.degree. F. which was effective to kill the
growing weeds and to keep most of the weed seeds that had dropped
from germinating.
EXAMPLE 4
Methyl oleate and ethyl oleate are known and used to assist in
speeding moisture evaporation through the waxy film that naturally
occurs on the skin of fruits such as raisin grapes and prune plums.
In an application of superheated steam for grape defoliation as
described by Example 1, an additional operation was simultaneously
performed by injecting Methyl oleate or ethyl oleate into the
flowline 50 before the superheated steam flowed into nozzle 20. In
this instance, the prototype had dual nozzles and a flow divisional
valve controlled the superheated steam flow to the, right or left
nozzle. The superheated steam, which included methyl- or ethyl
oleate, was thus applied to raisin grapes in conjunction to removal
prior to harvest. This permitted more rapid moisture evaporation
through the grape skin surfaces.
It is to be understood that while the invention has been described
above in conjunction with preferred specific embodiments, the
description and examples are intended to illustrate and not limit
the scope of the invention, which is defined by the scope of the
appended claims.
* * * * *