An air curtain incinerator and method for accelerating the burning
of material in an open burning pit. The apparatus with an improved
force draft air supply and manifold air distributor whereby the
rate of burning, temperature and volume of air is controlled within
the burning pit in such a manner that a down draft is created to
the left and right of the center line thus forcing additional air
into the burning pit and minimizing the amount of ash, smoke and
debris which is released into the atmosphere. The apparatus is further
provided with a centuri upstream of the manifold air distributor
wherein an adjustable air inlet control the amount of supplemental
air which is drawn into the supply conduit. The manifold air distributor
includes a plurality of nozzles that extend the full length of the
manifold and are directed into the burning pit at such an angle
to produce a swirling effect within the pit under the air curtain
to increase the resonant time long enough that all organic compounds
to be destroyed with very little smoke or ash escaping.
Having thus described my invention, I claim:
1. An apparatus for directing a curtain of air over material burning
in a generally rectangular burning pit wherein the improvement comprises:
a first sub-assembly and a second sub-assembly;
said first sub-assembly including drive means and a centrifugal
fan operatively connected thereto and having air carrier means connected
to said centrifugal fan;
said second sub-assembly including air distributor/accelerator
means and a plurality of conduit manifold nozzle sections attached
thereto wherein said air distributor/accelerator means increases
the velocity of air flowing therethrough and is provided with supplemental
air inlet means prior to its being distributed into five equal flow
passages for further distribution to said manifold sections and
their associate nozzles.
2. An apparatus of the character defined in claim 1 wherein said
drive means comprises a power source, a flexible drive member operatively
connecting said power source to said centrifugal fan to impart rotation
3. An apparatus of the character defined in claim 1 wherein said
air carrier means comprises a plurality of interconnected flanged
conduit sections, said flange conduit sections receiving discharged
air from said centrifugal fan and delivering the air to said air
distributor/accelerator means for further distribution.
4. An apparatus of the character defined in claim 1 wherein said
air distributor/accelerator means is provided with a plurality of
internal baffles for channeling said air flow into said five equal
5. An apparatus of the character defined in claim 4 wherein said
manifold and said air distributor/accelerator cooperate with further
baffles in said plurality of conduit manifold sections whereby the
central and two outermost sections of said plurality of conduit
manifold nozzle sections each receive 20% of the total air volume
and the remaining 40% of air volume is distributed to the remaining
four sections of said plurality of conduit manifold nozzle sections.
6. An apparatus of the character defined in claim 5 wherein said
remaining four sections of said plurality of conduit manifold nozzle
sections receives 8% and 12%, respectively, to each side of said
central conduit manifold nozzle sections.
7. An apparatus of the character defined in claim 1 wherein said
air distributor/accelerator means includes a venturi section wherein
the air velocity is at its maximum and its pressure is low, thus
creating an optimum condition for admitting supplemental air into
the air stream flowing therein.
8. An apparatus of the character defined in claim 7 wherein said
supplemental air inlet means includes an adjustable flat vane which
can be incrementally closed or opened to control the amount of supplemental
air entering therethrough.
9. A method of controlling the burning of trees, brush, roots,
and the like in an open burning pit wherein the temperature and
rate of burning is so controlled that downdrafts are produced over
portions of the pit to reduce the amount of pollutants released
into the atmosphere, said method comprising the steps of:
(a) providing pressurizing means to supply air to the fire;
(b) restricting the air flow passage sufficiently to produce a
venturi effect and a corresponding velocity increase and pressure
(c) admitting supplemental air in the area of said restricted air
(d) controlling the distribution of air entering into said burning
pit whereby the amount of air at the center and end portion of the
burning pit is sufficient to accelerate the rate of burning and
increase the temperature therein resulting in downdrafts being created
between the center and each end portion of said burning pit.
10. A method of controlling the burning of trees, brush, roots,
and the like as defined in claim 9 wherein said step of admitting
supplemental air is further defined as including the provision of
an air inlet with flow control means therein, whereby the amount
of air admitted through said supplemental air inlet is controllable.
11. A method of controlling the burning of trees, brush, roots,
and the like as defined in claim 9 wherein said step of controlling
the distribution of air entering said burning pit is further defined
as including the provision of an air distributor and a plurality
of manifold nozzle sections;
said air distributor and said manifold nozzle sections provided
with baffles therein;
said baffles forming passages which direct the air into said plurality
of manifold nozzle sections whereby the rate of burning and the
temperature of the fire are controlled to produce the desired downdrafts.
BACKGROUND OF THE INVENTION
Air curtain incinerators have been available in various forms for
approximately the past ten years. These older units were merely
designed as a source of pressurized air to feed a fire which was
burning in an open pit without much attention being directed to
the environmental effect. Air curtain incinerators have become more
popular in recent years mainly because of the rapid growth in our
economy and favorable economic conditions creating a need for more
housing, shopping centers, commercial office space and the like.
All these demands have increased the rate at which sites needed
to be cleared to keep up with the demands. In earlier years, when
the needs were not as great, it was common practice throughout the
country for local governments to provide designated landfill areas
where land site clearing debris could be trucked and buried. In
large metropolitan areas, where there has been significant construction
activities, this practice has resulted in the rapid unavailability
of adequate additional sites for this purpose.
In an attempt to overcome this problem, open burning of the trees,
grass, roots, etc. was undertaken. However, due to the many environmental
limitations imposed by Federal, State, and local jurisdictions,
a means had to be found whereby open burning can be carried out
without violating these statutes or ordinances.
The apparatus of the present invention provides for the rapid,
environmentally safe destruction of trees, brush, roots, etc. It
permits incineration with a minimum of ash and smoke being released
to the atmosphere, thereby meeting all Federal and State environmental
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of the apparatus showing the positioning
of the air manifold in place in an open pit.
FIG. 2 is a side view of the apparatus with the open pit in cross
FIG. 3 is a detailed view of the manifold section releasing the
air into the open pit.
FIG. 4 is an end view of the manifold system as it releases the
air into the pit showing the air currents produced by the burning
fire in the pit.
FIG. 5 is a detailed view of the manifold showing its multiple
passages preceeding the manifold section.
FIG. 6 is an end view taken along the lines 6--6 of FIG. 5.
FIG. 7 is a side view of the manifold section showing the supplemental
air intake and the nozzle section relative to the pit.
FIG. 8 is a showing of the trailer and all the components mounted
thereon prior to assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring initially to FIG. 1 the overall apparatus is illustrated
in an assembled condition and is shown in plan view. The overall
apparatus consists of two main sub-assemblies 10 and 20. Sub-assembly
10 consists of an eighteen foot trailer 11 having a double axle
to evenly distribute the load being carried thereon. Trailer 11
has a six cylinder diesel engine 12 securely mounted on its bed.
The output of diesel engine 11 is operatively connected to a double
intake centrifugal fan by means of a flexible belt or chain. Trailer
11 also provides space for fifty gallon fuel tank 14 for engine
12. The housing of fan 13 is provided with a transition zone 15
which changes the air flow passages as it leaves the fan 13 from
square cross section to circular cross section. The purpose of the
transition zone is to prepare the fan outlet for attachment to the
first carrier pipe 16. There being three additional carrier pipes
16 each being eight feet in length and having an eighteen inch outside
diameter. All four carrier pipes are provided with appropriate flanges
to permit their consecutive interconnection with fan transition
Sub-assembly 20 consists of an air accelerator/distributor manifold
section 21 and six additional manifold sections 22. There being
three manifold sections attached to each side flange portion of
the air accelerator/distributor manifold section 21. The two end
manifold sections 22 are capped at their outermost end to prevent
a longitudinal escape of the air. The air accelerator distributor
manifold section 21 and each of the six manifold sections is five
feet in length. The entire manifold section and accelerator with
its manifold produce a total length of thirty-five feet.
Sub-assembly 20 is shown positioned at the edge of burning pit
23. The approximate dimensions of burning pit 23 are as follows:
length 60 feet, width 9-12 feet, and depth 7-12 feet.
Referring now to FIG. 2 which is a side view of the apparatus shown
in FIG. 1 and further showing burning pit 23 in cross section to
illustrate the swirling action produced by the pressurized air leaving
the manifold sections and fire burning in the pit 23.
FIG. 3 is a plan view of the second sub-assembly 20 positioned
at ground level overlapping the edge of pit 23. As can be seen from
this drawing, air accelerator/distributor section 21 receives pressurized
air from carrier pipe 16. A second transition section 24 is provided
to change from circular to square cross-section and is located immediately
upstream of air accelerator/distributor section 21. Air accelerator
section 21 feeds air to the nozzles of the six manifold sections
22 as well as its own nozzles. The total volume of air received
from the second transition section 24 is divided into five equal
streams A, B, C, D and E within the air accelerator 21. The distribution
of air within the distributor/accelerator is as follows: 20% of
the air flow is directed to each of the end manifold sections 22
and also to the manifold section of accelerator 21 via air streams
A, C and E. The remaining 40%, air streams B and D, is split such
that approximately 12% will be discharged by each of the manifold
sections immediately inboard of each outermost manifold section
with the remaining 16% being equally divided between the next two
innermost manifold sections 22 resulting in an 8% distribution to
each of these last two sections. The length of the arrows coming
out of the nozzles is directly related to the quantity of flow coming
out of the respective manifold sections. The greatest concentration
of air being at the center and two outer end sections of the sub-assembly.
FIG. 4 is an illustration of the downdraft currents produced by
our unique manifold system. As pointed out supra, the distribution
is such that the amount of air is greatest at the center and outermost
ends of the manifold assembly resulting in a more intense fire in
the pit at these sections which cause the down draft as indicated
by arrow 25. Since the fires in the intermediate sections (between
the center and two outermost sections) are burning at a cooler and
lesser rate, they are trying to catch up with the more tense fire
sections, such, the formation of these down drafts. This feature
is a very significant aspect of the invention since the intense
burning ensures a complete, rapid fire and the formation of a down
draft pull outside air into the pit 23 rather than releasing smoke
and ash to the atmosphere above the fire pit 23.
FIG. 5 is a detailed showing of the air accelerator/distributor
section 21. As indicated earlier, accelerator/distributor section
21 is provided with an integrally second transition section 24 wherein
flow cross-section is changed. Immediately downstream of the second
transition section is an adjustable inlet 26 for controlling the
amount of additional air admitted into air accelerator/distributor
section 21. It is to be noted that the additional air inlet is located
in the venturi section 27 wherein the cross section of the internal
flow is at its minimum and the velocity is at its maximum. Thus
creating a suction at the adjustable inlet 26 to pull in additional
air. As the air leaves venturi section 27, the cross sectional flow
area increases significantly and the volume of air flows therethrough
is divided into five equal streams of air A, B, C, C and E. Accelerator/distributor
section 21 is shown with manifold 28-32 in dashed lines since they
are hidden by the upper housing portion of the accelerator/distributor
21. Manifold 30 takes its 20% of the air flow and feeds it all to
center manifold section of the second sub-assembly 20 for discharge
out through its nozzle 33.
FIG. 6 is an end view looking in the direction of arrows 6--6 of
FIG. 1 wherein air stream A, B, C, D and E are shown.
FIG. 7 is the left side view of FIG. 5 showing flow passages A,
B and C and manifold 32 and 31. In addition, the single nozzle 33
is shown as being positioned at an angle of 20.degree. below horizontal.
However it is to be kept in mind that there are a plurality of such
nozzles extending the full width of air accelerator/distributor
section 21 and each of the six manifold sections 22. Also there
is shown a raised air scoop 34 with an adjustable flap 35 to control
the amount of air being admitted through the adjustable inlet 26.
FIG. 8 is a showing of all the components mounted on trailer 11
to illustrate the compactness and portability of the apparatus.
The air accelerator/distributor 21 is shown in a vertical position
along side carrier pipe 4. The diesel engine 12 is centrally positioned
over the first axle considered the heaviest of the components. Fuel
tank 14 is positioned next to engine 12. Fan 13 is mounted close
to the second axle and is operatively connected to diesel engine
12 by an endless drive means (either belt or chain) which is covered
by a guard 17. Manifold sections 22 are attached on the backside
of fan 13. Appropriate means such as chains are utilized to secure
the pipe and manifold sections on the trailer.