A self-contained, transportable air curtain incinerator for combustion
of low calorific value waste comprises a transportable frame supporting
a firebox, a fuel supply tank, a fuel-burning electric power generator
in communication with the fuel supply tank, at least one fuel-burning
burner unit in communication with the fuel supply tank for directing
a flame into a combustion chamber defined by the firebox, and an
air curtain blower powered by the generator for providing a sheet
of high velocity air flow generally across an open top of the firebox.
What is claimed is:
1. A method of incinerating waste comprising the steps of: providing
a firebox, at least one fuel-burning burner unit for directing a
flame into the firebox, and air curtain means for providing a sheet
of high velocity air flow over a top opening of the firebox; loading
the firebox with waste; activating the at least one burner unit
until waste combustion is sustainable without energy from the at
least one burner unit, and then deactivating the at least one burner
unit to allow waste combustion to proceed on its own; activating
the air curtain means; monitoring particulate release from the waste
combustion; reactivating the at least one burner unit if particulate
release rises above an acceptable range, and then deactivating the
at least one burner unit when particulate release is in the acceptable
2. The method according to claim 1, wherein the step of monitoring
particulate release is performed visually using the Ringlemann smoke
3. The method according to claim 1, wherein the step of monitoring
particulate release is performed by one or more opacity sensors.
4. An incinerator apparatus comprising: a frame, wherein the frame
includes front and rear opposite ends, a pair of spaced skids extending
from the front end to the rear end for contacting the ground, and
a tow coupling at the front end; a firebox supported on the frame,
the firebox including an open top and a plurality of walls defining
a combustion chamber; a fuel supply tank supported on the frame;
a fuel-burning generator supported on the frame in communication
with the fuel supply tank, the generator supplying electric power;
a fuel-burning burner unit in communication with the fuel supply
tank, the burner unit being arranged to direct a flame into the
combustion chamber; and air curtain means supported on the frame
and powered by the generator for providing a sheet of high velocity
air flow generally across the open top of the firebox; and a control
room adjacent the firebox, wherein the fuel supply tank and the
generator are housed in the control room.
5. The apparatus according to claim 4, wherein the control room
is proximate to the front end of the frame.
6. The apparatus according to claim 4, further comprising an automatic
fuel injector regulating flow of fuel to the burner unit and a controller
connected to the fuel injector, whereby output intensity of the
burner unit is adjustable by the controller.
7. The apparatus according to claim 6, further comprising at least
one sensor connected to the controller for providing feedback to
the controller for automatically adjusting the output intensity
of the burner unit.
8. The apparatus according to claim 7, wherein the at least one
sensor includes a temperature sensor measuring temperature in the
9. The apparatus according to claim 7, wherein the at least one
sensor includes an opacity sensor measuring the opacity of smoke
from combustion of the waste material.
10. The apparatus according to claim 6, wherein the controller
is housed in the control room.
11. The apparatus according to claim 10, further comprising an
operator interface in the control room in communication with the
controller for enabling an operator to enter commands to the controller.
12. The apparatus according to claim 10, wherein the burner unit
is located remotely from the control room.
13. The apparatus according to claim 10, wherein a plurality of
burner units are provided.
14. The apparatus according to claim 13, wherein at least one of
the plurality of burner units is located remotely from the control
15. The apparatus according to claim 13, wherein at least one of
the plurality of burner units is located adjacent to the control
FIELD OF THE INVENTION
The invention relates to the field of waste disposal, and in particular
waste disposal by incineration.
BACKGROUND OF THE INVENTION
Incinerating waste is a known alternative to burying waste or transporting
it to another location. In order to reduce ash and smoke released
during waste incineration (particulate release), a flow of high
velocity air has been used to provide an "air curtain"
over a fire pit or firebox in which the waste is burned. U.S. Pat.
Nos. 4,756,258 and 5,415,113 describe portable apparatus for air
curtain incineration. The former patent teaches a fan and manifold
assembly that can be located at the edge of a fire pit, such as
may be found at a landfill site. The latter patent teaches a firebox,
fan, and manifold assembly mounted on a support frame for transport
to a desired site, for example a development site where vegetation
is being cleared, for incineration of waste without the need to
dig a fire pit. These solutions are suitable for applications where
there is ample supply of supplemental wood waste to fuel combustion,
or where the disposal waste itself has high calorific value. However,
in situations where supplemental wood waste is scarce and the disposal
waste will not readily burn on its own, these solutions tend to
be inefficient because it is difficult to maintain high combustion
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
portable air curtain incinerator for efficiently and cleanly burning
low calorific waste in locations where wood waste is scarce or unavailable
to supplement combustion.
It is another object of the present invention to provide an air
curtain incinerator that is self-contained and requires little or
no set up time.
It is a further object of the present invention to provide an air
curtain incinerator having on-board power generation and automated
In furtherance of these objects, an incinerator apparatus embodying
the present invention generally comprises a portable frame and a
firebox, fuel supply tank, fuel-burning generator, at least one
fuel-burning burner unit, and air curtain means all supported on
the frame. The firebox occupies most of the frame and includes rear
doors for loading waste material into a combustion chamber defined
by the firebox. The fuel supply tank and generator are housed in
a control room at a front end of the frame. Preferably, two burner
units are mounted on the firebox and connected to the fuel supply
tank, with one burner unit being located adjacent or near the control
room and the other being located remotely from the control room
(i.e. near the rear of the firebox) to direct flame into the combustion
chamber. The air curtain means includes an electric fan powered
by the generator and arranged to feed air to an air curtain manifold
assembly extending along a sidewall of the firebox to direct a sheet
of high velocity air flow generally across an open top of the firebox.
In a preferred embodiment, each burner unit has an automatic fuel
injector regulating flow of fuel to the burner unit, and a controller
in the control room signals each fuel injector to control output
intensity of the associated burner unit. The controller may be connected
to feedback sensors monitoring combustion temperature and/or particulate
release so that burner unit intensity is automatically adjusted
to maintain predetermined conditions.
The invention also encompasses a method of incinerating waste comprising
the steps of A) providing a firebox, at least one fuel-burning burner
unit for directing a flame into the firebox, and air curtain means
for providing a sheet of high velocity air flow over a top opening
of the firebox; B) loading the firebox with waste; C) activating
the at least one burner unit until waste combustion is sustainable
without energy from the at least one burner unit, and then deactivating
the at least one burner unit to allow waste combustion to proceed
on its own; D) activating the air curtain means; E) monitoring particulate
release from the waste combustion; F) reactivating the at least
one burner unit if particulate release rises above an acceptable
range, and then G) deactivating the at least one burner unit when
particulate release is in the acceptable range. The step of monitoring
particulate release can be performed visually using the Ringlemann
smoke scale, or by one or more opacity sensors.
BRIEF DESCRIPTION OF THE DRAWINGS
The nature and mode of operation of the present invention will
now be more fully described in the following detailed description
taken with the accompanying drawing figures, in which:
FIG. 1 is a perspective view of an air curtain incinerator formed
in accordance with an embodiment of the present invention, with
a control room of the incinerator being exposed to view;
FIG. 2 is another perspective view of the air curtain incinerator
shown in FIG. 1;
FIG. 3 is a perspective view of a control room enclosure of the
air curtain incinerator;
FIG. 4 is a schematic system diagram of the air curtain incinerator;
FIG. 5 is a flow diagram illustrating a procedure for operating
the air curtain incinerator to burn waste; and
FIG. 6 is a flow diagram illustrating a burner unit ignition sequence
of the air curtain incinerator.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1 4 illustrate a self-contained air curtain incinerator 10
formed in accordance with an embodiment of the present invention.
Air curtain incinerator 10 is designed for incinerating waste, particularly
low calorific value waste, at sites where electric and gas utilities
are either non-existent or are not dependable. For example, the
present invention is suited for use in remote and/or temporary military
installations, and in third-world countries where waste disposal
infrastructure is lacking.
Incinerator 10 is built upon an elongated structural steel frame
12 having a front end generally designated as 14 and a rear end
generally designated as 16. A pair of longitudinally extending,
laterally spaced skids 18 and 20 contact the ground so that incinerator
10 may be dragged from one location to another nearby location using
one or more tow couplings 21 provided at front end 14.
Frame 12 comprises upstanding rectangular openings for receiving
sets of thermo-ceramic panels 22 to provide a front wall 24, a pair
of sidewalls at 28 and 30, and rear doors at 26 hung on hinges 29.
Only one set of panels 22 is shown in the figures for sake of clarity.
In this manner, a firebox generally designated 23 having an open
top is supported on frame 12 and, with the cooperation of the ground,
defines a combustion chamber 25 for receiving waste to be burned.
Accordingly, the firebox is adjacent rear end 16 such that loading
of waste can take place through rear doors indicated symbolically
at 26. A more detailed description of a generally suitable frame
and firebox construction can be found in commonly owned U.S. Pat.
No. 5,415,113 at column 4, line 3 column 5, line 5, the description
found there and associated figures being incorporated herein by
Adjacent the front end 14 of frame 12, ahead of the front wall
24 of the firebox 23, is a control room generally identified by
reference numeral 19. Control room 19 abuts with firebox front wall
24 and includes a front control room wall 68, a pair of control
room sidewalls 70, a control room roof 72, and a control room door
74. Housed within control room 19 is a fuel tank 42 and a generator
44 connected to the fuel tank and providing electric power to various
systems of the incinerator 10 described below. The fuel tank is
preferably a sixty-nine gallon tank storing diesel fuel burned by
generator 44, while generator 44 is preferably a diesel-powered
70 kW, 460 volt, three-phase, 60 Hz generator. A fuel line coupling
80 is provided externally of control room 19 for connecting a fuel
supply line (not shown) running from an outside fuel source, such
as a tanker truck. It is advantageous that fuel tank 42 be equipped
with dual electronic level indicators (not shown) for feedback to
the fuel source and to an overflow valve to prevent damage to the
fuel tank from the outside source.
One of the systems powered by generator 44 is air curtain means
40 for providing a sheet of high velocity airflow generally across
the open top of firebox 23. As seen in FIGS. 1 and 2, air curtain
means 40 includes an air curtain fan 50, a transfer nozzle 61 channeling
a flow of air from air curtain fan 50, and a generally tubular manifold
assembly 64 receiving air flow from transfer nozzle 61. Manifold
assembly 64 extends the length of firebox 23 along the top of sidewall
30 and has a linear array 66 of nozzles 67 directed into firebox
23. Transfer nozzle 61, manifold assembly 64, and the array 66 of
nozzles 67 can be constructed generally as taught in the aforementioned
U.S. Pat. No. 5,415,113 at column 5, line 43 column 6, line 11 and
at column 6, lines 36 63, the description provided there and associated
figures being incorporated herein by reference. Air curtain fan
50 is driven by an electric motor 52 energized by a motor drive
controller 54 connected to receive power from generator 44. In a
preferred embodiment, motor 52 is a seventy-five horsepower AC motor
and motor drive controller 54 is a variable frequency drive incorporating
safety features such as over temperature protection, over speed
protection, and current overload protection. A three-speed motor
drive is suitable and results in a desirably simple operator interface.
Reference is also made now to FIG. 4 of the drawings. Incinerator
10 further comprises a burner system 31 powered by generator 44,
wherein burner units of the burner system are chosen to burn fuel
from fuel tank 42. In a preferred embodiment, the burner system
includes a front burner unit 32 mounted on firebox front wall 24
and a rear burner unit 34 mounted on firebox sidewall 30 at a location
remote from control room 19, with both burner units orientated to
direct their output flames into combustion chamber 25. In the embodiment
described herein, front burner unit 32 is preferably a six-million
BTU diesel burner, such as the "BBC 1108 Beta Burner"
manufactured by Hauck Manufacturing of Lebanon, Pa., while rear
burner unit 34 is preferably a two-million BTU diesel burner also
made by Hauck Manufacturing. The burner units can be baffle-type
burner units burning clean industrial No. 2 diesel fuel oil. The
burner units 32 and 34 have respective fuel injectors 48 and 49,
burner atomizers 33 and 35, spark ignitions 82 and 83, and pilot
lights 86 and 87 controlled by a digital burner controller 46, such
as the Hauck Model BCS-3000J. The burner controller 46 also runs
burner blower 56, which communicates with front burner unit 32 by
way of a duct 58 and with rear burner unit 34 by way of a pipeline
62 arranged to run along the exterior of firebox sidewall 30 just
below and parallel to air curtain manifold assembly 64. A propane
igniter tank 60 in control room 19 is connected to the pilot lights
86 and 87 of front and rear burner units 32 and 34 by gas lines
(not shown). Electrical wiring is housed in pipeline 62 for connecting
burner controller 46 with rear burner unit 34. Also, a fuel line
runs within pipeline 62 to deliver fuel from fuel tank 42 to rear
burner unit 34, and a gas line runs within pipeline 62 to deliver
propane from igniter tank 60 to pilot light 87 of rear burner unit
64. Pipeline 62 is suitably constructed of welded schedule 40 steel
Sensors 37, indicated schematically in FIG. 4, are arranged proximate
to combustion chamber 25 and burner units 32 and 34 to provide feedback
signals to the digital burner controller 46. More specifically,
temperature sensors arranged to measure combustion temperatures
and/or opacity sensors arranged to measure particulate release may
be used to provide signals to the digital burner controller 46,
wherein the burner controller can be programmed to control burner
units 32 and 34 to maintain a predetermined temperature range and/or
particulate release limit. Ultra-violet radiation sensors near the
burner units 32 and 34 are preferably provided to verify burner
ignition during start up.
An operator interface 47 powered by generator 44 is provided within
control room 19. As shown in FIG. 4, operator interface 47 communicates
with generator 44, burner controller 46, and motor drive 54. Operator
interface 47 is intended to be simple in design. According to one
embodiment, interface 47 includes a one button start switch, a voltage
meter, and an ampere meter for generator 44; a keypad and a digital
readout for burner controller 46; and an on/off button and a three-speed
selector switch for motor drive 54 to control the speed of air curtain
fan motor 52.
Control room 19 also houses lights and fans 90, and power outlets
92 for connecting auxiliary electrical devices to generator 44.
A general procedure for operating air curtain incinerator 10 to
burn waste will now be described with reference to flow diagram
shown in FIG. 5. Generator 44 is started in step 100, for example
by using the one button start switch in operator interface 47. The
waste material is loaded into combustion chamber 25 through rear
doors 26 as indicated by step 102. Then, in step 104, the burner
units 32 and 34 are ignited, for example by using the keypad in
operator interface 47 to enter a command that commences a burner
ignition sequence, described below in connection with FIG. 6. After
the burner units have been ignited, the operator checks for sustained
combustion in step 106 by visual observation and/or sensor readings,
and if combustion is sustained, the operator enters a command to
minimize fuel flow to the burner units in accordance with step 108.
At this stage, the system is ready for air curtain operation, which
can be started under step 110 using the on/off button in the operator
interface. Temperature information supplied by sensors 37 is read
continuously under step 112 and evaluated under step 114 by burner
controller 46. If the temperature is below a predetermined threshold,
the burner controller 46 automatically increases fuel flow to burner
units 32 and 34 pursuant to step 115; if not, the burner controller
automatically minimizes fuel flow to the burner units according
to step 116. Step 118 involves checking for more waste to burn.
If there is more waste, it is added to combustion chamber 25 in
step 119 and procedural flow resumes at step 112. If there is no
more waste to burn, air curtain incinerator 10 is shut-off at step
120 to complete operation.
It will be realized that the procedure illustrated in FIG. 5 assumes
that temperature sensors are used to provide temperature feedback
information to the burner controller, and that the burner controller
is programmed to maintain a threshold temperature. However, a temperature
readout may merely be displayed at operator interface 47 and the
operator can adjust burner intensity based on the temperature readout
to maintain a desired combustion temperature. Moreover, it is possible
to incorporate opacity sensor information for burner feedback control
if opacity sensors are provided, whereby burner intensity is increased
if the particulate release rises to an unacceptable level.
FIG. 6 shows a preferred burner unit ignition sequence in detail.
The ignition sequence begins at step 130 by reading all sensors
of incinerator 10 and then checking for anomalies in the sensor
readings at step 132. If any anomalies are found, a safety shut-off
is triggered at step 134 and the operator is notified in step 136,
for example by providing a malfunction message at operator interface
47. If the sensor check 130 reveals no anomalies, flow continues
to steps 137 and 138, wherein a gas supply valve from propane tank
60 is opened and a pilot spark igniter is activated. Ultra-violet
sensors provided with the burner unit are read at step 140 and the
result is evaluated at step 142 to verify ignition of the propane-fueled
pilot light. If the pilot light has failed to ignite, flow branches
to safety shut-off and notification steps 134 and 136. If the pilot
light has been successfully lit, then a blower and diesel fuel injector
associated with the burner unit are activated according to steps
144 and 146. The UV sensors are again sampled and the readings evaluated
in steps 148 and 150 to determine if burner light-off has been achieved.
If not, flow branches back to safety shut-off 134 and operator notification
136. If burner light-off is confirmed in step 150, then the pilot
light is extinguished in step 152 and fuel flow to the lit burner
is increased to full capacity in step 154.
In a preferred embodiment of the invention, air curtain incinerator
10 is approximately forty feet long, thirteen feet wide, and twelve
feet high, and it weighs approximately 60,000 lbs. Frame skids 18
and 20 permit the incinerator to be dragged along the ground up
to one-half mile, and it can lifted or dragged onto a low deck trailer
for transport across greater distances.
The air curtain incinerator 10 of the present invention represents
an improvement over state of the art air curtain incineration systems,
and is particularly well-suited for use in third-world countries
where there is a lack of infrastructure for waste pickup and disposal.
The air curtain incinerator described herein can be mobilized in
and around large cities to reduce waste piles where disease and
vermin thrive. The present invention is also well-suited for use
at temporary and/or remote military installations, thereby eliminating
the expense of flying the waste out on military transport planes.