Note: Descriptions are shown in the official language in which they were submitted.
~ ~ 1
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Method and apparatus for the igniting or burning of
combustible waste oils in a combustion dish, and method
of ereparing the cleanlng of the combustion dish
The present invention relates to a method of igniting
and burning combustible waste oils of high residue
conten~ in a furnace including at its base an upwardly
open combustion dish and, above said combustion dish,
an ~ optionally divided - combustion chamber, and
further including means-operative to supply the wasteoil
ln a metered fashion to said combustion dish. Further,
the present invention relates to a method of preparing ~r
the cleaning, required in the combustion of waste oil,
of the combustion dish upon interruption of the fuel
supply and burn-out of the csmbustible waste oil
volume still present ln said combustion dish. Finally,
the present invention relates to an apparatus for the
burning of combustible waste oils in a combustion dish.
The term "waste oils" includes especially such oil
mixtures as are collected ln service station operations.
Although the regeneratlon of these waste oils is in
principle possible, such regeneration requires an
expenditure of energy and power which is not justified
in many instances. Therefore~ such waste oils are
frequently burnt. ~uite often, such waste olls contain
a high proportion of contamlnants, namely, for example,
highly vlscous trans~ission oil residues, grease
components, carbon particles, metal particles resulting
'
2 122~ 2
1 from wear, and the like~ "Waste oils" of this kind may
also contain paint residues, (mechanical) wood pulp
particles and water, Still further, waste oils of the
abovemelltioned type may also include such oils which
contain coal dust, tar oils, bilge oils, waste substances
from refining plants, chemical com~ustible wastes as
well as carbon-water~oil mixtures. Of importance is
that the mixture, when properly heated, automatically
maintains the combustion thereof, and that it contains
at least parts of a liquid being combustible upon
evaporation thereof. The quality of the waste oil, as
measured by the calorific value of the fuel, may range
between O and 10,000 kcal. A value of O applies
substantially to pure water. Accordingly, it is
necessary to mix all components or constituents in
a reservoir, ln order to provide a combustible waste
o1l consistency.
So-cal1ed "waste oil furnaces" are known, for example,
20 from Swiss Patent 368,255. This conventional combustion
apparatus includes a drum-shaped housing with a
combustion dish being posltioned at the base thereof.
The fuel is supplied to the combustion dish in metered
volumes through a supply line~ The supply line termina-
tes above the combustion dish, whereby the waste oildrops from its mouth into the combustion dish~
The apparatus is ignited by first supplying priming
fuel to the combustion dish and igniting the waste
3~ oil by means of an igniting wick. When the combustion
dish is sufficiently heated up, the supply of the waste
oil is initiated. In this connection, it has to be
noted that a great amount of bl~ck smoke is produced
both in the ignition phase and in the combustion phase
as such, and that the flame "smokes" for a relatively
long time.
3 ~2~2
1 When the waste oil supply is interrupted, the fl~me
continues to burn for some period of time until all
evaporable residual constituents are burnt out. During
the burn-out phase, the temperature of the combustion
dish proper increases to about 350 to 400 C. Owing
to this temperature highly viscous bituminous xesidues
of high carbon contents, "slag" of high carbon contents,
etc., are left in the combustion dish, and these
substances form an extremely intimate compound with
the combustion dish which is difficult to remove.
Therefore, these residues, termed "bituminous slag",
must be removed from the dish by scraping or hammering in
a troublesome manner, after the combustion of about
30 to 80 liters of waste oil each.
Accordingly, it is the object of the present invention
to improve the conventional apparatus by providing a
method a~d an apparatus for the combustion of waste oil,
which facilitates the igniting process in a
controlled manner. The apparatus and
a method to be performed by such apparatus, respectively,
a 1 s o~ facllitate the cleaning of the
combustion dish after the combustion of waste oil.
These objects are attained with the same means which
also-ren~erSpossible the combustion of flowable (fluid)
waste oils by heating the empty combustion dish, prior
to igniting the waste oil, at least partially to a
temperature above the lgnition and evaporation tempe-
rature of the waste oil by means of an auxiliary heatsource adapted to be turned off. Then, the waste oil
is supplied onto the heated dish and ignited in the
latter, preferably without resorting to further measures.
However, it is also concei~able to use auxiliary
igniting aids, such as, for example, prelgnlters
(glow-type igniters~
~2~l~12
1 When ignition has taken place, the auxiliary heat
source is turned off; the combustion of the additionally
supplied ~uel is then self-sustaining.
Still,further, the combu~tion dish to be heated may be
used l:o prepare for the cleaning process which is
required in the combustion of waste oil. To this end,
upon interruption of the fuel supply and burn-out of
the fuel left in the combustion dish, the remaining
fuel residues (the 'bituminous slag") is pyrolyzed by
means of the re-activated heat source.
Of course, the method of igniting and the apparatus
used for carrying out such method, as well as the
normal burner operation, may be performed or operated,
respectively, also with high-purity fuels, e. g. fuel
oil of class EL, which produce almost no ash. On the
other hand, the conventional furnaces operated wlth
fuel oil can not at all be operated with waste oil.
In view of this, the technological expenditure spent
for the apparatus as described in the following is
justified primarily only for the combustion of highly
contaminated waste oils.
In view of the fact that the temperature existing
in the combustion dish must reach both the ignition
and the pyrolysis temperatures, it must be possible
to bring the combustion dish to a temperature of more
than 400 C. For example~ pyrolysts ls carried out
at a temperature of from 700 to 800 C~ whereas an
ignition and evaporation temperature of from about
350 to 400 C is sufficient for normal waste oils,such~as
tnosecollected in service stations. By means of a
corresponding thermostate control device, various
temperatures may be set With the combustion dish
temperature T beln~ between 400 and 800 C,
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1 An apparatus for carrying out the methods for the
eombustion of combustible waste oils in a combustion
dish includes a combustion dish at its base. Positioned
above the combustion dish is a - possibl~ divided -
combustion chamber, It is well known to let the fueldrop into the dish from above, or to cause the fuel
to flow into the dish from a lateral or central point,
as seen from the combustion dish surface. On principle,
various well-known methods of supplying the fuel may
be used~ In order that the abovementioned methods may
be carried out auxiliarly to the customary burner
operation, at least one additional heaterd~ice is
preferably disposed below the combustion dish. Such
additional heater devices comprise preferably electri-
cally operated heater colls. Also possible is an
inductive heating of the combustion dish, For special
cases, it is also conceivable to employ a connectible
or add-on type gas burner including a burning lance
which terminates below the combustion dish. Essential
is that the principle of the auxiliary heating system
adapted to be turned on and off is ensured.
In order to save energy and to more rapidly heat the
dish before the ignitton process, the combustion dish
is provided with a trough having a structured
(textured) surface and being arranged below the
end of the waste oil supply line. This trough which
may have, for example, a grooved or wafer-shaped
structure, has a slightly thinner bottom and is
locally provided with more intense heating means so
as to be heated in a shorter period of time than
the remaining portion of the combùstion dish. The
trough has an oval or kidney-shaped outline, and it
assumes about one-fifth to one-third of the bottom
surface of the com~ustion dish.
Preferably, the combustion dish has a relatively high
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1 heat capacity; therefore, th~ dish is preferably cast
from cast iron (DIN 1493) and then faced a~ its lower
side. On its upper side (flame side), the combustion
dish, similar to the trough portion, is provided
with concentric grooves, with a honeycomb (wafer)
structure, with bosses or with a similar s~ructure
increasing its surface. This structure results ln
the prevention of Leiden~rost's phenomenon; further-
more , such surf~ce structure provides for very
rapidly establishing a good thermal contact between
the waste oil droplets and the surface. Size (dimension)
and diameter of the combustion dish depend on the
capacity of the combustion apparatus.
Preferably, the oil supply line terminates with a
spacing of from 2 to 20 cm, advantageously from 7
to 10 ~m, above the combustion dish or the trough.
This arrangement offers the advantage'that the energy
contained in the dropping oil droplets disintegrates
these droplets thereby provlding for an accelerated
evaporating effect. The Leidenfrost's phenomenon
which may be observed in the starting phase and which
opposes a rapid evaporation of the droplets, is then
substantially fully suppressed by the great number of
relatively small droplets.
In order to increase the kinetic energy of the impinging
droplets, the supply nozzle forming the end portion of
the supply line is mounted with an angle of inslination
of between 25 and 35 relative to the horizontal. Also,
the supply nozzle has a substantially greater open
(inner~ cross-sectional area than the oil supply line
proper which ends at the supply nozzle. In this way,
the waste -oil supplied does not_ fill out the
full cross-sectional area in the end portion of the
oil supply line, whlch filling effect generally results
in undesira~le after-flow phenomena upon interruption
,
1 f the oil flow.
Further features which are disclosed in the claims
are explained in the course of the description cf
exemplary embodiments as illustrated in the drawing,
weherein: -
Figure 1 is a side elevational viewof an apparatusfor the combustion of waste oils in accordance
with the present invention,
Figure 2 is a front Yiew of the apparatus of Figure 1,
Figure 3 is a det~iled view of a different igniting
device,
Figure 4 is a plan view of part of the combustion dish
including the trough,
~ Figur~s 5 and 6 are a side elevational vlew and a
front view, respectively, of an oil supply
nozzle including a cleaning device, and
Figure 7 shows a specific kind of fresh air supply.
The apparatus for the combustion of waste oil, as shown
in Figures 1 and 2, has the exterior outline of a known
heatlng device, The base of the apparatus has arranged
therein a xeservoir 1 which receives the waste oil~
The reservoir 1 has a volume of, for example, 145
liters. Mounted laterally to the reservoir 1 is a
downwardly protruding sump vessel 5 in which coarse
deposits are separated. Above the sump vessel 5, but
within the reservoir 1, a cylindrical strainer basket
6 is placed around the sump vessel, which basket acts
to shield the inlet region of a metering oil pump 2.
Normally, the oil pump 2 is a gear-type pump or a
1 different pump adapted to pump and supply the waste oil
in metered fashion.
As can be seen, the suction port of the oil pump 2 is
situated within the strainer basket 6, but above the
sump level. The oil pump 2 is driven by a motor 3
via a shaft 4, with the motor being mounted on a cover
9 above the reservoir. A supply line 7 connected to
the oil pump 2 extends out from the strainer basket 6
1o in upward direction and acts to conduct the pumped
oil to a feed or supply nozzle 8. The oil pump 2,
i~cluding its motor, can be removed from the strainer
basket 6 for cleaning purposes, upon removing the
cover 9. In the embodiment shown, the supply (pumping)
capacity is between about 0.5 to 3 kg of oil per hour.
The waste oil volume pumped may be continuously metered
within this range by means of the pump.
Underneath the reservoir 1 formed as a base, four
supporting legs 17 are mounted which may be vertically
adjusted for adjusting the liquid level.
The actual apparatus according to the invention, formed
as a hot air-producing thermal device 10, has exterior
dimensions similar to conventional apparatuses used
for the same purpose. The apparatus comprises a housing
11 the base (bottom) side of which is defined by the
reservoir 1. A heat exchanger 13 is mounted to the
head port~on of the housing 11. An exhaustconduit or
duct 44 leads to the atmosphere through a stack. It is
possible and expedient to install suitable, conventional
filters in said stack.
A burner box 14 is installed ln the lower poxtion of
the housing 11, with the rear wall of such burner box
forming part of the housing 1~, This portlon of the
housing is placed on the reservoir by means of interposed
9 :~22~
1 legs 15. Within the burner box 14, a burner pot or
cylinder 18 is provided which has a cylindrical wall
being spac~d from the wall of the burner box 14 at a
distance equal to about one-half o~ the burner cylinder
diameter.
The bottom of the burner pot 18 has embedded therein
a heating and insulating plate 19 upon which a combustion
dish is placed. The combustion dish 21 has an approxi-
mately pan-shaped or dish-shaped configuration. The
upright walls of the dish 21 diverge from the bottom
22 thereof, such that the dish has at its upper edge
a greater free width than th~t corresponding to the
bottom area. The combustion dish 21 is formed of cast
iron, with its wall thickness being dimensioned, in
accordance with the expert's experience and the heat
capacity, such that continuous evaporation and combu-
stion of the inflowing liquidwaste oil is secured.
An electrical resistance wire coil 23 is embedded into
the heating and insulating plate 19, namely , directly
below the bottom of the combustion dish 21, with the
leads of said w~re coil be-ng extended to the outside,
while observing the relevant thermal insulation and
?rotection requirements. By means of the coil-23,
the combustion dish 21 may be heated to a temperature
of from 350 to 800 C (red heat). In order to provide
for partially (locally) increased heating of the comb-
ustion dish, the latter is provided with an auxiliary
heater device, namely another high-temperature coil 28,
in its portion directly beneath the mounth of the
supply nozzle 8. This high-temperature coil 28 is
located directly below a bottom trough 27 embedded
into the bottom 22 of the combustion dish 21, which
trough in the illustxated embodiment has an approxi-
mately kidney-shaped configuration and assumes about
25 % of the bottom surface of the combustion dish 21.
The bottom trough 27 is provided with a grooved or
1o
1 riffled structure. This structure is contemplated to
directly disintegrate the waste oil droplets falling
into the bottom trough 27, so as to be brought into
optimum irregular, large-surface contact with the
heated surface. These measures are taken in order
to avoid the Leidenfrost's phenomenon, i. e. the
formation of a steam or vapor laye_ ~round the droplets,
which layer would inhibit the rapid evaporation. Upon
ignition, the trough portion also is much more rapidly
heated than the remaining portion of the combustion
dish. In this way, a substantial amount of heat is
concentrated onto a small Yolume of waste oil, such
that this Yolume evaporates instantaneously. It is in
this way ensured that the very first droplet falling
onto the combustion dish 21 initiates the ignition,
because the droplet hits the area of the trough, to
hurst on the trough and evaporate at once. Ignition of
this first droplet takes place in an environment where
an excess of air exists. No (black) smoke is produced
since ignltion takes place in almost an explosion-like
manner.
Further, a temperature sensor or detector 37 is
installed below the combustion dish 21, which sensor may
be connected directly to the combustion dish 2~, too.
This temperature sensor acts to monitor and control the
functions to be described below. As mentioned above,
the combustion dish 21 is surrounded b~ the burner
cylinder 18. Above the edge of the combustion dlsh 21,
the wall or jacket of the burner cylinder 18 is provided
with a great number of vent holes 20 through which the
combustion air enters~ Approximately in the upper one-
third of the burner cylinder ~8, a supporting rlm 38
is formed in the wall or jacket, which rim supports
the edge of a glow hood 40, This hood 40, formed of
cast steel and adapted to be heated to red heat, is
likewise provided with perforations 4~, such that the
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1 1
1 combustion gases, and even the incompletely burned
gases, may flow through these perforations 41 to be
after-burnt within the hood 40. The hood 40has an
approximately frustoconical configuration with a wider
opening 42 in its upper end, with a glow converter
insert or element 43 being adapted to be placed into
said opening. The glow converter element is formed of
thin wire coils of a refractory wire. This wir~ glows
after a short period of combustion, such that a good
after-burning state is obtained also in the vicinity
of this wire. These components ensure that all combusti-
ble constituents of the waste oil are completely burnt,
namely fully into H20 and Co2.
The wall surfaces of the glow hood which define an angle
of from about 30 to 60 relative to the horizontal, act
to pass the hot gases, partially still burning and
partially burnt, through a combustion chamber 30 which
joins the burner box 14 directly at its upper portion.
The combustion chamber 30 is also of a cylindrical
configuration. The shell 31 of the combustion ch~mber
30 is provided, in vane-like fashion, with a plurality
of radiator ribs 32 acting to improve the thermal
contact with the air flowing along its outer side.
The upper side of the combustion chamber 30 is closed
by a cover 33, and the combustion chamber opens into
an outlet or exhaust opening 34 which is followed
directly by the labyrinth~type heat exchanger 13.
Figures 1, 5 and 6 illustr~te the supply nozzle 8.
The mouth 50 of the supply nozzle termlnates freely
within the burner cylinder ~8 above the burner dish
trough 27 at a level of about 15 cm above the surface.
The supply nozzle 8 has an inclination of between
about 25 and 35 relative to the horizontal, Further,
it has to be noted that the open cross~sectional area
of the supply nozzle 8 is substantlally greater than
1 2
12
1 that of the oil supply line 7 which ends at the supply
nozzle 8. Besides, the supply nozzle 8 has a constant
inner cross-sectional area from the inlet opening 51
to its lower mouth 50. Thus, the open cross-section
does not diverge. The oil pumped by the oil pump 2
through the inlet opening 51, thus, flows primarily
on the lower inner wall surface of the supply nozzle,
with increasing flow velocity, downward towards the
mouth 50. At the latter, the oil flows out and is
atomized at the edge into fine droplets. This flow
principle greatly prevents an incrustation or plugging
of the supply nozzle 8. Furthermore, in order to avoid
excessive heating of the supply nozzle 8, the latter
is arranged such that it passes from the front side
of the burner box 14 through the air conducting space
16, and so as to be positioned within the burner pot
18 with a relatively short length only. Also, the inner
cavity of the supply nozzle communicates with the
atmosphere. Accordingly, the oil is prevented from
flowing back within the nozzle to the fuel line 7.
Owing to the greatly different qualities of the waste
oils, in extreme exceptional cases depositions may be
formed within the supply nozzle 8. To provide for this,
a cleaning plunger 52 is provided with is movable within
the cavity of the nozzle and which, as shown in Figure
6, has a cross-sectional configuration resembling a
maltese (Geneva) cross, with free spaces 54 being
defined between the arms 53 of the plunger, through
which the waste oil may flow irrespective of the
plunger being installed in the nozzle. The cleaning
plunger 52 has a rod 55 passing outwards through a
cover 56 of the nozzle 8, with the rod terminating in
a knob 57. A helical spring 58 is inserted between
the knob and the cover. The plunger 52 must be urged
inwards against the force of the spring 58; having
been urged inwards, the plunger automatically resumes
13 ~ 12
1 its original position (when released). In this way, it
is ensured that the region of the mouth 50 is always
exposed. The maltese (Geneva~ cross configuration of
the plunger has been chosen for the reason that scrapexs
or cutting edges may be mounted to each of the heads
contacting the inn~r face of the supply nozzle 8.
I~lined position and frequent cleaning cooperate in
establishing an unrestricted, accelerating oil flow
within the supply nozzle 8, with the oil flow or
stream being disintegrated into small droplets and with
the vertical velocity component being transmitted to
a high degree to the droplets and resulting in in-
creasing the kinetic energy of these droplets. Particles
scraped off by the plunger5~ likewise drop into the
combustion dish to be burnt or pyrolyzed therein.
The automatic program(ming) system of the hot-air
thermal device is controlled in such a manner that
the combustion dish is heated first, before the oil
starts to flow into thls dish. Although a generally
automatic ignition takPs place in the region of the
trough due to the high temperatures of the combustion
dish, it must nevertheless be ensured that waste oils
containing components of relatively high flame point
can be reliably ignited, too. To this end, an ignition
device 39 is provided whichincludes a glow element 45
being installed in concentric fashion into the tubular
housing of the ignition device 39. The glow element
comprises a perforated ceramic tube having a heater
coil installed therein. Prior to admission of the oil,
the program control system causes the glow element to
assume a red hot state, whereby the fuel-air mixture
is ignited instantaneously. The above measures prevent
the generation of black smoke.
Instead of using the glow element 45, the fuel may be
14
1 ignited also with the aid of an infrared mirror reflec-
tor igniter 46. Such igniter has a heater coil 48 dis-
posed within a reflector casing 47. The heat radiation
ls focused onto the trough 27 so as to form an ignition
polnt. In addition, it is possible to connect to the
mirror reflector igniter 46 an air duct or line 49
which directs a combustion alr stream onto the ignition
region at the moment the fue] is ignited.
The apparatuses described abPve will allow the ignition
-of waste- oil in a safe manner.
Still further, a photocell system 24 for monitoring
the combustion process is mounted in the wall of the
lS burner box 14 and so as to extend into the burner
cylinder 1B, with the assoclated photocell 25 receiving
essentially the radiation emitted from the region of
the trough 27 -in the burner dish. The photocell system
24 acts to continuously monitor the combustion process.
The photocell system 24 which comprises essentially an
ocular tube, i5 further provided with a cooling air
nozzle 26 which is fed with cooling air, and the cooling
air is conducted to the end of the ocular tube to be
blown into the combustion zone of the trough. In this
way, it is provided that the combustion zone is con-
stantly fed with combustion air, such that combustion
is maintained as long as unburnt waste oil is still
present in the combustion dish 21. The flame goes out
when the combustible materlal is exhausted, and such
extinction is positively detected by the photocell
system 24.
The air guiding or conducting system is now explained
by referring to Figures 1 and 7. The suction ports
for the room air to be heated and for the combustion
a~r are located at a height of 1.40 meters above the
floor. This arrangement has been chosen in order to
~5 ~L~2~
1 avoid sucking in vapors of low boiling organic com-
pounds which might result in a detonation in the com-
bustion chamber.
A suction port 70 for the combustion air is shown in
Figure 7. The sucked in air is fed, via a duct 71,
to a combustion air blower or fan 72 which urges the
combustion air, metered in accordance with the respec-
tive thermal capacity, into the burner box. The air
is distributed within the burner bo~ and pressed through
the perforations 20 into the burner cylinder where
combustion takes place or where combustion gases are
produced. After-burning then takes place in the com-
bustion chamber. The burnt gases enter the heat exchan-
ger 13 and flow out from the latter as exhaust gasesvia the exhaust line 35.
Simultaneously, room air or fresh air to be heated,
respectively, is aspirated through a port 74 of
greater cross-section, and this air is supplied via
a conduit 75 to a hot-air blower or fan 76 which
transports the air to be heated in upward direction
through the heat exchanger 13 and in contact with the
heat exchanger elements heated by the exhaust gases.
Via the head (portion) 77 of the thermal device 10, the
heated air is conducted to a plurality of air outlets:
namely, an air outlet 78 in the upper portion and a
lower air outlet 79 in the lower portion. The air
conduction path is insulated by means of correspondingly
insulated walls of the housing 11. In particular, it is
thereby avoided that the hot burner portions in the interior
of the apparatus 10 are allowed to come into contact
with the environment. Accordingly, accidents by burning
from the outer portions of the apparatus are prevented.
Furthermore, as can be seen from Figure 2, a tank
16 ~ 2
1 (liquid) level indicator 80 including an associated
float 31 and an oil drain screw 82 at the sump 5 are
provided. The COA~bUStiOn dish 18, including the
auxiliary heater system, is arranged within a drawer
83 which may be drawn out from the housing.
To provide for safe operation, there is provided
a further security measure. In case that the flame
goes out in spite of the monitoring by tne photocell system
24, while the oil supply is not interrupted, unburnt
fuel will overflow the edge of the combustion dish 21
after some period of time. In order to detect this
malfu~ction, an overflow control sensor or detector
87 is desposed in the lower portion of the housing.
The furnace functions are controlled by means of an
electronic control unit 88 which is housed within a
switch box on the side of housing 11.
Description of functions
At the start of the ignition and combustion process,
the con~ustion dish 21 is empty, except for ash residues.
Upon turning on the hot-air thermal system, the heater
coil 23 and the high temperature coil 28 are supplied
with heating pow~r, so as to heat the dish to an
average temperature of about 400 C and to a tempera-
ture of 800 C in the region of the trough. The tem-
perature of the combustion dish 21 is constantly
monitored (detected) by the temperature detector 37.
When the temperature required for combustion and
ignition is reached, the oll pump 2 is activated.
A thin flow or stream of waste oil is initiated through
the line and the supply nozzle 8, so as to flow into
the com~ustion dish 27 through the mouth 50 in the
form of fine droplets. At this time, the lgnition
device 45 or 46 has been actlvatedr too. The first
droplet which drops onto the heated trough, bursts
17 :~21~
1 on the trough to become thoroughly evaporated
instantaneously. As experiments have shown, ignition
takes place at once, such that the further waste oil
supplied is also inflamed at once.
The resistance wire coil 23 is left activated during
this initial ignition process, but it is kept at a
lower temperature. The subsequently impinging oil
droplets burst and immediately come into intense contact
with the surface of the combustion dish. As the ignition
temperature is exceeded, the fuel-air mixture above
the combustion dish is instantaneously inflamed. As
soon as the photocell system 24 detects the ignition,
the fan (blower) 72 is activated to produce a continuous
combustion air flow.
After a given, presettable time delay, the flame
emitted from the combustion dish has heated the latter
to such degree that the combustion becomes self-sustain-
ing. It is to be noted that the combustion dish has arelatively high heat capacity because of the material
of which it is formed.
In case that ignition does not take place after a given
periodJfor example after four seconds, the oil pump 2
is deactivated through a time delay relay, and the fan
72 is also turned off after a further time delay~ Then,
the ignition process may be repeated after some period
of time. Normally, however, it is not necessary to
repeat the ignition process.
During the combustion process, only the oil pump 2 and
the combustion air fan or blower 72 are in operation
to sustain the flame, The other heating and ignlting
means described above are turned off during this period.
The starting hot-air fan or blower urges the room alr
or exterior air through the respective heat exchangers.
~2~
~8
1 The heated air is never directly contacted with the
exhaust gases.
The shut-down operation of the apparatus is effected
by interrupting the oil flow by deactivatlon of the
oil pump 2. After a further time delay, the combustion
air fan 72 is turned off. As long as combustible waste
oil residues are still present within the dish, these
residues are further burnt with the aid of the minor
air ~olumes sucked through the photocell system 24
and the air fan 72, while the flame is monitored by
the photocell 25. The resistance wire coil 23 is
energized again so that the combustion dish 21 is
heated up to a temperature of the dish from 600 to
700 C, thereby initiating pyrolyzing. At the end of
the combustion process, a viscous, solid bituminous
slag has formed within the dish because of the relatively
high quantities of foreign substances, which slag con-
tains a great amount of carbon and of other combustible
substances. The combustible residues are pyrolyzed and
burnt on the heated dish It can be seen that the
solid bltuminous slag is disintegrated into residual
dust during this pyrolyzing process, which dust may
be removed without problem when the box containing the
combustion dish is drawn out. Pyrolysis of the bitumi-
nous slag takes about five minutes. After this period,
the coil 23 is deenergized.
As the heater aggregate, including the combustion dish,
is arranged in a drawer 23, the respective part of the
apparatus may be drawn out. This arrangement greatly
facilitates maintenance and repair workO
The apparatus described above is suitable both for the
heating of rooms and for the generation of steam~ hot
water or hot gases. The apparatus can be put into
operation in a fully automatic manner. Mainten~nCe of
1 9
1 the apparatus can be performed generally without any
problem. In particular, the ash quantities are reduced
to an amount which was heretofore unknown in so-called
waste oil furnaces. Still further, it has been found
that ash formed i~n operation and which may contain
polluting quantities of heavy metals, can be readily
removed by means of fllter devices.
Besides, an intense heat exchange is effected by the
1~ ribbed shell of the combustion chamber 30. These ribs
are formed, for example, of copper. The air outlet
ports can be controlled with respect to direction
and intensity. Measurements have shown that the ex-
haust gas temperatures are in the range of from about
l5 180 to 200~ C. The C02 contents of the exhaust gases
were measured to amount to about 10 % by ~olume. This
provides an overall efficiency of 92%. Due to the capa~i-
lity of metering the combustion air by means of the
combustion air fan 72 and metering the waste oil by
means of the oil pump 2~ a substantially stoichiometric
combustion may be maintained. The contènt of soot is
extremely low in fact, extrem~ly low quantities o~ soot can be
observed even at the start of the combustion process.
The apparatus may be safely operated with a waste oil
quantity of as small as 0.5 kg per hour. At this low
oil volume, it is generally only a sustaining flame
that is maintained in the combustion dish. Stoichio-
metric conditions may be malntained even with these
low flow volumes. The heating power may thus be easily
increased in a short tlme.
